# Patent

## Title
Method of detecting mild impaired glucose tolerance or insulin secretory defect

## Abstract

It is intended to provide a noninvasive method of conveniently detecting mild impaired glucose tolerance and/or insulin hyposecretion at the early stage with the use of an enzyme. Namely, mild impaired glucose tolerance and/or hyposecretion at the early stage are detected by quantifying myoinositol secreted into the urine before loading glucose and after loading glucose for a definite period of time with the use of a reagent and comparing the increase (or the increase ratio) in the myoinositol content thus measured with a characteristic level which has been preliminarily determined in normal subjects.

## Background
FIELD OF THE INVENTION
The present invention relates to a method of examining mild impaired glucose tolerance or insulin secretory defect using a sample such as urine. In addition, the present invention can be applied to a method for predicting or diagnosing a disease that stems from mild impaired glucose tolerance or insulin secretory defect, such as diabetes mellitus, arteriosclerosis, or hypertension; a method of determining effects of prevention of, treatment of, or medical advice on those diseases; and a method of evaluating therapeutic agents for treatment of those diseases.
BACKGROUND OF THE INVENTION
A final goal of diabetic treatment is to prevent the onset of diabetic complications and to inhibit the development thereof. As demonstrated by clinical tests for achieving this goal it is important to find any abnormality and start treatment thereof at the earliest possible stage [e.g., Diabetes Research and Clinical Practice, 28, 103 (1995)].
Further, it is considered effective as a more advanced preventive method to find individuals with prediabetes or at prestage of diabetes, or individuals with mild impaired glucose tolerance or insulin secretory defect, who are not prediabetic at present but are highly likely to develop diabetes or prediabetes in the near future, and give them treatment or advice for exercise and dietary. Clinical tests have been conducted to scientifically demonstrate this [e.g., Diabetes Care, 21, 1720 (1998)]. Therefore, detecting individuals with prediabetes will be important for prevention of diabetes mellitus and also complications thereof. Furthermore, diagnosing individuals with mild impaired glucose tolerance or insulin secretory defect, who are not prediabetic at present but are highly likely to develop diabetes or prediabetes in the near future, is considered most important for purpose of preventing diabetes mellitus at an earlier date.
An example of the diagnostic method for diabetes mellitus is an oral glucose tolerance test. After a 75 gram oral glucose load, a group of individuals with the fasting blood glucose level being less than 110 mg/dl and the 2-hour postload blood glucose level being less than 140 mg/dl is defined as normal glucose tolerance (NGT). In addition, a group of individuals with the fasting blood glucose level being not less than 110 mg/dl but less than 126 mg/dl and the 2-hour postload blood glucose level being less than 140 mg/dl is defined as impaired fasting glycemia (IFG); and a group of individuals with the fasting blood glucose level being less than 126 mg/dl and the 2-hour postload blood glucose level being not less than 140 mg/dl but less than 200 mg/dl is defined as impaired glucose tolerance (IGT); and both groups IFG+IGT are defined as borderline type. A group of individuals with the fasting blood glucose level being not less than 126 mg/dl or the 2-hour postload blood glucose level being not less than 200 mg/dl is defined as diabetes mellitus.
The guideline of the Japan Diabetes Society teaches that among individuals defined as NGT on the basis of only the fasting blood glucose level and the 2-hour postload blood glucose level, those with the 1-hour postload blood glucose levels being 180 mg/dl or more are at higher risk to develop diabetes so that they should be handled as the borderline type.
The term “impaired glucose tolerance” or “glucose tolerance failure” refers to the condition of an increase in blood glucose level caused by insufficient uptake of blood glucose into peripheral tissues such as skeletal muscle, liver, and adipocyte after glucose is introduced into the blood through meals. In addition, the term “mild impaired glucose tolerance” refers to that the increment is slightly higher than that of healthy individuals.
Insulin is a hormone secreted from beta cells of pancreas and acts on skeletal muscle, liver and adipose tissue to lower the blood glucose level. The term “insulin secretory defect” refers to the condition of insufficient insulin secretion to uptake a sufficient amount of blood glucose into peripheral tissues such as skeletal muscle, liver, and adipocyte after glucose is introduced into the blood through meals or the like. Among the insulin secretory defect, the condition of insufficient insulin secretion to uptake the blood glucose into peripheral tissues just after glucose is introduced into the blood is referred to as “impaired early insulin secretion”. According to the guideline of the Japan Diabetes Society, the term “impaired early insulin secretion” refers to the condition in which the insulinogenic index I.I is less than 0.4. Insulinogenic index I.I is defined as ΔIRI (30-0)/ΔPG (30-0) wherein ΔIRI (30-0) means between the difference between the blood insulin levels at 30 min after glucose load and before glucose load; and ΔPG (30-0) means the difference between the blood glucose levels at 30 min after glucose load and before glucose load.
Assays of blood glucose levels and insulin levels for those diagnoses are invasive procedures that require blood drawing more than once within a short time, giving the subjects considerable pains. Therefore, there is a need for a simple assay with lower invasiveness, which can solve these disadvantages, preferably a noninvasive assay.
On the other hand, the quantitative determination of myo-inositol in a biological sample has been considered useful for the diagnosis of diabetes mellitus and the following reports have been provided.
(a) In diabetes mellitus, there was an increase in the urinary myo-inositol level [Larner J. et al., New Eng. J. Med., 323, 373-378 (1990)].
(b) No difference was found between NGT and the borderline type with respect to the urinary myo-inositol level [Susumu Suzuki, Diabetes Care, Vol. 17, No. 12 (1994) 1465-1468].
(c) The borderline type (IFG, IGT) and diabetes mellitus showed higher urinary myo-inositol level than that of NGT (JP 2001-190299 A).
The above reports (a) and (b) show the results obtained by determining the urinary myo-inositol levels with GC/MS. Nevertheless, the data are problematic in reproducibility and reliability because they varied among different examiners. On the other hand, in the report (c), the results are more precise and reliable than those obtained by GC/MS because they are obtained by determining the urinary myo-inositol level with a high-sensitive myo-inositol assay reagent using an enzyme. In this way, the detection of the group with prediabetes has become possible.
However, the myo-inositol assay reagent used in the report (c) has problems including: (i) an insufficient lower limit of detection because of a narrow measurement range and the need of diluting a sample for determination of various urinary myo-inositol levels; and (ii) insufficient avoidance of effects of coexisting substances in urine, particularly glucose. Therefore, the detection of mild impaired glucose tolerance and insulin secretory defect, which fall within NGT, has been impossible.
Furthermore, if a subject is judged to be NGT on the basis of only blood levels before a 75 g oral glucose load and at 2 hours after the glucose load, such judgment does not reflect the change in blood level from 0 to 2 hours. For example, even individuals (with mild impaired glucose tolerance and insulin secretory defect) who keep a higher blood glucose level from just after the glucose load, and thus are highly likely to develop diabetes or prediabetes in the near future are practically classified in NGT. As used herein, the term “mild impaired glucose tolerance” is classified in NGT, but refers to a slight decrease in glucose tolerance characterized by, when the loading test is carried out and blood samples are collected four times on fasting and at 30 minutes, 1 hour, and 2 hours after the load, (i) an oxyhyperglycemia, i.e., very high blood glucose levels (180 mg/dL or more) at 30 minutes and 1 hour after the load, (ii) a higher blood glucose level than that of healthy individuals at 2 hours after the load although the blood level is less than 140 mg/dL (e.g. not less than 120 mg/dL), (iii) high ΣPG (e.g. 530 mg/dL or more), i.e. the total of blood glucose levels just before 75g oral glucose load and at 30, 60, and 120 minutes after the glucose load Therefore, it can not be anticipated from the public disclosures (a)-(c) to identify the group of individuals who are highly likely to develop diabetes or prediabetes in the near future, for example, individuals with mild impaired glucose tolerance, by determining myo-inositol levels.
In this way, the conventional technology teaches no method of detecting mild impaired glucose tolerance and insulin secretory defect, which keep a higher blood glucose level from just after the glucose load, and thus are highly likely to develop to diabetes or prediabetes in the near future.
SUMMARY OF THE INVENTION
The present invention intends to provide an assay method for simple determination of mild impaired glucose tolerance and/or insulin secretory defect with good reproducibility.
For achieving this object, the present inventors considered that search for any marker for effectively determining mild impaired glucose tolerance and/or insulin secretory defect was advantageous. As a result of concentrated efforts, whereas myo-inositol is conventionally considered to be useful for detection of insulin resistance and prediabetes (borderline type and diabetes mellitus), the present inventors unexpectedly found that myo-inositol is also useful as a marker for effectively detecting mild impaired glucose tolerance or insulin secretory defect
Blood serum, plasma, or urine collected from the human body, or a homogenized extract of living tissue are used as a sample. Urine is preferable because it can be non-invasively obtained.
The present inventors continued to develop a high-sensitive quantitative determination assay of myo-inositol and a composition for the assay to provide a simple and cost-effective quantitative determination assay of myo-inositol with a high degree of accuracy (JP 06-61278 B). This enzymatic assay, which does not require any preliminary treatment, opened the way to obtain reliable data of myo-inositol for the first time. Such development of the high-sensitive quantitative determination assay and the composition for the quantitative determination allowed the first success of providing the method of the present invention for examining mild impaired glucose tolerance and/or insulin secretory defect.
Furthermore, after the administration of a given amount of glucose to a subject, urine samples were obtained non-invasively from the subject within a given time period and the myo-inositol levels thereof were determined using the myo-inositol assay reagent as described above. The determination revealed that not only individuals with prediabetes (of borderline type, IFG, IGT) and individuals of diabetes mellitus, but also individuals practically showing mild impaired glucose tolerance in spite of being of NGT and individuals practically showing a decrease in early insulin secretion in spite of being of NGT have higher levels than the characteristic value predetermined from healthy individuals. Therefore, it has been found that the assay reagent of the present invention enables not only the distinction between NGT and non-NGT with progressed impaired glucose tolerance (borderline type, IFG IGT, diabetes) but also the simple, highly reproducible and efficient distinction of individuals practically showing mild impaired glucose tolerance in spite of being of NGT or individuals practically showing a decrease in early insulin secretion in spite of being of NGT from healthy individuals.
In addition, the concentration of myo-inositol in a sample may be very low and some of myo-inositol dehydrogenases used may react weakly with glucose. Thus, the elimination of glucose may be required in advance. A method for the elimination of glucose includes one using extreme chemical stability of myo-inositol and one by modifying glucose using an enzyme as a catalyst. The method using the chemical stability includes, for example, one by heating a sample in the presence of 6 N HCl to allow the acid decomposition of sugars except myo-inositol and recovering myo-inositol remained in the decomposed product; and one by treating a sample with a reducing agent such as sodium borohydride to reduce sugars having carbonyl groups or formyl groups such as glucose except myo-inositol and modifying them to make compounds unreactive with myo-inositol dehydrogenase, i.e. an enzyme for the quantitative myo-inositol assay. The method by modifying glucose using an enzyme as a catalyst includes one by converting glucose in a sample into gluconic acid with glucose oxidase (EC1,1,3,4) and one by converting glucose in a sample into glucose-6-phosphate with hexokinase (EC2,7,1,1).
Various improvements are known in these converting methods. In relation to the method of converting glucose into gluconic acid with glucose oxidase, for example, known is a method to eliminate hydrogen peroxide products by catalase after the reaction with glucose oxidase (JP 63-185397 A).
Furthermore, in relation to the method of converting glucose into glucose-6-phosphate with hexokinase, there are known methods to convert glucose into fructose-1,6-bisphosphate using phosphohexose isomerase and 6-phosphofructokinase to prevent glucose-6-phosphate from being reconverted into glucose through an equilibrium reaction (JP 05-76397 A); to perform the reaction with glucose-6-phosphate dehydrogenase in the presence of an oxidized coenzyme (JP 01-320998 A, JP 03-27299 A); and to perform the reaction with pyruvate kinase in the presence of adenosine diphosphate to prevent the change of adenosine triphosphate level decreasing as glucose is eliminated and thus keep the adenosine triphosphate level constant (JP 02-104298 A).
However, when glucose is eliminated using hexokinase, the enzymatic reaction produces a large amount of ADP in the reaction solution, so that the effect thereof on the enzymatic reaction cannot be ignored. Thus, it is preferable to convert the resulting ADP to a compound that does not affect the reaction.
Thus, the present inventors have considered an effective method using an ADP eliminating agent to convert ADP generated in the reaction solution by the enzymatic reaction to a compound that does not affect the reaction.
Any substances capable of converting ADP to a compound that does not affect the reaction can be used as an ADP eliminating agent Of these, enzymes are preferable and kinases that catalyze conversion of ADP to AMP are more preferable. Kinases are also called phosphokinases or phosphotransferases. Examples of the kinases which catalyze conversion of ADP to AMP include pyrophosphate-glycerol transferase, 6phosphofructokinase, acetate kinase, and ADP-hexokinase.
As a result of keen investigations, the present inventors have found that 6phosophofructokinase and ADP-hexokinase are preferably used as an ADP eliminating agent in the present invention.
When 6phosphofructokinase is used as an ADP eliminating agent in the reaction of eliminating glucose in a sample, ADP is produced along with the conversion of glucose to glucose-6-phosphate using ATP-hexokinase in the presence of ATP and is simultaneously reacted with 6-phosphofructokinase to allow the conversion of ADP to AMP along with the conversion of preadded fructose-6-phosphate to fructose-1,6-bisphosphate.
When ADP-hexokinase is used as an ADP eliminating agent in the reaction of eliminating glucose in a sample, ADP is produced along with the conversion of glucose to glucose-6phosphate using ATP-hexokinase in the presence of ATP and can be converted to AMP.
In addition, it is preferable to perform such reaction in the presence of salts. Examples of the salts include: magnesium salts such as magnesium chloride and magnesium acetate; and potassium salts such as potassium chloride and potassium sulfate. The concentration of salts used is, but not limited to, preferably about 1 to 100 mM.
Any of these compounds produced by the enzymatic modification are not reactive with myo-inositol dehydrogenase, an enzyme for the quantitative myo-inositol determination. The present inventors have found that it is more preferable to previously eliminate glucose by these methods.
Further, the present inventors have found that myo-inositol can be determined more accurately when two kinds of kinases, ATP-hexokinase and ADP-hexokinase, are used simultaneously because the influence of sugars in a sample is reduced. In addition, the present inventors have found that the range of myo-inositol determination can be extended by about 10 times by adjusting thio-NAD level to a final concentration of 0.1 mM or more, preferably 2 to 10 mM. Thus, the present inventors have completed a higher sensitive assay system.
The term “characteristic value” refers to a value determined on the basis of an average of myo-inositol levels in urine samples of healthy subjects selected from those of NGT; standard deviation; and ROC (response operating characteristic) curve. When urine samples are used, the increment in urinary myo-inositol excretion between before the glucose load and at a predetermined time after the glucose load is in the range of 0 to 20 μg/mg creatinine; or 5 to 15 μg/mg creatinine; or more preferably 8 to 12 μg/mg creatinine. In addition, the characteristic value may be changed if a large-scale examination is conducted in the future and the determination is conducted for healthy individuals selected clinically. Furthermore, the characteristic value may also vary depending on the selected populations of race, sex, and age.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the results of study on thio-NAD levels according to Reference Example 1.
FIG. 2 shows the results of stability test of myo-inositol assay reagents according to Reference Example 2.
FIG. 3 shows the effects of ADP-hexokinase according to Reference Example 3.
FIG. 4 shows the calibration curve for myo-inositol levels according to Reference Example 4.
FIG. 5 shows the relationship between myo-inositol level and ΣPG according to Example 1.
FIG. 6 shows the relationship between inositol level and insulinogenic index according to Example 2.
FIG. 7 shows the relationship between each group and ΣPG according to Example 3.
FIG. 8 shows the relationship between each group and insulinogenic index according to Example 4.
FIG. 9 shows the relationship between each group and myo-inositol level according to Example 5.
FIG. 10 shows the relationship between each group and myo-inositol level according to Example 6.
FIG. 11 shows the correlation between urinary myo-inositol levels in the glucose tolerance test and in the meal tolerance test according to Example 7.
FIG. 12 shows the relationship in each group between Δ myo-inositol in the glucose tolerance test and Δ myo-inositol in the meal tolerance test according to Example 8.
FIG. 13 shows the relationship in urinary glucose negative individuals between urinary myo-inositol level in the meal tolerance test and mild impaired glucose tolerance according to Example 9.



BEST MODE FOR CARRYING OUT THE INVENTION
The present invention and preferred embodiments thereof will be described in more detail as below.
According to the present invention, the detection of mild impaired glucose tolerance and insulin secretory defect is carried out by determining the amounts of myo-inositol excreted in urine of a subject before the glucose load and at a predetermined time after the glucose load using the reagent of the present invention; and making a comparison of an increasing amount or increasing rate of myo-inositol between before and after the glucose load with the characteristic value defined in advance for healthy individuals.
The increasing amount is calculated as a difference between the myo-inositol content at a predetermined time after the glucose load and the myo-inositol content before the glucose load, and the increasing rate is calculated as a ratio of the myo-inositol content at a predetermined time after the glucose load to the myo-inositol content before the glucose load.
For the concentration of myo-inositol, an actually determined value may be used, or a relative value with respect to an appropriate standard index may be used for compensating the dilution of urine with drinking water. Preferably, the index is a urinary creatinine level. The subjects include all individuals in addition to those suspected of being lifestyle-related diseases such as diabetes.
Any amounts of glucose loaded and any types of the glucose loading methods may be used. However, preferable is an oral administration of an aqueous 75 g glucose solution as used in a typical glucose load test or a meal ingestion.
Urine samples may be collected before the glucose load and at any times until 6 hours passed just after the glucose load, preferably at 30 minutes to 3 hours after the glucose load. A urine collection period is suitably selected from 30 minutes to 3 hours.
When using urine as a sample, it is collected by a non-invasive method, so that there is no need to select the sampling method, time, and place. For instance, such a sample can be easily prepared by the subject at home, office, school, or the like, and the collected urine sample may be transported directly or in a form of urine-immersed filter paper or other suitable forms, these eliminating the need to be tied to medical institutions or the like. Thus, the present invention provides a prominent method in which, when a filter paper or the like is impregnated with urine, the sample dispatched is extracted by a suitable method and provided to the simple and rapid assay of the present invention and then immediately the results is sent to the subject.
In particular, urinary myo-inositol levels can be monitored as needed while the subject spends everyday life as usual without glucose load. For example, it is possible to grasp the degree of impaired glucose tolerance or the degree of insulin secretory defect using the maximum myo-inositol level or the difference between the maximum myo-inositol level and the minimum myo-inositol level in a day. In addition, monitoring urinary myo-inositol levels as needed allows the subject to reconsider the diet contents and control the amount of exercise to prevent diabetes or the progress thereof while having a regular life.
The methods of monitoring urinary myo-inositol levels include any types of methods capable of detecting myo-inositol, for example, a method using a test paper onto which an enzyme that acts on myo-inositol is fixed and a method of electrochemically detecting myo-inositol using an electrode as a sensor onto which an enzyme acting on myo-inositol is fixed.
In the test paper method, for example, hydrogen peroxide is generated by oxidase and reacted to peroxidase to generate active oxygen, and the active oxygen causes the oxidation of chromogen for coloration, the intensity of which may be observed. The chromogen includes, but not limited to, potassium iodide, tetramethylbenzidine, N-(3-sulfopropyl)-3,3′,5,5-′-sodium tetramethylbenzidine, 4-aminoantipyrine, and O-tolidine.
For detecting by means of the sensor, for example, when oxidase is used, hydrogen peroxide generated may be directly measured using an electrode; or the oxidation-reduction current obtained through an electron carrier such as a ferrocene derivative or a quinone derivative or the quantity of the electric current may be measured Likewise, when dehydrogenase is used, the reduced coenzyme may be directly measured using an electrode; or the oxidation-reduction current obtained through an electron carrier or the quantity of the electric current may be measured. Examples are shown in “Biosensor and Quantitative Assay of Substrate Using the Same (Application No. JP 09-263492)” and the like.
In addition, for example, daily monitoring of urinary myo-inositol levels can be more easily carried out by incorporating the above sensor directly into a toilet stool or the like or into a device attached thereto. Such a device may further have functions of memorizing the measurements and of connecting to a terminal of an information processor. In this way, even when the subject stays in a distant place, a medical practitioner or medical institution can make contact with the subject through an electric medium to manage vital data; to give a medical advice; and to examine the degree of impaired glucose tolerance and the degree of insulin secretory defect, leading to review of the diet contents, control of the amount of exercise, improvement of life style, and the medical treatment.
In the case of making quantitative determination of glucose together with myo-inositol in a sample to detect mild impaired glucose tolerance and/or insulin secretory defect, myo-inositol is quantitatively determined preferably by the method of the present invention, while glucose may be quantitatively determined using any conventional methods.
In addition, more precise management can be performed by combining the results of the determination and a doctor's observation. Furthermore, because it is possible to determine the risk to develop diabetes by finding the precondition to diabetes, i.e. prediabetes, and also mild impaired glucose tolerance and insulin secretory defect, which are not prediabetic at present but are highly likely to change to diabetes or prediabetes in the near future, though such finding being impossible by a conventional marker, for example, the risk can be used as an item of examination for life insurance or the like.
For quantitatively determining myo-inositol in a sample, 1 to 500 μL of the sample is added to the composition for myo-inositol quantitative determination to allow a reaction at 37° C. and then the amounts of a coenzyme changed may be directly or indirectly determined for several minutes or several tens of minutes between two time points after the reaction starts, for example, for 1 minute between 3 minutes and 4 minutes after the reaction initiation or for 5 minutes between 3 minutes and 8 minutes. In this case, the myo-inositol content in the sample can be determined by making a comparison with changes in absorbance which are measured for known concentrations of myo-inositol.
The composition (reagent) for the quantitative determination need to contain at least an enzyme that acts on myo-inositol and preferably it further contains a coenzyme.
In addition, a surfactant such as polyoxyethylene octylphenyl ether (OP-10) may be added to the present reagent as appropriate.
Furthermore, the present reagent is used in a form of a liquid product, a freeze-dried product, or a frozen product.
For quantitatively determining myo-inositol in a sample, any types of methods using an enzyme to quantitatively determine myo-inositol may be used. The enzyme to be used in the present invention, which is capable of quantitatively determining myo-inositol, includes any enzymes that act on at least myo-inositol. Of those, however, myo-inositol dehydrogenase is preferable, and myo-inositol dehydrogenase derived from Flavobaterium sp. 671 (FERM BP-7323, hereinafter abbreviated as F.sp.671) is most preferable. In addition, preferably, the myo-inositol dehydrogenase to be used has as low as possible or no contamination of substances that adversely affects coenzymes such as thio-NAD and NADH in the reagent, for example, substances having the activity of decomposing coenzymes, such as NADH oxidase.
The strain F.sp.671 is deposited on an international basis with the deposit number of FERM BP-7323 (date of deposit: Oct. 12, 2000) at the National Institute of Bioscience and Human-Technology, Agency of Industrial Science and Technology, The Ministry of International Trade and Industry, located at 1-1-3 Higashi, Tsukuba, Ibaraki, Japan (at present: International Patent Organism Depositary, the National Institute of Advanced Industrial Science and Technology, Independent Administrative Agency, located at Center 6, 1-1-1 Higashi, Tsukuba, Ibaraki, Japan).
For the detection of myo-inositol, any types of methods capable of detecting myo-inositol may be used. The methods include: a method using a visible light coloring reagent, for example, typically yellow coloring with thio-NAD, blue coloring with nitro blue tetrazolium (NBT), or red coloring with 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT); a luminescence method; a fluorescence method; a method involving detection of an electric change; and a combination of these methods with amplification techniques.
In addition, using a compact device which can utilize any one of the above methods, the determination of urinary myo-inositol can be carried out non-invasively without restriction on time and place.
The assay for determining the activity of myo-inositol dehydrogenase is as follows:
(1) Activity Assay
<Composition of Reaction Solution>

    
    
        100 mM Tris buffer (pH 8.5)
        20 mM myo-inositol (Sigma Co., Ltd.)
        2 mM nicotinamide adenine dinucleotide (NAD) (Oriental Yeast Co., Ltd.)
        5 U/ml diaphorase (Asahi Kasei Corporation)
        0.025% nitro blue tetrazolium (NBT; Wako Pure Chemical Industries, Ltd.)
        1.5% Triton-X100 (Wako Pure Chemical Industries, Ltd.)
    
    


One ml of the above reaction solution is added to a small test tube. After the reaction solution is incubated at 37° C. for 5 minutes, 20 μl of an enzyme solution diluted by B times is added thereto and mixed to start the reaction. After the reaction exactly for 5 minutes, 2 ml of 0.1 N HCl is added and mixed to stop the reaction. An absorbance at 550 nm is measured to obtain A1. In addition, the same reaction solution excluding myo-inositol is used to carry out a similar measurement to obtain the absorbance A0. The enzyme activity can be calculated from the following equation.

U/ml=[(A1−A0)/18.3]×[1/5]×[3.02/0.02]×B 

Numerals in the equation represent the following meanings.

    
    
        18.3: Molar absorption coefficient of NTB
        5: Reaction time
        3.02: Total volume of reaction solution
        0.02: Volume of enzyme solution
        B: Dilution factor of enzyme solution
    
    


The properties of myo-inositol dehydrogenase derived from the strain F.sp.671 are as follows:
(2) Enzyme Action
This enzyme produces inosose and a reduced coenzyme in the presence of at least myo-inositol and a coenzyme. The coenzyme includes nicotinamide adenine dinucleotides (hereinafter abbreviated as NADs) such as nicotinamide adenine dinucleotide (NAD), acetylpyridine adenine dinucleotide (acetyl-NAD), nicotinamide hypoxanthine dinucleotide (deamino-NAD), pyridine aldehyde adenine dinucleotide (aldehyde-NAD), nicotinamide adenine dinucleotide phosphate (NADP), thio-nicotinamide adenine dinucleotide (thio-NAD), and thio-nicotinamide adenine dinucleotide phosphate (thio-NADP).
Table 1 shows the ratio of relative activities on use of each coenzyme (as 100% when NAD is used as a coenzyme). The relative activities were determined with the coenzyme changed according to the following method.
Relative Activity Assay
<Composition of Reaction Solution>

    
    
        Buffer: 100 mM glycine buffer (pH 10.0)
        Substrate: 20 mM myo-inositol (Sigma, Co., Ltd.)
        Coenzyme: 2 mM (NAD, thio-NAD, NADP, thio NADP; Oriental Yeast Co., Ltd.)
    
    


One ml of the above reaction solution is added to a quartz cell. Then, the quartz cell is placed in a spectrophotometer adjusted at a temperature of 37° C. The cell is incubated for 5 minutes or more and then 20 μl of an enzyme solution of about 1.0 U/ml is added thereto and mixed. The initial velocity is obtained from an absorbance change per minute at a wavelength peculiar to each reduced coenzyme. The initial velocity obtained with each coenzyme is compared with the initial velocity (100%) obtained using NAD as a coenzyme to provide the relative activity.







TABLE 1







Relative activity ratio for each coenzyme used










Name of bacterial strain
F.sp.671



Coenzyme
myo-Inositol














NAD
100%



NADP
8%



Thio-NAD
29%



Thio-NADP
0%










(3) Substrate Specificity
According to the relative activity assay described above, the measurement was performed using the same concentration of D-chiro-inositol, D-mannose, D-fructose, D-galactose, mannitol, epi-inositol, or scyllo-inositol in place of the substrate in the reaction solution. Table 2 shows the enzyme activity for each substrate referring to the initial velocity of the reaction to myo-inositol as 100%. It is revealed that the enzyme derived from the strain F.sp.671 is dehydrogenase having high specificity to myo-inositol.
The substrates used include D-mannose, D-fructose, D-galactose, mannitol, D-chiro-inositol (as above: Wako Pure Chemical Industries, Ltd.), myo-inositol, epi-inositol, and scyllo-inositol (as above: Sigma, Co., Ltd.).







TABLE 2







Substrate specificity










Name of bacterial strain
F.sp.671



Coenzyme
NAD







myo-Inositol
100%



chiro-Inositol
 18%



scyllo-Inositol
less than 1%



epi-Inositol
 2%



Galactose
less than 1%



Fructose
less than 1%



Mannose
less than 1%



Mannitol
 0%










(4) Optimum pH
Following the relative activity assay described above, the measurement was performed using each of 100 mM tris buffer (pH 7.0-9.0) and 100 mM glycine buffer (pH 9.0-11.0) in place of 100 mM of pH 10.0 glycine buffer in the reaction solution. The measurement showed that the optimum pH was about 11.0 (substrate: myo-inositol).
(5) Molecular Weight
Used were TSK gel G300SW (0.75 Φ×600 mm), eluent: 50 mM phosphate buffer (pH 7.5) +0.2 M Na2SO4+0.05% NaN3, and a molecular marker set of Oriental Yeast Co., Ltd. (Japan), a chromatography apparatus made by Shimadzu Corporation (Japan). For the detection, the absorbance at UV 280 nm and the activity of each fraction were measured. myo-Inositol was used as a substrate in the activity measurement, revealing the molecular weight of 40,000±10,000.
(6) Heat Stability
The enzyme showed almost 100% remaining activity after treatment at 40° C. for 15 minutes. The enzyme solution of about 5 U/ml was subjected to heat treatment for 15 minutes. The remaining activity was measured using the enzyme activity assay described above. In the activity measurement, myo-inositol was used as a substrate.
(7) Km value
Using the relative activity assay described above, the concentration of myo-inositol and the concentrations of NAD and thio-NAD were changed to determine Km values respectively. Using the activity assay described above, the substrate concentration was changed to calculate the Km value.
Km value for substrate

    
    
        myo-Inositol: 1.7±0.2 mM
    
    


Km value for coenzyme

    
    
        NAD: 0.04±0.01 mM
        Thio NAD: 4.5±1 mM
    
    


For the quantitative determination of myo-inositol with higher sensitivity, the enzymatic cycling method can be used. An example of the enzymatic cycling method is illustrated in the following equation.




In the equation, A1 represents NAD(P) or thio-NAD(P); A2 represents a reduced form of A1; B1 represents reduced NAD(P) when A1 is thio-NAD(P) or reduced thio-NADP) when A1 is NAD(P); and B2 represents an oxidized product of B1. As used herein, NAD(P) represents nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate.
For the solution composition of the quantitative reaction of myo-inositol using the enzymatic cycling, two or more of coenzymes are appropriately selected in view of Km values of respective coenzymes of myo-inositol dehydrogenase, and the like, and subsequently the pH condition is adjusted between the optimal pH values of forward reaction/reverse reaction to make an efficient progress in the enzymatic cycling. The amounts of A1 and B 1 should be excess over the myo-inositol content in a sample and also excess over Km values of myo-inositol dehydrogenase for A1 and B1.
When using, for instance, myo-inositol dehydrogenase derived from F.sp.671, the Km values for NAD and thio-NAD are 0.04 mM and 4.5 mM, respectively. For the cycling reaction, thio-NAD and NADH may be selected as coenzymes. The concentrations of A1 and B1 are preferably 0.02 mM to 2 M, particularly preferably 0.05 to 100 mM. The amount of myo-inositol dehydrogenase is preferably 1 to 1000 U/mL, particularly preferably 1 to 100 U/mL. The amounts can be suitably selected on the basis of type and amount of the test sample, the myo-inositol content in the sample to be assayed, and the like; but other amounts may be also allowed.
When hexokinase is used as an enzyme for eliminating sugars presented in a sample, any hexokinase capable of catalyzing the reaction from glucose to glucose-6-phosphate may be used, including hexokinase derived from Bacillus sp. Preferable hexokinase is one having excellent heat stability. The hexokinase having excellent heat stability can be obtained by the method described in “Stable Hexokinase and Production Method Thereof” (JP 2000-078982 A).
Because ADP generated together with glucose-6-phosphate has some inhibitory effect on the reaction in the enzymatic cycling method, the present inventors successfully have used ADP-dependent hexokinase simultaneously with hexokinase to improve substantially the elimination of glucose without any influence on the reaction of myo-inositol dehydrogenase.

Glc+ATP+Mg2+→G-6-P+ADP

Glc+ADP+Mg2+→G-6-P+AMP

    
    
        ATP: Adenosine-5′-triphosphate
        ADP: Adenosine-5′-diphosphate
        AMP: Adenosine-5′-monophosphate
    
    


The assay of hexokinase activity is conducted as follows.
<Composition of Reaction Solution>

    
    
        50 mM Tris buffer (pH 8.5) (Sigma, Co., Ltd.)
        20 mM glucose (Wako Pure Chemical Industries, Ltd.)
        4 mM ATP (Oriental Yeast Co., Ltd.)
        5 U/mL glucose-6-phosphate dehydrogenase (Toyobo Co., Ltd.)
        1 mM NADP (Oriental Yeast Co., Ltd.)
        10 mM magnesium chloride (Wako Pure Chemical Industries, Ltd.)
    
    


Solution for dissolving and diluting the enzyme: 50 mM Tris buffer (pH 8.5)
One mL of the above reaction solution is added to a quartz cell with 1-cm optical path length, and incubated at 37° C. for 5 minutes. Then, 20 μL of the enzyme solution, which is diluted B times, is added thereto and mixed to start the reaction. The absorbance at 340 nm is measured from the initiation of the reaction to obtain the absorbance change A1 per minute, which shows a linear reaction. A blind test is also conducted in a similar reaction to obtain the absorbance change A0 per minute, except that 50 μL of the solution for dissolving and diluting the enzyme is added instead of the enzyme solution. The enzyme activity is calculated from the following equation.

U/ml=[(A1−A0)/6.22]×[1.02/0.02]×B 

Numerals in the equation represent the following meanings.

    
    
        6.22: Millimolar extinction coefficient of NADPH at 340 nm
        1.02: Total volume of reaction solution (mL)
        0.02: Volume of enzyme solution used in the reaction (mL)
        B: Dilution factor of enzyme solution
    
    


The assay of ADP-dependent hexokinase activity is conducted as follows.
<Composition of Reaction Solution>

    
    
        50 mM Tris buffer (pH 7.5)
        20 mM glucose solution (Wako Pure Chemical Industries, Ltd)
        2 mM ADP solution (pH 7.0) (Oriental Yeast Co., Ltd.)
        5 U/mL glucose-6-phosphate dehydrogenase (Asahi Kasei Corporation)
        1 mM NADP solution (Oriental Yeast Co., Ltd)
        2 mM magnesium chloride solution (Wako Pure Chemical Industries, Ltd)
    
    


Solution for dissolving and diluting the enzyme: 10 mM Tris buffer (pH 7.5)
Three mL of the above reaction solution is added to a small test tube, and incubated at 37° C. for 5 minutes. Then, 50 μL of the enzyme solution, which is diluted by B times, is added thereto and mixed to start the reaction. The absorbance at 340 nm is measured from the initiation of the reaction to obtain the absorbance change A1 per minute, which shows a linear reaction. A blind test is also conducted in a similar reaction to obtain the absorbance change A0 per minute, except that 50 μL of the solution for dissolving and diluting the enzyme is added instead of the enzyme solution. The enzyme activity is calculated from the following equation.

U/ml=[(A1−A0)/6.22]×[3.05/0.05]×B 

Numerals in the equation represent the following meanings.

    
    
        6.22: Millimolar extinction coefficient of NADPH at 340 nm
        3.05: Total volume of reaction solution (mL)
        0.05: Volume of enzyme solution used in the reaction (mL)
        B: Dilution factor of enzyme solution
    
    


The amount of hexokinase is preferably 1 to 1,000 u/mL, particularly preferably 1 to 100 u/mL. The amount of ADP-dependent hexokinase is preferably 1 to 1,000 u/ml, particularly preferably 1 to 100 u/mL. The amounts can be appropriately selected depending on type and amount of the test sample, and other amounts can be also used.
In addition, for the determination of urinary myo-inositol over a wide range of its concentration with good reproducibility, an enzymatic cycling reaction should be effectively performed. As a result of intensive examination on concentrations and ratio of thio-NAD and NADH, two coenzymes to be used in the enzymatic cycling reaction, the present inventors have found that the thio-NAD level is preferably 0.01 mM or more, particularly preferably 2 to 10 mM in a final concentration and the ratio of NADH/thio-NAD is preferably 0.01 to 0.5, particularly preferably 0.01 to 0.1. However, the amounts can be appropriately selected according to type and amount of the test sample, and other amounts may be applied.
EXAMPLES
The examples of the present invention and reference examples will be described in detail, but the present invention is not limited thereto.
Reference Example 1
Study on thio-NAD Levels
1) Reagents
<R-1>

    
    
        5 mM MES (2-Morpholinoethanesulfonic acid) (pH 6.0)
        0 to 40 mM thio-NAD (Oriental Yeast Co., Ltd.)
    
    


<R-2; Reagent for myo-Inositol Quantitative Determination>

    
    
        200 mM Bicine (pH 9.0)
        0.3 mM NADH (Oriental Yeast Co., Ltd.)
        25 u/mL myo-inositol dehydrogenase (Asahi Kasei Corporation)
    
    


2) Method
The measurement device used was Autoanalyzer 7170S (Hitachi Chemical Co., Ltd.). To 3 μL of myo-inositol solution at concentrations of 0 to 3,000 μM, 180 μL of R-1 reagent was added and incubated at 37° C. for 4.8 minutes, followed by the addition of 180 μL of R-2 reagent to start the reaction. Absorbances at 405 nm were measured at 5.4 and 7.8 minutes after the reaction initiation, and then the difference therebetween was obtained. An increasing rate of absorbance per minute (ΔmABS/min) was calculated and the sensitivity was then investigated with respect to the standard solution.
3) Results
The results are shown in FIG. 1. As shown in FIG. 1, using thio-NAD at final concentrations of 0.1 to 10 mM, the linearity of the calibration curve was observed over myo-inositol concentrations of 0 to 3,000 μm. In addition, it has been found that the final concentration of thio-NAD is preferably 2 to 10 mM to enhance the sensitivity of myo-inositol detection.
Reference Example 2
Study on Buffers in Reagents for myo-Inositol Quantitative Determination
1) Reagents
<R-1>

    
    
        5 mM MES (pH 6.0)
        5 mM thio-NAD (Oriental Yeast Co., Ltd.)
    
    


<R-2; Reagent for myo-Inositol Quantitative Determination>

    
    
        100 mM Buffer (pH 8.8)
        0.5 mM NADH (Oriental Yeast Co., Ltd)
        10 u/mL myo-inositol dehydrogenase (Asahi Kasei Corporation)
    
    


2) Method
R-2 reagents for myo-inositol quantitative determination were prepared following the above shown composition with a buffer being selected from:
Tris (Tris(hydroxymethyl)aminomethane),
Tricine (N-Tris(hydroxymethyl)methylglycine),
Bicine (N,N-Bis(hydroxyethyl)glycine),
TAPS (N-Tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid),
TEA (Triethanolamine),
CHES (2-Cyclohexylamino)ethanesulfonic acid), and
AMPSO(3-((1,1-Dimethyl-2-hydroxy-ethyl)amino)-2-hydroxypropanesulfonic acid).
The measurement device used was Autoanalyzer 7170S (Hitachi Chemical Co., Ltd.). To 15 μL of the standard 100-μM myo-inositol solution prepared in advance, 180 μL of R-1 reagent was added and incubated at 37° C. for 4.8 minutes, followed by the addition of 60 μL of R-2 reagent to start the reaction. Absorbances at 405 nm were measured at 5.4 and 7.8 minutes after the reaction initiation, and then the difference therebetween was obtained. An increasing rate of absorbance per minute (ΔmABS/min) was calculated and the sensitivity was then investigated with respect to the standard solution. The stability of each R-2 reagent was investigated by an acceleration test wherein only R-2 reagent was stored in an incubator at 30° C. for 20 days and then the same test as described above was conducted on the 7th, 12th, and 20th days.
3) Results
The results are shown in FIG. 2. The buffers showing stable sensitivity in comparison to the standard solution were Tris, Tricine, Bicine and TEA; and the buffer having the most stable sensitivity was Bicine.
Reference Example 3
Study on ADP-Hexokinase
1) Reagents
<R-1>

    
    
        5 mM MES (pH 6.0)
        5 mM MgCl2 (Wako Pure Chemical Industries, Ltd.)
        8 mM ATP (Oriental Yeast Co., Ltd.)
        10 mM thio-NAD (Oriental Yeast Co., Ltd.)
        10 u/mL ATP-hexolinase (Asahi Kasei Corporation)
        0 to 4 u/mL ADP-hexokinase (Asahi Kasei Corporation)
    
    


<R-2; Reagent for myo-Inositol Quantitative Determination>

    
    
        200 mM Bicine (pH 9.0)
        0.3 mM NADH (Oriental Yeast Co., Ltd.)
        25 u/mL myo-inositol dehydrogenase (Asahi Kasei Corporation)
    
    


2) Method
The measurement device used was Autoanalyzer 7170S (Hitachi Chemical Co., Ltd.). Samples were prepared by mixing 100 μL of 2,000 μM myo-inositol solution and 1 mL of 0 to 10 g/dL glucose solution. To 3 μL of each sample, 180 μL of R-1 reagent was added and incubated at 37° C. for 4.8 minutes, followed by the addition of 180 μL of R-2 reagent to start the reaction. Absorbances at 405 nm were measured at 5.4 and 7.8 minutes after the reaction initiation, and then the difference therebetween was obtained. An increasing rate of absorbance per minute (ΔmABS/min) was calculated and the sensitivity was then investigated for respective samples.
3) Results
The results are shown in FIG. 3. As is evident from FIG. 3, when using ATP-hexolinase alone, the increasing glucose level, e.g. of 10 g/dL causes an influence on the sensitivity. In contrast, when using ATP-hexolinase together with ADP-hexolinase, the increasing glucose level has no influence on the sensitivity. This indicates that glucose in a sample can be eliminated by simultaneous reaction with ATP-hexolinase and ADP-hexokinase; and thus myo-inositol level can be determined more accurately.
Reference Example 4
myo-Inositol Quantitative Determination with High Sensitivity using Enzyme
1) Reagents
Reagent for myo-Inositol Assay
<R-1; Glucose Eliminating Reagent>

    
    
        5 mM MES (pH 6.0)
        0.05% NaN3 (Wako Pure Chemical Industries, Ltd.)
        0.05% OP-10 (Nippon Chemicals)
        5 mM MgCl2 (Wako Pure Chemical Industries, Ltd.)
        8 mM ATP (Oriental Yeast Co., Ltd.)
        10 mM thio-NAD (Oriental Yeast Co., Ltd.)
        10 u/mL ATP-hexolinase (Asahi Kasei Corporation)
        4 u/mL ADP-hexokinase (Asahi Kasei Corporation)
    
    


<R-2; Reagent for myo-Inositol Quantitative Determination>

    
    
        200 mM Bicine (pH 9.0)
        0.05% NaN3 (Wako Pure Chemical Industries, Ltd.)
        40 mM KHCO3 (Wako Pure Chemical Industries, Ltd.)
        0.3 mM NADH (Oriental Yeast Co., Ltd.)
        25 u/mL myo-inositol dehydrogenase (Asahi Kasei Corporation)
    
    


2) Method
The measurement device used was Autoanalyzer 7170S (Hitachi Chemical Co., Ltd.). To 3 μL of the myo-inositol solution prepared in advance, 180 μL of the glucose eliminating reagent was added and incubated at 37° C. for 4.8 minutes for the glucose eliminating reaction, and then 180 μL of the reagent for myo-inositol quantitative determination was added thereto to start the reaction. Absorbances at 405 nm were measured at 5.4 and 7.8 minutes after the reaction initiation, and then the difference therebetween was obtained. An increasing rate of absorbance per minute (ΔmABS/min) was calculated.
3) Results
The results are shown in FIG. 4. As shown in FIG. 4, the present assay reagent allowed quantitative determination of myo-inositol in a simple way. The measurement range of myo-inositol was 0 to 2,000 μM and the lower limit of detection was 10 μM when the lower limit of detection was defined as the minimum concentration, which does not overlap “the mean of ΔmABS/min+2×standard deviation” obtained by multiple measurements of 0 mM myo-inositol.
Example 1
Detection of Mild Impaired Glucose Tolerance by Determination of Urinary myo-Inositol
1) Subjects:
One hundred and twelve subjects were examined by the standard 75 g oral glucose load test. Blood samples were collected just before the glucose load, and at 30, 60, 120, and 180 minutes after the glucose load to determine levels of blood glucose and insulin. Simultaneously, urine samples were collected just before the glucose load, and at 60, 120, and 180 minutes after the glucose load to determine levels of myo-inositol, urinary glucose, and creatinine.
2) Reagents and Assays:
Blood glucose: Electrode method (Kyoto Daiichi Kagaku Corporation: GA-1160)
Insulin: RIA2 Antibody method
myo-Inositol Assay Reagent: the same as that of Example 4
Urinary glucose: Electrode method (Kyoto Daiichi Kagaku Corporation: GA-1160)
Creatinine: Creatinine-HA Test Wako (Wako Pure Chemical Industries, Ltd.)
3) Method:
ΣPG, the total of blood glucose levels just before 75 g oral glucose load, and at 30, 60, and 120 minutes after the glucose load, was used as an index of glucose tolerance. myo-Inositol level and creatinine level in respective urine samples just before the 75 g oral glucose load, and at 30, 60, and 120 minutes after the glucose load were determined to calculate the myo-inositol amount to the amount of urinary creatinine excreted (myo-inositol/creatine). In addition, Δ myo-inositol content [(myo-inositol content at 60 min−myo-inositol content before load)/2]+[(myo-inositol content at 120 min−myo-inositol content before load)/2] was used as an index of myo-inositol level between before and after the glucose load The relationship between ΣPG and Δ myo-inositol content was investigated.
4) Results:
The results are shown in Table 3 and FIG. 5. As shown in FIG. 5, ΣPG and Δ myo-inositol content showed a very good correlation. Higher ΣPG indicates that blood glucose levels are kept higher after the glucose load, and thus the presence of impaired glucose tolerance. In addition, for example, if the characteristic value of Δ myo-inositol is set as 10 μg/mg Cre (creatinine), an effective detection can be made for cases having mild impaired glucose tolerance with ΣPG level of about 530 mg/dL.














TABLE 3









Blood glucose (mg/dL)
Insulin (μU/mL)
Urinary myo-inositol (μg/mg Cre)
Urinary Glucose (g/dL)
Δmyo-



































0 min.
30
60
120
180
ΣPG
0 min.
30
60
120
180
I.I
0 min.
60
120
180
Δmyo
0 min.
60
120
180
Inositol
ΣPG
ΔIRI/ΔPG



































1
Normal
89
150
161
135
94
535
5
23
23
22
13
0.30
13
24
33
26
15
0.03
0.02
0.02
0.01
15
535
0.30


2
Normal
105
160
153
65
107
483
6
59
40
24
22
0.96
23
24
40
26
9
0.02
0.01
0.01
0.01
9
483
0.96


3
Normal
102
119
158
121
76
500
2
26
47
20
11
1.41
11
12
13
13
1
0.01
0.02
0.02
0.02
1
500
1.41


4
Normal
85
170
143
98
85
496
5
41
76
21
14
0.42
46
60
51
43
9
0
0.07
0.01
0.01
9
496
0.42


5
Normal
106
164
162
115
83
547
5
17
19
20
8
0.21
13
13
19
15
3
0.02
0.03
0.03
0.02
3
547
0.21


6
Normal
96
125
139
134
125
494
5
10
24
25
16
0.17
26
38
69
68
23
0.01
0.01
0.01
0.01
23
494
0.17


7
Normal
92
130
139
90
78
451
5
16
13
19
11
0.29
21
24
32
29
7
0.01
0.02
0.02
0.01
7
451
0.29


8
Normal
101
144
135
108
107
488
7
37
27
36
34
0.70
24
17
23
22
−4
0.02
0.03
0.03
0.03
−4
488
0.70


9
Normal
87
161
172
109
60
529
3
25
21
17
4
0.30
25
35
46
44
16
0.01
0.03
0.01
0.01
16
529
0.30


10
Normal
106
175
167
133
60
581
13
83
124
107
14
1.01
17
26
35
25
14
0.02
0.01
0
0
14
581
1.01


11
Normal
106
158
129
128
72
521
12
63
50
73
11
0.98
9
16
14
14
6
0.01
0
0.01
0
6
521
0.98


12
Normal
101
137
101
83
82
422
11
87
86
25
10
2.11
9
12
20
13
7
0.01
0.01
0
0
7
422
2.11


13
Normal
98
129
81
101
97
409
7
49
10
18
11
1.35
13
23
18
20
8
0.01
0
0
0.01
8
409
1.35


14
Normal
92
127
123
85
70
427
9
39
25
18
8
0.86
11
12
11
12
0
0.02
0.01
0.01
0
0
427
0.86


15
Normal
95
132
103
102
69
432
8
39
30
28
12
0.84
9
12
11
11
3
0.01
0.01
0.01
0.01
3
432
0.84


16
Normal
106
167
107
102
85
482
10
75
32
21
9
1.07
9
11
12
12
2
0.03
0.03
0.02
0.02
2
482
1.07


17
Normal
88
121
138
100
79
447
6
18
32
15
5
0.36
9
10
15
17
4
0.01
0.01
0.01
0.01
4
447
0.36


18
Normal
97
130
88
103
102
418
5
28
18
14
8
0.70
14
13
11
11
−2
0.01
0.01
0.01
0.01
−2
418
0.70


19
Normal
99
151
114
105
106
469
7
7
8
24
16
0.00
8
10
12
18
3
0.02
0.02
0.02
0
3
469
0.00


20
Normal
102
148
178
127
89
553
8
62
59
38
20
1.17
41
70
92
47
40
0.01
0.24
0.4
0.03
40
553
1.17


21
Normal
89
108
120
92
102
409
10
51
65
21
37
2.16
35
34
40
31
2
0.01
0.01
0.01
0.01
2
409
2.16


22
Normal
91
144
153
105
72
493
9
75
67
38
7
1.25
28
26
25
17
−2
0.01
0.03
0.02
0.01
−2
493
1.25


23
Normal
101
154
148
91
73
494
5
26
36
14
5
0.40
7
8
8
9
1
0.02
0.02
0.02
0.01
1
494
0.40


24
Normal
96
148
177
124
52
545
10
29
59
67
10
0.37
11
11
11
11
0
0.02
0.03
0.02
0
0
545
0.37


25
Normal
95
168
98
84
76
445
6
78
20
16
4
0.99
24
34
30
31
8
0.01
0.02
0.01
0
8
445
0.99


26
Normal
89
147
93
84
55
413
5
26
23
21
4
0.36
7
9
14
8
5
0.02
0.01
0
0.01
5
413
0.38


27
Normal
90
129
93
101
81
413
7
36
14
17
6
0.74
25
22
20
19
−4
0
0.01
0.01
0
−4
413
0.74


28
Normal
75
96
75
84
60
330
3
37
17
13
4
1.62
11
13
13
14
2
0.03
0.03
0.02
0.02
2
330
1.62


29
Normal
92
127
87
83
69
389
5
37
25
11
5
0.91
25
21
20
18
−4
0.03
0.01
0
0.01
−4
389
0.91


30
Normal
83
109
107
101
78
400
9
32
27
26
12
0.88
16
15
17
14
0
0
0.01
0
0
0
400
0.88


31
Normal
100
123
71
89
79
383
7
32
33
13
3
1.09
5
8
13
10
5
0.03
0
0
0
5
383
1.09


32
Normal
96
110
75
89
82
370
6
46
20
18
7
2.86
15
18
17
12
2
0.01
0.01
0
0.02
2
370
2.86


33
Normal
91
108
82
80
82
361
7
16
17
19
8
0.53
10
13
16
15
4
0.02
0.01
0
0
4
361
0.53


34
Normal
91
140
152
99
59
482
3
2
5
7
3
−0.02
7
8
8
7
1
0.01
0.01
0.01
0
1
482
−0.02


35
Normal
79
119
120
89
60
407
4
9
5
7
2
0.13
10
12
15
14
4
0.02
0.01
0.01
0.01
4
407
0.13


36
Normal
100
151
148
139
100
538
10
41
45
49
27
0.61
18
26
38
36
14
0.02
0.03
0.03
0
14
538
0.61


37
Normal
96
119
110
85
63
410
5
38
34
18
5
1.43
20
22
28
29
5
0.01
0.01
0
0
5
410
1.43


38
Normal
99
145
149
109
63
502
9
21
31
17
7
0.26
23
36
40
32
15
0.01
0.02
0.01
0
15
502
0.26


39
Normal
85
98
101
82
50
366
4
14


4
0.77
8
8
8
9
0
0.01
0.01
0.02
0
0
386
0.77


40
Normal
89
114
87
91
63
381
7
9
10
15
3
0.08
27
35
44
44
12
0.01
0.02
0.01
0
12
381
0.08


41
Normal
95
169
175
109
59
548
11
35
46
29
7
0.32
9
10
9
9
0
0
0.02
0.01
0.01
0
548
0.32


42
Normal
76
78
66
90
84
310
2
7
4
10
5
2.50
8
8
8
8
−1
0.01
0.01
0.02
0.01
−1
310
2.50


43
Normal
100
124
92
87
65
403
8
51
29
18
5
1.79
8
7
9
12
1
0.01
0.03
0.01
0
1
403
1.79


44
Normal
95
138
117
91
67
441
7
26
44
27
6
0.44
10
17
23
26
10
0.02
0
0
0
10
441
0.44


45
Normal
89
106
85
82
79
362
6
79
32
16
4
4.29
7
8
9
12
2
0.02
0.01
0.01
0
2
362
4.29


46
Normal
103
192
153
96
80
544
9
33
44
20
5
0.27
18
56
38
28
28
0.02
0.77
0.06
0
28
544
0.27


47
Normal
87
131
123
109
69
450
6
42
36
24
4
0.82
7
10
10
9
3
0.01
0.01
0.01
0.01
3
450
0.82


48
Normal
99
126
104
83
66
412
10
47
9
15
5
1.37
27
18
21
18
−7
0
0.02
0
0.01
−7
412
1.37


49
Normal
88
106
86
85
89
363
3
22
18
17
8
0.95
14
20
19
14
5
0
0
0
0
5
363
0.95


50
Normal
84
131
89
89
80
393
6
40
24
12
10
0.72
10
15
17
16
5
0.03
0
0
0
5
393
0.72


51
Normal
85
116
99
110
83
410
6
17
17
18
9
0.35
13
13
12
11
−1
0.03
0.02
0.02
0
−1
410
0.35


52
Normal
87
122
89
96
88
394
6
27
30
35
13
0.60
11
16
20
24
7
0.02
0.02
0.01
0
7
394
0.60


53
Normal
90
147
112
116
52
465
6
72
53
50
8
1.16
17
16
22
26
2
0
0
0
0
2
465
1.16


54
Normal
92
187
186
133
49
598
3
17
25
27
4
0.15
368
487
623
395
186
0
0.23
0.15
0.03
186
598
0.15


55
Normal
99
146
181
133
137
559
5
19
16
15
13
0.30
4
4
4
3
1
0
0
0.01
0
1
559
0.30


56
Normal
99
160
206
138
68
603
11
30
49
72
18
0.31
7
7
14
10
4
0.03
0.04
0
0
4
603
0.31


57
Normal
107
151
189
115
44
562
6
16
44
38
7
0.23
13
20
42
30
18
0.02
0.03
0.05
0.02
18
562
0.23


58
Normal
105
194
234
110
81
643
5
17
40
23
11
0.13
24
32
72
29
28
0
0.04
0.13
0
28
843
0.13


59
Normal
89
167
187
130
108
573
22
133
142
104
79
1.42
26
34
41
27
12
0.02
0.02
0.01
0
12
573
1.42


60
IFG
117
165
154
90
80
526
8
37
108
27
11
0.60
24
46
72
45
35
0.01
0.06
0.08
0
35
526
0.60


61
IFG
115
174
206
136
65
631
4
8
19
20
4
0.07
12
33
84
25
46
0.01
0.23
0.55
0
46
631
0.07


62
IFG
117
204
220
103
152
644
7
31
37
33
16
0.28
37
113
140
56
90
0.01
0.61
1.04
0.12
90
644
0.28


63
IFG
110
185
240
127
120
662
8
15
28
15
14
0.12
17
26
59
29
26
0.02
0.05
0.12
0.03
26
682
0.12


64
IFG
111
183
200
83
75
577
4
16
22
12
4
0.17
16
26
48
28
22
0
0.1
0.17
0
22
577
0.17


65
IFG
110
153
60
88
82
411
5
44
22
18
15
0.91
13
15
19
19
4
0.01
0.01
0.02
0.01
4
411
0.91


66
IFG
117
236
192
101
71
646
24
196
100
48
17
1.45
12
19
19
13
7
0.02
0.03
0.02
0.01
7
646
1.45


67
IFG
111
166
167
124
70
568
12
53
55
40
8
0.75
9
22
21
14
13
0.01
0.02
0.03
0
13
568
0.75


68
IFG
113
204
229
115
58
661
5
20
47
44
12
0.16
49
111
96
42
54
0.01
0.89
0.53
0.03
54
661
0.16


69
IGT
111
192
237
161
63
701
10
18
26
48
9
0.10
22
67
146
94
85
0.01
0.37
1.31
0.41
85
701
0.10


70
IGT
104
153
130
141
141
528
7
28
24
17
16
0.43
15
22
29
28
10
0.02
0.02
0
0.01
10
528
0.43


71
IGT
113
195
224
170
147
702
7
19
44
48
31
0.15
63
114
185
176
86
0.01
0.67
0.38
0.14
86
702
0.15


72
IGT
98
158
213
143
48
612
5
14
22
33
5
0.15
59
72
149
75
52
0.03
0.19
1.16
0.17
52
612
0.15


73
IGT
95
119
147
142
73
503
5
20
21
29
6
0.63
40
31
36
40
−6
0.01
0.01
0.03
0.01
−6
503
0.63


74
IGT
103
187
217
164
111
671
6
18
30
35
11
0.14
21
55
74
27
44
0.01
0.02
0.01
0.01
44
671
0.14


75
IGT
123
196
232
150
158
701
3
30
60
67
56
0.37
31
88
119
88
72
0.01
0.95
0.53
0.66
72
701
0.37


76
IGT
108
150
192
168
124
618
3
17
22
32
26
0.33
15
14
15
13
0
0.02
0.02
0.02
0.02
0
618
0.33


77
IGT
114
178
204
172
136
668
4
10
13
17
12
0.09
29
47
89
49
39
0.02
0.04
0.13
0.03
39
668
0.09


78
IGT
108
211
214
167
69
700
6
36
50
41
10
0.29
15
66
116
28
76
0.01
0.22
0.43
0.03
76
700
0.29


79
IGT
97
211
256
196
117
760
6
20
28
34
16
0.12
15
29
29
26
15
0.03
0.06
0.05
0.01
15
760
0.12


80
IGT
123
218
244
160
83
745
2
11
13
21
7
0.09
17
73
150
27
95
0.02
1.41
1.54
0.02
95
745
0.09


81
IGT
100
161
204
173
101
638
7
9
12
14
12
0.03
15
15
21
18
3
0.02
0.02
0.03
0.02
3
638
0.03


82
IGT
110
219
240
186
100
755
6
15
21
31
13
0.08
32
117
210
178
131
0.03
3.12
4.13
1.44
131
755
0.08


83
Diabetic
127
206
250
178
125
761
8
21
25
37
21
0.16
15
14
36
27
11
0.02
0.03
0.14
0.08
11
761
0.16


84
Diabetic
128
249
279
214
89
870
6
22
25
31
15
0.13
50
119
221
144
120
0.02
1.6
1.33
0.31
120
870
0.13


85
Diabetic
151
228
263
256
166
898
5
12
13
16
7
0.09
50
152
262
208
157
0.03
0.85
2.33
1.02
157
898
0.09


86
Diabetic
170
278
326
322
197
1096
5
7
8
11
9
0.02
64
146
232
225
125
0.01
1.33
3.46
2.75
125
1096
0.02


87
Diabetic
204
281
337
363
286
1185
12
15
19
26
28
0.04
21
63
145
151
83
0.05
3.42
7.25
7.25
83
1185
0.04


88
Diabetic
112
209
262
237
91
820
4
10
18
15
7
0.06
33
106
195
112
117
0.01
1.17
0.98
0.16
117
820
0.06


89
Diabetic
129
232
288
225
122
874
4
11
15
10
7
0.07
14
71
170
80
106
0.03
2.82
5.89
1.16
106
874
0.07


90
Diabetic
106
171
253
243
115
773
4
9
20
32
14
0.08
27
44
135
79
63
0.02
0.99
5.11
1.96
63
773
0.08


91
Diabetic
110
203
232
201
105
746
8
41
43
46
14
0.38
16
83
112
90
82
0.02
1.57
1.92
1.25
82
746
0.38


92
Diabetic
139
225
286
326
245
976
4
5
8
10
8
0.01
36
86
191
202
103
0.05
2.71
6.43
8.73
103
976
0.01


93
Diabetic
118
232
285
232
114
865
7
15
20
31
15
0.07
16
50
155
62
87
0.02
1.09
0.73
0.11
87
865
0.07


94
Diabetic
132
220
329
318
223
999
30
49
80
105
74
0.22
38
40
244
167
104
0.03
0.12
0.4
0.61
104
999
0.22


95
Diabetic
102
178
250
250
122
780
2
9
13
36
16
0.09
18
26
148
91
69
0
0.08
3.31
1.16
69
780
0.09


96
Diabetic
173
239
352
311
201
1075
9
7
23
36
20
−0.03
49
108
236
227
123
0.04
2.21
6.46
4.85
123
1075
−0.03


97
Diabetic
152
236
224
264
263
876
6
17
14
12
11
0.13
40
62
146
167
64
0.01
0.15
0.18
0.11
64
876
0.13


98
Diabetic
166
252
306
274
205
998
3
11
17
20
10
0.09
15
71
161
114
100
0.01
1.38
4.5
1.68
100
998
0.09


99
Diabetic
101
249
373
444
342
1167
3
5
7
6
5
0.01
37
154
290
301
185
0.02
3.44
2.45
2.1
185
1167
0.01


100
Diabetic
162
239
314
299
162
1004
7
11
33
31
12
0.05
33
56
174
127
83
0.03
0.36
3.29
2.23
83
1004
0.05


101
Diabetic
141
208
261
189
138
799
3
4
7
11
8
0.01
28
66
154
67
82
0.02
0.12
0.66
0.02
82
799
0.01


102
Diabetic
136
236
262
225
209
859
7
14
18
20
10
0.07
73
160
268
181
141
0.01
0.92
1.76
0.53
141
859
0.07


103
Diabetic
101
128
193
206
138
628
6
15
25
58
46
0.33
13
19
46
28
20
0.02
0
0.02
0.02
20
628
0.33


104
Diabetic
110
198
241
257
151
806
5
24
32
55
31
0.22
45
55
99
118
32
0.01
0.15
1.3
1.61
32
806
0.22


105
Diabetic
152
253
346
291
158
1042
10
19
44
16
23
0.09
99
183
371
280
178
0.11
3.02
3.32
3.2
178
1042
0.09


106
Diabetic
129
239
202
130
86
700
5
39
65
24
6
0.31
24
69
67
40
44
0.03
1.76
0.59
0.12
44
700
0.31


107
Diabetic
112
200
250
283
246
845
6
11
15
29
27
0.06
33
66
157
178
78
0.01
0.42
1.62
2.5
78
846
0.06


108
Diabetic
111
198
251
254
171
814
5
17
20
32
21
0.14
17
43
180
167
94
0.02
0.48
0.99
0.84
94
814
0.14


109
Diabetic
137
198
258
232
141
825
5
11
30
21
8
0.10
27
105
177
138
114
0.08
3.88
6.04
3.78
114
825
0.10


110
Diabetic
134
201
276
233
151
844
5
13
19
20
11
0.12
22
43
138
85
68
0.02
0.65
4.88
2.69
68
844
0.12


111
Diabetic
111
169
240
201
101
721
4
12
28
28
10
0.14
27
63
132
90
70
0.01
0.43
1.44
0.1
70
721
0.14


112
Diabetic
136
201
200
137
141
674
7
8
10
20
13
0.02
26
35
38
31
11
0.01
0.01
0
0
11
674
0.02









Example 2
Detection of Impaired Early insulin Secretion by Determination of Urinary myo-Inositol
1) Subjects:
The same as those of Example 1.
2) Reagents and Assays:
The same as those of Example 1.
3) Method:
myo-Inositol levels and creatinine levels in each urine sample just before the 75 g oral glucose load, and at 60 and 120 minutes after the glucose load were determined, and then the myo-inositol amount to the amount of urinary creatinine excreted (myo-inositol/creatinine) was obtained. In addition, Δ myo-inositol content [(myo-inositol content at 60 min−myo-inositol content before load)/2]+[(myo-inositol content at 120 min−myo-inositol content before load)/2] was used as the index of myo-inositol level between before and after the glucose load. The relationship between the insulinogenic index (I.I) and Δ myo-inositol content was investigated.
4) Results:
The results are shown in FIG. 6. As shown in FIG. 6, the relationship between the insulinogenic index and Δ myo-inositol content was found. In a large percentage of cases where the Δ myo-inositol content was 15 μg/mg Cre or more, the insulinogenic index showed less than 0.4. According to the guideline of the Japan Diabetes Society, the insulinogenic index of less than 0.4 can judge the presence of impaired early insulin secretion. As is evident from FIG. 6, if the characteristic value of Δ myo-inositol is 15 μg/mg Cre, an effective detection can be made for cases showing the insulinogenic index of less than 0.4, or having impaired early insulin secretion.
Example 3
Detection of Mild Impaired Glucose Tolerance by Determination of Urinary myo-Inositol and Urinary Glucose
1) Subjects:
The same as those of Example 1.
2) Reagents and Assays:
The same as those of Example 1.
3) Method:
myo-Inositol levels and creatinine levels in each urine sample just before the 75 g oral glucose load, and at 60 and 120 minutes after the glucose load were determined. Then, the myo-inositol content to the amount of urinary creatinine excreted (myo-inositol/creatinine) was obtained. At the same time, urinary glucose levels were also obtained. Δ myo-inositol content [(myo-inositol content at 60 min−myo-inositol content before load)/2]+[(myo-inositol content at 120 min−myo-inositol content before load)/2] was used as the index of myo-inositol level between before and after the glucose load.
4) Results
The case showing Δ myo-inositol content of 10 μg/mg Cre or more was referred to as plus (+), while the other case was referred to as minus (−). Likewise for the urinary glucose, the case showing an urinary glucose level of 50 mg/dL or more at 2 hours after glucose load was referred to as “+”, while the other case was referred to as “−”. ΣPG values calculated in Example 5 were used.
Out of 112 subjects tested, 52 subjects were in the group of Δ myo-inositol (−) and urinary glucose (−), 12 subjects were in the group of Δ myo-inositol (+) and urinary glucose (−), and 48 subjects were in the group of Δ myo-inositol (+) and urinary glucose (+). Nobody corresponded to the group of Δ myo-inositol (−) and urinary glucose (+). The respective ΣPG values of the group of Δ myo-inositol (−) and urinary glucose (−), the group of Δ myo-inositol (+) and urinary glucose (−), and the group of Δ myo-inositol (+) and urinary glucose (+) were compared with one another.
The results are shown in FIG. 7. As shown in FIG. 7, the mean and standard deviation of ΣPG values of the group of Δ myo-inositol (−) and urinary glucose (−) were 453 mg/dL and 76.6 mg/dL, respectively. The mean and standard deviation of ΣPG values of the group of Δ myo-inositol (+) and urinary glucose (−) were 556 mg/dL and 81.1 mg/dL, respectively. The mean and standard deviation of ΣPG values of the group of Δ myo-inositol (+) and urinary glucose (+) were 791 mg/dL and 164.8 mg/dL, respectively. Furthermore, as compared with ΣPG of the group of Δ myo-inositol (−) and urinary glucose (−), ΣPG of the group of Δ myo-inositol (+) and urinary glucose (−) was significantly higher, and also ΣPG of the group of Δ myo-inositol (+) and urinary glucose (+) was significantly much higher. These show the degree of impaired glucose tolerance could be determined non-invasively by determining urinary myo-inositol and urinary glucose in combination.
Example 4
Detection of Impaired Early Insulin Secretion by Determination of Urinary myo-Inositol and Urinary Glucose
1) Subjects:
The same as those of Example 1.
2) Reagents and Assays:
The same as those of Example 1.
3) Method:
The same as that of Example 3.
4) Results:
The case showing Δ myo-inositol content of 10 μg/mg Cre or more was referred to as plus (+), while the other case was referred to as minus (−). Likewise for the urinary glucose, the case showing an urinary glucose level of 50 mg/dL or more at 2 hours after glucose load was referred to as “+”, while the other case was referred to as “−”. The insulinogenic index values calculated in Example 2 were used.
The respective insulinogenic index values (ΔIRI 30-0/ΔPG 30-0) of the group of Δ myo-inositol (−) and urinary glucose (−), the group of Δ myo-inositol (+) and urinary glucose (−), and the group of Δ myo-inositol (+) and urinary glucose (+) were compared with one another.
The results are shown in FIG. 8. As shown in FIG. 8, the mean and standard deviation of ΔIRI 30-0/ΔPG 30-0 of the group of Δ myo-inositol (−) and urinary glucose (−) were 1.32 and 0.79, respectively. The mean and standard deviation of ΔIRI 30-0/ΔPG 30-0 of the group of Δ myo-inositol (+) and urinary glucose (−) were 0.45 and 0.42, respectively. The mean and standard deviation of ΔIRI 30-0/ΔPG 30-0 of the group of Δ myo-inositol (+) and urinary glucose (+) were 0.16 and 0.19, respectively. Furthermore, as compared with ΔIRI 30-0/ΔPG 30-0 of the group of Δ myo-inositol (−) and urinary glucose (−), ΔIRI 30-0/ΔPG 30-0 of the group of Δ myo-inositol (+) and urinary glucose (−) was significantly lower, and also ΔIRI 30-0/ΔPG 30-0 of the group of Δ myo-inositol (+) and urinary glucose (+) was significantly much lower. These show that the degree of impaired early insulin secretion could be determined non-invasively by determining urinary myo-inositol and urinary glucose in combination.
Example 5
Detection of Mild Impaired Glucose Tolerance by Determination of Urinary myo-Inositol
1) Subjects:
Out of those shown in Example 1, 59 subjects judged as NGT showing the fasting blood glucose level of less than 110 mg/dl and the two-hour postload glucose level of less than 140 mg/dl.
2) Regents and Assays:
The same as those of Example 1.
3) Method:
Out of subjects judged as NGT, those having the one-hour postload glucose level of 180 mg/dL or more or the two-hour postload glucose level of 120 mg/dL or more were referred to as B group or cases showing slightly decreased glucose tolerance (mild impaired glucose tolerance) and the others were referred to as A group. Fifty nine subjects of NGT included 45 subjects of A group and 14 subjects of B group. The myo-inositol content to the amount of urinary creatinine excreted (myo-inositol/creatinine) in A or B group was obtained by determining myo-inositol levels and creatinine levels in each urine sample just before 75 g oral glucose load, and at 60 and 120 minutes after the glucose load.
In addition, Δ myo-inositol content [(myo-inositol content at 60 min−myo-inositol content before load)/2]+[(myo-inositol content at 120 min−myo-inositol content before load)/2] was used as the index of myo-inositol level between before and after the glucose load.
4) Results:
The results are shown in FIG. 9. As shown in FIG. 9, the mean of Δ myo-inositol content of A group was 3.9 μg/mg Cre and the mean of Δ myo-inositol content of B group was 25.8 μg/mg Cre. As compared with A group, B group (mild impaired glucose tolerance) with slightly decreased glucose tolerance resulted in higher Δ myo-inositol content.
Example 6
Detection of Insulin Secretory Defect by Determination of Urinary myo-Inositol
1) Subjects:
The same as those of Example 1.
2) Reagents and Assays:
The same as those of Example 1.
3) Method:
Out of subjects judged as NGT, those having the insulinogenic index of less than 0.4 were referred to as B group and the others were referred to as A group. Fifty nine subjects of NGT included 37 subjects of A group and 22 subjects of B group. The myo-inositol content to the amount of urinary creatinine excreted (myo-inositol/creatinine) in A or B group was obtained by determining myo-inositol levels and creatinine levels in each urine sample just before 75 g oral glucose load, and at 60 and 120 minutes after the glucose load.
In addition, Δ myo-inositol content [(myo-inositol content at 60 min−myo-inositol content before load)/2]+[(myo-inositol content at 120 min−myo-inositol content before load)/2] was used as the index of myo-inositol level between before and after the glucose load.
4) Results
The results are shown in FIG. 10. As shown in FIG. 10, the mean of Δ myo-inositol content of A group was 4.4 μg/mg Cre and the mean of Δ myo-inositol content of B group was 16.9 μg/mg Cre. As compared with A group, B group with impaired early insulin secretion resulted in higher Δ myo-inositol content
Example 7
Relationship between Urinary myo-Inositol in Glucose Load Test and Urinary myo-Inositol in Meal Load Test
1) Subjects:
Out of those shown in Example 1, 52 subjects who agreed with taking a meal load test, which included 22 subjects of NGT (C group), 14 subjects of borderline type (B group), and 16 subjects of diabetes meritus (D group). Blood samples were collected before the meal and at 120 minutes after the meal, and then blood glucose level and insulin level were determined. In addition, urine samples were collected before the meal and at 120 minutes after the meal, and then myo-inositol level, urinary glucose level, and creatinine level were determined.
2) Reagent and Assays:
The same as those of Example 1.
3) Method:
After Blood samples and urine samples were collected in fasting condition, the subjects ingested a meal. The meal included retort-packed cooked foods (Wellness Menus (Nichirei Corporation) and packed boiled rice (Sato Foods Industries, Co., Ltd.)) containing 91.6 g carbohydrate, 31.0 g protein, 13.9 g fat, and 1.1 g sodium with 662 kcal energy. At 120 minutes after taking the meal, blood samples and urine samples were collected. The myo-inositol content to the amount of urinary creatinine excreted (myo-inositol/creatinine) was obtained by determining myo-inositol level and creatinine level in each urine sample. In addition, Δ myo-inositol content [(myo-inositol content at 120 min−myo-inositol content before load)] was used as an index of myo-inositol content between before and after the meal.
4) Results:
FIG. 11 shows the relationship between Δ myo-inositol (X axis) in the glucose load test and Δ myo-inositol (Y axis) in the meal load test. As shown in FIG. 11, Δ myo-inositol in the glucose load test and Δ myo-inositol in the meal load test showed a very good correlation (Y=1.044X−2.0, r=0.83, P<0.0001) and showed almost the same values. These results reveal that mild impaired glucose tolerance or insulin secretory defect can be detected by determining urinary myo-inositol levels before and after a meal, even if the glucose load test is not performed.
Example 8
Relationship between Urinary myo-Inositol in Glucose Load Test and Urinary myo-Inositol in Meal Load Test
1) Subjects:
The same as those of Example 7.
2) Reagents and Assays:
The same as those of Example 1.
3) Method:
The same as that of Example 7.
4) Results
FIG. 12 shows the relationship between Δ myo-inositol in the glucose load test and Δ myo-inositol in the meal load test for each group. As shown in FIG. 12, Δ myo-inositol in the glucose load test and Δ myo-inositol in the meal load test were very well consistent with each other for each group. These results reveal that mild impaired glucose tolerance and insulin secretory defect can be detected by determining urinary myo-inositol levels before and after a meal, even if the glucose load test is not conducted.
Example 9
Relationship between Urinary myo-Inositol in Meal Load Test and Mild Impaired Glucose Tolerance in Urinary Glucose Negative Individuals
1) Subjects:
Out of those shown in Example 7, 32 individuals who were negative for urinary glucose (less than 50 mg/dL) at 2 hours after the meal.
2) Reagents and Assays:
The same as those of Example 1.
3) Method:
The same as that of Example 7, except that individuals having Δ myo-inositol of 7 μg/mg Cre or more in the meal load test were referred to as (+) group, and the others were referred to as (−) group.
4) Results:
The results are shown in FIG. 13. As shown in FIG. 13, even in individuals with urinary glucose negative at 2 hours after the meal, many of those of Δ myo-inositol (+) group showed higher ΣPG in the glucose load test, as compared with those of Δ myo-inositol (−) group. These results reveal that, even in individuals with urinary glucose negative at 2 hours after a meal, the degree of impaired glucose tolerance can be determined non-invasively by determining urinary myo-inositol levels before and after a meal.
INDUSTRIAL APPLICABILITY
As described above, the present invention provides a method of detecting mild impaired glucose tolerance and/or impaired early insulin secretion in a non-invasive and convenient manner with good reproducibility.
REFERENCE TO DEPOSITED BIOLOGICAL MATERIAL
(1) (a) Name and address of the deposition organization, to which the present biological material has been deposited:
Name: International Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology;
Address: Tsukuba Center 6, 1-1-1 Higashi, Tsukuba, Ibaraki, Japan;
(b) Date of Deposition to Organization of (a):

    
    
        Oct. 12, 2000 (original deposition date);
    
    


(c) Deposit Number for the Deposition given by Organization of (a):

    
    
        FERM BP-7323.

## Claims

1. A method of detecting mild impaired glucose tolerance or an insulin secretory defect in a subject, wherein the method comprises:
providing urine samples from said subject, wherein the samples are obtained before and after glucose load, or before and after a meal;
quantitatively determining the myo-inositol level in the samples; and
determining that the subject has mild impaired glucose tolerance or that the subject has an insulin secretory defect based on the concentration of myo-inositol in the samples,
wherein the increment of the concentration of myo-inositol at a characteristic value or higher than a characteristic value of 0 to 20 μg myo-inositol per mg creatinine when measured as an increasing amount of myo-inositol excreted in the urine in a period from 0.5 to 6 hours after 75 g glucose load indicates the subject has mild impaired glucose tolerance or the subject has an insulin secretory defect.

2. The method according to claim 1, wherein the quantitative determination of myo-inositol level in the sample is carried out using an enzyme.

3. The method according to claim 2, wherein the enzyme is myo-inositol dehydrogenase.

4. The method according to claim 2 or 3, wherein the quantitative determination of the myo-inositol level using the enzyme is carried out by an enzymatic cycling method.

5. The method according to claim 1 or 2, wherein the myo-inositol level is quantitatively determined after elimination of sugars other than myo-inositol in the sample.

6. The method according to claim 5, wherein two kinds of kinases are simultaneously used for the reaction of eliminating sugars other than myo-inositol in the sample.

7. The quantitative method according to claim 6, wherein said two kinds of kinases are ATP-hexokinase and ADP-hexokinase.

8. The quantitative method according to claim 2, wherein thio- NAD is used as a coenzyme at a final concentration of 0.1 mM or more in the reaction of quantitatively determining myo-inositol.

9. The quantitative method according to claim 2, wherein thio-NAD is used as a coenzyme at a final concentration of 2 to 10 mM in the reaction of quantitatively determining myo-inositol.

10. The method according to claim 1 or 2, wherein the characteristic value is 8 to 12 μg myo-inositol per mg creatinine when measured as an increasing amount of myo-inositol excreted in the urine after 75 g glucose load.

11. The method according to claim 1 or 2, wherein a glucose level in the sample is quantitatively determined in addition to the myo-inositol level in the sample.

12. The method of detecting mild impaired glucose tolerance or insulin secretory defect according to claim 1 or 2, wherein the myo-inositol level is quantitatively determined after glucose in the sample is eliminated by a method comprising:
reacting ATP with glucose in the sample to convert them to ADP and glucose-6-phosphate; and
reacting the thus obtained ADP with glucose in the sample to convert them to AMP and glucose-6-phosphate.