bluuebunny/crossref_metadata_2025 huggingface dataset:
Diabetes Mellitus in Sand Rats (Psammomys obesus): Metabolic Pattern During Development of the Diabetic Syndrome
Authors: Marquié G , Duhault J , Jacotot B
Published: September 2013

It has been reported that sand rats, naturally feedingon low-caloric-value plants containing a high concentration and develop hyperglycemia when fed on a standard laboratory diet. The aim of this study was to examine the long-term effects of a synthetic-chow diet on the metabolic pattern of the diabetic syndrome in a large group of sand rats. While a few animals had a fulminant reaction with markedly decreased glucose tolerance, low plasma insulin levels, and death within 3–4 wk, most sand rats developed obesity and elevated plasma insulin levels. From the third month and forward, 40% of sand rats presented with a diabetic syndrome with hyperinsulinemia, hyperglycemia, markedly decreased glucose tolerance, and insulin resistance. This diabetic syndrome can be compared with maturity-onset (type II) diabetes. When this synthetic-chow diet was given for more than 6 mo, the majority of animals lost considerable weight and showed a major depletion of fat stores. Serum immunoreactive insulin levels fell, while blood glucose rose to above 500 mg/dl with glycosuria and ketonuria. The elevated triglyceride content of plasma and the lipid deposits in the liver were greatly augmented, and no glycogen was present. Animals developed frank insulin-dependent diabetes, and diabetic animals not treated with insulin died in diabetic coma with presumed ketoacidosis. The disease was essentially confined to sand rats showing abnormal glucose tolerance, even before eating laboratory chow. This observation suggests a genetic factor. Thus, the sand rat appears to be a potentially interesting model for investigation of both maturity-onset and insulin-dependent diabetes.
A Postbinding Inhibitor of Insulin Action: Increased Concentrations in the Plasma of Non-insulin-dependent Diabetic Subjects
Authors: Dean Brian , Peluso Ivana , Harrison Len C
Published: September 2013

“Postreceptor” insulin resistance in persons with non-insulin-dependent diabetes (NIDDM) could be due to an intrinsic defect in insulin-sensitive pathways or to the action of a circulating inhibitor. Since evidence for the former is lacking, we have addressed the question of a circulating inhibitor by examining the effect of plasma and plasma extracts from NIDDM subjects on the lipogenic response of rat adipocytes to insulin.

A majority (77%) of plasma samples (1:20 dilution) from unselected, treated NIDDM subjects (N = 69) inhibited insulin-stimulated conversion of 3-3H-glucose to 3H-lipid in rat adipocytes to a greater extent than did control samples (N = 24). The mean ± SD inhibition by NIDDM plasma (81 ± 21%) was significantly greater (P < 0.01) than by control plasma (50 ± 14%). Diabetic and, to a lesser degree, control plasma both caused a significant decrease in the maximal response of lipogenesis to insulin. Inhibitory activity was extracted into acid/ethanol, present in the flow of a Seppak C18 column, heat-stable (56°C for 30 min [plasma], 80°C for 30 min [acid/ethanol]), resistant to proteases, and dialyzable through 1000-dalton-mol wt exclusion dialysis tubing. The inhibition by NIDDM plasma or partially purified inhibitor could not be explained by the presence of insulin antibodies, insulin receptor antibodies, other inhibitors of insulin binding, or the concentrations of known counterregulatory factors. There was no correlation between inhibitory activity and plasma glucose (r = 0.26), insulin (r = 0.33), C-peptide (r = 0.26), or HbA1c(r = 0.26).

Our findings suggest that a humoral inhibitor of postreceptor insulin action is present in increased concentrations in the plasma of NIDDM subjects. The nature of this inhibitory activity and its pathophysiologic significance deserve further investigation.
Insulin Resistance in Cushing's Disease: Evaluation by Studies of Insulin Binding to Erythrocytes
Authors: Wajchenberg Bernardo L , Leme Carlos E , Lerario Antonio C , Toledo Iracelia T , Souza E , Rodbard Helena W , Rodbard David
Published: September 2013

Studies of 125I-insulin binding to erythrocytes (RBC) from 5 patients with Cushing's disease were performed in an attempt to evaluate the insulin resistance in this disease. Five obese, nondiabetic patients and six normal subjects served as controls. Insulin resistance was present in both the obese, nondiabetic subjects and in the patients with Cushing's disease. Patients with Cushing's disease showed insulin resistance out of proportion to obesity, and of greater severity than in the obese subjects. As in previous studies, the insulin resistance of the obese subjects could be at least partially ascribed to a reduced number of receptors. In contrast, in our patients with Cushing's disease, no physiologically significant changes in the parameters of insulin-receptor interaction could be demonstrated. This suggests that the RBC insulin receptor is not involved in this type of insulin resistance.
Relationship Between the Plasma Insulin Response to Oral Glucose and Insulin-stimulated Glucose Utilization in Normal Subjects
Authors: Hollenbeck C B , Chen N , Chen Y-D I , Reaven G M
Published: September 2013

The relationship between in vivo insulin-stimulated glucose utilization (euglycemic clamp technique) and various estimates of the plasma insulin response to oral glucose was defined in 62 subjects with normal glucose tolerance. Both the incremental insulin increase above fasting (r = 0.61) and the total integrated insulin response (r = 0.65) were highly correlated (P < 0.001) with in vivo insulin action, and the relationship between total insulin response and insulin action remained significant (r = 0.61, P < 0.001) when corrected for variations in total glucose response, age, and obesity. In a subset of these subjects (N = 27) we were also able to assess state of habitual physical activity by estimating maximal oxygen consumption during bicycle ergometry. A significant correlation also existed between insulin action and response in these subjects (r = 0.67, P < 0.001), which remained significant (r = 0.65) when differences in total glucose response, obesity, age, and maximal oxygen consumption were taken into account. These data demonstrate that there is a significant correlation between insulin response and insulin action in normal individuals that can account for approximately one-third of the total variance in insulin action seen in subjects with normal glucose tolerance. Thus, determination of plasma insulin levels after an oral glucose challenge can only provide a qualitative estimate of insulin-stimulated glucose Utilization.
Glibenclamide Stimulates and Glucose Inhibits Glucagon Release Induced by Calcium Deprivation
Authors: Grill V , Nylén A , Östenson C G , Efendić S
Published: September 2013

The effects of low extracellular calcium levels on glibenclamide- and glucose-induced A-, B-, and D-cell secretion were investigated using the perfused pancreas preparation of the rat. At normal (2.6 mM) calcium, glucagon secretion was unaffected by glibenclamide (1 μg/ml) and transiently suppressed by glucose (6.7 and 16.7 mM). Reduction of extracellular calcium to 0.24 mM promptly and persistently enhanced glucagon secretion in the presence of 3.3 mM glucose; this effect of low calcium was, however, diminished (P < 0.001) by 54% and 61% when the glucose concentration was increased to 6.7 and 16.7 mM, respectively. In contrast, glibenclamide enhanced the glucagon response to calcium reduction, a twofold stimulation by the drug being observed at all glucose concentrations.

Reduction of calcium to 0.24 mM failed to inhibit first-phase glibenclamide or glucose-induced insulin release; second phase was, however, inhibited whether induced by glibenclamide (in the presence of 6.7 mM glucose) or by glucose 16.7 mM per se. Reduction of calcium uniformly and completely abolished glibenclamide and glucose-induced somatostatin responses. It is concluded that: (1) the glucagon response induced by calcium deprivation is inhibited by glucose but potentiated by glibenclamide, and (2) reversal of a D-cell paracrine effect could underlie the glibenclamide effect.
Is Somatostatin a True Local Inhibitory Regulator of Insulin Secretion?
Authors: Kanatsuka A , Makino H , Osegawa M , Kasanuki J , Suzuki T , Yoshida S , Horie H
Published: September 2013

Pancreatic somatostatin was depleted after oral administration of cysteamine to rats, yet the B-cells in the isolated islets were morphologically and functionally intact. Compared with islets from the rats not given cysteamine, the somatostatin-depleted islets released larger amounts of insulin during 1 h of incubation by glucose or 3-isobutyl-1-methylxanthine stimulation. Therefore, the possibility that pancreatic somatostatin may locally regulate the inhibitory effects of insulin secretion has to be considered.
Differential Sensitivity to β-Cell Secretagogues in “Early,” Type I Diabetes Mellitus
Authors: Ganda Om P , Srikanta S , Brink Stuart J , Morris Mary Ann , Gleason Ray E , Soeldner J Stuart , Eisenbarth George S
Published: September 2013

The insulin secretory response to various β-cell secretagogues was studied in four children (ages 11,11, 12, and 10 yr) in “early” stages or remission of type I diabetes mellitus. One child was an anti-islet antibody positive monozygotic twin of a type I diabetic subject, two children had impaired glucose tolerance and elevated levels of la-positive T-cells, and the fourth was in remission (off insulin) of type I diabetes 6 mo after immunotherapy. The peak first-phase (0–10 min) insulin increment after intravenous (i.v.) glucose was negligible in each patient, whereas the peak responses to i.v. glucagon, tolbutamide, arginine, and oral glucose ranged between 10% and 43% of median responses in normal control subjects. The rank order of response to a variety of secretagogues was remarkably similar in all four subjects: i.v. arginine > i.v. glucagon > oral glucose > i.v. tolbutamide > i.v. glucose. These studies indicate that a “functional” β-cell defect, namely a complete loss of response to i.v. glucose and a partial loss to other secretagogues, exists in type I diabetic patients before complete β-cell destruction. This alteration in β-cell responsiveness probably underlies our prior observation of slowly progressive loss of i.v.-glucose-induced insulin release in islet cell antibody-positive siblings of type I diabetic subjects.
Assessment of Perfusion in the Diabetic Foot by Regional Transcutaneous Oximetry
Authors: Hauser Carl J , Klein Stanley R , Mehringer C Mark , Appel Paul , Shoemaker William C
Published: September 2013

Regional transcutaneous oximetry is a new, noninvasive diagnostic technique for the investigation of peripheral vascular disease (PVD) that uses differences in limb and trunk transcutaneous PO2 to assess the adequacy of local perfusion. The application of such measurements would be of great importance in diabetes, in which limb ischemia is commonly difficult to assess. A group of diabetic subjects with symptomatic PVD was studied with regional oximetry, Doppler-assisted blood pressure measurements, and arteriography. Doppler studies correlated poorly to symptom grade and angiographie data, while oximetry clearly demonstrated limb hypoxia under the functional conditions appropriate to the patients’ clinical symptomatology. The superiority of oximetry to Doppler studies was highly significant (X2 = 12.64, P < 0.001). Regional transcutaneous oximetry should therefore be the non-invasive diagnostic test of choice in the initial evaluation of the diabetic limb for PVD.

Because of its dependence on the adequacy of local oxygenation, transcutaneous oximetry is a powerful tool for investigation of the pathophysiology of PVD and will, in the future, have wide-ranging applications to the diagnosis and therapy of PVD.
Total Lymphoid Irradiation Prevents Diabetes Mellitus in the Bio-Breeding/Worcester (BB/W) Rat
Authors: Rossini Aldo A , Slavin Shimon , Woda Bruce A , Geisberg Mark , Like Arthur A , Mordes John P
Published: September 2013

Total lymphoid irradiation (TLI) at doses of 2200 rads or greater prevented diabetes in susceptible BB/W rats. Two of 29 (7%) treated rats became diabetic compared with 23 of 39 (59%) controls (P < 0.001). TLI did not, however, prevent insulitis or thyroiditis in nondiabetic rats, nor did it restore the depressed concanavalin-A responsiveness of BB rat lymphocytes. T-lymphocyte subset proportions were the same in both groups. TLI was associated with significant radiation-related mortality, and nondiabetic TLI-treated rats weighed significantly less than controls. We conclude that TLI is effective in the prevention of BB rat diabetes. However, TLI fails to correct the subclinical immunologie abnormalities of the model and is associated with significant morbidity.
Effect of Somatostatin and Atropine Infusion on Intestinal Transit Time and Fructose Absorption in the Perfused Human Jejunum
Authors: Krejs Guenter J
Published: September 2013

Somatostatin has previously been shown to reduce nutrient absorption from the human jejunum. These studies were designed to examine whether changes in intestinal motility may be responsible for the inhibitory effect of somatostatin on intestinal absorption. Using triple-lumen perfusion techniques in healthy volunteers, somatostatin infusion (8 μg/kg/h) prolonged mean transit time from 9 to 16 min in a 30-cm jejunal test segment as estimated from dye dilution curves. Somatostatin infusion significantly reduced jejunal fructose absorption. Atropine (10 μg/kg/h, i. v.) caused a similar prolongation of mean transit time in the perfused jejunum. However, unlike somatostatin, atropine significantly increased fructose absorption. The observation that somatostatin and atropine affect absorption in opposite ways while prolonging intestinal transit time in a similar fashion suggests that the effects of somatostatin and atropine are due to a direct influence on absorption at the mucosal level that is independent Of any effect on intestinal motility.
Contrasting Patterns of Insulin Biosynthesis, Compartmental Storage, and Secretion: Rat Tumor Versus Islet Cells
Authors: Gold Gerald , Gishizky Mikhail L , Chick William L , Grodsky Gerold M
Published: September 2013

A series of 3H-leucine pulse-labeling experiments was carried out with dispersed cells freshly isolated from transplanted rat insulinomas. After secreted fractions were separated, insulin was purified and specific activities were determined for both secreted and average cellular insulins. Labeling patterns in this line of tumor cells were compared with those previously established for isolated rat islets. With both tumors and islets, conversion of labeled proinsulin to insulin occurred to the same extent by 2.5 h, suggesting similar onset and half-time of proteolysis in these cells. However, total cellular insulin in tumors attained a threefold higher specific activity than in islets. Because total B-cell mass in these tumors was unknown, either a more rapid proinsulin biosynthesis or diminished cellular storage (or both) could lead to this faster fractional replacement of total stored insulin. Insulin secretion in these tumor cells was insensitive to high glucose but responded, albeit poorly, to leucine plus 3-isobutyl-1-methylxanthine (IBMX). Under all secretory conditions tested, tumor cells continuously secreted insulin at elevated fractional rates, which were slightly higher than fractional insulin secretory rates in maximally glucose-stimulated islets. In contrast with normal islets, newly synthesized insulin was stored homogeneously in tumor cells, and compartmental storage characteristics were not generated by incubation with either 20 mM glucose or leucine plus IBMX in the marking period. Thus, preferential secretion of insulin was never observed in tumor cells. These altered labeling patterns in tumor cells suggested: (1) continuous, rapid proinsulin biosynthesis; (2) normal proinsulin-to-insulin proteolytic rates; (3) absence of marking by either glucose or a secretagogue of these tumor cells (leucine + IBMX); (4) loss of heterogeneous insulin storage characteristics; (5) diminished time of insulin storage before secretion, which probably reflects both loss of compartmental storage characteristics and diminished cellular storage capacity; and (6) continuous, elevated fractional rates of insulin secretion even with only low glucose concentrations present.
Alterations in Rat Pancreatic B-Cell Function Induced by Prenatal Exposure to Cyproheptadine
Authors: Chow Samson A , Fischer Lawrence J
Published: September 2013

Treatment of pregnant rats with cyproheptadine during the last 8 days of gestation produced alterations in the function of the endocrine pancreas in the offspring. The abnormalities exhibited by 50-day-old progeny of drug-treated dams included glucose intolerance, a twofold increase in levels of insulin in the pancreas, and an accentuated response to the insulin-lowering action of cyproheptadine in the endocrine pancreas. The alterations observed in these animals were limited to the insulin-containing cells, and no change was found in the pancreatic concentrations of glucagon and somatostatin. The results are the first to demonstrate that postnatal pancreatic B-cell function can be selectively altered by prenatal exposure to an exogenous chemical.
Preceding Hyperinsulinemia Prevents Demonstration of Insulin Effect on Fat-induced Gastric Inhibitory Polypeptide (GIP)
Authors: Stöckmann F , Ebert R , Creutzfeldt W
Published: September 2013

The effect of insulin on fat-induced gastric inhibitory polypeptide (GIP) release has been studied in seven healthy volunteers during euglycemic blood glucose clamping. In the first protocol, insulin (0.1 U/kg/h) was infused 2 h before ingestion of 100 g fat and continued for 2 h thereafter. In protocol II, saline was infused 2 h before the fat load and the insulin infusion started at the time of fat ingestion. During both insulin infusion studies, glucose levels were clamped at the fasting level by means of the Biostator and plasma levels of insulin, C-peptide, and GIP were estimated by radioimmunoassay. The response of GIP to oral fat was inhibited by 63% if insulin infusion was started at the time of fat ingestion, whereas no inhibition was seen if a 2-h hyperinsulinemic period preceded the fat load. The plasma insulin levels were comparable at the end of each experiment, ranging from 110 to 130 μU/ml. Plasma C-peptide levels decreased during the insulin infusion and increased after fat ingestion. These findings were not the result of inhibition of gastric emptying by insulin because they could be confirmed in four volunteers with intraduodenal infusion of fat. The present data show that insulin does inhibit fat-induced GIP secretion in normal man, but preceding hyperinsulinemic glucose clamping masks this insulin effect, probably by decreasing the sensitivity of the GIP cells to insulin.
Marked Improvement in Carbohydrate and Lipid Metabolism in Diabetic Australian Aborigines After Temporary Reversion to Traditional Lifestyle
Authors: O'dea Kerin
Published: September 2013

The rationale for the present study was that temporarily reversing the urbanization process in diabetic Aborigines should improve all aspects of their carbohydrate and lipid metabolism that are linked to insulin resistance. Ten full-blood, diabetic Aborigines from the Mowanjum Community (Derby, Western Australia) agreed to be tested before and after living for 7 wk as hunter-gatherers in their traditional country in northwestern Australia. They were middle aged (53.9 ±1.8 yr) and overweight (81.9 ± 3.4 kg), and all lost weight steadily over the 7-wk period (average, 8 kg). A detailed analysis of food intake over 2 wk revealed a low-energy intake (1200 kcal/person/day). Despite the high contribution of animal food to the total energy intake (64%), the diet was low in total fat (13%) due to the very low fat content of wild animals.

Oral glucose tolerance tests (75 g glucose) were conducted in the urban setting and repeated at the end of 7 wk of traditional lifestyle. The marked improvement in glucose was due to both a fall in fasting glucose (11.6 ± 1.2 mM before, 6.6 ± 0.8 mM after) and an improvement in postprandial glucose clearance (incremental area under the glucose curve: 15.0 ±1.2 mmol/ L/h before, 11.7 ± 1.2 mmol/L/h after). Fasting plasma insulin concentration fell (23 ± 2 mU/L before, 12 ± 1 mU/L after) and the insulin response to glucose improved (incremental area under the insulin curve: 61 ± 18 mU/L/h before, 104 ± 21 mU/L/h after). The marked fall in fasting plasma triglycerides (4.0 ± 0.5 mM before, 1.2 ± 0.1 mM after) was due largely to the fall in VLDL triglyceride concentration (2.31 ± 0.31 mM before, 0.20 ± 0.03 mM after).

In conclusion, the major metabolic abnormalities of type II diabetes were either greatly improved or completely normalized in this group of Aborigines by relatively short reversal of the urbanization process. At least three factors known to improve insulin sensitivity (weight loss, low-fat diet, and increased physical activity) were operating in this study and would have contributed to the metabolic changes observed.
Glomerular Polyol Accumulation in Diabetes and its Prevention by Oral Sorbinil
Authors: Beyer-Mears Annette , Ku Ling , Cohen Margo P
Published: September 2013

Although enhanced activity of the polyol pathway has been implicated in the pathogenesis of certain complications of diabetes, evidence that aldose reductase activity and sorbitol content are increased in the characteristic tissue site of the diabetic renal lesion has been lacking. We therefore measured polyols in glomeruli isolated from control and streptozotocin-diabetic rats, and assessed whether changes in diabetic glomeruli could be prevented by oral administration of the aldose reductase inhibitor sorbinil. Compared with control, polyol content of glomeruli isolated from diabetic rats was increased 10-fold and fourfold at 6 and 9 wk, respectively, after induction of diabetes, but was unchanged in glomeruli from rats treated with sorbinil throughout the experimental periods. In contrast, glomerular myo-inositol content was reduced in diabetic samples; this fall in myo-inositol levels was also completely prevented by sorbinil. These results establish that glomeruli contain aldose reductase activity and provide the first demonstration that glomerular polyol content increases while myo-inositol content decreases in diabetes and that oral sorbinil prevents these changes despite persistent hyperglycemia.
Functional Correlates of Reduced Central Conduction Velocity in Diabetic Subjects
Authors: Donald M W , Erdahl D L William , Surridge D H C , Monga T N , Lawson J S , Bird C E , Letemendia F J J
Published: September 2013

In a previous publication, we presented evidence of slowed conduction speed in the central nervous systems of insulin-dependent diabetic subjects, manifest in a delay in the latency of the brainstem auditory-evoked response (BAER). In this article, we present the results of a multivariate study conducted on a larger sample of 50 insulin-dependent, adult diabetic subjects. The purpose of the study was to determine some of the functional correlates of the BAER delay; each patient received an assessment of the BAER, the late auditory-evoked potential (EP), the conduction velocities of the sural, median, and common peroneal nerves, and intellectual and emotional function, in addition to neurologic and audiologie examinations. A nondiabetic control group was matched with the diabetic group as to age and sex.

The results indicated a delay in the latency of wave V, and in interpeak latencies I–III and I–V, of the BAER. The most reliable effect was on interpeak latency I–V; this suggested that the locus of the delay was in the central auditory projections, rather than in the acoustic nerve. In addition, BAER waves I, II, III, IV, and V were reduced in amplitude, as was the Ni component of the late auditory EP; the most reliable reduction in amplitude was in wave V. The effect was similar in magnitude for males and females, relative to their counterparts in the control group.

The slowed BAER response appeared early in the disease and was not related to the duration of insulin treatment. It was correlated with a chronic loss of energy and the presence of sexual dysfunction. It was not correlated with intellectual deterioration, clinical signs of peripheral or autonomie neuropathy, recent blood sugar regulation, or current blood sugar levels. The results of this study confirm the presence of abnormalities in the central nervous systems of diabetic subjects, and suggest that the BAER technique may prove useful in detecting early signs of central diabetic neuropathy.
A U-Shaped Bioartificial Pancreas with Rapid Glucose-Insulin Kinetics: In Vitro Evaluation and Kinetic Modelling
Authors: Reach Gérard , Jaffrin Michel Y , Desjeux Jehan-François
Published: September 2013

The lag in insulin release in response to glucose is an obstacle to the development of hybrid pancreatic devices, in which an artificial membrane protects transplanted islets against immune rejection. We designed a U-shaped bioartificial pancreas, in which the blood channel surrounds the islet chamber consisting of two flat membranes; blood circulates successively above the first membrane and then in the reverse direction, below the second membrane. Isolated rat islets were introduced into the chamber, which was perfused with Krebs buffer, and the kinetics of insulin release in response to glucose was determined. During a 20-min, 2.8–20-mM, square-wave glucose stimulation, insulin release in the effluent of the device rose from 0.7 ± 0.2 to 3.2 ±1.0 ng/100 islets/min (P < 0.05) within 3 min, and reached a maximal level of 12.8 ± 3.3 ng/100 islets/min at 10 min; 5 min after the return of the glucose concentration to substimulatory level, insulin release dropped from 11.3 ± 1.5 to 8.0 ± 1.7 ng/100 islets/min (P < 0.05), and reached basal value (1.0 ± 0.2 ng/100 islets/min) 40 min after the end of the stimulation. A 0.1-mM/L/min ramp increase in glucose concentration triggered a significant rise in insulin release (P < 0.02) when the glucose concentration reached 5.3 ± 0.2 mM; islets concomitantly perifused within a chamber set up without membrane responded to the same glucose stimulation 5 min earlier. For up to 1000 islets, insulin release in response to glucose was linearly correlated to the number of islets (N = 12, P < 0.01), indicating that insulin did not significantly inhibit its own secretion in this system. Finally, during glucose stimulation, the insulin concentration in the effluent from the chamber was found to be four times the concentration present at the turning point of the blood channel, suggesting that insulin was transferred into the perfusing medium in part by a countercurrent flux of ultrafiltrate crossing the membranes. We present herein the kinetic modelling of glucose and insulin transfer in this “Ultrafiltration chamber”, whose functional characteristics are compatible with closed-loop insulin delivery.
Phasic Glucose-stimulated Insulin Secretion by Neonatal Rat Pancreatic Islet Cells: Enhancement by Sodium Salicylate
Authors: Fujimoto Wilfred Y , Metz Stewart A
Published: September 2013

Monolayer cultures of neonatal rat pancreatic islets were superfused to examine phasic insulin secretion. When stimulated with a constant glucose concentration of 300 mg/dl, insulin secretion promptly rose to a peak more than eightfold higher than the basal levels observed with glucose 30 mg/dl. This first-phase peak was followed by a quick decline in insulin to a level about four- to fivefold higher than basal, representing second-phase insulin secretion. Addition of sodium salicylate 20 mg/dl enhanced glucose-stimulated insulin secretion. Addition of salicylate concurrently with glucose greatly enhanced second-phase insulin secretion, but did not affect the first-phase peak, thereby converting the biphasic pattern to one that appeared to be monophasic. However, when cultures were super-fused with salicylate both before and concurrent with stimulation by glucose, both the first-phase peak and the second phase of insulin secretion were increased, resulting in not only preservation but enhancement of the biphasic pattern. Salicylate had no effect on basal insulin secretion at glucose 30 mg/dl. During the transition from glucose 300 mg/dl to 30 mg/dl, immediately as glucose concentration began to fall in the superfusate, insulin secretion showed a transient increase (”off response”). Conclusions: (1) Cultures of neonatal rat pancreatic islet cells respond with a biphasic pattern of insulin secretion when exposed to a continuous and constant glucose stimulus. (2) When endogenous prostaglandin synthesis is inhibited by sodium salicylate, the biphasic pattern not only remains but is enhanced, indicating that endogenous prostaglandin synthesis exerts a tonic restraint throughout the entire period of glucose-stimulated phasic insulin release. (3) The biphasic pattern of glucose-stimulated insulin release is unlikely to be solely the consequence of an inhibitory action of prostaglandins. (4) Insulin responsiveness of neonatal rat islet B-cells to glucose is greater than previously reported. (5) A brief “off response” in insulin secretion is observed immediately upon removal of the glucose stimulus.
Inhibition of Insulin Release from Rat Pancreatic Islets by Drugs that Are Analogues of Dopamine
Authors: Arnerić Stephen P , Chow Samson A , Long John P , Fischer Lawrence J
Published: September 2013

Various synthetic dopamine (DA) analogues have been shown to produce glucose intolerance and inhibit the compensatory increase in serum insulin during an oral glucose tolerance test (OGTT). To investigate the possibility that there is a direct action of dopamine analogues to inhibit glucose-stimulated insulin release from the endocrine pancreas, the following compounds were compared with the effects of epinephrine (EPI) on isolated rat pancreatic islets: apomorphine (APO), pergolide, lergotrile, TL-99 (2-dimethylamino-6,7-dihydroxytetralin), and RDS-127 (2-di-n-propylamino-4,7-dimethoxyindane). EPI, TL-99, and pergolide inhibited insulin release in a concentration-dependent fashion (10 −7–10−5 M), whereas lergotrile inhibited at K)10−5 M but not at 10−6 M. RDS-127 and APO were ineffective at 10 −5 M, but produced a greater than 50% inhibition at 2 × 10−4;M. The potencies of the DA analogues fell into two groups: compounds that are approximately as active as EPI (e.g., TL-99 and pergolide) or compounds that are relatively inactive (e.g., APO, lergotrile, and RDS-127). The inhibitory actions of EPI, TL-99, and pergolide were blocked by the α2-adrenergic receptor antagonist yohimbine, whereas the DA receptor antagonist, sulpiride, had no effect, suggesting an action initiated at α2-adrenergic receptors. Drugs from both groups produced marked glucose intolerance and inhibited the compensatory increase in insulin during an OGTT. Adrenodemedullation blocked the glucose intolerance and inhibition of insulin release caused by RDS-127, whereas these effects of TL-99 were not attenuated. These data, obtained in vitro and in vivo, show that selective dopamine agonists, such as RDS-127, reduce glucose-stimulated insulin release indirectly through adrenal medullary secretions, whereas the effect of less selective agonists, such as TL-99, directly inhibit the release of insulin from the endocrine pancreas.
Identification of Insulin Variants in Patients with Hyperinsulinemia by Reversed-Phase, High-Performance Liquid Chromatography
Authors: Seino Susumu , Funakoshi Akihiro , Fu Zu Zhi , Vinik Aaron
Published: September 2013

We have characterized the molecular forms of circulating insulins in patients with hyperinsulinemia of diverse etiology. We have also compared the efficacy of various chromatographic conditions using reversedphase (RP) HPLC. Using 0.2% trifluoroacetic acid (TFA) and triethylamine (TEA) with acetonitrile as the organic modifier, at an elution rate of 0.17%/min, porcine, bovine, and human insulins could be easily separated as well as abnormal insulins in the plasma of a patient (J.R.) with hyperinsulinemia of unknown etiology. When the reversed-phase C18 column was changed and a gradient of 0.33%/min was used, the abnormal insulin in patient J.R. could not be separated. By changing the solvent system to acetonitrile and isopropanol (vohvol, 3:1) containing 0.1% TFA, omitting the TEA, and using a gentle gradient of 0.1%/min, various semisynthetic analogues of human insulin could be easily separated and the abnormal insulin could be identified in the plasma of the patient J.R. Abnormal insulin was also found in a patient with MEN-I, but in contrast, the insulins in eight patients with benign sporadic insulinomas appeared to be normal.

These results suggest that certain hyperinsulinemic states may be associated with an abnormal insulin and that RP-HPLC is useful for identification of insulin variants in the circulation. However, the conditions of RPHPLC may be critical if the abnormalities of the insulin are subtle.
Urinary and Renal Tissue Kallikrein in the Streptozocin-diabetic Rat
Authors: Mayfield Ronald K , Margolius Harry S , Bailey Graham S , Miller Donald H , Sens Donald A , Squires Josephine , Namm Donald H
Published: September 2013

The renal kallikrein-kinin system is thought to participate in blood pressure regulation and displays abnormalities in human hypertension, as well as in many animal models of hypertension. Urinary excretion and tissue levels of renal kallikrein were measured in streptozocin (STZ)-diabetic rats in relation to blood pressure, glycemia, and insulin treatment.

In study 1, STZ-diabetic rats with marked hyperglycemia showed reduced kallikrein-like esterase excretion, compared with control rats, when first measured after 7 days of diabetes (9.9 ± 2.5 versus 17.5 ± 2.4 EU/24 h, P < 0.05). This difference increased with time and, after 210 days, urinary esterase excretion in diabetic and control rats was 6.7 ± 2.1 and 39.0 ± 6.0 EU/24 h, respectively (P < 0.001). Urine kallikrein, measured by radioimmunoassay, was similarly reduced in diabetic rats (40.4 ± 8.0 versus 88.0 ± 6.5 μg/24 h, at 30 days, P < 0.001). At 120 days, systolic blood pressures were elevated in diabetic rats (P < 0.05), and at 180 days over 60% of the diabetic rats had pressures above the highest pressures of control rats.

In study 2, STZ-diabetic rats were treated with insulin for 2 wk (2 U NPH at 0800 h, or 2 U NPH at 0800 and 1600 h). In the single-dose group, with hyperglycemia similar to that of diabetic rats in study 1, kallikrein excretion was reduced as early as day 2, compared with nondiabetic rats (56.0 ± 6.1 versus 109 ± 9.4 μg/24 h, respectively, P < 0.001). In the diabetic rats treated with twice-daily insulin, glycemia was reduced and daily urine glucose was not significantly different from that in controls. Kallikrein excretion was normal in these rats.

In study 3, we measured renal tissue kallikrein i untreated and insulin-treated (2.25 U PZI) STZdiabetic rats. After 2 wk, untreated diabetic rats had decreased renal kallikrein compared with nondiabetic rats (22.8 ± 1.6 versus 29.7 ± 1.4 ng/mg protein, P < 0.001). In the insulin-treated diabetic rats with near-normal plasma glucose levels, renal kallikrein (35.8 ± 2.1 ng/mg protein) was increased above that of untreated diabetic (P < 0.001) or nondiabetic rats (P < 0.05).

These studies confirm that STZ-diabetic rats develop systolic hypertension as assessed by tail cuff measurement. There is an early reduction in kallikrein excretion, which reflects reduced renal enzyme content. These abnormalities in kallikrein can be prevented by insulin treatment. Relationships of these changes in urinary and renal kallikrein to the function of the diabetic kidney and development of hypertension in this model can now be explored.
Studies on the Possible Involvement of Prostaglandins in Insulin Generation of Pyruvate Dehydrogenase Activator
Authors: Begum Najma , Tepperman Helen M , Tepperman Jay
Published: September 2013

Insulin-exposed liver particulate fraction supernatants from control rats stimulated mitochondrial pyruvate dehydrogenase (PDH) activity by 26%, while the stimulation by similar preparations from indomethacin-injected rats (5 mg/kg twice daily, i.p., for 2 days) was 4%. In vitro addition of indomethacin to the particulate fraction during insulin exposure also inhibited stimulation of PDH by insulin. This inhibitory effect of indomethacin was completely overcome by the in vitro addition of prostaglandin E2 (PGE2) to the liver particulate incubation mixture. Intact adipocytes showed a similar (62%) decrease in insulin activation of PDH in the presence of indomethacin. In a cell-free adipocyte system (co-incubation of mitochondria and plasma membrane), indomethacin addition resulted in 90% decrease in insulin-stimulated PDH response. PGE2 addition completely reversed this inhibition. In contrast to its effects on PDH activation, indomethacin had no effect on insulin-stimulated glucose oxidation. In vitro incubation of fat cells with dexamethasone (1 μLM) also resulted in decreased insulin activation of PDH. Inclusion of arachidonic acid during dexamethasone exposure of fat cells resulted in partial restoration of the insulin effect on PDH in fat cells and in cell-free preparations. However, addition of PGE2 during insulin exposure of plasma membranes from dexamethasonetreated preparations showed no significant restoration of the insulin effect on PDH. These studies suggest that: (1) PG metabolism is involved in insulin's generation of the second messenger, and (2) the mechanism of dexamethasone-induced inhibition of insulin effect on PDH is a complex phenomenon involving the synthesis and action of eicosanoids.
Increased Muscle Glucose Uptake After Exercise: No Need for Insulin During Exercise
Authors: Richter Erik A , Ploug Thorkil , Galbo Henrik
Published: September 2013

It has recently been shown that insulin sensitivity of skeletal muscle glucose uptake and glycogen synthesis is increased after a single exercise session. The present study was designed to determine whether insulin is necessary during exercise for development of these changes found after exercise. Diabetic rats and controls ran on a treadmill and their isolated hindquarters were subsequently perfused at insulin concentrations of 0, 100, and 20,000 μU/ml. Exercise increased insulin sensitivity of glucose uptake and glycogen synthesis equally in diabetic and control rats, but insulin responsiveness of glucose uptake was noted only in controls. Analysis of intracellular glucose-6-phosphate, glucose, glycogen synthesis, and glucose transport suggested that the exercise effect on responsiveness might be due to enhancement of glucose disposal. After electrical stimulation of diabetic hindquarters in the presence of insulin antiserum, insulin sensitivity of 3-O-methylglucose transport was increased to the same extent as in muscle from healthy rats stimulated in the presence of insulin at 50 μU/ml. Furthermore, in muscle depleted of glycogen by contractions, transport of 3-O-methylglucose was increased in the presence of insulin antiserum and in the absence of increased regional perfusate flow. It is concluded that after exercise, increased sensitivity of muscle glucose metabolism to insulin can be found in the absence of insulin during exercise, but still involves increased membrane transport of glucose. At maximal insulin concentrations, the enhancing effect of exercise on glucose uptake may involve enhancement of glucose disposal, an effect that is probably less in muscle from diabetic rats. Finally, after exercise, increased glucose transport in glycogen-depleted muscle does not require increased muscle blood flow and, therefore, involves increased membrane permeability for glucose. The presence of insulin is not necessary for this effect of exercise.
Role of Muscle in CO2 Production After Oral Glucose Administration in Man
Authors: Meistas Mary T , Vlachokosta Frederika V , Gleason Ray E , Arcangeli Michael , Aoki Thomas T
Published: September 2013

A significant increase in CO2 production, reflecting carbohydrate oxidation and/or fat synthesis, is observed in normal subjects after the ingestion of glucose. The anatomic site(s) of this CO2 production has not yet been localized, although liver and muscle are logical considerations. To assess the contribution of skeletal muscle to this process, we measured whole-body and forearm CO2 flux in normal, postabsorptive subjects after the ingestion of 100 g of glucose and calculated their total muscle CO2 production. In the basal state, muscle accounted for 19% of total CO2 production, and, after glucose administration, muscle CO2 production did not change significantly. Thus, muscle is not the principal site of the observed increase in CO2 production.
Tissue-specific Antibodies Against the Fibroblast Insulin Receptor in a Patient with Lupus Nephritis and Hypoglycemia
Authors: Pirro Roberto De , Borboni Patrizia , Lauro Renato , Festa Antonella , Testa Ivano , Martinis Carlo De , Maddux Betty A , Goldfine Ira D
Published: September 2013

We recently reported that the serum from a patient with lupus nephritis, insulin resistance, and hypoglycemia contains multiple populations of antibodies directed at the human insulin receptor. In the present study, we found a subpopulation of antibodies (eluted from a protein A-Sepharose affinity column at pH 4.3) directed at the human fibroblast insulin receptor. When tested against human placental membranes, IM-9 lymphocytes, circulating monocytes and erythrocytes,and isolated adipocytes, the antibody subpopulation did not compete with 125I-insulin for binding to its receptor. In contrast, the antibody subpopulation competed with 125I-insulin for binding to the human fibroblast insulin receptor. This antibody subpopulation stimulated [3H]aaminoisobutyric acid ([3H]AIB) uptake to these cells. Unlike the effect of insulin, however, this regulation of transport was not antagonizedby a mouse monoclonal antibody to the human insulin receptor that inhibits 125Iinsulinbinding. These studies indicate, therefore, that a tissue-specific antibody subpopulation can occur spontaneously in patients with antibodies to the human insulin receptor. Furthermore, they indicate the presence of anti-insulin receptor autoantibodies specifically directed against a tissue that is not primarily involved in glucose metabolism.
The Nature of Insulin Secretory Defect in Aging Rats
Authors: Draznin Boris , Steinberg Jay P , Wayne J , Sussman Karl E
Published: September 2013

We have attempted to define the nature of insulin secretory defect(s) in aged animals. In these studies, pancreatic islets were isolated from 2- and 18-mo-old Fischer 344 rats. Margination of secretion vesicles during exocytosis was assessed by measuring the recruitment of somatostatin (SRIF) receptors to the surface membrane. Section vesicle lysis was studied by measuring insulin release into the incubation media.

Submaximal and maximal glucose-induced insulin secretion was significantly greater in islets isolated from younger rats (P < 0.01). SRIF recePtor recruitment was stimulated by glucosein both younger and older Fischer 344 rats. However, an increase in SRIF receptor recruitment wasreduced in islets isolated from older animals (from 2.14 ± 0.4 to 4.6 ± 0.4 fmol/10 islets) (P < 0.01) as compared with islets from younger animals (from 2.6 ± 0.2 to 6.2 ± 0.4 fmol/10 islets). When secretion vesicle lysis was inhibited by the presence of sodium isethionate in the incubation media, glucose (300 mg/dl) failed to stimulate secretion vesicle margination to the plasma membrane. In contrast, glyburide (0.6 μg/ml) continued to stimulate directly secretion vesicle margination in islets from aged animals (from 2.1 ± 0.3 to 6.0 ± 0.3 fmol/10 islets).

We conclude that glucose-induced margination of secretion vesicles at the plasma membrane is impaired by the aging process. This impairment results in lower submaximal and maximal insulin secretory response to glucose. The fact that glyburide is capable of stimulating secretion vesicle margination suggests that glucose signal recognition and/or stimulus-secretion coupling may be the locus of impairment in the process of insulin secretion in older animals.
Genetic Influences on the Immunologic Pathogenesis of Encephalomyocarditis (EMC) Virus-induced Diabetes Mellitus
Authors: Huber Sally A , Babu P George , Craighead John E
Published: September 2013

DBA/2 and Balb/cBY mice were infected with approximately 30 plaque-forming units of the M-variant of encephalomyocarditis (EMC-M) virus. Seven days after inoculation the majority of the animals of both strains were hyperglycemic. A significant correlation between increased concentrations of virus in the pancreas and hyperglycemia was found among individual DBA/2 animals, but not among Balb/cBY mice. T-lymphocyte depletion of DBA/2 mice before infection failed to alter the incidence or severity of hyperglycemia in comparison to intact animals. Conversely, hyperglycemia in Tlymphocyte-depleted Balb/cBY mice was reduced substantially in comparison to infected immunocompetent animals. There appears to be at least two genetically influenced pathogenic mechanisms of diabetes in EMCM virus-infected mice. In some strains of animals,hyperglycemia results exclusively from viral infection and the consequent injury to the beta cells, whereas in other animals, viral damage to the islets is compounded by immunologic events.
Improved Glycemic Control in C57BI/KsJ (db/db) Mice After Treatment with the Thermogenic β-Adrenoceptor Agonist, BRL 26830
Authors: Carroll M J , Lister Carolyn A , Sennitt M V , Stewart-Long N , Cawthorne M A
Published: September 2013

BRL 26830, (R*,R*)-(±)-methyl-4-(2-[{2-hydroxy-2-phenylethyl} amino]propyl)-benzoate, is a new type of β-adrenoceptor receptor agonist that combines antihyperglycemic and thermogenic properties. In C57BI/KsJ db/db mice, treatment with BRL 26830 (50 mg of the hemifumarate salt/kg diet) decreased blood glucose concentration and normalized water intake. As judged by the normalization of polydipsia, BRL 26830 was effective within 2 days and the effect was maintained throughout a treatment period of up to 11 wk. Treatment of db/db mice with BRL 26830 resulted in an increase in both plasmaand pancreatic insulin concentrations and a partial restoration of first-phase insulin secretion by the isolated, perfused pancreas in response to a high (16.7 mM) glucose pulse. Given acutely, BRL 26830 increased energy expenditure in both fed and fasted db/db mice. When given chronically, BRL 26830 increased significantly the dietary and thermoregulatory component of metabolic rate. It is suggested that the antidiabetic and thermogenic properties of BRL 26830 are linked and that blood glucose acts either directly or indirectly as a substrate for thermogenesis.
Spontaneous Activity of Primary Afferent Neurons in Diabetic BB/Wistar Rats: A Possible Mechanism of Chronic Diabetic Neuropathic Pain
Authors: Burchiel Kim J , Russell Lisa C , Lee Richard P , Sima Anders A F
Published: September 2013

The mechanism of painful diabetic neuropathy remains unknown. Spontaneous activity in nociceptive primary afferents has been implicated in the genesis of chronic pain due to peripheral nerve injury, and diabetic axonopathy shares some histologic features with traumatic neuropathy. We hypothesized that spontaneous hyperactivity of nociceptive neurons might represent the neurophysiologic mechanism of diabetic neuropathic pain. To test this, we examined the spontaneous activity of primary afferent axons from diabetic BB/Wistar and normal Wistar rat saphenous nerves isolated from central and peripheral connections. Microfilament recordings from diabetic nerves showed a significantly higher incidence of spontaneous discharges in comparison to normal nerves. Furthermore, this spontaneous hyperactivity occurred almost exclusively in potentially nociceptive C-fibers. We conclude that in the diabetic BB/Wistar rat, spontaneous impulses are generated in potential nociceptive primary afferent neurons, and that this may represent the mechanism of chronic diabetic neuropathic pain.