bluuebunny/crossref_metadata_2025 huggingface dataset:
Diabetes in Pregnancy: Skeletal Malformations in the Offspring of Diabetic Rats After Intermittent Withdrawal of Insulin in Early Gestation
Authors: Eriksson U J , Dahlström E , Hellerström C
Published: September 2013

Precise timing of the teratogenic period in diabetic pregnancy is of clinical importance since correction of the glucose intolerance during this period may protect the offspring from malformations. An experimental approach to elucidate this problem with regard to skeletal development was made in groups of pregnant streptozotocin-diabetic rats (MDI), which were treated with daily insulin injections except for a 2-day period in the first half of pregnancy. The degree of metabolic derangement was estimated by measurements of serum glucose concentrations. During the insulin-free period, the rats showed severe hyperglycemie (>20 mM) while during ongoing insulin treatment, only brief periods of hyper- or hypoglycemia were observed. Insulin treatment was withdrawn successively between gestational days 3 and 12. Control groups consisted of normal pregnant rats (N) or pregnant rats with manifest diabetes (MD) without insulin treatment. The serum glucose levels of the N animals were below 6 mM while those of the MD animals were above 25 mM throughout pregnancy. Skeletal malformations in the viable offspring were recorded on gestational day 20 after Alizarin staining of calcified ossification centers, which also allowed an estimate of skeletal development as a whole.

Untreated diabetes in the MD rats induced a high rate of fetal resorptions, a decrease in fetal weight and viability, as well as retardation of skeletal development. Intermittent insulin treatment in the MDI rats ameliorated, but did not abolish, these changes. In the MD group 9 of 48 viable fetuses showed severe malformations of either the lower jaw (micrognathia) or of the lumbosacral region (caudal dysgenesis). No skeletal malformations were observed in 151 offspring of the N group. Among the MDI animals, skeletal malformations occurred in 2 of 52 viable fetuses with interruption of maternal insulin treatment on gestational days 2–3, in 7 of 118 fetuses with interruption of insulin on days 4–5, and in 4 of 77 fetuses with interruption on days 6–7. No skeletal malformations were seen in a total of 75 MDI fetuses after interruption of insulin treatment on either days 8–9 or 10–11. However, a high rate of resorptions was also seen in these two groups.

These observations strongly suggest that in rats, the teratogenic impact of maternal diabetes on embryonic skeletal development manifests itself at an unexpectedly early embryonic age and that correction of metabolism with insulin during this critical period may protect the offspring from malformations.
The Independence of Insulin Release and Ambient Insulin In Vitro
Authors: Marincola Francesco , Frank William , Clark William , Douglas Marlene , Merrell Ronald
Published: September 2013

The effect of insulin on its own secretion was tested in three independent experimental models using insulin concentrations that approached physiologic values. The collected secretions from glucose-stimulated islet tissue had no effect on insulin release from other islets. Perifused insulin had no effect on the release of endogenous insulin even when the assay was completely controlled for dilutional effects. Perifused insulin had no effect on the release of prelabeled insulin from glucose-stimulated islets. Similarly, proinsulin did not affect insulin release. Porcine insulin did not affect the function of porcine or canine islets. These studies strongly support the independence of glucose-stimulated insulin secretion and ambient insulin.
Diabetic Glomerulopathy: Structural Characteristics of the Early and Advanced Stages
Authors: Østerby R , Gundersen H J G , Hørlyck A , Kroustrup J P , Nyberg G , Westberg G
Published: September 2013

Studies of the glomerular structure in diabetes mellitus have helped to elucidate the basis for some functional abnormalities. The decline in glomerular filtration occurring in many long-term diabetics is a functional disorder of great clinical importance. Quantitative structural studies of the glomeruli in diabetics at different stages of disease are necessary to learn about the development of structural changes leading to the endstage kidney disease.

Preliminary results of a study of glomeruli from longterm diabetics with clinical nephropathy are compared with those obtained in control subjects and in diabetics within the first 5 yr of disease. In the long-term diabetics the peripheral basement membrane thickness was doubled. On the average, mesangial regions occupied nearly 60% of the total tuft volume as compared with 33% in the early stages. A marked accumulation of basement membrane material in the mesangial regions had taken place so that 85% of the total basement membrane material of the tufts (i.e., peripheral basement membrane in the capillary walls plus mesangial basement membrane-like material) was localized within the mesangial regions. In the early stages equal amounts were found at these two different sites.

The distribution of the lesions within the kidney is under investigation in a light microscopic study of autopsy material from long-term diabetics with varying degrees of glomerulopathy. The severity of the diabetic glomerulopathy was quantitated separately within the superficial and the deep cortical zones. The results showed that there was no tendency toward increased severity in the deep glomeruli. It can therefore be concluded that factors related to the structural and functional differences between these two subgroups of glomeruli do not play a dominant role in the development of diabetic glomerulopathy.
Quantitative Evaluation of Fluorescein Angiograms: Microaneurysm Counts
Authors: Baudoin C , Maneschi F , Quentel G , Soubrane G , Hayes T , Jones G , Coscas G , Kohner E M
Published: September 2013

This study describes a method for quantifying microaneurysms (MA) from fluorescein angiograms. The method was validated by the reproducibility of the number of MA in 30 angiograms read twice each by two independent observers; and by the absolute difference in MA counts between two readings by the same observer, and difference in numbers counted by two different observers. The precise location of each MA on two readings was also studied and the reproducibility of location varied from 60 to 71%, depending on the quality of the angiograms.

Clinicians and technicians working in the same or in different centers obtained similar results. The coefficient of correlation between observers and between readings was satisfactory, r > 0.9.

The method is easy to learn and the reproducibility allows for its use in clinical trials.
Diabetic Nephropathy and Arterial Hypertension: The Effect of Antihypertensive Treatment
Authors: Parving Hans-Henrik , Andersen Allan R , Smidt Ulla M , Christiansen Jens Sandahl , Oxenbøll Birgitte , Svendsen Per Aa
Published: September 2013

Our longitudinal study of urinary albumin excretion rate in long-term insulin-dependent diabetics without proteinuria (negative albustix) suggests that early detection of patients at high and low risk of developing persistent proteinuria, i.e., diabetic nephropathy, is possible by using a sensitive method for albumin determination.

Our prospective studies in young insulin-dependent diabetics with diabetic nephropathy show that the rate of decline in giomerular filtration rate (GFR) varies considerably, with a mean of 0.75 ml/min/mo and a range from 0.1 to 1.50 ml/min/mo, and that an increase in arterial blood pressure to a hypertensive level is an early feature; 43% of the patients had diastolic blood pressure >100 mm Hg. Early and aggressive antihypertensive treatment reduces both albuminuria and the rate of decline in GFR in young patients with diabetic nephropathy.
Direct Modulation of Pancreatic CCK Receptors and Enzyme Secretion by Insulin in Isolated Pancreatic Acini from Diabetic Rats
Authors: Otsuki Makoto , Williams John A
Published: September 2013

The effect of insulin on pancreatic enzyme secretion was studied in vitro by using isolated pancreatic acini prepared from rats rendered diabetic with streptozotocin. Preincubation of acini with insulin increased the maximal release of amylase and ribonuclease in response to CCK8 but not to carbamylcholine, a secretagogue acting via a different receptor. Insulin by itself had no effect on enzyme release. The effect of insulin was time dependent and increased up to 2 h, the longest time studied. An effect was observed at 1 nM insulin and the maximal effect was observed at 100 nM The properties of CCK receptors on the acini were studied using biologically active 125I-BH-CCK33. Insulin pretreatment decreased both the affinity of the high-affinity CCK receptors and the capacity of the low-affinity CCK receptors. Within the framework of the current model, in which occupancy of high-affinity CCK receptors stimulates and low-affinity receptors inhibits amylase release, the change in receptors induced by insulin could account for the altered enzyme secretion. Thus, insulin appears to have a direct effect to regulate CCK receptors and CCK-induced secretion in isolated pancreatic acini.
Glucosylated and Normal Human of Rat Albumin Do Not Bind to Renal Basement Membranes of Diabetic and Control Rats
Authors: Jeraj Karim P , Michael Alfred F , Mauer S Michael , Brown David M
Published: September 2013

Hyperglucosylated and normal human and rat albumin were injected intravenously into control and streptozotocin-induced diabetic rats. Binding of injected human albumin to renal basement membranes was not observed by immunofluorescence microscopy in the diabetic or control rats irrespective of the form of injected albumin. However, human albumin was found as tubular droplets in both the control and diabetic rats injected with either form of albumin. Spontaneous binding of endogenous rat albumin was observed in a linear pattern on diabetic rat glomerular basement membranes (GBM), but not in the GBM of control rats. No appreciable differences in the intensity of staining for rat albumin was observed in diabetic rats injected with either glucosylated or normal rat albumin. Similarly, no binding of rat albumin to the GBM was observed in control rats irrespective of the type of albumin injected. These studies demonstrate that binding of albumin to renal basement membranes is not dependent on glucosylation.
Cellular Mechanisms of Insulin Release: Effects of Retinoids on Rat Islet Cell-to-Cell Adhesion, Reaggregation, and Insulin Release
Authors: Chertow Bruce S , Baranetsky Nicholas G , Sivitz William I , Meda Paolo , Webb Michael D , Shih Joyce C
Published: September 2013

We studied the effects of retinoids on islet cell-to-cell adhesiveness and glucose-induced insulin release from rat islets. For adhesion studies, islets were dispersed using low concentrations of trypsin. Thirteen cis-retinoic acid (13 cis-RA) was added to a suspension of 15 × 105 islet cells and adhesion of cells was quantitated using a hemocytometer. For functional studies, we measured biphasic insulin release from collagenase-isolated perifused islets, dispersed cells, and single large aggregates (clumps) of islet cells.

Thirteen cis-RA (10−4 M) stimulated insulin secretion at 9.7, 12.5, 16.7, and 27.7 mM glucose. Maximal effects of 13 cis-RA (174% of control) were evident during second phase release at 9.7 mM glucose.

Thirteen cis-RA (10−7 and 10−6 M) caused cells to adhere to each other, and at higher concentrations, 13 cis-RA caused dispersed cells to reaggregate into a single clump. These retinoid-induced clumps were perifused in a Bio-Gel P-2 gel column. Secretion from the clump was twofold greater than from an equal number of perifused dispersed cells. Electron microscopic and freeze-fracture examination of the clump showed reaggregated cells to be intact and the presence of gap junctions between cells.

In conclusion, 13 cis-RA has marked effects on islet cell-to-cell adhesiveness. Trypsin-dispersed cells reaggregated by 13 cis-RA have anatomical contacts and secrete more insulin as an aggregate than as dispersed cells. Thirteen cis-RA increases insulin release possibly by increasing adhesion or interactions between β-cellS.
Effects of Maternal Diabetes on Early Embryogenesis: Alterations in Morphogenesis Produced by the Ketone Body, B-Hydroxybutyrate
Authors: Horton W E , Sadler T W
Published: September 2013

The present study used the whole embryo culture technique to determine the effects of the ketone body, B-hydroxybutyrate (B-OHB), on organogenesis in mouse embryos. Embryosof two stages (3–4 and 5–6 somites) were exposed for 24 h to a racemic mixture of D-L B-OHB at levels of 8, 16, or 32 mM/L. An abnormal pattern of development resulted, consisting of growth reduction and inhibition or delay of neural tube closure in the cranial and/or caudal regions of the embryo. These effects were dose- and age-dependent, such that younger embryos were more frequently affected than older ones, and increasing doses produced a higher rate of malformation. Growth reduction as evidenced by embryonic protein showed similar relationships. Histologic analysis of embryos exposed to 32 mM/L B-OHB for 24 h revealed numerous cytoplasmic “vacuoles” widespread throughout the neuroepithelium, mesenchyme, and ectoderm. Ultrastructurally, these “vacuoles” proved to be mitochondria that had undergone high-amplitude swelling with a loss of matrix density and few identifiable cristae. No other consistent ultrastructural changes were noted, and the mitochondria of control tissues displayed a typical orthodox configuration. While this study does not conclusively limit the effects to the D-form of B-OHB, possible relationships exist between the ultrastructural alterations, ketone body metabolism, and abnormal morphogenesis.
Insulin Gene Expression in the Developing Rat Pancreas
Authors: Kakita Keiji , Giddings Stephen J , Rotwein Peter S , Permutt M Alan
Published: September 2013

In the developing rat pancreas from about day 15 until birth there is a marked increase in the concentration of insulin. The present experiments were designed to determine whether enhanced insulin biosynthesis is accompanied by a coordinate increment in proinsulin mRNA. Using a sensitive RNA filter hybridization technique and a cloned rat proinsulin 32P-cDNA as a hybridizing probe, the concentration of proinsulin mRNA was measured. A greater than 900-fold accumulation of proinsulin mRNA was found, which closely paralleled that of immunoreactive insulin. Proinsulin mRNA and immunoreactive insulin were highest 1–2 days after birth, more than eightfold higher than that in adult pancreas.

The patterns of digestion by a number of restriction endonucleases of the two nonallelic insulin genes were identical in adult and fetal DNA and in DNA from an insulinoma. We found no evidence of major gene rearrangement during embryogenesis as a prerequisite to insulin gene expression.

Glucose stimulated insulin biosynthesis at the earliest time examined (day 15 of gestation). Insulin biosynthesis was enhanced almost fourfold while proinsulin mRNA differed by less than 20% during a 2-h incubation. This suggested that the short-term effect of glucose on insulin biosynthesis in the developing rat pancreas occurs at the level of translation of existing mRNA, similar to that noted in adult pancreatic islets. These data taken together suggest that the same controls for insulin biosynthesis in the adult exist at these early times in pancreatic development and that the controls for insulin biosynthesis appear coordinately with the appearance of increased insulin during endocrine pancreatic differentiation.
Elevated Glucose Concentrations Increase Factor VIIIR:Ag Levels in Human Umbilical Vein Endothelial Cells
Authors: Mordes David B , Lazarchick John , Colwell John A , Sens Donald A
Published: September 2013

To determine if endothelial cell metabolism is affected by the elevated glucose concentrations known to occur in diabetes mellitus, we measured cellular Factor VIIIR:Ag in endothelial cells grown under conditions of increased glucose concentration. The results of this study illustrate that, under cell culture conditions, an increase in glucose concentration results in increased cellular levels of Factor VIIIR:Ag. Specifically, a glucose concentration of 300 mg/dl resulted in a 23% increase in Factor VIIIR:Ag levels while a glucose concentration of 600 mg/dl resulted in a 54% increase in Factor VIIIR:Ag levels. These in vitro findings may relate to the increase in plasma Factor VIIIR:Ag levels known to occur in diabetic patients.
Insulin-induced Internalization of the Insulin Receptor in the Isolated Rat Adipose Cell: Detection of Both Major Receptor Subunits Following Their Biosynthetic Labeling in Culture
Authors: Simpson Ian A , Hedo José A , Cushman Samuel W
Published: September 2013

A protocol has been developed for maintaining isolated rat adipose cells in primary tissue culture. Using this protocol, cells remain fully viable and responsive to insulin for at least 24 h, as assessed by measuring 3-0-methylglucose transport, lipogenesis from [U-14C]-glucose, and the incorporation of [35S] methionine into total membrane protein. The acute insulin-induced internalization of its own receptor was then examined by biosynthetically labeling cells in culture with either [35S] methionine or [3H[ glucosamine, maximally inducing receptor internalization with a 30-min incubation in the presence of saturating insulin, and preparing plasma and low-density microsomal membrane fractions by differential ultracentrifugation. Receptors were immunoprecipitated with anti-receptor antiserum, and the receptor subunits separated by NaDodSO4-PAGE under reducing conditions and analyzed by autoradtography. When cells not acutely treated with insulin are examined, both the 135K α- and 95K β-receptor subunits are prominently labeled in the plasma membrane fraction, but only faintly labeled in the low-density microsomal membrane fraction. Following the induction of maximal acute receptor internalization, both subunits are decreased by 20–30% in the plasma membrane fraction and concomitantly increased in the low-density microsomal membrane fraction. However, the relative molecular weights and labeling intensities of the two subunits remain constant and correspond to those observed in the biosynthetically labeled human lymphocyte receptor. A minor band of Mr ≃ 190K is also labeled, but its labeling intensity is similar in the two membrane fractions from basal cells and does not change in response to insulin. This band has not been previously detected in the rat adipose cell, but is thought to represent either a minor receptor component or a precursor of either or both of the major receptor subunits in human lymphocytes. Thus, an experimental system is now available for studying the chronic regulation of both the insulin receptor and the response to insulin in a primary target cell for insulin action. In addition, this system has been used to demonstrate that the acute insulin-induced internalization of its own receptor in the isolated rat adipose cell appears to comprise the subcellular translocation of intact receptors.
Quantitation of Glycosylated Hemoglobin by Boronate Affinity Chromatography
Authors: Flückiger Rudolf , Woodtli Thomas , Berger Willi
Published: September 2013

Total hemoglobin glycosylation and the contribution of glycosylation at the N-terminus of the beta-chains and at “non”-beta-N-terminal positions were quantitated by use of boronate affinity and ion exchange chromatography. Glycohemoglobin (y) was found to correlate linearly (y = 1.92x + 0.53; r = 0.96) with HbA1c (x) and to contain approximately 50% beta-N-terminally glycosylated hemoglobin. This result is in agreement with the binding on boronate agarose of the various hemoglobin components resolved by cation exchange chromatography. An amount of glycohemoglobin similar to that of HbA1c was isolatable from HbA. A slope of less than 2 results because HbA1c is retained only to 93% and the intercept of the regression line reflects the partial adherence (65%) of HbA1a+b to the resin.

These results confirm the occurrence of significant “non”-beta-N-terminal glycosylation and show that under optimal chromatographic conditions total glycohemoglobin can be determined with boronate affinity chromatography.
Lipoprotein-induced Insulin Resistance in Aortic Endothelium
Authors: Berliner J A , Frank H J L , Karasic D , Capdeville M
Published: September 2013

An in vitro model system employing cultured, adult, bovine aortic endothelial cells was used to study the mechanism of insulin stimulation of aminoisobutyric acid (AIB) uptake and the effects of low-density lipoprotein (LDL), malondialdehyde-altered LDL (MDA-LDL), and B-migrating very-low-density lipoprotein (B-VLDL) on this process. The insulin response was maximal after treatment with insulin for 2 h (at a concentration of 5 × 10−8M). Insulin increased the Vmax but not the KM of the uptake response. Increasing the cell cholesterol content by a 3-day incubation with malondialdehyde-altered low-density lipoprotein or B-very-low-density lipoprotein, but not low-density lipoprotein, resulted in resistance to the action of insulin. This resistance was not due to a decreased number of insulin receptors or to a decreased receptor affinity. Additionally, the resistance was not abolished by increasing the time of insulin exposure or the concentration of insulin to which the cells were exposed. These findings suggest a postreceptor defect either at the membrane level or intracellularly.
The Effect of Streptozocin-induced Diabetes on the Plasma Membrane Calcium Uptake Activity of Rat Liver
Authors: Chan Kwok-Ming , Junger Kurt D
Published: September 2013

The effect of streptozocin (STZ)-induced diabetes on the plasma membrane calcium uptake of rat liver was investigated. Plasma membrane preparations from diabetic rats showed a 2–3-fold increase in calcium uptake activity over controls 3–4 wk after the initial injections. Such an increase can be either reversed or blocked by treating the diabetic rats with exogenous insulin or administering nicotinamide 15 min before and 3 h after the STZ injection, respectively. The activity of 5'-nucleotidase and the [3H]ouabain binding to the plasma membranes were similar in samples from both the control and diabetic rats. These findings made it unlikely that preferential enrichment of plasma membranes or increased proportion of inside-out vesicles was the cause of the enhanced calcium uptake activity in membranes from diabetic animals. In addition, the effect of diabetes on the calcium uptake activity did not diminish even when the assay was performed in the presence of 2.5 μM ruthenium red, an inhibitor of calcium uptake by mitochondria, or when oxalate was omitted from the assay, suggesting that the effect was specifically on the plasma membrane pump. The enhanced calcium uptake activity was a result of an increase in the Vmax (58.8 versus 113.1 pmol calcium/mg protein/min for control and diabetic rats, respectively). No significant change in Km for calcium was detected.
The Effects of Acute and Chronic Diabetes on Myocardial Metabolism in Rats
Authors: Chen Victor , Ianuzzo C David , Fong Bing C , Spitzer John J
Published: September 2013

This study examined how the duration of experimentally induced diabetes affects myocardial metabolism. Both acutely (2-day) and chronically (30-day and 90-day) streptozocin (STZ)-diabetic rats exhibited hyperglycemia and hyperketonemia, while hyperlipemia was evident only in the chronically diabetic rats. The activity of succinate dehydrogenase was lower, whereas that of 3-hydroxyacyl-CoA-dehydrogenase was higher in the hearts of chronically diabetic rats. Although myocardial concentrations of glucose-6-phosphate, glycogen, and triacylglycerols were elevated in diabetes, the patterns of alterations differed between acute and chronic diabetes. The fructose-1,6-diphosphate/fructose-6-phosphate ratio declined progressively after STZ administration, which was not accompanied by a reciprocal increase in citrate levels, although citrate concentrations were elevated. Impaired glucose oxidation was more severe in the freshly isolated heart cells from 30-day than from 2-day diabetic rats. For a given substrate concentration, the oxidation rates of palmitate and 3-hydroxybutyrate were markedly reduced in myocytes from 30-day diabetic rats. However, they were similar to or even higher than the rates found in their control counterparts under conditions that reflected the respective in vivo concentrations of the substrates. Incubating isolated myocytes from 2-day diabetic rats in the presence of insulin only partially restored the impaired glucose oxidation. Insulin administered to the animals 4 h before the experiments restored the impaired glucose oxidation by the cells. Insulin in vitro or single injection in vivo had little or no effect on glucose oxidation in isolated myocytes from 30-day diabetic rats. Our findings suggest that the myocardium undergoes a continuous and prolonged metabolic adaption in the course of experimental diabetes.
Effect of Diabetic Hyperglycemia and Other Sugars on Plasma Dopamine-β-Hydroxylase Activity
Authors: Muñoz Andrés , Serrano Concepción , García-Estañ Joaquín , Quesada Tomás , Portugal Maria Teresa Miras
Published: September 2013

The plasma glycoprotein, dopamine-β-hydroxylase (DBH), is present in markedly increased amounts in experimental, streptozocin (STZ)-diabetic rats, reaching a maximum at about the first week and maintaining a plateau for several months afterward. High glycemia values are observed simultaneously. Insulin treatment is observed to keep the glycemia and plasma DBH activity values at levels seen in control rats. The heterologous half-life of DBH in STZ-diabetic rats is significantly increased compared with that of control animals. The glucose analogue, 2-deoxy-D-glucose, has a similar effect on plasma DBH activity levels, eliciting high glycemia values. In STZ-diabetic animals, this increase is more significant, as if it were the additive effect of the two sugars. Other sugars that can compete for glycoprotein catabolic receptors can also modulate the plasma DBH activity levels. The lack of effect of galactose on DBH levels, together with the induced increase of DBH by α-methyl-D-mannoside and, to a lesser extent, by inulin, suggest an important rate for the mannose/glucose/N-acetyl glucosamine/fructose receptor in the catabolic clearance of DBH from plasma and explain the abnormal values seen for DBH in diabetes mellitus.
Demonstration of a Dawn Phenomenon in Normal Human Volunteers
Authors: Bolli Geremia B , Feo Pierpaolo De , Cosmo Salvatore De , Perriello Gabriele , Ventura Mariarosa M , Calcinaro Filippo , Lolli Claudio , Campbell Peter , Brunetti Paolo , Gerich John E
Published: September 2013

To ascertain whether the dawn phenomenon occurs in nondiabetic individuals and, if so, whether it is due to an increase in glucose production or a decrease in glucose utilization, we determined plasma concentrations of glucose, insulin, C-peptide, and counter regulatory hormones, as well as rates of glucose production, glucose utilization, and insulin secretion at one-halfhourly intervals between 1:00 and 9:00 a.m. in eight normal volunteers. After 5:30 a.m., plasma glucose, insulin, and C-peptide concentrations all increased significantly; rates of glucose production, glucose utilization, and insulin secretion also increased (all P < 0.05). Plasma cortisol, epinephrine, and norepinephrine increased significantly from nocturnal nadirs between 4:00 and 6:30 a.m. Plasma growth hormone, which had increased episodically between 1:00 and 4:30 a.m., decreased thereafter nearly 50% (P < 0.05). Plasma glucagon did not change significantly throughout the period of observation. These results indicate that a dawn-like phenomenon, initiated by an increase in glucose production, occurs in nondiabetic individuals. Thus, early morning increases in plasma glucose concentrations and insulin requirements observed in IDDM and NIDDM may be an exaggeration of a physiologic circadian variation in hepatic insulin sensitivity induced by antecedent changes in catecholamine and/or growth hormone secretion.
A Polymorphic Locus Near the Human Insulin Gene Is Associated with Insulin-dependent Diabetes Melliitus
Authors: Bell Graeme I , Horita Shiro , Karam John H
Published: September 2013

A polymorphic region flanking the human insulin gene on the short arm of chromosome 11, the insulin-gene-linked DNA polymorphism, can be described as a locus with at least three classes of alleles: a common small “class 1” allele averaging 570 base pairs, a rare intermediate “class 2” allele of about 1320 base pairs, and a large “class 3” allele averaging 2470 base pairs in size.

We have determined the genotype at this locus of 393 unrelated diabetic and nondiabetic individuals. Differences were observed in the genotypie and allelic frequencies between groups of different races. Asians [17 nondiabetic, 2 with insulin-dependent diabetes mellitus (IDDM), and 8 with non-insulin-dependent diabetes mellitus (NIDDM)] exhibited the least variation in the size of this locus and 98% of the alleles in this group were class 1. A group of American blacks (32 nondiabetic, 5 with IDDM, and 40 with NIDDM) exhibited considerable variation in the size of this locus, and about 22% of the individuals examined had a genotype that included a rare class 2 allele. In neither of these two racial groups were the genotypie or allelic frequencies different between the nondiabetic and diabetic segments of these groups.

However, in a group of Caucasians (83 nondiabetic, 113 with IDDM, and 76 with NIDDM), there was a significantly higher frequency of class 1 alleles and genotypes containing two class 1 alleles in the diabetic patients compared with nondiabetic controls. A strikingly higher frequency of class 1 alleles (P < 0.0001) and genotypes containing two class 1 alleles (P < 0.0001) was observed in the IDDM group compared with nondiabetic Caucasians, whereas the difference between NIDDM and controls was only near the level of statistical significance (P = 0.025). Analysis of the combined data of our Caucasian population and those reported from studies of Caucasians from Denmark and St. Louis, Missouri, continued to show an increased frequency of class 1 alleles and genotypes containing two class 1 alleles in the IDDM group (P = 0.0001) compared with the nondiabetic group; however, there were no longer differences in genotypic or allelic frequencies between NIDDM and nondiabetic groups.
In Vivo Stimulation of Low-Density Lipoprotein Degradation by Insulin
Authors: Mazzone Theodore , Foster David , Chait Alan
Published: September 2013

The effect of insulin on low-density lipoprotein (LDL) metabolism in vivo was evaluated using the euglycemic insulin clamp technique. In seven subjects, mononuclear cells isolated after a 4-h insulin infusion degraded more 125I-Iabeled LDL than cells isolated after a saline infusion in six control subjects. In addition, insulin caused the accelerated disappearance of 125I-labeled LDL from plasma in subjects previously injected with autologous 125I-LDL. Infusion of saline had no such effect. These data suggest that insulin, in vivo, stimulates LDL catabolism and could thereby influence LDL cholesterol levels. Insulin-induced stimulation of LDL catabolism could account for the reduction of LDL-cholesterol levels observed in intensively treated type I diabetic patients.
Glucose-dependent Insulinotropic Polypeptide Augmentation of Insulin Physiology or Pharmacology?
Authors: Sarson D L , Wood S M , Kansal P C , Bloom S R
Published: September 2013

Glucose-dependent insulinotropic polypeptide (GIP) is said to be a major physiologic factor in the augmentation of the insulin response to oral glucose. Whether GIP promotes insulin release at physiologic concentrations of glucose or GIP, however, is questionable. To investigate this further, volunteers were infused with 10, 20, or 40 g intravenous (i.v.) glucose, with or without simultaneous GIP infusion, to produce plasma levels of GIP or glucose similar to those seen after oral glucose. The effect of 40 g i.v. glucose with three times the original dose of GIP was also investigated.

No significant enhancement of glucose-stimulated insulin secretion was seen when GIP was infused with 10 or 20 g i.v. glucose; however, with 40 g a doubling of the insulin response occurred. The higher dose of GIP caused a further increase in insulin response (30-min increment, 972 ±191 pmol/L; compared with glucose alone, 356 ±100 pmol/L, P < 0.01; and compared with low GIP, 602 ± 247 pmol/L, P < 0.02). The glucose increment after the 40-g i.v. dose was + 9.2 mmol/L.

The concentration of GIP and glucose required to produce significant potentiation of the insulin response appears to be in the pharmacologie, rather than physiologic, range.
Tolbutamide and Glyburide Differ in Effectiveness to Displace α-and β-Adrenergic Radioligands in Pancreatic Islet Cells and Membranes
Authors: Cherksey Bruce , Altszuler Norman
Published: September 2013

Previous in vivo findings indicated that α-adrenergic blocking agents enhanced tolbutamide-induced insulin secretion, whereas β-blockade attenuated it. In the present study, the interaction of tolbutamide and glyburide with the rat islet adrenergic receptors is examined directly by determining the effectiveness of these drugs to displace the specific α- and β-adrenergic radioligands, [3H]-clonidine and [3H]-dihydroalprenolol (DHA). It was found that both tolbutamide and glyburide had affinity constants for the adrenergic receptors that were similar to those for the natural receptor ligands and powerful antagonists. Tolbutamide displaced both α- and β-radioligands but had a higher affinity at the β-receptor. Glyburide also displaced radioligands from both types of receptors but had a higher affinity for the α-receptor. This study suggests that these two sulfonylurea hypoglycemic agents may affect insulin secretion by different mechanisms.
Localization of Aldose Reductase in the Human Eye
Authors: Akagi Y , Yajima Y , Kador P F , Kuwabara T , Kinoshita J H
Published: September 2013

The presence of the enzyme aldose reductase is increasingly being linked to diabetic complications. The distribution of this enzyme in human cornea, lens, retina, and optic nerve has been studied using specific antibodies against purified human placental aldose reductase raised in both rabbit and goat. The antisera from both animals gave equal, specific reactions.

In frozen sections of ocular tissues, significant aldose reductase localization was reproducibly demonstrated in the endothelium and epithelium of the cornea and in the basal cell layers of the conjunctiva. In the lens, staining was observed in the epithelium and superficial lens fibers. In retinal sections, the presence of aldose reductase was demonstrated in the Mueller's cells, especially near the inner limiting membrane. It was also found in some ganglion and cone cells. In the optic nerve, positive staining was observed in the axon. All other cells of the tissues examined revealed Only weak, nonspecific Staining.
The Mechanism of Action of Insulin on Phospholipid Metabolism in Rat Adipose Tissue: Requirement for Protein Synthesis and a Carbohydrate Source, and Relationship to Activation of Pyruvate Dehydrogenase
Authors: Farese Robert V , Farese Robert V , Sabir Mohammad Ayub , Larson Ronald E , Trudeau Walter L
Published: September 2013

We studied certain metabolic requirements for insulin-induced increases in phospholipids, and the relationship of phospholipid changes to the insulin-induced activation of pyruvate dehydrogenase, in rat adipocytes and fat pads in vitro. Increases in the contents of phosphatidylinositol and phosphatidylserine mass were maximal in rat fat pads within 10 min of incubation with insulin, and preceded or accompanied measurable increases in pyruvate dehydrogenase activity. In dose-response studies, the contents of these phospholipids and pyruvate dehydrogenase activity increased in parallel in response to increasing concentrations of insulin. Cycloheximide and puromycin inhibited insulin-induced increases in the mass of both of these phospholipids, as well as (in confirmation of previous reports) pyruvate dehydrogenase activity. Effects of insulin on phospholipid metabolism and pyruvate dehydrogenase were found to require an exogenous carbohydrate source, and fructose was nearly as effective as glucose in this regard. Insulin-induced increases in phosphatidylinositol and phosphatidylserine were demonstrated in the mitochondrial fraction, which is also the subcellular locus of pyruvate dehydrogenase. The present findings suggest that there is a relationship between insulin-induced increases in phospholipids and pyruvate dehydrogenase activity, but the nature of this relationship remains to be defined.
Immunochemical Studies of the Insulin-like Material in the Parotid Gland of Rats
Authors: Smith Phillip H , Patel D G
Published: September 2013

Through the use of radioimmunoassay and immunocytochemical techniques, it was found that the parotid glands of male rats possess a population of cells that contain an insulin-like substance. These cells were situated mainly in groups along the intercalated ducts of the gland, or less frequently as isolated cells, dispersed throughout the acini. No cells displaying insulin-like immunoreactivity were observed in the striated or main excretory ducts of the parotid. After intravenous (i.v.) injections of streptozotocin (STZ) there was a marked depletion of insulin from the pancreatic islets of rats having diabetes for a 3–27-day interval. Although this cytotoxin also reduced the amount of insulin extractable from the parotid, it did not destroy the insulin-like immunoreactive cells found in this gland. The results of this study suggest that the parotid may be an important source of extrapancreatic insulin. Moreover, these findings indicate that Insulin-immunoreactive cells of this salivary gland are spared from the cytotoxic action Of STZ.
Specific Class II Histocompatibility Gene Polymorphism in BB Rats
Authors: Buse John B , Ben-Nun Avraham , Klein Karen A , Eisenbarth George S , Seidman J G , Jackson Richard A
Published: September 2013

The BB rat spontaneously develops insulin-dependent diabetes mellitus of autoimmune etiology. From breeding studies, one of the genes necessary for the development of diabetes in these animals is linked to RT1, the rat major histocompatibility complex. To better define the BB rat's RT1-linked diabetogenic gene (RT1-DM), we have used restriction endonucleases BamH1 and EcoR1 in conjunction with an I-A alpha (class II mouse major histocompatibility complex) gene probe to study RT1 class II gene polymorphisms among diabetes-prone BB rats and the related non-diabetes-prone BBN rats. Both BB and BBN rats are indistinguishable RT1U by serologie methods. Four polymorphic chromosome types (la, lb, Ha, and lib) were recognized among the control BBN rats. In contrast, all BB rats were homozygous (IIa/IIa). From the multiple breeding programs involved, we hypothesize that the BB rat's RT1-linked diabetogenic gene is linked to an I-A alpha-defined gene of the type Ha chromosome. The ability to split the RT1U of BB rats will provide a powerful tool to localize and characterize RT1-DM.
The Role of Thymic Immunity and Insulitis in the Development of Streptozocin-induced Diabetes in Mice
Authors: Nakamura Minoru , Nagafuchi Seiho , Yamaguchi Keisuke , Takaki Ryosaburo
Published: September 2013

This article is concerned with the role of thymic immunity in the development of diabetes experimentally induced by multiple injections of subdiabetogenic doses of streptozocin (STZ). Euthymic + / +, + /nu, and athymic nu/nu mice of CD-1 and BALB/cAJcl origin were studied. Daily intraperitoneal (i.p.) injections of 30 mg /kg body wt of STZ for 5 consecutive days in CD-1 + / + and + /nu mice resulted in hyperglycemia and mononuclear cell infiltrations of islets (insulitis). The CD-1 nu/nu mice developed neither insulitis nor hyperglycemia after the same treatment. In the nu/nu mice, when thymic immunity was restored by thymus grafting, both insulitis and hyperglycemia developed, thus demonstrating that thymic immunity was a prerequisite for the development of insulitis and hyperglycemia. There was a positive correlation among the degrees of thymic immunity, insulitis, and hyperglycemia in CD-1 + /nu,nu/nu with thymus grafts, and nu/nu mice, indicating that thymic immunity may amplify the diabetogenic effect of STZ by eliciting insulitis. In contrast, in BALB/cAJcl mice, a nonsusceptible strain to insulitis, no significant differences in plasma glucose levels were observed between the + /nu and nu/nu or between the nu/nu and thymus-grafted nu/nu mice. Furthermore, no significant difference was found in plasma testosterone levels between the + /nu and nu/nu mice of both CD-1 and BALB/cAJcI origin.

In conclusion, our data indicate that thymic immunity enhances the diabetogenic effect of STZ by eliciting insulitis in susceptible mice.
Metabolism of Low-Density Lipoprotein from Patients with Diabetic Hypertriglyceridemia by Cultured Human Skin Fibroblasts
Authors: Hiramatsu Kazuko , Bierman Edwin L , Chait Alan
Published: September 2013

To test whether triglyceride-enriched low-density lipoprotein (LDL) obtained from subjects with diabetic hypertriglyceridemia is metabolized normally by cells, LDL was separated from seven healthy control subjects (fasting plasma glucose [FPG] 91 ± 10 mg/dl [mean ± SD], triglyceride [TG] 110 ± 47 mg/dl), six diabetic normolipidemic patients (FPG 218 ± 65 mg/dl; TG 139 ± 75 mg/dl), six diabetic hypertriglyceridemic patients (FPG 214 ± 71 mg/dl; TG 1915 ± 1680 mg/dl), and five nondiabetic hypertriglyceridemic patients (FPG 92 ± 8 mg/dl; TG 2013 ± 1889 mg/dl). Binding of 125l-labeled LDL from hypertriglyceridemic subjects with and without diabetes to cultured skin fibroblasts was significantly decreased to 74 ± 19% and 78 ± 14% of that seen with LDL from normolipidemic nondiabetic subjects and diabetic normolipidemic controls (100 ± 0%, 101 ± 25%; P < 0.005). Unlabeled LDL from hypertriglyceridemic subjects with and without diabetes failed to suppress LDL receptor activity and sterol synthesis from 14C-acetate as efficiently as unlabeled LDL from healthy subjects. The ability of LDL from hypertriglyceridemic subjects, whether diabetic or not, to suppress LDL binding was inversely related to the ratio of triglyceride to protein in LDL (r = 0.71, P < 0.01) and showed a positive correlation with the LDL cholesterol/protein ratio (0.69, P < 0.01). Thus, LDL from patients with hypertriglyceridemia, with or without coexistent diabetes, shows impaired binding to LDL receptors and less ability to downregulate LDL receptor activity and sterol synthesis than does LDL from normolipidemic diabetic and nondiabetic subjects. These findings suggest that factors associated with hypertriglyceridemia rather than with diabetes result in altered metabolism of LDL in these disorders.
The Effects of Duct Obliteration and of Autotransplantation on the Endocrine Function of Canine Pancreatic Segments
Authors: Gooszen Henricus G , Schilfgaarde Reinout Van , Frölich Marijke , Burg Michel P M Van Der
Published: September 2013

This study in dogs addresses itself to the endocrine function of the duct-obliterated left pancreatic lobe (body and tail), which is the portion of the pancreas used for segmental transplantation. The endocrine function was determined with intravenous (i.v.) glucose tolerance tests and expressed in K-values and insulinresponse curves. Duct obliteration of the nontransplanted left lobe was associated with normal K-values in the presence of the unmodified right lobe, but with reduced K-values in its absence. Removal of the left lobe while leaving the right lobe untouched was not associated with reduced K-values, but duct obliteration of the whole pancreas was. When the duct-obliterated left lobe was transplanted onto the iliac vessels (segmental autografts), K-values were reduced when compared with the unmodified situation, but were significantly higher than with nontransplanted, duct-obliterated left lobes. Insulin-response curves of nontransplanted, duct-obliterated segments differed both qualitatively and quantitatively from the unmodified situation, but insulin-response curves of duct-obliterated segmental autografts showed only qualitative differences with the unmodified situation. It is concluded that duct obliteration rather than the absence of the right lobe is the predominant cause of reduced glucose tolerance with duct-obliterated left pancreatic lobes. It is suggested that duct obliteration affects the endocrine pancreas both in a qualitative and quantitative fashion. The qualitative effect is similarly demonstrable with segmental autografts and nontransplanted segments, but the quantitative effect is largely dissolved with autografting by virtue of caval as opposed to portal venous drainage.
Platelet Glutathione and Thromboxane Synthesis in Diabetes
Authors: Thomas George , Skrinska Victor , Lucas Fred V , Schumacher O Peter
Published: September 2013

The relationship of the reduced glutathione (GSH) content in unstimulated platelets and their capacity to synthesize thromboxane A2 (TXA2), measured by radioimmunoassay of TXB2, was investigated in diabetic and matched control subjects. The GSH content in platelets from diabetic subjects (6.52 ± 0.73 μg/109 platelets, mean ± SD) was significantly (P < 0.001) lower than in platelets from control subjects (10.10 ± 1.58 μg/109 platelets). When platelet-rich plasma (PRP) was stimulated with 1.65 mM arachidonic acid, significantly (P < 0.001) more TXB2 was formed in PRP from diabetic subjects (344 ± 87 ng/2.5 × 108 platelets) than in PRP from control subjects (132 ± 35 ng/2.5 × 108 platelets). Furthermore, the plasma level of TXB2 was increased in diabetic subjects (522 ±117 pg/ml) in comparison with control subjects (187 ± 63 pg/ml). An inverse correlation (r = 0.98) was observed between the GSH content in unstimulated platelets and their capacity to synthesize TXA2 when stimulated with 1.65 mM arachidonic acid. These data suggest that platelet GSH may have an important regulatory effect on platelet TXA2 synthesis and that increased TXA2 synthesis by platelets from diabetic subjects may be the result of low intracellular GSH levels.
Pyruyate Dehydrogenase Activity in Cardiac Mitochondria from Genetically Diabetic Mice
Authors: Kuo Tuan H , Giacomelli Filiberto , Wiener Joseph , Lapanowski-Netzel Karen
Published: September 2013

Pyruvate dehydrogenase (PDH) was studied in isolated heart mitochondria from genetically diabetic mice (C57BL/KsJ db/db) with progressive cardiomyopathy. Both the basal activity (active enzyme) and the total activity (the sum of active and inactive enzyme) were determined. In mitochondrjal extracts from 8–18-wk-old db/db mice, there was a 73% decrease of basal activity accompanied by a 38% decrease of total activity as compared with controls. The lower basal activity at 8 wk of age suggests an increased conversion of the enzyme into the phosphorylated(inactive) form. Evidence is also given that the conversion of inactive (phosphorylated) enzyme into active (dephosphorylated) enzyme is inhibited in cardiac mitochondria prepared from 8-wk and older db/db mice. These changes coincide with the onset of defective oxidative metabolism andcan explain the depressed pyruvate oxidation reported previously.