bluuebunny/crossref_metadata_2025 huggingface dataset:
Erythrocyte Spectrin Glucosylation in Diabetes
Authors: Mcmillan Donald E , Brooks Susan M
Published: September 2013

Because reduced erythrocyte deformability in diabetes might be mediated by increased noneniymatic glucosylation of membrane proteins, we have isolated and studied the degree of glucosylation of spectrin, the major protein of the inner membrane surface. Spectrin was recovered from the erythrocytes of seven age-and sex-matched diabetic and nondiabetic individuals. The thiobarbituric acid (TBA) method was used to measure the glucosylation of spectrin and of 10 mg of hemoglobin from the same ceils. Increased glucosylation of both spectrin and hemoglobin was found in diabetes. Glucosylation, expressed as a ratio of TBA absorbance to protein weight was nearly three times as high for spectrin as for hemoglobin. The ratio of TBA absorbance to hemoglobin content was examined and found to be curvilinear. A reaction model with both first and second order components was fitted to the data to obtain a reaction constant. When this model and constant were used to adjust TBA ab-sorbances, spectrin's glucosylation became less than double that of hemoglobin. Spectrin forms an inner membrane network responsible for returning deformed erythrocytes to their original shape. The reported normal response to stretching of diabetic erythrocytes suggests that increased glucosylation of spectrin fails to stiffen the membrane. Some other mechanism, such as reduced phosphorylation of spectrin and other membrane proteins, may be responsible for reduced deformability of diabetic erythrocytes. But spectrin's increased glucosylation might be responsible for the increased number of poorly deformable erythrocytes found among aged diabetic erythrocytes. It may produce this effect by inhibiting the membrane protein transglutamidation responsible for removal of aged erythrocytes.
The Effect of Chronic Sulfonylurea Therapy on Hepatic Glucose Production in Non-insulin-dependent Diabetes
Authors: Best James D , Judzewitsch Roman G , Pfeifer Michael A , Beard James C , Halter Jeffrey B , Porte Daniel
Published: September 2013

In 20 patients with untreated non-insulin-dependent diabetes mellitus (NIDDM), there was a positive relationship between fasting plasma glucose (FPG) and glucose production rate, calculated by the isotope dilution technique (r = 0.72, P < 0.001). This suggests that glucose production rate is an important determinant of FPG in untreated NIDDM. Fifteen patients were also studied during therapy with chlorpropamide for 3–6 mo. During therapy, FPG was lower (133 ± 9 vs. 216 ± 20 mg/dl, mean ± SEM; P < 0.001), glucose production was lower (59.5 ± 2.0 vs 77.6 ± 4.9 mg/m2/min; P < 0.005), and there was a significant correlation between the fall in glucose production and the fall in FPG (r = 0.59, P < 0.05). Fasting IRI levels increased in some, but not all, patients during chlorpropamide (untreated 18 ± 2, treated 21 ± 2 μU/ml; P = NS). However, there was a significant relationship between the percent rise in IRI and the fall in glucose production during treatment (r = 0.75, P < 0.001). Patients with a rise in fasting insulin during therapy had a greater fall in glucose production than those whose insulin did not rise (25.4 ± 8.1 vs. 7.8 ± 2.4 mg/m2/min; P < 0.005). When a low-dose insulin infusion was given to approximate the increases of portal venous insulin during therapy, similar falls of glucose production occurred. We conclude that inhibition of endogenous glucose production during chronic chlorpropamide therapy is an important mechanism for the lowering of FPG and that enhanced insulin secretion is the reason for the major part of this inhibition. The small fall in glucose production in those patients whose insulin level did not rise during therapy suggests an additional contribution by some other mechanism.
Impaired Insulin Secretion in Human Diabetes Mellitus: The Effect of Naloxone-Induced Opiate Receptor Blockade
Authors: Giugliano Dario , Ceriello Antonio , Pinto Paolo Di , Saccomanno Franco , Gentile Salvatore , Cappiapuoti Federico
Published: September 2013

Human diabetes mellitus is characterized by impaired insulin response to intravenous glucose. In search of possible factors which impair insulin release, we have investigated the effect of naloxone, a specific opiate receptor blocker, on insulin responses to glucose in subjects with non-insulin-dependent diabetes, as well as in normal subjects. Naloxone was given as a priming dose of 0.4 mg followed by a constant infusion of either 0.4 mg (N = 7), 2 mg (N = 7), or 4 mg (N = 8) for 90 min. Acute insulin response to glucose (mean change 3–10 min insulin), second phase insulin secretion (change 10–60 min), as well as glucose disappearance rates (﹪/min) were significantly increased in the diabetics receiving the two higher doses of naloxone (2 and 4 mg, respectively). None of these effects were seen in diabetics receiving saline or in normal subjects receiving naloxone. These results seem to suggest that sensitivity to endogenous opiates may play some part in non-insulin-dependent diabetes.
An Improved Method for the Isolation of Islets from the Beef Pancreas
Authors: Lacy Paul E , Lacy Ellen T , Finke Edward H , Yasunami Yohichi
Published: September 2013

An improved method for the isolation of islets from the beef and pig pancreas Is described. The procedure involves the use of strips of Velcro that retain the partially-digested collagen during the isolation of islets by the collagenase technique. The spiny portion of the Velcro Is ideally suited to retain the collagen and yet permit the separation of islets from the pancreatic parenchyma. A remarkably high yield of islets has been obtained from the beef and pig pancreas USing this procedure.
The Reversal of Diabetes by Pancreatic Islet Transplantation
Authors: Prowse S J , Lafferty K J , Simeonovic C J , Agostino M , Bowen K M , Steele E J
Published: September 2013

In this paper the theoretical basis of aiioreactivity and its relevance to transplantation biology is discussed prior to a review of work showing that culture of adult mouse pancreatic islets for 7 days in 95% O2 and 5% CO2 facilitates successful grafting to nonimmunosuppressed allogeneic recipients. These allografts function by reversing both chemically induced and spontaneous diabetes. The fetal mouse pancreas is more immunogenic than adult islets, and even after a culture period of 10 days in 95% O2 and 5% CO2, BALB/c allografts are consistently rejected by nonimmunosuppressed recipient mice. The immunogenicity of fetal pancreas is thought to be due to the presence of contaminating lymphoreticular celis in the mesentery surrounding the fetal pancreas. Digestion of the fetal pancreas with coilagenase allows the isolation of proislets that develop into functional islet tissue on transplantation. Fetal proislets are less immunogeneic than the whole fetal pancreas and may provide a source of tissue for clinical transplantation.

Established islet allografts are relatively stable and are not rejected following nonspecific stimulation of the recipient's immune system or following passive transfer of either antibody or antibody and complement. After prolonged residence in the recipient a state of a I log raft tolerance develops and such grafts resist rejection by specific stimulation of the recipient. The administration of donor antigen in the form of uvirradiated cells enforces this state of eliografi tolerance.
The Effect of Diabetes Mellitus on Sterol Synthesis in the Intact Rat
Authors: Feingold Kenneth R , Wiley Millie H , MacRae Gordon , Moser Arthur H , Lear Steven R , Siperstein Marvin D
Published: September 2013

Diabetes mellitus in both humans and animals is characterized by elevations in plasma cholesterol concentrations. The cause of this hypercholesterolemia is unknown. The present study employed tritiated water to quantity sterol synthesis in intact diabetic and control animals. Sterologenesis was 60–246% greater in the gut of diabetic animals than in controls. This enhancement of sterol synthesis occurred soon after the onset of diabetes and persisted for at least 3 wk. Moreover, insulin therapy markedly decreased gut sterol synthesis in diabetic animals to levels only slightly greater than in controls. Diabetes increased sterol synthesis primarily in the small intestine, but a small increase was also observed in the large intestine. Subfractionation of the small intestine into epithelial cell and muscularis cell layers revealed an increased sterologenesis in both layers. Quantitatively, though, the epithelial layer accounted for the majority of the enhancement of small intestine sterol synthesis observed in diabetic animals. De novo sterologenesis in tissues other than the intestines (liver, skin, stomach, or remaining carcass) was not significantly altered by diabetes. This study demonstrates that diabetes markedly stimulates sterol synthesis, an effect that is specifically localized to the intestines.
Effect of Variations in Basal Plasma Glucose Concentration on Glucose Utilization (M) and Metabolic Clearance (MCR) Rates During Insulin Clamp Studies in Patients with Non-insulin-dependent Diabetes Mellitus
Authors: Doberne L , Greenfield M S , Rosenthal M , Widstrom A , Reaven G
Published: September 2013

Two insulin clamp studies were performed at different steady-state plasma glucose concentrations in 13 patients with non-insulin-dependent diabetes mellitus (NIDDM). Steady-state plasma insulin concentrations were comparable, with mean ± SEM levels of 94 ± 3 and 95 ± 4 μU/ml being achieved during the two studies. Glucose utilization rate (M) varied directly with plasma glucose concentration in each subject. Thus, the mean ± SEM value of M was 4.92 ± 0.73 mg/kg/min when patients were studied at a mean ± SEM plasma glucose concentration of 226 ± 15 mg/dl, and M was 2.71 mg/kg/min when the same subjects were studied at a glucose concentration of 118 ± 6 mg/dl. In contrast, the values for glucose metabolic clearance rate (MCR), which were 2.35 ± 0.50 and 2.49 ± 0.47 ml/kg/min, respectively, during the two studies, did not vary significantly with plasma glucose concentration. These data indicate that the glucose metabolic clearance rate (MCR), but not glucose utilization rate (M), can be used to compare in vivo insulin action when insulin clamp studies are performed in subjects with different basal plasma glucose concentrations.
35S-Glycosaminoglycan and 35S-Glycopeptide Metabolism by Diabetic Glomeruli and Aorta
Authors: Brown David M , Klein David J , Michael Alfred F , Oegema Theodore R
Published: September 2013

35S-glycosaminoglycan metabolism by glomeruli isolated from streptozotocin-diabetic and control rats was studied in vivo and in vitro. Total 35S-glycosaminoglycan synthesis and retention in the matrix by diabetic glomeruli was reduced while degradation was increased. 35S-glycosaminoglycan content of isolated GBM was similarly decreased. Whereas 35S-glycosaminoglycan content of glomeruli and GBM was decreased after in vitro incubation with 35SO4, a larger proportion of total 35S-glycosaminoglycans was found in the incubation medium from diabetic glomeruli. Both control and diabetic glomeruli synthesize 35S-labeled glycopeptides, the quantity from diabetic glomeruli being reduced. Aorta from 35SO4-injected diabetic rats also synthesized reduced quantities of 35S-glycosaminoglycans. There were no preferential metabolic alterations of species of 35S-glycosaminoglycans by diabetic glomeruli or aortas. These studies suggest that synthesis of 35S-glycosaminoglycans and 35S-glycopeptides by diabetic glomeruli are altered by disturbances of both synthetic as well as degradative pathways. An alteration of 35S-glycosaminoglycans interaction with matrix components in diabetes is postulated.
Interaction of Insulin and Prostacyclin Production in the Rat
Authors: Lasché Eunice M , Larson Ronald E
Published: September 2013

The effects of hyperinsulinemia on production of prostacyclin (PGI2), a potent inhibitor of platelet aggregation, was studied in vitro in the rat. Aortic rings following 1-h preincubation at 37°C and 1 h at 4°C were incubated with and without purified porcine insulin in Krebs' glucose at 37°C for 5 min and immediately percent inhibition of platelet aggregation was determined. PGI2 production in ng/mg aorta was estimated from a curve using PGI2 standard. The mean PGI2 production was significantly decreased in those rings incubated with insulin in concentration of 2500, 500, and 250 microunits/ml. Likewise, incubation of rings at 22°C for 30 min resulted in at least ten times less PGI2 with insulin. Since PGI2 appears to exert its antiaggregatory effect through cyclic AMP, theophylline was added to the incubation medium resulting in potentiation of inhibition of aggregation which was decreased to control levels when insulin was also added to the medium. Pancreatic slices yielded no significant change in insulin obtained when incubated with and without 5 ng of PGI2 in 2 ml of 2.8 mM glucose, but in a high glucose medium (28 mM) the PGI2-treated slices yielded significantly less insulin. Since PGI2 may play a role in the formation of atherosclerotic plaques, these results suggest a possible deleterious effect of elevated insulin levels in type II and in insulin-treated type I diabetics with regard to macrovascular disease. Suppression of insulin production in presence of PGI2 in high glucose medium resembles the action of other prostaglandins and suggests it may inhibit insulin secretion after a glucose load.
Trapping of Peripheral Blood Lymphocytes in the Pancreas of Patients with Acute-Onset Insulin-dependent Diabetes Mellitus
Authors: Kaldany A , Hill T , Wentworth S , Brink S J , D'elia J A , Clouse M , Soeldner J S
Published: September 2013

Involvement of humoral and cellular autoimmunity in the pathogenesis of insulin-dependent diabetes mellitus (IDDM) is demonstrated by the presence of circulating autoantibodies and the early pancreatic lesion of insulitis. In an effort to detect the early pancreatic lesion in acute onset IDDM, we have labeled peripheral blood lymphocytes with indium oxine 111, reinjected these autologous cells intravenously into the patients, and followed their kinetics over 96 h using an emission computerized tomography (ECT) scanner. The reinjected cells are acutely distributed in the patients' lungs, liver, and spleen (2–12 h). At 24, 48, and 72 h, the labeled lymphocytes are no longer detectable in the lungs or the liver, but are clearly present in the spleen and in the pancreas. Lymphocytic pancreatic infiltration was observed in two of three acute-onset IDDM patients, but not in large number of patients undergoing similar scans for other diseases, suggesting ongoing mononuclear cell infiltration of the pancreas, a possible marker of the lesion of insulitis. Lymphocyte scanning may provide a powerful noninvasive tool for studying patients with IDDM and for selecting those who might benefit from immunosuppressive therapy.
Role of the Kidney in the Metabolism of Fructose in 60-hour Fasted Humans
Authors: Björkman Ola , Felig Philip
Published: September 2013

Arterial (A) and renal venous (RV) concentrations and net splanchnic exchange of glucose, fructose, lactate, pyruvate, glycerol, and alanine were studied in the basal state and during a 135-min intravenous infusion of fructose at 2 mmol/min in healthy subjects after a 60-h fast. After 45 min of the fructose infusion, somatostatin (9 μg/min) was infused for 60 min to induce hypoglucagonemia.

Fructose infusion resulted in a net uptake of this hexose by the kidney as well as the splanchnic bed. Estimated renal uptake of fructose could account for the disposal of 20% of the administered fructose load while splanchnic uptake accounted for 38%. The fructose infusion resulted in a rise in blood glucose of 0.9 mmol/L, a 35% increase in net glucose output from the splanchnic bed, and a consistent net output of glucose from the kidney (A-RV = −0.17 ± 0.05 mmol/L as compared with 0 ± 0.03 in the basal state, P < 0.02). Net glucose release from the kidney could account for 55% of the net renal uptake of fructose. The fructose infusion also resulted in a marked change in renal lactate balance from a net uptake in the basal state (A − RV = 0.05 ± 0.01 mmol/L) to a net output during fructose administration (A − RV = −0.10 ± 0.04). Administration of somatostatih resulted in a fall in arterial glucagon levels and a 35% decrease in splanchnic glucose output but failed to alter the arterial-renal venous difference for glucose observed during the fructose infusion.

We conclude that in 60-h fasted man: (a) intravenous infusion of fructose results in a net uptake of this hexose by the kidney as well as the liver, (b) this uptake is accompanied by stimulation of renal as well as hepatic glucose production and renal production of lactate, and (c) hypoglucagonemia inhibits splanchnic but not renal glucose output during fructose infusion. These data indicate that the kidney is an important site of fructose disposal and that glucose and lactate are end products of renal fructose metabolism.
Selective Effects of Myo-inositol Administration on Sciatic and Tibial Motor Nerve Conduction Parameters in the Streptozocin-Diabetic Rat
Authors: Greene Douglas A , Lewis Richard A , Lattimer Sarah A , Brown Mark J
Published: September 2013

Time-dependent effects of experimental diabetes and dietary myo-inositol supplementation on motor nerve conduction velocity (MNCV) were assessed in two populations of motor nerve fibers in the rat hind limb. These two populations of large myelinated motor fibers, which innervate the musculature of the calf and the foot, were differentially affected by growth, experimental diabetes, and dietary myo-inositol. Dietary myo-inositol supplementation ameliorated the diabetes-induced MNCV impairment in both nerve fiber populations but with different time courses. These observations suggest metabolic or physiologic heterogeneity among populations of large myelinated motor fibers which may partially explain published discrepancies regarding the efficacy of dietary myo-inositol supplementation in improving slowed MNCV in the streptozocin-diabetic rat.
A Possible Mechanism of Insulin Resistance in the Rat Adipose Cell with High-Fat/Low-Carbohydrate Feeding: Depletion of Intracellular Glucose Transport Systems
Authors: Hissin Paul J , Karnieli Eddy , Simpson Ian A , Salans Lester B , Cushman Samuel W
Published: September 2013

The effects of high-fat/low-carbohydrate feeding on glucose transport activity and on the concentrations of glucose transport systems in the plasma and low-density microsomal membranes in isolated rat adipose cells have been examined. Glucose transport activity was assessed by measuring 3-O-methylglucose transport and the concentration of glucose transport systems estimated by measuring specific D-glucose-inhibitable cytochalasin B-binding. Basal glucose transport activity is not significantly influenced by high-fat/low-carbohydrate relative to low-fat/high-carbohydrate feeding and is accompanied by a constant 10 pmol of glucose transport systems/mg of membrane protein in the plasma membrane fraction. In contrast, maximally insulin-stimulated glucose transport activity decreases from 4.72 to 2.29 fmol/cell/min and is accompanied by a decrease from 44 to 26 pmol of glucose transport systems/mg of plasma membrane protein. These diminished effects of insulin on glucose transport activity and the concentration of glucose transport systems in the plasma membrane fraction are paralleled by a 48% decrease in the basal number of glucose transport systems/mg of membrane protein in the low-density microsomal membrane fraction, the source of those glucose transport systems appearing in the plasma membrane in response to insulin. Thus, the “insulin-resistant” glucose transport of the adipose cell with high-fat/low-carbohydrate feeding may be the consequence of a depletion of glucose transport systems in the intracellular pool.
Immunodetection of Insulin After Transfer from Gels to Nitrocellulose Filters: A Method of Analysis in Tissue Extracts
Authors: Kakita Keiji , O'connell Keith , Permutt M Alan
Published: September 2013

This report describes the development of a rapid method for detection of nanogram quantities of insulin in tissue extracts after electrophoresis. Following electrophoresis the proteins are transferred to nitro-cellulose filters and treated with a photoreactive crosslinking agent. Filter bound insulin is detected by antiinsulin antibody and 125I-protein A, followed by autoradiography. The photoaffinity crosslinking is simple, rapid, and stable, and does not require reactive binding sites on derivatized paper. Under these conditions insulin maintains its immunoreactivity yet can be washed extensively to reduce nonspecific background; as little as 10 ng can be visualized. The method has proven to be useful for rapid analysis of qualitative as well as quantitative differences in immunoreactive insulin in tissue extracts.
Effects of Growth Hormone on Insulin Action in Man: Mechanisms of Insulin Resistance, Impaired Suppression of Glucose Production, and Impaired Stimulation of Glucose Utilization
Authors: Rizza Robert A , Mandarino Lawrence J , Gerich John E
Published: September 2013

The present studies were undertaken to assess the mechanisms responsible for growth hormone-induced insulin resistance in man. The insulin dose-response characteristics for suppression of glucose production and stimulation of glucose utilization and their relationship to monocyte insulin binding were determined in six normal volunteers after 12-h infusion of growth hormone and 12-h infusion of saline. The infusion of growth hormone (2 μg · kg−1 · h−1) increased plasma growth hormone nearly threefold (to ≃9 ng/ml) within the range observed during sleep and exercise. This increased plasma insulin (14 ± 1 versus 8 ± 1 μU/ml, P < 0.005) concentrations without significantly altering plasma glucose concentrations or basal rates of glucose production and utilization. Insulin dose-response curves for both suppression of glucose production (half-maximal response at 37 ± 3 versus 20 ± 3 μu/ml, P < 0.01) and stimulation of glucose utilization (half-maximal response at 98 ± 8 versus 52 ± 8 μU/ml, P / 0.01) were shifted to the right with preservation of normal maximal responses to insulin. Monocyte insulin binding was unaffected. Thus, except at near maximal insulin receptor occupancy, the action of insulin on glucose production and utilization per number of monocyte insulin receptors occupied was decreased. These results indicate that increases in plasma growth hormone within the physiologic range can cause insulin resistance in man, which is due to decreases in both hepatic and extrahepatic effects of insulin. Assuming that insulin binding to monocytes reflects insulin binding in insulin sensitive tissues, this decrease in insulin action can be explained on the basis of a postreceptor defect.
Influence of Plasma Glucose and Insulin Concentration on Plasma Glucose Clearance in Man
Authors: DeFronzo Ralph A , Ferrannini Eleuterio
Published: September 2013

We examined the influence of plasma glucose concentration on whole-body glucose uptake and glucose clearance at two physiologic levels of hyperinsulinemia. Twelve healthy, young volunteers were divided into two groups (A and B); each subject participated in three studies. In group A, plasma insulin was raised and maintained by ∼100 μU/ml for 3 h, while plasma glucose concentration was clamped at hypoglycemic (60 ± 1 mg/dl), euglycemic (89 ± 1 mg/dl), or hyperglycemic (165 ± 3 mg/dl) levels. In group B, plasma insulin was raised by ∼50 μU/ml, while plasma glucose was clamped at 62 ± 1,86 ±2, or 143 ± 3 mg/dl for 3 h.

At the higher insulin level (group A), glucose uptake rose from 5.2 ± 0.5 to 7.3 ± 0.6 to 12.2 ±1.0 mg/min· kg as plasma glucose was varied from low to high levels; glucose clearance fell slightly from 8.8 ± 1.0 to 7.8 ± 0.7 to 7.3 ± 0.6 ml/min·kg during the hypo-, eu-, and hyperglycemic clamps (P = NS). At the lower insulin level (group B), glucose uptake rose from 6.0 ± 1.2 to 8.1 ±1.7 mg/min·kg (P < 0.05) with increasing glucose levels, whereas glucose clearance fell significantly (P < 0.01) from 9.7 ± 1.8 to 5.6 ±1.1 ml/min·kg. When the data from both groups were analyzed together, insulin had a stimulatory effect on both glucose uptake and clearance. Elevation of the plasma glucose level had a similar stimulatory effect on glucose uptake (P < 0.001) but inhibited glucose clearance (P < 0.01). This inhibition, however, was modest (14% for the change from hypo- to euglycemia, and 16% for the change from eu- to hyperglycemia).

We conclude that physiologic hyperglycemia exerts a modest inhibitory effect on glucose clearance, which is largely overcome at higher, yet still physiologic, plasma insulin levels (∼100 μU/ml).
The Measurement of Glycosylated Hemoglobin in Man and Animals by Aminophenylboronic Acid Affinity Chromatography
Authors: Yue D K , McLennan S , Church D B , Turtle J R
Published: September 2013

Glycosylated hemoglobin (GHb) was estimated in normal and diabetic human, rat, and dog hemolysate by m-aminophenylboronic acid (PBA) affinity chromatography and the results compared with the values determined using two ion-exchange (ION-E) methods and a colorimetric thiobarbituric acid (TBA) method. There was a good correlation between the values estimated by PBA and both ION-E chromatography methods for the human samples (r = 0.83, P < 0.0002, r = 0.86, P < 0.002). In diabetic rat and dog hemolysates, PBA chromatography demonstrated higher glycosylated hemoglobin than in normal hemolysate. In both species, there was an excellent correlation between the PBA-estimated GHb and plasma glucose levels (rat r = 0.79, P < 0.001; dog r = 0.67, P < 0.003). The IONE and TBA methods were not as effective in separating diabetic from normal samples and correlated less well with plasma glucose levels.

PBA chromatography relies on the interaction of mamino phenylboronate with the hydroxyl groups of the glucose residues attached to hemoglobin. It is not affected by intra- or interspecies variations in the hemoglobin moiety and should be adaptable for measurement of GHb in a number of laboratory animals and in patients with hemoglobinopathy. It is not affected significantly by temperature and may offer advantages over the ION-E method in the routine determination of human glycosylated hemoglobin.
Induction of Insulin-dependent Diabetes by Streptozotocin Inhibition by Estrogens and Potentiation by Androgens
Authors: Paik S-G , Michelis M A , Kim Y T , Shin S
Published: September 2013

Susceptibility of mice to experimental insulin-dependent diabetes as induced by multiple subdiabetogenic doses of streptozotocin has been shown to be strongly gender-dependent, males being much more susceptible than females. We examined this gender difference further in two strains of genetically susceptible mice to determine whether exogenous steroid sex hormones can both suppress the high susceptibility of males and potentiate the low susceptibility of females. Our results show that, in both BALB/cBOM and C57BL/6 mice, exogenous estrogens can suppress the high susceptibility of males. Conversely, the normally streptozotocin-resistant females become as highly susceptible as males after the administration of androgens. The inhibitory effect of estrogens and the potentiating effect of androgens can be demonstrated after the hormones are given to the mice either chronically (in slow-release capsules implanted at a subcutaneous site), or immediately prior to streptozotocin injection. These observations are consistent with the view that the critical factor that determines the susceptibility of mice to the hyperglycemic effects of streptozotocin is not the absolute concentration of androgens per se, but rather the relative overall level of androgens over estrogens in the recipient animal. Several alternative mechanisms for the effect of sex hormones on diabetogenic sensitivity are discussed.
Diabetes Susceptibility of BALB/cBOM Mice Treated with Streptozotocin: Inhibition by Lethal Irradiation and Restoration by Splenic Lymphocytes
Authors: Paik Sang-Gi , Blue Marie L , Fleischer Norman , Shin Seung-Il
Published: September 2013

In genetically susceptible strains of mice, repeated injections of a subdiabetogenic dose of streptozotocin induces the development of progressive insulin-dependent hyperglycemia. We showed previously that host T-cell functions play an obligatory etiologic role in this experimental disease by demonstrating that the athymic nude mouse is resistant to diabetes induction unless its T-cell functions are reconstituted by thymus graft (Paik et al., Proc. Natl. Acad. Sci. USA 77:6129–33, 1980).

Here we show that lethal irradiation of euthymic (+/nu) mice of BALB/cBOM background causes selective resistance of the mice to the diabetogenic effects of the multiple low doses of streptozotocin without affecting their sensitivity to a high pharmacologic dose of the toxin. We also show that reconstitution of the irradiated mice with splenic lymphocytes causes the restoration of diabetes susceptibility. Lethally irradiated mice thus represent a useful experimental model for analyzing the host functions involved in the development of this disease. These results provide an additional support for the hypothesis that the induction of diabetes in this model system is mediated by an autoimmune amplification mechanism.
Fatty Acid Incorporation into Phospholipids of Isolated Pancreatic Islets of the Rat: Relationship to Insulin Release
Authors: Laychock Suzanne G
Published: September 2013

Fatty acid incorporation into specific phospholipids of isolated islets of the rat was investigated using unsaturated [14C]arachidonic acid. Glucose (25 mM) stimulated the incorporation of arachidonic acid into phosphatidylinositol (PI) and phosphatidylcholine (PC) in a time-related manner correlated with two phases of insulin release. Arachidonate incorporation was inhibited by calcium deprivation. The sulfonylurea tolbutamide stimulated an early monophasic release of insulin that was accompanied by increased [14C]arachidonate incorporation into PI and PC. The cholinergic agonist and insulin secretagogue, carbamylcholine, also promoted the incorporation of [14C]arachidonate into PI/phosphatidylserine (PS) and PC fractions. 2-Deoxy-D-glucose, which does not support insulin release, did not enhance arachidonate incorporation into phospholipids. However, phenylephrine, an inhibitor of glucose-induced insulin secretion, stimulated arachidonate turnover in PI. p-Bromophenacyl bromide, an inhibitor of phospholipase A2, markedly depressed both glucose-stimulated arachidonate incorporation into phospholipids and insulin release. The stimulated release of arachidonate from endogenous radiolabeled phospholipids provided additional evidence that phospholipase A2 mediates glucose stimulation. However, since glucose also promoted the incorporation of saturated [14C]palmitic acid into PE (phosphatidylethanolamine) and PI/PS fractions, a phospholipase A1 may also mediate the glucose response. Thus, fatty acid incorporation into islet phospholipids mediates the effects of various secretagogues on insulin release. However, the ability of phenylephrine to stimulate arachidonyl PI turnover suggests that fatty acid turnover is not a sufficient stimulus for release. Augmented levels of unsaturated fatty acids in islet cell membranes may promote fusion or activate enzymes important for hormone release.
The Effect of Continuous Subcutaneous Insulin Infusion on Very-Low-Density Lipoprotein Triglyceride Metabolism in Type I Diabetes Mellitus
Authors: Pietri Angel O , Dunn Fredrick L , Grundy Scott M , Raskin Philip
Published: September 2013

The effect of continuous subcutaneous insulin infusion (CSII) on very-low-density lipoprotein triglyceride (VLDL-TG) metabolism was studied in seven normolipidemic type I diabetic patients. VLDL-TG transport was determined using 3H-glycerol as an endogenous precursor of VLDL-TG, and the resultant turnover curves were evaluated by multicompartmental analysis. Kinetic studies were performed in the diabetic patients during conventional insulin therapy and again after 3 wk of euglycemia achieved with CSII, and the results were compared with those obtained in 5 age-, weight-, and sex-matched normolipidemic nondiabetic subjects.

After 3 wk of CSII, the mean (± SEM) 24-h plasma glucose levels in the diabetic patients decreased from 238 ±15 mg/dl on conventional therapy to 99 ± 11 mg/dl (P < 0.05) on CSII therapy. The total glycosylated hemoglobin levels decreased from 10.2 ± 0.5 to 6.5 ± 0.4%. There was a significant decrease in fasting plasma cholesterol (172 ± 13 mg/dl to 136 ± 4 mg/dl), LDL cholesterol (104 ± 9 mg/dl to 82 ± 4 mg/dl), plasma triglyceride (114 ± 24 mg/dl to 71 ± 9 mg/dl), and VLDL-TG (68 ± 18 mg/dl to 37 ± 5 mg/dl) levels. There was no change in the HDL cholesterol concentration.

Results of the kinetic studies in the conventionally treated diabetic patients revealed normal VLDL-TG transport rates and fractional catabolic rates (FCR). CSII caused a marked and significant fall in mean VLDL-TG transport rates (12.2 ± 3.5 to 4.1 ± 0.8 mg/h/kg IW, P < 0.05) to levels below those observed in the nondiabetic subjects (10.2 ± 2.1 mg/h/kg IW, P < 0.05). There was no change in the mean FCR with CSII. These data thus suggest that the mechanism responsible for the observed change in plasma triglyceride levels in normolipidemic type I diabetic patients that occurs with 3 wk of CSII treatment is due to suppression of hepatic VLDL-TG synthesis rather than the result of increased lipoprotein clearance.
Cell-to-cell Communication in Rat Pancreatic Islet Monolayer Cultures is Modulated by Agents Affecting Islet-Cell Secretory Activity
Authors: Kohen Elli , Kohen Cahide , Rabinovitch Alexander
Published: September 2013

Single islet cells in monolayer cultures of neonatal rat pancreas were microinjected with the fluorescent dye Lucifer Yellow CH and the cultures were observed by combined phase contrast and fluorescent microscopy. The dye spread from an injected cell directly into neighboring islet cells, and successive microinjections of dye into different cells defined territories comprised of 2–6 communicating cells. The number of communicating cells could be modulated by addition to the cultures of different agents known to affect islet cell secretory activity. Cell communication was significantly increased by a high (16.7 mM) glucose concentration, by the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX, 0.1 mM), and by the calcium ionophore, A23187. The effect of A23187 was transient and dose-dependent. Somatostatin (1 μg/ml) significantly inhibited cell communication. These results demonstrate that cell-to-cell communication may participate in the regulation of islet cell secretory activity.
Hyperglycemia and β-Cell Adaptation During Prolonged Somatostatin Infusion with Glucagon Replacement in Man
Authors: Ward W Kenneth , Halter Jeffrey B , Best James D , Beard James C , Porte Daniel
Published: September 2013

To assess the relationship between β-cell function and the level and duration of hyperglycemia during generalized β-cell impairment, we studied the effects of acute and prolonged infusion of somatostatin in seven normal men. Twenty minutes after beginning an acute infusion of somatostatin (200 μg/h) plus glucagon replacement (0.75 ng/kg/min), plasma glucose (PG) remained unchanged, but plasma insulin (IRI) and acute insulin response to isoproterenol had fallen markedly. Seventy minutes after beginning somatostatin-plus-glucagon, a rise in PG was associated with an increase in the acute insulin response to isoproterenol, though not to the control level. In a separate study, after 46 h of the somatostatin-plus-glucagon infusion, at a glucose level similar to the 70-min level, plasma insulin had returned nearly to the control level and the acute insulin response to isoproterenol had returned completely to the control level. Such increases in basal and stimulated insulin secretion most likely represent a time-dependent adaptation by the β-cells to the persistent hyperglycemia. First- and second-phase insulin responses to intravenous glucose were markedly inhibited after 46 h of somatostatin-plus-glucagon. In summary, a 46-h infusion of somatostatin with glucagon replacement in humans leads to hyperglycemia, a slightly diminished basal insulin level, markedly decreased insulin responses to glucose, and an insulin response to isoproterenol maintained at a normal level by acute and probably chronic adaptation to the hyperglycemia. We speculate that β-cell adaptation to hyperglycemia may explain the similar abnormalities of islet function observed in patients with NIDDM.
Counterregulatory Hormone Release and Glucose Recovery After Hypoglycemia in Non-insulin-dependent Diabetic Patients
Authors: Boden Guenther , Soriano Myrna , Hoeldtke Robert D , Owen Oliver E
Published: September 2013

An increasing number of patients with non-insulin-dependent diabetes mellitus (NIDOM) is presently being treated with insulin, some aggressively with intensified treatment schedules. However, there is little information on the ability of these patients to recover from insulin-induced hypoglycemia. We have, therefore, determined glucose recovery and counterregulatory hormone secretion in response to insulin-induced hypoglycemia in 10 NIDDM patients without autonomie neuropathy and in 6 age- and weight-matched normal controls. Recovery of plasma glucose concentration and hypoglycemia-induced increments of plasma concentrations of glucagon, epinephrine, norepinephrine, and HGH were similar in the NIDDM patients and the age-and weight-matched nondiabetic controls. It appears likely, therefore, that these NIDDM patients, if treated aggressively with insulin, may be at lesser risk for severe and prolonged hypoglycemia than insulin-dependent diabetic patients, particularly those with autonomie neuropathy or those treated with beta-adrenergic antagonists.
Low Plasma Somatomedin-C in Streptozotocin-induced Diabetes Mellitus: Correlation with Changes in Somatogenic and Lactogenic Liver Binding Sites
Authors: Maes Marc , Ketelslegers Jean-Marie , Underwood Louis E
Published: September 2013

To determine the mechanism for the decrease of somatomedin levels in insulin-dependent diabetes, the relationships among plasma immunoreactive somatomedin-C (Sm-C), plasma growth hormone (GH) and prolactin (PRL), and the somatogenic and lactogenic binding sites in liver were assessed in rats with nonketotic diabetes mellitus of different duration (1 wk or 1 mo) and severity (50 or 60 mg streptozotocin/kg BW). One week after administration of 60 mg streptozotocin (STZ)/kg, plasma Sm-C concentrations were significantly decreased (0.23 ± 0.03 versus 0.43 ± 0.03 U/ml in controls; mean ± SEM, P < 0.01). In contrast, plasma GH concentrations, bovine GH (bGH) binding, and human GH (hGH) binding were not significantly changed. After 1 mo of diabetes, no further decrease in plasma Sm-C content was observed despite a reduction in plasma GH and PRL concentrations and reduced hepatic bGH binding capacity (5 ± 2 versus 38 ± 4 fmol/mg protein; P < 0.01). In the group of rats injected with 50 mg STZ/kg, the Sm-C was reduced at 1 mo but hepatic GH binding was not.

In a second study, diabetic rats (75 mg STZ/kg) were treated after 3 wk with insulin (10 U lente per day for 7 days). This treatment normalized Sm-C levels and partially restored the GH binding capacity (treated: 49 ± 4 fmol/mg protein versus untreated diabetics: 28 ± 6 fmol/mg protein; P < 0.01 and versus controls: 68 ± 4 fmol/mg protein; P < 0.05). In contrast, prolactin binding capacity remained low (treated: 23 ± 3 fmol/mg protein versus untreated diabetics: 13 ± 2 fmol/mg protein; P > 0.05) and mean plasma GH and PRL were unchanged.

The findings suggest that in an early phase of nonketotic diabetes, the low plasma Sm-C is not due primarily to reduced GH receptor number. Rather, it may reflect diminished Sm-C synthesis at a site distal to the binding of growth hormone to its tissue receptor.
Hyperglycemia-induced Intracellular Depletion of Ascorbic Acid in Human Mononuclear Leukocytes
Authors: Chen Mei S , Hutchinson Martha L , Pecoraro Roger E , Lee Winnie Y L , Labbé Robert F
Published: September 2013

It has recently been reported that glucose and its analogues inhibit in vitro ascorbic acid transport across the cell membrane of polymorphonuclear leukocytes and fibroblasts. We have studied the effect of in vivo hyperglycemia on the intracellular ascorbic acid level of mononuclear leukocytes in normal and diabetic human subjects. Administration of an intravenous glucose load resulted in a prompt decrease of mononuclear leukocyte ascorbic acid level in the normal subjects. The rate of its decline correlated closely with the rate of change of plasma glucose. Among the NIDDM subjects in the fasting state, the plasma glucose was high and the leukocyte ascorbic acid level was low when compared with that of the normal subjects. The decrease in the leukocyte ascorbic acid level during disposition of the i.v. glucose load was not statistically significant in the diabetics. The hyperglycemia-induced intracellular depletion of ascorbic acid could be clinically important and requires further evaluation.
Preparation of High-Potency, Non-aggregating Insulins Using a Novel Sulfation Procedure
Authors: Pongor Sándor , Brownlee Michael , Cerami Anthony
Published: September 2013

The marked propensity of insulin to self-associate into large aggregates causes significant mechanical problems in insulin delivery devices and may also stimulate production of a tissue-amyloid A precursor in some patients. Although conventionally prepared sulfated insulin (SI) resists aggregation, clinical application has been limited by major insulin bioactivity losses that occur during synthesis.

To eliminate this problem, insulin sulfation was carried out in the organic solvent dimethylformamide in the presence of condensing agents such as N,N'-dicyclohexyl carbodiimide (DCC) and a sulfate donor. With this new procedure, the degree of sulfation could be controlled over an eightfold range by varying the amount of condensing agent. The bioactivity of these new SI derivatives varied between 78% and 87% of unmodified insulin. Insulin aggregation, induced by passage through a syringe and needle, did not occur with derivatives having two or more sulfate moieties per insulin molecule. Diffusion velocity studies using “non-aggregated” insulin solutions demonstrated that aggregates were present in crystalline zinc and sodium porcine insulin. In contrast, SI having more than 0.5 mole sulfate per mole of insulin dialyzed as if it were predominantly in the monomeric form.

Results from the studies described in this report now provide the means for selectively designing and preparing specific high-potency, non-aggregating insulins, which may be necessary for optimal use of current and future insulin delivery devices.
Nutrition and Somatomedin. XI. Studies of Somatomedin Inhibitors in Rats with Streptozotocin-induced Diabetes
Authors: Phillips L S , Bajaj V R , Fusco A C , Matheson C K
Published: September 2013

Diabetics may have normal somatomedins by radioimmunoassay yet decreased somatomedin activity by bioassay. The discrepancy appears due to circulating inhibitory factors; inhibitors in whole diabetic serum antagonize the action of both somatomedins and insulin via noncompetitive interactions. Since little is known about the nature of the inhibitory activity, serum from streptozotocin-diabetic rats was fractionated, and inhibitory activity measured as the ability of fractions to blunt stimulation of SO4 uptake by hypophysectomized rat costal cartilage exposed in vitro to somatomedins in normal rat serum.

After establishing that inhibitory activity was stable to pH and lyophilization, diabetic rat serum was gel filtered at pH 7 (somatomedins bound to carrier proteins) and 2.4 (somatomedins dissociated, mol wt ∼8000). Using Sephadex and Sephacryl columns at neutral pH, inhibitors were detected at mol wt ∼250,000, ∼24,000, and ∼940. Predominant activity was at ∼24,000 and ∼940. In contrast, Sephadex columns at acid pH revealed inhibitors only at mol wt ∼21,000. Diabetic rat serum was also subjected to ion-exchange chromatog-raphy on CM-Sepharose. A single band of activity at pH 5–7 was found on elution with increasing pH, suggesting an isoelectric point(s) lower than that of the somatomedins. However, three areas of activity were seen on elution with increasing ionic strength at pH 5— at 0.02 M and 0.14–1.4 M and at 2.0 M pH 5.0–5.5.

These studies indicate that reduced anabolism in diabetes may be due in part to three species of circulating somatomedin inhibitors, largely of mol wt ∼ 21–24,000 and∼940, and also of mol wt ∼250,000. The inhibitors have generally acidic properties, and molecular weights both larger and smaller than the somatomedins.
Red Cell Deformability, Platelet Aggregation, and Insulin Action
Authors: Vague Philippe , Juhan Irène
Published: September 2013

Abnormalities of rheologic and hemostatic properties of blood are present in uncontrolled diabetics and play a role in the development of structural micro- and macroangiopathies.

Red blood cell deformability is decreased in diabetics and shows negative correlation with fast hemoglobin and actual blood glucose levels. In uncontrolled insulin-dependent diabetics, normalization of plasma glucose by an insulin infusion improves red cell deformability in 2 h. Insulin infusion (0.2 U/kg/h) [the initial hyperglycemia being maintained (hyperglycemic clamp)] also improves red cell deformability. Deformability of normal erythrocytes is reduced by incubation in plasma from uncontrolled diabetics but is normal in plasma from diabetics controlled by a 24-h insulin infusion or in diabetic plasma with insulin added in vitro. Therefore, insulin appears to have a direct effect on erythrocyte deformability.

Platelet aggregation measured in whole blood is raised in uncontrolled diabetics. Aggregation of normal platelets rises in the presence of “diabetic” red cells but not in the presence of red cells from the same patients controlled by 24-h treatment with insulin. The effect of insulin on platelet aggregation, therefore, seems to be at least partly mediated by erythrocytes.