bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glycosylated Insulin Complexed to Concanavalin A: Biochemical Basis for a Closed-Loop Insulin Delivery System
Authors: Brownlee Michael , Cerami Anthony 
Published: September 2013

The oligosaccharides maltose, maltotriose, mannotriose, and mannotetrose have been chemically attached to insulin molecules. Incubation of oligosaccharide and insulin at different molar ratios, with or without addition of cyanoborohydride, showed a nearly linear increase in carbohydrate attachment over time. The intravenous t½ of 125I-labeled sugar-insulinderivatives was identical to that of unmodified insulin (3.0 min). Biologic activity of these derivatives, assessed in rats by use of a blood glucose depression assay, did not differ significantly from control.
These glycosylated insulin molecules are reversibly bound to the glucose-binding lectin Concanavalin A (Con A). Such sugar-insulin/lectin complexes serve as an insulin reservoir from which sugar-insulin molecules are displaced by glucose. Release of sugar-insulin molecules is a function of the particular sugar-insulin and of the ambient glucose concentration. Glucose displacement of glycosylated insulin complexed to Con A is in direct proportion to the amount of glucose present in the surrounding fluid. At each glucose concentration, the relative binding affinity of the maltotriose derivative is less than that of the mannotriose derivative, while the relative binding affinity of both maltotriose and mannotriose are less than that of the mannotetrose derivative.
Prolonged incubation at 37°C causes sugar-insulin, like unmodified insulin, to spontaneously aggregate into high-mol-wt, nondiffusable complexes. This aggregation phenomenon was found to be markedly inhibited when glycosylated insulins were synthesized utilizing partially sulfated insulin.
Results from the studies described in this report provide the biochemical basis for a closed-loop, glucose-controlled insulin delivery system, utilizing glyco-sylated insulin complexed to Con A.
The Response of Plasma Triglyceride, Cholesterol, and Lipoprotein Lipase to Treatment in Non-insulin-dependent Diabetic Subjects Without Familial Hypertriglyceridemia
Authors: Pfeifer Michael A , Brunzell John D , Best James D , Judzewitsch Roman G , Halter Jeffrey B , Porte Daniel 
Published: September 2013

The effects of treatment on plasma total triglyceride, total cholesterol, and plasma postheparin lipase activities have not been evaluated in non-insulin-dependent diabetic (NIDD) subjects without a coexisting familial lipid disorder. In 49 untreated NIDD subjects, there was a linear relationship between glycosylated hemoglobin (GHb) and triglyceride (r = 0.35, P &lt; 0.02). This correlation was improved after adjusting for the effects of obesity by a partial correlation analysis. After therapy, there was a significant relationship between the change in GHb and the change in triglyceride.
To determine whether changes in lipid removal from plasma may contribute to the decrease in plasma lipid concentrations during treatment, the plasma postheparin lipoprotein lipase and hepatic lipase activities were evaluated in a subgroup (N = 8) of these NIDD subjects before and after 1 and 3 mo of therapy.
Plasma postheparin hepatic lipase activity in the NIDD subjects was not different from that observed in six normal control subjects and did not change during therapy. In contrast, plasma postheparin lipoprotein lipase activity was lower in the untreated NIDD subjects than in the control subjects. Analysis of the two phases (early and late) of the postheparin lipoprotein lipase activity in plasma showed that the abnormal early phase in untreated NIDD corrected to normal values in less than a month, but the late phase was not corrected until the 3-mo measurement. These findings suggest that some NIDD subjects have a defect in heparin releasable lipoprotein lipase activity, which is reversed with improved glycemic control. This defect in lipoprotein lipase could contribute to the elevation in plasma triglyceride concentration by limiting triglyceride removal from plasma.
Dissociation of Glucose Stimulation of Somatostatin and Insulin Release from Glucose Inhibition of Glucagon Release in the Isolated Perfused Rat Pancreas
Authors: Sorenson Robert L , Elde Robert P 
Published: September 2013

This study investigated the modulating role of glucose on 5 mM arginine stimulation of insulin, somatostatin, and glucagon release from the isolated perfused rat pancreas. As the concentration of glucose was increased linearly from 50 to 300 mg/dl, arginine-stimulated glucagon release was inhibited, with half-maximal inhibition occurring at 84 mg/dl glucose. As glucose increased above 80 mg/dl, somatostatin and insulin release was initiated and they continued to increase in a nearly parallel fashion during the glucose gradient (300 mg/dl). When 5 mM arginine was presented “en block” against varying backgrounds of glucose (30, 60, 75, 90, 120, 150, and 300 mg/dl), glucagon release was diminished in the presence of glucose concentrations greater than 60 mg/dl. Arginine elicited insulin release at all glucose concentrations and was significantly augmented in the presence of glucose greater than 90 mg/dl. Arginine-stimulated somatostatin release was detectable in the 90-mg/dl glucose group and was significantly augmented in the 120- and 150-mg/dl glucose treatment groups.
In conclusion, these studies indicate that glucose modulates the arginine effect on alpha, beta, and delta cells; and alpha cells have a lower threshold to glucose than beta and delta cells. Glucose inhibits arginine-stimulated glucagon release in the absence of a detectable glucose or arginine stimulation of somatostatin release. Thus, glucose appears to play a major role in the control of the putative hormonal influence among the islet cells.
Excessive Nonenzymatic Glycosylation of Peripheral and Central Nervous System Myelin Components in Diabetic Rats
Authors: Vlassara Helen , Brownlee Michael , Cerami Anthony 
Published: September 2013

The amount of nonenzymatic glycosylation present in normal and diabetic rat peripheral nerve myelin, whole brain, brain myelin, and individual myelin protein components was determined using NaB3H4 reduction followed by either boronic acid affinity chromatography or SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Diabetic peripheral nerve myelin (PNS-M) showed a 5.2-fold increase over normal, indicating that myelin is the major peripheral nerve component undergoing excessive glycosylation in diabetes. SDS-PAGE of diabetic and normal PNS-M showed no differences in the pattern of protein bands or in the distribution of glycosylated adducts. However, in the diabetic, the amount of incorporated radioactivity was 3.74 times greater in the P0 protein and 2.8 times greater in the high-molecular-weight material that did not enter the gel.
In whole brain, a 2.4-fold increase in the amount of nonenzymatic glycosylation was observed when diabetic was compared with normal, while diabetic brain myelin (CNS-M) was 3.8 times more glycosylated than normal brain myelin. SDS-PAGE of diabetic and normal CNS-M, like that of PNS-M, showed no differences in the pattern of protein bands or in the distribution of glycosylated adducts. The amount of incorporated radioactivity, however, was 3.18 times greater in the proteolipid region, 2.37 times greater for basic myelin protein, and 2.9 times greater for the high-molecular-weight proteins that did not enter the gel.
This excessive nonenzymatic glycosylation of the main peripheral and central nervous system myelin components may contribute to the functional abnormalities of myelinated neurons associated with diabetes.
Effect of Dynorphin on Insulin and Somatostatin Secretion, Calcium Uptake, and c-AMP Levels in Isolated Rat Islets of Langerhans
Authors: Green I C , Perrin D , Penman E , Yaseen A , Ray K , Howell S L 
Published: September 2013

Dynorphin-[1-13], at concentrations of 5.8 × 10−12 to 5.8 × 10−9 M, stimulated insulin secretion from isolated islets of Langerhans of the rat, in medium containing 6 mM glucose. Higher concentrations of dynorphin had no significant effect on secretion. Dynorphin (5.8 × 10−9 M) was unable to initiate insulin release from islets in the presence of 2 mM glucose, or to increase insulin secretion further in the presence of 20 mM glucose or 6 and 12 mM glyceraldehyde. Dynor-phin-induced insulin secretion from islets was blocked by verapamil (5 μM) or by chlorpropamide (72 μM), but not by a mu opiate receptor antagonist, naloxone (0.11 μM), or by ICI 154129, a specific antagonist for the delta receptor (0.25 μM).
Dynorphin had no effect on islet somatostatin secretion, under conditions in which insulin secretion was greatly stimulated. Glucose (20 mM) and glyceraldehyde (6 and 12 mM) significantly increased both insulin and somatostatin secretion.
Dynorphin (5.8×10−9 M) increased 45Ca2+ uptake into islets, and also increased intracellular islet c-AMP levels. These changes persisted when higher concentrations of dynorphin were used.
These results suggest that (1) dynorphin is a very potent stimulus for insulin secretion; (2) dynorphin does not affect somatostatin secretion in static incubations of islets, in the same way as does glucose and glyceraldehyde; (3) dynorphin's effects may involve increased calcium ion movement and can be blocked by verapamil; (4) dynorphin can also increase islet c-AMP, and could thereby modulate the responsiveness of other secretagogues; (5) the actions of dynorphin on insulin secretion are not mediated by delta or mu opiate receptors in islets.
Glucose Turnover During Recovery from Intensive Exercise
Authors: Calles Jorge , Cunningham John J , Nelson Lisa , Brown Nancy , Nadel Ethan , Sherwin Robert S , Felig Philip 
Published: September 2013

This study was undertaken to examine glucose turnover during a 30-min recovery period following an acute bout of intensive exercise (85% VO2 max) performed to exhaustion (11.7 ± 1.4 min). Plasma glucose (basal 85 ± 2 mg/dl) rose by 10 mg/dl at exhaustion and increased further during the initial phase of recovery, reaching a peak value of 35 mg/dl above basal at 5 min of recovery. Thereafter, there was a gradual decline, but the values remained 15–20 mg/dl above basal at 30 min. The early rise in plasma glucose during recovery was due to an imbalance between glucose production and utilization caused by a more rapid decline in utilization than production. At 5 min of recovery, glucose production was fivefold greater than in the basal state and comparable to peak values observed at exhaustion, while glucose utilization was 33% lower than observed at exhaustion and only 75% higher than in the basal state. Beyond 5 min of recovery glucose utilization and production again differed in the direction of response. Glucose production fell to basal values while glucose utilization remained 70–80% above baseline. The maintenance of basal rates of glucose production and increased rates of glucose utilization occurred in a setting in which plasma insulin levels were increased by 25–50%. Plasma catechol-amines, which rose 5–10-fold during exercise, fell rapidly during the initial 3 min of recovery.
We conclude that recovery from exhaustive exercise is characterized by a biphasic imbalance between glucose production and utilization in which production exceeds utilization for the initial 5 min and utilization exceeds production at 10–30 min. The hormone-substrate milieu (modest increments in plasma insulin and glucose) accompanying the changes in glucose kinetics observed beyond 5 min suggests that the recovery period from acute exercise may be characterized by an increase in peripheral sensitivity to insulin, which could provide a mechanism for facilitating muscle glycogen repletion during recovery from intensive exercise.
The Onset and Progression of Pancreatic Insulitis in the Overt, Spontaneously Diabetic, Young Adult BB Rat Studied by Pancreatic Biopsy
Authors: Logothetopoulos John , Valiquette Nancy , Madura Ewa , Cvet David 
Published: September 2013

A specially developed clamping procedure permitted the easy, complication-free removal of splenic pancreas from rats. Using this biopsy procedure pancreatic tissue was removed from 50- to 90-day-old BB rats to study in a retrospective experimental design the time at which insulitis appears in BB rats, which develop acute, overt diabetes before the age of 120 days. Islets in biopsies taken 18–53 days before the onset of diabetes showed normal structure and were free from any mononuclear infiltrations. Biopsies removed between 2 and 9 days before onset of diabetes in contrast showed widespread insulitis. In five rats in which the biopsy preceded the manifestation of diabetes by 11–16 days, only a small number of pancreatic islets showed small focal mononuclear cell infiltrations. Most of the islets in these five rats had a normal histologic appearance.
Thus the lesions within the islets develop rapidly starting about 2–3 wk before overt diabetes. As revealed by autoradiography, pancreatic beta-cells still surviving at the time of onset of diabetes show a modest increase in replicative activity. Replicative activity of mononuclear inflammatory cells also was observed, suggesting that their accumulation within the islet tissue may result in part from local replication.
Visualization of the Insulin Receptor by Immunoblotting
Authors: Maron Ruth , Kahn C Ronald , Jacobs Steven , Fujita-Yamaguchi Y 
Published: September 2013

Insulin receptors from rat hepatoma cells (Fao) and human placenta were partially purified by detergent solu-bilization and lectin purification. The insulin receptor preparations were subjected to sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis under reducing or nonreducing conditions. The proteins were transferred to nitrocellulose paper and the electropho-retic blots were treated with human anti-receptor auto-antibodies, rabbit antibody to purified insulin receptor, or a monoclonal antibody to human insulin receptor. The nitrocellulose paper was then treated with 125I protein A or 125I second antibody followed by autoradiog-raphy.
The rabbit polyclonal antiserum and one of the human autoantibodies recognized both the α(Mr = 135,000) and β (Mr = 95,000) subunits after transfer from a SDS gel to nitrocellulose paper. On transfers from nonreduced gels, several high-molecular species were labeled ranging from Mr = 200,000 to Mr = 330,000. Similar high-molecular bands of the receptor were seen if highly purified human placental receptor, as well as partially purified receptor from rat or human origin, were used. As little as 0.1–0.5 μg of pure receptor could be detected by this technique. Treatment of the receptor with neuraminidase (50 mU/ml) before gel electrophoresis resulted in a 50% increase in intensity of intact receptor and about a 70% increase in the labeling of the α-subunit of the receptor, but no change in labeling of the β-subunit. The monoclonal antibody used, as well as two other human autoantibodies, did not recognize the receptor after transfer to nitrocellulose paper.
In summary, it was possible to determine the reaction of different antisera with the antigenic domains of the insulin receptor using Western blotting techniques. Removal of terminal sialic acid residues appears to increase reactivity with some antisera.
Role of Sympathetic Nervous System in Glucagon Response to Insulin Hypoglycemia in Normal and Diabetic Rats
Authors: Patel D G 
Published: September 2013

The effects of adrenergic blockers on the glucagon response to insulin hypoglycemia were investigated in diabetic (10–15 days poststreptozocin [STZ] injection) and age-matched control rats, α-(Phentolamine nonspecific but predominantly α1), α2(yohimbine), or β-(propranolol) adrenergic blockers alone or in combination did not affect plasma glucose levels or plasma glucagon concentrations, in the basal state, in either control or diabetic rats. None of these adrenergic blockers, alone or in combination, inhibited the glucagon response to insulin hypoglycemia in control or diabetic rats. On the contrary, in control rats, the β-adrenergic blocker alone or in combination with an α-adrenergic blocker and in diabetic rats, the α-adrenergic blocker alone significantly stimulated the glucagon response to insulin hypoglycemia.
Second, the effects of yohimbine on the glucagon response to epinephrine infusion were studied in both young and old rats. Recently, Cherksey et al. (Proc. Soc. Exp. Biol. Med. 1982; 171:196–200) have reported that the adrenergic receptors on rat pancreatic islet cells are of the α2-subtype. Yohimbine (α2-adrenergic blocker) completely blocked the glucagon response to epinephrine infusion in both young and old rats, but had no inhibitory effect on the glucagon response to insulin hypoglycemia in control and short-term diabetic rats. From these observations, it could be inferred that the lack of glucagon response to insulin hypoglycemia in long-term diabetic rats is unlikely to be explained by an impairment of an adrenergic function.
Effects of Physical Training and Diet Therapy on Carbohydrate Metabolism in Patients with Glucose Intolerance and Non-insulin-dependent Diabetes Mellitus
Authors: Bogardus Clifton , Ravussin Eric , Robbins David C , Wolfe Robert R , Horton Edward S , Sims Ethan A H 
Published: September 2013

The effects of 12 wk of physical training in addition to hypocaloric diet (DPT group, N = 10) on body composition, carbohydrate (CHO) tolerance, and insulin secretion and action were compared with the effects of diet therapy alone (D group, N = 8) in CHO-intolerant and non-insulin-dependent diabetic subjects.
Fat mass, fat-free mass (FFM), mean fasting plasma glucose, serum C-peptide, and insulin concentrations decreased similarly in both groups. The mean plasma glucose response to a mixed meal decreased approximately 20% in both treatment groups, and, after i.v. glucose, decreased 12% in the D group (P &lt; 0.05), but did not change in the DPT group (NS between groups). The acute serum insulin response (0–6 min) after IG increased significantly in the DPT group only (NS between groups).
The mean basal endogenous glucose production (BEGP) decreased 17% (P &lt; 0.025) in the DPT group and by 31% (P &lt; 0.01) in the D group (NS between groups). Hepatic sensitivity to insulin, estimated by BEGP suppression during the euglycemic clamp, increased significantly by 25% in both groups. Total glucose disposal during the euglycemic clamp increased from 3.51 ± 0.04 milligrams of glucose per kilogram of fat-free mass per minute (mg/kg-FFM/min) to 4.45 ± 0.54 mg/kg-FFM/min (P &lt; 0.05) in the DPT group, but no change occurred in the D group (NS between groups). Separation of total glucose disposal rates into CHO oxidative and nonoxidative rates using indirect calorimetry during the euglycemic clamp showed that the mean CHO oxidation rate increased in the D group (P &lt; 0.05), but not in the DPT group (NS between groups). There was, however, a significant difference in the mean CHO nonoxidative rate between the two groups (P &lt; 0.05), increasing in the DPT group but decreasing in the D group.
In both groups, the improvements in fasting plasma glucose and meal tolerance appeared to be attributable mostly to decreased BEGP, with increased hepatic sensitivity to insulin. However, glucose disposal was accomplished by different mechanisms in the two groups.
The Insulin Sensitivity Index: Correlation in Dogs Between Values Determined from the Intravenous Glucose Tolerance Test and the Euglycemic Glucose Clamp
Authors: Finegood Diane T , Pacini Giovanni , Bergman Richard N 
Published: September 2013

We previously proposed the insulin sensitivity index, S1as an absolute measure of whole body tissue sensitivity to insulin. S1 is defined, in the physiologic range of insulin action, as the effect of insulin to augment glucose's ability to reduce its own plasma level. This parameter can be determined from the frequently sampled intravenous glucose tolerance test (IVGTT) by using a digital computer to find the coefficients of a minimal mathematical model of glucose kinetics. In the present study we compared, in normal dogs, S, determined from the IVGTT to an analogous parameter “S1(clamp)” calculated from the euglycemic glucose clamp (EGC). Fifteen pairs of experiments (1 IVGTT and 1 EGC) were performed on 12 animals. IVGTTs: After glucose injection (0.3 g/kg), frequent blood samples were taken over the subsequent 3 h. KG ranged from 1.7 to 4.7 %/min, and integrated insulin from 0.4 to 5.9 (μU/ml) min for 0–60 min. S1 varied over a ninefold range from 1.0 to 9.1 × 10−4 (min−1)/μU/ml), with a mean of 4.3 ± 0.7 × 10−4. Fractional glucose disappearance rate independent of insulin (p1) was 4.3 ± 0.5 %/min. EGCs: Low-rate insulin infusion (8 mU/min from 1 to 150 min) elevated plasma insulin (INS) from 15 ± 4 to 43 ± 10 μU/ml. Glucose was infused (GINF) at 119 ± 20 mg/min to maintain euglycemia. Moderate insulin infusion (40 mU/min: 151–300 min) further elevated plasma insulin (to 176 ± 37 μU/ml) and the requisite glucose infusion (to 372 ± 36 mg/min). S1(clamp) was calculated in steady state as the increase in glucose infusion per increment in insulin above basal, normalized to the basal glucose and body weight [GINF/(Gb × BW × δINS)]. S1(clamp) ranged from 3.1 to 40.5 × 10−4 (dl/kg/min)/μU/ml). The values of S1 and S1(clamp) were highly correlated (r = 0.82, P &lt; 0.005).
These studies suggest that the insulin sensitivity index, S1determined from the IVGTT is a useful measure of insulin sensitivity, which is capable of differentiating sensitivities among a normal population.
Stimulation of Retinal Capillary Pericyte Protein and Collagen Synthesis in Culture by High-Glucose Concentration
Authors: Li Weiye , Shen Shuyu , Khatami Mahin , Rockey John H 
Published: September 2013

The influence of glucose concentration on cell multiplication and protein synthesis was studied in synchronized, long-term cultures of bovine retinal microvessel pericytes. The cell multiplication rate and the mitotic rate were reduced in media containing 20 mM glucose to 57% and 54%, respectively, of that obtained in media containing 5 mM glucose. Elevated glucose, however, did not change the DNA content of individual cells.
Protein and collagen synthesis were measured by the incorporation of radioactive proline and lysine, or the posttranslational production of hydroxyproline and hydroxylysine, respectively. High glucose stimulated protein and collagen synthesis per cell 2.2 ± 0.10 (SD) and 2.1 ± 0.06 times, respectively. Aspirin (0.5 mM), an inhibitor of nonenzymatic glycosylation, did not alter the effect of elevated glucose concentration on protein and collagen synthesis.