bluuebunny/crossref_metadata_2025 huggingface dataset:
Determinants of the Penetration of Proteins Through the Glomerular Barrier in Insulin-dependent Diabetes Mellitus
Authors: Viberti Giancarlo , Mackintosh David , Keen Harry
Published: September 2013

To investigate the determinants of the glomerular filtration of proteins in insulin-dependent diabetic patients we studied the fractional clearance of albumin (θAlb) and IgG (θIgG) and the selectivity index (SI = IgG clearance/Alb clearance) in 32 subjects with macroproteinuria (albustix positive), in 29 subjects with microproteinuria (albustix negative), and in 24 healthy control subjects. Fractional clearances of both albumin and IgG were higher in macroproteinuric than in microproteinuric patients, with both groups having higher values than controls (all P < 0.001). In microproteinuric patients with albumin excretion rate (AER) not exceeding 60 μg/min, there was a highly significant correlation between the clearance of albumin and that of IgG. The SI was normal for AERs up to 30 μg/min, but above that albumin filtration increased disproportionately and SI progressively fell.

In insulin-dependent diabetics with macroproteinuria, there was a negative correlation between SI and glomerular filtration rate (GFR) (r = −0.68; P < 0.001); the lower SI (0.133 ± 0.06) at higher GFRs also was due to a preferential increase in albumin clearance. Selectivity was progressively lost as GFR declined, and the SI returned to normal values when GFR fell below 10 ml/min/1.73 m2; this was due to a progressively higher rise in the fractional clearance of IgG relative to albumin. We suggest that glomerular filtration of proteins is governed by different determinants at different stages of the disease. In microproteinurics with AER below 60 μg/min, increased intraglomerular pressure seems primarily responsible for the higher proportional filtration of both albumin and IgG. A charge selectivity defect accounts for the proteinuria of microproteinuric diabetics with AERs above 60 μg/min and for that of macroproteinuric diabetics with unreduced GFR since albumin, a polyanion, is preferentially filtered. Pore size selectivity loss is added to the depletion of membrane polyanions in the proteinuria of late nephropathy because the filtration of IgG, a larger but neutral protein, increases relatively more than that of albumin.
Effect of Experimental Diabetes on the Levels of Aromatic and Branched-Chain Amino Acids in Rat Blood and Brain
Authors: Crandall Elizabeth A , Fernstrom John D
Published: September 2013

Male rats treated 3 wk earlier with streptozotocin showed abnormally high blood levels of leucine, isoleucine, and valine throughout the 24-h period. Serum phenylalanine levels were slightly increased, while those of tryptophan and tyrosine were occasionally reduced. In brain, the level of each branched-chain amino acid was significantly increased above normal at all times. The brain concentration of each aromatic amino acid was always below normal. These changes were restored almost to normal by exogenous insulin therapy. Since the ingestion of protein is normally a major factor influencing blood amino acid levels, the effect of ingesting single, protein-containing meals on the blood and brain levels of these amino acids was also studied. After an overnight fast, the ingestion of a protein-containing meal by diabetic rats increased substantially both blood and brain levels of each branched-chain amino acid. No such increases occurred in normal rats. Ingestion of this meal produced only small changes in the brain and blood levels of the aromatic amino acids in both diabetic and normal rats. The changes in the brain level of each large neutral amino acid in some cases paralleled those in its blood level. More often, they paralleled the changes in the blood ratio of each amino acid to the sum of the other aromatic and branched-chain amino acids/. This ratio is often a good predictor of the competitive transport of these amino acids into brain (Fernstrom and Faller, 1978). The observed changes in the brain levels of these amino acids in diabetes may influence the rates at which they are consumed in metabolic pathways Within this organ.
Very-Low-Density Lipoprotein Triglyceride Metabolism in Non-insulin-dependent Diabetes Mellitus: Relationship to Plasma Insulin and Free Fatty Acids
Authors: Howard Barbara V , Reitman James S , Vasquez Barbara , Zech Loren
Published: September 2013

To investigate the mechanism of elevated plasma triglycerides in non-insulin-dependent (type II) diabetes, very-low-density lipoprotein triglyceride (VLDL-TG) metabolism was studied in 10 untreated male Pima Indian diabetics and compared with that of 15 weightmatched male nondiabetic controls. VLDL-TG metabolism was studied using tritiated glycerol as an endogenous precursor of VLDL-TG, and the resultant kinetic data were analyzed using a multicompartmental model, which includes two pathways for VLDL-TG synthesis and a stepwise delipidation process for VLDL catabolism. Pima diabetics had VLDL-TG concentrations approximately 150% those of nondiabetics. Rates of VLDL-TG production in the diabetics were not significantly different from those of controls. On the other hand, the fractional catabolic rate for VLDL-TG was significantly lower in the diabetics compared with the nondiabetics. Other catabolic parameters, such as the fraction of VLDL-TG delipidized at each step and the stepwise delipidation rate, were also decreased in the diabetics. To determine the relationships between the increased triglycerides and determinants of lipid metabolism that are altered in diabetes, insulin and free fatty acid concentrations were also assessed. Basal C-peptide levels in the diabetics during the metabolic study were slightly but not significantly higher than those of the nondiabetics. There was a highly significant correlation in the diabetics between plasma C-peptides and VLDL-TG production, whereas VLDL production in Pima nondiabetics was not related to insulin levels. Free fatty acid levels were not significantly elevated in the Pima diabetics. The data indicate that (1) the rise in VLDL-TG in Pima diabetics was a result of decreased capacity for clearance and (2) the absence of elevated VLDL-TG production may be attributed to the lack of increase in free fatty acids.
Effect of Poly(ADP-ribose) Synthetase Inhibitor Administration to Rats Before and After Injection of Alloxan and Streptozotocin on Islet Proinsulin Synthesis
Authors: Uchigata Yasuko , Yamamoto Hiroshi , Nagai Hideaki , Okamoto Hiroshi
Published: September 2013

Nicotinamide (10 mmol/kg) and 3-aminobenzamide (1.25 mmol/kg), poly(ADP-ribose) synthetase inhibitors, were injected intravenously to rats either 30 min before the intravenous administration of 12 mg/kg alloxan or 50 mg/kg streptozotocin (“Pretreatment”) or 5 min after the administration (“posttreatment”). Fifteen minutes after the injection of the diabetogenic agents, pancreatic islets were isolated from the rats and proinsulin synthesis was determined. Proinsulin synthesis was decreased in islets from rats treated with alloxan or streptozotocin. Pretreatment with poly(ADP-ribose) synthetase inhibitors was found to protect against alloxan- or streptozotocin-induced decrease in proinsulin synthesis. By posttreatment with poly(ADP-ribose) synthetase inhibitors, streptozotocin-induced decrease in proinsulin synthesis was also significantly reversed, whereas the decrease induced by alloxan was not.
Insulin and Insulin-like Growth Factor I: Effects on Protein Synthesis in Isolated Muscles from Lean and Goldthioglucose-Obese Mice
Authors: Monier Solange , Cam Alphonse Le , Marchand-Brustel Yannick Le
Published: September 2013

The effects of insulin and insulin-like growth factor I (IGF-I) on protein synthesis were compared in muscle isolated from lean and goldthioglucose (GTG)-obese mice. Two types of skeletal muscles, the red soleus and the white extensor digitorum longus (EDL) muscles, were studied. In muscles from lean mice, 6.7 nM insulin and 50 nM IGF-I caused a similar maximal stimulationof tyrosine incorporation in total proteins (40% increase). However, the potency of IGF-I was only 5–10% that of insulin both in soleus and in EDL muscles (EC50 ≅ 6 nM for IGF-Iand 0.5 nM for insulin). Basal rate of protein synthesis was identical in muscles from GTG-obese and lean mice. Similarly, a comparable increase in the rate of protein synthesis was obtained using maximally effective concentrations of insulin and IGF-I in both lean and GTG-obese animals. SDS-polyacrylamide gel electrophoresis analysis of proteins labeled with 35S-methionine confirmed that, in muscles from lean and GTG-obese animals, insulin and IGF-I increased overall protein synthesis in a similar manner. These results suggest that the protein synthesis machinery is not impaired in GTG-induced obesity, which is therefore not associated with resistance to insulin for its effect on protein metabolism.
Discrepancy Between Plasma C-Peptide and Insulin Response to Oral and Intravenous Glucose
Authors: Madsbad Sten , Kehlet Henrik , Hilsted Jannik , Tronier Bente
Published: September 2013

Plasma insulin, proinsulin, and C-peptide responses to 25 g glucose orally and intravenously administered were measured in 10 healthy males. Plasma insulin response was higher during the oral load in accordance with the “incretin” concept. However, the actual amountof insulin secreted, as measured by the plasma C-peptide response, was similar during the two glucose loads. The higher plasma insulin response after oral glucose was not due to crossreactivity with proinsulin in the insulin assay. These results suggest that the higher plasma insulin response during an oral glucose load is due at least partially to a lower hepatic extraction of insulin.
Glucose Insensitivity and Amino-acid Hypersensitivity of Insulin Release in Rats with Non-insulin-dependent Diabetes: A Study with the Perfused Pancreas
Authors: Giroix Marie-Hélène , Portha Bernard , Kergoat Micheline , Bailbe Danielle , Picon Luc
Published: September 2013

Non-insulin-dependent diabetes (NIDDM) was obtained in adult rats following a neonatal streptozotocin injection. Rats with NIDDM exhibited slightly lowered plasma insulin, slightly elevated basal plasma glucose values (<200 mg/dl), anancreatic insulin stores (50% of the controls). Insulin secretion was studied in this model using the isolated perfused pancreas technique.

Insulin response to glucose stimulation over the range 5.5–22 mM was lacking, thus indicating complete loss of B-cell sensitivity to glucose. Even in presence of theophylline, the B-cells remained insensitive to glucose. In contrast, glyceraldehyde elicited an insulin release as important as that obtained in the control pancreata. This could possibly suggest that the Bcell dysfunction in rats with NIDDM involves a block in glucose metabolism in the early steps of glycolysis prior to the triose-phosphate. Mannose stimulated insulin secretion less in the diabetics than in the controls. The insulin secretion obtained in response to isoproterenol indicated that the ability of the adenylcyclase to generate cAMP in the B-cells of the diabetics was not decreased. The insulinotropic actions of acetylcholine and tolbutamide were normal and increased, respectively, as compared with the controls.

In the absence of glucose, the B-cells of the diabetics were unexpectedly hypersensitive to arginine and leucine. The α-ketoisocaproate effect in the diabetics was not significantly different from that obtained in the controls. The possibility that enhancement of insulin response to leucine in the diabetics might be related to a more active conversion of leucine to ketoisocaproate along the first steps of intraislet leucine metabolism is proposed.
The Effect of an Aldose Reductase Inhibitor (Sorbinil) on the Level of Metabolites in Lenses of Diabetic Rats
Authors: Gonzalez Ana-Maria , Sochor Milena , McLean Patricia
Published: September 2013

This study examined the effect of an aldose reductase inhibitor (Sorbinil, CP 45634,Pfizer, Sandwich, Kent, United Kingdom) on the metabolite profile of the lens during the first week after induction of diabetes with alloxan. The lens content of sorbitol, fructose, glycerol 3-phosphate, and glucose 6-phosphate was, respectively, 0.33 ± 0.03, 0.55 ± 0.05, 0.10± 0.01, and 0.074 ± 0.006 μmol/g (means ± SEM) in the control group rising to 12.2 ± 0.52, 3.20 ± 0.10, 0.76 ± 0.10, and 0.200 ± 0.009 in lenses from alloxan-diabetic rats. Sorbinil treatment (40 mg/kg) decreased the lens content of sorbitol to 0.60 ± 0.06, fructose to 0.85 ± 0.08, and glycerol 3-phosphate to 0.36 ± 0.03 μmol/g; glucose 6-phosphate remained unchanged. Significantly, the lens content of glutathione was decreased to 60% of the normal value in the diabetic group, but was sustained at normal levels with Sorbinil treatment. The ATP content of the lens was not altered by diabetes or Sorbinil treatment at this time interval. Sorbinil has no significant effect on the above metabolites in the normal rat lens. The effect of Sorbinil in restoring normal levels of glutathione and glycerol 3-phosphate may be a potentially important facet of the action of this drug. The interlocking of metabolic pathways by the redox state of NAD+ /NADH and NADP+/NADPH, their derangement in diabetes, and the wider effects of Sorbinil on the network of reactions in the lens are discussed.
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.
Quantitative Vitreous Fluorophotometry in Insulin-treated Cystic Fibrosis Patients
Authors: Rodman Harvey M , Waltman Stephen R , Krupin Theodore , Lee Amy T , Frank Kay E , Matthews LeRoy W
Published: September 2013

A series of 22 patients with cystic fibrosis (CF) of similar clinical severity (9 with normal carbohydrate tolerance and 13 with insulin-treated fasting hyperglycemia) was examined with quantitative vitreous fluorophotometry. All of the CF patients studied had normal fundi on ophthalmoscopy, fundus photographs, and fluorescein angiography. Mean vitreous fluorescein concentration in the CF patients whose hyperglycemia was treated with insulin (11.79 ng/ml) was significantly higher than in CF patients with normal carbohydrate tolerance (6.98 ng/ml, P < 0.005). Thus, CF patients with fasting hyperglycemia demonstrate a breakdown of the bloodretinal barrier. When CF patients with fasting hyperglycemia were compared with age- and sex-matched type I diabetics, there was no significant difference in mean vitreous fluorescein accumulation. Thus, breakdown of the blood-retinal barrier, one of the earliest detectable functional abnormalities that may be associated with the microangiopathy of diabetes mellitus, also occurs with equal frequency and severity in the diabetes secondary to pancreatic fibrosis associated with CF.
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 < 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.
Developmental-Stage-dependent Teratogenic Effects of Maternal Spontaneous Diabetes in the Chinese Hamster
Authors: Funaki Kenji , Mikamo Kazuya
Published: September 2013

The effect of maternal diabetes on teratogenesis was examined utilizing female Chinese hamsters with typical diabetic symptoms from our closed colony (CHA) and F13–F19 of the brother-sister mating generations of a diabetic strain (CHAD). Both groups were mated with nondiabetic males from CHA. Embryologic studies on day 2.5, 4.5, and 18.5 of gestation were performed with 30, 31, 71 diabetic females that were impregnated during a normal 4-day estrous cycle. The preimplantation embryos of day 2.5 and 4.5 were also karyotyped. The results indicated that: (1) There was no decrease in the number of ovulated ova, of collected embryos, and of implantation sites in the diabetic females. (2) As far as the preimplantation stages were concerned, there was no decrease in the cleavage activity and no increase in the incidence of developmental anomalies. (3) There was no increase of chromosomal aberrations in the preimplantation embryos. (4) With respect to the postimplantation development, however, there were significant increases in embryonic death (P < 0.001), gross malformation (P < 0.001), and fetal hypoplasia (P < 0.001). Results (1), (2), and (3) indicated that in diabetic females capable of conceiving during a normal estrous cycle, the maternal diabetic milieu did not affect oogenesis, ovulation, fertilization, cleavage division, implantation, and chromosomal behavior. Result (4), however, showed definitely that maternal diabetes exerted deleterious effects on fetal development during the stage of organogenesis, and also markedly reduced fetal growth during later developmental stages.
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.
Diabetes-induced Metabolic Alterations in Heme Synthesis and Degradation and Various Heme-containing Enzymes in Female Rats
Authors: Bitar Milad , Weiner Myron
Published: September 2013

Diabetes-induced alterations in heme and hemoproteins, as well as its relationship to drug-mediated induction of ALA Synthase (ALA-S), were examined in female Sprague-Dawley rats. Animals were rendered diabetic by a single i.v. injection of streptozotocin (STZ, 65 mg/kg) and measurements were made at various times after treatment. The basal levels of the key enzymes involved in heme synthesis, ALA-S and ALAdehydratase (ALA-D), were decreased about 36% and 54%, respectively, 44–46 days after diabetes induction. Furthermore, the catabolism of heme that occurs via microsomal heme oxygenase progressively decreases in activity during the course of diabetes, and reaches 69% of control in 90-day diabetic animals. The basal levels of heme, cytochromes P-450 and b5 were elevated about twofold in diabetic rats as compared with their corresponding control values. The activity of benzo(a)pyrene hydroxylase in diabetic rats was also increased in proportion to the microsomal content of cytochrome P-450. In contrast, Δ4-hydrogenase, the rate-limiting enzyme in corticosterone metabolism, exhibited a 35–65% decrease in activity throughout the experimental period. Tryptophan pyrrolase activity (total, holo-, and apoenzyme) was elevated about 2.5-fold in STZ diabetic rats. In vivo insulin therapy of diabetic animals antagonized the effect of the diabetic state on the above measured parameters. Treatment with aminoglutethimide resulted in about a twofold elevation in ALA-S activity in control as well as chronically diabetic rats. However, a similar stimulatory response in ALA-S activity to CoCI2 administration was observed only in control or insulin-treated diabetic rats. These results suggest that diabetes produced subtle and important disruption in cellular hemoprotein metabolism, possibly as a consequence of a biochemical defect in the hepatic enzymes involved in heme synthesis and/or degradation.
Red Blood Cell Sorbitol as an Indicator of Polyol Pathway Activity: Inhibition by Sorbinil in Insulin-dependent Diabetic Subjects
Authors: Malone John I , Leavengood Hanzel , Peterson Michael J , O'brien Mark M , Page Michael G , Aldinger Charles E
Published: September 2013

In a double-blind crossover study of 15 diabetic patients, elevated red blood cell (RBC) sorbitol levels were reduced by oral doses of the potent aldose reductase inhibitor, sorbinil (250 mg o.d.), to near-normal ranges. In diabetic rats with severe hyperglycemia, oral sorbinil (5 mg/kg) dramatically reduced (80–90%) sorbitol levels in tissues without affecting blood glucose; the RBC dose-response curve was similar to that in lens and sciatic nerve. In streptozotocin-treated rats with varying degrees of diabetes sorbitol levels in the lens, sciatic nerve, and RBC were elevated in proportion to the degree of hyperglycemia. RBC sorbitol levels in these animals were positively correlated with the levels in lens and sciatic nerve. These results establish that orally administered sorbinil is effective in lowering elevated sorbitol levels, and strongly suggest that the reduction seen in RBC sorbitol levels in human diabetic subjects is likely to reflect comparable effects of the drug in less accessible tissues associated with the long-term complications of diabetes.
Collagen Aging In Vitro by Nonenzymatic Glycosylation and Browning
Authors: Kohn Robert R , Cerami Anthony , Monnier Vincent M
Published: September 2013

Aging and diabetes meliitus are associated with crosslinking and nonenzymatic glycosylation of collagen. Incubation of tendon fibers with reducing sugars results in increased breaking time in urea similar to that seen in aging, and in nonenzymatic glycosylation and browning. Effect of a sugar is proportional to the amount of sugar available in the open chain form. The increase in breaking time correlates with the appearance of chromophores characteristic of crosslinked browning products. Collagen altered by nonenzymatic browning may play a role in some age-like major complications Of diabetes.
Effect of Diabetes on In Vivo Metabolism of [35S]-labeled Glomerular Basement Membrane
Authors: Cohen Margo Panush , Surma Maria Linda
Published: September 2013

Glomerular basement membrane (GBM) was labeled in vivo by the injection of tracer amounts of [35S]-sulfate into normal and streptozotocin-diabetic rats. The biosynthesis and turnover of sulfated glycosaminoglycans in the GBM was determined from the specific activity of [35S] after pronase digestion of basement membranes purified from glomeruli isolated 1–7 days after injection. Peak radiolabeling of both normal and diabetic GBM occurred 24 h after injection and, when corrected for differences in serum sulfate specific activities, was less in diabetic than in normal samples. The specific activity of GBM sulfate, expressed as cpm/μg uronic acid, progressively diminished over the ensuing period of study in both normal and diabetic samples. The rate of decrease in specific activity of [35S]-labeled GBM was not significantly different in diabetic preparations compared with that in normal controls. The findings are compatible with diminished sulfation and/or production but normal turnover of glycosaminoglycans in the renal GBM in experimental diabetes.
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.
The Enteric Enhancement of Glucose-stimulated Insulin Release: The Role of GIP in Aging, Obesity, and Non-insulin-dependent Diabetes Mellitus
Authors: Elahi Dariush , Andersen Dana K , Muller Denis C , Tobin Jordan D , Brown John C , Andres Reubin
Published: September 2013

The effect of aging, obesity, and non-insulin-dependent diabetes mellitus on glucose-stimulated gastric inhibitory polypeptide (GIP) levels was studied in 55 male subjects, ranging in age from 19 to 84 yr, and in obesity, expressed as body mass index, from 21 to 34. Studies were performed using the hyperglycemie glucose clamp technique, in which the blood glucose was maintained at 125 mg/dl above basal for 2 h. Glucose (40 g/m2 body surface) was ingested at 60 min. Plasma immunoreactive GIP (IR-GIP) did not change during intravenous (i.v.) glucose alone, but began to rise within 10 min after glucose ingestion and reached a peak at 30–40 min. Basal and stimulated IR-GIP levels were markedly elevated in diabetic subjects and modestly elevated in obese subjects, compared with appropriately matched controls. In contrast, age had little effect on plasma IR-GIP levels either in the basal state or after glucose ingestion. When IR-GIP responses to oral glucose were expressed as a relative change from basal levels, IR-GIP rose 86% in diabetic subjects and 243% in obese subjects, compared with 185% and 165% in their respective controls. IR-GIP rose 179% in young subjects and 144% in middle-aged subjects, while, in old subjects, the increase was 265%. Plasma IRI levels were reduced in the diabetic subjects, slightly elevated in obese subjects, and were similar in older and younger subjects. Beta cell sensitivity to endogenous GIP decreases with age, and is unchanged in both obesity and nonmedicated diabetes.
Inhibition of Fibronectin Binding to Matrix Components by Nonenzymatic Glycosylation
Authors: Cohen Margo Panush , Ku Ling
Published: September 2013

We examined the effect of nonenzymatic glycosylation on the ability of fibronectin, an extracellular glycoprotein that interacts with cell surfaces and matrix components, to bind to collagen and heparin. Nonenzymatic glycosylation was accomplished by incubation of the protein with glucose, both cold and [14C]-labeled, and documented by measurement of ketoamine-bound carbohydrate with the thiobarbituric acid assay. Effect on binding was assessed with affinity chromatography on heparin-Sepharose and gelatin-Sepharose, and with an in vitro assay that detects complexation of fibronectin with [3H]-heparin. Glycosylated fibronectin did not bind to these immobilized matrix components, and in vitro binding of the glycosylated protein was reduced compared with that of nonglycosylated fibronectin. Inhibition of heparin binding in the in vitro assay was observed even with levels of glycosylation about threefold those of control, which is comparable to the degree of glycosylation determined in fibronectin isolated from plasma of two patients with uncontrolled diabetes. The findings indicate that nonenzymatic glycosylation of fibronectin inhibits its binding to connective tissue components, and suggest that this process contributes to faulty integrity of extracellular matrices in diabetes.
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.
Effect of Diabetes and its Control on Insulin-like Growth Factors in the Young Subject with Type I Diabetes
Authors: Amiel Stephanie A , Sherwin Robert S , Hintz Raymond L , Gertner Joseph M , Press C Martin , Tamborlane William V
Published: September 2013

The influence of diabetes and its control on circulating levels of growth hormone and growth hormone-dependent, insulin-like growth factors (IGF) remains controversial. In the present study, the effect of a 1-wk period of intensive insulin therapy on growth hormone and IGF I and II has been determined in 19 young (age 13–22 yr), insulin-dependent (type I) subjects with diabetes mellitus. IGF I was low during conventional insulin therapy (198 ± 20 versus 438 ± 38 ng/ml in nondiabetic subjects, P < 0.001), and rose within the week of intensified treatment (to 255 ±15 ng/ml, P < 0.005), concomitant with a reduction in plasma glucose from 233 ± 16 to 110 ± 5 mg/dl. IGF I rose despite a significant fall in mean 24-h growth hormone levels from 14.1 ± 2.2 to 9.0 ± 1.2 ng/ml (P < 0.02). The mean IGF II value for the diabetic subjects (504 ± 39 ng/ml) was not significantly different from that of the nondiabetic control group (506 ± 30 ng/ml, P > 0.3) and was not altered by intensified therapy. However, four individual patients with very low IGF I also had depressed IGF II (248 ±16 ng/ml), which was corrected (to 377 ± 35 ng/ml) with improved metabolic control. These data suggest that elevated growth hormone levels in poorly controlled diabetes are ineffective in IGF I generation and that this defect is at least partially corrected by acute improvement in control. The rise in IGF I levels accompanying intensive insulin treatment may suppress the excessive secretion of growth hormone. IGF II levels appear to be affected only by the most severe reductions of growth hormone activity.
Relationship Between Insulin Release and 65Zinc Efflux from Rat Pancreatic Islets Maintained in Tissue Culture
Authors: Formby Bent , Schmid-Formby Florence , Grodsky Gerold M
Published: September 2013

In short-term batch-incubation or perifusion experiments, we studied insulin release and associated 65Zn efflux from rat pancreatic islets loaded with 65Zn by 24-h tissue culture in low-glucose medium. The fractional basal insulin release and 65Zn efflux were 0.4% and 3% of total content/h/islet, respectively. Thus, basal 65Zn efflux was much greater than that to be accounted for if zinc was released proportionally with insulin release only; extragranular zinc flux was suggested. Two millimolar glucose, with or without 1 mM 3-isobutyl-1-methylxanthine (IBMX), affected neither insulin release nor associated 65Zn efflux. Twenty-five millimolar glucose produced a significant threefold increase in insulin release above baseline, but somewhat decreased 65Zn efflux at marginal significance. Glucose (25 mM) plus 1 mM IBMX provoked a high increase in insulin release and an associated 30% increase in fractional 65Zn efflux over basal. Calculations based on previous estimations of 65Zn distribution and equilibrium with islet zinc indicated that molar zinc efflux was more than sufficient to account for a 2-zinc-insulin hexamer. L-leucine (2 or 20 mM) plus 1 mM IBMX caused far greater 65Zn efflux for the amount of insulin released, indicating additional 65Zn mobilization not directly related to insulin secretion. To evaluate 65Zn efflux during inhibited insulin secretion, batch incubations were performed in 100% D2O or at 27°C, conditions that inhibited insulin release stimulated by high glucose plus IBMX. These agents decreased the 65Zn efflux far below the basal value (35% and 50%, respectively) and greater than could be accounted for by the attendent inhibition of insulin secretion. Perifusion experiments showed that the temporal kinetics for insulin release and associated 65Zn efflux stimulated by high glucose plus IBMX were parallel. We conclude that sufficient zinc is released from islets to permit insulin storage and secretion as a 2-zinc-insulin hexamer. In addition, 65Zn flux (presumably extragranular) is highly sensitive to secretagogues and cellularly active agents independent of insulin secretion.
The Pittsburgh Insulin-dependent Diabetes Mellitus (IDDM) Morbidity and Mortality Study: Mortality Results
Authors: Dorman J S , Laporte R E , Kuller L H , Cruickshanks K J , Orchard T J , Wagener D K , Becker D J , Cavender D E , Drash A L
Published: September 2013

A follow-up study of 1966 patients with insulin-dependent diabetes mellitus (IDDM) who were diagnosed at Children's Hospital of Pittsburgh (CHP) between 1950 and 1981 has been completed. The mean age of the population at follow-up was 21.2 yr with a mean duration of IDDM of 12.9 yr. Nine percent of the patients were deceased, a sevenfold excess in mortality compared with the U.S. population. The relative increase in mortality was greater for females than males and greater for blacks than whites. Before age 20, the primary excess in mortality was at onset of IDDM, or within 6 mo after onset, and was due to acute diabetic complications. After age 20, the annual mortality risk was approximately 2%, which was more than 20 times greater than for the U. S. population. Renal disease was responsible for the majority of these deaths. There was a reduced risk of dying for diabetic patients who were diagnosed between 1966 and 1971 compared with patients diagnosed during earlier years.