bluuebunny/crossref_metadata_2025 huggingface dataset:
Glucose Intolerance Due to Insulin Resistance in Patients with Spinal Cord Injuries
Authors: Duckworth William C , Solomon Solomon S , Jallepalli Panduranga , Heckemeyer Chris , Finnern James , Powers Alvin
Published: September 2013

Glucose intolerance occurs frequently in patients with spinal cord injury (SCI). To characterize this better, 45 patients with spinal cord injuries received oral glucose tolerance tests (OGTT). The subjects with glucose intolerance had significantly higher insulin levels than either the glucose-tolerant or normal control subjects.

Since hyperinsulinism in the presence of glucose intolerance suggests insulin resistance, the peripheral insulin activity (A) was calculated from the OGTT data. The glucose-intolerant SCI patients had significantly lower A values than the other groups. The most resistant SCI subjects (A<0.3) also had resistance to exogenous insulin. In 18 subjects receiving insulin tolerance tests, the A value calculated from the OGTT was 100% accurate in predicting the presence of sensitivity or resistance to exogenous insulin. In spite of the presence of insulin resistance, however, 125I-insulin binding to SCI patients' circulating monocytes was not significantly different from that in control subjects.
Effects of Acute Insulin Deficiency on Glucose and Ketone Body Turnover in Man: Evidence for the Primacy of Overproduction of Glucose and Ketone Bodies in the Genesis of Diabetic Ketoacidosis
Authors: Miles John M , Rizza Robert A , Haymond Morey W , Gerich J E
Published: September 2013

To assess the relative contribution of overproduction and underutilization of glucose and ketone bodies to the development of diabetic ketoacidosis in man, the effects of acute insulin deficiency on glucose and ketone body turnovers were determined in seven ketosis-prone (type I) diabetic subjects. After termination of prolonged intravenous infusions of insulin, which had been maintaining the subjects euglycemic, plasma free insulin decreased from 18 ± 4 μU/ml to 7 ± 1 μU/ml, P < 0.01; plasma glucagon increased from 67 ± 6 pg/ml to 259 ± 67 pg/ml, P < 0.05, but plasma growth hormone and cortisol did not increase. Plasma glucose increased from 5.4 ± 0.3 mM to 15.6 ± 1.0 mM, P < 0.01; plasma ketone bodies (β-hydroxybutyrate plus acetoacetate) increased from 1.4 ± 0.4 mM to 7.2 ± 1.5 mM, P < 0.01. Glucose production increased abruptly from 13.2 ± 1.1 μmol/kgmin to a maximum of 26.1 ± 2.9 μmol/kg-min at 2 h but then decreased toward baseline rates; glucose utilization also increased transiently. In contrast, both ketone body production and utilization increased progressively throughout the study from 5.4 ± 1.4 and 5.5 ± 1.1 to 18.3 ± 3.9 and 14.7 ± 2.1 μmol/kg-min, respectively, P < 0.01. Clearance of both glucose and ketone bodies decreased more than 50%, P < 0.01. These results indicate that overproduction of glucose and ketone bodies is the primary process involved in the initiation of diabetic ketoacidosis in man. However, persistent overproduction of glucose and ketone bodies may not be necessary for the maintenance of hyperglycemia and hyperketonemia, since clearance of both substrates is impaired. Finally, since, of all counter-insulin hormones measured, only plasma glucagon increased coincident with increases in glucose and ketone body production, these results provide further evidence that glucagon may be the most important counter-insulin hormone involved in the genesis Of ketoacidosis.
Multiple Redox Forms of the Insulin Receptor in Native Liver Membranes
Authors: Massagué Joan , Czech Michael P
Published: September 2013

Three forms of disulfide-linked insulin receptor complexes are labeled by covalent cross-linking to receptor- bound 125I-insulin in native adipocyte or liver membranes. These receptors of Mr 350,000, Mr 320,000, and Mr 290,000 are composed of α(Mr 125,000), β(Mr 90,000), and β1(Mr 49,000) subunits in stoichiometries of (αβ)2, (αβ)(αβ)1 and (αβ1)2, respectively. In adipocyte membranes, these receptor structures can undergo a first step of reduction by dithiothreitol, dissociating into Mr 210,000 (αβ) and Mr 160,000 (αβ1) partially reduced receptor fragments. Complete dissociation of such fragments into the free α,β , and β1 receptor subunits is achieved at high reductant concentrations. In liver plasma membranes the partially reduced receptor species of Mr 210,000 and Mr 160,000 are observed even when electrophoresis is performed under nonreducing conditions. This observation indicates that native liver plasma membranes contain multiple redox states of the high affinity insulin receptor.
Glucocorticoid-induced Recovery from Streptozotocin Diabetes in the Adult Rat
Authors: Roudier Michel , Portha Bernard , Picon Luc
Published: September 2013

The effect of a large dose of cortisol (5 mg/kg), injected 24h and 3h before or 3h and 24h after streptozotocin (SZ), on the course of SZ-induced diabetes has been studied in the rat. Glucose tolerance tests, performed 1 or 2, 8, and 30 days after the SZ injection (35 mg/kg), gave the same results in cortisol-treated rats regardless of the time of cortisol injection [before SZ (C.SZ) or after it (SZ.C)]. During the first test, elevated plasma glucose, decreased glucose tolerance, and decreased glucose-induced insulin secretion were present in SZ, C.SZ, and SZ.C rats. During the second and the third tests, glucose tolerance and insulin secretion were significantly improved in both groups of cortisol-treated rats. On the contrary, rats receiving only SZ showed a worsening of the diabetic state. It should be noted that cortisol-induced recovery of diabetes was not obtained with larger doses of SZ (50 mg/kg).

These findings indicate that an improvement of diabetes can be obtained by cortisol treatment after the onset of chemically induced diabetes. Whether this effect is obtained through an effect on pancreatic regeneration and/or through the anti-inflammatory properties of glucocorticoids is unknown at the present time.
Inhibition of Alloxan Action in Isolated Pancreatic Islets by Superoxide Dismutase, Catalase, and a Metal Chelator
Authors: Fischer L J , Hamburger S A
Published: September 2013

The possible participation of superoxide anions, hydrogen peroxide, and hydroxyl radicals in the action of alloxan was investigated using isolated rat pancreatic islets. Exposure of islets for 5 min to alloxan (0.15 or 0.2 mg/ml) inhibited subsequent glucose-stimulated insulin release. The presence of superoxide dismutase (1000 U/ml), catalase (50 μg/ml), or a metal chelator diethylenetriaminepentacetic acid (1 mM) markedly attenuated this effect of alloxan. Use of these agents afforded complete protection from the lower concentration of alloxan and partial protection from the higher concentration of the toxic compound. Inactivation of the enzymes or addition of excess iron to the chelating agent before its use with alloxan eliminated the protective action of these agents. The results are consistent with the proposal that hydroxyl radicals, generated via reactions that involve superoxide anions, hydrogen peroxide, and iron, mediate the deleterious effect of alloxan in pancreaticislets.
Effects of Acute Variation of Fetal Glycemia on Glycogen Storage and on Glycogen Synthase and Phosphorylase Activities in the Liver of the Rat Fetus
Authors: Gilbert M , Bourbon J
Published: September 2013

The effects of variations of glycemia from 1.7 to 35 mM on the activity of glycogen synthase and phosphorylase, on glycogen content, and on U-14C-glucose incorporation into glycogen in the liver of the near-term rat fetus were investigated. Hypoglycemia did not affect the activities of phosphorylase and synthase; total glycogen content was not modified, but incorporation of labeled glucose was markedly decreased. This is consistent with a decreased glycogen synthesis. A slight hyperglycemia (about 5.5 mM) sharply decreased phosphorylase a (active) activity but increased slightly glycogen synthase a activity; liver glycogen content and labeled glucose incorporation were both enhanced. Higher levels of glycemia induced a decrease of phosphorylase a activity of the same order, but by contrast, glycogen synthase a activity increased progressively with increasing glycemia. Sequential study showed that hyperglycemia first induced the decrease of phosphorylase activity, then increased synthase activity. Marked hyperglycemia strongly enhanced liver glycogen content and labeled glucose incorporation. The fetal liver appears very responsive to acute variations of glycemia. The mechanisms seem to be oriented toward maximal glycogen accumulation.
Effect of Insulin, Glucose, and 2-Deoxy-glucose Infusion into the Third Cerebral Ventricle of Conscious Dogs on Plasma Insulin, Glucose, and Free Fatty Acids
Authors: Taborsky G J , Bergman R N
Published: September 2013

Previous studies have demonstrated that exogenous insulin, injected into central cerebrospinal fluid cavities of dogs, stimulates the release of endogenous insulin from the pancreas. To determine whether this response was elicited by (1) insulin per se, (2) an effect of insulin on glucose transport, or (3) glucopenia in the cerebrospinal fluid, we measured plasma insulin, glucose, and free fatty acids during the infusion of insulin, glucose, and 2-deoxy-glucose (2DG), individually or in combination, into the third cerebral ventricle of conscious dogs. As expected, the third ventricular infusion of insulin alone elicited a small, but significant, rise of plasma insulin. Surprisingly, infusion of insulin with glucose produced a smaller increase of plasma insulin (P < 0.05) and the infusion of insulin with 2DG produced a much larger increase of plasma insulin (P < 0.05) than did the third ventricular infusion of insulin alone. The third ventricular infusion of either glucose alone or 2DG alone had no effect on the plasma levels of insulin. These data suggest that administration of insulin into the cerebral ventricles stimulates pancreatic insulin secretion but not by accelerating the transport of glucose into a chemosensitive area of the brain.
Altered Responsiveness to Cortisol, Epinephrine, and Glucagon in Insulin-infused Juvenile-onset Diabetics: A Mechanism for Diabetic Instability
Authors: Shamoon Harry , Hendler Rosa , Sherwin Robert S
Published: September 2013

To evaluate the mechanism of rebound and stress hyperglycemia in diabetes, cortisol, epinephrine, and glucagon were infused into normal and juvenile-onset diabetic subjects for 5–6 h in doses designed to simulate the increments observed in insulin hypoglycemia or severe stress. Plasma glucose and glucose kinetics were normalized in the diabetics before each experiment by infusion of insulin (0.25–1.0 U/h) for 4–6 h, which was then continued during anti-insulin hormone administration.

Infusion of cortisol and epinephrine produced comparable elevations in plasma cortisol (35–45 /μg/dl) and plasma epinephrine (350–450 pg/ml) in normal and diabetic subjects. However, the increment in plasma glucose in diabetics after cortisol (86 ± 15 mg/dl) and epinephrine (129 ± 12 mg/dl) infusion was fivefold to sevenfold greater than it was in normals (P < 0.001), despite ongoing insulin infusion. Whereas cortisol failed to alter glucose production in normals, in diabetics there was a progressive 35% increase in glucose production (P < 0.001). Similarly, epinephrine produced only a transient (<90 min) 60% rise in glucose production in normal subjects, but caused a sustained 50%–90% rise in glucose production in diabetics throughout the entire 5-h study. In contrast, both cortisol and epinephrine infusion was accompanied by a 25%–40% (P < 0.001) decline in glucose clearance, no different than in normal and diabetic subjects. Glucagon infusion produced a transient 35%–40% rise in glucose production, which was of comparable magnitude and duration in normal controls and diabetics. However, the glucagon-induced rise in plasma glucose was threefold greater in the diabetics due to failure of endogenous insulin secretion and consequent lack of an increase in glucose clearance as observed in normal controls. When saline was administered to the insulin-infused diabetics, neither plasma glucose nor glucose production were altered from baseline values.

It is concluded that (1) the hyperglycemic effect of each of the anti-insulin hormones is increased in diabetics, in spite of prior normalization of plasma glucose concentration, by continuous insulin infusion and (2) hyperglycemia is particularly exaggerated by elevations of cortisol and epinephrine in diabetes as a consequence of an altered response of the liver to these hormones.
Starvation-induced Changes of Somatostatin, Glucagon, and Insulin Secretion from the Isolated Perfused Rat Pancreas
Authors: Seino Susumu , Sakurai Hideo , Seino Yutaka , Tsuda Kinsuke , Tanigawa Keiichiro , Kuzuya Hideshi , Goto Yasuo , Imura Hiroo
Published: September 2013

The effect of 16- and 48-h fasting on pancreatic somatostatin, insulin, and glucagon secretion was studied, using the isolated perfused rat pancreas. In the presence of 4.4 mM glucose, basal somatostatin and insulin concentrations in the perfusate were significantly lower in 48-h fasted rats than in fed animals, whereas basal glucagon secretion was significantly elevated in fasted rats. The infusion of 19 mM arginine significantly augmented secretion of somatostatin and glucagon and attenuated insulin secretion in 48-h fasted rats. It is concluded that fasting causes a decrease in basal pancreatic somatostatin secretion in vitro, although the response to arginine is rather exaggerated. Insulin and glucagon secretion also changed during the fasting. These results suggest that not only insulin and glucagon, but also somatostatin contribute to nutrient homeostasis.
Duodenal Contribution to Pancreaticoduodenal Vein Islet Hormones During Stimulation of the Canine Pancreas with Calcium
Authors: Hermansen K
Published: September 2013

The possible influence of the duodenum on pancreatic hormones in the pancreaticoduodenal venous effluent of the canine pancreas was studied. The magnitude and dynamics of somatostatin, glucagon, and insulin responses during stimulation with 5 mM calcium were identical whether or not the duodenal remnant was excluded from the perfusion by clamping.

The results indicate that during perfusion with calcium the duodenal remnant is without any significant regulatory or contributory role on pancreatic hormone secretion from the isolated canine pancreas preparation.
Induction of Hyperglycemia with Insulin Antibodies to B-Chain Determinants
Authors: Kelso John M , Tamai Irene Y , Roth Michael D , Valdes Ignacio , Arquilla Edward R
Published: September 2013

Insulin antibodies measured by a radioimmune method (ABR) are significantly better inducers of hyperglycemia than are insulin antibodies measured by an immune hemolysis method (ABH) when injected intraperitoneally into mice. The ability to induce hyperglycemia by an insulin antiserum can be predicted by the titer of ABR measured. ABR interact in vitro with determinants severely perturbed on nickel-insulin, partially perturbed on proinsulin and desasparaginedesalanine insulin, and unaffected on zinc-insulin or zinc-free monocomponent insulin. ABH, on the other hand, interact in vitro with determinants severely perturbed on proinsulin and desasparagine-desalanine insulin but stabilized on nickel-insulin and zinc-insulin. Since the connecting peptide of proinsulin is probably in apposition to the A-chain residues on the solvent surface, the more effective reaction of proinsulin with ABR than with ABH is submitted as evidence that ABR are directed toward residues on the B-chain surface of insulin. Because ABR are more effective inducers of hyperglycemia than are ABH, it is proposed that the degree of hyperglycemia induced by antibodies in vivo is a result of interactions with determinants on the B-chain surface of insulin. These results support the possibility that insulin in vivo is more accessible for interaction with antibodies directed to the B-chain of insulin. It is also possible that ABR, which are directed to B-chain determinants, are of higher affinity than is the affinity between insulin and receptors or that the active site of insulin for maintaining euglycemia includes the B-chain surface residues.
Properdin Factor B(Bf) Allele BfF1 Specifies an HLA-B18 Diabetogenic Haplotype
Authors: Dornan John , Allan Patricia , Noel Elke P , Larsen Bodil , Farid Nadir R
Published: September 2013

We found the rare properdin factor B(Bf) variant F1 to be present in 11% of 72 patients suffering from insulindependent diabetes (IDDM) compared with 2% among 150 normal controls. BfF1 thus confers a relative risk for IDDM of 5.55. All eight patients and three controls who were BfF1 positive were also HLA-B18 positive, reflecting the strong linkage disequilibrium between these two factors. We suggest that BfF1 marks a ‘diabetogenic’ B18-bearing HLA haplotype. Studies of unselected families with one or more affected members suggest that the B18, BfF1 does not necessarily segregate with IDDM phenotype. This study provides further evidence for the genetic heterogeneity of IDDM.
Immunohistochemical Localization of Aldose Reductase: II. Rat Eye and Kidney
Authors: Ludvigson Mark A , Sorenson Robert L
Published: September 2013

Aldose reductase (AR) was purified from rat seminal vesicles. Specific antibodies to this enzyme were prepared in rabbits and were used in the unlabeled antibody-enzyme (PAP) technique to localize AR in a number of tissues known to be sites of diabetic lesions. AR was localized in the following structures in the eye: lens epithelial lining and cortical lenticular fibers; corneal endothelium; the inner, nonpigmented layer of ciliary body epithelium and its extension as the posterior surface of the iris; and neuroglial (Muller) cells in the retina. Retinal capillary endothelium did not contain immunoreactive AR.

In the kidney, staining was intense in the inner medulla. Specific structures included thin limbs of the loop of Henle, collecting tubules deep in the inner medulla, and transitional epithelial cells lining the pelvic space: structures in the cortex included gtomerular podocytes and distal convoluted tubules. Collecting tubules in the outer medulla and cortex, as well as proximal convoluted tubules and glomerular capillary endothelium did not contain immunoreactive AR.
Lysosomal Degradation of Receptor-bound 125I-labeled Insulin by Rat Adipocytes: Its Characterization and Dissociation from the Short-term Biologic Effects of Insulin
Authors: Hammons Glenn T , Jarett Leonard
Published: September 2013

In this study we used chloroquine to characterize the internalization and lysosomal degradation of receptorbound 125I-insulin by rat adipocytes and to determine the role of lysosomal processing of insulin in the shortterm biologic effects of the hormone. Chloroquine inhibited the degradation of 125I-insulin bound to adipocytes by both association and dissociation experiments. In the former experiments, chloroquine caused a time- and concentration-dependent increase in specifically bound insulin owing to an increase in intact insulin and a decrease in degradation products, as determined by trichloroacetic acid precipitability and gel chromatographic analysis of material extracted from the cells. In the dissociation experiments, 50 μM chloroquine decreased the rate of degradation by two thirds, as reflected in the release of degradation products from the cells. Chloroquine had no effect on the amount of 125I-insulin specifically bound to or degraded by isolated plasma membranes, on the degradation of 125I-insulin by proteases in the incubation medium, or on the endocytotic uptake of receptorbound insulin. Quantitative electron microscopy, using monomeric ferritin-insulin, showed 50 μM chloroquine doubled the number of lysosomal structures containing ferritin. These findings are consistent with an inhibition by chloroquine of lysosomal degradation of internalized receptor-bound insulin. Chloroquine, at these same concentrations, had no effect on the ability of insulin to stimulate glucose transport and oxidation or to inhibit epinephrine-stimulated lipolysis. In these studies, we show that lysosomal degradation of internalized receptor-bound insulin is not necessary for insulin to cause short-term biologic effects in the adipocyte.
Amelioration of Mesangial Volume and Surface Alterations Following Islet Transplantation in Diabetic Rats
Authors: Steffes Michael W , Brown David M , Basgen John M , Mauer S Michael
Published: September 2013

Highly inbred Lewis rats with streptozotocin-induced diabetes mellitus of 7 mo duration received intraportal transplants of neonatal pancreatic tissue. At 7 and 9 mo of diabetes (at the time of and at 2 mo after islet transplantation) renal biopsies for the evaluation of several morphometric parameters were obtained from control (C), diabetic-nontranspianted (D), and diabetic-transplanted (D-T: with normal plasma glucose values) rats.

Glomerular volume in D-T animals at 9 mo fell to a value less than that in C rats while glomerular volume in D animals exceeded that in C rats at both 7 and 9 mo. Electron microscopic morphometry of the total mesangium and its cellular and matrix components documented a nearly twofold increase in the volume of the mesangial matrix in D as compared with C rats at both 7 and 9 mo. While the mesangial cellular component was also increased in diabetes, the changes in the volume of the mesangial matrix in D rats at both 7 and 9 mo provided the major proportion of the increased volume of the total mesangium. With islet transplantation, significant reduction in the volumes of the mesangial matrix and a much smaller and not significant decrease in the cellular component gave normal values for those components and for the volume of the total mesangium in D-T animals.

The expanded volume of the total mesangium in diabetes concomitantly increased the proportion of the glomerular capillary surface interfaced with the mesangium. Similarly, the proportion of the glomerular basement membrane (GBM)-epithelium interface juxtaposed to the mesangium was elevated in diabetes. These two observations imply that the expanding mesangium interposed itself between the endothelial cells and the GBM, increasing the surface of the mesangium. With islet transplantation these surface alterations returned toward normal in conjunction with the reduction in volume of the mesangium.

These observations with electron microscopic morphometry provide detailed documentation of the alterations in the mesangium of experimental diabetes mellitus. The sensitivity with which these changes can be monitored permit detailed analysis of subtle increases in both mesangial surface and volume in diabetes mellitus.
The Contrasting Responses of Splanchnic and Renal Glucose Output to Gluconeogenic Substrates and to Hypoglucagonemia in 60-h-fasted Humans
Authors: Björkman Ola , Felig Philip , Wahren John
Published: September 2013

Arterial concentrations and splanchnic as well as renal exchange of glucose, lactate, pyruvate, glycerol, and alanine were studied in the basal state and during intravenous infusion of alanine or glycerol in healthy subjects who had fasted for 60 h. After 45 min of infusion of alanine or glycerol, somatostatin administration (SRIF, 9 μg/min) was added to induce hypoglucagonemia.

Alanine infusion, at a rate of 1 mmol/min, was accompanied by an 80% rise in splanchnic glucose output (SGO) and a small (16%) rise in arterial glucose. Splanchnic alanine uptake, which rose fivefold to sixfold above basal, could account for the entire rise in SGO. Intravenous administration of glycerol (1 mmol/min) resulted in an elevation of blood glucose (+ 9%) but no significant change in SGO, even though glycerol uptake by the splanchnic tissues rose eightfold above basal levels.

Measurements of renal exchange of glucose indicated a small but statistically significant release of glucose from the kidney (0.04 ± 0.01 mmol/min) in the basal state, which accounted for 10% of total (renal plus splanchnic) glucose production. Administration of glycerol at a rate of 2 mmol/min resulted in a rise in renal glucose output to 0.16 ± 0.03 mmol/min, which could be accounted for in its entirety by renal glycerol uptake. In contrast, infusion of alanine (2 mmol/min), did not alter the renal glucose exchange.

Infusion of SRIF was accompanied by a significant fall in the arterial glucagon level in all studies. Concomitante, large decreases in arterial glucose and SGO were observed during both alanine and glycerol administration. However, splanchnic uptake of gluconeogenic precursors was not influenced by SRIF administration. The elevated renal glucose output seen during glycerol administration was not altered by SRIF infusion.

It is concluded that, in 60-h-fasted man, (a) renal glucose output contributes significantly to total glucose production, (b) administration of glycerol stimulates renal glucose production, (c) alanine infusion increases splanchnic but may not affect renal glucose output, and (d) hypoglucagonemia inhibits splanchnic but not renal glucose output. These data indicate that hepatic and renal gluconeogeneses respond differently with respect to stimulation by specific substrates and to their dependence on basal glucagon levels.
The Role of Calcium in Alpha-adrenergic Inactivation of Glycogen Synthase in Rat Hepatocytes and its Inhibition by Insulin
Authors: Strickland Garrison W , Blackmore Peter F , Exton John H
Published: September 2013

The effects of epinephrine, vasopressin, and A23187 on glycogen synthase and phosphorylase were examined in isolated rat liver parenchymal cells from fed animals. In normal calcium-containing hepatocytes, epinephrine, vasopressin, and A23187 were more potent at inactivating glycogen synthase, previously activated with 30 mM glucose, than at activating phosphorylase. In calcium-depleted hepatocytes (cells washed and incubated with 1 mM EGTA), the effect of epinephrine on both enzyme activities was impaired, while the effects of vasopressin and A23187 were completely abolished. Insulin was more effective at inhibiting the effects of epinephrine in calcium-depleted cells, but it was without effect on vasopressin and A23187 actions. The ability of epinephrine, vasopressin, and A23187 to elicit calcium efflux from cells was not altered by the presence of 30 mM glucose. These findings are consistent with the idea that the α-adrenergic inactivation of liver glycogen synthase may be a result of the increased stimulation of a calcium-dependent protein kinase, possibly phosphorylase b kinase.
Increased Integrated Concentration of Norepinephrine, Epinephrine, Aldosterone, and Growth Hormone in Patients with Uncontrolled Juvenile Diabetes Mellitus
Authors: Zadik Zvi , Kayne Richard , Kappy Michael , Plotnick Leslie P , Avinoam Kowarski A
Published: September 2013

The 24-h integrated plasma concentration of glucose (IC-glucose), norepinephrine (IC-NE), epinephrine (IC-E), cortisol (IC-F), growth hormone (IC-QH), aldosterone (IC-ALDO), and plasma renin activity (IC-PRA) were measured in 11 nonobese juvenile-onset nonke-totic diabetic patients exhibiting hyperglycemie and glycosuria and 34 matched control subjects using a portable pump, drawing blood at a constant rate through a nonthrombogenic i.v. catheter. The diabetic patients had a noticeable rise of their IC-NE, IC-E, IC-GH, and IC-ALDO. There was no significant difference between the IC-F and IC-PRA of the patients and the control subjects.
Failure of Cortisol Blockade to Inhibit Early Morning Increases in Basal Insulin Requirements in Fasting Insulin-dependent Diabetics
Authors: Bright George M , Melton Terry W , Rogol Alan D , Clarke William L
Published: September 2013

Overnight basal insulin requirements to maintain euglycemia were determined in five insulin-dependent diabetic subjects using a closed-loop insulin infusion system. A significant increase in hourly insulin requirements occurred between 0600 h and 0900 h as compared with 0100 h–0600 h. Although the increased insulin requirement was coincident with only the physiologic diurnal increase in plasma cortisol, the oral administration of the 11-beta hydroxylase inhibitor, metyrapone, decreased only the total overnight (0100 h–0900 h) basal insulin requirement, but not the early morning (0600 h-0900 h) rise in insulin required to maintain euglycemia. It would appear that although cortisol is an important counterregulatory factor, its diurnal elevation cannot account for the increase in early morning basal insulin requirements to maintain euglycemia in insulin-dependent diabetics.
Insulin-like Effect of Zinc on Adipocytes
Authors: Coulston L , Dandona P
Published: September 2013

In view of the known effect of zinc on the crystalline nature of insulin, we have investigated whether zinc alters the biologic potency of this hormone. Using the rate of lipogenesis by rat epididymal adipocytes as an index of the biologic potency of insulin, we have shown that zinc exerts a potent stimulatory effect upon lipogenesis in vitro similar to, but quite independently of, insulin and that it has an additive effect with that of insulin when both are incubated together. This effect of zinc on adipocytes and the biologic potency of insulin, hitherto unreported, is of significance at the biologic, pharmacologie, and clinical level.
Antisomatostatin Gamma Globulin Augments Secretion of Both Insulin and Glucagon In Vitro: Evidence for a Physiologic Role for Endogenous Somatostatin in the Regulation of Pancreatic A- and B-Cell Function
Authors: Itoh Mitsuyasu , Mandarino Lawrence , Gerich John E
Published: September 2013

To assess the effects of endogenous somatostatin on pancreatic islet A- and B-cell function, isolated rat islets were incubated in antisomatostatin γ-globulin to bind endogenously released somatostatin, and the insulin and glucagon secretion of these islets was compared with that of islets incubated in γ-globulin isolated from nonimmune serum. Islets incubated in antisomatostatin γ-globulin released significantly more insulin at 4, 8,16, and 32 mM glucose and significantly more glucagon at 8,16, and 32 mM glucose, P < 0.05–0.005. For glucose-stimulated insulin release the threshold was decreased, the Vmax was increased, but the apparent Km was unaltered; for glucose-suppression of glucagon release the threshold was increased, maximal suppression was decreased, but the apparent Ki was unaltered. The augmentative effect of the antisomatostatin γ-globulin was most prominent at 4 mM glucose for insulin release and at 8 mM glucose for glucagon release, but was not limited to glucose since both insulin and glucagon release stimulated by arginine were also augmented by antisomatostatin γ-globulin. These results provide evidence that endogenous somatostatin may act as a physiologic local regulator of both insulin and glucagon secretion and that its effect on insulin and glucagon secretion is dependent on the prevailing glucose concentration.
Neurotransmitters and Glucagon Release From the Isolated, Perfused Canine Stomach
Authors: Lefebvre Pierre J , Luyckx Alfred S
Published: September 2013

The isolated, perfused, canine stomach was used to investigate the effect of three neurotransmitters—nor-epinephrine, acetylcholine (or its analogue carbamyl-choline), and VIP (vasoactive intestinal peptide)—on gastric glucagon release. Norepinephrine at the two concentrations tested (3.10−6 and 7.10−7 M) did not influence gastric glucagon release. In contrast, acetylcholine or carbamylcholine (5.10−6 M) as well as VIP (46–60 ng/ml) unequivocally stimulated gastric glucagon release, an effect apparently independent of the changes in blood flow. These results are in sharp contrast with the previously reported lack of effect of an electric stimulation of the vagus nerves on the release of glucagon from the dog stomach. An absence of innervation of the canine gastric A-cell would probably best explain this situation.
Dichloroacetate—Its In Vivo Effects on Carbohydrate Metabolism in the Conscious Dog
Authors: Diamond Michael P , Rollings Robert C , Erlendson Lee , Williams Phillip E , Lacy William W , Rabin David , Cherrington Alan D
Published: September 2013

The effects of sodium dichloroacetate (DCA) on carbohydrate metabolism in conscious, 48-h-fasted dogs were examined using the hepatic A-V difference technique and a double isotope infusion technique (3H-glu-cose to measure glucose production and 14C-alanine to assess gluconeogenesis). DCA infusion (0.4 mg/kg-min) resulted in an 82 ± 1% fall in the arterial plasma alanine level and a 53 ± 8% fall in the arterial whole blood lactate level. Hepatic uptake of alanine and lactate fell 67 ± 5% and 59 ± 15%, respectively, although the fractional extraction of these intermediates was not altered. DCA decreased the conversion of circulating alanine and lactate to glucose but by only 41 ± 7%, suggesting that a slight increase in the efficiency of the intrahepatic gluconeogenic process took place. This may be explained by the decrease in the plasma insulin level (39 ± 9%) that occurred in the presence of an unchanged plasma glucagon concentration. Despite the substantial fall in the levels of gluconeogenic precursors in blood and the considerable decrease in their rate of conversion to glucose, the overall rates of glucose production and the blood glucose concentration were not altered by DCA.

These data indicate that the alanine and lactate supplied by the periphery after a 48 h fast in the dog are not essential for the acute maintenance of glucose production or euglycemia. They suggest, further, that a compensatory increase in glucose production can occur by drawing on an alternate intrahepatic carbon source, the nature of which and signal for which remain unclear.
Generalized Diminution in the Response to Nutrients as Insulin-releasing Agents During the Early Neonatal Period in the Rat
Authors: Grill V , Lake W , Freinkel N
Published: September 2013

Glucose-induced insulin secretion is diminished during the fetal and neonatal period. To investigate whether the “defect” in B-cell secretion is specific for glucose and linked to glucose metabolism, the insulin-releasing effect of three nutrient secretagogues, glucose, glyceraldehyde, and leucine, were compared at different ages of the rat in vivo (1- and 7-day neo-nates) and in vitro (1- and 7-day neonates and adult animals). Intraperitoneal injections produced a marked insulin response to glucose, glyceraldehyde, and leucine in 7-day animals but only small increments that were not significant in 1-day neonates.

The accumulation of insulin from isolated islets of 1-day neonates during 60-min incubations was slightly but significantly enhanced by 11.1-34.4 m M glucose or 40 mM leucine. No response was seen with 1-16 mM glyceraldehyde. By contrast, all three secretagogues markedly stimulated insulin secretion from 7-day and adult islets. However, quantitative relationships differed. Thus, the response from 7-day islets to the highest concentration of glucose was 20%, to glyceraldehyde 10%, and to leucine 50% of adult values. A “basal” concentration of glucose (4.4 mM) amplified glyceraldehyde- or leucine-induced insulin release, but did not influence the age-related differences in secretory response.

The nutrient secregogues induced a small percent stimulation of (32P)-orthophosphate efflux from prelabeled islets of 1-day neonates. This stimulation increased progressively with age. However, in 1- and 7-day islets glucose and leucine stimulated the efflux of 32P more than glyceraldehyde; in adult islets the nutrients were equipotent. Glucose, glyceraldehyde, and leucine increased the accumulation of (3H) cyclic AMP in prelabeled adult but not in 7- or 1-day islets.

The foregoing indicates that the obtunded insulin secretion at birth in the rat may apply to all nutrient secretagogues. Because of the difference in metabolic disposition of tested secretagogues, the secretory limitation cannot be ascribed to faulty glycolysis but must involve some communally shared, probably early, step in stimulus-secretion coupling. Continued maturation includes preferential development of the secretory responsiveness to some secretagogues.
Organ Culture of Fetal Mouse Pancreas: The Effect of Culture Conditions on Insulin and Glucagon Secretion
Authors: Collier S , Mandel T E , Hoffman L , Caruso G
Published: September 2013

Seventeen-day-old mouse pancreas was grown in organ culture under various culture conditions and the insulin released into the medium, either chronically or during acute incubations, was measured. Three media, DME, RPMI 1640, and TC199, were tested, each at glucose concentrations of 1, 2, 3, and 4 g/L. Fetal pancreata maintained in RPMI 1640 at 4 g/L glucose secreted the most insulin over a 25-day period. Tissue grown in RPMI 1640 and DME secreted more insulin in higher glucose concentrations, but explants grown in TC199 secreted low levels of insulin regardless of glucose concentration. Fetal pancreata grown in medium supplemented with 5% FCS secreted less insulin in acute incubations than tissues grown in 10%, 15%, 20%, or 30% FCS, which secreted equivalent amounts. There was no difference in the amount of insulin released by islets grown in media supplemented with 15% FCS from four different batches.

Although fetal islets grown in high glucose concentrations generally secreted more insulin (and less glucagon) than “normoglycemic” controls, their ability to release insulin in subsequent acute incubations was impaired. Explants, which had been maintained for 2 wk in 2.5 or 4 g/L glucose and a further 3 days in normoglycemic medium, secreted less insulin and glucagon in acute release exeriments than tissue maintained in 1 g/L glucose throughout.

Light microscopy of cultured fetal pancreas showed that tissue remained viable at all glucose concentrations tested and differences in response could not be attributed to selective necrosis. Tranplantation of cultured islets indicated that tissue grown under normoglycemic conditions functioned better than tissue grown in hyperglycemic media.
Changes in the Volumes of the A-, B-, and D-Cell Populations in the Pancreatic Islets During the Postnatal Development of the Rat
Authors: McEvoy Robert C
Published: September 2013

The changes in the volumes of three of the principal islet cell types in the developing rat pancreas were quantitated from day 10 to day 210 of life. The insulin-, glucagon-, and somatostatin-positive cell populations of the islets were identified by immunocytochemical staining, and their volumes were determined by linear scanning. The insulin and glucagon content of the pancreata, and the concentrations of these hormones in plasma, were also determined at each age by radioimmunoassays. The volumes of the A- and D-cells reached their maximum values by day 50 and day 35, respectively. The content of glucagon within the pancreas reached adult levels by day 50. In contrast, the volume of B-cells and the insulin content were highest on day 210. The concentrations of both insulin and glucagon in the plasma reached adult levels by approximately day 50. There were no differences in the pancreatic parameters between male and female rats until day 25, when the wet weight of the male gland became significantly greater. The concentrations of the islet hormones and the percentages of the islet cell types within the pancreas did not differ between the sexes at any age. However, the greater weight of the pancreas resulted in a greater total content of islet cells and hormones in the male gland after day 25. The data suggest that, in the rat, the B-cell volume may continue to increase with age, while the A- and D-cells apparently do not. The physiologic consequences of these changes remain to be determined.
Correction of Exercise-induced Microalbuminuria in Insulin-dependent Diabetics After 3 Weeks of Subcutaneous Insulin Infusion
Authors: Viberti Giancarlo , Pickup John C , Bilous Rudolf W , Keen Harry , Mackintosh David
Published: September 2013

The effect of metabolic near-normalization, induced by continuous subcutaneous insulin infusion, on the exaggerated microalbuminuria of exercise was studied in eight insulin-dependent diabetic men selected for normal resting albuminuria. Patients were studied in randomized order during the ordinary glycemic control of conventional insulin treatment (CIT) and after 3 wk of “super-control” with continuous subcutaneous insulin infusion (CSII). Seven age-matched healthy men were used as controls. In the diabetics the albuminuric response to fixed-load bicycle exercise (600 kpm/min for 20 min) during CIT greatly exceeded that of the normal controls (P < 0.01). After 3 wk of optimal plasma glucose control, urinary albumin excretion rates in response to the same exercise load were significantly reduced (P < 0.02) in the diabetics and became statistically indistinguishable from that of the normal controls. The urinary excretion rate of β2-microglobulin, an index of tubular function, was not increased significantly by exercise either during CIT or CSII.

The plasma glucose fall after exercise was greater (P < 0.001) on CIT (8.5 ± 0.9 mmol/L) than on CSII (4.0 ± 0.6 mmol/L). The pulse rate acceleration in response to exercise was significantly reduced after 3 wk of CSII (P < 0.05). The exercise-induced systolic blood pressure rise was similar in controls and diabetics on both therapeutic regimens.

Thus, a period of metabolic near-normalization in the diabetic corrects the abnormal transglomerular passage of albumin induced by moderately strenuous muscular exercise and reduces the exercise tachycardia. Improved control with CSII appears to reduce greatly the risk of exercise-induced hypoglycemia, despite much tighter glycemic control.
Somatostatin: Mechanism of Action in Pancreatic Islet β-Cells
Authors: Pace Caroline S , Tarvin John T
Published: September 2013

The widespread role of somatostatin (SRIF) as a mediator of function in the brain and gut has stimulated interest in its mechanism of action. We have examined the mode of action of SRIF in stimulus-secretion coupling in the pancreatic islet β-cell to determine whether SRIF antagonizes the glucose-induced decrease in K+ permeability (PK). The influence of SRIF on 86Rb fluxes and insulin release in cultured rat islet cells, and also the electrical events recorded from cultured islets and microdissected mouse islets, was examined. In cultured islets, 100 ng/ml SRIF in the presence of 16.7 mM glucose inhibited the incidence of spike activity and evoked hyperpolarization. This effect was counteracted by 0.1 mM quinine and 20 mM tetraethylammonium (TEA), drugs that inhibit the Ca2+-sensitive or voltage-sensitive increase in PK, respectively. These agents also counteracted the inhibitory influence of SRIF on glucose-induced insulin release in cultured islets. SRIF disrupted the typical glucoseinduced oscillatory pattern of electrical activity (burst activity) during continuous microelectrode recordings in mouse β-cells, resulting in a transient 5 mV hyperpolarization and a decrease in the frequency of generation of burst activity. The presence of 20 mM TEA prevented the influence of SRIF on the electrical activity. SRIF had no effect on the accumulation of 86Rb into islet cells obtained in the presence of 16.7 mM glucose. However, SRIF enhanced the rate of 86Rb efflux from ceils exposed to glucose. SRIF-induced enhancement of 86Rb efflux was antagonized by TEA or quinine. These results indicate that SRIF may activate PK as its primary mode of action, an event that may be sufficient to reduce the accumulation of intracellular Ca2+ thereby disrupting glucose-induced stimulus-secretion coupling.
Subcutaneous, Isogeneic Transplantation of Duct-ligated Pancreas in Streptozotocin-Diabetic Mice: Relationships Between Carbohydrate Tolerance and Hormone Content in Transplant or Host Pancreas
Authors: Kramp Robert C , Burr Ian M
Published: September 2013

Mice with subcutaneous, isogeneic transplants of duct-ligated pancreas from either two or five donors displayed impaired glucose tolerance to gastric or intravenous glucose, or to an overnight fast followed by a 15-min meal of mouse food. Compared with peripheral insulin responses in normal controls, those of transplant recipients were less after gastric or intravenous glucqse, but no different after the meal. Despite normalization of peak insulin levels in the peripheral circulation of isografted mice, glucose clearance was still impaired and this probably resulted, in part, from a relative insufficiency of insulin in the portal circulation. Results of glucose tolerance tests, after transplant recipients consumed a relatively small amount of food, suggested that near-normal glucose homeostasis may be present for these mice under normal feeding conditions.

In mice that received incremental doses of streptozotocin, impaired glucose tolerance to a meal was observed if pancreatic insulin content fell below 26% of normal. We failed to show a similar relationship between glucose tolerance and pancreatic insulin content in transplant recipients since all showed impaired glucose tolerance. Despite the initial transplantation of different amounts of islet tissue, at termination insulin content (transplant plus endogenous pancreas) was essentially the same for all recipients, totaling 19–22% of that found in a normal mouse pancreas.
Nonenzymatic Glycosylation of Low Density Lipoproteins In Vitro: Effects on Cell-interactive Properties
Authors: Gonen B , Baenziger J , Schonfeld G , Jacobson D , Farrar P
Published: September 2013

Atherosclerosis occurs at an accelerated rate in patients with diabetes mellitus. Since some proteins undergo nonenzymatic glycosylation in diabetic patients and because certain chemical modifications of low density lipoproteins produced alterations in their interactions with certain cultgred cells, a fact that may be relevant to atherogenesis, we investigated the effect of in vitro glycosylation on cell-related properties of low density lipoproteins.

Glycosylation was carried out by incubating LDL (1–10 mg LDL-protein/ml) with glucose (0–100 mM) in 0.5 M phosphate buffer, pH 8.0, at 37°C. The amount of glucose incorporated into LDL after 1–2 wk of incubation was estimated to be in the range of 1–10 mol/mol LDL-protein. Amino acid analysis of glycosylated LDL showed that glucose was covalently bound to lysine residues.

In studies with cultured human fibroblasts, glycosylated LDL was internalized and degraded significantly less than control LDL, in proportion to the estimated degree of glycosylation (12% of control for the most extensively glycosylated LDL). Glycosylation of LDL also impaired significantly its ability to stimulate cholesteryl ester synthesis by cultured fibroblasts. Glycosylated LDL did not stimulate cholesteryl ester synthesis in rat peritoneal macrophages. If glycosylation of LDL occurs in diabetic patients, some pathophysiologic consequences related to the increased incidence of atherosclerosis in these patients may result.