bluuebunny/crossref_metadata_2025 huggingface dataset:
The Acute and Chronic Effects of Sulfonylurea Therapy in Type II Diabetic Subjects
Authors: Kolterman O G , Gray R S , Shapiro G , Scarlett J A , Griffin J , Olefsky J M
Published: September 2013

Although sulfonylurea agents have been used in the clinical management of type II diabetes (non-insulin-dependent diabetes mellitus, NIDDM) for over two decades, the mechanisms responsible for their hypoglycemie action remain controversial. We have quantitated glycemie control, endogenous insulin secretion in response to mixed meals, adipocyte insulin binding, insulin-mediated peripheral glucose disposal, and basal hepatic glucose output in 17 type II diabetic subjects before and after 3 mo of therapy with the second-generation, sulfonylurea compound glyburide in an attempt to identify the factors responsible for the clinical response to the drug. In addition, 9 subjects were treated for an additional 15 mo to see if the response to the drug changed with time.

The mean fasting serum glucose level fell from an initial value of 264 ± 17 mg/dl to 178 ± 16 mg/dl after 3 mo of drug therapy. Endogenous insulin secretion increased in all subjects, but the increase was most marked in those subjects who continued to exhibit fasting hyperglycemie (fasting serum glucose > 175 mg/dl) after 3 mo of therapy. Adipocyte insulin binding was unchanged after 3 mo of therapy, while the maximal rate of peripheral glucose disposal was increased by 23%, indicating enhancement of peripheral insulin action at a postreceptor site(s). Basal hepatic glucose output showed a significant correlation with the fasting serum glucose level both before and after therapy (r = 0.86, P < 0.001) and fell from 141 ±12 mg/m2/min before therapy to 107 ± 11 mg/m2/min after 3 mo of therapy. A significant correlation was also found between the decrease in the fasting glucose level and both the reduction in basal hepatic glucose output (r = 0.81, P < 0.001) and the enhancement of postreceptor function in peripheral tissues (r = 0.68, P < 0.005). After 18 mo of therapy, those subjects exhibiting an initial good response to the drug demonstrated a slight decrease in endogenous insulin secretion compared with the levels seen at 3 mo, adipocyte insulin binding had increased to the normal range, postreceptor function was further enhanced, and basal hepatic glucose output remained unchanged from the levels observed after 3 mo of therapy.

We conclude that (1) glyburide therapy increases endogenous insulin secretion, increases adipocyte insulin binding after 18, but not 3, mo of therapy, enhances peripheral insulin action by acting primarily at a post-receptor site, and reduces basal hepatic glucose output; (2) the increase in postreceptor function and the reduction of basal hepatic glucose output appear to be the crucial determinants of the clinical response to the sulfonylurea agent; and (3) the response pattern to sulfonylurea compounds in terms of these various parameters can vary as a function of the duration of treatment.
The Stimulus-Secretion Coupling of Amino Acid-induced Insulin Release: Secretory and Oxidative Response of Pancreatic Islets to L-Asparagine
Authors: Malaisse-Lagae Francine , Welsh Michael , Lebrun Philippe , Herchuelz Andre , Sener Abdullah , Hellerstrom Claes , Malaisse Willy J
Published: September 2013

L-Asparagine (2–10 mM) failed to affect insulin secretion from rat pancreatic islets incubated in the absence of exogenous nutrient or presence of D-glucose, but caused a dose-related and progressive enhancement of insulin release evoked by L-leucine, 2-aminobicyclo [2,2,1] heptane-2-carboxylate, or 2-ketoisocaproate. The secretory response to the combination of L-asparagine and L-leucine was augmented by theophylline and inhibited in the absence of extracellular Ca2+ or presence of either menadione or methylamine. L-Asparagine augmented leucine-stimulated 45Ca net uptake. The ATP content, rate of O2 uptake, and malate/ pyruvate ratio were not significantly different in islets exposed to L-leucine alone or to both L-asparagine and L-leucine, respectively. In the sole presence of L-asparagine, however, the malate/oxalacetate ratio was decreased and the malat/pyruvate ratio increased, relative to basal values. It is proposed that the enhancing action of L-asparagine upon insulin release evoked by L-leucine might be due to an accelerated generation rate of cytosolic NAOPH, rather than to any sizable increase in either islet respiration or steady-state cytosolic NADPH/NADP+ ratio.
Prevention and Reversal of Defective Axonal Transport and Motor Nerve Conduction Velocity In Rats with Experimental Diabetes by Treatment with the Aldose Reductase Inhibitor Sorbinil
Authors: Tomlinson David R , Moriarty Richard J , Mayer J Heidi
Published: September 2013

This investigation was designed to determine whether the aldose reductase inhibitor Sorbinil prevented the development of or reversed defects of nerve conduction and axonal transport in streptozotocin-diabetic rats. Untreated diabetes of either 3 or 6 wk duration caused a fall in sciatic motor nerve conduction velocity (MNCV) of 6–9 m/s (P < 0.001) and significantly reduced the accumulation of axonally transported choline acetyltransferase activity against a 24-h sciatic nerve crush. These functional defects were associated with accumulation of sorbitol and depletion of myo-/nositol in the sciatic nerve. Treatment with Sorbinil (25 mg/kg/day, p.o.) throughout the period of diabetes prevented the development of all these abnormalities in both 3- and 6-wk diabetic groups.

In a second study, three groups of rats were subject to 3 wk untreated diabetes followed by Sorbinil treatment (as above) for 1, 2, or 3 wk to determine whether the abnormalities expected from 3 wk of untreated diabetes could be reversed. One week of treatment significantly elevated both MNCV and choline acetyltransferase accumulation (P < 0.05). The longer treatments progressively ameliorated these defects such that the group that received Sorbinil for the second 3 wk of a 6-wk diabetic period gave values that were similar to controls and to diabetic rats that had been given Sorbinil throughout their diabetes. Sorbitol accumulation was markedly reduced by only 1 wk of Sorbinil treatment, but the normalization of myo-inositol levels required 2 wk of treatment. These findings indicate that Sorbinil treatment in diabetic rats prevented and reversed both Sorbitol accumulation and depletion of nerve myo-inositol in the sciatic nerve. The treatment also prevented and reversed defects of nerve conduction and orthograde axonal transport.
Inhibition of Heparin-Catalyzed Human Antithrombin III Activity by Nonenzymatic Glycosylation: Possible Role in Fibrin Deposition in Diabetes
Authors: Brownlee Michael , Vlassara Helen , Cerami Anthony
Published: September 2013

The effect of nonenzymatic glycosylation on the biologic function of human antithrombin III was evaluated using a chromogenie thrombin substrate assay in the presence of catalytic amounts of heparin. Experimental conditions that increased the rate of nonenzymatic protein glycosylation were associated with decreases in the thrombin-inhibiting activity of antithrombin III. This glycosylation-induced inhibition of heparin-catalyzed antithrombin III activity was completely reversible by preassay incubation with excess sodium heparin.

These observations provide a biochemical explanation for the heparin-reversible, accelerated fibrinogen disappearance rate induced by hyperglycemia in diabetic patients. Defective inhibition of the coagulation cascade induced by excessive nonenzymatic glycosylation of antithrombin III in vivo could contribute to accumulation of fibrin in various diabetic tissues.
Superoxide Dismutase in Diabetic Polymorphonuclear Leukocytes
Authors: Nath N , Chari S N , Rathi A B
Published: September 2013

The level of Superoxide anion was found to be significantly elevated in polymorphonuclear leukocytes (PMNL) from diabetic subjects as compared with those from normal subjects. This elevation was attributed to the significant reduction in the activities of both cytoplasmic and mitochondrial Superoxide dismutase (SOD), the effect being more pronounced in the cytoplasmic fraction. Although the content of copper decreased considerably in the diabetic PMNL, the decrease in the zinc content was less significant, with an insignificant alteration in the content of manganese. PMNL obtained from insulin-treated diabetic patients showed considerable alleviation of SOD levels. The implication of these results are discussed herein.
Adsorption Isotherms of Insulin onto Various Materials
Authors: Sefton Michael V , Antonacci G M
Published: September 2013

Insulin adsorption isotherms on various materials have been measured to begin to clarify the role of material surface energy in insulin aggregation. Using 125I-insulin and direct γ-counting of the exposed material, more insulin (per unit area) was adsorbed to hydrophobic materials (Teflon, Silastic) than to the hydrophilic ones (polyacrylamide, glass) from insulin solutions ranging from 0.1 to 100 U/ml. For example, after 30 min at room temperature, Teflon disks adsorbed 4.0 × 104 μU/cm2 and glass beads adsorbed 3.0 × 103 μU/ cm2 from a phosphate-buffered, 100-U/ml solution (pH 7.4). The Teflon value exceeded, by a factor of six, an estimated plateau surface concentration based on the molecule area (750 Å2), suggesting the occurrence of multilayer adsorption. Changing the buffer to acetate and lowering the pH to 3.5 resulted in an increased surface concentration, while the addition of glutamic or aspartic acid at pH 3.5 reduced the surface concentration to be comparable with that observed on glass and less than that observed on Teflon from phosphate buffer. Increasing the temperature to 37°C resulted in a small decrease in adsorption, consistent with the exothermic adsorption of other proteins on similar materials. However, the significance of the adsorbed molecules in nucleating aggregate formation relative to other contributing factors remains to be assessed.
Action of Sorbinil in Diabetic Peripheral Nerve: Relationship of Polyol (Sorbitol) Pathway Inhibition to a myo-Inositol-mediated Defect in Sodium-Potassium ATPase Activity
Authors: Greene Douglas A , Lattimer Sarah A
Published: September 2013

The small, but statistically significant, improvement in nerve conduction after treatment of diabetic patients with the aldose reductase inhibitor, sorbinil, suggests that increased polyol (sorbitol) pathway activity may contribute to diabetic nerve conduction slowing. Although classically viewed solely in terms of sorbitol-induced osmotic swelling, polyol pathway inhibition is now speculated to influence a concomitant myo-inositol-mediated alteration in nerve sodium-potassium ATPase activity in diabetic nerve. Therefore, we directly examined the effect of sorbinil treatment on sodium-potassium ATPase activity in crude homogenates of sciatic nerve from streptozotocin-diabetic and non-diabetic rats. We demonstrate that sorbinil treatment, which preserves normal nerve myo-inositol content, prevents the fall in nerve sodium-potassium ATPase activity that has been linked to conduction slowing in the diabetic rat.
A Reliable and Reproducible Test for Adequate Glucose Counterregulation in Type I Diabetes Mellitus
Authors: Bolli G B , Feo P De , Cosmo S De , Perriello G , Ventura M M , Benedetti M Massi , Santeusanio F , Gerich J E , Brunetti P
Published: September 2013

The safety, reproducibility, and reliability of an insulin infusion test for assessment of adequate glucose counterregulation were evaluated in 18 patients with type I (insulin-dependent) diabetes mellitus. When the test (a 60-min, 30-mU/m2/min insulin infusion) was administered on three separate occasions at 3–4-wk intervals, coefficients of variation for plasma glucose and counterregulatory hormone (glucagon, epinephrine, cortisol, and growth hormone) responses averaged less than 8%. No patient experienced symptoms requiring discontinuation of the test and plasma glucose concentrations increased spontaneously after stopping the insulin infusion. Using objective criteria based on plasma glucose nadirs or postnadir rates of plasma glucose recovery, no patient judged to have adequate glucose counterregulation by the test (post-nadir rates of plasma glucose recovery or plasma glucose nadir above 0.4 mg/dl/min and 45 mg/dl) developed severe hypoglycemia (plasma glucose < 40 mg/dl) during up to 7 mo of intensive insulin therapy, whereas nearly all patients with inadequate counter-regulation did. We conclude that this test, when performed in standardized conditions, is safe and reproducible and can reliably predict those patients with type I diabetes who are at risk of developing severe hypoglycemia during intensive insulin therapy.
Processing of Insulin by Bovine Endothelial Cells in Culture: Internalization Without Degradation
Authors: Jialal Ishwarlal , King George L , Buchwald Sherry , Kahn C Ronald , Crettaz Marco
Published: September 2013

Insulin binding and processing was studied in monolayer cultures of bovine aortic endothelial cells. Specific 125I-insulin binding was both time and temperature dependent. Maximum binding at 37°C occurred at 90 min, and was 3.8%/mg protein and, at 15°C, 7%/mg protein at 4 h. 125I-insulin was crosslinked to its receptor using disuccinimidyl suberate (DSS), and the structure of the receptor complex was identified by SDS-polyacrylamide gel electrophoresis and autoradiography; a major band with Mr = 145,000 was identified, which corresponds to the α-subunit of the insulin receptor reported in other tissues. Receptor-bound insulin was internalized, and both the rate and the amount of internalization were temperature dependent. The rate of internalization was slowest at 4°C, and fastest at 37°C, and the maximum amount of 125I-insulin internalized in 120 min was 16% at 4°C, 45% at 15°C, and 81% at 37°C. Despite the high rate of internalization, endothelial cells do not appear to degrade insulin significantly, as determined by gel chromatography and TCA solubility (7% at 4 h) of media-associated radioactivity. In addition, the majority of internalized insulin (75%) was released by 60 min, largely as intact insulin. Chloroquine treatment at high concentration did not exert any major effect on insulin binding or degradation within the first 60 min, but thereafter produced a marked increase in cell-associated radioactivity.

Owing to these unusual features of endothelial cells in rapidly internalizing and releasing the 125I-insulin with minimal degradation, we suggest that insulin receptors on these cells may serve to transport insulin from the intravascular space to the subendotheliai tissues.
Pituitary Response to Growth Hormone–releasing Factor in Diabetes: Failure of Glucose-mediated Suppression
Authors: Press Martin , Tamborlane William V , Thorner Michael O , Vale Wylie , Rivier Jean , Gertner Joseph M , Sherwin Robert S
Published: September 2013

To evaluate the mechanism underlying raised growth hormone levels in diabetes, we compared the response to growth hormone–releasing factor (GRF) in type I diabetic and healthy control subjects. In 12 poorly controlled diabetic subjects (fasting plasma glucose 276 ± 27 mg/dl) basal serum growth hormone levels were elevated by 200–300% (P < 0.02), yet the incremental increase in growth hormone after GRF injection was no greater than in control subjects. Furthermore, five additional diabetic subjects with normal growth hormone levels after long-term insulin pump treatment also showed an identical response to GRF. Thus, raised basal growth hormone levels in diabetes and the fall that follows intensive insulin treatment may reflect changes in hypothalamic regulation of, rather than in pituitary responsiveness to, GRF. However, when five normal subjects were restudied during glucose infusion, even quite modest hyperglycemie (plasma glucose ∼150 mg/dl) caused marked suppression of the response to GRF (P < 0.005). Thus, the “normal” response to GRF in poorly controlled diabetes is actually inappropriate. Failure of the pituitary to suppress in response to hyperglycemie in diabetes implies a second abnormality that may further aggravate disordered growth hormone secretion.
Restriction Fragment Polymorphisms in the Major Histocompatibility Complex of Diabetic BB Rats
Authors: Kastern W , Dyrberg T , Schøller J , Kryspin-Sørensen I
Published: September 2013

DNA isolated from diabetic BB (BB/Hagedorn) rats was examined for restriction fragment length differences within the major histocompatibility complex (MHC) as compared with nondiabetic (W-subline) BB rats. Polymorphisms were detected using a mouse class I MHC gene as probe. Specifically, a 2-kb BamHI fragment was present in all the nondiabetic rats examined, but absent in the diabetic rats. Similar polymorphisms were observed with various other restriction enzymes, particularly Xbal, Hindii, and Sacl. There were no polymorphisms detected using either a human DR-α (class II antigen heavy chain) or a human DC-β (class II antigen light chain) gene as probes. These results indicate that the BB rat diabetic syndrome may be linked to differences in class I MHC genes.
Factors Influencing Reticulophagocytic Function in Insulin-treated Diabetes
Authors: Lawrence Susan , Charlesworth J A , Pussell B A , Campbell Lesley V , Kotowicz M A
Published: September 2013

The splenic component of reticulophagocytic function (RPF) was examined in 29 insulin-treated diabetic subjects (13 type I and 16 type II) by measurement of clearance of altered, radiolabeled, autologous erythrocytes. Double-isotope studies were performed with cells altered by: (1) preincubation with N-ethylmaleimide (NEM) and (2) coating with IgG antibody to the Rhesus (Rh) D antigen, labeled with 99mTc and 51Cr, respectively. HLA typing for the A, B, and DR loci was performed in those patients showing a defect in the clearance of IgG-coated cells. Values for half-life (t½ were correlated with the incidence of diabetic complications, levels of HbA15 and circulating immune complexes (CIC). Two patterns of abnormal clearance were observed: first, an isolated defect of IgG-coated cell clearance in 7 patients (3 had the HLA B8/DR3 haplotype) and second, abnormal removal of both types of cell in a further 7 patients (3 had B8/DR3). There was no correlation between half-lives as measured by the two methods, although exclusion of the patients with a defect of IgG-coated cell clearance alone yielded a highly significant correlation for the remaining 15 Rh-positive patients (P < 0.01). Abnormalities of IgG-coated cell clearance were more frequent in patients with HbA1 > 9% (P < 0.02), while t½ of NEM-altered cells was significantly greater in patients with CIC (P < 0.05). There was no correlation between t½ and the incidence of peripheral complications.

The influence of splenic blood flow (as measured by organ weight and retention of injected radiolabeled microspheres) on the t½ of NEM-altered cells was examined in rabbits. The t½ correlated with both splenic weight (P < 0.001) and retention of microspheres (P < 0,001).

Our data emphasize the value of double-isotope studies in assessing RPF in vivo. The isolated abnormality of IgG-coated cell clearance probably resulted from a specific defect of the splenic macrophage receptor and the B8/DR3 haplotype, and blood sugar control appeared to influence this abnormality. In addition to these factors, our animal studies suggested that splenic blood flow could contribute to the dual defect seen in a further 7 patients. These factors could hinder the removal of potentially tissue damaging macromolecules from the circulation of patients with diabetes.
Diminished Bone Formation in Experimental Diabetes: Relationship to Osteoid Maturation and Mineralization
Authors: Goodman William G , Hori Mark T
Published: September 2013

The pathogenesis of osteopenia in clinical diabetes remains uncertain. Thus, bone formation, mineralization, and resorption were measured over a 10-day period using double-tetracycline labeling of bone in control (C, N = 18), untreated diabetic (I–, N = 14), and insulin-treated diabetic (l +, N = 16) rats. Diabetes was induced by the intravenous (i.v.) injection of streptozotocin (STZ), 90 mg/kg, in citrate buffer. Bone and matrix (osteoid) formation and apposition were decreased by 50% from C values in I– rats (P < 0.05), but were unchanged in I + rats. Osteoid seam width and osteoid area were also less in I– (P < 0.05), but similar in I +, when compared with C. In untreated diabetic rats that continued to actively form new bone, osteoid maturation and mineralization were not diminished when adjusted for the rate of bone formation. However, 5 of 14 untreated and 2 of 16 insulin-treated diabetic animals showed no uptake of tetracycline into bone (Chisquare, 8.54; P < 0.05), suggesting a defect in mineralization in a subset of diabetic rats. Measurements of serum glucose, calcium, and phosphorus concentrations, of urinary excretion rates for glucose, calcium, and phosphorus, and of creatinine clearance failed to correlate with the changes in bone growth and histology observed. The results indicate heterogeneity in the response of bone in diabetes, and suggest that bone formation and osteoid volume are reduced early in the course of this disorder. These data in short-term diabetes support previous observations in both man and rat that indicate a state of low bone turnover in diabetes.
Platelet Aggregation in Experimental Diabetes and Experimental Galactosemia
Authors: Kern Timothy S , Engerman Ronald L
Published: September 2013

Platelet aggregation and related plasma factors have been studied in experimentally diabetic dogs, experimentally galactosemic dogs, and in normal dogs. Platelet aggregation, when induced in vitro by ADP (up to 22 μM) or collagen (up to 4 μg/ml), was not significantly different from normal in the diabetic or galactosemic dogs. Plasma (platelet-deficient) from the diabetic or galactosemic dogs did not enhance ADP-induced aggregation of normal canine platelets. Fibrinogen concentration in blood tended to be elevated in hyperglycemie diabetic dogs, and was significantly correlated with the levels of HbA1 and blood glucose, whereas galactosemic animals had normal fibrinogen concentrations. The quantity of 6-keto prostaglandin F1α released from aortas of diabetic dogs was less than that released from aortas of normal dogs. Since alloxan-diabetic dogs and galactosemic dogs develop microaneurysms, occluded capillaries, and other retinal lesions characteristic of diabetic retinopathy in human patients, these studies suggest that retinopathy can develop in the absence of extraordinary in vitro platelet aggregation.
Effect of 2-Bromostearate on Glucose-Phosphorylating Activities and the Dynamics of Insulin Secretion in Islets of Langerhans During Fasting
Authors: Bedoya Francisco J , Ramírez Remedios , Arilla Eduardo , Goberna Raimundo
Published: September 2013

Glucose-phosphorylating activity and insulin secretion were measured in homogenates of isolated rat islets and of perfused rat pancreas, respectively. Fasting for 96 h produced a significant decrease of both low-and high-Km glucose-phosphorylating activities and blocked the insulin secretory response to glucose. In the presence of glucose, 0.25 mM 2-bromostearate, a known inhibitor of fatty acid oxidation, partially restored the insulin response to glucose that was lost during fasting. This effect paralleled the restoration of glucose-phosphorylation activities (primarily the high–Km component) seen when islets isolated from 96-h-fasted rats were preincubated with 0.25 mM 2-bromostearate.

It is concluded that fasting-induced adaptations of glucose-phosphorylating enzymes could account, at least in part, for the reduced insulin secretory response to glucose. 2-Bromostearate, an inhibitor of fatty acid oxidation, is able to restore both insulin secretory response and glucose-phosphorylating activities, suggesting possible interrelations among the correlated impairment in insulin secretion, islet glucose-phosphorylating activity, islet glucose metabolism, and the oxidation of fatty acids in the B-cell during fasting.
The Effect of Maternal Diabetes on Trace Element Status and Fetal Development in the Rat
Authors: Uriu-Hare Janet Y , Stern Judith'S , Reaven Gerald M , Keen Carl L
Published: September 2013

Despite improvements in prenatal care, there is a high incidence of congenital malformations in diabetic pregnancies. Not only is the diabetic patient characterized by a disorder of total fuel metabolism, but abnormal trace element metabolism occurs as well. In the present study, maternal and fetal zinc (Zn), copper (Cu), manganese (Mn), iron (Fe), magnesium (Mg), and calcium (Ca) status has been studied in Sprague-Dawley (SD) and Wistar rats. In addition, the effect of maternal diabetes on fetal development was also investigated. Rats were injected 27 days before mating with streptozocin (STZ, 45 mg/kg) in citrate buffer. On day 20 of gestation, litters were taken by cesarean section. Fetuses from diabetic dams weighed less, and had shorter crown-rump lengths and larger placentas than fetuses from controls. Evaluation of fetal skeletal development revealed fewer calcified sternal sites, anterior phalanges and caudal vertebrae, and an increased frequency of malformations in fetuses of diabetic dams. In dams, diabetics had larger adrenals, kidneys, and liver, and smaller thymus.

Abnormal trace element metabolism was evident in diabetic dams and their fetuses. Mn was elevated in maternal liver, kidney and placenta of diabetic animals as well as in fetal liver of pups from diabetic dams. Maternal Cu and Zn levels were also higher in the liver and kidney of diabetic rats. In contrast, fetal liver Zn from fetuses of diabetic mothers was significantly decreased when compared with controls. These results suggest that diabetes may have induced fetal Zn deficiency. If this deficiency is present during embryogenesis/organogenesis, this could be one of the mechanisms of the teratogenicity of the diabetic state.
The Influence of Body Fat Distribution on the Incidence of Diabetes Mellitus: 13.5 Years of Follow-up of the Participants in the Study of Men Born in 1913
Authors: Ohlson L -O , Larsson B , Svärdsudd K , Welin L , Eriksson H , Wilhelmsen L , Björntorp P , Tibblin G
Published: September 2013

In a prospective study of risk factors for ischemic heart disease, 792 54-yr-old men selected by year of birth (1913) and residence in Göteborg, Sweden, agreed to attend for questioning and a number of anthropometric and other measurements in 1967. Thirteen and one-half years later, these baseline findings were reviewed in relation to the number of men who had subsequently developed diabetes mellitus.

This analysis focused on the importance of abdominal adipose tissue distribution, measured as the waistto- hip circumference ratio, as a predictor for development of diabetes. Even when the confounding effect of body mass index, as a measure of the total body fat mass, was accounted for, the waist-to-hip ratio was positively and significantly associated with the risk for diabetes.

These results from a prospective study strongly support previous cross-sectional findings indicating that not only the degree of obesity but also the localization of fat is a risk factor for diabetes.
Insulin Antibodies Retard and Insulin Accelerates Growth and Differentiation in Early Embryos
Authors: Pablo Flora De , Girbau Matias , Gomez Juan A , Hernandez Eleuterio , Roth Jesse
Published: September 2013

The physiologic function of insulin in early embryonic life is unknown. We have shown that insulin is present in unfertilized eggs and in chick embryos at 2–3 days of development, even before the emergence of the endocrine pancreas. To define insulin's role, we exposed 2-day-old chick embryos to anti-insulin antibodies and followed their development up to day 5. Antibodytreated embryos had a higher rate of growth retardation and death by days 3–5 of embryogenesis, compared with controls. Among the survivors, biochemical maturation was delayed at days 4 and 5; weight, protein, total creatine kinase activity, and creatine kinase-MB were decreased in antibody-treated embryos.

By contrast, insulin (50 ng/embryo) administered to 2-day-old embryos yielded nearly symmetrical stimulatory results. These findings suggest that endogenous insulin plays a probable physiologic role regulating growth and differentiation in early embryos. In addition, the findings provide some clues to a possible function for insulin produced outside the organism's own beta cells.
The Insulin-Pancreatic Acinar Axis
Authors: Williams John A , Goldfine Ira D
Published: September 2013

Recent studies indicate that insulin directly regulates the acinar pancreas. Morphologic and hemodynamic studies indicate the presence of a portal system that conveys islet blood to acinar cells. Studies both in humans with diabetes mellitus and in animals given beta cell toxins indicate that insulin is necessary for normal acinar cell function. Studies in the perfused rat pancreas indicate that endogenous insulin potentiates zymogen release. Isolated rat and mouse acini have insulin receptors, and in these cells, after binding to its receptors, insulin regulates a number of functions including: sugar transport, protein synthesis, and the number of choiecystokinin receptors. These in vivo and in vitro studies suggest, therefore, that there is an insulin-pancreatic acinar axis that plays a major role in pancreatic function.
Effect of Culture Conditions on Fetal Mouse Pancreas In Vitro and After Transplantation in Syngeneic and Allogeneic Recipients
Authors: Mandel T E , Koulmanda M
Published: September 2013

Organ culture of fetal mouse pancreas under conditions designed to either maximally preserve islet cell survival or reduce immunogenicity was used to test the efficacy of islet graft function in diabetic syngeneic or fully allogeneic recipients. Organ culture in either 90% O2, or at low temperature (22°C), or in a combination of 90% O2 and 22°C for 14 days not only failed to reduce immunogenicity in fully allogeneic recipients but also diminished endocrine cell survival in grafts in syngeneic recipients. Monitoring of in vitro insulin secretion provided a better guide to future graft function than did the insulin content of the cultured tissue. It is concluded that culture conditions that have been shown to reduce immunogenicity (high O2 concentration and low temperature) are not synergistic when used together and are also potentially damaging to endocrine cells.
Interferon-γ Enhances the Expression of the Major Histocompatibility Class I Antigens on Mouse Pancreatic Beta Cells
Authors: Campbell Iain L , Wong Grace H W , Schrader John W , Harrison Leonard C
Published: September 2013

Cell surface antigens of the major histocompatibility complex (MHC) play a crucial role in the initiation of immune reactions. To investigate whether the expression of MHC antigens on pancreatic islet cells could be altered, we have cultured mouse islets in the presence of interferon-γ (IFN-γ) and subsequently examined the levels of MHC antigen by indirect immunofluorescence using monoclonal antibodies. IFN-γ induced a 10-fold increase in H-2K antigen expression on islet cells, the percentage of cells with detectable H-2K expression increasing from 24% to 98%. The effects of IFN-γ on H-2D and la antigen expression were less marked, with only a twofold increase in mean fluorescence levels, the percentage of cells with detectable levels ofexpression increasing from 10% to 48% and 5% to 16%, respectively. Using double-indirect immunofluorescence, it was demonstrated that IFN-γ enhanced expression of H-2K and H-2D antigens on β-cells. However la-positive-cells were undetectable in the presence or absence of IFN-γ.

The ability of IFN-γ to induce increased expression of H-2 antigens on β-cells may represent a mechanism for targeting immune (cytotoxic) reactions to β-cells, e.g., in autoimmune insulitis or allograft rejection.
Retrograde Axonal Transport in Rat Ileal Mesenteric Nerves: Characterization Using Intravenously Administered 125I-Nerve Growth Factor and Effect of Chemical Sympathectomy
Authors: Schmidt Robert E , Yip Henry K
Published: September 2013

We have previously demonstrated the reproducible occurrence of dystrophic axonopathy and a defect in the retrograde axonal transport of 125I-nerve growth factor (125I-NGF) involving postganglionic sympathetic axons in the alimentary tract of rats with chronic streptozocin (STZ)-induced diabetes. To avoid complexities inherent in monitoring the accumulation of 125I-NGF in the superior mesenteric ganglion as a measure of retrograde transport in the peripheral axons of the extensive alimentary territory, we have examined retrograde axonal transport of 125I-NGF directly in ileal mesenteric nerves. 125I-NGF was injected systemically, and 2–2.5 h later ileal mesenteric nerve pedicles were ligated in vivo for various intervals. Retrogradely transported 125I-NGF in rat mesenteric nerves was measured distal to a ligature placed on the ileal mesenteric pedicle. Transport-unrelated processes, such as mechanical compression or bleeding at the site of ligation, did not contribute significantly to accumulation measured in this fashion. Accumulation of retrogradely transported 125I-NGF at the ligature began 4 h after ligation and remained linear for approximately 12 h. The amount of retrogradely transported 125I-NGF accumulating distal to the ligature reflected the length of the ileal segment served by the pedicle, which allowed the standardization of accumulation based on length of ileum innervated. The results of several experiments showed that 125I-NGF transport originated largely from nerve terminals within the ileal wall with a smaller component from extramural sites, probably terminals within the walls of blood vessels. Accumulation at a ligature was greatly reduced in animals sympathectomized with guanethidine or 6-hydroxydopamine, indicating that at least 60–80% of axonal transport of 125I-NGF in ileal mesenteric nerves represented transport in postganglionic sympathetic axons. These results establish the feasibility of measurement of 125I-NGF transport in the minute fascicles of ileal mesenteric nerves serving the alimentary tract of the rat as a method to study retrograde axonal transport in sympathetic axons in pathologic processes such as diabetes.
Endogenous Gut-Derived Bacterial Endotoxin Tonically Primes Pancreatic Secretion of Insulin in Normal Rats
Authors: Cornell Robert P
Published: September 2013

This laboratory has proposed that endogenous gut-derived bacterial endotoxin primes the pancreatic secretion of insulin in normal rats. Endogenous lipopolysaccharide (LPS) is continually absorbed from the gut into intestinal capillaries, and low-grade portal venous endotoxemia is the status quo. Under physiologic conditions, Kupffer cells of the liver totally phagocytize and degrade endotoxin from the portal circulation. Evidence from this and other laboratories indicates that administration of exogenous LPS to humans and rats enhances pancreatic secretion of both insulin and glucagon. Conversely, findings of the present study demonstrate that restriction of endogenous LPS in fasted rats depresses the basal and arginine-stimulated concentrations of plasma insulin. Techniques used to restrict gut-derived LPS availability included chronic daily gavage with neomycin and cefazolin for gut sterilization and with cholestyramine or lactulose to reduce endotoxin within the gut, In addition, induction of endotoxin tolerance was produced by progressively higher doses of LPS intraperitoneally (i.p.), and polymyxin B was administered subcutaneously (s.c.) daily to neutralize the lipid A portion of circulating LPS. Finally, isolator-reared, defined flora rats, which were gram-negative-bacteria-deficient, and, therefore, LPSdeficient, were compared with conventional counterparts. Basal plasma insulin but not glucagon levels were consistently and significantly reduced in endogenous LPS-restricted animals. Glucose-stimulated plasma insulin was decreased only after parenteral treatment by tolerance induction and polymyxin B administration. Both plasma insulin and glucagon were depressed in response to arginine challenge in most LPS-restricted rats. Findings of this and previous studies suggest that routine phagocytosis of portal endotoxin by hepatic Kupffer cells releases humoral factors such as interleukin-1 to tonically prime the physiologic secretion of insulin by pancreatic beta cells. Enhanced insulin removal by the liver as an explanation for reduced plasma insulin levels in endogenous LPSrestricted rats does not fit the available evidence.
Effects of Cyclosporine on Glucose Tolerance in the Rat
Authors: Yale J F , Roy R D , Grose M , Seemayer T A , Murphy G F , Marliss E B
Published: September 2013

In a study of prevention of spontaneous diabetes in BB rats by therapeutic doses of cyclosporine (10 mg/kg/ day), the male control non-diabetes-prone rats showed glucose intolerance after a 0.25 g/kg glucose load by gavage, at 90 and 130 days of treatment. Non-BB male Wistar rats treated similarly showed glucose intolerance at 1 wk of treatment, with progressive worsening for 5 wk, then sustained up to 12 wk of treatment. Fasting euglycemia was maintained, but both pre- and postchallenge plasma insulin levels were significantly lower with cyclosporine at several time points. Total pancreatic insulin was decreased to one-third that of control after 5 wk. After withdrawal of cyclosporine, glucose tolerance returned to normal in 2 wk. Sprague-Dawley rats responded similarly and in both strains, an increase in the cyclosporine dose to 15 mg/kg/day augmented the glucose intolerance. These results demonstrate that therapeutic doses of this agent induce reversible glucose intolerance due, in part, to inhibition of insulin secretion and also possibly inhibition of synthesis, though a peripheral effect is not excluded. This hyperglycemic effect of cyclosporine has implications for its potential use in type I diabetes mellitus, transplantation, and other autoimmune disease.
Elevation of Factor VIII Coagulant Activity Over Factor VIII Coagulant Antigen in Diabetic Children Without Vascular Disease: A Sign of Activation of the Factor Coagulant Moiety During Poor Diabetes Control
Authors: Muntean Wolfgang E , Borkenstein Martin H , Haas Josef
Published: September 2013

To investigate whether the elevation of factor VIII coagulant activity observed in children with poor control of diabetes is due to increased levels of the factor VIII coagulant moiety of the factor VIII complex or reflects activation of the factor VIII coagulant moiety, factor VIII coagulant activity (VIII C), factor VIII coagulant antigen (VIM C:Ag), and factor VIII-related antigen (VIII R:Ag) were determined in 75 insulin-dependent children. All children were without signs of vascular disease based on negative funduscopy, negative fluorescein angiography, normal serum creatinine levels, and absence of proteinuria. Children with poor actual control of diabetes had significantly higher VIII C values than did children with good actual control of diabetes based on HbA1 values, but VIM C:Ag values did not differ in children with good or poor actual control of diabetes. A significant elevation of VIM C over VIII C:Ag values was observed in children with poor actual control of diabetes, but no elevation of VIII C over VIM C:Ag was found in children with good actual control. VIM R:Ag values were higher in children with poor actual control. VIM C, VIM C:Ag, and VIII R:Ag did not differ significantly in children with short or long duration of clinical diabetes.

Our observation of significantly higher VIM C values, than VIM C:Ag levels strongly suggests intravascular activation of the factor VIM coagulant moiety during poor diabetes control. The process leading to activation of the coagulant moiety seems to be different from the process leading to the elevation of the other moiety of the factor VIM complex, the factor VIII-related antigen, in diabetic subjects.
Stimulatory Effect of Insulin on Aortic Smooth Muscle Cell Migration Induced by 12-L-Hydroxy-5,8,10,14-Eicosatetraenoic Acid and Its Modulation by Elevated Extracellular Glucose Levels
Authors: Nakao Junko , Ito Hideki , Kanayasu Toshie , Murota Sei-Itsu
Published: September 2013

In investigations on the role of insulin on migration of rat aortic smooth muscle cells, migration of the cells was measured by a modified Boyden chamber technique with 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) as a chemoattractant. Insulin itself was not a chemoattractant for these cells, and insulin added just before the migration assay did not affect cell migration in the presence or absence of 12-HETE.

Cells pretreated with insulin in culture dishes for a long period, however, showed a significant increase in migration induced by 12-HETE, and the increase depended on the insulin concentration: concentrations of insulin of >50 μlU/ml caused about twofold increase in cell migration. On the other hand, long-term incubation with various concentrations of insulin (0.15–1000 μIU/ml) did not affect nonspecific cell migration in the absence of 12-HETE. The stimulatory effect of insulin on cell migration gradually increased with the duration of insulin treatment, reaching a plateau after 4 days. Thus, insulin stimulated 12-HETE-induced smooth muscle cell migration in a time- and dose-dependent manner.

When the extracellular D-glucose concentration in the Boyden chamber was increased from 100 to 300 mg/dl, the stimulatory effect of insulin on 12-HETE-induced cell migration was augmented. This modulation by D-glucose was not due to an increase in the osmotic pressure of the medium, since addition of mannitol to increase the osmotic pressure did not enhance the effect of insulin on cell migration. The present results indicate that insulin in a physiologic or pathophysiologic range stimulates 12-HETE-induced smooth muscle cell migration in a manner dependent on the extracellular D-glucose concentration. These findings are relevant to the increased development of atherosclerosis in subjects with hyperinsulinemia and hyperglycemia, as is seen in obesity and diabetes mellitus.
Gestational Diabetes Mellitus and Impaired Glucose Tolerance During Pregnancy: Long-Term Effects on Obesity and Glucose Tolerance in the Offspring
Authors: Pettitt David J , Bennett Peter H , Knowler William C , Robert Baird H , Aleck Kirk A
Published: September 2013

The effects of disturbances in carbohydrate metabolism during gestation were studied in the offspring of 1049 Pima Indian women who had no previous diagnosis of diabetes. Rates of fetal and maternal complications of pregnancy among women with diabetes first diagnosed during the pregnancy were similar to those among women in whom diabetes was recognized before gestation. Offspring, aged 5–19 yr, of women with abnormal glucose tolerance during pregnancy had a higher mean percent desirable weight and a higher mean postchallenge plasma glucose concentration than did offspring of women with normal glucose tolerance. Percent desirable weight and glucose concentration, however, were both lower than found in offspring of women with diabetes diagnosed before the pregnancy. Thus, metabolic events during pregnancy, as indicated by the detection of abnormal glucose tolerance during gestation, appear to have long-term effects on obesity and glucose tolerance in the offspring.
Review: Etiology and Pathophysiology of Gestational Diabetes Mellitus
Authors: Kühl Claus , Hornnes Peter J , Andersen Ole
Published: September 2013

In pregnancy, several physiologic changes take place, the sum of which tends to reset the glucose homeostasis in the direction of diabetes. About 1–2% of all pregnant women develop an abnormal glucose tolerance in pregnancy, but most often glucose tolerance returns to normal postpartum. This condition is called gestational diabetes mellitus (GDM). The possibility that glucose tolerance deteriorates in pregnancy because of diabetes-like changes in the secretory function of the endocrine pancreas has been investigated in healthy controls and in normal-weight gestational diabetic subjects. The insulin responses to oral glucose and mixed meals are equally large in these two groups, but the insulin response per unit of glycemic stimulus is significantly lower in the gestational diabetic subjects than in the controls. Diabetes-like changes in glucagon secretion are not observed in either group. Insulin degradation is unaffected by human pregnancy and the proinsulin share of the total plasma insulin immunoreactivity does not increase in pregnancy. Insulin receptor binding to monocytes from normal pregnant women is increased in midpregnancy but is significantly decreased in late pregnancy. No difference in insulin binding (at tracer insulin concentration) to monocytes from healthy pregnant controls and gestational diabetic subjects is found. The insulin concentration necessary to reduce tracer insulin binding by 50% (ID50) is lower in the gestational diabetic subjects diagnosed in late pregnancy than in the pregnant controls. Together, these findings indicate that the number of insulin receptors on monocytes is decreased in GDM at this stage of pregnancy. Thus, the cause of GDM could be a decreased insulin receptor binding to target cells combined with a relative lack of circulating insulin, but the possibility of postreceptor defects does also exist.
Influence of Maternal Diabetes in Rats on Hemoglobin Synthesis and Uridine Uptake by Fetal Liver Cells
Authors: Mulay Shree , Congote L Fernando
Published: September 2013

The effect of streptozocin (STZ)-induced maternal diabetes in rats on fetal erythropoiesis was studied in short-term cultures of fetal liver cells at the time of switch from embryonic to adult hemoglobins. Liver erythroid cell functions were monitored by measuring the incorporation of [3H]-uridine in trichloroacetic acid (TCA)-soluble and-insoluble cell fractions and of [3H]-leucine in hemoglobin chains. Fetal liver cells of diabetic rats showed a higher incorporation of [3H]-uridine compared with controls when the cells were obtained from 14-day-old fetuses. However, there were no significant differences in the uptake of uridine when cells were obtained from 16-day-old fetuses. In parallel cell cultures, incorporation of [3H]-leucine into adult and embryonic globin chains was studied by separation of the globin chains by high-performance liquid chromatography (HPLC). The overall globin chain synthesis was higher in the fetuses of diabetic mothers compared with controls on day 14 of gestation. Erythropoietin had similar effects on the stimulation of globin chains in the two groups of fetuses. However, in the fetuses of diabetic mothers, erythropoietin had a specific stimulatory effect on embryonic-type globins that was significantly higher in the fetuses of diabetic mothers compared with controls. Differences between fetuses of control and diabetic mothers completely disappeared at 16 days of gestation. It is concluded that maternal diabetes has an effect on the cells synthesizing embryonic hemoglobins on day 14 of gestation, but by the time the switch from embryonic to adult-type hemoglobins is complete, these differences are abolished.