bluuebunny/crossref_metadata_2025 huggingface dataset:
Interleukin 1 is Potent Modulator of Insulin Secretion from Isolated Rat Islets of Langerhans
Authors: Comens Patricia G , Wolf Bryan A , Unanue Emil R , Lacy Paul E , McDaniel Michael L
Published: September 2013

The effects of interleukin 1 (IL-1) on glucose-induced insulin secretion from isolated rat islets of Langerhans have been examined. IL-1 both inhibits and stimulates glucose-induced insulin secretion depending on the experimental design. Inhibition of glucose-induoed insulin secretion was observed after a 15-h treatment of islets with either purified IL-1, murine recombinant IL-1 (rIL-1), or human rIL-1. r IL-1 inhibition of glucose-induced insulin secretion was dose dependent with half-maximal inhibition observed at 25 pM human r IL-1. Basal insulin secretion was not affected by r IL-1 treatment. Mannose- and leucine-induced insulin secretion was also inhibited by a 15-h treatment with human rIL-1.

Islets treated 15 h with inhibitory concentrations of murine IL-1 were morphologically intact, well granulated, and retained normal concentrations of insulin compared with control islets. Furthermore, human rIL-1 treatment did not affect the islet plasma membrane permeability as assessed by the measurement of the islet intracellular volume. Finally, the viability of islets treated 15 h with murine rIL-1 was demonstrated by the observation that the inhibitory effects of murine rIL-1 on glucose-induced insulin secretion were reversible.

In addition to the inhibitory effects of IL-1 on glucose-induced insulin secretion, purified IL-1 and human rIL-1 had stimulatory effects on glucose-induced insulin secretion under the following conditions: 1) a 90-min incubation with purified IL-1 (10% vol/vol) or in the presence of human r IL-1 (1400 pM) or 2) a 15-h incubation with relatively low concentrations of human rIL-1 (0.5 or 5 pM). In conclusion, IL-1 has complex dual effects on glucose-induced insulin secretion that include both stimulation and inhibition and depend on IL-1 concentration and time of incubation. These studies suggest that IL-1 may have a physiological role as a potent modulator of insulin secretion by islets of Langerhans.
Endothelium-Dependent Relaxation in Aorta of BB Rat
Authors: Meraji Shokoufeh , Jayakody Laal , Senaratne Manohara P J , Thomson Alan B R , Kappagoda Tissa
Published: September 2013

The study was undertaken to determine whether the phenomenon of endothelium-dependent relaxation was impaired in the spontaneously diabetic BB Wistar rat. Endothelium-dependent relaxation in the aorta of overtly diabetic animals was compared with that in nondiabetic BB rats. The relaxative responses were elicited in vitro to acetylcholine (−8.0 to −5.5 log M) and histamine (−7.0 to −3.0 log M) after precontraction with norepinephrine (−6.0 log M). The maximum relaxations produced by both acetylcholine and histamine expressed as percentages of the contractions to norepinephrine were significantly lower in diabetic than in nondiabetic rats. Scanning electron microscopy revealed that in diabetic BB rats there was consistent evidence of swollen cells, raised nuclei, and sloughing of nuclei in endothelial cells of the aorta. In nondiabetic animals these features were not evident. These findings suggest the presence of a functional and morphological defect in endothelial cells in the aorta of the BB rat.
In Vitro Autoregulation of Glucose Utilization in Rat Soleus Muscle
Authors: Sasson Shlomo , Edelson David , Cerasi Erol
Published: September 2013

The possibility that glucose may directly regulate its rate of utilization in skeletal muscle was investigated in vitro with the rat soleus muscle. Preincubation of the muscles with varying glucose concentrations modulated the rate of glucose utilization through the glycolytic pathway during a subsequent incubation. At glucose concentrations below ∼3.0 mM, utilization was maximal (26.8 ± 2.4 and 87.5 ± 4.8 nmol · g−1 · min−1 when assayed in the presence of 0.5 and 5.0 mM glucose, respectively). Preincubation with higher glucose concentrations (up to 20 mM) reduced the utilization by 40–60% in a biphasic manner: a rapid fall between 1 and 4 mM, followed by a gradual ∼2% decrease per each millimolar increase of glucose. The effect of preexposure to glucose was not due to substrate dilution by the remaining glucose in the extracellular or intracellular space of the muscle. The uptake of the nonmetabolizable glucose analogues 3-O-methylglucose and 2-deoxyglucose was also modulated by extracellular glucose in a similar manner. Thus, the regulatory site seems to reside in the transport function of the hexose. The ATP content was very similar in muscles preexposed to 1.0 and 15.0 mM glucose for 3 h and therefore does not seem to be the mediator of the glucose effect. This substrate regulation of the rate of glucose transport and of the glycolytic flux may be operative in the in vivo glucose homeostatic system and may contribute to the reduced peripheral glucose utilization observed in diabetes.
In Vivo Insulin Effect on ATPase Activities in Erythrocyte Membrane From Insulin-Dependent Diabetics
Authors: Rahmani-Jourdheuil Dominique , Mourayre Yves , Vague Philippe , Boyer Jean , Juhan-Vague Irène
Published: September 2013

Na+-K+-dependent ouabain-sensitive ATPase and Mg2+-ATPase have been assayed in the erythrocyte membranes of control subjects and in uncontrolled type I (insulin-dependent) diabetics. A decrease in Na+-K+-ATPase activity was observed in the patients that was significantly correlated with glycemia. The Mg2+-ATPase was increased moderately, and no correlation with glycemia was found. To study the in vivo effect of insulin, ATPase activities were measured in uncontrolled diabetics before and after a 24-h continuous insulin perfusion administered by means of an artificial pancreas. ATPase activities were corrected after normalization of glycemia. It therefore seems that glycemia and/or insulinemia are involved in the regulation of erythrocyte Na+-K + ouabain-sensitive ATPase and to a lesser extent in that of Mg2+-dependent ATPase.
Alterations in Retrograde Axonal Transport in Streptozocin-Induced Diabetic Rats
Authors: Fink David J , Purkiss David , Mata Marina
Published: September 2013

Retrograde axonal transport in the sciatic nerve of rats with streptozocin-induced diabetes was studied by the [3H]N-succinimidyl propionate ([3H]NSP) method. The accumulation of retrogradely transported labeled proteins in the dorsal root ganglia and the ventral horn of spinal cord 1 day after [3H]NSP injection was not statistically significantly different from controls in rats diabetic for 1 or 14 days at the time of [3H]NSP injection. However, accumulation of labeled proteins in the dorsal root ganglia 7 days after [3H]NSP injection was reduced by 35% and transport to the ventral horn of spinal cord 7 days after [3H]NSP injection was reduced by 70% at the same time points. Partial control of the diabetes with insulin resulted in a partial reversal of these deficits. The early occurrence of defects in retrograde transport suggests that such defects may play a role in the pathogenesis of the neuropathy.
Influence of Aging on Hepatic and Peripheral Glucose Metabolism in Humans
Authors: Jackson Rodwin A , Hawa Mohammed I , Roshania Ranjan D , Sim Bushra M , DiSilvio Luciana , Jaspan Jonathan B
Published: September 2013

Mechanisms of glucose intolerance with aging were studied by comparing the metabolic response to glucose ingestion in 10 young (20–23 yr) and 10 elderly (73–80 yr) normal men with the simultaneous application of the forearm and double-isotope techniques. The latter technique consisted of a primed-constant infusion of [3-3H]glucose followed by the administration of an oral glucose load (mean ± SE, 90.7 ± 0.7 g) containing [1-14C]glucose. Fasting plasma glucose and insulin concentrations were similar in young and elderly subjects, but in the elderly, glucose tolerance was markedly impaired. Although in the elderly the initial rise in insulin levels (∆, i.e., the incremental area under the curve) from 0 to 30 min was delayed (P < .02), the response from 0 to 45 min, 0 to 60 min, and thereafter equaled that in the young group, and from 90 to 240 min insulin concentrations in the elderly exceeded those in young subjects. Basal hepatic glucose output (HGO) was similar in young and elderly men (2.13 ± 0.10 and 1.97 ± 0.14 mg.· kg−1 · min−1, respectively). Similar proportional reductions in HGO from 0 to 270 min after glucose loading occurred in young (59.7 ± 10.3%) and elderly (50.3 ± 4.9%) subjects but was delayed in the elderly. Suppression of HGO was observed in the young 30 min after glucose ingestion (P < .02), but not before 60 min in the elderly subjects (P < .05). The systemic appearance of ingested glucose (0–270 min) was slowed with age (80.7 ± 3.1 and 66.9 ± 4.3% of the oral load in the young and elderly groups, respectively; P < .02). Initial increments in both total glucose disappearance (Rd) and forearm glucose uptake (FGU) from 0 to 60 min after glucose loading were decreased in the elderly (Rd, 4.1 ± 0.7 vs. 11.5 ± 1.3 g, P < .001; FGU, 17.2 ± 1.4 vs. 24.6 ± 2.5 md/dl forearm, P < .02). The overall increment (∆, 0–270 min) in Rd was reduced with age (47.2 ± 2.9 and 34.5 ± 3.6 g, P < .02 in the young and elderly, respectively), but the corresponding data for FGU were similar in the two groups. However, the ratios of ∆Rd and ∆FGU to the corresponding insulin responses (∆l), mainly reflecting peripheral insulin sensitivity, were reduced in the elderly (∆Rα/∆I, 1.3 ± 0.2 vs. 3.0 ± 0.6 U, P < .01; ∆FGU/∆I, 0.7 ± 0.1 vs. 1.2 ± 0.2 U, P < .05). Assessment of the relative contribution by the liver and peripheral tissues to age-related glucose intolerance suggested that the deficit in Rd was twofold greater than that due to the delayed fall in HGO. We conclude that age-related glucose intolerance 1) develops despite slowed glucose absorption; 2) is characterized by delays in the initial rise in insulin levels, the suppression of HGO, and the rise in peripheral glucose uptake; but 3) is predominantly the result of impaired peripheral glucose utilization. While the latter reflects increased tissue insulin resistance, the delayed fall in HGO may be mainly the consequence of delayed insulin secretion.
Insulin Stimulation of Na+-K+ Pump in Clonal Rat Osteosarcoma Cells
Authors: De Luise Mario A , Harker Michael
Published: September 2013

Clonal osteoblast-like cells derived from a rat osteogenic sarcoma (UMR 106–06) were shown to possess specific, high-affinity binding sites for insulin, with a receptor density of 22,000/cell. The hormone, at physiologic concentrations (1–10 ng/ml), was found to stimulate active K+ transport into these cells, the effect being mediated via the Na+-K+ pump. Alterations in insulin-receptor status by treatment of cells with glucocorticoids or exposure to subphysiologic pH was reflected in parallel changes in the sensitivity of the K+-uptake process to the hormone. We conclude that insulin can directly affect the metabolism of bone cells and that the hormone's action on transmembrane ion transport may be linked to interaction with its cell surface receptors.
Specific Immunity to Streptozocin: Cellular Requirements for Induction of Lymphoproliferation
Authors: Klinkhammer Christiane , Popowa Poly , Gleichmann Helga
Published: September 2013

The mechanism(s) of the immunological reactions involved in the pathogenesis of hyperglycemia induced by multiple intraperitoneal injections of subdiabetogenic doses of streptozocin (STZ) in mice remains to be elucidated. We found that STZ can act as a hapten in vivo by using the popliteal lymph node (PLN) assay. With this assay a direct toxic effect of STZ on the pancreatic β-cells was dissociated from the effects exerted on the immune system. Subcutaneous injections of STZ induced immune reactivity in the draining PLN as determined by increase in weight, cell number, and [3H]thymidine incorporation. T-lymphocytes were required to induce the PLN response to STZ, because athymic nu/nu mice completely failed to respond to STZ, in contrast to their euthymic +/nu counterparts (P < .001). The STZ-induced PLN response was sex independent and unaffected by prior subcutaneous injections of 3-O-methylglucose known to protect pancreatic β-cells against STZ. STZ-primed mice exhibited an accelerated and enhanced STZ-specific secondary PLN response on challenge with subimmunogenic doses of STZ. In adoptive transfer experiments, STZ-sensitized splenic lymphocytes enriched for T-lymphocytes induced an STZ-specific significant (P < .005) PLN enlargement provided the syngeneic recipients had been pretreated with subimmunogenic doses of STZ. Presumably, such STZ-specific immune reactions enhance a subtoxic effect of STZ on the pancreatic β-cells.
Correlation Between Minimal Secretory Capacity of Pancreatic β-Cells and Stability of Diabetic Control
Authors: Fukuda Masahiro , Tanaka Akira , Tahara Yasuhiro , Ikegami Hiroshi , Yamamoto Yoshihiro , Kumahara Yuichi , Shima Kenji
Published: September 2013

The significance of the minimal secretory capacity of pancreatic β-cells for the stability of the plasma glucose level was studied in 20 patients with insulin-dependent diabetes mellitus. Changes in plasma concentrations of major counterregulatory hormones in response to hypoglycemia were also investigated in these patients to clarify their contribution to diabetic brittleness. β-Cell function was evaluated on the basis of elevation of plasma C-peptide immunoreactivity (CPR) during the intravenous glucagon test with a highly sensitive assay for plasma CPR that could detect as little as 0.03 ng/ml. After stimulation with glucagon, a significant increase in plasma CPR was observed in 10 of the patients whose β-cell function had been evaluated as completely depleted by a conventional assay for plasma CPR. A clear inverse correlation was found between the secretory capacity of pancreatic β-cells measured in this way and the degree of glycemic instability (r = −.74, P < .01). Infusion of insulin at a rate of 0.15 U.kg−1.h−1 for 60 min caused a continuous decrease in the plasma glucose level, resulting in neuroglycopenia in 7 of the 10 CPR nonresponders but only 2 of the CPR responders. During insulin-induced hypoglycemia, plasma glucagon immunoreactivity did not increase in the CPR nonresponders but increased significantly in the CPR responders. A positive correlation was found between the minimal residual β-cell capacity and the responsiveness of α-cells to hypoglycemia (r = .65, P < .01).In contrast to the difference in the responses of their pancreatic α-cells to hypoglycemia, the two groups showed more or less the same responses of plasma epinephrine, norepinephrine, growth hormone, and cortisol to hypoglycemia. Total lack of insulinogenic reserve inevitably results in loss of automatic regulation of the circulating insulin level and seems to be a major factor in causing hyperlability of diabetic control. The lack of β-cell function may be related causally to pancreatic α-cell dysfunction, which also contributes in part to metabolic variability in brittle diabetes.
Determinants of IDDM and Perinatal Mortality in Children of Diabetic Mothers
Authors: Warram James H , Krolewski Andrzej S , Kahn C Ronald
Published: September 2013

Offspring of women with insulin-dependent diabetes meilitus (IDDM) have a lower risk of developing IDDM than offspring of men with IDDM (1). To determine whether the risk of diabetes in offspring of diabetic mothers has changed after dramatic improvements in perinatal survival of these infants, we undertook a follow-up study of 1602 pregnancies of 739 women with IDDM who were patients at the Joslin Diabetes Center. Improvements in perinatal survival were abrupt rather than gradual. During the two decades before 1961, perinatal mortality was stable around 23%. After a sudden drop in 1961, it stabilized around 14% until 1975, when it was brought down to 4%, where it has remained. Of the 1391 offspring who survived the neonatal period, IDDM has developed in 21, a cumulative risk of 2.1 ± 0.5% (SE) by age 20 yr. This is one-third the risk previously reported for offspring of fathers with IDDM and is independent of the calendar time of the births (1). The risk of diabetes in offspring of diabetic mothers is increased in young mothers and is otherwise independent of risk factors for perinatal mortality in this series. We conclude that there is no evidence that selective loss of diabetes-susceptible fetuses in perinatal deaths is a mechanism for the lower incidence of IDDM in the offspring of mothers with IDDM than in those of fathers with IDDM. The principal alternative mechanism is that exposure in utero to an affected mother can protect a fetus from developing IDDM later in life. Induction of immunologie tolerance to the autoantigens of the β-cells is a plausible mechanism for this protective effect.
Alteration of Insulin-Receptor Kinase Activity by High-Fat Feeding
Authors: Watarai Takao , Kobayashi Masashi , Takata Yasumitsu , Sasaoka Toshiyasu , Iwasaki Makoto , Shigeta Yukio
Published: September 2013

It has been demonstrated in in vivo and in vitro experiments that high-fat (HF) feeding causes insulin resistance. To elucidate the mechanism for this effect, we have measured the kinase activity of the insulin receptor purified from livers of HF-fed rats that showed impaired insulin action in isolated rat adipocytes. In adipocyte experiments, HF feeding led to a 65% decrease in the maximal response stimulated by insulin in a 2-deoxyglucose uptake study. Although insulin binding to adipocytes of HF-fed rats also decreased to 50% of control due to decreased binding affinity, the postbinding defect should be accounted for by decreased insulin action in view of the presence of spare receptor. In contrast to adipocytes, insulin binding to the lectin-purified insulin receptor from livers showed no difference in receptor-binding affinity between HF-fed and control rats. Insulin-stimulated phosphorylation of the β-subunit of the insulin receptor was decreased to almost 50% throughout the entire dose-response curve. The study of glutamine-tyrosine (4:1) phosphorylation by the insulin-receptor kinase showed results similar to those of the autophosphorylation study. These results suggest that an HF diet causes insulin resistance by affecting insulin-receptor kinase, which plays an important role in transmembrane signaling between insulin binding and insulin action.
Association of Susceptibility to Spontaneous Diabetes in Rat With Genes of Major Histocompatibility Complex
Authors: Colle Eleanor , Ono Santa Jeremy , Fuks Abraham , Guttmann Ronald D , Seemayer Thomas A
Published: September 2013

This study was designed to map the diabetes susceptibility gene(s) associated with the rat major histocompatibility complex (MHC) RT1. We have crossed spontaneously diabetic male rats bearing the recombinant RT1r8 haplotype with female rats of the ACI. 1r4 congenie strain. Three diabetic rats were determined to be homozygous for the r4 haplotype by serotyping. The absence of recombination within the MHC was confirmed by inspection of restriction-fragment-length patterns of the diabetic animals and the parental strains. In conjunction with previous breeding studies, this study maps the diabetes susceptibility gene to the right of the RT1-A locus and to the left of the RT1-C locus. A low incidence of diabetes in the F2 (4.5%) emphasizes the multifactorial nature of the susceptibility. The presence of depressed responsiveness of peripheral blood lymphocytes to concanavalin A stimulation increases the prevalence of the overt disease. An unusual feature of the diabetic syndrome in this study is the sparse or absent pancreatic lymphocytic inflammatory response, with true insulitis being a rare finding.
T-Lymphocyte Clone Specific for Pancreatic Islet Antigen
Authors: Haskins Kathryn , Portas Mary , Bradley Brenda , Wegmann Dale , Lafferty Kevin
Published: September 2013

A cloned T-lymphocyte line, BDC-2.5, was derived from a nonobese diabetic (NOD) mouse and has been found to exhibit specificity for islet cell antigen in vitro and in vivo. This clone is a CD4+ T-lymphocyte that proliferates and makes lymphokine in response to islet cell antigen- and NOD antigen-presenting cells. In an in vivo transplantation system in which islet grafts were made in the presence or absence of the BDC-2.5 T-lymphocytes, it was found that incorporation of the islet-specific T-lymphocytes into the graft site resulted in complete destruction of the transplanted tissue. Similar grafts made with pituitary tissue were not affected by the T-lymphocyte clone. These results suggest that the islet-specific T-lymphocytes mediate islet destruction in a tissue-specific manner.
Influence of cAMP and Calcium on [3H]Inositol Efflux, Inositol Phosphate Accumulation, and Insulin Release From Isolated Rat Islets
Authors: Zawalich Walter S , Diaz Victoria A , Zawalic Kathleen C
Published: September 2013

The influence of cyclic AMP (cAMP) and extracellular calcium on phosphoinositide (PI) hydrolysis in isolated islets was assessed and related to insulin output. Three stimulants were chosen to activate the β-cell: sulfated cholecystokinin (CCK-8S, 200 nM), high-level glucose (20 mM), and the sulfonylurea tolbutamide (200 μM). The insulin secretory response to all three agonists was amplified by forskolin (which increases cAMP levels) and reduced by nitrendipine (which decreases calcium influx). All three stimulants increased the hydrolysis of inositol-containing phospholipids, an event monitored by an increase in [3H]inositol efflux from [3H]inositol-prelabeled islets and by the accumulation of labeled inositol phosphates. Forskolin, despite its positive impact on insulin secretion, reduced [3H]inositol efflux and inositol phosphate accumulation in response to all agonists. A similar inhibitory effect on these parameters was noted with nitrendipine; however, nitrendipine abolished secretion in response to all agonists. These findings support the following conclusions: 1) an increase in cellular cAMP levels reduces the quantitative impact of various agonists on these indices of PI hydrolysis; 2) despite this inhibitory effect, cAMP amplifies the insulin secretory response to these agonists; and 3) extracellular calcium is a crucial determinant of both PI hydrolysis and the ensuing insulin secretory response.
Alterations in T-Lymphocyte Subpopulations in Type I Diabetes: Exploration of Genetic Influence in Identical Twins
Authors: Johnston Colin , Alviggi Lorenzo , Millward B Ann , David R , Leslie G , Pyke David A , Vergani Diego
Published: September 2013

To evaluate factors influencing the alteration in subsets of T-lymphocytes, we studied 24 pairs of identical twins discordant for insulin-dependent (type I) diabetes mellitus. Subsets were assessed by monoclonal antibodies and a pure preparation of peripheral blood mononuclear cells obtained by centrifugation of heparinized whole blood with a Ficoll/Triosil gradient. In 12 pairs studied within 5 yr of diagnosis, we observed a reduction in the percentage of cells reacting with OKT8 (recognizing the CD8 antigen present on the suppressor/cytotoxic subset) (P < .05), but a similar level was detected in their nondiabetic cotwins. In 12 pairs studied >5 yr after the diagnosis and in whom the nondiabetic twin is less likely to develop diabetes, the percentage of cells reacting with OKT8 was reduced in both the diabetic (P < .05) and the nondiabetic (P < .01) twins. Reductions were also seen with OKT3 (recognizing the CD3 antigen present on the total T-lymphocyte population) and OKT4 (recognizing the CD4 antigen present on the helper/inducer subset), but only in the diabetic twins from the group with longer discordance. We conclude that a reduced percentage of suppressor/cytotoxic cells is associated with type I diabetes, but the reduction appears to be genetically determined. Total T-lymphocytes are also reduced but mainly in the helper/inducer subset and only in diabetic patients of long duration. Such a reduction cannot therefore be primarily genetically determined.
Prevention of Sugar-Induced Cataractogenesis in Rats by Butylated Hydroxytoluene
Authors: Srivastava Satish K , Ansari Naseem H
Published: September 2013

Senile cataractogenesis advanced by diabetes, thought mainly to be due to accumulation of polyols, is one of the major causes of blindness throughout the world. Rats fed a 50% galactose diet developed mature cataracts in 23 days, whereas rats fed a 50% galactose diet with 0.4% butylated hydroxytoluene (BHT) had clear lenses. On day 10, both groups had comparable galactitol levels in the lens, but hydration in the former group, as determined by the lens weight, was ∼10% more than in the latter. On day 23, galactitol levels in the latter group were 92% higher (∼85 mM) than in the former group, but lens weight was lower. These results indicate that sugar-induced cataractogenesis in rats is not solely due to polyol accumulation. Oxidative damage is probably a major cause of the advancement of cataractogenesis.
Control of Glucose Metabolism in Pancreatic β-Cells by Glucokinase, Hexokinase and Phosphofructokinase: Model Study With Cell Lines Derived From β-Cells
Authors: Shimizu Takao , Parker Janice C , Najafi Habiba , Matschinsky Franz M
Published: September 2013

Glucose usage by soluble fractions of cell extracts from two insulin-producing cell lines, RINm5F and HIT, was investigated. Analysis of enzyme activities indicated that glucose phosphorylation and phosphofructokinase are likely to be the rate-limiting steps of glycolysis in both RINm5F and HIT cell extracts. RINm5F extracts, which lack glucokinase, exhibited relatively flat concentration-dependency curves of glucose usage and showed substantial inhibition of hexokinase. HIT cell extracts, which contain glucokinase but lack hexokinase, exhibited sigmoidal concentration-dependency curves of glucose usage,reflecting almost fully expressed glucokinase activity. A reconstituted system prepared from RINm5F and HIT cell extracts exhibited a composite concentration-dependency curve of glucose usage and showed substantial inhibition of hexokinase and almost fully expressed glucokinase. However, conditions that activate phosphofructokinase, such as addition of ammonium sulfate or fructose 2,6-bisphosphate or alkalization, removed the inhibition of hexokinase without noticeably affecting the glucokinase component of usage. Results obtained with a reconstituted system containing RINm5F cell extract and purified glucokinase were consistent with these findings. The data presented here indicate that this reconstituted cell-free system serves as a valid model for the study of aspects of glycolytic control in the islet. This model illustrates the preeminent role of glucokinase in the control of glycolysis, consistent with its glucose-sensor function in the islet. In addition, these studies help to define the contribution of phosphofructokinase to the control of glycolysis and the mechanism whereby changes in phosphofructokinase activity could modulate, viachanges in the glucose 6-phosphate concentration, the activity of hexokinase and hence the net glycolyticflux.
Hypolipidemic, Antiobesity, and Hypoglycemic-Hypoinsulinemic Effects of β,β′-Methyl-Substituted Hexadecanedioic Acid in Sand Rats
Authors: Tzur Ruth , Rose-Kahn Gene , Adler Jonathan H , Bar-Tana Jacob
Published: September 2013

Treatment of male sand rats kept on a balanced laboratory chow diet ad libitum with β,β'tetramethylsubstituted hexadecanedioic acid (MEDICA 16) resulted in a hypolipidemic effect accompanied by an extensive reduction in adiposity, with a concomitant hypoglycemic-hypoinsulinemic effect. The overall effect was sustained as long as the drug was administered. The hypolipidemic effect of MEDICA 16 consisted of a 70 and 40% decrease in plasma triacylglycerols and cholesterol, respectively, and resulted from inhibition of liver lipogenesis and cholesterogenesis. Adipose reduction by MEDICA 16 treatment or calorie restriction consisted of a 75–90% decrease in the perirenal, omental, epididymal, and subcutaneous fat, with a 50% decrease in liver neutral lipids. The reduction in adiposity was accounted for by a respective decrease in the lipid content of individual adipocytes, with a concomitant decrease in the number of adipocytes of selected adipose tissues. The decrease induced in adiposity by MEDICA 16 treatment could not be accounted for by anorectic or cathartic effects of the drug. The hypoglycemic-hypoinsulinemic effect of MEDICA 16 consisted of amelioration of the tolerance of glucose with normalization of plasma insulin. It was accompanied by an eightfold increase in the number of insulin receptors in epididymal adipocytes, which was, however, counteracted by a decrease in their affinity for insulin. The receptor and postreceptor effects exerted by MEDICA 16 were similar to those of calorie restriction. The overall effect of MEDICA 16 in sand rats may reflect the pharmacological potential of MEDICA compounds in pathological hyperlipidemic-obesity-diabetic syndromes.
Reduced Risk of IDDM Among Breast-Fed Children: The Colorado IDDM Registry
Authors: Mayer Elizabeth J , Hamman Richard F , Gay Elizabeth C , Lezotte Dennis C , Savitz David A , Klingensmith Georgeanna J
Published: September 2013

The hypothesis that breast-feeding can provide protection against the development of insulindependent diabetes mellitus (IDDM) and would, therefore, be less common among subjects with IDDM was tested with a retrospective design. Cases (n = 268) were selected from the Colorado IDDM Registry and the Barbara Davis Center for Childhood Diabetes (Denver, CO). Two control groups were recruited, one from physicians' practices throughout Colorado (n = 291) and the second through random-digit dialing from the Denver area (n = 188). Cases were less likely to have been breast-fed than controls after adjustment for birth year, maternal age, maternal education, family income, race, and sex [adjusted odds ratio (OR) = 0.70; 95% confidence interval (Cl) = 0.50–0.97]. This finding was consistent for both control groups and by birth-year intervals. A greater decrease in risk of IDDM was seen among subjects who had been breast-fed to an older age (for breast-feeding duration of ≥12 mo, adjusted OR = 0.54, 95% Cl = 0.27–1.08). The amount of IDDM that might be explained by breast-feeding habits (population percentage attributable risk) ranged from 2 to 26%, varying according to the breast-feeding prevalence reported in other studies. Replication of this work in different populations, controlled for the strong secular trends in breast-feeding habits, is critical before the hypothesis of protection is accepted.
Elevated mRNA Levels of Major Histocompatibility Complex Class II Genes in Lymphocytes of Autoimmune BB Rats
Authors: Holowachuk Eugene W , Greer Mary K , Martin Diego R
Published: September 2013

The BB rat spontaneously develops autoimmune abnormalities such as insulin-dependent diabetes mellitus and thyroiditis. The autoimmunity of the BB rat is controlled in part by genes of the major histocompatibility complex (MHC), known as the RT1 complex in the rat, and accumulating evidence suggests the involvement of MHC class II molecules. The RT1 complex specifies two types of class II molecules, which are encoded by the loci RT1.B and RT1.D. We have determined the relative steady-state mRNA levels of the class II genes RTI.Bβ, RTI.Dα, and RT1.Dβ in splenic lymphocytes from individual autoimmune BB rats of various ages and from agematched histocompatible normal Wistar-Furth (WF) rats. The relative steady-state mRNA levels of the RTI.Dα and RT1.Dβ genes, but not of the RT1.Bβ gene, were elevated ∼2.5-fold in lymphocytes of prediabetic BB rats 45–75 days old in comparison with age-matched normal WF rats and older BB rats >75 days old. In the diabetic and nondiabetic BB rats >75 days old, the RTI.Dα and RT1.Dβ transcripts were found at lower normal levels, similar to that of WF rats. In contrast, the RTI.Bβ transcripts were found at comparable levels in lymphocytes of the BB and WF rats at all ages examined. The increased steady-state mRNA levels of the RTI.Dα and RTI.Dβ genes in the prediabetic BB rats may reflect differences in the proportion of lymphocytes expressing these genes and thus differences in splenic lymphocyte populations. These elevated steady-state mRNA levels of both RT1.D genes in lymphocytes of prediabetic BB rats correlate with the age when the autoimmune effector mechanisms are highly activated and suggest an involvement of RT1.D class II antigens with the autoimmune disease process in the BB rat. The differences in steady-state class II mRNA levels in prediabetic BB rats and the age-matched normal WF rats and older BB rats suggest that the RTI.Dα and RTI.Dβ genes are similarly regulated, but not coordinately regulated with the RTI.Bβ gene, in splenic lymphocytes of young autoimmune BB rats.
Renal Response to Restricted Protein Intake in Diabetic Nephropathy
Authors: Bending Jeremy J , Dodds Rosemary A , Keen H , Viberti Gian Carlo
Published: September 2013

Proteinuria in diabetes is associated with progressive glomerular damage. We studied the effects of 3-wk dietary protein restriction on proteinuria and renal function in 10 insulin-dependent diabetic men with diabetic nephropathy. Patients were randomly assigned by a crossover design to 40-g low-protein diet (LPD) or usual-protein diet (UPD). Glomerular filtration rate and renal plasma flow were measured by inulin and p-aminohippurate clearance at the end of each period under conditions of sustained euglycemia. Total calorie intake, body weight, serum albumin and total protein concentrations, hematocrit, blood pressure, and glucose control were similar during the two diets. Achieved protein intake was 46 ± 3 g/day during LPD and 81 ± 4 g/day during UPD (P < .001). Urinary urea appearance and plasma urea were significantly lower on LPD. Median total urinary protein was reduced from 3.9 g/day (range 0.5–12.3) on UPD to 2.4 (range 0.2–9.0) on LPD (P < .006), and there was a significant fall in the median fractional clearance of albumin from 2.0 × 10−4 (range 0.1–90.9) on UPD to 1.0 × 10−4 (range 0.1–51.4) on LPD and IgG from 2.1 × 10−5 (range 0.2–238) to 1.5 × 10−5 (range 0.1–77) (P < .006 and P < .02, respectively). The reabsorption rate of β2-microglobulin was similar on the two diets and glomerular filtration rate, renal plasma flow, and filtration fraction remained unchanged. Thus, short-term dietary protein restriction reduces diabetic proteinuria independently of blood glucose or systemic blood pressure changes by improving glomerular permselectivity.
Myocardial Insulin Resistance During Acute Endotoxin Shock in Dogs
Authors: Raymond Richard M , McLane Michael P , Law William R , King Nicholas F , Leutz Darr W
Published: September 2013

Myocardial insulin responsiveness was determined in open-chest pentobarbital sodium-anesthetized dogs before and after endotoxin administration. Animals were instrumented to measure mean arterial blood pressure (MABP), heart rate (HR), and coronary blood flow. Myocardial glucose uptake and myocardial oxygen uptake (MVO2) were determined during a basal control period and after a hyperinsulinemic-euglycemic clamp procedure over a wide range of insulin concentrations. The clamp was accomplished by intravenously infusing insulin (0–4000 mU/min) and 20% glucose in sufficient amounts to maintain arterialglucose concentrations within 5 mg/dl of the control value. In a separate series of experiments, myocardial insulin responsiveness was determined by use of a single dose of insulin (4000 mU/min). This was done to determine whether antecedent insulin infusions during the sequential clamp procedure would affect the responsiveness of the heart. In control experiments, myocardial glucose uptake increased without any changes in HR, MVO2, or MABP. Maximum myocardial glucose uptake occurred at an insulin infusion rate between 400 and 4000 mU/min. A single concentration of insulin resulted in similar increases in myocardial glucose uptake as with the sequential clamp protocol. Acute endotoxin shock was induced by bolus injection of 1 mg/kg Salmonella typhimurium endotoxin (Difco Labs, Detroit, MI). One hour after administration of endotoxin, basal myocardial glucose uptake was decreased compared with the control animals. After 1 h of endotoxin shock, the heart was refractory to all concentrations of insulin, suggesting the site for altered insulin response was being mediated by a postreceptor mechanism.
Increased Rate of Cori Cycle in Obese Subjects With NIDDM and Effect of Weight Reduction
Authors: Zawadzki Joanna K , Wolfe Robert R , Mott David M , Lillioja Stephen , Howard Barbara V , Bogardus Clifton
Published: September 2013

To determine the contribution of the rate of glucose recycling via the Cori cycle (glucose→3-carbon compounds→glucose) to the higher rate of endogenous glucose production (EGPR) in subjects with non-insulin-dependent diabetes mellitus (NIDDM), we studied eight obese, weight-stabilized diabetic Pima Indians before [93.1 ± 5.4 kg, 38 ± 2% body fat, fasting plasma glucose (FPG) 254 ± 11 mg/dl] and after (87.7 ± 4.7 kg, 36 ± 2% body fat, FPG 153 ± 17 mg/dl) a 5-wk weight-loss diet and eight obese Indians (95.0 ± 4.2 kg, 36 ± 2% body fat, FPG 97 ± 1 mg/dl) with normal glucose tolerance. EGPR and glucose recycling rate were measured during a 4-h primed continuous tracer infusion of [1-13C]glucose, and the rate of reincorporation of 1-13C of glucose into C2–6 positions in glucose was quantified by gas chromatography mass spectrometry. Substrate utilization rates were measured by simultaneous indirect calorimetry. EGPR (corrected for measured rate of recycling) decreased in the diabetic subjects from 3.80 to 2.74 mg·min−1·kg−1 fat-free mass (FFM) (P < .01) after weight loss, approaching the rate observed in nondiabetic subjects (2.09 mg·min−1·kg−1 FFM). The decrease in EGPR was associated with a decrease in nonoxidative carbohydrate disposal. Before weight loss, the measured rate of [1-13C]glucose recycling was higher in diabetic (0.23 ± 0.02 mg · min−1 · kg−1 FFM) than in nondiabetic (0.14 ± 0.01 mg min−1 · kg−1 FFM, P < .005) subjects. The glucose recycling rate did not change in diabetic subjects after weight loss (0.20 mg · min−1 · kg−1 FFM). We conclude that the rates of endogenous glucose production and the Cori cycle are increased in subjects with NIDDM compared with the rates observed in obese subjects with normal glucose tolerance. After a modest weight loss, the endogenous glucose production rate, but not the glucose recycling rate, in diabetic subjects approaches the rate observed in obese nondiabetic subjects.
Insulin Biosynthesis in HIT Cells: Effects of Glucose, Forskolin, IBMX, and Dexamethasone
Authors: Gold Gerald , Qian Rong-Li , Grodsky Gerold M
Published: September 2013

Glucose, forskolin, 3-isobutyl-1-methylxanthine (IBMX), and dexamethasone were tested as regulators of proinsulin biosynthesis in HIT T-15 cells, which are glucose-responsive simian virus 40-transformed hamster β-cells. Rate of [3H]leucine incorporation into proinsulin was increased as glucose concentrations were raised from 0 to 20 mM. Biosynthetic rate increases were significant after 48 but not at 4 or 24 h of glucose and were greater for proinsulin than for total extractable proteins. After 48 h, glucose-stimulated proinsulin biosynthesis was unaffected by 10−6 M forskolin and/or 3 × 10−5 M IBMX but was specifically and significantly inhibited by 10−6 M dexamethasone. Four hours of exposure to dexamethasone had no effect. When cells were incubated for 24 h and then continuously labeled for an additional 24 h, cellular conversion of labeled proinsulin to insulin was increased by glucose, and this increase was reversed or inhibited by 10−6 M dexamethasone. Therefore, proinsulin biosynthesis in transformed HIT T-15 cells is regulated in several ways by metabolites and hormones in a manner that compares with biosynthetic regulation in normal β-cells.
Frequency and Specificity of Protamine Antibodies in Diabetic and Control Subjects
Authors: Nell Laura J , Thomas James W
Published: September 2013

Protamines are cationic fish chromosomal proteins that retard absorption of isophane (NPH) insulins. Protamines are also administered in large doses for heparin neutralization in cardiac procedures. This study used a rapid enzyme-linked immunosorbent assay to examine frequency of protamine antibodies in diabetic and control populations. Antigen specificity of the IgG binding to protamine-coated plates was verified by competitive inhibition with other protamines, histone, glucagon, thyroid-stimulating hormone, arginine, and lysine. All antibodies tested cross-reacted completely with all protamines. Only 4 of 18 had any cross-reactivity with histones. None cross-reacted with the other inhibitors. In population surveys, 122 (38%) of 319 NPH insulin-treated diabetic subjects, 3 (8%) of 39 diabetic subjects treated with protamine-free lente insulins, and 5 (2.5%) of 202 normal control subjects had protamine antibody. No correlation was found between insulin and protamine antibodies. Because more than one-third of insulin-treated diabetic subjects have circulating IgG specific for protamine, they are potentially at risk for acute immunologic or anaphylactoid reactions when protamine is administered for heparin neutralization.
New Approach for Oral Administration of Insulin With Polyalkylcyanoacrylate Nanocapsules as Drug Carrier
Authors: Damgé Christiane , Michel Christine , Aprahamian Marc , Couvreur Patrick
Published: September 2013

Polyalkylcyanoacrylate nanocapsules (mean size 220 nm), composed of spheric polymeric structures, have been used as a drug carrier for insulin. The rate of encapsulation of insulin is 54.9%, and we studied the therapeutic efficiency of the nanocapsules in diabetic and normal rats. When administered subcutaneously, insulin-loaded nanocapsules prolonged the hypoglycemic effect of insulin; the duration of this effect increased with the doses. When administered orally by force-feeding to diabetic rats, insulin nanocapsules (12.5, 25, and 50 U/kg) decreased fasted glycemia 50–60% by day 2. This effect was maintained for 6 or 20 days with 12.5 or 50 U/kg, respectively. Only the dose of 100 U/kg decreased fed glycemia by 25% in diabetic rats. In normal rats, hyperglycemia induced by an oral glucose load was reduced by 50% with the same dose of oral insulin nanocapsules. We concluded that polyalkylcyanoacrylate nanocapsules preserve the therapeutic effect of insulin when administered orally and prolong this effect when administered subcutaneously and orally.
Speculations on Etiology of Diabetes Mellitus: Tumbler Hypothesis
Authors: Rossini Aldo A , Mordes John P , Handler Eugene S
Published: September 2013

Although clinically useful, the conventional partition of diabetes mellitus into two major classes, insulin dependent and non-insulin dependent, has become obsolete from an etiological standpoint. Contemporary research, particularly that with advanced cellular and molecular methodologies, suggests that the expression of diabetes depends on a wide range of factors. We suggest that the etiology of diabetes has become analogous to the cylinder of a lock containing many tumblers. Each tumbler, e.g., environment, genetics, or cellular interactions, must be aligned before the key can be turned and an understanding of the etiologic process claimed.
Maturation of Insulin Response to Glucose During Human Fetal and Neonatal Development: Studies with Perifusion of Pancreatic Isletlike Cell Clusters
Authors: Otonkoski Timo , Andersson Sture , Knip Mikael , Simell Olli
Published: September 2013

The insulin release in response to glucose was studied in perifused isletlike cell clusters (ICCs) obtained from human fetal or neonatal pancreases at various stages of development: 12–15 gestational wk (n = 7), 17–20 wk (n = 13), 22.5 wk (n = 2, 1 diabetic pregnancy), and 26–44 wk (n = 6, postnatal samples). The ICCs were stimulated with 20 mM glucose and subsequently with 10 mM theophylline plus 20 mM glucose as a viability test. Insulin release increased to a detectable level (> 0.1 pg · ICC−1 · min−1) during glucose stimulation in four of seven of the youngest fetuses. At 17–20 wk the basal rate of insulin release had increased by at least 15-fold above the detection limit (1.5 pg · ICC−1 · min−1), and glucose promoted a sustained monophasic response that was on the average 1.6-fold higher than the basal level. The response was significant (P < .05) in 9 of 13 experiments. With postnatal ICC (gestational age 26–44 wk), an early-phase peak response was observed in 5 of 6 experiments. The mean rates of insulin release after 5–12 min of glucose stimulation were 4.8 pg.ICC−1 · min−1 in newborn infants and 2.1 pg.ICC−1 · min−1 in 17- to 20-wk fetuses. The corresponding mean relative insulin responses (stimulated to basal) were 3.3-fold (range 1.1–7.5) and 1.6-fold (1.0–3.4), respectively (P < .05, Mann-Whitney U test). The results suggest that the human fetal pancreas is already responsive to glucose during the first half of gestation, but the biphasic insulin release does not start to mature until the postnatal phase.
Lysosomes and Pancreatic Islet Function: Time Course of Insulin Biosynthesis, Insulin Secretion, and Lysosomal Transformation After Rapid Changes in Glucose Concentration
Authors: Landström Annika H Schnell , Westman Jan , Borg L A Håkan
Published: September 2013

The aim of this study was to estimate the time course of lysosomal transformations associated with crinophagy, i.e., the degradation of insulin within lysosomes, in the beta-cells of pancreatic islets. Primary and secondary lysosomes were identified in mouse islet β-cells and subjected to ultrastructural morphometry. Islets from an in situ preparation were compared with isolated islets incubated in vitro. Under the in vitro conditions, the islets were initially exposed to 28 or 3.3 mM glucose for 24 h. Then the glucose concentration was rapidly changed to 3.3 and 28 mM glucose, respectively, and the islets were incubated for up to an additional 24 h. The β-cell lysosomes were analyzed and related to alterations in insulin biosynthesis and secretion and islet insulin content after the rapid change in glucose concentration. In vivo, the β-cell lysosomal population was predominantly composed of secondary lysosomes, which frequently contained secretory granule cores. After the initial 24-h period at 3.3 mM glucose, the volume density and the average volume of the secondary β-cell lysosomes were increased, suggesting increased crinophagic activity. The mean diameter of the primary β-cell lysosomes was decreased after 24 h at either 28 or 3.3 mM glucose. The change in glucose from 28 to 3.3 mM resulted in alterations in insulin biosynthesis and secretion, leading to an accumulation of insulin within the β-cells. Lysosomal transformations suggestive of increased crinophagy were observed 24 h after the alteration in glucose concentration. The change from 3.3 to 28 mM glucose resulted in a parallel increase in insulin biosynthesis and secretion without a change in islet insulin content. Twenty-four hours after the change in glucose concentration, the lysosomal population was changed from one composed predominantly of secondary lysosomes to one composed predominantly of primary lysosomes. The results lend support to the notion that there is significant crinophagic activity in the pancreatic β-cell in vivo. It is further suggested that an increase in β-cell secretory granule content, resulting from differences in the glucose-stimulated response of insulin biosynthesis and secretion, stimulates crinophagy. The time course of the lysosomal alterations after rapid changes in glucose concentration suggests that the lysosomes are mainly involved in the long-term adaptation of the pancreatic β-cell to varying functional demands.