bluuebunny/crossref_metadata_2025 huggingface dataset:
Reversal of Diabetes in BB Rats by Transplantation of Encapsulated Pancreatic Islets
Authors: Fan Mei-Ying , Lum Zhao-Ping , Fu Xiao-Wen , Levesque Lyne , Tai Isabella T , Sun Anthony M
Published: September 2013

Prolonged survival of pancreatic islet allografts implanted in diabetic BB rats was achieved by encapsulation of individual islets in a protective biocompatible alginate-polylysine-alginate membrane without immunosuppression. Intraperitoneal transplantation of the encapsulated islets reversed the diabetic state of the recipients within 3 days and maintained normoglycemia for 190 days. Normal body weight and urine volume were maintained during this period, and no cataracts were detected in the transplant recipients. In contrast, control rats receiving transplants of unencapsulated islets experienced normoglycemia for <2 wk. These results demonstrated that microencapsulation can protect allografted islets from both graft rejection and autoimmune destruction without immunosuppression in an animal model that mimics human insulin-dependent diabetes.
Nonprogression of Subclinical β-Cell Dysfunction Among First-Degree Relatives of IDDM Patients: 5-Yr Follow-Up of the Seattle Family Study
Authors: McCulloch David K , Klaff Leslie J , Kahn Steven E , Schoenfeld Steven L , Greenbaum Carla J , Mauseth Richard S , Benson Edward A , Nepom Gerald T , Shewey Linda , Palmer Jerry P
Published: September 2013

It is unknown among first-degree relatives of individuals with insulin-dependent diabetes mellitus (IDDM) whether the disease process occurs in relatively few but always progresses to clinical IDDM or whether subclinical disease is more common but remains nonprogressive in many cases. Islet cell antibodies (ICAs) were found in 21 of 724 (2.9%) first-degree relatives during screening in the greater Seattle area between 1983 and 1988. Measures of β-cell function (glucose disappearance rate [Kg], fasting insulin, acute insulin response to intravenous arginine [AIRarg]. acute insulin response to intravenous glucose [AIRgluc], slope of glucose potentiation of AIRarg) and insulin sensitivity were obtained. Twenty individuals, 9 ICA+ relatives and 11 ICA− relatives, were evaluated prospectively. When expressed in relation to the expected AIRgluc based on each subject's sensitivity index, AIRgluc in 18 of 20 relatives fell below 100%, indicating inappropriately low insulin secretion (subclinical β-cell dysfunction). After a median follow-up of 42 mo, 10 of 11 ICA− relatives remained ICA−. None showed deteriorating β-cell dysfunction, and none developed diabetes. Five ICA+ relatives showed persistent immunologie positivity. β-Cell function remained remarkably stable in all except 2 relatives. One was a 15-yr-old boy who developed IDDM shortly after screening and before evaluation of β-cell function could be carried out. The other was an 18-yr-old monozygotic twin who developed IDDM after 27 mo. Both of these individuals had ICAs of 80 Juvenile Diabetes Foundation U and had been discordant for <5 yr. Five subjects showed fluctuating ICA status with stable β-cell function, and none have developed IDDM so far. These subjects were older and had been discordant for >10 yr at entry into the study. These data suggest that, although the persistent presence of ICAs is sometimes associated with deteriorating β-cell function, this is not invariable. Subclinical and nonprogressive β-cell dysfunction and fluctuation in ICA status can occur among first-degree relatives of individuals with IDDM. These data suggest that the disease process of IDDM encompasses a wide spectrum—relatively few people show the full-blown disease (clinical IDDM), whereas many more may have nonprogressive subclinical β-cell dysfunction.
Studies on Autoimmunity For Initiation of β-Cell Destruction: V. Decrease of Macrophage-Dependent T Lymphocytes and Natural Killer Cytotoxicity in Silica-Treated BB Rats
Authors: Amano Kazuhiko , Yoon Ji-Won
Published: September 2013

Administration of silica, which is selectively toxic to macrophages, to young BB rats resulted in the prevention of insulitis and diabetes. However, the mechanism leading to the prevention of an autoimmune process in silica-treated BB rats is not known. This study was undertaken to investigate the mechanism involved in prevention of insulitis and diabetes. Neonates of diabetes-prone BB (DPBB) rats injected with concanavalin A (ConA)-activated spleen cells from silica-treated DPBB (STDPBB) rats did not develop insulitis or diabetes, whereas DPBB neonates injected with ConA-activated spleen cells from the untreated DPBB rats developed both insulitis and diabetes. Not only was there a decrease of natural killer (NK) cell activity in splenocytes from STDPBB rats, but there was also a significant reduction in the number of immunocytes such as T lymphocytes (helper/inducer and cytotoxic/suppressor) and NK cells. The number of macrophages in both spleen and peripheral blood was significantly decreased in STDP rats compared with untreated DP rats. In contrast to the changes in T lymphocytes and NK cell activity, there was no change in target β-cells in STDPBB rats with regard to the susceptibility to adoptive transfer of insulitis. It is concluded that the prevention of insulitis and diabetes in STDPBB rats is due to a decrease in macrophage-dependent T lymphocytes and NK cell cytotoxicity.
Diabetic Glycemic Control and Retinal Blood Flow
Authors: Grunwald Juan E , Brucker Alexander J , Schwartz Stanley S , Braunstein Seth N , Baker Lester , Petrig Benno L , Riva Charles E
Published: September 2013

The effect of strict glycmic control on retinal volumetric blood flow rate (Q) was investigated in 13 insulin-dependent diabetic patients with laser Doppler velocimetry and monochromatic fundus photography. Strict glycemic control was achieved by glucose monitoring and four daily insulin injections. Q was determined in a major retinal vein at baseline and then 5days, 2 mo, and 6 mo after the institution of strict control. Level of retinopathy was assessed from stereocolor fundus photographs taken at baseline and 6 mo. After 6 mo of strict diabetic control, five eyes demonstrated progression (P) by one or more retinopathy levels, and eight eyes showed no progression (NP). At 5 days, there was a significant decrease in Q of 1.4 ± 0.9 μU/min (P < 0.005) in NP eyes and a nonsignificant increase in Q of 1.2 ± 1.7 μU/min in P eyes. Changes in Q from baseline observed at 5 days were strongly correlated with changes in retinopathy level at 6 mo (r = 0.79, P <0.005). No significant changes in Q from baseline were observed at 2 and 6 mo. A lack of decrease in Q at 5 days was associated with the progression of retinopathy that occurs in some patients after the institution of strict glycemic control and may serve as a predictor for progression of retinopathy.
Autoimmune Destruction of Islets Transplanted Into RT6-Depleted Diabetes-Resistant BB/Wor Rats
Authors: Gottlieb Peter A , Berrios Javier P , Mariani Gabriella , Handler Eugene S , Greiner Dale , Mordes John P , Rossini Aldo A
Published: September 2013

We report a novel animal model of islet transplantation that distinguishes recurrence of autoimmunity from allograft rejection. In this study, diabetes-resistant (DR) BB rats, <1% of which develop spontaneous diabetes, were made hyperglycemic by either a single injection of streptozocin (STZ) or in vivo immune elimination of a regulatory T-lymphocyte subset that expresses the RT6 alloantigen. DR islet grafts were then transplanted into both groups. DR transplants into STZ-induced diabetic DR rats produced long-term normoglycemia. In contrast, DR transplants into DR rats that had been treated with anti-RT6 monoclonal antibody were all destroyed within an average of 4 days. Allogeneic islets transplanted into both STZ-induced and RT6-depleted diabetic DR rats were rejected within a mean of 3 days. We conclude that failure of DR islet grafts in RT6-depleted diabetic DR BB rats represents recurrent autoimmunity.
Insulin Regulation of IGF-I Expression in Rat Aorta
Authors: Murphy Liam J , Ghahary Aziz , Chakrabarti Subrata
Published: September 2013

Smooth muscle cell proliferation may be important in pathogenesis of atherosclerosis. Because insulinlike growth factor I (IGF-I) is a potent mitogen for arterial smooth muscle cells in culture, we examined the hypothesis that IGF-I functions as an autocrine growth factor in the aorta. We also investigated the role of insulin in regulation of IGF-I expression in the aorta. With immunohistochemical and in situ hybridization techniques, IGF-I immunoreactivity and IGF-I mRNA were localized to the smooth muscle layer of the aorta. In diabetic rats, aortic IGF-I mRNA abundance was significantly reduced to 60.3 ± 2.9% of controls (P < 0.01). In nondiabetic rats, administration of insulin as an acute bolus (10 U i.p.) or a chronic infusion (2.4 U/day for 5 days) resulted in an approximately twofold increase in abundance of IGF-I mRNA in the aorta. These observations are consistent with the hypothesis that IGF-I may function as an autocrine growth factor in the aorta and suggest that one of the mechanisms whereby hyperinsulinism may favor atherogenesis is enhanced expression of IGF-I in the vessel wall.
Increase in Diacylglycerol Mass in Isolated Glomeruli by Glucose From De Novo Synthesis of Glycerolipids
Authors: Craven Patricia A , Davidson Catherine M , DeRubertis Frederick R
Published: September 2013

An increase in glucose concentration in the medium from 5 to 30 mM transiently enhanced diacylglycerol mass and activated protein kinase C in glomeruli isolated from nondiabetic rats as assessed by translocation of enzyme activity from the soluble to participate fraction. Effects of glucose on both diacylglycerol mass and protein kinase C were evident at 5 and 15 min but waned by 30 min. An increase in glucose concentration in the medium also increased the incorporation of [14C]glucose into the glycerol backbone of diacylglycerol, triacylglycerol, and phospholipids. Several observations implied that [14C]glucose was being incorporated into diacylglycerol through the de novo pathway for glycerolipid synthesis rather than being derived from phospholipids. 1) [14C]glucose incorporation into all the lipids was suppressed by 2-deoxyglucose. 2) The incorporation of [14C] glucose into diacylglycerol and triacylglycerol was evident by 1 min and increased linearly for at least 30 min. In contrast, incorporation into phosphatidylcholine occurred with a lag of at least 5 min. 3) Although only 10% of the [14C]glucose incorporated into lipids was present in diacylglycerol versus >50% in phospholipids, the specific activity of [14C]glucose in diacylglycerol was fivefold higher than that in phospholipid when expressed as a function of mass. 4) Glucose had no effect on labeled diacylglycerol or phosphatidic acid production in glomeruli that had been prelabeled with [3H]glycerol. Glucose-induced increases in diacylglycerol may contribute to the activation of glomerular protein kinase C observed in early diabetes.
Persistent Cutaneous Insulin Allergy Resulting From High-Molecular-Weight Insulin Aggregates
Authors: Ratner Robert E , Phillips Terence M , Steiner Malcolm
Published: September 2013

Cutaneous insulin allergy remains a clinical problem despite the use of highly purified human insulins. We used in vitro lymphocyte-transformation studies to examine the reactivity of various insulin formulations in diabetic patients with (n = 4) and without (n = 8) cutaneous allergies. Nonspecific response to concanavalin A demonstrated a >40-fold response in both groups. Control patients did not respond to the addition of commercial insulin preparations (stimulation index [SI] <4), whereas allergic patients had an 11-fold response to beef (P < 0.01), a 10-fold response to pork (P < 0.01), and a 6-fold response to human (P < 0.01) insulins. This response was limited to a single insulin manufacturer's preparations and was uniform in all three species tested. Efforts to identify the offending agent revealed no lymphoblast transformation when crystalline insulin was used or when commercial preparations were purified to a single peak by high-performance liquid chromatography (HPLC). Pure crystalline insulin dimers of beef, pork, and human species were tested; control subjects responded with mean Sis of 1.9,1.9, and 1.8, respectively, whereas allergic patients showed greater reactivity to beef (SI 7.3) and pork (S114.8). The lymphoblast-transformation response to crystalline human dimer was dose dependent with mean Sis of 0.9 at low concentration (2.8 ng/ml) and 19.2 at a higher concentration (20.4 ng/ml). The commercial insulin preparations were run on size-exclusion HPLC to determine high-molecular-weight aggregate content. Independent of species, a single manufacturer had products demonstrating aggregate levels 3- to 6-fold higher than those found in other manufacturers’ preparations. Our in vitro data suggest that insulin aggregates rather than native monomers cause cutaneous allergy and that antigenicity of commercial preparations correlates with the relative concentration of aggregates. In vivo testing is needed to confirm our results.
Altered Cellular Ca2+ and Na+ Transport in Diabetes Mellitus
Authors: Mazzanti Laura , Rabini Rosa A , Faloia Emanuela , Fumelli Paolo , Bertoli Enrico , Pirro Roberto De
Published: September 2013

Platelet intracellular Ca2+ concentration ([Ca2+]i) and its response to stimuli (ADP and thrombin) were studied in 15 insulin-dependent and 22 non-insulin-dependent diabetes mellitus patients with the fluorescent probe Fura 2. The activity of Ca2+-ATPase and Na+-K+-ATPase, membrane fluidity, and cholesterol and phospholipid content were also determined in platelet membranes. Compared with control subjects, diabetic patients showed 1) increased platelet [Ca2+]1 in the resting state, 2) higher Ca2+ levels after stimulation with thrombin and ADP, due entirely to increased resting concentrations, 3)reduced activity of Na+-K+-ATPase, 4)increased activity of Ca2+-ATPase, 5) higher fluidity of the platelet membrane, and 6)increased membrane concentration of total phospholipids. Na+-K+-ATPase activity was inversely related to platelet [Ca2+]1 in each group studied, whereas Ca2+-ATPase activity was positively correlated with intracellular Ca2+ levels. The data obtained in diabetic subjects suggest an abnormality in Ca2+ and Na+ transport across the platelet membrane that might be responsible for the reported platelet hyperreactivity to stimuli in diabetes.
Secular Trends in Incidence of Childhood IDDM in 10 Countries
Authors:   Diabetes Epidemiology Research International Group
Published: September 2013

Standardized childhood insulin-dependent diabetes mellitus (IDDM) incidence data were collected from 21 ethnic groups in 10 countries to evaluate temporal trends in the disease between 1966 and 1986. Population-based registries contributed information concerning periods from 6 to 21 yr. The incidence rates were modeled with Poisson regression. For the past 2 decades, a linear increase in IDDM risk for people <15 yr of age has been observed in most of Europe and the Western Pacific but not in North America. The temporal variation did not appear to differ significantly by age or sex in most locations. The observed pattern of temporal variation suggests that a proportion of diabetes in childhood may be caused by a potentially preventable environmental factor.
Evidence Against Altered Expression of GLUT1 or GLUT4 in Skeletal Muscle of Patients With Obesity or NIDDM
Authors: Pedersen Oluf , Bak Jens F , Andersen Per H , Lund Sten , Moller David E , Flier Jeffrey S , Kahn Barbara B
Published: September 2013

Studies of experimental diabetes in rodents induced by the β-cell toxin streptozocin have shown that the insulin-resistant glucose transport of peripheral tissues (muscle and adipose) in these animals can be ascribed in part to a pretranslational reduction of the major insulin-sensitive glucose transporter (GLUT4) in these tissues. Because a central feature of non-insulin-dependent diabetes mellitus (NIDDM) is an impaired ability of insulin to enhance glucose disposal in skeletal muscle, we examined the hypothesis that reduced expression of GLUT4 is a characteristic finding in the skeletal muscle of subjects with NIDDM. Biopsies of skeletal muscles were obtained from 17 patients with NIDDM and 10 lean and 9 obese nondiabetic subjects. Among the diabetic subjects, 7 were newly diagnosed and untreated. Compared with age-matched and body-weight-matched healthy control subjects, there was no significant alteration in the level of GLUT4 mRNA demonstrated by Northern blot and slot blot or GLUT4 protein determined by immunoblotting muscle membranes. Neither GLUT4 mRNA nor protein concentration correlated with the degree of glycemic control, fasting plasma insulin or glucose, diabetes duration, body mass index, sex, or age. GLUT1 mRNA and protein levels were also not significantly different between diabetic and matched control subjects. Thus, unlike streptozocin-induced diabetes in rodents, there is no evidence that impaired expression of the major insulin-responsive glucose transporter is responsible for insulin-resistant glucose transport in the skeletal muscle of these lean and moderately obese NIDDM patients.
Selective Elimination of Fibroblasts From Pancreatic Islet Monolayers by Basic Fibroblast Growth Factor–Saporin In Mitotoxin
Authors: Beattie Gillian M , Lappi Douglas A , Baird Andrew , Hayek Alberto
Published: September 2013

Fibroblast proliferation regularly impedes the initiation and maintenance of pancreatic islet monolayers in culture. We recently characterized a specific cytotoxin to cells expressing the basic fibroblast growth factor receptor by conjugating the growth factor to saporin-6, a ribosome-inactivating protein. In contrast to untreated islets, isolated adult rat islets grown on a substrate prepared from bovine corneal endothelial cells and incubated with the mitotoxin at 10-nM concentration for 96 h were free of contaminating fibroblasts. Histological and functional studies revealed there was no damage to the islets. The results suggest that treatment of this cell type with basic fibroblast growth factor mitotoxins may be an important tool for culture of pure islets for physiological and clinical studies.
Cell Surface Alteration in Epstein-Barr Virus-Transformed Cells From Patients With Extreme Insulin Resistance
Authors: Gorden D Lee , Robert A , Moncada Victoria Y , Taylor Simeon I , Mühlhauser J , Carpentier Jean-Louis
Published: September 2013

An abnormality was detected in the morphology of the cell surface of Epstein-Barr virus-transformed lymphocytes of patients with genetic forms of insulin resistance. In cells from two patients with leprechaunism and two patients with type A extreme insulin resistance, scanning electron microscopy demonstrated a decrease in the percentage of the cell surface occupied by microvilli in cells from the patients with leprechaunism and type A insulin resistance compared with control cells. When cells from a healthy control subject and one of the patients with leprechaunism (Lep/Ark-1) were incubated with 125I-labeled insulin, there was a decrease in the percentage of 125I-insulin associated with microvilli on the cell surface. Thus, the decreased localization of insulin receptors with the microvillous region of the cell surface was in proportion to the decrease in microvilli.
Adoptive Transfer of Diabetes in BB Rats Induced by CD4 T Lymphocytes
Authors: Métroz-Dayer Marie-Dominique , Mouland Andrew , Brideau Christine , Duhamel Dominique , Poussier Philippe
Published: September 2013

Unseparated splenocytes (SPCs) or purified SPC subsets from diabetes-prone BB (BBdp) or diabetic BB (BBd) rats were activated in vitro with either phorbol myristate acetate (PMA) and ionomycin (I) or concanavalin A (ConA). Such activated SPCs were then injected intravenously into 30-day-old BBdp rats, and their capacity to induce adoptive transfer (AT) of diabetes was studied. The proliferative response in vitro of BBd unseparated SPCs or purified W3/13+ SPCs (i.e., T lymphocytes + large granular lymphocytes) to PMA + I far exceeded that of ConA, resulting in mean stimulation indices of 68 and 112 (PMA + I) and 1.9 and 30 (ConA). The incidence of AT was similar when equal numbers of unseparated SPCs from the same BBd donor were injected after activation by either PMA + I + interleukin 2 (Pll) or ConA (57 vs. 50%, respectively); however, injection of Pll-activated and macrophage-depleted W3/13+ SPCs from BBd animals resulted in a significantly higher incidence of AT (90%, P < 0.05). As few as 0.5 × 106 Pll-activated W3/13+ SPCs were sufficient to induce AT. Sixteen percent of recipients developed diabetes after injection of activated W3/13+ cells from 40-dayold BBdp donors. To determine which W3/13+ cells might mediate such transfer, purified and Pll-preactivated CD4 T lymphocytes from BBd rats were injected, and they succeeded in AT in 44% of the recipients. Preactivated BBd B lymphocytes were unable to induce AT. Although a possible role for large granular lymphocytes cannot be excluded, the results demonstrate that in the BB rat, the β-cell destruction can be induced by CD4 T lymphocytes.
Effect of Medial Arterial Calcification on O2 Supply to Exercising Diabetic Feet
Authors: Chantelau E , Ma X Y , Herrnberger S , Dohmen C , Trappe P , Baba T
Published: September 2013

We investigated whether medial arterial calcification (MAC) impairs O2 supply to the exercising foot in diabetic patients with foot lesions. Transcutaneous O2 tension (tcPo2) was monitored at the dorsum of the foot before and after bicycle exercise in 11 diabetic patients with peripheral ischemic vascular disease (PIVD) with or without concomitant existence of MAC, 10 patients with MAC but without PIVD, 10 diabetic control subjects, and 6 nondiabetic control subjects. The mean preexercise tcPo2 level was comparable in these four groups. However, tcPo2 decreased significantly with exercise in feet with PIVD (mean ± SE −17.9 ± 2.7%, P < 0.01, n = 11), regardless of presence or absence of vascular calcification. On the other hand, the value increased significantly with exercise in feet with MAC but without PIVD (21.2 ± 3.5%, P < 0.01, n = 10) and in those of diabetic control subjects (14.9 ± 3.6%, P < 0.01), respectively. The tcPo2 remained unchanged in the feet of nondiabetic control subjects (1.7 ± 1.1%). The results suggest that MAC is not associated with reduced O2 supply to the exercising foot in diabetic patients.
Immunogenetic Analysis of β-Cell Autoimmunity in NOD Mice: Relationship of Insulitis to T-Lymphocyte—Receptor βnod and Aβnod Genes
Authors: Winter William E , Shimpo Kan , Obata Masafumi , Yamada Keiki , Luchetta Roberto
Published: September 2013

An early molecular event in the evolution of insulindependent diabetes in humans and NOD mice appears to involve the interaction of MHC class II molecules, β-cell autoantigen-derived peptides, and receptor molecules of helper T lymphocytes. To examine the influence of T-lymphocyte-receptor p-genes on the development of β-cell autoimmunity, (NOD × NZW)F1 × NOD backcrossed (BC) mice were studied for the development of insulitis, because insulitis is the pathognomonic histological lesion of autoimmune diabetes. Heterozygosity for H-2nod was permissive for the development of pancreatic interstitial inflammation and peri-islet insulitis, whereas homozygosity for H-2nod was highly associated with insulitis. However, (NOD × NZW)F1 × NOD BC mice developed insulitis regardless of homozygosity or heterozygosity for T-lymphocyte receptor βnod. Therefore, in our study, T-lymphocyte receptor βnod did not function as an autosomal-recessive β-cell autoimmunity gene.
Elevation of Plasma Thrombomodulin Level in Diabetic Patients With Early Diabetic Nephropathy
Authors: Iwashima Yasunori , Sato Takao , Watanabe Kiyoshi , Ooshima Eiji , Hiraishi Sayuri , Ishii Hidemi , Kazama Mutsuyoshi , Makino Isao
Published: September 2013

Thrombomodulin (TM) is a membrane protein in the vascular endothelium, and it plays an important role as a cofactor in the thrombin-catalyzed activation of protein C. It has also been found in human plasma; however, its clinical significance is not known. In this study, fasting plasma TM concentrations in 67 diabetic patients with different degrees of albuminuria (39 men aged 57 ± 8 yr, 28 women aged 57 ± 11 yr; means ± SD) and 34 age- and sex-matched healthy subjects were investigated by use of a one-step sandwich enzyme immunoassay, a new method developed by H.I. and others. As a screening, the patients were divided into three groups according to the first morning urinary concentrations of albumin: group 1, <30 μg/ml (normoalbuminuria); group 2, 30–140 μg/ml (microalbuminuria); group 3, >140 μg/ml (clinical nephropathy). There was no significant difference in plasma TM level between the control group (17.7 ± 3.7 ng/ml, n = 34) and group 1 (16.9 ± 3.4 ng/ml, ± = 30); however, plasma TM concentrations in group 2 (22.8 ± 3.4 ng/ml, n = 22) and group 3 (29.6 ± 6.1 ng/ml, n = 15) increased significantly compared with those in the control group and group 1, respectively. As a further investigation, three timed overnight urine collections were made. The patients were allocated to three groups according to their rates of albumin excretion: group I, <20 μg/min (normoalbuminuria); group II, 20–200 μg/min (microalbuminuria); group III >200 μg/min (clinical nephropathy). No significant difference was found in plasma TM level between the control group (17.8 ± 3.8 ng/ml, n = 16) and group I (17.8 ± 3.0 ng/ml, n = 17); however, plasma concentrations in group II (22.1 ± 2.8 ng/ml, n = 18) and group III (29.2 ± 6.0 ng/ml, n = 13) increased significantly compared with those in the control group and group I, respectively. No significant differences were found in blood pressure between the control group, group I, and group II. The vascular endothelium could be injured by various metabolic derangements because of diabetes. Accordingly, it is supposed that an injury in the vascular endothelial cell may progress with the advance of diabetic angiopathy, and TM existing on the endothelial membrane surface may be released into the plasma. The vascular permeability that permits glomerular leakage of albumin may also be found in other vessels. Thus, our findings suggest that an increased influx of TM to the plasma may be caused by generalized endothelial damage in patients with early diabetic nephropathy.
The Insulin Receptor: A Multifunctional Protein
Authors: Olefsky Jerrold M
Published: September 2013

The insulin receptor is a multifunctional protein encoded by a modular gene. Certain discrete domains within the insulin-receptor structure subserve specific functional properties. In some instances, these discrete domains are encoded by individual exons. This organizational model of the insulin receptor predicts the existence of divergent signaling pathways facilitating specific bioeffects. Some of these signaling pathways are shared with the closely related insulinlike growth factor I receptor (convergent pathways), whereas others are different (divergent). The concept of discrete functional domains also provides several mechanisms whereby inactive insulin receptors (no kinase activity) can inhibit the function of normal receptors. The ability of kinase-inactive insulin receptors to inhibit the signaling function of normal insulin receptors may be an operative mechanism in certain insulin-resistant states.
Differential Effects of Human and Pork Insulin–Induced Hypoglycemia on Neuronal Functions in Humans
Authors: Kern Werner , Lieb Klaus , Kerner Wolfgang , Born Jan , Fehm Horst L
Published: September 2013

Insulin has been found to cross the blood-brain barrier, and insulin receptors have been detected in different structures of the brain. However, the biological significance of insulin acting in the brain remains unclear. Reports of differential awareness of hypoglycemic symptoms during human insulin (Hl)- and pork insulin (Pl)-induced hypoglycemia hint at a modulatory influence of insulin on sensory processing. In a double-blind study, we recorded auditory-evoked potentials (AEPs), indexing neuronal transmission along sensory pathways, in 30 healthy male subjects during a baseline condition and HI- and PI-induced mild hypoglycemia of 2.65 mM. Fifteen subjects were tested after 20 min and another 15 after 50 min of constant hypoglycemia. During hypoglycemia, subjects had to indicate the severity of hypoglycemic symptoms and their current mood. Hypoglycemia increased latencies of the P3 component and reduced amplitudes of the N1, P2, and P3 components. Despite identical blood glucose and serum insulin levels in both sessions, effects of PI-induced hypoglycemia on AEP components were significantly stronger than those of HI-induced hypoglycemia (P < 0.05). Differences between the effects of the insulins were consistently apparent after 20 min of hypoglycemia, indicating a short-term action of these hormones on central nervous system functions. Also, after 20 min, but not after 50 min, of steady-state hypoglycemia, subjects felt more excited during PI than HI infusion (P < 0.05). The results indicate different influences of HI and PI on sensory function during hypoglycemia. These differences, occurring during early hypoglycemia, could contribute to the differential awareness of hypoglycemic warning symptoms during HI- and PI-induced hypoglycemia in diabetic patients.
Effects of Single and Repeated Blood Withdrawals on Circulating Mononuclear Cells in BB Rats: Failure to Prevent Diabetes Despite Acute Changes in Counts
Authors: Marliss Errol B , Métroz-Dayer Marie-Dominique , Montambault Marie , Faucher Madeleine , Grose Mark
Published: September 2013

Repeated large-volume blood withdrawals started at a young age previously appeared to correct lymphopenia and prevent diabetes in Ottawa diabetes-prone BB (BBdp) rats. Therefore, we sought an early effect 24 h after withdrawal of 25% of estimated blood volume and then reexamined the long-term effects in BBdp rats. The reexamination was prompted by the occurrence of variable numbers of BBdp rats positive for RT6.1 (a T-lymphocyte differentiation alloantigen) whose presence appears to “protect” against diabetes development (identified as BBp rats). Four groups were studied: non–diabetes-prone (BBn), RT6.1− BBdp, RT6.1+ BBp, and acutely diabetic BB (BBd) rats. An acute increase in the number of peripheral blood mononuclear cells and many subsets occurred in BBd and BBp rats. Despite these acute effects, a long-term effect of repeated blood withdrawal was not found in circulating cell counts or prevention of diabetes in BBdp rats. Thus, the previous finding was probably attributable to the presence of BBp rats. The long-term study demonstrated that RT6.1 expression in BBn rats increased from low levels at 15 days, peaked at 50 days, and decreased thereafter, an important finding in interpreting RT6.1 status at different ages. Furthermore, in contrast with other subsets, MARK-1+B lymphocytes and 0X42+ monocytes/macrophages decreased markedly in number at 120 and 150 days in BBn and BBp rats, whereas counts were higher and sustained in BBdp rats. The latter finding could be related to BBdp rats successfully resisting the autoaggressive process beyond the peak age of diabetes onset.
Prevalence of Complications in IDDM by Sex and Duration: Pittsburgh Epidemiology of Diabetes Complications Study II
Authors: Orchard Trevor J , Dorman Janice S , Maser Raelene E , Becker Dorothy J , Drash Allan L , Ellis Demetrius , LaPorte Ronald E , Kuller Lewis H
Published: September 2013

The prevalence of and interrelationships among all four major complications of insulin-dependent diabetes mellitus (IDDM) and their risk factors are being examined in a large epidemiologic study of IDDM subjects diagnosed in childhood. This article focuses on the baseline prevalence of complications in the 657 subjects diagnosed between 1950 and 1980 and currently aged 8–48 yr, with a mean duration of 20 yr. In addition to background retinopathy being virtually universal after 20 yr of diabetes, proliferative retinopathy affects 70% of IDDM subjects after 30 yr duration. As with overt nephropathy, prevalence of proliferative retinopathy is marginally higher in females than in males at short durations; the previously reported male excess is limited to the subjects with IDDM of longer duration (≥25 yr). Somewhat different patterns of microalbuminuria are also seen by sex. Males show a threefold increase in prevalence from 10 to 25 yr duration, whereas females show a more constant prevalence across these durations. A further rise in microalbuminuria is seen in males but not females at ≥30 yr duration, giving a combined prevalence of microalbuminuria and overt nephropathy at ≥30 yr duration of 84% (males) and 59% (females). Distal symmetrical polyneuropathy shows a constant rise with duration and is only marginally higher in men. Prevalence of cardiovascular (coronary and cerebral) disease shows no sex difference, whereas peripheral vascular disease is particularly common in women after 30 yr duration (>30%) compared with men (11%) when determined by ankle/arm blood pressure ratio <0.8 at rest or after exercise. These results suggest that the natural history of IDDM complications varies considerably by sex and that the prevalence of complications (especially renal complications in males) may be higher than previously recognized.
G Proteins and Modulation of Insulin Secretion
Authors: Robertson R Paul , Seaquist Elizabeth R , Walseth Timothy F
Published: September 2013

Guanine nucleotide–binding proteins (G proteins) are critically important mediators of many signal-transduction systems. Several important sites regulating stimulus-secretion coupling and release of insulin from pancreatic β-cells are modulated by G proteins. Gs mediates increases in intracellular cAMP associated with hormone-induced stimulation of insulin secretion. GI, mediates decreases in intracellular cAMP caused by inhibitors of insulin secretion, e.g., epinephrine, somatostatin, prostaglandin E2, and galanin. G proteins also regulate ion channels, phospholipases, and distal sites in exocytosis. Cholera and pertussis toxins irreversibly ADP ribosylate G proteins and are important tools that can be used both to manipulate G-protein–dependent modulators of insulin secretion and detect and quantify G proteins by electrophoretic techniques. The stage is set to pursue these initial observations in greater depth and ascertain whether G-protein research will provide important new insights into normal and abnormal regulation of insulin secretion.
Clinical and Neurophysiological Studies of Aldose Reductase Inhibitor Ponalrestat in Chronic Symptomatic Diabetic Peripheral Neuropathy
Authors: Florkowski Christopher M , Rowe Bethan R , Nightingale Simon , Harvey Timothy C , Barnett Anthony H
Published: September 2013

Increased flux through the polyol pathway mediated by the enzyme aldose reductase may be associated with the development of diabetic neuropathy. Fifty-four diabetic patients (median age 56 yr, range 25–65 yr) with chronic neuropathic symptoms were randomly allocated to placebo or aldose reductase inhibition (300 or 600 mg ponalrestat IC1128436) groups for 24 wk. Patients with vibration perception thresholds (VPTs) >35 V at the great toe or thermal difference thresholds (TTs) >10°C on the dorsum of the foot were excluded from the trial. No significant changes were observed in symptoms of pain, numbness, or paresthesia between ponalrestat and placebo groups, and there were no improvements in VPT or TT at several sites. Posterior tibial nerve conduction velocity changed from 35.3 ± 4.9 m/s at baseline to 33.4 ±4.0 m/s at 24 wk (NS) with placebo compared with 37.6 ± 5.6 vs. 37.2 ± 8.7 m/s (NS) with 300 mg ponalrestat and 34.5 ± 6.1 vs. 36.2 ± 6.8 m/s (NS) with 600 mg ponalrestat. Further studies are indicated with intervention at an earlier stage in the evolution of neuropathy and for longer periods.
Progressive Deterioration of Endocrine Function After Intraportal but Not Kidney Subcapsular Rat Islet Transplantation
Authors: Hiller Wolfgang F A , Klempnauer Jürgen , Lück Rainer , Steiniger Birte
Published: September 2013

In inbred streptozocin-induced diabetic rats, the long-term function of different endocrine pancreatic isografts was compared. Isolated islets transplanted into the portal vein showed a progressive deterioration of function over time. In contrast, islets under the kidney capsule sustained a constant long-term function controlling all clinical signs of diabetes. Recipients of kidney subcapsular islets displayed normal growth rate, peripheral serum glucose and insulin levels, and metabolic parameters. However, their functional reserve was markedly reduced as revealed by diminished glucose tolerance and reduced insulin-secreting capacity after an intravenous glucose challenge. Vascularized whole-organ pancreatic grafts with portal venous drainage led to complete normalization of all parameters determined in this study. This study showed that the long-term function of islets transplanted under the kidney capsule is superior compared with islets transplanted into the portal vein.
Coordinate Phosphorylation of Insulin-Receptor Kinase and Its 175,000-Mr Endogenous Substrate in Rat Hepatocytes
Authors: Okamoto Motozumi , Karasik Avraham , White Morris F , Kahn C Ronald
Published: September 2013

To investigate the early events in insulin signal transmission in liver, isolated rat hepatocytes were labeled with 32P, and proteins phosphorylated in response to insulin were detected by immunoprecipitation with anti-phosphotyrosine and anti-receptor antibodies and analyzed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and autoradiography. In these cells, insulin rapidly stimulated tyrosine phosphorylation of the 95,000-/Mr β-subunit of the insulin receptor and a 175,000-Mr phosphoprotein (pp175). Both proteins were precipitated by anti-phosphotyrosine antibody, whereas only the insulin receptor was recognized with anti-insulin-receptor antibody. In the insulin-stimulated state, both pp175 and the receptor β-subunit were found to be phosphorylated on tyrosine and serine residues. Based on precipitation by the two antibodies, receptor phosphorylation was biphasic with an initial increase in tyrosine phosphorylation followed by a more gradual increase in serine phosphorylation over the first 30 min of stimulation. The time course of phosphorylation of pp175 was rapid and paralleled that of the β-subunit of the insulin receptor. The pp175 was clearly distinguished from the insulin receptor, because it was detected only when boiling SDS was used to extract cellular phosphoproteins, whereas the insulin receptor was extracted with either Triton X-100 or SDS. In addition, the tryptic peptide maps of the two proteins were distinct. The dose-response curve for insulin stimulation was shifted slightly to the left of the insulin receptor, suggesting some signal amplification at this step. These data suggest that pp175 is a major endogenous substrate of the insulin receptor in liver and may be a cytoskeletal-associated protein. Both serine and tyrosine sites are involved in insulin-stimulated phosphorylation in hepatocytes.
Nutrition and Somatomedin: XXIII. Molecular Regulation of IGF-I by Amino Acid Availability in Cultured Hepatocytes
Authors: Harp Joyce B , Goldstein Steven , Phillips Lawrence S
Published: September 2013

The poor growth associated with protein-calorie malnutrition occurs despite circulating growth hormone levels that are normal or elevated and is thought to be mediated partly by blunted generation of insulinlike growth factor I (IGF-I) in the liver. To explore underlying mechanisms, we asked whether altered availability of amino acids could regulate hepatic IGF-I release independent of the contributions of regulatory hormones. Normal rat hepatocytes were isolated by collagenase digestion and maintained in serum-free medium with fixed concentrations of insulin and dexamethasone. Levels of immunoassayable albumin and IGF-I accumulation in daily changes of medium were sustained for 3–5 days, and all studies were performed within this period. Cellular viability and content of DNA were unaffected by deprivation of the essential amino acids lysine or tryptophan and the nonessential amino acids cysteine and/or cystine. However, deletion of tryptophan or lysine from the culture medium led to 63 and 76% declines in IGF-I release, respectively (both P < 0.001 vs. complete medium), although omission of cysteine or cysteine plus cystine produced no significant change. Over 5 days of culture, release of albumin was maintained in complete medium, but omission of tryptophan depressed albumin release over days 2—5 (P < 0.001). In complete medium, IGF-I release rose for 3 days and then declined. In tryptophan-deficient medium, IGF-I levels were comparable to control values after 24 h but did not rise at 48 h and then fell rapidly after 72 h in culture, with values significantly below levels in complete medium (all P < 0.005). Although tryptophan deprivation led to decreased release of IGF-I on day 3 of culture, release of albumin did not fall until day 4, suggesting that IGF-I is more sensitive to the presence of this essential amino acid. Because availability of tryptophan could affect formation of IGF-I via either utilization of this substrate for protein synthesis or alternate regulatory mechanisms, we searched for the basis of tryptophan effects by measuring the impact of tryptophan provision on levels of hepatic IGF-I mRNA. Omission of tryptophan led to a 50% decline in levels of IGF-I mRNA measured by dot blotting of total hepatic RNA (P < 0.05 vs. RNA from cells cultured in complete medium) but had little effect on levels of mRNA for the structural protein p-actin. This study demonstrates that amino acid availability may modulate hepatic production of IGF-I independent of the contributions of regulatory hormones, which change along with circulating metabolic fuels in the malnourished state. In addition to potential limitations on utilization of substrate, underlying mechanisms appear to involve changes in the level of hepatic mRNA, which directs synthesis of IGF-I for delivery to the circulation.
Stimulation of Lipolysis in Humans by Physiological Hypercortisolemia
Authors: Divertie Gavin D , Jensen Michael D , Miles John M
Published: September 2013

The effect of glucocorticoids on adipose tissue lipolysis in animals and humans is controversial. To determine whether a physiological increase in plasma cortisol, similar to that observed in diabetic ketoacidosis and other stress conditions, stimulates lipolysis, palmitate kinetics were measured in seven nondiabetic volunteers on two occasions with [1-14C]palmitate as a tracer. Subjects received a 6-h infusion of either 2 μg · kg−1 · min−1 hydrocortisone or saline in random order. On both occasions, a pancreatic clamp (0.12 μg · kg−1 · min−1 somatostatin, 0.05 mU · kg−1 · min−1 insulin, and 3 ng · kg−1 · min−1 growth hormone) was used to maintain plasma hormone concentrations at desired levels. Plasma cortisol concentrations increased to ∼970 nM during cortisol infusion. Palmitate rate of appearance (Ra) and concentration increased by ∼60% during cortisol infusion but did not change during saline infusion. Increments in palmitate Ra and concentration over the 6-h study were significantly greater during cortisol than saline infusion when compared by area-under-the-curve analysis (152 ± 52 vs. −48 ± 23 μmol · kg−1 and 12.2 ± 4.1 vs. −4.9 ± 4.1 mmol · min−1 · L−1, respectively; P < 0.02). Plasma glucose concentrations did not change significantly during cortisol (5.0 ± 0.3 vs. 6.1 ± 0.6 mM, NS) or saline (4.9 ± 0.2 vs. 4.9 ± 0.1 mM, NS) infusion. In nondiabetic volunteers, a 6-h cortisol infusion was associated with a 60% increase in palmitate Ra that did not occur with saline infusion. Thus, physiological hypercortisolemia may contribute to the increased rates of lipolysis observed in humans during stress.
Alteration of Cholecystokinin-Mediated Phosphatidylinositol Hydrolysis in Pancreatic Acini From Insulin-Deficient Rats: Evidence for Defective G Protein Activation
Authors: Chandrasekar Bysani , Korc Murray
Published: September 2013

Insulin deficiency leads to a decreased ability of cholecystokinin octapeptide (CCK-8) to raise cytosolic free-calcium levels in the pancreatic acinar cell. To elucidate the mechanisms underlying this defect, we studied the effects of CCK-8 on phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis in pancreatic acini prepared from nondiabetic and streptozocin-induced diabetic rats. Analysis by high-pressure liquid chromatography indicated that, in diabetic rat acini, the CCK-8–mediated increase in [3H]inositol 1,4,5-trisphosphate ([3H]IP3) levels was delayed, and the increase in [3H]inositol 1,3,4,5-tetrakisphosphate ([3H]IP4) levels was markedly attenuated compared with nondiabetic rat acini. The expected increase in the mass levels of IP3, measured in a competitive binding assay, was reduced in the diabetic group after incubation with CCK-8, carbachol, and bombesin. Phospholipase C activity was decreased by 30% in diabetic rat acini, whereas the specific activity of PIP2 and the amount of myo-[3H]inositol in the free and trichloroacetic acid–precipitable pools were similar in both groups. The nonhydrolyzable analogue of GTP guanosine-5′-O-(3′-thiotriphosphate) rapidly enhanced IP3 levels in permeabilized acini, and the percent increase above basal was greater in the diabetic group. When added for 5 s or 2 h, insulin did not alter basal or CCK-8–stimulated [3H]IP3 and [3H]IP4 levels in either nondiabetic or diabetic rat acini. However, after a 4-h incubation, insulin increased basal [3H]IP3 and [3H]IP4 levels in diabetic rat acini and potentiated the actions of CCK-8 on both inositol phosphates. Insulinlike growth factor I did not alter [3H]IP3 and [3H]IP4 levels either acutely or after a 4-h incubation. These findings point to a defect in the signal-transduction pathway that is activated by CCK-8 and other calcium-mobilizing agonists in the diabetic rat pancreas and suggest that insulin, acting via its own receptor, exerts long-term regulatory effects on PIP2 hydrolysis in the pancreatic acinar cell.
Glucagonlike Peptide-I-(7–36)-Amide Receptors Only in Islets of Langerhans: Autoradiographic Survey of Extracerebral Tissues in Rats
Authors: Ørskov Cathrine , Poulsen Steen S
Published: September 2013

We demonstrated specific binding of the insulin-releasing hormone glucagonlike peptide (GLP)-I-(7–36)-amide, an intestinal product of proglucagon, to pancreatic islet cells by autoradiography using 125I-labeled GLP-I-(7–36)-amide incubated with tissue specimens of extracerebral rat organs. We also found binding of 125I-GLP-I to insulin-, glucagon-, and somatostatin-immunoreactive cells by combined autoradiographic and immunohistochemical analysis of pancreatic specimens using antisera against insulin, glucagon, and somatostatin. An accumulation of radioactivity was also observed in the stomach surface epithelium but could not be prevented by excess unlabeled peptide. No binding was found in other tissues investigated, including the lungs and the small intestinal mucosa. Localization of the binding sites identifies the pancreatic islets as the prime target for GLP-I-(7–36)-amide and suggests that it exerts direct effects on islet cells.