bluuebunny/crossref_metadata_2025 huggingface dataset:
Epidermal Growth Factor Induces Glucose Storage in Transgenic 3T3-L1 Adipocytes Overexpressing Epidermal Growth Factor Receptors
Authors: Van Epps-Fung Mark , Hardy Robert W , Williford Jodie , Gupta Kiran , Wells Alan
Published: September 2013

3T3-L1 adipocytes represent an established physiological model for studying glucose uptake and storage. Overexpression of epidermal growth factor (EGF) receptors in these cells (200,000–250,000 receptors per cell) confers EGF-inducible GLUT4-mediated glucose uptake (17). We now report that EGF receptor (EGFR)-mediated signals can induce incorporation of glucose into glycogen and lipids in these cells. Incorporation into lipids was stimulated to similar levels by insulin or EGF in adipocytes expressing full-length (wild type) EGFR (2.05 ± 0.26-fold for insulin vs. 2.28 ± 0.15-fold for EGF). EGF induced incorporation into glycogen at roughly 60% of the level of insulin (4.53 ± 0.57-fold for insulin vs. 2.76 ± 0.25-fold for EGF); this corresponded with similarly lower levels of glycogen synthase activation by EGF relative to insulin stimulation. EGFR kinase activity was required for induced storage because a kinase-inactive (M721) EGFR failed to stimulate glucose incorporation into glycogen or lipids. EGFRs that lack all or part of the unique EGFR COOH-terminal tail induced glucose incorporation at levels similar to that stimulated by full-length (wild type) EGFR. Thus, domains in the COOH-terminal tail of the EGFR, which are necessary for stimulating glucose transport, are not required for signaling EGF-induced glucose storage. EGF-induced glucose storage did not require de novo protein synthesis, suggesting that EGFR signaling uses existing pathways in the adipocytes. These data demonstrate that signaling pathways for EGFR-mediated glucose storage and GLUT4-mediated glucose transport diverge at the receptor level. Thus, EGF-induced glucose storage can be achieved in the absence of induced GLUT4-mediated glucose transport.
Nicotinamide's Effects on Glucose Metabolism in Subjects at Risk For IDDM
Authors: Greenbaum Carla J , Kahn Steven E , Palmer Jerry P
Published: September 2013

Nicotinamide is being used in trials to prevent or delay the development of clinical IDDM. A related compound, niacin, has been shown to cause insulin resistance in normal subjects, resulting in increased insulin secretion. This study was designed to answer the question: Does the short-term administration of nicotinamide cause insulin resistance in subjects who have a high risk of developing IDDM? Eight islet cell antibody-positive (ICA+) relatives of IDDM patients were given nicotinamide at a dose of 2 g/day for 2 weeks. Measurements of first-phase insulin release, insulin sensitivity, glucose effectiveness, and the constant for glucose disappearance (Kg) were measured at baseline, at the end of 2 weeks of therapy, and after subjects had been off therapy for at least 2 weeks. Nicotinamide administration caused a 23.6% decrease in insulin sensitivity (P = 0.02). This decrease was associated with a fall in Kg despite increased insulin secretion. Our data suggest that the use of nicotinamide in subjects who are at risk of developing IDDM may be complicated by the drug's effects on insulin sensitivity. By inducing insulin resistance, a therapeutic effect of nicotinamide on the diabetes disease process may be missed, and the interpretation of insulin secretion measurements that are obtained during the intervention trials using nicotinamide may be complicated by the changes in insulin secretion that are caused by the increased insulin resistance. Therefore, we strongly support the recommendation that at least one subgroup of subjects enrolled in clinical trials to prevent IDDM have regular measurements of both insulin sensitivity and insulin secretion performed. This subgroup should be randomly assigned and large enough for statistical analysis to interpret properly the changes in insulin secretion that may occur.
Thiazolidinediones in the Treatment of Insulin Resistance and Type II Diabetes
Authors: Saltiel Alan R , Olefsky Jerrold M
Published: September 2013

Insulin resistance, characterized by reduced responsiveness to normal circulating concentrations of insulin, is a common feature of almost all patients with type II diabetes. The presumed central roles of both peripheral and hepatic insulin resistance suggest that the enhancement of insulin action might be an effective pharmacological approach to diabetes. Thiazolidinediones are a new class of orally active drugs that are designed to enhance the actions of insulin. These agents reduce insulin resistance by increasing insulin-dependent glucose disposal and reducing hepatic glucose output. Clinical studies in patients with type II diabetes, as well as other syndromes characterized by insulin resistance, have demonstrated that thiazolidinediones may represent a safe and effective new treatment. Although the precise mechanism of action of these drugs remains unknown, transcriptional changes are observed in tissue culture cells that produce enhanced insulin action. This regulation of gene expression appears to be mediated by the interactions of thiazolidinediones with a family of nuclear receptors known as the peroxisome proliferator-activated receptors (PPARs). The further elucidation of the molecular actions of these drugs may reveal much about the underlying mechanisms of insulin resistance.
Abnormally Expressed Low-Voltage-Activated Calcium Channels in β-Cells From NOD Mice and a Related Clonal Cell Line
Authors: Wang Lin , Bhattacharjee Arin , Fu Jian , Li Ming
Published: September 2013

A macroscopic low-voltage-activated (LVA) inward current was found in pancreatic β-cells isolated from NOD mice. However, this current was not present in nondiabetic prone mouse (e.g., Swiss-Webster) pancreatic β-cells. We performed pharmacological analyses on this current in NOD insulinoma tumor cells (NIT-1). This cell line was developed from pancreatic β-cells of a transgenic NOD mouse. The sodium-channel blocker, tetrodotoxin (TTX; 2 micromol/l) had no effect on this LVA current. The amplitudes of currents elicited by a –20 mV test pulse retained similarity when the extracellular sodium concentration was increased from 0 to 115 mmol/l; when the extracellular calcium concentration was decreased from 10 to 2 mmol/l, there was an approximate 50% reduction of this current elicited by a –30 mV test pulse. Neither the L-type calcium-channel blocker, nifedipine (3 μmol/l), nor the N-type calcium-channel blocker, ω-CgTx-GVIA (1 μmol/l), at –30 mV produced an appreciable effect. The T-type calcium-channel blockers, nickel (3 μmol/l) and amiloride (250 μmol/l), effectively reduced the peak of this current. In 2 mmol/l calcium external solution, the threshold of voltage-dependent activation of this calcium current was approximately –65 mV, and the peak current occurred at –20 mV. Half-maximum steady-state inactivation was around –43 mV. The mean time constant of slow deactivating tail currents generated by a preceding 20 mV pulse was 2.53 ms. The intracellular free calcium concentration was two- to threefold higher in NOD mouse pancreatic β-cells compared with Swiss-Webster pancreatic β-cells. We concluded that there are LVA calcium channels abnormally expressed in NOD mouse β-cells. This LVA calcium channel may be factorial to the high cytosolic free calcium concentration observed in these cells, and thereby may contribute to the pathogenesis of NOD mouse β-cells.
Major Histocompatibility Complex Class II Molecules Function as a Template for the Processing of a Partially Processed Insulin Peptide into a T-cell Epitope
Authors: Lang Ying , Forquet Frederique , Speck Edwin , Blum Janice , Delovitch Terry L
Published: September 2013

Our understanding of how an autoantigen is processed and presented during the development of a major histocompatibility complex (MHC) class II-dependent and T-cell-mediated autoimmune disease, such as IDDM, is incompletely understood. We have used insulin as a model autoantigen in IDDM to address the question of whether MHC class II molecules play a role in the generation and/or preservation of an autoantigen peptide that stimulates T-cell activation. Analyses of the requirement of I-Ad class II molecules in the processing of the partially processed porcine insulin peptide A1-A14/B1-B16 demonstrate that the binding of this peptide to I-Ad is essential for it to be further processed and tailored into a T-cell epitope. Based on our observations, we propose a two-step model for insulin processing in which insulin is first processed by an enzyme(s) into an intermediate peptide that binds to class II and then class II functions as a template to guide the processing of this partially processed peptide by cathepsin D into a T-cell epitope. Our data further underscore the important realization that MHC class II-directed processing of an autoantigen (e.g., insulin) may regulate 1) the relative immunodominance of T-cell determinants in an autoantigen, 2) the self-reactivity to cryptic T-cell epitopes in autoantigens, and 3) the susceptibility to autoimmune disease.
Interactions of Age, Islet Cell Antibodies, Insulin Autoantibodies, and First-Phase Insulin Response in Predicting Risk of Progression to IDDM in ICA+ Relatives: The ICARUS Data Set
Authors: Bingley Polly J
Published: September 2013

Many studies have examined the role of age, islet cell antibodies (ICAs), insulin autoantibodies (IAAs), and first-phase insulin responses (FPIRs) to an intravenous glucose tolerance test (IVGTT) as markers of risk of progression to IDDM, but a large data set is required for the analysis of the interactions between these markers. The Islet Cell Antibody Register Users Study (ICARUS) register includes 456 first-degree relatives with ICA levels ≥5 JDF U confirmed in a reference laboratory, 108 of whom have progressed to IDDM in the course of prospective follow-up. Analysis of this data set confirmed the importance of the loss of FPIR, high ICA titer, coexistence of IAA, and young age in enhancing the risk of progression to the disease. The influence of any given marker of risk is modified by the presence or absence of the other markers. Cox regression analysis performed in a subset of 217 subjects for whom IVGTT, ICA, and IAA data were available showed that risk was most strongly associated with loss of FPIR; IAA and ICA titer contributed equally to the model, while age was also an independent risk determinant.
Immunologic Effects of Insulin Lispro [Lys (B28), Pro (B29) Human Insulin] in IDDM and NIDDM Patients Previously Treated With Insulin
Authors: Fineberg Naomi S , Fineberg S Edwin , Anderson James H , Birkett Martin A , Gibson Reid G , Hufferd Suzan
Published: September 2013

Insulin lispro [Lys (B28), Pro (B29) human insulin] is a rapidly absorbed analog that has diminished tendency to self-associate. In four open-label, 1-year-long international randomized trials, we contrasted the immunogenicity of insulin lispro versus regular human insulin (RHI) in patients previously treated with insulin who had IDDM or NIDDM. Using a self-blank subtraction assay, we assessed sera for the presence of insulin-specific antibodies (ISA), insulin lispro-specific antibodies (LSA), and cross-reactive antibodies (CRA). Basal insulin needs were provided either with human ultralente (UL) or NPH insulins. After 2 to 4 weeks of therapy with RHI plus UL or RHI plus NPH, 50% of patients were randomly assigned to begin insulin lispro or continue on RHI. At baseline, few pretreated patients had LSA (0–4%) and ∼ 10% had ISA, whereas 41–45% of patients with IDDM and 23–27% of patients with NIDDM had CRA (IDDM vs. NIDDM, P < 0.001). Within studies, no significant differences were noted over time in ISA, LSA, or CRA attributable to the type of short-acting insulin. When data were pooled, inconsistent changes were noted in ISA and LSA (LSA were greater in NIDDM vs. IDDM at baseline, P = 0.001, and ISA were greater in IDDM vs. NIDDM at 6 months, P = 0.007). Significant levels of CRA were more common in IDDM at all times (P < 0.001, P = 0.022, and P = 0.002 at baseline, 6 months, and 12 months, respectively). For patients receiving insulin lispro, no significant changes occurred in antibody status among IDDM and NIDDM patients throughout the study (became positive, remained positive, became negative, or remained negative). IDDM patients were more likely to develop or maintain CRA levels (P = 0.008 vs. NIDDM), whereas antibody levels were comparable among positive individuals. No evidence was noted that insulin lispro differs in immunogenicity from RHI in previously treated IDDM and NIDDM patients.
Cellular Immune Response to Cow's Milk β-Lactoglobulin in Patients With Newly Diagnosed IDDM
Authors: Vaarala Outi , Klemetti Paula , Savilahti Erkki , Reijonen Helena , Ilonen Jorma , Åkerblom Hans K
Published: September 2013

Elevated levels of antibodies to cow's milk proteins, i.e., β-lactoglobulin (BLG) and bovine serum albumin (BSA), have been associated with IDDM. We observed enhanced cellular immune response by a proliferation test of peripheral blood mononuclear cells to BLG in 22 of 40 (55%) patients with newly diagnosed IDDM compared with 7 of 32 healthy children (22%) (P = 0.004, X2 test). The median stimulation index to BLG was 3.3 in patients and 1.5 in healthy children (P = 0.003, Mann-Whitney U test). No difference was found in cellular reactivity to other cow's milk proteins, such as BSA or α-casein, or to a dietary immunogenic protein, ovalbumin. Cellular responsiveness to BLG was not associated with HLA-DQB1* risk alleles of IDDM, which suggests that immune response to the protein does not only reflect the accumulation of these HLA alleles in the patients with IDDM. We suggest that enhanced cellular immune response to dietary BLG may reflect a disturbance in the regulation of immune response to oral antigens in IDDM. This kind of defect may play a fundamental role in the development of β-cell autoimmunity in IDDM.
Tumor Necrosis Factor-α and Interferon-γ Inhibit Insulin Secretion and Cause DNA Damage in Unweaned-Rat Islets: Extent of Nitric Oxide Involvement
Authors: Dunger Annemarie , Cunningham James M , Delaney Carol A , Lowe Jillian E , Green Michael H L , Bone Adrian J , Green Irene C
Published: September 2013

Nitric oxide has been implicated as one possible mediator of interleukin-1β (IL-1)-induced inhibition of insulin secretion and islet cell damage. The aim of this study was to define the effects of tumor necrosis factor-α (TNF) and interferon-γ (IFN) on nitric oxide production, insulin secretion, and DNA damage in islets from unweaned rats. Treatment of islets with 0.5–500 U/ml of either TNF or IFN on their own inhibited glucose-stimulated insulin secretion in a dose-dependent manner (minimum effective dose 5 U/ml). In combination, the cytokines exerted a pronounced synergistic inhibitory effect on secretion and were equipotent at causing a significant and concentration-dependent increase in culture medium nitrite levels, islet cyclic GMP formation, and DNA damage. Used alone or in combination, TNF and IFN significantly enhanced the activity of inducible nitric oxide synthase as determined by measuring the conversion of 14C-labeled arginine to 14C-labeled citrulline and nitric oxide. Use of arginine-free medium, without or with NG-monomethyl-L-arginine, resulted in inhibition of nitrite formation by 5–1,000 U/ml IFN + TNF and partial restoration of the insulin secretory response to glucose. Treatment of rat islets with increasing doses of TNF + IFN (5, 50, and 500 U/ml) resulted in a progressive increase in DNA damage, as shown by the comet assay, which detects DNA strand breaks in individual islet cells. The DNA damage caused by an intermediate concentration (50 U/ml) of TNF + IFN was comparable to that generated by IL-1 when used at 20 U/ml. We conclude that TNF and IFN induce nitric oxide formation, which partially inhibits glucose-induced insulin secretion and causes significant DNA strand breakage, but that as cytokine concentrations increase, non-nitric-oxide-mediated events predominate.
Altered GAP-43 Immunoreactivity in Regenerating Sciatic Nerve of Diabetic Rats
Authors: Pekiner Can , Dent Erik W , Roberts Richard E , Meiri Karina F , McLean W Graham
Published: September 2013

Experimental diabetes in the rat is associated with impaired axon regeneration. Successful regeneration depends on the construction of axonal growth cones and establishment of appropriate target connections. The growth-associated protein (GAP)–43 is a major component of the axonal growth cone, and its synthesis and axonal transport are markedly increased during regeneration. The purpose of this study was to determine the effect of experimental diabetes on the synthesis and axonal transport of GAP–43 in regenerating sciatic nerves. Rats were rendered diabetic with 50 mg/kg streptozotocin i.p. Four weeks later, the rats were anesthetized, and one sciatic nerve was crushed to induce regeneration. After 2 weeks, nerves were ligated, and 6 h later, nerve pieces proximal to the ligature and dorsal root ganglia were removed, and proteins were separated by PAGE. Western blots of gels were probed with antibody 10E8/E7 against GAP-43. The presence of GAP-43 was confirmed by immunohistochemistry of nerve sections. Densitometric analysis of the blots showed a 45% reduction in native GAP-43 immunoreactivity in nerve pieces proximal to the ligature (P < 0.05; n = 7). Northern blots of total RNA extracted from pooled dorsal root ganglia were probed with a 32P-radiolabeled cDNA probe for GAP-43. There was no significant difference in the amount of GAP-43 mRNA between diabetic and nondiabetic rats. Immunohistochemistry of sciatic nerve confirmed the reduction in GAP-43 immunoreactivity. We conclude that a defect in turnover or axonal transport of GAP-43 may contribute to the impaired peripheral nerve regeneration in diabetes.
Effect of Aminoguanidine on the Frequency of Neuroaxonal Dystrophy in the Superior Mesenteric Sympathetic Autonomic Ganglia of Rats With Streptozocin-Induced Diabetes
Authors: Schmidt Robert E , Dorsey Denise A , Beaudet Lucie N , Reiser Karen M , Williamson Joseph R , Tilton Ronald G
Published: September 2013

Aminoguanidine, which prevents formation of advanced glycation end products and is a relatively selective potent inhibitor of the inducible (versus constitutive) isoform(s) of nitric oxide synthase, has been reported to ameliorate structural and functional abnormalities in peripheral somatic nerves in rats with streptozocin (STZ)-induced diabetes. In the present studies, the effects of aminoguanidine treatment on ultrastructural changes in the autonomic nervous system of rats with STZ-induced diabetes were examined. The frequency of neuroaxonal dystrophy, the neuropathological hallmark of sympathetic autonomic neuropathy in diabetic rats, increased 9- to 11-fold in the superior mesenteric ganglia of 7- and 10-month STZ-diabetic rats compared with that in age-matched controls. Administration of aminoguanidine continuously from the time of induction of diabetes at a dose equal to or in excess of that providing a salutary effect in the diabetic somatic peripheral nervous system did not alter the severity of diabetes as assessed by plasma glucose level, 24-h urine volume, and levels of glycated hemoglobin. Chronic aminoguanidine therapy did not diminish the frequency or affect the ultrastructural appearance of neuroaxonal dystrophy in diabetic or age-matched control rat sympathetic ganglia after 7 or 10 months of continuous administration. Our findings (under these experimental conditions) do not support a role for aminoguanidine-sensitive processes in the development of sympathetic neuroaxonal dystrophy in diabetic rats. Glycation-linked aminoguanidine-insensitive processes, however, such as the formation of early glucose adducts (Schiff bases and Amadori products) with intracellular and/or extracellular proteins and amine-containing lipids, superoxide anion generation during subsequent autoxidation of these glucose adducts, and non-glycative processes, remain potential pathogenetic mechanisms for diabetic autonomic neuropathy.
Increased Glutamine:Fructose-6-Phosphate Amidotransferase Activity in Skeletal Muscle of Patients With NIDDM
Authors: Yki-Järvinen Hannele , Daniels Marc C , Virkamäki Antti , Mäkimattila Sari , DeFronzo Ralph A , McClain Don
Published: September 2013

Overactivity of the hexosamine pathway mediates glucose-induced insulin resistance in rat adipocytes. Glutamine:fructose-6-phosphate amidotransferase (GFA) is the rate-limiting enzyme of this pathway. We determined GFA activity in human skeletal muscle biopsies and rates of insulin-stimulated whole-body, oxidative, and nonoxidative glucose disposal using the euglycemic insulin clamp technique combined with indirect calorimetry (insulin infusion rate (1.5 mU · kg−1 · min−1) in 12 male patients with NIDDM (age 54 ± 2 years, BMI 27.5 ± 0.9 kg/m2, fasting plasma glucose 8.5 ± 0.6 mmol/l) and 9 matched normal men. GFA activity was detectable in human skeletal muscles and completely inhibited by uridine-5′-diphospho-N-acetylglucosamine (UDP-GlcNAc) in all subjects. GFA activity was 46% increased in the NIDDM patients compared with the normal subjects (9.5 ± 1.3 vs. 6.5 ± 1.2 pmol, P < 0.05). Whole-body glucose uptake was 58% decreased in patients with NIDDM (20 ± 3 μmol · kg body wt−1 · min−1) compared with normal subjects (47 ± 4 μmol · kg body wt−1 · min−1 P < 0.001). This decrease was attributable to decreases in both glucose oxidation (9 ± 1 vs. 15 ± 1 μmol · kg−1 · min−1, NIDDM patients vs. control subjects, P < 0.002) and nonoxidative glucose disposal (11 ± 2 vs. 31 ± 4 μmol · kg−1 · min−1 P < 0.001). In patients with NIDDM, both HbA1c (r = 0.51, P < 0.05) and BMI (r = −0.57, P < 0.05) correlated with whole-body glucose uptake. HbA1c but not BMI or insulin sensitivity was correlated with basal GFA activity (r = −0.57,P < 0.01) in NIDDM patients and control subjects. We conclude that GFA is found in human skeletal muscle and that all this activity is sensitive to feedback inhibition by UDP-GlcNAc. Chronic hyperglycemia is associated with an increase in skeletal muscle GFA activity, suggesting that increased activity of the hexosamine pathway may contribute to glucose toxicity and insulin resistance in humans.
Hypertriglyceridemia and Hyperinsulinemia Are Potent Inducers of Endothelin-1 Release in Humans
Authors: Piatti PierMarco , Monti Lycilla D , Conti Morena , Baruffaldi Laura , Galli Laura , Phan Chuong V , Guazzini Barbara , Pontiroli Antonio E , Pozza Guido
Published: September 2013

The purpose of the study was to evaluate fasting endothelin-1 levels in subjects with syndrome X, in subjects with insulinoma, and in normal subjects. The single and synergistic contributions of insulin and triglyceride levels to endothelin-1 release were studied in normal subjects. This was achieved by the evaluation of endothelin-1 levels in response to an insulin bolus combined with a euglycemic clamp (protocol A) and during intralipid (test 1) or saline (test 2) infusions lasting 360 min (protocol B). In protocol B, a euglycemic two-step hyperinsulinemic (25 and 125 mU · kg−1 · h−1) clamp was started at 120 min. Subjects with syndrome × showed significantly higher endothelin-1 levels than normal subjects and subjects with insulinoma (7.22 ± 0.89 vs. 2.61 ± 0.38 and 2.49 ± 0.24 pg/ml, P < 0.01). After an insulin bolus, endothelin-1 levels peaked at 10 min (3.71 ± 0.96 pg/ml). The incremental area of endothelin-1 was significantly higher after insulin than after a saline bolus. In test 1, an acute increase in triglyceride levels significantly enhanced endothelin-1 levels, with were further increased by the synergistic contribution of high insulin and triglyceride levels. In test 2, endothelin-1 release was achieved at high insulin levels but remained significantly lower than in test 1. In conclusion, subjects with syndrome × showed higher endothelin-1 levels than normal subjects and subjects with insulinoma. These levels were reproduced in normal subjects by a simultaneous increase in insulin and triglyceride levels.
Treatment of Diabetes by Xenogeneic Islets Without Immunosuppression: Use of a Vascularized Bioartificial Pancreas
Authors: Maki Takashi , Otsu Ichiro , O'Neil John J , Dunleavy Karen , Mullon Claudy JP , Solomon Barry A , Monaco Anthony P
Published: September 2013

Tight glycemic control by intensive insulin therapy effectively delays the onset and slows the progression of diabetic complications but is associated with frequent dose adjustments and a high incidence of hypoglycemia. Successful pancreas transplantation corrects abnormal glucose metabolism but subjects patients to morbidity and mortality associated with chronic immunosuppression. A vascularized artificial pancreas device containing pancreatic islets is designed to provide glycemic control without immunosuppression. We report here that devices seeded with porcine islets implanted into pancreatectomized severely diabetic dogs maintained a marked improvement in glycemic control with reduced exogenous insulin requirements for up to 9 months with improved glucose tolerance and a reduction in glycosylated hemoglobin levels. No immunosuppression was used. Thus, use of a vascularized artificial pancreas containing xenogeneic porcine islets could be an alternative to intensive insulin therapy and pancreatic transplantation in treating diabetic patients before the development of severe diabetic complications.
Human Arterial Smooth Muscle Cell Proliferation in Diabetes
Authors: Oikawa Shinichi , Hayasaka Kyoko , Hashizume Eiji , Kotake Hidetoshi , Midorikawa Hiroshi , Sekikawa Akihiro , Kikuchi Akiko , Toyota Takayoshi
Published: September 2013

In the present study, we focus on the proliferation of human arterial smooth muscle cells (SMCs) from NIDDM patients (DM-SMCs) to clarify the reactivity to the growth factor(s) in fetal calf serum (FCS) and the factors) secreted by T-cells. The proliferation of DM-SMCs was significantly greater than SMCs from nondiabetic patients (nonDM-SMC). DM-SMC conditioned medium (DM-condMed) increased the growth of nonDM-SMCs. These results suggest that the growth factor is secreted from DM-SMCs as an autocrine system, which increases the proliferation of nonDM-SMCs. T-cells increased DNA synthesis of SMCs, and DM-SMCs strikingly reacted to T-cells. The present results support a function of T-cells in stimulating SMC growth. In conclusion, human arterial SMC proliferation is increased in diabetes in the same fashion as in experimentally induced diabetes in animals through responses to growth factors and an increased autocrine system. These results provide a mechanism for the increase in atherosclerotic disease in diabetes.
Hypertriglyceridemia and Low HDL Cholesterol in Japanese Patients With NIDDM
Authors: Okubo Minoru , Murase Toshio
Published: September 2013

Diabetes is frequently associated with the combination of hypertriglyceridemia and low HDL cholesterol level, a known risk factor for cardiovascular disease. We evaluated the frequency of elevated serum triglyceride and reduced HDL cholesterol levels in Japanese male NIDDM patients. Hypertriglyceridemia (>1.69 mmol/l) and low HDL cholesterol level (<0.91 mmol/l) were frequently found in Japanese male NIDDM patients (30.4 and 14.2%, respectively). The combined abnormality, i.e., hypertriglyceridemia with concomitant low HDL cholesterol level, was more common in patients with poor glycemic control. We observed that inpatient diet therapy markedly reduced serum triglyceride but serum HDL cholesterol did not change significantly. This is in marked contrast to primary hypertriglyceridemia, in which HDL cholesterol level generally increases in parallel with a reduction in serum triglyceride level. We discuss the defective removal of triglyceride-rich lipoprotine and ineffective HDL production caused by lipoprotein lipase (LPL) deficiency. We also discuss possible correction of this combined abnormality by certain maneuvers that increase LPL activity.
Infrainguinal Reconstruction in Diabetes
Authors: DePalma Ralph G , John Y
Published: September 2013

Dramatic changes have occurred in the efficacy of infrainguinal reconstruction in diabetic patients. Enhanced limb salvage resulted from comprehensive understanding of patterns of macrovascular involvement, better perioperative control of sepsis and hyperglycemia, and advances in techniques for limb salvage. This report summarizes the applicability of recently evolving surgical techniques. Advances in pattern recognition have eliminated the misconception that microvascular involvement of the foot precludes successful reconstruction. A decreasing incidence of amputation in diabetic patients is currently seen. Interventions applicable to the usual patterns of diabetic macroangiopathy include femorodistal bypass to ankle or foot and popliteal distal bypass using autogenous vein usually in situ. In the absence of usable vein (a rare occurrence), the authors have observed intermediate patency using polytetrafluoroethylene to a vein cuff and anticoagulation. Initially, successful bypasses in diabetic and nondiabetic patients exhibit comparable long-term patency. Local toe or foot amputations are used more frequently to maintain bipedal gait. With careful management, a high rate of limb salvage is practical for nonsmoking, nonuremic diabetic patients.
Coronary Heart Disease and NIDDM in Japanese-Americans
Authors: Fujimoto Wilfred Y , Bergstrom Richard W , Boyko Edward J , Leonetti Donna L , Newell-Morris Laura L , Wahl Patricia W
Published: September 2013

Glucose intolerance is associated with increased risk of coronary heart disease (CHD) in Japanese-Americans, especially in men. Intra-abdominal fat, assessed by computed tomography, is increased in those with both NIDDM and CHD. Increased intra-abdominal fat (visceral adiposity) with CHD is independent of NIDDM or impaired glucose tolerance. The association between NIDDM and CHD may be explained by the association of each of these conditions with visceral adiposity. However, hyperinsulinemia is associated with CHD only in the presence of diabetes, whereas triglyceride levels are elevated with CHD independent of glucose tolerance category. These findings suggest that factors other than insulin levels, such as lipids, may mediate the relationship between visceral adiposity and CHD. Moreover, these relationships are influenced by gender.
Hyperinsulinemia and Atherosclerosis
Authors: Stout Robert W
Published: September 2013

For more than 25 years, there has been an expansion in the clinical and experimental evidence linking hyperinsulinemia with cardiovascular disease and atherosclerosis. Assessment of the evidence under the headings of the strength of the association, dose response, temporality, consistency, specificity, and plausibility supports the concept that hyperinsulinemia has a causal role in atherogenesis. Evidence that reducing insulin levels prevents atherosclerosis is lacking. The evidence available is strong enough to support preventive measures to lower insulin levels such as regular physical exercise and avoidance of obesity.
Growth Hormone–Induced Insulin Resistance and Its Relationship to Lipid Availability in the Rat
Authors: Hettiarachchi Manthinda , Watkinson Allan , Jenkins Arthur B , Theos Vicki , Ho Ken K Y , Kraegen Edward W
Published: September 2013

The role of increased lipid availability in the generation of insulin resistance by growth hormone has not been established. We investigated this in rats infused with saline (controls) or human growth hormone (hGH) (500 μg · kg− · 24 h−1) for 5 h or 3 days. hGH infusion increased basal plasma insulin at 5 h (335 ± 33 vs. 197 ± 15 [controls]; P < 0.005) and at 3 days (396 ± 34 vs. 218 ± 14 pmol/1; P < 0.0001). Plasma nonesterified fatty acid (0.26 ± 0.01 vs. 0.21 ± 0.01 [controls] g/l) and liver long-chain acyl-CoA (21.2 ± 1.9 vs. 14.1 ± 1.1 [controls] nmol/g wet wt) were elevated at 5 h (P < 0.01 for both) but were below control levels after 3 days of hGH infusion (P < 0.01 for both); indirect calorimetry after 3 days demonstrated decreased lipid oxidation. Clamp studies showed similar degrees of peripheral insulin resistance at 5-h and 3-day hGH infusion (glucose disposal reduced by 25% versus controls). Insulin-stimulated glucose metabolic index CRg′) in red gastrocnemius muscle (red muscle) was reduced (P < 0.05 and P < 0.01) at 5 h and 3 days of hGH infusion, respectively (e.g., 5 h, 10.0 ± 1.8 vs. 24.1 ± 4.4 [controls] μmol · 100 g−1 · min−1), whereas insulinmediated muscle glycogen synthesis was reduced (P < 0.03) only in rats infused with hGH for 3 days. We conclude that in the rat, hGH rapidly induces persistent peripheral insulin resistance and basal hyperinsulinemia. However, the transient nature of increased lipid mobilization suggests that it is not an important factor in the manifestation of muscle insulin resistance during prolonged hGH elevation. The persistent insulin resistance is not associated with increased lipid oxidation but is associated with hyperinsulinemia and reduced insulin-mediated muscle glycogen synthesis.
Hepatic Glucose Production Is Regulated Both by Direct Hepatic and Extrahepatic Effects of Insulin in Humans
Authors: Lewis Gary F , Zinman Bernard , Groenewoud Yolanda , Vranic Mladen , Giacca Adria
Published: September 2013

The present study examines the effect of the route of insulin delivery on glucose turnover in humans. By using a new noninvasive in vivo method, the acute effect of insulin secreted by the pancreas can be compared with that of insulin delivered by a peripheral vein. Three euglycemic-hyperinsulinemic studies were performed in lean healthy men. In the first study (n = 10), constant portal hyperinsulinemia was produced using a programmed intravenous tolbutamide infusion algorithm, and the insulin secretion rate was mathematically derived by deconvolution from peripheral plasma C-peptide levels. In the second study (n = 10), exogenous insulin was infused by peripheral vein at the same rate as that determined in the first study. In the third study (n = 7), the peripheral insulin levels in the first study were matched by infusing exogenous insulin into a peripheral vein at half that rate. Peripheral insulin levels were higher (P < 0.001) with the full-rate peripheral insulin infusion (266.3 ± 28.1 pmol/l) than with the portal delivery of insulin (171.1 ± 30.4 pmol/l) or the half-rate peripheral insulin infusion (158.6 ± 7.4 pmol/l) (portal versus half-rate peripheral insulin infusion, NS). Calculated hepatic insulin levels were higher (P < 0.001) in the portal insulin study (443.1 ± 52.6 pmol/l) than in the full-rate peripheral insulin study (303.6 ± 30.9 pmol/l) or in the half-rate peripheral insulin study (204.5 ± 9.8 pmol/l). Hepatic glucose production (HGP) was suppressed to a greater extent with the full-rate peripheral insulin infusion (69.3 ± 7.8%, P < 0.001 vs. portal or half-rate peripheral insulin) than portal (50.3 ± 9.8%) or half-rate peripheral insulin infusion (36.8 ± 3.8%). In the portal insulin study, however, suppression was > in the half-rate peripheral insulin study (P < 0.01), in spite of equal peripheral insulin levels. The assumption that tolbutamide, when used in this fashion, has no independent effect on glucose turnover, glucagon, or gluconeogenic precursor and energy substrates for gluconeogenesis was validated in five C-peptide-negative patients with IDDM. We conclude that in nondiabetic humans, 1) peripheral effects of insulin are important in suppressing HGP, as evidenced by the greater suppression of HGP with equivalent rate peripheral versus portal insulin delivery, and 2) because HGP was suppressed to a greater extent with portal verus peripheral insulin delivery at half the rate when peripheral insulin levels were matched, insulin-induced suppression of HGP is also partly mediated by a direct hepatic effect.
Clinical Phenotypes, Insulin Secretion, and Insulin Sensitivity in Kindreds With Maternally Inherited Diabetes and Deafness Due to Mitochondrial tRNALeu(UUR) Gene Mutation
Authors: Velho Gilberto , Byrne Maria M , Clément Karine , Sturis Jeppe , Pueyo Maria E. , Blanché Helène , Vionnet Nathalie , Fiet Jean , Passa Philippe , Robert Jean-Jacques , Polonsky Kenneth S , Froguel Philippe
Published: September 2013

An A-to-G transition in the mitochondrial tRNALeu(UUR) gene at base pair 3243 has been shown to be associated with the maternally transmitted clinical phenotype of NIDDM and sensorineural hearing loss in white and Japanese pedigrees. We have detected this mutation in 25 of 50 tested members of five white French pedigrees. Affected (mutation-positive) family members presented variable clinical features, ranging from normal glucose tolerance (NGT) to insulin-requiring diabetes. The present report describes the clinical phenotypes of affected members and detailed evaluations of insulin secretion and insulin sensitivity in seven mutation-positive individuals who have a range of glucose tolerance from normal (n = 3) to impaired (n = 1) to NIDDM (n = 3). Insulin secretion was evaluated during two experimental protocols: the first involved the measurement of insulin secretory responses during intravenous glucose tolerance test, hyperglycemic clamp, and intravenous injection of arginine. The second consisted of the administration of graded and oscillatory infusions of glucose and studies to define C-peptide kinetics. This protocol was aimed at assessing two sensitive measures of β-cell dysfunction: the priming effect of glucose on the glucose-insulin secretion rate (ISR) dose-response curve and the ability of oscillatory glucose infusion to entrain insulin secretory oscillations. Insulin sensitivity was assessed by euglycemic-hyperinsulinemic clamp. Evaluation of insulin secretion demonstrated a large degree of between- and within-subject variability. However, all subjects, including those with NGT, demonstrated abnormal insulin secretion on at least one of the tests. In the four subjects with normal or impaired glucose tolerance, glucose failed to prime the ISR response, entrainment of ultradian insulin secretory oscillations was abnormal, or both defects were present. The response to arginine was always preserved, including in subjects with NIDDM. Insulin resistance was observed only in the subjects with overt diabetes. In conclusion, the pathophysiological mechanisms responsible for the development of NIDDM and insulin-requiring diabetes in this syndrome are complex and might include defects in insulin production, glucose toxicity, and insulin resistance. However, our data suggest that a defect of glucose-regulated insulin secretion is an early possible primary abnormality in carriers of the mutation. This defect might result from the progressive reduction of oxidative phosphorylation and implicate the glucose-sensing mechanism of β-cells.
Fast Reversibility of Glucose-Induced Desensitization in Rat Pancreatic Islets: Evidence for an Involvement of Ionic Fluxes
Authors: Anello Marcello , Rabuazzo Agata Maria , Degano Claudia , Caltabiano Venera , Patanè Giovanni , Vigneri Riccardo , Purrello Francesco
Published: September 2013

The present study was done to achieve a better understanding of the role of ionic flux alterations in glucose-induced desensitization of pancreatic β-cells. Moreover, we investigated the reversibility of glucose-induced desensitization after different times of exposure to high glucose to ascertain the time necessary for desensitization reversal and to determine whether it depends on the length of high glucose exposure. Glucose desensitization was obtained by incubating rat pancreatic islets for 6 h in CMRL medium containing 16.7 mmol/l glucose. At the end of this period, insulin release, 86Rb efflux, and 45Ca uptake were measured in parallel experiments. In islets cultured at 16.7 mmol/l glucose, maximal glucose-induced insulin release was reduced (848 ± 97 pg · islet™1 · 30 min−1) in comparison to islets incubated at 5.5 mmol/l glucose (1,436 ± 144, n = 7, P < 0.01). In contrast, insulin content was similar in the two groups, being 41.0 ± 2.7 and 47.8 ± 2.2 ng/islet in islets exposed to 16.7 or 5.5 mmol/l glucose, respectively (P = 0.167). The effect of glucose on both 86Rb efflux and 45Ca uptake was also significantly reduced in 16.7 mmol/l glucose-cultured islets. 86Rb efflux was inhibited only 19 ± 4% in islets cultured at high glucose with respect to 56 ± 7% in control islets (n = 5, P < 0.001). 45Ca uptake was 10.5 ± 1.7 pmol/islet (mean ± SE, n = 9) in islets cultured at high glucose with respect to 19.7 ± 2.4 pmol/islet in control islets (P < 0.001). In contrast, the effect of glyburide (10 μmol/l) on insulin release, 86Rb efflux, and 45Ca uptake was similar in islets exposed to 5.5 or 16.7 mmol/l glucose. All the abnormalities observed in islets cultured at 16.7 mmol/l glucose were promptly and simultaneously reversible after islets were transferred in culture medium at 5.5 mmol/l glucose; both insulin secretion and glucose effects on 86Rb efflux and 45Ca uptake returned to values similar to control islets within 5 min. Also, islets exposed to high glucose for a longer period (24 h) recovered from both secretory and ionic abnormalities after 5 min of incubation in CMRL medium at 5.5 mmol/l glucose. Reversal from glucose desensitization was slower (45–60 min) when islets were incubated at 5.5 mmol/l glucose in Krebs-Ringer HEPES buffer instead of CMRL medium. The present data suggest that ion flux and consequent membrane-potential changes play a key role in the mechanism leading to glucose-induced desensitization of pancreatic β-cells. Because a normal response to glyburide was observed in islets exposed to high glucose, a proximal signal defect for closure of K+ channels rather than an intrinsic defect in the channel is likely.
Neutralization of TGF-β by Anti-TGF-β Antibody Attenuates Kidney Hypertrophy and the Enhanced Extracellular Matrix Gene Expression in STZ-Induced Diabetic Mice
Authors: Sharma Kumar , Jin Yulin , Guo Jia , Ziyadeh Fuad N
Published: September 2013

Diabetic nephropathy is characterized by renal hypertrophy, thickening of basement membranes, and accumulation of extracellular matrix in the glomerular mesangium and the interstitium. Our previous investigations have shown that high glucose concentration increases transforming growth factor (TGF)-β1 mRNA in mesangial and proximal tubule cells and that treatment with anti-TGF-β antibody results in prevention of the effects of high glucose on cell growth (e.g., induction of cellular hypertrophy) and the stimulation of collagen biosynthesis. We evaluated in vivo the functional role of the renal TGF-β system in diabetic kidney disease by treatment of streptozotocin-induced diabetic mice with either a neutralizing monoclonal antibody against TGF-β1, -β2, and -β3 (αT) or nonimmune murine IgG for 9 days. Diabetic mice given IgG demonstrated total kidney and glomerular hypertrophy, significantly elevated urinary TGF-β1 protein, and increased mRNAs encoding TGF-β1, type II TGF-β receptor, α1(IV) collagen, and fibronectin. Treatment of diabetic mice with αT prevented glomerular hypertrophy, reduced the increment in kidney weight by ∼ 50%, and significantly attenuated the increase in mRNA levels without having any effect on blood glucose. The antibody was without significant effect on mRNA levels in nondiabetic mice. This is the first demonstration that the early characteristic features of diabetic renal involvement, which include hypertrophy and increased matrix mRNAs, are largely mediated by increased endogenous TGF-β activity in the kidney and that they can be significantly attenuated by treatment with neutralizing anti-TGF-β antibodies.
Kilham Rat Virus Triggers T-Cell–Dependent Autoimmune Diabetes in Multiple Strains of Rat
Authors: Ellerman Karen E , Richards Cindy A , Guberski Dennis L , Shek William R , Like Arthur A
Published: September 2013

Kilham rat virus (KRV) infection of BB/Wor diabetes-resistant (DR) RT1u rats induces autoimmune diabetes without direct cytolytic infection of pancreatic β-cells and is a new model of virus-induced IDDM. To investigate genetic susceptibility to KRV-induced diabetes, major histocompatibility complex congenic and other inbred rats were infected with the virus and studied for the appearance of diabetes and insulitis. KRV infection alone induced insulitis, selective β-cell necrosis, and diabetes in BB/Wor DR and LEW1.WR1 (RT1 Au B/Du Ca) but not other rats. Thus, KRV, an environmentally ubiquitous rat parvovirus, can precipitate autoimmune diabetes in rats that are not susceptible to spontaneous diabetes. If rats are injected with poly(I·C) immediately before KRV infection, diabetes frequency increases to >90% in BB/Wor DR and LEW1.WR1 rats, and PVG.RT1u rats are converted from KRV-resistant to KRV-susceptible status. Susceptibility to KRV-induced diabetes thus requires the presence of class I Au and class II B/Du gene products, which are shared by DR, LEW1.WR1, and PVG.RT1u rats. The RT1u haplotype is not sufficient for susceptibility, however, because while WF rats are RT1u, they resist KRV-induced diabetes. If rats are depleted of RT6.1+ regulatory T-cells before KRV infection, the frequency of diabetes is dramatically increased in DR and LEW1.WR1, but not PVG.RT1u or other rats. These data confirm a regulatory role of RT6.1+ T-cells in diabetes induction, but indicate that they may not operate as such in all rat strains. KRV-induced diabetes is T-cell–mediated: DR and LEW1.WR1 rats are protected from diabetes by treatment with monoclonal antibodies directed against αβ T-cell receptor (TCR)+, CD5+, and CD8+ T-cells. Concanavalin A–activated spleen cells from KRV-infected DR rats adoptively transfer diabetes and insulitis into class IIu compatible rats, suggesting that KRV infection of susceptible rats leads to the activation of diabetogenic class IIu restricted T-cells. The ability of a common rat virus to initiate IDDM in multiple strains of rats strengthens the possibility that viruses may also initiate IDDM in human populations.
Abdominal Fat and Insulin Resistance in Normal and Overweight Women: Direct Measurements Reveal a Strong Relationship in Subjects at Both Low and High Risk of NIDDM
Authors: Carey David G , Jenkins Arthur B , Campbell Lesley V , Freund Judith , Chisholm Donald J
Published: September 2013

Insulin resistance appears to be central to obesity, NIDDM, hyperlipidemia, and cardiovascular disease. While obese women with abdominal (android) fat distribution are more insulin resistant than those with peripheral (gynecoid) obesity, in nonobese women, the relationship between abdominal fat and insulin resistance is unknown. By measuring regional adiposity with dual-energy X-ray absorptiometry and insulin sensitivity by euglycemic-hyperinsulinemic clamp in 22 healthy women, with a mean ± SE body BMI of 26.7 ± 0.9 kg/m2 and differing risk factors for NIDDM, we found a strong negative relationship between central abdominal (intra-abdominal plus abdominal subcutaneous) fat and whole-body insulin sensitivity (r = −0.89, P < 0.0001) and nonoxidative glucose disposal (r = −0.77, P < 0.001), independent of total adiposity, family history of NIDDM, and past gestational diabetes. There was a large variation in insulin sensitivity, with a similar variation in central fat, even in those whose BMI was <25 kg/m2. Abdominal fat had a significantly stronger relationship with insulin sensitivity than peripheral nonabdominal fat (r2 = 0.79 vs. 0.44), and higher levels were associated with increased fasting nonesterified fatty acids, lipid oxidation, and hepatic glucose output. Because 79% of the variance in insulin sensitivity in this heterogeneous population was accounted for by central fat, abdominal adiposity appears to be a strong marker and may be a major determinant of insulin resistance in women.