bluuebunny/crossref_metadata_2025 huggingface dataset:
Leptin Increases Hypothalamic Pro-opiomelanocortin mRNA Expression in the Rostral Arcuate Nucleus
Authors: Schwartz Michael W , Seeley Randy J , Woods Stephen C , Weigle David S , Campfield L Arthur , Burn Paul , Baskin Denis G
Published: September 2013

Melanocortins are peptides, cleaved from the pro-opiomelanocortin (POMC) precursor, that act in the brain to reduce food intake and are potential mediators of leptin action. In the forebrain, melanocortins are derived from POMC-containing neurons of the hypothalamic arcuate nucleus. To test the hypothesis that these POMC neurons are regulated by leptin, we used in situ hybridization to determine whether reduced leptin signaling (as occurs in fasting), genetic leptin deficiency (in obese ob/ob mice), or genetic leptin resistance (in obese db/db mice) lower expression of POMC mRNA. We further hypothesized that leptin administration would raise hypothalamic POMC mRNA levels in leptin-deficient animals, but not in mice with defective leptin receptors. In wild-type mice (n = 12), fasting for 48 h lowered POMC mRNA levels in the rostral arcuate nucleus by 53%, relative to values in fed controls (n = 8; P < 0.001). Similarly, arcuate nucleus POMC mRNA levels were reduced by 46 and 70% in genetically obese ob/ob (n = 6) and db/db mice (n = 6), respectively, as compared with wild-type mice (n = 5) (P < 0.01 for both comparisons). Five daily intraperitoneal injections of recombinant murine leptin (150 μg) raised levels of POMC mRNA in the rostral arcuate nucleus of ob/ob mice (n = 8) by 73% over saline-treated ob/ob control values (n = 8; P < 0.01), but was without effect in db/db mice (n = 6). In normal rats, two injections of a low dose of leptin (3.5 μg) into the third cerebral ventricle (n = 15) during a 40-h period of fasting also increased POMC mRNA levels in the rostral arcuate nucleus to values 39% greater than those in vehicle-treated controls (n = 14; P = 0.02). We conclude that reduced central nervous system leptin signaling owing to fasting or to genetic defects in leptin or its receptor lower POMC mRNA levels in the rostral arcuate nucleus. The finding that leptin reverses this effect in ob/ob, but not db/db, mice suggests that leptin stimulates arcuate nucleus POMC gene expression via a pathway involving leptin receptors. These findings support the hypothesis that leptin signaling in the brain involves activation of the hypothalamic melanocortin system.
Low Stress Response Enhances Vulnerability of Islet Cells in Diabetes-Prone BB Rats
Authors: Bellmann Kerstin , Hui Liu , Radons Jürgen , Burkart Volker , Kolb Hubert
Published: September 2013

In islet cells isolated from normal outbred Wistar rats, the known high vulnerability of islet cells toward oxygen radicals or nitric oxide can be abolished by inducing a stress response, such as by heat shock. We show here that islet cells from diabetes-prone BB rats are unable to mount such a protective response. Islet cells from diabetes-prone BB rats without recognizable insulitis were heat stressed. Subsequently, cells were exposed to nitric oxide, to oxygen radicals, or to the β-cell toxin streptozotocin. While prior heat shock substantially increased the survival of toxin-treated Wistar rat islet cells, no protective stress response was noted for islet cells from diabetes-prone BB rats. Islet cells from diabetes-resistant BB rats were protected by heat stress to the same extent as Wistar rats. A survey of four additional major histocompatibility complex (MHC)-disparate rat strains confirmed the existence of a low and high responder type to stress. Parallel analysis of heat shock protein (hsp)70 induction by Western blot showed a low and high hsp70 response phenotype. A high hsp70 response coincided with a protective stress response. The presence (or absence) of a protective stress response correlated with the preservation (or loss) of intracellular NAD+ in toxin-treated islet cells. The lack of a protective stress response in islet cells from diabetes-prone BB rats, but not in diabetes-resistant BB rats, may promote β-cell lysis and autoantigen release, and hence could be important for initiation or propagation of the disease process.
Aldose Reductase Inhibition Protects Diabetic and Nondiabetic Rat Hearts from Ischemic Injury
Authors: Ramasamy Ravichandran , Oates Peter J , Schaefer Saul
Published: September 2013

Diabetes increases the incidence of cardiovascular disease as well as the complications of myocardial infarction. Studies using animal models of diabetes have demonstrated that the metabolic alterations occurring at the myocyte level may contribute to the severity of ischemic injury in diabetic hearts. Of the several mechanisms being investigated to understand the pathogenesis of diabetic complications, the increased metabolism of glucose via the polyol pathway has received considerable attention. Deviant metabolic regulation due to increased flux through aldose reductase in diabetic hearts may influence the ability of the myocardium to withstand ischemia insult. To determine if aldose reductase inhibition improves tolerance to ischemia, hearts from acute type I diabetic and nondiabetic control rats were isolated and retrograde perfused. Each group was exposed to 1 μmol/l zopolrestat, a specific inhibitor of aldose reductase, for 10 min, followed by 20 min of global ischemia and 60 min of reperfusion in the absence of zopolrestat. Zopolrestat reduced sorbitol levels before ischemia in diabetic hearts. The cytosolic redox state (NADH/NAD+), as measured by lactate-topyruvate ratios, was significantly lowered under baseline, ischemic, and reperfusion conditions in diabetic hearts perfused with zopolrestat. In these diabetic hearts, ATP was significantly higher in zopolrestat hearts during ischemia, as were phosphocreatine and left ventricular–developed pressure on reperfusion. Zopolrestat provided similar metabolic and functional benefits in nondiabetic hearts. Creatine kinase release was reduced by ∼50% in both nondiabetic and diabetic hearts treated with zopolrestat. These data indicate that inhibition of aldose reductase activity preserves high-energy phosphates, maintains a lower cytosolic NADH/NAD+ ratio, and markedly protects both diabetic and nondiabetic hearts during ischemia and reperfusion.
No Independent Associations of LMP2 and LMP7 Polymorphisms With Susceptibility to Develop IDDM
Authors: Undlien Dag E , Akselsen Hanne E , Joner Geir , Dahl-Jørgensen Knut , Søvik Oddmund , Rønningen Kjersti S , Thorsby Erik
Published: September 2013

Results from a recent study suggested that polymorphisms within the HLA class II genes LMP2 and LMP7 were associated with the susceptibility for developing IDDM, and that this association could not be explained by linkage disequilibrium to HLA-DR or -DQ genes. We typed 285 IDDM patients and 337 HLA-DRB1-DQA1-DQB1 genotypically matched control subjects from an ethnically homogeneous population for both the G/T polymorphism in intron 6 of the LMP7 gene and the Arg-His polymorphism in the LMP2 gene. In addition, we typed IDDM families in which at least one parent was homozygous for a DRB1-DQA1-DQB1 haplotype and performed a transmission/disequilibrium test of these LMP polymorphisms. Our data suggest that none of these LMP2 or LMP7 polymorphisms are independently associated with IDDM susceptibility, in contrast to what has been previously reported by others. Further, our results suggest that one partial explanation for the previously reported independent association between IDDM and these LMP polymorphisms may have been that patients and control subjects were not matched for DRB1*04 subtypes. Our results emphasize the need for a complete matching for DRB1, DQA1, and DQB1 alleles between patients and control subjects when attempting to detect independent effects of other polymorphisms in the HLA complex on IDDM susceptibility or protection.
The Role of Nutritional Modifications in the Prevention of Macrovascular Complications of Diabetes
Authors: Mann Jim I
Published: September 2013

A wide range of dietary changes is likely to reduce the risk of macrovascular complications of diabetes. It is critically important to recommend a balance of macronutrients different from that currently consumed in most Western countries. Saturated fatty acids, especially myristic and palmitic acids, and trans fatty acids must be reduced to lower LDL cholesterol. Intake of polyunsaturated fatty acids should not be excessive (less than 10% total energy). Fiber-rich carbohydrate, derived from cereals, vegetables, and fruit with intact cell walls, and cis monounsaturated fatty acids should provide the bulk of total energy. These changes are likely to be associated with the most favorable lipoprotein profile and increase intake of dietary antioxidants and so reduce the level of oxidative stress. A reduction of sodium to below 6 g per day will help to reduce blood pressure levels. Optimal glycemie control has not yet been proved to reduce the risk of macrovascular complications, though this is a desirable goal for many other reasons. Ensuring appropriate energy balance (so that BMI is within the desirable range), using low glycemie index foods, and appropriately balancing carbohydrate intake with hypoglycemic drug therapy provide the best nutritional means of achieving satisfactory blood glucose levels. Successful implementation of nutritional recommendations requires the availability of dietitians capable of translating appropriate nutrition into appropriate foods acceptable to people with diabetes and their families. Clear food labeling and the availability of appropriate manufactured foods will further help patients with diabetes to achieve the dietary recommendations.
Pharmacological Strategies to Prevent Macrovascular Disease in NIDDM
Authors: Colwell John A
Published: September 2013

The pathogenesis of atherosclerosis and vascular thrombosis in NIDDM is reviewed. Evidence that suggests a role for chronic hyperglycemia, in association with other vascular risk markers, is presented. Based on this framework, a multifactorial approach to the prevention of progression of macrovascular disease in NIDDM is discussed. Results from a recent consensus conference sponsored by the American Diabetes Association regarding approaches to glycemic regulation in people with NIDDM are reviewed. It is concluded that preventive approaches will materially alter the course of macrovascular disease, reduce health care costs, and improve the quality of life for people with NIDDM.
Diagnosis of Cardiovascular Autonomic Neuropathy in Diabetes
Authors: Spallone Vincenza , Menzinger Guido
Published: September 2013

The utility of standard cardiovascular tests for diagnosis of cardiac autonomie neuropathy in diabetes has been well documented. Attention must be paid to standardizing the procedure with regard to time of day, metabolic status, distance from meal and insulin, coffee and smoking avoidance, and patient's collaboration. In the presence of cardiovascular disease or drugs affecting the cardiovascular or autonomic nervous system, some caution is needed in interpreting the results. More recent reflex tests, which evaluate mainly sympathetic or baroreflex activity, despite their ability to detect early autonomic involvement, lack sufficient standardization and still need to be proved as valid alternatives. Of the different methods of measuring heart rate variability, spectral analysis has a greater ability to differentiate vagal and sympathetic modulation of heart rate than do time-domain methods. However, since these latter methods are easier and more widely available, they can be used as a screening approach. Twenty-four-hour evaluation of heart rate variability provides data on the circadian rhythm of sympathovagal activity, which can be affected earlier than and differently from cardiovascular reflex tests. Information obtained could have prognostic implications in terms of cardiovascular morbidity and mortality and offer therapeutic opportunities. However, a wide consensus on many technical aspects of both time-domain and frequency-domain methods is needed. Furthermore, large prospective studies in the diabetic population to assess the prognostic value of 24-h heart rate variability parameters on cardiovascular morbidity and mortality are lacking. Recently, I123 meta-iodobenzylguanidine (MIBG) scintigraphy has documented abnormalities of sympathetic myocardial innervation also in newly diagnosed IDDM. The meaning of this finding, whether it is an expression of functional or structural defects, needs to be clarified. Preliminary data point to a possible pathogenetic meaning of the known association between autonomic neuropathy and other diabetic complications. This area of investigation could provide useful insights into the complex and multifactorial pathogenesis of diabetic complications.
Improved Insulin Sensitivity by Bezafibrate in Rats: Relationship to Fatty Acid Composition of Skeletal-Muscle Triglycerides
Authors: Matsui Hideo , Okumura Kenji , Kawakami Kei , Hibino Michitaka , Toki Yukio , Ito Takayuki
Published: September 2013

We investigated the effect of the lipid-lowering agent, bezafibrate, on insulin sensitivity in a dietary model of insulin resistance. Male Sprague-Dawley rats were divided into four groups: control group, administered a standard diet; high-fructose group, given a 40% fructose diet; high-fructose plus lard group, given a 40% fructose diet with 7% lard; and bezafibrate group, given a 40% fructose plus 7% lard diet with 10 mg · kg−1 · day−1 of oral bezafibrate. Insulin action was assessed after 2 weeks with a steady-state plasma glucose (SSPG) level. The fatty acid (FA) composition of skeletal-muscle triglycerides was also determined. A higher SSPG level (20.9 ± 0.9 vs. 16.5 ±1.1 mmol/l in the control group, P < 0.05) as well as a higher systolic blood pressure (120 ± 2 vs. 101 ± 2 mmHg, P < 0.01) was observed in the high-fructose plus lard group, but not in the high-fructose group. These changes were prevented by bezafibrate administration. The FA composition of skeletal-muscle triglycerides demonstrated a higher percentage of saturated and monounsaturated FAs (P < 0.01) and a lower percentage of polyunsaturated FAs (P < 0.01) in the highfructose plus lard group versus the control group. These changes were consistent with differences in the dietary intake of FAs. Bezafibrate virtually normalized the FA composition in the high-fructose plus lard group. The ratio of C20:4 to C20:3, an index of ∆5 desaturase activity, was significantly higher in the bezafibrate group versus the high-fructose plus lard group (8.60 ± 0.76 vs. 2.04 ± 0.27, P < 0.01). In conclusion, the dietary FA composition was closely related to insulin resistance in rats fed 40% fructose. Bezafibrate increased ∆5 desaturase activity. Such action may contribute to the improvement of insulin sensitivity.
Insulin Resistance Prevented by Portal Delivery of Insulin in Rats With Renal Subcapsular Islet Grafts
Authors: Guan Jiayan , Zucker Peter F , Behme Margaret T , Zhong Robert , Atkison Paul , Dupré John
Published: September 2013

We determined the metabolic effects of insulin derived from renal subcapsular islet grafts, either with systemic delivery of insulin through renal venous drainage (REN) or with portal delivery of insulin after renal vein–to–superior mesenteric vein anastomosis (RMA), in streptozotocin-induced diabetic Lewis rats, in comparison with normal rats. After gavage glucose, the plasma glucose responses were similar to normal in REN and RMA rats; however, hyperinsulinemia occurred in REN rats (area under the concentration curves [AUCs] of insulin, 27 ± 3 nmol · l−1 · min) in comparison with RMA (14 ± 2) and normal rats (19 ± 2), P < 0.003, with no difference in C-peptide responses. The ratio of AUC C-peptide to AUC insulin was lower in REN (2.0 ± 0.2) than in RMA (3.4 ± 0.3) and normal animals (3.2 ± 0.3), P < 0.0005. In euglycemic-hyperinsulinemic clamp studies using the same insulin infusion rate (10 pmol · kg−1 · min−1), insulin resistance was found in REN animals (mean glucose infusion rate [GIR], REN: 7.5 ± 1.2; RMA: 12.0 ± 1.2; normal: 12.7 ± 1.0 mg · kg−1 · min−1; P < 0.008), with higher steady-state insulin levels in REN (554 ± 63 pmol/l) than in RMA (291 ± 26) and normal rats (269 ± 60), P < 0.0001. With matching steady-state insulin levels in RMA and REN rats during infusion of insulin at 20 pmol · kg−1 · min−1 in RMA rats (steady-state insulin 623 ± 64 pmol/l), GIR was 15.7 ± 0.7 mg · kg−1 · min−1. Thus, systemic delivery of insulin from islet grafts is associated with hyperinsulinemia, insulin resistance, and decreased metabolic clearance of insulin. These abnormalities are prevented by portal delivery of insulin from islet grafts in the same site. The findings are consistent with the hypothesis that portal delivery of insulin is important in maintenance of normal whole-body insulin sensitivity.
The Receptor for Advanced Glycation End Products Mediates the Chemotaxis of Rabbit Smooth Muscle Cells
Authors: Higashi Takayuki , Sano Hiroyuki , Saishoji Tetsushi , Ikeda Kazuyoshi , Jinnouchi Yoshiteru , Kanzaki Tetsuto , Morisaki Nobuhiro , Rauvala Heikki , Shichiri Motoaki , Horiuchi Seikoh
Published: September 2013

Long-term incubation of proteins with glucose leads to advanced glycation end products (AGEs) with fluorescence and a brown color. We recently demonstrated immunologically the intracellular AGE accumulation in smooth muscle cell (SMC)–derived foam cells in advanced atherosclerotic lesions. To understand the mechanism of AGE accumulation in these foam cells, we have now characterized the interaction of AGE proteins with rabbit-cultured arterial SMCs. In experiments at 4°C, 125I-labeled AGE-bovine serum albumin (AGE-BSA) showed a dose-dependent saturable binding to SMCs with an apparent dissociation constant (Kd) of 4.0 μg/ml. In experiments at 37°C, AGE-BSA underwent receptor-mediated endocytosis and subsequent lysosomal degradation. The endocytic uptake of 125I-AGE-BSA was effectively inhibited by unlabeled AGE proteins such as AGE-BSA and AGE-hemoglobin, but not by acetylated LDL and oxidized LDL, well-known ligands for the macrophage scavenger receptor (MSR). Moreover, the binding of 125I-AGE-BSA to SMCs was affected neither by amphoterin, a ligand for one type of the AGE receptor, named RAGE, nor by 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole–hexanoic acid–BSA, a ligand for the other AGE receptors, p60 and p90. This indicates that the endocytic uptake of AGE proteins by SMCs is mediated by an AGE receptor distinct from MSR, RAGE, p60, and p90. To examine the functional role of this AGE receptor, the migratory effects of AGE-BSA on these SMCs were tested. Incubation with 1–50 μg/ml of AGE-BSA for 14 h resulted in significant dose-dependent cell migration. The AGE-BSA–induced SMC migration was chemotactic in nature and was significantly inhibited (∼80%) by an antibody against transforming growth factor-β (TGF-β), and the amount of TGF-β secreted into the culture medium from SMC by AGE-BSA was sevenfold higher than that of control, indicating that TGF-β is involved in the AGE-induced SMC chemotaxis. These data suggest that AGE may play a role in SMC migration in advanced atherosclerotic lesions.
Identification of a Common Amino Acid Polymorphism in the p85α Regulatory Subunit of Phosphatidylinositol 3-Kinase: Effects on Glucose Disappearance Constant, Glucose Effectiveness, and the Insulin Sensitivity Index
Authors: Hansen Torben , Andersen Carsten B , Echwald Søren M , Urhammer Søren A , Clausen Jesper O , Vestergaard Henrik , Owens David , Hansen Lars , Pedersen Oluf
Published: September 2013

Phosphatidylinositol 3-kinase (PI3-K) may regulate the basal plasma membrane glucose transporter recycling and the organization of the transporter intracellular pool in addition to being an insulin signal for translocation of glucose transporters to the plasma membrane. The objectives of the present study were to examine for genetic variability in the human regulatory p85α subunit of PI3-K, to look for an association between gene variants and NIDDM in a case-control study, and to relate identified variability to potential changes in whole-body insulin sensitivity and glucose turnover in a phenotype study. Single-strand conformational polymorphism and heteroduplex analysis of the coding region of the regulatory p85α subunit in cDNA isolated from human muscle tissue from 70 insulin-resistant NIDDM patients and 12 control subjects revealed three silent polymorphisms and a missense mutation at nucleotide position 1020 (G→A), changing a Met to He at codon 326. Using allele-specific oligohybridization, we found a similar allelic frequency of the codon 326Met→Ile variant in 404 NIDDM patients (0.15 [95% CI 0.13–0.17]) and 224 matched glucose tolerant control subjects (0.16 [0.13–0.19]). In a random sample of 380 unrelated healthy young Caucasians aged 18–32 years, in whom we have performed a tolbutamide modified intravenous glucose tolerance test, we identified 263 wildtype subjects, 109 heterozygous subjects, and 8 subjects homozygous for the codon 326 variant (allelic frequency = 0.16 [0.13–0.19]). No difference in glucose disappearance constant (KG), insulin sensitivity index (SI), and glucose effectiveness (SG) was observed between wildtype and heterozygous subjects. However, compared with the combined values for wildtype and heterozygous carriers, KG was reduced by 40% (P = 0.004) and SG by 23% (P = 0.03) in homozygous carriers of the p85α variant. Moreover, in homozygous carriers, a 32% reduction was found in SI (P = 0.08). In conclusion, a codon 326Met→Ile variant in the gene encoding the PI3-K p85α regulatory subunit is found in 31% of a random sample of young healthy Caucasians. About 2% of the subjects in this population carry the gene variant in its homozygous form, and these carriers are characterized by significant reductions in whole-body glucose effectiveness and intravenous glucose disappearance constant. In itself, the gene variant does not confer an increased risk of diabetes.
Immunological Aspects of Nutritional Diabetes Prevention in NOD Mice: A Pilot Study for the Cow's Milk–Based IDDM Prevention Trial
Authors: Karges Wolfram , Hammond-McKibben Denise , Cheung Roy K , Visconti Marc , Shibuya Noriko , Kemp Don , Dosch Hans-Michael
Published: September 2013

Human epidemiological studies delineated early exposure to intact dietary protein (e.g., most infant formulas) as an environmental risk factor for the development of IDDM. The Trial to Reduce IDDM in the Genetically at Risk (TRIGR), an international IDDM prevention trial, has been designed to determine if avoidance of intact dairy protein in high-risk infants ≤6 months of age can reduce the subsequent diabetes incidence. We here studied the casein hydrolysate-based trial diet (Nutramigen) in NOD mice. When given either continuously or for 10 weeks after weaning, the test diet was highly effective in preventing autoimmune diabetes (32-week incidence: 4.6 vs. 58.8%) and in preserving pancreatic insulin levels, with little effect on islet inflammation. Spleen cells from protected NOD mice failed to adoptively transfer diabetes into irradiated syngeneic recipients. When co-transferred with splenocytes from diabetic donors, cells from diet-protected mice inhibited adoptive diabetes transfer (incidence 50 vs. 94%, P < 0.001). T-cell reactivity to the islet cell autoantigens ICA69 (islet cell antigen 69) and GAD65 developed only in diabetic re recipients of spleen cell grafts, indicating that diabetes protection extends to more than one autoantigen. In protected mice, ICA69 T-cell reactivity was not detectable spontaneously nor after priming with this autoantigen; however, priming with the cross-reactive non-self-antigen bovine serum albumin recruited T-cells responsive to ICA69. Thus, diabetes prevention with the clinical trial diet is effective in NOD mice, where it affects some T-cell repertoires and allows development of regulatory cells that interfere with destructive autoimmunity.
Potential Mechanisms by Which Certain Foods Promote or Inhibit the Development of Spontaneous Diabetes in BB Rats: Dose, Timing, Early Effect on Islet Area, and Switch in Infiltrate From Th1 to Th2 Cells
Authors: Scott Fraser W , Cloutier Heather E , Kleemann Rainer , Wöerz-Pagenstert Ute , Rowsell Paul , Modler H Wayne , Kolb Hubert
Published: September 2013

Certain diets can have major effects on the development of IDDM in DP-BB rats, but data are scant on the timing, dose, and mechanisms involved. We therefore determined the dose response, timing, and duration of exposure required to induce diabetes, and characterized the effects of nutritionally adequate diets with widely different diabetogenicity on the pancreatic islet area and cytokines. DP-BB rats were fed a diabetogenic, cerealbased, NIH-07 (NIH) diet or a protective, casein or hydrolyzed casein (HC)-based, semipurified diet. Rats were fed from weaning to 50 or 100 days with the HC diet and then switched to the NIH diet, or fed the NIH diet from weaning to 50 days and switched to the HC diet. Pancreas histology and diabetes outcome were determined. Semiquantitative morphometric analyses of hematoxylin and eosin–stained sections of pancreas from 41-day-old rats were also carried out. Diet-induced effects on pancreatic cytokine levels were measured at 70 days using reverse transcriptase–polymerase chain reaction analysis of γ-interferon (IFN-γ), interleukin-10 (IL-10), and transforming growth factor-β (TGF-β). Long-term daily exposure, particularly around the beginning of puberty to late adolescence (50–100 days), was important for development of diabetes. DP-BB rats could be rescued from diabetes development by feeding them a low-diabetogen HC diet as late as 50 days. Diabetes frequency was highest in rats fed 70% and 100% NIH diets. By age 41 days, before classic insulitis, the islet area in HC-fed DP-BB rats was 65% greater than in NIH-fed rats. By 70 days, when mononuclear cells were visible in the islets of most NIH-fed, but not HC-fed rats, the more pronounced inflammatory process in NIH-fed rats was associated with a Thl cytokine pattern (high IFN-γ and low IL-10 and TGF-β), whereas the pancreases of HC-fed rats showed fewer infiltrating cells, low levels of IFN-7, and high levels of TGF-p, typical of a Th2 cytokine pattern. Thus dietary modification can occur as late as puberty. Further, long-term exposure to sufficient amounts of food diabetogens between 50 and 100 days was required for maximum diabetes induction. The islet area was modified by diet before signs of classic insulitis. Pancreatic inflammation in NIH-fed animals is a Thl-dependent phenomenon. The HC diet inhibited insulitis and was associated with a Th2 cytokine pattern in the pancreas, protecting diabetes-prone rats from developing diabetes.
Renal Glucose Production During Insulin-Induced Hypoglycemia
Authors: Cersosimo Eugenio , Molina Patricia E , Abumrad Naji N
Published: September 2013

Recent in vivo studies have rekindled interest in the role of the kidney in glucose metabolism. We therefore undertook the present study to evaluate the contribution of the kidney to systemic glucose production and utilization rates during insulin-induced hypoglycemia using arteriovenous balance combined with a tracer technique. Ten days after the surgical placement of sampling catheters in the right and left renal veins and femoral artery and of an infusion catheter in the left renal artery of dogs, systemic and renal glucose kinetics were measured with the peripheral infusion of [6-3H]glucose. Renal blood flow was determined with a flowprobe. After baseline, six dogs received 2-h simultaneous infusions of peripheral insulin (4 mU · kg−1 · min−1) and left intrarenal [6,6-2H]dextrose (14 μmol · kg−1 · min−1) to achieve and maintain left renal normoglycemia during systemic hypoglycemia. Arterial glucose decreased from 5.3 ± 0.1 to 2.2 ± 0.1 mmol/1; insulin increased from 46 ± 5 to 1,050 ± 50 pmol/1; epinephrine increased from 130 ± 8 to 1,825 ± 50 pg/ml; norepinephrine increased from 129 ± 6 to 387 ± 15 pg/ml; and glucagon increased from 52 ± 2 to 156 ± 12 pg/ml (all P < 0.01). Systemic glucose appearance increased from 16.6 ± 0.4 μmol · kg−1 · min−1 in the baseline to 24.2 ± 0.6 μmol · kg−1 · min−1 during hypoglycemia when endogenous glucose production was 10.2 ± 1.0 μmol · kg−1 · min−1 (P < 0.01). In the baseline, the liver accounted for 80% (13.3 ± 0.8 μmol · kg−1 · min−1) and each kidney contributed 10% (1.6 ± 0.2 μmol · kg−1 · min−1) to endogenous glucose production. During hypoglycemia, however, hepatic glucose production decreased to 4.0 ± 0.4 μmol · kg−1 · min−1, whereas right renal glucose production doubled to 3.2 ± 0.2 μmol · kg−1 · min−1 (P < 0.01). Left renal glucose production was 17 ± 2 μmol · kg−1 · min−1, 14 of which were derived from the exogenous infusion. These results indicate that glucose production by the kidney is stimulated by counterregulatory hormones and represents an important component of the body's defense against insulin-induced hypoglycemia.
Nitric Oxide and Ocular Blood Flow in Patients With IDDM
Authors: Schmetterer Leopold , Findl Oliver , Fasching Peter , Ferber Wolfgang , Strenn Karin , Breiteneder Helene , Adam Hiltrud , Eichler Hans-Georg , Wolzt Michael
Published: September 2013

Endothelial dysfunction has been implicated in the pathogenesis of diabetic vascular disorders such as diabetic retinopathy. We hypothesized that either local endogenous nitric oxide (NO) synthesis or local reactivity to endogenous NO might be impaired in patients with IDDM and that this may contribute to the development of diabetic retinopathy. Ten otherwise healthy patients with long-standing IDDM and ten healthy control subjects were studied according to an open randomized two-way cross-over design. Subjects received intravenous infusions of either NG-monomethyl-L-arginine, an inhibitor of NO-synthase, or L-arginine, the precursor of NO synthesis, on two separate study days. Ocular hemodynamics were assessed by laser interferometric measurement of fundus pulsations and Doppler sonographic measurement of blood flow velocity in the ophthalmic artery. NG-monomethyl-L-arginine decreased fundus pulsations and blood flow velocity in the ophthalmic artery and increased blood pressure in healthy subjects. The responses to NO-synthase inhibition were significantly less in diabetic subjects. In contrast, L-arginine caused a comparable increase in fundus pulsations and decrease in blood pressure in both cohorts. These results indicate that systemic and ocular hemodynamic reactivity to NO-synthase inhibition is reduced in patients with long-standing IDDM, compared with healthy control subjects. Thus, this study indicates that either NO-synthase activity is increased or NO sensitivity is decreased in patients with IDDM and supports the concept of an involvement of the Larginine–NO system in the pathophysiology of diabetic retinopathy.
Troglitazone Reduces Contraction by Inhibition of Vascular Smooth Muscle Cell Ca2+ Currents and Not Endothelial Nitric Oxide Production
Authors: Song Jianben , Walsh Mary F , Igwe Robert , Ram Jeffrey L , Barazi Mohamad , Dominguez Ligia J , Sowers James R
Published: September 2013

The insulin-sensitizing compound troglitazone has evolved into a promising therapeutic agent for type II diabetes. It improves insulin sensitivity and lipoprotein metabolic profiles and lowers blood pressure in humans and rodents. Because troglitazone has insulinlike effects on a number of tissues, we hypothesized that it may reduce vascular tone through stimulation of endothelial-derived nitric oxide (NO) production or by diminution of vascular smooth muscle cell (VSMC) intracellular calcium ([Ca2+]i). Our results show that troglitazone decreases norepinephrine-induced contractile responses in the rat tail artery, an effect not reversed by the NO inhibitor L-nitroarginine methyl ester (L-NAME). In contrast, troglitazone significantly inhibited L-type Ca2+ currents in freshly dissociated rat tail artery and aortic VSMCs and in cultured VSMCs. The data suggest that troglitazone attenuates vascular contractility via a mechanism involving VSMC [Ca2+]i but independent from endothelial generation of NO. Because insulin has been shown to affect vascular tone by both of these mechanisms, troglitazone only partially mimics insulin action in this tissue.
Effect of Polymorphism of Apolipoprotein E and Angiotensin-Converting Enzyme Genes on Arterial Wall Thickness
Authors: Kogawa Kyoko , Nishizawa Yoshiki , Hosoi Masayuki , Kawagishi Takahiko , Maekawa Kiyoshi , Shoji Tetsuo , Okuno Yasuhisa , Morii Hirotoshi
Published: September 2013

We examined the association between the polymorphism of the apolipoprotein E (apoE) and the ACE genes and the intima-media thickness (IMT) of the carotid and femoral arteries measured using ultrasonography. The values of IMT of each artery were significantly higher in NIDDM patients (n = 356) than in control subjects (n = 235). The E4 allele or the D allele did not affect clinical characteristics, including age, fasting plasma glucose, total cholesterol, HDL cholesterol, LDL cholesterol, or blood pressure, in NIDDM or control subjects. No difference in the carotid IMT value was noted among the apoE genotypes in control or diabetic subjects. The carotid IMT was significantly higher in diabetic patients with the DD genotype (1.200 ± 0.586 mm) than in those with the II genotypes (0.990 ± 0.364 mm). Neither the E4 allele nor the D allele affected the femoral IMT in control or diabetic subjects. Multiple regression analysis demonstrated that the carotid IMT of NIDDM patients was associated with age, the D allele, and LDL cholesterol but not with the E4 allele, whereas that of control subjects was associated with age, sex, systolic blood pressure, LDL cholesterol, and HDL cholesterol, inversely. These results suggested that the E4 allele was not associated with the carotid or femoral IMTs, but that the D allele was statistically associated with carotid IMT in NIDDM patients but not control subjects. However, since the association was weak (2.3% explanatory power), its biological significance remains to be determined.
Mapping of the IDDM Locus Idd3 to a 0.35-cM Interval Containing the Interleukin-2 Gene
Authors: Denny Paul , Lord Christopher J , Hill Natasha J , Goy Juliet V , Levy Elaine R , Podolin Patricia L , Peterson Laurence B , Wicker Linda S , Todd John A , Lyons Paul A
Published: September 2013

Currently, 16 loci that contribute to the development of IDDM in the NOD mouse have been mapped by linkage analysis. To fine map these loci, we used congenic mapping. Using this approach, we localized the Idd3 locus to a 0.35-cM interval on chromosome 3 containing the Il2 gene. Segregation analysis of the known variations within this interval indicated that only one variant, a serine-to-proline substitution at position 6 of the mature interleukin-2 (IL-2) protein, consistently segregates with IDDM in crosses between NOD and a series of nondiabetic mouse strains. These data, taken together with the immunomodulatory role of IL-2, provide circumstantial evidence in support of the hypothesis that Idd3 is an allelic variation of the Il2 gene, or a variant in strong linkage disequilibrium.
Glucagon-Like Peptide I and Glucose-Dependent Insulinotropic Polypeptide Stimulate Ca2+-Induced Secretion in Rat α-Cells by a Protein Kinase A–Mediated Mechanism
Authors: Ding Wei-Guang , Renström Erik , Rorsman Patrik , Buschard Karsten , Gromada Jesper
Published: September 2013

High-resolution capacitance measurements were used to explore the effects of the gut hormones GLP-1(7-36) amide [glucagon-like peptide I(7-36) amide] and GIP (glucose-dependent insulinotropic polypeptide) on Ca2+-dependent exocytosis in glucagon-secreting rat pancreatic ケ-cells. Both peptides produced a greater than threefold potentiation of secretion evoked by voltage-clamp depolarizations, an effect that was associated with an ∼35% increase of the Ca2+ current. The stimulatory actions of GLP-I(7-36) amide and GIP were mimicked by forskolin and antagonized by the protein kinase A (PKA)- inhibitor Rp-8-Br-cAMPS. The islet hormone somatostatin inhibited the stimulatory action of GLP-I(7-36) amide and GIP via a cyclic AMP–independent mechanism, whereas insulin had no effect on exocytosis. These data suggest that the α-cells are equipped with receptors for GLP-I and GIP and that these peptides, in addition to their well-established insulinotropic capacity, also stimulate glucagon secretion. We propose that the reported inhibitory action of GLP-I on glucagon secretion is accounted for by a paracrine mechanism (e.g., mediated by stimulated release of somatostatin that in turn suppresses exocytosis in the α-cell).
Parallel Reduction of Pancreas Insulin Content and Insulin Secretion in 48-h Tolbutamide-Infused Normoglycemic Rats
Authors: Hosokawa Y A , Leahy Jack L
Published: September 2013

The overworked–β-cell hypothesis proposes that lowered glucose-potentiated insulin secretory responses in diabetes are secondary to hyperstimulated insulin secretion and depletion of the β-cell insulin stores. We tested this hypothesis in normal rats using a 48-h infusion of 200 mg · kg−1 · day−1 tolbutamide in 20% glucose. Insulin secretion was measured by in vitro pancreas perfusion. Twice daily blood glucose values were equal in the tolbutamide-infused and control rats. Pancreas insulin content was 47 ± 7% that of the controls (P < 0.004). Insulin responses to 16.7 mmol/l glucose, 16.7 mmol/l glucose/10 mmol/l arginine, and 5.5 mmol/l glucose/ 10 mmol/l arginine were reduced in parallel, except for the first phase response to 16.7 mmol/l glucose/arginine. Pancreas amylin content was unchanged in the tolbutamide-infused rats as was amylin secretion, resulting in higher than normal stored and secreted amylin-to-insulin molar ratios. Importantly, a raised amylin-to-insulin ratio and a relatively unimpaired first versus second phase insulin response for high glucose/arginine both occur in diabetic rats. Thus, our results support the overworked–β-cell hypothesis by showing chronic β-cell stimulation without hyperglycemia replicates part of the β-cell dysfunction found with diabetes.
Blood Glucose Lowering and Glucagonostatic Effects of Glucagon-Like Peptide I in Insulin-Deprived Diabetic Dogs
Authors: Freyse E-J , Becher T , El-Hag El , Knospe S , Göke B , Fischer U
Published: September 2013

To establish potential effects of glucagon-like peptide I (GLP-I) on blood glucose control in insulin-deficient states, GLP-I [GLP-I(7-36) amide; 10 pmol · kg−1 · min−1] was infused intravenously in six fasting, canine C-peptide–negative, chronically diabetic dogs for 8 h. Blood samples were saved for the analysis of hormones, metabolites, and turnover rates of glucose (6-3H-glucose), alanine (U-14C-alanine), and urea (15N2-urea) starting 22 h after the last subcutaneous dose of exogenous insulin. Circulating plasma GLP-I levels rose under infusion from 2.9 ± 0.8 to 41.4 ± 10.1 pmol/l. This was efficient to significantly reduce the preexisting diabetic hyperglucagonemia. Since in the utilized model functioning pancreatic β-cells are lacking, GLPI had no insulinogenic effect. Compared with control experiments in the same animals receiving saline infusion, glycemia dropped from 20.8 ± 1.9 to 16.2 ± 1.0 mmol/l (P < 0.05). This was in parallel to the infusion of GLP-I and was most likely caused by a decrease of elevated glucose production since overall glucose turnover decreased with no alteration in glucose metabolic clearance. Alanine turnover was significantly reduced, obviously reflecting a decline in alanine production in relation to changed muscle glucose uptake under conditions of lower glycemia and overall glucose turnover. There was, however, neither an effect of GLPI on alanine conversion into circulating glucose nor an effect on urea production rate, indicating unchanged gluconeogenesis from amino acid precursors. We conclude that the blood glucose–lowering effect of GLP-I in an animal model of insulinopenia was shown to be due to a reduction in hepatic glucose output, possibly secondary to reduction in glucagon concentrations leading to decreased glycogenolysis. Whether GLP-I might be therapeutically useful in clinical insulin-deficient diabetes needs to be verified.
Regulation of Glomerular Epithelial Cell Production of Fibronectin and Transforming Growth Factor-β by High Glucose, Not by Angiotensin II
Authors: van Det Nicole F , Verhagen Nicole A M , Tamsma Jouke T , Berden Jo H M , Bruijn Jan A , Daha Mohamed R , van der Woude Fokko J
Published: September 2013

Accumulation of matrix proteins is a prominent feature of diabetic nephropathy. Glomerular visceral epithelial cells (GVECs) are important contributors to extracellular matrix (ECM) production in the glomerulus. Factors involved with increased accumulation of ECM proteins are high glucose, angiotensin II (ANG II), and transforming growth factor (TGF)-β. Therefore, we investigated the effects of high glucose and ANG II on fibronectin and TGF-β production by human GVECs in vitro. We found that ANG II had no effect on the production of fibronectin and TGF-β by GVECs. Using reverse transcriptase–polymerase chain reaction analysis, no ANG II receptor could be detected on these cells. However, high glucose induced a twofold increase in fibronectin (P < 0.01) and a three- to sixfold increase in TGF-β (P < 0.001) production. Similar results were obtained by analyzing the mRNA levels of fibronectin (increased 2.7-fold) and TGF-β (increased 3.5-fold). Addition of increasing concentrations of rTGF-β to control cells resulted in increased fibronectin production. Neutralizing antibodies against TGF-β significantly reversed the increase in fibronectin protein and mRNA caused by high glucose back to control levels. We conclude that high glucose concentrations stimulate the synthesis of fibronectin and that this effect is mediated by induction of TGF-β. These results suggest that in diabetic nephropathy, high glucose levels play a role in changing the matrix composition of the glomerular basement membrane through induction of TGF-β. Our results indicate that a contribution to this process by an effect of ANG II on GVECs seems unlikely.
A Prevalent Amino Acid Polymorphism at Codon 98 in the Hepatocyte Nuclear Factor-1α Gene Is Associated With Reduced Serum C-Peptide and Insulin Responses to an Oral Glucose Challenge
Authors: Urhammer Søen A , Fridberg Marianne , Hansen Torben , Rasmussen Søren K , Merete Møller Ann , Clausen Jesper O , Pedersen Oluf
Published: September 2013

Mutations in the hepatocyte nuclear factor-1α (HNF-1α) gene cause the type 3 form of maturity-onset diabetes of the young (M0DY3), which is characterized by a severe impairment of insulin secretion. In addition to disease-associated mutations, three common amino acid polymorphisms have been identified in the HNF-1α gene: Ile/Leu27, Ala/Val98, and Ser/Asn487. We have addressed the question of whether these variants of the HNF-1α gene are associated with altered glucoseinduced C-peptide and insulin responses or late-onset NIDDM. Among 245 NIDDM patients, the allelic frequency of the Val98 variant was 3.7% (95% CI 2.0–5.4%) vs. 4.4% (2.6–6.2%) among 240 glucose tolerant control subjects (NS). Studies of genotype-phenotype interactions in 240 middle-aged control subjects showed, however, that heterozygous subjects (i.e., genotype Ala/Val98) had an 18% decrease in 30-min serum C-peptide level (P = 0.004) as well as a 23% decrease in 30-min serum insulin level (P = 0.03) during an oral glucose tolerance test. One Val98 homozygote subject had a more severe reduction in stimulated insulin and C-peptide levels. The impact of the homozygous carrier status was similar in a study of 377 healthy young subjects. In contrast, the Ile/Leu27 and Ser/Asn487 polymorphisms were not associated with altered C-peptide and insulin release or NIDDM. In conclusion, 8% of white subjects of Danish ancestry are heterozygous for the Ala/Val98 polymorphism in the HNF-1α gene, which in middle-aged subjects is associated with a ∼20% reduction in serum C-peptide and insulin responses 30 min after an oral glucose challenge. Val98 homozygotes may exhibit a more severe defect in the early glucose-induced insulin response.
Regulation of Glycogen Synthase Activity in Cultured Skeletal Muscle Cells From Subjects With Type II Diabetes: Role of Chronic Hyperinsulinemia and Hyperglycemia
Authors: Nikoulina Svetlana E , Ciaraldi Theodore P , Abrams-Carter Leslie , Mudaliar Sunder , Park Soo Kyong , Robert Henry R
Published: September 2013

Human skeletal muscle cultures (HSMCs) from type II diabetic subjects were used to determine whether metabolic abnormalities such as hyperglycemia or hyperinsulinemia contribute to the defective muscle glycogen synthase (GS) activity present in this disorder. Following ∼6 weeks of growth, diabetic cultures were fused for 4 days in normal, hyperglycemia, or hyperinsulinemia medium. Fusion of diabetic HSMCs in hyperglycemia medium (20 mmol/l vs. 5.5 mmol/l) had no effect on GS fractional velocity (FV) or mRNA levels, but impaired acute insulin-stimulation of glycogen synthesis and GS activity at 0.1 mmol/l glucoses-phosphate, and reduced GS protein content by ∼15% (P < 0.05). Fusion of diabetic muscle cultures in hyperinsulinemia medium (30 μmol/l vs. 22 pmol/l) improved basal GS activity, increasing the reduced GS FV by ∼50% (P < 0.05), and decreasing the elevated Km0.1 (half-maximal substrate concentration) by ∼47% (P < 0.05). Hyperinsulinemia also significantly increased (P < 0.05) the reduced GS mRNA and protein levels of diabetic muscle to levels similar to that in nondiabetic subjects. In contrast to the improvements in the basal state, hyperinsulinemia completely abolished acute insulin responsiveness of GS activity and glycogen synthesis in muscle of type II diabetic subjects. The combination of hyperinsulinemia and hyperglycemia produced effects on both basal and insulin-responsive GS FV and mRNA similar to hyperinsulinemia alone, but hyperinsulinemia prevented hyperglycemia's effect of lowering GS protein and glycogen synthesis. We concluded that, in diabetic muscle, hyperinsulinemia may serve to partially compensate for the impaired basal GS activity and for the adverse effects of hyperglycemia on GS protein content, activity, and glycogen formation by both pre- and posttranslational mechanisms. Despite these beneficial effects, hyperinsulinemia also induces severe impairment of insulin-stimulated GS activity and glycogen formation, which may contribute to acquired muscle insulin resistance of type II diabetes.
Treatment With Neutralizing Antibodies Specific for IL-1β Prevents Cyclophosphamide-Induced Diabetes in Nonobese Diabetic Mice
Authors: Cailleau Catherine , Diu-Hercend Anita , Ruuth Erik , Westwood Robert , Carnaud Claude
Published: September 2013

Interleukin-1 (IL-1) has been shown to be involved in the pathogenesis of IDDM, but it is not clear which form, IL-1α or IL-1β, is predominantly implicated. In this study, we have evaluated the contribution of IL-1β by treating diabetes-prone nonobese diabetic (NOD) mice with specific neutralizing antibodies. First, we assessed the neutralizing potential of these antibodies in C57BL/6 mice under acute septic shock by measuring IL-1β in sera 4 h after lipopolysaccharide injection. One milligram and 0.1 mg of anti–IL-1β antibodies (Abs) were capable of neutralizing the IL-1β produced, and the effect persisted for at least 5 days. Second, we evaluated the role of IL-1β in the cyclophosphamide (CY)-accelerated model of diabetes. Nondiabetic male NOD mice were injected with 200 mg/kg CY and treated twice weekly with anti–IL-1β Ab. The incidence of diabetes reached 76 and 100% in the control groups treated with 0.25 and 0.1 mg rabbit IgG, respectively. In contrast, only 34% of mice treated with 0.25 mg of anti–IL-1β Ab became diabetic. In the group treated with 0.1 mg of anti–IL-1β Ab, 89% of the mice became diabetic in the same period of time, demonstrating that the protective effect was dose dependent. Our results show that IL-1β is a critical effector molecule in this model of IDDM and that its specific inhibition could be an attractive target for therapeutic intervention.