bluuebunny/crossref_metadata_2025 huggingface dataset:
Genome-Wide and Fine-Mapping Linkage Studies of Type 2 Diabetes and Glucose Traits in the Old Order Amish
Authors: Hsueh Wen-Chi , St. Jean Pamela L. , Mitchell Braxton D. , Pollin Toni I. , Knowler William C. , Ehm Margaret G. , Bell Callum J. , Sakul Hakan , Wagner Michael J. , Burns Daniel K. , Shuldiner Alan R.
Published: March 2007

We conducted a genome scan using a 10-cM map to search for genes linked to type 2 diabetes in 691 individuals from a founder population, the Old Order Amish. We then saturated two regions on chromosomes 1 and 14 showing promising linkage signals with additional markers to produce a ∼2-cM map for fine mapping. Analyses of both discrete traits (type 2 diabetes and the composite trait of type 2 diabetes and/or impaired glucose homeostasis [IGH]), and quantitative traits (glucose levels during a 75-g oral glucose challenge, designated glucose 0–180 and HbA1c) were performed. We obtained significant evidence for linkage to type 2 diabetes in a novel region on chromosome 14q11 (logarithm of odds [LOD] for diabetes = 3.48, P = 0.00005). Furthermore, we observed evidence for the existence of a diabetes-related locus on chromosome 1q21-q24 (LOD for type 2 diabetes/IGH = 2.35, P = 0.0008), a region shown to be linked to diabetes in several other studies. Suggestive evidence for linkage to glucose traits was observed on three other regions: 14q11-q13 (telomeric to that above with LOD = 1.82–1.85 for glucose 150 and 180), 1p31 (LOD = 1.28–2.30 for type 2 diabetes and glucose 120–180), and 18p (LOD = 3.07, P = 0.000085 for HbA1c and LOD = 1.50 for glucose 0). In conclusion, our findings provide evidence that type 2 diabetes susceptibility genes reside on chromosomes 1, 14, and 18.
Glucose Toxicity in β-Cells: Type 2 Diabetes, Good Radicals Gone Bad, and the Glutathione Connection
Authors: Robertson R. Paul , Harmon Jamie , Tran Phuong Oanh , Tanaka Yoshito , Takahashi Hiroki
Published: March 2007

Chronic exposure to hyperglycemia can lead to cellular dysfunction that may become irreversible over time, a process that is termed glucose toxicity. Our perspective about glucose toxicity as it pertains to the pancreatic β-cell is that the characteristic decreases in insulin synthesis and secretion are caused by decreased insulin gene expression. The responsible metabolic lesion appears to involve a posttranscriptional defect in pancreas duodenum homeobox-1 (PDX-1) mRNA maturation. PDX-1 is a critically important transcription factor for the insulin promoter, is absent in glucotoxic islets, and, when transfected into glucotoxic β-cells, improves insulin promoter activity. Because reactive oxygen species are produced via oxidative phosphorylation during anaerobic glycolysis, via the Schiff reaction during glycation, via glucose autoxidation, and via hexosamine metabolism under supraphysiological glucose concentrations, we hypothesize that chronic oxidative stress is an important mechanism for glucose toxicity. Support for this hypothesis is found in the observations that high glucose concentrations increase intraislet peroxide levels, that islets contain very low levels of antioxidant enzyme activities, and that adenoviral overexpression of antioxidant enzymes in vitro in islets, as well as exogenous treatment with antioxidants in vivo in animals, protect the islet from the toxic effects of excessive glucose levels. Clinically, consideration of antioxidants as adjunct therapy in type 2 diabetes is warranted because of the many reports of elevated markers of oxidative stress in patients with this disease, which is characterized by imperfect management of glycemia, consequent chronic hyperglycemia, and relentless deterioration of β-cell function.
Selective Glycogen Synthase Kinase 3 Inhibitors Potentiate Insulin Activation of Glucose Transport and Utilization In Vitro and In Vivo
Authors: Ring David B. , Johnson Kirk W. , Henriksen Erik J. , Nuss John M. , Goff Dane , Kinnick Tyson R. , Ma Sylvia T. , Reeder John W. , Samuels Isa , Slabiak Trina , Wagman Allan S. , Hammond Mary-Ellen Wernette , Harrison Stephen D.
Published: March 2007

Insulin resistance plays a central role in the development of type 2 diabetes, but the precise defects in insulin action remain to be elucidated. Glycogen synthase kinase 3 (GSK-3) can negatively regulate several aspects of insulin signaling, and elevated levels of GSK-3 have been reported in skeletal muscle from diabetic rodents and humans. A limited amount of information is available regarding the utility of highly selective inhibitors of GSK-3 for the modification of insulin action under conditions of insulin resistance. In the present investigation, we describe novel substituted aminopyrimidine derivatives that inhibit human GSK-3 potently (Ki < 10 nmol/l) with at least 500-fold selectivity against 20 other protein kinases. These low molecular weight compounds activated glycogen synthase at ∼100 nmol/l in cultured CHO cells transfected with the insulin receptor and in primary hepatocytes isolated from Sprague-Dawley rats, and at 500 nmol/l in isolated type 1 skeletal muscle of both lean Zucker and ZDF rats. It is interesting that these GSK-3 inhibitors enhanced insulin-stimulated glucose transport in type 1 skeletal muscle from the insulin-resistant ZDF rats but not from insulin-sensitive lean Zucker rats. Single oral or subcutaneous doses of the inhibitors (30–48 mg/kg) rapidly lowered blood glucose levels and improved glucose disposal after oral or intravenous glucose challenges in ZDF rats and db/db mice, without causing hypoglycemia or markedly elevating insulin. Collectively, our results suggest that these selective GSK-3 inhibitors may be useful as acute-acting therapeutics for the treatment of the insulin resistance of type 2 diabetes.
Palmitate-Induced Activation of the Hexosamine Pathway in Human Myotubes
Authors: Weigert Cora , Klopfer Karsten , Kausch Christiana , Brodbeck Katrin , Stumvoll Michael , Häring Hans U. , Schleicher Erwin D.
Published: March 2007

The nutrient sensing capacity of the hexosamine biosynthetic pathway (HBP) has been implicated in the development of insulin resistance of skeletal muscle. To study the molecular mechanism of the free fatty acid (FFA)-induced activation of the HBP myotubes obtained from muscle biopsies of metabolically characterized, subjects were stimulated with different fatty acids for 20 h. Incubation with the saturated fatty acids palmitate and stearate (0.5 mmol/l) resulted in a three- to fourfold increase in mRNA expression of glutamine:fructose-6-phosphate aminotransferase (GFAT), the key and rate-limiting enzyme of the hexosamine pathway. Unsaturated fatty acids or 30 mmol/l glucose had little or no effect. Palmitate increased the amount of GFAT protein nearly two-fold, and subsequently, the concentration of UDP-N-acetylglucosamine, the end product of the HBP, was 1.3-fold enhanced in the palmitate-stimulated myotubes. The nonmetabolized fatty acid bromopalmitate had no effect. The DNA binding activity of the transcription factor Sp1, a target downstream of the HBP, was increased by palmitate and completely lost after enzymatic removal of O-GlcNAc. No correlation was found between the palmitate-induced increase in GFAT protein and the insulin resistance in the respective subjects. The findings reveal a new mechanism for how FFAs induce the activation of the HBP.
Adeno-Associated Virus-Mediated IL-10 Gene Therapy Inhibits Diabetes Recurrence in Syngeneic Islet Cell Transplantation of NOD Mice
Authors: Zhang Y. Clare , Pileggi Antonello , Agarwal Anupam , Molano R. Damaris , Powers Matthew , Brusko Todd , Wasserfall Clive , Goudy Kevin , Zahr Elsie , Poggioli Raffaella , Scott-Jorgensen Marda , Campbell-Thompson Martha , Crawford James M. , Nick Harry , Flotte Terence , Ellis Tamir M. , Ricordi Camillo , Inverardi Luca , Atkinson Mark A.
Published: March 2007

Islet transplantation represents a potential cure for type 1 diabetes, yet persistent autoimmune and allogeneic immunities currently limit its clinical efficacy. For alleviating the autoimmune destruction of transplanted islets, newly diagnosed NOD mice were provided a single intramuscular injection of recombinant adeno-associated viral vector encoding murine IL-10 (rAAV-IL-10) 4 weeks before renal capsule delivery of 650 syngeneic islets. A dose-dependent protection of islet grafts was observed. Sixty percent (3 of 5) of NOD mice that received a transduction of a high-dose (4 × 109 infectious units) rAAV-IL-10 remained normoglycemic for at least 117 days, whereas diabetes recurred within 17 days in mice that received a low-dose rAAV-IL-10 (4 × 108 infectious units; 5 of 5) as well as in all of the control mice (5 of 5 untreated and 4 of 4 rAAV-green fluorescent protein-transduced). Serum IL-10 levels positively correlated with prolonged graft survival and were negatively associated with the intensity of autoimmunity. The mechanism of rAAV-IL-10 protection involved a reduction of lymphocytic infiltration as well as induction of antioxidant enzymes manganese superoxide dismutase and heme oxygenase 1 in islet grafts. These studies support the utility of immunoregulatory cytokine gene therapy delivered by rAAV for preventing autoimmune disease recurrence in transplant-based therapies for type 1 diabetes.
l-Arginine-Nitric Oxide Kinetics in Normal and Type 2 Diabetic Subjects
Authors: Avogaro Angelo , Toffolo Gianna , Kiwanuka Edward , de Kreutzenberg Saula Vigili , Tessari Paolo , Cobelli Claudio
Published: March 2007

Defective endothelium is a key event in the development of atherosclerosis in diabetes: alteration of the l-arginine-nitric oxide (NO) pathway has been suggested. We propose a modeling approach of the l-arginine-NO pathway in vivo in both control and type 2 diabetic subjects based on the intravenous bolus injection of l-[15N]arginine and subsequent noncompartmental and compartmental model analysis of l-[15N] arginine in plasma and [15N]nitrate in the urine. No differences in arginine kinetics were observed between normal subjects and diabetic patients. [15N]nitrates were detectable up to 48 h from the l-15[N]arginine administration; no differences were found in the tracer-to-tracee ratio in each urine collection. However, the NO synthesis in plasma from arginine was lower (P = 0.05 for the noncompartmental and 0.1208 for the compartmental analysis, by Mann-Whitney test) in diabetic patients than in control subjects when expressed both in absolute terms (50% decrease) and as percentage of NO turnover (30% decrease). This new modeling approach of l-arginine-NO pathway provides a detailed picture of arginine kinetics and nitrate metabolism. From our data, it appears that noncomplicated type 2 diabetic patients have a decreased conversion of arginine to NO.
Differential Regulation of Lipoprotein Kinetics by Atorvastatin and Fenofibrate in Subjects With the Metabolic Syndrome
Authors: Watts Gerald F. , Barrett P. Hugh R. , Ji Juying , Serone Adrian P. , Chan Dick C. , Croft Kevin D. , Loehrer Franziska , Johnson Anthony G.
Published: March 2007

The metabolic syndrome is characterized by insulin resistance and abnormal apolipoprotein AI (apoAI) and apolipoprotein B-100 (apoB) metabolism that may collectively accelerate atherosclerosis. The effects of atorvastatin (40 mg/day) and micronised fenofibrate (200 mg/day) on the kinetics of apoAI and apoB were investigated in a controlled cross-over trial of 11 dyslipidemic men with the metabolic syndrome. ApoAI and apoB kinetics were studied following intravenous d3-leucine administration using gas-chromatography mass spectrometry with data analyzed by compartmental modeling. Compared with placebo, atorvastatin significantly decreased (P < 0.001) plasma concentrations of cholesterol, triglyceride, LDL cholesterol, VLDL apoB, intermediate-density lipoprotein (IDL) apoB, and LDL apoB. Fenofibrate significantly decreased (P < 0.001) plasma triglyceride and VLDL apoB and elevated HDL2 cholesterol (P < 0.001), HDL3 cholesterol (P < 0.01), apoAI (P = 0.01), and apoAII (P < 0.001) concentrations, but it did not significantly alter LDL cholesterol. Atorvastatin significantly increased (P < 0.002) the fractional catabolic rate (FCR) of VLDL apoB, IDL apoB, and LDL apoB but did not affect the production of apoB in any lipoprotein fraction or in the turnover of apoAI. Fenofibrate significantly increased (P < 0.01) the FCR of VLDL, IDL, and LDL apoB but did not affect the production of VLDL apoB. Relative to placebo and atorvastatin, fenofibrate significantly increased the production (P < 0.001) and FCR (P = 0.016) of apoAI. Both agents significantly lowered plasma triglycerides and apoCIII concentrations, but only atorvastatin significantly lowered (P < 0.001) plasma cholesteryl ester transfer protein activity. Neither treatment altered insulin resistance. In conclusion, these differential effects of atorvastatin and fenofibrate on apoAI and apoB kinetics support the use of combination therapy for optimally regulating dyslipoproteinemia in the metabolic syndrome.
Aldose Reductase Inhibitor Fidarestat Prevents Retinal Oxidative Stress and Vascular Endothelial Growth Factor Overexpression in Streptozotocin-Diabetic Rats
Authors: Obrosova Irina G. , Minchenko Alexander G. , Vasupuram Rukmini , White Lauren , Abatan Omorodola I. , Kumagai Arno K. , Frank Robert N. , Stevens Martin J.
Published: March 2007

The study addressed the role for aldose reductase (AR) in 1) retinal oxidative stress and vascular endothelial growth factor (VEGF) overexpression in early diabetes, and 2) high glucose-induced oxidative stress in retinal endothelial cells. In vivo experiments were performed on control rats and diabetic rats treated with or without low or high dose of the AR inhibitor (ARI) fidarestat (2 or 16 mg · kg−1 · day−1). In vitro studies were performed on bovine retinal endothelial cells (BREC) cultured in either 5 or 30 mmol/l glucose with or without 1 μmol/l fidarestat. Intracellular reactive oxygen species were assessed using the 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate (H2DCFDA) probe and flow cytometry. Both low and high doses of fidarestat (i.e., the doses that partially and completely inhibited sorbitol pathway hyperactivity) arrested diabetes-induced retinal lipid peroxidation. This was achieved due to upregulation of the key antioxidative defense enzyme activities rather than changes in reduced glutathione, oxidized glutathione, ascorbate and dehydroascorbate concentrations, and the glutathione and ascorbate redox states. Diabetes-associated 2.1-fold VEGF protein overexpression (enzyme-linked immunosorbent assay; ELISA) was dose-dependently prevented by fidarestat, whereas total VEGF mRNA and VEGF-164 mRNA (RT-PCR) abundance were not affected by either diabetes or the ARI. In BREC, fidarestat corrected hyperglycemia-induced increase in H2DCFDA fluorescence but not oxidative stress caused by three different pro-oxidants in normoglycemic conditions. In conclusion, increased AR activity contributes to retinal oxidative stress and VEGF protein overexpression in early diabetes. The findings justify the rationale for evaluation of fidarestat on diabetic retinopathy.
Insulin Autoantibodies Are Associated With Islet Inflammation But Not Always Related to Diabetes Progression in NOD Congenic Mice
Authors: Robles David T. , Eisenbarth George S. , Dailey Natalie J.M. , Peterson Laurence B. , Wicker Linda S.
Published: March 2007

Susceptibility to diabetes in humans and nonobese diabetic (NOD) mice is believed to arise from the combined effect of multiple genetic loci, resulting in immune-mediated destruction of the insulin-secreting β-cells. Insulin autoantibodies (IAAs) are often present in humans for years, and in NOD mice for weeks, before the onset of diabetes. We have evaluated the expression of IAAs in NOD mice and in diabetes-resistant NOD congenic strains to characterize the association of autoantibody expression with insulitis and diabetes. In NOD congenic strains with genes that contribute to protection from insulitis and diabetes (Idd3, Idd5, Idd10, and Idd18), the prevalence of IAAs is reduced relative to NOD mice. In contrast, NOD.B10 Idd9 mice have a high prevalence of IAAs and a high degree of insulitis, despite a nearly complete resistance to diabetes. These data indicate that IAA expression is a phenotype that is associated with insulitis and correlates with overall disease progression in some strains of congenic mice but not in others. It is likely that patients with type 1 diabetes will also show non-major histocompatibility complex genetically determined variation in expression of autoantibodies and progression to diabetes.
The Functional −374 T/A RAGE Gene Polymorphism Is Associated With Proteinuria and Cardiovascular Disease in Type 1 Diabetic Patients
Authors: Pettersson-Fernholm Kim , Forsblom Carol , Hudson Barry I. , Perola Markus , Grant Peter J. , Groop Per-Henrik ,   for the FinnDiane Study Group
Published: March 2007

The hyperglycemic milieu in diabetes results in the formation of advanced glycation end products (AGEs) that predominantly act through specific receptors, particularly the receptor for AGEs (RAGE). Two functional polymorphisms in the promoter of the RAGE gene (−429 T/C and −374 T/A) and one in the AGE binding domain in exon 3 (G82S) were studied in 996 Finnish type 1 diabetic patients. In patients with poor metabolic control (HbA1c >9.5%), the AA genotype of the −374 T/A polymorphism was more common in those with a normal albumin excretion rate than in those with proteinuria (30 vs. 10%, P = 0.01). We observed less coronary heart disease (6 vs. 14%, P < 0.05), acute myocardial infarction (2 vs. 14%, P = 0.01), and peripheral vascular disease (2 vs. 14%, P < 0.05) in patients with the AA genotype of the −374 T/A polymorphism than in those with the TT + TA genotype. Thus, the association between the RAGE −374 T/A homozygous AA genotype and cardiovascular disease as well as albumin excretion in type 1 diabetic patients with poor metabolic control suggests a gene-environment interaction in the development of diabetic nephropathy and cardiovascular complications.
Genetic Liability of Type 1 Diabetes and the Onset Age Among 22,650 Young Finnish Twin Pairs
Authors: Hyttinen Valma , Kaprio Jaakko , Kinnunen Leena , Koskenvuo Markku , Tuomilehto Jaakko
Published: March 2007

Finland has the world’s highest incidence of type 1 diabetes, and it is steadily increasing. We determined concordance rates and estimated heritability for type 1 diabetes in the Finnish Twin Cohort, a population-based twin cohort of 22,650 twin pairs. In addition, we studied age of onset in the first affected twin and discordance time between concordant twin pairs. Finnish twins born between 1958 and 1986 were followed for type 1 diabetes until 1998. We identified 228 twin pairs with type 1 diabetes: 44 monozygotic (MZ), 183 dizygotic (DZ), and 1 pair with unknown zygosity. The pairwise concordance for type 1 diabetes was 27.3% (95% CI 22.8–31.8) in MZ and 3.8% (2.7–4.9) in DZ twins. The probandwise concordance was 42.9% (26.7–59.2) and 7.4% (2.2–12.6), respectively. The longest discordance times were 6.9 years among concordant MZ twins and 23.6 years among DZ twins. The risk for type 1 diabetes was highest in cotwins of the index twins diagnosed at a very young age. The model with additive genetic and individual environmental effects was the best-fitting liability model, with 88% of phenotypic variance due to genetic factors and the remaining variance due to unshared environmental factors. In conclusion, these nationwide twin data demonstrated high genetic liability for type 1 diabetes. Early-onset diabetes increases the risk in cotwins. However, the majority of affected MZ twin pairs remain discordant for type 1 diabetes.
Glucose Allostasis
Authors: Stumvoll Michael , Tataranni P. Antonio , Stefan Norbert , Vozarova Barbora , Bogardus Clifton
Published: March 2007

In many organisms, normoglycemia is achieved by a tight coupling of nutrient-stimulated insulin secretion in the pancreatic β-cell (acute insulin response [AIR]) and the metabolic action of insulin to stimulate glucose disposal (insulin action [M]). It is widely accepted that in healthy individuals with normal glucose tolerance, normoglycemia can always be maintained by compensatorily increasing AIR in response to decreasing M (and vice versa). This has been mathematically described by the hyperbolic relationship between AIR and M and referred to as glucose homeostasis, with glucose concentration assumed to remain constant along the hyperbola. Conceivably, glucose is one of the signals stimulating AIR in response to decreasing M. Hypothetically, as with any normally functioning feed-forward system, AIR should not fully compensate for worsening M, since this would remove the stimulus for the compensation. We provide evidence from cross-sectional, longitudinal, and prospective data from Pima Indians (n = 413) and Caucasians (n = 60) that fasting and postprandial glucose concentrations increase with decreasing M despite normal compensation of AIR. For this physiologic adaptation to chronic stress (insulin resistance), we propose to use the term “glucose allostasis.” Allostasis (stability through change) ensures the continued homeostatic response (stability through staying the same) to acute stress at some cumulative costs to the system. With increasing severity and over time, the allostatic load (increase in glycemia) may have pathological consequences, such as the development of type 2 diabetes.
Exercise Increases Nuclear AMPK α2 in Human Skeletal Muscle
Authors: McGee Sean L. , Howlett Kirsten F. , Starkie Rebecca L. , Cameron-Smith David , Kemp Bruce E. , Hargreaves Mark
Published: March 2007

An acute bout of exercise increases skeletal muscle glucose uptake, improves glucose homeostasis and insulin sensitivity, and enhances muscle oxidative capacity. Recent studies have shown an association between these adaptations and the energy-sensing 5′ AMP-activated protein kinase (AMPK), the activity of which is increased in response to exercise. Activation of AMPK has been associated with enhanced expression of key metabolic proteins such as GLUT-4, hexokinase II (HKII), and mitochondrial enzymes, similar to exercise. It has been hypothesized that AMPK might regulate gene and protein expression through direct interaction with the nucleus. The purpose of this study was to determine if nuclear AMPK α2 content in human skeletal muscle was increased by exercise. Following 60 min of cycling at 72 ± 1% of Vo2peak in six male volunteers (20.6 ± 2.1 years; 72.9 ± 2.1 kg; Vo2peak = 3.62 ± 0.18 l/min), nuclear AMPK α2 content was increased 1.9 ± 0.4-fold (P = 0.024). There was no change in whole-cell AMPK α2 content or AMPK α2 mRNA abundance. These results suggest that nuclear translocation of AMPK might mediate the effects of exercise on skeletal muscle gene and protein expression.
Defective Signaling Through Akt-2 and -3 But Not Akt-1 in Insulin-Resistant Human Skeletal Muscle
Authors: Brozinick Joseph T. , Roberts Brian R. , Dohm G. Lynis
Published: March 2007

Recent evidence has shown that activation of phosphatidyinositol-3-kinase (PI3K) and Akt, necessary for insulin stimulation of glucose transport, is impaired in insulin resistance. It is unknown, however, which Akt isoform shows impaired activation in insulin resistance. Additionally, related growth factors (epidermal or platelet-derived vascular) also stimulate PI3K, but it is unknown whether production of 3,4,5 phosphatidyinositol is sufficient to stimulate glucose transport in insulin-resistant muscle. Moreover, these studies were performed in rodents, and little data exists from humans. Hence, we investigated the stimulation of PI3K and Akt-1, -2, and -3 by insulin and epidermal growth factors (EGFs) in skeletal muscles from lean and obese insulin-resistant humans. Insulin activated all Akt isoforms in lean muscles, whereas only Akt-1 was activated in obese muscles. Insulin receptor substrate (IRS)-1 was associated with PI3K activity, which is necessary for Akt activation by insulin, and was reduced in obese muscles, and this was accompanied by decreased IRS-1 expression. In contrast, insulin- or EGF-stimulated phosphotyrosine-associated PI3K activity was not different between lean and obese muscles. These results show that a defect in the ability of insulin to activate Akt-2 and -3 may explain the impaired insulin-stimulated glucose transport in insulin resistance. Additionally, these data also show that different upstream or downstream signals may regulate the activity of the various Akt isoforms.
A Role for Suppressed Thermogenesis Favoring Catch-Up Fat in the Pathophysiology of Catch-Up Growth
Authors: Crescenzo Raffaella , Samec Sonia , Antic Vladan , Rohner-Jeanrenaud Francoise , Seydoux Josiane , Montani Jean-Pierre , Dulloo Abdul G.
Published: March 2007

Catch-up growth is a risk factor for later obesity, type 2 diabetes, and cardiovascular diseases. We show here that after growth arrest by semistarvation, rats refed the same amount of a low-fat diet as controls show 1) lower energy expenditure due to diminished thermogenesis that favors accelerated fat deposition or catch-up fat and 2) normal glucose tolerance but higher plasma insulin after a glucose load at a time point when their body fat and plasma free fatty acids (FFAs) have not exceeded those of controls. Isocaloric refeeding on a high-fat diet resulted in even lower energy expenditure and thermogenesis and increased fat deposition and led to even higher plasma insulin and elevated plasma glucose after a glucose load. Stepwise regression analysis showed that plasma insulin and insulin-to-glucose ratio after the glucose load are predicted by variations in efficiency of energy use (i.e., in thermogenesis) rather than by the absolute amount of body fat or plasma FFAs. These studies suggest that suppression of thermogenesis per se may have a primary role in the development of hyperinsulinemia and insulin resistance during catch-up growth and underscore a role for suppressed thermogenesis directed specifically at catch-up fat in the link between catch-up growth and chronic metabolic diseases.
A New Murine Model of Islet Xenograft Rejection
Authors: Schmidt Peter , Krook Henrik , Maeda Akira , Korsgren Olle , Benda Birgitta
Published: March 2007

A new murine model of porcine islet-like cell cluster (ICC) xenograft rejection, avoiding interference of unspecific inflammation, was introduced and used to investigate rejection mechanisms. Athymic (nu/nu) mice were transplanted with syngeneic, allogeneic, or xenogeneic islets under the kidney capsule. After the original transplantation, immune cells in porcine ICC xenografts undergoing rejection in native immunocompetent mice were transferred to the peritoneal cavity of the athymic mice. At defined time points after transfer, the primary grafts were evaluated by immunohistochemistry and real-time quantitative RT-PCR to estimate cytokine and chemokine mRNA expression. Transfer of immunocompetent cells enabled athymic (nu/nu) mice to reject a previously tolerated ICC xenograft only when donor and recipient were matched for major histocompatibility complex (MHC). In contrast, allogeneic and syngeneic islets were not rejected. The ICC xenograft rejection was mediated by transferred T-cells. The main effector cells, macrophages, were shown to be part of a specific immune response. By day 4 after transplantation, there was an upreglation of both Th1- and Th2-associated cytokine transcripts. The transferred T-cells were xenospecific and required MHC compatibility to induce rejection. Interaction between the TCR of transferred T-cells and MHC on host endothelial cells and/or macrophages seems necessary for inducing ICC xenograft rejection.
An Association of Autoantibody Status and Serum Cytokine Levels in Type 1 Diabetes
Authors: Hanifi-Moghaddam Pejman , Schloot Nanette C. , Kappler Simone , Seiβler Jochen , Kolb Hubert
Published: March 2007

At onset of type 1 diabetes, the islet autoantibody status of patients has been reported to predict progression of the disease. We therefore tested the hypothesis that the systemic immunoregulatory balance, as defined by levels of circulating cytokines and chemokines, is associated with islet autoantibody status. In 50 patients with recent-onset type 1 diabetes, antibodies to GAD and insulinoma-associated antigen 2 (IA-2) were analyzed by radioimmunoassay; cytoplasmic islet cell antibodies were determined by indirect immunofluorescence. Cytokine and chemokine concentrations were measured by rigidly evaluated double antibody enzyme-linked immunosorbent assay. Of four classically defined Th1/Th2 cytokines (γ-interferon, interleukin [IL]-5, IL-10, IL-13), none showed an association with multiple autoantibody positivity. Of six mediators mainly produced by innate immunity cells, three were associated with multiple autoantibody status (IL-18 increased, MIF and MCP-1 decreased) and three were unaffected (IL-12, MIP-1β, IP-10). GAD and/or IA-2 antibody titers negatively correlated with systemic concentrations of MIF, MIP-1β, and IL-12. Combining the data of several cytokine and chemokine levels made it possible to predict islet antibody positivity in individual patients with 85% sensitivity and 94% specificity. These data suggest a close association of islet antibody status with systemic immunoregulation in type 1 diabetes.
Deleterious Effects of Acute Treatment With a Peroxisome Proliferator–Activated Receptor-γ Activator in Myocardial Ischemia and Reperfusion in Pigs
Authors: Xu Ya , Lu Li , Greyson Clifford , Lee Jenny , Gen Michael , Kinugawa Koichiro , Long Carlin S. , Schwartz Gregory G.
Published: March 2007

Thiazolidinediones exert electrophysiologic effects in noncardiac cells in vitro, but to date there have been no reports of effects on cardiac rhythm. We previously demonstrated that chronic pretreatment with a thiazolidinedione peroxisome proliferator–activated receptor (PPAR)-γ activator, troglitazone, improves recovery of left ventricular (LV) function and substrate metabolism after ischemia and reperfusion, without causing arrhythmias. In this study, we determined whether similar salutary effects are achieved with acute treatment with troglitazone. Anesthetized pigs underwent 90 min of regional LV ischemia and 90 min of reperfusion. Fifteen pigs were treated with troglitazone (10 mg/kg load, 5 mg · kg−1 · h−1 infusion i.v.) beginning 1 h before ischemia. Seven pigs received corresponding vehicle. Plasma troglitazone concentration (mean 5 μg/ml) was similar to that achieved in clinical use of this agent. Before ischemia, acute troglitazone treatment had no effect on LV function, electrocardiogram, or substrate utilization. During ischemia or reperfusion, eight pigs in the troglitazone group died of ventricular fibrillation, compared with no pigs in the vehicle group (P < 0.05). Pigs that developed ventricular fibrillation had shorter QT intervals than survivors of either group. Among survivors, neither LV function nor substrate utilization differed between groups. Acute treatment with troglitazone increases susceptibility to ventricular fibrillation during myocardial ischemia and reperfusion. Whether thiazolidinediones have proarrhythmic potential in clinical use requires further investigation.
Maternal Diabetes In Vivo and High Glucose In Vitro Diminish GAPDH Activity in Rat Embryos
Authors: Wentzel Parri , Ejdesjö Andreas , Eriksson Ulf J.
Published: March 2007

The aim of the present study was to investigate whether diabetic embryopathy may be associated with the inhibition of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) resulting from an excess of reactive oxygen species (ROS) in the embryo. Recent demonstrations of enhanced ROS production in mitochondria of bovine aortic endothelial cells exposed to high glucose have supported the idea that the pathogenesis of diabetic complications may involve ROS-induced GAPDH inhibition. We investigated whether a teratogenic diabetic environment also inhibits embryonic GAPDH activity and alters GAPDH gene expression and whether antioxidants diminish such GAPDH inhibition. In addition, we determined whether the inhibition of GAPDH with iodoacetate induces dysmorphogenesis, analogous to that caused by high glucose concentration, and whether antioxidants modulated the putative teratogenic effect of such direct GAPDH inhibition. We found that embryos from diabetic rats and embryos cultured in high glucose concentrations showed decreased activity of GAPDH (by 40–60%) and severe dysmorphogenesis on gestational days 10.5 and 11.5. GAPDH mRNA was decreased in embryos of diabetic rats compared to control embryos. Supplementing the high-glucose culture with the antioxidant N-acetylcysteine (NAC) increased GAPDH activity and diminished embryonic dysmorphogenesis. Embryos cultured with iodoacetate showed both decreased GAPDH activity and dysmorphogenesis; supplementing the culture with NAC increased both parameters toward normal values. In conclusion, dysmorphogenesis caused by maternal diabetes is correlated with ROS-induced inhibition of GAPDH in embryos, which could indicate that inhibition of GAPDH plays a causal role in diabetic embryopathy.
A Novel Role for CD36 in VLDL-Enhanced Platelet Activation
Authors: Englyst Nicola A. , Taube Janis M. , Aitman Timothy J. , Baglin Trevor P. , Byrne Christopher D.
Published: March 2007

Type 2 diabetes is characterized by increased plasma triglyceride levels and a fourfold increase in ischemic heart disease, but the mechanism is unclear. CD36 is a receptor/transporter that binds fatty acids of lipoproteins. CD36 deficiency has been linked with insulin resistance. There is strong evidence of in vivo interaction between platelets and atherogenic lipoproteins suggesting that atherogenic triglyceride-rich lipoproteins, such as VLDL, that are increased in diabetic dyslipidemia are important in this process. This study demonstrates that VLDL binds to the platelet receptor CD36, enhances platelet thromboxane A2 production, and causes increased collagen-mediated platelet aggregation. VLDL enhanced collagen-induced platelet aggregation by 1) shortening the time taken for aggregation to begin (lag time) to 70% of control (P = 0.001); 2) increasing maximum aggregation to 170% of control (P = 0.008); and 3) increasing thromboxane production to 3,318% of control (P = 0.004), where control represents platelets stimulated with collagen (100%). A monoclonal antibody against CD36 attenuated VLDL-enhanced collagen-induced platelet aggregation by 1) inhibiting binding of VLDL to platelets by 75% (P = 0.041); 2) lengthening lag time to 190% (P < 0.001); and 3) decreasing thromboxane production to 8% of control (P < 0.001). In support of this finding, platelets from Cd36-deficient rats showed no increase in aggregation, thromboxane production, and VLDL binding in contrast to platelets from rats expressing CD36. These data suggest that platelet Cd36 has a key role in VLDL-induced collagen-mediated platelet aggregation, possibly contributing to atherothrombosis associated with increased VLDL levels.
Combined Infusion of Epinephrine and Norepinephrine During Moderate Exercise Reproduces the Glucoregulatory Response of Intense Exercise
Authors: Kreisman Stuart H. , Halter Jeffrey B. , Vranic Mladen , Marliss Errol B.
Published: March 2007

Intense exercise (IE) (>80% V̇o2max) causes a seven- to eightfold increase in glucose production (Ra) and a fourfold increase in glucose uptake (Rd), resulting in hyperglycemia, whereas moderate exercise (ME) causes both to double. If norepinephrine (NE) plus epinephrine (Epi) infusion during ME produces the plasma levels and Ra of IE, this would prove them capable of mediating these responses. Male subjects underwent 40 min of 53% V̇o2max exercise, eight each with saline (control [CON]), or with combined NE + Epi (combined catecholamine infusion [CCI]) infusion from min 26–40. In CON and CCI, NE levels reached 7.3 ± 0.7 and 33.1 ± 2.9 nmol/l, Epi 0.94 ± 0.08 and 7.06 ± 0.44 nmol/l, and Ra 3.8 ± 0.4 and 12.9 ± 0.8 mg · kg−1 · min−1 (P < 0.001), respectively, at 40 min. Rd increased to 3.5 ± 0.4 vs. 11.2 ± 0.8 mg · kg−1 · min−1 and glycemia 5.2 ± 0.2 mmol/l in CON vs. 6.5 ± 0.2 mmol/l in CCI (P < 0.001). The glucagon-to-insulin ratio did not differ. Comparing CCI data to those from 14-min IE (n = 16), peak NE (33.6 ± 5.1 nmol/l), Epi (5.32 ± 0.93 nmol/l), and Ra (13.0 ± 1.0 mg · kg−1 · min−1) were comparable. The induced increments in NE, Epi, and Ra, all of the same magnitude as in IE, strongly support that circulating catecholamines can be the prime regulators of Ra in IE.
Polymorphisms in the Insulin-Degrading Enzyme Gene Are Associated With Type 2 Diabetes in Men From the NHLBI Framingham Heart Study
Authors: Karamohamed Samer , Demissie Serkalem , Volcjak Jeannine , Liu Chunyu , Heard-Costa Nancy , Liu Jun , Shoemaker Christina M. , Panhuysen Carolien I. , Meigs James B. , Wilson Peter , Atwood Larry D. , Cupples L. Adrienne , Herbert Alan
Published: March 2007

Linkage studies have mapped a susceptibility gene for type 2 diabetes to the long arm of chromosome 10, where we have previously identified a quantitative trait locus that affects fasting blood glucose within the Framingham Heart Study cohort. One candidate gene in this region is the insulin-degrading enzyme (IDE), which, in the GK rat model, has been associated with nonobese type 2 diabetes. Single nucleotide polymorphisms (SNPs) were used to map a haplotype block in the 3′ end of IDE, which revealed association with HbA1c, fasting plasma glucose (FPG), and mean fasting plasma glucose (mFPG) measured over 20 years. The strongest associations were found in a sample of unrelated men. The lowest trait values were associated with a haplotype (TT, f∼0.32) containing the minor allele of rs2209772 and the major allele of the rs1887922 SNP (FPG P < 0.001, mFPG P < 0.003, HbA1c P < 0.025). Another haplotype (CC, f∼0.16) was associated with elevated HbA1c (P < 0.002) and type 2 diabetes (P < 0.001, odds ratio 1.96, 95% CI 1.28–3.00). The evidence presented supports the possibility that IDE is a susceptibility gene for diabetes in populations of European descent.
A Quantitative Trait Locus on 7q31 for the Changes in Plasma Insulin in Response to Exercise Training
Authors: Lakka Timo A. , Rankinen Tuomo , Weisnagel S. John , Chagnon Yvon C. , Rice Treva , Leon Arthur S. , Skinner James S. , Wilmore Jack H. , Rao D.C. , Bouchard Claude
Published: March 2007

Several genome-wide linkage scans have been carried out to identify quantitative trait loci for type 2 diabetes and related metabolic phenotypes. However, no previous linkage scans have focused on the response to exercise training of relevant metabolic traits. We performed a genome-wide linkage scan for baseline fasting glucose, insulin, and C-peptide and their responses to a 20-week exercise training program in nondiabetic white and black men and women from the HERITAGE Family Study. In SIBPAL linkage analyses, the maximum number of sibpairs available was 344 and 93 for baseline phenotypes and 300 and 72 for exercise training response phenotypes in whites and blacks, respectively. A total of 509 markers with an average spacing of 6.0 Mb were used. The strongest linkage was found for the changes in fasting insulin in response to exercise training with a marker in the leptin gene on 7q31 (empirical multipoint P = 0.0004) in whites. In blacks, the strongest linkage was observed for baseline fasting glucose on 12q13-q14 (empirical multipoint P = 0.0006). These regions harbor several potential candidate genes. The present findings may be important in identifying individuals at increased risk of developing type 2 diabetes and who are most likely to benefit from a physically active lifestyle.
A Promoter Genotype and Oxidative Stress Potentially Link Resistin to Human Insulin Resistance
Authors: Smith Steve R. , Bai Fulu , Charbonneau Chantal , Janderová Lenka , Argyropoulos George
Published: March 2007

Insulin resistance is a component of type 2 diabetes and often precedes pancreatic β-cell failure. Contributing factors include obesity and a central pattern of fat accumulation with a strong genetic component. The adipocyte secreted hormone resistin has been proposed as a link between the adipocyte and insulin resistance by inhibition of insulin-stimulated glucose uptake and/or blocking adipocyte differentiation. Here we report that the G/G genotype of a single nucleotide polymorphism (SNP) in the promoter of the human resistin gene, −180C>G, had significantly increased basal promoter activity in adipocytes. These data were recapitulated in vivo, where G/G homozygotes had significantly higher resistin mRNA levels in human abdominal subcutaneous fat. A significant interaction was also found between the −180C>G SNP, a marker of oxidative stress (NAD[P]H quinone oxidoreductase mRNA) and homeostasis model assessment of insulin resistance. In addition, resistin mRNA was positively and independently correlated with insulin resistance and hepatic fat as measured by liver X-ray attenuation. These data implicate resistin in the pathophysiology of the human insulin resistance syndrome, an effect mediated by the −180C>G promoter SNP and potentially cellular oxidative stress.
What Does the Measurement of Whole-Body Fatty Acid Rate of Appearance in Plasma by Using a Fatty Acid Tracer Really Mean?
Authors: Mittendorfer Bettina , Liem Olivia , Patterson Bruce W. , Miles John M. , Klein Samuel
Published: March 2007

We evaluated the validity of using a single fatty acid tracer to assess total plasma long-chain free fatty acid (FFA) kinetics and the relationship between the rate of appearance (Ra) of fatty acids in plasma and the fatty acid composition of adipose tissue triglyceride (TG). A mixture of [13C]-labeled myristate, palmitate, stearate, oleate, and linoleate was infused in healthy men during basal conditions and during conditions that stimulate (epinephrine infusion) and inhibit (insulin infusion) lipolysis of adipose tissue TGs. Calculated total FFA, Ra based on palmitate, oleate, or linoleate tracers, was within 15% of the measured sum of the individual fatty acid Ra under all conditions, whereas stearate and myristate tracers consistently underestimated and overestimated total FFA Ra, respectively. The fatty acid Ra profile closely matched the fatty acid profile of subcutaneous adipose tissue TGs during epinephrine infusion, but not during basal conditions and insulin infusion. Our data support the common practice of using labeled palmitate or oleate as fatty acid tracers for assessing total plasma FFA kinetics and suggest that a source of lipids other than adipose tissue TG release fatty acids into the systemic circulation.
Estrogen Blunts Neuroendocrine and Metabolic Responses to Hypoglycemia
Authors: Sandoval Darleen A. , Ertl Andrew C. , Richardson M. Antoinette , Tate Donna B. , Davis Stephen N.
Published: March 2007

This study tested the hypothesis that estrogen is the mechanism responsible for the sexual dimorphism present in the neuroendocrine and metabolic responses to hypoglycemia. Postmenopausal women receiving (E2; n = 8) or not receiving (NO E2; n = 9) estrogen replacement were compared with age- and BMI-matched male subjects (n = 8) during a single-step 2-h hyperinsulinemic-hypoglycemic clamp. Plasma insulin (599 ± 28 pmol/l) and glucose (2.9 ± 0.03 mmol/l) levels were similar among all groups during the glucose clamp. In response to hypoglycemia, epinephrine (2.8 ± 0.6 vs. 5.8 ± 0.8 and 4.4 ± 0.5 nmol/l), glucagon (57 ± 8 vs. 77 ± 8 and 126 ± 18 ng/l), and endogenous glucose production (2 ± 2 vs. 10 ± 2 and 6 ± 3 μmol · kg−1 · min−1) were significantly lower in E2 vs. both NO E2 and male subjects (P < 0.05). These reduced counterregulatory responses resulted in significantly greater glucose infusion rates (16 ± 2 vs. 6 ± 2 and 6 ± 3 μmol · kg−1 · min−1; P < 0.01) in E2 vs. both NO E2 and male subjects. Pancreatic polypeptide was significantly lower (P < 0.05) in both the E2 and NO E2 groups compared with the male subjects (136 ± 20 and 136 ± 23 vs. 194 ± 16 pmol/l). Last, glycerol (36 ± 3 vs. 47 ± 5 μmol/l; P < 0.05), lactate (1.4 ± 0.1 vs. 1.8 ± 0.2 mmol/l; P < 0.05), and muscle sympathetic nerve activity (19 ± 4 to 27 ± 4 vs. 27 ± 5 to 42 ± 6 bursts/min; P < 0.05) responses to hypoglycemia were all significantly lower in E2 vs. NO E2 subjects. We conclude that estrogen appears to play a major role in the sexual dimorphism present in counterregulatory responses to hypoglycemia in healthy humans.
Adiponectin Expression From Human Adipose Tissue
Authors: Kern Philip A. , Di Gregorio Gina B. , Lu Tong , Rassouli Negah , Ranganathan Gouri
Published: March 2007

Adiponectin is a 29-kDa adipocyte protein that has been linked to the insulin resistance of obesity and lipodystrophy. To better understand the regulation of adiponectin expression, we measured plasma adiponectin and adipose tissue adiponectin mRNA levels in nondiabetic subjects with varying degrees of obesity and insulin resistance. Plasma adiponectin and adiponectin mRNA levels were highly correlated with each other (r = 0.80, P < 0.001), and obese subjects expressed significantly lower levels of adiponectin. However, a significant sex difference in adiponectin expression was observed, especially in relatively lean subjects. When men and women with a BMI <30 kg/m2 were compared, women had a twofold higher percent body fat, yet their plasma adiponectin levels were 65% higher (8.6 ± 1.1 and 14.2 ± 1.6 μg/ml in men and women, respectively; P < 0.02). Plasma adiponectin had a strong association with insulin sensitivity index (SI) (r = 0.67, P < 0.0001, n = 51) that was not affected by sex, but no relation with insulin secretion. To separate the effects of obesity (BMI) from SI, subjects who were discordant for SI were matched for BMI, age, and sex. Using this approach, insulin-sensitive subjects demonstrated a twofold higher plasma level of adiponectin (5.6 ± 0.6 and 11.2 ± 1.1 μg/ml in insulin-resistant and insulin-sensitive subjects, respectively; P < 0.0005). Adiponectin expression was not related to plasma levels of leptin or interleukin-6. However, there was a significant inverse correlation between plasma adiponectin and tumor necrosis factor (TNF)-α mRNA expression (r = −0.47, P < 0.005), and subjects with the highest levels of adiponectin mRNA expression secreted the lowest levels of TNF-α from their adipose tissue in vitro. Thus, adiponectin expression from adipose tissue is higher in lean subjects and women, and is associated with higher degrees of insulin sensitivity and lower TNF-α expression.
Low-Grade Systemic Inflammation and the Development of Type 2 Diabetes
Authors: Duncan Bruce B. , Schmidt Maria Inês , Pankow James S. , Ballantyne Christie M. , Couper David , Vigo Alvaro , Hoogeveen Ron , Folsom Aaron R. , Heiss Gerardo
Published: March 2007

To examine the association of low-grade systemic inflammation with diabetes, as well as its heterogeneity across subgroups, we designed a case-cohort study representing the ∼9-year experience of 10,275 Atherosclerosis Risk in Communities Study participants. Analytes were measured on stored plasma of 581 incident cases of diabetes and 572 noncases. Statistically significant hazard ratios of developing diabetes for those in the fourth (versus first) quartile of inflammation markers, adjusted for age, sex, ethnicity, study center, parental history of diabetes, and hypertension, ranged from 1.9 to 2.8 for sialic acid, orosomucoid, interleukin-6, and C-reactive protein. After additional adjustment for BMI, waist-to-hip ratio, and fasting glucose and insulin, only the interleukin-6 association remained statistically significant (HR = 1.6, 1.01–2.7). Exclusion of GAD antibody-positive individuals changed associations minimally. An overall inflammation score based on these four markers plus white cell count and fibrinogen predicted diabetes in whites but not African Americans (interaction P = 0.005) and in nonsmokers but not smokers (interaction P = 0.13). The fully adjusted hazard ratio comparing white nonsmokers with score extremes was 3.7 (P for linear trend = 0.008). In conclusion, a low-grade inflammation predicts incident type 2 diabetes. The association is absent in smokers and African-Americans.