bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Proinsulin C-Peptide in Experimental Diabetic Neuropathy
Authors: Cotter Mary A. , Ekberg Karin , Wahren John , Cameron Norman E.
Published: March 2007

Proinsulin C-peptide treatment can partially prevent nerve dysfunction in type 1 diabetic rats and patients. This could be due to a direct action on nerve fibers or via vascular mechanisms as C-peptide stimulates the nitric oxide (NO) system and NO-mediated vasodilation could potentially account for any beneficial C-peptide effects. To assess this further, we examined neurovascular function in streptozotocin-induced diabetic rats. After 6 weeks of diabetes, rats were treated for 2 weeks with C-peptide to restore circulating levels to those of nondiabetic controls. Additional diabetic groups were given C-peptide with NO synthase inhibitor NG-nitro-l-arginine (l-NNA) co-treatment or scrambled C-peptide. Diabetes caused 20 and 16% reductions in sciatic motor and saphenous sensory nerve conduction velocity, which were 62 and 78% corrected, respectively, by C-peptide. l-NNA abolished C-peptide effects on nerve conduction. Sciatic blood flow and vascular conductance were 52 and 41%, respectively, reduced by diabetes (P < 0.001). C-peptide partially (57–66%) corrected these defects, an effect markedly attenuated by l-NNA co-treatment. Scrambled C-peptide was without effect on nerve conduction or perfusion. Thus, C-peptide replacement improves nerve function in experimental diabetes, and the data are compatible with the notion that this is mediated by a NO-sensitive vascular mechanism.
Exercise Training Improves Baroreflex Sensitivity in Type 2 Diabetes
Authors: Loimaala Antti , Huikuri Heikki V. , Kööbi Tiit , Rinne Marjo , Nenonen Arja , Vuori Ilkka
Published: March 2007

Type 2 diabetes is a strong risk factor for coronary heart disease and sudden cardiac death. It is associated with reduced baroreflex sensitivity (BRS) and heart rate variability (HRV), which are indicators of increased risk for mortality and morbidity in various patient populations. This study was designed to assess the effects of exercise training on BRS, HRV, and hemodynamics in patients with type 2 diabetes. Subjects (50 men, mean age 53.3 ± 5.1 years) with type 2 diabetes were randomized into either a control group, in which they received conventional treatment only, or an exercise group, in which they received conventional treatment together with heart rate−controlled endurance training twice a week and supervised muscle strength training twice a week for 12 months. Measurements taken at baseline and follow-up included Vo2max, standard time and frequency domain measures of HRV during 24-h recording, and BRS by the phenylephrine method. Cardiac index, systemic vascular resistance index, stroke index, and pulse wave velocity were measured by whole-body impedance cardiography. Significant improvements in Vo2max (exercise group: +2.3 ml · kg−1 · min−1; P < 0.005 vs. control group), muscle strength, and glycemic control (exercise group: HbA1c −0.9%; P < 0.001 vs. control group) were observed in the exercise group. BRS increased in the exercise group, from 6.8 to 8.6 ms/mmHg, and decreased in the control group, from 7.5 to 6.4 ms/mmHg (95% CI for the difference between 0.05 and 4.36 ms/mmHg; P < 0.05). No significant changes in the time or frequency domain measures of HRV or in systemic hemodynamics were observed. We concluded that exercise training improves BRS sensitivity in type 2 diabetes subjects in addition to increasing the exercise capacity and muscle strength and improving glucose control. These beneficial effects in reflectory autonomic regulation and glucose control caused by exercise may be associated with improved prognosis of type 2 diabetes patients.
Insulin Acutely Increases Fibrinogen Production in Individuals With Type 2 Diabetes but Not in Individuals Without Diabetes
Authors: Barazzoni Rocco , Kiwanuka Edward , Zanetti Michela , Cristini Michela , Vettore Monica , Tessari Paolo
Published: March 2007

Fibrinogen is an acute-phase reactant and an independent cardiovascular risk factor. Insulin without amino acid replacement acutely suppressed fibrinogen production in nondiabetic and type 1 diabetic individuals. Fibrinogen production and plasma concentration increase in insulin-resistant type 2 diabetes. It is not known whether altered response to insulin contributes to hyperfibrinogenemia in type 2 diabetes. Fibrinogen fractional (FSR) and absolute (ASR) synthesis rates were measured using a leucine isotopic model in type 2 diabetic men (n = 7; age = 51 ± 3 years; BMI = 26.7 ± 1 kg/m2) compared with matched nondiabetic subjects under basal conditions and following a 4-h euglycemic-, euaminoacidemic-hyperinsulinemic clamp. Basal fibrinogen concentration (+35%, P < 0.05) and ASR (+35%, P < 0.05) were greater in the diabetic subjects. Following clamp, fibrinogen FSR and ASR were unchanged in the control subjects. In contrast, fibrinogen FSR and ASR increased by 41 and 43%, respectively (P < 0.05), in the diabetic subjects. Thus, fibrinogen production is acutely increased by insulin when euglycemia and euaminoacidemia are maintained in type 2 diabetic individuals but not in nondiabetic individuals. Enhanced fibrinogen production by insulin is likely to be a key alteration contributing to hyperfibrinogenemia and therefore cardiovascular risk in type 2 diabetes. Unchanged fibrinogen production in nondiabetic individuals suggests a role of plasma amino acids in regulating fibrinogen production in humans.
Blockade of Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Exacerbates Type 1 Diabetes in NOD Mice
Authors: Mi Qing-Sheng , Ly Dalam , Lamhamedi-Cherradi S.-E. , Salojin Konstantin V. , Zhou Li , Grattan Marsha , Meagher Craig , Zucker Peter , Chen Youhai H. , Nagle James , Taub Dennis , Delovitch Terry L.
Published: March 2007

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is expressed in different tissues and cells, including pancreas and lymphocytes, and can induce apoptosis in various tumor cells but not in most normal cells. The specific roles of TRAIL in health and disease remain unclear. Here we show by cDNA array analyses that TRAIL gene expression is upregulated in pancreatic islets during the development of autoimmune type 1 diabetes in nonobese diabetic (NOD) mice and in Min6 islet β-cells activated by TNF-α + interferon-γ. However, stimulation of freshly isolated pancreatic islets or Min6 cells with TRAIL did not induce their apoptosis. TRAIL blockade exacerbates the onset of type 1 diabetes in NOD.Scid recipients of transferred diabetogenic T-cells and in cyclophosphamide-treated NOD mice. TRAIL inhibits the proliferation of NOD diabetogenic T-cells by suppressing interleukin (IL)-2 production and cell cycle progression, and this inhibition can be rescued in the presence of exogenous IL-2. cDNA array and Western blot analyses indicate that TRAIL upregulates the expression of the cdk inhibitor p27kip1. Our data suggest that TRAIL is an important immune regulator of the development of type 1 diabetes.
Prevention of Diabetes in NOD Mice by Administration of Dendritic Cells Deficient in Nuclear Transcription Factor-κB Activity
Authors: Ma Linlin , Qian Shiguang , Liang Xiaoyan , Wang Lianfu , Woodward Jennifer E. , Giannoukakis Nick , Robbins Paul D. , Bertera Suzanne , Trucco Massimo , Fung John J. , Lu Lina
Published: March 2007

Abnormalities of dendritic cells (DCs) have been identified in type 1 diabetic patients and in nonobese diabetic (NOD) mice that are associated with augmented nuclear transcription factor (NF)-κB activity. An imbalance that favors development of the immunogenic DCs may predispose to the disease, and restoration of the balance by administration of DCs deficient in NF-κB activity may prevent diabetes. DCs propagated from NOD mouse bone marrow and treated with NF-κB–specific oligodeoxyribonucleotide (ODN) in vitro (NF-κB ODN DC) were assessed for efficacy in prevention of diabetes development in vivo. Gel shift assay with DC nuclear extracts confirmed specific inhibition of NF-κB DNA binding by NF-κB ODN. The costimulatory molecule expression, interleukin (IL)-12 production, and immunostimulatory capacity in presenting allo- and islet-associated antigens by NF-κB ODN DC were significantly suppressed. NF-κB ODN renders DCs resistant to lipopolysaccharide stimulation. Administration of 2 × 106 NF-κB ODN DCs into NOD mice aged 6–7 weeks effectively prevented the onset of diabetes. T-cells from pancreatic lymph nodes of NF-κB ODN DC–treated animals exhibited hyporesponsiveness to islet antigens with low production of interferon-γ and IL-2. These findings provide novel insights into the mechanisms of autoimmune diabetes and may lead to development of novel preventive strategies.
Pancreatic Precursors and Differentiated Islet Cell Types From Murine Embryonic Stem Cells
Authors: Kahan Brenda W. , Jacobson Lynn M. , Hullett Debra A. , Ochoada Jaime M. , Oberley Terry D. , Lang Katharine M. , Odorico Jon S.
Published: March 2007

Embryonic stem (ES) cells differentiating in vitro reproduce many facets of early embryonic development, including the expression of developmentally regulated transcription factors and the differentiation of multipotent precursor cells. ES cells were evaluated for their ability to differentiate into pancreatic and islet lineage-restricted stages including pancreatic duodenal homeobox 1 (PDX1)-positive pancreatic precursor cells, early endocrine cell progenitors, and islet hormone-producing cells. Following growth and differentiation in nonselective medium containing serum, murine ES cells spontaneously differentiated into cells individually expressing each of the four major islet hormones: insulin, glucagon, somatostatin, and pancreatic polypeptide. PDX1 immunostaining cells appeared first, before hormone-positive cells had emerged. Hormone-positive cells appeared within focal clusters of cells coexpressing PDX1 and the nonclassical hormone markers peptide YY (YY) and islet amyloid polypeptide (IAPP) in combination with the definitive hormones, characteristic of endocrine cells appearing during early pancreaticogenesis. This system allows the investigation of many facets of islet development since it promotes the appearance of the complete range of islet phenotypes and reproduces important developmental stages of normal islet cytodifferentiation in differentiating ES cell cultures.
Insulin Constitutively Secreted by β-Cells Is Necessary for Glucose-Stimulated Insulin Secretion
Authors: Srivastava Siddhartha , Goren H. Joseph
Published: March 2007

Four hypotheses have been posited on the role of insulin in glucose-stimulated insulin secretion; available evidence has supported insulin as being 1) essential, 2) a positive modulator, 3) a negative modulator, or 4) not necessary. Because circulating insulin levels in mice, before or after intraperitoneal glucose injection, are sufficient to elicit insulin responses in insulin-sensitive tissues, it is likely that β-cell insulin receptors are continuously exposed to stimulating concentrations of insulin. To determine whether constitutively secreted insulin is necessary for glucose-stimulated insulin secretion, CD1 male mouse islets were incubated for 30 min at 4°C in the absence (control) or presence of anti-insulin (1 μg/ml) or anti-IgG (1 μg/ml). Then islets were exposed to 3, 11, or 25 mmol/l glucose or to 20 mmol/l arginine. Nontreated islets exhibited first- and second-phase glucose-stimulated insulin secretion. Control and anti-IgG–treated islets, after a 5-min lag phase, increased their insulin secretion in 25 mmol/l glucose. Anti-insulin−treated islets secreted insulin at a basal rate in 3 or 25 mmol/l glucose buffers. Insulin secretion stimulated by 20 mmol/l arginine was the same in islets pretreated with either antibody and showed no lag phase. Taken together, these data suggest that constitutively secreted insulin is required and sufficient for β-cells to maintain sensitivity to glucose.
Leptin Increases Lipoprotein Lipase Secretion by Macrophages: Involvement of Oxidative Stress and Protein Kinase C
Authors: Maingrette Fritz , Renier Geneviève
Published: March 2007

Recent data suggest that plasma leptin may represent a cardiovascular risk factor in diabetic patients. To gain further insight into the role of leptin in atherogenesis associated with diabetes, we investigated in the present study the role of this hormone in the regulation of macrophage lipoprotein lipase (LPL), a proatherogenic cytokine overexpressed in patients with type 2 diabetes. Treatment of human macrophages with leptin (1–10 nmol/l) increased LPL expression, at both the mRNA and protein levels. Pretreatment of these cells with anti-leptin receptor (Ob-R) antibody, protein kinase C (PKC) inhibitors, calphostin C, and GF109203X, or the antioxidant N-acetylcysteine (NAC) blocked the effects of leptin. Similar results were observed in leptin-treated J774 macrophages. In these cells, leptin increased the membrane expression of conventional PKC isoforms and downregulation of endogenous PKC expression abolished the effects of leptin on macrophage LPL expression. In leptin-treated J774 cells, enhanced LPL synthetic rate and increased binding of nuclear proteins to the activated protein-1 (AP-1) consensus sequence of the LPL gene promoter were also observed. This latter effect was abrogated by GF109203X. Overall, these data demonstrate that binding of leptin at the macrophage cell surface increases, through oxidative stress- and PKC-dependent pathways, LPL expression. This effect appears to be exerted at the transcriptional level and to involve AP-1 activation.
Microarray Analysis of Gene Expression in the Kidneys of New- and Post-Onset Diabetic NOD Mice
Authors: Wilson Karen H.S. , Eckenrode Sarah E. , Li Quan-Zhen , Ruan Qing-Guo , Yang Ping , Shi Jing-Da , Davoodi-Semiromi Abdoreza , McIndoe Richard A. , Croker Byron P. , She Jin-Xiong
Published: March 2007

We profiled the expression of 5,760 clones from a kidney subtraction library in the kidneys of three groups of NOD mice: nondiabetic, new-onset, and long-term diabetic. A total of 27 genes had lower expression and 1 gene (Gpx3) had higher expression in the new-onset diabetic mice compared with nondiabetic control NOD mice (P < 0.001). Similarly, 19 of the above 27 genes and 7 additional genes had higher expression and the Gpx3 gene had lower expression in long-term diabetic mice compared with controls (P < 0.001). Interestingly, only three genes may be different between new-onset and long-term diabetic mice (P < 0.0004). These genes are from diverse functional groups, including oxidative phosphorylation, free radical neutralization, channels, pumps, lipid processing, transcription and translation machinery, protein trafficking, constitutive protein processing, and immune function. The majority of these genes fall into four signaling pathways: insulin, transforming growth factor-β, tumor necrosis factor-α, and peroxisome proliferator–activated receptor. The most significant expression change was found for the stearoyl-coenzyme A desaturase 1 (SCD1) gene (P < 10−7). The lower expression levels of the SCD1 gene in both diabetic groups compared with controls were further confirmed by Northern blot analysis and immunohistochemistry.
Identification of Epistatic Interaction Involved in Obesity Using the KK/Ta Mouse as a Type 2 Diabetes Model
Authors: Gohda Tomohito , Makita Yuichiro , Shike Toshihide , Tanimoto Mitsuo , Funabiki Kazuhiko , Horikoshi Satoshi , Tomino Yasuhiko
Published: March 2007

The KK/Ta strain serves as a suitable polygenic mouse model for the common form of type 2 diabetes associated with obesity in humans. Recently, we reported the susceptibility loci contributing to type 2 diabetes and related phenotypes in KK/Ta mice. In this study, we focused on expression in the kidneys and liver of KK/Ta and BALB/c mice using differential display (DD) PCR. Zn-α2 glycoprotein-1 (Azgp1) mRNA levels were increased in the kidneys and liver in KK/Ta mice, and sequence analysis revealed a missense mutation. We analyzed the relationship between this polymorphism and various phenotypes in 208 KK/Ta × (BALB/c × KK/Ta) F1 backcross mice. Statistical analysis revealed that Azgp1 and D17Mit218 exhibit a suggestive linkage to body weight (8 weeks) (logarithm of odds 2.3 and 2.9, respectively). Moderate gene-gene interactions were observed at these loci. Adiponectin mRNA levels in 3T3-L1 cells transfected with the expression pcDNA 3.1 vector containing Azgp1 coding sequence of KK/Ta mice were significantly higher than those of BALB/c mice. These results suggest that Azgp1 is a possible candidate gene for regulation of body weight, elucidation of polygenic inheritance, and age-dependent changes in the genetic control of obesity.
Enhanced Fat Oxidation Through Physical Activity Is Associated With Improvements in Insulin Sensitivity in Obesity
Authors: Goodpaster Bret H. , Katsiaras Andreas , Kelley David E.
Published: March 2007

Skeletal muscle insulin resistance entails dysregulation of both glucose and fatty acid metabolism. This study examined whether a combined intervention of physical activity and weight loss influences fasting rates of fat oxidation and insulin-stimulated glucose disposal. Obese (BMI >30 kg/m2) volunteers (9 men and 16 women) without diabetes, aged 39 ± 4 years, completed 16 weeks of moderate-intensity physical activity combined with caloric reduction. Body composition was determined by dual-energy X-ray absorptiometry and computed tomography. Glucose disposal rates (Rd) were measured during euglycemic hyperinsulinemia (40 mU · m−2 · min−1), and substrate oxidation was determined via indirect calorimetry. Fat mass and regional fat depots were reduced and Vo2max improved by 19%, from 38.8 ± 1.2 to 46.0 ± 1.0 ml · kg fat-free mass (FFM)−1 · min−1 (P < 0.05). Insulin sensitivity improved 49 ± 10% (6.70 ± 0.40 to 9.51 ± 0.51 mg · min−1 · kg FFM−1; P < 0.05). Rates of fat oxidation following an overnight fast increased (1.16 ± 0.06 to 1.36 ± 0.05 mg · min−1 · kg FFM−1; P < 0.05), and the proportion of energy derived from fat increased from 38 to 52%. The strongest predictor of the improved insulin sensitivity was enhanced fasting rates of fat oxidation, accounting for 52% of the variance. In conclusion, exercise combined with weight loss enhances postabsorptive fat oxidation, which appears to be a key aspect of the improvement in insulin sensitivity in obesity.
A Novel Insulin Analog With Unique Properties
Authors: Rakatzi Irini , Ramrath Stefanie , Ledwig Daniela , Dransfeld Olaf , Bartels Thomas , Seipke Gerhard , Eckel Jürgen
Published: March 2007

The potentially enhanced mitogenic activity of insulin analogs represents a safety risk that requires detailed analysis of new analogs considered for therapeutic applications. We assessed the signaling properties and mitogenic potency of two novel rapid-acting insulin analogs, LysB3,GluB29 insulin (HMR 1964) and LysB3,IleB28 insulin (HMR 1153) using myoblasts and cardiomyocytes. In myoblasts, both binding and internalization were two- to threefold higher for AspB10 insulin and HMR 1153 when compared with HMR 1964 and regular insulin. This finding correlated with a prominent Shc/IGF-I receptor interaction, tyrosine phosphorylation of Shc, activation of extracellular signal-regulated protein kinase (ERK)-1 and -2, and stimulation of DNA synthesis by HMR 1153 and AspB10 insulin. In contrast, HMR 1964 produced a marginal activation of the Shc/ERK kinase cascade and was equipotent to insulin in stimulating DNA synthesis in myoblasts. Further, the in vivo growth-promoting activity of this analog was found to be identical to that of regular human insulin. In myoblasts, HMR 1964 produced a minor activation of insulin receptor substrate (IRS)-1 tyrosine phosphorylation, but a prominent activation of IRS-2, with a significantly stronger effect than insulin in human myoblasts. Predominant activation of IRS-2 was also observed in adult cardiomyocytes where HMR 1964 increased 3-O-methylglucose transport and the activation of Akt and glycogen synthase kinase-3 to the same extent as human insulin. We concluded that 1) the mitogenic properties of insulin analogs may result from a series of initial receptor interactions, including internalization and phosphorylation; 2) the mitogenic and metabolic potential of HMR 1964 is identical to that of insulin; and 3) predominant activation of IRS-2 may open new avenues for optimized insulin therapies.
Increased β-Cell Apoptosis Prevents Adaptive Increase in β-Cell Mass in Mouse Model of Type 2 Diabetes
Authors: Butler Alexandra E. , Janson Juliette , Soeller Walter C. , Butler Peter C.
Published: March 2007

Nondiabetic obese humans adapt to insulin resistance by increasing β-cell mass. In contrast, obese humans with type 2 diabetes have an ∼60% deficit in β-cell mass. Recent studies in rodents reveal that β-cell mass is regulated, increasing in response to insulin resistance through increased β-cell supply (islet neogenesis and β-cell replication) and/or decreased β-cell loss (β-cell apoptosis). Prospective studies of islet turnover are not possible in humans. In an attempt to establish the mechanism for the deficit in β-cell mass in type 2 diabetes, we used an obese versus lean murine transgenic model for human islet amyloid polypeptide (IAPP) that develops islet pathology comparable to that in humans with type 2 diabetes. By 40 weeks of age, obese nontransgenic mice did not develop diabetes and adapted to insulin resistance by a 9-fold increase (P < 0.001) in β-cell mass accomplished by a 1.7-fold increase in islet neogenesis (P < 0.05) and a 5-fold increase in β-cell replication per islet (P < 0.001). Obese transgenic mice developed midlife diabetes with islet amyloid and an 80% (P < 0.001) deficit in β-cell mass that was due to failure to adaptively increase β-cell mass. The mechanism subserving this failed expansion was a 10-fold increase in β-cell apoptosis (P < 0.001). There was no relationship between the extent of islet amyloid or the blood glucose concentration and the frequency of β-cell apoptosis. However, the frequency of β-cell apoptosis was related to the rate of increase of islet amyloid. These prospective studies suggest that the formation of islet amyloid rather than the islet amyloid per se is related to increased β-cell apoptosis in this murine model of type 2 diabetes. This finding is consistent with the hypothesis that soluble IAPP oligomers but not islet amyloid are responsible for increased β-cell apoptosis. The current studies also support the concept that replicating β-cells are more vulnerable to apoptosis, possibly accounting for the failure of β-cell mass to expand appropriately in response to obesity in type 2 diabetes.
Intramuscular Heat Shock Protein 72 and Heme Oxygenase-1 mRNA Are Reduced in Patients With Type 2 Diabetes
Authors: Bruce Clinton R. , Carey Andrew L. , Hawley John A. , Febbraio Mark A.
Published: March 2007

To examine whether genes associated with cellular defense against oxidative stress are associated with insulin sensitivity, patients with type 2 diabetes (n = 7) and age-matched (n = 5) and young (n = 9) control subjects underwent a euglycemic-hyperinsulinemic clamp for 120 min. Muscle samples were obtained before and after the clamp and analyzed for heat shock protein (HSP)72 and heme oxygenase (HO)-1 mRNA, intramuscular triglyceride content, and the maximal activities of β-hyroxyacyl-CoA dehydrogenase (β-HAD) and citrate synthase (CS). Basal expression of both HSP72 and HO-1 mRNA were lower (P < 0.05) by 33 and 55%, respectively, when comparing diabetic patients with age-matched and young control subjects, with no differences between the latter groups. Both basal HSP72 (r = 0.75, P < 0.001) and HO-1 (r = 0.50, P < 0.05) mRNA expression correlated with the glucose infusion rate during the clamp. Significant correlations were also observed between HSP72 mRNA and both β-HAD (r = 0.61, P < 0.01) and CS (r = 0.65, P < 0.01). HSP72 mRNA was induced (P < 0.05) by the clamp in all groups. Although HO-1 mRNA was unaffected by the clamp in both the young and age-matched control subjects, it was increased (P < 0.05) ∼70-fold in the diabetic patients after the clamp. These data demonstrate that genes involved in providing cellular protection against oxidative stress are defective in patients with type 2 diabetes and correlate with insulin-stimulated glucose disposal and markers of muscle oxidative capacity. The data provide new evidence that the pathogenesis of type 2 diabetes involves perturbations to the antioxidant defense mechanism within skeletal muscle.
Level of an Advanced Glycated End Product Is Genetically Determined
Authors: Leslie R. David G. , Beyan Huriya , Sawtell Pam , Boehm Bernard O. , Spector Tim D. , Snieder Harold
Published: March 2007

Reducing sugars react with amino groups in proteins, lipids, and nucleic acids to produce advanced glycation end products (AGEs), including Nε-carboxymethyl lysine (CML), which have been implicated in oxidative stress and vascular damage. The aim of this study was to determine whether genetic factors influence serum CML levels in normal subjects. We performed a classical twin study of CML in healthy nondiabetic female twins, 39 monozygotic and 45 dizygotic pairs, aged 21–74 years. Serum CML levels were estimated by enzyme-linked immunosorbent assay. Twin correlations (r) for serum CML levels were higher in monozygotic (r = 0.71) compared with dizygotic (r = 0.50) twin pairs, suggesting a substantial genetic effect and confirmed by quantitative genetic model fitting. Additive genetic effects (heritability) explained 74% (95% CI 58–84) of population variance in CML. Heritability (%) of fasting glucose (51%) and HbA1c (62%) could not explain CML heritability, which was not associated with them. CML levels are, therefore, predominantly genetically determined and independent of genes influencing fasting glucose or HbA1c. Thus familial, largely genetic factors influence AGE implicating these glycoxidation products in the genetic contribution to macro- and microvascular disease.
Transmission of Maternal Islet Antibodies and Risk of Autoimmune Diabetes in Offspring of Mothers With Type 1 Diabetes
Authors: Koczwara Kerstin , Bonifacio Ezio , Ziegler Anette-Gabriele
Published: March 2007

It is suggested that the maternal transmission of islet autoantibodies increases the risk of autoimmune diabetes in mice. The aim of this study was to determine whether fetal exposure to islet autoantibodies modified the risk of type 1 diabetes in humans. Islet autoantibodies were measured at birth in 720 offspring of mothers with type 1 diabetes. Offspring were prospectively followed for the development of multiple islet autoantibodies and diabetes. Offspring who were GAD or IA-2 autoantibody positive at birth (n = 678) had significantly lower risks for developing multiple islet autoantibodies (5-year risk 1.3%) and diabetes (8-year risk 1.1%) than offspring who were islet autoantibody negative at birth (5.3%, P = 0.008; and 3%, P = 0.04, respectively). Risk remained reduced after adjustment for birth weight, gestational age, or maternal diabetes duration (adjusted hazards ratio 0.25, P = 0.007 for multiple islet autoantibodies; 0.25, P = 0.04 for diabetes). Protection in offspring with islet autoantibodies at birth was most striking in offspring without the HLA DRB1*03/DRB1*04-DQB1*0302 genotype. Maternal transmission of antibodies to exogenous insulin did not affect diabetes risk in offspring. These findings suggest that fetal exposure to islet autoantibodies in children born to mothers with type 1 diabetes may be protective against future islet autoimmunity and diabetes.
Regulation of the Early Subnormal Retinal Oxygenation Response in Experimental Diabetes by Inducible Nitric Oxide Synthase
Authors: Berkowitz Bruce A. , Luan Hongmei , Gupta Rita R. , Pacheco Daniel , Seidner Andres , Roberts Robin , Liggett Jessica , Knoerzer Deborah L. , Connor Jane R. , Du Yunpeng , Kern Timothy S. , Ito Yasuki
Published: March 2007

We aimed to test the hypothesis that the inducible form of nitric oxide synthase (iNOS) contributes to the development of an early subnormal retinal oxygenation response in preclinical models of diabetic retinopathy. In urethane anesthetized Sprague Dawley rats or C57BL/6 mice, functional magnetic resonance imaging was used to noninvasively measure the change in retinal oxygen tension (ΔPO2) during a carbogen-inhalation challenge. In the rat experiments, the retinal ΔPO2 of the following groups were compared: control rats (n = 9), 3-month diabetic rats (n = 5), and 3-month diabetic rats treated orally with l-N(6)-(1-iminoethyl)lysine 5-tetrazole amide, a prodrug of an inhibitor of iNOS (n = 6). In addition, the retinal ΔPO2 of the following mouse groups were compared: C57BL/6 mice (n = 20), C57BL/6-Nos2tm1Lau mice (n = 10), 4-month diabetic mice (n = 13), and 4-month diabetic knockout mice (n = 6). Only the ΔPO2 of the superior hemiretina of the diabetic rat and mice groups were significantly subnormal (P < 0.05). The superior ΔPO2 of the diabetic rats treated with the prodrug was not significantly (P > 0.05) different from their respective normal controls. In the mice experiments, the superior retinal ΔPO2 of the iNOS null mice was not statistically different (P > 0.05) from that of normal control mice. iNOS is required for the development of an early subnormal ΔPO2 in experimental diabetic retinopathy.
Retinal Vessel Diameters and the Incidence of Gross Proteinuria and Renal Insufficiency in People With Type 1 Diabetes
Authors: Wong Tien Yin , Shankar Anoop , Klein Ronald , Klein Barbara E.K.
Published: March 2007

Early retinal vessel caliber changes may predict risk of diabetic nephropathy. We examined the association of retinal vessel diameters and the incidence of gross proteinuria and renal insufficiency in a population-based cohort of people with type 1 diabetes (n = 557). Baseline retinal photographs were digitized, and diameters of individual retinal vessels were measured and summarized. Incident cases of gross proteinuria and renal insufficiency were identified over a 16-year period. Larger retinal venular diameter was associated with higher cumulative incidence of gross proteinuria (18.6, 25.4, 37.7, and 50.4%, comparing increasing venular diameter quartiles) and renal insufficiency (10.7, 15.5, 23.2, and 32.8%). After adjusting for age, sex, duration of diabetes, HbA1c levels, baseline retinopathy levels, and other factors, larger retinal venular diameter was associated with an increased risk of gross proteinuria (RR 1.53, 95% CI 1.19–1.97, comparing 4th vs. 1st to 3rd quartiles of venular diameter) and renal insufficiency (1.51, 1.05–2.17). Retinal arteriolar diameter was not associated with either gross proteinuria or renal insufficiency. We conclude that in individuals with type 1 diabetes, larger retinal venular diameter is independently associated with the long-term incidence of gross proteinuria and renal insufficiency and may provide additional predictive information regarding risk of nephropathy.
Caspase-1 Is Not Required for Type 1 Diabetes in the NOD Mouse
Authors: Schott William H. , Haskell Bradford D. , Tse Hubert M. , Milton Martha J. , Piganelli Jon D. , Choisy-Rossi Caroline Morgane , Reifsnyder Peter C. , Chervonsky Alexander V. , Leiter Edward H.
Published: March 2007

Interleukin (IL)-1β and IL-18 are two cytokines associated with the immunopathogenesis of diabetes in NOD mice. Both of these cytokines are cleaved by caspase-1 to their biologically active forms. IL-1 is a proinflammatory cytokine linked to β-cell damage, and IL-18 stimulates production of interferon (IFN)γ in synergy with IL-12. To examine the effects produced by caspase-1 deficiency on diabetes development in NOD/Lt mice, a disrupted Casp1 gene was introduced by a speed congenic technique. Casp1−/− bone marrow-derived macrophages stimulated with lipopolysaccharide produced no detectable IL-18, fourfold lower IL-1β, and 20–30% less IL-1α than macrophages from wild-type Casp1+/+ or Casp1+/− controls. Unexpectedly, despite reduced IL-1 and IL-18, there was no change in the rate of diabetes or in total incidence as compared with that in wild-type NOD mice. IL-1 reportedly makes an important pathological contribution in the multidose streptozotocin model of diabetes; however, there was no difference in sensitivity to streptozotocin between NOD mice and NOD.Casp1−/− mice at 40 mg/kg body wt or at 25 mg/kg body wt dosage levels. These findings show that caspase-1 processing of IL-1β and IL-18 is not absolutely required for mediation of spontaneous or chemically induced diabetes pathogenesis in the NOD mouse.
Response of Human Islets to Isolation Stress and the Effect of Antioxidant Treatment
Authors: Bottino Rita , Balamurugan A.N. , Tse Hubert , Thirunavukkarasu C. , Ge Xinhui , Profozich Jennifer , Milton Martha , Ziegenfuss Audra , Trucco Massimo , Piganelli Jon D.
Published: March 2007

The process of human islet isolation triggers a cascade of stressful events in the islets of Langerhans involving activation of apoptosis and necrosis and the production of proinflammatory molecules that negatively influence islet yield and function and may produce detrimental effects after islet transplantation. In this study, we showed that activation of nuclear factor-κB (NF-κB) and poly(ADP-ribose) polymerase (PARP), two of the major pathways responsible for cellular responses to stress, already occurs in pancreatic cells during the isolation procedure. NF-κB−dependent reactions, such as production and release of interleukin-6 and -8 and macrophage chemoattractant protein 1, were observed days after the isolation procedure in isolated purified islets. Under culture conditions specially designed to mimic isolation stress, islet proinflammatory responses were even more pronounced and correlated with higher islet cell loss and impaired secretory function. Here we present novel evidence that early interventions aimed at reducing oxidative stress of pancreatic cells and islets through the use of the catalytic antioxidant probe AEOL10150 (manganese [III] 5,10,15,20-tetrakis [1,3,-diethyl-2imidazoyl] manganese-porphyrin pentachloride [TDE-2,5-IP]) effectively reduces NF-κB binding to DNA, the release of cytokines and chemokines, and PARP activation in islet cells, resulting in higher survival and better insulin release. These findings support the concept that the isolation process predisposes islets to subsequent damage and functional impairment. Blocking oxidative stress can be beneficial in reducing islet vulnerability and can potentially have a significant impact on transplantation outcome.
Investigation of the Role of B-Cells in Type 1 Diabetes in the NOD Mouse
Authors: Wong F. Susan , Wen Li , Tang Michelle , Ramanathan Murugappan , Visintin Irene , Daugherty Joanne , Hannum Lynn G. , Janeway Charles A. , Shlomchik Mark J.
Published: March 2007

B-cells are important in the development of type 1 diabetes, but their role is not completely defined. Although B-cells produce autoantibodies, these are not thought to be pathogenic; however, their antigen-presenting function is postulated to be critical. To examine the relative importance of these functions of B-cells, we have generated nonobese diabetic (NOD) B-cell–deficient mice that express a transgene encoding a mutant heavy chain immunoglobulin transgene on the cell surface but cannot secrete immunoglobulins (mIgs). This allowed us to dissect the importance of the relative roles of antigen presentation, dissociated from antibody production. We found that the expression of the mIg transgene increased insulitis and the incidence of diabetes compared with transgene-negative NOD B-cell–deficient mice, indicating that the ability to produce antibodies is not necessary for B-cells to have some effect on the development of diabetes. However, diabetes was not restored to the level seen in normal NOD mice. This may relate to reduced ability to activate an islet-specific T-cell repertoire, presumably due to the reduced islet-specific B-cell repertoire. Our results implicate a specific antigen-presenting function for B-cells.
Nitric Oxide–Sensitive Soluble Guanylyl Cyclase Activity Is Preserved in Internal Mammary Artery of Type 2 Diabetic Patients
Authors: Witte Klaus , Hachenberger Jochen , Castell Maria F. , Vahl Christian F. , Haller Christlieb
Published: March 2007

Vascular reactivity to nitric oxide (NO) is mediated by NO-sensitive soluble guanylyl cyclase (sGC). Since a diminished activity of vascular sGC has been reported in an animal model of type 2 diabetes, the sGC activity was assayed in vitro in internal mammary artery specimens obtained during bypass surgery from patients with and without type 2 diabetes. The sensitivity of sGC to NO, which is dependent on Fe2+-containing heme, was measured in vitro using stimulation with diethylamine NONOate (DEA/NO). In addition, the novel cyclic guanosine monophosphate–elevating compound HMR-1766 was used to test the stimulation of the oxidized heme-Fe3+–containing form of sGC. Basal activity of sGC and its sensitivity to stimulation by DEA/NO and HMR-1766 were not different between control and type 2 diabetic patients: maximum stimulation by DEA/NO amounted to 475 ± 67 and 418 ± 59 pmol · mg−1 · min−1 in control and type 2 diabetic patients, respectively. The maximum effects of HMR-1766 were 95 ± 18 (control subjects) and 83 ± 11 pmol · mg−1 · min−1 (type 2 diabetic patients). Hypertension, hyperlipidemia, drug treatment with statins, ACE inhibitors, or nitrates had no effect on sGC activity. In conclusion, the present findings do not support the hypothesis that desensitization of sGC contributes to the pathogenesis of diabetic vascular dysfunction in humans.
Glycation Inactivation of the Complement Regulatory Protein CD59
Authors: Qin Xuebin , Goldfine Allison , Krumrei Nicole , Grubissich Luciano , Acosta Juan , Chorev Michael , Hays Arthur P. , Halperin Jose A.
Published: March 2007

Micro- and macrovascular diseases are major causes of morbidity and mortality in the diabetic population, but the cellular and molecular mechanisms that link hyperglycemia to these complications remain incompletely understood. We proposed that in human diabetes, inhibition by glycation of the complement regulatory protein CD59 increases deposition of the membrane attack complex (MAC) of complement, contributing to the higher vascular risk. We report here 1) the generation and characterization of an anti–glycated human CD59 (hCD59) specific antibody, 2) the detection with this antibody of glycated hCD59 colocalized with MAC in kidneys and nerves from diabetic but not from nondiabetic subjects, and 3) a significantly reduced activity of hCD59 in erythrocytes from diabetic subjects, a finding consistent with glycation inactivation of hCD59 in vivo. Because hCD59 acts as a specific inhibitor of MAC formation, these findings provide a molecular explanation for the increased MAC deposition reportedly found in the target organs of diabetic complications. We conclude that glycation inactivation of hCD59 that leads to increased MAC deposition may contribute to the extensive vascular pathology that complicates human diabetes.
Differences in the Contribution of HLA-DR and -DQ Haplotypes to Susceptibility to Adult- and Childhood-Onset Type 1 Diabetes in Japanese Patients
Authors: Murao Satoshi , Makino Hideichi , Kaino Yukikazu , Konoue Etsushi , Ohashi Jun , Kida Kaichi , Fujii Yasuhisa , Shimizu Ikki , Kawasaki Eiji , Fujiyama Masao , Kondo Shiori , Tanaka Kiyonobu , Tarumi Yoshinao , Seto Isamu , Kato Kenichi , Ohno Keizo , Kusunoki Yukiko , Ebisui Osamu , Takada Yasuharu , Tanabe Katsuya , Takemoto Koji , Onuma Hiroshi , Nishimiya Tatsuya , Osawa Haruhiko
Published: March 2007

To clarify heterogeneity in Japanese adult-onset type 1 diabetes, we analyzed the HLA-DR and -DQ haplotypes, depending on the clinical phenotype, and compared them with those in childhood-onset type 1 diabetes (CO). The patients in a previously reported Ehime Study were divided into subgroups by the mode of onset of diabetes: 68 acute-onset type 1 diabetic patients (AO) and 28 slowly progressive type 1 diabetic patients (SO). HLA haplotypes were compared with those of 80 CO patients and 190 control subjects. Two major susceptible HLA haplotypes in the Japanese, DRB1*0405-DQB1*0401 (DR4) and DRB1*0901-DQB1*0303 (DR9), were significantly increased in the AO and CO groups, but only DR9 was increased in the SO group. AO subjects had a higher frequency of DR9 than CO subjects. Accordingly, the DR9:DR4 frequency increased with increasing age of onset. Another susceptible haplotype, DRB1*0802-DQB1*0302 (DR8), was involved only in the CO group. Analysis of haplotype combinations revealed that DR4 and DR9 had significant dosage effects on the AO and CO groups (P < 0.0001), but only DR9 had such an effect in the SO group (P < 0.03). These results suggest differences in the contribution of HLA class II haplotypes to susceptibility of type 1 diabetes depending on the clinical phenotype and also indicate that HLA class II haplotypes may be associated with the onset age of type 1 diabetes.
Intercellular Adhesion Molecule-1 Concentration Is Genetically Correlated With Insulin Resistance, Obesity, and HDL Concentration in Mexican Americans
Authors: Kent Jack W. , Comuzzie Anthony G. , Mahaney Michael C. , Almasy Laura , Rainwater David L. , VandeBerg John L. , MacCluer Jean W. , Blangero John
Published: March 2007

The metabolic syndrome and type 2 diabetes are associated with endothelial activation (and thus with inflammatory processes leading to atherosclerosis), but the mechanisms that underlie these associations are not fully understood. Endothelial intercellular adhesion molecule (ICAM)-1 plays an important role in the recruitment of immune cells during the development of atherosclerotic plaque and is a marker of inflammatory disease. We performed bivariate quantitative genetic analyses to estimate genetic and environmental correlations between circulating ICAM-1 concentration and 17 phenotypes associated with the metabolic syndrome. Our study population comprised 428 adults in 20 extended Mexican-American families from the San Antonio Family Heart Study (SAFHS). Circulating ICAM-1 concentration is heritable (h2 = 0.56). ICAM-1 concentration showed significant positive genetic correlations (range 0.32–0.52, P < 0.05) with fasting insulin, insulin 2 h after oral glucose challenge, homeostasis model assessment of insulin resistance, BMI, waist circumference, and leptin concentration; negative genetic correlation with HDL3 cholesterol concentration; and negative environmental correlation with adiponectin concentration. Significant genetic correlations were not found between ICAM-1 and fasting or 2-h serum glucose or systolic or diastolic blood pressure. Thus, ICAM-1 expression may share common genetic modulation with traits related to obesity, insulin resistance, and HDL3 cholesterol, but not with hyperglycemia or hypertension per se.
CCAAT/Enhancer Binding Protein and Nuclear Factor-Y Regulate Adiponectin Gene Expression in Adipose Tissue
Authors: Park Sang-kyu , Oh So-Young , Lee Min-Young , Yoon Sarah , Kim Kyung-Sup , Kim Jae-woo
Published: March 2007

Adiponectin is one of the adipokines secreted by adipocytes and regulates energy homeostasis associated with insulin sensitivity, suggesting a possibility of nutritional regulation of adiponectin gene expression. In this study, we showed that the transcription of adiponectin gene was induced 4–6 h after refeeding of mice. Also, differentiated 3T3-L1 adipocytes that were treated with high glucose expressed significantly increased adiponectin mRNA. Promoter analysis using nuclear extracts from white adipose tissue revealed that CCAAT/enhancer binding protein (C/EBP) and nuclear factor-Y (NF-Y) bound on the −117/−73 region of the adiponectin promoter. This region was critical for the activity of the adiponectin promoter as the deletion or mutation of this region markedly diminished the promoter activity to a basal level. Furthermore, the C/EBP binding increased in both refed animal and high glucose-treated 3T3-L1 adipocytes in an electrophoretic mobility shift assay, suggesting that C/EBP is responsible for the dietary response of the adiponectin gene expression. Chromatin immunoprecipitation studies demonstrated the binding of C/EBP and NF-Y in both mouse and differentiated 3T3-L1 adipocytes and also that C/EBP binding increased in response to high glucose. These findings demonstrated that C/EBP and NF-Y are critical for the regulation of the adiponectin expression in response to nutrients and in the course of adipocyte differentiation.
Activated Protein C Preserves Functional Islet Mass After Intraportal Transplantation
Authors: Contreras Juan L. , Eckstein Christopher , Smyth Cheryl A. , Bilbao Guadalupe , Vilatoba Mario , Ringland Sharman E. , Young Carlton , Thompson J. Anthony , Fernández José A. , Griffin John H. , Eckhoff Devin E.
Published: March 2007

Clinical studies indicate that significant loss of functional islet mass occurs in the peritransplant period. Islets are injured as a result of detrimental effects of brain death, pancreas preservation, islet isolation, hypoxia, hyperglycemia, and immune-mediated events. In addition, recent studies demonstrated that islets are injured as a result of their exposure to blood and of activation of intrahepatic endothelial and Kupffer cells, resulting in inflammation and thrombosis. Activated protein C (APC) is an anticoagulant enzyme that also exerts anti-inflammatory and antiapoptotic activities by acting directly on cells. Here, we report that exogenous administration of recombinant murine APC (mAPC) significantly reduced loss of functional islet mass after intraportal transplantation in diabetic mice. Animals given mAPC exhibited better glucose control, higher glucose disposal rates, and higher arginine-stimulated acute insulin release. These effects were associated with reduced plasma proinsulin, intrahepatic fibrin deposition, and islet apoptosis early after the transplant. In vitro and in vivo data demonstrated that mAPC treatment was associated with a significant reduction of proinflammatory cytokine release after exposure of hepatic endothelial cells to islets. mAPC treatment also prevented endothelial cell activation and dysfunction elicited by intrahepatic embolization of isolated islets inherent to pancreatic islet transplantation (PIT). This study demonstrates multiple remarkable beneficial effects of mAPC for PIT and suggests that APC therapy may enhance the therapeutic efficacy of PIT in diabetic patients.
A Possible Link Between Skeletal Muscle Mitochondrial Efficiency and Age-Induced Insulin Resistance
Authors: Iossa Susanna , Mollica Maria Pina , Lionetti Lillà , Crescenzo Raffaella , Tasso Rosaria , Liverini Giovanna
Published: March 2007

The transition from young to adult age is associated with decreased insulin sensitivity. To investigate whether changes in skeletal muscle mitochondrial function could be involved in the development of insulin resistance, we measured the oxidative capacity and energetic efficiency of subsarcolemmal and intermyofibrillar mitochondria isolated from the skeletal muscle of 60- and 180-day-old rats. Mitochondrial efficiency was tested by measuring the degree of thermodynamic coupling and optimal thermodynamic efficiency, as well as mitochondrial proton leak, which was determined in both the absence (basal) and the presence (fatty acid induced) of palmitate. Serum glucose, insulin, and HOMA index were also measured. The results show that in adult rats, concomitant with increased HOMA index, skeletal muscle mitochondria display higher respiratory capacity and energy efficiency. In fact, thermodynamic coupling and optimal thermodynamic efficiency significantly increased and fatty acid-induced proton leak was significantly lower in the skeletal muscle mitochondria from adult than in younger rats. A deleterious consequence of increased mitochondrial efficiency would be a reduced utilization of energy substrates, especially fatty acids, leading to intracellular triglyceride accumulation and lipotoxicity, thus contributing to the onset of skeletal muscle insulin resistance.