bluuebunny/crossref_metadata_2025 huggingface dataset:
Deconstructing and Reconstructing Obesity-Induced Diabetes (Diabesity) in Mice
Authors: Reifsnyder Peter C. , Leiter Edward H.
Published: March 2007

Obesity-driven type 2 diabetes (diabesity) involves complex genetic and environmental interactions to trigger disease. Here, we combine variable numbers of known quantitative trait loci (QTL) for obesity and diabetes contributed by New Zealand Obese (NZO/HlLt) and Nonobese Nondiabetic (NON/Lt) strains in the form of 10 interval-directed recombinant congenic strains (RCS), with NON/Lt as the background strain, to dissect the genetic interactions involved. All 10 RCS gain significantly more weight than the NON parental strain, but none are as obese as the parental, diabetes-prone NZO. Diabetes development in these RCS at F12 ranges between 0 and 100%, depending on genetic constitution. RCS-2, -1, and -10 represent a step-wise increase in numbers of specific diabetogenic QTL, resulting in a step-wise increase in diabetes incidence. RCS-10 recreates the 100% incidence seen in (NZOxNON)F1 males, but with less weight gain. Similarly, RCS-6, -7, -8, and -9 represent diabetes-prone strains with different combinations of diabetogenic QTL. RCS-3, -4, and -5 represent obese strains that do not transit to diabetes. Because these obesity and diabetes syndromes reflect different collections of QTL, rather than null mutations in the leptin or leptin receptor genes, they are extremely relevant as models for the polygenic obesity/diabesity syndromes in humans.
Human Obesity and Type 2 Diabetes Are Associated With Alterations in SREBP1 Isoform Expression That Are Reproduced Ex Vivo by Tumor Necrosis Factor-α
Authors: Sewter Ciaran , Berger Dirk , Considine Robert V. , Medina Gema , Rochford Justin , Ciaraldi Theodore , Henry Robert , Dohm Lynis , Flier Jeffrey S. , O’Rahilly Stephen , Vidal-Puig Antonio J.
Published: March 2007

Sterol regulatory element binding protein (SREBP)-1 is a transcription factor with important roles in the control of fatty acid metabolism and adipogenesis. Little information is available regarding the expression of this molecule in human health or disease. Exposure of isolated human adipocytes to insulin enhanced SREBP1 gene expression and promoted its proteolytic cleavage to the active form. Furthermore, 3 h of in vivo hyperinsulinemia also significantly increased SREBP1 gene expression in human skeletal muscle. Transcript levels of SREBP1c, the most abundant isoform in adipose tissue, were significantly decreased in the subcutaneous adipose tissue of obese normoglycemic and type 2 diabetic subjects compared with that of nonobese normoglycemic control subjects. In skeletal muscle, SREBP1 expression was significantly reduced in type 2 diabetic subjects but not in obese subjects. Within the diabetic group, the extent of SREBP1 suppression was inversely related to metabolic control and was normalized by 3 h of in vivo hyperinsulinemia. Exposure of isolated human adipocytes to tumor necrosis factor-α (TNF-α) produced a marked and specific decrease in the mRNA encoding the SREBP1c isoform and completely blocked the insulin-induced cleavage of SREBP1 protein. Thus, both the expression and proteolytic maturation of human SREBP1 are positively modulated by insulin. The specific reduction in the SREBP1c isoform seen in the adipose tissue of obese and type 2 diabetic subjects can be recapitulated ex vivo by TNF-α, suggesting a possible mechanism for this association.
Low Production Capacity of Interleukin-10 Associates With the Metabolic Syndrome and Type 2 Diabetes
Authors: van Exel Eric , Gussekloo Jacobijn , de Craen Anton J.M. , Frölich Marijke , Bootsma-van der Wiel Annetje , Westendorp Rudi G.J.
Published: March 2007

It has been suggested that the metabolic syndrome and type 2 diabetes are manifestations of the inflammatory host response. This host response is orchestrated by the production of pro- and anti-inflammatory cytokines that are under genetic control. We therefore hypothesized that a low production capacity of interleukin-10 (IL-10), a centrally operating cytokine with strong anti-inflammatory properties, associates with the metabolic syndrome and type 2 diabetes in old age. In the current study, 599 inhabitants of the city of Leiden, age 85 years, were visited at their place of residence. The production capacity of the anti-inflammatory cytokine IL-10 was assessed in a whole-blood assay in which lipopolysaccharide was used as a stimulus. Serum concentrations of lipids, lipoproteins, glucose, and HbA1c were determined, and a history of type 2 diabetes was obtained. Serum concentrations of total cholesterol, LDL cholesterol, triglycerides, glucose, and HbA1c gradually decreased over strata representing higher IL-10 production capacity, whereas the concentration of HDL cholesterol gradually increased (all P < 0.01). The odds ratio for type 2 diabetes was 2.7 (95% confidence interval 1.5–4.9) when subjects with the lowest IL-10 production capacity were compared with those with the highest IL-10 production capacity. These findings showed that low IL-10 production capacity (i.e., a pro-inflammatory response) is associated with the metabolic syndrome and type 2 diabetes.
Overexpression of the Sarcoplasmic Reticulum Ca2+-ATPase Improves Myocardial Contractility in Diabetic Cardiomyopathy
Authors: Trost Susanne U. , Belke Darrell D. , Bluhm Wolfgang F. , Meyer Markus , Swanson Eric , Dillmann Wolfgang H.
Published: March 2007

Diabetic cardiomyopathy is characterized by reduced cardiac contractility due to direct changes in heart muscle function independent of vascular disease. An important contributor to contractile dysfunction in the diabetic state is an impaired sarcoplasmic reticulum (SR) function, leading to disturbed intracellular calcium handling. We investigated whether overexpression of the SR calcium pump (SERCA2a) in transgenic mice could reduce the impact of diabetes on the development of cardiomyopathy. Diabetes was induced by streptozotocin injection (200 mg/kg), and left ventricular (LV) function was analyzed in isolated hearts 3 weeks later. In diabetic hearts systolic LV pressure was decreased by 15% and maximum speed of relaxation (−dP/dt) by 34%. Functional changes were also assessed in isolated papillary muscles. Active force was reduced by 61% and maximum speed of relaxation by 65% in the diabetic state. The contractile impairment was accompanied by a 30% decrease in SERCA2a protein in diabetic mice. We investigated whether increased SERCA2a expression in transgenic SERCA2a-overexpressing mice could compensate for the diabetes-induced decrease in cardiac function. Under normal conditions, SERCA2a overexpressors show improved contractile performance relative to wild-type (WT) mice (−dP/dt: 3,169 vs. 2,559 mmHg/s, respectively). Measurement of LV function in hearts from diabetic SERCA2a mice revealed systolic and diastolic functions that were similar to WT control mice and markedly improved relative to diabetic WT mice (−dP/dt: 2,534 vs. 1,690 mmHg/s in diabetic SERCA2a vs. diabetic WT mice, respectively). Similarly, the contractile behavior of isolated papillary muscles from diabetic SERCA2a mice was not different from that of control mice. SERCA2a protein expression was higher (60%) in diabetic SERCA2a mice than WT diabetic mice. These results indicate that overexpression of SERCA2a can protect diabetic hearts from severe contractile dysfunction, presumably by improving the calcium sequestration of the SR.
Polymorphism in Ecto-Nucleotide Pyrophosphatase/Phosphodiesterase 1 Gene (ENPP1/PC-1) and Early Development of Advanced Diabetic Nephropathy in Type 1 Diabetes
Authors: Canani Luis H. , Ng Daniel P.K. , Smiles Adam , Rogus John J. , Warram James H. , Krolewski Andrzej S.
Published: March 2007

A polymorphism in the ecto-nucleotide pyrophosphatase/phosphodiesterase 1 gene (ENPP1) (previously known as PC-1), resulting in an amino acid change from lysine to glutamine at codon 121 (K121Q), is associated with insulin resistance. A small follow-up study of patients with type 1 diabetes and proteinuria found that renal function declines more rapidly in carriers of the Q variant than in noncarriers. To examine this finding further, we conducted a large case-control study and a family-based study. Genomic DNA was obtained from 659 patients: 307 with normal urinary albumin excretion despite diabetes duration of >15 years (control subjects) and 352 with advanced diabetic nephropathy, of whom 200 had persistent proteinuria and 152 had end-stage renal disease (ESRD). Individuals were genotyped for Q and K variants using a previously described protocol. The frequency of Q variant carriers was 21.5% in control subjects, 31.5% in subjects with proteinuria, and 32.2% in subjects with ESRD (P = 0.012). In a stratified analysis according to duration of diabetes, the risk of early-onset ESRD for carriers of the Q variant was 2.3 times that for noncarriers (95% CI, 1.2–4.6). The Q variant was not associated with late-onset ESRD. Similar findings were obtained in a family-based study. We conclude that carriers of the Q variant of ENPP1 are at increased risk for developing ESRD early in the course of type 1 diabetes.
A Common Promoter Polymorphism in the Hepatic Lipase Gene (LIPC-480C>T) Is Associated With an Increase in Coronary Calcification in Type 1 Diabetes
Authors: Hokanson John E. , Cheng Suzanne , Snell-Bergeon Janet K. , Fijal Bonnie A. , Grow Michael A. , Hung Chi , Erlich Henry A. , Ehrlich James , Eckel Robert H. , Rewers Marian
Published: March 2007

Type 1 diabetes is associated with coronary heart disease (CHD) and coronary artery calcification (CAC), a measure of subclinical CHD. The hepatic lipase gene promoter polymorphism (LIPC-480C>T) is a common variant affecting lipid metabolism. This study examined the relation between the LIPC-480C>T and CAC in type 1 diabetes. In the type 1 diabetic patients studied, 56% had CAC >0 Agatston units (AU). These subjects had a longer duration of diabetes (26.2 ± 1.3 vs. 17.8 ± 1.4 years; P < 0.001), lower HDL cholesterol levels (55.7 ± 2.4 vs. 61.0 ± 2.5 mg/dl; P = 0.05), higher triglyceride levels (101 ± 17.3 vs. 66 ± 7.6 mg/dl; P < 0.05), and higher diastolic blood pressure (79.7 ± 1.0 vs. 76.0 ± 1.4 mmHg; P < 0.05). The LIPC-480 T allele was more common in subjects with CAC (frequency = 0.31 ± 0.05 vs. 0.14 ± 0.04; P = 0.006). The proportion with CAC was 44% in LIPC-480CC subjects, 71% in heterozygotes, and 83% in LIPC-480TT subjects (P < 0.01). LIPC-480 T allele frequency increased as the amount of CAC increased (P = 0.007). LIPC-480 genotype was independently associated with the CAC (odds ratio = 2.90, 95% CI 1.22–6.92, P < 0.05) after adjusting for duration of diabetes, age, sex, diastolic blood pressure, HDL cholesterol, and triglyceride levels. In conclusion, the LIPC-480C>T polymorphism was associated with subclinical CHD in type 1 diabetes. This genetic variant may identify subjects in which early intervention to prevent CHD may be appropriate.
Peroxisome Proliferator-Activated Receptor-γ Coactivator-1 Gene Locus
Authors: Esterbauer Harald , Oberkofler Hannes , Linnemayr Veronika , Iglseder Bernhard , Hedegger Margot , Wolfsgruber Peter , Paulweber Bernhard , Fastner Gerd , Krempler Franz , Patsch Wolfgang
Published: March 2007

Peroxisome proliferator–activated receptor-γ coactivator-1 (PPARGC1) is a transcriptional coactivator that has been implicated in the regulation of genes involved in energy metabolism. We studied associations of two polymorphisms identified in PPARGC1 transcripts with obesity indices in 591 middle-aged men and 467 middle-aged women of a cross-sectional Austrian population. Because neither polymorphic site was likely to be a functional site, we analyzed sex-specific associations of two loci haplotype combinations with obesity indices. Significant associations with BMI (P = 0.006), waist (P = 0.01) and hip circumference (P = 0.03), and total body fat (P = 0.005) and borderline significant associations with abdominal visceral and subcutaneous fat were observed in women but not men. In women, plasma triglycerides, HDL cholesterol, and glucose significantly differed by haplotype combinations, but these associations were not maintained after statistical consideration of BMI. The haplotype combination of the double-variant allele with the double–wild-type allele was associated with the lowest obesity indices, whereas homozygosity for the double-variant allele was not discriminatory among haplotype combinations. These studies suggest functional differences of PPARGC1 haplotypes in human energy metabolism and support a role of PPARGC1 in obesity.
Decreased Vascular Density in Mouse Pancreatic Islets After Transplantation
Authors: Mattsson Göran , Jansson Leif , Carlsson Per-Ola
Published: March 2007

An adequate revascularization is crucial for islet survival and function after transplantation. Previous studies have suggested that islet revascularization is concluded within 14 days after transplantation. We investigated if the vascular density of transplanted islets and endogenous pancreatic islets differs. Cultured islets were syngeneically transplanted into the kidney, liver, or spleen of C57BL/6 mice. One month later, the graft-bearing organ was removed, and histological specimens were prepared and stained for endothelium with the lectin Bandeiraea simplicifolia. Pancreata from nontransplanted control animals were prepared similarly. Uniform staining of endothelium within the grafts and endogenous islets was obtained. The vascular density was markedly decreased in transplanted islets at all implantation sites, but preferentially in islets implanted into the spleen. The vascular density in the connective tissue surrounding the transplanted islets was very high compared with that of graft intra-islet capillaries. A much lower vascular density was detected in connective tissue surrounding implanted microspheres of a size similar to the islets, which suggests that the islets per se induced blood vessel formation in their vicinity. We conclude that the vascular density in revascularized transplanted islets is markedly decreased compared with endogenous islets. This has potential implications for islet graft metabolism and function.
Increased Efficiency of Fatty Acid Uptake Contributes to Lipid Accumulation in Skeletal Muscle of High Fat-Fed Insulin-Resistant Rats
Authors: Hegarty Bronwyn D. , Cooney Gregory J. , Kraegen Edward W. , Furler Stuart M.
Published: March 2007

In humans and animal models, increased lipid content of skeletal muscle is strongly associated with insulin resistance. However, it is unclear whether this accumulation is due to increased uptake or reduced utilization of fatty acids (FAs). We used 3H-R-bromopalmitate tracer to assess the contribution of tissue-specific changes in FA uptake to the lipid accumulation observed in tissues of insulin-resistant, high fat-fed rats (HFF) compared with control rats (CON) fed a standard diet. To study FA metabolism under different metabolic states, tracer was infused under basal conditions, during hyperinsulinemic-euglycemic clamp (low FA availability) or during the infusion of intralipid and heparin (high FA availability). FA clearance was significantly increased in the red gastrocnemius muscle of HFF under conditions of low (HFF = 10.4 ± 1.1; CON = 7.4 ± 0.5 ml · min−1 · 100 g−1; P < 0.05), basal (HFF = 8.3 ± 1.4; CON = 4.5 ± 0.7 ml · min−1 · 100 g−1; P < 0.01), and high (HFF = 7.0 ± 0.8; CON = 4.3 ± 0.5 ml · min−1 · 100 g−1; P < 0.05) FA levels. This indicates an adaptation by muscle for more efficient uptake of lipid. Associated with the enhanced efficiency of FA uptake, we observed increases in CD36/FA translocase mRNA expression (P < 0.01) and acyl-CoA synthetase activity (P < 0.02) in the same muscle. FA clearance into white adipose tissue was also increased in HFF when circulating FA were elevated, but there was little effect of the high-fat diet on hepatic FA uptake. In conclusion, insulin resistance induced by feeding rats a high-fat diet is associated with tissue-specific adaptations that enhance utilization of increased dietary lipid but could also contribute to the accumulation of intramuscular lipid with a detrimental effect on insulin action.
Direct Evidence for Insulin-Induced Capillary Recruitment in Skin of Healthy Subjects During Physiological Hyperinsulinemia
Authors: Serné Erik H. , IJzerman Richard G. , Gans Reinold O.B. , Nijveldt Robin , de Vries Greetje , Evertz Reinder , Donker Ab J.M. , Stehouwer Coen D.A.
Published: March 2007

It has been proposed that insulin-mediated changes in muscle perfusion modulate insulin-mediated glucose uptake. However, the putative effects of insulin on the microcirculation that permit such modulation have not been studied in humans. We examined the effects of systemic hyperinsulinemia on skin microvascular function in eight healthy nondiabetic subjects. In addition, the effects of locally administered insulin on skin blood flow were assessed in 10 healthy subjects. During a hyperinsulinemic clamp, we measured leg blood flow with venous occlusion plethysmography, skin capillary density with capillaroscopy, endothelium-(in)dependent vasodilatation of skin microcirculation with iontophoresis of acetylcholine and sodium nitroprusside combined with laser Doppler fluxmetry, and skin vasomotion by Fourier analysis of microcirculatory blood flow. To exclude nonspecific changes in the hemodynamic variables, a time-volume control study was performed. Insulin iontophoresis was used to study the local effects of insulin on skin blood flow. Compared to the control study, systemic hyperinsulinemia caused an increase in leg blood flow (−0.54 ± 0.93 vs. 1.97 ± 1.1 ml · min−1 · dl−1; P < 0.01), an increase in the number of perfused capillaries in the resting state (−3.7 ± 3.0 vs. 3.4 ± 1.4 per mm2; P < 0.001) and during postocclusive reactive hyperemia (−0.8 ± 2.2 vs. 5.1 ± 3.7 per mm2; P < 0.001), an augmentation of the vasodilatation caused by acetylcholine (722 ± 206 vs. 989 ± 495%; P < 0.05) and sodium nitroprusside (618 ± 159 vs. 788 ± 276%; P < 0.05), and a change in vasomotion by increasing the relative contribution of the 0.01- to 0.02-Hz and 0.4- to 1.6-Hz spectral components (P < 0.05). Compared to the control substance, locally administered insulin caused a rapid increase (∼13.5 min) in skin microcirculatory blood flow (34.4 ± 42.5 vs. 82.8 ± 85.7%; P < 0.05). In conclusion, systemic hyperinsulinemia in skin 1) induces recruitment of capillaries, 2) augments nitric oxide−mediated vasodilatation, and 3) influences vasomotion. In addition, locally administered insulin 4) induces a rapid increase in total skin blood flow, independent of systemic effects.
The Genetics of Hypertension Modifies the Renal Cell Replication Response Induced by Experimental Diabetes
Authors: Silveira Lilia A. , Bacchi Carlos E. , Pinto Glauce A. , de Faria José B. Lopes
Published: March 2007

To investigate whether the genetics of hypertension modifies renal cell responses in experimental diabetes, we studied the renal cell replication and its regulation by two cyclin-dependent kinase (Cdk) inhibitors, p27Kip1 and p21Cip1, in prehypertensive spontaneously hypertensive rats (SHR) and their genetically normotensive counterparts, Wistar Kyoto (WKY) rats, with and without streptozotocin-induced diabetes. In diabetic SHR, the number of proliferating glomerular (0.6 ± 0.3 positive cells/50 glomeruli) and tubulointerstitial (2.8 ± 0.6 positive tubulointerstitial cells/50 grid fields) cells assessed by the bromodeoxyuridine technique was significantly (P = 0.0002) lower than in control SHR (13.2 ± 1.7 and 48.6 ± 9.7, respectively) and control (14.0 ± 1.8 and 63.9 ± 10.6) and diabetic (14.3 ± 3.5 and 66.4 ± 11.5) WKY rats. Proliferating cell nuclear antigen, another marker of cell proliferation, was significantly reduced in replicating glomerular (P = 0.0002) and tubulointerstitial (P < 0.0001) cells in diabetic SHR. In freshly isolated glomeruli, the level of p27Kip1 detected by Western blotting was significantly higher in diabetic SHR than in nondiabetic SHR (1.52 ± 0.14 vs. 1.00 ± 0.10% of control, P = 0.014). The expression of p21Cip1 in isolated glomeruli did not differ among the groups of rats. In conclusion, the response of renal cell replication to diabetes differs markedly between prehypertensive SHR and their WKY control rats. The decreased glomerular cell proliferation in prehypertensive diabetic SHR is at least partly mediated by a higher expression of the Cdk inhibitor p27Kip1.
IL12B Polymorphism and Type 1 Diabetes in the Italian Population
Authors: Nisticò Lorenza , Giorgi Gabriele , Giordano Mara , Galgani Andrea , Petrone Antonio , D’Alfonso Sandra , Federici Massimo , Di Mario Umberto , Pozzilli Paolo , Buzzetti Raffaella , Cascino Isabella
Published: March 2007

A polymorphism in the interleukin 12B gene was recently reported to be strongly associated with type 1 diabetes in 422 Australian and British families. We analyzed the same polymorphism in 470 Italian type 1 diabetic patients and 544 matched control subjects and found no evidence of association with the disease.
Differential Effects of Fenofibrate or Simvastatin Treatment of Rats on Hepatic Microsomal Overt and Latent Diacylglycerol Acyltransferase Activities
Authors: Waterman Ian J. , Zammit Victor A.
Published: March 2007

Hepatic triacylglycerol secretion is elevated in insulin-resistant states. Microsomal diacylglycerol acyltransferase (DGAT) catalyzes the final reaction in the synthesis of triacylglycerol (TAG). We have previously described two DGAT activities in rat liver microsomes, one overt (cytosol-facing) and one latent (endoplasmic reticulum lumen–facing) (Owen MR, Corstorphine CG, Zammit VA: Overt and latent activities of diacylglycerol acytransferase in rat liver microsomes: possible roles in very-low-density lipoprotein triacylglycerol secretion. Biochem J 323:17–21, 1977). It was suggested that they are involved in the synthesis of TAG for the cytosolic droplet and VLDL lipidation, respectively. In the present study, we measured the overt and latent DGAT activities in rats fed diets containing one of two hypolipidemic drugs: fenofibrate (a peroxisome proliferator–activated receptor α [PPARα] agonist) and simvastatin (a 3-hydroxy-3-methylglutaryl [HMG]-CoA reductase inhibitor). We found that the activities of the two DGATs could be varied independently by these treatments. Fenofibrate raised overt DGAT activity but lowered that of latent DGAT. In contrast, simvastatin markedly lowered overt DGAT activity without affecting that of latent DGAT. The increase in overt DGAT activity induced by fenofibrate could not be mimicked by feeding a diet enriched in n-3 polyunsaturated fatty acids (PUFA), which lowered overt DGAT activity but did not affect latent DGAT, suggesting that n-3 PUFA act through a mechanism independent of PPARα activation. The fibrate-induced increase in overt DGAT activity and the inhibition of latent DGAT may provide a mechanism through which acyl moieties are retained within the liver for oxidation through the pathways concomitantly upregulated by PPARα activation.
Sterol Regulatory Element Binding Protein-1c Expression and Action in Rat Muscles: Insulin-Like Effects on the Control of Glycolytic and Lipogenic Enzymes and UCP3 Gene Expression
Authors: Guillet-Deniau Isabelle , Mieulet Virginie , Le Lay Soazig , Achouri Younes , Carré Denis , Girard Jean , Foufelle Fabienne , Ferré Pascal
Published: March 2007

Sterol regulatory element binding protein-1c (SREBP-1c) is a transcription factor that mediates insulin effects on hepatic gene expression. It is itself transcriptionally stimulated by insulin in hepatocytes. Here we show that SREBP-1c mRNA is expressed in adult rat skeletal muscles and that this expression is decreased by diabetes. The regulation of SREBP-1c expression was then assessed in cultures of adult muscle satellite cells. These cells form spontaneously contracting multinucleated myotubes within 7 days of culture. SREBP-1c mRNA is expressed in contracting myotubes. A 4-h treatment with 100 nmol/l insulin increases SREBP-1c expression and nuclear abundance by two- to threefold in myotubes. In cultured myotubes, insulin increases the expression of glycolytic and lipogenic enzyme genes and inhibits the 9-cis retinoic acid-induced UCP3 expression. These effects of insulin are mimicked by adenovirus-mediated expression of a transcriptionally active form of SREBP-1c. We conclude that in skeletal muscles, SREBP-1c expression is sensitive to insulin and can transduce the positive and negative actions of the hormone on specific genes and thus has a pivotal role in long-term muscle insulin sensitivity.
The Novel Diazoxide Analog 3-Isopropylamino-7-Methoxy-4H-1,2,4-Benzothiadiazine 1,1-Dioxide Is a Selective Kir6.2/SUR1 Channel Opener
Authors: Dabrowski Michael , Ashcroft Frances M. , Ashfield Rebecca , Lebrun Philippe , Pirotte Bernard , Egebjerg Jan , Bondo Hansen John , Wahl Philip
Published: March 2007

ATP-sensitive K+ (KATP) channels are activated by a diverse group of compounds known as potassium channel openers (PCOs). Here, we report functional studies of the Kir6.2/SUR1 Selective PCO 3-isopropylamino-7-methoxy-4H-1,2,4-benzothiadiazine 1,1-dioxide (NNC 55-9216). We recorded cloned KATP channel currents from inside-out patches excised from Xenopus laevis oocytes heterologously expressing Kir6.2/SUR1, Kir6.2/SUR2A, or Kir6.2/SUR2B, corresponding to the β-cell, cardiac, and smooth muscle types of the KATP channel. NNC 55-9216 reversibly activated Kir6.2/SUR1 currents (EC50 = 16 μmol/l). This activation was dependent on intracellular MgATP and was abolished by mutation of a single residue in the Walker A motifs of either nucleotide-binding domain of SUR1. The drug had no effect on Kir6.2/SUR2A or Kir6.2/SUR2B currents. We therefore used chimeras of SUR1 and SUR2A to identify regions of SUR1 involved in the response to NNC 55-9216. Activation was completely abolished and significantly reduced by swapping transmembrane domains 8–11. The reverse chimera consisting of SUR2A with transmembrane domains 8–11 and NBD2 consisting SUR1 was activated by NNC 55-9216, indicating that these SUR1 regions are important for drug activation. [3H]glibenclamide binding to membranes from HEK293 cells transfected with SUR1 was displaced by NNC 55-9216 (IC50 = 105 μmol/l), and this effect was impaired when NBD2 of SUR1 was replaced by that of SUR2A. These results suggest NNC 55-9216 is a SUR1-selective PCO that requires structural determinants, which differ from those needed for activation of the KATP channel by pinacidil and cromakalim. The high selectivity of NNC 55-9216 may prove to be useful for studies of the molecular mechanism of PCO action.
Mutations in the Human Leptin and Leptin Receptor Genes as Models of Serum Leptin Receptor Regulation
Authors: Lahlou Najiba , Issad Tarik , Lebouc Yves , Carel Jean-Claude , Camoin Luc , Roger Marc , Girard Jean
Published: March 2007

A part of serum Ob leptin, an adipocyte-secreted peptide, is bound to a soluble Ob receptor (sObR). Immunoreactive sObR was measured in 125 lean or obese control subjects (group 1), 18 individuals with a mutation in the leptin gene impairing leptin secretion (group 2), and 10 individuals with a mutation in the ObR gene, leading to production of a truncated ObR not anchored to cell membranes (group 3). In group 1, sObR levels were negatively correlated with age and BMI in children and with BMI in adults. sObR levels were also negatively correlated with leptin levels. Leptin binding activity and sObR levels coeluted in gel-filtration chromatography. In group 2, sObR levels did not differ from those in lean control subjects and were not correlated with BMI. A single peak was detected in chromatographic fractions. In group 3, sObR levels were high and positively correlated with BMI. Immunoreactive sObR coeluted with leptin binding activity. These data demonstrate that leptin is not needed for ObR gene expression, and they suggest that leptin plays a role in receptor downregulation because sObR levels are negatively correlated with leptin levels and BMI in control subjects, whereas sObR levels are not depressed in obese leptin-deficient or leptin receptor–deficient individuals.
Improved Insulin Sensitivity Is Associated With Restricted Intake of Dietary Glycoxidation Products in the db/db Mouse
Authors: Hofmann Susanna M. , Dong Heng-Jiang , Li Zhu , Cai Weijing , Altomonte Jennifer , Thung Swan N. , Zeng Feng , Fisher Edward A. , Vlassara Helen
Published: March 2007

Advanced glycation end products (AGEs), known promoters of diabetic complications, form abundantly in heated foods and are ingested in bioreactive forms. To test whether dietary AGEs play a role in the progression of insulin resistance, C57/BL/KsJ db/db mice were randomly placed for 20 weeks on a diet with either a low AGE content (LAD) or a 3.4-fold higher content of AGE (high AGE diet [HAD]), including εN-carboxymethyllysine (CML) and methylglyoxal (MG). LAD-fed mice showed lower fasting plasma insulin levels throughout the study (P = 0.01). Body weight was reduced by ∼13% compared with HAD-fed mice (P = 0.04) despite equal food intake. LAD-fed mice exhibited significantly improved responses to both glucose (at 40 min, P = 0.003) and insulin (at 60 min, P = 0.007) tolerance tests, which correlated with a twofold higher glucose uptake by adipose tissue (P = 0.02). Compared with the severe hypertrophy and morphological disorganization of islets from HAD-fed mice, LAD-fed mice presented a better-preserved structure of the islets. LAD-fed mice demonstrated significantly increased plasma HDL concentrations (P < 0.0001). Consistent with these observations, LAD-fed mice exhibited twofold lower serum CML and MG concentrations compared with HAD-fed mice (P = 0.02). These results demonstrate that reduced AGE intake leads to lower levels of circulating AGE and to improved insulin sensitivity in db/db mice.
Minor Effect of GLUT1 Polymorphisms on Susceptibility to Diabetic Nephropathy in Type 1 Diabetes
Authors: Ng Daniel P.K. , Canani Luis , Araki Shin-ichi , Smiles Adam , Moczulski Dariusz , Warram James H. , Krolewski Andrzej S.
Published: March 2007

Elevation of intracellular glucose in mesangial cells as mediated by GLUT1 may be important in initiating cellular mechanisms that cause diabetic nephropathy. To determine whether DNA sequence differences in GLUT1 confer susceptibility to this complication, single-nucleotide polymorphisms (SNPs) in this gene were examined using a large case-control study. SNPs examined included the known XbaI (intron 2) and HaeIII SNPs (exon 2). Four novel SNPs located in three putative enhancers were also investigated. Homozygosity for the XbaI(-) allele was associated with diabetic nephropathy (odds ratio 1.83 [95% CI 1.01–3.33]). Furthermore, homozygosity for the A allele for a novel SNP (enhancer-2 SNP 1) located in a putative insulin-responsive enhancer-2 was associated with diabetic nephropathy (2.38 [1.16–4.90]). Patients who were homozygous for risk alleles at both XbaI SNP and enhancer-2 SNP 1 [i.e., homozygosity for XbaI(-)/A haplotype] also had an increased risk of diabetic nephropathy (2.40 [1.13–5.07]). Because enhancer-2 SNP 1 may directly control GLUT1 expression, the strong linkage disequilibrium between the two SNPs likely accounts for XbaI SNP being associated with diabetic nephropathy. In conclusion, our study confirms that SNPs at the GLUT1 locus are associated with susceptibility to diabetic nephropathy in type 1 diabetes. Although these SNPs confer a considerable personal risk for diabetic nephropathy, they account for a limited proportion of cases among type 1 diabetic patients.
Maturity-Onset Diabetes of the Young Caused by a Balanced Translocation Where the 20q12 Break Point Results in Disruption Upstream of the Coding Region of Hepatocyte Nuclear Factor-4α (HNF4A) Gene
Authors: Gloyn Anna L. , Ellard Sian , Shepherd Maggie , Howell Rodney T. , Parry Elizabeth M. , Jefferson Andrew , Levy Elaine R. , Hattersley Andrew T.
Published: March 2007

Monogenic human disorders have been used as paradigms for complex genetic disease and as tools for establishing important insights into mechanisms of gene regulation and transcriptional control. Maturity-onset diabetes of the young (MODY) is a monogenic dominantly inherited form of diabetes that is characterized by defective insulin secretion from the pancreatic β-cells. A wide variety of mutation types in five different genes have been identified that result in this condition. There have been no reports of a chromosome deletion or translocation resulting in MODY. We report a pedigree where MODY cosegregates with a balanced translocation [karyotype 46, XX t(3;20) (p21.2;q12)]. The chromosome 20 break point, 20q12, is within the region of one of the known MODY genes, hepatocyte nuclear factor-4α (HNF4A). Fluorescence in situ hybridization analysis demonstrated that the break point does not disrupt the coding region of this gene, but it lies at least 6 kb upstream of the conventional promoter (P1). We propose that this mutation disrupts the spatial relationship between the recently described alternate distal pancreatic promoter (P2) and HNF4A. This is the first case of MODY due to a balanced translocation, and it provides evidence to confirm the crucial role of an upstream regulator of HNF4A gene expression in the β-cell.
IL-12p40Is Associated With Type 1 Diabetes in Caucasian-American Families
Authors: Davoodi-Semiromi Abdoreza , Yang James J. , She Jin-Xiong
Published: March 2007

The IL-12p40 locus has recently been shown to be associated with type 1 diabetes (1). Here, we report the identification of novel microsatellite and single-nucleotide polymorphisms (SNPs) within the IL-12p40 gene and a significant association between a (ATT)n repeat marker and type 1 diabetes in 364 U.S. Caucasian sib-pair families (P < 0.006). Haplotype analysis using the (ATT)n repeat (D5S2941) and the C1159A SNP at the 3′ untranslated region of IL-12p40 showed a significant association (P = 0.02). Expression studies in individuals heterozygous for the C1159A SNP indicated that the expression of the 1159A allele is ∼50% higher than that of the 1159C allele. These results provide genetic and functional evidence for IL-12p40 as a type 1 diabetes susceptibility gene.
The Role of CC Chemokine Receptor 5 (CCR5) in Islet Allograft Rejection
Authors: Abdi Reza , Smith R. Neal , Makhlouf Leila , Najafian Nader , Luster Andrew D. , Auchincloss Hugh , Sayegh Mohamed H.
Published: March 2007

Chemokines are important regulators in the development, differentiation, and anatomic location of leukocytes. CC chemokine receptor 5 (CCR5) is expressed preferentially by CD4+ T helper 1 (Th1) cells. We sought to determine the role of CCR5 in islet allograft rejection in a streptozotocin-induced diabetic mouse model. BALB/c islet allografts transplanted into CCR5−/− (C57BL/6) recipients survived significantly longer (mean survival time, 38 ± 8 days) compared with those transplanted into wild-type control mice (10 ± 2 days; P < 0.0001). Twenty percent of islet allografts in CCR5−/− animals without other treatment survived >90 days. In CCR5−/− mice, intragraft mRNA expression of interleukin-4 and -5 was increased, whereas that of interferon-γ was decreased, corresponding to a Th2 pattern of T-cell activation in the target tissues compared with a Th1 pattern observed in controls. A similar Th2 response pattern was also observed in the periphery (splenocytes responding to donor cells) by enzyme-linked immunosorbent spot assay. We conclude that CCR5 plays an important role in orchestrating the Th1 immune response leading to islet allograft rejection. Targeting this chemokine receptor, therefore, may provide a clinically useful strategy to prevent islet allograft rejection.
Sulfatide Controls Insulin Secretion by Modulation of ATP-sensitive K+-Channel Activity and Ca2+-Dependent Exocytosis in Rat Pancreatic β-Cells
Authors: Buschard Karsten , Høy Marianne , Bokvist Krister , Olsen Hervør L. , Madsbad Sten , Fredman Pam , Gromada Jesper
Published: March 2007

The glycosphingolipid sulfatide is present in secretory granules and at the surface of pancreatic β-cells, and antisulfatide antibodies (ASA; IgG1) are found in serum from the majority of patients with newly diagnosed type 1 diabetes. Here we demonstrate that sulfatide produced a glucose- and concentration-dependent inhibition of insulin release from isolated rat pancreatic islets. This inhibition of insulin secretion was due to activation of ATP-sensitive K+-(KATP) channels in single rat β-cells. No effect of sulfatide was observed on whole-cell Ca2+-channel activity or glucose-induced elevation of cytoplasmic Ca2+ concentration. It is interesting that sulfatide stimulated Ca2+-dependent exocytosis determined by capacitance measurements and depolarized-induced insulin secretion from islets exposed to diazoxide and high external KCl. The monoclonal sulfatide antibody Sulph I as well as ASA-positive serum reduced glucose-induced insulin secretion by inhibition of Ca2+-dependent exocytosis. Our data suggest that sulfatide is important for the control of glucose-induced insulin secretion and that both an increase and a decrease in the sulfatide content have an impact on the secretory capacity of the individual β-cells.
Nitric Oxide Synthase Inhibition Reduces Glucose Uptake During Exercise in Individuals With Type 2 Diabetes More Than in Control Subjects
Authors: Kingwell Bronwyn A. , Formosa Melissa , Muhlmann Michael , Bradley Scott J. , McConell Glenn K.
Published: March 2007

Nitric oxide (NO) synthase inhibition reduces leg glucose uptake during cycling without reducing leg blood flow (LBF) in young, healthy individuals. This study sought to determine the role of NO in glucose uptake during exercise in individuals with type 2 diabetes. Nine men with type 2 diabetes and nine control subjects matched for age, sex, peak pulmonary oxygen uptake (Vo2 peak), and weight completed two 25-min bouts of cycling exercise at 60 ± 2% Vo2 peak, separated by 90 min. NG-monomethyl-l-arginine (l-NMMA) (total dose 6 mg/kg) or placebo was administered into the femoral artery for the final 15 min of exercise in a counterbalanced, blinded, crossover design. LBF was measured by thermodilution in the femoral vein, and leg glucose uptake was calculated as the product of LBF and femoral arteriovenous glucose difference. During exercise with placebo, glucose uptake was not different between control subjects and individuals with diabetes; however, LBF was lower and arterial plasma glucose and insulin levels were higher in individuals with diabetes. l-NMMA had no effect on LBF or arterial plasma glucose and insulin concentrations during exercise in both groups. l-NMMA significantly reduced leg glucose uptake in both groups, with a significantly greater reduction (P = 0.04) in the diabetic group (75 ± 13%, 5 min after l-NMMA) compared with the control group (34 ± 14%, 5 min after l-NMMA). These data suggest a greater reliance on NO for glucose uptake during exercise in individuals with type 2 diabetes compared with control subjects.
Dissection of Metabolic, Vascular, and Nerve Conduction Interrelationships in Experimental Diabetic Neuropathy by Cyclooxygenase Inhibition and Acetyl-l-Carnitine Administration
Authors: Pop-Busui Rodica , Marinescu Victor , Van Huysen Carol , Li Fei , Sullivan Kelli , Greene Douglas A. , Larkin Dennis , Stevens Martin J.
Published: March 2007

Alterations in cyclooxygenase (COX) pathway activity have been implicated in the pathogenesis of experimental diabetic neuropathy (EDN). These studies explore the relationships between COX-mediated and acetyl-l-carnitine (ALC)-sensitive defects that contribute to functional, metabolic, and vascular abnormalities of EDN. The effects of nonselective COX inhibition with flurbiprofen were contrasted with selective COX-2 inhibition with meloxicam, administered alone and in combination with ALC in nondiabetic (ND) and streptozotocin-induced diabetic (STZ-D) rats. Flurbiprofen treatment of ND rats replicated many of the biochemical and physiological abnormalities of EDN, i.e., reduced motor nerve conduction velocity (MNCV), total and endoneurial nerve blood flow (NBF), Na,K-ATPase activity, and myo-inositol (MI) and taurine content. In STZ-D rats, however, flurbiprofen paradoxically prevented endoneurial NBF deficits but not MNCV slowing. Coadministration of 50 mg · kg−1 · day−1 ALC prevented reductions in MNCV, Na,K-ATPase activity, and endoneurial NBF in flurbiprofen-treated ND and STZ-D rats. In contrast, selective COX-2 inhibition with meloxicam was without effect on MNCV, NBF, or MI content in ND rats and prevented MNCV slowing and NBF deficits in STZ-D rats. Western blot analysis showed unchanged sciatic nerve COX-1 protein but increased COX-2 protein abundance in STZ-D versus ND rats. These results imply 1) a tonic role of the COX-1 pathway in the regulation of nerve osmolytes and Na,K-ATPase activity and the maintenance of NBF in ND animals and 2) activation of the COX-2 pathway as an important mediator of NBF and MNCV deficits in EDN.
Variants in the Calpain-10 Gene Predispose to Insulin Resistance and Elevated Free Fatty Acid Levels
Authors: Orho-Melander Marju , Klannemark Mia , Svensson Malin K. , Ridderstråle Martin , Lindgren Cecilia M. , Groop Leif
Published: March 2007

The calpain-10 gene (CAPN10) has been associated with type 2 diabetes, but information on molecular and physiological mechanisms explaining this association is limited. Here we addressed this question by studying the role of CAPN10 for phenotypes associated with type 2 diabetes and free fatty acid (FFA) metabolism. Among 395 type 2 diabetic patients and 298 nondiabetic control subjects from Finland, the SNP-43 allele 1 (P = 0.011), SNP-63 allele 2 (P = 0.010), and the haplotype combination SNP-44/43/19/63 1121/1121 (P = 0.028) were associated with type 2 diabetes. The SNP-43 genotypes 11 and 12 were associated with higher fasting insulin and homeostasis model assessment (HOMA) insulin resistance index among control subjects (P = 0.021 and P = 0.0076) and with elevated FFA among both control subjects (P = 0.0040) and type 2 diabetic patients (P = 0.0025). Multiple regression analysis further indicated that SNP-43 is an independent predictor of FFA levels (P = 0.0037). Among 80 genotype discordant sibling pairs, the SNP-43 allele 1 was associated with elevated fasting serum insulin and HOMA index (P = 0.013 and P = 0.0068). None of the four SNPs showed distorted transmission of alleles to patients with type 2 diabetes in a qualitative transmission disequilibrium test, including 108 trios. Because FFA and insulin resistance are known to predict type 2 diabetes, the finding that variation in the CAPN10 gene influences FFA levels and insulin resistance may provide an explanation for how the CAPN10 gene increases susceptibility to type 2 diabetes.
The Effectiveness of Treatments of Diabetic Autonomic Neuropathy Is Not the Same in Autonomic Nerves Supplying Different Organs
Authors: Shotton Hannah R. , Clarke Simon , Lincoln Jill
Published: March 2007

The aim of the study was to investigate antioxidant (α-lipoic acid [LA]) and γ-linolenic acid treatments in the prevention of changes in autonomic nerves induced in streptozotocin-diabetic rats. Autonomic nerves supplying the heart, penis, and gut were examined using immunohistochemical and biochemical techniques. LA and γ-linolenic acid (present in evening primrose oil [EPO]) were administered as dietary supplements (∼80 and 200 mg · kg−1 · day−1, respectively). LA treatment prevented the diabetes-induced decrease of norepinephrine (NA) in the heart and of type I nitric oxide synthase (NOS-I) expression in erectile tissue of the penis but failed to prevent diabetes-induced changes in NA-, vasoactive intestinal polypeptide-, or calcitonin gene-related peptide-containing nerves supplying the ileum. LA partially prevented and EPO totally prevented the increase in NOS-I activity induced by diabetes in the ileum. EPO treatment failed to prevent any other diabetes-induced changes in the heart, penis, or ileum. These results demonstrate that, whereas LA treatment is more effective than EPO in preventing diabetes-induced changes in autonomic nerves, the effectiveness of LA treatment varies with the target organ studied. Diabetes-induced changes in nerves supplying the ileum are more resistant to treatment than those of the heart and penis.
A Susceptibility Allele From a Non-Diabetes-Prone Mouse Strain Accelerates Diabetes in NOD Congenic Mice
Authors: Brodnicki Thomas C. , Quirk Fiona , Morahan Grant
Published: March 2007

The nonobese diabetic (NOD) mouse is genetically predisposed for the spontaneous development of type 1 diabetes. Linkage analyses have identified at least 19 susceptibility loci (Idd1–Idd19) that contribute to disease pathogenesis in which lymphocytes mediate the specific destruction of insulin-producing β-cells. Interestingly, nondiabetic mouse strains have been shown to confer susceptibility alleles to affected progeny in NOD outcrosses for some of the Idd loci. In particular, we noted that diabetic backcross progeny, derived from NOD and C57BL/6 (B6) mouse strains, demonstrated increased heterozygousity for an interval encompassing Idd14 on chromosome 13. This result suggested that B6 mice harbor a more diabetogenic allele(s) than NOD mice for this locus. To confirm this observation, a NOD congenic mouse strain, containing a B6-derived interval covering the majority of chromosome 13, was generated. Adding to the combination of already potent susceptibility alleles elsewhere in the NOD genome, the chromosome 13 B6-derived interval was able to increase the overall risk of developing type 1 diabetes, which resulted in an earlier onset and increased incidence of type 1 diabetes in congenic mice as compared with NOD mice. Furthermore, this B6-derived interval, in combination with the NOD genetic background, was able to overcome environmental conditions that typically suppressed type 1 diabetes in the NOD mouse strain.
Primacy of Hepatic Insulin Resistance in the Development of the Metabolic Syndrome Induced by an Isocaloric Moderate-Fat Diet in the Dog
Authors: Kim Stella P. , Ellmerer Martin , Van Citters Gregg W. , Bergman Richard N.
Published: March 2007

Obesity is highly correlated with insulin resistance and the development of type 2 diabetes. Insulin resistance will result in a decrease in insulin’s ability to stimulate glucose uptake into peripheral tissue and will suppress glucose production by the liver. However, the development of peripheral and hepatic insulin resistance relative to one another in the context of obesity-associated insulin resistance is not well understood. To examine this phenomena, we used the moderate fat-fed dog model, which has been shown to develop both subcutaneous and visceral adiposity and severe insulin resistance. Six normal dogs were fed an isocaloric diet with a modest increase in fat content for 12 weeks, and they were assessed at weeks 0, 6, and 12 for changes in insulin sensitivity and glucose turnover. By week 12 of the diet, there was a more than twofold increase in trunk adiposity as assessed by magnetic resonance imaging because of an accumulation in both subcutaneous and visceral fat depots with very little change in body weight. Fasting plasma insulin had increased by week 6 (150% of week 0) and remained increased up to week 12 of the study (170% of week 0). Surprisingly, there appeared to be no change in the rates of insulin-stimulated glucose uptake as measured by euglycemic-hyperinsulinemic clamps throughout the course of fat feeding. However, there was an increase in steady-state plasma insulin levels at weeks 6 and 12, indicating a moderate degree of peripheral insulin resistance. In contrast to the moderate defect seen in the periphery, there was a marked impairment in insulin’s ability to suppress endogenous glucose production during the clamp such that by week 12 of the study, there was a complete inability of insulin to suppress glucose production. Our results indicate that a diet enriched with a moderate amount of fat results in the development of both subcutaneous and visceral adiposity, hyperinsulinemia, and a modest degree of peripheral insulin resistance. However, there is a complete inability of insulin to suppress hepatic glucose production during the clamp, suggesting that insulin resistance of the liver may be the primary defect in the development of insulin resistance associated with obesity.