bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Heterogeneity in Association of the SUMO4 M55V Variant With Susceptibility to Type 1 Diabetes
Authors: Noso Shinsuke , Ikegami Hiroshi , Fujisawa Tomomi , Kawabata Yumiko , Asano Katsuaki , Hiromine Yoshihisa , Tsurumaru Masako , Sugihara Shigetaka , Lee Inkyu , Kawasaki Eiji , Awata Takuya , Ogihara Toshio
Published: March 2007

Association studies are a potentially powerful approach to identifying susceptibility variants for common multifactorial diseases such as type 1 diabetes, but the results are not always consistently reproducible. The IDDM5 locus has recently been narrowed to an ∼200-kb interval on chromosome 6q25 by two independent groups. These studies demonstrated that alleles at markers in the mitogen-activating protein kinase 7 interacting protein 2 (MAP3K7IP2)/SUMO4 region were associated with susceptibility to type 1 diabetes. Subsequent studies, however, showed inconsistency in the association of the SUMO4 gene with type 1 diabetes. To clarify the contribution of the M55V polymorphism of the SUMO4 gene to type 1 diabetes susceptibility, 541 type 1 diabetic patients and 768 control subjects were studied in Asian populations. The M55V polymorphism was significantly associated with type 1 diabetes in Asian populations (summary odds ratio [OR] 1.46, P = 0.00083, Mantel-Haenszel test). Meta-analysis of published studies and the present data confirmed a highly significant association in Asian populations (summary OR 1.29, P = 7.0 × 10−6) but indicated heterogeneity in the genetic effect of the SUMO4/MAP3K7IP2 locus on type 1 diabetes among diverse ethnic groups. These data indicate that the MAP3K7IP2/SUMO4 locus in the IDDM5 interval is associated with type 1 diabetes in Asian populations.
Single Nucleotide Polymorphisms in the Peroxisome Proliferator–Activated Receptor δ Gene Are Associated With Skeletal Muscle Glucose Uptake
Authors: Vänttinen Markku , Nuutila Pirjo , Kuulasmaa Teemu , Pihlajamäki Jussi , Hällsten Kirsti , Virtanen Kirsi A. , Lautamäki Riikka , Peltoniemi Pauliina , Takala Teemu , Viljanen Antti P.M. , Knuuti Juhani , Laakso Markku
Published: March 2007

The peroxisome proliferator–activated receptors (PPARs) belong to a superfamily of nuclear receptors. It includes PPAR-δ, a key regulator of fatty acid oxidation and energy uncoupling, universally expressed in different tissues. The PPAR-δ gene (PPARD) maps to 6p21.2-p21.1 and has 11 exons and spans 35 kbp. We investigated the effects of single nucleotide polymorphisms (SNPs) of PPARD on whole-body, skeletal muscle, and subcutaneous adipose tissue glucose uptake in 129 healthy individuals using the hyperinsulinemic-euglycemic clamp technique combined with fluorine-18–labeled fluorodeoxyglucose ([18F]FDG) and positron emission tomography (PET). Three of six SNPs of PPARD and their haplogenotypes were significantly associated with whole-body insulin sensitivity. [18F]FDG-PET scanning indicated that SNPs of PPARD primarily affected insulin sensitivity by modifying glucose uptake in skeletal muscle but not in adipose tissue. Our results give evidence that SNPs of PPARD regulate insulin sensitivity particularly in skeletal muscle.
Insulin Glulisine
Authors: Hennige Anita M. , Lehmann Rainer , Weigert Cora , Moeschel Klaus , Schäuble Myriam , Metzinger Elisabeth , Lammers Reiner , Häring Hans-Ulrich
Published: March 2007

In recent years, recombinant DNA technology has been used to design insulin molecules that overcome the limitations of regular insulin in mealtime supplementation. However, safety issues have been raised with these alternatives, as the alteration of the three-dimensional structure may alter the interaction with the insulin and/or IGF-I receptors and therefore lead to the activation of alternate metabolic as well as mitogenic signaling pathways. It is therefore essential to carefully study acute and long-term effects in a preclinical state, as insulin therapy is meant to be a lifelong treatment. In this study, we determined in vivo the insulin receptor signaling characteristics activated by insulin glulisine (LysB3, GluB29) at the level of insulin receptor phosphorylation, insulin receptor substrate phosphorylation, and downstream signaling elements such as phosphatidylinositol (PI) 3-kinase, AKT, and mitogen-activated protein kinase. C57BL/6 mice were injected with insulin glulisine or regular insulin and Western blot analysis was performed for liver and muscle tissue. The extent and time course of insulin receptor phosphorylation and activation of downstream signaling elements after insulin glulisine treatment was similar to that of human regular insulin in vivo. Moreover, insulin signaling in hypothalamic tissue determined by PI 3-kinase activity was comparable. Therefore, insulin glulisine may be a useful tool for diabetes treatment.
Fatty Acid Translocase (FAT/CD36) Is Localized on Insulin-Containing Granules in Human Pancreatic β-Cells and Mediates Fatty Acid Effects on Insulin Secretion
Authors: Noushmehr Houtan , D’Amico Eugenio , Farilla Loredana , Hui Hongxiang , Wawrowsky Kolja A. , Mlynarski Wojciech , Doria Alessandro , Abumrad Nada A. , Perfetti Riccardo
Published: March 2007

The membrane receptor FAT/CD36 facilitates the major fraction of long-chain fatty acid (FA) uptake by muscle and adipose tissues. In line with the well-known effects of FA metabolism on carbohydrate utilization and insulin responsiveness, altered expression of CD36 has been linked to phenotypic features of the metabolic syndrome including insulin resistance and dyslipidemia. FA metabolism is also known to significantly affect insulin secretion. However, the role of CD36 in this process remains unknown, since its expression levels and function in the pancreas have not been explored. In the present study, freshly isolated human islets and a mouse-derived β-cell line (MIN6) were shown positive for CD36 expression by RT-PCR, Western blot, and immunofluorescence. The identity of the PCR product was confirmed by microsequencing. The identified transcript was translated and the protein was expressed and subjected to the known posttranslational glycosylation. Fluorescence resonance energy transfer analysis and subcellular protein fractionation indicated that insulin and CD36 are colocalized in the secretory granules of β-cells. Islet CD36 functioned in FA uptake because this process was blocked by the irreversible CD36 inhibitor sulfosuccinimidyl-oleate. More importantly, sulfosuccinimidyl-oleate reversed enhancing and inhibiting effects, respectively, of acute and long-term palmitate incubations on glucose-dependent insulin secretion. In conclusion, our study demonstrates that human islets express CD36 in the plasma membrane as well as in the insulin secretory granules. CD36 activity appears important for uptake of FA into β-cells as well as for mediating their modulatory effects on insulin secretion.
Cumulative Incidence of Type 1 Diabetes in 10,168 Siblings of Finnish Young-Onset Type 1 Diabetic Patients
Authors: Harjutsalo Valma , Podar Toomas , Tuomilehto Jaakko
Published: March 2007

The aims of our analysis were to obtain the empirical risk estimates for type 1 diabetes in the siblings of a Finnish population-based cohort of childhood-onset diabetic patients and search for demographic and other factors predicting the risk of type 1 diabetes in siblings. We defined the diabetes status of all siblings of all probands who are included in the nationwide register of Finnish cases for whom type 1 diabetes was diagnosed before age 18 years between 1965 and 1979. Siblings’ diabetes status was ascertained by a record search of nationwide registries through 2001, and the type of diabetes and date of its manifestation were obtained from medical records. The total number of person-years during the follow-up was 405,685. Of the 10,168 siblings at risk, 647 (6.4%) had been diagnosed with type 1 diabetes by 2001. The cumulative incidence of type 1 diabetes by ages 10, 20, 30, 40, and 50 years in all siblings was 1.5, 4.1, 5.5, 6.4, and 6.9%, respectively. A young age at diagnosis in the index case, paternal young-onset diabetes, male sex, and older parental age at delivery considerably increased the risk of type 1 diabetes for siblings. This large prospective family study of type 1 diabetes in siblings of childhood-onset diabetic patients provides reliable empirical estimates for the sibling recurrence risk.
Complement C3 Is a Risk Factor for the Development of Diabetes
Authors: Engström Gunnar , Hedblad Bo , Eriksson Karl-Fredrik , Janzon Lars , Lindgärde Folke
Published: March 2007

Cross-sectional studies have reported strong correlations between plasma levels of complement C3, insulin, and glucose. This prospective study explored whether elevated levels of C3, C4, and other inflammation-sensitive plasma proteins (ISPs; fibrinogen, orosomucoid, α1-antitrypsin, haptoglobin, and ceruloplasmin) are associated with the development of diabetes. Plasma proteins were measured in 2,815 nondiabetic healthy men, age 38–50 years, who were reexamined after a mean follow-up of 6.1 years. Diabetes development (n = 123) was studied in relation to baseline levels of plasma proteins. After adjusting for age, screening year, and glucose at baseline, the odds ratio (95% CI) for developing diabetes was 1.00, 2.4 (1.1–5.3), 2.9 (1.4–6.0), and 5.6 (2.8–10.9), respectively, for men with C3 in the 1st, 2nd, 3rd, and 4th quartiles (trend: P < 0.00001). Fibrinogen, haptoglobin, C4, and the number of elevated ISPs were also related to future diabetes in this model. Only C3 was significantly associated with diabetes development after further adjustments for potential confounders, including BMI, insulin, and other inflammatory markers. We concluded that the risk of developing diabetes is related to levels of complement C3.
Genetic Regulation of Birth Weight and Fasting Glucose by a Common Polymorphism in the Islet Cell Promoter of the Glucokinase Gene
Authors: Weedon Michael N. , Frayling Timothy M. , Shields Beverley , Knight Beatrice , Turner Tina , Metcalf Bradley S. , Voss Linda , Wilkin Terence J. , McCarthy Anne , Ben-Shlomo Yoav , Davey Smith George , Ring Sue , Jones Richard , Golding Jean ,   ALSPAC Study Team, Byberg Liisa , Mann Vera , Axelsson Tomas , Syvänen Ann-Christine , Leon David , Hattersley Andrew T.
Published: March 2007

Rare mutations in the glucokinase (GCK) gene cause fasting hyperglycemia and considerably influence birth weight when present in a mother or her offspring. The role of common variation of GCK is uncertain. A polymorphism at position −30 of the GCK β-cell-specific promoter, present in 30% of the population, has been variably associated with type 2 diabetes and diabetes-related quantitative traits. Using 1,763 U.K. Caucasian normoglycemic adult subjects, we demonstrated that the A allele at GCK(−30) is associated with a 0.06-mmol/l increase in fasting plasma glucose (FPG) (P = 0.003). The A allele was also associated with an increase in FPG in 755 women who were 28 weeks pregnant (0.075 mmol/l, P = 0.003). We then went on to analyze the effect of GCK(−30) on birth weight using 2,689 mother/child pairs. The presence of the A allele in the mother was associated with a 64-g (25–102 g) increase in offspring birth weight (P = 0.001). We did not detect a fetal genotype effect. The increase in offspring birth weight in the 30% of mothers carrying an A allele at GCK(−30) is likely to reflect an elevated FPG during pregnancy. This study establishes that common genetic variation, in addition to rare mutations and environmental factors, can affect both FPG and birth weight.
Calcineurin Does Not Mediate Exercise-Induced Increase in Muscle GLUT4
Authors: Garcia-Roves Pablo M. , Jones Terry E. , Otani Kenichi , Han Dong-Ho , Holloszy John O.
Published: March 2007

Exercise induces a rapid increase in expression of the GLUT4 isoform of the glucose transporter in skeletal muscle. One of the signals responsible for this adaptation appears to be an increase in cytosolic Ca2+. Myocyte enhancer factor 2A (MEF2A) is a transcription factor that is involved in the regulation of GLUT4 expression. It has been reported that the Ca2+-regulated phosphatase calcineurin mediates the activation of MEF2 by exercise. It has also been shown that the expression of activated calcineurin in mouse skeletal muscle results in an increase in GLUT4. These findings suggest that increases in cytosolic Ca2+ induce increased GLUT4 expression by activating calcineurin. However, we have obtained evidence that this response is mediated by a Ca2+-calmodulin−dependent protein kinase. The purpose of this study was to test the hypothesis that calcineurin is involved in mediating exercise-induced increases in GLUT4. Rats were exercised on 5 successive days using a swimming protocol. One group of swimmers was given 20 mg/kg body weight of cyclosporin, a calcineurin inhibitor, 2 h before exercise. A second group was given vehicle. GLUT4 protein was increased ∼80%, GLUT4 mRNA was increased ∼2.5-fold, MEF2A protein was increased twofold, and hexokinase II protein was increased ∼2.5-fold 18 h after the last exercise bout. The cyclosporin treatment completely inhibited calcineurin activity but did not affect the adaptive increases in GLUT4, MEF2A, or hexokinase expression. We conclude that calcineurin activation does not mediate the adaptive increase in GLUT4 expression induced in skeletal muscle by exercise.
Free Fatty Acid Regulation of Glucose-Dependent Intrinsic Oscillatory Lipolysis in Perifused Isolated Rat Adipocytes
Authors: Getty-Kaushik Lisa , Richard Ann-Marie T. , Corkey Barbara E.
Published: March 2007

Free fatty acids (FFAs) and glycerol oscillate in plasma. This study examined intrinsic lipolytic oscillations within adipocytes. Rat adipocytes were perifused with Krebs-Ringer bicarbonate buffer: 1) ± 2 mmol/l glucose; 2) +1 μmol/l isoproterenol ± 2 mmol/l glucose; 3) + increasing oleate; and 4) + increasing percent BSA. At 2 mmol/l glucose, there were 9 ± 1 glycerol, FFAs, and lactate pulses per hour with a pulse duration of 5 ± 1 min. Lipolytic stimulation caused a 50–80% increase in the amplitude of lipolytic oscillations. Removal of glucose caused a 40–70% decrease in the amplitude of lipolytic oscillations and disturbed the pulsatility. Exogenous FFAs suppressed lipolysis and oscillatory amplitude, possibly because of increased cytosolic long-chain coenzyme A (LC-CoA). Increasing percent BSA increased stimulated lipolysis and oscillatory amplitude, possibly because of decreased intracellular LC-CoA. These data show, for the first time, intrinsic lipolytic oscillations, which are glucose dependent and modulated by FFAs. We hypothesize that lipolytic oscillations are driven by oscillatory glucose metabolism, which leads to oscillatory relief of LC-CoA inhibition of triglyceride lipase(s). The results contribute to the understanding of physiological and biochemical regulators of lipolysis, such as glucose and FFAs. Lipolytic oscillations may be beneficial in the delivery of FFAs to liver, pancreas, and other tissues.
Apolipoprotein C3 Deficiency Results in Diet-Induced Obesity and Aggravated Insulin Resistance in Mice
Authors: Duivenvoorden Ilse , Teusink Bas , Rensen Patrick C. , Romijn Johannes A. , Havekes Louis M. , Voshol Peter J.
Published: March 2007

Our aim was to study whether the absence of apolipoprotein (apo) C3, a strong inhibitor of lipoprotein lipase (LPL), accelerates the development of obesity and consequently insulin resistance. Apoc3−/− mice and wild-type littermates were fed a high-fat (46 energy %) diet for 20 weeks. After 20 weeks of high-fat feeding, apoc3−/− mice showed decreased plasma triglyceride levels (0.11 ± 0.02 vs. 0.29 ± 0.04 mmol, P < 0.05) and were more obese (42.8 ± 3.2 vs. 35.2 ± 3.3 g; P < 0.05) compared with wild-type littermates. This increase in body weight was entirely explained by increased body lipid mass (16.2 ± 5.9 vs. 10.0 ± 1.8 g; P < 0.05). LPL-dependent uptake of triglyceride-derived fatty acids by adipose tissue was significantly higher in apoc3−/− mice. LPL-independent uptake of albumin-bound fatty acids did not differ. It is interesting that whole-body insulin sensitivity using hyperinsulinemic-euglycemic clamps was decreased by 43% and that suppression of endogenous glucose production was decreased by 25% in apoc3−/− mice compared with control mice. Absence of apoC3, the natural LPL inhibitor, enhances fatty acid uptake from plasma triglycerides in adipose tissue, which leads to higher susceptibility to diet-induced obesity followed by more severe development of insulin resistance. Therefore, apoC3 is a potential target for treatment of obesity and insulin resistance.
Caveolin-1 Expression Is Essential for Proper Nonshivering Thermogenesis in Brown Adipose Tissue
Authors: Cohen Alex W. , Schubert William , Brasaemle Dawn L. , Scherer Philipp E. , Lisanti Michael P.
Published: March 2007

Recently, we have shown that loss of caveolin-1 leads to marked alterations in insulin signaling and lipolysis in white adipose tissue. However, little is known about the role of caveolin-1 in brown adipose tissue (BAT), a tissue responsible for nonshivering thermogenesis. Here, we show that caveolin-1 null mice have a mildly, yet significantly, decreased resting core body temperature. To investigate this in detail, we next subjected the mice to fasting (for 24 h) or cold treatment (4°C for 24 h), individually or in combination. Interestingly, caveolin-1 null mice showed markedly decreased body temperatures in response to fasting or fasting/cold treatment; however, cold treatment alone had no effect. In addition, under these conditions caveolin-1 null mice failed to show the normal increase in serum nonesterified fatty acids induced by fasting or fasting/cold treatment, suggesting that these mice are unable to liberate triglyceride stores for heat production. In accordance with these results, the triglyceride content of BAT was reduced nearly 10-fold in wild-type mice after fasting/cold treatment, but it was reduced only 3-fold in caveolin-1 null mice. Finally, electron microscopy of adipose tissue revealed dramatic perturbations in the mitochondria of caveolin-1 null interscapular brown adipocytes. Taken together, our data provide the first molecular genetic evidence that caveolin-1 plays a critical functional and structural role in the modulation of thermogenesis via an effect on lipid mobilization.
Redistribution of Glucose From Skeletal Muscle to Adipose Tissue During Catch-Up Fat
Authors: Cettour-Rose Philippe , Samec Sonia , Russell Aaron P. , Summermatter Serge , Mainieri Davide , Carrillo-Theander Claudia , Montani Jean-Pierre , Seydoux Josiane , Rohner-Jeanrenaud Françoise , Dulloo Abdul G.
Published: March 2007

Catch-up growth, a risk factor for later obesity, type 2 diabetes, and cardiovascular diseases, is characterized by hyperinsulinemia and an accelerated rate for recovering fat mass, i.e., catch-up fat. To identify potential mechanisms in the link between hyperinsulinemia and catch-up fat during catch-up growth, we studied the in vivo action of insulin on glucose utilization in skeletal muscle and adipose tissue in a previously described rat model of weight recovery exhibiting catch-up fat caused by suppressed thermogenesis per se. To do this, we used euglycemic-hyperinsulinemic clamps associated with the labeled 2-deoxy-glucose technique. After 1 week of isocaloric refeeding, when body fat, circulating free fatty acids, or intramyocellular lipids in refed animals had not yet exceeded those of controls, insulin-stimulated glucose utilization in refed animals was lower in skeletal muscles (by 20–43%) but higher in white adipose tissues (by two- to threefold). Furthermore, fatty acid synthase activity was higher in adipose tissues from refed animals than from fed controls. These results suggest that suppressed thermogenesis for the purpose of sparing glucose for catch-up fat, via the coordinated induction of skeletal muscle insulin resistance and adipose tissue insulin hyperresponsiveness, might be a central event in the link between catch-up growth, hyperinsulinemia and risks for later metabolic syndrome.
Impaired Retinal Angiogenesis in Diabetes
Authors: Stitt Alan W. , McGoldrick Ciara , Rice-McCaldin Aine , McCance David R. , Glenn Josephine V. , Hsu Daniel K. , Liu Fu-Tong , Thorpe Suzanne R. , Gardiner Tom A.
Published: March 2007

Suppression of angiogenesis during diabetes is a recognized phenomenon but is less appreciated within the context of diabetic retinopathy. The current study has investigated regulation of retinal angiogenesis by diabetic serum and determined if advanced glycation end products (AGEs) could modulate this response, possibly via AGE-receptor interactions. A novel in vitro model of retinal angiogenesis was developed and the ability of diabetic sera to regulate this process was quantified. AGE-modified serum albumin was prepared according to a range of protocols, and these were also analyzed along with neutralization of the AGE receptors galectin-3 and RAGE. Retinal ischemia and neovascularization were also studied in a murine model of oxygen-induced proliferative retinopathy (OIR) in wild-type and galectin-3 knockout mice (gal3−/−) after perfusion of preformed AGEs. Serum from nondiabetic patients showed significantly more angiogenic potential than diabetic serum (P < 0.0001) and within the diabetic group, poor glycemic control resulted in more AGEs but less angiogenic potential than tight control (P < 0.01). AGE-modified albumin caused a dose-dependent inhibition of angiogenesis (P < 0.001), and AGE receptor neutralization significantly reversed the AGE-mediated suppression of angiogenesis (P < 0.01). AGE-treated wild-type mice showed a significant increase in inner retinal ischemia and a reduction in neovascularization compared with non-AGE controls (P < 0.001). However, ablation of galectin-3 abolished the AGE-mediated increase in retinal ischemia and restored the neovascular response to that seen in controls. The data suggest a significant suppression of angiogenesis by the retinal microvasculature during diabetes and implicate AGEs and AGE-receptor interactions in its causation.
Hyperglycemia in Streptozotocin-Induced Diabetic Rat Increases Infarct Size Associated With Low Levels of Myocardial HO-1 During Ischemia/Reperfusion
Authors: Filippo Clara Di , Marfella Raffaele , Cuzzocrea Salvatore , Piegari Elena , Petronella Pasquale , Giugliano Dario , Rossi Francesco , D’Amico Michele
Published: March 2007

This study investigated the role of heme oxygenase (HO)-1 in the cardiac tissue injury of acute ischemia/reperfusion (I/R) in diabetic streptozotocin (STZ)-induced hyperglycemic rats. The effects of 1) hemin, an inducer of HO expression and activity, and 2) zinc protoporphyrin IX (ZnPP-IX), an inhibitor of HO activity, have also been investigated on the tissue injury by I/R and some mediators released in these circumstances. STZ hyperglycemic rats had impaired levels of HO-1 within the cardiac tissue and increased myocardial infarct size (IS) following I/R, as compared with the nondiabetic rats. In these rats, administration of hemin 4 mg/kg 18 h before I/R increases the levels of HO-1 within the tissue. However, the values of HO-1 assayed in these circumstances were significantly lower (P < 0.01) than those assayed in nondiabetic animals subjected to the same procedures; IS was much more extended (P < 0.01) than in the parent nondiabetic group. STZ hyperglycemic rats also predisposed the heart to produce high levels of the cytokines interleukin (IL)-1β and CXCL8. Subsequent I/R further increased (P < 0.01) the cytokine production, an effect partly prevented by hemin treatment. This recovered the huge number of infiltrated polymorphonuclear (PMN) leukocytes within the cardiac tissue associated with the STZ hyperglycemic state and I/R damage.
Experimental Diabetic Neuropathy With Spontaneous Recovery
Authors: Kennedy James M. , Zochodne Douglas W.
Published: March 2007

Progressive diabetic neuropathy has hitherto been irreversible in humans. New approaches raise the question of whether islet cell reconstitution rendering euglycemia can reverse specific features of neuropathy. We evaluated physiological and structural features of experimental neuropathy in a long-term murine model of diabetes induced by streptozotocin. By serendipity, a subset of these diabetic mice spontaneously regained islet function and attained near-euglycemia. Our hypotheses were that this model might better reflect axon loss observed in human disease and that spontaneous recovery from diabetes might identify the features of neuropathy that are reversible. In this model, experimental neuropathy closely modeled that in humans in most critical aspects: declines in motor conduction velocities, attenuation of compound muscle (M waves) and nerve action potentials, axon atrophy, myelin thinning, loss of epidermal axons, and loss of sweat gland innervation. Overt sensory neuron loss in dorsal root ganglia was a feature of this model. In mice with recovery, there was robust electrophysiological improvement, less myelin thinning, and remarkable epidermal and sweat gland reinnervation. There was, however, no recovery of populations of lost sensory neurons. Our findings identify a robust model of human diabetic neuropathy and indicate that overt, irretrievable loss of sensory neurons is one of its features, despite collateral reinnervation of target organs. Sensory neurons deserve unique protective strategies irrespective of islet cell reconstitution.
N-Acetyl-Seryl-Aspartyl-Lysyl-Proline Prevents Renal Insufficiency and Mesangial Matrix Expansion in Diabetic db/db Mice
Authors: Shibuya Kazuyuki , Kanasaki Keizo , Isono Motohide , Sato Haruhisa , Omata Mitsugu , Sugimoto Toshiro , Araki Shin-ichi , Isshiki Keiji , Kashiwagi Atsunori , Haneda Masakazu , Koya Daisuke
Published: March 2007

We have previously reported that N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), which is a tetrapeptide hydrolyzed by ACE, inhibits the transforming growth factor-β (TGF-β)-induced expression of extracellular matrix proteins via inhibition of the Smad signaling in human mesangial cells. To test in vivo the antifibrotic efficacy of Ac-SDKP, we examined whether long-term Ac-SDKP treatment can prevent renal insufficiency and glomerulosclerosis in diabetic db/db mice. Diabetic db/db mice or nondiabetic db/m mice were treated with Ac-SDKP for 8 weeks using osmotic minipumps. The treatment with Ac-SDKP increased plasma Ac-SDKP concentrations by approximately threefold in both groups but did not affect the blood glucose levels. Histologically, the increased glomerular surface area, mesangial matrix expansion, and overproduction of extracellular matrix proteins in db/db mice were significantly inhibited by Ac-SDKP. Furthermore, Ac-SDKP treatment normalized the increased plasma creatinine value in db/db mice, whereas the albuminuria in Ac-SDKP–treated db/db mice was somewhat decreased as compared with nontreated db/db mice, although the difference was not statistically significant. In addition, the nuclear translocation of Smad3 was inhibited by Ac-SDKP. These results demonstrate that long-term Ac-SDKP treatment ameliorates renal insufficiency and glomerulosclerosis in db/db mice via inhibition of TGF-β/Smad pathway, suggesting that Ac-SDKP could be useful in the treatment of diabetic nephropathy.
PDX-1/VP16 Fusion Protein, Together With NeuroD or Ngn3, Markedly Induces Insulin Gene Transcription and Ameliorates Glucose Tolerance
Authors: Kaneto Hideaki , Nakatani Yoshihisa , Miyatsuka Takeshi , Matsuoka Taka-aki , Matsuhisa Munehide , Hori Masatsugu , Yamasaki Yoshimitsu
Published: March 2007

Diabetes is the most prevalent and serious metabolic disease, and the number of diabetic patients worldwide is increasing. The reduction of insulin biosynthesis in pancreatic β-cells is closely associated with the onset and progression of diabetes, and thus it is important to search for ways to induce insulin-producing cells in non−β-cells. In this study, we showed that a modified form of the pancreatic and duodenal homeobox factor 1 (PDX-1) carrying the VP16 transcriptional activation domain (PDX-1/VP16) markedly increases insulin biosynthesis and induces various pancreas-related factors in the liver, especially in the presence of NeuroD or neurogenin 3 (Ngn3). Furthermore, in streptozotocin-induced diabetic mice, PDX-1/VP16 overexpression, together with NeuroD or Ngn3, drastically ameliorated glucose tolerance. Thus PDX-1/VP16 expression, together with NeuroD or Ngn3, markedly induces insulin gene transcription and ameliorates glucose tolerance. This approach warrants further investigation and may have utility in the treatment of diabetes.
Achieving Permanent Survival of Islet Xenografts by Independent Manipulation of Direct and Indirect T-Cell Responses
Authors: Mirenda Vincenzo , Golshayan Dela , Read Joseph , Berton Ivan , Warrens Anthony N. , Dorling Anthony , Lechler Robert I.
Published: March 2007

Recent success in pancreatic islet allotransplantation has raised expectations but has equally highlighted the acute shortage of donor tissue. The use of xenogeneic tissue would help to address this shortage; however, strong cellular immunity limits the application of this approach. T-cell responses to xenogeneic tissues involve recognition of intact species-mismatched major histocompatibility complex (MHC) molecules, the direct pathway, and xenogeneic proteins presented as peptides by responder-type MHC molecules, the indirect pathway. In this study, we exploited the species difference to selectively and sequentially inhibit direct and indirect xenoresponses after transplantation of porcine islets into mice. Selective inhibition of the direct response was achieved using porcine CTLA4-Ig, which binds preferentially to pig versus mouse B7 molecules. Selective inhibition of the indirect response was achieved using murine CTLA4-Ig, which binds preferentially to mouse B7 molecules. Administration of porcine CTLA4-Ig alone caused modest prolongation of islet survival. Injection of murine CTLA4-Ig alone had a minimal effect. However, the injection of the porcine fusion protein early and the murine homolog late after grafting led to permanent survival of the porcine islets, in the absence of any other immunosuppression. These results suggest that a similar approach could have clinical utility in porcine islet xenotransplantation.
Serum- and Glucocorticoid-Inducible Kinase 1 (SGK1) Mediates Glucocorticoid-Induced Inhibition of Insulin Secretion
Authors: Ullrich Susanne , Berchtold Susanne , Ranta Felicia , Seebohm Guiscard , Henke Guido , Lupescu Adrian , Mack Andreas F. , Chao Cho-Ming , Su Jiping , Nitschke Roland , Alexander Dorothea , Friedrich Björn , Wulff Peer , Kuhl Dietmar , Lang Florian
Published: March 2007

Glucocorticoid excess predisposes to the development of diabetes, at least in part through impairment of insulin secretion. The underlying mechanism has remained elusive. We show here that dexamethasone upregulates transcription and expression of the serum- and glucocorticoid-inducible kinase 1 (SGK1) in insulin-secreting cells, an effect reversed by mifepristone (RU486), an antagonist of the nuclear glucocorticoid receptor. When coexpressed in Xenopus oocytes, SGK1 increases the activity of voltage-gated K+ channel Kv1.5. In INS-1 cells, dexamethasone stimulates the transcription of Kv1.5, increases the repolarizing outward current, reduces peak values of [Ca2+]i oscillations, and decreases glucose-induced insulin release. The latter effect is reversed by K+ channel blockers 4-aminopyridine and tetraethylammonium and by a more selective Kv1.5 channel inhibitor MSD-D. Dexamethasone also increases expression of Kv1.5 in mouse islets and reduces glucose-induced insulin secretion, an effect reversed by MSD-D. In islets isolated from wild-type but not SGK1 knockout mice, dexamethasone significantly blunted glucose-, forskolin-, and phorbol myristic acid-induced insulin release. In conclusion, dexamethasone stimulates the transcription of SGK1, which in turn upregulates the activity of voltage-gated K+ channels. Increased K+ channel activity reduces Ca2+ entry through voltage-gated Ca2+ channels and insulin release.
Metformin Prevents Glucose-Induced Protein Kinase C-β2 Activation in Human Umbilical Vein Endothelial Cells Through an Antioxidant Mechanism
Authors: Gallo Alessandra , Ceolotto Giulio , Pinton Paolo , Iori Elisabetta , Murphy Ellen , Rutter Guy A. , Rizzuto Rosario , Semplicini Andrea , Avogaro Angelo
Published: March 2007

Hyperglycemia determines the vascular complications of diabetes through different mechanisms: one of these is excessive activation of the isoform β2 of protein kinase C (PKC-β2). Metformin, a widely used antidiabetic agent, is associated with decreased cardiovascular mortality in obese type 2 diabetic patients. Therefore, we assessed the role of metformin in glucose-induced activation of PKC-β2 and determined the mechanism of its effect in human umbilical venous endothelial cells grown to either normo- (5 mmol/l) or hyperglycemia (10 mmol/l) and moderately and acutely exposed to 25 mmol/l glucose. We studied PKC-β2 activation by developing adenovirally expressed chimeras encoding fusion protein between green fluorescent protein (GFP) and conventional β2 isoform (PKC-β2–GFP). Glucose (25 mmol/l) induced the translocation of PKC-β2–GFP from the cytosol to the membrane in cells grown to hyperglycemia but not in those grown in normal glucose medium. Metformin (20 μmol/l) prevented hyperglycemia-induced PKC-β2–GFP translocation. We also assessed oxidative stress under the same conditions with a 4-((9-acridine-carbonyl)amino)-2,2,6,6-tetramethylpiperidin-oxyl,free radical (TEMPO-9-AC) fluorescent probe. We observed significantly increased radical oxygen species production in cells grown in hyperglycemia medium, and this effect was abolished by metformin. We show that in endothelial cells, metformin inhibits hyperglycemia-induced PKC-β2 translocation because of a direct antioxidant effect. Our data substantiate the findings of previous large intervention studies on the beneficial effect of this drug in type 2 diabetic patients.
Direct Activation of Glucose Transport in Primary Human Myotubes After Activation of Peroxisome Proliferator–Activated Receptor δ
Authors: Krämer David Kitz , Al-Khalili Lubna , Perrini Sebastio , Skogsberg Josefin , Wretenberg Per , Kannisto Katja , Wallberg-Henriksson Harriet , Ehrenborg Ewa , Zierath Juleen R. , Krook Anna
Published: March 2007

Activators of peroxisome proliferator–activated receptor (PPAR)γ have been studied intensively for their insulin-sensitizing properties and antidiabetic effects. Recently, a specific PPARδ activator (GW501516) was reported to attenuate plasma glucose and insulin levels when administered to genetically obese ob/ob mice. This study was performed to determine whether specific activation of PPARδ has direct effects on insulin action in skeletal muscle. Specific activation of PPARδ using two pharmacological agonists (GW501516 and GW0742) increased glucose uptake independently of insulin in differentiated C2C12 myotubes. In cultured primary human skeletal myotubes, GW501516 increased glucose uptake independently of insulin and enhanced subsequent insulin stimulation. PPARδ agonists increased the respective phosphorylation and expression of AMP-activated protein kinase 1.9-fold (P < 0.05) and 1.8-fold (P < 0.05), of extracellular signal–regulated kinase 1/2 mitogen-activated protein kinase (MAPK) 2.2-fold (P < 0.05) and 1.7-fold (P < 0.05), and of p38 MAPK 1.2-fold (P < 0.05) and 1.4-fold (P < 0.05). Basal and insulin-stimulated protein kinase B/Akt was unaltered in cells preexposed to PPARδ agonists. Preincubation of myotubes with the p38 MAPK inhibitor SB203580 reduced insulin- and PPARδ-mediated increase in glucose uptake, whereas the mitogen-activated protein kinase kinase inhibitor PD98059 was without effect. PPARδ agonists reduced mRNA expression of PPARδ, sterol regulatory element binding protein (SREBP)-1a, and SREBP-1c (P < 0.05). In contrast, mRNA expression of PPARγ, PPARγ coactivator 1, GLUT1, and GLUT4 was unaltered. Our results provide evidence to suggest that PPARδ agonists increase glucose metabolism and promote gene regulatory responses in cultured human skeletal muscle. Moreover, we provide biological validation of PPARδ as a potential target for antidiabetic therapy.
The Exon 1 Cys7Gly Polymorphism Within the Betacellulin Gene Is Associated With Type 2 Diabetes in African Americans
Authors: Silver Kristi , Tolea Magdalena , Wang Jian , Pollin Toni I. , Yao Flora , Mitchell Braxton D.
Published: March 2007

In vitro and in vivo studies suggest a role for betacellulin in islet neogenesis and regeneration. Since abnormalities in β-cell function play a role in the development of type 2 diabetes, a mutation in the betacellulin gene could potentially contribute to the development of type 2 diabetes. Using RT-PCR, we initially determined that betacellulin was expressed in 9- to 24-week-old human fetal pancreas. We then screened the betacellulin gene for mutations in subjects with type 2 diabetes and identified seven polymorphisms in segments encompassing the 5′ untranslated region (G-233C, A-226G), exon 1 (T̅GC19G̅GC, Cys7Gly), exon 2 (C̅TC130T̅TC, Leu44Phe), exon 4 (T̅TG370A̅TG, Leu124Met), intron 2 (T-31C), and intron 4 (C-4T). These polymorphisms were genotyped in an expanded set of diabetic case and control subjects. Among African Americans (n = 334), the frequency of the Gly7 allele in exon 1 was 31.9% in diabetic case subjects compared with 45.1% in nondiabetic control subjects (P = 0.0004). Allele frequencies for the other polymorphisms did not differ significantly between African-American case and control subjects. Additionally, there were no significant differences in allele frequencies between case and control subjects among the Caucasian sample (n = 426) for any of the seven polymorphisms, including the Gly7 variant. Further studies will be needed to understand the different roles that betacellulin polymorphisms play in susceptibility to type 2 diabetes in Caucasians and African Americans.
Genetic Analysis of HNF4A Polymorphisms in Caucasian-American Type 2 Diabetes
Authors: Bagwell Allison M. , Bento Jennifer L. , Mychaleckyj Josyf C. , Freedman Barry I. , Langefeld Carl D. , Bowden Donald W.
Published: March 2007

Hepatocyte nuclear factor 4α (HNF4A), the gene for the maturity-onset diabetes of the young type 1 monogenic form of type 2 diabetes, is within the type 2 diabetes–linked region on chromosome 20q12-q13.1 and, consequently, is a positional candidate gene for type 2 diabetes in the general population. Previous studies have identified only a few rare coding mutations. However, recent studies suggest that single nucleotide polymorphisms (SNPs) located near the P2 (β-cell) promoter of HNF4A are associated with diabetes susceptibility. In this study, we evaluated 23 SNPs spanning 111 kb including the HNF4A gene for association with type 2 diabetes in a collection of Caucasian type 2 diabetic patients with end-stage renal disease (n = 300) and control subjects (n = 310). None of the individual SNPs were associated with type 2 diabetes in this collection of case subjects (P values ranging from 0.06 to 0.99). However, haplotype analysis identifies significant differences between haplotype frequencies in type 2 diabetic case and control subjects (P = 0.013 to P < 0.001), with two uncommon “risk” haplotypes (2.4 and 2.2% of chromosomes) and two uncommon “protective” haplotypes (7.1 and 5.0% of chromosomes) accounting for the evidence of association. Our results suggest that type 2 diabetes linked to 20q12–13 is a heterogeneous disease in which different populations may have different type 2 diabetes susceptibility loci.
A Single Nucleotide Polymorphism in MGEA5 Encoding O-GlcNAc–selective N-Acetyl-β-d Glucosaminidase Is Associated With Type 2 Diabetes in Mexican Americans
Authors: Lehman Donna M. , Fu Dong-Jing , Freeman Angela B. , Hunt Kelly J. , Leach Robin J. , Johnson-Pais Teresa , Hamlington Jeanette , Dyer Thomas D. , Arya Rector , Abboud Hanna , Göring Harald H.H. , Duggirala Ravindranath , Blangero John , Konrad Robert J. , Stern Michael P.
Published: March 2007

Excess O-glycosylation of proteins by O-linked β-N-acetylglucosamine (O-GlcNAc) may be involved in the pathogenesis of type 2 diabetes. The enzyme O-GlcNAc–selective N-acetyl-β-d glucosaminidase (O-GlcNAcase) encoded by MGEA5 on 10q24.1-q24.3 reverses this modification by catalyzing the removal of O-GlcNAc. We have previously reported the linkage of type 2 diabetes and age at diabetes onset to an overlapping region on chromosome 10q in the San Antonio Family Diabetes Study (SAFADS). In this study, we investigated menangioma-expressed antigen-5 (MGEA5) as a positional candidate gene. Twenty-four single nucleotide polymorphisms (SNPs), identified by sequencing 44 SAFADS subjects, were genotyped in 436 individuals from 27 families whose data were used in the original linkage report. Association tests indicated significant association of a novel SNP with the traits diabetes (P = 0.0128, relative risk = 2.77) and age at diabetes onset (P = 0.0017). The associated SNP is located in intron 10, which contains an alternate stop codon and may lead to decreased expression of the 130-kDa isoform, the isoform predicted to contain the O-GlcNAcase activity. We investigated whether this variant was responsible for the original linkage signal. The variance attributed to this SNP accounted for ∼25% of the logarithm of odds. These results suggest that this variant within the MGEA5 gene may increase diabetes risk in Mexican Americans.
Association of the Diabetes Gene Calpain-10 With Subclinical Atherosclerosis
Authors: Goodarzi Mark O. , Taylor Kent D. , Guo Xiuqing , Quiñones Manuel J. , Cui Jinrui , Li Yanjie , Saad Mohammad F. , Yang Huiying , Hsueh Willa A. , Hodis Howard N. , Rotter Jerome I.
Published: March 2007

The powerful relation between atherosclerosis and diabetes may have a common genetic basis. However, few genes predisposing to both have been identified. Calpain-10 (CAPN10) was the first gene for type 2 diabetes identified by positional cloning, wherein a combination of haplotypes conferred increased risk of diabetes. We sought to determine whether CAPN10 influences subclinical atherosclerosis. Among nondiabetic subjects from 85 Mexican-American families with a history of coronary artery disease, subclinical atherosclerosis was assessed by common carotid artery intima-media thickness (IMT), insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp, and insulin secretion was estimated by the oral glucose tolerance test. These phenotypes were tested for association with CAPN10 haplotypes. Haplotype 1112 (of single nucleotide polymorphisms [SNPs] 44, 43, 56, and 63) was associated with increased IMT, while haplotype 1221 was associated with decreased IMT. The 112/121 haplotype combination (of SNPs 43, 56, and 63), originally found to confer increased risk for diabetes, was associated with the largest IMT in our study population. CAPN10 was also associated with both insulin sensitivity and insulin secretion. Covariate analysis suggested that CAPN10 affects IMT independently of these diabetes-related phenotypes. The fact that the diabetes gene CAPN10 also influences the risk for atherosclerosis shows that inherited factors may underlie the frequent co-occurrence of these two conditions.
Genetic Variation at the ACE Gene Is Associated With Persistent Microalbuminuria and Severe Nephropathy in Type 1 Diabetes
Authors: Boright Andrew P. , Paterson Andrew D. , Mirea Lucia , Bull Shelley B. , Mowjoodi Alireza , Scherer Stephen W. , Zinman Bernard ,   and the DCCT/EDIC Research Group
Published: March 2007

The development and progression of microvascular complications have been extensively documented in a cohort of type 1 diabetic subjects enrolled in the Diabetes Control and Complications Trial (DCCT) and followed in the Epidemiology of Diabetes Interventions and Complications (EDIC) study. We describe the association of genetic variation in the ACE gene in 1,365 DCCT/EDIC subjects with incident persistent microalbuminuria (n = 312) and severe nephropathy (n = 115). We studied three markers (rs1800764, insertion/deletion, and rs9896208) in the ACE gene that allowed us to capture genetic variation in the common haplotypes occurring at frequencies of >5% in Caucasians. Compared with the more frequent genotype (D/I) for the insertion/deletion polymorphism, in multivariate models, the I/I genotype conferred a lower risk for persistent microalbuminuria (hazard ratio [HR] 0.62 [95% CI 0.43–0.89], P = 0.009) and severe nephropathy (0.56 [0.32–0.96], P = 0.033). Variation at the two other markers, rs1800764 and rs9896208, were also associated with these renal outcomes. In addition, homozygosity for the common haplotype TIC (which corresponded to the T, insertion, and C alleles at the three markers, rs1800764, insertion/deletion, and rs9896208, respectively) versus the CDT/TIC haplotype pair was associated with lower risk for development of persistent microalbuminuria (HR 0.49 [0.32–0.75], P = 0.0009) and severe nephropathy (0.41 [0.22–0.78], P = 0.006). Our findings in the DCCT/EDIC cohort provide strong evidence that genetic variation at the ACE gene is associated with the development of nephropathy in patients with type 1 diabetes.
Is Puberty an Accelerator of Type 1 Diabetes in IL6-174CC Females?
Authors: Gillespie Kathleen M. , Nolsøe Runa , Betin Virginie M. , Kristiansen Ole P. , Bingley Polly J. , Mandrup-Poulsen Thomas , Gale Edwin A.M.
Published: March 2007

The pubertal peak in onset of type 1 diabetes occurs earlier in girls than boys. We postulated that this sex difference might be mediated in part by estrogen or by genes regulated by estrogen, such as the interleukin-6 (IL6) gene. Previous studies concerning the role of an estrogen-sensitive single nucleotide polymorphism (SNP) in the IL6 promoter in type 1 diabetes have proved contradictory. We therefore selected a large, genetically homogenous population-based cohort, analyzed by age at onset and sex, to test the hypothesis that the IL6-174G>C SNP affects age at onset of type 1 diabetes in females but not in males. We found that the IL6-174CC genotype was significantly less frequent in females diagnosed after than in those diagnosed before the age of 10 years (19 vs. 13%, P = 0.016). No genotype difference was observed in males stratified for age at onset. Among children diagnosed after age 10, the median age of onset was 11.9 years (intraquartile range 10.7–14.6) in 34 girls homozygous for IL6-174C compared with 13.2 years (11.6–15.4) in 229 girls with other genotypes and 13.5 years (12.0–15.6) in 339 males with any IL6-174 genotype (P = 0.012). These data support the hypothesis that pubertal changes may contribute to accelerated onset of type 1 diabetes in genetically susceptible females. This phenomenon may be orchestrated by the action of estrogen on the IL6 promoter.