bluuebunny/crossref_metadata_2025 huggingface dataset:
Association Between Mannose-Binding Lectin and Vascular Complications in Type 1 Diabetes
Authors: Hansen Troels K. , Tarnow Lise , Thiel Steffen , Steffensen Rudi , Stehouwer Coen D. , Schalkwijk Casper G. , Parving Hans-Henrik , Flyvbjerg Allan
Published: March 2007

Complement activation and inflammation have been suggested in the pathogenesis of diabetic vascular lesions. We investigated serum mannose-binding lectin (MBL) levels and polymorphisms in the MBL gene in type 1 diabetic patients with and without diabetic nephropathy and associated macrovascular complications. Polymorphisms in the MBL gene and serum MBL levels were determined in 199 type 1 diabetic patients with overt nephropathy and 192 type 1 diabetic patients with persistent normoalbuminuria matched for age, sex, and duration of diabetes, as well as in 100 healthy control subjects. The frequencies of high- and low-expression MBL genotypes were similar in patients with type 1 diabetic and healthy control subjects. High MBL genotypes were significantly more frequent in diabetic patients with nephropathy than in the normoalbuminuric group, and the risk of having nephropathy given a high MBL genotype assessed by odds ratio (OR) was 1.52 (1.02–2.27, P = 0.04). Median serum MBL concentrations were significantly higher in patients with nephropathy than in patients with normoalbuminuria: 2,306 μg/l (interquartile range [IQR] 753–4,867 μg/l) vs. 1,491 μg/l (577–2,944 μg/l), P = 0.0003. In addition, even when comparing patients with identical genotypes, serum MBL levels were higher in the nephropathy group than in the normoalbuminuric group. Patients with a history of cardiovascular disease had significantly elevated MBL levels independent of nephropathy status (3,178 μg/l [IQR 636–5,231 μg/l] vs. 1,741 μg/l [656–3,149 μg/l], P = 0.02). The differences in MBL levels between patients with and without vascular complications were driven primarily by pronounced differences among carriers of high MBL genotypes (P < 0.0001). Our findings suggest that MBL may be involved in the pathogenesis of micro- and macrovascular complications in type 1 diabetes, and that determination of MBL status might be used to identify patients at increased risk of developing these complications.
A New Mouse Model of Type 2 Diabetes, Produced by N-Ethyl-Nitrosourea Mutagenesis, Is the Result of a Missense Mutation in the Glucokinase Gene
Authors: Toye Ayo A. , Moir Lee , Hugill Alison , Bentley Liz , Quarterman Julie , Mijat Vesna , Hough Tertius , Goldsworthy Michelle , Haynes Alison , Hunter A. Jacqueline , Browne Mick , Spurr Nigel , Cox Roger D.
Published: March 2007

Here we report the first cloned N-ethyl-nitrosourea (ENU)-derived mouse model of diabetes. GENA348 was identified through free-fed plasma glucose measurement, being more than 2 SDs above the population mean of a cohort of >1,201 male ENU mutant mice. The underlying gene was mapped to the maturity-onset diabetes of the young (MODY2) homology region of mouse chromosome 11 (logarithm of odds 6.0). Positional candidate gene analyses revealed an A to T transversion mutation in exon 9 of the glucokinase gene, resulting in an isoleucine to phenylalanine change at amino acid 366 (I366F). Heterozygous mutants have 67% of the enzyme activity of wild-type littermates (P < 0.0012). Homozygous mutants have less enzyme activity (14% of wild-type activity) and are even less glucose tolerant. The GENA348 allele is novel because no mouse or human diabetes studies have described a mutation in the corresponding amino acid position. It is also the first glucokinase missense mutation reported in mice and is homozygous viable, unlike the global knockout mutations. This work demonstrates that ENU mutagenesis screens can be used to generate models of complex phenotypes, such as type 2 diabetes, that are directly relevant to human disease.
Genome-wide Scan for Type 2 Diabetes Loci in Hong Kong Chinese and Confirmation of a Susceptibility Locus on Chromosome 1q21-q25
Authors: Ng Maggie C.Y. , So Wing-Yee , Cox Nancy J. , Lam Vincent K.L. , Cockram Clive S. , Critchley Julian A.J.H. , Bell Graeme I. , Chan Juliana C.N.
Published: March 2007

We conducted an autosomal genome scan to map loci for type 2 diabetes in a Hong Kong Chinese population. We studied 64 families, segregating type 2 diabetes, of which 57 had at least one member with an age at diagnosis of ≤40 years. These families included a total of 126 affected sibpairs and 4 other affected relative pairs. Nonparametric linkage analysis revealed seven regions showing nominal evidence for linkage with type 2 diabetes (logarithm of odds [LOD] >0.59, Ppointwise < 0.05): chromosome 1 at 173.9 cM (LOD = 3.09), chromosome 3 at 26.3 cM (LOD = 1.27), chromosome 4 at 135.3 cM (LOD = 2.63), chromosome 5 at 139.3 cM (LOD = 0.84), chromosome 6 at 178.9 cM (LOD = 1.91), chromosome 12 at 48.7 cM (LOD = 1.99), and chromosome 18 at 28.1 cM (LOD = 1.00). Simulation studies showed genome-wide significant evidence for linkage of the chromosome 1 region (Pgenome-wide = 0.036). We have confirmed the results of previous studies for the presence of a susceptibility locus on chromosome 1q21-q25 (173.9 cM) and suggest the locations of other loci that may contribute to the development of type 2 diabetes in Hong Kong Chinese.
Mechanisms of Early Insulin-Sensitizing Effects of Thiazolidinediones in Type 2 Diabetes
Authors: Tonelli Julia , Li Weijie , Kishore Preeti , Pajvani Utpal B. , Kwon Elize , Weaver Charles , Scherer Philipp E. , Hawkins Meredith
Published: March 2007

Whereas thiazolidinediones (TZDs) are known to rapidly improve insulin action in animals, short durations of TZD therapy have never been studied in humans. Among the many known actions of TZDs, increased circulating levels of the high molecular weight (HMW) multimer of adiponectin may be an important insulin-sensitizing mechanism. We examined the effects of only 21 days of 45 mg of pioglitazone (P+) versus placebo (P−) in nine subjects with type 2 diabetes (HbA1c, 10.9 ± 0.6%; BMI, 31.9 ± 1.5 kg/m2). Total adiponectin levels increased by approximately twofold in P+ in association with increased adipose tissue gene expression. However, plasma free fatty acid and glucose levels were unchanged, and there were only minimal changes in other “adipokines.” Glucose fluxes ([3-3H]glucose infusion) were measured during 6-h euglycemic (5 mmol/l) “pancreatic clamp” studies (somatostatin/glucagon/growth hormone) with stepped insulin levels. Pioglitazone induced marked decreases in endogenous glucose production (P+ = 0.9 ± 0.1 vs. P− = 1.7 ± 0.3 mg · kg−1 · min−1; P < 0.05) at physiologic hyperinsulinemia (∼50 μU/ml), which was highly correlated with an increased ratio of HMW adiponectin/total levels (r2 = 0.90). Maximal insulin stimulation (∼400 μU/ml) revealed pioglitazone-associated increases in glucose uptake (P+ = 10.5 ± 0.9 vs. P− = 8.9 ± 0.8 mg · kg−1 · min−1; P < 0.05), which did not correlate with HMW or total adiponectin levels. Thus, only 21 days of pioglitazone therapy improved insulin action in humans with type 2 diabetes. Increased abundance of the HMW adiponectin multimer may contribute to the hepatic insulin-sensitizing effects of these agents.
Lilly Lecture 2003
Authors: Accili Domenico
Published: March 2007

Type 2 diabetes arises from a combination of impaired insulin action and defective pancreatic β-cell function. Classically, the two abnormalities have been viewed as distinct yet mutually detrimental processes. The combination of impaired insulin-dependent glucose metabolism in skeletal muscle and impaired β-cell function causes an increase of hepatic glucose production, leading to a constellation of tissue abnormalities that has been referred to as the diabetes “ruling triumvirate.” Targeted mutagenesis in mice has led to a critical reappraisal of the integrated physiology of insulin action. These studies indicate that insulin resistance in skeletal muscle and adipose tissue does not necessarily lead to hyperglycemia, so long as insulin sensitivity in other tissues is preserved. Additional data suggest a direct role of insulin signaling in β-cell function and regulation of β-cell mass, thus raising the possibility that insulin resistance may be the overarching feature of diabetes in all target tissues. I propose that we replace the original picture of a ruling triumvirate with that of a squabbling republic in which every tissue contributes to the onset of the disease.
Glucose- and Interleukin-1β-Induced β-Cell Apoptosis Requires Ca2+ Influx and Extracellular Signal-Regulated Kinase (ERK) 1/2 Activation and Is Prevented by a Sulfonylurea Receptor 1/Inwardly Rectifying K+ Channel 6.2 (SUR/Kir6.2) Selective Potassium Channel Opener in Human Islets
Authors: Maedler Kathrin , Størling Joachim , Sturis Jeppe , Zuellig Richard A. , Spinas Giatgen A. , Arkhammar Per O.G. , Mandrup-Poulsen Thomas , Donath Marc Y.
Published: March 2007

Increasing evidence indicates that a progressive decrease in the functional β-cell mass is the hallmark of both type 1 and type 2 diabetes. The underlying causes, β-cell apoptosis and impaired secretory function, seem to be partly mediated by macrophage production of interleukin (IL)-1β and/or high-glucose-induced β-cell production of IL-1β. Treatment of type 1 and type 2 diabetic patients with the potassium channel opener diazoxide partially restores insulin secretion. Therefore, we studied the effect of diazoxide and of the novel potassium channel opener NN414, selective for the β-cell potassium channel SUR1/Kir6.2, on glucose- and IL-1β-induced apoptosis and impaired function in human β-cells. Exposure of human islets for 4 days to 11.1 and 33.3 mmol/l glucose, 2 ng/ml IL-1β, or 10 and 100 μmol/l of the sulfonylurea tolbutamide induced β-cell apoptosis and impaired glucose-stimulated insulin secretion. The deleterious effects of glucose and IL-1β were blocked by 200 μmol/l diazoxide as well as by 3 and 30 μmol/l NN414. By Western blotting with phosphospecific antibodies, glucose and IL-1β were shown to activate the extracellular signal-regulated kinase (ERK) 1/2, an effect that was abrogated by 3 μmol/l NN414. Similarly, 1 μmol/l of the mitogen-activated protein kinase/ERK kinase 1/2 inhibitor PD098059 or 1 μmol/l of the l-type Ca2+ channel blocker nimodipine prevented glucose- and IL-1β-induced ERK activation, β-cell apoptosis, and impaired function. Finally, islet release of IL-1β in response to high glucose could be abrogated by nimodipine, NN414, or PD098059. Thus, in human islets, glucose- and IL-1β-induced β-cell secretory dysfunction and apoptosis are Ca2+ influx and ERK dependent and can be prevented by the β-cell selective potassium channel opener NN414.
In Vivo and In Vitro Characterization of Insulin-Producing Cells Obtained From Murine Bone Marrow
Authors: Tang Dong-Qi , Cao Li-Zhen , Burkhardt Brant R. , Xia Chang-Qi , Litherland Sally A. , Atkinson Mark A. , Yang Li-Jun
Published: March 2007

Efforts toward routine islet cell transplantation as a means for reversing type 1 diabetes have been hampered by islet availability as well as allograft rejection. In vitro transdifferentiation of mouse bone marrow (BM)-derived stem (mBMDS) cells into insulin-producing cells could provide an abundant source of autologous cells for this procedure. For this study, we isolated and characterized single cell-derived stem cell lines obtained from mouse BM. In vitro differentiation of these mBMDS cells resulted in populations meeting a number of criteria set forth to define functional insulin-producing cells. Specifically, the mBMDS cells expressed multiple genes related to pancreatic β-cell development and function (insulin I and II, Glut2, glucose kinase, islet amyloid polypeptide, nestin, pancreatic duodenal homeobox-1 [PDX-1], and Pax6). Insulin and C-peptide production was identified by immunocytochemistry and confirmed by electron microscopy. In vitro studies involving glucose stimulation identified glucose-stimulated insulin release. Finally, these mBMDS cells transplanted into streptozotocin-induced diabetic mice imparted reversal of hyperglycemia and improved metabolic profiles in response to intraperitoneal glucose tolerance testing. These results indicate that mouse BM harbors cells capable of in vitro transdifferentiating into functional insulin-producing cells and support efforts to derive such cells in humans as a means to alleviate limitations surrounding islet cell transplantation.
Effects of Low and Moderate Antecedent Exercise on Counterregulatory Responses to Subsequent Hypoglycemia in Type 1 Diabetes
Authors: Sandoval Darleen A. , Guy Deanna L. Aftab , Richardson M. Antoinette , Ertl Andrew C. , Davis Stephen N.
Published: March 2007

Antecedent moderate-intensity exercise has been shown to blunt autonomic, neuroendocrine, and metabolic counterregulatory responses to subsequent hypoglycemia in nondiabetic individuals. The aims of the current study were to determine 1) whether this occurs in type 1 diabetic patients and 2) whether the degree of blunting is dependent on exercise intensity. Twenty-seven type 1 diabetic patients (13 women and 14 men) were studied during a single-step, 2-h hyperinsulinemic (9 pmol · kg−1 · min−1)-hypoglycemic (∼2.8 mmol/l) clamp 1 day after two 90-min exercise bouts at 30% (n = 11) or at 50% (n = 11) Vo2max or after no prior stress (control subjects, n = 25). After prior exercise at both 30 and 50% Vo2max, epinephrine (1,959 ± 553 and 1,528 ± 424 vs. 3,420 ± 424 pmol/l, respectively; P < 0.05) and pancreatic polypeptide (97 ± 32 and 98 ± 8 vs. 223 ± 32 pmol/l, respectively; P < 0.05) responses to subsequent hypoglycemia were significantly lower compared with those of control subjects. Endogenous glucose production was significantly lower, while glucose utilization and, consequently, the exogenous glucose infusion rate needed to maintain hypoglycemia were significantly greater after both exercise intensities compared with that of control subjects. Muscle sympathetic nerve activity was significantly reduced by prior exercise of both intensities at baseline (16 ± 4 and 22 ± 4 vs. 31 ± 3 bursts/min) and during hypoglycemia (22 ± 4 and 27 ± 5 vs. 41 ± 3 bursts/min) compared with that of control subjects (P < 0.05). Total hypoglycemic symptoms were also significantly lower (P < 0.05) in both exercise groups compared with the control group. In summary, repeated episodes of prolonged exercise of both low and moderate intensities blunted key autonomic (epinephrine and pancreatic polypeptide) and metabolic (endogenous glucose production and peripheral glucose uptake) counterregulatory responses to next-day hypoglycemia in type 1 diabetes.
Ciliary Neurotrophic Factor Improves Nerve Conduction and Ameliorates Regeneration Deficits in Diabetic Rats
Authors: Mizisin Andrew P. , Vu Yvonne , Shuff Michelle , Calcutt Nigel A.
Published: March 2007

Ciliary neurotrophic factor (CNTF) protein and bioactivity are reduced in the peripheral nerve of hyperglycemic rats with a cause related to metabolism of hexose sugars by aldose reductase. Here the efficacy of CNTF treatment against disorders of nerve function in hyperglycemic rats was investigated. CNTF treatment from the onset of 8 weeks of galactose feeding prevented nerve conduction slowing in a dose-dependent manner. Streptozotocin-induced diabetic rats were maintained for 4 weeks before CNTF treatment was initiated. Four weeks of CNTF treatment significantly improved nerve conduction compared with untreated diabetic rats and also normalized the recovery of toe spread after sciatic nerve crush. One week of CNTF treatment significantly improved the distance of sensory nerve regeneration achieved after nerve crush injury compared with untreated diabetic rats. CNTF was without effects on any parameter in nondiabetic rats. Eight weeks of diabetes did not impair macrophage recruitment 1 and 7 days after nerve crush; neither did intraneural injections of CNTF and CNTFRα enhance recruitment in diabetic or control rats. These observations point to the potential utility of CNTF in treating nerve dysfunction in experimental diabetes.
Tumstatin Peptide, an Inhibitor of Angiogenesis, Prevents Glomerular Hypertrophy in the Early Stage of Diabetic Nephropathy
Authors: Yamamoto Yoshihiko , Maeshima Yohei , Kitayama Hiroyuki , Kitamura Shinji , Takazawa Yuki , Sugiyama Hitoshi , Yamasaki Yasushi , Makino Hirofumi
Published: March 2007

In the early stage of diabetic nephropathy (one of the major microvascular complications of diabetes) glomerular hyperfiltration and hypertrophy are observed. It is clinically important to regulate glomerular hypertrophy for preventing glomerulosclerosis. The number of glomerular endothelial cells is known to be increased in diabetic nephropathy associated with enlarged glomerular tufts, suggesting that the mechanism is similar to that of angiogenesis. Tumstatin peptide is an angiogenesis inhibitor derived from type IV collagen and inhibits in vivo neovascularization induced by vascular endothelial growth factor (VEGF), one of the mediators of glomerular hypertrophy in diabetic nephropathy. Here, we show the effect of tumstatin peptide in inhibiting alterations in early diabetic nephropathy. Glomerular hypertrophy, hyperfiltration, and albuminuria were suppressed by tumstatin peptide (1 mg/kg) in streptozotocin-induced diabetic mice. Glomerular matrix expansion, the increase of total glomerular cell number and glomerular endothelial cells (CD31 positive), and monocyte/macrophage accumulation was inhibited by tumstatin peptide. Increase in renal expression of VEGF, flk-1, and angiopoietin-2, an antagonist of angiopoietin-1, was inhibited by tumstatin treatment in diabetic mice. Alteration of glomerular nephrin expression, a podocyte protein crucial for maintaining glomerular filtration barrier, was recovered by tumstatin in diabetic mice. Taken together, these results demonstrate the potential use of antiangiogenic tumstatin peptide as a novel therapeutic agent in early diabetic nephropathy.
Genome-wide Linkage Analysis for Severe Obesity in French Caucasians Finds Significant Susceptibility Locus on Chromosome 19q
Authors: Bell Christopher G. , Benzinou Michael , Siddiq Afshan , Lecoeur Cécile , Dina Christian , Lemainque Arnaud , Clément Karine , Basdevant Arnaud , Guy-Grand Bernard , Mein Charles A. , Meyre David , Froguel Philippe
Published: March 2007

To ascertain whether distinct chromosomal loci existed that were linked to severe obesity, as well as to utilize the increased heritability of this excessive phenotype, we performed a genome-wide scan in severely obese French Caucasians. The 109 selected pedigrees, totaling 447 individuals, required both the proband and a sibling to be severely obese (BMI ≥35 kg/m2), and 84.8% of the nuclear families possessed ≥1 morbidly obese sibling (BMI ≥40). Severe and morbid obesity are still relatively rare in France, with rates of 2.5 and 0.6%, respectively. The initial genome scan consisted of 395 evenly spaced microsatellite markers. Six regions were found to have suggestive linkage on 4q, 6cen-q, 17q, and 19q for a BMI ≥35 phenotypic subset, and 5q and 10q for an inclusive BMI ≥27 group. The highest peak on chromosome 19q (logarithm of odds [LOD] = 3.59) was significant by genome scan simulation testing (P = 0.042). These regions then underwent second-stage mapping with an additional set of 42 markers. BMI ≥35 analysis defined regions on 17q23.3–25.1 and 19q13.33–13.43 with an maximum likelihood score LOD of 3.16 and 3.21, respectively. Subsequent pooled data analysis with an additional previous population of 66 BMI ≥35 sib-pairs led to a significant LOD score of 3.8 at the 19q locus (empirical P = 0.023). For more moderate obesity and overweight susceptibility loci, BMI ≥27 analysis confirmed suggestive linkage to chromosome regions 5q14.3–q21.3 (LOD = 2.68) and 10q24.32–26.2 (LOD = 2.47). Plausible positional candidate genes include NR1H2 and TULP2.
Wolcott-Rallison Syndrome
Authors: Senée Valérie , Vattem Krishna M. , Delépine Marc , Rainbow Lynn A. , Haton Céline , Lecoq Annick , Shaw Nick J. , Robert Jean-Jacques , Rooman Raoul , Diatloff-Zito Catherine , Michaud Jacques L. , Bin-Abbas Bassan , Taha Doris , Zabel Bernard , Franceschini Piergiorgio , Topaloglu A. Kemal , Lathrop G. Mark , Barrett Timothy G. , Nicolino Marc , Wek Ronald C. , Julier Cécile
Published: March 2007

Wolcott-Rallison syndrome (WRS) is a rare autosomal-recessive disorder characterized by the association of permanent neonatal or early-infancy insulin-dependent diabetes, multiple epiphyseal dysplasia and growth retardation, and other variable multisystemic clinical manifestations. Based on genetic studies of two inbred families, we previously identified the gene responsible for this disorder as EIF2AK3, the pancreatic eukaryotic initiation factor 2α (eIF2α) kinase. Here, we have studied 12 families with WRS, totalling 18 cases. With the exception of one case, all patients carried EIF2AK3 mutations resulting in truncated or missense versions of the protein. Exclusion of EIF2AK3 mutations in the one patient case was confirmed by both linkage and sequence data. The activities of missense versions of EIF2AK3 were characterized in vivo and in vitro and found to have a complete lack of activity in four mutant proteins and residual kinase activity in one. Remarkably, the onset of diabetes was relatively late (30 months) in the patient expressing the partially defective EIF2AK3 mutant and in the patient with no EIF2AK3 involvement (18 months) compared with other patients (<6 months). The patient with no EIF2AK3 involvement did not have any of the other variable clinical manifestations associated with WRS, which supports the idea that the genetic heterogeneity between this variant form of WRS and EIF2AK3 WRS correlates with some clinical heterogeneity.
The −866A/A Genotype in the Promoter of the Human Uncoupling Protein 2 Gene Is Associated With Insulin Resistance and Increased Risk of Type 2 Diabetes
Authors: D’Adamo Monica , Perego Lucia , Cardellini Marina , Marini Maria Adelaide , Frontoni Simona , Andreozzi Francesco , Sciacqua Angela , Lauro Davide , Sbraccia Paolo , Federici Massimo , Paganelli Michele , Pontiroli Antonio E. , Lauro Renato , Perticone Francesco , Folli Franco , Sesti Giorgio
Published: March 2007

Uncoupling protein (UCP)-2 is a member of the mitochondrial inner membrane carriers that uncouple pro-ton entry in the mitochondrial matrix from ATP synthesis. The −866G/A polymorphism in the UCP2 gene, which enhances its transcriptional activity, was associated with enhanced risk for type 2 diabetes in obese subjects. We addressed the question of whether the −866G/A polymorphism contributes to variation in insulin sensitivity by genotyping 181 nondiabetic offspring of type 2 diabetic patients. Insulin sensitivity, assessed by the hyperinsulinemic-euglycemic clamp, was reduced in −866A/A carriers compared with −866A/G or −866G/G carriers (P = 0.01). To directly investigate the correlation between UCP2 expression and insulin resistance, UCP2 mRNA levels were measured by real-time RT-PCR in subcutaneous fat obtained from 100 obese subjects who underwent laparoscopic adjustable gastric banding. UCP2 mRNA expression was significantly correlated with insulin resistance as assessed by the homeostasis model assessment index (r = 0.27, P = 0.007). We examined the association of the −866A/A genotype in a case-control study including 483 type 2 diabetic subjects and 565 control subjects. The −866A/A genotype was associated with diabetes in women (odds ratio 1.84, 95% CI 1.03–3.28; P = 0.037), but not in men. These results indicate that the −866A/A genotype of the UCP2 gene may contribute to diabetes susceptibility by affecting insulin sensitivity.
No Association Between Variation of the FOXP3 Gene and Common Type 1 Diabetes in the Sardinian Population
Authors: Zavattari Patrizia , Deidda Elisabetta , Pitzalis Maristella , Zoa Barbara , Moi Loredana , Lampis Rosanna , Contu Daniela , Motzo Costantino , Frongia Paola , Angius Efisio , Maioli Mario , Todd John A. , Cucca Francesco
Published: March 2007

Mutations of the forkhead/winged helix transcription factor FOXP3 gene on chromosome Xp11.23 cause a rare recessive monogenic disorder called IPEX (immune dysregulation, polyendocrinopathy, including type 1 diabetes, enteropathy, and X-linked syndrome). FOXP3 is necessary for the differentiation of a key immune suppressive subset of T-cells, the CD4+CD25+ regulatory T-cells. Previously, we reported a significant male-female bias in the common, multifactorial form of type 1 diabetes in Sardinia and evidence of linkage of chromosome Xp11 to the disease. These findings indicate that FOXP3 is a prime functional and positional candidate locus for the common form of type 1 diabetes. In the present study, we initially scanned 82 kb of the FOXP3 region for common polymorphisms, including sequencing all of the coding and functionally relevant portions of the gene in 64 Sardinian individuals. Then the most informative polymorphisms in 418 type 1 diabetic families and in 268 male case and 326 male control subjects were sequentially genotyped and tested for disease association. There is no evidence that variants in the FOXP3 regions analyzed are associated with type 1 diabetes and account for the male-female bias observed in Sardinia. Our data indicate that allelic variation in or near the coding regions of the FOXP3 gene does not have a major role in the inherited susceptibility to the common form of type 1 diabetes.
Restoration of Cardiomyocyte Functional Properties by Angiotensin II Receptor Blockade in Diabetic Rats
Authors: Raimondi Laura , De Paoli Petra , Mannucci Edoardo , Lonardo Giuseppe , Sartiani Laura , Banchelli Grazia , Pirisino Renato , Mugelli Alessandro , Cerbai Elisabetta
Published: March 2007

Recent evidence suggests that blockade of the renin-angiotensin system ameliorates diabetes-induced cardiac dysfunction, but the mechanisms involved in this process remain elusive. We investigated the effect of treatment with an angiotensin II receptor blocker, losartan, on the metabolic and electrophysiological properties of cardiomyocytes isolated from streptozotocin-induced diabetic (STZ) rats. Glucose uptake and electrophysiological properties were measured in ventricular cardiomyocytes from normoglycemic and STZ-induced diabetic rats given vehicle or 20 mg · kg−1 · day−1 losartan for 8 weeks. Insulin and β-adrenergic stimulation failed to increase the glucose uptake rate in STZ cardiomyocytes, whereas the α-adrenergic effect persisted. Concurrently, a typical prolongation of action potential duration (APD) and a decrease of transient outward current (Ito) were recorded in patch-clamped STZ myocytes. Treatment with losartan did not affect body weight or glycemia of diabetic or control animals. However, in losartan-treated STZ-induced diabetic rats, β-adrenergic−mediated enhancement of glucose uptake was completely recovered. APD and Ito were similar to those measured in losartan-treated control rats. A significant (P < 0.0001) correlation between metabolic and electrophysiological parameters was found in control, diabetic, and losartan-treated diabetic rats. Thus, angiotensin receptor blockade protects the heart from the development of cellular alterations typically associated with diabetes. These data suggest that angiotensin receptor blockers may represent a new therapeutic strategy for diabetic cardiomyopathy.
PYY3–36 Reinforces Insulin Action on Glucose Disposal in Mice Fed a High-Fat Diet
Authors: van den Hoek Anita M. , Heijboer Annemieke C. , Corssmit Eleonora P.M. , Voshol Peter J. , Romijn Johannes A. , Havekes Louis M. , Pijl Hanno
Published: March 2007

Peptide YY3–36 (PYY3–36) is released by the gut in response to nutrient ingestion. It modulates the activities of orexigenic neuropeptide Y (NPY) neurons and anorexigenic proopiomelanocortin (POMC) neurons in the hypothalamus to inhibit food intake. Because both NPY and POMC have also been shown to impact insulin action, we wondered whether PYY3–36 could improve insulin sensitivity. To address this question, we examined the acute effect of intravenous PYY3–36 on glucose and free fatty acid (FFA) flux during a hyperinsulinemic-euglycemic clamp in mice maintained on a high-fat diet for 2 weeks before the experiment. We also evaluated the effects of PYY3–36 infusion on glucose uptake in muscle and adipose tissue in this experimental context. Under basal conditions, none of the metabolic parameters were affected by PYY3–36. Under hyperinsulinemic conditions, glucose disposal was significantly increased in PYY3–36-infused compared with vehicle-infused mice (103.8 ± 10.9 vs. 76.1 ± 11.4 μmol · min−1 · kg−1, respectively; P = 0.001). Accordingly, glucose uptake in muscle and adipose tissue was greater in PYY3–36- treated animals, although the difference with controls did not reach statistical significance in adipose tissue (muscle: 2.1 ± 0.5 vs. 1.5 ± 0.5 μmol/g tissue, P = 0.049; adipose tissue: 0.8 ± 0.4 vs. 0.4 ± 0.3 μmol/g tissue, P = 0.08). In contrast, PYY3–36 did not impact insulin action on endogenous glucose production or FFA metabolism. These data indicate that PYY3–36 reinforces insulin action on glucose disposal in mice fed a high-fat diet, through a mechanism that is independent of food intake and body weight. In contrast, it leaves glucose production and lipid flux largely unaffected in this experimental context.
Potential Role for AMP-Activated Protein Kinase in Hypoglycemia Sensing in the Ventromedial Hypothalamus
Authors: McCrimmon Rory J. , Fan Xiaoning , Ding Yuyan , Zhu Wanling , Jacob Ralph J. , Sherwin Robert S.
Published: March 2007

The mechanisms by which specialized glucose-sensing neurons within the hypothalamus are able to detect a falling blood glucose remain largely unknown but may be linked to some gauge of neuronal energy status. We sought to test the hypothesis that AMP-activated protein kinase (AMPK), an intracellular kinase purported to act as a fuel sensor, plays a role in hypoglycemia sensing in the ventromedial hypothalamus (VMH) of the Sprague-Dawley rat by chemically activating AMPK in vivo through bilateral microinjection, before performing hyperinsulinemic-hypoglycemic or hyperinsulinemic-euglycemic clamp studies. In a subgroup of rats, H3-glucose was infused to determine glucose kinetics. The additional chemical activation by AICAR of AMPK in the VMH during hypoglycemia markedly reduced the amount of exogenous glucose required to maintain plasma glucose during hypoglycemia, an effect that was almost completely accounted for by a three- to fourfold increase in hepatic glucose production in comparison to controls. In contrast, no differences were seen between groups in hypoglycemia-induced rises in the principal counterregulatory hormones. In conclusion, activation of AMPK within the VMH may play an important role in hypoglycemia sensing. The combination of hypoglycemia- and AICAR-induced AMPK activity appears to result in a marked stimulus to hepatic glucose counterregulation.
The Regulation of Glucose-Excited Neurons in the Hypothalamic Arcuate Nucleus by Glucose and Feeding-Relevant Peptides
Authors: Wang R. , Liu X. , Hentges S.T. , Dunn-Meynell A.A. , Levin B.E. , Wang W. , Routh V.H.
Published: March 2007

Glucosensing neurons in the hypothalamic arcuate nucleus (ARC) were studied using electrophysiological and immunocytochemical techniques in neonatal male Sprague-Dawley rats. We identified glucose-excited and -inhibited neurons, which increase and decrease, respectively, their action potential frequency (APF) as extracellular glucose levels increase throughout the physiological range. Glucose-inhibited neurons were found predominantly in the medial ARC, whereas glucose-excited neurons were found in the lateral ARC. ARC glucose-excited neurons in brain slices dose-dependently increased their APF and decreased their ATP-sensitive K+ channel (KATP channel) currents as extracellular glucose levels increased from 0.1 to 10 mmol/l. However, glucose sensitivity was greatest as extracellular glucose decreased to <2.5 mmol/l. The glucokinase inhibitor alloxan increases KATP single-channel currents in glucose-excited neurons in a manner similar to low glucose. Leptin did not alter the activity of ARC glucose-excited neurons. Although insulin did not affect ARC glucose-excited neurons in the presence of 2.5 mmol/l (steady-state) glucose, they were stimulated by insulin in the presence of 0.1 mmol/l glucose. Neuropeptide Y (NPY) inhibited and α-melanocyte–stimulating hormone stimulated ARC glucose-excited neurons. ARC glucose-excited neurons did not show pro-opiomelanocortin immunoreactivity. These data suggest that ARC glucose-excited neurons may serve an integrative role in the regulation of energy balance.
Increased Serum Levels of MRP-8/14 in Type 1 Diabetes Induce an Increased Expression of CD11b and an Enhanced Adhesion of Circulating Monocytes to Fibronectin
Authors: Bouma Gerben , Lam-Tse Wai Kwan , Wierenga-Wolf Annet F. , Drexhage Hemmo A. , Versnel Marjan A.
Published: March 2007

The recruitment of monocytes from the bloodstream is crucial in the accumulation of macrophages and dendritic cells in type 1 diabetic pancreases. Adhesion via integrins to endothelium and extracellular matrix proteins, such as fibronectin (FN), and the production of myeloid-related protein (MRP)-8, -14, and -8/14 by recently transmigrated monocytes are thought to be instrumental in such recruitment. We determined the FN-adhesive capacity and integrin expression of monocytes of type 1 and type 2 diabetic patients and related them to the subjects’ serum levels of MRP-8, -14 and -8/14. Monocytes of type 1 diabetic patients displayed an increased adhesion to fibronectin in comparison with type 2 patients and healthy control subjects but had a normal expression of the FN binding integrins CD29, CD49a, CD49d, and CD49e (although CD11b and CD18 expression was increased). MRP-8/14, which was increased in the sera of type 1 diabetic patients, induced healthy donor monocytes to adhere to FN and upregulate CD11b expression in a dosage-dependent manner. The observed MRP-induced increased adhesion of monocytes to FN and upregulation of CD11b most likely contributed to a facilitated accumulation of monocytes and monocyte-derived cells at the site of inflammation, in this case the pancreatic islets.
GAD65-Specific CD4+ T-Cells with High Antigen Avidity Are Prevalent in Peripheral Blood of Patients With Type 1 Diabetes
Authors: Reijonen Helena , Mallone Roberto , Heninger Anne-Kristin , Laughlin Elsa M. , Kochik Sharon A. , Falk Ben , Kwok William W. , Greenbaum Carla , Nepom Gerald T.
Published: March 2007

Negative selection of self-reactive T-cells during thymic development, along with activation-induced cell death in peripheral lymphocytes, is designed to limit the expansion and persistence of autoreactive T-cells. Autoreactive T-cells are nevertheless present, both in patients with type 1 diabetes and in at-risk subjects. By using MHC class II tetramers to probe the T-cell receptor (TcR) specificity and avidity of GAD65 reactive T-cell clones isolated from patients with type 1 diabetes, we identified high-avidity CD4+ T-cells in peripheral blood, coexisting with low-avidity cells directed to the same GAD65 epitope specificity. A variety of cytokine patterns was observed, even among T-cells with high MHC-peptide avidity, and the clones utilize a biased set of TcR genes that favor two combinations, Vα12-β5.1 and Vα17-Vβ4. Presence of these high-avidity TcRs indicates a failure to delete autoreactive T-cells that likely arise from oligoclonal expansion in response to autoantigen exposure during the progression of type 1 diabetes.
Inhibition of Activin Signaling Induces Pancreatic Epithelial Cell Expansion and Diminishes Terminal Differentiation of Pancreatic β-Cells
Authors: Zhang You-Qing , Cleary Mary Malo , Si Yingjie , Liu Guoxun , Eto Yuzuru , Kritzik Marcie , Dabernat Sandrine , Kayali Ayse G. , Sarvetnick Nora
Published: March 2007

Activins regulate the growth and differentiation of a variety of cells. During pancreatic islet development, activins are required for the specialization of pancreatic precursors from the gut endoderm during midgestation. In this study, we probed the role of activin signaling during pancreatic islet cell development and regeneration. Indeed, we found that both activins and activin receptors are upregulated in duct epithelial cells during islet differentiation. Interestingly, the expression of endogenous cellular inhibitors of activin signaling, follistatin and Cripto, were also found to be augmented. Inhibition of activins significantly enhanced survival and expansion of pancreatic epithelial cells but decreased the numbers of differentiated β-cells. Our results suggest that the homeostasis of growth and terminal differentiation requires a precise context-dependent regulation of activin signaling. Follistatin participates in this process by promoting expansion of precursor cells during pancreas growth.
Proinflammatory Cytokines, Markers of Cardiovascular Risks, Oxidative Stress, and Lipid Peroxidation in Patients With Hyperglycemic Crises
Authors: Stentz Frankie B. , Umpierrez Guillermo E. , Cuervo Ruben , Kitabchi Abbas E.
Published: March 2007

Acute and chronic hyperglycemia are proinflammatory states, but the status of proinflammatory cytokines and markers of oxidative stress and cardiovascular risks is not known in hyperglycemic crises of diabetic ketoacidosis (DKA) and nonketotic hyperglycemia (NKH). We studied 20 lean and 28 obese patients with DKA, 10 patients with NKH, and 12 lean and 12 obese nondiabetic control subjects. We measured 1) proinflammatory cytokines (tumor necrosis factor-α, interleukin [IL]-6, IL1-β, and IL-8), 2) markers of cardiovascular risk (C-reactive protein [CRP], homocysteine, and plasminogen activator inhibitor-1 [PAI-1]), 3) products of reactive oxygen species (ROS; thiobarbituric acid [TBA]-reacting material, and dichlorofluorescein [DCF]), and 4) cortisol, growth hormone (GH), and free fatty acids (FFAs) on admission (before insulin therapy) and after insulin therapy and resolution of hyperglycemia and/or ketoacidosis. Results were compared with lean and obese control subjects. Circulating levels of cytokines, TBA, DCF, PAI-1, FFAs, cortisol, and GH on admission were significantly increased two- to fourfold in patients with hyperglycemic crises compared with control subjects, and they returned to normal levels after insulin treatment and resolution of hyperglycemic crises. Changes in CRP and homocysteine in response to insulin therapy did not reach control levels after resolution of hyperglycemia. We conclude that DKA and NKH are associated with elevation of proinflammatory cytokines, ROS, and cardiovascular risk factors in the absence of obvious infection or cardiovascular pathology. Return of these values to normal levels with insulin therapy demonstrates a robust anti-inflammatory effect of insulin.
Diminished Loss of Proteoglycans and Lack of Albuminuria in Protein Kinase C-α—Deficient Diabetic Mice
Authors: Menne Jan , Park Joon-Keun , Boehne Martin , Elger Marlies , Lindschau Carsten , Kirsch Torsten , Meier Matthias , Gueler Faikah , Fiebeler Annette , Bahlmann Ferdinand H. , Leitges Michael , Haller Hermann
Published: March 2007

Activation of protein kinase C (PKC) isoforms has been implicated in the pathogenesis of diabetic nephropathy. We showed earlier that PKC-α is activated in the kidneys of hyperglycemic animals. We now used PKC-α−/− mice to test the hypothesis that this PKC isoform mediates streptozotocin-induced diabetic nephropathy. We observed that renal and glomerular hypertrophy was similar in diabetic wild-type and PKC-α−/− mice. However, the development of albuminuria was almost absent in the diabetic PKC-α−/− mice. The hyperglycemia-induced downregulation of the negatively charged basement membrane heparan sulfate proteoglycan perlecan was completely prevented in the PKC-α−/− mice, compared with controls. We then asked whether transforming growth factor-β1 (TGF-β1) and/or vascular endothelial growth factor (VEGF) is implicated in the PKC-α–mediated changes in the basement membrane. The hyperglycemia-induced expression of VEGF165 and its receptor VEGF receptor II (flk-1) was ameliorated in PKC-α−/− mice, whereas expression of TGF-β1 was not affected by the lack of PKC-α. Our findings indicate that two important features of diabetic nephropathy—glomerular hypertrophy and albuminuria—are differentially regulated. The glucose-induced albuminuria seems to be mediated by PKC-α via downregulation of proteoglycans in the basement membrane and regulation of VEGF expression. Therefore, PKC-α is a possible therapeutic target for the prevention of diabetic albuminuria.
Oxidative Stress Affects Synaptosomal γ-Aminobutyric Acid and Glutamate Transport in Diabetic Rats
Authors: Duarte Ana I. , Santos Maria S. , Seiça Raquel , Oliveira Catarina R.
Published: March 2007

Evidence suggests that oxidative stress is involved in the pathophysiology of diabetic complications and that insulin has a neuroprotective role in oxidative stress conditions. In this study, we evaluated the in vitro effect of insulin in the susceptibility to oxidative stress and in the transport of the amino acid neurotransmitters γ-aminobutyric acid (GABA) and glutamate in a synaptosomal fraction isolated from male type 2 diabetic Goto-Kakizaki (GK) rat brain cortex. The ascorbate/Fe2+-induced increase in thiobarbituric acid reactive substances (TBARSs) was similar in Wistar and GK rats and was not reverted by insulin (1 μmol/l), suggesting that other mechanisms, rather than a direct effect in membrane lipid peroxidation, may mediate insulin neuroprotection. Diabetes did not affect GABA and glutamate transport, despite the significant decrease in membrane potential and ATP/ADP ratio, and insulin increased the uptake of both GABA and glutamate in GK rats. Upon oxidation, there was a decrease in the uptake of both neurotransmitters and an increase in extrasynaptosomal glutamate levels and in ATP/ADP ratio in GK rats. Insulin treatment reverted the ascorbate/Fe2+-induced decrease in GABA accumulation, with a decrease in extrasynaptosomal GABA. These results suggest that insulin modulates synaptosomal GABA and/or glutamate transport, thus having a neuroprotective role under oxidizing and/or diabetic conditions.
Polymorphic Variations in the Neurogenic Differentiation-1, Neurogenin-3, and Hepatocyte Nuclear Factor-1α Genes Contribute to Glucose Intolerance in a South Indian Population
Authors: Jackson Alan E. , Cassell Paul G. , North Bernard V. , Vijayaraghavan Shanti , Gelding Susan V. , Ramachandran Ambady , Snehalatha Chamukuttan , Hitman Graham A.
Published: March 2007

The neurogenic differentiation-1 (NEUROD1), neurogenin-3 (NEUROG3), and hepatic nuclear factor-1α (TCF1) genes are interacting transcription factors implicated in controlling islet cell development and insulin secretion. Polymorphisms of these genes (Ala45Thr [NEUROD1], Ser199Phe [NEUROG3], and Ala98Val [TCF1]) have been postulated to influence the development of type 2 diabetes. We have investigated the role and interaction between these variants using PCR/restriction fragment–length polymorphism assays in 454 subjects recruited as part of a population survey in South India. Additionally, 97 South Indian parent-offspring trios were studied. Polymorphisms of all three genes were associated with either fasting blood glucose (FBG) and/or 2-h blood glucose (BG) in either the total dataset or when restricted to a normoglycemic population. A monotonically increasing effect, dependent on the total number of risk-associated alleles carried, was observed across the whole population (P < 0.0001 for FBG and 2-h BG), raising FBG by a mean of 2.9 mmol/l and 2-h BG by a mean of 4.3 mmol/l. Similarly, an ascending number of the same risk alleles per subject increased the likelihood of type 2 diabetes (P = 0.002). In conclusion, we observed a combined effect of variations in NEUROD1, NEUROG3, and TCF1 in contributing to overall glucose intolerance in a South Indian population.
CD36 in Myocytes Channels Fatty Acids to a Lipase-Accessible Triglyceride Pool That Is Related to Cell Lipid and Insulin Responsiveness
Authors: Bastie Claire C. , Hajri Tahar , Drover Victor A. , Grimaldi Paul A. , Abumrad Nada A.
Published: March 2007

High levels of intramyocellular triglycerides are linked to insulin resistance and reflect conditions in which fatty acid uptake exceeds the myocyte oxidative capacity. CD36 facilitates fatty acid uptake by myocytes, and its level is increased in diabetic muscle. We examined whether high CD36 levels would increase lipid content and susceptibility of myocytes to fatty acid–induced insulin resistance. C2C12 myoblasts with stable fivefold overexpression of CD36 (+CD36) were generated and differentiated into myotubes. CD36 expression increased palmitate uptake, oxidation, and lipid incorporation but had no effect on cell triglyceride content. Importantly, glycerol release increased fourfold, indicating enhanced triglyceride turnover and suggesting that CD36 promotes futile cycling of fatty acids into triglyceride. When +CD36 myotubes were incubated with excess palmitate, CD36 enhancement of glycerol release was blunted, triglyceride content increased above wild-type cells, and insulin resistance of glucose metabolism was observed. In contrast to palmitate, oleate-treated +CD36 cells exhibited enhanced glycerol release and no alteration in triglyceride content or insulin responsiveness. Furthermore, increased expression of hormone-sensitive lipase was measured with CD36 expression and with oleate treatment. In conclusion, high futile cycling of fatty acids is important for maintaining low triglyceride content and insulin responsiveness of myocytes. The findings provide a new perspective related to the etiology of lipid accumulation and insulin resistance in myocytes.
Syntaxin 4 Transgenic Mice Exhibit Enhanced Insulin-Mediated Glucose Uptake in Skeletal Muscle
Authors: Spurlin Beth A. , Park So-Young , Nevins Angela K. , Kim Jason K. , Thurmond Debbie C.
Published: March 2007

Insulin-stimulated translocation of GLUT4 vesicles from an intracellular compartment to the plasma membrane in 3T3L1 adipocytes is mediated through a syntaxin 4 (Syn4)- and Munc18c-dependent mechanism. To investigate the impact of increasing Syn4 protein abundance on glucose homeostasis in vivo, we engineered tetracycline-repressible transgenic mice to overexpress Syn4 by fivefold in skeletal muscle and pancreas and threefold in adipose tissue. Increases in Syn4 caused increases in Munc18c protein, indicating that Syn4 regulates Munc18c expression in vivo. An important finding was that female Syn4 transgenic mice exhibited an increased rate of glucose clearance during glucose tolerance tests that was repressible by the administration of tetracycline. Insulin-stimulated glucose uptake in skeletal muscle was increased by twofold in Syn4 transgenic mice compared with wild-type mice as assessed by hyperinsulinemic-euglycemic clamp analysis, consistent with a twofold increase in insulin-stimulated GLUT4 translocation in skeletal muscle. Hepatic insulin action was unaffected. Moreover, insulin content and glucose-stimulated insulin secretion by islets isolated from Syn4 transgenic mice did not differ from that of wild-type mice. In sum, these data suggest that increasing the number of Syn4-Munc18c “fusion sites” at the plasma membrane of skeletal muscle increases the amount of GLUT4 available to increase the overall rate of insulin-mediated glucose uptake in vivo.