bluuebunny/crossref_metadata_2025 huggingface dataset:
Association Testing in 9,000 People Fails to Confirm the Association of the Insulin Receptor Substrate-1 G972R Polymorphism With Type 2 Diabetes
Authors: Florez Jose C. , Sjögren Marketa , Burtt Noël , Orho-Melander Marju , Schayer Steve , Sun Maria , Almgren Peter , Lindblad Ulf , Tuomi Tiinamaija , Gaudet Daniel , Hudson Thomas J. , Daly Mark J. , Ardlie Kristin G. , Hirschhorn Joel N. , Altshuler David , Groop Leif
Published: March 2007

The insulin receptor substrate (IRS)-1 is an important component of the insulin signal transduction cascade. Several reports suggest that a Gly→Arg change in codon 972 is associated with type 2 diabetes and related traits, and a recent meta-analysis reported a modest but nominally significant association with type 2 diabetes (odds ratio [OR] 1.25 in favor of carriers of the Arg allele [95% CI 1.05–1.48). To test the reproducibility of the model in a recent meta-analysis, we examined genotype-phenotype correlation in three large Caucasian samples (not previously reported for this variant) totaling 9,000 individuals (estimated to have >95% power to obtain a P < 0.05 for the OR of 1.25 estimated in the meta-analysis). In our combined sample, comprising 4,279 case and 3,532 control subjects, as well as 1,189 siblings discordant for type 2 diabetes, G972R was not associated with type 2 diabetes (OR 0.96 [0.84–1.10], P = 0.60). Genotype at G972R had no significant effect on various measures of insulin secretion or insulin resistance in a set of Scandinavian samples in whom we had detailed phenotypic data. In contrast, the well-documented associations of peroxisome proliferator-activated receptor γ P12A and Kir6.2 E23K with type 2 diabetes are both robustly observed in these 9,000 subjects, including an additional (previously unpublished) confirmation of Kir6.2 E23K and type 2 diabetes in the Polish and North American samples (combined OR 1.15 [1.05–1.26], P = 0.001). Despite genotyping 9,000 people and >95% power to reproduce the estimated OR from the recent meta-analysis, we were unable to replicate the association of the IRS-1 G972R polymorphism with type 2 diabetes.
Association Studies of Insulin Receptor Substrate 1 Gene (IRS1) Variants in Type 2 Diabetes Samples Enriched for Family History and Early Age of Onset
Authors: Zeggini Eleftheria , Parkinson James , Halford Stephanie , Owen Katharine R. , Frayling Timothy M. , Walker Mark , Hitman Graham A. , Levy Jonathan C. , Sampson Mike J. , Feskens Edith J.M. , Hattersley Andrew T. , McCarthy Mark I.
Published: March 2007

The gene encoding insulin receptor substrate-1 (IRS1) represents a strong biological candidate for a contributory role in type 2 diabetes susceptibility. Indeed, functional studies have implicated the G971R variant, and a recent meta-analysis of 27 association studies suggested that carriage of 971R was associated with a 25% increase in disease risk. However, this association has not been evaluated in large samples. The present study genotyped the P512A and G971R IRS1 variants in 971 U.K. type 2 diabetic subjects ascertained for strong family history and/or early onset, as well as 1,257 control subjects matched by ethnicity. There was no evidence for association with type 2 diabetes for either variant. (For example, the odds ratio [OR] for carriage of 971R was 1.11 [95% CI 0.86–1.44, P = 0.44].) An updated meta-analysis (31 studies: 5,104 case and 7,418 control subjects) remained significant for the G971R association (P = 0.025), albeit with a diminished OR (1.15 [95% CI 1.02–1.31]). Additional studies of IRS1 variation will be required to obtain a robust estimate of the overall contribution of IRS1 variation to type 2 diabetes susceptibility, but the current study suggests that previous studies have overestimated the magnitude of this effect.
Polymorphisms in Both Promoters of Hepatocyte Nuclear Factor 4-α Are Associated With Type 2 Diabetes in the Amish
Authors: Damcott Coleen M. , Hoppman Nicole , Ott Sandra H. , Reinhart Laurie J. , Wang Jian , Pollin Toni I. , O’Connell Jeffrey R. , Mitchell Braxton D. , Shuldiner Alan R.
Published: March 2007

Hepatocyte nuclear factor 4-α (HNF4A) is a transcription factor located on chromosome 20q13 that regulates expression of genes involved in glucose metabolism and homeostasis. Recently, two groups independently identified single nucleotide polymorphism (SNPs) in an alternate upstream promoter (P2) of HNF4A that were associated with type 2 diabetes in Ashkenazi Jews and Finns. We genotyped haplotype-tagging SNPs (htSNPs) across the two promoter regions and the coding region of HNF4A in individuals with type 2 diabetes (n = 137), impaired glucose tolerance (IGT) (n = 139), and normal glucose tolerance (n = 342) from the Amish Family Diabetes Study (AFDS) to test for association with type 2 diabetes. In the P1 promoter region, we observed a significant association between the A allele of rs2425640 and type 2 diabetes (odds ratio [OR] 1.60, P = 0.03). Furthermore, the mean age of type 2 diabetes onset was, on average, 5.1 years earlier in those with the AA or GA genotype at SNP rs2425640 than in those with the GG genotype (57.8 vs. 62.9 years, P = 0.011). In the P2 promoter, the htSNP rs1884614 showed borderline association with both type 2 diabetes (OR 1.40, P = 0.09) and the combined type 2 diabetes/IGT trait (1.35, P = 0.07). In an expanded set of 698 nondiabetic AFDS subjects, we found association between rs1884614 and glucose area under the curve during an oral glucose tolerance test (additive model, P = 0.022; dominant model, P = 0.010). The results of this study provide evidence that variants in both the P1 and P2 promoters of HNF4A increase risk for typical type 2 diabetes.
Proinsulin Expression by Hassall’s Corpuscles in the Mouse Thymus
Authors: Chentoufi Aziz Alami , Palumbo Michael , Polychronakos Constantin
Published: March 2007

The thymus expresses proinsulin, among many other tissue-specific antigens, and the inheritance of genetically determined low thymic proinsulin expression has been associated with impaired proinsulin-specific autoreactive T-cell tolerance and type 1 diabetes susceptibility. The cellular and molecular biology of proinsulin expression in the thymus remains unknown, and contradictory reports exist regarding the identity of proinsulin-producing cells. Using knock-in mice expressing β-galactosidase (β-Gal) under the control of an endogenous insulin promoter, we found that thymic proinsulin and β-Gal transcripts were detectable at high levels in purified thymic epithelial cells. Immunohistochemical analysis of β-Gal activity showed that most proinsulin expression can be accounted for by rare medullary epithelial cells of the Hassall’s corpuscles. Moreover, flow cytometry analyses of β-Gal-positive cells showed that only 1–3% of all epithelial cells express proinsulin, and this technique will now provide us with a method for isolating the proinsulin-producing cells in mouse thymus.
Insulin Secretion in Type 1 Diabetes
Authors: Steele Chynna , Hagopian William A. , Gitelman Stephen , Masharani Umesh , Cavaghan Melissa , Rother Kristina I. , Donaldson David , Harlan David M. , Bluestone Jeffrey , Herold Kevan C.
Published: March 2007

Type 1 diabetes, a chronic autoimmune disease, causes destruction of insulin-producing β-cells over a period of years. Although many markers of the autoimmune process have been described, none can convincingly predict the rate of disease progression. Moreover, there is relatively little information about changes in insulin secretion in individuals with type 1 diabetes over time. Previous studies document C-peptide at a limited number of time points, often after a nonphysiologic stimulus, and under non–steady-state conditions. Such methods do not provide qualitative information and may not reflect physiologic responses. We have studied qualitative and quantitative insulin secretion to a 4-h mixed meal in 41 patients with newly diagnosed type 1 diabetes and followed the course of this response for 24 months in 20 patients. Newly diagnosed diabetic patients had an average total insulin secretion in response to a mixed meal that was 52% of that in nondiabetic control subjects, considerably higher than has been described previously. In diabetic patients there was a decline of β-cell function at an average rate of 756 ± 132 pmol/month to a final value of 28 ± 8.4% of initial levels after 2 years. There was a significant correlation between the total insulin secretory response and control of glucose, measured by HbA1c (P = 0.003). Two persistent patterns of insulin response were seen depending on the peak insulin response following the oral meal. Patients with an early insulin response (i.e., within the first 45 min after ingestion) to a mixed meal, which was also seen in 37 of 38 nondiabetic control subjects, had a significantly accelerated loss of insulin secretion, as compared with those in whom the insulin response occurred after this time (P < 0.05), and significantly greater insulin secretory responses at 18 and 24 months (P < 0.02). These results, which are the first qualitative studies of insulin secretion in type 1 diabetes, indicate that the physiologic metabolic response is greater at diagnosis than has previously been appreciated, and that the qualitative insulin secretory response is an important determinant of the rate of metabolic decompensation from autoimmune destruction.
Insulin Sensitivity of Muscle Capillary Recruitment In Vivo
Authors: Zhang Lei , Vincent Michelle A. , Richards Stephen M. , Clerk Lucy H. , Rattigan Stephen , Clark Michael G. , Barrett Eugene J.
Published: March 2007

We have reported that insulin exerts two vascular actions in muscle; it both increases blood flow and recruits capillaries. In parallel hyperinsulinemic-euglycemic clamp studies, we compared the insulin dose response of muscle microvascular recruitment and femoral blood flow as well as hindleg glucose uptake in fed, hooded Wistar and fasted Sprague-Dawley rats. Using insulin doses between 0 and 30 mU−1 · min−1 · kg−1, we measured microvascular recruitment at 2 h by 1-methylxanthine (1-MX) metabolism or contrast-enhanced ultrasound (CEU), and muscle glucose uptake was measured by either arteriovenous differences or using 2-deoxyglucose. We also examined the time course for reversal of microvascular recruitment following cessation of a 3 mU · min−1 · kg−1 insulin infusion. In both groups, whether measured by 1-MX metabolism or CEU, microvascular recruitment was fully activated by physiologic hyperinsulinemia and occurred at lower insulin concentrations than those that stimulated glucose uptake or hindleg total blood flow. The latter processes were insulin dose dependent throughout the entire dose range studied. Upon stopping the insulin infusion, increases in microvascular volume persisted for 15–30 min after insulin concentrations returned to basal levels. We conclude that the precapillary arterioles that regulate microvascular recruitment are more insulin sensitive than resistance arterioles that regulate total flow.
Liver Glucokinase Can Be Activated by Peroxisome Proliferator-Activated Receptor-γ
Authors: Kim So-youn , Kim Ha-il , Park Sang-Kyu , Im Seung-Soon , Li Tianzhu , Cheon Hyae Gyeong , Ahn Yong-ho
Published: March 2007

Thiazolidinediones (TZDs), synthetic ligands of peroxisome proliferator-activated receptor (PPAR)-γ, are known to decrease hepatic glucose production and increase glycogen synthesis in diabetic animals. Recently it was reported that glucokinase (GK) expression was increased by TZDs in the liver of diabetic ZDF rats. However, the mechanism whereby TZDs increase GK expression is not yet studied. We have assumed that liver type glucokinase (LGK) induction by TZDs could be achieved by direct transcriptional activation. Thus, we have dissected the LGK promoter to explore the presence of a PPAR response element (PPRE) in the promoter. From this study, we were able to localize a PPRE in the −116/−104 region of the rat LGK gene. The PPAR-γ/retinoid X receptor-α heterodimer was bound to the element and activated the LGK promoter. The LGK promoter lacking the PPRE or having mutations in the PPRE could not be activated by PPAR-γ. Furthermore, troglitazone increased endogenous GK mRNA in primary hepatocytes. These results indicate that PPAR-γ can directly activate GK expression in liver and may contribute to improving glucose homeostasis in type 2 diabetes.
Mice with Targeted Disruption of the Dio2 Gene Have Cold-Induced Overexpression of the Uncoupling Protein 1 Gene but Fail to Increase Brown Adipose Tissue Lipogenesis and Adaptive Thermogenesis
Authors: Christoffolete Marcelo A. , Linardi Camila C.G. , de Jesus Lucia , Ebina Katia Naomi , Carvalho Suzy D. , Ribeiro Miriam O. , Rabelo Rogerio , Curcio Cyntia , Martins Luciane , Kimura Edna T. , Bianco Antonio C.
Published: March 2007

The Dio2 gene encodes the type 2 deiodinase (D2) that activates thyroxine (T4) to 3,3′,5-triiodothyronine (T3), the disruption of which (Dio2−/−) results in brown adipose tissue (BAT)-specific hypothyroidism in an otherwise euthyroid animal. In the present studies, cold exposure increased Dio2−/− BAT sympathetic stimulation ∼10-fold (normal ∼4-fold); as a result, lipolysis, as well as the mRNA levels of uncoupling protein 1, guanosine monophosphate reductase, and peroxisome proliferator–activated receptor γ coactivator 1, increased well above the levels detected in the cold-exposed wild-type animals. The sustained Dio2−/− BAT adrenergic hyperresponse suppressed the three- to fourfold stimulation of BAT lipogenesis normally seen after 24–48 h in the cold. Pharmacological suppression of lipogenesis with ββ′-methyl-substituted α-ω-dicarboxylic acids of C14–C18 in wild-type animals also impaired adaptive thermogenesis in the BAT. These data constitute the first evidence that reduced adrenergic responsiveness does not limit cold-induced adaptive thermogenesis. Instead, the resulting compensatory hyperadrenergic stimulation prevents the otherwise normal stimulation in BAT lipogenesis during cold exposure, rapidly exhausting the availability of fatty acids. The latter is the preponderant determinant of the impaired adaptive thermogenesis and hypothermia in cold-exposed Dio2−/− mice.
A Genome-Wide Search for Type 2 Diabetes Susceptibility Genes in West Africans
Authors: Rotimi Charles N. , Chen Guanjie , Adeyemo Adebowale A. , Furbert-Harris Paulette , Guass Debra , Zhou Jie , Berg Kate , Adegoke Olufemi , Amoah Albert , Owusu Samuel , Acheampong Joseph , Agyenim-Boateng Kofi , Eghan Benjamin A. , Oli Johnnie , Okafor Godfrey , Ofoegbu Ester , Osotimehin Babatunde , Abbiyesuku Fayeofori , Johnson Thomas , Rufus Theresa , Fasanmade Olufemi , Kittles Rick , Daniel Harold , Chen Yuanxiu , Dunston Georgia , Collins Francis S.
Published: March 2007

The incidence of type 2 diabetes is growing rapidly, not only in developed countries but also worldwide. We chose to study type 2 diabetes in West Africa, where diabetes is less common than in the U.S., reasoning that in an environment where calories are less abundant, incident cases of type 2 diabetes might carry a proportionately greater genetic component. Through the Africa America Diabetes Mellitus (AADM) study, we carried out a genome-wide linkage analysis of type 2 diabetes in a cohort of 343 affected sibling pairs (691 individuals) enrolled from five West African centers in two countries (Ghana: Accra and Kumasi; Nigeria: Enugu, Ibadan, and Lagos). A total of 390 polymorphic markers were genotyped, and multipoint linkage analysis was conducted using the GENEHUNTER-PLUS and ASM programs. Suggestive evidence of linkage was observed in four regions on three chromosomes (12, 19, and 20). The two largest logarithm of odds scores of 2.63 and 1.92 for chromosomes 20q13.3 and 12q24, respectively, are particularly interesting because these regions have been reported to harbor diabetes susceptibility genes in several other populations and ethnic groups. Given the history of forced migration of West African populations during the slave trade, these results should have considerable relevance to the study of type 2 diabetes in African Americans.
The Metabolic Syndrome, Circulating Oxidized LDL, and Risk of Myocardial Infarction in Well-Functioning Elderly People in the Health, Aging, and Body Composition Cohort
Authors: Holvoet Paul , Kritchevsky Stephen B. , Tracy Russell P. , Mertens Ann , Rubin Susan M. , Butler Javed , Goodpaster Bret , Harris Tamara B.
Published: March 2007

The object of this study was to establish the association between the metabolic syndrome and oxidized LDL (oxLDL) and to determine the risk for coronary heart disease (CHD) in relation to the metabolic syndrome and levels of oxLDL. OxLDL was measured in plasma from 3,033 elderly participants in the Health, Aging, and Body Composition study. The metabolic syndrome was defined according to criteria established in the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. We observed that the metabolic syndrome was associated with higher levels of oxLDL due to a higher fraction of oxLDL, not to higher levels of LDL cholesterol. Individuals with the metabolic syndrome had twice the odds of having high oxLDL (>1.90 mg/dl) compared with those not having the metabolic syndrome, after adjusting for age, sex, ethnicity, smoking status, and LDL cholesterol. Among those participants who had the metabolic syndrome at study entry, incidence rates of future CHD events were 1.6-fold higher, after adjusting for age, sex, ethnicity, and smoking status. OxLDL was not an independent predictor of total CHD risk. However, those with high oxLDL showed a greater disposition to myocardial infarction (relative risk 2.25, 95% confidence interval 1.22–4.15). We concluded that the metabolic syndrome, a risk factor for CHD, is associated with higher levels of circulating oxLDL that are associated with a greater disposition to atherothrombotic coronary disease.
Oxidative Stress Impairs Skeletal Muscle Repair in Diabetic Rats
Authors: Aragno Manuela , Mastrocola Raffaella , Catalano Maria Graziella , Brignardello Enrico , Danni Oliviero , Boccuzzi Giuseppe
Published: March 2007

Alongside increased proteolysis, the inability to repair damaged skeletal muscle is a characteristic feature of uncontrolled diabetes. This study evaluates the role of oxidative stress in muscle-specific gene regulatory regions and myosin chain synthesis in streptozotocin (STZ)-induced diabetic and ZDF rats. In the gastrocnemius muscle of diabetic rats, prooxidant compounds were seen to increase while antioxidant levels fell. Myogenic regulatory factors—Myo, myogenin, and Jun D—were also reduced, and muscle enhancer factor (MEF)-1 DNA binding activity was impaired. Moreover, synthesis of muscle creatine kinase and both heavy and light chains of myosin were impaired, suggesting that oxidative stress triggers the cascade of events that leads to impaired muscle repair. Dehydroepiandrosterone has been reported to possess antioxidant properties. When it was administered to diabetic rats, in addition to an improved oxidative imbalance there was a recovery of myogenic factors, MEF-1 DNA binding activity, synthesis of muscle creatine kinase, and myosin light and heavy chains. Vitamin E administration to STZ-induced diabetic rats reverses oxidative imbalance and improves muscle gene transcription, reinforcing the suggestion that oxidative stress may play a role in diabetes-related impaired muscle repair.
Regression of Advanced Diabetic Nephropathy by Hepatocyte Growth Factor Gene Therapy in Rats
Authors: Cruzado Josep M. , Lloberas Núria , Torras Joan , Riera Marta , Fillat Cristina , Herrero-Fresneda Immaculada , Aran Josep M. , Alperovich Gabriela , Vidal August , Grinyó Josep M.
Published: March 2007

Diabetic nephropathy is the main cause of end-stage renal disease requiring dialysis in developed countries. In this study, we demonstrated the therapeutic effect of hepatocyte growth factor (HGF) on advanced rather than early diabetic nephropathy using a rat model of streptozotocin-induced diabetes. Early diabetic nephropathy (16 weeks after induction of diabetes) was characterized by albuminuria, hyperfiltration, and glomerular hypertrophy, whereas advanced diabetic nephropathy showed prominent transforming growth factor (TGF)-β1 upregulation, mesangial expansion, and glomerulosclerosis. An SP1017-formulated human HGF (hHGF) plasmid was administered by intramuscular injection combined with electroporation over a 30-day follow-up in rats with early and advanced diabetic nephropathy. hHGF gene therapy upregulated endogenous rat HGF in the diabetic kidney (rat HGF by RT-PCR was threefold higher than in diabetic rats without therapy). hHGF gene therapy did not improve functional or morphologic abnormalities in early diabetic nephropathy. hHGF gene therapy reduced albuminuria and induced strong regression of mesangial expansion and glomerulosclerosis in advanced diabetic nephropathy. These findings were associated with suppression of renal TGF-β1 and mesangial connective tissue growth factor (CTGF) upregulation, inhibition of renal tissue inhibitor of metalloproteinase (TIMP)-1 expression, and reduction of renal interstitial myofibroblasts. In conclusion, our results suggest that hHGF gene therapy may be considered as an innovative therapeutic strategy to treat advanced diabetic nephropathy.
Heritability of Multivariate Factors of the Metabolic Syndrome in Nondiabetic Japanese Americans
Authors: Austin Melissa A. , Edwards Karen L. , McNeely Marguerite J. , Chandler Wayne L. , Leonetti Donna L. , Talmud Philippa J. , Humphries Steve E. , Fujimoto Wilfred Y.
Published: March 2007

A rapidly growing body of evidence demonstrates important associations between the metabolic syndrome, characterized by a cluster of risk factors or phenotypes that include dyslipidemia, central obesity, hypertension, and hyperinsulinemia, and both cardiovascular disease and type 2 diabetes. The purpose of the present study was to characterize the metabolic syndrome in a sample of 432 individuals from 68 Japanese-American families, using factor analysis of quantitative phenotypes, and to estimate the heritability of these independent factors. Using nine characteristic phenotypes that included LDL particle size and C-reactive protein (CRP), factor analysis identified three multivariate factors interpreted as lipids, body fat/insulin/glucose/CRP, and blood pressure, explaining 65% of the variance. Heritability analysis revealed significant genetic effects on all of the factors: lipids (h2 = 0.52, P < 0.001), body fat/insulin/glucose/CRP (h2 = 0.27, P = 0.016), and blood pressure (h2 = 0.25, P = 0.026). This analysis shows that independent, multivariate factors of the metabolic syndrome are heritable, demonstrating genetic influences on the underlying pathophysiological mechanisms of the syndrome.
Novel Adipose Tissue–Mediated Resistance to Diet-Induced Visceral Obesity in 11β-Hydroxysteroid Dehydrogenase Type 1–Deficient Mice
Authors: Morton Nicholas M. , Paterson Janice M. , Masuzaki Hiroaki , Holmes Megan C. , Staels Bart , Fievet Catherine , Walker Brian R. , Flier Jeffrey S. , Mullins John J. , Seckl Jonathan R.
Published: March 2007

The metabolic syndrome (visceral obesity, insulin resistance, type 2 diabetes, and dyslipidemia) resembles Cushing’s Syndrome, but without elevated circulating glucocorticoid levels. An emerging concept suggests that the aberrantly elevated levels of the intracellular glucocorticoid reamplifying enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD-1) found in adipose tissue of obese humans and rodents underlies the phenotypic similarities between idiopathic and “Cushingoid” obesity. Transgenic overexpression of 11β-HSD-1 in adipose tissue reproduces a metabolic syndrome in mice, whereas 11β-HSD-1 deficiency or inhibition has beneficial metabolic effects, at least on liver metabolism. Here we report novel protective effects of 11β-HSD-1 deficiency on adipose function, distribution, and gene expression in vivo in 11β-HSD-1 nullizygous (11β-HSD-1−/−) mice. 11β-HSD-1−/− mice expressed lower resistin and tumor necrosis factor-α, but higher peroxisome proliferator–activated receptor-γ, adiponectin, and uncoupling protein-2 mRNA levels in adipose, indicating insulin sensitization. Isolated 11β-HSD-1−/− adipocytes exhibited higher basal and insulin-stimulated glucose uptake. 11β-HSD-1−/− mice also exhibited reduced visceral fat accumulation upon high-fat feeding. High-fat–fed 11β-HSD-1−/− mice rederived onto the C57BL/6J strain resisted diabetes and weight gain despite consuming more calories. These data provide the first in vivo evidence that adipose 11β-HSD-1 deficiency beneficially alters adipose tissue distribution and function, complementing the reported effects of hepatic 11β-HSD-1 deficiency or inhibition.
Assessment of the Severity of Hypoglycemia and Glycemic Lability in Type 1 Diabetic Subjects Undergoing Islet Transplantation
Authors: Ryan Edmond A. , Shandro Tami , Green Kristy , Paty Breay W. , Senior Peter A. , Bigam David , Shapiro A.M. James , Vantyghem Marie-Christine
Published: March 2007

Currently, the major indications for solitary islet transplantation are recurrent severe hypoglycemia and labile glucose control. Quantifying these problems remains subjective. We have developed a scoring system for both hypoglycemia and glycemic lability, established normative data, and used them in patients who have undergone islet transplantation. A composite hypoglycemic score (HYPO score) was devised based on the frequency, severity, and degree of unawareness of the hypoglycemia. In addition, using 4 weeks of glucose records, a lability index (LI) was calculated based on the change in glucose levels over time and compared with a clinical assessment of glycemic lability. A mean amplitude of glycemic excursions (MAGE) was also calculated based on 2 consecutive days of seven readings each day. These scores were determined in 100 randomly selected subjects with type 1 diabetes from our general clinic to serve as a control group and in patients before and after islet transplantation. The mean age of the control diabetic subjects was 38.4 ± 1.3 years (±SE), with a duration of diabetes of 21.5 ± 1.1 years. The median HYPO score in the control subjects was 143 (25th to 75th interquartile range: 46–423). The LI in the diabetic control subjects was 223 (25th to 75th interquartile range: 130–329 mmol/l2/h · week−1). The LI correlated much more closely than the MAGE with the clinical assessment of lability. A HYPO score of ≥1,047 (90th percentile) or an LI ≥433 mmol/l2/h · week−1 (90th percentile) indicated serious problems with hypoglycemia or glycemic lability, respectively. The islet transplant patients (n = 51) were 42.1 ± 1.4 years old, with a duration of diabetes of 25.7 ± 1.4 years. Islet transplant patients had a mean HYPO score of 1,234 ± 184 pretransplant, which was significantly higher than that of the control subjects (P < 0.001), which became negligible posttransplantation with the elimination of hypoglycemia. The median LI pretransplant was 497 mmol/l2/h · week−1 (25th to 75th interquartile range: 330–692), significantly higher than that of control subjects (P < 0.001), and fell to 40 (25th to 75th interquartile range: 14–83) within a month after the final transplant. In those who had lost graft function, the LI rose again. The HYPO score and LI provide measures of the extent of problems with hypoglycemia and glycemic lability, respectively, complement the clinical assessment of the problems with glucose control before islet transplantation, and will allow comparison of selection of subjects for transplants between centers.
T-Cell Receptor Transgenic Response to an Endogenous Polymorphic Autoantigen Determines Susceptibility to Diabetes
Authors: Pauza Mary E. , Dobbs Cathleen M. , He Jing , Patterson Tricia , Wagner Steven , Anobile Brian S. , Bradley Brenda J. , Lo David , Haskins Kathryn
Published: March 2007

We have produced a T-cell receptor (TCR) transgenic NOD mouse, 6.9TCR/NOD, in which the expression of both diabetogenic T-cells and naturally occurring autoantigen were simultaneously controlled. The parent T-cell clone, BDC-6.9, and T-cells from 6.9TCR/NOD mice recognize a currently unidentified antigen present in NOD but not in BALB/c islet cells. A gene that codes for the antigen, or a protein that regulates the antigen, was previously mapped to a locus on chromosome 6. We have developed transgenic mice bearing the TCR α- and β-chains from the BDC-6.9 T-cell clone on a NOD congenic background in which the antigen locus on chromosome 6 of the NOD mouse is replaced by a segment from BALB/c. These NOD.C6 congenic mice lack the NOD islet cell antigen to which the BDC-6.9 T-cell clone responds. Diabetes in both male and female 6.9TCR/NOD mice is dramatically accelerated, but in 6.9TCR/NOD.C6 mice lacking the NOD islet cell autoantigen, we have not observed diabetes for up to 1 year of age. Thus, the generation of 6.9TCR transgenic mice provides a model of autoimmune diabetes whereby controlled expression of an endogenous polymorphic autoantigen effectively determines disease development.
Evaluation of Insulin Sensitivity and β-Cell Function Indexes Obtained From Minimal Model Analysis of a Meal Tolerance Test
Authors: Steil Garry M. , Hwu Chi-min , Janowski Robert , Hariri Farzam , Jinagouda Sujata , Darwin Christine , Tadros Sameh , Rebrin Kerstin , Saad Mohammed F.
Published: March 2007

Modeling analysis of glucose, insulin, and C-peptide following a meal has been proposed as a means to estimate insulin sensitivity (Si) and β-cell function from a single test. We compared the model-derived meal indexes with analogous indexes obtained from an intravenous glucose tolerance test (IVGTT) and hyperglycemic clamp (HGC) in 17 nondiabetic subjects (14 men, 3 women, aged 50 ± 2 years [mean ± SE], BMI 25.0 ± 0.7 kg/m2). Si estimated from the meal was correlated with Si estimated from the IVGTT and the HGC (r = 0.59 and 0.76, respectively; P < 0.01 for both) but was ∼2.3 and 1.4 times higher (P < 0.05 for both). The meal-derived estimate of the β-cell’s response to a steady-state change in glucose (static secretion index) was correlated with the HGC second-phase insulin response (r = 0.69; P = 0.002), but the estimated rate-of-change component (dynamic secretion index) was not correlated with first-phase insulin release from either the HGC or IVGTT. Indexes of β-cell function obtained from the meal were significantly higher than those obtained from the HGC. In conclusion, insulin sensitivity and β-cell indexes derived from a meal are not analogous to those from the clamp or IVGTT. Further work is needed before these indexes can be routinely used in clinical and epidemiological studies.
Double Incretin Receptor Knockout (DIRKO) Mice Reveal an Essential Role for the Enteroinsular Axis in Transducing the Glucoregulatory Actions of DPP-IV Inhibitors
Authors: Hansotia Tanya , Baggio Laurie L. , Delmeire Dominique , Hinke Simon A. , Yamada Yuichiro , Tsukiyama Katsushi , Seino Yutaka , Holst Jens J. , Schuit Frans , Drucker D.J.
Published: March 2007

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are gut-derived incretins that potentiate glucose clearance following nutrient ingestion. Elimination of incretin receptor action in GIPR−/− or GLP-1R−/− mice produces only modest impairment in glucose homeostasis, perhaps due to compensatory upregulation of the remaining incretin. We have now studied glucose homeostasis in double incretin receptor knockout (DIRKO) mice. DIRKO mice exhibit normal body weight and fail to exhibit an improved glycemic response after exogenous administration of GIP or the GLP-1R agonist exendin-4. Plasma glucagon and the hypoglycemic response to exogenous insulin were normal in DIRKO mice. Glycemic excursion was abnormally increased and levels of glucose-stimulated insulin secretion were decreased following oral but not intraperitoneal glucose challenge in DIRKO compared with GIPR−/− or GLP-1R−/− mice. Similarly, glucose-stimulated insulin secretion and the response to forskolin were well preserved in perifused DIRKO islets. Although the dipeptidyl peptidase-IV (DPP-IV) inhibitors valine pyrrolidide (Val-Pyr) and SYR106124 lowered glucose and increased plasma insulin in wild-type and single incretin receptor knockout mice, the glucose-lowering actions of DPP-IV inhibitors were eliminated in DIRKO mice. These findings demonstrate that glucose-stimulated insulin secretion is maintained despite complete absence of both incretin receptors, and they delineate a critical role for incretin receptors as essential downstream targets for the acute glucoregulatory actions of DPP-IV inhibitors.
Haplotype Structure and Genotype-Phenotype Correlations of the Sulfonylurea Receptor and the Islet ATP-Sensitive Potassium Channel Gene Region
Authors: Florez Jose C. , Burtt Noël , de Bakker Paul I.W. , Almgren Peter , Tuomi Tiinamaija , Holmkvist Johan , Gaudet Daniel , Hudson Thomas J. , Schaffner Steve F. , Daly Mark J. , Hirschhorn Joel N. , Groop Leif , Altshuler David
Published: March 2007

The genes for the sulfonylurea receptor (SUR1; encoded by ABCC8) and its associated islet ATP-sensitive potassium channel (Kir6.2; encoded by KCNJ11) are adjacent to one another on human chromosome 11. Multiple studies have reported association of the E23K variant of Kir6.2 with risk of type 2 diabetes. Whether and how E23K itself—or other variant(s) in either of these two closely linked genes—influences type 2 diabetes remains to be fully determined. To better understand genotype-phenotype correlation at this important candidate gene locus, we 1) characterized haplotype structures across the gene region by typing 77 working, high-frequency markers spanning 207 kb and both genes; 2) performed association studies of E23K and nearby markers in >3,400 patients (type 2 diabetes and control) not previously reported in the literature; and 3) analyzed the resulting data for measures of insulin secretion. These data independently replicate the association of E23K with type 2 diabetes with an odds ratio (OR) in the new data of 1.17 (P = 0.003) as compared with an OR of 1.14 provided by meta-analysis of previously published, nonoverlapping data (P = 0.0002). We find that the E23K variant in Kir6.2 demonstrates very strong allelic association with a coding variant (A1369S) in the neighboring SUR1 gene (r2 > 0.9) across a range of population samples, making it difficult to distinguish which gene and polymorphism in this region are most likely responsible for the reported association. We show that E23K is also associated with decreased insulin secretion in glucose-tolerant control subjects, supporting a mechanism whereby β-cell dysfunction contributes to the common form of type 2 diabetes. Like peroxisome proliferator–activated receptor γ, the SUR1/Kir6.2 gene region both contributes to the inherited risk of type 2 diabetes and encodes proteins that are targets for hypoglycemic medications, providing an intriguing link between the underlying mechanism of disease and validated targets for pharmacological treatment.
Genome-Wide Scans Reveal Quantitative Trait Loci on 8p and 13q Related to Insulin Action and Glucose Metabolism
Authors: Cai Guowen , Cole Shelley A. , Freeland-Graves Jeanne H. , MacCluer Jean W. , Blangero John , Comuzzie Anthony G.
Published: March 2007

Type 2 diabetes is a complex disease that arises from physiological disruptions of the body’s sensitivity to insulin and ability to metabolize glucose. Multipoint linkage analyses for insulin sensitivity phenotypes were conducted in 1,280 Mexican Americans from 41 families who participated in the San Antonio Family Heart Study. A significant linkage signal (logarithm of odds [LOD] = 2.98) affecting corrected insulin response to glucose was detected on chromosome 13q between D13787 and D13S252, in the region where the MODY-4 gene has previously been mapped. Another signal on chromosome 13 was observed at D13S285 (LOD = 1.86), where the insulin receptor substrate 2 gene resides. Significant linkage (LOD = 3.09) for insulin response to glucose was found on chromosome 8 between D8S1130 and D8S1106, near the lipoprotein lipase and macrophage scavenger receptor genes. Multipoint analysis of abdominal skinfold with an LOD of 2.68 showed signals in the same region. There was also suggestive evidence for linkage of quantitative insulin sensitivity check index and fasting glucose to a previously reported location at D9S301 (LOD = 2.19). These results indicate that chromosomal locations on 8p and 13q might harbor genes that affect a variety of insulin- and glucose-related phenotypes that contribute to the observed variations in these important risk factors for diabetes in Mexican Americans.
Identification of a Locus for Maturity-Onset Diabetes of the Young on Chromosome 8p23
Authors: Kim Sung-Hoon , Ma Xiaowei , Weremowicz Stanislawa , Ercolino Tonino , Powers Christine , Mlynarski Wojciech , Bashan K. Aviva , Warram James H. , Mychaleckyj Josyf , Rich Stephen S. , Krolewski Andrzej S. , Doria Alessandro
Published: March 2007

Maturity-onset diabetes of the young (MODY) is a subtype of diabetes defined by an autosomal dominant inheritance and a young onset. Six MODY genes have been discovered to date. To identify additional MODY loci, we conducted a genome scan in 21 extended U.S. families (15 white and 6 from minorities, for a total of 237 individuals) in which MODY was not caused by known MODY genes. Seven chromosomal regions (1q42, 2q24, 2q37, 4p13, 8p23, 11p15, and 19q12) had a parametric heterogeneity logarithm of odds (HLOD) ≥1.00 or a nonparametric logarithm of odds (LOD) ≥0.59 (P ≤ 0.05) in the initial screen. After typing additional markers at these loci to reduce the spacing to 2–3 cM, significant linkage was detected on 8p23 (HLOD = 3.37 at D8S1130 and nonparametric LOD = 3.66; P = 2 × 10−5 at D8S265), where a 4.7-Mb inversion polymorphism is located. Thirty percent of the families (6 of 21) were linked with this region. Another linkage peak on chromosome 2q37 with an HLOD of 1.96 at D2S345/D2S2968 accounted for diabetes in an additional 25% of families (5 of 21). All 6 minority families were among the 11 families linked to these loci. None of the other loci followed up had an HLOD exceeding 1.50. In summary, we have identified a MODY locus on 8p23 that accounts for diabetes in a substantial proportion of MODY cases unlinked to known MODY genes. Another novel MODY locus may be present on 2q37. Cloning these new MODY genes may offer insights to disease pathways that are relevant to the cause of common type 2 diabetes.
Genome-Wide Linkage to Chromosome 6 for Waist Circumference in the Framingham Heart Study
Authors: Fox Caroline S. , Heard-Costa Nancy L. , Wilson Peter W.F. , Levy Daniel , D’Agostino Ralph B. , Atwood Larry D.
Published: March 2007

While several loci for BMI have been identified, it is not known whether genes underlie the process of regional fat deposition. We sought to test whether waist circumference, a measure of central adiposity, contains a genetic component. Variance components linkage analysis was performed on 330 families from the Framingham Heart Study original and offspring cohorts, using a 10-cM genome-wide linkage analysis. Overall, 2,086 subjects (51% women), mean age 48 years, were available for analysis. The overall heritability of waist circumference was 0.41. The maximum logarithm of odds (LOD) score in the full dataset was 3.3 on chromosome 6 at marker D6S1009; when subjects were limited to those aged <60 years, the peak LOD score was 3.7 at the same location. Substantial evidence exists for linkage to waist circumference, a measure of central adiposity. Potential candidate genes include ESR1, OPRM1, and NMBR. Further research is necessary to understand the genes involved in central adiposity.
AMP Kinase-Induced Skeletal Muscle Glucose But Not Long-Chain Fatty Acid Uptake Is Dependent on Nitric Oxide
Authors: Shearer Jane , Fueger Patrick T. , Vorndick Brittney , Bracy Deanna P. , Rottman Jeffery N. , Clanton Jeffery A. , Wasserman David H.
Published: March 2007

The purpose of this study was to examine the effects of AMP kinase (AMPK) activation on in vivo glucose and long-chain fatty acid (LCFA) uptake in skeletal muscle and to examine the nitric oxide (NO) dependence of any putative effects. Catheters were chronically implanted in the carotid artery and jugular vein of male Sprague-Dawley rats. After 4 days of recovery, rats were given either water or water containing 1 mg/ml nitro-l-arginine methylester (l-NAME) for 2.5 days. After an overnight fast, rats underwent one of five protocols: saline, 5-aminoimidazole-4-carboxamide-1-B-d-ribofuranoside (AICAR) (10 mg · kg−1 · min−1), l-NAME, AICAR + l-NAME, or AICAR + Intralipid (20%, 0.02 ml · kg−1 · min−1). Glucose was clamped at ∼6.5 mmol/l in all groups, and an intravenous bolus of 2-deoxy[3H]glucose and [125I]-15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid was administered to obtain indexes of glucose (Kg) and LCFA (Kf) uptake and clearance. At 150 min, soleus, gastrocnemius, and superficial vastus lateralis were excised for tracer determination. Both Kg and Kf increased with AICAR in all muscles studied. Kg decreased with increasing muscle composition of type 1 slow-twitch fibers, whereas Kf increased. In addition, AICAR-induced increases in Kg but not Kf were abolished by l-NAME in the majority of muscles examined. This shows that the mechanisms by which AMPK stimulates glucose and LCFA uptake are distinct.
Effects of Insulin, Contraction, and Phorbol Esters on Mitogen-Activated Protein Kinase Signaling in Skeletal Muscle From Lean and ob/ob Mice
Authors: Leng Ying , Steiler Tatiana L. , Zierath Juleen R.
Published: March 2007

Effects of diverse stimuli, including insulin, muscle contraction, and phorbol 12-myristate-13-acetate (PMA), were determined on phosphorylation of mitogen-activated protein kinase (MAPK) signaling modules (c-Jun NH2-terminal kinase [JNK], p38 MAPK, and extracellular signal-related kinase [ERK1/2]) in skeletal muscle from lean and ob/ob mice. Insulin increased phosphorylation of JNK, p38 MAPK, and ERK1/2 in isolated extensor digitorum longus (EDL) and soleus muscle from lean mice in a time- and dose-dependent manner. Muscle contraction and PMA also elicited robust effects on these parallel MAPK modules. Insulin action on JNK, p38 MAPK, and ERK1/2 phosphorylation was significantly impaired in EDL and soleus muscle from ob/ob mice. In contrast, muscle contraction-mediated JNK, p38 MAPK, and ERK1/2 phosphorylation was preserved. PMA effects on phosphorylation of JNK and ERK1/2 were normal in ob/ob mice, whereas effects on p38 MAPK were abolished. In conclusion, insulin, contraction, and PMA activate MAPK signaling in skeletal muscle. Insulin-mediated responses on MAPK signaling are impaired in skeletal muscle from ob/ob mice, whereas the effect of contraction is generally well preserved. In addition, PMA-induced phosphorylation of JNK and ERK1/2 are preserved, whereas p38 MAPK pathways are impaired in skeletal muscle from ob/ob mice. Thus, appropriate MAPK responses can be elicited in insulin-resistant skeletal muscle via an insulin-independent mechanism.
Tracking the Recruitment of Diabetogenic CD8+ T-Cells to the Pancreas in Real Time
Authors: Moore Anna , Grimm Jan , Han Bingye , Santamaria Pere
Published: March 2007

Development of autoimmune diabetes in both humans and mice is preceded by a prolonged period of inflammation of pancreatic islets by autoreactive T-cells. Noninvasive imaging techniques, including positron-emission tomography and optical or magnetic resonance imaging, have been used to track the recruitment of lymphocytes to sites of inflammation. These techniques, however, rely on labeling strategies that are non–antigen specific and do not allow specific tracking of the recruitment of autoreactive lymphocytes. Here we describe an antigen-specific magnetic label to selectively target a prevalent population of diabetogenic CD8+ T-cells that contribute to the progression of insulitis to overt diabetes in NOD mice. Superparamagnetic nanoparticles coated with multiple copies of a high-avidity peptide/major histocompatibility complex ligand of these T-cells (NRP-V7/Kd) are endocytosed by CD8+ T-cells in an antigen-specific manner. Using these T-cells as probes, we show that inflammation of pancreatic islets by autoreactive T-cells can be detected in real time by magnetic resonance imaging. This study demonstrates the feasibility of visualizing the presence of ongoing autoimmune responses noninvasively.
The Role of Calcium/Calmodulin-Dependent Protein Kinase Cascade in Glucose Upregulation of Insulin Gene Expression
Authors: Yu Xiao , Murao Koji , Sayo Yoshitaka , Imachi Hitomi , Cao Wen M. , Ohtsuka Shouji , Niimi Michio , Tokumitsu Hiroshi , Inuzuka Hiroyuki , Wong Norman C.W. , Kobayashi Ryoji , Ishida Toshihiko
Published: March 2007

A number of factors have been reported to affect insulin synthesis in β-cells. Although glucose is the most important regulator of insulin gene expression in pancreatic β-cells, the mechanisms whereby glucose stimulates insulin gene transcription in response to changes in glucose concentration have not been clarified yet. In this study, we examined the role of the Ca2+/calmodulin (CaM)-dependent protein kinase (CaM-K) cascade in transcriptional activation of insulin. RT-PCR, Western blotting, and immunohistochemical staining analysis revealed that CaM-K kinase-α (CaM-KKα) and CaM-KIV were localized in rat pancreatic β-cells and their cell line, INS-1. Exposure of INS-1 cells to 11.2 mmol/l glucose elicited an increase of insulin promoter activity as well as upregulation of CaM-KIV activity within 2 min after stimulation. We investigated the influence on insulin promoter activity of the constitutively active form (CaM-KIVc) or dominant-negative mutant (CaM-KIVdn) of CaM-KIV in transfected INS-1 cells. CaM-KIVc alone was sufficient, and the upstream kinase, CaM-KK, was enhanced to upregulate the insulin promoter activity in INS-1 cells. Furthermore, cotransfection of CaM-KIVdn suppressed to a significant degree the glucose-upregulated activity of the insulin promoter. Taken together, these results indicated that the CaM-KK/CaM-KIV cascade might play an important role in glucose-upregulated transcriptional activation of the insulin gene.
Leptin and Leptin Receptor Gene Polymorphisms and Changes in Glucose Homeostasis in Response to Regular Exercise in Nondiabetic Individuals
Authors: Lakka Timo A. , Rankinen Tuomo , Weisnagel S. John , Chagnon Yvon C. , Lakka Hanna-Maaria , Ukkola Olavi , Boulé Normand , Rice Treva , Leon Arthur S. , Skinner James S. , Wilmore Jack H. , Rao D.C. , Bergman Richard , Bouchard Claude
Published: March 2007

We recently reported that a genomic region close to the leptin locus was linked to fasting insulin response to exercise training in nondiabetic white subjects. We tested the hypothesis that common exonic variants in the leptin (LEP) and leptin receptor (LEPR) genes modify the effects of regular physical activity on glucose homeostasis in nondiabetic whites (n = 397) and blacks (n = 143). In whites, exercise increased insulin sensitivity index (P = 0.041) and disposition index (P = 0.046) in the LEPR 109R allele carriers but not in the K109K homozygotes, increased glucose disappearance index more in the R109R homozygotes than in the K109 allele carriers (P = 0.039), and decreased fasting glucose only in the 109R allele carriers (P = 0.018). We also found an interaction between the LEP A19G and LEPR K109R polymorphisms on the change in fasting insulin in whites (P = 0.010). The association between the LEP A19G polymorphism and the change in insulin was evident only in the LEPR 109R carriers (P = 0.019). The decrease in insulin was strongest in the LEP A19A homozygotes who carried the LEPR 109R allele. Similar interaction was observed in blacks (P = 0.046). Variations in the LEP and LEPR genes are associated with the magnitude of the effects of regular exercise on glucose homeostasis in nondiabetic individuals.