Variation in CAPN10 in relation to type 2 diabetes, obesity and quantitative metabolic traits: studies in 6018 whites

ADCY5, CAPN10 and JAZF1 Gene Polymorphisms and Placental Expression in Women with Gestational Diabetes

Gestational diabetes mellitus (GDM) is carbohydrate intolerance that occurs during pregnancy. This disease may lead to various maternal and neonatal complications; therefore, early diagnosis is very important. Because of the similarity in pathogenesis of type 2 diabetes and GDM, the genetic variants associated with type 2 diabetes are commonly investigated in GDM. The aim of the present study was to examine the associations between the polymorphisms in the ADCY5 (rs11708067, rs2877716), CAPN10 (rs2975760, rs3792267), and JAZF1 (rs864745) genes and GDM as well as to determine the expression of these genes in the placenta. This study included 272 pregnant women with GDM and 348 pregnant women with normal glucose tolerance. The diagnosis of GDM was based on a 75 g oral glucose tolerance test (OGTT) at 24–28 weeks gestation, according to International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria. There were no statistically significant differences in the distribution of the ADCY5 gene (rs11708067, rs2877716) and CAPN10 gene (rs2975760, rs3792267) polymorphisms between pregnant women with normal carbohydrate tolerance and pregnant women with GDM. We have shown a lower frequency of JAZF1 gene rs864745 C allele carriers among women with GDM CC + CT vs. TT (OR = 0.60, 95% CI = 0.41–0.87, p = 0.006), and C vs. T (OR = 0.75, 95% CI = 0.60–0.95, p = 0.014). In addition, ADCY5 and JAZF1 gene expression was statistically significantly increased in the placentas of women with GDM compared with that of healthy women. The expression of the CAPN10 gene did not differ significantly between women with and without GDM. Our results indicate increased expression of JAZF1 and ADCY5 genes in the placentas of women with GDM as well as a protective effect of the C allele of the JAZF1 rs864745 gene polymorphism on the development of GDM in pregnant women.

Candidate gene analysis supports a role for polymorphisms at TCF7L2 as risk factors for type 2 diabetes in Sudan

Background

Genetic susceptibility to type 2 diabetes (T2D) is multifactorial. A growing number of genes have been identified as risk factors for T2D across multiple ethnicities in trans-ancestry meta-analysis of large-scale genome-wide association studies. Few studies have looked at these genes in Sub-Saharan African populations. This study was undertaken to look for associations between T2D and single nucleotide polymorphisms (SNPs) in a number of the top candidate genes in a selected Sudanese population.

Methods

A total 240 T2D cases and 128 unrelated healthy control subjects were included in this study. Age, sex, weight and height were recorded, blood pressure and biochemical profiles of glucose and lipids were analysed. Single nucleotide polymorphism (SNP) genotyping was performed using the Sequenom MassARRAY® system. Fourteen SNPs were selected across 7 genes: CAPN10 (rs2975760 and rs5030952), PPARG (rs17036314 and rs1801282), IGF2BP2 (rs4402960 and rs1470579), CDKAL1 (rs9465871), HHEX (rs1111875), TCF7L2 (rs7903146, rs11196205 and rs12255372), and KCNJ11 (rs5215, rs1800467 and rs5219). Allelic and haplotype association analyses were performed under additive models in PLINK. P ≤ 0.007 (=0.05/7 genes) was the P-value required to achieve correction for multiple testing.

Results

A significant genetic association between the SNPs rs7903146 (odds ratio 1.69, 95 % confidence interval 1.21–2.38, P = 0.002) and rs12255372 (odds ratio 1.70, 95 % confidence interval 1.20–2.41, P = 0.003) at TCF7L2 and T2D was found in Sudanese population. These associations were retained after adjusting for age, sex and BMI (e.g. rs7903146: odds ratio 1.70, P_{adj:age/sex/BMI} = 0.005). The strongest haplotype association (odds ratio 2.24; P_{adj:age/sex/BMI} = 0.0003) comprised the two point haplotype T_C across rs7903146 and rs11196205. Stepwise logistic regression demonstrated that SNP rs7903146 added significant main effects to rs11196205 or rs12255372, whereas the reverse was not true, indicating that the main effect for association with T2D in this population is most strongly tagged by SNP rs7903146. Adjusted analyses also provided support for protection from T2D associated with minor alleles at SNPs rs2975760 at CAPN10 (odds ratio 0.44, 95 % confidence interval 0.20-0.97, P_{adj:age/sex/BMI} = 0.042) and rs1111876 at HHEX (odds ratio 0.60, 95 % confidence interval 0.39- 0.93, P_{adj:age/sex/BMI} = 0.022).

Conclusions

Multiethnic associations between T2D and SNPs at TCF7L2, CAPN10 and HHEX extend to Sub-Saharan Africa, specifically Sudan.

Biofluid proteases profiling in diabetes mellitus

The investigation of protease relevance in biologic systems beyond catabolism of proteins and peptides to amino acids has stimulated interest as to their role in the pathogenesis of several disorders including diabetes mellitus (DM). Evaluation of proteases and the assessment of their activity in biofluids are fundamental to elucidate these proteolytic systems in DM and its related complications. In contrast to traditional immunoassay or substrate based approaches that targeted specific proteases and their inhibitors, the field of degradomics has provided a comprehensive approach to study these enzymes. Although the degradome contains over 500 proteases, very few have been associated with DM and its micro- and macrovascular complications. In this paper, we review these proteases and their respective inhibitors with emphasis on DM. It is likely that future research will expand these initial studies and look to develop high throughput automated technologies to identify and characterize biofluid proteases of diagnostic and prognostic value in other pathologies.

Role of calpain-10 in the development of diabetes mellitus and its complications

Calpain activity has been implicated in several cellular processes such as cell signaling, apoptosis, exocytosis, mitochondrial metabolism and cytoskeletal remodeling. Evidence has indicated that the impairment of calpain expression and the activity of different calpain family members are involved in diverse pathologies. Calpain-10 has been implicated in the development of type 2 diabetes, and polymorphisms in the CAPN10 gene have been associated with an increased risk of developing this disease. The present work focused on the molecular biology of calpain-10, supporting its key participation in glucose metabolism. Current knowledge regarding the role of calpain-10 in the development of type 2 diabetes mellitus and diabetes-related diseases is additionally reviewed.

New type 2 diabetes risk genes provide new insights in insulin secretion mechanisms

Type 2 diabetes results from the inability of beta cells to increase insulin secretion sufficiently to compensate for insulin resistance. Insulin resistance is thought to result mainly from environmental factors, such as obesity. However, there is compelling evidence that the decline of both insulin sensitivity and insulin secretion have also a genetic component. Recent genome-wide association studies identified several novel risk genes for type 2 diabetes. The vast majority of these genes affect beta cell function by molecular mechanisms that remain unknown in detail. Nevertheless, we and others could show that a group of genes affect glucose-stimulated insulin secretion, a group incretin-stimulated insulin secretion (incretin sensitivity or secretion) and a group proinsulin-to-insulin conversion. The most important so far type 2 diabetes risk gene, TCF7L2, interferes with all three mechanisms. In addition to advancing knowledge in the pathophysiology of type 2 diabetes, the discovery of novel genetic determinants of diabetes susceptibility may help understanding of gene-environment, gene-therapy and gene-gene interactions. It was also hoped that it could make determination of the individual risk for type 2 diabetes feasible. However, the allelic relative risks of most genetic variants discovered so far are relatively low. Thus, at present, clinical criteria assess the risk for type 2 diabetes with greater sensitivity and specificity than the combination of all known genetic variants.

Association of diabetes susceptibility gene calpain-10 with pancreatic cancer among smokers

OBJECTIVE

The objective of this study was to test the association between calpain-10 (CAPN10), a diabetes susceptibility gene, with risk of pancreatic cancer (PC).

METHODS

DNA samples from 83 incident exocrine PC cases and 166 controls, all of whom were smokers, were genotyped for four markers of CAPN10 in a nested case-control study based on the Beta-Carotene and Retinol Efficacy Trial (CARET), a randomized chemoprevention trial of subjects at high risk of lung cancer. Controls were matched on sex, race, age, CARET intervention arm, duration of exposure to asbestos, and smoking history. Conditional logistic regression was used for statistical analyses.

RESULTS

The minor allele of SNP-43 (rs3792267) in intron 3 was associated with increased risk of PC with an odds ratio of 1.57 (95%CI 1.03-2.38, p = 0.035) per allele. The three markers of the highest risk haplotype had an odds ratio of 1.98 (95%CI 1.12-3.49, p = 0.019) for risk of PC compared to the most common haplotype. There was no evidence of interaction between either of these associations by diabetes status.

CONCLUSION

These results suggest that variation in CAPN10 may be associated with increased risk of PC among smokers. Thus, studies of genes associated with diabetes risk in PC are warranted in a larger population.

Diabetes genes and prostate cancer in the Atherosclerosis Risk in Communities study

There is a known inverse association between type 2 diabetes (T2D) and prostate cancer (PrCa) that is poorly understood. Genetic studies of the T2D-PrCa association may provide insight into the underlying mechanisms of this association. We evaluated associations in the Atherosclerosis Risk in Communities study between PrCa and nine T2D single nucleotide polymorphisms from genome-wide association studies of T2D (in CDKAL1, CDKN2A/B, FTO, HHEX, IGF2BP2, KCNJ11, PPARG, SLC30A8, and TCF7L2) and four T2D single nucleotide polymorphisms from pre-genome-wide association studies (in ADRB2, CAPN10, SLC2A2, and UCP2). From 1987 to 2000, there were 397 incident PrCa cases among 6,642 men ages 45 to 64 years at baseline. We used race-adjusted Cox proportional hazards models to estimate associations between PrCa and increasing number of T2D risk-raising alleles. PrCa was positively associated with the CAPN10 rs3792267 G allele [hazard ratio (HR) 1.20; 95% confidence interval (CI), 1.00-1.44] and inversely associated with the SLC2A2 rs5400 Thr110 allele (HR, 0.85; 95% CI, 0.72, 1.00), the UCP2 rs660339 Val55 allele (HR, 0.84; 95% CI, 0.73, 0.97) and the IGF2BP2 rs4402960 T allele (HR, 0.79; 95% CI, 0.61-1.02; blacks only). The TCF7L2 rs7903146 T allele was inversely associated with PrCa using a dominant genetic model (HR, 0.79; 95% CI, 0.65-0.97). Further knowledge of T2D gene-PrCa mechanisms may improve understanding of PrCa etiology.

Association of CAPN10 gene with insulin sensitivity, glucose tolerance and renal function in essential hypertensive patients

BACKGROUND

Essential hypertension (EH) is a common disorder, which can increase the risk for type 2 diabetes (T2D). Calpain-10 (CAPN10) gene was the first candidate gene of T2D identified through genome-wide linkage and positional cloning, but few works have focused on the relationship of CAPN10 with impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) in EH patients.

METHODS

To identify the effect of UCSNP-43 and UCSNP-44 in CAPN10 gene on susceptibility to IFG/IGT, we conducted a case-control study in 961 EH patients with and without IFG/IGT among Han Chinese population. We also evaluated the impact of two SNPs on insulin sensitivity and glucose tolerance estimated through oral glucose tolerance test and renal functions by blood chemical assays.

RESULTS

The major findings of this study were that UCSNP-43 displayed higher G120 and AUCg. In addition, UCSNP-44 was found associated with IFG/IGT in EH patients, and associated with increased G30, G60, AUCg, Cederholm index, Scr and eGFR. The haplotype UCSNP-43-44 was detected associated with IFG/IGT susceptibility, G60, G120, I0, AUCg, Scr and eGFR by the linear regression with the adjustment for sex, age, BMI, mean blood pressures and ACEI/ARB treatment.

CONCLUSIONS

These findings provided some evidence that CAPN10 gene may play an important role in the pathogenesis of IFG/IGT in EH patients.

Pathomechanisms of type 2 diabetes genes

Type 2 diabetes mellitus is a complex metabolic disease that is caused by insulin resistance and beta-cell dysfunction. Furthermore, type 2 diabetes has an evident genetic component and represents a polygenic disease. During the last decade, considerable progress was made in the identification of type 2 diabetes risk genes. This was crucially influenced by the development of affordable high-density single nucleotide polymorphism (SNP) arrays that prompted several successful genome-wide association scans in large case-control cohorts. Subsequent to the identification of type 2 diabetes risk SNPs, cohorts thoroughly phenotyped for prediabetic traits with elaborate in vivo methods allowed an initial characterization of the pathomechanisms of these SNPs. Although the underlying molecular mechanisms are still incompletely understood, a surprising result of these pathomechanistic investigations was that most of the risk SNPs affect beta-cell function. This favors a beta-cell-centric view on the genetics of type 2 diabetes. The aim of this review is to summarize the current knowledge about the type 2 diabetes risk genes and their variants' pathomechanisms.

Calpain-10 gene and protein expression in human skeletal muscle: effect of acute lipid-induced insulin resistance and type 2 diabetes

OBJECTIVE

Our objective was to investigate the effect of lipid-induced insulin resistance and type 2 diabetes on skeletal muscle calpain-10 mRNA and protein levels.

RESEARCH DESIGN AND METHODS

In the first part of this study, 10 healthy subjects underwent hyperinsulinemic euglycemic (4.5 mmol/liter) clamps for 6 h with iv infusion of either saline or a 20% Intralipid emulsion (Fresenius Kabi AG, Bad Homburg, Germany). Skeletal muscle biopsies were taken before and after 3- and 6-h insulin infusion and analyzed for calpain-10 mRNA and protein expression. In the second part of the study, muscle samples obtained after an overnight fast in 10 long-standing, sedentary type 2 diabetes patients, 10 sedentary, weight-matched, normoglycemic controls, and 10 age-matched, endurance-trained cyclists were analyzed for calpain-10 mRNA and protein content.

RESULTS

Intralipid infusion in healthy subjects reduced whole body glucose disposal by approximately 50% (P<0.001). Calpain-10 mRNA (P=0.01) but not protein content was reduced after 6-h insulin infusion in both the saline and Intralipid emulsion trials. Skeletal muscle calpain-10 mRNA and protein content did not differ between the type 2 diabetes patients and normoglycemic controls, but there was a strong trend for total calpain-10 protein to be greater in the endurance-trained athletes (P=0.06).

CONCLUSIONS

These data indicate that skeletal muscle calpain-10 expression is not modified by insulin resistance per se and suggest that hyperinsulinemia and exercise training may modulate human skeletal muscle calpain-10 expression.

Targeted suppression of calpain-10 expression impairs insulin-stimulated glucose uptake in cultured primary human skeletal muscle cells

Calpain-10 was identified as a novel type 2 diabetes susceptibility gene, although the mechanisms by which it increases susceptibility to type 2 diabetes remain unclear. As skeletal muscle is the principal site of the peripheral insulin resistance for glucose disposal in type 2 diabetes, we investigated whether targeted suppression of calpain-10 expression directly affects insulin action in cultured human skeletal muscle cells. Short interfering RNAs (siRNAs) were employed to specifically suppress CAPN10 gene expression. Suppression was seen at both the transcript and protein level, as assessed by quantitative PCR and Western blotting. Suppression of CAPN10 mRNA expression (75% decrease compared to untransfected myotubes) was associated with a significant decrease (p=0.04) in insulin-stimulated glucose uptake (1.03+/-0.06 [mean+/-SEM]-fold increase over basal) compared to the untransfected myotubes (1.43+/-0.16-fold increase). In contrast, decreased suppression of calpain-10 expression did not affect insulin-stimulated glycogen synthesis nor insulin-stimulated phosphorylation of protein kinase B, a key component of the insulin-signalling pathway. This study confirms that calpain-10 plays a role in insulin-stimulated glucose uptake in human skeletal muscle cells. Suppression of calpain-10 expression did not affect insulin-stimulated glycogen synthesis nor insulin-signalling via PKB, suggesting that calpain-10 may exert a direct regulatory effect upon the glucose uptake mechanism.