Genetic variation in the gene encoding calpain-10 is associated with type 2 diabetes mellitus.

Type 2 or non-insulin-dependent diabetes mellitus (NIDDM) is the most common form of diabetes worldwide, affecting approximately 4% of the world's adult population. It is multifactorial in origin with both genetic and environmental factors contributing to its development. A genome-wide screen for type 2 diabetes genes carried out in Mexican Americans localized a susceptibility gene, designated NIDDM1, to chromosome 2. Here we describe the positional cloning of a gene located in the NIDDM1 region that shows association with type 2 diabetes in Mexican Americans and a Northern European population from the Botnia region of Finland. This putative diabetes-susceptibility gene encodes a ubiquitously expressed member of the calpain-like cysteine protease family, calpain-10 (CAPN10). This finding suggests a novel pathway that may contribute to the development of type 2 diabetes.

Novel linkage and association of TCF7L2 variants with PCOS in Italian families.

OBJECTIVE: Transcription factor 7-like 2 (TCF7L2) gene variants confer risk for type 2 diabetes and metabolic traits. We investigated the role of TCF7L2-variants in polycystic ovarian syndrome (PCOS), which is a common endocrine metabolic disorder affecting women of reproductive age. We tested whether TCF7L2 variants are in linkage to and/or in linkage disequilibrium [(LD), namely linkage and association)] with PCOS. PATIENTS AND METHODS: Within 212 families from the Italian peninsular population, we analyzed 78 variants using Pseudomarker software for linkage to and LD with PCOS under the dominant model with complete penetrance (D1). In a secondary analysis, we tested the variants under the recessive models with complete penetrance (R1), dominant with incomplete penetrance (D2), and recessive with incomplete penetrance (R2). We tested through in silico analysis the risk variants to detect any potential functional effects. RESULTS: We identified a total of 14 variants in the TCF7L2 gene significantly linked to and/or in LD with the risk of PCOS (p < 0.05) across different models. CONCLUSIONS: This study is the first to report TCF7L2 linkage and linkage disequilibrium in Italian families with PCOS.

Novel TCF7L2 familial linkage and association with Type 2 diabetes, depression, and their comorbidity.

OBJECTIVE: Alterations in the activity of the transcription factor 7-like 2 (TCF7L2) generate defects previously associated with neuropsychiatric disorders. We investigated the role of the TCF7L2 gene in major depressive disorder (MDD), type 2 diabetes (T2D), and MDD-T2D comorbidity. We tested whether TCF7L2 is in linkage to and/or in linkage disequilibrium (LD, namely association) with MDD, T2D, and MDD-T2D. PATIENTS AND METHODS: In 212 families with T2D and MDD in the Italian population, we analyzed 80 microarray-based SNPs using Pseudomarker software for linkage to and LD with T2D and MDD under the recessive model with complete penetrance (R1). In a secondary analysis, we tested the variants under the dominant models with complete penetrance (D1), recessive with incomplete penetrance (R2), and recessive with incomplete penetrance (R2). RESULTS: We found several novel linkage signals and genetic associations. In addition, we found two new transcription-factor (TF) binding sites created by two risk variants found: the MDD-risk variant rs12255179 creates a new TF-binding site for the CCAAT/enhancer-binding protein α (C/EBPα), and the T2D-risk variant rs61872794 creates a new TF-binding site for the organic cation-uptake transporter (OCT1). Both new binding sites are related to insulin metabolism. CONCLUSIONS: These results highlight the cross-interactivity between T2D and MDD. Further replication is needed in diverse ethnic groups.

PSMD9 is linked to T2D age of onset, years of isolated and combined insulin therapy, irregular menses, and hot flashes.

OBJECTIVE: PSMD9 is a ubiquitous protein present at high concentrations in eukaryotic cells. It contributes to the degradation of intracellular proteins in the immune system. It is part of the 26S proteasome complex, and its regulatory role on proteasomal activity as well as its effect on genetic transcription have been recognized. PSMD9 has been related with insulin secretion, and it regulates the ligand-dependent retinoid-target genes transcription. Importantly, PSMD9 rs74421874 (IVS3+nt460-G>A), rs3825172 (IVS3+nt437-C>T), and rs14259 SNPs have been previously linked to type 2 diabetes (T2D), maturity-onset diabetes of the young 3 (MODY3), overweight status and waist circumference, hypertension, hypercholesterolemia, cardiovascular disease, microvascular disease (retinopathy, neuropathy, and nephropathy), carpal tunnel syndrome, depression, anxiety, insomnia, and sleep hours. MATERIALS AND METHODS: In this study, we analyzed the above-mentioned PSMD9 rs74421874 (IVS3+nt460-G>A), rs3825172 (IVS3+nt437-C>T), and rs14259 SNPs for linkage to the T2D quantitative traits of T2D age of onset, duration in years of combined oral hypoglycemic agents and insulin therapy and only insulin therapy, stress, and the birth weight of the subjects' children; and with the T2D qualitative phenotypes of irregular menses, couple infertility, and menopausal hot flashes. RESULTS: We found that PSMD9 was linked to irregular menses of reproductive age, menopausal hot flashes, T2D age of onset, years of combined oral and insulin therapy and of insulin therapy; we also found that it shows only a tendency towards linkage to stress, birthweight, and couple infertility. CONCLUSIONS: This is the first time that this gene is implicated with irregular menses of reproductive age (a trait of polycystic ovarian syndrome), hot flashes, T2D onset age, and duration years of combined oral and insulin therapy and only insulin therapies.

Heavy metals as risk factors for human diseases - a Bayesian network approach.

Modern industrial agricultural processes expose human beings to multifactorial environmental pollution including heightened levels of heavy metals. The effects of acute heavy metal exposures at toxic levels are usually known; they are tested for and treated promptly. The effects of low/moderate-level chronic heavy metal exposures are less known as they may be subclinical, and pathogenic effects may only manifest clinically over time under the disguise of a diagnosable disease or miscellaneous symptoms attributed to aging. Consequently, the health impact of low-moderate heavy metal exposure is unlikely to be identified. Furthermore, established heavy metal safety levels often fail to recognize the potential toxic effects on humans. We report in this review what is known about the sub-chronic and chronic effects of exposure to heavy metals, particularly lead, mercury, cadmium, arsenic, and nickel, and we highlight their possible effects in the brain, cardiovascular and endocrine-metabolic systems, and on reproduction.

Mutations in the coding region of the neurogenin 3 gene (NEUROG3) are not a common cause of maturity-onset diabetes of the young in Japanese subjects.

Mutations in transcription factors that play a role in the development of the endocrine pancreas, such as insulin promoter factor-1 and NeuroD1/BETA2, have been associated with diabetes. Cell type-specific members of the basic helix-loop-helix (bHLH) family of transcription factors play essential roles in the development and maintenance of many differentiated cell types, including pancreatic beta-cells. Neurogenin 3 is a bHLH transcription factor that is expressed in the developing central nervous system and the embryonic pancreas. Mice lacking this transcription factor fail to develop any islet endocrine cells and die postnatally from diabetes. Because neurogenin 3 is required for the development of beta-cells and other pancreatic islet cell types, we considered it a candidate diabetes gene. We screened the coding region of the human neurogenin 3 gene (NEUROG3) for mutations in a group of unrelated Japanese subjects with maturity-onset diabetes of the young (MODY). We found three sequence variants: a deletion of 2-bp in the 5'-untranslated region (NEUROG3-g.-44-45delCA), a G-to-A substitution in codon 167 (g.499G/ A), resulting in a Gly-to-Arg replacement (G/R167), and a T-to-C substitution in codon 199 (g.596T/C), resulting in a Phe/Ser polymorphism F/S199. These polymorphisms were not associated with MODY, thereby suggesting that mutations in NEUROG3 are not a common cause of MODY in Japanese patients.

Analysis of the glucokinase gene in Mexican families displaying early-onset non-insulin-dependent diabetes mellitus including MODY families.

Non-insulin-dependent diabetes mellitus (NIDDM) is the most common form of diabetes, affecting 5% of the general population. Genetic factors play an important role in the development of the disease. While in other populations NIDDM is usually diagnosed after the fifth decade of life, in Mexico a large proportion of patients develop the disease at an early age (between the third and the fourth decade). In Caucasian population, mutations in the glucokinase gene, the TCF1, and TCF14 genes, have been identified in a subgroup of early-onset NIDDM patients denominated MODY (maturity-onset diabetes of the young), which show an autosomal dominant pattern of inheritance. As a first step in the molecular characterization of Mexican families displaying early-onset NIDDM we searched for mutations in the glucokinase gene through SSCP analysis and/or direct sequencing in 26 individuals from 22 independent families, where at least four can be classified as MODY. No mutations were detected in the exons or the intron-exon boundaries of the gene in any of the screened individuals. The phenotype and clinical profile of some of the studied patients is compatible with that of patients carrying mutations in the TCF1 or TCF14 genes, while others may carry mutations in different loci. Through computer simulation analysis we identified at least four informative families which will be used for further linkage studies.

Population genetics of CAPN10 and GPR35: implications for the evolution of type 2 diabetes variants.

A positional cloning study of type 2 diabetes in Mexican Americans identified a region, termed "NIDDM1," on chromosome 2q37 with significant linkage evidence. Haplotype combinations at the calpain-10 gene (CAPN10) within this region were shown to increase diabetes risk in several populations. On the basis of the thrifty genotype hypothesis, variants that increase susceptibility to type 2 diabetes under modern lifestyle conditions provided a survival advantage in past environments by increasing the efficiency of energy use and storage. Here, our goal is to make inferences about the evolutionary forces shaping variation in genes in the NIDDM1 region and to investigate the population genetics models that may underlie the thrifty genotype hypothesis. To this end, we surveyed sequence variation in CAPN10 and in an adjacent gene, G-protein-coupled receptor 35 (GPR35), in four population samples from different ethnic groups. These data revealed two distinct deviations from the standard neutral model in CAPN10, whereas GPR35 variation was largely consistent with neutrality. CAPN10 showed a significant deficit of variation in the haplotype class defined by the derived allele at SNP44, a polymorphism that is significantly associated with diabetes in meta-analysis studies. This suggests that this haplotype class was quickly driven to high frequency by positive natural selection. Interestingly, the derived allele at SNP44 is protective against diabetes. CAPN10 also showed a local excess of polymorphism and linkage disequilibrium decay in intron 13. Simulations show that this pattern may be explained by long-standing balancing selection that maintains multiple selected alleles. Alternatively, it is possible that the local mutation and recombination rates changed since the divergence of human and chimpanzee; this scenario does not require the action of natural selection on intron 13 variation.