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.

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.