IRS1 gene variants, dysglycaemic metabolic changes and type-2 diabetes risk.

BACKGROUND AND AIMS: A recent genome-wide association study identified rs2943641C > T, 500 kb from the insulin receptor substrate-1 gene (IRS1), as a type-2 diabetes (T2D) susceptibility locus. We aimed to replicate this association by meta-analysis and examine whether common variants within IRS1, present on the HumanCVD BeadChip, were associated with T2D risk. METHODS AND RESULTS: We genotyped rs2943641 in 2389 prevalent or incident T2D patients and 6494 controls from two prospective and three case studies based in UK and in the European Atherosclerosis Research Study-II (EARSII; n = 714). Thirty-three IRS1 variants had been genotyped in the prospective Whitehall-II study (n = 4752) using the HumanCVD BeadChip. In a fixed-effects meta-analysis of the UK study cohorts rs2943641T allele was associated with 6% lower risk of T2D (p = 0.18), with T-allele carriers having an odds ratio (OR) of 0.89 (95% confidence interval [CI]: 0.80-1.00, p = 0.056) compared to CC subjects. The T-allele was also associated with lower fasting insulin and homeostasis model assessment index of insulin resistance in Whitehall-II and with lower post-load insulin after an oral glucose tolerance test in EARSII (all p < 0.05). None of the IRS1 variants on the chip showed linkage disequilibrium with rs2943641. In silico analysis with follow-up genotyping (total n = 9313) identified that the rare allele of the IRS1 promoter variant rs6725556A > G showed association with reduced T2D risk (OR per G-allele: 0.82, 95%CI: 0.69-0.96, p = 0.015). CONCLUSIONS: We confirm the association of rs2943641T with T2D protection. There is a possible independent effect on risk of a putative IRS1 promoter variant.

Variants of ADRA2A are associated with fasting glucose, blood pressure, body mass index and type 2 diabetes risk: meta-analysis of four prospective studies.

AIMS/HYPOTHESIS: We quantified the effect of ADRA2A (encoding α-2 adrenergic receptor) variants on metabolic traits and type 2 diabetes risk, as reported in four studies. METHODS: Genotype data for ADRA2A single nucleotide polymorphisms (SNPs) rs553668 and rs10885122 were analysed in >17,000 individuals (1,307 type 2 diabetes cases) with regard to metabolic traits and type 2 diabetes risk. Two studies (n = 9,437), genotyped using the Human Cardiovascular Disease BeadChip, provided 12 additional ADRA2A SNPs. RESULTS: Rs553668 was associated with per allele effects on fasting glucose (0.03 mmol/l, p = 0.016) and type 2 diabetes risk (OR 1.17, 95% CI 1.04-1.31; p = 0.01). No significant association was observed with rs10885122. Of the 12 SNPs, several showed associations with metabolic traits. Overall, after variable selection, rs553668 was associated with type 2 diabetes risk (OR 1.38, 95% CI 1.09-1.73; p = 0.007). rs553668 (per allele difference 0.036 mmol/l, 95% CI 0.008-0.065) and rs17186196 (per allele difference 0.066 mmol/l, 95% CI 0.017-0.115) were independently associated with fasting glucose, and rs17186196 with fasting insulin and HOMA of insulin resistance (4.3%, 95% CI 0.6-8.1 and 4.9%, 95% CI 1.0-9.0, respectively, per allele). Per-allele effects of rs491589 on systolic and diastolic blood pressure were 1.19 mmHg (95% CI 0.43-1.95) and 0.61 mmHg (95% CI 0.11-1.10), respectively, and those of rs36022820 on BMI 0.58 kg/m(2) (95% CI 0.15-1.02). CONCLUSIONS/INTERPRETATION: Multiple ADRA2A SNPs are associated with metabolic traits, blood pressure and type 2 diabetes risk. The α-2 adrenergic receptor should be revisited as a therapeutic target for reduction of the adverse consequences of metabolic trait disorders and type 2 diabetes.

APOE, CETP and LPL genes show strong association with lipid levels in Greek children.

BACKGROUND AND AIMS: Studies have consistently demonstrated that variants in a number of candidate genes are significant determinants of lipid levels in adults. However, few studies have investigated the impact of these variants in children. Therefore, in the present investigation we examined the influence of ten common variants in the genes for lipoprotein lipase (LPL-S447X), cholesterol ester transfer protein (CETP-Taq1B) apolipoprotein (APO) E (epsilon2, epsilon3, epsilon4), APOA5 (-1131C>T and S19W), APOA4 (S347T) and APOC3 (-482C>T; 1100C>T and 3238G>C) on lipoprotein levels children from the Gene-Diet Attica Investigation on childhood obesity (GENDAI). METHODS AND RESULTS: The ten variants selected were genotyped in 882 Greek children, mean age: 11.2+/-0.7 years (418 females and 464 males). Genotypes were assessed using TaqMan technology. Significantly higher total cholesterol (TC) (p=0.0001) and low-density lipoprotein cholesterol (LDL-C) (p<0.0001) were observed in APOE epsilon4 carriers compared to epsilon3/epsilon3 homozygotes and epsilon2 carriers. The association of APOE genotype with TC and high-density lipoprotein cholesterol (HDL-C) ratio (p=0.0008) was further modulated by body mass index. Carriers of the CETP TaqIB B2 allele had significantly higher HDL-C (p<0.0001) and significantly lower TC: HDL-C ratio (p<0.0001) compared to B1/B1 individuals. No significant associations were observed between APOA4, APOA5 and APOC3 variants and serum lipids. CONCLUSION: This study demonstrates that these common variants are associated with lipid levels in this healthy paediatric cohort, suggesting that even in these young children there may be potential in predicting their lifelong exposure to an adverse lipid profile.

Candidate gene association studies in abdominal aortic aneurysm disease: a review and meta-analysis.

BACKGROUND: Candidate gene analysis has been frequently used in attempts to understand the pathological processes involved in many aspects of AAA disease. METHODS: This paper sets out a systems approach to reviewing AAA candidate gene analysis studies, whilst, explaining the key principles and design limitations of this universally applied technique. In addition we have performed a meta-analysis of six gene polymorphisms (ACE I/D, MTHFR+677C>T, MMP9-1562C>T, Il-1Beta/3953C>T, eNOS 4a/4b & TIMP1/+434C>T) reported in multiple case control studies. RESULTS AND CONCLUSIONS: Three of these polymorphisms were associated with a significant risk of AAA, ACE RR 1.33 [95% CI 1.20-1.48], MTHFR RR 1.14 [1.08-1.21] and MMP9 RR 1.09 [1.01-1.18]. These differences have been previously reported as equivocal, within a context of contradictory studies and as such this meta-analysis provides new evidence for their involvement in AAA disease. The plausibility of these findings is discussed within the context of a systems approach to the pathology of AAA disease.

Haplotype and genotype effects of the F7 gene on circulating factor VII, coagulation activation markers and incident coronary heart disease in UK men.

BACKGROUND: Evidence for the associations of single nucleotide polymorphisms (SNPs) in the F7 gene and factor (F)VII levels and with risk of coronary heart disease (CHD) is inconsistent. We examined whether F7 tagging SNPs (tSNPs) and haplotypes were associated with FVII levels, coagulation activation markers (CAMs) and CHD risk in two cohorts of UK men. METHODS: Genotypes for eight SNPs and baseline levels of FVIIc, FVIIag and CAMs (including FVIIa) were determined in 2773 healthy men from the Second Northwick Park Heart Study (NPHS-II). A second cohort, Whitehall II study (WH-II, n = 4055), was used for replication analysis of FVIIc levels and CHD risk. RESULTS: In NPHS-II the minor alleles of three SNPs (rs555212, rs762635 and rs510317; haplotype H2) were associated with higher levels of FVIIag, FVIIc and FVIIa, whereas the minor allele for two SNPs (I/D323 and rs6046; haplotype H5) was associated with lower levels. Adjusted for classic risk factors, H2 carriers had a CHD hazard ratio of 1.34 [95% confidence interval (CI): 1.12-1.59; independent of FVIIc], whereas H5 carriers had a CHD risk of 1.29 (95% CI: 1.01-1.56; not independent of FVIIc) and significantly lower CAMs. Effects of haplotypes on FVIIc levels were replicated in WH-II, as was the association of H5 with higher CHD risk [pooled-estimate odds ratio (OR) 1.16 (1.00-1.36), P = 0.05], but surprisingly, H2 exhibited a reduced risk for CHD. CONCLUSION: tSNPs in the F7 gene strongly influence FVII levels. The haplotype associated with low FVIIc level, with particularly reduced functional activity, was consistently associated with increased risk for CHD, whereas the haplotype associated with high FVIIc level was not.

Increase of plasma fibrinogen levels and variability with age in a sample of middle aged healthy men.

According to predictions from the current theoretical models for ageing the heterogeneity of the population is increasing with increasing age. Although the direct observation of such changes in humans is extremely difficult, supporting evidence should be identifiable in key biomarkers associated with health and mortality. Using data from the Northwick Park Heart Study II of 3052 healthy middle-aged men (mean 56 years of age, range 49-69 years), with 5 annual measures of CHD risk factors, ageing effects were tested for plasma fibrinogen, cholesterol and triglycerides. Fibrinogen levels increased with age (p < 0.0001), while cholesterol showed a decrease, and triglycerides did not show any change with age. There was a significant increase in the variance of fibrinogen with age (p < 0.0007) but not for cholesterol or triglycerides. The raising effect on fibrinogen levels associated with the A allele of the FIBB - 455G>A promoter variant also decreased with age (p = 0.005). The age-associated changes observed in the fibrinogen variability and the association of phenotype to genotype are discussed in light of the evolutionary theory, and their implications are considered.

The use of meta-analysis risk estimates for candidate genes in combination to predict coronary heart disease risk.

Although the risk for coronary heart disease (CHD) associated with single SNPs is modest it has been suggested that, in combination, several common risk-associated alleles could lead to a substantially better heart disease risk prediction. We have modelled this using 10 SNPs in ten candidate genes (APOB, NOS3, APOE, ACE, SERPINE1, MTHFR, ITGA2B, PON 1, LPL, and CETP) and their predicted summary risk estimates from meta-analysis. Based on published allele frequencies, approximately 29% of the general population would be expected to carry less than three risk alleles, approximately 55% would carry 3 or 4 risk alleles, 4% would have 6 and 1% 7 or more risk alleles. Compared to the mean of those with 3 or 4 risk associated genotypes, those with 6 and 7-or-more alleles have a significantly higher risk odds ratio (OR) of CHD (mean OR (95% Confidence Intervals), 1.70 (1.14 to 2.55); and 4.51 (2.89 to 7.04) respectively), while compared to those in the lowest decile of risk, those in the highest decile have a CHD odds ratio in the range of 3.05 (2.24 to 4.14). Taking into account age and the risk alleles carried, the mean 10 year probability for developing CHD for a 55 year old man was calculated to be 15% (8.6% to 24.8%), with nearly 1 in 5 having more than 20% risk. Whether this particular group of 10 SNPs will improve the accuracy of CHD predictions over the combination of classical risk factors in clinical use requires further experimental evidence.