Association between the adiponectin promoter rs266729 gene variant and oxidative stress in patients with diabetes mellitus.

AIMS: Low levels of adiponectin are associated with type 2 diabetes and coronary heart disease (CHD). Recent evidence also suggests that low levels of adiponectin are associated with increased oxidative stress. Our aim was to examine the association between the rs266729 promoter gene variant (-11377C > G) and plasma markers of oxidative stress in diabetes subjects. METHODS AND RESULTS: Seven hundred and sixty-seven Caucasian subjects with diabetes were successfully genotyped (CC/CG/GG). Genotype data were analysed in relation to plasma total antioxidant status (TAOS) and Oxidized-LDL (Ox-LDL). Plasma adiponectin measurements were available in 206 samples. There was a significant association between genotype and plasma TAOS (CC: 42.1 +/- 13.4% vs. CG: 42.0 +/- 12.0% vs. GG: 47.9 +/- 12.0%, P = 0.02; for CC/CG vs. GG, P = 0.006). With respect to Ox-LDL, CC subjects had 8% higher plasma Ox-LDL compared with CG/GG [CC vs. CG vs. GG: 48.5 (36.3-60.2) U/L vs. 44.8 (35.6-54.1) U/L vs. 44.9 (41.2-49.1) U/L, for CC vs. CG/GG P = 0.03]. For plasma adiponectin, GG subjects had the highest levels [CC vs. CG vs. GG: 8.18 (5.69-15.38) microg/mL vs. 7.12 (5.34-12.97) microg/mL vs. 11.84 (6.98-25.25) microg/mL, P = 0.09; for CC/CG vs. GG, P = 0.05]. CONCLUSION: This study shows an association between a promoter variant in the adiponectin gene and plasma markers of oxidative stress. In line with previous studies, this work supports an antioxidant role for adiponectin which may explain its cardioprotective effect. Further prospective study is necessary to explore the effect of this gene variant in diabetes in relation to CHD risk and oxidative stress.

The effect of WNT5B IVS3C>G on the susceptibility to type 2 diabetes in UK Caucasian subjects.

BACKGROUND AND AIMS: The wnt signaling pathway regulates adipogenesis and insulin secretion. The WNT5B gene has been reported to confer susceptibility to type 2 diabetes (T2D) in the Japanese population, and we therefore evaluated this in Caucasian subjects with respect to obesity status. METHODS AND RESULTS: Two thousand seven hundred and one Caucasian middle-aged men from the prospective Northwick Park Heart Study II (NPHSII) of whom 153 developed T2D over 15 years and 1268 Caucasian middle-aged patients with T2D (60% male) were genotyped using a TaqMan assay for the IVS3C>G variant (rs2270031) in the WNT5B gene. The frequency of the G allele was 0.026 (0.022-0.031) in controls and 0.031 (0.025-0.039) in patients with diabetes, p=0.24. In the prospective analysis, G allele carriers with BMI below 26 kg/m(2) had significantly higher T2D hazard risk [3.46 (1.34-8.96), p=0.01]. Comparing T2D cases with NPHSII controls, the G allele was associated with a significantly higher T2D odds ratio (OR) of 1.50 (1.06-2.12), p=0.02 in subjects with BMI lower than 30 kg/m(2). Increasing BMI had a smaller effect on risk in G allele carriers. The effect on risk was not explained by genotype being associated with any classical T2D risk factor. When the combined effect of this SNP and the TCF7L2 IVS3C>T SNP (rs7903146) was evaluated, a 2.07 (1.40-3.07), p<0.0001 fold higher OR was observed in carriers of both the rare alleles. CONCLUSION: Variation in WNT5B predisposes to T2D in the absence of obesity. The increase in risk conferred by the presence of both WNT5B and TCF7L2 variants strengthens the role of wnt signaling in T2D.

Is the influence of variation in the ACE gene on the prospective risk of Type 2 diabetes in middle-aged men modified by obesity?

There is strong evidence for the presence of a functional renin-angiotensin system in diabetogenic tissues, and ACE (angiotensin-converting enzyme) inhibitors may improve glucose metabolism in those individuals at high risk of developing T2DM (Type 2 diabetes). In the present study, we tested the hypothesis that subjects with genetically lower plasma and tissue ACE activity, because of their ACE [I/D (insertion/deletion)] genotype, would have a lower risk of T2DM in 2642 healthy middle-aged Caucasian men (mean age, 56 years) followed-up for 15 years. Obesity was the strongest predictor of T2DM, with an HR (95% CI) [hazard ratio (95% confidence interval)] of 3.74 (2.66-5.26) (P<0.0001). Overall there was no association between ACE genotype (II homozygotes, n=623; and D allele carriers, n=2019) and risk of T2DM, and although in lean men there was no genotype difference in risk in D allele carriers compared with II homozygotes [adjusted HR=0.75 (95% CI, 0.46-1.22)], in obese (body mass index >30 kg/m(2)) men the risk of T2DM was higher [adjusted HR=4.26 (95% CI, 1.30-13.93)] with a genotype-obesity interaction of P=0.01. A similar pattern of risk was seen by re-analysis of a previously published case-control study, where D allele carriers had a non-significant 1.30 (0.97-1.74)-fold higher risk of developing T2DM than II homozygotes when non-obese, but a 1.79 (1.17-2.72) (P=0.007)-fold higher risk when obese. Further prospective studies are needed to confirm these findings. The ACE D allele may worsen glucose metabolism, which could raise the prospective T2DM risk in obese men, but not in lean men. In obesity, adipose tissue undergoes inflammatory infiltration and the subsequent higher levels of pro-inflammatory angiotensin II may explain this association.

Variation in the UCP2-UCP3 gene cluster predicts the development of type 2 diabetes in healthy middle-aged men.

The impact of the UCP2 -866G>A and UCP3 -55C>T variants on prospective risk of type 2 diabetes was examined over 15 years in 2,936 healthy middle-aged men (mean age 56 years). Conversion to diabetes (n = 169) was associated with higher BMI, blood pressure, cholesterol, triglycerides and C-reactive protein. The hazard ratio (HR) for diabetes of a BMI >30 kg/m(2) was 3.96 (95% CI 2.87-5.47). Homozygosity for the UCP2A or UCP3T alleles accelerated the onset of diabetes, with significant differences in risk of diabetes at 10 years (HR [95% CI] UCP2AA vs. GA+GG 1.94 [1.18-3.19], P = 0.009; UCP3TT vs. CC+ CT 2.06 [1.06-3.99], P = 0.03) but less so at 15 years (UCP2AA 1.42 [0.92-2.19], P = 0.1; UCP3TT 1.57 [0.87-2.04], P = 0.13). Men who were homozygous for both UCP2AA and UCP3TT (1.5% of men) had a risk for diabetes at 10 years of 4.20 (1.70-10.37), P = 0.002. These genotype effects were additive with obesity, and men with a BMI >30 kg/m(2) and this genotype combination had a 10-year risk of diabetes of 19.23 [5.63-63.69], P < 0.0001. Functional promoter variants UCP2 and UCP3 increase the prospective risk of diabetes. Although the mechanism of the UCP2 effect is likely to be caused by increased expression in the pancreas and subsequent reduced insulin secretion, the mechanism of the UCP3 effect is currently unknown. Both effects are exacerbated by obesity.

Increased plasma markers of oxidative stress are associated with coronary heart disease in males with diabetes mellitus and with 10-year risk in a prospective sample of males.

BACKGROUND: Increased oxidative stress is associated with coronary heart disease (CHD). We examined the association between plasma markers of oxidative stress and CHD in a cross-sectional sample of patients with diabetes and prospective CHD risk in a sample of men predominantly without diabetes. METHODS: Plasma total antioxidant status (TAOS) and the ratio of oxidized LDL (Ox-LDL) to LDL-cholesterol (LDL-C) were determined in a cross-section of 761 Caucasian individuals with diabetes (UDACS study). Plasma TAOS was also determined in 310 baseline samples from a 10-year prospective cohort of 3012 healthy males (NPHSII). RESULTS: Within UDACS, males with CHD had lower mean (SD) plasma TAOS [no CHD, 43.4 (13.2)%; CHD, 40.3 (13.8)%; P = 0.04]. The prevalence of CHD was higher in the lowest compared with the upper quartiles (32.7% vs 19.7%; P = 0.004). We observed a significant association between plasma Ox-LDL:LDL-C and CHD status [no CHD vs CHD, 16.9 (3.1) vs 19.3 (5.0) units/mmol; P = 0.04], with the prevalence of CHD being higher among men in the upper compared with lower quartiles (18.4% vs 35.1%; P = 0.003). No association was observed in females. In NPHSII, TAOS was lower in those who developed CHD [35.1 (8.0)% vs 37.1 (7.9)%; P = 0.04]. The odds ratio for CHD in the lowest compared with the upper quartile was 1.91 (95% confidence interval, 0.99-3.70; P = 0.04). This remained unchanged after adjustment for classic risk factors. CONCLUSIONS: A cross-sectional and prospective association exists between baseline plasma measures of oxidative stress and CHD risk. The association with prospective CHD risk remained after adjustment for "traditional" risk factors, implying an independent role for oxidative stress in CHD risk.