Attempts to associate methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism with hypertension have been extensively evaluated, but mostly in Caucasians. We therefore meta-analysed this polymorphism in association with hypertension and hypertensionin-pregnancy (HIP) among Chinese subjects. A randomeffects model was applied irrespective of between-study heterogeneity, which was evaluated by subgroup and meta-regression analyses. Study quality was assessed in duplicate. Publication bias was weighed using Egger's test and funnel plot. Data on 20 qualified studies totalling 4461 Chinese subjects were meta-analysed. In overall allelic/genotypic models, carriers of 677T or 677TT were consistently at significantly increased risk of developing hypertension and HIP. No between-study heterogeneity was identified for all genetic models, with the exception for contrast of allele 677T versus 677C in hypertension association studies (P ¼ 0.03), and the dominant contrast in HIP association studies (P ¼ 0.025). Both the subgroup and meta-regression analyses indicated that study design was a potential source of between-study heterogeneity. Funnel plot and Egger's test suggested no evidence of publication bias. Taken together, our results supported the notion that carriers of 677T or 677TT were at significantly increased risk of developing hypertension and HIP, but indicated caution in interpreting this result, because the study design made marginal significant contribution to the heterogeneity.
Mounting evidence suggests that hypertension is strongly linked to a variety of lipoprotein metabolism abnormalities. Apolipoprotein E gene (ApoE) is one such candidate with its common ɛ2/ɛ3/ɛ4 polymorphism ranking high in hypertension association. To derive more specific information, we pinpoint our research scope in Chinese to test whether this polymorphism is associated with hypertension via a meta-analysis. Random-effects model was performed irrespective of the between study heterogeneity. Data and study quality were assessed in duplicate. Publication bias was evaluated using the fail-safe number. Overall, 12 studies with 14 study groups totalling 1532 hypertensive patients and 2172 controls were identified. Carriers of ApoE ɛ2 allele had no significant increased risk for hypertension (pooled odds ratio (OR)=1.04; 95% confidence interval (CI): 0.80-1.35; P=0.78), compared with those carrying ɛ3 allele, whereas those with ɛ4 allele had a significant increased risk for hypertension (pooled OR=2.03; 95% CI: 1.61-2.55; P<0.00001). After excluding those with other small nationalities, we observed comparison of ApoE ɛ2 with ɛ3 allele yielded a pooled OR of 0.99 (95% CI: 0.82-1.19; P=0.89) among Han Chinese, and that of ɛ4 with ɛ3 yielded a pooled OR of 1.99 (95% CI: 1.48-2.67; P<0.00001). The fail-safe number at the level of 0.05 supported these significant associations. Taken together, our results expand previous findings and show that ApoE ɛ4 allele is associated with a twofold increased risk of developing hypertension in Chinese.
Association of the lipoprotein lipase (LPL) gene S447X variant with hypertension has been investigated extensively, whereas the results are often irreproducible. We therefore conducted a meta-analysis to examine whether S447X variant was associated with hypertension and blood pressure variation. Case-control reports published in English language and humans were identified from MEDLINE, EMBASE and Web of Science search engines as of 10 December 2009. Fixed-effects model was applied to pool data in the absence of between-studies heterogeneity, and random-effects model otherwise. A total of five studies (960 cases and 1145 controls) for hypertension and four studies (n=2777) for blood pressure were included. Compared with 447SS homogeneous carriers, those with 447X variant had a lower risk of hypertension (odds ratio (OR)=0.78; 95% confidence interval (CI): 0.62-0.98; P=0.03), and this effect reached significance under the fixed-effects model (I(2)=30% and P=0.22). Similarly, compared with 447S allele carriers, those with 447X allele carriers also had a lower risk of hypertension (OR=0.79; 95% CI: 0.64-0.98; P=0.03). In case of pregnancy-induced hypertension, no significance was observed (P>0.05). As for blood pressure association, there was no significant difference between 447X variant and 447SS homogeneous carriers for both systolic and diastolic blood pressure in the whole population, even stratified by gender (P>0.05). The Egger test told no publication bias for all associations. This meta-analysis demonstrated that LPL gene S447X variant was significantly associated with hypertension and showed no obvious relation with pregnancy-induced hypertension and blood pressure variation.
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