Women with mitochondrial haplogroup N9a are protected against metabolic syndrome

To identify mitochondrial haplogroups that confer resistance against or susceptibility to metabolic syndrome, we performed a large-scale association study on 1,337 unrelated Japanese individuals, including 871 subjects with metabolic syndrome and 466 control subjects. Metabolic syndrome was diagnosed according to modified National Cholesterol Education Program Adult Treatment Panel III guidelines, using the cutoff point for obesity as a BMI of >/=25 kg/m(2) instead of waist circumference. The genotypes for 25 polymorphisms in the coding region of the mitochondrial genome were determined, and the haplotypes were classified into 10 major haplogroups, i.e., F, B, A, N9a, M7a, M7b, G1, G2, D5, and D4. Multivariate logistic regression analysis revealed that the haplogroup N9a was significantly associated with resistance against metabolic syndrome in women with an odds ratio (OR) of 0.21 (95% CI 0.07-0.58, P = 0.0042). Women with haplogroups G1 and D5 tended to be resistant against metabolic syndrome with an OR of 0.22 (0.06-0.68, P = 0.0129) for G1 and with an OR of 0.32 (0.10-0.96, P = 0.0469) for D5, respectively. These results indicate that mitochondrial haplogroup N9a may be a protective factor against metabolic syndrome in Japanese women.