Mitochondrial genetic haplogroups and incident obesity: a longitudinal cohort study

Background/Objectives A small number of case-control studies have suggested that mitochondrial haplogroups could be associated with obesity. We examined whether obesity risk was influenced by mitochondrial haplogroup in a large North American cohort across an 8-year period. We conducted a longitudinal cohort study including individuals from the Osteoarthritis Initiative. Subjects/Methods Mitochondrial haplogroups were determined by sequencing and PCR-RFLP techniques using this nomenclature: HV, JT, KU, IWX, and super HV/others. The strength of the association between mitochondrial haplogroups and incident obesity was quantified with hazard ratios (HRs), adjusted for potential confounders using a Cox's regression analysis. Results Overall, 2342 non-obese Caucasian participants (56.7% women) with a mean +/- SD age of 62.0 +/- 9.5 years at baseline were included. During a median follow-up of 8 years, 334 individuals (= 14.3% of baseline population) became obese. After adjusting for nine potential confounders, the haplogroups IWX carried a significant 48% higher risk of obesity (HR = 1.48; 95% CI: 1.02-2.39) compared to the HV haplotype (the most frequent type). Conclusion Only the presence of the IWX haplogroups appears to be linked to increased obesity risk, independent of potential baseline confounders. Future cohort studies are needed to confirm these findings and to determine potential underlying mechanisms.