Objective: Homocysteine is a sex-related risk factor for cardiovascular disease but the reason for dimorphism is unclear. It has been hypothesized that fat-free mass is an independent determinant of the circulating homocysteine and methionine concentrations.
Methods: The relationship of homocysteine to body composition was investigated in 52 healthy middle-aged 40-60 year olds. Plasma total homocysteine, methionine, folates, vitamins B6 and B12 concentrations were measured with fat mass, bone mineral content, lean body mass, fat-free mass, body water compartments and resting energy expenditure by Anthropometry, Dual X-ray Absorptiometry, Bioimpedentiometry and Indirect Calorimetry.
Results: Men had higher homocysteine (+28%) and methionine (+18%) concentrations than women, but a similar ratio between the two concentrations. Men also had higher lean body mass and fat-free mass. Homocysteine and methionine concentrations were significantly related to fat-free mass, lean body mass, total, extracellular and intracellular water both in simple correlations and in multivariate models including age, smoking habits and vitamin concentrations. Fat-free mass related measures explained the sex effect on homocysteine and methionine concentrations but not the ratio of homocysteine to methionine concentrations.
Conclusion: In healthy middle-aged adults homocysteine concentration independently relates to fat-free mass and to water components. Homocysteine and methionine concentrations increase together in relation to the proportion of fat-free mass but their ratio is unrelated to fat-free mass.