Interactions between genetic variants of folate metabolism genes and lifestyle affect plasma homocysteine concentrations in the Boston Puerto Rican population.

OBJECTIVE To investigate genetic and lifestyle factors and their interactions on plasma homocysteine (Hcy) concentrations in the Boston Puerto Rican population. DESIGN Cross-sectional study. Plasma concentrations of Hcy, folate, vitamin B12 and pyridoxal phosphate were measured, and genetic polymorphisms were determined. Data on lifestyle factors were collected in interviews. SETTING A population survey of health and nutritional measures. SUBJECTS A total of 994 Puerto Rican men and women residing in the Boston metropolitan area. RESULTS Smoking status was positively associated with plasma Hcy. Genetic polymorphisms MTHFR 677C→T, FOLH1 1561C→T, FOLH1 rs647370 and PCFT 928A→G interacted significantly with smoking for Hcy. MTHFR 1298A→C (P = 0·040) and PCFT 928A→G (P = 0·002) displayed significant interactions with alcohol intake in determining plasma Hcy. Subjects with PCFT 928GG genotype had significantly higher plasma Hcy concentrations compared with carriers of the A allele (AA+AG; P = 0·030) among non-drinking subjects. When consuming alcohol, GG subjects had lower plasma Hcy levels compared with AA+AG subjects. Physical activity interacted significantly with MTR 2756A→G in determining plasma Hcy (P for interaction = 0·002). Smoking interacted with physical activity for plasma Hcy (P for interaction = 0·023). CONCLUSIONS Smoking and drinking were associated plasma Hcy concentrations. Genetic variants involved in folate metabolism further modify the effects of lifestyle on plasma Hcy.