PLASMA TOTAL HOMOCYSTEINE IN HEALTHY-SUBJECTS - SEX-SPECIFIC RELATIONWITH BIOLOGICAL TRAITS

Fasting plasma total homocysteine (tHcy) concentration was measured in 380 men and 204 women selected for health on the basis of clinical hi story, physical examination, and normal results of a biochemical profi le. We sought to define tHcy reference values in healthy individuals a nd to determine relations between tHcy and plasma folic acid, vitamin B-12, and pyridoxal phosphate (vitamin B-6) concentrations. Men had si gnificantly higher plasma tHcy than women (9.7 +/- 4.9 compared with 7 .6 +/- 4.1 mu mol/L, (x) over bar +/- SD) and lower folate concentrati ons (8.6 +/- 5.2 compared with 9.8 +/- 6.6 nmol/L, P < 0.05). Signific ant correlations were found between tHcy and uric acid, creatinine, al bumin, folate, and vitamin B-12 concentrations. There was no correlati on with age, body mass index, blood pressure, glucose, and total and l ipoprotein lipids. When divided in quartiles of vitamin concentrations , subjects with the lowest vitamin B-12 and folate values had signific antly higher tHcy concentrations than those in the other three quartil es. Interestingly, after exclusion of subjects in the lowest quartiles of folate and vitamin B-12 concentration, correlations between tHcy a nd vitamin concentrations were no longer observed, except for vitamin B-12 in men. Stepwise-multiple-regression analyses showed that the sex -specific influence of biological variables on tHcy concentrations was twice as important in healthy women than in healthy men. This study e mphasizes the significance of sex-associated differences in the biolog y of homocysteine and underlines the importance of considering these i n the determination of threshold values.