Biological Determinants of Fasting and Postload Plasma Homocysteine Levels in Healthy Italian Subjects

Genetic and nutritional factors are determinants of total plasma homocysteine (tHCy) whose increased levels play a pathogenic role in atherothrombosis and cardiovascular disease. This study investigated the influence of sex, age, creatinine, serum folate, vitamin B12 and vitamin B6 (pyridoxal- 5-phosphate, PLP) on fasting (FtHCy) and two hour postmethionine loading levels of tHCy in 147 apparently healthy subjects (M/F= 82/65, age range: 14-94 y). FtHCy was higher in men than women (9.89 vs 8.00 μmol/L, p< 0.01). In males, the main determinants of FtHCy were age and folate levels, respectively explaining 20.5% and 19.0% of FtHCy variance. In women, besides age (22.6%), vitamin B12 (17.8%) rather than folate was a major determinant of FtHCy. Two hour postload tHCy, expressed both as absolute value (PML) and as the difference between 2 hour postload tHCy and FtHCy (delta tHCy) was negatively correlated with folate in both sexes, and with vitamin B12 and age in women only. In males folate was the main determinant, explaining 20% of the variance of postload values, while in females vitamin B12 and PLP were predominant, explaining respectively 40% and 20% of that variance. Age was not among the main determinants of postload values in either sex. These results demonstrate that age and vitamin status differently influence both the fasting and the postmethionine plasma homocysteine levels in normal subjects.