title: Effective homocysteine metabolism may protect South African blacks against coronary heart disease.
abstract: L-Methionine (0.1 g/kg body wt) was administered to young white [n = 18; mean (+/- SD) age 20.0 +/- 1.0 y] and black [n = 12; mean (+/- SD) age 22.0 +/- 1.3 y] volunteers who had a similar lifestyle and who did not differ significantly from each other with respect to plasma folate or vitamin B-12 concentrations. Blacks, however, had significantly lower plasma pyridoxal-5'-phosphate concentrations compared with whites (P < 0.001). Fasting plasma homocysteine concentrations in blacks and whites were not significantly different. The mean (+/- SD) maximum increase in plasma homocysteine concentration measured after methionine loading was significantly lower (P < 0.01) in blacks (11.0 +/- 3.6 mumol/L) than in whites (18.0 +/- 6.2 mumol/L). Six weeks of vitamin supplementation (1.0 mg folic acid, 400 micrograms vitamin B-12, and 10 mg pyridoxine/d) reduced the mean (+/- SD) fasting plasma homocysteine concentration from 9.6 +/- 3.5 to 7.2 +/- 1.6 mumol/L in whites (P < 0.05) and from 8.4 +/- 2.4 to 5.6 +/- 1.4 mumol/L in blacks (P < 0.01). The mean (+/- SD) maximum increase in plasma homocysteine concentration after methionine loading declined from 18.0 +/- 6.2 to 11.1 +/- 2.3 mumol/L (P < 0.01) in whites, but vitamin supplementation did not have a significant effect on the methionine-load test in black volunteers. A significant race-by-time interaction shows that blacks metabolized homocysteine more effectively than did whites, which may partly explain their relative resistance against coronary heart disease despite a high prevalence of obesity, hypertension, and smoking.
authors.affiliation: Department of Chemical Pathology, University of Pretoria, South Africa.
authors.forename: J B
authors.initials: JB
authors.lastname: Ubbink
authors.forename: W J
authors.initials: WJ
authors.lastname: Vermaak
authors.forename: R
authors.initials: R
authors.lastname: Delport
authors.forename: A
authors.initials: A
authors.lastname: van der Merwe
authors.forename: P J
authors.initials: PJ
authors.lastname: Becker
authors.forename: H
authors.initials: H
authors.lastname: Potgieter
mesh_terms: D000328:Adult; D044383:Black People / Q000235:genetics; D003327:Coronary Disease / Q000208:ethnology* / Q000235:genetics; D005492:Folic Acid / Q000097:blood; D006710:Homocysteine / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D008715:Methionine / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D013019:South Africa / Q000453:epidemiology; D014805:Vitamin B 12 / Q000097:blood; D014815:Vitamins / Q000008:administration & dosage; D044465:White People / Q000235:genetics
chemical_list: D014815:Vitamins; D006710:Homocysteine; D005492:Folic Acid; D008715:Methionine; D014805:Vitamin B 12