H-Type Hypertension among Black South Africans and the Relationship between Homocysteine, Its Genetic Determinants and Estimates of Vascular Function

Abstract

Elevated homocysteine (Hcy) increases cardiovascular disease (CVD) risk. Our objective was to emphasize Hcy’s contribution in hypertension and CVD management by determining H-type hypertension (hypertension with Hcy ≥ 10 µmol/L) and associations between Hcy, blood pressure (BP) and estimates of vascular function among Black South Africans. We included 1995 adults (63% female). Plasma Hcy and cardiovascular measures (systolic and diastolic BP (SBP, DBP), pulse pressure, heart rate (HR), carotid-radialis pulse wave velocity (cr-PWV), intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1) were quantified. Five Hcy-related polymorphisms (cystathionine β-synthase (CBS 844ins68, T833C, G9276A); methylenetetrahydrofolate reductase (MTHFR C677T) and methionine synthase (MTR A2756G)) were genotyped. Hcy was >10 µmol/L in 41% (n = 762), and of the 47% (n = 951) hypertensives, 45% (n = 425) presented with H-type. Hcy was higher in hypertensives vs. normotensives (9.86 vs. 8.78 µmol/L, p < 0.0001, effect size 0.56) and correlated positively with SBP, DBP, cr-PWV and ICAM-1 (r > 0.19, p < 0.0001). Over Hcy quartiles, SBP, DBP, HR, cr-PWV and ICAM-1 increased progressively (all p-trends ≤ 0.001). In multiple regression models, Hcy contributed to the variance of SBP, DBP, HR, cr-PWV and ICAM-1. H-type hypertensives also had the lowest MTHFR 677 CC frequency (p = 0.03). Hcy is positively and independently associated with markers of vascular function and raised BP.

Homocysteine, blood pressure and gene–diet interactions in relation to vascular function measures of Black South Africans

“…The difference between the hypertension vs H-type hypertension groups' energy intake was not attributed to age, weight, GGT, alcohol, added sugar and carbohydrates alone or combined, but due to differences in either total protein or fat intake. Genotype frequency differences among BP subgroups are detailed in another study [20].…”

New Perspectives and Strategies for the Management of Hypertension

“…A cross-section investigation analyzing data from the South African arm of the Prospective Urban and Rural Epidemiology (PURE–SA) study reported an H-type hypertension (hypertension associated with homocysteine levels ≥ 10 µmol/L) prevalence of 23% among all participants and a 45% prevalence among those with hypertension in a relatively large sample of Black South Africans recruited from both rural and urban communities [ 7 ].…”