4While South Africa has one of the highest hypertension rates globally, there are few data on masked hypertension (MHT) and white-coat hypertension (WCHT). This study measured the frequency of MHT and WCHT in low-income (<$500 US per month) South African adults, evaluating cardiovascular risk by arterial stiffness. Participants (n=101, 50% male; mean age 39.4AE9.7 years) were recruited from a large North-West Province employer. Clinic and 24-hour blood pressure (BP) and pulse wave analysis were recorded. Clinic BP identified 18% of patients as hypertensive, while 24-hour BP showed that 63% of patients were hypertensive. The frequency of MHT was high (33 of 81, 41%) with only one case of WCHT. In comparison to those with normal clinic and 24-hour BP, augmentation index and pulse wave velocity were significantly higher in those with hypertensive 24-hour BP irrespective of clinic BP, indicating that, in this group, masked and sustained hypertension carry a similar elevated cardiovascular risk.

Objective:The objective of this study was to make use of a quantitative and qualitative approach comparing the systemic renin-angiotensin system (RAS) of hypertensive black and white African men by using RAS equilibrium analysis.Materials and methods:This sub-study involved 23 black (n = 15) and white (n = 8) hypertensive men aged 39.5–41 years, living in the North West Province of South Africa. The RAS-Fingerprinting was determined with LC-MS/MS quantification of angiotensin peptides. Blood pressure and other variables were determined with known methods.Results:The main finding of this study was the significant lower Ang I (<5.0 and 45.1 pg/ml; p = 0.005) and Ang II (15.6 and 123.9 pg/ml; p ⩽ 0.001) encountered in the hypertensive black African men compared to their white counterparts. Levels of Ang 1-5 (downstream metabolite of Ang 1-7) (1.8 and 3.0 pg/ml), were detected in black and white hypertensive men, respectively.Conclusions:The observed differences between circulating RAS components, which are reflected via equilibrium angiotensin levels, point to a distinctive molecular regulation of the RAAS in the two study cohorts. The increased peripheral resistance observed in hypertensive black individuals might take over a dominant role in control of blood pressure in this study population. A novel highly sensitive LC-MS/MS method resolved the issue of peptide recovery variations during sample preparation by using internal standards for each individual angiotensin metabolite.

Low plasma renin levels and augmented cardiovascular reactivity to stress are common in blacks and have been linked to the development of hypertension in this population. We (i) compared cardiovascular and plasma renin reactivity to a cold pressor test between a black and white population; and (ii) investigated the associations between cardiovascular and plasma renin reactivity within the black and white populations. Our population consisted of 153 black and 188 white men and women (age range, 20-65 years). We measured blood pressure (BP), heart rate (HR), stroke volume (SV), total peripheral resistance (TPR), Windkessel arterial compliance, and determined plasma renin levels at rest and during the cold pressor test. Reactivity was calculated for each participant as the percentage change from the resting value. We found lower renin and elevated BP in blacks compared with whites at rest and during stress (both, P<0.001). During stress, HR increased more in blacks (P<0.001), whereas SV (P<0.001) and arterial compliance (P=0.013) decreased more in blacks compared with whites. TPR reactivity was positively associated with renin reactivity in blacks only (β=0.17; P=0.041), while in whites diastolic BP reactivity was positively associated with renin reactivity (β=0.21; P=0.005). Although blacks had suppressed renin levels at rest and during acute stress, vascular resistance reactivity associated positively with renin reactivity only in the black population. These results suggest that low renin levels in blacks during rest and stress are linked to increased peripheral vascular responses to stress, which may contribute to elevated BP in blacks.

Vascular calcification and cardiovascular diseases have been associated with altered bone metabolism. We explored the relationships of arterial pressures and carotid intima-media thickness (CIMT) with parathyroid hormone, 25-hydroxycholecalciferol and their ratio (PTH:25(OH)D3) as well as a marker of bone resorption (CTX) in lean and overweight/obese African women. A population of 434 African women older than 46 years was divided into lean and overweight/obese groups. We assessed brachial blood pressure, central pulse pressure (cPP) and CIMT, and determined PTH, 25(OH)D3 and CTX concentrations. Overweight/obese women had elevated PTH and PTH:25(OH)D3 compared with lean women (both P<0.001), whereas lean women had higher CTX (P<0.001). Single, partial and multiple regression analyses indicated that, in lean women CIMT was independently associated with PTH:25(OH)D3 (R(2)=0.22; β=0.26; P=0.003), whereas in obese women cPP was associated with both PTH:25(OH)D3 (R2=0.20; β=0.17; P=0.017) and CTX (R2=0.20; β=0.17; P=0.025). In conclusion, we found that in African women with increased adiposity, cPP (as a surrogate measure of arterial stiffness), was positively associated with alterations in bone metabolism and calciotropic hormones, whereas CIMT of lean women was positively associated with PTH:25(OH)D3. Our results suggest that alterations in bone and calcium metabolism may contribute to arterial calcification in older African women.

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