Blood glucose and nocturnal blood pressure in African and Caucasian men: The SABPA study

Prospective associations between cardiac stress, glucose dysregulation and executive cognitive function in Black men: The Sympathetic activity and Ambulatory Blood Pressure in Africans study

OBJECTIVE

Glucose dysregulation is an independent risk factor for cardiovascular and neurodegenerative disease development through synaptic dysfunction resulting in cognitive decline. The aim of this study was to study the interplay between impaired glycaemic metabolism (hyperglycaemia and insulin resistance), cardiac stress (cardiac troponin T and N-terminal brain natriuretic peptide) and executive cognitive function prospectively, in a bi-ethnic sex cohort.

METHODS

Black and White teachers (N = 338, aged 20-63 years) from the Sympathetic activity and Ambulatory Blood Pressure in Africans study were monitored over a 3-year period. Fasting blood samples were obtained for cardiac troponin T, N-terminal brain natriuretic peptide, glycated haemoglobin and the homeostatic model assessment-insulin resistance for insulin resistance. The Stroop colour-word conflict test was applied to assess executive cognitive function at baseline.

RESULTS

Over the 3-year period, Black men revealed constant high levels of cardiac troponin T (⩾4.2 ng/L), pre-diabetes (glycated haemoglobin > 5.7%) and insulin resistance (homeostatic model assessment-insulin resistance >3). %Δ Glycated haemoglobin was associated with %Δ insulin resistance (p < 0.001) and increases in %ΔN-terminal brain natriuretic peptide (p = 0.02) in Black men only. In the latter, baseline Stroop colour-word conflict test was inversely associated with %Δ cardiac troponin T (p = 0.001) and %Δ insulin resistance levels (p = 0.01).

CONCLUSION

Progressive myocyte stretch and chronic myocyte injury, coupled with glucose dysregulation, may interfere with processes related to interference control in Black men.

Using MutPred derived mtDNA load scores to evaluate mtDNA variation in hypertension and diabetes in a two-population cohort: The SABPA study

Mitochondrial DNA (mtDNA) variation has been implicated in many common complex diseases, but inconsistent and contradicting results are common. Here we introduce a novel mutational load hypothesis, which also considers the collective effect of mainly rare variants, utilising the MutPred Program. We apply this new methodology to investigate the possible role of mtDNA in two cardiovascular disease (CVD) phenotypes (hypertension and hyperglycaemia), within a two-population cohort (n = 363; mean age 45 ± 9 yrs). Very few studies have looked at African mtDNA variation in the context of complex disease, and none using complete sequence data in a well-phenotyped cohort. As such, our study will also extend our knowledge of African mtDNA variation, with complete sequences of Southern Africans being especially under-represented. The cohort showed prevalence rates for hypertension (58.6%) and prediabetes (44.8%). We could not identify a statistically significant role for mtDNA variation in association with hypertension or hyperglycaemia in our cohort. However, we are of the opinion that the method described will find wide application in the field, being especially useful for cohorts from multiple locations or with a variety of mtDNA lineages, where the traditional haplogroup association method has been particularly likely to generate spurious results in the context of association with common complex disease.

Cardiovascular function is not associated with creatine kinase activity in a black African population: The SABPA study

Background

Higher creatine kinase (CK) activity is associated with the development of cardiovascular disease in black African populations. We compared CK activity and investigated associations of blood pressure with CK activity in black and white men as well as black and white women.

Methods

Ambulatory blood pressure, total peripheral resistance and pulse wave velocity of 197 black and 208 white participants were determined and serum CK activity was measured.

Results

Blood pressure and pulse wave velocity were higher in black men and women (all p < 0.001) when compared to their white counterparts. CK activity only varied between black and white women (75.9 U/l vs 62.8 U/l, p = 0.009), even after adjusting for age, body mass index and physical activity. Despite the worse cardiovascular profile of black men and women, and the higher CK activity in the black women, we were unable to link blood pressure, pulse wave velocity or total peripheral resistance with CK activity, in the black African population. In white men, total peripheral resistance was associated with CK activity (R² = 0.32; β = 0.25; p = 0.009), whereas systolic blood pressure (R² = 0.46; β = 0.17; p = 0.03) and pulse pressure (R² = 0.31; β = 0.21; p = 0.01) were associated with CK activity in white women.

Conclusions

The lack of associations in the black African population suggests that the link between a worse cardiovascular profile and CK activity may be overshadowed by other contributing factors. Whereas, the established link between cardiovascular function and CK activity in the white groups may be the result of enhanced smooth muscle cell contractility and/or attenuated nitric oxide synthesis capacity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0315-2) contains supplementary material, which is available to authorized users.

Relationship between blood pressure reverse dipping and type 2 diabetes in hypertensive patients

Recent studies suggested that nocturnal variations of blood pressure (BP) were closely related to type 2 diabetes. However, little information has been revealed about the relationship between reverse-dipper pattern of BP and type 2 diabetes. In this cross-sectional study, BP variations of 531 hypertensive patients were evaluated with ambulatory BP monitoring (ABPM). Diagnosis of diabetes in Chinese adults was made according to diabetes diagnostic criteria of 2015. Multivariate logistic regression was used to examine the relationships between type 2 diabetes and ABPM results. In the study, patients with reverse-dipper pattern (32.3%) had the highest prevalence of type 2 diabetes compared with dippers (21.4%) and nondippers (23.3%). After multivariate logistic regression, reverse-dipper BP pattern (OR 2.067, P = 0.024) and nondipper BP pattern (OR 1.637, P = 0.039) were found to be correlated with type 2 diabetes compared with dipper pattern. The results of our study also suggested that type 2 diabetes might contribute to the reverse-dipper pattern of BP (OR 1.691, P = 0.023). In addition, fasting glucose was negatively correlated with the decline rate of nocturnal SBP (r = -0.095, P = 0.029). Reverse-dipper pattern of BP in ABPM may be independently associated with type 2 diabetes in patients with hypertension.

Novel Association Between the Reverse-Dipper Pattern of Ambulatory Blood Pressure Monitoring and Metabolic Syndrome in Men But Not in Women

The aim of this study was to investigate the relationships between nocturnal variations in blood pressure (BP) and metabolic syndrome (MetS) in different gender.This cross-sectional study involved 509 hypertensive patients (254 males and 255 females, 45 to 75 years old) from September 2013 to March 2014. BP values were acquired from ambulatory BP monitoring (ABPM). The dipper pattern of BP was defined as 10% to 20% reduction of the mean systolic BP (SBP) values at night compared with the daytime values. The diagnosis of MetS was made according to NCEP ATP-III definition. Multivariate logistic regression analyses were used to explore the relationships between ABPM results and MetS.In our study, MetS were observed in 29.1% of male and 18.4% of female participants. The prevalence of MetS was higher in the patients with reverse-dipper pattern than in others. After multivariate logistic regression analysis, the reverse-dipper pattern of BP (odds ratio 2.298; P = 0.006) and 24-SBP (odds ratio 1.063; P = 0.021) were independently correlated with MetS in males. However, there was no association between MetS and BP reverse dipping in females.Our cross-sectional study showed that the reverse-dipper pattern of BP is associated with MetS in male, while the underlying mechanism deserves further investigation.

Are behavioural risk factors to be blamed for the conversion from optimal blood pressure to hypertensive status in Black South Africans? A 5-year prospective study

BACKGROUND

Longitudinal cohort studies in sub-Saharan Africa are urgently needed to understand cardiovascular disease development. We, therefore, explored health behaviours and conventional risk factors of African individuals with optimal blood pressure (BP) (≤ 120/80 mm Hg), and their 5-year prediction for the development of hypertension.

METHODS

The Prospective Urban Rural Epidemiology study in the North West Province, South Africa, started in 2005 and included African volunteers (n = 1994; aged > 30 years) from a sample of 6000 randomly selected households in rural and urban areas.

RESULTS

At baseline, 48% of the participants were hypertensive (≥ 140/90 mmHg). Those with optimal BP (n = 478) were followed at a success rate of 70% for 5 years (213 normotensive, 68 hypertensive, 57 deceased). Africans that became hypertensive smoked more than the normotensive individuals (68.2% vs 49.8%), and they also had a greater waist circumference [ratio of geometric means of 0.94 cm (95% CI: 0.86-0.99)] and greater amount of γ-glutamyltransferase [0.74 U/l (95% CI: 0.62-0.88)] at baseline. The 5-year change in BP was independently explained by baseline γ-glutamyltransferase [R(2) = 0.23, β = 0.13 U/l (95% CI: 0.01-0.19)]. Alcohol intake also predicted central systolic BP and carotid cross-sectional wall area (CSWA) at follow-up. Waist circumference was another predictor of BP changes [β = 0.18 cm (95% CI: 0.05-0.24)] and CSWA. HIV infection was inversely associated with increased BP.

CONCLUSIONS

During the 5 years, 24% of Africans with optimal BP developed hypertension. The surge in hypertension in Africa is largely explained by modifiable risk factors. Public health strategies should focus aggressively on lifestyle to prevent a catastrophic burden on the national health system.