Risk factor profile of coronary artery disease in black South Africans

Objectives: The aim of this study was to investigate the risk factor profile of coronary artery disease (CAD) in black South Africans. The study was motivated by the increased prevalence of CAD in South Africa, probably as a result of urbanisation. Despite this increase, however, very little is known regarding the cause, risk factor profile and clinical presentations of CAD in the black South African population. Design: A case control study was performed investigating 40 (33 men, 7 women) angiographically defined CAD patients and 20 (13 men and 7 women) age and body composition matched controls. Results: There was no difference in physical activity, sociodemographic factors or dietary intakes between the CAD and control group, except for the CAD patients consuming less vit C (40.9 vs 61.3 mg). The CAD group had significantly higher LDL-C, fasting glucose and CRP. There was also a significantly higher prevalence of smokers (35 vs 10%), hypertension (95 vs 75%) small dense LDL (73 vs 15%) and insulin resistance (M-value of 4.15 vs 12.5 mg/kg/min) in the CAD compared to the control group. In a logistic regression model, small dense LDL and insulin resistance were the main predictors of CAD. Conclusions: Black South African CAD patients had increased levels of the same risk factors that are typically seen in Caucasians with insulin resistance and small dense LDL being particularly significant in their contribution

The characteristics of coronary artery disease in Soweto

Ph.D., Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, 2008.In many developing countries with advanced stages of the nutrition transition, the burden of coronary artery disease (CAD) has shifted from the rich to the poor. Much of this transition is caused by changes in lifestyle, in particular: dietary changes, an increase in weight and obesity, a decrease in physical activity, high levels of stress, and increasing tobacco and alcohol consumption. However, we have come to appreciate a prominent role for inflammation in atherosclerosis and its complications. Globalization, urbanization and Westernization of lifestyle will increase the socioeconomic burden posed by non-communicable diseases in middle-to-low-income countries. In South Africa, it is mainly the African population that is experiencing rapid urbanization and the nutrition transition. Reliable ischaemic heart disease (IHD) mortality data are not available for the black population of South Africa. The purpose of this thesis was: to determine whether factors such as inflammation, postprandial lipaemia and hyperglycaemia are important determinants in black patients with documented CAD (with no previous known history of diabetes mellitus) and their age matched controls; to assess the prevalence of the metabolic syndrome (MS) in black patients and abnormal glucose regulation on black patients with CAD; and to compare the metabolic syndrome prevalence rates using the National Cholesterol Education Program Adult Treatment III (NCEP: ATP III) and International Diabetes Federation (IDF) definitions. Socio-economic status, anthropometric data, glucometabolic variables, LDL particles and MS prevalence rates were measured using 40 patients and 20 controls. The patients were selected consecutively on the basis of a coronary angiogram performed during the preceding 24 months. All subjects had significant CAD, which was defined as more than 50% lesions in one or more major coronary arteries. Subjects with severe hypercholesterolaemia, defined as an untreated total cholesterol level over 7.5 mmol/l, were excluded from the study. Those subjects with diabetes mellitus or HIV/AIDS were excluded from the study. Paper 1, titled ‘Metabolic syndrome, undiagnosed diabetes mellitus and insulin resistance are highly prevalent in urbanized South African blacks with coronary artery disease’, demonstrated a high prevalence of MS in black patients with established CAD. To our knowledge, this is the first report from South Africa that documents the prevalence of the syndrome in black patients with CAD. Almost all of our patients had previously diagnosed hypertension (95%). The second most frequent risk factor was an elevated glucose concentration, which was seen in half the patient cohort. The importance of obesity, particularly abdominal obesity expressed as waist circumference (WC), is well documented as a risk factor for MS. An unexpected outcome of our study was that half of the patients had abnormal glucose regulation, despite the exclusion of previously diagnosed DM. This high prevalence was revealed by the oral glucose tolerance test (OGTT). Paper 2 compares the MS prevalence estimates, as defined by NCEP: ATP III and IDF, amongst urbanized black South Africans with CAD. The IDF proposed a single unifying definition in 2005, as different definitions used different sets of criteria; this led to confusing and inconsistent estimations of MS prevalence. The new definition standardizes the criteria for the diagnosis of MS and offers a fresh assessment of the syndrome. The main findings that arose from the study were that both definitions generated similar prevalence estimates of MS and the two definitions similarly identified the presence or absence of MS in more than 80% of patients. This study demonstrated that postprandial lipaemia and hyperglycemia were common in black CAD patients. Small dense LDL particles were highly associated with CAD. Fasting triglyceride concentrations was the strongest determinant. Prolonged exposure of the endothelium to TG–rich atherogenic remnant particles might be the reason why postprandial increases in TG account for greater CAD risk. Paper 3 assessed postprandial lipaemia in black CAD patients with and without metabolic syndrome. This study was the first to contribute information about postprandial lipaemia and hyperglycaemia in urbanized South African blacks with CAD. Fasting lipid profiles and postprandial responses to the oral fat load were similar in patients with and without metabolic syndrome. A possible explanation might be that because patients in both groups had established CAD, they exhibited some of the underlying features of CAD, such as atherogenic dyslipidaemia. The main finding was that postprandial lipaemia was common in black CAD patients, including patients with metabolic syndrome. Fasting triglycerides concentration was the strongest determinant. Small, dense LDL particles were highly associated with CAD. Paper 4 reports on the assessment of postprandial hyperglycaemia in urbanized blacks with and without CAD. Results showed that glucose AUC was significantly higher in the patients than in control subjects and 120 min. glucose, followed by 0 min. glucose concentration, were the strongest determinants of postprandial hyperglycaemia. Our study demonstrated that as glucose tolerance declined across the normal glucose tolerance, impaired glucose tolerance and diabetes mellitus categories, peak glucose concentrations occurred later in the oral glucose tolerance test; insulin and proinsulin responses were also delayed. A comparison between CAD patients and control subjects drawn from the same ethnic population verified that abnormal glucose tolerance and insulin resistance were more prevalent in the patients with CAD. Paper 5 aimed at investigating whether carotid intima-media thickness (CIMT) is a predictor of CAD in South African black patients. The results showed that CIMT correlated with evidence of angiographically proven CAD. The findings of this study need to be considered within the context of its limitations, i.e. the low number of women and some bias towards only hospital referred CAD patients. It was not our intention to recruit more men than women, but because CAD is more prevalent in men, the majority of participants happened to be male. Performance of the OGTT and hyperinsulinaemic euglycaemic clamp technique is time consuming and requires considerable laboratory resources; therefore a relatively small number of patients and control subjects were studied. These limitations do not detract from the overall conclusions. Paper 6 evaluated markers of inflammation in black CAD patients, some of whom had MS. Leptin was the only marker that increased with additional MS criteria. Elevated hs- CRP concentrations indicated an inflammatory state in CAD patients. Association of leptin with BMI, waist circumference (WC) and hs-CRP revealed a close link with MS, obesity and inflammation in urban black South African CAD patients. Paper 7 investigated the role of diet, socio-demographics and physical activity in a black South African population with CAD, compared to a healthy control group. While diet is known to be affected by urbanisation, differences in dietary intake were observed between the two urban groups, despite the similarity in their socio-demographic profile. The study highlighted the clinical relevance of MS, its likely impact on morbidity and mortality, and that its identification is, therefore, important in risk assessment of patients with CAD. Increasing recognition of MS is, therefore, an initial step in addressing the metabolic problems associated with the syndrome. Furthermore, it was shown that a preponderance of small, dense LDL particles was highly associated with CAD in black patients. Although CAD prevalence is still low at this stage, it is likely to increase rapidly among urban dwellers as they adopt a Western lifestyle

Greater impairment of postprandial triacylglycerol than glucose response in metabolic syndrome subjects with fasting hyperglycaemia

Abstract Objective: Studies have started to question whether a specific component or combinations of metabolic syndrome (MetS) components may be more important in relation to cardiovascular disease risk. Our aim was to examine the impact of the presence of raised fasting glucose as a MetS component on postprandial lipaemia. Methods: Men classified with the MetS underwent a sequential test meal investigation, in which blood samples were taken at regular intervals after a test breakfast (t=0 min) and lunch (t=330 min). Lipids, glucose and insulin were measured in the fasting and postprandial samples. Results: MetS subjects with 3 or 4 components were subdivided into those without (n=34) and with (n=23) fasting hyperglycaemia (≥ 5.6 mmol/l), irrespective of the combination of components. Fasting lipids and insulin were similar in the two groups, with glucose significantly higher in the men with glucose as a MetS component (P<0.001). Following the test meals, there was a higher maximum concentration (maxC), area under the curve (AUC) and incremental AUC (P≤0.016) for the postprandial triacylglycerol (TAG) response in men with fasting hyperglycaemia. Greater glucose AUC (P<0.001) and insulin maxC (P=0.010) was also observed in these individuals after the test meals. Multivariate regression analysis revealed fasting glucose to be an important predictor of the postprandial TAG and glucose response. Conclusion: Our data analysis has revealed a greater impairment of postprandial TAG than glucose response in MetS subjects with raised fasting glucose. The worsening of postprandial lipaemic control may contribute to the greater CVD risk reported in individuals with MetS component combinations which include hyperglycaemia

Household, community, sub-national and country-level predictors of primary cooking fuel switching in nine countries from the PURE study

Introduction. Switchingfrom polluting (e.g. wood, crop waste, coal)to clean (e.g. gas, electricity) cooking fuels can reduce household air pollution exposures and climate-forcing emissions.While studies have evaluated specific interventions and assessed fuel-switching in repeated cross-sectional surveys, the role of different multilevel factors in household fuel switching, outside of interventions and across diverse community settings, is not well understood. Methods.We examined longitudinal survey data from 24 172 households in 177 rural communities across nine countries within the Prospective Urban and Rural Epidemiology study.We assessed household-level primary cooking fuel switching during a median of 10 years offollow up (∼2005–2015).We used hierarchical logistic regression models to examine the relative importance of household, community, sub-national and national-level factors contributing to primary fuel switching. Results. One-half of study households(12 369)reported changing their primary cookingfuels between baseline andfollow up surveys. Of these, 61% (7582) switchedfrom polluting (wood, dung, agricultural waste, charcoal, coal, kerosene)to clean (gas, electricity)fuels, 26% (3109)switched between different polluting fuels, 10% (1164)switched from clean to polluting fuels and 3% (522)switched between different clean fuels

Postprandial Hyperglycemia in Urban South African Blacks with and without Coronary Artery Disease

Background: Coronary artery disease (CAD) is increasing in urban black South Africans during their transition from a rural to a western lifestyle. This study assessed postprandial hyperglycemia, which a risk factor for CAD, in blacks with and without CAD. Methods: Fasting lipid levels and postprandial glucometabolic profiles were measured in 40 patients and 20 controls. Normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and diabetes mellitus (DM) were categorized according to American Diabetes Association criteria. Postprandial hyperglycemia was assessed by the oral glucose tolerance test (OGTT) and area under curve (AUC) analysis. Insulin resistance was evaluated by hyperinsulinemic euglycemic clamp (insulin-mediated glucose disposal, M-value). Results: Glucose AUC was higher in patients than controls (p < 0.0001). Highest correlations were between AUC and 0-minute glucose (r = 0.7847; p < 0.0001), and 120-minute glucose (r = 0.9187; p < 0.0001). Patients had higher fasting and postprandial glucose responses (p < 0.05). Glucose concentrations increased among NGT, IGT, and DM categories in patients (p < 0.001) and controls (p < 0.01). Abnormal glucose tolerance was more prevalent in patients (50%) than controls (40%). M-values were lower in patients (p < 0.0001) and decreased between categories, significantly in DM patients (p < 0.02). More patients (70%) than controls (13%) had low M-values (p < 0.001). Conclusions: Postprandial hyperglycemia was common in black CAD patients and glucose concentrations at 0 minute and 120 minutes were the strongest determinants. As glucose tolerance declined, glycemic control deteriorated and insulin resistance worsened. Abnormal glucose tolerance and insulin resistance were more prevalent in patients with CAD

Leptin, Adiponectin, and High-Sensitivity C-Reactive Protein in Relation to the Metabolic Syndrome in Urban South African Blacks With and Without Coronary Artery Disease

Background: Metabolic syndrome and coronary artery disease (CAD) are increasing in urban black South Africans during their transition from a rural to a western lifestyle. Inflammation is frequently associated with metabolic syndrome and CAD. This study evaluated markers of inflammation in black CAD patients, some of whom had metabolic syndrome. Methods: Metabolic syndrome was defined according to International Diabetes Federation criteria. Inflammatory markers leptin, adiponectin, and high-sensitivity C-reactive protein (hs-CRP) were measured in 40 patients and 20 control subjects. Results: Metabolic syndrome was present in 23 patients and absent in 17 patients. Leptin was the only significantly higher marker in patients with metabolic syndrome compared to patients without metabolic syndrome (P < 0.01). Leptin was higher in women than men (P < 0.01) and higher in both genders with metabolic syndrome (P < 0.03 and P < 0.04, respectively). Leptin levels rose significantly with increasing metabolic syndrome criteria (P < 0.05). hs-CRP concentrations were elevated in both patient groups. Positive correlations were found between leptin and body mass index (BMI) (r = 0.7107; P < 0.0001), waist circumference (WC) (r = 0.4981; P < 0.002), and hs-CRP (r = 0.3886; P < 0.02). Conclusions: Leptin differentiated between CAD patients with and without metabolic syndrome and determined metabolic syndrome status in women and men. Leptin was the only marker that increased with additional metabolic syndrome criteria. Elevated hs-CRP concentrations may indicate a low-grade inflammatory state in CAD patients. Association of leptin with BMI, WC, and hs-CRP revealed a close link with metabolic syndrome, obesity, and inflammation in urban black South African CAD patients

The metabolic syndrome using the National Cholesterol Education Program and International Diabetes Federation definitions among urbanised black South Africans with established coronary artery disease

Background. The International Diabetes Federation (IDF) introduced a new definition of the metabolic syndrome (MS) that emphasises ethnic-specific cut-offs for waist circumference (WC). Objective. To compare MS prevalence rates using the National Cholesterol Education Program Adult Treatment Panel III (NCEP: ATP III) and IDF definitions. Methods. Anthropometric data, fasting biochemical variables and MS prevalence rates were measured in 40 black patients with established coronary artery disease (CAD). Glucose metabolism was assessed using the oral glucose tolerance test (OGTT), and insulin-mediated glucose disposal (M-value) was evaluated using the hyperinsulinaemic euglycaemic clamp technique. Results. Based on the NCEP: ATP III definition, MS prevalence was 60% and using the IDF definition, it was 57.5%. The two definitions similarly classified ~83% of patients as being MS positive or MS negative. Lower WC cut-offs in the IDF definition classified greater numbers of men and women as having WC as a risk factor – IDF v. NCEP: ATP III men 57.6% v. 36.4%; women 100% v. 71.4%. Impaired glucose tolerance (IGT) was found in 12 of the 40 patients (30%) and diabetes mellitus (DM) in 8 (20%). Mean M-value was reduced in IGT and DM groups compared with the normal group, significantly so in the DM group (p = 0.01). Conclusions. NCEP: ATP III and IDF definitions both generated similar MS prevalence estimates. The two definitions similarly identified the presence or absence of the MS in the majority of patients. The IDF definition classified greater numbers of men and women as having WC as a risk factor. There was a high prevalence of previously undiagnosed IGT and DM in our South African black patients with established CAD. Journal of Endocrinology, Metabolism and Diabetes of South Africa Vol. 12 (1) 2007: pp. 6-1