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

Abstract

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. 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). 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). 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.