The vascular effects of metabolic impairment clusters in subjects of different ethnicities.
Although metabolic syndrome affects vascular function, the impact of individual impairments and their clustering is unclear. To assess the vascular impact of metabolic impairments before they reach treatment thresholds in different ethnic groups. Metabolic variables, inflammatory markers, endothelium dependent vasodilatation (EDV) and carotid intima media thickness (CIMT) were measured in population samples of 82 Caucasians and 78 matched Afro-Caribbeans with no vascular disease. Insulin resistance was assessed using homeostasis model assessment (HOMA-IR). EDV was measured as the change in the height of the inflection point of the digital volume pulse following intravenous infusion of 5 mcg/min of albuterol (DeltaRIDeltaLB). Regression models were used to investigate the independent effects of metabolic impairment clusters and their interaction with ethnicity on EDV and CIMT. HOMA-IR (2.4-3.8, p < 0.0001), IL-6 levels (1.1-2.8 pg/mL, p = 0.02) and CIMT (0.71-0.83 mm, p = 0.009) increased whereas in DeltaRIBASELINE (77.6-72.9 percentage points, p < 0.0001) and DeltaRIDeltaLB (15.5-7.1 percentage points, p < 0.0001) decreased with the number of metabolic impairments present. DeltaRIDeltaLB decreased by 1.6 (95% CI 0.2-3.7) percentage points and CIMT increased by 0.06 (95% CI 0.02-0.10) mm for each metabolic impairment present after adjusting for age, gender, ethnicity and HOMA-IR. There were significant interactions between Afro-Caribbean ethnicity and metabolic impairments for IL-6 (p = 0.037) and DeltaRIDeltaLB (p = 0.002). Clustering of metabolic impairments is associated with inflammatory activation, impaired EDV and increased CIMT even before reaching treatment thresholds for individual impairments. This effect was more marked in Afro-Caribbean subjects.