An international matched cohort study of the contribution of metabolic impairments to subclinical atherosclerosis in United Kingdom and Jamaican African-Caribbeans.

BACKGROUND: A gradient of increased vascular risk exists across the African diaspora. We hypothesised that increased insulin resistance with environmental transition contributes to this risk. METHODS: The study was undertaken in 73 healthy African-Caribbeans in the UK and 151 age and sex matched African-Caribbeans in Jamaica. Body mass index (BMI), fasting insulin, insulin resistance, carotid intima media thickness (CIMT) and endothelium dependent vasodilatation (EDV) were compared. CIMT was measured ultrasonographically in the distal 1cm of both common carotid arteries. EDV was measured the absolute change from baseline in the Reflection index (RI) of the digital volume pulse during intravenous infusion of albuterol (DeltaRI(ALB)). RESULTS: UK African-Caribbeans had greater CIMT (mean difference 0.124 [95% C.I. 0.075-0.173] mm, p<0.0001) and decreased EDV (mean difference in DeltaRI(ALB) 5.1 [95% C.I. 2.5-7.6] percentage points, p<0.0001). This was associated with higher insulin concentrations (mean difference 1.6 [95% C.I. 1.3-4.1] microU/mL, p=0.038) and greater HOMA score (2.8 versus 2.0; p=0.035) despite no significant differences in BMI (28.8 versus 27.6; p=0.168) or the waist to hip ratio (0.86 versus 0.85; p=0.188). HOMA scores correlated positively with CIMT (r=0.35, p=0.01) and negatively with DeltaRI(ALB) (r=-0.17; p=0.02) in UK, but not in Jamaican, African-Caribbeans. A significant interaction was seen between HOMA and UK domicile for CIMT (p<0.0001) and between fasting insulin and UK domicile for DeltaRI(ALB) (p<0.0001). CONCLUSIONS: Increased insulin resistance, associated with living in a nutritionally enriched environment, may contribute to early subclinical atherosclerosis in UK African-Caribbeans.

The role of inheritance and environment in predisposition to vascular disease in people of African descent.

OBJECTIVES: This study sought to compare vascular reactivity and carotid intima media thickness (CIMT) between Afro-Caribbean people in the United Kingdom (UK) and the West Indies and Afro-Caribbean and Caucasian people in the UK. BACKGROUND: Attenuated vascular reactivity and increased CIMT in black patients is seen as evidence for predisposition to vascular disease, but no comparisons exist between Afro-Caribbean people in different settings, which can provide insight into non-inherited determinants of increased ethnic susceptibility. METHODS: A representative community sample of 81 healthy Afro-Caribbean people and 101 Caucasian people in the UK was compared with 197 matched Afro-Caribbean people in Jamaica. Small vessel reactivity was assessed by measuring the absolute change from baseline in the reflection index (RI) of the digital volume pulse during intravenous infusion of albuterol (5 microg/min, DeltaRI(ALB)) and glyceryl trinitrate (5 microg/min, DeltaRI(GTN)). The CIMT was measured ultrasonographically in the distal 1 cm of the common carotid artery. RESULTS: Mean DeltaRI(ALB) was 4.2 percentage points (95% confidence interval [CI], 2.3 to 6.1, p < 0.001) lower in UK Afro-Caribbean people compared with Jamaican Afro-Caribbean people and 2.6 percentage points (95% CI, 0.4 to 4.7, p = 0.02) lower compared with Caucasian people, after adjusting for vascular risk profile. Adjusted mean CIMT of UK Afro-Caribbean people was 0.13 mm (95% CI, 0.08 to 0.17, p < 0.001) greater compared with Jamaican Afro-Caribbean people and 0.05 mm (95% CI, 0.01 to 0.10, p = 0.02) greater compared with Caucasian people. CONCLUSIONS: Healthy UK Afro-Caribbean people have greater and Jamaican Afro-Caribbean people have less impairment of vascular reactivity and intima media thickness compared with UK Caucasian people, suggesting that potentially modifiable environmental interactions may contribute to excess vascular disease in Afro-Caribbean people.

Ethnic differences in arterial responses and inflammatory markers in Afro-Caribbean and Caucasian subjects.

OBJECTIVE: Small vessel disease is more common in Afro-Caribbeans than Caucasians. We investigated underlying differences in metabolic, inflammatory, and vascular responses that may predispose Afro-Caribbeans to small vessel pathology. METHODS AND RESULTS: Seventy-eight Afro-Caribbeans aged 35-75 years, with no vascular disease or medications, were compared with 82 matched Caucasians for metabolic variables, fasting insulin, interleukin 6, tumor necrosis factor (TNF) alpha, and cytoplasmic repressor protein levels. Carotid intima media thickness (CIMT) was measured ultrasonographically. Small vessel function was assessed by measuring the absolute change from baseline in the reflectance index (RI) of the digital volume pulse during IV infusion of albuterol (5 microg/min, DeltaRIALB) and glyceryl tri nitrate (5 microg/min, DeltaRIGTN). Large artery elasticity was measured as the stiffness index (SI) and derived from the time to pulse wave reflection adjusted for subject height. Afro-Caribbeans had significantly higher diastolic blood pressure (80.3 versus 77.6 mm Hg; P=0.033), fasting insulin (14.0 versus 10.6 microU/mL; P=0.026), TNF-alpha (6.7 versus 4.3; pg/mL; P=0.001), and interleukin 6 (2.3 versus 1.5 pg/mL; P=0.036) levels compared with Caucasians. CIMT was greater (0.81+/-0.20 versus 0.75+/-0.18 mm; P=0.02) and small vessel reactivity attenuated (mean DeltaRIALB 6.8+/-8.0% versus 12.3+/-8.%; P<0.0001) in Afro-Caribbeans, but their large artery elasticity (mean index of large artery stiffness 9.9 versus 9.7 m/s; P=0.48) was comparable with Caucasians. CIMT was independently associated with an index of large artery stiffness (beta=0.03; P=0.002) in Caucasians but not in Afro-Caribbeans. There were independent relationships among Afro-Caribbean ethnicity, TNF-alpha, and insulin levels. CONCLUSIONS: Selective impairment of small artery function may contribute to excess small vessel disease in Afro-Caribbeans.