Differences in the association between type 2 diabetes and impaired microvascular function among Europeans and African Caribbeans

Abstract

Aims/hypothesis: Diabetes is associated with microvascular damage in all populations, but diabetic patients of Black African descent (African Caribbeans) have a greater risk of vascular target organ damage than would be anticipated for any given blood pressure level. We investigated whether this may be due to differences in the microvasculature. Materials and methods: To assess the maximum hyperaemic response to heating and the post-ischaemic response, Laser Doppler fluximetry was performed on 51 and 100 Europeans, and on 66 and 88 African Caribbeans with and without diabetes, respectively. Subjects were aged between 40 and 65 years and recruited from the general population. Echocardiographic interventricular septal thickness (IVST) was measured as a proxy for vascular target organ damage. Results: In diabetic subjects of both ethnic groups, the maximum hyperaemic response and peak response to ischaemia were attenuated as compared to the corresponding non-diabetic subjects (p=0.08 for diabetic and 0.03 for non-diabetic Europeans; p=0.03 and 0.1 for African Caribbeans). Adjustment for cardiovascular risk factors, in particular insulin and blood pressure, abolished these differences in Europeans (p=0.8 for diabetic and 0.2 for non-diabetic Europeans), but not in African Caribbeans (p=0.03 and 0.05). Conclusions/interpretation: Persisting microvascular dysfunction in African Caribbeans may contribute to the increased risk of target organ damage observed in diabetes in this population. The weak contribution of conventional cardiovascular risk factors to these disturbances indicates that conventional therapeutic interventions may be less beneficial in these patients. There was a risk-factor-independent, inverse association between IVST and maximal hyperaemia. These ethnic differences in microvascular responses to temperature and arterial occlusion could account for increased target organ damage in African Caribbeans.

Comparison of the retinal microvasculature in European and African-Caribbean people with diabetes

“…The family practice register is probably the most accurate and comprehensive register of the general population in the UK and it is estimated that more than 97% of the population is registered with a practitioner [15]. Ethnicity was confirmed with the participants' own self assessment [25].…”

“…Nineteen European and 18 African-Caribbean subjects also agreed to undergo 24 hour ambulatory BP monitoring using a Duolter device (Novocor, Rueil-Malmaison, France). Fasting blood samples were taken for glucose, insulin and lipid measurements [25]. Retinal photography was performed in all participants using a Zeiss FF 450 plus fundus camera (Carl Zeiss Ltd., Welwyn Garden City, UK) with a 50º field of view following mydriasis with tropicamide (1%) eye drops.…”

“…Previous studies have also suggested that people of African or African-Caribbean ethnicity are more vulnerable than Europeans to retinopathy [18][19][20][21][22][23][24] and also suffer more microvascular disease in other tissues [25][26][27]. In this study we investigated whether retinal microvascular changes differed between people of European and African-Caribbean ethnicity with type 2 diabetes, and explored the role of blood pressure in these differences.…”

Microvascular autoregulation in children and adolescents with type 1 diabetes mellitus

“…Regarding the origin of biological zero, several physiological sources of this signal have been discussed: apart from collateral circulation through bones, fluid or cellular movement within the interstitial space, movements within vessels unrelated to flow (e.g. red cell sedimentation) and Brownian motion of interstitial macromolecules, residual microvascular vasomotion might contribute to biological zero [19,34]. However, since the mechanisms causing biological zero are poorly understood, it can only be speculated that the lower biological zero in children with type 1 diabetes might be caused by impaired spontaneous vasomotion.…”

Metabolic Syndrome in Blacks: Are the Criteria Right?

“…Blacks have also greater carotid artery intima-media thickness (CIMT), a surrogate for subclinical atherosclerosis, than their white counterparts [7][8][9][10]17]. Recent studies have found lack of significant or weak associations among insulin resistance and serum HDLC-triglycerides ratio [12-16••, 17-24], blood pressure and body composition, [2••, 4, 5•, 6, 12, 14, 22, 25] and CIMT [8][9][10] in blacks. Thus, current data on MetS are unable to explain the higher and excess CVD deaths in blacks than whites [1, 2••, 3-5•].…”