Background: Augmented a-adrenergic response patterns are associated with vascular risk in Africans. Therefore, the aims of this study were (a) to assess ethnic differences related to glucose and cardiovascular responses during acute laboratory stress, and (b) to assess whether these responses are associated with chronic hyperglycemia (HbA1cZ5.7%) and albumin : creatinine ratio (ACR).

Materials and methods: Ambulatory blood pressure of 81 African and 100 Caucasian men was recorded. Beat-tobeat blood pressure was obtained during exposure to the Color Word Conflict (STROOP) and Cold Pressor Tests (CPT). Overnight 8 h fasting urine, basal and post-stress blood samples were collected for biochemical analyses.

Results: Augmented glucose responses (P < 0.001) were shown by the African men in response to the STROOP and CPT, in contrast to their Caucasian counterparts, who showed attenuated responses. In hyperglycemic African men, an enhanced a-adrenergic profile was revealed, with decreased stroke volume (P = 0.07) and cardiac output responses (P = 0.05). Augmented systolic blood pressure changes during the CPT predicted elevated ACR in African men [adjusted R2 0.31: b, 0.54 (0.23, 0.85), P =0.002]. In hyperglycemic Caucasian men, however, metabolic changes, that is augmented glucose changes to the STROOP test, predicted elevated ACR [adjusted R2 0.19: b, 0.33 (0.02, 0.64), P = 0.04].

Conclusion: An a-adrenergic-driven cardiovascular response profile acted in tandem with augmented glucose responses in African men when exposed to acute laboratory stress. Pressure overload in Africans in contrast to metabolic responses in Caucasians may suggest different underlying mechanisms for ACR, a marker of renal impairment, when in a state of chronic hyperglycemia.