Objectives: Evidence exists that leptin enhances sympathetic activity and may thereby contribute to the development of obesity-related hypertension. Sympathetic activation also seems more prominent in Africans than whites. We compared leptin levels, and different markers of autonomic activity between Africans and whites, and determined whether a relationship exists between leptin and autonomic activity.
Methods: The study included 409 African and white school teachers (aged, 44.6 ± 9.6 years). We determined leptin in serum and measured ambulatory blood pressure. Markers reflecting autonomic activity included renin, cortisol, baroreflex sensitivity, ambulatory heart rate and heart rate variability (HRV) components (assessed by 24-h ECG recordings in the frequency and geometric domain).
Results: Africans had higher leptin levels, BMI, blood pressure and heart rate (all P < 0.001) as well as lower HRV triangular index and HRV total power (P < 0.001). After also adjusting for BMI in multivariate regression analyses, in African men, renin (β = 0.228; P = 0.033), night-time heart rate (β = 0.184; P = 0.034), HRV triangular index (β = −0.230; P = 0.010) and HRV total power (β = −0.214; P = 0.046) associated with leptin. In white men, leptin associated with 24-h heart rate (β = 0.376; P < 0.001), as well as day and night-time heart rate (both P < 0.01), HRV triangular index (β = −0.335; P < 0.001) and HRV total power (β = −0.403; P < 0.001). In African women, we observed an association of leptin with the total power component of HRV (β = −0.221; P = 0.015) and a borderline association with renin (β = 0.219; P = 0.057). No significant associations were apparent in the white women.
Conclusion: We found that leptin is independently associated with different markers of autonomic activity, especially in men.
Hypertension in Africa Research Team, North-West University, Potchefstroom, South Africa
Correspondence to Rudolph Schutte, PhD, Private Bag x6001, North-West University, Potchefstroom 2520, South Africa. Tel: +27 18 299 2435; fax: +27 18 299 1053; e-mail: email@example.com
Abbreviations: ABPM, ambulatory blood pressure measurement; BRS, baroreflex sensitivity; HF, high frequency; HRV, heart rate variability; LF, low frequency; Std β, standardised β
Received 8 July, 2013
Revised 10 December, 2013
Accepted 10 December, 2013
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