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: firstname.lastname@example.org
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
Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Website (http://www.jhypertension.com).