Gender and obesity effects on cardiovagal baroreflex gain in humans

Abstract

A series of studies focusing on the influence of gender obesity, and body fat distribution on cardiovagal baroreflex gain were conducted to determine I) if women would demonstrate lower cardiovagal baroreflex gain compared with men; 2) if cardiovagal baroreflex gain would be reduced in overweight/obese (35>body mass index<25 kg/m2) individuals compared to their age-matched, non-obese peers (body mass index<25 kg/m2); and 3) if cardiovagal baroreflex gain would be reduced in men with elevated abdominal visceral fat compared to their peers with lower levels of abdominal visceral fat but similar levels of total body and abdominal subcutaneous. To accomplish this, we measured cardiovagal baroreflex gain via modified Oxford technique in sedentary, non-obese premenopausal women and men and sedentary non-obese and obese men 18-40 years of age. The results from these studies suggest that cardiovagal baroreflex gain is lower in non-obese women compared to men (13.2±1.5 vs 20.0±2.8 ms/mmHg; P<0.05). The lower cardiovagal baroreflex gain in the women was not related to their lower aerobic fitness and was only marginally related to their higher body fat percentage. This may have important implications for understanding the reduced orthostatic tolerance observed in women. Furthermore, cardiovagal baroreflex gain is reduced in men with elevated total body and abdominal fat independent of aerobic fitness level (13.2±1.6 vs. 23.1±3.8 ms/mmHg; P<0.05). These findings may have important implications regarding the development of cardiovascular diseases in overweight and obese individuals. Finally, cardiovagal baroreflex gain was ~35% lower in men with elevated abdominal visceral fat compared with total body- and abdominal subcutaneous matched-men with lower levels of abdominal visceral fat (13.0±2.0 vs. 21.4±3.6 ms/mmHg; P<0.05). Therefore, reduced cardiovagal baroreflex gain observed in men with abdominal obesity may contribute to the elevated cardiovascular disease-related mortality associated with the metabolic syndrome. Future studies will be necessary to gain insight into mechanisms responsible for the reduced cardiovagal baroreflex gain in women compared with men, in overweight and obese men compared to non-obese men, and in men with elevated abdominal visceral fat compared to men with lower levels of abdominal visceral fat.