Autonomic responsiveness to acute cold exposure in obese and non-obese young women

OBJECTIVE: Conflicting results have emerged over the nature of autonomic ne rvous system abnormalities in human obesity. This present study was designe d to investigate the sympatho-vagal activities and their responsiveness to acute cold exposure in age- and height-matched obese and non-obese young wo men. SUBJECTS: Twenty-four age- and height-matched obese (Weight: 68.1 +/- 2.64 kg, BMI: 26.3 +/- 0.74 kg/m(2), %Fat: 39.9 +/- 1.23%) and non-obese young w omen (Weight: 46.9 +/- 0.77 kg, BMI: 18.5 +/- 0.18 kg/m(2), %Fat: 22.9 +/- 0.8%). MEASUREMENTS: Plasma leptin, insulin, glucose and lipid concentrations were measured at rest. The sympathetic (SNS) and parasympathetic (PNS) nervous system activities were assessed by means of power spectral analysis of hear t rate variability (HRV) for 15 min under control (25 degrees C) or acute c old exposure (10 degrees C) conditions. The very low (VLO) frequency compon ent, and SNS (low/high power), and PNS (high/total power) indexes were used to evaluate thermoregulatory sympathetic function, and cardiac sympathetic and parasympathetic nervous activities, respectively. RESULTS: Plasma lept in concentration was significantly greater in the obese than in the control group (47.3 +/- 7.00 vs 12.1 +/- 1.22 ng.ml(-1), P < 0.001). There was a h ighly positive correlation between plasma leptin concentration and percent of body fat (r = 0.863, P < 0.001). During the resting condition, there was no significant difference in any of the parameters of the HRV between the obese and control groups. Upon acute cold exposure, the VLO frequency compo nent associated with thermoregulation (309 +/- 49.9 vs 578 +/- 142.2 ms(2), P < 0.05) as well as its responsiveness (25 - 10 degrees C delta changes: 17 +/- 82.9 vs 326 +/- 138.2 ms(2), Pt 0.05) were significantly lower in th e obese than in the control group. CONCLUSION: Our data indicate that a reduced autonomic, especially sympathe tic responsiveness associated with thermoregulation and possibly leptin res istance might be aetiological factors of obesity in young women.