Influência da distribuição de gordura no controle autonômico de mulheres obesas

Abstract

Background: Obesity causes negative changes in autonomic control with an adverse effect on cardiovascular risk. The relationship of obesity and autonomic dysfunction seems to be dependent on the distribution of body fat. Objectives: The objective of the present study was to investigate an influence of central or peripheral body fat distribution, in the cardiac sympatho-vagal balance and heart rate behavior in cardiopulmonary exercise test of obese young women. Methods: Fourty-nine healthy young obese women (BMI 30 to 40 kg/m2 and CA ≥ 88 cm) aged 20 to 42 years, divided into two groups according to waist-to-hip ratio (WHR): central fat with WHR ≥ 0.85 (CF, n=26, 34 ± 1.4 years) and peripheral fat with WHR <0.85 (PF, n=23, 33±1.4 years). A group of eutrophic women with BMI 18.5 a 24.9 kg/m2 (control, n=12, 29±1.2 years) were also studied. All volunteers were submitted to anthropometric, body composition (bioimpedance) and clinical evaluation to obtain indicators of obesity and health. We realized cardiopulmonary exercise test (CPET) to assess the heart rate behavior in the phases of rest, exercise and recovery, as well as we registred 10 minutes of rest HR to analyze HR variability in time and frequency domain. Results: The 3 groups studied were similar in age, clinical systolic blood pressure (BP), total cholesterol, VLDL, LDL fasting glycemia and glycated hemoglobin. As expected, CF and PF presented higher values of weight, BMI, waist circumference (WC), WHR, percentage of fat mass, as well as higher levels of triglycerides and lower values of lean mass and HDL-c when compared with control. Despite of similar body weight in CF and PF, GF group had higher WC than PF and control (107 [103-111], 101 [97-105] and 72 [66-73] cm, respectively, p<0.001). In addition, only CF presented higher clinical diastolic pressure than control (85 [80-90], 80 [70-90] and 70 [70-80], p=0.017). Regarding the metabolic and ventilatory responses in CPET, CF and PF presented reduced values of oxygen uptake (VO2) at ventilatory threshold 1 (LV1), ventilatory threshold 2 (LV2), maximal effort (peak VO2), achieved percentage of peak VO2 predicted for age, as well as respiratory quotient in maximal effort (RQ max=VCO2/VO2) when compared to control group (p<0.05). Observing the chronotropic response of CPET, obese women groups, regardless of fat distribution, presented significantly reduced HR values LV2 and reserve HR (HR peak - HR rest) compared to control. CF group (WHR ≥ 0.85) presented attenuated heart rate recovery after 1st minute of recovery when compared to PF group. All groups presented high values in the sympatho-vagal balance. There was a positive correlation of BMI and low frequency spectral band (r=0.32, p=0.040), between BMI and the ratio low/high frequency spectral bands (r=0.32, p=0.040), and negative correlation of BMI and high frequency spectral bands (r=-0.32 p=0.040). Conclusion: Young obese women showed impairment in the sympathetic-vagal balance observed by HR reserve in CPET. The central body fat distribution potentiates the vagal autonomic impairment, characterized by attenuated HR recovery at 1st min after CPET.