The aim of this study was to investigate the association between cardiac parasympathetic activity and cardiorespiratory fitness, insulin, and hemodynamic profile in overweight and obese adolescent girls and boys (aged 12-16 years). Data were taken from the Multidisciplinary Obesity Treatment Program. Only post-intervention measurements are presented herein. Body composition, cardiorespiratory fitness, blood pressure, and metabolic profile (insulin and glucose profile) of adolescents were assessed. Cardiac parasympathetic activity was determined by resting heart rate variability, which was analyzed using a heart rate monitor. Greater parasympathetic cardiac activity was associated with higher levels of cardiorespiratory fitness in both girls and boys (0.375 ≤ r ≤ 0.900), while the sympathetic-vagal balance was negatively related to maximal oxygen uptake (VO2max) in girls (r = 0.478). An association between lower parasympathetic activity and insulin resistance was noted in girls (mean of R-R intervals [RRmean] and homeostasis model assessment insulin-resistance index [HOMA-IR]: r = -0.678), while greater systolic blood pressure (SBP) and lower parasympathetic activity were associated in both sexes (RRmean and SBP: r = -0.526; high frequency [HF (nu)] and SBP: r = -0.754). In conclusion, autonomic nervous system activity was associated with cardiorespiratory fitness, insulin resistance, and SBP in overweight and obese adolescents. The identification of these potential relationships assists with the establishment of future long-term exercise interventions that evaluate the improvements in parasympathetic nervous system activity, in addition to metabolic profile and cardiorespiratory fitness in overweight and obese adolescents.
Exogenous melatonin protects the liver of OVX rats against steatosis and cellular oxidative stress, possibly via activation of antioxidant enzymes related to glutathione metabolism and by a direct radical scavenging activity.
This study aimed to investigate the effects of tibolone, a synthetic steroid, on several metabolic dysfunctions induced by oestrogen deficiency, in rats. Ovariectomised (OVX) rats were used as animal model of postmenopausal metabolic syndrome. The OVX rats were treated with daily doses of tibolone (0.16 mg/kg) and the results were compared with control (sham-operated) and OVX untreated rats. Tibolone reduced the adiposity and the visceral adipocyte size in OVX rats. The insulin sensitivity was also improved, and a decrease in the activity of the adipose tissue hormone-sensitive lipase enzyme was recorded. The lower lipolysis by visceral adipocytes, associated with the recovery of peroxisomal β-oxidation by tibolone may have contributed to the reversion of NAFLD in treated OVX rats. The reduction of liver lipid contents resulted in a general improvement in the liver redox state. In addition, tibolone reduced the mitochondrial ROS generation and restored the activity of glucose-6-phosphate dehydrogenase. Tibolone also exerted antioxidant effects on inguinal adipose tissue. Tibolone exerted several beneficial effects on cellular and metabolic dysfunctions induced by ovariectomy in rats. One important mode of action of tibolone was the reduction of the visceral adipocyte size, corroborating the relationship between this one and the development and progression of several comorbidities associated with metabolic syndrome.
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