Association between metabolic syndrome, hepatic steatosis, and testosterone deficiency: evidences from studies with men and rodents.

Testosterone is the predominant androgen in men and the lack of it can be a trigger to the development of the metabolic syndrome. Here we review the relationship between testosterone deficiency, metabolic syndrome, and hepatic steatosis reported by studies with men and rodents. The prevalence of metabolic syndrome and testosterone deficiency is higher among older subjects. Low total and free testosterone levels were positively associated with disturbs on energy metabolism, changes in body fat distribution, and body composition. Studies reported visceral fat accumulation in men with hypogonadism and castrated rats. Despite some contradictions, the association between higher adiposity, low testosterone, and metabolic syndrome was a common point among the studies. Few studies evaluated the hepatic steatosis and found an association with hypogonadism. Most of the studies with rodents combined the castration with a high-fat diet to study metabolic disturbs. The importance of proper levels of testosterone for energy metabolism homeostasis in men was also underlined by studies that investigated the metabolic effects of testosterone replacement therapy and androgen deprivation therapy.

Melatonin protects female rats against steatosis and liver oxidative stress induced by oestrogen deficiency.

AIMS: Melatonin has been shown to protect cells against oxidative and inflammatory damage via endocrine, paracrine and autocrine actions. Postmenopausal condition is associated with a high incidence of many features of metabolic syndrome including obesity, steatosis and liver oxidative injuries. The aim of this work was to investigate whether treatment with melatonin improves metabolic disturbances associated with oestrogen deficiency in ovariectomised (OVX) rats. MAIN METHODS: OVX and control (CON) female rats were treated with melatonin (10mg/kg×day for 3weeks, p.o.). Body weight gain, adiposity index, plasma biochemical parameters, liver lipid content, hepatic mitochondrial respiration, fatty acid oxidation and mitochondrial H2O2 generation and the activity of the most important enzymatic and non-enzymatic reactive oxygen species (ROS) scavenger systems were measured. KEY FINDINGS: In OVX rats, melatonin suppressed lipid accumulation and cellular oxidative stress in the liver. There was a reduction in the levels of carbonylated proteins in the mitochondria and cytosol, reduction in the malondialdehyde contents in the liver homogenates, stimulation of cytosolic glutathione peroxidase and glutathione reductase activities and restoration of reduced glutathione contents to normal levels. SIGNIFICANCE: 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.

Parasympathetic cardiac activity is associated with cardiorespiratory fitness in overweight and obese adolescents.

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.