Effect of training judo in the competition period on the plasmatic levels of leptin and pro-inflammatory cytokines in high-performance male athletes.

The purpose this study was to evaluate the effect of training judo in the competition period on the plasmatic levels of bioactive molecules in high-performance male athletes. The subjects were divided into two groups, a trained group with 11 judokas and a nontrained group also with 11 subjects. Blood samples obtained 60 h after training to measure plasma tumor necrosis factor (TNF-alpha), interleukin-6 (IL-6), monocyte chemotactic protein 1 (MCP-1), and leptin levels. The trained group presented a significant reduction in the percentage of fat and fat mass and an increase in the lumbar and lower limbs traction forces and the maximum VO(2) when compared to the nontrained group. There was no significant difference in the serum concentrations of TNF-alpha and IL-6 between the two groups. The trained group presented a lower concentration of leptin, both as absolute values as well as relative to the percentage of fat, and a higher concentration of MCP-1, in relation to the nontrained group. Our results suggest an adaptation in the capacity of synthesizing and secreting leptin in response to chronic stress in judo, what suggests a neuro-hormonal adjustment that guarantees the efficiency of metabolism. The changes of MCP-1 indicated a possible inflammatory state.

Melatonin enhances leptin expression by rat adipocytes in the presence of insulin.

Leptin and melatonin play an important role in the regulation of body mass and energy balance. Both hormones show a circadian rhythm, with increasing values at night. In addition, melatonin receptors were recently described in adipocytes, where leptin is synthesized. Here, we investigated the influence of melatonin and its interaction with insulin and dexamethasone on leptin expression. Isolated rat adipocytes were incubated with melatonin (1 nM) alone or in combination with insulin (5 nM) and/or dexamethasone (7 nM) for 6 h. Melatonin or insulin alone did not affect leptin expression, but together they increased it by 120%. Dexamethasone increased leptin mRNA content (105%), and this effect was not enhanced by melatonin. Simultaneous treatment with the three hormones provoked a further increase in leptin release (250%) and leptin mRNA (100%). Melatonin prevented the forskolin-induced inhibition (95%) of leptin expression. In addition, melatonin's ability to stimulate leptin release (in the presence of insulin) was completely blocked by pertussis toxin and luzindole. To gain further insight into the molecular basis of melatonin and insulin synergism, the insulin-signaling pathway was investigated. Melatonin increased the insulin-induced insulin receptor-beta tyrosine phosphorylation, which led to an increased serine phosphorylation of the downstream convergent protein Akt. We concluded that melatonin interacts with insulin and upregulates insulin-stimulated leptin expression. These effects are caused by melatonin binding to the pertussis toxin-sensitive G(i) protein-coupled membrane receptor (MT1 subtype) and the cross talk with insulin, since insulin receptor and its convergent target Akt are coactivated by melatonin.