The maintenance of the tissue mass results of the delicate balance between protein synthesis and protein breakdown. Previous studies from our laboratory have demonstrated that sympathetic nervous system (SNS) exerts an anabolic effect on skeletal muscle and cardiac protein metabolism, inhibiting proteolysis and stimulating protein synthesis. However, the physiological role of this innervation in the maintenance of brown adipose tissue (BAT) mass, the main site of organism heat production, is still unknown. Thus, the goal of the present work is to investigate the adrenergic mechanisms related to the control of protein metabolism in BAT. For this, unilateral sympathetic denervation of the BAT will be performed in male Wistar rats, which will be submitted to two experimental situations of sympathetic activation: 1) exposure to cold and 2) to systemic treatment with norepinephrine. Correlations will be made between the activation of thermogenesis (estimated by recording the BAT temperature and the UCP-1 mRNA expression and the activities of synthesis process and protein degradation (lysosomal/autophagic and Ub-proteasome pathways). Biochemical methods will be used for the quantification of Ub-conjugates proteins, proteasome activity and lysosomal enzymes. The autophagic flux will be estimated by the gene expression of LC3 and beclin. For the investigation of the synthesis processes will be analyzed by Western blotting the phosphorylation status of the key proteins of Akt/mTOR pathway. Also will be used preparations of isolated tissues to investigate the role of cAMP signaling pathway in the alterations of synthesis and protein degradation induced by norepinephrine. The cAMP content will be determined by enzyme-immunoassay method and noradrenaline by HPLC. Understanding these mechanisms will provide evidence of new strategies that can increase the thermogenic capacity of BAT and thereby contribute to increase energy expenditure.
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