EFFECT OF ENDURANCE TRAINING ON MESSENGER-RNA EXPRESSION OF UNCOUPLING PROTEIN-1, PROTEIN-2, AND PROTEIN-3 IN THE RAT

Endurance exercise training has been shown to decrease diet-induced th ermogenesis (DIT) in rats and humans, Zn rodents, most thermogenesis i s thought to occur in brown adipose tissue via activation of the uncou pling protein-1 (UCP1) and in skeletal muscle, Since the level of UCP1 mRNA in rat BAT was reported to be unmodified by exercise training, t he newly described uncoupling proteins UCP2 and UCP3 could be responsi ble for the decreased DIT in trained rats, UCP3 mRNA levels in enduran ce-trained rats were found to be reduced by 76% and 59% in tibialis an terior and soleus muscles, respectively, UCP2 mRNA levels were also de creased in tibialis anterior and in heart by 54% and 41%, respectively , Neither white adipose tissue UCP2 nor brown adipose tissue UCP1, UCP 2, and UCP3 mRNA levels were modified, The results of this study show that a need for a higher metabolic efficiency is associated with decre ased mRNA expression of the uncoupling proteins in skeletal and heart muscles, which would decrease energy dissipation in these tissues, The down-regulation of UCP3 and UCP2 expressions might also contribute to the rapid weight gain known to occur when exercise training ceased.