Interleukin 15 (IL-15) has previously been shown to have important effects on lipid metabolism in adipose tissue, particularly influencing the rate of the de novo
fatty acid synthesis. The results presented here show that chronic administration to rats (100 microg/kg
body weight) has important effects on the metabolic fate of an exogenous [(14)C]-
triolein load, decreasing the incorporation of
lipid into adipose tissue and significantly increasing the total (14)CO(2) formation from [(14)C]-
triolein. Skeletal muscle and possibly liver seem to be the main organs involved in the action of
IL-15 on
lipid oxidation, since the presence of the
cytokine in incubated EDL muscle with [(14)C]-
palmitic acid increased (14)CO(2) formation by 39%. Concerning the mechanism, the results suggest that the transport of
fatty acids into mitochondria could be involved in the action of
IL-15 since the
cytokine clearly increases the presence of L-
CPT-I and
CPT-II in liver tissue. In addition,
IL-15 treatment resulted in a significant increment in the gene expression of
PPARdelta, a
transcription factor clearly related with
lipid catabolism in many tissues. Altogether, the results presented here suggest that
IL-15 alters exogenous
lipid partitioning, limiting adipose tissue uptake and favouring oxidation.