Interleukin-15 mediates reciprocal regulation of adipose and muscle mass: A potential role in body weight control

Interleukin (IL)-15 is a cytokine which is highly expressed in skeletal mus cle. Cell culture studies have indicated that IL-15 may have an important r ole in muscle fiber growth and anabolism. However, data concerning the meta bolic effects of this cytokine in vivo are lacking. In the present study, I L-15 was administered to adult rats for 7 days. While IL-15 did not cause c hanges in either muscle mass or muscle protein content, it induced signific ant changes in the fractional rates of both muscle protein synthesis and de gradation, with no net changes in protein accumulation. Additionally, IL-15 administration resulted in a 33% decrease in white adipose tissue mass and a 20% decrease in circulating triacylglycerols; this was associated with a 47% lower hepatic lipogenic rate and a 36% lower plasma VLDL triacylglycer ol content. The decrease in white fat induced by IL-15 was in adipose tissu e. No changes were observed in the rate of lipolysis as a result of cytokin e administration. These findings indicate that IL-15 has significant effect s on both protein and lipid metabolism, and suggest that this cytokine may participate in reciprocal regulation of muscle and adipose tissue mass. (C) 2001 Elsevier Science B.V. All rights reserved.