Association between IL-15 and obesity: IL-15 as a potential regulator of fat mass.
Objective: Interleukin 15 (IL-15) decreases lipid deposition in preadipocytes and decreases the mass of white adipose tissue in rats, indicating that IL-15 may take part in regulating this tissue. IL-15 is expressed in human skeletal muscle and skeletal muscle may be a source of plasma IL-15 and in this way regulate adipose tissue mass. Design: The relation between skeletal muscle IL-15 mRNA expression, plasma IL-15, and adipose tissue mass was studied in 199 humans divided into four groups on the basis of obesity and type 2 diabetes. Furthermore, using a DNA electrotransfer model we assessed the effect of IL-15 over-expression in skeletal muscle of mice. Results: In humans, multiple regression analysis showed a negative association between plasma IL-15 and total fat mass (p < 0.05), trunk fat mass (p < 0.01), and percent fat mass (p < 0.05), independent of type 2 diabetes. Negative associations were also found between muscle IL-15 mRNA and obesity parameters. IL-15 over-expression in skeletal muscle of mice reduced trunk fat mass, but not subcutaneous fat mass. Conclusions: Our results indicate that IL-15 may be a regulator of trunk fat mass.
