Interleukin-17A inhibits adipocyte... : Biochemical Pharmacology (original) (raw)

Graphical abstract

IL-17A inhibits adipocyte differentiation in hBM-MSCs. IL-17A also stimulates the secretion of pro-inflammatory PGE2, IL-6, and IL-8 from adipocytes. This implicates that IL-17A may play a role in the crosstalk between adipose tissue and Th17 cell-associated immune responses. It is still unclear whether adipocyte-derived IL-6 contributes to the development of Th17 cells.

ABSTRACT

The immune system is closely linked to human metabolic diseases. Serum levels of IL-6 increase with obesity and insulin resistance. Not only does IL-6 decrease the insulin sensitivity of human cells such as adipocytes, but it also regulates the lineage commitment of naïve T cells into interleukin (IL)-17A-producing CD4(+) T (Th17) cells. Although IL-17A exerts a variety of effects on somatic tissues, its functional role in human adipocytes has not been identified. In this work, we show that IL-17A inhibits adipocyte differentiation in human bone marrow mesenchymal stem cells (hBM-MSCs), while promoting lipolysis of differentiated adipocytes. We find that IL-17A increases both mRNA and protein secretion of IL-6 and IL-8 during adipocyte differentiation in hBM-MSCs. IL-17A up-regulates cyclooxygenase (COX)-2 gene expression and thereby increases the level of prostaglandin (PG) E2 in differentiated adipocyes. The suppression of anti-adipogenic PGE2 by COX inhibitors such as aspirin and NS-398 partially blocked the effect of IL-17A on adipocyte differentiation in hBM-MSCs. Therefore, IL-17A exhibits its inhibitory effect in part via the COX-2 induction in differentiated adipocytes. In addition, treatment with anti-IL-17A antibody neutralizes IL-17A-mediated effects on adipocyte differentiation and function. These results suggest that IL-17A plays a regulatory role in both the metabolic and inflammatory processes of human adipocytes, similar to other pro-inflammatory cytokines such as IL-1, IFNγ, and TNFα.