T cell-derived IL-22 amplifies IL-1β-driven inflammation in human adipose tissue: relevance to obesity and type 2 diabetes.

Proinflammatory cytokines are critically involved in the alteration of adipose tissue biology leading to deterioration of glucose homeostasis in obesity. Here we show a pronounced proinflammatory signature of adipose tissue macrophages in type 2 diabetic obese patients, mainly driven by increased NLRP3-dependent interleukin (IL)-1β production. IL-1β release increased with glycemic deterioration and decreased after gastric bypass surgery. A specific enrichment of IL-17- and IL-22-producing CD4(+) T cells was found in adipose tissue of type 2 diabetic obese patients. Coculture experiments identified the effect of macrophage-derived IL-1β to promote IL-22 and IL-17 production by human adipose tissue CD4(+) T cells. Reciprocally, adipose tissue macrophages express IL-17 and IL-22 receptors, making them sensitive to IL-17 and IL-22. IL-22 increased IL-1β release by inducing pro-IL-1β transcription through activation of C-Jun pathways in macrophages. In sum, these human data identified IL-1β and the T-cell cytokine IL-22 as key players of a paracrine inflammatory pathway previously unidentified in adipose tissue, with a pathological relevance to obesity-induced type 2 diabetes. These results provide an additional rationale for targeting IL-1β in obesity-linked type 2 diabetes and may have important implications for the conception of novel combined anti-IL-1β and anti-IL-22 immunotherapy in human obesity.