Downregulation of IL-22 can be considered as a risk factor for onset of type 2 diabetes.

There is some controversy as for the roles played by tumor growth factor-β (TGF-β), interleukin-1β (IL-1β), and IL-22 in the onset process of type 2 diabetes (T2D). The main aim of this project was to examine serum levels of TGF-β, IL-1β, and IL-22 in the new cases and long period T2D patients as well as healthy controls. In this study, 115 new T2D patient cases (group 1), 434 T2D patients who have suffered from the disease more than 2 years (group 2), and 104 healthy controls have been selected from 6240 (3619 females) patients who were under study population from Kerman Coronary Artery Disease Risk Factor Study. Serum levels of TGF-β, IL-1β, and IL-22 have been evaluated using commercial kits. Serum levels of TGF-β and IL-1β significantly increased, while IL-22 decreased in 2 groups in comparison to healthy controls. Serum levels of IL-22, but not TGF-β and IL-1β, were significantly decreased in group 1 in comparison to healthy controls. There were no significant differences between groups 1 and 2 as for the cytokine levels. Serum levels of IL-22 increased in the females in group 2 when compared to females in group 1. It appears that TGF-β and IL-1β participate in the induction of inflammation after establishment of T2D, while decrease in IL-22 may be considered as a key factor for onset of the disease. Gender can also be considered as the main risk factor for variation in cytokine levels.