BACKGROUNDInsulin resistance is an underlying feature of both type 2 diabetes and metabolic syndrome. Currently, it is unclear whether nuclear factor (NF)-κB inducing kinase (NIK) plays a role in the development of insulin resistance. The present in vivo study investigated the roles of NIK and IκB kinase α (IKKα) in obesity-induced insulin resistance using animal models.

METHODSNIK expression was evaluated by Western blotting in male Lep(ob) mice and C57BL/6J mice fed a high-fat diet (HFD) (45% fat). After metformin and sulfasalazine treatment, NIK expression was investigated during the improvement of insulin resistance.

RESULTSNIK was increased by about 1-fold in the renal tissues of Lep(ob) mice and C57BL/6J mice fed a HFD for 12 weeks. After 1 and 3 weeks of high-fat feeding, we observed an almost 50% decrease in NIK and IKKα expression in the liver and renal tissues of C57BL/6J mice. NIK expression was significantly lower in the liver and renal tissues of HFD-fed mice that were treated with insulin sensitizers, metformin and sulfasalazine. However, IKKα expression was increased after metformin treatment in both tissues.

CONCLUSIONThese results suggest a possible role of NIK in the liver and renal tissues of insulin-resistant mice.