Deficiency of the Tumor Promoter Gene wip1 Induces Insulin Resistance

Diabetes is a growing health care issue, and prediabetes has been established as a risk factor for type 2 diabetes. Prediabetes is characterized by deregulated glucose control, and elucidating pathways which govern this process is critical. We have identified the wild-type (WT) p53-inducible phosphatase (WIP1) phosphatase as a regulator of glucose homeostasis. Initial characterization of insulin signaling in WIP1 knockout (WIP1(KO)) murine embryo fibroblasts demonstrated reduced insulin-mediated Ak mouse transforming activation. In order to assess the role of WIP1 in glucose homeostasis, we performed metabolic analysis on mice on a low-fat chow diet (LFD) and high fat diet (HFD). We observed increased expression of proinflammatory cytokines in WIP1(KO) murine embryo fibroblasts, and WIP1(KO) mice fed a LFD and a HFD. WIP1(KO) mice exhibited glucose intolerance and insulin intolerance on a LFD and HFD. However, the effects of WIP1 deficiency cause different metabolic defects in mice on a LFD and a HFD. WIP1(KO) mice on a LFD develop hepatic insulin resistance, whereas this is not observed in HFD-fed mice. Mouse body weights and food consumption increase slightly over time in LFD-fed WT and WIP1(KO) mice. Leptin levels are increased in LFD-fed WIP1(KO) mice, compared with WT. In contrast, HFD-fed WIP1(KO) mice are resistant to HFD-induced obesity, have decreased levels of food consumption, and decreased leptin levels compared with HFD-WT mice. WIP1 has been shown to regulate the nuclear factor kappa-light-chain-enhancer of activated B cells pathway, loss of which leads to increased inflammation. We propose that this increased inflammation triggers insulin resistance in WIP1(KO) mice on LFD and HFD.