EP4 receptor-associated protein regulates gluconeogenesis in the liver and is associated with hyperglycemia in diabetic mice.

Prostaglandin E2 receptor 4-associated protein (EPRAP) is a key molecule in suppressing inflammatory responses in macrophages. EPRAP is expressed not only in macrophages but also in hepatocytes; however, the role of EPRAP in hepatocytes has not yet been defined. To examine the physiological role of hepatic EPRAP in mice, we performed the glucose tolerance test and the hyperinsulinemic-euglycemic clamp in high-fat sucrose diet (HFSD)-fed wild-type (WT) and Eprap null mice. We evaluated the contribution of EPRAP to gluconeogenesis by pyruvate tolerance test and primary hepatocyte experiments. Furthermore, lentivirus-expressing Eprap-specific small-hairpin RNA was injected in db/ db mice. HFSD-fed Eprap null mice had significantly lower blood glucose levels than HFSD-fed WT mice. Eprap null mice also had low glucose levels after fasting or pyruvic acid injection. Moreover, primary hepatocytes from Eprap-deficient mice showed decreased glucose production and lower expression of the Phosphoenol pyruvate carboxykinase and Glucose 6-phosphatase genes. Lentivirus-mediated hepatic Eprap suppression decreased glucose levels and the expression of gluconeogenic genes in db/ db mice. We conclude that EPRAP regulates gluconeogenesis in hepatocytes and is associated with hyperglycemia in diabetic mice. Our data suggest that suppression of EPRAP could be a novel strategy for the treatment of diabetes.