1202-P: Hepatic NgBR Is a Potential Resilience Factor for Preventing Obesity-Caused Insulin Resistance

Abstract

Adiponectin is an adipocyte-secreted protein hormone and prevents the development of insulin resistance. The adiponectin-mediated activation of AMP-activated protein kinase (AMPK) pathway is essential for decreasing the expression of hepatic gluconeogenic enzymes and enhancing the hepatic effects of insulin. However, the resilience factors required to maintain adiponectin-mediated AMPK activation signaling in the liver remain unclear. Recent studies from our laboratory suggest that NgBR plays a previously unrecognized role in preserving AMPK activation. The loss of NgBR in the obesity liver impairs adiponectin-dependent gluconeogenesis and insulin sensitivity. NgBR hepatocyte-specific knockout (hepKO) mice resemble many features of prediabetes, such as moderately increased fasting blood glucose levels and insulin resistance, as well as facilitating the high-fat diet (HFD)-induced onset of T2D. NgBR was identified as a cell surface receptor for soluble Nogo-B (sNogo-B). Also, NgBR binds the farnesylated form of liver kinase B1 (LKB1-farn), a key regulator of AMPK. NgBR depletion in hepatocytes abolishes the localization of LKB1 in the plasma membrane and impairs AMPK activation, the critical signal for adiponectin-mediated insulin sensitivity. NgBR expression is decreased in the liver of diabetic mice. Similar changes also occur in diabetes patients. The NgBR transcript level is reduced in T2D obese patients’ liver compared to non-T2D obese and lean subjects. Additional in vitro studies show that NgBR deficiency in hepatocyte prevents AMPK activation induced by AdipoRon (an agonist of adiponectin receptor) and increases the gluconeogenesis. Our data suggest that NgBR is a potential resilience factor required for preserving adiponectin-mediated insulin sensitivity and preventing the onset of obesity-caused T2D, and disruption of the NgBR-dependent regulation system leads to impairing gluconeogenesis regulation and insulin sensitivity in the liver. Disclosure W. Hu: None. X. Wang: None. Q. Miao: None. Funding National Institutes of Health (R01DK112971)