578-P: A Loss-of-Function Mutation of NRG4 Contributes to the Pathogenesis of NAFLD and Insulin Resistance

Neuregulin 4 (Nrg4), as an adipose tissue-enriched endocrine factor, participates in adipocyte-to-hepatocyte communication which elicits beneficial metabolic effects in NAFLD. We identified a mutation of NRG4 by whole exome sequencing in 151 severe obese subjects and exome array in a community-based population of 2388 subjects. Nrg4 R44H mutation carriers have increased visceral fat area, abnormal liver function and hyperlipidemia. Then we hypothesized that the mutation would affect the function of Nrg4 and accelerated the development of NAFLD. Compared with Nrg4 WT mice, Nrg4 R44H mice gained more weight, accompanied by significantly increased fat mass and lipid accumulation in the liver upon HFD feeding. In vitro, we found that Nrg4 WT activated ErbB4 and stimulated the STAT5 signaling pathway and decreased transcriptional activation of srebp1c. As we hypothesized, the primary hepatocytes treated with Nrg4 R44H purified protein didn’t showed the same activation of cell signaling as Nrg4 WT. In order to reveal the potential mechanisms of loss-of-function of Nrg4 R44H, we performed surface plasmon resonance (SPR) experiments to test the binding affinity of purified Nrg4 and ErbB4 proteins. The SPR results showed Nrg4 WT bind to ErbB4 with an affinity of 2.20uM, while Nrg4 R44H showed no binding. Taken together, these results suggested Nrg4 WT prevented HFD-induced NAFLD and alleviated insulin resistance, and demonstrated Nrg4 R44H lost its ability to bind to the receptor ErbB4, thus losing its physiological function.