Hepatic Nitric Oxide Synthase 1 Adaptor Protein Regulates Glucose Homeostasis and Hepatic Insulin Sensitivity in Obese Mice Depending on Its PDZ Binding Domain

Abstract

Background: NOS1AP is an adaptor protein and its SNP rs12742393 was associated with type 2 diabetes (T2D). However, it remains uncertain whether NOS1AP plays a role in regulation of insulin sensitivity. Hepatic insulin resistance contributed to the development of T2D. Here, we investigated whether NOS1AP is involved in the regulation of hepatic insulin sensitivity and its underlying mechanisms. Methods: Liver specific NOS1AP condition knockout (CKO) and NOS1AP overexpression mice were generated and fed with a high fat diet. SNPs of NOS1AP gene were genotyped in 86 human subjects. Findings: NOS1AP protein is highly expressed in human and mouse liver. CKO mice exhibited impaired pyruvate, glucose and insulin tolerance, and increased lipid deposits in the liver. Conversely, overexpression of NOS1AP in liver of obese mice improved pyruvate and/or glucose, and insulin tolerance, and attenuated liver lipid accumulation. Moreover, hepatocytes from CKO mice exhibited an elevated glucose production and mRNA expressions of Pc and Pck1. Overexpression of NOS1AP potentiated insulin-stimulated activation of IR/Akt in liver from obese mice. The insulin sensitizing effect of NOS1AP could be mimicked by overexpression of C-terminal domain of NOS1AP in ob/ob mice. Furthermore, NOS1AP expression in liver was associated with ER homeostasis through down-regulation of p-eIF2a-ATF4-CHOP pathway. Subjects with rsl2742393 of NOS1AP have a higher risk for hepatic steatosis. Interpretation: Our data demonstrate a novel role of NOS1AP in regulating hepatic insulin sensitivity and maintenance of ER homeostasis in liver, which implicates NOS1AP a therapeutic target for the prevention and treatment of T2D. Funding Statement: This work was supported by the National Natural Science Foundation of China (81670707, 31340072) (to C. Wang), and National Basic Research Program of China (Nation 973 Program) (2011CB504001) (to W. Jia). Declaration of Interests: The authors declare no conflict of interests. Ethics Approval Statement: The protocol was approved by the Ethics Committee of the Shanghai Jiao Tong University Affiliated Sixth People’s Hospital (2018-KY-026 (K)) and followed the principles of the Declaration of Helsinki.