Inhibition of hepatocyte nuclear factor 1b induces hepatic steatosis through DPP4/NOX1-mediated regulation of superoxide

Abstract

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder that is closely associated with insulin resistance and type 2 diabetes. Previous studies have suggested that hepatocyte nuclear factor 1b (HNF1b) ameliorates insulin resistance. However, the role of HNF1b in the regulation of lipid metabolism and hepatic steatosis remains poorly understood. We found that HNF1b expression was decreased in steatotic livers. We injected mice with lentivirus (LV) expressing HNF1b shRNA to generate mice with hepatic knockdown of HNF1b. We also injected high fat (HF) diet-induced obese and db/db diabetic mice with LV expressing HNF1b to overexpress HNF1b. Knockdown of HNF1b increased hepatic lipid contents and induced insulin resistance in mice and in hepatocytes. Knockdown of HNF1b worsened HF diet-induced increases in hepatic lipid contents, liver injury and insulin resistance in mice and PA-induced lipid accumulation and impaired insulin signaling in hepatocytes. Moreover, overexpression of HNF1b alleviated HF diet-induced increases in hepatic lipid content and insulin resistance in mice. Knockdown of HNF1b increased expression of genes associated with lipogenensis and endoplasmic reticulum (ER) stress. DPP4 and NOX1 expression was increased by knockdown of HNF1b and HNF1b directly bound with the promoters of DPP4 and NOX1. Overexpression of DPP4 or NOX1 was associated with an increase in lipid droplets in hepatocytes and decreased expression of DPP4 or NOX1 suppressed the effects of knockdown of HNF1b knockdown on triglyceride (TG) formation and insulin signaling. Knockdown of HNF1b increased superoxide level and decreased glutathione content, which was inhibited by downregulation of DPP4 and NOX1. N-acetylcysteine (NAC) suppressed HNF1b knockdown-induced ER stress, TG formation and insulin resistance. Palmitic acid (PA) decreased HNF1b expression which was inhibited by NAC. Taken together, these studies demonstrate that HNF1b plays an essential role in controlling hepatic TG homeostasis and insulin sensitivity by regulating DPP4/NOX1mediated generation of superoxide.

Palmitic acid, but not high-glucose, induced myocardial apoptosis is alleviated by N‑acetylcysteine due to attenuated mitochondrial-derived ROS accumulation-induced endoplasmic reticulum stress

“…NAC also reversed pregestational diabetes-induced oxidative production and decreased the coronary artery volume in fetal hearts of mice 11 , demonstrating the cardioprotective effects of NAC. Consistently, NAC has also been reported to abolish palmitic acid (PA)-induced ERS, total triglyceride (TG) formation and insulin resistance 12 . These studies raise an intriguing hypothesis that the beneficial effect of NAC on diabetic hearts may rely on attenuated ERS and metabolic disorders.…”

Dipeptidyl peptidase-4 inhibitor protects against non-alcoholic steatohepatitis in mice by targeting TRAIL receptor-mediated lipoapoptosis via modulating hepatic dipeptidyl peptidase-4 expression

“…Treatment with DPP4i inhibited interaction between membrane-bound DPP4 and integrin β1 and decreased renal DPP4 expression levels in the diabetic kidney mouse model, possibly by suppressing the endothelial-to-mesenchymal transition pathway loop 49 . In the present study, the increased levels of hepatic DPP4 might have induced the ER stress-driven TRAIL signaling pathway 11,40,41 and the enhanced TRAIL-R-induced apoptotic pathway could have further augmented ER stress by upregulating ATF4 16,47 . As a result, DPP4 expression would have been subsequently increased in a positive feedback loop of ER stress, in response to the possible transcriptional upregulation by ATF4 21 .…”

“…Increased DPP4 expression levels in hepatocytes could be responsible for promoting intracellular ER stress through several pathways and DPP4i might suppress these pathways. Overexpression of hepatic DPP4 upregulated lipogenic gene expression with lipid accumulation, resulting in increased intracellular ER stress 11,40,41 . Furthermore, the hepatic DPP4 overexpression leads to further increase of intracellular ER stress by inhibiting the hepatocyte nuclear factor 1b (HNF1b)-associated suppression of superoxide generation 40 .…”

“…Overexpression of hepatic DPP4 upregulated lipogenic gene expression with lipid accumulation, resulting in increased intracellular ER stress 11 , 40 , 41 . Furthermore, the hepatic DPP4 overexpression leads to further increase of intracellular ER stress by inhibiting the hepatocyte nuclear factor 1b (HNF1b)-associated suppression of superoxide generation 40 . Similar to our findings, DPP4i significantly alleviated ER stress indicators in both high fat diet- and methionine/choline-deficient diet-induced NASH mouse models in previous studies 42 , 43 .…”

Five Constituents in Psoralea corylifolia L. Attenuate Palmitic Acid-Induced Hepatocyte Injury via Inhibiting the Protein Kinase C-α/Nicotinamide-Adenine Dinucleotide Phosphate Oxidase Pathway

“…Oxidative stress refers to a shift in the balance toward increased intracellular reactive oxygen species (ROS) generation, compared to breakdown (Mann et al, 2017). Nicotinamideadenine dinucleotide phosphate oxidase (NOX) is considered the major cellular ROS source (Loffredo et al, 2016;Long et al, 2017;Rabelo et al, 2018). Its activation has been associated with hepatic injury (Matsumoto et al, 2018;Zheng et al, 2018) and also plays a very plausible role as the starting point of extrahepatic damage, leading to inflammation and fibrosis through activation of Kupffer cells and hepatic stellate cells (HSCs) (Das et al, 2015;, thus causing a self-perpetuating circle of ROS formation and ROS-mediated damage (Masarone et al, 2018;Zhong and Liu, 2018).…”