Xi Cao1,2,3,4, Li-Ni Song1,2,3, Yi-Chen Zhang1,2,3, Qi Li1,2,3, Ting-Ting Shi1,2,3, Fang-Yuan Yang1,2,3, Ming-Xia Yuan1,2,3, Zhong Xin1,2,3, Jin-Kui Yang1,2,3. 1. Department of Endocrinology, Beijing Tongren Hospital, Capital Medical University, Beijing, China. 2. Beijing Key Laboratory of Diabetes Research and Care, Beijing Tongren Hospital, Capital Medical University, Beijing, China. 3. Beijing Diabetes institute, Beijing Tongren Hospital, Capital Medical University, Beijing, China. 4. Department of Physiology and Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Abstract
BACKGROUND: Previous works indicated that the stress on the endoplasmic reticulum (ER) affected nonalcoholic fatty liver disease (NAFLD). However, there is no clear evident on the effect of the regulation of ER stress by angiotensin-converting enzyme 2 (ACE2) on the prevention of NAFLD. METHODS: HepG2 cells were treated with thapsigargin (Tg) or palmitic acid (PA). We analysed ACE2 expression using Western-blotting analyses. ER stress-related proteins were detected in ACE2 knockout mice and Ad-ACE2-treated db/db mice by immunofluorescence or Western-blotting analyses. In ACE2-overexpression HepG2 cells, the triglyceride (TG), total cholesterol (TC), and glycogen content were detected by assay kits. Meanwhile, the expression of hepatic lipogenic proteins (ACCα, SREBP-1c, FAS, and LXRα), enzymes for gluconeogenesis (PEPCK, G6Pase, and IRS2), and IKKβ/NFκB/IRS1/Akt pathway were analysed by Western-blotting analyses. RESULTS: ACE2 was significantly increased in Tg/PA-induced cultured hepatocytes. Additionally, ACE2 knockout mice displayed elevated levels of ER stress, while Ad-ACE2-treated db/db mice showed reduced ER stress in liver. Furthermore, activation of ACE2 can ameliorate ER stress, accompanied by decreased TG content, increased intracellular glycogen, and downregulated expression of hepatic lipogenic proteins and enzymes for gluconeogenesis in Tg/PA-induced hepatocytes. As a consequence of anti-ER stress, the activation of ACE2 led to improved glucose and lipid metabolism through the IKKβ/NFκB/IRS1/Akt pathway. CONCLUSIONS: This is the first time documented that ACE2 had a notable alleviating role in ER stress-induced hepatic steatosis and glucose metabolism via the IKKβ/NFκB/IRS1/Akt-mediated pathway. This study may further provide insight into a novel underlying mechanism and a strategy for treating NAFLD.
BACKGROUND: Previous works indicated that the stress on the endoplasmic reticulum (ER) affected nonalcoholic fatty liver disease (NAFLD). However, there is no clear evident on the effect of the regulation of ER stress by angiotensin-converting enzyme 2 (ACE2) on the prevention of NAFLD. METHODS:HepG2 cells were treated with thapsigargin (Tg) or palmitic acid (PA). We analysed ACE2 expression using Western-blotting analyses. ER stress-related proteins were detected in ACE2 knockout mice and Ad-ACE2-treated db/db mice by immunofluorescence or Western-blotting analyses. In ACE2-overexpression HepG2 cells, the triglyceride (TG), total cholesterol (TC), and glycogen content were detected by assay kits. Meanwhile, the expression of hepatic lipogenic proteins (ACCα, SREBP-1c, FAS, and LXRα), enzymes for gluconeogenesis (PEPCK, G6Pase, and IRS2), and IKKβ/NFκB/IRS1/Akt pathway were analysed by Western-blotting analyses. RESULTS:ACE2 was significantly increased in Tg/PA-induced cultured hepatocytes. Additionally, ACE2 knockout mice displayed elevated levels of ER stress, while Ad-ACE2-treated db/db mice showed reduced ER stress in liver. Furthermore, activation of ACE2 can ameliorate ER stress, accompanied by decreased TG content, increased intracellular glycogen, and downregulated expression of hepatic lipogenic proteins and enzymes for gluconeogenesis in Tg/PA-induced hepatocytes. As a consequence of anti-ER stress, the activation of ACE2 led to improved glucose and lipid metabolism through the IKKβ/NFκB/IRS1/Akt pathway. CONCLUSIONS: This is the first time documented that ACE2 had a notable alleviating role in ER stress-induced hepatic steatosis and glucose metabolism via the IKKβ/NFκB/IRS1/Akt-mediated pathway. This study may further provide insight into a novel underlying mechanism and a strategy for treating NAFLD.
Authors: Mir S Adil; Arti Verma; Madhuri Rudraraju; S Priya Narayanan; Payaningal R Somanath Journal: J Cell Physiol Date: 2021-02-24 Impact factor: 6.513