Jujuboside A through YY1/CYP2E1 signaling alleviated type 2 diabetes-associated fatty liver disease by ameliorating hepatic lipid accumulation, inflammation, and oxidative stress

Non-alcoholic fatty liver disease (NAFLD) was a chronic complication of type 2 diabetes mellitus (T2DM), and this comorbid disease lacked therapeutic drugs. Semen Ziziphi Spinosae (SZS) was the seed of Ziziphus jujuba var. Spinosa (Bunge) Hu ex H.F. Chow, and it could alleviate the symptoms of T2DM patients. As a triterpene saponin, Jujuboside A (Ju A) was the main active substance isolated from SZS and could improve hyperglycemia of diabetic mice. However, it was still unknown whether Ju A has protective effects on T2DM-associated NAFLD. Our study showed that Ju A attenuated T2DM-associated liver damage by alleviating hepatic lipid accumulation, inflammatory response, and oxidative stress in the liver of db/db mice, and high glucose (HG) and free fatty acid (FFA) co-stimulated human hepatocellular carcinomas (HepG2) cells. Along with the improved hyperglycemia and liver injury, Ju A restrained Yin Yang 1 (YY1)/cytochrome P450 2E1 (CYP2E1) signaling in vivo and in vitro. YY1 overexpression intercepted the protective effects of Ju A on T2DM-induced liver injury via promoting hepatic lipid accumulation, inflammatory response, and oxidative stress. While, the blocking effect of YY1 overexpression on Ju A's hepatoprotective effect was counteracted by further treatment of CYP2E1 specific inhibitor diethyldithiocarbamate (DDC) in vitro. In-depth mechanism research showed that Ju A through YY1/CYP2E1 signaling promoted hepatic fatty acid beta-oxidation, and inhibited inflammatory response and oxidative stress by activating peroxisome proliferator-activated receptor alpha (PPAR alpha), leading to the improvement of T2DMassociated NAFLD. Ju A might be a potential agent in the treatment and health care of T2DM-associated liver disease, especially NAFLD.