Expression analysis of mitophagy indicator AMBRA1 in a rat model of fatty liver

Abstract

The incidence of nonalcoholic fatty liver disease (NAFLD) is on the rise worldwide. The risk of some of patients progressing to steatohepatitis and then to cirrhosis and hepatocellular carcinoma is a concern, and the elucidation of the pathogenesis of the disease is an important issue to be addressed. In this study, we focused on mitophagy (mitochondria-selective autophagy) and determined the relationship between hepatic precancerous foci and mitophagy in high-fat diet (HFD)-fed rats using AMBRA1, a mitophagy indicator, using flutamide (FL), an antineoplastic drug that shows mitochondrial toxicity. The rats were divided into a basal diet group and a HFD group, and a portion of each group was mixed with FL (500 ppm, 17~23 mg/kg) in feed. The NAFLD activity score was significantly increased in the HFD group and it was aggravated by FL administration. The number of GST-P- positive foci was significantly increased by HFD feeding alone or in combination with FL. AMBRA1-positive granules were observed in the cytoplasm of hepatocytes surrounding foci, and its expression tended to decrease after FL administration. AMBRA1-negative/weakly positive and strong positive responses were observed in the foci, and the area of negative/weakly positive foci was significantly increased by HFD feeding, but this was not affected by FL. These results indicated that AMBRA1 was expressed in the surrounding hepatocytes, suggesting mitophagy suppression, but in foci where its expression was reduced by HFD feeding, it enhanced foci by induction of mitophagy.