Oral Presentation Australian and New Zealand Obesity Society Annual Scientific Conference 2023

Identification of novel protein zc3hav1 in regulating hepatic lipid metabolism in mice  (97581)

Cooper T Bowring 1 , Stacey N Keenan 1 , Ayenachew Bezawork-Geleta 1 , Jacqueline Bayliss 1 , William De Nardo 1 , Camille Devereux 1 , Garron Dodd 1 , Matthew Watt 1
  1. Anatomy and Physiology , University of Melbourne, Melbourne, VIC, Australia

Obesity is linked to the development of non-alcoholic fatty liver disease (NAFLD). Dysregulated lipid metabolism is a hallmark of NAFLD and leads to excessive lipid deposition, liver inflammation and fibrosis.

An understudied yet important aspect of hepatic lipid metabolism is understanding how fatty acids (FA) are trafficked from their site of storage in lipid droplets (LD) to their site of oxidation within the mitochondria. However, the identity of proteins residing at LD-mitochondria contact sites remains unknown. To address this knowledge gap, we conducted a proximity labelling experiment called ‘Split-BioID’ at the LD-mitochondria interface in HepG2 cells and identified 74 proteins. One of the most abundant proteins was zinc finger CCC-H containing antiviral protein-1 (ZC3HAV1). CRISPR-Cas9 mediated deletion of ZC3HAV1 in HeLa cells reduced contact between LDs and mitochondria and FA oxidation. Thus, we hypothesized that ZC3HAV1 plays an important role in lipid metabolism and its deletion would induce hepatic steatosis and NAFLD.

Therefore, we generated hepatocyte-specific deletion of ZC3HAV1 by injecting adeno-associated virus encoding distinct guide RNAs targeting Zc3hav1 into mice expressing Cas9 in hepatocytes (Alb-Cre:lox-STOP-lox-Cas9-GFP mouse). Wildtype (WT) and ZC3HAV1 knockout (ZC3HAV1KO) mice were fed a high-fat diet for 10 weeks. Mice exhibited similar body mass and composition, whole-body substrate utilisation and energy expenditure, and glucose tolerance. ZC3HAV1KO mice were more insulin insensitive than WT mice. Using radiometric techniques in precision-cut liver slices derived from mice, we report a decrease in FA oxidation from triglycerides stored in LDs in ZC3HAV1KO compared with WT mice. There was no difference between FA uptake, storage into various lipid types or lipogenesis. Altogether, this demonstrates that ZC3HAV1 is required to facilitate oxidation of FA stored in LDs and thereby plays an important role in regulating hepatic lipid metabolism. Ongoing studies will delineate the role of ZC3HAV1 in regulating serum lipids and liver histopathology.