Comparative proteomic study reveals 17β-HSD13 as a pathogenic protein in nonalcoholic fatty liver disease

Abstract

Nonalcoholic fatty liver disease (NAFLD) is characterized by a massive accumulation of lipid droplets (LDs). The aim of this study was to determine the function of 17β-hydroxysteroid dehydrogenase-13 (17β-HSD13), one of our newly identified LD-associated proteins in human subjects with normal liver histology and simple steatosis, in NAFLD development. LDs were isolated from 21 human liver biopsies, including 9 cases with normal liver histology (group 1) and 12 cases with simple steatosis (group 2). A complete set of LD-associated proteins from three liver samples of group 1 or group 2 were determined by 2D LC-MS/MS. By comparing the LD-associated protein profiles between subjects with or without NAFLD, 54 up-regulated and 35 down-regulated LD-associated proteins were found in NAFLD patients. Among them, 17β-HSD13 represents a previously unidentified LD-associated protein with a significant up-regulation in NAFLD. Because the 17β-HSD family plays an important role in lipid metabolism, 17β-HSD13 was selected for validating the proteomic findings and exploring its role in the pathogenesis of NAFLD. Increased hepatic 17β-HSD13 and its LD surface location were confirmed in db/db (diabetic) and high-fat diet-fed mice. Adenovirusmediated hepatic overexpression of human 17β-HSD13 induced a fatty liver phenotype in C57BL/6 mice, with a significant increase in mature sterol regulatory element-binding protein 1 and fatty acid synthase levels. The present study reports an extensive set of human liver LD proteins and an array of proteins differentially expressed in human NAFLD. We also identified 17β-HSD13 as a pathogenic protein in the development of NAFLD.lipogenesis | SCDR9 | HSDI7β13

Quantitative analysis of the murine lipid droplet-associated proteome during diet-induced hepatic steatosis

“…From this analysis, we determined that 671 out of 1,520 proteins identifi ed have been reported in previous mammalian LD proteomics studies. In addition, 72 and 95% of the proteins found in previous studies on human ( 14 ) and mouse ( 15 ) hepatic LDs, respectively, were identifi ed in our analysis (supplementary Table 1). Using confocal microscopy, we show that three of these proteins, RPLP0, GPI, and ME1, show partial colocalization with the LD marker protein, PLIN2, in mouse liver tissue sections (supplementary Fig.…”

“…However, the peroxisomal marker protein, catalase, was not depleted in the LD fraction. Although the LD fraction is largely free of contaminant proteins, the sucrose centrifugation method to isolate LD does yield some contaminant proteins, as has been reported in other LD proteomic studies (14)(15)(16).…”

“…Of the proteins that were increased, eight were also increased on LDs in humans with NAFLD ( Table 1 , supplementary Table 1) ( 14 ). IPA was used to identify biological function category enrichment ( Fig.…”

“…The nucleus was ( 12,13 ). Recently, the human hepatic LD proteome has been described for the fi rst time in NAFLD subjects ( 14 ). A few studies have examined the murine hepatic LD proteome ( 11,15 ); however, changes in the LD proteome have not been quantifi ed in a chronic animal model of steatosis.…”

The why, when and how of lipid droplet diversity

“…In terms of the lipid-dropletassociated proteins, a core set of about 50 proteins has been found to decorate lipid droplets in various cellular systems (reviewed in Hodges and Wu, 2010). However, a diverse and large number of additional proteins has been identified across many studies (a selection of studies is given in Beilstein et al, 2013;Beller et al, 2006;Cermelli et al, 2006;Chen et al, 2016;Currie et al, 2014;Dahlhoff et al, 2015;Ivashov et al, 2013;Khan et al, 2015;Khor et al, 2014;Krahmer et al, 2013;Li et al, 2016;Na et al, 2013;Schmidt et al, 2013;Su et al, 2014;Zhang et al, 2011;Zhu et al, 2015), suggesting a significant amount of variability in terms of the lipid droplet protein composition between lipid droplets isolated from different cell types.…”