Dysregulated sphingolipid metabolism contributes to NASH-HCC disease progression

Abstract

Background: Nonalcoholic fatty liver disease (NAFLD) is the fastest-rising cause of end-stage liver disease for liver transplantation. The underlying mechanisms of NAFLD disease progression from nonalcoholic steatohepatitis (NASH) to hepatocellular carcinoma (HCC) remain unclear. It has been well-accepted that inflammation and dysregulation of sphingolipid metabolism are two important contributors to NASH progression. Recent advances in gene profiling technologies have significantly improved the current understanding of NASH-HCC pathogenesis. However, the key pathway changes underlying liver fibrosis and dysregulation of sphingolipid metabolism haven’t been fully elucidated and are the focus of this study. Methods: DIMOND NASH mouse model (C57BL/6J and 129S1/SvlmJ mixed background) was used in this study. Male mice (21 to 24-week-old) were fed with WDSW (Western diet, Harlan, TD88137, and a high fructose-glucose solution, 23.1g/L D-fructose plus 18.9g/L D-glucose) or standard chow diet ad libitum for six months or one year. At the end of the study, liver tissues were harvested for total RNA isolation using Trizol. Gene profiles were analyzed using the NanoString nCounter® Gene Expression Fibrosis V2 panel with sphingolipid metabolism pathways. The differentially expressed genes (DEGs) between groups were determined using Rosalind. QIAGEN Ingenuity Pathway Analysis (IPA) was used to analyze the DEGs. Human HCC patient data were downloaded from The Cancer Genome Atlas Program (TCGA). The sphingolipid profiles in the serum and liver were determined using LC-MS/MS. Results: All the mice developed NASH and HCC after feeding with WDSW for 6 months and 1 year, respectively. Bioinformatic analysis identified 191 DEGs in the NASH group and 250 DEGs in HCC group compared to the corresponding controls. The IPA analysis revealed that the major pathways related to inflammation and fibrosis were upregulated in both NASH and HCC mice. The expression levels of key genes related to ceramide synthesis and metabolism [serine palmitoyltransferase long chain base subunit 2 (Sptlc2), ceramide synthase 6 (Cers6), N-acylsphingosine amidohydrolase 2 (Asah2)] and sphingosine-1-phosphate receptor 2 (S1PR2) were significantly upregulated in NASH mice. In HCC group, Cers5, Cers6, sphingomyelin synthase 1 (Sgms1), Asah1, and S1PR3 were significantly increased. The expression levels of sphingosine kinase 2 and S1P lyase 1 were decreased both in NASH and HCC. Analysis of the TCGA data set showed that CERS5, CERS6, SPTLC2, ASAH1 and SGMS1 were highly expressed in HCC compared to healthy controls. The LC-MS/MS data also showed significant changes in sphingolipid profiles in serum and liver NASH and HCC. Conclusion: Our study suggests that dysregulated sphingolipid metabolism is associated with NASH and HCC disease progression. Further validation and research are needed for the potential application of sphingolipid profiles as diagnostic or prognostic markers in the clinic. This study was supported by VA Merit Award I01BX004033; Research Career Scientist Award (IK6BX004477); VA ShEEP grants (1IS1BX005517-01 and 1 IS1 BX004777-01) National Institutes of Health Grant R01 DK104893, R01DK-057543 and R21 AA026629-01. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.