Abstract 4360: ALDH2 and the TGF-β/SMAD3 adaptor, Sptbn1 suppress hepatic steatosis and obesity
Authors: Rao Shuyun , Zaidi Sobia , Jogunoori Wilma , Gu Shoujun , White Jon , Mishra Bibhuti , Deng Chu-Xia , Latham Patricia , Mishra Lopa 
Published: August 2019

Background: Previously we have demonstrated that TGF-β-deficient mutants derived from the loss of Smad3 and the Smad adaptor β2SP (Sptbn1) phenocopy a human cancer stem cell syndrome, are exquisitely sensitive to alcohol, with dysregulation DNA damage repair and have raised levels of aldehyde dehydrogenase (ALDH2). Moreover, β2SP and β2SP/Smad3 mutant mice develop multiple liver abnormalities that include steatosis, chronic hepatitis, inflammation, and cancer. ALDH2 is a key intermediate enzyme for aldehyde and alcohol metabolism. We, therefore, hypothesized that disruption of TGF-β signaling combined with ALDH2 deficiency would increase the susceptibility of liver cancer.

Methods: Aldh2 knockout mice were intercrossed with Sptbn1 heterozygous knockout mice to explore the role of Aldh2 and Sptbn1 in liver steatosis and liver cancer. Conditional knockout of Sptbn1 mice was generated by the intercross of Albumin-Cre mice with mice carrying Loxp sites flanked exons of Sptbn1. Sptbn1 conditional mice were fed with high-fat diet or chow diet. Further analysis included blood lipid panel analysis and tissue profiles including western and RNA analysis, lipidomics and metabolomics analysis of liver tissues from the mutant mice and wild-type controls.

Results: Interestingly, we found that Aldh2-/-Sptbn1+/- mice on a normal diet demonstrated early signs of truncal obesity. Within 6 months of age, we observed a greater than 23% increase in body weight, with predominantly abdominal fat accumulation in Aldh2-/-Sptbn1+/- mice compared to Aldh2-/- mice or wild type (WT) mice (Aldh2-/-Sptbn1+/- vs Aldh2-/- or WT, p&lt;0.05). A marked increase in zone 3 hepatic micro and macro-steatosis with some inflammation was observed in liver tissues of mutant Aldh2-/-Sptbn1+/- mice as well as the conditional Sptbn1 knockout (Alb-Cre+Sptbn1F/+) mice in a high-fat diet. In addition to significant increased blood glucose levels in Aldh2-/-Sptbn1+/- mice compared with Aldh2-/- mice (165±23 VS 135±13, p&lt;0.05), further analysis revealed that the fatty liver phenotype accompanied with abnormal expression of genes related to glucose uptake, metabolisms and homeostasis as demonstrated by decrease of glucose transporter and increased expression of Ceramide which is known to promote insulin resistance. Moreover, we also observed disruption of lipid metabolism as demonstrated by significantly increased serum and liver triglyceride and cholesterol ester levels in Aldh2-/-Sptbn1+/- mice.

Conclusions: Our data suggest that the TGF-β pathway plays an important role in maintaining normal glucose metabolism homeostasis and patients with SPTBN1 and ALDH2 defects may have increased susceptibility to obesity as well as fatty liver (NASH), and cancer.

Citation Format: Shuyun Rao, Sobia Zaidi, Wilma Jogunoori, Shoujun Gu, Jon White, Bibhuti Mishra, Chu-Xia Deng, Patricia Latham, Lopa Mishra. ALDH2 and the TGF-β/SMAD3 adaptor, Sptbn1 suppress hepatic steatosis and obesity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4360.