Long non‐coding RNA H19 serves as a lipid sensor to reprogram hepatic lipid and glucose homeostasis by interaction with RNA binding protein PTBP1
Authors: Yang Zhihong , Liu Chune , Wu Jianguo , Shin Dong‐Ju , Tran Melanie , Wang Li 
Published: June 2021

Purpose

Long non‐coding RNA (lncRNA) H19 is a maternally expressed and paternally imprinted gene, which is mainly expressed in embryonic liver but diminished in adult liver. Intriguingly, H19 is reactivated in human chronic liver diseases, implicating an important regulatory role in hepatic function. This study aims at elucidating the novel function of H19 in hepatic lipid and glucose homeostasis.

Methods

C57BL/6J male mice, at 6 weeks of age, were injected with AAV8‐Null or AAV8‐H19 virus driven by a thyroxine binding globulin (TBG) promoter for hepatic‐specific overexpression. Due to the paternal imprint of H19, we used maternal H19‐deleted mice as H19 knock out (H19KO) and paternal H19‐deleted mice as wild type control (WT). WT and H19KO mice were fed a high fat and high sugar (HFHS) diet to induce steatosis. RNA pull down and LC/MS were used to identify H19‐interacting proteins. Metabolomics and lipidomics analyses were performed to identify metabolites that were altered in response to H19 overexpression. Other methods: qPCR, Western blots, H&E and Oil O Red staining.

Results

LncRNA H19 expression was markedly upregulated in hepatocytes treated with fatty acids and in livers of mice fed the HFHS diet. Prolonged hepatic overexpression of H19 promoted steatosis and insulin resistance, which was accompanied with significantly increased liver weight and TG content, as well as serum glucose and insulin levels under fasting conditions. Consistently, the expression of SREBP1, a key de novo lipogenic transcription factor, and its targets FASN and ACC, were coordinately elevated, whereas PPARα protein was downregulated. In addition, metabolomics analysis revealed altered metabolites in H19 overexpressed mice in glucose metabolic pathways. Among them, glucose‐1‐phosphate (G1P) and glucose‐6‐phosphate (G6P) were most highly enriched in H19 vs. Null mice under fast conditions. Furthermore, lipidomics analysis identified that majority of individual TG lipid species were highly upregulated in H19 mice. Mechanistically, RNA binding protein polypyrimidine tract‐binding protein 1 (PTBP1) was identified to interact with H19RNA by LC/MS after RNA pull down assay. The interaction of H19 enhanced PTBP1's binding to SREBP1 mRNA and protein, which in turn increased SREBP1 protein cleavage, facilitated its nuclear translocation and transcriptional activity by fasting. Deletion of H19 (H19KO) prevented the mice from developing hepatic steatosis by a high‐fat high sucrose (HFHS)‐diet. In agreement with this observation, hepatic TG content, as well as the protein levels of SREBP1, PTBP1, and FASN, were concurrently diminished in H19KO vs. WT mice. Knockdown of PTBP1 prevented H19 and HFHS‐diet induced steatosis. Both H19RNA and PTBP1 protein were highly elevated in human NASH/NAFLD liver specimens.

Conclusions

These results unveiled a novel H19/PTBP1/SREBP1 feedforward amplifying signaling pathway to exacerbate the development of fatty liver disease by pushing the liver into a “pseudo fed” state in response to fasting.

Support or Funding Information

NIH R01DK104656, R01DK080440, R01ES025909, R21AA022482, R21AA024935, VA Merit Award 1I01BX002634, R01AA026322.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.