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Visceral adipose tissue micro-RNA may contribute to the progression and pathogenesis of non-alcoholic fatty liver disease (NAFLD)

Haveesh Sharma, Michael Estep, Vikas Chandhoke, Zobair Younossi, Ancha Baranova

This is a collaborative project between

Molecular and Microbiology Department, College of Science,George Mason University, Fairfax, VA

Translational Reseach Institute, Inova Hospital, VA

MicroRNA (miRNA) are members in an ancient pedigree of regulatory molecules that have been conserved through time with near perfect fidelity. Recently, they have been discovered to play a role in the pathogenesis non-alcoholic fatty liver disease (NAFLD) and its progression to non-alcoholic steatohepatitis (NASH), a disease afflicting 8.6 million Americans. Several miRNA have been previously established to be upregulated during NASH, while other miRNA normally involved in regulation have been notably underexpressed in the wake of this disease. First transcribed as primary transcripts (pri-miRNA), these molecules are further processed and refined into the ~22 nucleotide molecules known to affect the outcome of many diseases. This study analyzed the visceral adipose tissue (VAT) of non-NASH NAFLD patients (n=12) and NASH patients (n=12) via RT-qPCR in order to determine the relative expression levels of seven pri-miRNA (pri-miR-125b-2, pri-miR-16-2, pri-miR-26a-1, pri-miR-26a-2, pri-miR-7-1, pri-miR-7-2, and pri-miR-7-3) and elements of the miRNA processing apparatus (Drosha, DGCR8, and Dicer1). The pri-miRNA expression profiles were also compared against those of their potential mature counterparts. The differential expression profiles of Dicer1, Drosha, and DGCR8 were significantly greater (p<0.05) in the NASH cohort. Of the seven pri-miRNA analyzed, the final two were below the detection threshold. Expression analysis suggest that pri-miR-125b-2, pri-miR-26-a-1, pri-miR-16-2, and pri-miR-7-1 are all upregulated during NASH pathogenesis, whereas pri-miR-26a-2 correlations suggested downregulation during NASH. Mature miRNA expression data generated by Estep, et al in a previous study was utilized in order to develop correlations between pri-miRNA and their potential mature counterparts. Pri-miR-26a-2 correlated strongly with hsa-miR-26a expression, suggesting that it matures into the latter within the VAT. Data demonstrates that while hsa-miR-7 and pri-miR-7-1 are coexpressed in VAT, their respective expression profiles do not mutually correlate with one another. The downregulation of pri-miR-26a-2, and the upregulation of pri-miR-7-1 suggest a similar fate for their repsective host genes, CTDSP2 (SCP2) and HNRNPK.