Dwi Setyowati Karolina, Arunmozhiarasi Armugam, Sugunavathi Sepramaniam, Sharon Li Ting Pek, Michael TK Wong, Su Chi Lim, Chee Fung Sum, Subramaniam Tavintharan and Kandiah Jeyaseelan
In obese individuals, a high efflux of glycerol from accumulated fat in adipose tissue into the liver is known to be associated with the development of type 2 diabetes. Aquaporin 9 (AQP9) is an aquaglyceroporin which serves as the primary route of hepatic glycerol uptake for gluconeogenesis. Hence, development of AQP9 blockers/regulators may be of potential benefit in controlling hyperglycaemia especially in obese and diabetic individuals. HTS13286 was recently identified as a specific AQP9 inhibitor, even so its limited solubility renders the molecule unsuitable for in vivo application. microRNAs are naturally occurring gene regulators that are often associated with various diseases. The feasibility in selective modulation of microRNAs has introduced a new paradigm for therapeutic applications. In this study, we explore the possibility of using microRNAs to regulate AQP9 expression and eventually glycerolbased gluconeogenesis. In silico prediction of microRNAs targeting the 3’ untranslated region of AQP9 was conducted using miRWalk database. Among the list of potential microRNAs, miR-22 and miR-23a were shortlisted for their high expression in liver and further confirmed to interact with AQP9 via luciferase assay. Over-expression of miR-22 or miR- 23a was able to reduce AQP9 expression (mRNA and protein) and ultimately inhibit glycerol-based gluconeogenesis in HepG2 cells. Livers of diabetic rats were also observed to exhibit an inverse correlation between miR-22, miR-23a and AQP9 expression. As negative modulators of AQP9 expression, miR-22 and miR-23a suggest a potential role in regulating glycerol entry into hepatocytes which could be beneficial in managing glycerol-dependent hyperglycaemic conditions.
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