Increased let‐7d‐5p in non‐alcoholic fatty liver promotes insulin resistance and is a potential blood biomarker for diagnosis

Abstract

AbstractBackground and AimsThe molecular mechanisms driving non‐alcoholic fatty liver disease (NAFLD) are poorly understood; however, microRNAs might play a key role in these processes. We hypothesize that let‐7d‐5p could contribute to the pathophysiology of NAFLD and serve as a potential diagnostic biomarker.MethodsWe evaluated let‐7d‐5p levels and its targets in liver biopsies from a cross‐sectional study including patients with NAFLD and healthy donors, and from a mouse model of NAFLD. Moreover, the induction of let‐7d‐5p expression by fatty acids was evaluated in vitro. Further, we overexpressed let‐7d‐5p in vitro to corroborate the results observed in vivo. Circulating let‐7d‐5p and its potential as a NAFLD biomarker was determined in isolated extracellular vesicles from human plasma by RT‐qPCR.ResultsOur results demonstrate that hepatic let‐7d‐5p was significantly up‐regulated in patients with steatosis, and this increase correlated with obesity and a decreased expression of AKT serine/threonine kinase (AKT), insulin‐like growth factor 1 (IGF1), IGF‐I receptor (IGF1R) and insulin receptor (INSR). These alterations were corroborated in a NAFLD mouse model. In vitro, fatty acids increased let‐7d‐5p expression, and its overexpression decreased AKT, IGF‐IR and IR protein expression. Furthermore, let‐7d‐5p hindered AKT phosphorylation in vitro after insulin stimulation. Finally, circulating let‐7d‐5p significantly decreased in steatosis patients and receiver operating characteristic (ROC) analyses confirmed its utility as a diagnostic biomarker.ConclusionsOur results highlight the emerging role of let‐7d‐5p as a potential therapeutic target for NAFLD since its overexpression impairs hepatic insulin signalling, and also, as a novel non‐invasive biomarker for NAFLD diagnosis.