MicroRNAs as molecular targets of quercetin and its derivatives underlying their biological effects: A preclinical strategy

Quercetin is a well-known flavonoid naturally occurring in most of the plant foods and is often found in the human diet. It can act as a potent antioxidant and anti-inflammatory agent, and plays significant roles in the prevention of various chronic diseases. Recent findings revealed that quercetin could affect metabolic traits by regulating certain transcription factors or key proteins involved in cellular signal pathways and influencing the expression of functional genes along with related regulatory pathway(s), and that microRNAs (miRNAs) circulate in body fluids and are involved in post-transcriptional gene silencing and regulation of gene expression in various biological processes including development, proliferation, metabolism and inflammation. This article reviews the studies into the molecular pathways underlying the beneficial bioactivities of quercetin and its derivatives, and the modulatory effects of miRNAs by quercetin and its derivatives on miRNAs-mediated cellular processes. MicroRNAs as molecular targets of quercetin and its derivatives and as predictive biomarkers for early diagnosis of the outcome of quercetin-rich diets are highlighted. Current limitations and future directions of research on the impact and associated mechanism(s) of the synergies between quercetin species and other co-existing nutrients/bioactives on the expression of miRNAs as well as the roles of miRNAs in overall nutritional control are critically discussed.