S. Georgiou, V. Pantazopoulou, Ema Anastasiadou
MicroRNAs (miRNAsMicroRNAs) is a unique class of small, non-coding RNAs that dictate the fine tuning of fundamental biological processes such as cell cycle, cell differentiation, proliferation, and apoptosis. They coordinate hepatic growth and pattern formation during embryonic development, mediating control and maintenance of hepatic metabolic homeostasis, linking the gut microbiome and the intestinal barrier integrity to the liver condition in the adult healthy liver. Tissue-specific miRNAs dysregulation contributes to fibrogenesis, lipid and glucose metabolic abnormalities, altered bacterial flora and bile acids turnover, leading to fatty liver disease onset and progression, coupled with alterations in gut microbiota and intense inflammatory response. Circulating miRNAs communicate messages between close or distant cells and/or tissues and can demonstrate unique expression profile patterns. In the liver-gut crosstalk, miR-122 is the most profound paradigm of the fine-tuned regulatory mechanisms exerted on the apoptotic, inflammatory, lipogenetic, hypoxic, and carcinogenetic signaling pathways circuit. The altered expression of miRNAs could provide a powerful implementation to distinguish different types and stages of diseases and strongly advocates miRNA profiling as a viable alternate means for diagnosis and patient prognosis. Finally, miRNAs are a realistic and promising prospect for novel therapies as currently a handful of clinical studies have being conducted to exploit their therapeutic value in gut-liver axis pathological conditions. This chapter summarizes the current understanding of miRNAs’ expression and interactions in the gut and liver axis, their contribution in normal and pathological conditions and their potential value as diagnostic/prognostic biomarkers and therapeutic targets.