The risk of developing metabolic diseases is conferred by genetic predisposition from risk genes and by environmental exposures that can manifest in epigenetic changes. The global rise in obesity and type II diabetes has motivated a search for the epigenetic factors underlying these diseases. The possibility of transgenerational inheritance of epigenetic changes raises questions regarding how spermatozoa transmit acquired epigenetic changes that affect the metabolic health of the next generation. The purpose of this review is to describe current key literature concerning small non-coding RNA (sncRNA), specifically (1) the effects of high-fat or low-protein diets on sncRNA presence in spermatozoa; (2) sncRNA transmission from father to offspring; and (3) the functional effects of inherited sncRNA on offspring metabolic phenotype. Current research has identified alterations in the content of sncRNA subtypes, including microRNA (miRNA), Piwi-interacting RNA (piRNA), and transferRNA (tRNA)-derived small non-coding RNA (tsncRNA), in spermatozoa in response to both high-fat diets and low-protein diets. The altered content of spermatozoa sncRNA due to high-fat diets was associated with a changed phenotype in offspring, with offspring displaying insulin resistance, altered body weight, and glucose intolerance. The altered sncRNA content of spermatozoa due to a low-protein diet was associated with altered levels of lipid metabolites in offspring and decreased expression of specific genes starting in two-cell embryos. The current literature suggests that sncRNAs mediate paternal intergenerational epigenetic inheritance and thus has a direct functional importance, as well as possess biomarker potential, for metabolic diseases. Further research is urgently required to identify the specific sncRNAs with the most profound impacts.
Keywords: Epigenetics; Epigenome; Epitranscriptome; Phenotype inheritance; Small non-coding RNA.