Role of the Paternal Microbiome‐Metabolome Axis in the Epigenetic Programming of Sperm

Abstract

There is growing evidence that a range of toxicants adversely affects developmental programming in sperm, which negatively influences the next generation's health and development. Alcohol consumption is socially accepted across a large percentage of the globe and will continue to be a part of society for the foreseeable future. Using a mouse model, our laboratory has identified fetal growth restriction and long-term alterations in the metabolic health of offspring sired by alcohol-exposed males. However, the mechanisms by which alcohol changes paternally-inherited epigenetic programming remain undefined. Spermatozoa require specific circulating metabolites for proper structure, function, and motility. Microbial populations within the gastrointestinal tract produce these metabolites, which then travel through the circulatory system and interact with the male reproductive tract. As alcohol is metabolized to acetate, we hypothesized that the blood serum of males consuming varying doses of ethanol (EtOH) before insemination would exhibit alterations in short-chain fatty acids (SCFA). Using a voluntary model of exposure, we exposed postnatal day 90, C57BL/6J male mice to five treatment groups: Control (water), 6% EtOH, 10% EtOH, 0.066% Sweet'N Low® Control (SC), and 0.066% Sweet'N Low® 10% EtOH (SA). The Sweet'N Low® additive is used to promote higher levels of consumption. We utilized GC-MS analysis on blood serum from each male after weeks 4 and 7 of the exposure period, then analyzed the SCFAs acetic, butyric, propanoic, and isobutyric acid. After four weeks of exposure, we identified significantly elevated acetic acid concentrations in the SA and SC males. In contrast, butyric acid blood serum concentrations in the 10% EtOH cohort were notably greater than the other four treatments. After seven weeks of alcohol exposure, only SA blood serum had a significant increase in acetic acid concentration than the other treatment groups. We followed this study with deep sequencing and informatic analysis of the gut microbiome between the treatment groups. Collectively, our data indicate that alcohol impacts the SCFA of blood serum. The analysis of the microbiome-metabolome axis of males' microbiota populations and effects in the reproductive tract are ongoing.