Senescence and declining reproductive potential: Insight into molecular mechanisms through testicular metabolomics

Aging is associated with structural and functional changes in the organism that result in the declining of its functioning. Postponed parenthood has renewed the interest in age-related decline of testicular function and male fertility. Still, little is known about the molecular mechanisms associated with testicular senescence and related decline of fertility. Here we sought to elucidate the molecular basis of metabolic changes associated with testicular aging and reproductive potential using an NMR-based metabolomics approach. Testicular metabolic profiles of rats from 3 to 24 months-of-age were analysed. An age-associated decrease in most antioxidant metabolites, like betaine, creatine and glutathione was observed. Amino acid content changed as early as 6 months-of-age, with an increase in branched chain and aromatic amino acids, accompanied by decrease of nucleotide synthesis (IMP, CMP, ATP). Testicular content of phospholipid precursors (choline, ethanolamine, myo-inositol, glycerol) increased with advanced age and was accompanied by a decrease in the levels of their phosphorylated products, suggesting compromised spermatogenesis. This is the first metabolomics study of testicular tissue of aged rats and we were able to identify metabolites associated with reproductive maturity from the onset to senescence. Our results provide evidence for an influence of aging on global testicular metabolome, as early as 6 months-of-age, with a profound alteration of several key metabolic pathways associated with the male reproductive potential.