Novel Insights into circRNA Saga Coming from Spermatozoa and Epididymis of HFD Mice

Obesity and male fertility disorders

Often associated with obesity, male infertility represents a widespread condition that challenges the wellbeing of the couple. In this article, we provide a comprehensive and critical analysis of studies exploring the association between obesity and male reproductive function, to evaluate the frequency of this association, and establish the effects of increased body weight on conventional and biofunctional sperm parameters and infertility. In an attempt to find possible molecular markers of infertility in obese male patients, the numerous mechanisms responsible for infertility in overweight/obese patients are reviewed in depth. These include obesity-related functional hypogonadism, insulin resistance, hyperinsulinemia, chronic inflammation, adipokines, irisin, gut hormones, gut microbiome, and sperm transcriptome. According to meta-analytic evidence, excessive body weight negatively influences male reproductive health. This can occurr through a broad array of molecular mechanisms. Some of these are not yet fully understood and need to be further elucidated in the future. A better understanding of the effects of metabolic disorders on spermatogenesis and sperm fertilizing capacity is very useful for identifying new diagnostic markers and designing therapeutic strategies for better clinical management of male infertility.

Antioxidants positively regulate obesity dependent circRNAs - sperm quality - functional axis

Obesity is a pathophysiological condition, dependent on body fat accumulation, that progressively induces systemic oxidative stress/inflammation leading to a set of associated clinical manifestations, including male infertility. CircRNAs, covalently closed RNA molecules, are key regulators of sperm quality. Recently, we have characterized a complete profile of high-fat diet (HFD) spermatic circRNA cargo, predicting paternal circRNA dependent networks (ceRNETs), potentially involved in sperm oxidative stress and motility anomalies. In the current work, using HFD C57BL6/J male mice, orally treated with a mix of bioactive molecules (vitamin C; vitamin B12; vitamin E; selenium-L-methionine; glutathione-GSH) for 4 weeks, a reversion of HFD phenotype was observed. In addition, the functional action of the proposed formulations on circRNA biogenesis was evaluated by assessing the endogenous spermatic FUS-dependent backsplicing machinery and related circRNA cargo. After that, spermatic viability and motility were also analyzed. Paternal ceRNETs, potentially involved in oxidative stress regulation and sperm motility defects, were identified and used to suggest that the beneficial action of the food supplements here conveniently formulated on sperm motility was likely due to the recovery of circRNA profile. Such a hypothesis was, then, verified by an in vitro assay.