Polysaccharides are complex compounds including different carbohydrates with various bioactivities and have attracted more concerns in recent years [1, 2]. Numerous studies have revealed that polysaccharides have the ability to regulate the immunity of intestinal mucosal, alter the composition of gut microbiota, inhibit cancer cell proliferation and improve spermatogenesis [3–10]. Polysaccharides can work as health care products because of these biological functions in regulating body health. Chestnut polysaccharides (CPs) are bioactive substances with multiple nutrients extracted from the chestnut fruits and possesses several health benefits. CPs are compounds containing many monosaccharides in different proportions including glucose, galactose, arabinose, mannose, xylose, rhamnose, and fructose [11, 12].
The link between gut microorganism and the reproductive system has attracted the attention of scientists in recent years. Studies have demonstrated that changes in the gut microbiota were related to body health maintenance because the microbiota formed a network regulating the immune system homeostasis, the metabolome, and the reproductive system [13–22]. So, bacteria derived from the gut can help us to understand the health status of an individual. It was revealed that gut microbiota could act as protectors or invaders in the female reproductive system [23, 24]. There are many studies about the roles of gut microbe disturbance in inducing the polycystic ovary syndrome (PCOS) pathogenesis. Researchers have found that the gut bacteria of healthy women differed from those of patients with PCOS [25–27], including changes in bacterial composition or global diversity (α-diversity or β-diversity) [25, 28–32]. The aberrant behavior of gut microbes also disrupted normal physiological process in causing the reproductive problem in the host such as gestational diabetes mellitus (GDM) and early preeclampsia (PE) [24, 33, 34]. The researchers also found that gut microbiota was not only involved in inducing of reproductive problems, but also protected against reproductive problems in PCOS mice by transplanting microbes from healthy bodies [23]. The study of gut microbiota on male reproductive system was also conducted by researchers. Ding et al. revealed the mechanism of gut microbiota facilitating male reproduction, and that gut microbiota altered the expression of important genes in the testis [35]. Recent studies also suggested that the gut microbiota changes could rescue male infertility following administration of alginate oligosaccharides (AOS). The authors explored the sperm quality and spermatogenesis in AOS-dosed animals after fecal microbiota transplantation into Busulfan-treated mice and found that healthy-body microbiota transplantation could improve spermatogenesis by altering bacterial species [36, 37].
Studies have shown that CPs also played the profound role in inhibiting tyrosinase, oxidative activity and benefiting the spermatogenesis of mice which exposed to busulfan by improving the expression of important genes [11, 12, 38], but whether the rescue process is caused by the gut microbiota is unknown. 16S rRNA sequencing is a method to detect microbiota landscape, and bioinformatic analysis can indicate changes in microbiota and predict functional pathways of microbiota. In present study, 16S rRNA sequencing technology was used to do comprehensive research on the combined effects of CPs and gut microbes in promoting spermatogenesis in vivo (Figure S1). The aim of this research was to investigate the mechanism of improving spermatogenesis via CPs and its relevance at the gut microbial level.