Interaction between Host and Microbes in the Semen of Patients with Idiopathic Nonobstructive Azoospermia

Abstract

Men with nonobstructive azoospermia (NOA) face the dual problems of low sperm count and low sperm quality. Most men with NOA without a clear cause are classified as having idiopathic NOA (iNOA). Previous studies found that microbes exist in semen, and the semen microbes of NOA men are different from those of normal men. However, the relevant mechanism is not clear. In this study, we answered the three questions of "who is there," "what is it doing," and "who is doing it" by combining 16s rRNA, nontargeted metabolome detection and metabolite traceability analysis. We found that the composition and interaction of seminal plasma microbes in the iNOA group changed. Metabolite traceability analysis and metabolic pathway analysis revealed that microbial abnormalities in the NOA group were closely related to the decrease of microbial degradation of toluene and the increase of metabolism of fructose or mannose. In addition, the metabolic relationship between microbes and the host in male semen in iNOA revealed that such microbes can produce harmful metabolites that affect sperm quality, the microbes compete with sperm for essential nutrients, and their presence reduces sperm production of essential nutrients. IMPORTANCE Idiopathic nonobstructive azoospermia is one of the great challenges in assisted reproductive therapy. Although microdissection testicular sperm extraction technology is currently available, many men with iNOA still face the problem of poor sperm retrieval and poor sperm quality. The role of seminal plasma microbes in male disease has been continuously investigated since semen was demonstrated to harbor commensal microbes. To our knowledge, this is the first detailed description of the microbe-host relationship in iNOA semen. This study is an important complement to research on the treatment and etiology of iNOA and the rationale for our ongoing research.

Keywords: assisted reproductive technology; idiopathic nonobstructive azoospermia; infertility; metabolome; seminal microbiota; sperm.

FIG 1

Composition and linkages of the semen microbiota. (A) Boxplots comparing the Shannon index α-diversity of microbial communities in NOA and CON groups. (B) Principal-components analysis plots of β-diversity in the two groups. (C) Stacked plot of genus composition of NOA group, CON group, and negative-control group. (D) The co-occurrence network of the two groups of microbiota suggested that the relationship between the two groups of genera had changed.

FIG 2

Functional alterations and indicator genera of the microbiota. (A) Indicator genus analysis for both groups. (B to D) Difference analyses of KEGG orthology (B), level 3 KEGG pathway (C), and clusters of orthologous groups (D) between the NOA group and CON group.

FIG 3

Metabolite composition and traceability analysis. (A) Compositional patterns of metabolites in NOA group and CON group. (B) Heatmap of differential metabolites. (C) Metabolite source statistics. (D) MEPA enrichment statistics. (E) MEPA of metabolites from various sources.

FIG 4

Integrative analysis of metabolites and bacteria. (A) Microbial-derived metabolite network. (B) Host and microbial shared metabolite networks. The diamond and dot shapes represent the relevant metabolites and microorganisms, respectively. (C and D) BIO-Sankey (C) and STA-Sankey (D) network diagrams of the glycerophospholipid metabolism pathway (GenBank accession number R02746).