Characterizing semen abnormality male infertility using non-targeted blood plasma metabolomics

Semen abnormality (SA) male infertility has become a worldwide reproductive health problem. The invasive tests (e.g., testicular biopsy) and labor-intensive methods of semen collection severely inhibit diagnosis of male infertility. In addition, the pathogenesis and biological interpretation of male infertility are still obscure. In this report, a total of 84 semen abnormality (SA) patients, diagnosed as teratozoospermia (TE, n = 21), asthenozoospermia (AS, n = 23), oligozoospermia (OL, n = 20), azoospermia (AZ, n = 20), and age-matched healthy controls (HC, n = 29) were analyzed by GC-MS for discrimination analysis and discovery of potential biomarkers. Twenty-three biomarkers were obtained by multivariate statistical method (partial least squares-discriminant analysis, PLS-DA) and univariate statistical method (analysis of variance, ANOVA) with comparisons of TE versus HC, AS versus HC, OL versus HC and AZ versus HC. Based on those biomarkers, the most relevant pathways were mainly associated with the metabolism of carbohydrates, amino acids, and lipids. The principal metabolic alternations in SA male infertility included increased levels of energy-related metabolisms, such as tricarboxylic acid cycle, pyruvate metabolism, glyoxylate and dicarboxylate metabolism, glycine, serine, threonine metabolism and saturated fatty acid metabolism. Furthermore, increased levels of glutathione metabolism were related to oxidative stress. Finally, decreased levels of arginine and proline metabolism and inositol phosphate metabolism were observed. In conclusion, blood plasma metabolomics is powerful for characterizing metabolic disturbances in SA male infertility. From metabolic pathway analysis, energy production, oxidation stress and the released enzyme during spermatogenesis take the primary responsibilities for SA male infertility.

精液异常（Semen abnormality, SA）相关性男性不育已成为全球性生殖健康难题。侵入性检查（如睾丸活检（testicular biopsy））及劳动密集型精液采集方法严重阻碍了男性不育的临床诊断。此外，男性不育的发病机制与生物学阐释仍尚不明确。本研究共纳入84例精液异常（SA）患者，分别确诊为畸精症（teratozoospermia, TE，n=21）、弱精症（asthenozoospermia, AS，n=23）、少精症（oligozoospermia, OL，n=20）、无精症（azoospermia, AZ，n=20），并设置29例年龄匹配的健康对照（healthy controls, HC）。所有样本均采用气相色谱-质谱联用（gas chromatography-mass spectrometry, GC-MS）技术进行分析，以开展判别分析并筛选潜在生物标志物。通过多变量统计方法（偏最小二乘判别分析，partial least squares-discriminant analysis, PLS-DA）与单变量统计方法（方差分析，analysis of variance, ANOVA），针对TE与HC、AS与HC、OL与HC及AZ与HC四组对照分别进行比较，最终筛选得到23个生物标志物。基于上述生物标志物，显著富集的代谢通路主要涉及糖类、氨基酸及脂类代谢。精液异常性男性不育的核心代谢改变表现为能量相关代谢通路活性上调，包括三羧酸循环、丙酮酸代谢、乙醛酸与二羧酸代谢、甘氨酸-丝氨酸-苏氨酸代谢以及饱和脂肪酸代谢。此外，谷胱甘肽代谢通路上调与氧化应激密切相关。最终观察到精氨酸-脯氨酸代谢与肌醇磷酸代谢通路活性降低。综上，血浆代谢组学可有效表征精液异常性男性不育的代谢紊乱特征。通过代谢通路分析可知，能量生成、氧化应激及精子发生过程中释放的酶类是精液异常性男性不育的主要致病因素。