Metabolic and transcriptional changes in seminal plasma of asthenozoospermia patients

Abstract

This study was designed to investigate the metabolic and transcriptional alterations in seminal fluid caused by asthenozoospermia (AS). To address these issues, a method of metabonomics based on ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) and real‐time quantitative PCR (RT‐qPCR) was performed to identify some crucial biomarkers and transcription levels of the enzymes in seminal fluid. Seminal fluid samples were collected from 87 AS patients and 73 healthy males with normozoospermia. The quantitative analysis by UPLC–MS/MS showed that 19 metabolites in seminal plasma were associated with AS, and they were involved in several metabolic pathways, such as energy metabolism, purine metabolism, methionine cycle, and branched chain amino acid metabolism. Among these metabolites, the levels of citric acid, malic acid, succinic acid, and pyruvic acid, which are related to energy metabolism, were collectively reduced in the AS group, whereas the lactic acid level was enhanced. These results indicated that lesser energy source (adenosine triphosphate) was produced through the anaerobic glycolysis pathway rather than via aerobic catabolism of suger and tricarboxylic acid cycle, resulting in reduced power of sperms. Meanwhile, partial least squares discriminant analysis showed significant differences in metabolic profiles between the AS and control groups. In addition, RT‐qPCR results revealed that the expression levels of four genes encoding fructokinase citrate synthase, succinate dehydrogenase, and spermine synthase, which were related to energy metabolism, were decreased in the AS group. The 23 descriptors with differential expression in AS may be valuable for the diagnosis and sequential study on AS. These results will help highlight the role of sperm inactivity in AS pathogenesis.

Metabolomic signature of the seminal plasma in men with severe oligoasthenospermia

“…On the other hand, we noted a significant decrease in six amino acids (glutamate, aspartate, methionine, tryptophan, proline, and alanine) in men with SOA compared to controls. Previous metabolomic studies have also reported a significant decrease in various amino acids, including the ones we identified, in the seminal plasma of men with male factor infertility 12,43 . Among these amino acids, glutamate is the most abundant in the seminal plasma, and its concentration is correlated with the sperm concentration, 31 whereas aspartate is correlated with the number and motility of the sperm 16 .…”

“…Previous metabolomic studies have also reported a significant decrease in various amino acids, including the ones we identified, in the seminal plasma of men with male factor infertility. 12,43 Among these amino acids, glutamate is the most abundant in the seminal plasma, and its concentration is correlated with the sperm concentration, 31 whereas aspartate is correlated with the number and motility of the sperm. 16 Both these amino acids have been repeatedly shown to be decreased in men with male factor infertility.…”

“…However, there is a large heterogeneity in the methods used, the populations included, and the results reported, and no clear conclusion has been made so far. [7][8][9][10][11][12][13][14][15][16] Moreover, the majority of these studies used the World Health Organization (WHO) reference values for sperm characteristics. 17 The WHO classification has important clinical implications, but has some limits, in particular its low predictive value for spontaneous pregnancies.…”

“…It has recently been used in the analysis of the seminal fluid in men with male factor infertility. However, there is a large heterogeneity in the methods used, the populations included, and the results reported, and no clear conclusion has been made so far 7‐16 . Moreover, the majority of these studies used the World Health Organization (WHO) reference values for sperm characteristics 17 .…”

Assessment of Blood Plasma Free-amino Acid Levels in Infertile Men

“…Several studies have shown the important roles of the metabolic pathways involving AAs in the regulation of parameters associated with semen quality (8)(9)(10). For example, metabolic disorders involving AAs are thought to be involved in the structural and functional alterations of spermatozoa in men with severe oligoasthenospermia (8).…”