Researchers identified three amino acid metabolism–related genes that may warrant further study as diagnostic biomarkers for nonobstructive azoospermia, according to an observational bioinformatics study published in Medicine.
The researchers analyzed testicular tissue gene-expression data from men with nonobstructive azoospermia (NOA) and obstructive azoospermia (OA), a clinically important comparison because NOA diagnosis currently relies on invasive procedures and lacks reliable noninvasive molecular markers. Using the GSE9210 training data set, which included 47 NOA samples and 11 OA samples, the researchers identified 1,233 differentially expressed genes. Intersecting those genes with 2,352 amino acid metabolism–related genes yielded 115 candidate genes.
Protein-protein interaction network analysis and receiver operating characteristic (ROC) curve analysis identified AKT1, ASNS, and SHC1 as candidate biomarkers. In the GSE9210 training data set and the GSE108886 validation data set, which included 8 NOA samples and 3 OA samples, all three genes demonstrated area under the curve (AUC) values greater than 0.7.
The researchers also constructed a nomogram incorporating AKT1, ASNS, and SHC1. The model demonstrated an AUC of 0.996 in the training data set used to build the model, although the researchers noted that the findings require external validation because of the small sample size and potential for overfitting.
Reverse transcription quantitative polymerase chain reaction validation in an independent set of 5 NOA and 5 OA tissue samples showed statistically significant upregulation of AKT1 and SHC1 in patients with NOA. ASNS expression was lower in the NOA group, but the difference was not statistically significant. Given the limited RT-qPCR sample size, the findings should be considered preliminary.
Functional enrichment analyses suggested that the biomarkers may participate in pathways related to male gamete generation, sexual reproduction, chromosome organization, and DNA repair, supporting a possible role in germ cell development and spermatogenesis.
Immune infiltration analyses identified associations between the biomarkers and several immune cell populations, including T follicular helper cells, resting natural killer cells, and regulatory T cells. The findings may be relevant because immune dysregulation within the testicular microenvironment has been implicated in NOA pathophysiology.
The researchers also explored potential regulatory networks and predicted interacting compounds linked to the biomarkers. Genistein was identified as a candidate interacting compound and subsequently evaluated using molecular docking analyses, which suggested the strongest predicted binding with ASNS. Other predicted compounds, including disodium selenite and aflodac, were not evaluated further because of toxicity concerns. The computational findings do not establish biologic activity or therapeutic potential.
The study was limited by its reliance on small public gene-expression data sets, tissue-based sampling, and limited experimental validation. The findings do not yet support clinical use of the biomarkers, and larger prospective studies are needed to determine whether they could improve noninvasive diagnosis or clinical management of NOA.
The researchers reported no funding or conflicts of interest.
Source: Medicine