Association Between Vitamin D Levels, miRNA Expression, and Sperm Parameters in Infertile Men

Abstract

Objective: To examine the impact of vitamin D levels and the miRNA profiles of miR-34b, miR-19a-3p, and miR- 122 on sperm parameters of men with male-factor infertility.

Study Design: Comparative cross-sectional study.
Place and Duration of Study: This study was conducted at the Department of Urology, Teaching Hospital of Hilla, Hilla City, Iraq, between June 2024 and August 2025.

Methods: The current case control study was conducted involving 75 infertile and 75 fertile men. Semen samples were collected through masturbation after a time of abstinence and sperm analysis was performed on computer- assisted semen analysis (CASA). Serum vitamin D levels were measured by chemiluminescence, and RT-qPCR approach was used to investigate expression profiles of sperm-born miR-34b, miR-19a-3p, and miR-122.

Results: Infertile men were presented with significantly lower semen quality, including low semen volume, reduced sperm concentration, and lower motility. Infertile men were also presented with lower levels of vitamin D compared to control, (p < 0.001). MiRNA expression revealed miR-34b was reduced in infertile men, whereas miR-19a-3p and miR-122 levels were found upregulated. Examining correlation between vitamin D and miRNA expression revealed inverse correlation with miR-19a-3p (r = –0.267, p < 0.001), while no significant relationships were observed for miR-34b or miR-122. ROC analysis displayed moderate diagnostic potential for miR-19a-3p (AUC = 0.696, p < 0.001) and miR-122 (AUC = 0.614, p = 0.015).

Conclusion: Vitamin D deficiency and dysregulation of specific sperm miRNAs are closely linked to reduced sperm motility and viability. The inverse relationship between vitamin D and miR-19a-3p indicates a regulatory function through which vitamin D may control expression of miR-19a-3p and preserve normal sperm function. These results support the use of sperm-borne miRNAs as promising biomarkers for the evaluation of male infertility.