Monocarboxylic acid transporter 2 (MCT2) transports pyruvate and lactate outside and inside of sperms, mainly as energy sources and plays roles in the regulation of spermatogenesis. We investigated the association among genetic variations in the MCT2 gene, male infertility and MCT2 expression levels in sperm. The functional and genetic significance of the intron 2 (+28201A > G, rs10506398) and 3' untranslated region (UTR) single nucleotide polymorphism (SNP) (+2626G > A, rs10506399) of MCT2 variants were investigated. Two MCT2 polymorphisms were associated with male infertility (n = 471, P < 0.05). In particular, the MCT2-3' UTR SNP (+2626 G > A) had a strong association with the oligoasthenoteratozoospermia (OAT) group. The +2626GG type had an almost 2.4-fold higher sperm count than that of the +2626AA type (+2626GG; 66 × 10 6vs +2626AA; 27 × 10 6, P < 0.0001). The MCT2-3' UTR SNP may be important for expression, as it is located at the MCT2 3' UTR. The average MCT2 protein amount in sperm of the +2626GG type was about two times higher than that of the +2626AA type. The results suggest that genetic variation in MCT2 has functional and clinical relevance with male infertility.
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