Taurine content in human semen was reported to be from 319 to 1590 μmol/L and was maintained at a 10 times higher level than in the blood ( 27). Cumulative data show that taurine is much higher than other amino acids in semen of humans, hamsters, bulls, boars, dogs, pigs and guinea pigs ( 14, 23, 24, 27). In male reproductive organs, taurine has been detected by immunohistochemistry in Leydig cells of the testis, vascular endothelial cells, and other Leydig cells, as well as epithelial cells of the efferent ducts ( 26). Taurine exists in high concentrations in reproductive tissues and interstitial fluids of both male and female mammals, such as uterine fluid ( 19) and oviduct ( 20, 21) of females, semens ( 22– 24) and epididymal tissues ( 24, 25) of males. Here, we review the role of taurine in maintaining physiological function of the male reproductive system, inhibiting pathological developments and alleviating toxic damage, hoping it provides ideas for future research. These results indicated that taurine may be beneficial to the male reproductive system. Additionally, further studies have found that taurine has protective effects on reproductive toxicity induced by heavy metals or some drugs ( 13, 18). Secondly, taurine may also act as a capacitating agent ( 14, 15), as well as a membrane-stabilized factor ( 16) and sperm motility factor ( 17). First, taurine is concentrated in the mitochondria of various cells ( 11), which can be used as an antioxidant to prevent oxidative stress in testicular tissue by protecting mitochondrial structure and functional integrity ( 12), and improve the sperm viability and motility ( 13). Taurine, as a simple but unique amino acid, has a wide range of physiological functions in the male reproductive system. Studies have shown that CSD mRNA and protein are expressed in vas deferens, epididymis and testis, especially in Leydig cells of testis ( 10). Cysteine sulfinate decarboxylase (CSD) is a key enzyme in taurine biosynthesis pathway ( 9). Taurine has been proved to be biosynthesized in the reproductive system of male animals. Therefore, taurine treatment is beneficial to various pathologies. In addition, dietary taurine deficiency in species with low taurine biosynthesis rate (such as cats and foxes) can lead to many diseases, such as retinal degeneration ( 5), dilated cardiomyopathy ( 6), immune dysfunction ( 7) and reproductive defects ( 8).

On the other hand, dietary taurine is mainly obtained from meat, seafood, or energy drinks ( 3, 4). Taurine is mainly synthesized by methionine and cysteine in liver, and its synthesis ability is limited ( 2). The sources of taurine in the body are biosynthesis and dietary intake. Although taurine is not involved in the synthesis and metabolism of protein, as a functional component, it is involved in a variety of physiological functions, including bile formation in the liver, modulation of calcium flow, osmoregulation, neurotransmitter or neuromodulator, antiarrhythmic activity, etc. Taurine is a sulfur-containing nonprotein amino acid that has been found to be one of the most abundant amino acids in mammalian plasma and tissues. Therefore, this article reviewed the protective effect of taurine on male reproductive function and its detailed mechanism, in order to provide reference for further research and clinical application. Related mechanisms include reduced oxidative stress, increased antioxidant capacity, inhibited inflammation and apoptosis, restored the secretory activity of the HPT axis, reduced chromosomal variation, enhanced sperm mitochondrial energy metabolism, cell membrane stabilization effect, etc. In addition, taurine acts as a protective agent against toxic damage to the male reproductive system by exogenous substances (e.g., therapeutic drugs, environmental pollutants, radiation). In pathology, taurine supplement may be beneficial to alleviate pathological damage of male reproductive system, including oxidative damage of sperm preservation in vitro, testicular reperfusion injury and diabetes -induced reproductive complications. In physiology, taurine can promote the endocrine function of the hypothalamus-pituitary-testis (HPT) axis, testicular tissue development, spermatogenesis and maturation, delay the aging of testicular structure and function, maintain the homeostasis of the testicular environment, and enhance sexual ability. Recently, accumulating data showed that taurine has a potential protective effect on reproductive function of male animals. Taurine has been proved to be synthesized and abundant in male reproductive organs. Taurine, a sulfur-containing amino acid, has a wide range of biological effects, such as bile salt formation, osmotic regulation, oxidative stress inhibition, immunomodulation and neuromodulation.

Taurine bull sperm