Myo-inositol in health and disease: its impact on semen parameters and male fertility.

BACKGROUND: Myo-inositol (cis-1,2,3,5-trans-4,6-cyclohexanehexol; MI) is the most prominent of nine inositol stereoisomers. MI, its phosphate derivatives, and associated lipids are widely found in vegetables and animal tissues and are known to participate in numerous biological processes.
OBJECTIVES: To perform a review analysis on MI presence, functions, and impact in male fertility.
MATERIALS AND METHODS: A thorough search of listed publications in PubMed on MI and its derivatives was done.
RESULTS: Published information was found and compiled on MI identification, natural dietary sources and absorption, biosynthesis, concentrations, as well as MI as its derivatives (PI, PIP, GPI, IPG) roles in several human tissues and body fluids in health and disease. A section was focused on MI presence, biosynthesis, and functions in the mammalian male genital tract and in spermatozoa, and summarized reports describing the impact of in vivo and in vitro MI supplementation on human semen quality and fertility. Studies reported a discrete improvement in sperm motility in fresh and frozen-thawed semen, and a better sperm performance in natural and assisted fertility. DISCUSSION AND
CONCLUSION: MI was reported as an effective supplement for sperm quality. In any case, several study designs lack appropriate controls or data analysis to confirm the relevance of the findings. While promising, larger prospective randomized controlled studies will be required to confirm the positive effect of MI supplementation in male infertility management. Moreover, further investigations are encouraged to unravel MI roles in sperm physiology and the underlying molecular mechanisms.