Background: Studies have shown that the amount of protein in the diet affects the hypothalamic-pituitary-testis axis and sub-optimal quantity reduces male fertility potential in both animals and humans. However, individual research reports on the factors associated with male infertility are collectively uncharacterized. Aim: We systematically reviewed, and meta-analysed animal (rats) studies on the effect of low protein diet on factors associated with male infertility. Methods: PubMed Central, EMBASE and Scopus databases were searched from inception to 30 March 2019 for the study concepts and related keywords in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Data on the outcome measures were extracted and pooled across trials using random-effects model and expressed as mean differences (MD) at a 95% confidence interval (CI). Results: Twelve trials identified from 3327 studies, met our inclusion criteria in the comparison of a low protein diet (2–10% protein) vs control protein diet (17–23% protein). The results showed that a low protein diet caused a significant reduction in the body weight ( P = 0.0001) testis weight ( P = 0.0001), seminal vesicle weight ( P = 0.0003), epididymis weight P = 0.02), serum testosterone ( P = 0.001) and follicle-stimulating hormone (FSH) concentrations ( P = 0.04) compared with the control treatments. No effect on luteinizing hormone (LH) plasma concentration ( P = 0.13) was observed. Conclusion: This study revealed that low protein diet caused significant reductions in body weight, testis, epididymis and seminal vesicle weights, serum testosterone and FSH concentration in rats. We infer that sub-optimal protein consumption reduces the gonadal and endocrine function, and consequently male infertility.
Cyathula prostrata (Linn.) Blume is a tropical herbal plant known for its important phytochemical contents and medicinal properties. But its impact on animal reproduction and fertility is yet to be fully established. Therefore, we tested the hypothesis that C. prostrata (Linn.) Blume will improve the semen quality characteristics of New Zealand White buck rabbit. Twenty-eight post-pubertal buck rabbits were used for the study. The animals were randomly assigned to four treatment groups (n = 7 per treatment) where they were fed either the control diet—0 g C. prostrata (Linn.) Blume or any of the three experimental diets containing the graded levels of C. prostrata (Linn.) Blume incorporated into rabbit pellets at 10, 20 or 30 g C. prostrata (Linn.) Blume per kg feed. The results showed that the semen volume and pH were not different between groups. Interestingly, sperm motility significantly decreased (P < 0.05) in a dose-dependent manner. Similarly, the sperm morphology also decreased in a dose-related fashion with 20 g (77.75 ± 1.31%) and 30 g (79.00 ± 2.20%) C. prostrata (Linn.) Blume being significantly (P < 0.05) lower compared with groups 0 g (88.50 ± 1.44%) and 10 g (87.50 ± 4.33%) C. prostrata (Linn.) Blume, respectively. In conclusion, the addition of C. prostrata (Linn.) Blume into the normal rabbit feeds had a positive effect on sperm count, but reduced sperm motility and morphology, and may be associated with spermatogenesis-related problems.
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