The effect of dietary protein intake on factors associated with male infertility: A systematic literature review and meta-analysis of animal clinical trials in rats.

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.

The influence of graded levels of Cyathula prostrata (Linn.) Blume on semen quality characteristics of adult New Zealand white bucks.

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.

Hormonal changes, semen quality and variance in reproductive activity outcomes of post pubertal rabbits fed Moringa oleifera Lam. leaf powder.

ETHNOPHARMACOLOGICAL RELEVANCE: Moringa oleifera Lam. (Moringaceae) is an important plant based staple food, known for its nutritional and medicinal value and is usually prescribed by herbal practitioners in Nigeria and in other tropical countries for the treatment of male infertility problems and reproductive diseases in females. Although the aphrodisiac properties and fertility enhancement potential in males have been reported, the underlying mechanisms for the activity remain unclear. In this study, we investigated the influence of supplementing the diet with M. oleifera Lam. leaf powder on reproductive hormones and semen quality of New Zealand White (NZW) rabbits. MATERIALS AND METHODS: Thirty-two (32) NZW rabbits of 50:50 ratio bucks to does, were randomly distributed to four treatment groups (n = 4 bucks, n = 4 does per group). Graded levels (0, 5, 10 and 15 g/kg) of M. oleifera Lam. leaf powder was incorporated into rabbit growers pellet. The does and bucks were housed separately in hutches and sheltered under the same environmental conditions with free access to their respective treatment diets for a period of 12 weeks. RESULTS: In female rabbits, treatment revealed significant (P < 0.05) dose-dependent reduction in the concentration of serum FSH, LH and oestrogen. While in contrast the highest dose of leaf powder significantly (P < 0.05) increased progesterone and prolactin concentrations remained unaffected. On the other hand, the concentration of FSH and LH in bucks was significantly (P < 0.05) increased in treatment groups compared to the control group. Serum testosterone concentrations were significantly lower in the 5 and 10 g/kg treatment groups. Semen volume, sperm count and motility were significantly improved in a dose dependent manner with increasing amounts of M. oleifera Lam. leaf powder in the diet. CONCLUSIONS: We conclude that M. oleifera Lam. leaf powder supplementation to the diet was more beneficial to male rabbit fertility than the female, where it tended to have a negative impact through the hypothalamic-pituitary-gonadal axis. However, with the varying impact of M. oleifera Lam. leaf powder on the hypothalamic-pituitary-gonadal axis of male and female animals, further investigation is necessary to determine the mechanism through which it operates.