## 5 Studies on the Effects of _M. oleifera_ Leaf Extracts on Male Reproductive Function
### Environmental Toxicants and Heavy Metals  
Environmental toxicants have adverse effects on male reproductive potential. For example, these contaminants affect the quality of the semen. In addition, they disrupt the Leydig and Sertoli cells, disrupting DNA integrity, hormone biosynthesis, gene expression and epigenetic modifications [7]. These contaminants also reduce testis size, leading to testicular dysfunction [11]. Table 2 summarises the respective treatment of _M. oleifera_ on different models, length and mode of treatment. \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Male Infertility Risk Factors** & **Oxidative Stress Parameters** & **Homonal Levels** & **Sperm Parameters** & **Gene Expression** & **Testicular Histology Examination** & **Authors** \\ \hline \multirow{6}{*}{Environment toxicants} & \(\downarrow\) testicular tissue GST activity and MDA. & \(\uparrow\) testosterone, \(\uparrow\) stem motility, \(\uparrow\) sperm serum FSH and \(\uparrow\) SEM abnormalities. & \(\uparrow\) SEM abnormalities. & \(\downarrow\) weight of the reproductive organ. \(\uparrow\) clamped SSTmatics and \(\uparrow\) CYP1A1 and \(\uparrow\) EDN1/B3 genes of the epididymal bomb, \(\uparrow\) SAT & \(\uparrow\) EDN1/  
Some environmental toxicants damage the reproductive system via the induction of oxidative stress [11]. _M. Oleifera_ leaf extracts in animal models exposed to environmental toxicants have demonstrated their antioxidative capacity by significantly increasing superoxide dismutase (SOD) and catalase (CAT) levels and reducing malondialdehydedehyde (MDA) molecules [85]. _M. Oleifera_ also increased the testicular levels of glutathione peroxidase (GPv) [81, 84] and reduced glutathione S-transferase (GST) activity [82]. _M. Oleifera_ leaf extract increased the concentration of serum testosterone, FSH and LH [84, 85]. _M. Oleifera_ also increased testicular testosterone levels in male rats [81, 82]. Additionally, _M. Oleifera_ leaf extracts upregulated CYP11A1 and HSD17B3 genes of the steroidogenesis hormones downregulated CYP19A1 aromatase gene [84] and upregulated StAR and cytochrome p450c17 subfamily A (CYP17A) genes [82]. _M. Oleifera_ leaf extracts also demonstrated its beneficial effects on semen quality of male rats by increasing the percentage of viable and normal spermatozoa [85], sperm count, sperm motility and reduced sperm abnormality [82, 84] and reduced sperms with morphological damage [81]. _M. Oleifera_ leaf extracts in male rats exposed to environmental toxicants increased the weight, volume of the testis [81] and gonadosomatic index [84]. The extracts also preserved the Leydig cells and prevented the disruption of the semimiferous tubules by heavy metals [83]. More so, _M. Oleifera_ leaf extract increased elongated spermatids and spermatozoa in the semimiferous tubules. The epididymal histological integrity and sperm density were also improved, while congestion and interstitial oedema reduction were noted [82]. Lastly, _M. Oleifera_ leaf extract reduced the vacuolisation of germinal epithelium [84].