Improvement in Heat Stress-Induced Damage to Sperm Quality Following Fecal Microbiota Transplantation from L-Arginine-Treated Mice

Heat stress has become a significant concern in animal husbandry, as it adversely affects reproductive performance, particularly sperm quality, through mechanisms that are not fully understood. This study aimed to investigate the protective effects of L-arginine against heat stress-induced sperm damage and explore its potential mechanisms through the modulation of the intestinal microbiota. This study consisted of two experiments. First, in a heat-stressed mouse model, L-arginine was administered to evaluate its effects on the reproductive health of heat-stressed mice. In the second experiment, by transplanting L-arginine-induced changes in the gut microbiota into heat-stressed mice, the protective effects of the microbiota on the sperm of heat-stressed mice were assessed. The findings revealed a significant amelioration of decreased sperm quality and testicular injury induced by heat stress. Post heat stress, mice supplemented with L-arginine presented an increase in seminal vesicle gland weight and index, partial alleviation of testicular tissue morphology, and a substantial increase in testosterone concentration (<i>p</i> < 0.05). Additionally, L-arginine upregulated the expression of testosterone synthesis genes and the mRNA levels of sperm generation-related genes, including <i>3β-HSD</i>, <i>Stra8</i>, <i>WT1</i>, and <i>Gdnf</i> (<i>p</i> < 0.05). Concurrently, L-arginine-induced microbial communities mitigated heat stress-induced decreases in sperm quality and testicular injury, coupled with increases in the mRNA expression levels of <i>Cyp17a1</i>, <i>17β-HSD</i>, <i>Plzf</i>, and <i>Gdnf</i> (<i>p</i> < 0.05). Furthermore, there was a reduction in the expression of proinflammatory factors, namely, NFκB, <i>MyD88</i>, TNF-α, and <i>TGF-β3</i> (<i>p</i> < 0.05). In conclusion, L-arginine may influence the ratio of beneficial bacteria to harmful bacteria in the intestinal microbiota, thereby reducing inflammation caused by heat stress, maintaining intestinal health, and influencing the microenvironment for spermatogenesis.