The Combination Effects of Orchidectomy and Antibiotics on Bone in Male Rats

Gut microbiotas play a critical role in maintaining bone health. While the influence of oestrogen deficiency on the gut-bone axis is well-established, evidence regarding testosterone deficiency is relatively scarce. This study aims to investigate the effects of the interaction between gut microbiota and testosterone deficiency induced by orchidectomy (ORX) on the skeletal system in male rats. Three-month-old Sprague Dawley male rats were assigned to four groups (n=6/group): sham (SHAM), ORX, SHAM+antibiotics (SHAM+ANT), and ORX+antibiotics (ORX+ANT). The ORX groups underwent bilateral orchidectomy, while the ANT groups received a combination of ampicillin, sulfamethoxazole, and trimethoprim for three months. At the end of the study period, the rats were sacrificed, and their faeces and femurs were harvested for analysis. Mild side effects, including diarrhoea, weight loss, and reduced appetite, were observed in the ANT groups. Faecal DNA analysis confirmed a significant reduction in gut microbiota in the ANT groups. Whole-body bone mineral density (BMD) and bone mineral content (BMC) showed no significant differences among groups (p>0.05). However, the femoral BMC of the SHAM+ANT group was significantly lower than that of the ORX group in the first month and lower than that of the SHAM group in the second month (p<0.05). Bone biomechanical strength analysis revealed that the SHAM+ANT group had lower Young’s modulus values than the ORX group (p<0.05). The ORX+ANT group exhibited reduced maximum force, stress, and stiffness compared to the ORX and SHAM groups (p<0.05), while displacement and strain values were higher (p<0.05), suggesting increased bone fragility. In conclusion, testosterone deficiency, in combination with gut dysbiosis, profoundly impacts the skeletal health of male rats.