7964 Manipulation of the Gut Microbiome Using Antibiotics Is Associated With Sex-Specific Reductions in Systemic Testosterone Levels in Rats

Abstract Disclosure: G. Parodi: None. G. Leite: None. W. Morales: None. S.R. Weitsman: None. G.M. Barlow: None. M. Sanchez: None. M. Pimentel: None. M. Villanueva-Millan: None. M. Pimentel: None. R. Mathur: None. The gut microbiome has impacts on metabolic endocrine and reproductive functions. It is known that specific bacteria can impact host metabolism by synthesizing, secreting, and/or metabolizing sex-related hormones. However, the impacts of gut bacterial biosynthesis and/or metabolism of steroids on host metabolism and reproduction have not been fully addressed. In this study we challenged the gut microbiome of wild-type male and female rats with broad-spectrum antibiotics and examined the effects on circulating testosterone levels. Methods: Male (M) and female (F) Sprague-Dawley rats (8 weeks old) were housed with phytoestrogen-free bedding and received a phytoestrogen-free diet with water from glass bottles. Rats were given a combination of vancomycin (0.5g/L), ampicillin (1g/L), neomycin (1g/L), and metronidazole (1g/L) in their water for 8 days, and then returned to normal drinking water for another 13 days. Control rats were given normal water throughout the study. Serum and stool samples were collected before the start of antibiotics (baseline), on day 8 of antibiotics (AbxD8), and at 13 days post-removal of antibiotics (PAbxD13). Stool total DNA was extracted with the MagAttract PowerSoil DNA KF kit and quantified on a Qubit. Circulating testosterone levels were analyzed on a Luminex platform. Paired-ANOVA test was used to determine changes in testosterone levels in each group over time. Results: A total of 31 rats (M=16, F=15) received antibiotics, and 28 (M=14, F=14) were controls. Antibiotic exposure resulted in significant decreases in total stool DNA quantity in both male and female exposed rats relative to controls on AbxD8 (P<0.0001), which returned to baseline levels by PAbxD13. Antibiotic exposed male rats had a continuous decrease in testosterone levels throughout the timepoints collected (baseline: 5.78±2.74 ng/mL, AbxD8: 3.11±2.46 ng/mL, PAbxD13: 2.55±1.80 ng/mL, P=0.0027), however, in control male rats, circulating testosterone levels remained stable throughout the timepoints analyzed (baseline: 3.81±1.73 ng/mL, AbxD8: 3.72±1.12 ng/mL, PAbxD13: 3.92±3.38 ng/mL, P=0.49). There was no effect on circulating testosterone levels in female rats, with both groups, control and exposed, following the same cyclical pattern throughout the timepoints analyzed. Conclusions: Antibiotic depletion of the gut microbiome is associated with changes in systemic levels of testosterone in rats. These changes are sex-specific, and only detected in males. These results suggest a potential involvement of the gut microbiome in testosterone metabolism that is sex-specific. Presentation: 6/1/2024