ODP630 Antibiotics Transiently Reduce Circulating Cortisol and Inflammatory Biomarker Levels in Healthy Sprague Dawley Rats
Authors: Barlow Gillian , Fiorentino Alyson , Leite Gabriela , Morales Walter , Parodi Gonzalo , Pimentel Mark , Pimentel Maya , Sanchez Maritza , Villanueva-Millan Maria Jesus , Weitsman Stacy , Mathur Ruchi 
Published: November 2022

Abstract

Introduction
Antibiotics are over-used in healthcare, but little is known regarding their effects on cortisol levels in healthy individuals. Furthermore, antibiotics influence the gut microbiome, but the interrelationships between these drugs, cortisol and the microbiome are unknown. Here, we exposed the gut microbiome of rats to a multi-drug antibiotic cocktail and examined effects on circulating cortisol and inflammatory biomarker levels.

Methods
Male and female (M,F) Sprague-Dawley rats (aged 8 weeks) were housed with phytoestrogen-free bedding, and received a phytoestrogen-free diet with water from glass bottles. Exposed rats received vancomycin (0.5g/L), ampicillin (1g/L), neomycin (1g/L), and metronidazole (1g/L) in their water for 8 days, then returned to normal water for another 13 days. Control rats received normal water throughout the study. Stool and serum samples were collected before starting antibiotics (Abx) (baseline), on day 8 of Abx (AbxD8), and at 13 days post-Abx (PAbxD13). Circulating levels of cortisol and a panel of 12 inflammatory biomarkers were analyzed using MILLIPLEX Hormone Panels and RECYTMAG-65K multiplex panels, respectively. Stool DNA was extracted and 16S V3/V4 libraries were sequenced on an Illumina MiSeq. Operational Taxonomic Unit (OTU) clustering and taxonomic analyses were performed using CLC Microbial Genomics Module v.2.5 (Qiagen).

Results
A total of 31 rats (M=16, F=15) received Abx and 17 (M=9, F=8) were controls. At baseline, mean cortisol levels were similar between groups (control=34. 08±10.21ng/mL, exposed=35. 05±9.72ng/mL, P=0.96). On AbxD8, cortisol levels decreased in the exposed group relative to controls (control=29.77±9.34ng/mL, exposed=17.35±8.21ng/mL, P&lt;0. 0001), and returned to normal in the exposed group at PAbxD13 (control=33.88±16.65ng/mL, exposed=36.62±8.68ng/mL, P=0.85). Levels of all 12 inflammatory biomarkers were also decreased at AbxD8, and all except MCP1 returned to baseline levels by PAbxD13. Antibiotic exposure resulted in significant decreases in total stool DNA levels in exposed rats relative to controls on AbxD8 (P&lt;0. 0001), but returned to baseline levels by PAbxD13. Stool microbial diversity was also decreased in exposed rats on AbxD8 relative to controls (P=1e-08 and P&lt;0. 0001, respectively), and gut microbiome alterations were seen at multiple taxonomic levels. At PAbxD13, the stool microbiome of exposed rats remained perturbed, and only one phylum, Bacteroidetes, returned to baseline. Abx exposure changed associations between different phyla and levels of cortisol on AbxD8 relative to baseline, and although most of the associations reestablished at PAbxD13, the RA of phylum Proteobacteria was positively associated with levels of cortisol (R=0.243, P=0. 04), as opposed to baseline (R=-0.144, P=0.4).

Conclusions
Antibiotic exposure results in significant decreases in levels of cortisol as well as inflammatory biomarkers that are associated with perturbations of the gut microbiome, the majority of which returned to baseline following a 13-day antibiotic recovery period. These interrealtionships between cortisol, the gut microbiome and inflammatory biomarkers may have clinical significance.
Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.