Prednisone (PRED) is a synthetic glucocorticoid (GC) widely used in immune-mediated diseases for its immunosuppressive and anti-inflammatory properties. The effects of GC are achieved by genomic and nongenomic mechanisms. However, the nongenomic effects are largely unknown. Thus, we aimed to investigate how long-term prednisone therapy changes the composition of the gut microbiota and fecal metabolites in rats. Male Sprague-Dawley rats were randomly assigned to a control (CON) group and a PRED group, which received prednisone treatment daily for 6 weeks by gavage. The V3 to V4 regions of bacterial 16S rRNA genes were amplified and sequenced after the total bacterial DNA was extracted from fecal samples. The alpha and beta diversities were calculated. The compositional alteration of the gut microbiota at different taxonomic levels was analyzed using the Metastats method. Meanwhile, the fecal metabolites were quantitated in an ultra-performance liquid chromatography system. Similar microbial richness and diversity between the CON and PRED groups were indicated by the alpha diversity results. The gut microbial communities differed significantly between two groups. The relative abundances of the genera Eisenbergiella, Alistipes, and Clostridium XIVb decreased, whereas that of Anaerobacterium increased significantly in rats after the 6-week prednisone treatment. In total, 11 downregulated and 10 upregulated fecal metabolites were identified. Differential fecal metabolites were enriched in the pathways, including phenylalanine metabolism, butanoate metabolism, and propanoate metabolism. The lowered production of short-chain fatty acids was associated with the decreased relative abundance of the genera Alistipes and Clostridium XIVb and increased abundance of the genus Anaerobacterium. The composition of the gut microbiota and fecal metabolites was changed after long-term prednisone treatment. This may help us to understand the pharmacology of prednisone. IMPORTANCE Prednisone is widely used in chronic glomerular diseases, immunological disorders, and rheumatic diseases for its anti-inflammatory and immunosuppressive properties. It is a synthetic glucocorticoid (GC) that shows therapeutic effects after conversion to prednisolone by the liver. Prolonged GC therapy causes anti-inflammatory effects; it also results in a variety of adverse events, including obesity, hypertension, psychiatric symptoms, and dyslipidemia. The therapeutic effects and adverse events of GCs may be associated with changes in the gut microbiota, as the host might be affected by the metabolites generated by the altered gut microbes. Thus, we investigated how long-term prednisone therapy changed the composition of the gut microbiota and fecal metabolites in rats. This study may shed new light on the pharmacology of prednisone.
Keywords: fecal metabolite; gut microbiota; prednisone; short-chain fatty acid.