Isolation and Quantification of Uremic Toxin Precursor-Generating Gut Bacteria in Chronic Kidney Disease Patients

• Main Authors: Tessa Gryp, Geert R.B. Huys, Marie Joossens, Wim Van Biesen, Griet Glorieux, Mario Vaneechoutte
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: International Journal of Molecular Sciences
• Subjects: qpcr; bacterial culture; fecal bacteria; chronic kidney disease; protein-bound uremic toxins; bacterial metabolization; aromatic amino acids; <i>p</i>-cresol; indole; indole-3-acetic acid; phenol
• Online Access: https://www.mdpi.com/1422-0067/21/6/1986

In chronic kidney disease (CKD), impaired kidney function results in accumulation of uremic toxins, which exert deleterious biological effects and contribute to inflammation and cardiovascular morbidity and mortality. Protein-bound uremic toxins (PBUTs), such as <i>p</i>-cresyl sulfate, indoxyl sulfate and indole-3-acetic acid, originate from phenolic and indolic compounds, which are end products of gut bacterial metabolization of aromatic amino acids (AAA). This study investigates gut microbial composition at different CKD stages by isolating, identifying and quantifying PBUT precursor-generating bacteria. Fecal DNA extracts from 14 controls and 138 CKD patients were used to quantify total bacterial number and 11 bacterial taxa with qPCR. Moreover, isolated bacteria from CKD 1 and CKD 5 fecal samples were cultured in broth medium supplemented with AAA under aerobic and anaerobic conditions, and classified as PBUT precursor-generators based on their generation capacity of phenolic and indolic compounds, measured with U(H)PLC. In total, 148 different fecal bacterial species were isolated, of which 92 were PBUT precursor-generators. These bacterial species can be a potential target for reducing PBUT plasma levels in CKD. qPCR indicated lower abundance of short chain fatty acid-generating bacteria, <i>Bifidobacterium</i> spp. and <i>Streptococcus</i> spp., and higher <i>Enterobacteriaceae</i> and <i>E. coli</i> with impaired kidney function, confirming an altered gut microbial composition in CKD.