UC Davis Researchers Identify Gut Microbiome Feedback Loop That Accelerates Chronic Kidney Disease Progression

UC Davis scientists discover a gut-kidney feedback loop involving nitrate and E. coli that accelerates kidney damage, pointing to a new drug target.

By: AXL Media

Published: Mar 20, 2026, 11:30 AM EDT

Source: Information for this report was sourced from University of California - Davis Health

The Biological Catalyst of Renal Decay

New research from the UC Davis School of Medicine has mapped a sophisticated feedback loop between the gut and the kidneys that significantly worsens chronic kidney disease (CKD). The study indicates that when kidney function begins to fail, the body increases the production of nitrates within the colon. These nitrates act as a biological "switch" for Enterobacteriaceae, a family of bacteria that includes E. coli. Once activated by high nitrate levels, these bacteria turbocharge the production of indole, an organic compound that the body subsequently converts into indoxyl sulfate—a known toxin that causes further, aggressive damage to the kidneys.

Indoxyl Sulfate and the Limitations of Dialysis

The discovery is particularly significant because of how indoxyl sulfate behaves within the human body. While hemodialysis is the standard life-saving procedure for patients with kidney failure, it is notoriously ineffective at removing indoxyl sulfate. This specific waste product binds tightly to serum albumin, a common blood protein, allowing it to bypass the filtration process of dialysis machines. As a result, patients with higher levels of this toxin experience more rapid disease progression. By identifying the exact mechanism that generates this toxin, researchers have found a potential way to intervene where traditional dialysis fails.

The Role of iNOS in the Destructive Cycle

The research team, led by First Author Jee-Yon Lee and Senior Author Andreas Bäumler, identified the enzyme inducible nitric oxide synthase (iNOS) as the critical driver of the nitrate surge. Through mouse models and the analysis of human fecal samples, the team found that kidney dysfunction triggers the Nos2 gene, which creates iNOS in the colon's mucous layer. This enzyme leads to an increase in nitric oxide, which then reacts to form the nitrates that fuel E. coli growth. By pinpointing iNOS as the source of the "fuel" for harmful bacteria, the study provides a clear target for future pharmacological intervention.