# Serum Trimethylamine N-Oxide as a Diagnostic and Prognostic Biomarker in Dogs with Chronic Kidney Disease: A Pilot Study

## TL;DR

This study explores whether TMAO, a gut-derived chemical, can help diagnose and predict outcomes in dogs with chronic kidney disease.

## Contribution

The study is the first to investigate TMAO as a biomarker for diagnosing and predicting prognosis in canine chronic kidney disease.

## Key findings

- TMAO levels were significantly higher in dogs with CKD compared to healthy dogs.
- Non-surviving dogs had significantly higher TMAO levels than survivors after six months.
- TMAO levels tended to increase with more advanced CKD stages.

## Abstract

Trimethylamine N-oxide (TMAO) is a gut microbiota-derived metabolite that has been widely studied in human medicine due to its association with cardiovascular and renal diseases. Although it has shown promise as a biomarker for early detection and prognosis in human kidney dysfunction, its clinical utility in veterinary medicine has not yet been explored. This study investigated the potential of TMAO as a supportive biomarker in dogs with chronic kidney disease (CKD). Serum TMAO levels were significantly higher in dogs with CKD than in healthy controls, and the levels tended to increase with the progression of CKD stage. Furthermore, TMAO concentrations were significantly elevated in non-survivors compared to survivors during a six-month follow-up. These findings suggest that TMAO may serve as a useful biomarker for both the diagnosis and prognosis of canine CKD, offering a novel tool for the clinical evaluation and management of renal disease in veterinary practice.

Trimethylamine N-oxide (TMAO) is known to increase in human cardiovascular, metabolic, and renal diseases. In human medicine, TMAO has recently been utilized as a diagnostic and prognostic biomarker for renal dysfunction, and research is ongoing regarding its potential as a therapeutic target. This study aimed to evaluate the diagnostic and prognostic potential of TMAO as a supportive biomarker in dogs with chronic kidney disease (CKD). To assess its diagnostic utility, TMAO concentrations were compared between a CKD group (n = 32) and a healthy control group (n = 32). In addition, patients with CKD were subdivided into stages 2 (n = 12), 3 (n = 11), and 4 (n = 9) and compared individually with the healthy controls. For prognostic evaluation, the CKD group was monitored over six months, and the TMAO levels were compared between survivors (n = 18) and non-survivors (n = 14). The TMAO concentrations showed a highly significant difference between patients with CKD and healthy controls (p < 0.0001). Patients with each different CKD stage exhibited statistically significant differences compared with the healthy controls (p < 0.05). Furthermore, the median TMAO levels tended to increase with advancing CKD stage; however, the differences among stages were not statistically significant. In addition, within the CKD group, TMAO concentrations were significantly higher in non-survivors than in survivors at the six-month follow-up (p = 0.0142). This pilot study highlights the potential of TMAO as a supportive renal biomarker for diagnostic and prognostic evaluation in canine CKD.