Gut microbiota-dependent trimethylamine N-oxide (TMAO) pathway contributes to both development of renal insufficiency and mortality risk in chronic kidney disease

Abstract

Rationale: Trimethylamine-N-oxide (TMAO), a gut microbial-dependent metabolite of dietary choline, phosphatidylcholine (lecithin), and l-carnitine, is elevated in chronic kidney diseases (CKD) and associated with coronary artery disease pathogenesis.

Objective: To both investigate the clinical prognostic value of TMAO in subjects with versus without CKD, and test the hypothesis that TMAO plays a direct contributory role in the development and progression of renal dysfunction.

Methods and results: We first examined the relationship between fasting plasma TMAO and all-cause mortality over 5-year follow-up in 521 stable subjects with CKD (estimated glomerular filtration rate, <60 mL/min per 1.73 m(2)). Median TMAO level among CKD subjects was 7.9 μmol/L (interquartile range, 5.2-12.4 μmol/L), which was markedly higher (P<0.001) than in non-CKD subjects (n=3166). Within CKD subjects, higher (fourth versus first quartile) plasma TMAO level was associated with a 2.8-fold increased mortality risk. After adjustments for traditional risk factors, high-sensitivity C-reactive protein, estimated glomerular filtration rate, elevated TMAO levels remained predictive of 5-year mortality risk (hazard ratio, 1.93; 95% confidence interval, 1.13-3.29; P<0.05). TMAO provided significant incremental prognostic value (net reclassification index, 17.26%; P<0.001 and differences in area under receiver operator characteristic curve, 63.26% versus 65.95%; P=0.036). Among non-CKD subjects, elevated TMAO levels portend poorer prognosis within cohorts of high and low cystatin C. In animal models, elevated dietary choline or TMAO directly led to progressive renal tubulointerstitial fibrosis and dysfunction.

Conclusions: Plasma TMAO levels are both elevated in patients with CKD and portend poorer long-term survival. Chronic dietary exposures that increase TMAO directly contributes to progressive renal fibrosis and dysfunction in animal models.

Keywords: cardiovascular diseases; chronic kidney disease; fibrosis; gut microbiota; trimethylamine N-oxide.

© 2014 American Heart Association, Inc.

Figures

Figure 1. Prognostic Value of Plasma trimethylamine N-oxide (TMAO) Levels in the CKD Cohort

In a cohort of stable cardiac patients undergoing elective diagnostic coronary evaluation, subjects with underlying Stage 3+ chronic kidney disease demonstrated higher levels of fasting plasma TMAO than those with no CKD (p

Figure 2. Comparative Prognostic Value of Plasma TMAO and Cystatin C in the Non-CKD Cohort

Subjects with elevated cystatin C (>0.9 mg/dL) and TMAO (>3.4 μM) had the highest 5-year mortality risk in this non-CKD cohort (n=3,188).

Figure 3. Dietary choline/TMAO Exposure Contributes to Progressive Renal Fibrosis in Murine Model

Plasma TMAO (A) levels are increased after 6 week feeding TMAO (0.12%), or Choline (1.0%) diets vs chow (0.08% choline) fed mice. Representative Mason trichrome histology (B) quantitative morphometry (C) and its relationship with TMAO levels (D), SMAD3 activation by phosphorylation at serine 423/425 (E) and its relationship with TMAO levels (F) in mouse kidneys after 6 week feeding of chow (0.08% choline), TMAO (0.12%), and Choline (1.0%) diets. Scale bar represents 100 um. **P

Figure 4. Dietary choline/TMAO Exposure Contributes to Progressive Renal Injury and Dysfunction in Murine Model

Immunoblot of KIM-1 expression (A) and its relationship with TMAO levels (B) in mouse kidneys after 6 week feeding of chow (0.08% choline), TMAO (0.12%), and Choline (1.0%) diets. Also shown are plasma cystatin C levels (C) after 16 week feeding of chow, TMAO (0.12%), and Choline (1.0%) diets. **P