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 to 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 [eGFR] <60 ml/min/1.73m2). Median TMAO level among CKD subjects was 7.9 μM (interquartile range 5.2–12.4μM), which was markedly higher (P<0.001) than in non-CKD subjects (n=3,166). Within CKD subjects, higher (4th vs. 1st quartile) plasma TMAO level was associated with a 2.8-fold increased mortality risk. Following adjustments for traditional risk factors, hsCRP and eGFR, elevated TMAO levels remained predictive of 5-year mortality risk (HR 1.93 [95%CI 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% vs. 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. Conclusion Plasma TMAO levels are both elevated in patients with CKD and portend poorer long-term survival. Chronic dietary exposures that increase TMAO appear to directly contribute to progressive renal fibrosis and dysfunction.

Trimethylamine N‐Oxide Promotes Vascular Inflammation Through Signaling of Mitogen‐Activated Protein Kinase and Nuclear Factor‐κB

“…The dose of TMAO used produced an initial spike in circulating levels to ≈100 μmol/L over the first hour, which returned essentially to near baseline levels ≈5 hours after injection in mice fed a normal chow diet (data not shown). Of note, the peak plasma TMAO levels with this protocol were similar to levels observed in mice chronically exposed to the choline‐supplemented diet (Figure 1C) and in some human clinical studies 9, 10, 17. At 30 minutes after intraperitoneal injection of TMAO, aortas were harvested and then assessed for changes in activation of p38 mitogen‐activated protein kinase, extracellular signal–related kinase 1/2, and p65 NF‐κB, all of which have been shown to play substantial roles in cellular inflammation contributing to the development of atherosclerosis 18, 20, 21, 22, 23, 24.…”

High mass accuracy assay for trimethylamine N-oxide using stable-isotope dilution with liquid chromatography coupled to orthogonal acceleration time of flight mass spectrometry with multiple reaction monitoring

“…When comparing with reported TMAO concentrations, healthy control participants showed similar median values to previous healthy cohorts [2,6]. Patients suffering from SHF reported elevated levels to other HF cohorts [2,3], but similar to those suffering from chronic kidney disease [6]. This result, although interesting, is derived from a limited patient population but demonstrates the clinical applicability of the described method.…”

“…It is also being investigated in other diseases where the aetiology is thought to be related to a perturbance of the gut microbiome, including colorectal cancer [4], diabetes [5] and renal disease [6] as well as being a putative central mediator in cholesterol balance [7]. Described methods for detecting TMAO are centred on the use of liquid chromatographytandem mass spectrometry with multiple reaction monitoring (LC-MS/MS-MRM), often utilising a stable isotopically labelled standard for quantitation [e.g.…”

Non-alcoholic fatty liver disease: an emerging driving force in chronic kidney disease

“…Plasma levels of TMAO are increased in patients with CKD, are associated with poorer long-term survival outcomes; and in animal studies diets that increase the circulating levels of TMAO, may contribute to progressive renal fibrosis and dysfunction 78 . Table 1 insertion here.…”