• Yachun Li, Hongmei Lu, Jing Guo, Meiling Zhang, Huijuan Zheng, Yuning Liu, and Weijing Liu.
• Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing University of Chinese Medicine, Beijing, P.R. China.
• Ann. Med. 2023 Dec 1; 55 (1): 22155422215542.

BackgroundTrimethylamine N-oxide (TMAO) derived from gut microbiota causes kidney-heart damage in chronic kidney disease (CKD) patients. However, it is controversial whether CKD patients with higher TMAO are associated with a higher risk of death. We aimed to assess the correlation between circulating TMAO concentration and the risk of all-cause and cardiovascular death in CKD patients of different dialysis statuses and different races by dose-response analyses, and the underlying mechanisms were also explored by analyzing the correlations of TMAO with glomerular filtration rate (GFR) and inflammation.MethodPubMed, Web of Science, and EMBASE were systematically searched up to 1 July 2022. A total of 21 studies involving 15,637 individuals were included. Stata 15.0 was used to perform the meta-analyses and dose-response analyses with extracted data. Subgroup analyses were conducted to recognize possible sources of heterogeneity.ResultsThe risk of all-cause mortality was increased in non-dialysis CKD patients (RR = 1.26, 95%CI = 1.03-1.54, p = 0.028) and non-black dialysis patients (RR = 1.62, 95%CI = 1.19-2.22, p = 0.002) with the highest circulating TMAO concentration, and the association was confirmed to be linear. In addition, an increased risk of cardiovascular mortality was also found in non-black dialysis patients with the highest circulating TMAO concentration (RR = 1.72, 95%CI = 1.19-2.47, p = 0.004), likewise, a linear association was identified. However, for dialysis patients including blacks with high TMAO concentrations, there was no significant increase in either all-cause mortality (RR = 0.98, 95%CI = 0.94-1.03, p = 0.542) or cardiovascular mortality (RR = 0.87, 95% CI = 0.65-1.17, p = 0.362). Meanwhile, we verified strong correlations between TMAO and both GFR (r= -0.49; 95% CI= -0.75, -0.24; p < 0.001) and inflammatory markers (r = 0.43; 95% CI= 0.03, 0.84; p = 0.036) in non-dialysis patients.ConclusionsIncreased circulating TMAO concentrations increase the risk of all-cause mortality in non-dialysis and non-black dialysis CKD patients. Moreover, elevated TMAO levels raise the cardiovascular mortality risk in non-black dialysis patients.Key messagesNon-dialysis and non-black dialysis CKD patients with higher circulating TMAO concentrations are associated with an increased risk of all-cause mortality.Non-black dialysis patients with higher concentrations of TMAO are associated with an increased risk of cardiovascular mortality.Circulating TMAO concentrations have a strong negative correlation with GFR and a positive correlation with inflammation biomarkers in non-dialysis CKD patients.

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