Gut microbiota-derived trimethylamine N-oxide is associated with the risk of all-cause and cardiovascular mortality in patients with chronic kidney disease: a systematic review and dose-response meta-analysis

Figures & data

Figure 1. Flow chart of the literature search and study selection process.

Table 1. Characteristics of the selected studies.

First author	Year/ Country	Study design	Subjects (% male)	Age (years)	Follow-up (years)	Disease status	Sample Source	Events for analysis	Adjusted confounders
Tang [30]	2015/ United States	Cohort	521 (48.0)	70 (10)	5	Non-dialysis CKD	Plasma	All-cause mortality, GFR, inflammatory biomarkers	Age, gender, SBP, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, smoking, DM, hsCRP, and eGFR
Kaysen [31]	2015/ United States	Cohort	235 (55.3)	61.8 (14.2)	4	HD	Serum	All-cause mortality, inflammatory biomarkers	_
Stubbs [32]	2016/ United States	Cross-sectional	56 (50)	<60	—	Non-dialysis CKD and HD	Serum	GFR	_
Missailidis [22]	2016/ Sweden	Cohort	170 9(65)	55 (14)	5	Non-dialysis CKD	Serum	All-cause mortality, GFR, inflammatory biomarkers	Gender, age,DM,hsCRP,GFR
Robinson- Cohen [24]	2016/ United States	Cohort	339 (68.4)	57.3 (13.5)	3.3	Non-dialysis CKD	Plasma	All-cause mortality	Age, race, sex, SBP, LDL, HDL, Smoking, CRP, eGFR
Mafune [33]	2016/Japan	Cross-sectional	227(70)	68 (61–74)	_	Non-dialysis CKD	Serum	GFR	_
Kim [34]	2016/Canada	Cohort	2529 (62.5)	68.2 (12.7)	3	Non-dialysis CKD	Plasma	GFR	_
Al-Obaide [13]	2017/ United States	Cross-sectional	20(/)	64.4(2.3)	_	Non-dialysis T2DM and CKD	Serum	Inflammatory biomarkers	_
Gruppen [35]	2017/ Netherlands	Cohort	5469 (48.7)	<60	8.3	Non-dialysis CKD	Plasm	All-cause mortality, GFR	Age, sex, body mass index, smoking, type 2 DM, history of CVD, history of cancer, anti-hypertensive medication, lipid-lowering drugs, SBP, total cholesterol, high density lipoprotein cholesterol and triglycerides, UAE, eGFR crea-cysC
Shafi [36]	2017/ United States	Cohort	1232 (43.3)	57.7 (13.8)	2.3	HD	Serum	All-cause mortality, cardiovascular mortality	Age, sex, ICED severity score, cause of ESRD, BMI, SBP, albumin, and relative calculated from urinary urea clearance
Stubbs [37]	2019/ United States	Cohort	1243 [38]	54 (14)	5.3	HD	Serum	All-cause mortality, cardiovascular mortality	Age, sex, BMI, SBP, albumin, race, dialysis duration, history of smoking, history of cardiovascular disease, history of percutaneous coronary intervention, history of stroke, history of MI, BUN, and the Evaluation of Cinacalcet Hydrochloride Therapy to Lower Cardiovascular Events study design
Winther [39]	2019/ Denmark	Cohort	484 (-)	46(13)	15	Type 1-diabetes and macroalbuminuria	Plasma	All-cause mortality, cardiovascular mortality	Age, sex, diabetes duration, HbA1c, SBP, total cholesterol, smoking status, and UAER
EI-Deeb [40]	2019/Egypt	Cross-sectional	80 (48.8)	<60	_	Non-dialysis CKD	Plasma	GFR, inflammatory biomarkers	_
Zhang [41]	2020/China	Cohort	252 (56)	57.1 (14.5)	6.1	HD	Plasma	All-cause mortality, cardiovascular mortality	Age, sex, DM, BMI and rGFR
Fu [42]	2021/China	Cohort	1032(57)	48 (14)	5.3	PD	Serum	All-cause mortality, cardiovascular mortality	Age, sex, DM, history of CVD, BMI, MAP, albumin, TG, LDL-C, hs-CRP, rGFR, and total Kt/V
Winther [43]	2021/ Denmark	Cohort	311 (75.2)	57.2 (8.2)	6.8	type 2-diabetes and albuminuria	Plasma	All-cause mortality, cardiovascular mortality	Age, sex, HbA1c, SBP, BMI, total cholesterol, smoking, UAER, and eGFR
Chang [44]	2021/China	Cohort	513 (58.1)	54.0 (15.5)	2.9	PD	Serum	All-cause mortality, cardiovascular mortality	Age, sex, DM, CVD, BMI, Alb, hs-CRP, potassium, phosphorus, RRF, nPNA, and calendar year of the catheter implantation
Hernandez [45]	2022/ Sweden	Cohort	216 (56)	66 (51–74)	5	HD	Serum	All-cause mortality, inflammatory biomarkers	Sex, age, DM, and CVD
Sapa [46]	2022/ United States	Cohort	555 (47)	70 (9)	6.2	Non-dialysis DKD	Plasma	All-cause mortality, cardiovascular mortality, GFR	Age, sex, race, education, BMI, SBP, hypertension meds, smoking, CHD, stroke, LDL, HDL, lipid-lowering meds, UACR and eGFR
Zhang [47]	2022/China	Cohort	144 (52.8)	46 (15)	2.4	PD	Serum	Inflammatory biomarkers	Sex, age, Diabetes, BMI, and rGFR

Figure 2. Meta-analysis of the association between circulating TMAO concentrations and all-cause mortality in non-dialysis patients and dialysis patients respectively. RR: relative risk; CI: confidence interval.

Table 2. Subgroup analysis of the association between circulating TMAO concentrations and all-cause mortality in non-dialysis CKD patients.

Subgroup	Studies	RR	95%CI	Z	P	Heterogeneity
						I^2, %	^*P
Age
<60	5 [26,4,43,45,40]	1.09	0.93, 1.28	1.08	0.280	30.9	0.216
>60	2 [41,39]	1.72	1.26, 2.37	3.36	0.001	0.000	0.605
GFR
<60	4 [26,28,41,39]	1.77	1.32, 2.37	3.82	0.000	0.000	0.397
>60	3 [43,45,40]	1.06	0.95, 1.17	1.06	0.289	0.000	0.846
Underlying diseases
CKD	4 [26,28,41,43]	1.61	1.01, 2.56	1.99	0.047	50.6	0.108
DKD	3 [39,45,40]	1.12	0.93, 1.35	1.2	0.229	54.8	0.109

*For heterogeneity among subgroups.

RR: relative risk; CI: confidence interval.

Table 3. Subgroup analysis of the association between circulating TMAO concentrations and all-cause mortality in dialysis patients.

Subgroup	Studies	RR	95%CI	Z	P	Heterogeneity
						I^2, %	^*P
Age
<60	6 [13,35,47,36]	1.29	0.93,1.80	1.52	0.129	79.0	0.000
>60	2 [42,48]	0.99	0.94,1.04	0.34	0.733	0.000	0.603
Race
Including blacks	4 [42,36,37,48]	0.98	0.94,1.03	0.61	0.542	0.000	0.649
Non-blacks	4 [13,35,47,36]	1.62	1.19,2.22	3.05	0.002	56.7	0.074
Dialysis modality
PD	2 [35,47]	1.32	0.98,1.79	1.82	0.069	0.000	0.928
HD	6 [13,42,36,37,48]	1.19	0.90,1.55	1.23	0.219	82.1	0.000

*For heterogeneity among subgroups.

RR: relative risk; CI: confidence interval.

Figure 3. Meta-analysis of the association between circulating TMAO concentrations and cardiovascular mortality in non-dialysis patients and dialysis patients respectively. HR: hazard risk; CI: confidence interval.

Table 4. Subgroup analysis of the association between circulating TMAO concentrations and cardiovascular mortality in dialysis patients.

Subgroup	Studies	RR	95%CI	Z	P	Heterogeneity
						I^2, %	^*P
Race
Including blacks	2 [36,37]	0.87	0.65,1.17	0.91	0.362	0.000	0.463
Non-blacks	4 [13,35,47,36]	1.72	1.19,2.47	2.89	0.004	44.4	0.145
Dialysis modality
PD	2 [34,47]	1.33	0.92,1.92	1.51	0.132	0.000	0.937
HD	4 [13,36,37]	1.39	0.80,2.43	1.16	0.248	81.3	0.001

*For heterogeneity among subgroups.

RR: relative risk; CI: confidence inter.

Figure 4. Dose-response meta-analysis of the association between TMAO and all-cause mortality in non-dialysis patients.

Figure 5. Dose-response meta-analysis of the association between TMAO and all-cause mortality in non-black dialysis patients.

Figure 6. Dose-response meta-analysis of the association between TMAO and cardiovascular mortality in non-black dialysis patients.

Figure 7. Meta-analysis of the correlations between circulating TMAO concentrations and GFR in non-dialysis CKD patients. r, coefficient of association; CI, confidence interval.

Table 5. Subgroup analysis of the correlations between circulating TMAO concentrations and GFR in non-dialysis CKD patients.

Subgroup	Studies	r	95%CI	Z	P	Heterogeneity
						I^2, %	^*P
Age
<60	4 [26,44,43,49]	–0.59	−1.08, −0.09	2.31	0.021	99.8	0.000
>60	4 [33,41,46,39]	–0.41	–0.46, −0.35	17.11	0.000	53.1	0.094
GFR
<60	6 [26,41,44,46,39,49]	–0.58	–0.83,–0.33	4.5	0.000	99.3	0.000
>60	2 [33,43]	–0.24	–0.40, −0.07	2.76	0.006	99.6	0.000

*For heterogeneity among subgroups. RR: relative risk; CI: confidence interval.

Figure 8. Meta-analysis of the correlations between circulating TMAO concentrations and inflammatory biomarkers in non-dialysis patients and dialysis patients respectively. r, coefficient of association; CI, confidence interval.

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Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.