Association of trimethylamine N-Oxide with cardiovascular and all-cause mortality in hemodialysis patients.

BACKGROUND: Trimethylamine-N-Oxide (TMAO) is a proatherogenic and prothrombotic metabolite. Our study examined the association of plasma TMAO level with cardiovascular and all-cause mortality in hemodialysis (HD) patients. METHODS: Patients who were at least 18 years-old and received HD for at least 6 months were enrolled within 6 months. Patients with coronary heart disease, congestive heart failure, arrhythmia, or stroke within 3 months before study onset were excluded. The primary endpoints were cardiovascular and all-cause death, and the secondary endpoint was cerebrovascular death. RESULTS: We recruited 252 patients and divided them into a high-TMAO group (>4.73 µg/mL) and a low-TMAO group (≤4.73 µg/mL). The median follow-up time was 73.4 months (interquartile range: 42.9, 108). A total of 123 patients died, 39 from cardiovascular disease, 19 from cerebrovascular disease, and 65 from other causes. Kaplan-Meier analysis indicated that the high-TMAO group had a greater incidence of cardiovascular death (Log-Rank: p = 0.006) and all-cause death (Log-Rank: p < 0.001). Cox regression analysis showed that high TMAO level was significantly associated with cardiovascular and all-cause mortality. After adjustment for confounding, this association remained significant for cardiovascular mortality (TMAO as a continuous variable: HR: 1.18, 95%CI: 1.07, 1.294, p < 0.001; TMAO as a dichotomous variable: HR: 3.44, 95%CI: 1.68, 7.08, p < 0.001) and all-cause mortality (TMAO as a continuous variable: HR: 1.14, 95%CI: 1.08, 1.21, p < 0.001; TMAO as a dichotomous variable: HR: 2.54, 95%CI: 1.71, 3.76, p < 0.001). CONCLUSIONS: High plasma TMAO level is significantly and independently associated with cardiovascular and all-cause mortality in HD patients.

Association of indoxyl sulfate with heart failure among patients on hemodialysis.

BACKGROUND AND OBJECTIVES: Indoxyl sulfate, a protein-bound uremic toxin, may be associated with cardiovascular events and mortality in patients with CKD. This study aimed to investigate the relationship between indoxyl sulfate and heart failure in patients on hemodialysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Patients on hemodialysis for >6 months were enrolled within 6 months. Patients with congestive heart failure, angina pectoris, acute myocardial infarction, cerebral infarction, or cerebral hemorrhage within 3 months before the study or those <18 years old were excluded. The primary end point was first heart failure event during follow-up. RESULTS: In total, 258 patients (145 men) with a mean age of 57.0 ± 14.6 years old were enrolled. Median plasma indoxyl sulfate level was used to categorize patients into two groups: the low-indoxyl sulfate group (indoxyl sulfate ≤ 2.35 µg/ml) and the high-indoxyl sulfate group (indoxyl sulfate >32.35 µg/ml). Then, patients were prospectively followed up for a median of 48.0 (interquartile range: 33.5-48.0) months. During follow-up, 68 patients experienced episodes of first heart failure. Kaplan-Meier analysis revealed the incidence of first heart failure event in the high-indoxyl sulfate group was significantly higher than in the low-indoxyl sulfate group (log rank P<0.001). Cox regression analysis showed indoxyl sulfate was significantly associated with first heart failure event (indoxyl sulfate as the continuous variable: hazard ratio, 1.02; 95% confidence interval [95% CI], 1.01 to 1.03; P=0.001; indoxyl sulfate as the dichotomous variable: hazard ratio, 3.49; 95% CI, 1.97 to 6.20; P<0.001). After adjustment for other confounding factors, the results remained significant (indoxyl sulfate as the continuous variable: hazard ratio, 1.04; 95% CI, 1.02 to 1.06; P<0.001; indoxyl sulfate as the dichotomous variable: hazard ratio, 5.31; 95% CI, 2.43 to 11.58; P<0.001). CONCLUSIONS: Plasma indoxyl sulfate was associated with first heart failure event in patients on hemodialysis. Whether indoxyl sulfate is only a biomarker or involved in the pathogenesis of heart failure in hemodialysis warrants additional study.

Inappropriately elevated endothelin-1 plays a role in the pathogenesis of intradialytic hypertension.

The aim of this study is to investigate the effects of endogenous vasoactive substances on the occurrence of intradialytic hypertension (IDH) in patients during maintenance hemodialysis. Thirty-four maintenance hemodialysis patients were enrolled in this trial, and 17 of them were diagnosed with IDH (defined as an increase in blood pressure of at least 10 mmHg during or immediately after a hemodialysis session), while 17 age-matched and sex-matched controls without IDH were selected for a retrospective comparison. We collected patients' blood samples before and after a dialysis session and measured the plasma levels of N-terminal fragment brain natriuretic peptide, renin, angiotensin-II, aldosterone (ALD), angiotensin-converting enzyme (ACE), endothelin-1 (ET-1), nitric oxide (NO), norepinephrine (NOR), and adrenomedullin. The post-dialysis serum ET-1 concentrations were significantly higher (4.09 ± 2.06 vs. 2.75 ± 1.34 pg/mL, P < 0.05), while the post-dialysis ratio of NO to ET-1 was lower (17.79 ± 5.65 vs. 24.78 ± 12.04, P < 0.05) in IDH patients compared with the control group. Post-dialysis ALD and NOR values were significantly lower (P < 0.01) and ACE levels were significantly higher (P < 0.01) than the pre-dialysis concentrations only in the control and not in the IDH group. All other measured factors did not differ significantly between the groups and between pre-dialysis and post-dialysis determinations. Compared with blood angiotensin-II, ALD, ACE, NOR, adrenomedullin, N-terminal fragment brain natriuretic peptide, and NO status, inappropriately elevated ET-1 plasma concentrations may play a predominant role in the pathogenesis of IDH.

ELISA examining urinary angiotensinogen as a potential indicator of intrarenal renin-angiotensin system (RAS) activity: a clinical study of 128 chronic kidney disease patients.

In the current study, we measured urinary angiotensinogen (AGT) through enzyme-linked immunoadsordent assay (ELISA) and analyzed its correlation with intrarenal renin-angiotensin system (RAS) activity in 128 chronic kidney disease (CKD) patients. Urinary and plasma renin activity, AGT, angiotensin II (Ang II) and aldosterone levels were also measured by radioimmunoassay (RIA) or ELISA in these participants. Further, the expression level of intrarenal renin, AGT, Ang II and Ang II receptors were examined by immunohistochemistry staining (IHCS) in 72 CKD patients. Their correlations with urinary AGT were also analyzed. We found that the urinary AGT level was positively correlated with hypertension (ρ = 0.28, P < 0.01), urinary protein (r = 0.38, P < 0.01), urinary Ang II (r = 0.29, P < 0.05), urinary type IV collagen (Col IV) (r = 0.56, P < 0.01), and was negatively correlated with estimated glomerular filtration rate (eGFR) (r = -0.28, P < 0.01), urinary sodium (r = -0.22, P < 0.05) and serum AGT (r = -0.27, P < 0.01). Multiple regression analysis indicated low serum AGT (P < 0.01), high urinary protein (P < 0.01), high urinary Ang II (P < 0.05) and high urinary Col IV (P < 0.01) were correlated significantly with high urinary AGT. Urinary AGT level was positively correlated with intrarenal expression level of AGT (ρ = 0.46, P < 0.01), Ang II (ρ = 0.56, P < 0.01) and Ang II type 1 receptor (ρ = 0.32, P < 0.01), as detected by IHCS. Together, these data suggest that urinary AGT might be a potential biomarker of intrarenal RAS and Ang II activities in CKD patients.