Race, Interleukin-6, TMPRSS6 Genotype, and Cardiovascular Disease in Patients With Chronic Kidney Disease.

Background Differences in death rate and cardiovascular disease (CVD) between Black and White patients with chronic kidney disease is attributed to sociocultural factors, comorbidities, genetics, and inflammation. Methods and Results We examined the interaction of race, plasma IL-6 (interleukin-6), and TMPRSS6 genotype as determinants of CVD and mortality in 3031 Chronic Renal Insufficiency Cohort study participants. The primary outcomes were all-cause mortality and a composite of incident myocardial infarction, peripheral artery disease, stroke, and heart failure. During the median follow-up of 10 years, Black patients with chronic kidney disease experienced a significantly higher mortality (34% versus 26%) and CVD composite (41% versus 28%) compared with White patients. After adjustment, TMPRSS6 genotype did not associate with the outcomes. The adjusted hazard ratio for mortality (4.11 [2.48-6.80], P<0.001) and CVD composite (2.52 [1.96-3.24], P<0.001) were higher for the highest versus lowest IL-6 quintile. The adjusted hazards for death per 1-quintile increase in IL-6 in White and Black individuals were 1.53 (1.42-1.64) versus 1.29 (1.20-1.38) (P<0.001), respectively. For CVD composite they were 1.61 (1.50-1.74) versus 1.30 (1.22-1.39) (P<0.001), respectively. In Cox proportional hazard models that included IL-6, there was no longer a racial disparity for death (1.01 [0.87-1.16], P=0.92), but significant unexplained mediation remained for CVD (1.24 [1.07-1.43]; P=0.004). Path models that included IL-6, diabetes, and urine albumin to creatinine ratio were able to identify variables responsible for racial disparity in mortality and CVD. Conclusions Racial differences in mortality and CVD among patients with chronic kidney disease could be explained by good-fitting path models that include selected mediator variables including diabetes and plasma IL-6.

Inflammation, Immunity, and Oxidative Stress in Hypertension-Partners in Crime?

Hypertension is considered as the most common risk factor for cardiovascular disease. Inflammatory processes link hypertension and cardiovascular disease, and participate in their pathophysiology. In recent years, there has been an increase in research focused on unraveling the role of inflammation and immune activation in development and maintenance of hypertension. Although inflammation is known to be associated with hypertension, whether inflammation is a cause or effect of hypertension remains to be elucidated. This review describes the recent studies that link inflammation and hypertension and demonstrate the involvement of oxidative stress and endothelial dysfunction-two of the key processes in the development of hypertension. Etiology of hypertension, including novel immune cell subtypes, cytokines, toll-like receptors, inflammasomes, and gut microbiome, found to be associated with inflammation and hypertension are summarized and discussed. Most recent findings in this field are presented with special emphasis on potential of anti-inflammatory drugs and statins for treatment of hypertension.

Gut Colonization with Methanogenic Archaea Lowers Plasma Trimethylamine N-oxide Concentrations in Apolipoprotein e-/- Mice.

A mechanistic link between trimethylamine N-oxide (TMAO) and atherogenesis has been reported. TMAO is generated enzymatically in the liver by the oxidation of trimethylamine (TMA), which is produced from dietary choline, carnitine and betaine by gut bacteria. It is known that certain members of methanogenic archaea (MA) could use methylated amines such as trimethylamine as growth substrates in culture. Therefore, we investigated the efficacy of gut colonization with MA on lowering plasma TMAO concentrations. Initially, we screened for the colonization potential and TMAO lowering efficacy of five MA species in C57BL/6 mice fed with high choline/TMA supplemented diet, and found out that all five species could colonize and lover plasma TMAO levels, although with different efficacies. The top performing MA, Methanobrevibacter smithii, Methanosarcina mazei, and Methanomicrococcus blatticola, were transplanted into Apoe-/- mice fed with high choline/TMA supplemented diet. Similar to C57BL/6 mice, following initial provision of the MA, there was progressive attrition of MA within fecal microbial communities post-transplantation during the initial 3 weeks of the study. In general, plasma TMAO concentrations decreased significantly in proportion to the level of MA colonization. In a subsequent experiment, use of antibiotics and repeated transplantation of Apoe-/- mice with M. smithii, led to high engraftment levels during the 9 weeks of the study, resulting in a sustained and significantly lower average plasma TMAO concentrations (18.2 ± 19.6 µM) compared to that in mock-transplanted control mice (120.8 ± 13.0 µM, p < 0.001). Compared to control Apoe-/- mice, M. smithii-colonized mice also had a 44% decrease in aortic plaque area (8,570 µm [95% CI 19587-151821] vs. 15,369 µm [95% CI [70058-237321], p = 0.34), and 52% reduction in the fat content in the atherosclerotic plaques (14,283 µm [95% CI 4,957-23,608] vs. 29,870 µm [95% CI 18,074-41,666], p = 0.10), although these differences did not reach significance. Gut colonization with M. smithii leads to a significant reduction in plasma TMAO levels, with a tendency for attenuation of atherosclerosis burden in Apoe-/- mice. The anti-atherogenic potential of MA should be further tested in adequately powered experiments.

Interleukin-6 Is a Risk Factor for Atrial Fibrillation in Chronic Kidney Disease: Findings from the CRIC Study.

Atrial fibrillation (AF) is the most common sustained arrhythmia in patients with chronic kidney disease (CKD). In this study, we examined the association between inflammation and AF in 3,762 adults with CKD, enrolled in the Chronic Renal Insufficiency Cohort (CRIC) study. AF was determined at baseline by self-report and electrocardiogram (ECG). Plasma concentrations of interleukin(IL)-1, IL-1 Receptor antagonist, IL-6, tumor necrosis factor (TNF)-α, transforming growth factor-ß, high sensitivity C-Reactive protein, and fibrinogen, measured at baseline. At baseline, 642 subjects had history of AF, but only 44 had AF in ECG recording. During a mean follow-up of 3.7 years, 108 subjects developed new-onset AF. There was no significant association between inflammatory biomarkers and past history of AF. After adjustment for demographic characteristics, comorbid conditions, laboratory values, echocardiographic variables, and medication use, plasma IL-6 level was significantly associated with presence of AF at baseline (Odds ratio [OR], 1.61; 95% confidence interval [CI], 1.21 to 2.14; P = 0.001) and new-onset AF (OR, 1.25; 95% CI, 1.02 to 1.53; P = 0.03). To summarize, plasma IL-6 level is an independent and consistent predictor of AF in patients with CKD.

Associations of Soluble CD14 and Endotoxin with Mortality, Cardiovascular Disease, and Progression of Kidney Disease among Patients with CKD.

BACKGROUND AND OBJECTIVES: CD14 plays a key role in the innate immunity as pattern-recognition receptor of endotoxin. Higher levels of soluble CD14 (sCD14) are associated with overall mortality in hemodialysis patients. The influence of kidney function on plasma sCD14 levels and its relationship with adverse outcomes in patients with CKD not yet on dialysis is unknown. This study examines the associations between plasma levels of sCD14 and endotoxin with adverse outcomes in patients with CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We measured plasma levels of sCD14 and endotoxin in 495 Leuven Mild-to-Moderate CKD Study participants. Mild-to-moderate CKD was defined as presence of kidney damage or eGFR<60 ml/min per 1.73 m(2) for ≥3 months, with exclusion of patients on RRT. Study participants were enrolled between November 2005 and September 2006. RESULTS: Plasma sCD14 was negatively associated with eGFR (ρ=-0.34, P<0.001). During a median follow-up of 54 (interquartile range, 23-58) months, 53 patients died. Plasma sCD14 was predictive of mortality, even after adjustment for renal function, Framingham risk factors, markers of mineral bone metabolism, and nutritional and inflammatory parameters (hazard ratio [HR] per SD higher of 1.90; 95% confidence interval [95% CI],1.32 to 2.74; P<0.001). After adjustment for the same risk factors, plasma sCD14 was also a predictor of cardiovascular disease (HR, 1.30; 95% CI, 1.00 to 1.69; P=0.05). Although plasma sCD14 was associated with progression of CKD, defined as reaching ESRD or doubling of serum creatinine in models adjusted for CKD-specific risk factors (HR, 1.24; 95% CI, 1.01 to 1.52; P=0.04), significance was lost when adjusted for proteinuria (HR, 1.19; 95% CI, 0.96 to 1.48; P=0.11). There was neither correlation between plasma endotoxin and sCD14 (ρ=-0.06, P=0.20) nor was endotoxin independently associated with adverse outcome during follow-up. CONCLUSIONS: Plasma sCD14 is elevated in patients with decreased kidney function and associated with mortality and cardiovascular disease in patients with CKD not yet on dialysis.

Association between Inflammation and Cardiac Geometry in Chronic Kidney Disease: Findings from the CRIC Study.

BACKGROUND: Left ventricular hypertrophy (LVH) and myocardial contractile dysfunction are independent predictors of mortality in patients with chronic kidney disease (CKD). The association between inflammatory biomarkers and cardiac geometry has not yet been studied in a large cohort of CKD patients with a wide range of kidney function. METHODS: Plasma levels of interleukin (IL)-1ß, IL-1 receptor antagonist (IL-1RA), IL-6, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-ß, high-sensitivity C-Reactive protein (hs-CRP), fibrinogen and serum albumin were measured in 3,939 Chronic Renal Insufficiency Cohort study participants. Echocardiography was performed according to the recommendations of the American Society of Echocardiography and interpreted at a centralized core laboratory. RESULTS: LVH, systolic dysfunction and diastolic dysfunction were present in 52.3%, 11.8% and 76.3% of the study subjects, respectively. In logistic regression analysis adjusted for age, sex, race/ethnicity, diabetic status, current smoking status, systolic blood pressure, urinary albumin- creatinine ratio and estimated glomerular filtration rate, hs-CRP (OR 1.26 [95% CI 1.16, 1.37], p<0.001), IL-1RA (1.23 [1.13, 1.34], p<0.0001), IL-6 (1.25 [1.14, 1.36], p<0.001) and TNF-α (1.14 [1.04, 1.25], p = 0.004) were associated with LVH. The odds for systolic dysfunction were greater for subjects with elevated levels of hs-CRP (1.32 [1.18, 1.48], p<0.001) and IL-6 (1.34 [1.21, 1.49], p<0.001). Only hs-CRP was associated with diastolic dysfunction (1.14 [1.04, 1.26], p = 0.005). CONCLUSION: In patients with CKD, elevated plasma levels of hs-CRP and IL-6 are associated with LVH and systolic dysfunction.