Cytokines, atherogenesis, and hypercatabolism in chronic kidney disease: a dreadful triad

Increased expression of pro-inflammatory genes in abdominal subcutaneous fat in advanced chronic kidney disease patients

OBJECTIVES

Low-grade systemic inflammation, oxidative stress and peripheral insulin resistance are intimately associated and contribute to the increased risk of cardiovascular complications in advanced chronic kidney disease (CKD). Because altered adipose tissue activities have previously been linked to pathophysiological processes in various inflammatory and metabolic diseases we hypothesized that the uraemic milieu in patients with CKD may interact with the adipose tissue, provoking an unfavourable shift in its transcriptional output.

DESIGN

Twenty-one adipokine mRNAs were quantified in abdominal subcutaneous adipose tissue (SAT) biopsies and serum/plasma concentrations of inflammatory markers and related protein products were measured.

SETTING

The study was conducted at the Karolinska University Hospital, Huddinge, and Karolinska Institutet, Stockholm, Sweden.

SUBJECTS

Thirty-seven patients with CKD [15 women, median 58 (interquartile range 49-65) years] and nine nonuraemic individuals [four women, age 62 (45-64) years] were recruited prior to initiation of peritoneal dialysis catheter insertion or elective hernia repair/laparoscopic cholecystectomy, respectively.

RESULTS

Even after correction for body mass index, SAT from patients showed a significant upregulation of inflammatory pathway genes interleukin 6 (3.0-fold, P=0.0002) and suppressor of cytokine signalling 3 (2.5-fold, P=0.01), as well as downregulation of leptin (2.0-fold, P=0.03) and the oxidative stress genes uncoupling protein 2 (1.5-fold, P=0.03) and cytochrome b-245, alpha polypeptide (1.5-fold, P=0.005), in relation to controls.

CONCLUSIONS

These gene expression differences suggest that inflammatory and oxidative stress activities may be important features of the intrinsic properties of uraemic adipose tissue, which may have significant effects on the uraemic phenotype.

Vascular health, systemic inflammation and progressive reduction in kidney function; clinical determinants and impact on cardiovascular outcomes

INTRODUCTION

Systemic inflammation, endothelial dysfunction and arterial thickening contribute to the elevated cardiovascular risk of dialysis patients. However, the course of these derangements and their relative contribution to the cardiovascular risk of nondialysed chronic kidney disease (CKD) are scarcely investigated.

METHODS

Flow-mediated dilatation (FMD) and intima-media thickness (IMT) were assessed in 304 nondialysed CKD patients Stages 1-5 (mean age 46 ± 12 years, 158 men), together with routine biochemical measurements, C-reactive protein (CRP) and insulin resistance. Patients were then followed for time-to-event analysis of cardiovascular outcomes (fatal and nonfatal).

RESULTS

CRP and IMT increased, while FMD decreased in parallel with estimated glomerular filtration rate (eGFR) decline (P < 0.001 for all). CRP and intact parathormone, as well as eGFR, appeared as strong determinants of FMD and IMT in multivariate analyses. After a median follow-up of 41 (range 6-46) months, 30 fatal and 59 nonfatal cardiovascular events occurred. In univariate analysis, FMD, IMT and CRP were significant predictors of outcome. In a multivariate Cox model excluding IMT, both FMD [hazard ratios 0.52 (95% confidence intervals 0.37-0.73) per %] and CRP [1.07 (1.03-1.11) per mg/L] predicted cardiovascular outcomes independently of confounders. In a model excluding FMD, only CRP (and not IMT) was a significant predictor.

CONCLUSIONS

Endothelial dysfunction, arterial thickening and inflammation occur in parallel with the decline in eGFR, contributing to the increased cardiovascular risk of nondialysed CKD. Our results support the use of FMD over IMT measurements to monitor nondialysed CKD patients at risk.

TNF-α levels are not increased in inflamed patients carrying the CCR5 deletion 32

BACKGROUND AND AIMS

Recently we reported on a genetically predisposed protection from C-reactive protein (CRP) related mortality in dialysis patients carrying the functional CC-chemokine receptor 5 deletion 32 allele (CCR5Δ32) mutation. Since CCR5Δ32 is associated with a less pro-inflammatory immune response in mice, we hypothesized that the observed protection is (in part) due to a less pro-inflammatory cytokine profile.

METHODS

Cross-sectional observational study including 263 incident dialysis patients aged 18-70years, without clinical signs of infection and/or acute vasculitis. TNF-α, IL-6, IL-10 and hsCRP levels were determined and studied in relation to the CCR5 genotype.

RESULTS

In the presence of elevated hsCRP, IL-6 concentration was higher irrespective of the CCR5 genotype. However, in patients with the CCR5 deletion, TNF-α did not differ in the presence/absence of elevated hsCRP and was not correlated with hsCRP levels in carriers of the CCR5Δ32 polymorphism.

CONCLUSIONS

A possible underlying mechanism of the impact of CCR5Δ32 genotype on inflammation driven mortality in dialysis patients could be a reduced Th1 immune response as represented by decreased TNF-α levels.

Trimestral variations of C-reactive protein, interleukin-6 and tumour necrosis factor-α are similarly associated with survival in haemodialysis patients

BACKGROUND

The impact of intra-individual changes of inflammatory markers [other than C-reactive protein (CRP)] on mortality in haemodialysis (HD) patients is unknown. We therefore studied survival in relation to trimestral variations of CRP, interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α).

METHODS

In 201 prevalent HD patients from the Mapping of Inflammatory Markers in Chronic Kidney Disease cohort, serum CRP, IL-6 and TNF-α were measured 3 months apart and survival was assessed during follow-up. Based on fluctuations along tertiles of distribution, four patterns were defined for each inflammatory marker: stable low, decrease, increase and stable high. Hazard ratios were calculated by the Cox proportional hazard model, and Pearson's test was used to correlate changes. CRP analyses were replicated in 472 incident HD patients from the Netherlands Cooperative Study on the Adequacy of Dialysis.

RESULTS

Patients with persistently elevated CRP values had the worst mortality in crude [HR 2.98 (95% CI 1.71-5.20)] and adjusted [2.79 (1.58-4.94)] Cox models, together with those who increased in their CRP levels [crude 3.27 (1.91-5.60); adjusted 3.13 (1.79-5.45)]. Similar survival patterns were observed for IL-6 and TNF-α variation categories. Correlations among these changes were, however, not strong. In the replication cohort, individuals with persistently elevated CRP values also showed the highest mortality risk [crude 3.38 (2.31-4.94); adjusted 2.33 (1.58-3.45)].

CONCLUSIONS

Trimestral variations of TNF-α, IL-6, and CRP are similarly associated with survival in HD patients. The agreement between changes of these biomarkers was low, suggesting that different pathways may trigger each of these markers.

Platelet/Leukocyte activation, inflammation, and uremia

Chronic kidney disease (CKD) is a state of chronic, low-grade inflammation which contributes to the accelerated progression of chronic inflammatory disturbances of which atherosclerosis is a major example. Platelet and leukocyte activation and interaction, evoked by the uremic condition, play an important role in this process. The effect of specific uremic retention solutes, progressively retained in uremia, on important platelet and leukocytes functions is discussed and summarized. The main uremic toxins involved are molecules with a molecular weight above 500 Da (the so-called "middle molecules") and/or protein-bound molecules. Classification of the molecules and elucidation of the pathophysiological pathways involved will result in new therapeutic strategies pursuing specific removal or pharmacological neutralization of molecular impact.