Strong association between malnutrition, inflammation, and atherosclerosis in chronic renal failure

The role of C-reactive protein in cardiovascular disease risk

Over the past few years, a flurry of data in the medical literature has strongly implicated C-reactive protein (CRP) as a marker of inflammation in coronary artery disease (CAD). Recognizing the likely integral role that inflammation plays in the pathogenesis of atherosclerosis, many hospital laboratories have tests to measure CRP concentration in the clinical setting. However, the clinical use of these tests still need definition. To date, of the plasma-based markers investigated, CRP provides the strongest risk prediction for cardiovascular disease in men and women. Questions remain regarding the degree to which CRP can improve risk stratification beyond that of the traditional risk factors of CAD.

The role of lipoprotein[a] in atherosclerosis

Recent studies confirm and extend previous evidence that lipoprotein (Lp) plays a significant role in atherosclerosis and is one of the top five or six risk factors for cardiovascular disease. In Japanese patients, Lp levels and apo phenotypes are significant predictors for myocardial infarction. Lp levels are significantly higher in ischemic stroke patients than in controls. However, plasma concentrations of Lp are not predictive of ischemic cerebral infarction in either men or women. Serum Lp levels are significantly higher in patients with carotid plaques or measurable intima-media thickness than in controls without. Despite these associations, there is no significant relationship between Lp level and arterial endothelial function, smooth muscle response, or carotid wall thickness, even though other lipid risk factors like low-density lipoprotein cholesterol (LDL-C) and LDL-C/high-density lipoprotein cholesterol (HDL-C) ratio are correlated with abnormal arterial function and structure. There is new evidence that the association of Lp with extracellular matrix (ECM) secreted by arterial smooth muscle cells increases two- to threefold the subsequent specific binding of LDL. Alpha-defensins released from activated or senescent neutrophils stimulate the binding of Lp to ECM of endothelial cells. Several factors that affect the accumulation of Lp and oxidized LDL in the arterial intima have been identified. Several recent studies have provided new insights into the physiologic role that Lp might play in compromising fibrinolysis. The interaction of Lp with cells is clearly distinct from that with ECM and with fibrinogen; the regulation sites within Lp and plasminogen for these regulatory molecules are not identical. These recent advances bring us significantly closer to understanding how Lp exerts its atherogenic and thrombogenic properties.

Influence of convection on small molecule clearances in online hemodiafiltration

BACKGROUND

Dialysis efficacy is mostly influenced by dialyzer clearance. Urea clearance may be estimated in vitro by total ion clearance, which can be obtained by conductivity measurements. We have previously used this approach to assess in vitro clearances in a system mimicking predilutional and postdilutional online hemodiafiltration with a wide range of QD, QB, and ultrafiltration rates. Our current study elaborates on a formula that allows the prediction of the influence of ultrafiltration on small molecule clearances, and validates the mathematical approach both experimentally in vitro and clinically in vivo data.

METHODS

Two conductivimeters in the dialysate side of an E-2008 Fresenius machine were used. HF80 and HF40 polysulfone dialyzers were used; reverse osmosis water and dialysate were used for blood and dialysate compartments, respectively. Study conditions included QB of 300 and 400 mL/min and QD of 500 and 590 mL/min, with a range of ultrafiltration rate from 0 to 400 mL/min in postdilutional hemodiafiltration and to 590 mL/min in predilutional hemodiafiltration. Urea clearances were determined in the in vivo studies, which included 0, 50, 100, and 150 mL/min ultrafiltration rates.

RESULTS

The ultrafiltration rate and clearance were significantly correlated (R > 0.9, P < 0.001) and fitted a linear model (P < 0.001) in all of the experimental conditions. The following formula fitted the experimental points with an error <2% for both postdilutional and predilutional online diafiltration in vitro, respectively. K = K0 + [(QB - K0)/(QB)] x ultrafiltration rateK = K0 + [((QD x QB)/(QB + QD) - K0)/QD] x ultrafiltration rate where K is the clearance; K0 is the clearance with nil ultrafiltration rate; QD is the total dialysate produced (in commercial HDF, QD = QDi + Qinf). Since weight loss was maintained at 0, ultrafiltration rate = infusion flow. QB is the "blood" line flow. The formula was also verified in vivo in clinical postdilutional hemodiafiltration with a QB taking into account the cellular and water compartments.

DISCUSSION

In vitro, by simply determining the clearance in conventional dialysis, the total clearance for any ultrafiltration rate may be estimated in both predilutional and postdilutional online diafiltration with an error of less than 2%. The same applies to in vivo postdilutional hemodiafiltration when the formula takes into account the cellular and water composition of blood.

C-Reactive protein predicts all-cause and cardiovascular mortality in hemodialysis patients

Hypoalbuminemia predicts death in dialysis patients. Although hypoalbuminemia has been attributed to malnutrition, evidence of inflammation (C-reactive protein [CRP] and cytokine levels) has recently been recognized to predict albumin concentration in dialysis patients. We measured CRP and albumin levels in October 1995 in 91 hemodialysis (HD) patients. During a 34-month follow-up period, we determined the incidence and cause of death. Patients were divided into four groups based on serum albumin levels (<3.5 [lowest quartile], 3.5 to 3.8, 3.9 to 4.0, and >4.0 g/dL [highest quartile]). Survival differed among the four groups (P = 0.0063). Patients with albumin levels greater than 4.0 g/dL had the greatest survival. Kaplan-Meier survival estimates of patients from varying CRP quartiles (<2.6, 2.6 to 5.2, 5.3 to 11.5, and >11.5 microg/mL) differed among the four groups (P < 0.0001). The group with the greatest CRP level (>11.5 microg/mL) had the lowest survival. Multivariate analysis using the Cox proportional hazards model showed that only CRP level (chi-square = 21.11; P < 0.0001) and age (chi-square = 5.44; P = 0.020) predicted death. Albumin level (chi-square = 0.16; P = 0.69) was not predictive. Only when CRP was excluded from the model did low serum albumin level (chi-square = 12. 04; P = 0.0004) predict death. CRP level (chi-square = 16.79; P < 0. 0001) and age (chi-square = 6.38; P = 0.012) also superceded albumin level (chi-square = 0.45; P = 0.51) in predicting cardiovascular mortality. Although values for blood urea nitrogen, creatinine, and normalized protein catabolic rate were significantly less among patients who died, these parameters, as well as cholesterol level and diabetes, were not important predictors of death in multivariate analysis. The acute-phase response or the cause of the acute-phase response is largely responsible for the effect of hypoalbuminemia on mortality in HD patients.

High serum hyaluronan indicates poor survival in renal replacement therapy

Atherosclerotic cardiovascular disease (CVD), malnutrition, and inflammation are common clinical features of chronic renal failure and are associated with increased mortality. Elevated levels of C-reactive protein (CRP) and cytokines are commonly observed in dialysis patients and have been shown to predict mortality. Serum hyaluronan previously has been used as a marker of an inflammatory reaction, irrespective of its cause. We have determined serum levels of albumin and hyaluronan, as well as the prevalence of malnutrition (subjective global assessment, 2 to 4), inflammation (CRP >/= 10 mg/L), and overt CVD in a cohort of 97 predialysis patients (52 +/- 13 years). Moreover, we determined the outcome of these patients 29 +/- 11 months after the basal measurement of hyaluronan. Serum levels of hyaluronan (median) were markedly elevated in predialysis patients with signs of malnutrition (127.1 v 50.5 ng/mL; P < 0.0001), inflammation (130.1 v 55.0 ng/mL; P < 0.0001) and CVD (118.8 v 56.0 ng/mL; P < 0.001). The levels of log hyaluronan correlated significantly to log CRP (R = 0.35; P < 0.001), serum albumin (R = -0.40; P < 0.0001), CVD (R = 0.36; P < 0.001), and age (R = 0.40; P < 0.0001), respectively. Survival analysis by the Cox regression model showed that elevated hyaluronan levels were, independent of CVD, CRP, and age, significantly related to an increased mortality rate. The current study showed that markedly elevated serum hyaluronan levels are found in predialysis patients with malnutrition, inflammation, and CVD and that serum hyaluronan is a risk predictor of poor survival in dialysis.