The microinflammatory state in uremia: causes and potential consequences

Mortality is markedly elevated in patients with end-stage renal disease. The leading cause of death is cardiovascular disease. Lipoprotein levels are only slightly elevated in dialysis patients, and cardiovascular risk is inversely correlated with serum cholesterol, suggesting that a process other than hyperlipidemia plays a role in the incidence of cardiovascular disease. Hypoalbuminemia, ascribed to malnutrition, has been one of the most powerful risk factors that predict all-cause and cardiovascular mortality in dialysis patients. The presence of inflammation, as evidenced by increased levels of specific cytokines (interleukin-6 and tumor necrosis factor alpha) or acute-phase proteins (C-reactive protein and serum amyloid A), however, has been found to be associated with vascular disease in the general population as well as in dialysis patients. The process of inflammation, also called the acute-phase response, additionally causes loss of muscle mass and changes in plasma composition-decreases in serum albumin, prealbumin, and transferrin levels, also associated with malnutrition. Inflammation alters lipoprotein structure and function as well as endothelial structure and function to favor atherogenesis and increases the concentration of atherogenic proteins in serum, such as fibrinogen and lipoprotein (a). Inflammation in dialysis patients is episodic. The causes are likely to be multifactorial and include vascular access infection, less-than-sterile dialysate, dialysate back leak, and nonbiocompatible membranes in addition to clinically apparent infection. In addition, proinflammatory compounds, such as advanced glycation end products, accumulate in renal failure, and defense mechanisms against oxidative injury are reduced, contributing to inflammation and to its effect on the vascular endothelium.