Hyperlipidemia is a cardiovascular risk factor. In patients with idiopathic dilated cardiomyopathy (IDC), prognostic roles of endogenous lipoproteins are not fully clarified. It has been known that there is a direct relationship between the levels of cytokines (tumor necrosis factor-alpha [TNF-alpha] and interleukin-6 [IL-6]) and deteriorating functional classes of heart failure and mortality. The present study compared the levels of circulating TNF-alpha, IL-6, lipoproteins, and apolipoproteins in patients with stable IDC (n = 28) with those of patients with unstable IDC (n = 26) and controls (n = 24). Mean serum total. cholesterol (TC) was significantly lower in stable IDC patients than controls (p < 0.05). In unstable IDC patients, mean serum TC was also lower than controls but not statistically significant. The IDC patients had significantly higher concentrations of IL-6 and TNF-alpha than the controls (p < 0.01). Serum IL-6 and Apo AI levels were significantly different between stable and unstable IDC patients (p = 0.021 and p = 0.012, respectively). Increased levels of IL-6 were associated with decreased levels of TC (r = -0.266, p = 0.019), LDL-C (r = -0.376, p = 0.001) and apolipoprotein AI (apo AI) (r = -0.495, p < 0.001) in all IDC patients. TNF-a was also inversely related to apo AI (r = -0.455, p < 0.001) and LDL-C (r = -0.364, p = 0.001) in all patients. Thus, elevated serum levels of cytokines in patients with IDC are associated with decreased lipoprotein concentrations, which may indicate impaired prognosis. (c) 2005 Tohoku University Medical Press.