An increased serum level of free Apo(a) in renal patients is more strikingthan that of Lp(a) and is influenced by homocysteine

Lipoprotein(a) [Lp(a)] excess combined with hyperhomocysteinaemia and hyper fibrinogenaemia may contribute to the high incidence of vascular diseases i n dialysis patients. This study is aimed at investigating the role of free apolipoprotein(a) [fapo(a)] in renal patients. We have been able to show th at, as compared with controls (0.53 mg/l), the median serum concentrations of fapo(a) in patients with nephrotic syndrome (2.58 mg/l) and with periton eal dialysis (3.40 mg/l) were strongly elevated (5- to 7-fold), while the f apo(a) levels in patients undergoing haemodialysis (1.02 mg/l) and after re nal transplantation (0.90 mg/l) were about doubled. The observed difference s in fapo(a) levels indicate that several mechanisms may increase the level of fapo(a), i.e., reduced renal clearance, enhanced hepatic synthesis, or homocysteine releasing apolipoprotein(a) from Lp(a). In the study collectiv e, the median total homocysteine levels were significantly elevated in all patient groups, stronger in patients on haemodialysis (31.4 mu mol/l) and p eritoneal dialysis (31.2 mu mol/l) than in patients with nephrotic syndrome (19.7 mu mol/l) and after renal transplantation (19.5 mu mol/l). In transp lant patients with adequate renal function and without other apolipoprotein (a)-increasing factors, fapo(a) was significantly increased when total homo cysteine exceeded 22 mu mol/l. In conclusion, our findings let us presume t hat an increased fapo(a) level in renal patients possibly could be one of t he reasons contributing to the high incidence of vascular diseases in these patients, because fapo(a) not covalently linked with Lp(a) is even more ea sily able to inhibit the fibrinolytic system than the complete Lp(a). These preliminary results have to be confirmed by further investigations. Copyri ght (C) 2000 S. Karger AG, Basel.