Serum Lipoprotein (a) Concentration Is Increased in Moderate Renal Failure

Dr. Margret Arnadottir, Department of Medicine, Landspitali University Hospital, IS-101 Reykjavik (Iceland) Table 1. Concentrations of serum lipids, lipoproteins including Lp(a), apolipoprotein B, plasma albumin and urine albumin in groups with different GFRs Dear Sir, Lipoprotein (a) (Lp(a)) consists of an LDL particle linked by a disulfide bridge to apolipoprotein (a) [1], a glycoprotein which has structural homologies with plasminogen [2]. Increased serum concentrations of Lp(a) have been shown to be a strong, independent risk factor for the development of atherosclerosis in the general population [3] and in hemodialysis patients [4]. Moreover, Lp(a) has been found in atherosclerotic lesions in arterial walls, implying pathogenetic significance [5]. There are several reports of increased serum concentrations of Lp(a) in advanced renal failure: in predialytic patients [6], in hemodialysis patients [6-11], and in CAPD patients [10-13]. Less is known about serum Lp(a) concentrations earlier in renal failure. Lipid, lipoprotein including Lp(a), and apolipoprotein concentrations were analyzed in serum from 72 patients with a wide range of glomerular filtration rates (GFRs). The patients were divided into three GFR groups: a reference group (67-107 ml/min), patients with moderate renal failure (36-63 ml/min), and patients with severe renal failure (6-32 ml/min). Factors other than renal insufficiency, known to influence lipoprotein metabolism, were strictly excluded (diabetes, endocrine disease, obesity, liver disease, active inflammatory disease, malignancy, treatment with lipid-lowering agents, steroids or cyclosporin). Patients with urine albumin concentrations exceeding 500 mg/l (50 mg/dl) and/or signs of moderate-severe inflammatory activity in the plasma protein pattern were excluded. Serum Lp(a) concentrations were measured with a radioimmunoassay with reagents from Pharmacia, Uppsala, Sweden. The results were expressed as median/range and nonparametric statistical tests were applied. GFR was estimated by a single sample method with iohexol as a marker [14, 15]. Plasma iohexol concentrations were analyzed by high-performance liquid chroma-tography. The results of the Lp(a) analyses are shown in table 1. As estimated by the Krus-kal-Wallis test, the variance between the groups was significantly different. Serum Lp(a) concentrations were significantly increased in moderate and severe renal failure as compared with the reference group, and they were inversely correlated with GFR (r = -0.33, p = 0.005). A trend was observed in the renal failure groups towards an increase in the number of subjects with serum Lp(a)