Apo(a)-isoform size, nutritional status and inflammatory markers in chronic renal failure

Abstract

Atherosclerotic cardiovascular disease and malnutrition are widely recognized as leading causes of the increased morbidity and mortality observed in uremic patients. Levels of lipoprotein (a) [Lp(a)], an established cardiovascular risk factor, are elevated in uremic patients. Moreover, low serum albumin levels indicating malnutrition have been associated with elevated plasma Lp(a) levels in dialysis patients. However, serum albumin levels are also influenced by an inflammatory reaction. The present study was undertaken to further investigate the relationship between Lp(a), inflammation and malnutrition in patients with chronic renal failure (CRF) prior to the initiation of renal replacement therapy, and to investigate the potential relation between these factors and apo(a)-isoform size, an important determinant of plasma Lp(a) levels. A total of 83 patients (mean age 52 ± 1 year) with terminal (creatinine clearance 9 ± 1 ml/min) CRF were cross sectionally investigated. In addition to lipid parameters and apo(a)-isoform size, C-reactive protein (CRP), nutritional parameters including serum levels of albumin and body composition (dual energy x-ray absorptiometry), as well as a subjective global assessment (SGA) and the prevalence of cardiovascular disease (CVD) were evaluated. Malnourished patients (N = 39) had a significantly (P < 0.05) higher median plasma Lp(a) level (19.5 mg/dl) as compared to 44 well-nourished patients, (11.7 mg/dl). No difference was found for other lipid or lipoprotein parameters. A significant relationship was found between CRP and plasma Lp(a), whereas no significant relation was observed between plasma Lp(a) and serum albumin levels. The apo(a)-isoform distribution was similar among malnourished and well-nourished patients. There was no difference in nutritional parameters when comparing patients with small- and large-size apo(a) isoforms. However, a subgroup of patients (12%) with no detectable apo(a)-bands and low Lp(a) levels had significantly higher lean body mass. The present study demonstrates elevated plasma Lp(a) levels in CRF patients with signs of malnutrition, even though no direct relationships between plasma Lp(a) levels and various nutritional parameters were observed. The observed relationship between Lp(a) and CRP suggests that inflammatory factors, more prevalent in patients with malnutrition, may contribute to the Lp(a) increase in malnourished CRF.