HDL composition and HDL antioxidant capacity in patients on regular haemodialysis

Recent evidence suggests that HDL can directly inhibit LDL oxidation, a key early stage in atherogenesis. Patients with chronic renal failure are at i ncreased cardiovascular risk, have reduced HDL levels and altered HDL compo sition. We have therefore investigated whether compositional changes in HDL lead to decreased HDL antioxidant capacity in these patients. In compariso n to control subject HDL, patient HDL contained less total cholesterol, cho lesterol esters, phospholipids and alpha-tocopherol. LDL, HDL and LDL + HDL were standardised for protein and oxidised in the presence of Cu2+. The ra te of propagation during HDL oxidation was reduced in the patient group (3. 28 +/- 0.65 x 10(-5) vs. 4.60 +/- 0.97 x 10(-5) abs. U/min, P < 0.01). Lipi d peroxide generation in patient HDL was decreased: 6.56 +/- 4.4 versus 13. 42 +/- 7.0 nmol malondialdehyde (MDA)/mg HDL protein after 90 min and 14.45 +/- 3.8 versus 20.11 +/- 7.8 nmol MDA/mg HDL protein after 180 min. This i s attributable to reduced HDL polyunsaturated fatty acid content in patient s (0.53 +/- 0.12 vs. 0.72 +/- 0.16 mmol/g HDL, P < 0.01). The inhibitory ef fect of HDL on LDL oxidation was similar: 71 and 33% for patient HDL compar ed to 68 and 31% for control HDL, after 90 and 180 min, respectively Compos itional changes of HDL in patients on haemodialysis did not affect the anti oxidant capacity of HDL after standardisation for HDL protein. However, red uced HDL levels in vivo may result in reduced HDL antioxidant capacity in t hese patients. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.