Atherosclerosis risk is higher in continuous ambulatory peritoneal dialysis patients than in hemodialysis patients

While it has been reported that myocardial infarction and cerebrovascular disease are more common in continuous ambulatory peritoneal dialysis (CAPD) patients than in hemodialysis patients, some studies have not supported these results. The aim of this study was to compare CAPD and hemodialysis patients with regard to atherosclerotic changes and to assess which factors might be responsible for atherosclerosis in dialysis patients. Group 1 consisted of 65 CAPD patients, and Group 2 consisted of 109 hemodialysis patients who were age-, gender-, and duration-of-dialysis-matched with CAPD patients. We used ultrasonographic measurement of carotid artery intima media thickness to identify atherosclerosis. Known risk factors for atherosclerosis including hypertension, smoking, serum levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, lipoprotein (a) [Lp(a)], albumin, intact parathormone, fibrinogen, and C-reactive protein were determined in all patients. More atherosclerotic changes were seen in CAPD than in hemodialysis patients. Of all the atherosclerosis risk factors, only serum total cholesterol, LDL-C, and Lp(a) levels were significantly higher in patients on CAPD.

Does renal failure cause an atherosclerotic milieu in patients with end-stage renal disease?

PURPOSE

Atherosclerotic vascular disease is the main cause of morbidity and mortality in patients with end-stage renal disease, but the independent contribution of renal failure rather than associated risk factors is unclear. We sought to examine the relative contribution of these factors to the severity of atherosclerosis by measuring intima-medial thickness and brachial artery reactivity in uremic patients and controls.

SUBJECTS AND METHODS

Cardiovascular risk factors, including lipid and homocysteine levels, were evaluated in 213 patients (69 on hemodialysis, 60 on peritoneal dialysis, and 82 nonuremic controls). High-resolution B-mode ultrasonography with automated off-line analysis was used to measure the intima-medial thickness in the common carotid artery and to measure the lumen diameter of the brachial artery at rest, during reactive hyperemia, and after sublingual nitroglycerine. The correlations of risk factors with intima-medial thickness and brachial reactivity were examined using a general linear regression model.

RESULTS

Patients with renal failure had a greater mean (+/- SEM) maximum intima-medial thickness than controls (0.83 +/- 0.02 mm versus 0.70 +/- 0.02 mm, P < 0.05), but the brachial artery response to reactive hyperemia was not significantly different between the renal failure patients and the control group (4.7% +/- 6.1% versus 6.1% +/- 8.6% dilatation, P > 0.05). The uremic state was an independent predictor of intima-medial thickness (r2 = 0.16, P < 0.001) but not of brachial artery reactivity (P = 0.99).

CONCLUSION

The atherosclerotic burden in patients with renal failure, as indicated by an increased intima-medial thickness, may reflect effects of uremia that are independent of cardiovascular risk factors.

Effect of apolipoprotein E polymorphism on serum lipid, lipoproteins, and atherosclerosis in hemodialysis patients

Atherosclerosis and cardiovascular disease are the main causes of death in hemodialysis patients. Possession of the apolipoprotein E4 (ApoE4) allele has been associated with increased levels of serum lipids and with coronary and carotid artery atherosclerosis. We investigated the possible relationship between ApoE polymorphism and atherosclerosis risk factors in hemodialysis patients. Two hundred sixty-nine hemodialysis patients (115 women, 154 men) were included in our study. The mean patient age and mean hemodialysis duration were 45.8 +/- 15.3 years and 52.6 +/- 40.6 months, respectively. Testing was done on all patients to determine ApoE genotype and serum levels of total cholesterol (T-Cho), low-density lipoprotein (LDL-C), high-density cholesterol (HDL-C), triglyceride (TG), lipoprotein (a) (Lp[a]), intact parathormone (iPTH), and fibrinogen. ApoE genotype was identified with the polymerase chain reaction. Ultrasonographic measurement of carotid artery intima media thickness (IMT) was used to diagnose atherosclerosis. We also analyzed ApoE polymorphism and risk factors such as age, gender, duration of hemodialysis, smoking, and hypertension in relation to the presence of atherosclerosis. Serum T-Cho and LDL-C levels were higher in patients with the ApoE4/3 phenotype than in those with ApoE3/3 and ApoE3/2 phenotypes (P < 0.05). However, there was no statistically significant link between ApoE polymorphism and serum levels of TG, HDL-C, or Lp(a) (P > 0.05). Apart from a relationship with age and duration of hemodialysis (P < 0.05), we found no significant association between atherosclerosis and ApoE polymorphism or the other risk factors analyzed (P > 0.05). In conclusion, although ApoE polymorphism significantly affects serum levels of T-Cho and LDL-C in hemodialysis patients, this study indicates that ApoE polymorphism is not associated with the presence of atherosclerosis in these individuals. The high incidence of atherosclerosis in these patients underlines the need for further research on other possible causative factors.

Homogentisic acid and structurally related compounds as intermediates in plasma soluble melanin formation and in tissue toxicities

Homogentisic acid (HGA) spontaneously starts to undergo oxidation and polymerization soon after the beginning of incubation in human blood or plasma at 37 degrees C, and forms plasma soluble melanins (PSM). Haemolysis accompanies this process in blood. The addition of equimolar quantities of antioxidants delays this oxidation significantly (isoascorbic acid by 2:30-4:00 h; glutathione by 3:20-4:05 h; D-penicillamine by 5:00-5:45 h). HGA is a phenylalanine and tyrosine metabolite, related structurally to the catecholamines and other precursors of melanins. HGA is normally metabolized by the enzyme homogentisic acid oxidase. When this enzyme is genetically missing, part of HGA is excreted in the urine, another part polymerizes darkens many tissues (ochronosis), and produces widespread degenerative changes in cartilage and other connective tissues, joints, blood vessels, heart valves, kidneys and in other tissues. Collectively this disorder is known as alcaptonuria, for which no satisfactory treatment is known. The causes of both alcaptonuric arthritis and rheumatoid arthritis are thought to involve increased oxidative stress. Inflammation of joints and connective tissue damage are involved in both diseases. Oxygen radicals are suspected to cause inflammation and cellular damage. Hydroxyl radicals degrade hyaluronic acid (the viscous synovial fluid of joints). High levels of products of free radical reactions, with fluorescence excitation (ex) and emission (em) maxima in the wavelength ranges of those of PSM (ex 320-400 and em 400-470) were reported in the blood sera and synovial fluids of patients with rheumatoid arthritis.(ABSTRACT TRUNCATED AT 250 WORDS)