Lipoprotein profile in men with peripheral vascular disease. Role of intermediate density lipoproteins and apoprotein E phenotypes

Impaired chylomicron remnant clearance in familial combined hyperlipidemia

Postprandial chylomicron remnant clearance was studied in six patients with familial combined hyperlipidemia (FCH) and seven control subjects by using an oral retinyl palmitate (RP) fat-loading test. The chylomicron remnant clearance (Sf < 1,000 fraction), expressed as the area under the RP curve (AUC-RP), was delayed in FCH subjects (65.05 +/- 12.84 hours x [mg/L]) compared with control subjects (25.1 +/- 5.4 hours x [mg/L]; p = 0.01). Postprandial lipoprotein particle size and composition in the Sf > 1,000 fraction were different between FCH and control subjects as analyzed by molecular-sieve chromatography. Fasting high density lipoprotein cholesterol was lower in FCH patients (0.54 +/- 0.09 mmol/L) than in control subjects (0.89 +/- 0.05 mmol/L; p < 0.01). Mean plasma postheparin lipoprotein lipase and hepatic lipase activities were similar between FCH patients (94 +/- 25 and 427 +/- 57 milliunits/mL, respectively) and control subjects (126 +/- 16 and 362 +/- 33 milliunits/mL, respectively). In FCH, a 54% reduction (p < 0.05) of plasma triglycerides to 2.63 +/- 0.41 mmol/L by drug treatment resulted in an enhanced, but not normalized, clearance of chylomicron remnants (39.4 +/- 6.0 hours x [mg/L]). Univariate regression analysis revealed that in FCH subjects the changes in fasting plasma apolipoprotein C-III concentrations after therapy were significantly associated with the changes in chylomicron remnant AUC-RP (r = 0.87; p = 0.02). Delayed elimination of atherogenic chylomicron remnants may contribute to the increased risk of premature atherosclerosis in FCH.

Lipoprotein abnormalities in hyperlipidemic and normolipidemic men on hemodialysis with chronic renal failure

Lipids, lipoproteins, apolipoproteins (apo) and apo E polymorphism were determined in 101 men with chronic renal failure (CRF) were were on hemodialysis and 101 healthy controls matched for age and sex. Patients with CRF on hemodialysis had significantly higher levels of serum triglycerides, very-low-density lipoprotein (VLDL) cholesterol, intermediate-density lipoproteins (IDL), and lower levels of low- and high-density lipoproteins (LDL and HDL, respectively) than controls. Regarding apolipoproteins, serum apo B concentrations were decreased. Apo C-III concentrations in sera and in VLDL and HDL fractions were significantly increased in 35 hemodialysis patients compared with 32 controls. Seventy-eight of the 101 CRF patients had normal serum cholesterol and triglycerides (less than 5.2 mmol/liter and less than 2.3 mmol/liter, respectively). However, this subgroup also showed a significant increase in VLDL-triglycerides and serum apo E concentration in addition to changes observed in the group as a whole. Apo E polymorphism in our study population did not differ from that reported for other European populations. According to the different apo E phenotypes, lipids and lipoprotein composition showed no significant differences in controls or patients. We conclude that accumulation of triglyceride-rich lipoproteins in patients with CRF on hemodialysis may thus be at least in part related to the enrichment of apo C-III in VLDL and HDL fractions. Lipoprotein profile in hemodialysis patients, including those with normal serum cholesterol and triglyceride levels, is consistent with high cardiovascular risk.