Lipoprotein particles in hypertriglyceridemic states

Plasma lipoprotein particle concentrations in postmenopausal women with unstable coronary artery disease. Analysis of diagnostic accuracy using receiver operating characteristics

BACKGROUND

The contribution of plasma lipids to cardiovascular risk is usually evaluated by measuring plasma concentrations of total cholesterol, triglycerides and HDL cholesterol, and calculating LDL cholesterol concentration. We investigated plasma concentrations of apolipoproteins and lipoprotein particles in women with unstable coronary artery disease (CAD) to evaluate whether these, better than the routine lipid status, could differentiate women with and without coronary atherosclerosis.

METHODS

Blood samples for lipid analyses were collected from 119 angiographically examined postmenopausal 49-79-year-old women with unstable CAD, and from 101 age-matched controls. Mean plasma concentrations were compared and the discriminatory ability of the different variables were tested using receiver operating characteristics (ROC).

RESULTS

At coronary angiography 19% had normal vessels and 81% had coronary atherosclerosis. A disturbed triglyceride metabolism was the most pronounced lipid abnormality in women with unstable CAD and coronary atherosclerosis. ROC showed that none of the evaluated variables had a particularly high discriminatory power regarding unstable CAD or coronary atherosclerosis. The ratio cholesterol/HDL cholesterol was best with an ROC area of 0.79. Furthermore, the newer lipid variables, i.e. lipoprotein particles and apolipoproteins, were no better than the traditional variables.

CONCLUSION

Lipoprotein changes reflecting a disturbed triglyceride metabolism are most pronounced in women with unstable CAD and coronary atherosclerosis. Lipoprotein particles and apolipoproteins alone were no better than lipids and lipoproteins in separating women with from those without coronary atherosclerosis. Our study does not support the measurement of apolipoproteins and lipoprotein particles on the basis of diagnostic accuracy alone.

Triglyceride enriched lipoprotein particles correlate with the severity of coronary artery disease

A group of 100 male normotensive, non-obese, non-diabetic subjects who had undergone coronary angiography were studied to determine relationship between the severity of coronary artery disease (CAD) and plasma lipids, apolipoproteins and lipoprotein particles defined by their apolipoprotein composition. CAD was found in 84 and no measurable lesions were found in 26 subjects. The severity of CAD was determined on the basis of size and number of lesions and expressed in terms of a global CAD score. Low density lipoprotein (LDL)-cholesterol showed a tendency to be higher in CAD patients than in CAD-free subjects (216 vs. 205 mg/dl, P = 0.07). HDL-cholesterol showed a tendency towards lower values in CAD patients compared to CAD-free subjects 35 vs. 41 mg/dl, P = 0.07). In univariate analysis the severity of CAD correlated with (i) complex, apolipoprotein (apo) B containing particles (Lp-B-complex, r = 0.31, P = 0.005), (ii) HDL-cholesterol (r = -0.30, P = 0.005), (iii) apoC-III in heparin precipitate (r = 0.30, P = 0.005) and (iv) plasma triglycerides (r = 0.25, P = 0.02), all of which are related to triglyceride-rich lipoproteins. A comparison between the two subspecies of complex lipoprotein particles revealed that those containing apolipoproteins B, C-III and E (Lp-B:C:E complex) were more closely associated with CAD score (r = 0.27, P = 0.01) than those containing apolipoproteins A-II, B, C, D and E (Lp-A-II:B-complex). LDL-cholesterol also correlated with the global CAD score (r = 0.23, P = 0.03). In multiple regression analysis only HDL-cholesterol (P = 0.003), apoC-III-ratio (P = 0.007), Lp-B-complex (P = 0.02) and Lp-B:C:E-complex (P = 0.04) showed significant correlation with CAD score. The results of this study demonstrate that some of the triglyceride rich lipoprotein particles represent a risk factor for CAD and support the clinical usefulness of specific assays capable of distinguishing lipoprotein particles on the basis of apolipoprotein composition.

Effects of lovastatin on ApoA- and ApoB-containing lipoproteins. Families in a subpopulation of patients participating in the Monitored Atherosclerosis Regression Study (MARS)

To establish whether lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, exhibits a specific effect on apolipoprotein (apo) A- and apoB-containing lipoproteins, 63 subjects, a subset of the 270 Monitored Atherosclerosis Regression Study (MARS) patients with hypercholesterolemia (190 to 295 mg/dL) and documented coronary artery disease, were randomized into either lovastatin 40 mg twice daily or matching placebo tablets twice daily. Both groups consumed a diet containing 27% calories as fat (polyunsaturated fat/saturated fat ratio, 2.85) and a daily cholesterol intake of less than 250 mg. The plasma lipid and apolipoprotein profiles were determined at the time of randomization and after 2 years of treatment, and the levels of apoA- and apoB-containing lipoprotein families were measured after 2 years of treatment. After this treatment period, the drug group was characterized in comparison with the placebo group by significantly reduced levels of total cholesterol (33%), triglycerides (30%), very-low-density lipoprotein cholesterol (36%), low-density lipoprotein cholesterol (43%), apoB (36%), apoC-III (18%), and apoE (17%) and slightly but insignificantly increased levels of high-density lipoprotein cholesterol (6%) and apoA-I (1%). The 2-year levels of lipoprotein containing apoA-I but no apoA-II (LpA-I) and lipoprotein containing both apoA-I and apoA-II (LpA-I/A-II) particles separated by immunoaffinity chromatography on an anti-apoA-II immunosorber did not differ between the two treatment groups. However, the apoB-containing lipoprotein (Lp) families defined by apolipoprotein composition and separated by immunoaffinity chromatography on anti-apoA-II and anti-apoC-III immunosorbers were affected in a selective manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced LDL oxidation in uremic patients: an additional mechanism for accelerated atherosclerosis?

Since oxidized low-density lipoprotein (LDL) is more atherogenic than native LDL, LDL oxidation was investigated in uremic patients who often develop accelerated atherogenesis. Three groups of uremic patients were studied (10 on predialysis conservative therapy, 11 on repetitive hemodialysis, 13 on peritoneal dialysis) and compared with seventy matched controls. LDL oxidation was evaluated in all patients as: (i) the susceptibility to in vitro oxidation (by measuring the resistance to Cu(++)-induced formation of conjugated dienes), (ii) vitamin E concentration in LDL, and (iii) presence of plasma anti-oxidized LDL antibodies, expressed as the ratio anti-oxLDL/anti-nativeLDL antibodies. The lipid profile was studied in all patients. Vitamin E concentration did not differ between the various groups, although LDL from uremic patients appeared more susceptible to in vitro and in vivo oxidation (as demonstrated by an earlier generation of conjugated dienes and by the presence of an higher antibody ratio) compared to control subjects. Subclass analysis of the different patients revealed that peritoneal dialysis treatment ameliorated the oxidation markers. However, a prolonged dialytic treatment caused a decrease in vitamin E concentration in LDL and increased their susceptibility to oxidation.

Disturbances of lipid metabolism in children with chronic renal failure

This review discusses the pathogenesis, clinical significance and current therapy of hyperlipoproteinaemia (HLP) in children with chronic renal failure. Uraemic dyslipidaemia, characterized by hypertriglyceridaemia and low high-density lipoprotein-cholesterol levels, is present in the majority patients with chronic renal failure. In addition, serum levels of total cholesterol, very low-density lipoprotein-cholesterol, low-density lipoportein-cholesterol and apolipoprotein B are frequently elevated. The pathophysiological mechanisms causing these disturbances are complex and mainly involve a diminished catabolism of triglyceride-rich lipoproteins. For unknown reasons and independent of other lipoproteins, serum levels of the highly atherogenic and thrombogenic lipoprotein(a) are also often elevated. HLP is an important factor in cardiovascular morbidity and mortality. In addition, dyslipidaemia may enhance progression of renal disease in patients with residual renal function. Therefore, treatment of HLP seems indicated in overtly hyperlipidaemic patients, but until there is more experience with lipid-lowering drugs in children, no safe recommendations for pharmacological treatment of HLP can be given. Dietary modifications can be recommended only to a limited extent.