Chylomicron remnant concentrations in patients with coronary artery disease

Lipoprotein removal mechanisms and aging: implications for the cardiovascular health of the elderly

PURPOSE OF REVIEW

The speed of removal from the plasma of apolipoprotein B-containing lipoproteins, for example, chylomicrons, VLDL and LDL is determinant of the plasma concentration of these lipoproteins, is influenced by genetic features and ambient factors, and has implications in atherogenesis. As aging increases the clinical complications of atherosclerosis, it is important to appraise the status of the removal mechanisms in elderly individuals.

RECENT FINDINGS

Removal of triglyceride-rich lipoproteins remnants is delayed but the triglyceride breakdown is unchanged in elderly individuals. The discovery of PCSK9, enzyme that degrades LDL receptors, and the recent observation that PCSK9 is elevated in the elderly raises another hypothesis to account for the increased LDL-cholesterol levels in the elderly. The removal of cholesterol from cells by HDL, the first step of cholesterol reverse transport is also less efficient in the elderly, which may compromise the body cholesterol homeostasis.

SUMMARY

Aging determines reduction of the efficiency of lipoprotein plasma removal mechanisms, which is implicated in increased incidence of cardia complications. Moreover, aging is frequently accompanied by physical activity reduction, weight gain, and metabolic disturbances that can further decrease the efficacy of the removal mechanisms. This knowledge is important for promoting cardiovascular health in the elderly and prolonging survival.

Fasting apoprotein B-48 level and coronary artery disease in a population without frank fasting hypertriglyceridemia

The aim of this study was to test the hypothesis that fasting apoprotein B-48 level might be a surrogate marker of postprandial lipemia in evaluating the risk of coronary artery disease (CAD) in a population without frank abnormality in fasting lipid profile. One hundred twenty-three patients tested by coronary angiography were selected on the criteria of absence of treatment with hypolipidemic drugs, obvious hypertriglyceridemia (>2.85 mmol/L), or other conditions that may interfere with lipoprotein metabolism except diabetes. CAD was defined by more than 50% narrowing of vessel lumen, and its severity is determined by the number of arteries involved. Fasting apoprotein B-48 was measured by a competitive enzyme-linked immunosorbent assay method. There was no difference in fasting apoprotein B-48 levels between the groups with and without CAD (0.123+/-0.096 vs 0.136+/-0.125 microg/mL, respectively), whatever the sex or whether with or without diabetes. The apoprotein B-48 level was not related to the presence or the severity of CAD. There was also no correlation between fasting apoprotein B-48 levels and age, sex, body mass index, and usual fasting lipid parameters in both patients with and without angiographically proven CAD. Finally, among the features of metabolic syndrome, apoprotein B-48 was correlated with fasting triglyceride levels (r=0.357, P<.01) only. In conclusion, the present study shows that in the absence of any major fasting abnormality in plasma lipid parameters, fasting apoprotein B-48 level, which has been associated with postprandial hyperlipidemia, does not predict the risk of CAD.

The influence of natural menopause on postprandial lipemia in heterozygotes for familial hypercholesterolemia

BACKGROUND

Heterozygous familial hypercholesterolemia (hFH) is a genetic disease that leads to premature atherosclerosis. Natural menopause leads to an adverse lipid profile and an enhanced risk of coronary heart disease (CHD). Raised plasma triglyceride (TG) levels also contribute to the risk of vascular events. The aim of this study was to evaluate the postprandial TG levels (after a standardized fatty meal) in premenopausal and postmenopausal women with hFH.

METHODS

Thirty-three Greek women with hFH were divided into the premenopausal group--n = 16, mean age 34(SD = 7), mean total cholesterol = 330(30) mg/dl--and the postmenopausal group--n = 17, mean age 62(5), mean total cholesterol = 346(63) mg/dl. Plasma TG concentrations were measured before and 2, 4, 6, and 8 hours after a standardized fat load. A value of >219 mg/dl (2.5 mmol/L) was taken as an abnormal response to the fat load, according to our previous studies.

RESULTS

Postmenopausal women had higher TG levels at 2 (p = 0.001), 4 (p = 0.003), 6 (p = 0.003), and 8 hours (p = 0.005) after the fatty meal compared to premenopausal women. Forty-one percent of postmenopausal hFH women had abnormal TG response (hFH-A) after a fatty meal, and such women had higher fasting TG levels than postmenopausal hFH women with a normal response to the fatty meal (hFH-N) (p = 0.0014).

CONCLUSIONS

Women with hFH tend to have an abnormal TG response to a fatty meal after the menopause. Fasting TG levels may be able to predict the abnormal response to a fatty meal.