Lipoproteins in familial dysbetalipoproteinemia. Variation of serum cholesterol level associated with VLDL concentration

Family history of coronary heart disease: evidence-based applications

Clinicians sometimes consider family history of CHD when evaluating CHD risk and deciding whether to prescribe a lipid medication. Most clinicians who take family history of CHD into account do so by categorically adjusting the aggressiveness of patient education and preventive medication recommendations (eg, from a low-key informational mode to a more direct influential or persuasive mode). Quantitative methods exist for taking into account any family history of CHD in parents and siblings, when estimating an individual's 10-year risk for a CHD event; at present, these methods are not readily available. For those individuals who have a positive family history of CHD, using family history-adjusted risk estimates could help clinicians more accurately target high-risk individuals who are the most appropriate candidates for therapeutic lifestyle changes and dyslipidemia drug therapy. Electronic health records (EHR) that now include CHD risk estimation as a decision support feature exclude family history from the calculation. Unless family CHD history is included in EHR decision support modules, family history of CHD will be increasingly discounted or ignored, as clinicians come to rely more and more on computerized decision support aids.

The effect of tibolone on the lipoprotein profile of postmenopausal women with type III hyperlipoproteinemia

OBJECTIVE

To investigate the short-term effect of treatment with tibolone on plasma lipid and lipoprotein levels in postmenopausal women with type III hyperlipoproteinemia (HLP).

DESIGN AND INTERVENTION

Patients were randomized to receive, in a double-blind cross-over fashion, a fixed dose of tibolone, 2.5 mg once daily or placebo for 8 weeks. The two treatment periods were separated by a wash-out period of 6 weeks. At each visit body weight and blood pressure were determined. Before and after each treatment period, fasting venous blood samples were obtained from the patients for biochemical measurements.

SETTING

The Leiden University Medical Center.

SUBJECTS

Postmenopausal women with type III HLP (aged < or = 65 years) were recruited from the Lipid Clinics of the Leiden University Medical Center, the Amsterdam Medical Center, the Utrecht Medical Center and the University Hospital Rotterdam. Five out of 25 women with type III HLP were eligible to be included in the study. Four of the five included patients completed the study according to the protocol. One patient was excluded from blinded therapy because total cholesterol levels increased above 20 mmol L(-1).

MAIN OUTCOME MEASURES

A significant reduction of plasma triglyceride, total cholesterol, VLDL cholesterol and VLDL triglyceride levels.

RESULTS

Plasma triglyceride and total cholesterol levels decreased from 6.82 +/- 3.58 to 2.45 +/- 1.36 mmol L(-1) and from 13.53 +/- 3.64 to 6.61 +/- 2.03 mmol L(-1), respectively (both P < 0.05). The body mass index remained unchanged. The glycated haemoglobin percentage decreased significantly from 5.8 to 5.3%. Treatment with tibolone resulted in a profound reduction in plasma apolipoprotein E, VLDL cholesterol and VLDL triglyceride levels (mean reductions of 66, 77 and 70%, respectively, P < 0.05).

CONCLUSIONS

Tibolone is a valuable adjuvant to current therapy in postmenopausal women with type III HLP.

Dietary vegetable oil and wood derived plant stanol esters reduce atherosclerotic lesion size and severity in apoE*3-Leiden transgenic mice

The hypolipidemic and anti-atherosclerotic effects of vegetable oil- and wood-based dietary plant stanol esters were compared in female apoE*3-Leiden transgenic mice at relevant plasma cholesterol levels. The plant stanol esters derived from vegetable oil (sitostanol 65.7%, campestanol 30.1%) had different contents of sitostanol and campestanol than the plant stanol esters derived from wood (sitostanol 87.6%, campestanol 9.5%) or from a mixture of vegetable oil and wood (sitostanol 73.0%, campestanol 24.7%). The mice (10 per group) received for 38 weeks a control diet or diets containing 1.0% (w/w) plant stanol esters derived from either vegetable oil, wood or a mixture of both. Vegetable oil (-46%), wood (-42%) and vegetable oil/wood (-51%) plant stanol esters decreased the plasma cholesterol levels (P<0.0001) by reducing the cholesterol content in plasma very low density-, intermediate density- and to a lesser extent in low density-lipoprotein. Plant stanol ester feeding did not change plasma triglyceride levels. Dietary plant stanol esters reduced the atherosclerotic lesion area by 91+/-13% (vegetable oil), 97+/-4% (wood) and 78+/-34% (vegetable oil/wood) (P<0.0001) and the severity from regular intimal fatty streaks/mild plaques (on average type 2--3 lesions) in controls to individual intimal foam cells (<type 1 lesions) in the treatment groups (P<0.0001). Plant stanol esters had no effect on adherence of monocytes to the vessel wall. Feeding of plant stanol esters dramatically reduced, independent of its sources, the extent and severity of atherosclerotic lesions, by decreasing VLDL-, IDL- and to a lesser extent LDL-cholesterol in apoE*3-Leiden transgenic mice.

Comparison of the hypolipidemic effect of gemfibrozil versus simvastatin in patients with type III hyperlipoproteinemia

BACKGROUND

Type III hyperlipoproteinemia is characterized by the accumulation of chylomicron and very low density lipoprotein (VLDL) remnants. Individuals with this disorder have a high risk of premature atherosclerosis, and hypolipidemic drugs are useful in their management.

METHODS

We compared, in a double-blind, placebo-controlled, randomized crossed study, the effects of gemfibrozil (1200 mg/day) and simvastatin (20 mg/day) on lipids, apolipoprotein AI, apolipoprotein B, and apolipoprotein E and on lipids and apolipoprotein B content in VLDL, intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) in 10 patients with type III hyperlipoproteinemia.

RESULTS

Levels of total cholesterol, VLDL cholesterol, IDL cholesterol, and apolipoprotein B decreased with both drugs. Larger reductions in triglycerides (109 +/- 28.2 mg/dL, P =.005), VLDL cholesterol (24.7 +/- 10.9 mg/dL, P =.05), and VLDL triglycerides (86.3 +/- 20.2 mg/dL, P =.003) were obtained with gemfibrozil compared with simvastatin. LDL cholesterol reduction was more effective with simvastatin than with gemfibrozil (44.3 +/- 17.1 mg/dL, P =.03). HDL cholesterol after gemfibrozil was 5.71 +/- 2.37 mg/dL higher than after simvastatin.

CONCLUSIONS

In patients with type III hyperlipoproteinemia gemfibrozil is more effective in reducing total triglyceride and VLDL lipid levels than simvastatin, and simvastatin is better in reducing LDL cholesterol than gemfibrozil is. IDL and apolipoprotein E levels were reduced similarly with both drugs.

Apo E variants in patients with type III hyperlipoproteinemia

Type III hyperlipoproteinemia (HLP III) is characterized by the reduced catabolism and accumulation of chylomicron and very low density lipoprotein (VLDL) remnants. Most HLP III patients are homozygous for the apolipoprotein E2 (Cys112, Cys158) allele; however, several other mutations at this gene locus have been associated with this HLP. In order to assess the presence of rare apo E variants in our population, we have examined apo E phenotypes by isoelectric focusing (IEF) and genotypes by restriction enzyme analysis of polymerase chain reaction (PCR) amplified DNA in 15 patients with HLP III. Lack of concordance between these two methods was observed in 11 subjects (73.3%). DNA sequencing analysis of the receptor binding domain of the apo E gene in the 11 HLP III patients with discrepancies demonstrated the presence of six carriers of the epsilon 3(Arg136-->Ser) allele and three carriers of the epsilon 2(Gly127-->Asp) allele. Five HLP III patients were apo E2/E2 using IEF, but only 2 of them were epsilon 2 homozygous using PCR. Two patients were E3/E3 homozygous with normal DNA sequence in the low density lipoprotein receptor binding domain of apo E. In conclusion, our results show that a number of different apo E genotypes are associated with HLP III in this population. More specifically, mutations at positions 127 and 136 might be frequent in Spain and occur in patients with HLP III.

Effect of apolipoprotein E and insulin resistance on VLDL particles in combined hyperlipidemic patients

Apolipoprotein (apo) E2 and high insulin levels are associated with the severity of hypertriglyceridemia in patients with combined hyperlipidemia. To study how these determinants affect very low-density lipoprotein (VLDL) in combined hyperlipidemic patients, we characterized VLDL particles in 106 unrelated patients with combined hyperlipidemia. The study was performed after 9 weeks of standardized dietary intake and after an overnight fast. Patients heterozygous for apoE2 had significantly higher mean levels of VLDL cholesterol by 0.71 mmol/l (95% CI, 0.30 to 1.12 mmol/l, P < 0.005) and VLDL triglycerides by 0.88 mmol/l, (95% CI, 0.30 to 1.47 mmol/l, P < 0.005) compared to patients without apoE2. The VLDL triglyceride content per particle and the calculated diameter of the VLDL particles were similar in both groups, which indicate a higher number of circulating VLDL particles in heterozygous apoE2 carriers. Patients with high fasting insulin levels (> or = 80 pmol/l) had a higher mean serum VLDL triglyceride level by 0.56 mmol/l (95% CI, 0.04 to 1.07 mmol/l, P < 0.05). The calculated VLDL diameter was larger by 3.7 nm (95% CI, 1.2 to 6.2 nm, P < 0.005) and the particles contained more triglycerides by 2.7 weight percent (95% CI, 0.3 to 5.1 weight percent, P < 0.05). These insulin-dependent changes in VLDL particles were only present in the absence of apoE2. In conclusion, patients heterozygous for apoE2 have higher numbers of circulating VLDL particles, whereas patients with high fasting insulin levels have larger, triglyceride enriched VLDL particles.

Triglyceride-rich lipoproteins of subjects heterozygous for apolipoprotein E2(Lys146-->Gln) are inefficiently converted to cholesterol-rich lipoproteins

The APOE*2(Lys146-->Gln) allele behaves like a dominant trait in the expression of familial dysbetalipoproteinemia (FD) (Smit et al., J. Lipid Res. 1990; 31: 45-53). FD patients carrying the APOE*2(Lys146-->Gln) allele exhibit less elevated cholesterol to triglyceride ratios in the d < 1.019 g/ml lipoprotein density fraction as compared to classical FD patients displaying homozygosity for the APOE*2(Arg158-->Cys) allele (0.8 vs. 1.4). Upon treatment of complete serum with lipoprotein lipase (LPL), the mean cholesterol to triglyceride molar ratio of the d < 1.019 g/ml lipoprotein fraction in these FD patients increased only marginally (from 0.8 to 1.1), as compared with that of classical FD subjects (from 1.4 to 2.6) and non-FD control subjects (from 0.7 to 1.5). In order to obtain further evidence for an inefficient lipolysis of the d < 1.019 g/ml lipoprotein fraction in APOE*2(Lys146-->Gln) carriers, possibly in combination with a less efficient cholesteryl ester transfer protein (CETP) activity, blood samples of APOE*2(Lys146-->Gln) allele carrying FD patients were analysed and compared with classical FD patients and controls. In the APOE*2(Lys149-->Gln) allele carrying FD patients were analysed and compared with classical FD patients and controls. In the APOE*2(Lys146-->Gln) FD patients, the increase in plasma cholesterol was mainly confined to the very low density lipoprotein (VLDL) fraction, whereas in classical FD patients, the levels of cholesterol in the intermediate density lipoprotein (IDL) fraction was also dramatically increased (ratios of VLDL to IDL cholesterol are 4.7 and 2.6, respectively). Family analyses of the APOE*2(Lys146-->Gln) FD subjects showed that the apo E to apo B ratio in the d < 1.019 g/ml lipoprotein fraction of allele carriers is 3.5 times as high as that found in non-carriers (2.8 vs. 0.8, by wt.). Also, in the APOE*2(Lys146-->Gln) allele carrying family members, the ratio of cholesterol to triglyceride of the d < 1.019 g/ml lipoprotein fraction is less markedly elevated upon addition of LPL when compared to that in non-carrying controls (from 1.1 to 1.8 vs 0.7 to 1.6). The efficiency of the d < 1.019 g/ml lipoprotein fraction of APOE*2(Lys146-->Gln) FD patients to compete with low density lipoprotein (LDL) for binding to the LDL receptor is intermediate to that of controls and classical APOE*2(Arg158-->Cys) homozygous FD patients. These findings suggest that in APOE*2(Lys146-->Gln) allele carriers, the conversion of VLDL into IDL is impaired due to an inefficient lipolysis, possibly in combination with a retarded CETP activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative effects of gemfibrozil and clofibrate in type III hyperlipoproteinemia

Type III hyperlipoproteinemia (dysbetalipoproteinemia) is characterized by elevated concentrations of plasma cholesterol and triglycerides due to an increase in very low density lipoprotein (VLDL) remnant lipoproteins. In a retrospective analysis we observed that in 12 patients with this disorder, gemfibrozil reduced concentrations of total cholesterol, VLDL cholesterol and triglycerides by 48%, 72% and 68%, respectively. These changes were greater than those reported in a similar number of patients treated with clofibrate. Comparative data on the efficacy of different fibrates in this disorder are very limited; to assess this further we have compared the hypolipidemic effects of gemfibrozil (600 mg twice daily) and clofibrate (1 g twice daily) in six patients with well-characterized type III hyperlipoproteinemia. Baseline values were obtained after at least 8 weeks on diet and treatment values were obtained after 6 and 8 weeks of treatment with each drug. Treatment with clofibrate and gemfibrozil both resulted in significant reductions in the plasma concentrations of total cholesterol (40% and 54%), VLDL cholesterol (59% and 79%) and total triglycerides (48% and 70%), as well as a significant increase in HDL cholesterol (9% and 7%). Gemfibrozil was, however, significantly (P < 0.05) more effective in reducing plasma concentrations of total cholesterol, VLDL cholesterol and triglycerides than was clofibrate, in the same patients.