Plasma lipoproteins in familial dysbetalipoproteinemia associated with apolipoproteins E2(Arg158-->Cys), E3-Leiden, and E2(Lys146-->Gln), and effects of treatment with simvastatin

Composition and distribution of lipoproteins after evolocumab in familial dysbetalipoproteinemia: A randomized controlled trial

BACKGROUND

Proprotein convertase subtilisin kexin type 9 (PCSK9) monoclonal antibodies (mAbs) reduce fasting and post fat load cholesterol in non-HDL and intermediate density lipoprotein (IDL) in familial dysbetalipoproteinemia (FD). However, the effect of PCSK9 mAbs on the distribution and composition of atherogenic lipoproteins in patients with FD is unknown.

OBJECTIVE

To evaluate the effect of the PCSK9 mAb evolocumab added to standard lipid-lowering therapy in patients with FD on fasting and post fat load lipoprotein distribution and composition.

METHODS

Randomized placebo-controlled double-blind crossover trial comparing evolocumab (140 mg subcutaneous every 2 weeks) with placebo during two 12-week treatment periods. Patients received an oral fat load at the start and end of each treatment period. Apolipoproteins (apo) were measured with ultracentrifugation, gradient gel electrophoresis, retinyl palmitate and SDS-PAGE.

RESULTS

PCSK9 mAbs significantly reduced particle number of all atherogenic lipoproteins, with a stronger effect on smaller lipoproteins than on larger lipoproteins (e.g. IDL-apoB 49%, 95%confidence interval (CI) 41-59 and very low-density lipoprotein (VLDL)-apoB 33%, 95%CI 16-50). Furthermore, PCSK9 mAbs lowered cholesterol more than triglyceride (TG) in VLDL, IDL and low-density lipoprotein (LDL) (e.g. VLDL-C 48%, 95%CI 29-63%; and VLDL-TG 20%, 95%CI 6.3-41%). PCSK9 mAbs did not affect the post fat load response of chylomicrons.

CONCLUSION

PCSK9 mAbs added to standard lipid-lowering therapy in FD patients significantly reduced lipoprotein particle number, in particular the smaller and more cholesterol-rich lipoproteins (i.e. IDL and LDL). PCSK9 mAbs did not affect chylomicron metabolism. It seems likely that the observed effects are achieved by increased hepatic lipoprotein clearance, but the specific working mechanism of PCSK9 mAbs in FD patients remains to be elucidated.

Effect of adding bezafibrate to standard lipid-lowering therapy on post-fat load lipid levels in patients with familial dysbetalipoproteinemia. A randomized placebo-controlled crossover trial

Familial dysbetalipoproteinemia (FD) is a genetic disorder associated with impaired postprandial lipid clearance. The effect of adding bezafibrate to standard lipid-lowering therapy on postprandial and fasting lipid levels in patients with FD is unknown. In this randomized placebo-controlled double-blind crossover trial, 15 patients with FD received bezafibrate and placebo for 6 weeks in randomized order in addition to standard lipid-lowering therapy (statin, ezetimibe, and/or lifestyle). We assessed post-fat load lipids, expressed as incremental area under the curve (iAUC) and area under the curve (AUC), as well as fasting levels and safety, and found that adding bezafibrate did not reduce post-fat load non-HDL-cholesterol (non-HDL-C) iAUC (1.78 ± 4.49 mmol·h/l vs. 1.03 ± 2.13 mmol·h/l, P = 0.57), but did reduce post-fat load triglyceride (TG) iAUC (8.05 ± 3.32 mmol·h/l vs. 10.61 ± 5.92 mmol·h/l, P = 0.03) and apoB (0.64 ± 0.62 g·h/l vs. 0.93 ± 0.71 g·h/l, P = 0.01). Furthermore, bezafibrate significantly improved AUC and fasting levels of non-HDL-C, TG, total cholesterol, HDL-C, and apoB. Bezafibrate was associated with lower estimated glomerular filtration rate (78.4 ± 11.4 ml/min/1.73 m2 vs. 86.1 ± 5.85 ml/min/1.73 m2, P = 0.002). In conclusion, in patients with FD, the addition of bezafibrate to standard lipid-lowering therapy resulted in improved post-fat load and fasting plasma lipids. Combination therapy of statin/fibrate could be considered as standard lipid-lowering treatment in FD.

Familial dysbetalipoproteinemia: an underdiagnosed lipid disorder

PURPOSE OF REVIEW

To review pathophysiological, epidemiological and clinical aspects of familial dysbetalipoproteinemia; a model disease for remnant metabolism and remnant-associated cardiovascular risk.

RECENT FINDINGS

Familial dysbetalipoproteinemia is characterized by remnant accumulation caused by impaired remnant clearance, and premature cardiovascular disease. Most familial dysbetalipoproteinemia patients are homozygous for apolipoprotein ε2, which is associated with decreased binding of apolipoprotein E to the LDL receptor. Although familial dysbetalipoproteinemia is an autosomal recessive disease in most cases, 10% is caused by autosomal dominant mutations. Of people with an ε2ε2 genotype 15% develops familial dysbetalipoproteinemia, which is associated with secondary risk factors, such as obesity and insulin resistance, that inhibit remnant clearance by degradation of the heparan sulfate proteoglycan receptor. The prevalence of familial dysbetalipoproteinemia ranges from 0.12 to 0.40% depending on the definition used. Clinical characteristics of familial dysbetalipoproteinemia are xanthomas and mixed hyperlipidemia (high total cholesterol and triglycerides); the primary lipid treatment goal in familial dysbetalipoproteinemia is non-HDL-cholesterol; and treatment consists of dietary therapy and treatment with statin and fibrate combination.

SUMMARY

Familial dysbetalipoproteinemia is a relatively common, though often not diagnosed, lipid disorder characterized by mixed hyperlipidemia, remnant accumulation and premature cardiovascular disease, which should be treated with dietary therapy and statin and fibrate combination.

Apolipoprotein E genotype as a most significant predictor of lipid response at lipid-lowering therapy: mechanistic and clinical studies

APOE alleles and apolipoprotein E isoforms control plasma cholesterol level on population level. Among three ɛ2, ɛ3, ɛ4 alleles, ɛ4 allele is associated with the increase in cholesterol level, risk of atherosclerosis and Alzheimer disease, while ɛ2 allele is associated with the decrease in cholesterol level and risk of atherosclerosis. The increase in plasma triglyceride is an independent risk factor of atherosclerosis and triglyceride-high density lipoprotein coupling determines the efficiency of reverse cholesterol transport. The impairment of this coupling specifically at hypertriglyceridemia may be followed by specific lipoprotein markers. The influence of major lipid-lowering drugs on lipoprotein metabolism and association of apoE isoforms with the efficiency of therapy by statins and fibrates are summarized both at isolated and combined increase in plasma triglyceride and cholesterol. APOE polymorphism seems to be a single genetic variant with a confirmed stratification both at candidate gene and at wide genome analyses.

Time-dependent lipid response on fluvastatin therapy of patients with hypercholesterolemia sensitive to apoE phenotype

Sixty-seven male patients with hypercholesterolemia, divided into three groups according to apolipoprotein E phenotype (33 with apoE3/ 3 phenotype, E3 group; 23 with 2/2 or 2/3, E2+ group; 11 with 4/4 or 4/3, E4+ group), received daily 20-40 mg of fluvastatin for 12 weeks. The levels of triglyceride (TG), cholesterol (Chol), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were measured after 0, 4, 8 and 12 weeks on fluvastatin and after 4 weeks washout period. Lipid percentage changes (delta) were not associated with apoE phenotype for any treatment time. Cholesterol decreased by 14% after 12 weeks and HDL-C increased by 14-16% after 12 weeks for three phenotype groups. deltaTG, deltaChol, deltaLDL-C were associated positively, while negatively for deltaHDL-C, with the corresponding basal lipid values for the three groups. The positive deltaTG values occurred at a low basal TG0 level and became negative at TG0 > 1.6-1.9 mM. For E3 and E4+ groups, only a single parameter contributed significantly into a variation of lipid percentage changes. For the E2+ group, TG0 and Chol0 contributed in a reciprocal manner into deltaTG12/0, both positively into deltaChol8/0; Chol0 and HDL-C0 both negatively contributed into deltaHDL-C12/0. HDL-C0 contributed reciprocally into LDL-C variability for E2+ and E4+ groups. Three effects seem to contribute differently into lipid response among patients with different apoE phenotype: the inhibition of hepatic and lipoprotein lipase activities, the competition between TG-rich and low-density lipoproteins for LDL-receptor and the accumulation of intermediate-density lipoproteins in patients bearing E2 isoform.

Long term efficacy and safety of atorvastatin in the treatment of severe type III and combined dyslipidaemia

BACKGROUND

Fibric acid derivatives and HMG-CoA reductase inhibitors are effective in combination for treating patients with familial dysbetalipoproteinaemia and severe combined dyslipidaemia, but combination therapy affects compliance and increases the risk of side effects.

AIM

To evaluate the efficacy and safety of monotherapy with atorvastatin, an HMG-CoA reductase inhibitor with superior efficacy in lowering low density lipoprotein cholesterol and triglyceride concentrations, in patients with dysbetalipoproteinaemia and severe combined dyslipidaemia.

METHODS

Atorvastatin was tested as single drug treatment in 36 patients with familial dysbetalipoproteinaemia and 23 patients with severe combined dyslipidaemia.

RESULTS

After 40 weeks of 40 mg atorvastatin treatment decreases in total cholesterol, triglycerides, and apolipoprotein B of 40%, 43%, and 41%, respectively, were observed in the combined dyslipidaemia group, and of 46%, 40%, and 43% in the dysbetalipoproteinaemic patients. Target concentrations of total cholesterol (< 5 mmol/l) were reached by 63% of the patients, and target concentrations of triglycerides (< 3.0 mmol/l) by 66%. Treatment with atorvastatin was well tolerated and no serious side effects were reported.

CONCLUSIONS

Atorvastatin is very effective as monotherapy in the treatment of familial dysbetalipoproteinaemia and severe combined dyslipidaemia.

Coexisting dysbetalipoproteinemia and familial hypercholesterolemia. Clinical and laboratory observations

Type III dysbetalipoproteinemia and familial hypercholesterolemia (FH) are two metabolic disorders giving rise to severe disturbances of lipid homeostasis and premature atherosclerosis. Both metabolic abnormalities have a genetic basis and co-occurrence in the same patient has seldom been described. Because of the unique structure of the French Canadian population, there was an opportunity to observe patients with both dysbetalipoproteinemia (E2/2 homozygotes) and FH (N=14) and to compare their clinical data with that of patients with type III (N=75), patients with FH (N0.7 and the presence of beta-VLDL on electrophoresis. Presence of a low density lipoprotein receptor, LDL-R, mutation should be suspected in a type III patient with a LDL-C level above 3.0 mmol/l and a family history of premature CAD. In the group of patients studied, the coexistence of dysbetalipoproteinemia and heterozygous FH does not appear to increase the prevalence of cardiovascular complications above that observed among control type III or control E3/3-FH patients. Thus, the presence of two epsilon2 alleles in these patients affects the expression of the abnormal LDL-R allele and the resulting phenotype substantiates the non additive effects of alleles at these two loci (epistasis).

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.

Hypolipidemic and hyperlipidemic phenotypes in transgenic mice expressing human apolipoprotein E2

Transgenic mice were produced that expressed different plasma levels (3-60 mg/dl) of human apolipoprotein (apo) E2(Arg158 --> Cys), which is associated with the recessive form of human type III hyperlipoproteinemia (HLP). In transgenic mice fed a normal chow diet, low levels of apoE2 (<10 mg/dl) did not significantly alter the lipid phenotype. Mice expressing intermediate levels of apoE2 (10-30 mg/dl) had a 50-60% decrease in total cholesterol compared with nontransgenic mice. The decrease was almost entirely due to a reduction in high density lipoprotein (HDL) cholesterol. These hypolipidemic apoE2 transgenic mice were cross-bred with human apoB transgenic mice, which have increased total cholesterol and low density lipoprotein (LDL) levels. The apoE2/apoB double transgenics revealed that expression of apoE2 on the background of human apoB overexpression resulted in a substantial decrease in LDL and HDL cholesterol and a corresponding accumulation of very low density lipoproteins (VLDL) and intermediate density lipoproteins (IDL). Thus, the double transgenics had a lipid phenotype resembling human type III HLP. In contrast to the hypolipidemic mice, mice expressing high levels of apoE2 (>50 mg/dl) were hyperlipidemic. The VLDL and IDL in these mice were significantly increased and cholesterol-enriched and had other characteristics of remnant lipoproteins. Upon agarose gel electrophoresis, the VLDL and IDL from both intermediate and high expressers migrated more slowly toward the beta position compared with the pre-beta-mobility of nontransgenic mouse VLDL and IDL. Thus, depending on plasma apoE2 levels, the expression of human apoE2 in the transgenic mice leads to either a hypolipidemic or hyperlipidemic phenotype. This animal model provides the opportunity to study the factors that cause hypolipidemia and those that precipitate the hyperlipidemia of type III HLP.