Construction and in vitro functional evaluation of a low-density lipoprotein receptor/transferrin fusion protein as a therapeutic tool for familial hypercholesterolemia

A cDNA sequence encoding a soluble form of the human low-density lipoprotein receptor (LDL-R) was produced by RT-PCR amplification. This form of the receptor contains the N-terminal cysteine-rich domain, the EGF homology domain, and the serine/threonine-rich domain, but lacks the membrane anchor as well as the cytoplasmic domain. By the same technical approach a cDNA sequence encoding rabbit transferrin was generated. In-frame fusion of the two cDNAs produced a sequence encoding a chimeric protein potentially capable of binding LDL on the N-terminal side and the transferrin receptor on the C-terminal side. It was expected that LDL bound to the chimeric protein could be internalized, targeted to an acidic compartment, and processed through the pathway of the transferrin receptor. Cells transfected with the LDL-R/transferrin cDNA translate, glycosylate, and secrete the corresponding protein in the culture medium. The secreted protein binds LDL in a ligand-blotting experiment. Finally, the chimeric protein mediates the binding and internalization of LDL in mutant cells lacking the LDL receptor. In fact, Watanabe rabbit fibroblasts, incubated with the chimeric protein show a fourfold increase in LDL binding, a fivefold increase in LDL internalization, and a sixfold increase in LDL degradation, with respect to unincubated fibroblasts.

An update on familial hypercholesterolaemia

A report of a World Health Organization consultation on familial hypercholesterolaemia (FH) was recently presented in Geneva. The report provides an update on several aspects of FH such as the molecular basis, DNA diagnosis, clinical criteria for the diagnosis, treatment of FH adults and children, the role of diet, psychosocial aspects of FH, contacting and helping relatives with FH and gives suggestions for government cooperation. The report is reviewed here.

[Serum triglycerides as a risk factor for atherosclerosis]

The importance of plasma triglycerides as a risk factor for the development of coronary artery disease (CAD) has been controversial for many years. In univariate analysis plasma triglycerides predict CAD in several studies, but this effect is attenuated when high-density lipoprotein (HDL) cholesterol is included in the analysis. The controversy can be explained by the complexity of lipoprotein metabolism. Plasma triglycerides serve as markers for metabolic and clinical conditions associated with increased CAD risk. Several recent studies shed new light on the significance of triglycerides for the development of CAD, depending on their level in plasma: there appears to be an optimal concentration < 1.1 mmol/l, an intermediate range with increased risk at values 1.1-4 mmol/l, above which level the risk decreases. Very high levels of triglycerides confer increased risk of pancreatitis.

Enhanced plasma cholesterol lowering effect of retrovirus-mediated LDL receptor gene transfer to WHHL rabbit liver after improved surgical technique and stimulation of hepatocyte proliferation by combined partial liver resection and thymidine kinase--ganciclovir treatment

In this study we report an improved method for in vivo gene transfer to liver. Repeated injections of Moloney murine leukemia virus-derived retroviruses containing LDL receptor cDNA were given to the portal vein in combination with a 10% partial liver resection and stimulation of hepatocyte proliferation by plasmid/liposome-mediated thymidine kinase gene transfer and ganciclovir treatment. The method was used for the treatment of LDL receptor deficiency in Watanabe heritable hyperlipidemic rabbits. We demonstrate an increase in hepatocyte proliferation index by thymidine kinase and ganciclovir treatment from 0.9 to 1.35% and a maximum of 35% decrease in total plasma cholesterol level 2-3 months after the gene transfer. A 20% decline was still present after a 52-week follow-up period. A 50% decrease was also observed in plasma triglycerides. Liver function tests indicated a transient increase in plasma alkaline phosphatase level up to 12 weeks after the gene transfer. In situ PCR and RT-PCR analyses indicated that the transgene was present in periportal areas and was transcribed to mRNA 1 week after the gene transfer. Because of the relatively simple and controllable technique we suggest that repeated retrovirus injections via a portal vein catheter together with the limited partial liver resection and plasmid/liposome-mediated thymidine kinase gene transfer-ganciclovir treatment may be used to improve the results of retrovirus-mediated liver gene therapy.

Mortality in treated heterozygous familial hypercholesterolaemia: implications for clinical management. Scientific Steering Committee on behalf of the Simon Broome Register Group

Clinical management of heterozygous familial hypercholesterolaemia is largely based on evidence from a small number of observational studies and extrapolation from the results of clinical trials of lipid-lowering in patients with polygenic hypercholesterolaemia The objectives of this study were (i) to determine the absolute and relative mortality of patients with treated heterozygous familial hypercholesterolaemia, (ii) to estimate the effect of changes in treatment efficacy on mortality trends over time, and (iii) to examine the implications of these findings for patient management. A cohort of 605 men and 580 women aged 20-79 years with heterozyous familial hypercholesterolaemia were recruited from 21 out-patient lipid clinics in the UK. Patients were followed prospectively from 1980 to 1995 for 8770 person-years. Absolute mortality was calculated, and relative risk was expressed as the ratio of the number of observed deaths to the number expected in the general population of England and Wales. Forty six of the 73 deaths were due to coronary heart disease. In women aged 20-39, despite treatment, the relative risk of a fatal coronary event was increased 125-fold (95% confidence intervals 15-451) and the annual coronary mortality was 0.17%. In men aged 20-39 the relative risk was increased 48-fold (17-105) and the annual coronary mortality was 0.46%. The relative risk decreased with age but the absolute risk increased. For men and women aged 60-79, the annual coronary mortality was 1.1% representing a significant excess mortality for women (relative risk 2.6, 1.3-4.5) but not for men (RR 1.1, 0.5-2.3). Non-coronary mortality was not increased at any age (RR for all ages 0.68, 0.45-0.99). There was a decline in the relative risk for coronary mortality in patients aged 20-59 from an eight-fold (4.8-7.2) increased risk before 1992 to 3.7 (1.6-7.2.) thereafter (P=0.08). The results suggest that the prognosis for patients with heterozygous familial hypercholesterolaemia has improved with the introduction of more effective treatment, and that lipid-lowering therapy is not associated with increased non-coronary mortality. These findings and the excess coronary mortality observed suggest that all affected adult men and post-menopausal women should be treated with HMG-CoA reductase inhibitors.

Long-term efficacy of low-density lipoprotein apheresis on coronary heart disease in familial hypercholesterolemia. Hokuriku-FH-LDL-Apheresis Study Group

Familial hypercholesterolemia (FH) is characterized by severe hypercholesterolemia and premature coronary heart disease (CHD). The lower the plasma cholesterol level, the more likely it is that CHD can be prevented or retarded; aggressive cholesterol-lowering therapies may be indicated for FH patients with CHD. This study describes the long-term (6 years) safety and efficacy of intensive cholesterol-lowering therapies with low-density lipoprotein (LDL) apheresis in heterozygous FH patients with CHD. One hundred thirty heterozygous FH patients with CHD documented by coronary angiography had been treated by cholesterol-lowering drug therapy alone (n=87) or LDL apheresis combined with cholesterol-lowering drugs (n=43). Serum lipid levels and outcomes in each treatment group were compared after approximately 6 years. Both treatment groups had significant reductions in serum cholesterol, LDL cholesterol, and high density lipoprotein cholesterol levels. LDL apheresis significantly reduced LDL cholesterol levels from 7.42+/-1.73 to 3.13+/-0.80 mmol/L (58%) compared with group taking drug therapy, from 6.03+/-1.32 to 4.32+/-1.53 mmol/L (28%). With Kaplan-Meier analyses of the coronary events including nonfatal myocardial infarction, percutaneous transluminal coronary angioplasty, coronary artery bypass grafting, and death from CHD, the rate of total coronary events was 72% lower in the LDL-apheresis group (10%) than in drug therapy group (36%) (p=0.0088). It is concluded that LDL-apheresis is effective as treatment of CHD in FH heterozygotes, and may become the therapy of choice in severe types of FH.

Detection and measurement of hypercholesterolaemia in South Africans attending general practitioners in private practice--the cholesterol monitor

BACKGROUND

This paper reports data on the detection and management of hypercholesterolaemia in patients attending general practitioners in private practice in South Africa.

METHODS

The frequency of cholesterol testing and the level at which active therapeutic intervention occurred at medical practices were monitored over a 2-year period. A sample of 200 medical practitioners was selected from private practices in major cities. Data on patients seen by the selected doctors during a 5-day monitoring period were recorded on a standardised form.

RESULTS

12,842 patients were seen by the 200 private practice GPs. More men (18.7%) than women (10.4%) had coronary heart disease (CHD), and their mean total cholesterol (TC) levels were 5.9 mmol/l and 6.0 mmol/l, respectively. Only 3.1% of the patients were reported to have familial hypercholesterolaemia (FH) and 12.8% were reported to have a family history of CHD. Reported smoking rates were exceptionally high (77.5% of women and 64.4% of men). The most commonly prescribed group of lipid-lowering agents was HMG-CoA reductase inhibitors.

CONCLUSIONS

Inadequate management of hypercholesterolaemia leaves many patients with a high risk of CHD mortality in South Africa. Appropriately investigated patients with hypercholesterolaemia should receive treatment to reduce cardiovascular disease using more effective TC control programmes than are currently used in South Africa.

DALI-the first human whole-blood low-density lipoprotein and lipoprotein (a) apheresis system in clinical use: procedure and clinical results

BACKGROUND

The DALI low-density lipoprotein (LDL) apheresis system is the first whole-blood apheresis system in regular clinical use. DALI stands for direct adsorption of lipoproteins, which describes the basic principle of operation of this newly developed LDL apheresis procedure.

METHODS

The selective removal of LDLs and lipoprotein (a) [Lp(a)] is performed in human whole blood by adsorption onto polyacrylate-coated polyacrylamide beads in an adsorber. This article describes the results of the first open multicentre clinical trial in 14 patients in whom the safety and the efficacy of the system were tested. All patients were treated on average 17 times on a weekly basis. In total, 238 sessions were carried out during the study without severe side-effects. On average, 7675 mL of the patients' whole blood was processed in about 2 h. Anticoagulation in the extracorporeal system was carried out by first giving a heparin bolus followed by continuous addition of an acid citrate dextrose (ACD-A) infusion during the treatment.

RESULTS

The processing of nearly 1.6 times the patient blood volumes resulted in a reduction in the median LDL-cholesterol level by 66-77% (dependent on the system configuration). The Lp(a) concentrations were reduced by 59-73% (dependent on the system configuration). HDL-cholesterol, blood cell count and the other clinical parameters were not significantly affected.

CONCLUSION

Based on this short-term evaluation, the DALI apheresis system is a well-tolerated, effective and simple way of reducing LDL and Lp(a) in human whole blood. The system has been introduced to clinical practice. However, to use the DALI apheresis system in clinical routine, further evaluation of long-term effects is required.

Genetic risk factors in the development of heart disease: familial hypercholesterolemia and hyperhomocysteinemia

Cardiovascular disease continues to be the leading cause of death in the United States. Several risk factors for heart disease are genetically based. Two of these risk factors are familial hypercholesterolemia and hyperhomocysteinemia. Effective and relatively inexpensive treatments have been established for these risk factors. This article reviews the genetic basis for familial hypercholesterolemia and hyperhomocysteinemia, presents strategies for diagnosis and treatment, and discusses implications for nursing practice.

Lipid and lipoprotein profiles in children with familial hypercholesterolaemia: effects of therapy

In 71 children with familial hypercholesterolaemia the effect of dietary and/or medical treatment was evaluated. Initial total cholesterol and low density lipoprotein (LDL)-cholesterol levels were significantly lower in children who were consecutively treated by diet (Step-One-Diet) than in those who received additional medication. By dietary treatment, the median total cholesterol level (236.5 mg/dl; range 210-510 mg/dl) was reduced by 7.4% and the median LDL-cholesterol level (162 mg/dl; range 126-423 mg/dl) by 9.9%. By dietary and medical therapy, the median total cholesterol level (330 mg/dl; range 270-424 mg/dl) was reduced by 29.7% and the median LDL-cholesterol level (263 mg/dl; 192-333 mg/dl) by 25.9%. High density lipoprotein (HDL)-cholesterol and HDL 3 remained unchanged. HDL 2 showed a significant decrease of 15.6% up to 27 mg/dl (13-42 mg/dl) on medical treatment. Apolipoprotein A I levels did not change during therapy. Initial apolipoprotein B levels were significantly higher in children who were treated by diet and medication and were reduced by 28.9% by combined therapy. In 28 patients (39.4%) an excess of lipoprotein (a) was detected. Regarding the apolipoprotein E phenotype, 32.2% of the patients carried the risk gene epsilon4 in a hetero- or homozygous form.

CONCLUSION

Early dietary and/or medical treatment in hypercholesterolaemic children significantly ameliorates the lipoprotein status. The pretherapy lipoprotein status seems to prognosticate the effectiveness of therapy.

Garlic extract therapy in children with hypercholesterolemia

OBJECTIVE

To determine whether garlic extract therapy is efficacious and safe in children with hypercholesterolemia.

DESIGN

Randomized, double-blind, placebo-controlled clinical trial.

SETTING

Specialized pediatric lipid disorders ambulatory clinic.

PARTICIPANTS

Thirty pediatric patients, aged 8 to 18 years, who had familial hyperlipidemia and a minimum fasting total cholesterol level greater than 4.8 mmol/L (> 185 mg/dL).

INTERVENTION

An 8-week course of a commercially available garlic extract (Kwai [Lichtwer Pharma, Berlin, Germany], 300 mg, 3 times a day) or an identical placebo.

MAIN OUTCOME MEASURES

Absolute and relative changes in fasting lipid profile parameters.

RESULTS

The groups were equivalent at baseline and compliance was similar in the 2 groups (P = .45). There was no significant relative attributable effect of garlic extract on fasting total cholesterol (+0.6% [95% confidence interval, -5.8% to +6.9%1) or low-density lipoprotein cholesterol (-0.5% [95% confidence interval, -8.7% to +7.6%]). The lower limits of the confidence intervals did not include -10%, the minimum relative attributable effect believed to be clinically important. Likewise, no significant effect was seen on the levels of high-density lipoprotein, triglycerides, apolipoprotein B-100, lipoprotein (a), fibrinogen, homocysteine, or blood pressure. There was a small effect on apolipoprotein A-I (+10.0% [95% confidence interval, +1.2% to +16.5%] P=.03). There were no differences in adverse effects between groups.

CONCLUSION

Garlic extract therapy has no significant effect on cardiovascular risk factors in pediatric patients with familial hyperlipidemia.

Weekly versus biweekly lipid removal and effect of statins in severe hypercholesterolemia

Lipid removal using a continuous-flow extracorporeal system is of proven efficacy in severe hypercholesterolemia. Because of the inconveniences and expenses of extracorporeal removal of lipids, the effects of two treatment intervals (weekly versus biweekly) were assessed in two adolescents with circulating cholesterol higher than 20.0 mmol/L. In both patients, circulating levels were largely lower on a weekly lipid removal interval when compared with a biweekly interval. A rapid reaccumulation of cholesterol was noted after lipid removal. Treatment with simvastatin decreased the rapid reappearance of total cholesterol noted during the first 2 days after lipid removal but without any major effect on the subsequent reaccumulation of cholesterol. Aggressive treatment of severe hypercholesterolemia with statins and especially with extracorporeal lipid removal is now possible and of proven efficacy. The minimal practical lipid removal treatment interval should be used.

[The plasma antioxidant status and trace elements in patients with familial hypercholesterolemia treated with LDL-apheresis]

Oxidation of low density lipoprotein is involved in the pathogenesis of atherosclerosis. Epidemiological studies suggest a negative correlation between the occurrence of cardiovascular diseases and blood concentrations of lipophilic antioxidants such as vitamin A and E and beta-carotene. Trace elements such as selenium, zinc and copper are involved in the activity of antioxidant enzymes: glutathione peroxidase and superoxide dismutase. The aim of this work was to determine the antioxidant and trace elements status of patients with very severe hypercholesterolemia and who were treated by dextran sulphate low density lipoprotein apheresis, in comparison with two control populations: one constituted by normocholesterolemic subjects and the other by hypercholesterolemic patients before treatment. Our results showed that, as compared with normocholesterolemic subjects, patients treated by LDL-apheresis were not deficient in vitamin E, beta-carotene and copper but had low plasma levels of selenium, zinc and vitamin A. The low selenium and vitamin A levels were due to the treatment by LDL-apheresis by itself, while the hypercholesterolemia of these patients might have provoked the low plasma levels of zinc. This study pointed out the interest of a supplement of selenium, zinc and vitamin A in patients treated by LDL-apheresis.

Double filtration plasmapheresis maintains normal adhesion molecule levels

Levels of plasma soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1), and von Willebrand factor (vWF) increase in patients with peripheral vascular or ischemic heart disease. These factors are related to the progression of atherosclerosis. Furthermore, these substances and thrombomodulin (TM) are indicators for assessing the degree of damage to the endothelium. To evaluate the effect of double filtration plasmapheresis (DFPP) on these molecules, the plasma levels of vWF, sICAM-1, sVCAM-1, and TM were measured in 4 familial hypercholesterolemia (FH) patients who underwent treatment with DFPP at 2 week intervals for more than 3 years. The levels of sVCAM-1 and sICAM-1 in hypercholesterolemia patients with ischemic heart disease as a control was 773 +/- 109 and 334 +/- 82 ng/ml. These values were higher than the normal value. In the FH patients who underwent DFPP treatment, the average sICAM-1 levels were 221 +/- 47 and 197 +/- 36 ng/ml before and after, respectively. The average sVCAM-1 levels were 601 +/- 87 and 486 +/- 60 ng/ml. There were no significant differences between the pre- and post-DFPP values. The activities of plasma vWF before and after DFPP treatment were 158 +/- 23 and 45 +/- 9%. The levels of plasma TM before and after treatment were 3.0 +/- 0.3 and 3.4 +/- 0.5 FU/ml. From these results, it is suggested that DFPP treatment does not damage the endothelium and may prevent the progression of atherosclerosis by removing the substances that induce the production of sICAM-1 and sVCAM-1 due to long-term treatment.

The effect of selective low-density lipoprotein apheresis on plasma lipoperoxides and antioxidant vitamins in familial hypercholesterolemic patients

Familial hypercholesterolemia (FH) is an autosomal dominant genetic disorder characterized by a lifelong elevation in the concentration of low-density lipoprotein (LDL) bound cholesterol in blood by cholesterol deposits and by early coronary artery disease. The LDL apheresis technique has been introduced with the goal of reducing LDL cholesterol levels, thereby preventing the development of atherosclerosis. The literature on LDL apheresis reports 2 different facets, the therapeutic aspect associated with the lessening of LDL concentration and the initiation of a peroxidation process associated with the biocompatibility of the artificial membrane. Lipid and protein peroxidation gives rise to toxic and atherogenic hydroperoxide, mostly lipid hydroperoxides, and derivative compounds, which may offset the benefit of the procedure. In this paper, plasma hydroperoxide levels are determined along with the elevation of the serum and LDL antioxidant status in hypercholesterolemic patients before and following repeated LDL apheresis sessions. Hydroperoxide concentration has been expressed both in terms of plasma volume and LDL concentration. A highly significant increase in LDL lipid hydroperoxides is demonstrated when expressed in terms of LDL concentration and is associated with the LDL apheresis procedure. The usefulness of antioxidant supplementation in LDL apheresis is discussed.

Correction of hypoalphalipoproteinemia in LDL receptor-deficient rabbits by lecithin:cholesterol acyltransferase

Familial hypercholesterolemia (FH), a disease caused by a variety of mutations in the low density lipoprotein receptor (LDLr) gene, leads not only to elevated LDL-cholesterol (C) concentrations but to reduced high density lipoprotein (HDL)-C and apolipoprotein (apo) A-I concentrations as well. The reductions in HDL-C and apoA-I are the consequence of the combined metabolic defects of increased apoA-I catabolism and decreased apoA-I synthesis. The present studies were designed to test the hypothesis that overexpression of human lecithin:cholesterol acyltransferase (hLCAT), a pivotal enzyme involved in HDL metabolism, in LDLr defective rabbits would increase HDL-C and apoA-I concentrations. Two groups of hLCAT transgenic rabbits were established: 1) hLCAT+/LDLr heterozygotes (LDLr+/-) and 2) hLCAT+/LDLr homozygotes (LDLr-/-). Data for hLCAT+ rabbits were compared to those of nontransgenic (hLCAT-) rabbits of the same LDLr status. In LDLr+/- rabbits, HDL-C and apoA-I concentrations (mg/dl), respectively, were significantly greater in hLCAT+ (62 +/- 8, 59 +/- 4) relative to hLCAT- rabbits (21 +/- 1, 26 +/- 2). This was, likewise, the case when hLCAT+/ LDLr-/- (27 +/- 2, 19 +/- 6) and hLCAT-/LDLr-/- (5 +/- 1, 6 +/- 2) rabbits were compared. Kinetic experiments demonstrated that the fractional catabolic rate (FCR, d(-1)) of apoA-I was substantially delayed in hLCAT+ (0.376 +/- 0.025) versus hLCAT- (0.588) LDLr+/- rabbits, as well as in hLCAT+ (0.666 +/- 0.033) versus hLCAT- (1.194 +/- 0.138) LDLr-/- rabbits. ApoA-I production rate (PR, mg x kg x d(-1)) was greater in both hLCAT+/LDLr+/- (10 +/- 2 vs. 6) and hLCAT+/LDLr-/- (9 +/- 1 vs. 4 +/- 1) rabbits. Significant correlations (P < 0.02) were observed between plasma LCAT activity and HDL-C (r = 0.857), apoA-I FCR (r = -0.774), and apoA-I PR (r = 0.771), while HDL-C correlated with both apoA-I FCR (-0.812) and PR (0.751). In summary, these data indicate that hLCAT overexpression in LDLr defective rabbits increases HDL-C and apoA-I concentrations by both decreasing apoA-I catabolism and increasing apoA-I synthesis, thus correcting the metabolic defects responsible for the hypoalphalipoproteinemia observed in LDLr deficiency.

[Selection criteria for treatment of severe hyperlipoproteinemias with LDL apheresis]

LDL (low density lipoprotein) - apheresis has been established as an alternative management of severe hypercholesterolaemia after failure of conventional diet and drug therapy. General indication criteria for LDL-apheresis have yet been established. Indication guidelines in USA, Europe and japan are based on whether coronary heart disease is present and on the degree of lDL cholesterol elevation after treatment with diet and maximal drug therapy. It is reasonable to consider LDL apheresis therapy for: 1. patient with coronary heart disease and LDL cholesterol 4.9 mmol/l (190 mg/dl); 2. patients without coronary heart disease, but at high risk for disease (due to an LDL cholesterol above 6.4 mmol/l (250 mg/dl), a first-degree relative with premature coronary heart disease, and the presence of one or more additional risk factor. The therapeutical goal with present coronary heart disease is lDL cholesterol less than 3.4 mmol/l (130 mg/dl), with asymptomatic coronary heart less than 5.2 mmol/l (200 mg/dl). In addition, LDL apheresis is recommended for the management of all patients with homozygous familial hypercholesterolaemia due to the very high risk of coronary heart disease and the poor response to usual lipid-lowering treatments. In the end present two typical cases, treated by LDL-apheresis.

[Primary hypercholesterolemia: mechanisms of its development in man]

The review is devoted to hypercholesterolemia which is one of the leading risk factors for IHD. By its origin it can be primary and secondary. Three major mechanisms of primary hypercholesterolemia in humans are discussed. They are: low activity of LDL receptors, reduced affinity of LAL for receptors and overproduction of lipoproteins containing apo B. Depending on mechanism nonidentical molecular defects leading to cholesterol imbalance in cells or in circulating lipoproteins are occurred. The understanding of the nature and mechanisms of hypercholesterolemia development is of great clinical value, because having determined molecular defect and using drugs combinations the majority of patients are a success to have their lipids normal. Only in the case of homozygous familial hypercholesterolemia medicamentous treatment becomes secondary and the principal therapeutic methods are plasmapheresis or selective LDL apheresis. Gene therapy as a method of homozygous familial hypercholesterolemia correction is in forthcoming future.

Long-term effect of low-density lipoprotein apheresis on plasma lipoproteins and coronary heart disease in native vessels and coronary bypass in severe heterozygous familial hypercholesterolemia

Low-density lipoprotein (LDL) apheresis is a potent treatment for patients with coronary heart disease and severe hereditary forms of LDL hypercholesterolemia not adequately responsive to drug treatment. Until now, the beneficial effect of aggressive reduction of LDL cholesterol by LDL apheresis on the course of coronary heart disease has been demonstrated in one 3-year study and several studies lasting 2 years. We now report on the clinical course, lipoprotein concentrations, coronary angiograms, and side effects in patients undergoing LDL apheresis for as long as 8.6 years. Thirty-four patients (21 men and 13 women) with coronary heart disease and heterozygous familial hypercholesterolemia (FH) not adequately responsive to lipid-lowering drugs received weekly (four patients biweekly) LDL apheresis for 4.6 +/- 2.6 years under diet and lipid-lowering drug therapy; after 0.5 to 3 years, simvastatin in the maximal tolerable dose was added. The baseline LDL cholesterol concentration was 6.9 +/- 1.6 mmol/L. Combined treatment in the steady state yielded a pretreatment and posttreatment LDL cholesterol concentration of 4.8 +/- 0.9 and 1.8 +/- 0.4 mmol/L, respectively. The calculated interval mean LDL cholesterol was 3.3 +/- 0.6 mmol/L. Evaluation of the coronary angiographies revealed a definite regression of coronary lesions in four patients (11.8%); in 19 patients, there was a cessation of progression. Two patients developed atheromatous lesions in bypass grafts (L.H., 60% stenosis; S.M., occlusion). Of 23 patients eligible for the scoring of anginal symptoms, five (21.7%) reported a reduction of the frequency and severity of angina pectoris. The mean coronary symptom score in 23 patients changed from 1.65 +/- 0.83 at baseline to 1.39 +/- 0.66 at the end of the study. During the whole observation period, we observed three sudden deaths, one nonfatal myocardial infarction, and five patients requiring hospital admission because of unstable angina pectoris, one of which was followed by a transluminal coronary angioplasty. Aggressive reduction of LDL cholesterol with combined LDL apheresis and drugs induced regression of coronary lesions in four of 34 patients and prevented progression in 29 patients for as long as 8.6 years. The effect on LDL and high-density lipoprotein (HDL) cholesterol and lipoprotein(a) [Lp(a)] was comparable with all three apheresis techniques. Therefore, no obvious difference between the three techniques was found regarding changes in coronary lesions.

Watanabe rabbits with heritable hypercholesterolaemia: a model of atherosclerosis

Many factors play important roles in the development of atherosclerotic lesions. The leading risk factor for atherosclerosis is familial hypercholesterolaemia (FH). FH is a genetic disease characterized by a deficiency of receptors for low density lipoprotein (LDL) on the plasmalemma of endothelial cells, a high level of serum LDL, and early development of atherosclerosis and skin xanthoma. Watanabe and colleagues have developed a line of rabbits with unprovoked hypercholesterolaemia, increased blood level of LDL, pronounced atherosclerosis and skin xanthoma. These Watanabe Heritable Hyperlipidaemic (WHHL) rabbits possess an inheritable mutation of one gene, similar to that in human FH. The morphogenesis of atherosclerosis in patients with FH is characterized by multifocal deposit of lipids in the stromal cells of thymus, spleen, skin, interstitial and parenchymatous cells of kidneys and the presence of some single foam cells in aorta. The manifestation of atherosclerotic lesions in WHHL rabbits increases progressively with age but the presence of atherosclerotic lesions in newborn WHHL rabbits suggest that the process may commence in utero. Moreover, the main mass of plasma cholesterol in WHHL rabbits is first found in LDL and to a lesser degree in lipoproteins of intermediate density. This is contrary to diet-induced atherosclerosis in rabbits where the main mass of serum cholesterol is found in very low density beta-lipoproteins. Thus the distribution of cholesterol among lipoprotein fractions differs from that in WHHL rabbits. Atherosclerotic damage of arteries in WHHL rabbits goes through several stages. During the progression of intimal damage, lipid and foam cell deposits are found in the internal surface together with developing plaques and increased content of lipids in the tunica media. Calcification often follows this process. The main factors initiating atherosclerosis in WHHL rabbits are adhesion of leukocytes and platelets to endothelial cells and the accumulation of lipids in the aortic wall. The deposits of lipids in macrophages and intimal smooth muscle cells in WHHL rabbits occurs mostly at the expense of cytoplasmic neutral lipid particles with some accumulation in lysosomes. Hypertension as a risk factor increases the area of atherosclerotic damage in all arterial vessels in WHHL rabbits, particularly in the thoracic and abdominal aorta. Morphogenesis of the development of atherosclerosis in WHHL and diet-induced atherosclerosis in rabbits was similar, but differs from rats with heritable hypercholesterolaemia. Damage or loss of endothelial cells can predispose the atherosclerotic vessels to vasospasm and can leave vessels unprotected against vasoconstrictor stimuli. The development of the WHHL model has not only given insight into the mechanisms of development of familial hypercholesterolaemia but has also provided a model for assessing various therapeutic approaches for the prevention and treatment of atherosclerosis.

Human gene therapy for hereditary diseases: a review of trials

Human gene therapy trials directed at hereditary diseases, including adenosine deaminase (ADA) deficiency, familial hypercholesterolemia, and cystic fibrosis, are reviewed. Human gene therapy involves the introduction and expression of recombinant genes in somatic, nonreproductive cells with the intent to reverse or prevent a particular disease. Two methods for introducing genes into human cells are currently being used in clinical trials. Ex vivo gene delivery involves removing targeted cells from the patient's body, introducing the recombinant gene into the cells, and placing the modified cells back into the patient's body. In vivo gene delivery involves placing the recombinant gene directly into the patient's body, targeting the tissue or cell of interest. The transfer of the recombinant gene into the cell and the subsequent expression of the transgene product are the rate-limiting steps for successful gene therapy. A variety of methods, including the use of modified viruses and synthetic vectors, are currently being used in clinical trials. Since the approval and initiation of the first human gene therapy trial to treat ADA deficiency in 1989, there have been more than 170 approved gene therapy trials in the United States. More than 1500 patients have been enrolled in human gene therapy trials worldwide. Preliminary clinical trials have targeted diseases such as ADA deficiency, familial hypercholesterolemia, and cystic fibrosis. These trials have employed variable designs and strategies, making interpretation of the results difficult. However, the initial data are encouraging, and the procedures have been well tolerated. The clinical utility of human gene therapy remains to be defined; immediate efforts will focus on improving vector design to limit toxicity and enhance the efficiency of gene transfer.