Effects of ML-236b (compactin) on sterol synthesis and low density lipoprotein receptor activities in fibroblasts of patients with homozygous familial hypercholesterolemia

Familial hypercholesterolemia with special focus on Japan

Familial hypercholesterolemia (FH) is an inherited disorder characterized by increased low-density lipoprotein LDL) cholesterol and atherosclerotic cardiovascular disease. Although initial genetic analysis linked FH to LDL receptor mutations, subsequent work demonstrated that a gain-of-function mutation in the proprotein convertase subtilisin/kexin type 9 (PCSK9), which causes LDL-R degradation, was shown to be the cause of FH. In this review, we describe the history of research on FH, its clinical phenotyping and genotyping and advances in treatment with special focus on Japan.

Function and Immunogenicity of Gene-corrected iPSC-derived Hepatocyte-Like Cells in Restoring Low Density Lipoprotein Uptake in Homozygous Familial Hypercholesterolemia

Gene correction of induced pluripotent stem cells (iPSCs) has therapeutic potential for treating homozygous familial hypercholesterolemia (HoFH) associated with low-density lipoprotein (LDL) receptor (LDLR) dysfunction. However, few data exist regarding the functional recovery and immunogenicity of LDLR gene-corrected iPSC-derived hepatocyte-like cells (HLCs) obtained from an HoFH patient. Therefore, we generated iPSC-derived HLCs from an HoFH patient harbouring a point mutation (NM_000527.4:c.901 G > T) in exon 6 of LDLR, and examined their function and immunogenicity. From the patient’s iPSCs, one homozygous gene-corrected HoFH-iPSC clone and two heterozygous clones were generated using the CRISPR/Cas9 method. Both types of iPSC-derived HLCs showed recovery of the function of LDL uptake in immunofluorescence staining analysis. Furthermore, these gene-corrected iPSC-derived HLCs showed little immunogenicity against the patient’s peripheral blood mononuclear cells in a cell-mediated cytotoxicity assay. These results demonstrate that LDL uptake of iPSC-derived HLCs from HoFH can be restored by gene correction without the appearance of further immunogenicity, suggesting that gene-corrected iPSC-derived HLCs are applicable to the treatment of HoFH.

Half a Century Tales of Familial Hypercholesterolemia (FH) in Japan

Familial hypercholesterolemia (FH) is a disease characterized by a triad: elevated low-density lipoprotein (LDL) cholesterol, tendon xanthomas, and premature coronary heart disease. Thus, it can be considered as a model disease for hypercholesterolemia and atherosclerotic cardiovascular disease (ASCVD). For the diagnosis of hetero-FH, the detection of Achilles tendon xanthomas by palpation or on X-ray is an indispensable diagnostic skill in clinical lipidology. To prevent the under-diagnosis and under-treatment of FH, the diagnostic criteria should be more convenient and user-friendly. For a patient with cutaneous or tendon xanthomas, the probability of FH is very high; however, an absence of xanthoma does not rule out FH.

Brown and Goldstein elucidated the pathogenesis of FH by their work on LDL-receptor (LDL-R), for which they were awarded the Nobel Prize in 1985. In the 1950s, FH patients were divided into heterozygous (hetero-) and homozygous (homo-) FH, and diagnosing homo- and hetero-FH based on the phenotypic features of ASCVD or xanthomas frequently became difficult without the DNA analysis of FH genes. It is estimated that heterozygous mutations in the LDL-R or the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene will be found at a combined frequency of 0.005, which corresponds to 1/199 people in the general population in Japan.

Statins and anti-PCSK9 monoclonal antibodies are highly specific and efficient drugs for treating hetero- or homo-FH patients. Most clinical studies have reported an amelioration of ASCVD using long-term statin therapy. Clinical results using anti-PCSK9 monoclonal antibodies will emerge in a few years. In homo-FH patients, mipomersen and lomitapide are expected to yield good results. It is important to sequentially unravel the unrecognized pathogenetic mechanisms of FH to reduce its under-recognition and develop new management strategies for it.

Ethical challenges in preclinical Alzheimer's disease observational studies and trials: Results of the Barcelona summit

Alzheimer's disease (AD) is among the most significant health care burdens. Disappointing results from clinical trials in late-stage AD persons combined with hopeful results from trials in persons with early-stage suggest that research in the preclinical stage of AD is necessary to define an optimal therapeutic success window. We review the justification for conducting trials in the preclinical stage and highlight novel ethical challenges that arise and are related to determining appropriate risk-benefit ratios and disclosing individuals' biomarker status. We propose that to conduct clinical trials with these participants, we need to improve public understanding of AD using unified vocabulary, resolve the acceptable risk-benefit ratio in asymptomatic participants, and disclose or not biomarker status with attention to study type (observational studies vs clinical trials). Overcoming these challenges will justify clinical trials in preclinical AD at the societal level and aid to the development of societal and legal support for trial participants.

LDL-receptor gene mutations and the hypocholesterolemic response to statin therapy

Studies of the cholesterol lowering effect of statin therapy as a function of low-density lipoprotein (LDL)-receptor mutation type have not produced a clear picture, possibly because they included patients with several different kinds of LDL-receptor mutations. We studied the response to treatment with fluvastatin in 28 patients with heterozygous familial hypercholesterolemia as a result of a receptor-negative mutation (Trp23-stop) and in 30 patients with a receptor-binding defective mutation (Trp66-Gly) to test the hypothesis that response to treatment depends on the type of mutation. Patients were randomized to 12 weeks of treatment with fluvastatin 40 mg daily and 12 weeks of placebo treatment, preceded by a placebo run-in period of 8 weeks in a double-blind, cross-over design. Untreated plasma concentrations of lipids and lipoproteins were similar in the two groups of patients. Plasma cholesterol and LDL cholesterol response to therapy tended to be less marked in receptor-binding defective patients, but the differences were not statistically significant. A tabulation of the results of the present and earlier studies suggests that differences in treatment response as an apparent function of LDL-receptor gene mutational type occur mainly in populations with recent genetic admixture (<400 years). In such populations, persons with the same mutation in the LDL-receptor gene are more likely to share other but undetermined genetic variations affecting the pharmacology of statins.

Low-density lipoprotein receptor genotype-dependent response to cholesterol lowering by combined pravastatin and cholestyramine in familial hypercholesterolemia

We compared the effects of cholesterol-lowering therapy on 2 patient groups genetically defined as heterozygous for familial hypercholesterolemia (FH), 5 with a deletion of exon 15 (FH(Tonami-1)), and 7 with a point mutation at codon 664 (FH(Kanazawa-2)). There were significant differences in both serum and low-density lipoprotein cholesterol reductions between the 2 groups after combination therapy with pravastatin and cholestyramine, and the overall effect of genotype on serial changes in both was significant.

Pathological and angiographic regression of coronary atherosclerosis by LDL-apheresis in a patient with familial hypercholesterolemia

We present the case of a 42-year-old male with familial hypercholesterolemia (FH) who had received long-term low-density lipoprotein (LDL)-apheresis before death occurred, presumably from an arrhythmia. He had been treated with double filtration plasmapheresis (DFPP) for 4 years and selective LDL adsorbent plasmapheresis (LAPP) for 2 years and 7 months. During the period of treatment (6 years and 7 months) he had received a total of 129 sessions of LDL-apheresis. Serum total cholesterol of the patient before the treatment was 638 mg/dl and during the treatment, the time-averaged values ranged from 336 mg/dl to 411 mg/dl for the first 4 years (with DFPP) and from 257 mg/dl to 364 mg/dl for the sequential 2 years and 7 months (with LAPP). Coronary angiograms were analysed for 13 segments of the coronary arteries using a digitized processing system. Analysis documented regression by identifying a reduction in percent stenosis from 34% to 20% in the proximal left circumflex artery (LCX), from 78% to 61% in the proximal right coronary artery (RCA), and from 92% to 72% in the middle RCA. In the other 10 segments analysed no significant regression and no progression were observed. The autopsy findings of the step-wise serial sections of the native coronary arteries did not record the formation of new and/or typical atheroma. In addition, a thickened intima, and an eccentric thickened wall lesion rich in collagen fiber were observed, although an accumulation of foam cells in the thickened wall lesions was found in some segments. This observation suggested scarring of the atheromatous plaque. We confirmed that LDL-apheresis performed over a period of 6 years and 7 months induced angiographic regression of coronary atherosclerosis in the patient with FH, and found that most of the atherosclerotic lesions were changed pathologically into sclerotic lesions rich in collagen fiber.

Hypercholesterolemia and atherosclerosis: present and future therapy including LDL-apheresis

Atherosclerosis-induced coronary heart disease remains the major cause of death and disability in industrialized countries. Hypercholesterolemia is recognized as a causative factor in the development of atherosclerosis. While the lowering of cholesterol levels as a treatment goal has met with general agreement and acceptance, the preferred methods for doing so are still open to conjecture. This literature review discusses various factors in the hypercholesterolemia-atherosclerosis link and surveys a variety of treatment protocols including diet modification, drug therapy, surgical intervention, and plasmapheresis. Evidence is accumulating to prove that the ideal hypercholesterolemia therapy is one that reduces LDL levels while maintaining or increasing HDL levels. Because LDL-apheresis has this potential, this paper also reviews the various LDL-apheresis methods, including immunoadsorption, chemical affinity, and double-membrane filtration.

Treatment of homozygous patients with familial hypercholesterolemia by double-filtration plasmapheresis

Two homozygous patients with familial hypercholesterolemia were treated by double-filtration plasmapheresis. The plasma separated by the first filter was subsequently led to the second filter of ethylene vinylalcohol co-polymer hollow fibers, which trap very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL) and low density lipoprotein (LDL) preferentially to other plasma constituents. Serum, VLDL, IDL, LDL cholesterol levels decreased by 55, 68, 59 and 55%, respectively. HDL cholesterol levels decreased by 39%. Immunoglobulins and fibrinogen levels decreased significantly. Cutaneous and tendinous xanthomas became smaller. off

Coronary ectasia in a homozygous patient with familial hypercholesterolemia

A 23-year-old man with homozygous familial hypercholesterolemia was found to have coronary ectasia by coronary angiography. This case showed generalized xanthomatosis and severe hyper low density lipoproteinemia, and his cultured skin fibroblasts showed LDL receptor activities compatible with the receptor-defective homozygous type of familial hypercholesterolemia. Coronary angiography showed fusiform aneurysmal involvements in the right coronary artery and left circumflex artery, and 50% stenosis in the right coronary artery and left anterior descending artery. Thus, homozygous familial hypercholesterolemia produces coronary ectasia as well as premature coronary stenosis.

Homozygous familial hypercholesterolemic patients in China

Five homozygous patients with familial hypercholesterolemia (FH) are described. Their serum cholesterol levels were between 603 and 907 mg/dl, with an average of 714 mg/dl. The mean value of serum cholesterol levels of the obligate heterozygous parents was 270 mg/dl. In the patient group, 87% of the serum cholesterol was distributed in low density lipoprotein (LDL) and the mean LDL cholesterol level was about 8.4 times that in a control group. Phospholipids in HDL in the patient group were significantly lower than in the controls. Lipid assays of xanthoma tissues revealed that the major lipid was cholesterol and its esters. LDL receptor activity in fibroblasts from the homozygotes was markedly decreased. Two patients yielded less than 2% of normal receptor activity and were classified as receptor-negative. The other 3 revealed receptor activities greater than 2% but less than 25% of normal receptor activity and were classified as receptor-defective.

Normalization of low-density lipoprotein levels and disappearance of xanthomas during pregnancy in a woman with heterozygous familial hypercholesterolemia

Serum lipids and lipoproteins were studied prior to conception, during pregnancy, and after delivery in a woman heterozygous for familial hypercholesterolemia. Prior to conception, serum and low-density lipoprotein (LDL) cholesterol levels were 613 and 528 mg/dL, respectively. At 37-week gestation, serum and LDL cholesterols decreased to the normal levels, 226 and 90 mg/dL, respectively. At two-week postpartum serum and LDL cholesterols returned to the preconception levels, 547 and 427 mg/dL, respectively. At delivery her cutaneous xanthomas almost disappeared. The patient was challenged by ethinyl estradiol of 120 micrograms/d for two months, as a result serum cholesterol decreased from 565 to 385 mg/dL, and LDL cholesterol fell from 460 to 208 mg/dL. During her second pregnancy, serum and LDL cholesterol decreased again significantly. Thus, this case, which showed dramatic reductions of serum and LDL cholesterol levels, may be considered a new variant of heterozygous familial hypercholesterolemia, and the reductions were probably brought about by the action of estrogens, which are known to increase LDL degradation through LDL receptors.

A case of heterozygous familial hypercholesterolemia associated with hyperthyroidism: effects of triiodothyronine on low-density lipoprotein receptor and cholesterol synthesis

A 58-year-old patient with heterozygous familial hypercholesterolemia (FH) showed normal levels of serum cholesterol (193 mg/dL) in coexistence with hyperthyroidism. After hyperthyroidism therapy with radioiodine and methimazole, the patient's lipid profile showed high concentrations of cholesterol (whole serum 318 mg/dL, VLDL 35 mg/dL, LDL 217 mg/dL, HDL 44 mg/dL). There was a significant inverse correlation between serum cholesterol levels and serum thyroxine levels (r = -0.815, p less than 0.01). Effects of triiodothyronine on LDL degradation and cholesterol synthesis from 14C-labeled acetate were studied in cultured skin fibroblasts. Triiodothyronine (T3) stimulated both LDL degradation and cholesterol synthesis in the cells from normal subjects and patients with heterozygous FH. The T3 increased cellular cholesterol synthesis markedly in the cells from patients with homozygous FH but did not increase LDL receptor activity. These results suggest that normal serum cholesterol levels in our case result in part from an enhancement of LDL receptors by thyroid hormone.

The LDL receptor defect in familial hypercholesterolemia. Implications for pathogenesis and therapy

Familial hypercholesterolemia results from one of several genetic defects in a cell surface receptor that normally controls the degradation of low density lipoprotein. The clinical and genetic features and the pathophysiology of these defects are discussed. Knowledge of the regulation of LDL receptors in the liver can be exploited in the design of a physiologically rooted therapy for familial hypercholesterolemia.

Effects of an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase on serum lipoproteins and ubiquinone-10-levels in patients with familial hypercholesterolemia

We studied the effects of ML-236B, a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, on serum levels of lipoproteins and ubiquinone-10-in seven heterozygous patients with familial hypercholesterolemia. ML-236B was given at doses of 30 to 60 mg per day for 24 weeks. Serum cholesterol decreased from 390 +/- 9 to 303 +/- 8 mg per deciliter (101 +/- 0.2 to 7.88 +/- 0.2 mmol per liter, mean +/- S.E.M.; p less than 0.001) and serum triglyceride decreased from 137 +/- 18 to 87 +/- 9 mg per deciliter (1.55 +/- 0.20 to 0.98 +/- 0.01 mmol per liter; p less than 0.05). Intermediate-density-lipoprotein (DL) cholesterol, IDL triglyceride, low-density-lipoprotein (LDL) cholesterol, and LDL triglyceride decreased significantly (p less than 0.01, P less than 0.001, and P less than 0.001, respectively). However, there were no significant changes in very-low-density-lipoprotein (VLDL) cholesterol and triglyceride or high-density-lipoprotein (HDL) cholesterol. Serum ubiquinone-10 levels did not change, and LDL levels of ubiquinone-10 decreased by 50 per cent, from 0.39 +/- 0.07 to 0.20 +/- 0.01 microgram per milliliter (P less than 0.05). No adverse effects were observed. We conclude that ML-236B is effective in lowering serum cholesterol without lowering serum ubiquinone-10 in heterozygous patients with familial hypercholesterolemia.