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Severe hypercholesterolemia in a pediatric cohort: Familial homozygous and autosomal recessive hypercholesterolemia.

BACKGROUND: Familial hypercholesterolemia (FH) is a genetic disorder characterized by impaired clearance of low-density lipoprotein cholesterol (LDL-C), leading to severe hypercholesterolemia and increased risk of premature cardiovascular disease (CVD). Our study aims to describe and compare the clinical, biochemical, and genetic profiles of pediatric patients diagnosed with FH based on LDL-C levels exceeding 400 mg/dL (10.4 mmol/L) and confirmed by biallelic pathogenic variants in low-density lipoprotein receptor (LDLR) or low-density lipoprotein receptor adapter protein-1 (LDLRAP1) genes. METHODS: This retrospective cohort study included 39 pediatric patients diagnosed with FH at a tertiary care center. Clinical data were analyzed, including age at diagnosis, family history, lipid profile, presence of xanthomas, and cardiovascular complications. Molecular analysis was conducted using next-generation sequencing (NGS) and Sanger sequencing to confirm pathogenic variants. Statistical comparisons were performed between the LDLR and LDLRAP1 variant groups regarding lipid profiles, treatment response, and cardiovascular outcomes. RESULTS: Among 39 patients, 32 and 7 had pathogenic variants in LDLR and LDLRAP1 genes, respectively. Genetic analysis identified 27 unique pathogenic variants in LDLR (including 5 novel mutations) and 4 in LDLRAP1 causal for autosomal recessive hypercholesterolemia (ARH), highlighting the molecular diversity of FH. Compared to the LDLR variant group, LDLRAP1 variant patients had significantly lower untreated LDL-C levels (640.0 ± 155.6 mg/dL [16.6 ± 4.0 mmol/L] vs 506.9 ± 130.1 mg/dL [13.1 ± 3.4 mmol/L], P = .026] and showed a superior response to lipid-lowering therapy (LLT), with a greater percentage (70.6% ± 12.0%) reduction in LDL-C levels (P = .015). While xanthomas were present in 62.5% of LDLR variant patients, they were less frequent (42.9%) in the LDLRAP1 group (P = .107). Cardiovascular complications were observed exclusively in LDLR variant patients. Fourteen patients required lipoprotein apheresis (LA), and one underwent liver transplantation due to severe aortic stenosis. CONCLUSION: This study highlights the importance of genetic testing in differentiating classical semidominant homozygous FH from ARH, given their phenotypic overlap but distinct treatment responses. LDLRAP1 variant patients with ARH exhibit better LDL-C reductions with conventional LLT, suggesting a milder phenotype. Early diagnosis, aggressive LLT, and novel treatments are essential to mitigate cardiovascular risk. Future studies with larger cohorts and long-term follow-ups are needed to refine treatment strategies for pediatric FH.

Humans

[Drug therapy of hypercholesterolemia. Treatment of hypercholesterolemia in adults--a Norwegian therapeutic program 1988].

There are indications that treatment of hypercholesterolemia by means of drugs reduce risk of atherosclerosis in patients with increased concentrations of atherogenic lipoproteins. Such therapy should be initiated only after satisfactory exclusion of secondary causes of hyperlipoproteinemia, and should be regarded as an adjunct to appropriate dietary therapy. Drug therapy should be strongly considered in patients with total cholesterol above 8-9 mmol/l on diet therapy only. Drug therapy should be considered at even lower concentrations of cholesterol when coronary heart disease is present and in familial forms of hyperlipidemia when increased risk of atherosclerosis has been documented. In patients with increased plasma concentrations of total cholesterol the drugs of choice are agents which enhance the rate of LDL catabolism (resins) or reduce the rate of LDL synthesis (nicotinic acid). Fibrates should be used when triglycerides and cholesterol are both increased. HMG CoA reductase inhibitors offer considerable promise in the therapy of patients with primary hypercholesterolemia. Probucol may be used in combination with other drugs, particularly when xanthomas are present in patients with familial hypercholesterolemia.

Humans

The treatment of hypercholesterolemia with beta-pyridylcarbinol. Part 5. Report on 16 cases with severe hypercholesterolemia treated for 12 years.

A group of 78 patients with severe hypercholesterolemia (-X = 464 mg/dl) and symptoms of vascular disease of the heart, the extremities, or the brain, started a beta-pyridylcarbinol treatment with an average daily dosage of 1.2 g in 1964. In 1976 we could re-examine 12 patients, still on the same therapy. No myocardial infarction has occurred in this group since 1973, only 2 patients have had more attacks of angina pectoris that 1964. In contrast patients discontinuing therapy or replacing beta-pyridylcarbinol by other hypolipidemic drugs had a higher mortality.

Adult

Hypercholesterolemia in renal allograft recipients. Comparison with non-renal hypercholesterolemia and normal subjects.

In order to investigate the degree of similarity between renal transplant and non-renal hypercholesterolemia, serum and lipoprotein lipid compositions were compared in female transplant hypercholesterolemic patients (serum cholesterol greater than 240 mg/100 ml, serum triglyceride less than 150 mg/100 ml) and female non-renal hypercholesterolemic and normal subjects. A number of lipid abnormalities were demonstrated: (1) Serum and LDL cholesterol and phospholipid levels were significantly elevated in both transplant and non-renal hypercholesterolemic patients; (2) Serum triglyceride, VLDL choelsterol, triglyceride and phospholipid, and LDL and HDL triglyceride were significantly increased in transplant hypercholesterolemic patients. Changes of this nature are usually found in hypertriglyceridemia, and were not observed in non-renal hypercholesterolemic subjects. Finally, a number of changes in the ratio of esterified to free cholesterol and in the ratios of other lipoprotein-lipids, most of which did not correspond to any changes found in the common non-renal hyperlipidemias, were also demonstrated.

Cholesterol

Metabolic basis of primary hypercholesterolemia.

BACKGROUND: Hypercholesterolemia is a well-established risk factor for coronary heart disease. However, the mechanisms underlying hypercholesterolemia, elevated low density lipoprotein (LDL) in particular, are not well understood. To determine these mechanisms, we studied LDL kinetics in a group of men with primary hypercholesterolemia. METHODS AND RESULTS: LDL kinetics in 134 middle-aged men with high-risk levels of LDL cholesterol (more than 160 mg/dl) were compared with kinetics in 16 men with borderline high-risk levels of LDL cholesterol (120-159 mg/dl) and 14 men with heterozygous familial hypercholesterolemia (FH). Patients with primary hypercholesterolemia (non-FH) were further divided into moderate hypercholesterolemia (LDL cholesterol, 160-210 mg/dl; n = 108) and severe hypercholesterolemia groups (LDL cholesterol, more than 210 mg/dl; n = 26). Four factors contributed to increasing LDL cholesterol concentrations above the borderline range to moderately elevated levels: 37 patients had no increase in LDL apolipoprotein (apo) B levels but had abnormally high LDL cholesterol-to-apo B ratios; 14 patients had very low fractional catabolic rates (FCRs) for LDL, similar to FH patients; 35 patients had FCRs for LDL in the borderline range but high production rates for LDL; and 22 patients had a high flux of LDL (high production rates and high FCRs). In general, patients with severe hypercholesterolemia resembled those with moderate LDL elevations, except that their LDL particles were enriched with cholesterol. CONCLUSIONS: Data from the present study reveal that there are several distinct patterns of LDL metabolism responsible for primary hypercholesterolemia. These patterns can serve as the basis for further investigation to determine the molecular defects responsible for each pattern.

Adult

Family history fails to identify many children with severe hypercholesterolemia.

Optimal strategies for identifying children with hypercholesterolemia have not been established. Several groups have advocated that testing of serum cholesterol levels be limited to those children who have family histories of hyperlipidemia or premature coronary heart disease. We studied the ability of comprehensive family histories to identify children with hyperlipidemia in a group of 114 children (mean age, 8 +/- 4 years) who were referred for treatment of hypercholesterolemia. A positive family history was defined according to guidelines of the American Academy of Pediatrics. The mean fasting total cholesterol in the children was 5.74 +/- 1.42 mmol/L (222 mg/dL). Family history was negative for hypercholesterolemia or premature coronary heart disease in 22 (22%) of 100 children with total cholesterol levels greater than the 75th percentile for their ages, in 13 (18.3%) of 71 children with total cholesterol levels greater than the 95th percentile for their ages, and in four (11.8%) of 34 children with presumed heterozygous familial hypercholesterolemia. Of the 78 children who had both hypercholesterolemia and positive family histories, hyperlipidemia was reported in 72 families, whereas premature heart disease was reported in only 27. We conclude that in a population of children referred because of known hypercholesterolemia, a detailed family history not only fails to identify many children with mild hypercholesterolemia, but also fails to identify a significant proportion of children with markedly elevated cholesterol levels. Additionally, in families of children with hypercholesterolemia, a history of hyperlipidemia is more common than a history of premature heart disease.

Adolescent

[Diagnostic and functional significance of arcus lipoides in hypercholesterolemia].

Twenty-eight patients were studied who required treatment for hypercholesterolemia type IIa. Familial hypercholesterolemia was found in 53%. Sixty percent of all patients had arcus senilis. When familial and non-familial hypercholesterolemia were compared the incidence of arcus senilis was 80% and 38%, respectively. The gradation of the condition was minor (n = 9), moderate (n = 4), or pronounced (n = 4); all patients with a strong degree and 7 of 8 patients with either moderate or pronounced arcus senilis had familial hypercholesterolemia. The mean cholesterol level was 345 +/- 82 in patients with familial hypercholesterolemia and 353 +/- 120 mg/dl in patients with non-familial hypercholesterolemia. Although the correlation between the cholesterol level and the degree of arcus senilis was higher in patients with familial hypercholesterolemia than in those with non-familial hypercholesterolemia (r = 0.45 versus r = 0.17), neither had clinical relevance. There was no connection between the cholesterol level, refraction or visual acuity. The mean contrast sensitivity measured for five different spatial frequencies in all patients was normal. In comparison with patients without arcus senilis, the mean values in patients with severe arcus senilis showed lower contrast sensitivity for the higher spatial frequencies.

Adult

Interactions of hypercholesterolemia and hypertension in initiation of glomerular injury.

In the Dahl S rat (DS), salt induces systemic and glomerular capillary hypertension associated with progressive glomerulosclerosis, while Dahl R rats (DR) remain normotensive, without glomerular abnormalities. Studies in experimental models have suggested that hypercholesterolemia may play a role in the development of glomerulosclerosis; however, it is unclear whether hypercholesterolemia alone, in the absence of hypertension, can initiate injury. To answer this question we induced hypercholesterolemia in salt-supplemented DS (DSC) and DR (DRC) by feeding a high cholesterol (4%) chow. Control rats (DS, DR) received high-salt, normal cholesterol chow. After eight weeks, DS and DSC developed equivalent hypertension (161 +/- 3 vs. 153 +/- 3 mm Hg, respectively, P = NS), while DR and DRC remained normotensive (138 +/- 5 vs. 131 +/- 5 mm Hg, P = NS; P less than 0.05 vs. DS and DSC). Cholesterol fed rats developed marked and equivalent hypercholesterolemia compared to controls (DS vs. DSC, 71 +/- 3 vs. 289 +/- 91 mg/dl, P less than 0.05; DR vs. DRC, 52 +/- 2 vs. 327 +/- 54 mg/dl, P less than 0.05). Hypertensive rats (DS, DSC) developed worse proteinuria and glomerular injury than normotensive rats (DR, DRC), but hypercholesterolemia exacerbated proteinuria and glomerulosclerosis only in DSC and not in DRC. Proteinuria significantly correlated with serum cholesterol in hypertensive rats (DS, DSC, P less than 0.05), but not normotensive rats (DR, DRC, P = NS). Furthermore, DSC had increased renal vascular resistance compared to DS, while no differences were found between DRC and DR. Thus, in the Dahl rat, hypercholesterolemia alone does not initiate glomerular injury. In this model, hypercholesterolemia is a pathogenetic factor in glomerular injury only when it coexists with systemic hypertension.

Animals

Family studies of the LDL receptor gene of relatively severe hereditary hypercholesterolemia associated with Achilles tendon xanthomas.

To assess the relationship between relatively severe hereditary hypercholesterolemia with Achilles tendon xanthomas and the defect of the low density lipoprotein (LDL) receptor gene, family studies were carried out in 17 hypercholesterolemic families. In 16 out of the 17 families, hypercholesterolemia co-segregated with four different gross rearrangements, six different restriction fragment length polymorphism (RFLP) haplotypes, or an abnormal TaqI band of the LDL receptor gene. These findings are compatible with the interpretation that hypercholesterolemia is caused by defective LDL receptor genes, and that the origin of the mutant LDL receptor genes in Japanese generally differs among different pedigrees. In the remaining family, the proband and his sibling, both having relatively severe hypercholesterolemia and Achilles tendon xanthomas, shared an RFLP haplotype, although the proband's other sibling with moderate hypercholesterolemia but without Achilles tendon xanthomas did not. The mutant gene for familial defective apolipoprotein B-100 was not detected in the 17 probands. These data suggest that most, if not all, of the relatively severe hereditary hypercholesterolemia associated with Achilles tendon xanthomas is caused by a defect of the LDL receptor gene.

Achilles Tendon

Hypercholesterolemia enhances macrophage recruitment and dysfunction of regenerated endothelium after balloon injury of the rabbit iliac artery.

BACKGROUND: We studied the effects on and possible interaction of balloon denudation and hypercholesterolemia on large arteries in the rabbit with special regard to structure and vascular reactivity. METHODS AND RESULTS: New Zealand White rabbits fed a 1% cholesterol diet or a standard diet for 14 weeks underwent balloon denudation of the left iliac artery 4 weeks before death. Both the balloon-injured and the control iliac arteries were harvested for in vitro studies of vascular reactivity, for immunohistochemical staining with monoclonal antibodies directed at smooth muscle cells and macrophages, and for scanning electron microscopy. Balloon injury caused intimal smooth muscle proliferation with little macrophage infiltration and was followed by recovery of endothelium-dependent vasodilator function within 4 weeks. Hypercholesterolemia caused macrophage-rich lesions confined to the intima with moderate impairment of endothelial vasodilator function. Balloon injury in the setting of hypercholesterolemia caused intimal smooth muscle cell proliferation and intense macrophage infiltration throughout the arterial wall and severe impairment of endothelial vasodilator function. Scanning electron microscopy confirmed regrowth of the endothelium in all balloon-injured vessels. In the balloon-injured arteries of hypercholesterolemic animals, the regenerated endothelium exhibited areas of atypical morphology not seen after balloon injury or hypercholesterolemia alone. CONCLUSIONS: The present study shows that balloon injury, hypercholesterolemia, and their combination cause distinct lesions and functional disturbances. An arterial balloon injury in the setting of hypercholesterolemia produces a diffuse inflammatory response that is accompanied by a sustained impairment of endothelial function and a marked proliferative response.

Animals

Loss of selective endothelial cell vasoactive functions caused by hypercholesterolemia in pig coronary arteries.

The influence of hypercholesterolemia on the reactivity of coronary arteries was investigated after feeding a high-cholesterol diet to pigs for 9 weeks. After this duration of hypercholesterolemia, the fatty or intimal proliferative changes of atherosclerosis were not yet evident in the coronary arteries by light or electron microscopy. Changes in isometric tension were compared in isolated ring segments of coronary arteries from normal and hypercholesterolemic animals. The endothelium failed to inhibit contractions caused by 5-hydroxytryptamine in coronary arteries from hypercholesterolemic animals, but it did so in normal vessels. In contracted arteries, endothelium-dependent relaxations caused by 5-hydroxytryptamine and substance P were reduced by hypercholesterolemia. In contrast, endothelium-dependent relaxations mediated by norepinephrine acting at alpha 2-adrenoceptors and those caused by the calcium ionophore A23187 were unaffected. Endothelium-independent beta-adrenergic relaxations caused by norepinephrine, as well as those caused by nitroprusside, and papaverine also were unaffected by hypercholesterolemia. The loss of selective endothelial cell receptor-mediated relaxation suggests that it is not the ability of the coronary artery endothelium to elaborate vasodilators, but the initiation of the coronary artery endothelial cell response to 5-hydroxytryptamine and substance P that is affected by hypercholesterolemia. Thus, during hypercholesterolemia, selective endothelial cell dysfunction giving rise to abnormal coronary artery reactivity precedes the onset of coronary artery atherosclerosis.

Animals

Genetics of the low density lipoprotein receptor. Diminished receptor activity in lymphocytes from heterozygotes with familial hypercholesterolemia.

Using circulating mononuclear cells as a readily available tissue and using the rate of high affinity degradation of 125-I-labeled low density lipoprotein (LDL) as an index of cell surface LDL receptor activity, we have measured receptor activity in cells from 53 individuals. This group includes 32 healthy subjects, 15 subjects with the heterozygous form of familial hypercholesterolemia, and 6 subjects with hyperlipidemic disorders other than familial hypercholesterolemia. 7 of the healthy subjects and 10 of the heterozygotes were members of a single large kindred with five-generation transmission of the mutant familial hypercholesterolemia gene. LDL receptor activity was assayed in blood mononuclear cells under two sets of conditions. First, 125I-LDL degradation was measured in purified lymphocytes that had been incubated for 3 days in the absence of lipoproteins so as to induce a high level of LDL receptor activity. Phase-contrast autoradiograms of cells incubated with 125I-LDL and electron micrographs of cells incubated with ferritin-labeled LDL confirmed the existence of LDL receptors on lymphocytes. Second, 125I-LDL degradation was measured in mixed mononuclear cells (85-90% lymphocytes and 5-15% monocytes) immediately after their isolation from the bloodstream. This assay represented an attempt to assess the number of receptors actually expressed on the cells when they were in the circulation. Under both sets of conditions, cells from the familial hypercholesterolemia heterozygotes expressed an average of about one-half the normal number of LDL receptors. The current findings are consistent with the conclusion that heterozygotes with familial hypercholesterolemia possess only one functional allele at the LDL receptor locus and that the consequent deficiency of LDL receptors produces the clinical syndrome of heterozygous familial hypercholesterolemia.

Adhesiveness

Relationship of metabolic control and body weight to hypercholesterolemia in NIDDM patients with apolipoprotein E4.

OBJECTIVE: We previously reported that non-insulin-dependent diabetes mellitus (NIDDM) patients with apolipoprotein E4 (apoE4) are more susceptible to hypercholesterolemia. The purpose of this study was to clarify whether metabolic control or body weight is related to hypercholesterolemia in NIDDM patients with apoE4. RESEARCH DESIGN AND METHODS: Two hundred forty NIDDM patients with apoE4 or apoE3/3 who had either hypercholesterolemia or normolipidemia were studied. ApoE phenotypes were determined by isoelectric focusing method. RESULTS: The apoE4-carrying NIDDM patients with hypercholesterolemia (n = 39) showed significantly higher fasting plasma glucose (8.4 vs. 7.2 mM, P less than 0.05), HbA1 (9.3 vs. 8.1%, P less than 0.05), and percentage of ideal body weight values (116 vs. 102%, P less than 0.01) than the apoE4-carrying NIDDM patients with normolipidemia (n = 26), whereas there was no significant difference in their levels between the apoE3/3-carrying NIDDM patients with hypercholesterolemia (n = 47) and normolipidemia (n = 128). CONCLUSIONS: In addition to our previous finding, this study indicates that hypercholesterolemia in apoE4-carrying NIDDM patients may be more closely related to poor metabolic control and increased percentage of ideal body weight.

Adult

Hypolipidemic effects of HMG-CoA reductase inhibitors in patients with hypercholesterolemia.

Hypercholesterolemia with increased plasma concentrations of low density lipoproteins (LDL) is a major risk factor for the premature development of coronary atherosclerosis in humans and is best exemplified by patients with familial hypercholesterolemia. The recent development of several specific competitive inhibitors of the rate-limiting enzyme in cholesterol biosynthesis (3-hydroxy-3-methylglutaryl-coenzyme A reductase, HMG CoA reductase) has opened up an important new avenue of therapy for patients with hypercholesterolemia who are not responsive to dietary treatment alone. Three drugs, lovastatin (mevinolin), simvastatin (synvinolin) and pravastatin (CS 514), are currently undergoing clinical trials in North America and Europe; the former has recently been approved for general use. Experience with lovastatin and simvastatin in the treatment of patients with primary and secondary causes of hypercholesterolemia is reviewed. The relative potency of simvastatin appears to be greater than that of lovastatin and pravastatin but, with each drug, decreases in the plasma concentrations of LDL cholesterol of 30% to 50% can be achieved. The hypocholesterolemic effects of HMG CoA reductase inhibitors can be potentiated by combination therapy with other approved lipid-lowering medications including the bile acid sequestrants and nicotinic acid. If long-term safety can be satisfactorily established, specific inhibitors of HMG CoA reductase represent a major advance in the therapy of hypercholesterolemia and afford the potential to reduce substantially the high incidence of premature atherosclerosis that occurs in patients with persistent hypercholesterolemia.

Anticholesteremic Agents

Genetically determined hypercholesterolemia in a rhesus monkey family due to a deficiency of the LDL receptor.

A family of rhesus monkeys comprising a sire, a dam, and four male offspring were fed a cholesterol-free Purina Chow diet for several months. The sire, 431-J, and two of the offspring, B-8204 and B-8806, had persistent plasma cholesterol levels in the range of 100-130 mg/dl, whereas the dam, 766-I, and the two other offspring, B-1000 and B-7643, exhibited a marked hypercholesterolemia in the 250-300 mg/dl range associated with an elevation of plasma LDL and apoB. When fed for 12 weeks a diet containing 12.5% lard and 0.25% cholesterol, sire, dam, B-1000 and B-7643 exhibited a marked hypercholesterolemia (500-800 mg/dl range), whereas B-8204 and B-8806 developed only a modest hypercholesterolemia (200-250 mg/dl). All animals were Lp[a]+. Skin fibroblasts from each animal and from control cells were grown in 10% fetal calf serum, transferred to 10% lipoprotein-deficient serum for 48 hr, and then incubated at 4 degrees C or 37 degrees C with 125I-labeled Lp[a]-free LDL. The fibroblasts from dam and offspring B-1000 and B-7643 bound and internalized 125I-labeled LDL less efficiently than control cells. Mathematical analyses of the 4 degrees C binding data indicated that there were no significant differences in LDL binding affinity between test and control cells suggesting that cells from the animals with a spontaneous hypercholesterolemia had a decreased number of LDL receptors. This conclusion was supported by the results of ligand and immunoblot analyses carried out on cell lysates separated by gradient gel electrophoresis. We conclude that a genetically determined LDL receptor deficiency was responsible, in part, for the spontaneous hypercholesterolemia observed in three out of the six family members and that this deficiency accounted for the hyperresponsiveness to a dietary fat and cholesterol challenge by the dam and the two offspring, B-1000 and B-7643. The hyperresponsiveness noted in the sire that had no evidence for LDL-receptor deficiency illustrates that factors other than the LDL receptor were responsible for the hypercholesterolemia attending the fat challenge.

Animals