Comparison of iodine-123 low-density lipoprotein (LDL) and indium-111 LDL binding to mononuclear cells of healthy normolipaemic controls and patients with heterozygous familial hypercholesterolaemia

The binding of radiolabelled lipoproteins, iodine-123-labelled low-density. lipoprotein (LDL) and indium-111-labelled LDL, to peripheral blood mononuclear cells (MNCs) was compared in normolipaemic subjects and in patients with heterozygous familial hypercholesterolaemia (FH). ¹²³I-LDL and ¹¹¹In-LDL binding to MNCs exhibited high-affinity, highly specific, time- and temperature-dependent binding reaching saturation at concentrations above 50 nM. The number of LDL binding sites (B_max) was significantly (P<0.01) lower in FH patients (P<0.001; ¹²³I-LDL: B_max 279±44 ng protein/10⁸MNCs; ¹¹¹In-LDL: B_max 309±43 ng protein/10⁸MNCs) as compared with controls (¹²³I-LDL: B_max 2874±246 ng protein/10⁸ MNCs; ¹¹¹In-LDL: B_max 3145±339 ng protein/10⁸ MNCs). The corresponding dissociation constants (K _d) were 16±8 nM for ¹²³I-LDL and 12±6 nM for ¹²³In-LDL in healthy volunteers (¹²³In-LDL vs ¹¹¹In-LDL, P<0.05). In FH patients, the K _d values were 20±8 nM for ¹²³I-LDL and 16±6 nM for ¹²³In-LDL (P<0.05 vs controls for both ¹²³I-LDL and ¹¹¹In-LDL). ¹¹¹In-LDL binding to MNCs was inhibited (IC₅₀) by 30±8 nM in healthy controls and 38±12 nM in FH patients (P<0.05). ¹²³In-LDL binding to MNCs was inhibited (IC₅₀) by 34±8 nM in healthy controls and 46±10 nM in FH patients (P<0.05). Taken together, these results suggest a reduced number of LDL receptors expressed on MNCs from FH patients. We conclude that ¹¹¹In-LDL and ¹²³I-LDL are equally well suited as a probe of receptor-mediated binding and uptake of LDL.     

Predominance of a 6 bp deletion in exon 2 of the LDL receptor gene in Africans with familial hypercholesterolaemia

In South Africa, the high prevalence of familial hypercholesterolaemia (FH) among Afrikaners, Jews, and Indians as a result of founder genes is in striking contrast to its reported virtual absence in the black population in general. In this study, the molecular basis of primary hypercholesterolaemia was studied in 16 Africans diagnosed with FH. DNA analysis using three screening methods resulted in the identification of seven different mutations in the coding region of the low density lipoprotein (LDLR) gene in 10 of the patients analysed. These included a 6 bp deletion (GCGATG) accounting for 28% of defective alleles, and six point mutations (D151H, R232W, R385Q, E387K, P678L, and R793Q) detected in single families. The Sotho patient with missense mutation R232W was also heterozygous for a de novo splicing defect 313+1G→A. Several silent mutations/polymorphisms were detected in the LDLR and apolipoprotein B genes, including a base change (g→t) at nucleotide position −175 in the FP2 LDLR regulatory element. This promoter variant was detected at a significantly higher (p<0.05) frequency in FH patients compared to controls and occurred in cis with mutation E387K in one family. Analysis of four intragenic LDLR gene polymorphisms showed that the same chromosomal background was identified at this locus in the four FH patients with the 6 bp deletion. Detection of the 6 bp deletion in Xhosa, Pedi, and Tswana FH patients suggests that it is an ancient mutation predating tribal separation approximately 3000 years ago.


Keywords: apolipoprotein B; hypercholesterolaemia; low density lipoprotein receptor; mutation     

Apolipoprotein E polymorphism is not associated with lipid levels and coronary artery disease in Greek patients with familial hypercholesterolaemia

Abstract Familial hypercholesterolaemia is a genetic disorder characterised by high low-density lipoprotein (LDL) cholesterol concentrations, which frequently gives rise to premature coronary artery disease (CAD). The clinical expression of familial hypercholesterolaemia is highly variable even in patients carrying the same LDL receptor gene mutation. This variability may be due to environmental and other genetic factors. Apolipoprotein E (Apo-E) has been extensively studied for its effects on the phenotype of familial hypercholesterolaemia. In this study we examined the influence of Apo-E genotype on lipid parameters and the incidence of CAD in 93 Greek patients with familial hypercholesterolaemia. Apo-E E2, E3 and E4 allele frequencies were 0.06, 0.86 and 0.09 respectively. The levels of total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, apolipoproteins A and B and lipoprotein α did not differ significantly among carriers and non-carriers of the E4 allele. The prevalence of CAD and hypertension did not differ either. Our results suggest that the E4 allele is not associated with lipid levels or with the prevalence of CAD among familial hypercholesterolaemia patients of the Greek population. *The two authors were equally involved in the work     

新型调脂药ezetimibe--胆固醇吸收的选择性抑制剂

传统的树脂类、贝特类等药物因为不良反应大，降低胆固醇效果差而不易被病人接受。他汀类药物降低胆固醇效果好，但某些病人单用他汀类药物不能有效降低体内胆固醇水平。因此本文介绍了新近在美国上市的ezetimibe，一种新型胆固醇吸收的选择性抑制剂，在单用或与他汀类药物联用时，都能稳定降低血浆低密度脂蛋白胆固醇(LDL-C)水平，为临床治疗高脂血症提供了新的选择。     

Familial hypercholesterolaemia: what’s new?

Autosomal Dominant Familial Hypercholesterolaemia (FH) is the commonest inherited disorder of lipoprotein metabolism. Untreated monogenic FH caused by mutations in the LDLR, APOB or PCSK9 genes result in early onset cardiovascular death (below the age of 60 years). In the UK the prevalence of heterozygous FH is 1 in 270 and homozygous FH is 160,000 approximately.The introduction of statins nearly three decades ago has altered the natural history of FH, with a significant reduction of cardiovascular related morbidity and mortality. There is increasing evidence that early childhood interventions such as lifestyle choices, healthy eating and commencing statins by the age of 10 years would potentially prevent early onset cardiovascular disease and mortality in monogenic FH. The medium term safety of statins in children has been demonstrated. The UK paediatric FH register data has shown that children with FH are less obese than the normal population and the register aims to monitor the longer-term safety of statins in children with FH. Child-parent screening would potentially benefit the child and enables identifying a parent with FH, before the onset of a life threatening cardiovascular event. In addition, genetic cascade testing of relatives of an affected individual has been shown to be highly cost effective.We review the current literature with brief updates on genetics, the UK paediatric FH register data, published recommendations for the management of homozygous and heterozygous FH, lipid lowering therapies in children and screening for FH in childhood.     

Reduction in cholesterol absorption in Caco-2 cells through the down-regulation of Niemann-Pick C1-like 1 by the putative probiotic strains Lactobacillus rhamnosus BFE5264 and Lactobacillus plantarum NR74 from fermented foods

Hypercholesterolaemia is a major risk factor related to atherosclerosis, and it may be influenced by our diet. This study addresses the impact of Lactobacillus rhamnosus BFE5264 (isolated from Maasai fermented milk) and Lactobacillus plantarum NR74 (from Korean kimchi) on the control of cholesterol absorption through down-regulation of Niemann-Pick C1-like 1 (NPC1L1) expression. Caco-2 enterocytes were treated with the live, heat-killed (HK) bacteria, bacterial cell wall extracts and metabolites; mRNA level and protein expression were measured. Caco-2 cells showed lower NPC1L1 expression in the presence of the live test strains than the control, elucidating down-regulation of cholesterol uptake, and were compared well with the positive control, L. rhamnosus GG. This effect was also observed with HK bacteria and cell wall fractions but not with their metabolites. The potential of some Lactobacillus strains associated with traditional fermented foods to suppress cholesterol uptake and promote its efflux in enterocytes has been suggested from these data.     

Daily life,experience and needs of persons suffering from homozygous familial hypercholesterolaemia: Insights from a patient survey

Homozygous familial hypercholesterolaemia (HoFH) is a rare and severe hereditary lipid disorder that is typically associated with high serum levels of low-density lipoprotein cholesterol (LDL-C). Excessive exposure to high levels of LDL-C puts affected individuals at very high risk of premature onset coronary heart disease, and this considerably limits life expectancy. Although the clinical features and treatment of HoFH have been extensively researched, societal and socio-psychological impacts of the disease have not been reported to date. The current study was conducted to investigate the burden of disease and treatment from the patient's perspective by means of semi-structured interviews with 24 HoFH patients. The findings of the survey indicate that HoFH represents a considerable burden for patients, not only due to physical signs and limitations caused by the disease but also a number of psychosocial factors, treatment-related issues and impact on their education and employment situation.