Two mutations in LDLR gene were found in two Chinese families with familial hypercholesterolemia

Impact of LDLR polymorphisms on lipid levels and atorvastatin's efficacy in a northern Chinese adult Han cohort with dyslipidemia

BACKGROUND

Dyslipidemia, a significant risk factor for atherosclerotic cardiovascular disease (ASCVD), is influenced by genetic variations, particularly those in the low-density lipoprotein receptor (LDLR) gene. This study aimed to elucidate the effects of LDLR polymorphisms on baseline serum lipid levels and the therapeutic efficacy of atorvastatin in an adult Han population in northern China with dyslipidemia.

METHODS

In this study, 255 Han Chinese adults receiving atorvastatin therapy were examined and followed up. The 3' untranslated region (UTR) of the LDLR gene was sequenced to identify polymorphisms. The associations between gene polymorphisms and serum lipid levels, as well as changes in lipid levels after intervention, were evaluated using the Wilcoxon rank sum test, with a P < 0.05 indicating statistical significance. Assessment of linkage disequilibrium patterns and haplotype structures was conducted utilizing Haploview.

RESULTS

Eleven distinct polymorphisms at LDLR 3' UTR were identified. Seven polymorphisms (rs1433099, rs14158, rs2738466, rs5742911, rs17249057, rs55971831, and rs568219285) were correlated with the baseline serum lipid levels (P < 0.05). In particular, four polymorphisms (rs14158, rs2738466, rs5742911, and rs17249057) were in strong linkage disequilibrium (r2 = 1), and patients with the AGGC haplotype had higher TC and LDL-C levels at baseline. Three polymorphisms (rs1433099, rs2738467, and rs7254521) were correlated with the therapeutic efficacy of atorvastatin (P < 0.05). Furthermore, carriers of the rs2738467 T allele demonstrated a significantly greater reduction in low-density lipoprotein cholesterol (LDL-C) levels post-atorvastatin treatment (P = 0.03), indicating a potentially crucial genetic influence on therapeutic outcomes. Two polymorphisms (rs751672818 and rs566918949) were neither correlated with the baseline serum lipid levels nor atorvastatin's efficacy.

CONCLUSIONS

This research outlined the complex genetic architecture surrounding LDLR 3' UTR polymorphisms and their role in lipid metabolism and the response to atorvastatin treatment in adult Han Chinese patients with dyslipidemia, highlighting the importance of genetic profiling in enhancing tailored therapeutic strategies. Furthermore, this investigation advocates for the integration of genetic testing into the management of dyslipidemia, paving the way for customized therapeutic approaches that could significantly improve patient care.

TRIAL REGISTRATION

This multicenter study was approved by the Ethics Committee of Xiangya Hospital Central South University (ethics number K22144). It was a general ethic. In addition, this study was approved by The First Hospital of Hebei Medical University (ethics number 20220418).

Recent developments in the regulation of cholesterol transport by natural molecules

The dysregulation of cholesterol metabolism is a high-risk factor for non-alcoholic fatty liver disease (NAFLD), dyslipidemia, and atherosclerosis (AS). Cholesterol transport maintains whole-body cholesterol homeostasis. Low-density apolipoprotein receptor (LDLR) mediates cholesterol uptake in cells and plays an important role in the primary route of circulatory cholesterol clearance in liver cells. Caveolins 1 is an integral membrane protein and shuttle between the cytoplasm and cell membrane. Caveolins 1 not only plays a role in promoting cholesterol absorption in cells but also in the transport of cellular cholesterol efflux by interacting with the ATP-binding cassette transporter A1 (ABCA1) and scavenger receptor class B type I (SR-BI). These proteins, which are associated with reverse cholesterol transport (RCT), are potential therapeutic targets for NAFLD and AS. Many studies have indicated that natural products have lipid-lowering effects. Moreover, natural molecules, derived from natural products, have the potential to be developed into novel drugs. However, the mechanisms underlying the regulation of cholesterol transport by natural molecules have not yet been adequately investigated. In this review, we briefly describe the process of cholesterol transport and summarize the mechanisms by which molecules regulate cholesterol transport. This article provides an overview of recent studies and focuses on the potential therapeutic effects of natural molecules; however, further high-quality studies are needed to firmly establish the clinical efficacies of natural molecules.

Independent Severe Cases of Heterozygous Familial Hypercholesterolemia Caused by the W483X and Novel W483G Mutations in the Low-Density Lipoprotein Receptor Gene That Were Clinically Diagnosed as Homozygous Cases

Background and Aims: The genetic spectrum underlying familial hypercholesterolemia (FH) remains unclear, especially in northeastern China. The aim of this study was to delineate the FH genetic spectrum and identify specific characteristics of FH patients in this region. Materials and Methods: The family history, personal medical history, and lifestyle habits of two unrelated patients clinically diagnosed with homozygous FH were recorded. DNA samples of the patients and their relatives were subjected to a newly designed next-generation sequencing panel using an Illumina Miseq platform. Detected variants were annotated and functionally predicted with in silico algorithms, and protein structures were modeled. Results: The patients' cholesterol levels were effectively reduced to 33.8% and 17.2% of the original level under conventional ezetimibe and statin treatment. Two pathogenic mutations, W483X and the novel mutation W483G, in the low-density lipoprotein receptor (LDLR) gene were identified. Both patients were heterozygous for the respective mutations. Under a high cholesterol/carbohydrate diet, these mutations could trigger a severe FH phenotype, but both patients responded well to regular medical treatments and dietary control. The W483X mutation results in a premature stop codon, leading to incomplete protein formation. Although the W483G mutation results in translation of the complete protein with no apparent structural difference, it still led to a severe FH phenotype similar to W483X. Conclusions: Identification of the novel W483G mutation expands the genetic spectrum of FH. Both mutations cause a severe FH phenotype under certain conditions, suggesting that W483 is important for LDLR function, highlighting potential targets for genetic screening or drug development.

Novel compound heterozygous mutations in low density lipoprotein receptor gene causes a severe phenotype in a Chinese hypercholesterolemia family

Mutations in the low density lipoprotein receptor (LDLR) gene serve a causative role in the pathophysiology of familial hypercholesterolemia (FH), a common autosomal inherited disorder characterized by abnormal lipid metabolism. The aim of the present study was to investigate genetic defects in a Chinese family with FH. Clinical features and family histories were collected, as were the results of various laboratory tests, including determinations of serum lipid concentrations, ultrasonography and angiography results. Potential mutations in LDLR were screened using direct polymerase chain reaction (PCR) sequencing. Multiple sequence alignments, structure and hydrophobicity predictions were performed in silico. Novel compound heterozygote mutations in LDLR of the proband were identified, with a Trp577Term-bearing maternal allele and a Pro685Leu-bearing paternal allele. The proband, a 27-year-old male, had severe and diffuse coronary stenosis and non-ST segment elevation myocardial infarction, as well as multiple skin xanthomas and high serum lipid levels. The allele-dosage-dependent clinical features, including hypercholesterolemia and peripheral arterial atherosclerosis, were observed in the proband and the other heterozygous patients. Therefore, the coexistence of Pro685Leu and Trp577Term mutations in LDLR is a novel compound heterozygosis in Chinese patients and may lead to a severe FH phenotype. The explanation for the existence of compound heterozygous mutations instead of homozygous mutations in this particular family requires further study.

Alleviative effects of resveratrol on nonalcoholic fatty liver disease are associated with up regulation of hepatic low density lipoprotein receptor and scavenger receptor class B type I gene expressions in rats

Lipid metabolic disorders are widely considered to be one of the most critical and basic link in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). The aim of this study was to illustrate the alleviation function of resveratrol (Res) on NAFLD and the roles of hepatic fatty acid synthase (FAS), low density lipoprotein receptor (LDLr), scavenger receptor class B type I (SR-BI), and thyroid hormone receptor β1 (TRβ1), which are the key molecules involved in lipid metabolism. Adult male Wistar rats were fed a normal diet or high fat/sucrose diet (HFS) with or without resveratrol for 13 weeks. HFS induced NAFLD formation and increased the lipids concentrations in serum and livers of rats, while noticeable improvement has been reached by Res intervention. Moreover, Res protected against HFS-induced decrease in hepatic LDLr and SR-BI mRNA and protein expressions, whereas TRβ1 expressions were impervious with/without Res. Unexpectedly, hepatic FAS gene expressions were markedly diminished in NAFLD rats and were gradually increased by treatment with Res. These data indicate that the alleviative effects of Res on NAFLD are associated with up regulation of hepatic LDLr and SR-BI gene expressions, which provide new insights into the pharmacological targets of Res in the prevention of NAFLD.

A novel pathogenic nonsense triple-nucleotide mutation in the low-density lipoprotein receptor gene and its clinical correlation with familial hypercholesterolemia

AIM

The aim of this study was to determine the genetic basis of familial hypercholesterolemia in a Pakistani family with a history of myocardial infarction and premature coronary artery disease.

RESULTS

Direct sequencing of the low-density lipoprotein receptor gene resulted in the identification of a novel missense mutation c.264G>C (p.R88S) in exon 3 and a novel nonsense triple-nucleotide polymorphism (TNP) c.887-889GCA>AGC (p.C296X) in exon 6, the latter being probably the disease-causing mutation in this family. Both of these mutations were not present in the probands of 14 familial hypercholesterolemia families, 100 myocardial infarction patients, as well as 150 normolipidemic ethnically matched control individuals.

CONCLUSIONS

The identification of the novel nonsense TNP is the first report of a nonsense pathogenic TNP in low-density lipoprotein receptor or any other gene and only the fourth report of a pathogenic TNP of any type, which emphasizes the importance of screening for TNPs in patients and in familial studies that might otherwise be missed if only analyzed on single-nucleotide polymorphism arrays.

Antioxidant activities of recombinant amphioxus (Branchiostoma belcheri) apolipoprotein D

Apolipoprotein D (ApoD), a member of lipocalin, has been recently shown to be involved in regulating protection from oxidative stress. The absence of ApoD in mouse and Drosophila can reduce the resistance to oxidative stress and shorten lifespan. However, little information is available regarding the expression in vitro of ApoD and its biochemical properties. Amphioxus (Branchiostoma belcheri) ApoD, BbApoD, is an archetype of vertebrate ApoD proteins. In this study, the prokaryotic expression plasmid pET32a-BbApoD was constructed and recombinant BbApoD expressed in Escherichia coli BL21 and purified. Antioxidation assays showed that the recombinant BbApoD protein had the capacities to scavenge hydroxyl radicals (≥ 240 μg/ml) and to prevent nicking of the supercoiled DNA (≥ 100 μg/ml) in vitro, providing a biochemical evidence for antioxidant role of ApoD. This supports the notion that ApoD is part of the mechanisms regulating protection from oxidative stresses.

Hypervariability in a minisatellite 3' of the apolipoprotein B gene: allelic distribution and influence on lipid profiles in Han Children from central China

BACKGROUND

Apolipoprotein B (apoB) gene 3' variable number tandem repeat (VNTR) is highly variable, and thereby be considered as an informative marker for associative analysis of lipid metabolism.

METHODS

We conducted this study to probe the effect of apoB 3' VNTR alleles on lipid profiles in 500 Han children from central China, and to compare the allelic distribution of our subjects with multiple Chinese populations. 14 different alleles of the apoB gene 3' VNTR comprising from HVE22 to HVE44 were identified in our subjects.

RESULTS

Allele size distribution followed unimodal curve with the main peak at HVE35 (58.0%). We detected 37 genotypes in this sampling, the most frequently seen was HVE35/35 with a frequency of 36.4%. M/L carriers had significantly higher total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C) and apoB concentrations than did S/S, M/M or S/M carriers (p<0.05). Individuals with L allele exhibited significantly higher TC, LDL-C, and apoB levels than those with M or S allele (p<0.05). The allelic distribution in Central Han Chinese differed from Southern Han Chinese (X(2)=41.2, p=0.00), Zhuang Chinese (X(2)=65.4, p=0.00), and Uighur Chinese (X(2)=45.6, p=0.00). No significant differences in allelic frequencies were observed for apoB 3' VNTR in Central Han Chinese as compared to Northern Han Chinese (X(2)=2.5, p=0.29).

CONCLUSION

This study identified the higher repeat alleles as potential risk factor for dyslipidemia in Han children from Central China. Although five Chinese populations demonstrated uniformly unimodal distributions of allelic frequencies with the main peaks at HVE32-HVE37, there was obvious heterogeneity among these populations.

LDL-R AvaII and NcoI polymorphisms: an indirect risk factor for coronary heart disease among a Mendelian population of Delhi, India

AvaII and NcoI polymorphisms in the low-density lipoprotein receptor (LDL-R) gene are reported to alter cholesterol levels. Although found to be highly polymorphic worldwide, these mutations have not been validated in any Indian population. This case-control association study was conducted in an endogamous business community of Delhi. Blood samples from 100 cases and 100 age- and sex-matched controls belonging to the same ethnic group were subjected to biochemical and molecular analyses. Medical history and anthropometric measurements were taken from all the enrolled subjects. Linkage disequilibrium between the two polymorphisms was found to be significant (P = 0.0016). Significant variability was observed for the AvaII polymorphism among cases concerning waist-hip ratio, serum triglyceride, and low-density lipoprotein, which in turn was found to be associated with coronary heart disease.