Association and linkage of LDLR gene variation with variation in plasma low density lipoprotein cholesterol

Interaction between Sex and LDLR rs688 Polymorphism on Hyperlipidemia among Taiwan Biobank Adult Participants

Hyperlipidemia is one of the strong risk factors for ischemic heart disease. Using the Taiwan Biobank (TWB) database, we evaluated the risk of hyperlipidemia and its interaction with sex and rs688 polymorphism on the low-density lipoprotein receptor (LDLR) gene. Data collection in the biobank started in 2008 and is ongoing. Data analysis was performed on the participants’ data collected between 2008 and 2015. In general, 27.92% of the 9237 female participants and 32.65% of the 8690 male participants were identified with hyperlipidemia. Compared to the C/C genotype, C/T and T/T genotypes were not significant risk factors for hyperlipidemia (OR = 1.061, CI: 0.976–1.153 for C/T and OR = 1.052, CI: 0.845–1.309 for T/T genotype) in the general model. However, there was a significant interaction between sex and rs6888 on hyperlipidemia risk (p-interaction = 0.0321). With the male sex/CC genotype being the reference group, only the female sex/CT and T/T genotypes were closely associated with hyperlipidemia, with respective ORs of 1.153 (CI: 1.014–1.311) and 1.423 (CI: 1.056–1.917). Our data indicate that rs688 C/T and T/T genotypes may be associated with increased risk of hyperlipidemia in Taiwanese women. These findings may be relevant in lipid-modification therapy.

SNP rs688 within the low-density lipoprotein receptor (LDL-R) gene associates with HCV susceptibility

BACKGROUND & AIMS

Despite high-risk behaviour, 10%-20% of HCV multiple exposed individuals remain uninfected (MEU), whilst the remainder become infected (MEI). We hypothesize that host factors play a role in HCV susceptibility. We aimed to identify polymorphisms in host genes that encode for proteins involved in viral entry: CD81, Scavenger receptor 1 (SR-1), Low-density lipoprotein receptor (LDL-R), Claudin-1 (CLDN1), Occludin (OCLN) and Niemann-Pick C1-like 1 (NPC1L1).

METHODS

Multiple exposed infected and MEU from two observational cohorts were selected. From the MSM study of acute infection with HCV (MOSAIC), HIV-1 infected MEU cases (n = 30) and HIV-1 infected MEI controls (n = 32) were selected based on reported high-risk behaviour. From the Amsterdam Cohorts Studies (ACS) injecting drug users (IDU) cohort, MEU cases (n = 40) and MEI controls (n = 22) were selected who injected drugs for ≥2 years, in the nineties, when HCV incidence was high. Selected single nucleotide polymorphisms (SNPs) were determined by sequencing or SNP assays.

RESULTS

No associations were found for SNPs within genes coding for CD81, SR-1, Claudin-1 or Occludin between the MEU and MEI individuals from either cohort. We did observe a significant association for rs688 within the LDL-R gene with HCV infection (OR: 0.41 P = 0.001), however, LDL cholesterol levels did not vary between individuals carrying the differential SNPs. Additionally, a marginal significant effect was found for rs217434 and rs2072183 (OR: 2.07 P = 0.032 and OR: 1.76 P = 0.039, respectively) within NPC1L1.

CONCLUSIONS

Our results demonstrate that the rs688 SNP within the LDL-R gene associates with HCV susceptibility through mucosal as well as intravenous exposure.

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.

LDLR rs688 TT Genotype and T Allele Are Associated with Increased Susceptibility to Coronary Artery Disease-A Case-Control Study

PURPOSE

The low-density lipoprotein receptor is responsible for the binding and uptake of plasma LDL particles and plays a critical role in maintaining cellular cholesterol homeostasis. LDLR gene SNP rs688 has been reported to be associated with increased plasma total and LDL cholesterol in several populations and can lead to elevated plasma LDL levels, resulting in an increased risk for atherosclerosis and coronary artery disease. This study aimed to explore genetic LDLR variant rs688 for its potential roles in coronary artery disease.

METHODOLOGY

This study recruited 200 coronary artery disease patients and 200 healthy individuals. Genotyping of LDLR-rs688C > T gene variations was performed using the allele specific PCR method. Correlation of LDLR-rs688C > T gene variants with different clinicopathological features of coronary artery disease patients was performed. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were applied to evaluate the correlation of this microRNA polymorphism with coronary artery disease risk.

RESULTS

A significant difference was observed in genotype distribution among the coronary artery disease and matched healthy controls (p = 0.003). The frequencies of all three genotypes CC, CT, TT reported in the patient samples were 14%, 65% and 21% and in the healthy controls samples were 18%, 73% and 9%, respectively. The increased risk of developing CAD in Indian patients was found to be associated with LDLR rs688 TT genotype (OR = 3.0, 95% CI, 1.43 × 6.2; p = 0.003) RR 1.87 (1.20⁻2.91) p = 0.0037) and also the increased risk of developing CAD was reported to be associated with LDLR rs688 T allele (OR = 0.74, 95% CI, 1.57⁻0.97; p = 0.03) RR 0.85 (0.73⁻0.99) p = 0.03) compared to the C allele. Therefore, it was observed that more than a 3.0- and 0.74-fold increase risk of developing CAD was associated with TT genotype and T allele in Indian coronary artery disease patients.

CONCLUSION

The findings indicated that LDLR rs688 TT genotype and T allele are associated with an increased susceptibility to coronary artery disease patients. LDLR-rs688C > T gene variation can be used as a predisposing genetic marker for coronary artery disease. Further studies with larger sample sizes are necessary to confirm our findings.

Identification of the Functional Variant(s) that Explain the Low-Density Lipoprotein Receptor (LDLR) GWAS SNP rs6511720 Association with Lower LDL-C and Risk of CHD

Background

The Low-Density Lipoprotein Receptor (LDLR) SNP rs6511720 (G>T), located in intron-1 of the gene, has been identified in genome-wide association studies (GWAS) as being associated with lower plasma levels of LDL-C and a lower risk of coronary heart disease (CHD). Whether or not rs6511720 is itself functional or a marker for a functional variant elsewhere in the gene is not known.

Methods

The association of LDLR SNP rs6511720 with incidence of CHD and levels of LDL-C was determined by reference to CARDIoGRAM, C4D and Global lipids genetics consortium (GLGC) data. SNP annotation databases were used to identify possible SNP function and prioritization. Luciferase reporter assays in the liver cell line Huh7 were used to measure the effect of variant genotype on gene expression. Electrophoretic Mobility Shift Assays (EMSAs) were used to identify the Transcription Factors (TFs) involved in gene expression regulation.

Results

The phenotype-genotype analysis showed that the rs6511720 minor allele is associated with lower level of LDL-C [beta = -0.2209, p = 3.85 x10^-262], and lower risk of CHD [log (OR) = 0.1155, p = 1.04 x10^-7]. Rs6511720 is in complete linkage. Rs6511720 is in complete linkage disequilibrium (LD) with three intron-1 SNPs (rs141787760, rs60173709, rs57217136). Luciferase reporter assays in Huh7 cells showed that the rare alleles of both rs6511720 and rs57217136 caused a significant increase in LDLR expression compared to the common alleles (+29% and +24%, respectively). Multiplex Competitor-EMSAs (MC-EMSA) identified that the transcription factor serum response element (SRE) binds to rs6511720, while retinoic acid receptor (RAR) and signal transducer and activator of transcription 1 (STAT1) bind to rs57217136.

Conclusion

Both LDLR rs6511720 and rs57217136 are functional variants. Both these minor alleles create enhancer-binding protein sites for TFs and may contribute to increased LDLR expression, which is consequently associated with reduced LDL-C levels and 12% lower CHD risk.

Association Between Paraoxonase Gene Polymorphisms and Intracerebral Hemorrhage in a Korean Population

The human paraoxonase (PON) gene family includes three members: PON1, PON2, and PON3. PON, which prevents the oxidative modification of lipoproteins, has been implicated as a potential risk factor of the cerebrovascular disease. In this study, we investigated associations between coding region single-nucleotide polymorphisms (cSNPs) of PON1, PON2, and PON3 genes and intracerebral hemorrhage (ICH) in a Korean population. Six cSNPs [rs13306698 and rs662 for PON1; rs12026 and rs7493 for PON2; rs13226149 and rs1053275 for PON3] were genotyped using direct sequencing in 145 ICH patients and 372 control subjects. Of the six cSNPs, rs12026 and rs7493, which were in complete linkage disequilibrium, were associated with ICH in log-additive (GC vs. CC vs. GG, p = 0.0008, OR = 0.53, 95 % CI = 0.36-0.78) and dominant models (GC/CC vs. GG, p = 0.0006, OR = 0.47, 95 % CI = 0.30-0.73). In addition, rs13226149 was associated with ICH in log-additive model (GA vs. AA vs. GG, p = 0.0033, OR = 0.58, 95 % CI = 0.39-0.84). In the allele frequency analysis, the C alleles of rs12026 and rs7493 and the A allele of rs13226149 were also shown to contribute to the decreased risk of ICH (p = 0.001, OR = 0.55, 95 % CI = 0.38-0.80 in rs12026 and rs7493; p = 0.003, OR = 0.58, 95 % CI = 0.40-0.83 in rs13226149). These results suggest that PON genes may be involved in the susceptibility of ICH.

The lipoprotein lipase S447X and cholesteryl ester transfer protein rs5882 polymorphisms and their relationship with lipid profile in human serum of obese individuals

BACKGROUND

Obesity is often associated with an alter lipid profile, e.g., raised serum triglycerides (TG) and low high-density lipoprotein (HDL) cholesterol levels, both important risk factor for cardiovascular-diseases. The aim of current study was to explore the association of a polymorphism of the lipoprotein lipase (LPL) rs328 and cholesteryl-ester-transfer-protein (CETP) rs5882 genes in relation to lipid profile in subjects with/without obesity.

SUBJECTS/METHODS

Genotyping was carried out in 271 individuals, (151 obese subjects and 120 non-obese). Univariate/multivariate analyses were conducted to evaluate the association of these genetic-polymorphisms with obesity and lipid components.

RESULTS

Obese subjects had a significantly (P<0.05) higher level of triglyceride (TG), blood pressure, waist-circumference and fasting-blood-glucose, and lower level of HDL-C. LPL and CETP polymorphisms were not associated with obesity in our population. However, the LPL rs328-GG-GC genotype was significantly related to a higher concentration of TG, compared to the CC wild-type; and a higher HDL-C level in the obesity-group with respect to the control group. Moreover, obese-subjects carrying the G allele of CETP had a significantly lower level of HDL-C (P<0.05) compared to those with C allele.

CONCLUSION

We demonstrate a significant association of LPL and CETP polymorphisms with serum triglycerides and HDL-cholesterol.

G-protein estrogen receptor as a regulator of low-density lipoprotein cholesterol metabolism: cellular and population genetic studies

OBJECTIVE

Estrogen deficiency is linked with increased low-density lipoprotein (LDL) cholesterol. The hormone receptor mediating this effect is unknown. G-protein estrogen receptor (GPER) is a recently recognized G-protein-coupled receptor that is activated by estrogens. We recently identified a common hypofunctional missense variant of GPER, namely P16L. However, the role of GPER in LDL metabolism is unknown. Therefore, we examined the association of the P16L genotype with plasma LDL cholesterol level. Furthermore, we studied the role of GPER in regulating expression of the LDL receptor and proprotein convertase subtilisin kexin type 9.

APPROACH AND RESULTS

Our discovery cohort was a genetically isolated population of Northern European descent, and our validation cohort consisted of normal, healthy women aged 18 to 56 years from London, Ontario. In addition, we examined the effect of GPER on the regulation of proprotein convertase subtilisin kexin type 9 and LDL receptor expression by the treatment with the GPER agonist, G1. In the discovery cohort, GPER P16L genotype was associated with a significant increase in LDL cholesterol (mean±SEM): 3.18±0.05, 3.25±0.08, and 4.25±0.33 mmol/L, respectively, in subjects with CC (homozygous for P16), CT (heterozygotes), and TT (homozygous for L16) genotypes (P<0.05). In the validation cohort (n=339), the GPER P16L genotype was associated with a similar increase in LDL cholesterol: 2.17±0.05, 2.34±0.06, and 2.42±0.16 mmol/L, respectively, in subjects with CC, CT, and TT genotypes (P<0.05). In the human hepatic carcinoma cell line, the GPER agonist, G1, mediated a concentration-dependent increase in LDL receptor expression, blocked by either pretreatment with the GPER antagonist G15 or by shRNA-mediated GPER downregulation. G1 also mediated a GPER- and concentration-dependent decrease in proprotein convertase subtilisin kexin type 9 expression.

CONCLUSIONS

GPER activation upregulates LDL receptor expression, probably at least, in part, via proprotein convertase subtilisin kexin type 9 downregulation. Furthermore, humans carrying the hypofunctional P16L genetic variant of GPER have increased plasma LDL cholesterol. In aggregate, these data suggest an important role of GPER in the regulation of LDL receptor expression and consequently LDL metabolism.

Association of polymorphisms modulating low-density lipoprotein cholesterol with susceptibility, severity, and progression of rheumatoid arthritis

OBJECTIVE

Dyslipidemia, a risk factor for cardiovascular diseases, is more prevalent in patients with rheumatoid arthritis (RA) than in the general population. We investigated whether single-nucleotide polymorphisms (SNP) modulating low-density lipoprotein (LDL) cholesterol affect susceptibility, severity, and progression of RA.

METHODS

We enrolled 302 patients with RA and 1636 healthy controls, and investigated the SNP modulating LDL cholesterol. Clinical characteristics of RA, serum adipocytokine concentrations, and radiographic severity were analyzed according to genotype score based on the number of unfavorable alleles. The influence of genotype score on radiographic progression was also investigated using multivariable logistic models.

RESULTS

We identified 3 SNP (rs688, rs693, and rs4420638) modulating LDL cholesterol in Koreans, which correlated well with LDL cholesterol levels in both patients with RA and controls. Among them, 2 SNP, rs688 and rs4420638, were more prevalent in patients with RA than in controls. In patients with RA carrying more unfavorable alleles (genotype score ≥ 3), disease activity measures, serum adipocytokine levels, and radiographic severity were all increased. The genotype score was an independent risk factor for radiographic progression of RA over 2 years, and its effect was greater than the influence of conventional risk factors.

CONCLUSION

SNP modulating LDL cholesterol influence the risk, activity, and severity of RA. These results provide the first evidence that genetic mechanisms linked to dyslipidemia may directly contribute to the susceptibility and prognosis of RA, a representative of chronic inflammatory diseases, explaining the high incidence of dyslipidemia in RA.

A common polymorphism in the LDL receptor gene has multiple effects on LDL receptor function

A common synonymous single nucleotide polymorphism in exon 12 of the low-density lipoprotein receptor (LDLR) gene, rs688, has been associated with increased plasma total and LDL cholesterol in several populations. Using immortalized lymphoblastoid cell lines from a healthy study population, we confirmed an earlier report that the minor allele of rs688 is associated with increased exon 12 alternative splicing (P < 0.05) and showed that this triggered nonsense-mediated decay (NMD) of the alternatively spliced LDLR mRNA. However, since synonymous single nucleotide polymorphisms may influence structure and function of the encoded proteins by co-translational effects, we sought to test whether rs688 was also functional in the full-length mRNA. In HepG2 cells expressing LDLR cDNA constructs engineered to contain the major or minor allele of rs688, the latter was associated with a smaller amount of LDLR protein at the cell surface (-21.8 ± 0.6%, P = 0.012), a higher amount in the lysosome fraction (+25.7 ± 0.3%, P = 0.037) and reduced uptake of fluorescently labeled LDL (-24.3 ± 0.7%, P < 0.01). Moreover, in the presence of exogenous proprotein convertase subtilisin/kexin type 9 (PCSK9), a protein that reduces cellular LDL uptake by promoting lysosomal degradation of LDLR, the minor allele resulted in reduced capacity of a PCSK9 monoclonal antibody to increase LDL uptake. These findings are consistent with the hypothesis that rs688, which is located in the β-propeller region of LDLR, has effects on LDLR activity beyond its role in alternative splicing due to impairment of LDLR endosomal recycling and/or PCSK9 binding, processes in which the β-propeller is critically involved.

Prospective analysis of association between use of statins and melanoma risk in the Women's Health Initiative

BACKGROUND

Melanoma is the most lethal form of skin cancer, with an estimated 68,130 new cases and 8700 deaths in the United States in 2010. The increasing incidence and high death rate associated with metastatic disease support the need to focus on prevention. The authors used data from the Women's Health Initiative (WHI) to assess whether 3-hydroxy-3 methylglutaryl coenzyme A inhibitors (statins) are associated with a decreased risk of melanoma.

METHODS

The study population consisted of 119,726 postmenopausal white women, in which 1099 cases of malignant melanoma were identified over an average (± standard deviation) of 11.6 ± 3.2 years. All diagnoses were confirmed by medical record review and pathology reports. Information on statin use was collected at baseline and during follow-up. Self-administered and interview-administered questionnaires were used to collect information on other risk factors. Cox proportional hazards regression was used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs). Analyses investigated the association of any statin use, type, potency, lipophilic status, and duration of use with melanoma.

RESULTS

Statins were used by 8824 women (7.4%) at baseline. The annualized rate of melanoma was 0.09% among statin users and 0.09% among nonusers The multivariable adjusted HR for statin users compared with nonusers was 1.14 (95% CI, 0.91-1.43). There were no significant differences in risk based on statin type, potency, category, duration, or in time-dependent models.

CONCLUSIONS

There was no significant association between statin use and melanoma risk among postmenopausal women in the WHI.

Association between paraoxonase 2 Ser311Cys polymorphism and ischemic stroke risk: a meta-analysis involving 5,008 subjects

Epidemiological studies have evaluated the association between paraoxonase 2 (PON2) Ser311Cys polymorphism and ischemic stroke risk which developed inconsistent conclusions. The aim of this study was to perform a meta-analysis to investigate a more authentic association between PON2 Ser311Cys polymorphism and ischemic stroke. Systematic searches in PUBMED, EMBASE, CBM, and CNKI databases were performed. Data analyses were carried out by Review Manager 5.1.2 and Stata 11.0. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used for additive model (Cys/Cys vs. Ser/Ser), dominant model (Ser/Cys+Cys/Cys vs. Ser/Ser), recessive model (Cys/Cys vs. Ser/Cys+Ser/Ser), and allelic model (Cys allele vs. Ser allele), respectively. Publication bias was analyzed by Begg's funnel plot and Egger's test. A total of 7 studies including 2,046 cases and 2,962 controls were involved. Overall, no significant association was found between PON2 Ser311Cys polymorphism and ischemic stroke risk when all studies were pooled into the meta-analysis (for additive model: OR = 0.87, 95% CI = 0.67-1.14; for dominant model: OR = 1.05, 95% CI = 0.91-1.22; for recessive model: OR = 0.90, 95% CI = 0.77-1.05; and for allelic model: OR = 1.17, 95% CI = 0.86-1.59). In the subgroup analysis by ethnicity, significant association was found among Europeans (for recessive model: OR = 0.83, 95% CI = 0.69-0.99). However, due to the small number of studies included in subgroup analysis, the result for European population should be interpreted cautiously.

Polymorphisms at LDLR locus may be associated with coronary artery disease through modulation of coagulation factor VIII activity and independently from lipid profile

High levels of coagulation factor VIII (FVIII) have been associated with cardiovascular disease. Low-density lipoprotein receptor (LDLR) has been recently demonstrated to contribute to FVIII clearance from plasma. The aim of this study was to evaluate 3 single nucleotide polymorphisms in SMARCA4-LDLR gene locus (rs1122608, rs2228671, and rs688) and FVIII coagulant activity (FVIII:c) in subjects with (n = 692) or without (n = 291) angiographically confirmed coronary artery disease (CAD). High FVIII:c levels were an independent risk factor for CAD. The rs688 and rs2228671 genotypes were predictors of FVIII:c with T alleles associated with higher FVIII:c levels. The rs2228671T allele was associated also with reduced total and LDL-cholesterol levels. With respect to the risk of CAD, no association was found for rs2228671. Consistently with higher FVIII:c levels, the rs688T allele was associated with CAD, whereas, consistently with a favorable lipid profile, the rs1122608T allele was associated with a decreased CAD prevalence. After adjustment for classic cardiovascular risk factors, including plasma lipids, rs688 remained associated with CAD (OR for T carriers: 1.67 with 95% confidence interval, 1.10-2.54). Haplotype analysis confirmed such results. Our data suggest that polymorphisms at LDLR locus modulate FVIII:c levels and may be associated with CAD risk independently from plasma lipids.

A gene score of nine LDL and HDL regulating genes is associated with fluvastatin-induced cholesterol changes in women

While conventional pharmacogenetic studies have considered single gene effects, we tested if a genetic score of nine LDL- and HDL-associated single nucleotide polymorphisms, previously shown to predict cardiovascular disease, is related to fluvastatin-induced lipid change. In patients with asymptomatic plaque in the right carotid artery, thus candidates for statin therapy, we related score LDL [APOB(rs693), APOE(rs4420638), HMGCR(rs12654264), LDLR(rs1529729), and PCSK9(rs11591147)] and score HDL [ABCA1(rs3890182), CETP(rs1800775), LIPC(rs1800588), and LPL(rs328)] as well as the combined score LDL+HDL to fluvastatin-induced LDL reduction (+/- metoprolol) (n = 395) and HDL increase (n = 187) following 1 year of fluvastatin treatment. In women, an increasing number of unfavorable alleles (i.e., alleles conferring higher LDL and lower HDL) of score LDL+HDL (P = 0.037) and of score LDL (P = 0.023) was associated with less pronounced fluvastatin-induced LDL reduction. Furthermore, in women, both score LDL+HDL (P = 0.001) and score HDL (P = 0.022) were directly correlated with more pronounced fluvastatin-induced HDL increase, explaining 5.9-11.6% of the variance in treatment response in women. There were no such associations in men. This suggests that a gene score based on variation in nine different LDL- and HDL-associated genes is of importance for the magnitude of fluvastatin HDL increase in women with asymptomatic plaque in the carotid artery.

TaqIB polymorphism in the CETP gene modulates the impact of HC/LF diet on the HDL profile in healthy Chinese young adults

The aim of this study was to investigate the interactions of genetic variants in the genes of cholesterol ester transfer protein (CETP) and low-density lipoprotein receptor (LDLR) with high carbohydrate and low fat (HC/LF) diet on lipid profiles in a young and healthy Chinese Han population. Fifty-six healthy subjects (22.89±1.80 years) were given washout diets of 31% fat and 54% carbohydrate for 7 days, followed by HC/LF diets of 15% fat and 70% carbohydrate for 6 days, with no total energy restriction. Serum lipid profiles at baseline, after washout and following HC/LF diets, as well as CETP and LDLR polymorphisms were analyzed. Carriers of B2 allele of CETP TaqIB polymorphism had significantly higher levels of high density lipoprotein cholesterol (HDL-C) and apo A-I in the whole study population after the diet intervention. Notably, males with CETP TaqIB B1B1 experienced significantly increased HDL-C and apo A-I after HC/LF diet. Regarding the LDLR Pvu II polymorphism, both P1P1 subjects and P2 carriers experienced decreased total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels after HC/LF diet with no statistically significant differences between the genotypes. Our results demonstrate that the elevated HDL-C levels after HC/LF diet in healthy Chinese Han youth are associated with CETP TaqI B2 allele while males with B1B1 genotype are more susceptible to the influence of HC/LF diet on their HDL-C levels. The decreased TC and LDL-C levels after HC/LF diet are not associated with LDLR Pvu II polymorphism.

Polymorphisms associated with cholesterol and risk of cardiovascular events

BACKGROUND

Common single-nucleotide polymorphisms (SNPs) that are associated with blood low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol modestly affect lipid levels. We tested the hypothesis that a combination of such SNPs contributes to the risk of cardiovascular disease.

METHODS

We studied SNPs at nine loci in 5414 subjects from the cardiovascular cohort of the Malmö Diet and Cancer Study. We first validated the association between SNPs and either LDL or HDL cholesterol and subsequently created a genotype score on the basis of the number of unfavorable alleles. We used Cox proportional-hazards models to determine the time to the first cardiovascular event in relation to the genotype score.

RESULTS

All nine SNPs showed replication of an association with levels of either LDL or HDL cholesterol. With increasing genotype scores, the level of LDL cholesterol increased from 152 mg to 171 mg per deciliter (3.9 to 4.4 mmol per liter), whereas HDL cholesterol decreased from 60 mg to 51 mg per deciliter (1.6 to 1.3 mmol per liter). During follow-up (median, 10.6 years), 238 subjects had a first cardiovascular event. The genotype score was associated with incident cardiovascular disease in models adjusted for covariates including baseline lipid levels (P<0.001). The use of the genotype score did not improve the clinical risk prediction, as assessed by the C statistic. However, there was a significant improvement in risk classification with the use of models that included the genotype score, as compared with those that did not include the genotype score.

CONCLUSIONS

A genotype score of nine validated SNPs that are associated with modulation in levels of LDL or HDL cholesterol was an independent risk factor for incident cardiovascular disease. The score did not improve risk discrimination but did modestly improve clinical risk reclassification for individual subjects beyond standard clinical factors.

A common polymorphism decreases low-density lipoprotein receptor exon 12 splicing efficiency and associates with increased cholesterol

Single nucleotide polymorphisms (SNPs) that alter exon splicing efficiency are an emerging class of functional genetic variants. Since mutations in low-density lipoprotein receptor (LDLR) are a primary cause of familial hypercholesterolemia, we evaluated whether LDLR SNPs may alter splicing efficiency and cholesterol homeostasis. A SNP within LDLR exon 12, rs688, was identified in silico as neutralizing a putative exon splicing enhancer. Studies in human liver samples established that this SNP was associated with significantly decreased LDLR exon 12 splicing efficiency in women in vivo. In vitro minigene splicing studies qualitatively replicated these in vivo results and demonstrated that rs688 specifically modulates splicing efficiency. These effects on splicing may be physiologically relevant because the presence of the rs688 minor allele associates with increased total and LDL-cholesterol in female members of the Framingham Offspring Study. The largest rs688-associated cholesterol differences were observed in pre-menopausal women. In summary, these studies identify an LDLR SNP present in approximately 60% of Caucasians that is associated with significant 10% increases in total and LDL-cholesterol in pre-menopausal women.

Genetic variation in BEACON influences quantitative variation in metabolic syndrome-related phenotypes

The BEACON gene (also known as UBL5) was identified as differentially expressed between lean and obese Psammomys obesus, a polygenic animal model of obesity, type 2 diabetes, and dyslipidemia. The human homologue of BEACON is located on chromosome 19p, a region likely to contain genes affecting metabolic syndrome-related quantitative traits as established by linkage studies. To assess whether the human BEACON gene may be involved in influencing these traits, we exhaustively analyzed the complete gene for genetic variation in 40 unrelated individuals and identified four variants (three novel). The two more common variants were tested for association with a number of quantitative metabolic syndrome-related traits in two large cohorts of unrelated individuals. Significant associations were found between these variants and fat mass (P = 0.026), percentage of fat (P = 0.001), and waist-to-hip ratio (P = 0.031). The same variants were also associated with total cholesterol (P = 0.024), LDL cholesterol (P = 0.019), triglycerides (P = 0.006), and postglucose load insulin levels (P = 0.018). Multivariate analysis of these correlated phenotypes also yielded a highly significant association (P = 0.0004), suggesting that BEACON may influence phenotypic variation in metabolic syndrome-related traits.

A locus influencing total serum cholesterol on chromosome 19p: results from an autosomal genomic scan of serum lipid concentrations in Pima Indians

A genome-wide linkage study was analyzed to identify loci that influence serum lipid concentrations in Pima Indians. Linkage analyses were conducted for total cholesterol measured in 998 siblings from 292 nuclear families, for total triglycerides in 547 siblings from 188 families, and for high density lipoprotein (HDL) cholesterol in 590 siblings from 201 families. Genotypes were generated for 516 autosomal microsatellite markers. Multipoint variance components methods were used to assess linkage. The strongest evidence for linkage with total cholesterol was on chromosome 19p (lod score 3.89), in the vicinity of the marker D19S1034, which is near the low density lipoprotein receptor gene. The strongest evidence for linkage with HDL cholesterol was on chromosome 3q (lod score 2.64) near D3S3053. For triglycerides, the strongest evidence for linkage was on chromosome 2p near D2S1788 (lod score 1.70) and on chromosome 3p near D3S2406 (lod score 1.77). This genomic scan provides evidence for a locus influencing total cholesterol concentration on chromosome 19p. It also suggests a locus influencing HDL cholesterol on chromosome 3q.