Functional variants in the lipoprotein lipase gene and risk cardiovascular disease

Modifier variant of METTL13 suppresses human GAB1-associated profound deafness

A modifier variant can abrogate the risk of a monogenic disorder. DFNM1 is a locus on chromosome 1 encoding a dominant suppressor of human DFNB26 recessive, profound deafness. Here, we report that DFNB26 is associated with a substitution (p.Gly116Glu) in the pleckstrin homology domain of GRB2-associated binding protein 1 (GAB1), an essential scaffold in the MET proto-oncogene, receptor tyrosine kinase/HGF (MET/HGF) pathway. A dominant substitution (p.Arg544Gln) of METTL13, encoding a predicted methyltransferase, is the DFNM1 suppressor of GAB1-associated deafness. In zebrafish, human METTL13 mRNA harboring the modifier allele rescued the GAB1-associated morphant phenotype. In mice, GAB1 and METTL13 colocalized in auditory sensory neurons, and METTL13 coimmunoprecipitated with GAB1 and SPRY2, indicating at least a tripartite complex. Expression of MET-signaling genes in human lymphoblastoid cells of individuals homozygous for p.Gly116Glu GAB1 revealed dysregulation of HGF, MET, SHP2, and SPRY2, all of which have reported variants associated with deafness. However, SPRY2 was not dysregulated in normal-hearing humans homozygous for both the GAB1 DFNB26 deafness variant and the dominant METTL13 deafness suppressor, indicating a plausible mechanism of suppression. Identification of METTL13-based modification of MET signaling offers a potential therapeutic strategy for a wide range of associated hearing disorders. Furthermore, MET signaling is essential for diverse functions in many tissues including the inner ear. Therefore, identification of the modifier of MET signaling is likely to have broad clinical implications.

Triglycerides Revisited to the Serial

This review discusses the role of triglycerides (TGs) in the normal cardiovascular system as well as in the development and clinical manifestation of cardiovascular diseases. Regulation of TGs at the enzymatic and genetic level, in addition to their possible relevance as preclinical and clinical biomarkers, is discussed, culminating with a description of available and emerging treatments. Due to the high complexity of the subject and the vast amount of material in the literature, the objective of this review was not to exhaust the subject, but rather to compile the information to facilitate and improve the understanding of those interested in this topic. The main publications on the topic were sought out, especially those from the last 5 years. The data in the literature still give reason to believe that there is room for doubt regarding the use of TG as disease biomarkers; however, there is increasing evidence for the role of hypertriglyceridemia on the atherosclerotic inflammatory process, cardiovascular outcomes, and mortality.

Relationship Between Two Common Lipoprotein Lipase Variants and the Metabolic Syndrome and Its Individual Components

BACKGROUND

Common lipoprotein lipase (LPL) variants are important determinants of triglycerides (TG) and high-density lipoprotein (HDL) cholesterol (C) concentrations. High TG/low HDL-C tend to cluster with hypertension, glucose intolerance, and abdominal obesity and comprise the metabolic syndrome (MetS). The role of LPL variants as a cause of MetS is unclear. This study investigated the relationship between two common LPL variants and the presence of MetS and its individual components.

METHODS

Cross-sectional study, including 2348 Danish women (50.7%) and men, age 41-72 years, without known cardiovascular disease. Carrier status for the two common LPL variants: 447Ter (low TG/high HDL-C) and 291Ser (high TG/low HDL-C) was determined. The prevalence of MetS according to the National Cholesterol Education Program criteria was 16.6%.

RESULTS

Of the 2348 participants, 19.8% had the 447Ter variant and 4.9% had the 291Ser variant. Compared with the reference variant, the prevalence of MetS was lower in carriers of the 447Ter variant (11.2% vs. 17.9%, P < 0.001) but with no difference in carriers of the 291Ser variant (18.4% vs. 16.5%, P = 0.59). Adjusted for age, sex, smoking, physical activity, alcohol consumption, and highest sex-specific insulin quartile, the relative risk of MetS was 0.63 (95% confidence interval [CI] 0.45-0.89, P < 0.01) for carriers of the 447Ter variant and 1.20 (95% CI 0.70-2.03, P > 0.05) for carriers of the 291Ser variant. Both LPL variants were associated with high TG/low HDL-C (P < 0.01), but not with the MetS components waist circumference, hypertension, and glucose intolerance (P > 0.05).

CONCLUSION

The two common LPL variants were associated with MetS through their effect on high TG/low HDL-C.

Pathogenic classification of LPL gene variants reported to be associated with LPL deficiency

BACKGROUND

Lipoprotein lipase (LPL) deficiency is a serious lipid disorder of severe hypertriglyceridemia (SHTG) with chylomicronemia. A large number of variants in the LPL gene have been reported but their influence on LPL activity and SHTG has not been completely analyzed. Gaining insight into the deleterious effect of the mutations is clinically essential.

METHODS

We used gene sequencing followed by in-vivo/in-vitro and in-silico tools for classification. We classified 125 rare LPL mutations in 33 subjects thought to have LPL deficiency and in 314 subjects selected for very SHTG.

RESULTS

Of the 33 patients thought to have LPL deficiency, only 13 were homozygous or compound heterozygous for deleterious mutations in the LPL gene. Among the 314 very SHTG patients, 3 were compound heterozygous for pathogenic mutants. In a third group of 51,467 subjects, from a general population, carriers of common variants, Asp9Asn and Asn291Ser, were associated with mild increase in triglyceride levels (11%-35%).

CONCLUSION

In total, 39% of patients clinically diagnosed as LPL deficient had 2 deleterious variants. Three patients selected for very SHTG had LPL deficiency. The deleterious mutations associated with LPL deficiency will assist in the diagnosis and selection of patients as candidates for the presently approved LPL gene therapy.

Newborn LpL (Ser447Stop, Asn291Ser) genotypes and the interaction with maternal genotypes influence the risk for different types of preeclampsia: modulating effect on lipid profile and pregnancy outcome

AIM

To establish that newborn Ser447Stop and Asn291Ser may have interactive effects with maternal genotypes on the plasma lipoprotein levels, risk of preeclampsia as well as on the prognosis of preeclampsia.

MATERIALS AND METHODS

Seventy preeclamptic women and 94 normotensive pregnant women, and their newborns were genotyped using PCR-RFLP methods.

RESULTS

The risk of mild and severe preeclampsia was 4 (p = 0.004) and 5.18 (p = 0.001), respectively, if both the mother and newborn were carriers of the Ser447/Ser477 genotype. If both the mother and newborn were carriers of the Asn291Ser variant, the risk to develop severe preeclampsia was 6.07 (p = 0.03). Women with mild and severe preeclampsia had higher TG (p < 0.001; p < 0.001) and LDL-C levels (p = 0.008; p < 0.001) if both the mother and newborn were carriers of the Ser447/Ser447 genotype. Women with severe preeclampsia had significantly higher TG (p = 0.03) and LDL-C levels (p = 0.037) if both the mother and newborn were carriers of Asn291Ser. Newborn/maternal LpL interaction had no statistically significant influence on pregnancy outcome.

CONCLUSIONS

The newborn/maternal LpL interaction influences the severity of preeclampsia and modulates the lipid profile particularly in severe preeclampsia.

Global O-GlcNAc Levels Modulate Transcription of the Adipocyte Secretome during Chronic Insulin Resistance

Increased flux through the hexosamine biosynthetic pathway and the corresponding increase in intracellular glycosylation of proteins via O-linked β-N-acetylglucosamine (O-GlcNAc) is sufficient to induce insulin resistance (IR) in multiple systems. Previously, our group used shotgun proteomics to identify multiple rodent adipocytokines and secreted proteins whose levels are modulated upon the induction of IR by indirectly and directly modulating O-GlcNAc levels. We have validated the relative levels of several of these factors using immunoblotting. Since adipocytokines levels are regulated primarily at the level of transcription and O-GlcNAc alters the function of many transcription factors, we hypothesized that elevated O-GlcNAc levels on key transcription factors are modulating secreted protein expression. Here, we show that upon the elevation of O-GlcNAc levels and the induction of IR in mature 3T3-F442a adipocytes, the transcript levels of multiple secreted proteins reflect the modulation observed at the protein level. We validate the transcript levels in male mouse models of diabetes. Using inguinal fat pads from the severely IR db/db mouse model and the mildly IR diet-induced mouse model, we have confirmed that the secreted proteins regulated by O-GlcNAc modulation in cell culture are likewise modulated in the whole animal upon a shift to IR. By comparing the promoters of similarly regulated genes, we determine that Sp1 is a common cis-acting element. Furthermore, we show that the LPL and SPARC promoters are enriched for Sp1 and O-GlcNAc modified proteins during insulin resistance in adipocytes. Thus, the O-GlcNAc modification of proteins bound to promoters, including Sp1, is linked to adipocytokine transcription during insulin resistance.

The roles of genetic polymorphisms and human immunodeficiency virus infection in lipid metabolism

Dyslipidemia has been frequently observed among individuals infected with human immunodeficiency virus type 1 (HIV-1), and factors related to HIV-1, the host, and antiretroviral therapy (ART) are involved in this phenomenon. This study reviews the roles of genetic polymorphisms, HIV-1 infection, and highly active antiretroviral therapy (HAART) in lipid metabolism. Lipid abnormalities can vary according to the HAART regimen, such as those with protease inhibitors (PIs). However, genetic factors may also be involved in dyslipidemia because not all patients receiving the same HAART regimen and with comparable demographic, virological, and immunological characteristics develop variations in the lipid profile. Polymorphisms in a large number of genes are involved in the synthesis of structural proteins, and enzymes related to lipid metabolism account for variations in the lipid profile of each individual. As some genetic polymorphisms may cause dyslipidemia, these allele variants should be investigated in HIV-1-infected patients to identify individuals with an increased risk of developing dyslipidemia during treatment with HAART, particularly during therapy with PIs. This knowledge may guide individualized treatment decisions and lead to the development of new therapeutic targets for the treatment of dyslipidemia in these patients.

Association between triglycerides and cardiovascular events in primary populations: a meta-regression analysis and synthesis of evidence

Background

Triglyceride levels were found to be independently predictive of the development of primary coronary heart disease in epidemiologic studies. The objective of this study was to determine whether triglyceride levels were predictive of cardiovascular events in randomized controlled trials (RCTs) of lipid-modifying drugs.

Methods

We performed a systematic review and meta-regression analysis of 40 RCTs of lipid-modifying drugs with cardiovascular events as an outcome. The log of the rate ratio of cardiovascular events (eg, coronary death or myocardial infarction) was plotted against the proportional difference between treatment and control groups in triglyceride and other lipid levels (high density lipoprotein cholesterol [HDL-C], low density lipoprotein cholesterol [LDL-C], and total cholesterol) for all trials and for trials of primary and secondary prevention populations. Linear regression was used to determine the statistical significance of the relationship between lipid values and cardiovascular events.

Results

The proportional difference in triglyceride levels was predictive of cardiovascular events in all trials (P=0.005 for the slope of the regression line; N=40) and in primary prevention trials (P=0.010; N=11), but not in secondary prevention trials (P=0.114; N=25). The proportional difference in HDL-C was not predictive of cardiovascular events in all trials (P=0.822; N=40), or in trials of primary (P=0.223; N=11) or secondary (P=0.487; N=25) prevention. LDL-C levels were predictive of cardiovascular events in both primary (P=0.002; N=11) and secondary (P<0.001; N=25) populations.

Conclusions

Changes in triglyceride levels were predictive of cardiovascular events in RCTs. This relationship was significant in primary prevention populations but not in secondary prevention populations.

Mixed dyslipidemias in primary care patients in France

OBJECTIVE

To determine the prevalence of single and mixed dyslipidemias among patients treated with statins in clinical practice in France.

METHODS

This is a prospective, observational, cross-sectional, pharmacoepidemiologic study with a total of 2544 consecutive patients treated with a statin for at least 6 months.

MAIN OUTCOME MEASURES

Prevalence of isolated and mixed dyslipidemias of low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), and triglycerides among all patients and among patients at high cardiovascular risk; clinical variables associated with attainment of lipid targets/normal levels in French national guidelines.

RESULTS

At least one dyslipidemia was present in 50.8% of all patients and in 71.1% of high-risk patients. Dyslipidemias of LDL-C, HDL-C, and triglycerides were present in 27.7%, 12.4%, and 28.7% of all patients, respectively, and in 51.0%, 18.2%, and 32.5% of high-risk patients, respectively. Among all subjects with any dyslipidemia, 30.9% had mixed dyslipidemias and 69.4% had low HDL-C and/or elevated triglycerides, while 30.6% had isolated elevated LDL-C; corresponding values for high-risk patients were 36.8%, 58.9%, and 41.1%. Age, gender, body mass index and Framingham Risk Score >20% were the factors significantly associated with attainment of normal levels for ≥2 lipid levels.

CONCLUSIONS

At least one dyslipidemia persisted in half of all patients and two-thirds of high cardiovascular risk patients treated with a statin. Dyslipidemias of HDL-C and/or triglycerides were as prevalent as elevated LDL-C among high cardiovascular risk patients.

Genetic variants at the APOE, lipoprotein lipase (LpL), cholesteryl ester transfer protein (CETP), and endothelial nitric oxide (eNOS) genes and coronary artery disease (CAD): CETP Taq1 B2B2 associates with lower risk of CAD in Asian Indians

Coronary artery disease (CAD) arises due to a complex interplay between the environment and genetic factors. Alterations in many of the biomarkers such as lipids and lipoprotein levels are characteristic of CAD. The phenotypes themselves have genetic determinants, and many single-nucleotide polymorphisms (SNPs) have been identified which influence them. The current study aims to evaluate the effect of six common polymorphisms at four loci, lipoprotein lipase (D9N, N291S, S447X), apolipoprotein E (APOE), cholesteryl ester transfer protein (C277T), and endothelial nitric oxide synthase (E298D), on lipid and lipoprotein levels and its association with CAD. Genotyping for the SNPs was done in 240 Indians of which 90 had proven CAD. The other 150 were clinically free from CAD and acted as controls. Relation of genetic variants, clinical history, and biochemical parameters with CAD were analyzed by multiple regression analysis. The frequency of the B2 allele in the CETP gene was significantly lower in cases than in controls (0.40 vs 0.49, P = 0.042). Significant association of CETP Taq1B SNP was seen with total cholesterol and low density lipoprotein cholesterol. Multivariate analysis accounting for clinical and metabolic predictors of CAD showed smoking to be a significant risk factor (odds ratio (OR) 4.347, 95% confidence interval (CI) 1.888-10.012, P = 0.001) and the CETP B2 variant imparting atheroprotection (OR 0.312, 95% CI 0.116-0.841, P = 0.021) possibly through a favorable lipid profile. None of the other SNPs were associated with the risk of CAD.

Novel LPL mutations associated with lipoprotein lipase deficiency: two case reports and a literature review

Lipoprotein lipase (LPL) is a key enzyme involved with hydrolysis and removal of triglycerides from plasma. LPL deficiency is a rare condition with an estimated prevalence of 1 in 106. It is characterized biochemically by elevated triglycerides and lowered HDL in the plasma and clinically by a constellation of signs and symptoms during childhood including failure to thrive, lipemia retinalis, eruptive xanthomas, hepatosplenomegaly, and acute pancreatitis. Nearly 100 mutations in the LPL gene have been associated with LPL deficiency. Here we report 2 unrelated pedigrees with LPL deficiency from 2 novel disease-causing LPL mutations: a Gly159Glu missense mutation in exon 5 and a 4-bp ACGG deletion at the 3' boundary of exon 2. We present molecular findings of these 2 cases and review the biochemical, clinical, and genetic features of LPL deficiency.

Seven lipoprotein lipase gene polymorphisms, lipid fractions, and coronary disease: a HuGE association review and meta-analysis

Lipoprotein lipase (LPL) is a key enzyme in lipoprotein metabolism and a major candidate gene for coronary heart disease (CHD). The authors assessed associations between 7 LPL polymorphisms and lipid fractions and CHD risk in population-based cohort, case-control, and cross-sectional studies published by January 2007. Meta-analyses of 22,734 CHD cases and 50,177 controls in 89 association studies focused on the relations of the T-93G (rs1800590), D9N (rs1801177), G188E, N291S (rs268), PvuII (rs285), HindIII (rs320), and S447X (rs328) polymorphisms to high density lipoprotein cholesterol, triglycerides, myocardial infarction, or coronary stenosis. Carriers of 9N or 291S had modestly adverse lipid profiles. Carriers of the less common allele of HindIII or of 447X had modestly advantageous profiles. The combined odds ratio for CHD among carriers was 1.33 (95% confidence interval (CI): 1.14, 1.56) for 9N, 1.07 (95% CI: 0.96, 1.20) for 291S, 0.89 (95% CI: 0.81, 0.98) for the less common HindIII allele, and 0.84 (95% CI: 0.75, 0.94) for 447X. For T-93G (odds ratio (OR) = 1.22, 95% CI: 0.98, 1.52) and PvuII (OR = 0.96, 95% CI: 0.89, 1.04), there were null associations with lipid levels or CHD risk; information on G188E was limited (OR = 2.80, 95% CI: 0.88, 8.87). The study of LPL genotypes confirms the existence of close interrelations between high density lipoprotein cholesterol and triglyceride pathways. The influence of these genotypes on CHD risk warrants further investigation.

Genome scan of a nonword repetition phenotype in families with dyslexia: evidence for multiple loci

To understand the genetic architecture of dyslexia and identify the locations of genes involved, we performed linkage analyses in multigenerational families using a phonological memory phenotype--Nonword Repetition (NWR). A genome scan was first performed on 438 people from 51 families (DS-1) and linkage was assessed using variance components (VC), Bayesian oligogenic (BO), and parametric analyses. For replication, the genome scan and analyses were repeated on 693 people from 93 families (DS-2). For the combined set (DS-C), analyses were performed with all three methods in the regions that were identified in both samples. In DS-1, regions on chromosomes 4p, 6q, 12p, 17q, and 22q exceeded our initial threshold for linkage, with 17q providing a parametric LOD score of 3.2. Analysis with DS-2 confirmed the locations on chromosomes 4p and 12p. The strongest VC and BO signals in both samples were on chromosome 4p in DS-C, with a parametric multipoint LOD(max) of 2.36 for the 4p locus. Our linkage analyses of NWR in dyslexia provide suggestive and reproducible evidence for linkage to 4p12 and 12p in both samples, and significant evidence for linkage to 17q in one of the samples. These results warrant further studies of phonological memory and chromosomal regions identified here in other datasets.

Mapping of genetic modifiers of Nr2e3 rd7/rd7 that suppress retinal degeneration and restore blue cone cells to normal quantity

The retinal degeneration 7 (rd7) mouse, lacking expression of the Nr2e3 gene, exhibits retinal dysplasia and a slow, progressive degeneration due to an abnormal production of blue opsin-expressing cone cells. In this study we evaluated three strains of mice to identify alleles that would slow or ameliorate the retinal degeneration observed in Nr2e3 (rd7/rd7) mice. Our studies reveal that genetic background greatly influences the expression of the Nr2e3 (rd7/rd7) phenotype and that the inbred mouse strains CAST/EiJ, AKR/J, and NOD.NON-H2 (nb1) carry alleles that confer resistance to Nr2e3 (rd7/rd7)-induced retinal degeneration. B6.Cg-Nr2e3 (rd7/rd7) mice were outcrossed to each strain and the F(1) progeny were intercrossed to produce F(2) mice. In each intercross, 20-24% of the total F(2) progeny were homozygous for the Nr2e3 (rd7/rd7) mutation in a mixed genetic background; approximately 28-48% of the Nr2e3 (rd7/rd7) homozygotes were suppressed for the degenerative retina phenotype in a mixed genetic background. The suppressed mice had no retinal spots and normal retinal morphology with a normal complement of blue opsin-expressing cone cells. An initial genome scan revealed a significant association of the suppressed phenotype with loci on chromosomes 8 and 19 with the CAST/EiJ background, two marginal loci on chromosomes 7 and 11 with the AKR/J background, and no significant QTL with the NOD.NON-H2 (nb1) background. We did not observe any significant epistatic effects in this study. Our results suggest that there are several genes that are likely to act in the same or parallel pathway as NR2E3 that can rescue the Nr2e3 (rd7/rd7) phenotype and may serve as potential therapeutic targets.

Functional significance of lipoprotein lipase HindIII polymorphism associated with the risk of coronary artery disease

Lipoprotein lipase (LPL) plays a pivotal role in lipid metabolism by hydrolyzing triglyceride (TG)-rich lipoprotein particles. Abnormalities in normal LPL function are associated with the risk of coronary artery disease (CAD). A number of genetic variants have been identified in the LPL gene that affects different functions of the LPL protein. A common HindIII polymorphism in intron 8 (T/G) of the LPL gene has been found to be associated with altered plasma TG and HDL-cholesterol, and CAD risk in several studies, but its functional significance is unknown. It has been shown that certain intronic sequence contain regulatory elements that are important for transcription and translational regulation of a gene. In this study we tested the hypothesis that this polymorphism affects the binding site of a transcription factor that regulates the transcription of LPL gene. Electrophoretic mobility shift assays (EMSAs) revealed that the HindIII site binds to a transcription factor and that the mutant allele has lower binding affinity than the wild type allele. Transcription assays containing the entire intron 8 sequence along with full-length human LPL promoter were carried out in COS-1 and human vascular smooth muscle cells. The mutant allele was associated with significantly decreased luciferase expression level compared to the wild type allele in both the muscle (3.394+/-0.022 vs. 4.184+/-0.028; P=4.7 x 10(-6)) and COS-1 (11.603+/-0.409 vs. 14.373+/-1.096; P<0.0001) cells. In conclusion, this study demonstrates for the first time that the polymorphic HindIII site in the LPL gene is functional because it affects the binding of a transcription factor and it also has an impact on LPL expression.

Familial lipoprotein lipase deficiency caused by known (G188E) and novel (W394X) LPL gene mutations

Lipoprotein lipase (LPL) is the key enzyme in the catabolism of triglyceride-rich lipoproteins in the circulation. Familial LPL deficiency is characterized by hypertriglyceridaemia and absence of LPL activity. We report a case of LPL deficiency in a 43-year-old woman, who initially presented in childhood with chylomicronaemia syndrome. At that time, her plasma triglyceride concentration was ∼30 mmol/L and post-heparin lipolytic activity was very low. In addition to having the known missense mutation LPL G188E, the patient was also found to have a novel nonsense mutation in exon 8, namely LPL W394X. The novel substitution in exon 8 (c.1262G > A) predicts a truncated protein product of 393 amino acids that lacks the carboxyl-terminal 12% of the mature LPL. Trp394 is part of a cluster of exposed tryptophan residues in the carboxyl-terminal domain of LPL important for binding lipid substrate. Of 11 members from her three-generation family, three were heterozygotes for G188E (mean plasma triglyceride, 3.5 ± 2.0 mmol/L), whereas six were heterozygotes for W394X (triglyceride, 4.3 ± 1.8 mmol/L). In summary, we describe a case of familial LPL deficiency caused by compound heterozygosity for known (G188E) and novel (W394X) LPL gene mutations.

Allelic variation in ApoC3, ApoA5 and LPL genes and first and second generation antipsychotic effects on serum lipids in patients with schizophrenia

Schizophrenic patients who are treated with antipsychotics, especially second generation antipsychotics, such as clozapine and olanzapine, manifest an increase in cholesterol and triglycerides as well as other changes associated with diabetes or the metabolic syndrome. Previous studies have shown that polymorphisms in several genes that regulate lipid metabolism can influence the levels of these lipids and response to drug treatment. We have investigated in an exploratory study whether polymorphisms in the apolipoprotein C-III (ApoC3), apolipoprotein A-V gene (ApoA5) and lipoprotein lipase genes influence differential lipid response to treatment with three second generation antipsychotics-olanzapine, clozapine and risperidone-or treatment with a first generation antipsychotic. A total of 189 patients with schizophrenia or schizoaffective disorder who were being treated with a single antipsychotic were studied in a cross-sectional study design in which fasting serum cholesterol and triglycerides and selected single-nucleotide polymorphosms (SNPs) in the three lipid metabolism genes were assessed. The treatment with antipsychotic monotherapy makes drug haplotype ascertainment less complex. Our analyses showed several nominally significant drug x gene and drug x haplotype interactions. The rarer C allele or the ApoA5_1131 (T/C) SNP was associated with higher cholesterol levels in patients treated with first generation antipsychotics and lower cholesterol levels in patients treated with olanzapine or clozapine. The rarer C allele of the ApoA5_SW19 (G/C) SNP was associated with higher cholesterol in risperidone-treated patients. An ApoA5 CG haplotype was associated with decreased cholesterol in olanzapine- or clozapine-treated patients and higher cholesterol in patients treated with first generation antipsychotics. The presence of the rarer T allele of the ApoC3_1100 (C/T) SNP or the presence of the ApoC3 TG haplotype was associated with decreased triglyceride levels in patients treated with olanzapine or clozapine and a nonsignificant trend for increased triglycerides in patients treated with first generation antipsychotics. The presence of the ApoC3 CC haplotype was associated with increased triglycerides in patients treated with olanzapine or clozapine. The overall magnitude of the effects was not large. These results provide a potential initial step toward a pharmacogenetic approach to selection of antipsychotic treatment which may help minimize the side effect of increases in serum lipids.

The lipoprotein lipase gene serine 447 stop variant influences hypertension-induced left ventricular hypertrophy and risk of coronary heart disease

LVH [LV (left ventricular) hypertrophy] is an independent risk factor for CHD (coronary heart disease). During LVH, the preferred cardiac energy substrate switches from FAs (fatty acids) to glucose. LPL (lipoprotein lipase) is the key enzyme in triacylglycerol (triglyceride) hydrolysis and supplies FAs to the heart. To investigate whether substrate utilization influences cardiac growth and CHD risk, we examined the association between the functional LPL S447X (rs328) variant and hypertension-induced LV growth and CHD risk. LPL-X447 has been shown to be more hydrolytically efficient and would therefore release more free FAs than LPL-S477. In a cohort of 190 hypertensive subjects, LPL X447 was associated with a greater LV mass index [85.2 (1.7) in S/S compared with 91.1 (3.4) in S/X+X/X; P=0.01], but no such association was seen in normotensive controls (n=60). X447 allele frequency was higher in hypertensives with than those without LVH {0.14 [95% CI (confidence interval), 0.08-0.19] compared with 0.07 (95% CI, 0.05-0.10) respectively; odds ratio, 2.52 (95% CI, 1.17-5.40), P=0.02}. The association of LPL S447X with CHD risk was then examined in a prospective study of healthy middle-aged U.K. men (n=2716). In normotensive individuals, compared with S447 homozygotes, X447 carriers were protected from CHD risk [HR (hazard ratio), 0.48 (95% CI, 0.23-1.00); P=0.05], whereas, in the hypertensives, X447 carriers had increased risk [HR, 1.54 (95% CI, 1.13-2.09) for S/S (P=0.006) and 2.30 (95% CI, 1.53-3.45) for X447+ (P<0.0001)] and had a significant interaction with hypertension in CHD risk determination (P=0.007). In conclusion, hypertensive LPL X447 carriers have increased risk of LVH and CHD, suggesting that altered FA delivery constitutes a mechanism through which LVH and CHD are associated in hypertensive subjects.

The lipoprotein lipase gene in combined hyperlipidemia: evidence of a protective allele depletion

Background

Lipoprotein Lipase (LPL), a key enzyme in lipid metabolism, catalyzes the hydrolysis of triglycerides (TG) from TG-rich lipoproteins, and serves a bridging function that enhances the cellular uptake of lipoproteins. Abnormalities in LPL function are associated with pathophysiological conditions, including familial combined hyperlipidemia (FCH). Whereas two LPL susceptibility alleles were found to co-segregate in a few FCH kindred, a role for common, protective alleles remains unexplored. The LPL Ser447Stop (S447X) allele is associated with anti-atherogenic lipid profiles and a modest reduction in risk for coronary disease. We hypothesize that significant depletion of the 447X allele exists in combined hyperlipidemia cases versus controls. A case-control design was employed. The polymorphism was assessed by restriction assay in 212 cases and 161 controls. Genotypic, allelic, and phenotypic associations were examined.

Results

We found evidence of significant allelic (447X_control: 0.130 vs. 447X_case: 0.031, χ² = 29.085; 1df; p < 0.001) and genotypic association (SS: 0.745 vs. 0.939, and SX+XX: 0.255 vs. 0.061) in controls and cases, respectively (χ² = 26.09; 1df; p < 0.001). In cases, depletion of the 447X allele is associated with a significant elevation in very-low-density lipoprotein cholesterol (VLDL-C, p = 0.045). Consonant with previous studies of this polymorphism, regression models predict that carriers of the 447X allele displayed significantly lower TG, low-density lipoprotein cholesterol (LDL-C) and TG/high-density lipoprotein cholesterol (HDL-C) ratio.

Conclusion

These findings suggest a role for the S447X polymorphism in combined hyperlipidemia and demonstrate the importance of evaluating both susceptibility and protective genetic risk factors.

Gene polymorphisms in the Quebec population: a risk to develop hypertriglyceridemia

In Eastern Québec, two major lipoprotein lipase (LPL) gene mutations, P207L and G188E, lead to complete LPL deficiency in homozygote subjects and contribute to elevated predisposition to hypertriglyceridemia in heterozygotes. First, we determined the allele frequencies of LPL (D9N, G188E, P207L, D250N, N291S, and S447X), APOE (C112R and C158R), PPARalpha (L162V), and PPARgamma2 (P12A) single nucleotide polymorphisms (SNPs) in a random-based cohort of the metropolitan Québec city area. Second, we compared the LPL X447 allele frequencies observed in the random cohort and in a cohort of LPL P207L deficient patients. In the random cohort, the LPL N9 rare allele exhibited a higher prevalence than previously expected (p=0.0001). The LPL X447 allele frequency was lower in the patient cohort (Freq: 4.4%) than in the random cohort (Freq: 11.2%) (p=0.0001). These results reveal the importance of genetic screening for LPL gene mutations D9N and S447X in a population at risk to develop hypertriglyceridemia.

Lipoprotein metabolism of pregnant women is associated with both their genetic polymorphisms and those of their newborn children

To explore whether the placenta contributes to the lipoprotein metabolism of pregnant women, we took advantage of the fact that placental proteins are encoded from the fetal genome and examined the associations between lipids of 525 pregnant women and the presence, in their newborns, of genetic polymorphisms of LPL and apolipoprotein E (APOE), two genes expressed in placenta. After adjustment for maternal polymorphisms, newborn LPL*S447X was associated with lower triglycerides (-21 +/- 9 mg/dl), lower LDL-cholesterol (LDL-C; -12 +/- 5 mg/dl), lower apoB (-14 +/- 4 mg/dl), higher HDL-C (5 +/- 2 mg/dl), and higher apoA-I (9 +/- 4 mg/dl) in their mothers; newborn LPL*N291S was associated with higher maternal triglycerides (114 +/- 31 mg/dl); and newborn APOE*E2 (compared to E3E3) was associated with higher maternal LDL-C (14 +/- 6 mg/dl) and higher maternal apoB (14 +/- 5 mg/dl). These associations (all P < 0.05) were independent of polymorphisms carried by the mothers and of lipid concentrations in newborns and were similar in amplitude to the associations between maternal polymorphisms and maternal lipids. Such findings support the active role of placental LPL and APOE in the metabolism of maternal lipoproteins and suggest that fetal genes may modulate the risk for problems related to maternal dyslipidemia (preeclampsia, pancreatitis, and future cardiovascular disease).

Missense mutation W86R in exon 3 of the lipoprotein lipase gene in a boy with chylomicronemia

BACKGROUND

Familial LPL deficiency is a rare inborn error of metabolism caused by mutational change within the LPL gene, which leads to massive hypertriglyceridemia.

METHODS

The underlying molecular defect in a boy of Croatian descent was studied by SSCP analysis, DNA sequencing and finally confirmed by RFLP.

RESULTS

DNA analysis showed the child to be a homozygote and his parents heterozygotes for TGG-->CGG change in codon 86 of the LPL gene, which leads to W86R amino acid substitution. DNA sequence analysis also showed a silent mutation in the third exon of father's DNA, V108V. Determination of some LPL gene polymorphisms showed the child and his parents to have HindIII/H+H+ and both S447 wild-type alleles, whereas for PvuII the parents had P(+)P- and the child P(+)P+ genotype.

CONCLUSIONS

In this case, W86R mutation was the reason for the production of nonfunctional enzyme and consequently triacylglycerol (TG) exceeding 15 mmol/l. This implies the risk of frequent episodes of acute pancreatitis. Decreased LPL activity leads to elevated triacylglycerol levels and reduced HDL-cholesterol, both risk factors for the development of coronary artery disease. LPL genotyping especially of young patients with hypertriglyceridemia is therefore necessary and justifiable.

Much lower prevalence of coronary calcium detected by electron-beam computed tomography among men aged 40-49 in Japan than in the US, despite a less favorable profile of major risk factors

BACKGROUND

Since World War II (WWII), exposures to westernized lifestyle have occurred in many non-Western countries, including Japan. National surveys showed that risk factor profiles for atherosclerosis around 1990 were similar in men in the post WWII birth cohorts in the US and Japan. We compared the degree of coronary calcium and other factors in men in the post WWII birth cohort: men aged 40-49 in the US and Japan.

METHODS

We conducted a cross-sectional study examining randomly selected 100 men from Kusatsu, Japan, and 100 men from Allegheny County, US. Coronary calcium was assessed using electron-beam computed tomography.

RESULTS

Systolic blood pressure, total cholesterol, low density lipoprotein (LDL)-cholesterol, and smoking rates were higher among the Japanese (122.6 +/- 14.1 versus 113.7 +/- 9.6 mmHg, P < 0.01; 5.72 +/- 0.90 versus 4.99 +/- 0.81 mmol/l (220.9 +/- 34.6 versus 192.8 +/- 31.3 mg/dl), P < 0.01; 3.52 +/- 1.01 versus 3.10 +/- 0.78 mmol/l (136.0 +/- 39.0 versus 119.7 +/- 30.0 mg/dl), P < 0.01; and 48 versus 15%, P < 0.01, respectively). Triglycerides and fibrinogen were similar. High density lipoprotein (HDL)-cholesterol was higher among the Japanese. Body mass index, fasting insulin, and C-reactive protein were higher among the Americans. Prevalence of coronary artery calcium score >0 was strikingly lower among the Japanese than the Americans (13% versus 47%, P < 0.01).

CONCLUSIONS

Much lower prevalence of coronary calcium despite a less favourable profile of many major independent risk factors in the Japanese might imply that there are strong protective factors against atherosclerosis in the Japanese. Further investigation is of critical importance.

The lipoprotein lipase S447X polymorphism and plasma lipids

We studied 4,058 subjects from a representative sample of the Singapore population 1) to determine the association between the S447X polymorphism at the LPL locus and serum lipid concentration in Chinese, Malays, and Asian Indians living in Singapore and 2) to explore any interactions with apolipoprotein E (APOE) genotype, exercise, obesity, cigarette smoking, and alcohol intake. Information on obesity, lifestyle factors (including smoking, alcohol consumption, and exercise frequency), glucose tolerance, and fasting lipids was obtained. Male and female carriers of the X447 allele had lower serum triglyceride concentrations and higher HDL cholesterol (HDL-C) concentrations. The association between the X447 allele and serum HDL-C concentration was modulated by APOE genotype in males and cigarette smoking and alcohol intake in females. The effect of the X447 allele was greatest in men who carried the E4 allele and women who smoked or consumed alcohol. The X447 allele at the LPL locus is common and associated with a less atherogenic lipid profile in Asian populations. Interactions with APOE genotype, cigarette smoking, and alcohol intake reinforce the importance of examining genetic associations, such as this one, in the context of the population of interest.

Lipoprotein concentrations in newborns are associated with allelic variations in their mothers

BACKGROUND

Factors determining lipoprotein concentrations in the fetus are not yet fully understood. We postulated that an important factor is the genetic make-up of the mother. In the present study, we examined the associations between the cord blood concentrations of lipoproteins of 525 newborns and the polymorphisms present in their mothers on the genes of apolipoprotein E (APOE*E2, *E3, *E4), apolipoprotein C-III (APOC3*C3238G also called APOC3*S2) and lipoprotein lipase (LPL*S447X).

RESULTS

Newborns born of mothers with APOE*E2 allele had significantly lower cord blood LDL-C (P < 0.01) and apoB (P < 0.01) and significantly higher cord blood HDL-C and apoA1 (all P-values < 0.03) compared to those born of mothers with APOE*E3E3 genotype. These associations were independent of the presence of APOE*E2 allele in the newborns. Similarly, APOC3*S2 in mothers was associated with significantly lower (all P < 0.001) cord blood LDL-C, apoB, HDL-C and apoA1. In contrast, LPL*S447X in mothers lowered significantly cord blood LDL-C and apoB only when LPL*S447X was present in newborns. Most of the effects of these maternal polymorphisms on the newborns were independent of the changes of maternal lipoproteins generated by these polymorphisms.

CONCLUSIONS

This is the first evidence that maternal genetic variations influence fetal lipoprotein concentrations, independent of the genetic status of the fetus and of the variations of maternal lipoprotein concentrations generated by these genetic variants. It suggests that proteic components of maternal lipoproteins strongly control the metabolism of maternal lipoproteins carried out at the surface of the placenta to assure the cholesterol delivery to the fetus.

Familial HDL deficiency due to ABCA1 gene mutations with or without other genetic lipoprotein disorders

Mutations in ABCA1 have been shown to be the cause of Tangier disease (TD) and some forms of familial hypoalphalipoproteinemia (HA), two genetic disorders characterized by low plasma HDL levels. Here we report six subjects with low HDL, carrying seven ABCA1 mutations, six of which are previously unreported. Two mutations (R557X and H160FsX173) were predicted to generate short truncated proteins; two mutations (E284K and Y482C) were located in the first extracellular loop and two (R1901S and Q2196H) in the C-terminal cytoplasmic domain of ABCA1. Two subjects found to be compound heterozygotes for ABCA1 mutations did not have overt clinical manifestations of TD. Three subjects, all with premature coronary artery disease (pCAD), had a combination of genetic defects. Besides being heterozygotes for ABCA1 mutations, two of them were also carriers of the R3500Q substitution in apolipoprotein B and the third was a carrier of N291S substitution in lipoprotein lipase. By extending family studies we identified 17 heterozygotes for ABCA1 mutations. Plasma HDL-C and Apo A-I values in these subjects were 38.3 and 36.9% lower than in unaffected family members and similar to the values found in heterozygotes for Apo A-I gene mutations which prevent Apo A-I synthesis. This survey underlines the allelic heterogeneity of ABCA1 mutations and suggests that: (i) TD subjects, if asymptomatic, may be overlooked and (ii) there may be a selection bias in genotyping towards carriers of ABCA1 mutations who have pCAD possibly related to a combination of genetic and environmental cardiovascular risk factors.

Association between single-nucleotide polymorphisms in the endothelial lipase (LIPG) gene and high-density lipoprotein cholesterol levels

Endothelial lipase (LIPG) is the latest addition to the triglyceride lipase family of genes that includes pancreatic lipase (PL), hepatic lipase (HL), and lipoprotein lipase (LPL). These lipolytic enzymes demonstrate both triglyceride lipase as well as phospholipase activities and are integrally involved in lipid absorption, transport, and metabolism. Several studies have demonstrated that LIPG is important for affecting lipid levels in mice but the data in humans is less complete. To more thoroughly characterize the LIPG gene, we resequenced it from an ethnically diverse population. Thirteen novel single-nucleotide polymorphisms (SNPs) were identified and seven others confirmed. High linkage disequilibrium was found among these SNPs spanning the length of the transcript, allowing interrogation of the entire gene for functional variation. Subjects with either high or low HDL cholesterol were used to investigate its association with LIPG gene variation. Associations were found with the most significant being the intronic variants C+42T/In5 and T+2864C/In8 (P=0.007 and 0.004, respectively). A trend for an association of the same SNPs with fewer myocardial infarctions (P=0.03) was also observed but was not significant after correction for multiple testing. The results of this study provide data linking variation in the human LIPG gene with HDL cholesterol levels as well as further evidence in support of LIPG as a potential target for therapeutic intervention.

Effect of obesity on HDL and LDL particle sizes in carriers of the null P207L or defective D9N mutation in the lipoprotein lipase gene: the Québec LipD Study

BACKGROUND

We have recently demonstrated that French Canadians bearing a mutation in the lipoprotein lipase (LPL) gene present an impaired lipoprotein-lipid profile characterized by small low-density lipoprotein (LDL) and high-density lipoprotein (HDL) particles compared with healthy subjects. It has also been documented that obesity has a significant impact on HDL and LDL particle sizes.

OBJECTIVE

To examine the extent to which obesity modulates HDL and LDL particle sizes among carriers of mutations in the LPL gene.

SUBJECTS

Analyses were carried out in 206 heterozygous carriers of the D9N mutation (N=118) or the P207L mutation (N=88).

MEASUREMENTS

Lipoprotein particle sizes were measured on whole plasma by nondenaturing polyacrylamide gradient gel electrophoresis.

RESULTS

In general, body mass index (BMI) and waist circumference were significant correlates of LDL and HDL particle sizes among heterozygous carriers of the P207L or D9N mutation in the LPL gene, with relatively similar associations among men and women. Multivariate analyses indicated that variations in waist circumference but not BMI were an independent predictor of variations in both HDL particle size (5.2%, P=0.0005) and LDL particle size (5.9%, P=0.01) in the entire group of heterozygotes for LPL mutation in a model that included the nature of the LPL mutation (D9N vs P207L), gender, age, cholesterol and plasma TG levels. Interestingly, there was a significant interaction between plasma TG levels and waist circumference or BMI in modulating HDL particle size. Indeed, an increased waist circumference or BMI was associated with a significant reduction in HDL particle size among subjects with plasma TG levels <or=3.5 mmol/l, but not among those with marked hypertriglyceridemia (TG levels >3.5 mmol/l).

CONCLUSION

These results suggest that abdominal obesity, more so that overall obesity, is an important determinant of variations in LDL and HDL particle size among heterozygous carriers of mutations in the LPL gene, perhaps further contributing to modulate the risk of CHD in these individuals.

Lipoprotein lipase gene polymorphisms in Croatian patients with coronary artery disease

Modifications in lipoprotein lipase levels lead to elevated triglycerides and reduced high density lipoprotein (HDL), both of which are risk factors for coronary artery disease (CAD). Hence, we examined the influence of the -93T/G, D9N, N291S, and S447X polymorphisms in the lipoprotein lipase (LPL) gene on CAD risk and lipid levels in Croatian patients with and without angiographically confirmed CAD. The N291S polymorphism was significantly associated with CAD (OR = 0.36; 95% CI = 0.13, 0.99; p = 0.048). This association was only moderately affected by adjusting for various lipids (OR = 0.36; 95% CI = 0.12, 1.08; p = 0.068). HDL2-cholesterol and apolipoprotein A-I levels were significantly higher in non-carriers of the -93T/G and D9N polymorphisms in the CAD group (p = 0.017 and 0.028, respectively). The N291S genetic variant did not show any significant difference between carriers and non-carriers in either group studied for any of the lipids. Lower triglyceride and higher HDL2-cholesterol levels in the control group were associated with carriers of the S447X mutation (p = 0.043 and 0.056, respectively). LPL gene polymorphisms might be involved in predisposition to CAD and determination of lipid profiles.

A "natural experiment" in cardiovascular epidemiology in the early 21st century

Despite similar traditional risk factors, morbidity and mortality rates from coronary heart disease in western and non-western cohorts remain substantially different. Careful study of such cohorts may help identify novel risk factors for CHD, and contribute to the formulation of new preventive strategies

Common Variants in the Lipoprotein Lipase Gene in Brazil: Association with Lipids and Angiographically Assessed Coronary Atherosclerosis

Lipoprotein lipase is the rate-limiting enzyme in the lipolysis of plasma triglyceride-rich lipoproteins. We studied six variants (T-93G, D9N, N291S, PvuII, HindIII and S447X) in the lipoprotein lipase (LPL) gene in 309 non-diabetic patients with angiographically assessed coronary artery disease and in 197 controls in a southern Brazilian population of European descent. The HindIII H-allele was associated with lower triglycerides (p < 0.01) and higher high-density lipoprotein cholesterol (p = 0.03) levels, and the S447X mutation was associated with lower triglyceride levels (p < 0.01) in males, but not females. No other significant lipid associations were observed. Haplotypes were derived from these two sites (HindIII/S447X), and carriers of H-S and H-X haplotypes showed lower triglycerides (p < 0.01) and increased high-density lipoprotein cholesterol (p = 0.01) levels when compared to the H+S haplotype in males. In this gender, the H-X haplotype was associated with a protective effect (OR = 0.36, 95%CI = 0.13-0.97) for significant disease (> or = 60% of luminal coronary stenosis), even controlling for other classical risk factors.

Lipoprotein lipase: genetics, lipid uptake, and regulation

Lipoprotein lipase (LPL) regulates the plasma levels of triglyceride and HDL. Three aspects are reviewed. 1) Clinical implications of human LPL gene variations: common mutations and their effects on plasma lipids and coronary heart disease are discussed. 2) LPL actions in the nervous system, liver, and heart: the discussion focuses on LPL and tissue lipid uptake. 3) LPL gene regulation: the LPL promoter and its regulatory elements are described.

Hypertriglyceridemia and risk of coronary heart disease

Mounting evidence indicates that elevated triglyceride level is a risk factor for coronary heart disease (CHD). The role of triglyceride as a causative agent for CHD is less clear. Hypertriglyceridemia is frequently associated with a set of complex metabolic abnormalities, including low high-density lipoprotein cholesterol, small dense low-density lipoprotein, central obesity, insulin resistance, and type 2 diabetes. Understanding the physiologic processes that lead to the metabolic disturbances associated with hypertriglyceridemia is essential in investigating the effect of triglyceride on CHD risk.

Identification of genetic variants in endothelial lipase in persons with elevated high-density lipoprotein cholesterol

BACKGROUND

Elevated high-density lipoprotein cholesterol (HDL-C) is associated with reduced risk of cardiovascular disease, and variation in HDL-C levels has been shown to be approximately 50% heritable. Overexpression of endothelial lipase (EL), a member of the lipoprotein lipase gene family, markedly reduces HDL-C levels in mouse models. We hypothesized that genetic variation in EL might be associated with elevated HDL-C.

METHODS AND RESULTS

All exons and 1.2 kilobase of promoter of the EL gene were sequenced in 20 unrelated human subjects with high HDL-C levels. A total of 17 variants were identified. Six of these were potentially functional and were confirmed by restriction enzyme analysis. Four variants result in amino acid changes (Gly26Ser, Thr111Ile, Thr298Ser, and Asn396Ser,) and 2 variants were in the promoter (-303A/C and -410C/G). The genotype frequencies of each variant were determined in 176 black controls, 165 white controls, and 123 whites with high HDL-C. The Thr111Ile variant was the most common, with an allele frequency of 10.3% in blacks, 31.2% in white controls, and 32.6% in the high HDL-C group. The remaining variants all had allele frequencies <5.0% but differed in frequency among the 3 groups. Interestingly, Gly26Ser, Thr298Ser, and -303A/C were found in the black and high HDL-C white cohorts but were absent in the control white group.

CONCLUSIONS

Six new potentially functional variants in EL were discovered through sequencing of the EL gene in subjects with high HDL-C levels. Differences in allele frequencies exist between blacks and whites and between control subjects and those with high HDL-C levels.

Lipoprotein lipase and APOE/APOC-I/APOC-II gene cluster diversity in native Brazilian populations

Allele and haplotype frequencies for the T-93G, Hind III, and Pvu II variants of the lipoprotein lipase gene (LPL), and Hpa I and Ava II restriction site polymorphisms (RSP) of the APOE/C-I/C-II gene cluster were determined in 143 individuals from five Brazilian Indian tribes. These results were integrated with those previously reported for APOE. Marked interethnic variability occurs in these sites. A strong linkage disequilibrium was observed between the APOE and APOC-I loci (D' = 0.81; P < 0.00001). Linkage disequilibrium between the Hind III and Pvu II RSPs of the LPL gene was also observed (D' = 1; P < 0.001), but none of these RSPs were in linkage disequilibrium with the T-93G mutation. Considering both loci, heterozygosity was estimated as 0.45, but it was lower in the Xavante and Surui populations, in accordance with the historical and biodemographical data of these Amerindians. The results reported here may have implications for understanding interpopulation differences in lipid levels and coronary heart disease prevalences.

Characterization of LDL particle size among carriers of a defective or a null mutation in the lipoprotein lipase gene: the Québec LIPD Study

OBJECTIVE

The objective of the present study was to compare the impact of the null P207L and defective D9N mutations in the LPL gene on LDL particle size among heterozygous carriers.

METHODS AND RESULTS

LDL particle size was measured on whole plasma by 2% to 16% non-denaturing polyacrylamide gradient gel electrophoresis in a cohort of 206 heterozygous carriers of either the P207L or the D9N mutation. The P207L carriers (N=88) presented with a more atherogenic lipoprotein-lipid profile compared with the D9N carriers (N=118). Accordingly, LDL particle size was smaller in the P207L carriers than in the D9N subjects (248.8+/- 1.0 vs 254.5+/-1.0 A, P< 0.001), and the difference remained significant after adjustment for plasma triglyceride (TG) levels. The difference in LDL diameter between the P207L and the D9N carriers was 3-fold greater in individuals with plasma TG levels >3.5 mmol/L than in subjects with TG < or =3.5 mmol/L. The factors that statistically contributed to LDL particle size variation in multivariate analyses were plasma TG levels (11.6%) and age (6.4%) in subjects with TG levels < or =3.5 mmol/L and HDL cholesterol levels (15.5%) and the LPL gene mutation (null versus defective, 7.0%) in patients with TG levels >3.5 mmol/L.

CONCLUSIONS

These results suggest that the null P207L mutation in the LPL gene has a greater impact on LDL particle size than the defective D9N mutation and that this mutation-specific effect is amplified at greater plasma TG concentrations.

Activity and concentration of lipoprotein lipase in post-heparin plasma and the extent of coronary artery disease

Numerous studies have found polymorphisms in the lipoprotein lipase (LPL) gene to be associated with the risk of coronary artery disease (CAD), implicating LPL in the development of atherothrombotic disease. It remains controversial, however, whether LPL acts in a pro- or anti-atherogenic fashion. We quantitated activity and concentration of LPL in post-heparin plasma from 194 male patients undergoing coronary angiography. HDL cholesterol was significantly associated with LPL activity quartiles (1.09+/-0.26 the highest vs. 0.96+/-0.25 mmol/l the lowest quartile, P<0.01). There was also a trend towards higher total (5.61+/-1.33 vs. 5.16+/-1.44 mmol/l, P=0.059) and LDL cholesterol (3.92+/-1.39 vs. 3.46+/-1.06 mmol/l, P=0.09) with higher LPL activity. In contrast, measures of CAD extent showed no differences between LPL quartiles (P>0.30 for prior myocardial infarction, number of diseased vessels, Gensini and extent scores). Additionally, there was no difference in LPL activity (CAD: n=158, 168+/-70 nmol/ml/min, no CAD: n=36, 180+/-89 nmol/ml/min, P=0.47) or concentration (280+/-121 ng/ml and 288+/-111 ng/ml, P=0.72) between patients with and without CAD. Our data show that, in spite of an association with lipoprotein parameters, LPL in post-heparin plasma is unrelated to the presence or the extent of CAD. Therefore, lipoprotein lipase determination in plasma does not appear to be a useful marker in the assessment of CAD risk.

A case of hyperlipidemia with homozygous apolipoprotein E5 (Glu3-->Lys)

In this study, we present clinical feature of a novel case with homozygous apolipoprotein (apo) E5. The patient was a 53-year-old Japanese woman. She was from a small island off the coast of Kagoshima Prefecture, Japan. Her parents were first degree cousins. No corneal opacification, xanthomatosis, lymphadenopathy, or hepatosplenomegaly was observed. There have been no signs of clinically overt atherosclerosis to date. Her serum total cholesterol, triglycerides (TG) and high-density lipoprotein (HDL)-cholesterol levels were 11.6, 6.1 and 1.2 mmol/l, respectively, and apo A-I, A-II, B, C-II, C-III and E levels were 121, 34.8, 269, 10.4, 25.7 and 10.3 mg/dl, respectively. Serum lipoprotein profile analyzed by agarose gel electrophoresis and differential staining revealed markedly increased cholesterol and TG in both beta and prebeta-migrated lipoproteins, whereas alpha-migrated lipoprotein showed decreased cholesterol. Her apo E isoform analyzed by isoelectric focusing (IEF) was found to be homozygous apo E5. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis of her apo E and lipoprotein lipase (LPL) genes revealed that she had a homozygous apo E (Glu3-->Lys) and heterozygous LPL variant Ser447 to Ter. Her son and daughter, both of whom had hyperlipidemia, were found to have apo E3/5 phenotype. Direct sequencing analysis of her apo E gene confirmed a homozygous one nucleotide change: G to A at nucleotide position of 2836 in the exon 3, resulting in Glu3-->Lys mutation. This is the first report of lipids and lipoprotein profiles in patients with homozygous apo E5 (Glu3-->Lys).

Coronary artery disease and dyslipidemia within Europe: genetic variants in lipid transport gene loci in German subjects with premature coronary artery disease

Fifteen polymorphisms in six lipid transport genes were studied in a German population for relationships with dyslipidemia and coronary artery disease (CAD), to investigate a possible genetic basis for the marked differences in mortality rates from coronary heart disease within Europe. In other populations these polymorphisms have all been associated with CAD or with phenotypes known to predispose to CAD. The apoAI PstI polymorphism (P<0.005) and the lipoprotein lipase Ser(447)-Ter mutation (P<0.005) were associated with plasma triglyceride concentrations. Additionally, the apoAI PstI polymorphism (P<0.05), the apoB XbaI polymorphism (P<0.05) and apoE phenotypes (P<0.05) were associated with plasma cholesterol concentrations. However, none of the allele frequencies of the polymorphisms studied were related to the presence, or absence, of coronary artery disease. Associations between five polymorphisms representing four lipid transport gene loci and dyslipidemia were demonstrated in this German population. It is possible that predisposition to dyslipidemia in Germany involves a particular selection of polymorphic loci, which are different from those identified in other European countries.

Structure-function analysis of D9N and N291S mutations in human lipoprotein lipase using molecular modelling

Lipoprotein lipase (LPL) plays a central role in lipid metabolism. The D9N and N291S mutations in the LPL gene are associated with elevated triglyceride and decreased HDL-cholesterol levels. Published in vitro expression studies suggest that these two mutations are associated with reduced LPL enzymatic activity. We sought to gain further insight on the impact of these two mutations on the LPL structure and function by molecular modelling techniques. Homology modelling was used to develop a three-dimensional (3D) structure of LPL from human pancreatic lipase. Two separate LPL models for the D9N and N291S substitutions were constructed and compared with the wild type LPL for differences in hydrophobicity, atomic burial, hydrogen bond pattern, and atomic mobility. In comparison to the wild type model, the 9N model was associated with significantly increased atomic mobility of its neighboring residues, but the catalytic site was not affected. The region near residue 9 in the upper part of the N-domain was considered a candidate site for protein-protein interaction. In the N291S model, alterations in H-bonds and constrained atomic mobility were among conformational changes in the region where the substitution had occurred. These are hypothesized to cause an increase in the rate of dissociation in LPL dimerization, subsequently affecting the LPL enzymatic activity. We also modelled the C-domain of apoCII, the obligatory cofactor of LPL, from 2D NMR data and docked the model with LPL to explore their interaction site. These docking experiments suggest that the C-domain of apoCII interacts with the interface of N- and C-domains of LPL and part of the lid structure that covers the catalytic site. In summary, we provide molecular modelling data on two well-known mutations in the LPL gene to help explain the published in vitro expression findings and propose a possible LPL-apoCII interaction site. Our data indicate that molecular modelling of LPL mutations could provide a valuable tool to understand the effects of a mutation on the structure-function of this important enzyme.

O componente genético da determinação dos lipídeos séricos

Os níveis de lipídeos séricos são características multifatoriais determinadas por um grande número de fatores genéticos e ambientais. A identificação do componente genético dessas características tem sido intensamente investigada nos últimos anos. Esses estudos têm enfocado principalmente polimorfismos nos genes que codificam proteínas estruturais e enzimas relacionadas com o metabolismo de lipídeos. Estudos mais recentes mostraram que o efeito desses polimorfismos depende em parte das interações dos diferentes genótipos com os fatores de risco clássicos tais como tabagismo, sobrepeso ou sedentarismo. A variabilidade encontrada nesses genes parece também influir na resposta a fármacos comumente utilizados no tratamento das hiperlipidemias.

Candidate genes as potential links between periodontal and cardiovascular diseases

Recent epidemiological associations between periodontal disease and cardiovascular disease have led to a search for biological mechanisms that explain the associations. Genetic factors that influence biological processes involved in both diseases represent one of the potential mechanisms that may link periodontitis and cardiovascular disease. At present, several candidate genes have been investigated in one of the diseases but not the other. Although there are limited data to support a specific candidate gene as the explanation for observed associations between the 2 diseases, a few candidates look promising. One candidate that influences inflammation, interleukin-1 gene polymorphisms, has been associated with periodontal disease and cardiovascular disease. This review will consider biological mechanisms and genes that may be reasonable candidates for an etiological mechanism that influences the clinical characteristics of both periodontal disease and cardiovascular disease.