Detection of missense mutations in the genes for lipoprotein lipase and hepatic triglyceride lipase in patients with dyslipidemia undergoing coronary angiography

Associations between LPL gene polymorphisms and coronary artery disease: evidence based on an updated and cumulative meta-analysis

Lipoprotein lipase (LPL) is widely linked to lipid and lipoprotein metabolism, but its effects on coronary artery disease (CAD) are not clearly elucidated. The aim of this study was to clarify the association between LPL gene polymorphisms and CAD susceptibility. The pooled odds ratio (OR) and 95% confidence interval (CI) were calculated to estimate the strength of the relationship between LPL gene polymorphisms and CAD risk. Comprehensive electronic databases, including PubMed, EMBASE, Web of Science, and the Cochrane Library, were systematically searched. A total of 45 records containing 80 eligible studies were analyzed. The results indicated an increased risk between the LPL D9N polymorphism and susceptibility to CAD in the dominant genetic model (AA + GA vs. GG: OR = 1.46, 95% CI = 1.14-1.87), whereas the LPL HindIII polymorphism showed a protective effect against CAD under all tested models (GG+GT vs. TT: OR = 0.85, 95% CI = 0.75-0.97; GG vs. TT + TG: OR = 0.62, 95% CI = 0.47-0.83; G vs. T: OR = 0.81, 95% CI = 0.71-0.92). No significant association was identified for the LPL N291S and PvuII polymorphisms. Stratification analysis by ethnicity suggested a significant correlation between the LPL S447X polymorphism and CAD susceptibility in Caucasians under the dominant and allele genetic models. In summary, our meta-analysis indicated that the LPL D9N polymorphism was associated with an increased risk of CAD, whereas the S447X and HindIII polymorphisms showed protective effects. There was no association observed between the N291S and PvuII polymorphisms and CAD risk.

Hyperlipoproteinemia type 3: the forgotten phenotype

Hyperlipoproteinemia type 3 (HLP3) is caused by impaired removal of triglyceride-rich lipoproteins (TGRL) leading to accumulation of TGRL remnants with abnormal composition. High levels of these remnants, called β-VLDL, promote lipid deposition in tuberous xanthomas, atherosclerosis, premature coronary artery disease, and early myocardial infarction. Recent genetic and molecular studies suggest more genes than previously appreciated may contribute to the expression of HLP3, both through impaired hepatic TGRL processing or removal and increased TGRL production. HLP3 is often highly amenable to appropriate treatment. Nevertheless, most HLP3 probably goes undiagnosed, in part because of lack of awareness of the relatively high prevalence (about 0.2% in women and 0.4-0.5% in men older than 20 years) and largely because of infrequent use of definitive diagnostic methods.

Dysbetalipoproteinaemia: a mixed hyperlipidaemia of remnant lipoproteins due to mutations in apolipoprotein E

Atherosclerosis is strongly associated with dyslipoproteinaemia, and especially with increasing concentrations of low-density lipoprotein and decreasing concentrations of high-density lipoproteins. Its association with increasing concentrations of plasma triglyceride is less clear but, within the mixed hyperlipidaemias, dysbetalipoproteinaemia (Fredrickson type III hyperlipidaemia) has been identified as a very atherogenic entity associated with both premature ischaemic heart disease and peripheral arterial disease. Dysbetalipoproteinaemia is characterized by the accumulation of remnants of chylomicrons and of very low-density lipoproteins. The onset occurs after childhood and usually requires an additional metabolic stressor. In women, onset is typically delayed until menopause. Clinical manifestations may vary from no physical signs to severe cutaneous and tendinous xanthomata, atherosclerosis of coronary and peripheral arteries, and pancreatitis when severe hypertriglyceridaemia is present. Rarely, mutations in apolipoprotein E are associated with lipoprotein glomerulopathy, a condition characterized by progressive proteinuria and renal failure with varying degrees of plasma remnant accumulation. Interestingly, predisposing genetic causes paradoxically result in lower than average cholesterol concentration for most affected persons, but severe dyslipidaemia develops in a minority of patients. The disorder stems from dysfunctional apolipoprotein E in which mutations result in impaired binding to low-density lipoprotein (LDL) receptors and/or heparin sulphate proteoglycans. Apolipoprotein E deficiency may cause a similar phenotype. Making a diagnosis of dysbetalipoproteinaemia aids in assessing cardiovascular risk correctly and allows for genetic counseling. However, the diagnostic work-up may present some challenges. Diagnosis of dysbetalipoproteinaemia should be considered in mixed hyperlipidaemias for which the apolipoprotein B concentration is relatively low in relation to the total cholesterol concentration or when there is significant disparity between the calculated LDL and directly measured LDL cholesterol concentrations. Genetic tests are informative in predicting the risk of developing the disease phenotype and are diagnostic only in the context of hyperlipidaemia. Specialised lipoprotein studies in reference laboratory centres can also assist in diagnosis. Fibrates and statins, or even combination treatment, may be required to control the dyslipidaemia.

Genome-wide linkage scan for plasma high density lipoprotein cholesterol, apolipoprotein A-1 and triglyceride variation among American Indian populations: the Strong Heart Family Study

BACKGROUND

Recent studies have identified chromosomal regions linked to variation in high density lipoprotein cholesterol (HDL-C), apolipoprotein A-1 (apo A-1) and triglyceride (TG), although results have been inconsistent and previous studies of American Indian populations are limited.

OBJECTIVE

In an attempt to localise quantitative trait loci (QTLs) influencing HDL-C, apo A-1 and TG, we conducted genome-wide linkage scans of subjects of the Strong Heart Family Study.

METHODS

We implemented analyses in 3484 men and women aged 18 years or older, at three study centres.

RESULTS

With adjustment for age, sex and centre, we detected a QTL influencing both HDL-C (logarithm of odds (LOD) = 4.4, genome-wide p = 0.001) and apo A-1 (LOD = 3.2, genome-wide p = 0.020) nearest marker D6S289 at 6p23 in the Arizona sample. Another QTL influencing apo A-1 was found nearest marker D9S287 at 9q22.2 (LOD = 3.0, genome-wide p = 0.033) in the North and South Dakotas. We detected a QTL influencing TG nearest marker D15S153 at 15q22.31 (LOD = 4.5 in the overall sample and LOD = 3.8 in the Dakotas sample, genome-wide p = 0.0044) and when additionally adjusted for waist, current smoking, current alcohol, current oestrogen, lipid treatment, impaired fasting glucose, and diabetes, nearest marker D10S217 at 10q26.2 (LOD = 3.7, genome-wide p = 0.0058) in the Arizona population.

CONCLUSIONS

The replication of QTLs in regions of the genome that harbour well known candidate genes suggest that chromosomes 6p, 9q and 15q warrant further investigation with fine mapping for causative polymorphisms in American Indians.

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.

APOA5 genetic variants are markers for classic hyperlipoproteinemia phenotypes and hypertriglyceridemia

BACKGROUND

Several known candidate gene variants are useful markers for diagnosing hyperlipoproteinemia. In an attempt to identify other useful variants, we evaluated the association of two common APOA5 single-nucleotide polymorphisms across the range of classic hyperlipoproteinemia phenotypes.

METHODS

We assessed plasma lipoprotein profiles and APOA5 S19W and -1131T>C genotypes in 678 adults from a single tertiary referral lipid clinic and in 373 normolipidemic controls matched for age and sex, all of European ancestry.

RESULTS

We observed significant stepwise relationships between APOA5 minor allele carrier frequencies and plasma triglyceride quartiles. The odds ratios for hyperlipoproteinemia types 2B, 3, 4 and 5 in APOA5 S19W carriers were 3.11 (95% CI 1.63-5.95), 4.76 (2.25-10.1), 2.89 (1.17-7.18) and 6.16 (3.66-10.3), respectively. For APOA5 -1131T>C carriers, the odds ratios for these hyperlipoproteinemia subtypes were 2.23 (95% CI 1.21-4.08), 3.18 (1.55-6.52), 3.95 (1.85-8.45) and 4.24 (2.64-6.81), respectively. The overall odds ratio for the presence of either allele in lipid clinic patients was 2.58 (95% CI 1.89-3.52).

CONCLUSIONS

A high proportion of patients with four classic hyperlipoproteinemia phenotypes are carriers of either the APOA5 S19W or -1131T>C variant or both. These two variants are robust genetic biomarkers of a range of clinical hyperlipoproteinemia phenotypes linked by hypertriglyceridemia.

Severe Hypercholesterolemia Associated with Decreased Hepatic Triglyceride Lipase Activity and Pseudohyponatremia in Patients after Allogeneic Stem Cell Transplantation

A 55-year-old woman with Ph-negative acute lymphoblastic leukemia in primary induction failure received allogeneic peripheral blood stem cell transplantation from her HLA-compatible sister. Pseudohyponatremia developed due to extreme hypercholesterolemia of 4091 mg/dL accompanied by lipoprotein X and lipoprotein Y. The hypercholesterolemia was caused by cholestasis due to chronic GVHD and ischemic cholangiopathy. In addition, we found that hepatic triglyceride lipase (HTGL) activity was severely decreased, which could be another novel factor causing extreme hypercholesterolemia after allogeneic transplantation. The total cholesterol has been gradually decreasing followed by the improvement of cholestasis with bezafibrate, ursodeoxycholic acid and prednisone treatments, and by a slight increase in HTGL-protein. To our knowledge, this is the first report to describe the association of decreased HTGL with extreme hypercholesterolemia after allogeneic transplantation.

Polymorphisms in the gene encoding lipoprotein lipase in men with low HDL-C and coronary heart disease: the Veterans Affairs HDL Intervention Trial

Our goal was to further define the role of LPL gene polymorphisms in coronary heart disease (CHD) risk. We determined the frequencies of three LPL polymorphisms (D9N, N291S, and S447X) in 899 men from the Veterans Affairs HDL Intervention Trial (VA-HIT), a study that examined the potential benefits of increasing HDL with gemfibrozil in men with established CHD and low high density lipoprotein cholesterol (HDL-C; < or =40 mg/dl), and compared them with those of men without CHD from the Framingham Offspring Study (FOS). In VA-HIT, genotype frequencies for LPL D9N, N291S, and S447X were 5.3, 4.5, and 13.0%, respectively. These values differed from those for men in FOS having an HDL-C of >40, who had corresponding values of 3.2% (P = 0.06), 1.5% (P < 0.01), and 18.2% (P < 0.01). On gemfibrozil, carriers of the LPL N9 allele in VA-HIT had lower levels of large LDL (-32%; P < 0.01) but higher levels of small, dense LDL (+59%; P < 0.003) than did noncarriers. Consequently, mean LDL particle diameter was smaller in LPL N9 carriers than in noncarriers (20.14 +/- 0.87 vs. 20.63 +/- 0.80 nm; P < 0.003). In men with low HDL-C and CHD: 1) the LPL N9 and S291 alleles are more frequent than in CHD-free men with normal HDL-C, whereas the X447 allele is less frequent, and 2) the LPL N9 allele is associated with the LDL subclass response to gemfibrozil.

Genetic study of common variants at the Apo E, Apo AI, Apo CIII, Apo B, lipoprotein lipase (LPL) and hepatic lipase (LIPC) genes and coronary artery disease (CAD): variation in LIPC gene associates with clinical outcomes in patients with established CAD

BACKGROUND

Current evidence demonstrates that positive family history and several alterations in lipid metabolism are all important risk factors for coronary artery disease (CAD). All lipid abnormalities themselves have genetic determinants. Thus, objective of this study was to determine whether 6 genetic variants potentially related to altered lipid metabolism were associated with CAD and with lipid abnormalities in an Italian population. These genetic variables were: apolipoprotein E (Apo E), Apo AI, Apo CIII, Apo B, lipoprotein lipase (LPL) and the hepatic lipase (LIPC) genes. Furthermore, an 8 years prospective analysis of clinical cardiovascular events was related to the various genetic markers.

METHODS

102 subjects with established coronary artery disease and 104 unrelated normal subjects were studied. CAD Patients were followed up for 8 years, and clinical CAD outcomes (a second coronary angioplasty (PTCA), myocardial infarction, coronary artery by-pass graft (CABG), cardiovascular deaths), available from 60 subjects, were related to the genetic variants by multiple regression analysis. Results. Of the six lipid loci studied (for a total of 11 polymorphisms) only the apolipoprotein E, Apo B and LIPC polymorphisms distinguished between case and controls. However, multivariate analysis accounting for clinical and metabolic predictors of CAD showed that only the ApoB Xba1 and ApoE4 polymorphism associated with CAD in this Italian population. When lipid parameters were related to genotypes, the ApoE, ApoB, and LIPC gene polymorphisms were associated to various markers of dyslipidaemia in the CAD patients, confirming previous reports. When the occurrence of a second cardiovascular event was related to genotypes, an independent role was observed for the LIPC gene T202T variant.

CONCLUSIONS

variation in LIPC (hepatic lipase) gene associates with clinical outcomes in Italian patients with established CAD. Further studies on the LIPC gene in CAD patients are warranted, in particular looking at the possible influences on clinical outcomes.

Bovine growth hormone-transgenic mice have major alterations in hepatic expression of metabolic genes

Transgenic mice overexpressing growth hormone (GH) have been extensively used to study the chronic effects of elevated serum levels of GH. GH is known to have many acute effects in the liver, but little is known about the chronic effects of GH overexpression on hepatic gene expression. Therefore, we used DNA microarray to compare gene expression in livers from bovine GH (bGH)-transgenic mice and littermates. Hepatic expression of peroxisome proliferator-activated receptor-alpha (PPARalpha) and genes involved in fatty acid activation, peroxisomal and mitochondrial beta-oxidation, and production of ketone bodies was decreased. In line with this expression profile, bGH-transgenic mice had a reduced ability to form ketone bodies in both the fed and fasted states. Although the bGH mice were hyperinsulinemic, the expression of sterol regulatory element-binding protein (SREBP)-1 and most lipogenic enzymes regulated by SREBP-1 was reduced, indicating that these mice are different from other insulin-resistant models with respect to expression of SREBP-1 and its downstream genes. This study also provides several candidate genes for the well-known association between elevated GH levels and cardiovascular disease, e.g., decreased expression of scavenger receptor class B type I, hepatic lipase, and serum paraoxonase and increased expression of serum amyloid A-3 protein. We conclude that bGH-transgenic mice display marked changes in hepatic genes coding for metabolic enzymes and suggest that GH directly or indirectly regulates many of these hepatic genes via decreased expression of PPARalpha and SREBP-1.

Lipoprotein lipase (LPL) gene variation and progression of carotid artery plaque

BACKGROUND AND PURPOSE

Coding single nucleotide polymorphisms (cSNPs) in the lipoprotein lipase (LPL) gene have been associated with lipoprotein phenotypes and vascular disease risk. We studied the association between LPL cSNPs and a novel noninvasive measure of disease, namely, cross-sectional carotid plaque area (CPA) on B-mode ultrasound.

METHODS

Four hundred fifty-two patients from an atherosclerosis prevention clinic had determinations of baseline and total CPA. Traditional atherosclerosis risk factors were recorded, and the LPL D9N, N291S, and S447X cSNPs were genotyped. Multiple regression analysis was used to identify determinants of CPA.

RESULTS

Minor allele frequencies for LPL D9N, N291S, and S447X were 2.8%, 0.9%, and 4.4%, respectively. There were no significant between-genotype differences in treated fasting lipids. The LPL D9N genotype was a significant predictor of both baseline CPA (P=0.008) and plaque progression from baseline to 1 year later (P=0.001). Heterozygotes for the N9 allele had higher mean baseline CPA and plaque progression than did LPL D9/D9 homozygotes.

CONCLUSIONS

LPL D9N genotype may be a determinant of atherosclerosis as estimated by static baseline CPA and by progression of CPA.

Single-nucleotide polymorphisms in the lipoprotein lipase gene associated with coronary heart disease in Chinese

Coronary heart disease is a complex disease reflecting the interaction of multiple genes with the environment (e.g. diet, life style). Lipoprotein lipase (LPL) plays an important role in lipid metabolism and the pathogenesis of coronary atherosclerosis. Recent associations between single-nucleotide polymorphisms in the LPL gene and heart disease have been reported, but little is known in Chinese. The LPL gene spans >26 kb, with an mRNA of 3549 bp. In the present study, we screened 5155 bp (565 bp of 5' flanking region, nine exons and donor- and acceptor-splice sites, and some intronic bases) in 160 Chinese patients with confirmed coronary heart disease and 150 age- and gender-matched controls. Thirteen of the sixteen single-nucleotide polymorphisms that we found have not been previously reported. In males, significant (P<0.05) differences between the coronary heart disease patients and controls were found for five single-nucleotide polymorphisms: -421G>A (5' flanking region); +13,577C>A (intron 2); +16,052G>A, R192Q (exon 5); +16,173C>G and +16,177T>C (intron 5). In females, significant differences between the patients with coronary heart disease and controls were found for only the -421G>A and +16,052G>A (R192Q) mutations. Among the coronary heart disease males, significant (P<0.05) associations were found between the low-HDL high-triglyceride (LHDL/HTG) phenotype and the non-LHDL/HTG trait for the 5' flanking-421G, the intron 2+13,577C, and the exon 5+16,052G mutations, with odds-ratios (ORs)[confidence intervals] of 3.90[1.12-13.66], 3.38[1.22-9.40], and 3.22[1.04-10.01], respectively; no corresponding associations were found in females. There were 69, 51, 57 and 41 unphased haplotype patterns in male coronary heart disease, male control, female coronary heart disease and female control groups, respectively; the computer program PM-Plus found the heterogeneity model by far the best fit (P<0.0001 in males, >0.01 in females). These data show that some single-nucleotide polymorphisms in the LPL gene among Chinese are associated with abnormal lipid and lipoprotein profiles and predisposition to coronary heart disease, a genetically heterogeneous complex disease, and that they are gender-specific.