Interaction effect of Serine447Stop variant of the lipoprotein lipase gene and C-514T variant of the hepatic lipase gene on serum triglyceride levels in young adults: the Bogalusa Heart Study

Decreased Plasma Level of Lipoprotein Lipase Predicted Verbal Disfluency in Chinese Type 2 Diabetes Mellitus Patients with Early Cognitive Deficits

BACKGROUND

Lipoprotein Lipase (LPL) is the rate-limiting enzyme catalyzing the hydrolysis of triglycerides and contributes to the amyloid-β formation, which shows promise as a pathological factor of cognitive decline in Type 2 Diabetes Mellitus (T2DM). This study aimed to investigate the pathogenetic roles of LPL and rs328 polymorphism in Mild Cognitive Impairment (MCI) in patients with T2DM.

METHODS

Chinese patients with T2DM were recruited and divided into two groups based on the Montreal Cognitive Assessment score. Demographic data were collected, LPL was measured and neuropsychological test results were examined.

RESULTS

Seventy-nine patients with diabetes and MCI had significantly decreased plasma LPL levels (p = 0.007) when compared with health-cognition controls (n = 91). Correlation analysis revealed that LPL was positively correlated with clock drawing test (r = 0.158, p = 0.043) and logical memory test (r = 0.162, p = 0.037), while lipoprotein a (r = -0.214, p = 0.006) was inversely associated with LPL. Logistic regression analysis further demonstrated that LPL concentration was an independent factor for diabetic MCI (p = 0.036). No significant differences were observed in the distributions of rs328 variants between patients with MCI and the controls. Moreover, no remarkable association was found among plasma LPL levels, cognitive performances, and lipid levels between the genotypic subgroups. The trail making test A was increased in the GC group when compared with the CC genotype in the control group.

CONCLUSION

Decreased plasma level of LPL could probably predict early cognitive deficits, especially verbal disfluency.

Gender-related relation between metabolic syndrome and S447X and HindIII polymorphisms of lipoprotein lipase gene in northern Iran

BACKGROUND

Metabolic syndrome is a cluster of conditions that increase risk of cardiovascular morbidity and mortality. Among genetic factors that contributed to incidence of metabolic syndrome, Polymorphisms of Lipoprotein lipase (LPL) are major candidates especially because of their effect on obesity and dyslipidemia. S447X (rs328) and Hind III (rs320) Polymorphisms of LPL gene have been reported to change LPL activity, resulting in altered triglyceride (TG) and high density lipoprotein Cholesterol (HDL-C) levels. This study investigates the effects of these gene polymorphisms on factors affecting metabolic syndrome in northern population of Iran.

METHODS

Studied population included 223 adults consisting 90 women and 133 men with body mass index (BMI) ≥ 30 kg/m² as obese subjects, and 156 healthy participants as a control group with BMI <25 that included 68 women and 88 men. All factors causing metabolic syndrome were evaluated. Also DNA was extracted from blood samples and HindIII and S447X LPL gene polymorphisms were screened by polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP).

CONCLUSIONS

The present study proves that some genotypes of S447X were associated with a reduced risk of developing low HDL-C only in men, while the protective effects of HindIII on hypertriglyceridemia were only seen in women [corrected]. The point is that this relation is affected by the weight profile of the participants. It can be concluded that there is a gender-related relation between the polymorphisms of LPL gene and the risk factors for incidence of metabolic syndrome in the northern population of Iran.

Knowledge-driven analysis identifies a gene-gene interaction affecting high-density lipoprotein cholesterol levels in multi-ethnic populations

Total cholesterol, low-density lipoprotein cholesterol, triglyceride, and high-density lipoprotein cholesterol (HDL-C) levels are among the most important risk factors for coronary artery disease. We tested for gene–gene interactions affecting the level of these four lipids based on prior knowledge of established genome-wide association study (GWAS) hits, protein–protein interactions, and pathway information. Using genotype data from 9,713 European Americans from the Atherosclerosis Risk in Communities (ARIC) study, we identified an interaction between HMGCR and a locus near LIPC in their effect on HDL-C levels (Bonferroni corrected P_c = 0.002). Using an adaptive locus-based validation procedure, we successfully validated this gene–gene interaction in the European American cohorts from the Framingham Heart Study (P_c = 0.002) and the Multi-Ethnic Study of Atherosclerosis (MESA; P_c = 0.006). The interaction between these two loci is also significant in the African American sample from ARIC (P_c = 0.004) and in the Hispanic American sample from MESA (P_c = 0.04). Both HMGCR and LIPC are involved in the metabolism of lipids, and genome-wide association studies have previously identified LIPC as associated with levels of HDL-C. However, the effect on HDL-C of the novel gene–gene interaction reported here is twice as pronounced as that predicted by the sum of the marginal effects of the two loci. In conclusion, based on a knowledge-driven analysis of epistasis, together with a new locus-based validation method, we successfully identified and validated an interaction affecting a complex trait in multi-ethnic populations.

Genome-wide association studies (GWAS) have identified many loci associated with complex human traits or diseases. However, the fraction of heritable variation explained by these loci is often relatively low. Gene–gene interactions might play a significant role in complex traits or diseases and are one of the many possible factors contributing to the missing heritability. However, to date only a few interactions have been found and validated in GWAS due to the limited power caused by the need for multiple-testing correction for the very large number of tests conducted. Here, we used three types of prior knowledge, known GWAS hits, protein–protein interactions, and pathway information, to guide our search for gene–gene interactions affecting four lipid levels. We identified an interaction between HMGCR and a locus near LIPC in their effect on high-density lipoprotein cholesterol (HDL-C) and another pair of loci that interact in their effect on low-density lipoprotein cholesterol (LDL-C). We validated the interaction on HDL-C in a number of independent multiple-ethnic populations, while the interaction underlying LDL-C did not validate. The prior knowledge-driven searching approach and a locus-based validation procedure show the potential for dissecting and validating gene–gene interactions in current and future GWAS.

Genetic screening of the lipoprotein lipase gene for mutations in Chinese subjects with or without hypertriglyceridemia

OBJECTIVE

To investigate the association between the mutations in lipoprotein lipase gene and hypertriglyceridemia (HTG).

METHODS

The lipoprotein lipase (LPL) gene was screened for mutations in 386 Chinese subjects with (108 cases in the HTG group) or without HTG (278 cases in the control group), by single-strand conformation polymorphism (SSCP) analysis and DNA sequencing.

RESULTS

One novel silent mutation L103L, one missense mutation P207L, three splicing mutations Int3/3'-ass/C(-6) --> T, and the common S447X polymorphism has been identified in the whole coding region and exon-intron junctions of the LPL gene were examined. Heterozygous P207L found in the HTG group was the first case reported in Asia and subsequently another P207L heterozygote was found in the proband's family, all of which suggested that P207L was one of the causes of familial combined hyperlipidemia, but was not so prevalent as that in French Canadian. Int3/3'-ass/C(-6) --> T was found in both groups in the present study although it was regarded as a pathogenic variant to HTG earlier on. Moreover about the beneficial polymorphism S447X, there was also some supportive evidence that the levels of triglycerides (TG) in S447X carriers were significantly lower than noncarriers in the subjects without HTG.

CONCLUSIONS

The association between the LPL variants and HTG is quite complicated and versatile, genotyping of LPL in a larger-scale screening should be necessary and justifiable.

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.

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.

Association of lipoprotein lipase S447X, apolipoprotein E exon 4, and apoC3 -455T>C polymorphisms on the susceptibility to diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. In DN patients, triglyceride (TG) level is elevated and lipoprotein lipase (LPL) activity, which hydrolyzes TG, is decreased. The LPL S447X and apolipoprotein E (APOE) exon 4 polymorphisms affect TG levels, and the APOC3 -455T>C polymorphism affects LPL activity. Our aim was to examine the association of these polymorphisms with nephropathy in type 2 diabetes. We examined these polymorphisms in a case-control study of type 2 diabetic patients including 374 with DN and 392 without DN. LPL 447X-containing genotypes (447X+) were significantly decreased in DN patients [18.6 vs 25.6%, odds ratio (OR) = 0.66, p = 0.02], as were APOE epsilon3/epsilon3 genotypes (64.8 vs 73.1%, OR = 0.68, p = 0.01). In addition, combinations of genotypes [APOE epsilon3/epsilon3 and LPL 447X+ (OR = 0.56), APOC3 CC and LPL 447X+ (OR = 0.31), APOE epsilon3/epsilon3 and APOC3 CC (OR = 0.61] were protective for DN compared with the most common combination of the respective polymorphisms. Our findings suggest the importance of interactions among lipid genes in modulating the risk of DN.

Genetic variants predisposing to cardiovascular disease

PURPOSE OF REVIEW

The goal of this review is to provide an update on the most recent and relevant findings in the area of genotype-phenotype associations as well as the relationships between genetic factors and cardiovascular disease risk markers and events. In addition, emphasis will be placed on the methodological problems associated with studying the genetics of complex disorders, specifically cardiovascular diseases.

RECENT FINDINGS

Genes associated with cardiovascular disease predisposition have been examined, including traditional cardiovascular disease candidate genes, such as ACE, AGT, eNOS, PON and MTHFR, new loci that have recently been added to the growing list of cardiovascular disease candidate genes (i.e. MEF2A, ALOX5, LTA, APOM, PDE4D), and genes that have been shown to be at the intersection of several age-related disorders through interaction with one another or with environmental factors (i.e. APOA5, APOE, PPARgamma, LPL and LIPC).

SUMMARY

During the last year, tremendous effort has been made in elucidating new genes associated with cardiovascular disease predisposition. For the most part, however, major breakthroughs have not been made, primarily due to the poor replication of results among studies, as a consequence of poor experimental design. Nevertheless, we have increased our understanding of the complexity of cardiovascular disease and the relevance of gene-environment interactions as the ultimate drivers of the individual predisposition to the disease. It is essential, therefore, that present and future genetic studies in this area take into consideration the inclusion of high-quality environmental data in the analytical process to test the clinical usefulness of a genetic marker as a risk predictor.

The effect of the APOE polymorphism on HDL-C concentrations depends on the cholesterol ester transfer protein gene variation in a Southern European population

BACKGROUND

Apolipoprotein E (ApoE) locus has consistently shown a significant association with low-density lipoprotein cholesterol (LDL-C). However, its impact on high-density lipoprotein cholesterol (HDL-C) has been highly controversial suggesting that it may be context-dependent. We examined the gene-gene interaction between the common ApoE and the CETP polymorphisms in determining HDL-C concentrations in men and women from the general population.

METHODS

550 unrelated Caucasian subjects were randomly selected from a Mediterranean Region in Spain. Plasma lipids, anthropometric, clinical and lifestyle variables were measured. Common ApoE and CETP-TaqIB polymorphisms were determined.

RESULTS

We have found a gene-gene interaction between and ApoE and the CETP loci in determining HDL-C concentrations. Thus, after adjustment for gender, age, body mass index, tobacco smoking, alcohol consumption, physical exercise and medication, carriers of the E4 allele had lower HDL-C concentrations [mean and (standard error): 40.1 (2.6) mg/dL] than E2 subjects [47.7 (3.2) mg/dL; p=0.019], and even lower than those of the E3 subjects [44.7 (1.4) mg/dL; p=0.042], only if they had the B1B1 genotype. However, mean HDL-C concentrations were higher among those with E4 allele carrying the B2 allele at the CETP gene locus [50.5 (2.3) mg/dL], and lower among E2 subjects carrying the B2 allele [45.5 (2.6) mg/dL]. This interaction was observed in both men and women. This gene-gene interaction remained statistically significant even after additional adjustment for triglycerides.

CONCLUSIONS

The effect of the ApoE polymorphism on HDL-C concentrations depends on the CETP polymorphism, explaining some of the controversial results previously reported for this polymorphism.

Higher order lipase gene association with plasma triglycerides

Lipoprotein lipase, HL, and endothelial lipase (EL) are proteoglycan-bound enzymes that regulate plasma lipoprotein levels through coordinated triglyceride (TG) lipase and phospholipase activity. We hypothesized that single nucleotide polymorphisms (SNPs) in lipase genes would have higher order impact on plasma lipoproteins beyond the influence of individual SNPs. In a sample of asymptomatic Caucasian subjects (n = 738), we used a two-stage approach, first identifying groups of subjects with similar multilocus lipase genotypes and then characterizing the relationships between genotype groups and plasma lipids. Using complementary methods, including a permutation test procedure and a mixed-effects modeling approach, we found a higher order interaction between four SNPs in three lipase genes (EL 2,237 3' untranslated region, EL Thr111Ile, HL -514C/T, and LPL HindIII) and plasma TG levels. Subjects who were heterozygous for all four lipase SNPs had significantly higher plasma TG levels beyond the effect of individual lipase SNPs and environmental factors, even after correcting for multiple comparisons. In conclusion, lipase genes had synergistic association with plasma TG beyond individual gene effects. Higher order multilocus genotype contributions to dyslipidemia and atherosclerotic cardiovascular disease need to be considered a priori because they may have an important effect even in the absence of significant main effects of the individual genes.

The -514 C->T hepatic lipase promoter region polymorphism and plasma lipids: a meta-analysis

Investigations of the -514 C-->T single nucleotide polymorphism (SNP) in the hepatic lipase (HL) gene promoter region (LIPC) have yielded contradictory results regarding its association with changes in plasma lipids. The current study is a meta-analysis of 25 publications on this SNP, comprising over 24,000 individuals, and its relationship with total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL), triglycerides, and HL activity. Significant decreases were observed in HL activity for both the CT and TT genotypes compared with the CC genotype [weighted mean difference (WMD), -5.83 mmol/liter.h (95% confidence interval, -8.48, -3.17) and -11.05 mmol/liter.h (95% confidence interval, -14.74, -7.36), respectively]. Moreover, significant increases in HDL were found; the CT to CC comparison showed an increase in WMD of 0.04 mmol/liter (95% confidence interval, 0.02, 0.05) mmol/liter, and the increase in the TT vs. CC difference was WMD of 0.09 mmol/liter (95% confidence interval, 0.07, 0.12). These changes appear to be stepwise, implying an allele dosage effect. All P values for these associations were less than 0.001. This meta-analysis demonstrates the importance of the -514C-->T SNP in determining HL activity and plasma HDL concentration and helps quantify the role that hepatic lipase plays in the metabolism of HDL.