G-250A substitution in promoter of hepatic lipase gene is associated with dyslipidemia and insulin resistance in healthy control subjects and in members of families with familial combined hyperlipidemia

The -514C>T polymorphism in the LIPC gene modifies type 2 diabetes risk through modulation of HDL-cholesterol levels in Mexicans

PURPOSE

Both type 2 diabetes (T2D) and low levels of high-density lipoprotein cholesterol (HDL-C) are very prevalent conditions among Mexicans. Genetic variants in the LIPC gene have been associated with both conditions. This study aimed to evaluate the association of the -514C < T (rs1800588) LIPC gene polymorphism with different metabolic traits, particularly the effects of this polymorphism on HDL-C plasma levels and T2D risk.

METHODS

Mediation analysis was used to assess the direct and indirect effects of the -514C>T LIPC gene variant on HDL-C levels, T2D risk, and body mass index (BMI), in 2105 Mexican mestizo participants. We also assessed the functional effect of the -514C>T LIPC variant on the promoter activity of a reporter gene in the HepG2 cell line.

RESULTS

Direct effects show that the -514C>T LIPC polymorphism is significantly associated with increased HDL-C plasma levels (β = 0.03; p < 0.001). The -514C>T variant resulted in an indirect protective effect on T2D risk through increasing HDL-C levels (β = - 0.03; p < 0.001). Marginal direct association between -514C>T and T2D was found (β = 0.08; p = 0.06). Variables directly influencing T2D status were European ethnicity (β = - 7.20; p < 0.001), age (β = 0.04; p < 0.001), gender (β = - 0.15; p = 0.017) and HDL-C (β = - 1.07; p < 0.001). In addition, we found that the -514C>T variant decreases the activity of LIPC promoter by 90% (p < 0.001).

CONCLUSIONS

The -514C>T polymorphism was not directly associated with T2D risk. HDL-C acts as a mediator between -514C>T LIPC gene variant and T2D risk in the Mexican population.

Progression of insulin resistance: A link between risk factors and the incidence of diabetes

AIMS

Insulin resistance (IR) changes over time during the development of type 2 diabetes. Some reports showed that obesity was associated with progression of IR. However, no study has explored if change of IR predicts incident diabetes, and no study has investigated other factors associated with the change.

METHODS

In this study, 1184 subjects without diabetes at baseline were enrolled in 2006-2016 with a median follow-up period of 4.5 years. Diabetes was diagnosed by oral glucose tolerance test and hemoglobin A1c, or if anti-diabetic agents were used. HOMA2-IR and ISI_0,120 were used to estimate IR.

RESULTS

The annual changes of HOMA2-IR(ΔHOMA2-IR/year) and ISI_0,120(ΔISI_0,120/year) were associated with BMI, waist circumference(WC), glucose, HbA1c, triglyceride and HDL-cholesterol. Subjects with pre-diabetes or metabolic syndrome were associated with a more rapid increase of IR. ΔHOMA2-IR/year and ΔISI_0,120/year were correlated with annual changes of BMI and WC. The hazard ratios for ΔHOMA2-IR/year and ΔISI_0,120/year to predict incident diabetes were 1.39 (95% CI 1.22-1.59, p < 0.001) and 0.13 (95% CI 0.09-0.19, p < 0.001) in adjusted models, respectively.

CONCLUSIONS

Change of IR can be used as a surrogate marker of incident diabetes. The progression of IR is an important pathophysiologic link between risk factors and the incidence of diabetes.

The cross-sectional study of hepatic lipase SNPs and plasma lipid levels

By the combination of meta-analysis, the data of the 1,000 Genomes Project Phase 3, and the promoter sequence of hepatic lipase (LIPC), we performed the cross-sectional study to explore the associations of four variants (rs1077835; rs1077834; rs1800588 [C-514T], and rs2070895 [G-250A]) in LIPC promoter with plasma lipid levels. Our results indicate that the first and the next three of the four SNPs are, respectively, reported to be associated with the decreased and increased HDL-c level. Meta-analysis of 87 studies with 101,988 participants indicates that HDL-c level in rs1800588 (C-514T) (pooled mean difference = 0.03, 95%CI (0.03, 0.04), p < .001) and rs2070895 (G-250A) (pooled mean difference = 0.07, 95%CI (0.05, 0.09), p < .001) is higher in allele T or A carriers. Similarly, LDL-c, TC, TG, and BMI levels are generally increased in T or A alleles carriers. We failed to conduct the meta-analysis of rs1077835 and rs1077834 due to the limited previous reports. Data from the 1,000 Genomes indicate that the allele frequencies of the four SNPs in total or subpopulations are almost equal to each other. The paired value r 2 and D' of the four SNPs are larger than 0.8, which indicate the linkage disequilibrium of the four variants. The analysis of LIPC promoter indicate that C-514T and G-250A are, respectively, located in transcriptional factor binding sites of USF1and Pbx1b, which may partly explain the effect of the two SNPs on the decreased LIPC activity in the alleles carriers and the corresponding increased plasma lipids hydrolyzed by LIPC. These results may help us to better understand the different effects of the four SNPs on the plasma lipid levels among subpopulations and offer clues for future clinical treatment of dyslipidemia-related diseases.

Association of LIPC -250G/A and -514C/T polymorphisms and hypertension: a systematic review and meta-analysis

Background

Hypertension is the most common chronic disease, and most important risk factor for cardiovascular disease. This meta-analysis aimed to explore the association between hepatic lipase gene (LIPC) gene -250G/A (rs2070895) and -514C/T (rs1800588) polymorphisms and the susceptibility to hypertension.

Methods

Published studies were searched using the PubMed, Embase and Cochrane Library databases. Newcastle-Ottawa Scale (NOS) was used to assess the quality of the included studies. Sensitivity analysis was performed using “leave one out” method. Egger’s test was used to evaluate the publication bias. The random effect model was used to calculate the pooled effect size if P < 0.05 or I² ≥ 50%; otherwise, the fixed effect model was selected.

Results

Four eligible studies, including 2599 participants, were enrolled in the included studies from 2007 to 2014. Quality evaluation revealed that each study had high NOS scores ranged from 5 to 7. The LIPC rs1800588 polymorphism was not found to be associated with the susceptibility to hypertension under all genetic models (T vs C, P = 0.38; CT vs CC, P = 0.46; TT vs CC, P = 0.38; TT vs CC + CT, P = 0.54; TT + CT vs CC, P = 0.34). Notably, the frequencies of the AA+GA genotypes of LIPC rs2070895 polymorphism were related to an increased risk of hypertension (AA+GA vs. GG, OR = 1.1954, 95% CI: 1.0001–1.4288, P = 0.05).

Conclusion

The LIPC rs2070895 polymorphism was found to be related to an increased risk of hypertension. However, LIPC rs1800588 polymorphism was not associated with the susceptibility to hypertension.

Association of APOB and LIPC polymorphisms with type 2 diabetes in Chinese Han population

BACKGROUND

Apolipoprotein B (APOB), and hepatic lipase (LIPC) genes have been shown to play a key role in lipid metabolism in type 2 diabetes (T2D). This study aimed to investigate the association of the three polymorphisms (rs679899 in APOB and rs6078 and rs6083 in LIPC) with T2D and related clinical quantitative traits.

METHODS

We conducted a case-control study in Chinese Han population, with a total of 929 T2D patients and 1044 healthy subjects in Chinese Han population. Polymorphisms were genotyped by MassARRAY Genotyping System.

RESULTS

The risk allele G of the polymorphism rs679899 was related to T2D (odds ratio (OR): 1.207, 95% confidence interval (CL): 1.006-1.448, P = 0.043) and the polymorphism rs679899 was associated with glutamyl transpeptidase (GGT) levels (P = 0.001). We also showed that the polymorphism rs6083 was associated with cholesterol (CHOL) levels (P = 0.012), triglyceride (TG) levels (P = 0.040), and low-density lipoprotein cholesterol (LDL) levels (P = 0.033). No significant difference in genotypic frequencies of rs6078 and rs6083 was observed between T2D patients and controls.

CONCLUSION

This study suggests that the APOB polymorphism rs679899 is associated with type 2 diabetes and GGT levels, while the LIPC polymorphism rs6083 may influence CHOL, TG, and LDL levels in Chinese Han population.

LIPC variants as genetic determinants of adiposity status, visceral adiposity indicators, and triglyceride-glucose (TyG) index-related parameters mediated by serum triglyceride levels

BACKGROUND

Visceral adiposity indicators and the product of triglyceride and fasting plasma glucose (TyG) index-related parameters are effective surrogate markers for insulin resistance (IR) and are predictors of metabolic syndrome and diabetes mellitus. However, their genetic determinants have not been previously reported. Pleiotropic associations of LIPC variants have been observed in lipid profiles and atherosclerotic cardiovascular diseases. We aimed to investigate LIPC polymorphisms as the genetic determinants of adiposity status, visceral adiposity indicators and TyG index-related parameters.

METHODS

A total of 592 participants from Taiwan were genotyped for three LIPC single nucleotide polymorphisms (SNPs).

RESULTS

The LIPC SNPs rs2043085 and rs1532085 were significantly associated with body mass index (BMI), waist circumference (WC), lipid accumulation product, visceral adiposity index, and TyG index-related parameters [including the TyG index, TyG with adiposity status (TyG-BMI), and TyG-WC index], whereas the rs1800588 SNP was only significantly associated with the TyG index. The associations became nonsignificant after further adjustment for serum TG levels. No significant association was observed between any the studied LIPC SNPs and IR status.

CONCLUSION

Our data revealed a pleiotropic association between the LIPC variants and visceral adiposity indicators and TyG index-related parameters, which are mediated by serum TG levels.

Dietary fat modulation of hepatic lipase variant -514 C/T for lipids: a crossover randomized dietary intervention trial in Caribbean Hispanics

The hepatic lipase (LIPC) locus is a well-established determinant of high-density lipoprotein cholesterol (HDL-C) concentrations, an association that is modified by dietary fat in observational studies. Dietary interventions are lacking. We investigated dietary modulation of LIPC rs1800588 (-514 C/T) for lipids and glucose using a randomized crossover design comparing a high-fat Western diet and a low-fat traditional Hispanic diet in individuals of Caribbean Hispanic descent (n = 42, 4 wk/phase). No significant gene-diet interactions were observed for HDL-C. However, differences in dietary response according to LIPC genotype were observed. In major allele carriers (CC/CT), HDL-C (mmol/l) was higher following the Western diet compared with the Hispanic diet: phase 1 (Western: 1.3 ± 0.03; Hispanic: 1.1 ± 0.04; P = 0.0004); phase 2 (Western: 1.4 ± 0.03; Hispanic: 1.2 ± 0.03; P = 0.0003). In contrast, HDL-C in TT individuals did not differ by diet. Only major allele carriers benefited from the higher-fat diet for HDL-C. Secondarily, we explored dietary fat quality and rs1800588 for HDL-C and triglycerides (TG) in a Boston Puerto Rican Health Study (BPRHS) subset matched for diabetes and obesity status (subset n = 384). In the BPRHS, saturated fat was unfavorably associated with HDL-C and TG in rs1800588 TT carriers. LIPC rs1800588 appears to modify plasma lipids in the context of dietary fat. This new evidence of genetic modulation of dietary responses may inform optimal and personalized dietary fat advice and reinforces the importance of studying genetic markers in diet and cardiometabolic health.

The rs2070895 (-250G/A) Single Nucleotide Polymorphism in Hepatic Lipase (HL) Gene and the Risk of Coronary Artery Disease in North Indian Population: A Case-Control Study

INTRODUCTION

Several Single Nucleotide Polymorphisms (SNPs) in lipid transport genes have been shown to be associated with Coronary Artery Disease (CAD). The Hepatic Lipase (HL)glycoprotein is a key component that catalyzes the hydrolysis of triglycerides and phospholipids in all major classes of lipoproteins.

AIM

We studied whether the HL gene-250G/A polymorphism affect blood lipid level and the CAD in a North Indian population.

MATERIALS AND METHODS

A total number of 477 subjects were enrolled in the study after approval of the Institutional Ethics Committee. Out of 477 subjects, 233 were with coronary artery disease as study group and 244 subjects without coronary artery disease as control group. All subjects recruited with matched ethnicity in age group of 40-70 years. Blood samples were collected in EDTA vials and genomic DNA was extracted from blood using the phenol-chloroform method. Lipid profile was estimated by using a commercially available kit. Polymorphisms in the HL (-250 G/A) gene were analysed by using restriction fragment length polymorphism-polymerase chain reaction (PCR-RFLP) method. The effect of this polymorphism on plasma lipids, lipoproteins and coronary artery disease was determined.

RESULTS

In Human Hepatic Lipase (LIPC)-250G/A genotype, the frequencies of GG, GA and AA genotype in CAD group was 80.69%, 15.45% and 3.86%, respectively; in the control group, the corresponding frequencies were 90.16%, 9.02% and 0.82%, respectively. A significant difference was found in the genotype (LIPC-250G/A) distribution between the two groups. Further logistic regression analysis indicated that the GA and AA genotypes in SNP-250G/A were significantly associated with CAD in all genetic models (In codominant model- GA vs. GG, OR=1.91, 95% CI=1. 09-3.37, p=0. 03 and AA vs. GG, OR= 5.26, 95% CI= 1.10-24.60, p=0.04; in dominant model- GA+AA vs. GG, OR=2.19, p=0.004 and in recessive model- AA vs. GG+GA, OR=5.26, p=0.04 whereas, A allele at nucleotide -250G/A in the LIPC gene had an association with increased risk of CAD (OR=2.33, p=<0.008).

CONCLUSION

Our findings indicated that the higher frequency of a dominant model (GA+AA) as well as mutant allele A of LIPC-250 G/A polymorphism is significantly associated with risk of CAD and the lipid profile can be used as a predictor of CAD.

Association between two common polymorphisms (single nucleotide polymorphism -250G/A and -514C/T) of the hepatic lipase gene and coronary artery disease in type 2 diabetic patients

BACKGROUND

Variations in the hepatic lipase (HL) gene are the potential candidate for coronary artery disease (CAD) especially in type 2 diabetes mellitus (T2DM) in diverse populations. We assessed the association of -514C/T and -250G/A polymorphisms in HL (LIPC) gene with CAD risk in Iranian population with type 2 diabetes.

MATERIALS AND METHODS

We evaluated 322 type 2 diabetic patients, 166 patients with normal angiograms as controls and 156 patients those identified with CAD undergoing their first coronary angiography as CAD cases. Genotyping of -514C/T and -250G/A polymorphisms in the promoter of the LIPC gene were studied by polymerase chain reaction (PCR)-restriction fragment length polymorphism technique.

RESULTS

Genotype distributions in CAD cases (73.7%, 20.5%, and 5.8% for -250G/A) and (62.2%, 32.7%, and 5.1% for -514C/T) were significantly different from those in controls (60.8%, 37.4%, and 1.8% for -250G/A) and (51.2%, 48.2%, and 0.6% for -514C/T). CAD cases had lower A-allele frequency than controls (0.131 vs. 0.196, P = 0.028). The odds ratio for the presence of -250 (GG + GA) genotype and A allele in CAD cases were 2.206 (95% confidence interval [CI] =1.33-3.65, P = 0.002) and 1.609 (95% CI = 1.051 -2.463, P = 0.029) respectively. Haplotype analysis demonstrated a significant association between especially LIPC double mutant (-250 A/-514 T) haplotype and presence of CAD.

CONCLUSION

Our findings indicated that -250 G/A polymorphism rather than -514 C/T polymorphism of LIPC gene is more associated with the increased risk of CAD particularly in women with T2DM.

Gender specific effect of LIPC C-514T polymorphism on obesity and relationship with plasma lipid levels in Chinese children

Hepatic lipase (LIPC) is a key rate-limiting enzyme in lipoprotein catabolism pathways involved in the development of obesity. The C-514T polymorphism in the promoter region is associated with decreased LIPC activity. We performed a case-controlled study (850 obese children and 2119 controls) and evaluated the association between LIPC C-514T polymorphism, obesity and plasma lipid profile in Chinese children and adolescents. Additionally, we conducted a meta-analysis of all results from published studies as well as our own data. A significant association between the polymorphism and obesity is observed in boys (P = 0.042), but not in girls. And we observed a significant relationship of the polymorphism with total cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) independent of obesity in boys. The T allele carriers have higher levels of low density lipoprotein cholesterol (LDL-C) in obese boys, and triglyceride (TG), TC and LDL-C in non-obese girls (all P < 0.05). In the meta-analysis, under dominant model the T allele increased body mass index (BMI) level in boys, while it decreased BMI in girls, and increased the levels of TC both in the overall and subgroups, TG and HDL-C in the overall and boys, and LDL-C in the overall (all P < 0.05). Our results suggest that the T allele might carry an increased risk of obesity in Chinese boys. The meta-analysis suggests that T allele acts as a risk allele for higher BMI levels in male childhood, while it is a protective allele in female childhood. And the polymorphism is associated with the levels of plasma lipids, which may be modulated by obesity and gender.

Association of hepatic lipase gene polymorphisms with hypertriglyceridemia and low high-density lipoprotein-cholesterol levels among South Indian subjects without diabetes

AIM

The aim of this study was to investigate the association of four variants of the hepatic lipase (HL [or LIPC]) gene with various lipid parameters among South Indian subjects with normal glucose tolerance (NGT).

SUBJECTS AND METHODS

In total, 747 NGT subjects were randomly selected from the Chennai Urban Rural Epidemiological Study (CURES). Serum triglycerides, serum cholesterol, and high-density lipoprotein cholesterol (HDL-C) were measured using a Hitachi-912 autoanalyzer (Roche Diagnostics GmbH, Mannheim, Germany). Genotyping of HL gene variants was done by the polymerase chain reaction-restriction fragment length polymorphism method, and 20% of samples were sequenced to validate the genotypes obtained. Haplotype analysis was also carried out.

RESULTS

The TT genotype of the rs1800588 C/T (C-480T) polymorphism was significantly associated with hypertriglyceridemia, with an adjusted odds ratio of 2.58 (95% confidence interval 1.38-4.85, P=0.003), whereas those with the CC genotype of the rs6074 A/C (Thr479Thr) had significantly lower HDL-C levels (41.3±9.8 mg/dL) compared with the AA genotype (43.6±10.2 mg/dL, P=0.02). Haplotype analysis showed the TGC haplotype was significantly associated with low HDL-C levels.

CONCLUSIONS

Among South Indian subjects without diabetes, the rs1800588 C/T (C-480T) and rs6074 C/A (Thr479Thr) variants of the HL gene are associated with hypertriglyceridemia and low HDL-C, respectively. The TGC haplotype was significantly associated with low HDL-C.

Association of the G-250A promoter polymorphism in the hepatic lipase gene with the risk of type 2 diabetes mellitus

OBJECTIVE

Variants in hepatic lipase (HL) gene which is a lipolytic enzyme involved in the metabolism of plasma lipoprotein and regulating lipid and lipoprotein metabolism are potential candidate genes for type 2 diabetes. Association of the polymorphisms in the promoter region of the HL gene (LIPC) to the plasma HDL-C concentration has been investigated. In this study, we investigated whether the G-250A polymorphism of LIPC is associated with type 2 diabetes in Chinese Han population.

SUBJECTS AND METHODS

A total of 130 patients with type 2 diabetes and 133 healthy subjects as control were randomly selected from January 2008 to January 2011 in endocrine wards of Zhengzhou People's Hospital. The G-250A polymorphisms were studied by polymerase chain reaction and restriction fragment length polymorphism. A logistic regression analysis was performed to determine the association between the rare allele and type 2 diabetes mellitus.

RESULTS

The frequency of the -250A allele was 0.297 in the T2DM group and 0.388 in the control group (P<0.05), with the difference remaining significant.

CONCLUSIONS

Patients who are carrying of the -250A allele in the promoter of the LIPC gene are susceptible to type 2 diabetes mellitus in Chinese Han population.

The genetics of familial combined hyperlipidaemia

Almost 40 years after the first description of familial combined hyperlipidaemia (FCHL) as a discrete entity, the genetic and metabolic basis of this prevalent disease has yet to be fully unveiled. In general, two strategies have been applied to elucidate its complex genetic background, the candidate-gene and the linkage approach, which have yielded an extensive list of genes associated with FCHL or its related traits, with a variable degree of scientific evidence. Some genes influence the FCHL phenotype in many pedigrees, whereas others are responsible for the affected state in only one kindred, thereby adding to the genetic and phenotypic heterogeneity of FCHL. This Review outlines the individual genes that have been described in FCHL and how these genes can be incorporated into the current concept of metabolic pathways resulting in FCHL: adipose tissue dysfunction, hepatic fat accumulation and overproduction, disturbed metabolism and delayed clearance of apolipoprotein-B-containing particles. Genes that affect metabolism and clearance of plasma lipoprotein particles have been most thoroughly studied. The adoption of new traits, in addition to the classic plasma lipid traits, could aid in the identification of new genes implicated in other pathways in FCHL. Moreover, systems genetic analysis, which integrates genetic polymorphisms with data on gene expression levels, lipidomics or metabolomics, will attribute functions to genetic variants in addition to revealing new genes.

Novel drugs in familial combined hyperlipidemia: lessons from type 2 diabetes mellitus

PURPOSE OF REVIEW

Familial combined hyperlipidemia (FCHL) and type 2 diabetes mellitus (T2DM) are prevalent entities that share many features of the metabolic syndrome. Recent findings suggest that FCHL and T2DM are less distinct than initially anticipated, which could offer new insights for their therapeutic approach.

RECENT FINDINGS

Genetic association studies have provided evidence for a common genetic background (upstream transcription factor 1, activating transcription factor 6, transcription factor 7-like 2 and hepatocyte nuclear factor 4 alpha) between FCHL and T2DM. The metabolic overlap can be illustrated by the presence of ectopic fat accumulation and insulin resistance (muscle, adipose tissue and liver). We have shown that FCHL patients are at increased risk to develop T2DM. This indicates that both entities are not static, but instead the former is able to migrate to the latter as insulin resistance progresses. Given these new findings, it can be anticipated that FCHL patients could also benefit from insulin-sensitizing therapy such as pioglitazone and metformin. Indeed, pilot studies have demonstrated that pioglitazone might be advantageous in FCHL patients.

SUMMARY

Recent studies suggest that FCHL patients have an increased risk to develop T2DM, which has important clinical implications. Further studies are necessary to evaluate whether FCHL patients can be protected from new-onset T2DM and premature cardiovascular events with insulin-sensitizing therapy.

WWOX gene is associated with HDL cholesterol and triglyceride levels

Background

Altered lipid profile, and in particular low HDL and high triglyceride (TG) plasma levels, are within the major determinants of cardiovascular diseases. The identification of quantitative trait loci (QTL) affecting these lipid levels is a relevant issue for predictive purposes. The WWOX gene has been recently associated with HDL levels. This gene is located at chromosome 16q23, a region previously linked to familial combined hyperlipidemia (FCHL) and HDL. Our objective is to perform a genetic association analysis at the WWOX gene region with HDL, TG and TG/HDL ratio.

Methods

A quantitative association analysis performed in 801 individuals selected from the Spanish general population.

Results

For HDL levels, two regions of intron 8 display clustering of positive signals (p < 0.05) but none of them was associated in the haplotypic analysis (0.07 ≤ p ≤ 0.165). For TG levels not only intron 8 but also a 27 kb region spanning from the promoter region to intron 4 are associated in this study. For the TG/HDL genetic association analysis, positive signals are coincident with those of the isolated traits. Interestingly, haplotypic analysis at the 5' region showed that variation in this region modified both HDL and TG levels, especially the latter (p = 0.003).

Conclusions

Our results suggest that WWOX is a QTL for both TG and HDL.

Association of LIPC -250G>A polymorphism and several environmental factors with serum lipid levels in the Guangxi Bai Ku Yao and Han populations

Background

The association between -250G>A polymorphism in the promoter region of the hepatic lipase gene (LIPC) and plasma high-density lipoprotein cholesterol (HDL-C) concentration is contradictory in diverse ethnics. Bai Ku Yao is an isolated subgroup of the Yao minority in China. This study was designed to detect the association of LIPC -250G>A (rs2070895) polymorphism and several environmental factors with serum lipid levels in the Guangxi Bai Ku Yao and Han populations.

Methods

A total of 778 subjects of Bai Ku Yao and 648 participants of Han Chinese aged 15-80 were randomly selected from our previous stratified randomized cluster samples. Genotyping of the LIPC -250G>A was performed by polymerse chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing.

Results

The levels of serum total cholesterol (TC), HDL-C, low-density lipoprotein cholesterol (LDL-C) and apolipoprotein (Apo) AI were lower in Bai Ku Yao than in Han (P < 0.01 for all). The frequencies of GG, GA and AA genotypes were 50.0%, 43.3% and 6.7% in Bai Ku Yao, and 35.7%, 50.6% and 13.7% in Han (P < 0.01); respectively. The frequencies of G and A alleles were 71.7% and 28.3% in Bai Ku Yao, and 61.0% and 39.0% in Han (P < 0.01). The levels of HDL-C and the ratio of ApoAI to ApoB in Bai Ku Yao were lower in GG genotype than in GA or AA genotype (P < 0.05-0.01). The levels of TC, HDL-C, LDL-C and ApoB in Han were lower in GG genotype than in GA or AA genotype (P < 0.05-0.01). The levels of HDL-C and the ratio of ApoAI to ApoB in Bai Ku Yao, and the levels of HDL-C, LDL-C and ApoB in Han were correlated with genotype and/or allele (P < 0.05 for all). Serum lipid parameters were also correlated with age, sex, alcohol consumption, cigarette smoking, blood pressure, body weight, and body mass index in both ethnic groups.

Conclusions

The differences in the serum lipid profiles between the two ethnic groups might partly result from different genotypic frequency of LIPC -250G>A or different LIPC-enviromental interactions.

Glucose increases hepatic lipase expression in HepG2 liver cells through upregulation of upstream stimulatory factors 1 and 2

AIMS/HYPOTHESIS

Elevated hepatic lipase (HL, also known as LIPC) expression is a key factor in the development of the atherogenic lipid profile in type 2 diabetes and insulin resistance. Recently, genetic screens revealed a possible association of type 2 diabetes and familial combined hyperlipidaemia with the USF1 gene. Therefore, we investigated the role of upstream stimulatory factors (USFs) in the regulation of HL.

METHODS

Levels of USF1, USF2 and HL were measured in HepG2 cells cultured in normal- or high-glucose medium (4.5 and 22.5 mmol/l, respectively) and in livers of streptozotocin-treated rats.

RESULTS

Nuclear extracts of cells cultured in high glucose contained 2.5 +/- 0.5-fold more USF1 and 1.4 +/- 0.2-fold more USF2 protein than cells cultured in normal glucose (mean +/- SD, n = 3). This coincided with higher DNA binding of nuclear proteins to the USF consensus DNA binding site. Secretion of HL (2.9 +/- 0.5-fold), abundance of HL mRNA (1.5 +/- 0.2-fold) and HL (-685/+13) promoter activity (1.8 +/- 0.3-fold) increased in parallel. In chromatin immunoprecipitation assays, the proximal HL promoter region was immunoprecipitated with anti-USF1 and anti-USF2 antibodies. Co-transfection with USF1 or USF2 cDNA stimulated HL promoter activity 6- to 16-fold. USF and glucose responsiveness were significantly reduced by removal of the -310E-box from the HL promoter. Silencing of the USF1 gene by RNA interference reduced glucose responsiveness of the HL (-685/+13) promoter region by 50%. The hyperglycaemia in streptozotocin-treated rats was associated with similar increases in USF abundance in rat liver nuclei, but not with increased binding of USF to the rat Hl promoter region.

CONCLUSIONS/INTERPRETATION

Glucose increases HL expression in HepG2 cells via elevation of USF1 and USF2. This mechanism may contribute to the development of the dyslipidaemia that is typical of type 2 diabetes.

Interactions between hepatic lipase and apolipoprotein E gene polymorphisms affect serum lipid profiles of healthy Canadian adults

The purpose of this study was to assess the individual and interactive effects between hepatic lipase (LIPC; C-514T, G-250A) and apolipoprotein E (APOE) (E2, E3, E4) gene polymorphisms on levels of plasma lipoprotein cholesterol and triglyceride among healthy, young, Canadian adults (n = 440). All subjects with at least one APOE2 allele had significantly lower low-density lipoprotein cholesterol, total cholesterol, and total cholesterol – high-density lipoprotein cholesterol ratio when compared with those with the APOE3 or APOE4 allele. There were significant differences in the LIPC allele and genotype frequencies between Caucasian (n = 207) and Asian (n = 211) individuals, but ethnicity did not contribute to the variations in circulating lipids. In addition, the lowest triglyceride levels (0.87 ± 0.27 mmol·mL–1) were found in all APOE2 individuals carrying LIPC-514-CC and LIPC-250-GG genotypes, whereas the highest triglyceride levels (1.29 ± 0.34 –1.32 ± 0.32 mmol·mL–1) were found in APOE2 individuals carrying the opposite genotypes, LIPC-514TT and LIPC-250AA. These observations, distinct from the anti-atherogenic effects of APOE2 through the lowering of low-density lipoprotein cholesterol and LIPC on high-density lipoprotein cholesterol, suggest that there is an interactive effect between APOE and LIPC genotypes on plasma triglyceride levels. These results provide the basis for further studies on establishing which genotype combinations would be the most protective against hypertriglyceridemia.

Thiazolidinediones and the preservation of beta-cell function, cellular proliferation and apoptosis

The thiazolidinediones (TZDs) or glitazones are pharmaceutical agents that have profound effects on energy expenditure and conservation. They also exert significant anti-inflammatory effects and influence cell proliferation and cell death. The drugs are primarily used in clinical practice in the treatment of patients with type 2 diabetes mellitus, a disorder of insulin resistance that occurs when the pancreatic beta-cells are unable to produce adequate amounts of insulin to maintain euglycaemia. Loss of pancreatic beta-cell function in type 2 diabetes is progressive and often precedes overt diabetes by 10 years or more, as was shown by the United Kingdom Prospective Diabetes Study. Any therapeutic or preventive approach that would limit or reverse loss of beta-cell function in diabetes would have profound effects on the morbidity associated with this widespread disease. Evidence suggesting a potential role of TZDs in preserving beta-cell function in type 2 diabetes as well as the ability of these agents to exert anti-inflammatory and proapoptotic anticancer effects, and their ability to promote cellular proliferation in various organs is reviewed.

The G-250A polymorphism in the hepatic lipase gene promoter is associated with changes in hepatic lipase activity and LDL cholesterol: The KANWU Study

BACKGROUND AND AIMS

Hepatic lipase (HL) catalyzes the hydrolysis of triglycerides and phospholipids from lipoproteins, and promotes the hepatic uptake of lipoproteins. A common G-250A polymorphism in the promoter of the hepatic lipase gene (LIPC) has been described. The aim was to study the effects of the G-250A polymorphism on HL activity, serum lipid profile and insulin sensitivity.

METHODS AND RESULTS

Altogether 151 healthy subjects (age 49+/-8 years, BMI 26.5+/-3.0kg/m(2)) were randomly assigned for 3 months to an isoenergetic diet containing either a high proportion of saturated fatty acids (SFA diet) or monounsaturated fatty acids (MUFA diet). Within groups there was a second random assignment to supplements with fish oil (3.6g n-3 FA/day) or placebo. At baseline, the A-250A genotype was associated with high serum LDL cholesterol concentration (P=0.030 among three genotypes). On the MUFA diet carriers of the A-250A genotype presented a greater decrease in LDL cholesterol concentration than subjects with other genotypes (P=0.007 among three genotypes). The rare -250A allele was related to low HL activity (P<0.001 among three genotypes). The diet did not affect the levels of HL activity among the genotypes.

CONCLUSION

The A-250A genotype of the LIPC gene was associated with high LDL cholesterol concentration, but the MUFA-enriched diet reduced serum LDL cholesterol concentration especially in subjects with the A-250A genotype.

Exercise, genetics and prevention of type 2 diabetes

Type 2 diabetes is one of the fastest growing public health problems in both developed and developing countries. Cardiovascular disease is the most prevalent complication of type 2 diabetes. In the past decade, the associations of physical activity, physical fitness and changes in the lifestyle with the risk of type 2 diabetes have been assessed by a number of prospective studies and clinical trials. A few studies have also evaluated the joint associations of physical activity, body mass index and glucose levels with the risk of type~2 diabetes. The results based on prospective studies and clinical trials have shown that moderate or high levels of physical activity or physical fitness and changes in the lifestyle (dietary modification and increase in physical activity) can prevent type 2 diabetes.

Promoter SNPs in G1/S checkpoint regulators and their impact on the susceptibility to childhood leukemia

Mutations leading to the alteration of cell-cycle checkpoint functions are a common feature of most cancers. Because of the highly regulated nature of the cell cycle, it seems likely that variation in gene dosage of key components due to functional regulatory polymorphisms could play an important role in cancer development. Here we provide evidence of the involvement of promoter single-nucleotide polymorphisms (pSNPs) in the cyclin-dependent–kinase inhibitor genes CDKN2A, CDKN2B, CDKN1A, and CDKN1B in the etiology of childhood pre-B acute lymphoblastic leukemia (ALL). A case-control study, conducted in 240 patients with pre-B ALL and 277 healthy controls, combined with a family-based analysis using 135 parental trios, all of French-Canadian origin, were used to evaluate single-site genotypic as well as multilocus haplotypic associations for a total of 10 pSNPs. Using both study designs, we showed evidence of association between variants CDKN2A −222A, CDKN2B −593A, and CDKN1B −1608A, and an increased risk of ALL. These findings suggest that variable expression levels of cell-cycle inhibitor genes CDKN2A, CDKN2B, and CDKN1B due to regulatory polymorphisms could indeed influence the risk of childhood pre-B ALL and contribute to carcinogenesis.

Upstream transcription factor 1 gene polymorphisms are associated with high antilipolytic insulin sensitivity and show gene–gene interactions

Upstream transcription factor 1 (USF1) regulates the expression of many genes involved in lipid and glucose metabolism, among them genes regulating lipolysis. USF1 specifically regulates the expression of the hormone-sensitive lipase gene (HSL) in adipocytes and the hepatic lipase gene (LIPC) in the liver, which was found to be involved in liver fat accumulation. The usf1s1 C > T and usf1s2 G > A single-nucleotide polymorphisms (SNPs) in USF1 are associated with increased in vitro catecholamine-induced lipolysis in adipocytes. We investigated first whether SNPs in USF1 affect the lipolysis-suppressing action of insulin in vivo, and second, whether they interact with the -60C > G SNP in HSL on lipolysis and the -514C > T SNP in LIPC on liver fat. The usf1s1 C > T and usf1s2 G > A SNPs, together with the SNPs in HSL and LIPC, were determined in 407 Caucasians. Lipolysis was estimated as a change in free fatty acid (FFA) levels from baseline to 2 h of a 75-g oral glucose tolerance test (OGTT). Fifty-four subjects had data from a euglycemic hyperinsulinemic clamp with calculation of antilipolytic insulin sensitivity. Subjects carrying the minor alleles (T of usf1s1 and A of usf1s2) had lower 2 h FFA (p = 0.01) and a larger decrease in FFA concentrations during the OGTT (p = 0.02). Antilipolytic insulin sensitivity was higher in these individuals (p = 0.03). No interaction of the usf1s1 C > T and usf1s2 G > A SNPs with the -60C > G SNP in HSL on antilipolytic insulin sensitivity was detected. Liver fat, measured by (1)H magnetic resonance spectroscopy, was elevated only in subjects who were both homozygous for the major alleles of usf1s1 and usf1s2 and carriers of the T allele of the -514C > T SNP in LIPC (p = 0.01). In conclusion, subjects carrying the T allele of SNP usf1s1 and the A allele of SNP usf1s2 have a higher antilipolytic insulin sensitivity. Moreover, both SNPs may interact with the -514C > T SNP in LIPC to determine liver fat.

Polymorphisms of interleukin-6, hepatic lipase and calpain-10 genes, and preeclampsia

OBJECTIVE

We determined whether single nucleotide polymorphisms (SNPs) in interleukin-6 (IL-6), hepatic lipase (HL) and calpain-10 (CAPN-10) genes contribute to susceptibility to develop preeclampsia.

STUDY DESIGN

The study involved 133 preeclamptic and 115 healthy pregnant women who were genotyped for the C-174G polymorphism in the IL-6 gene, the G-250A polymorphism in the HL gene and SNP 43 (G/A) in the CAPN-10 gene. The chi2-test was used to assess genotype and allele frequency differences between the preeclamptic and control groups.

RESULTS

No significant differences were detected in genotype and allele distributions of the C-174G polymorphism in the IL-6 gene, between the preeclampsia and control groups (p=0.98 and 0.85, respectively). With respect to the G-250A polymorphism in the HL gene, the genotype and allele distributions were similar in both groups (p=0.64 and 0.48, respectively). The genotype and allele distributions of SNP 43 in the CAPN-10 gene also showed no statistical differences in the preeclampsia and control groups (p=0.73 and 0.45, respectively).

CONCLUSIONS

The C-174G polymorphism in the IL-6 gene, the G-250A polymorphism in the HL gene and SNP 43 (G/A) in the CAPN-10 gene are unlikely to be major genetic factors predisposing Finnish women to preeclampsia.

Common hepatic lipase gene promoter variant predicts the degree of neointima formation after carotid endarterectomy: Impact of plaque composition and lipoprotein phenotype

BACKGROUND

The common -514 C-T promoter polymorphism of the hepatic lipase gene (LIPC) and the cholesteryl ester transfer protein (CETP) gene TaqIB polymorphism affect atherogenesis. We investigated the potential relationship between these polymorphisms and the maximum-intima-media thickness (M-IMT) after carotid endarterectomy.

METHODS

The LIPC and CETP genotypes were determined by PCR in 68 patients undergoing endarterectomy. Plaque specimens were analysed for cell composition by immunocytochemistry. Six month after surgery the M-IMT of the revascularized vessel was assessed by B-mode ultrasonography.

RESULTS

The CC carriers had denser LDL particles (p<0.0005), an abundance of macrophages (p<0.0005), fewer SMCs in the carotid plaque (p<0.0005), and higher prevalence of cerebrovascular events (72% versus 28%, p=0.002) compared to CT/TT carriers. After endarterectomy, CC carriers showed a lower M-IMT than the CT/TT group (1.36 mm versus 1.76 mm, p=0.04). No association between the CETP polymorphism and either carotid plaque cellular composition or M-IMT was observed. In a multivariate analysis, M-IMT was associated with plaque cell composition (macrophages, r=-0.39; SMC, r=0.44; p<0.005 for both) but not with pre-operative LDL-C, HDL-C, triglycerides, or LDL density.

CONCLUSIONS

The LIPC promoter -514 C-T polymorphism is associated with a significantly reduced development of neointima after surgery. This effect seems to be mediated by scarcity of SMC in the plaque of CC carriers who display an excess prevalence of cerebrovascular events prior endarterectomy but are at low risk for restenosis. The pre-operative lipid phenotype plays a marginal role in the neointima formation.

Detection and characterization of DNA variants in the promoter regions of hundreds of human disease candidate genes

Understanding genetic variation might reveal the cause of individual susceptibility to a variety of complex diseases such as asthma, diabetes, and cancer. Current efforts to identify functional DNA variants have essentially been oriented toward single nucleotide polymorphisms (SNPs) found in coding regions of candidate genes since they have direct impact on the structure and function of the affected proteins. Abnormal expression of finely regulated genes could also lead to disequilibria in different metabolic pathways and/or biological processes. Thus investigation of SNPs in the promoter regions (pSNPs) of genes should improve our knowledge of the etiology of complex diseases. Unfortunately, little is known about the nature and the prevalence of pSNPs. We have analyzed 197 genes targeting the promoter region, arbitrarily defined as a 2-kb genomic segment upstream of the transcription initiation site, by screening by dHPLC for the presence of SNPs in a worldwide panel of 40 individuals. As a result 1838 pSNPs were detected, 75% of which modify (by either gain or loss) putative binding sites of known transcription factors. We also examined the distribution of these pSNPs among features such as conserved regions, repeats, and dinucleotides as well as Gene Ontology terms. This report supports the functional relevance of several of the pSNPs investigated and suggests a putative impact on disease susceptibility.

Genetic variation in the hepatic lipase gene is associated with combined hyperlipidemia, plasma lipid concentrations, and lipid-lowering drug response

BACKGROUND

Combined hyperlipidemia (CHL) is a very frequent dyslipidemia, being lipid-lowering drugs often necessary in its management. Some genetic loci have been associated with CHL, and modulation of lipid-lowering treatment by genetic polymorphisms has been reported. We have investigated whether common polymorphisms in the hepatic lipase gene (LIPC) influence the baseline lipid concentration and the response to atorvastatin or bezafibrate in patients with CHL.

METHODS

Two genetic polymorphisms in LIPC (-514C-->T and +651A-->G) were determined by polymerase chain reaction and restriction analysis in 118 subjects of the ATOMIX (Atorvastatin in Mixed dyslipidemia) study who were randomized to treatment with either atorvastatin or bezafibrate and in 114 normolipidemic controls.

RESULTS

The -514T allele frequency was higher in the ATOMIX group (0.297) than in the control group (0.193) (P = .01). The -514T allele carriers in the control group showed higher high-density lipoprotein cholesterol (HDL-C) concentrations than the -514C homozygotes, 50.8 +/- 1.86 versus 45.9 +/- 1.40 mg/dL (P = .02). The +651G carriers in the ATOMIX group showed lower total cholesterol and low-density lipoprotein cholesterol than the +651A homozygotes, 274 +/- 3.72 and 181 +/- 3.50 mg/dL versus 289 +/- 4.0 and 194 +/- 3.76 mg/dL, respectively (P < .01). Homozygotes for the -514C allele on bezafibrate treatment had greater decrease in triglycerides and greater increase in HDL-C than -514T allele carriers after 12 months of bezafibrate treatment, -39.4% and +35.8% versus -25.5% and +20.4%, respectively (P = .080 and P = .007, respectively).

CONCLUSIONS

A higher frequency of the -514T allele of LIPC suggests a role of this locus in the pathogenesis of CHL. The -514T allele is associated with higher HDL-C concentration in normolipidemic population. The -514C-->T polymorphism modulates the lipid-lowering response to bezafibrate, with a better effect in homozygous CC subjects.

Hepatic lipase gene polymorphism, pre-pregnancy overweight status and risk of preeclampsia among Peruvian women

We examined the association between the hepatic lipase (LIPC) gene promoter polymorphism (-514C/T) and risk of preeclampsia among Peruvian women. We also evaluated whether this association is modified by maternal pre-pregnancy overweight status. Using a case control study design, 157 preeclampsia cases and 180 normotensive controls were enrolled in the study. Genotyping was conducted using PCR amplification, NlaIII enzyme digestion and gel electrophoresis. Logistic regression procedures were used to calculate adjusted odds ratios (ORs) and 95% confidence intervals (CI). After adjusting for confounding by maternal age, parity and pre-pregnancy body mass index (BMI), the relative risks of preeclampsia for women with LIPC -514CT and LIPC -514TT genotypes were 1.0 (95% CI 0.5-2.2) and 1.5 (95% CI 0.7-3.3) respectively, using women with LIPC -514CC genotype as a reference. Women who were both overweight and who had the LIPC -514TT genotype had a significant 3-fold increased risk of preeclampsia (Adj. OR:3.0 95% CI 1.3-6.8) as compared to those women who were not overweight and had the LIPC -514CC/CT genotype. In this study, we found that LIPC -514TT genotype and overweight status, when occurring together, were associated with a 3-fold increase in risk of preeclampsia among Peruvian women.

Functional promoter SNPs in cell cycle checkpoint genes

A substantial number of genes mutated in human cancers encode components of the cell cycle processes. As the G1/S transition in the cell cycle is a finely regulated biological process, we hypothesized that sequence variations in the promoter region of the related genes might indeed lead to abnormal expression, thus predisposing the individuals carrying these genetic variants to cancer. In this report, we screened the promoter regions of 16 cell cycle checkpoint genes for DNA variants and assessed the functional impact of these promoter region single nucleotide polymorphisms (pSNPs) by combining in silico analysis and in vitro functional assays. We identified 127 pSNPs including 90 with predicted impact on putative binding sites of known transcription factors. Eleven pSNPs were selected for electrophoresis mobility shift assays because of their association with predicted gains of binding sites, and nine pSNPs showed differential allelic shifts in at least one cell line tested. Following the subcloning of the promoter regions into a gene reporter system, we found that at least four promoter haplotypes associated with CCND1, E2F1, HDAC1 and RB1 significantly influenced transcriptional activity in an allele-specific manner. Although the biological significance of these observations still remains to be demonstrated, the expected variability of expression levels in key cell cycle components might influence individual's risk of cancer.

Interaction between insulin (VNTR) and hepatic lipase (LIPC−514C>T) variants on the response to an oral glucose tolerance test in the EARSII group of young healthy men

Insulin resistance is polygenic in origin, and can be observed at an early age. We have shown that variations in APOC3-482T>C and hepatic lipase (LIPC)-514C>T), individually (APOC3 alone) and interactively, modulate insulin and glucose levels after an OGTT in young healthy men participating in the European Atherosclerosis Research Study II (EARSII). Variation in the insulin gene (INS) variable number tandem repeat (VNTR) has been found to predispose to type 1 and type 2 diabetes. We have evaluated the HphI site 23 bp upstream of the INS gene (a surrogate marker for the VNTR) in EARSII (n=822), to determine if variation in INS contributes to insulin resistance. Carriers of the INS VNTR class III (HphI-) allele (frequency=0.29 (95%CI 0.27, 0.31)) had significantly higher 60-min insulin concentrations after the OGTT (P=0.014) and a marginally higher AUC insulin (P=0.07), compared to class I (HphI+) homozygotes. However, this effect on AUC insulin was modified by the level of physical activity, displaying significant gene:environment interaction (P=0.03). We tested for gene:gene interaction between the INS VNTR and both the LIPC-514C>T and APOC3-482T>C. While there was a significant interaction between INS VNTR and LIPC-514C>T on AUC glucose (P=0.013) and on AUC insulin (P=0.015), there was no interaction with APOC3-482T>C. Thus, despite a modest effect of the INS VNTR alone, the influence of this variant on insulin sensitivity was modified by gene:environment and gene:gene interactions, illustrating the biological complexity of insulin resistance.

The G-250A substitution in the promoter region of the hepatic lipase gene is associated with the conversion from impaired glucose tolerance to type 2 diabetes: the STOP-NIDDM trial

OBJECTIVES

Dyslipidaemia that includes high levels of triglycerides and low high-density lipoprotein cholesterol is a risk factor for type 2 diabetes. Hepatic lipase gene encoding a lipolytic enzyme participating in remodelling of plasma lipoproteins and formation of serum lipid profile is a promising candidate gene for type 2 diabetes. The purpose of the study was to investigate whether the G-250A promoter polymorphism of the LIPC gene predicts the conversion from impaired glucose tolerance (IGT) to type 2 diabetes.

SUBJECTS AND DESIGN

Study population comprised of subjects who participated in the STOP-NIDDM trial aiming to investigate the effect of acarbose compared with placebo on the prevention of type 2 diabetes in subjects with IGT.

RESULTS

Compared with subjects carrying the G-250G genotype, subjects with the A-250A genotype of the LIPC gene had a 2.35-fold [95% confidence interval (CI) 1.27-4.33, P = 0.006] higher risk of developing type 2 diabetes. Subjects in the placebo group and all women carrying the A-250A genotype had an especially high risk for the conversion to type 2 diabetes [odds ratio (OR) 2.74, 95% CI 1.14-6.61, P = 0.024 and OR 3.70, 95% CI 1.35-10.1, P = 0.011 respectively].

CONCLUSION

The G-250A promoter polymorphism of the LIPC gene is associated with an increased risk of development of type 2 diabetes in high-risk subjects with IGT. Therefore, genes regulating atherogenic dyslipidaemia are promising candidate genes for type 2 diabetes.

Hepatic lipase mRNA, protein, and plasma enzyme activity is increased in the insulin-resistant, fructose-fed Syrian golden hamster and is partially normalized by the insulin sensitizer rosiglitazone

Postheparin plasma hepatic lipase (HL) activity has been shown to correlate with features of the metabolic syndrome and type 2 diabetes in humans. We examined HL postheparin plasma enzyme activity, hepatocyte mRNA, and protein mass in the insulin-resistant, fructose-fed Syrian golden hamster, and the response of the insulin-sensitizing peroxisome proliferator-activated receptor-gamma agonist rosiglitazone. Male Syrian golden hamsters were treated for 5 weeks with 1) normal diet (DIET group), 2) 60% fructose diet (FRUC group), or 3) 60% fructose and rosiglitazone (20 mmol . kg(-1) . day(-1)) (FRUC+RSG group). Hepatocyte HL mRNA, protein mass, and postheparin plasma HL activity were increased in FRUC compared with DIET hamsters. FRUC+RSG hamsters had partial normalization of HL mRNA, mass, and activity. There was a shift in the size of LDL particles from large to small in FRUC animals and a shift back to large LDL size in FRUC+RSG. This is the first demonstration that HL hepatocyte mRNA, mass, and plasma enzymatic activity increase concomitantly with induction of an insulin-resistant state and can be partially normalized by treatment with an insulin sensitizer. The increase in HL in insulin-resistant states may play an important role in the typical dyslipidemia of these conditions, and reduction of HL could explain some of the beneficial effects of insulin sensitizers on the plasma lipid profile.

Dietary fat interacts with the -514C>T polymorphism in the hepatic lipase gene promoter on plasma lipid profiles in a multiethnic Asian population: the 1998 Singapore National Health Survey

We have previously reported an interaction between -514C>T polymorphism at the hepatic lipase (HL) gene and dietary fat on high-density lipoprotein-cholesterol (HDL-C) metabolism in a representative sample of white subjects participating in the Framingham Heart Study. Replication of these findings in other populations will provide proof for the relevance and consistency of this marker as a tool for risk assessment and more personalized cardiovascular disease prevention. Therefore, we examined this gene-nutrient interaction in a representative sample of Singaporeans (1324 Chinese, 471 Malays and 375 Asian Indians) whose dietary fat intake was recorded by a validated questionnaire. When no stratification by fat intake was considered, the T allele was associated with higher plasma HDL-C concentrations (P = 0.001), higher triglyceride (TG) concentrations (P = 0.001) and higher HDL-C/TG ratios (P = 0.041). We found a highly significant interaction (P = 0.001) between polymorphism and fat intake in determining TG concentration and the HDL-C/TG ratio (P = 0.001) in the overall sample even after adjustment for potential confounders. Thus, TT subjects showed higher TG concentrations only when fat intake supplied >30% of total energy. This interaction was also found when fat intake was considered as continuous (P = 0.035). Moreover, in the upper tertile of fat intake, TT subjects had 45% more TG than CC individuals (P < 0.01). For HDL-C concentration, the gene-diet interaction was significant (P = 0.015) only in subjects of Indian origin. In conclusion, our results indicate that there are differences in the association of -514C>T polymorphism with plasma lipids according to dietary intake and ethnic background. Specifically, the TT genotype is associated with a more atherogenic lipid profile when subjects consume diets with a fat content > 30%.

Hepatic lipase mutation may reduce vascular disease prevalence in hemodialysis patients with high CETP levels

BACKGROUND

Uremic dyslipidemia characterized by reduced high-density lipoprotein (HDL) cholesterol levels is one of the major contributors to the high incidence of cardiovascular disease in hemodialysis patients. Hepatic lipase (HL), together with cholesteryl ester transfer protein (CETP), may not only promote reverse cholesterol transport but also enhance production of small, dense, more atherogenic low-density lipoprotein (LDL). A common C-514T mutation of the promoter region of the HL gene reportedly increases HDL cholesterol levels. However, whether the HL mutation is antiatherogenic or proatherogenic has remained unknown in uremic patients and the general population.

METHODS

We investigated the influence of the mutation and its interaction with CETP on HDL cholesterol levels and the apparent atherosclerotic complications in 183 hemodialysis patients aged over 30 years who had received no antilipemic drugs.

RESULTS

In patients with CETP levels > or =2.2 microg/mL [high CETP (HCT) group, N = 97], subjects with the TT genotype had a significantly higher level of HDL cholesterol than those without TT genotype (56.8 +/- 15.9 mg/dL vs. 45.7 +/- 13.4 mg/dL, P < 0.001), but not in patients with CETP levels <2.2 microg/mL [low CETP (LCT) group]. Multiple linear regression analysis showed that the TT genotype was a major independent positive determinant for HDL cholesterol levels in the HCT not LCT group. Among the HCT group patients, subjects with the TT genotype (N = 25) had a tendency toward lower prevalence of vascular disease than those without TT genotype (N = 72) (4.0% vs. 22.2%, P < 0.07). In this subgroup, TT genotype had an independent odds ratio of 0.041 (95% CI 0.002 to 0.75, P < 0.05) after adjusting for other risk factors.

CONCLUSION

The TT genotype of HL mutation may serve as a protective factor against vascular disease by increasing HDL cholesterol levels in hemodialysis patients with higher CETP levels.

The G-250A promoter polymorphism of the hepatic lipase gene predicts the conversion from impaired glucose tolerance to type 2 diabetes mellitus: the Finnish Diabetes Prevention Study

In population-based studies, dyslipidemia related to insulin resistance (high triglyceride level and low high-density lipoprotein cholesterol level) is a risk factor for type 2 diabetes. Therefore, variants in genes regulating lipid and lipoprotein metabolism are potential candidate genes for diabetes. We investigated whether the G-250A polymorphism of the hepatic lipase gene (LIPC) predicts the conversion from impaired glucose tolerance (IGT) to type 2 diabetes in the Finnish Diabetes Prevention Study. This study randomized subjects to either the intervention group (lifestyle modification aimed at weight loss, such as changes in diet and increased physical exercise) or the control group. Genotyping at position -250 of the LIPC gene was performed with PCR amplification, DraI enzyme digestion, and gel electrophoresis in 490 subjects with IGT whose DNA was available. In the entire study population, the conversion rate to type 2 diabetes was 17.8% among subjects with the G-250G genotype and 10.7% among subjects with the -250A allele (P = 0.032). In univariate analysis, the odds ratio for the G-250G genotype to predict the conversion from IGT to type 2 diabetes was 1.80 (95% confidence interval, 1.05-3.10; P = 0.034). In multivariate logistic regression analysis, the G-250G genotype predicted the conversion to diabetes independently of the study group (control or intervention), gender, weight, waist circumference at baseline, and change in weight and waist circumference. In the intervention group, 13.0% of subjects with the G-250G genotype and 1.0% of the subjects with the -250A allele converted to diabetes (P = 0.001). We conclude that the G-250G genotype of the LIPC gene is a risk factor for type 2 diabetes. Therefore, genes regulating lipid and lipoprotein metabolism may be potential candidate genes for type 2 diabetes.

Association between −250G/A polymorphism of the hepatic lipase gene promoter and coronary artery disease and HDL-C levels in a Southern Brazilian population

Hepatic lipase (HL) is a glycoprotein that plays a major role in remodeling high-density lipoprotein (HDL). The effect of the -250G/A promoter polymorphism on coronary artery disease (CAD) and lipid levels was studied in 231 male CAD patients and in a population-based sample of men and women (n = 514). A sample of 140 men was chosen among those included in the population-based sample as controls for the CAD sample. In the total group of CAD patients, the frequency of the -250A allele was somewhat lower (25% in CAD patients and 32% in controls; p = 0.06), but when the control samples were compared only with the CAD(+) sample (more than 60% of luminal stenosis in at least one coronary artery or major branch segment) the -250A allele was significantly less frequent (23% in the patients vs 32% in controls; p = 0.02). A multiple logistic regression analysis showed that this association was independent of classical CAD risk factors [odds ratio (OR) = 1.79, p = 0.025]. Using multiple linear regression analyses, it has been shown that this polymorphism was a significant factor affecting HDL-C levels in men from the population-based sample (p = 0.001), an interaction between -250G/A variant and wine consumption was also detected (p = 0.001). Thus, our results show that the -250G/A polymorphism in the HL gene is associated with significant variations in HDL-C levels and CAD risk in males.

Gene variants, insulin resistance, and dyslipidaemia

PURPOSE OF REVIEW

Both insulin resistance and dyslipidaemia are determined by genetic and environmental factors. Depending on their expression and their function, gene variants (mutations, polymorphisms) can primarily regulate either insulin action or dyslipidaemia. The purpose of this review is to give some examples from recent studies on gene variants regulating primarily insulin signalling or lipoprotein metabolism.

RECENT FINDINGS

Common polymorphisms in the PC-1, insulin receptor substrate 1 and 2, and PPAR-gamma 2 genes have been linked to insulin resistance and dyslipidaemia, although the results have not been consistent. However, the Pro12Pro genotype of the PPAR-gamma 2 gene has been consistently associated with insulin resistance and the risk of type 2 diabetes. Promoter polymorphisms in the hepatic lipase gene, the 54Thr allele of the fatty acid binding protein 2 gene, and genes regulating LDL particle size have been associated with lipid metabolism, but on the other hand their association with insulin resistance is not consistent.

SUMMARY

Although results have not always been consistent, gene variants affecting primary insulin action or dyslipidaemia, and particularly their interaction with the environment, are important modulators of glucose and lipoprotein metabolism.

Rat model of familial combined hyperlipidemia as a result of comparative mapping

Total genome scan was carried out in 266 F2intercrosses from the Prague hypertriglyceridemic (HTG) rat that shares several clinical characteristics with human metabolic syndrome. Two loci for plasma triglycerides (TG) were localized on chromosome 2 (Chr 2) (LOD 4.4, 3.2). The first locus overlapped with the rat syntenic region of the human locus for the metabolic syndrome and for small, dense LDL, while the second overlapped with the syntenic region of another locus for small, dense LDL in humans by the comparative mapping approach. Loci for TG on rat Chr 13 (LOD 3.3) and Chr 1 (LOD 2.7) overlapped with the syntenic region of loci for human familial combined hyperlipidemia (FCHL) in Finnish and Dutch populations, respectively. The concordances of loci for TG localized in this study with previously reported loci for FCHL and its related phenotypes are underlying the generalized importance of these loci in dyslipidemia. These data suggest the close relationship between dyslipidemia in HTG rats and human FCHL, establishing a novel animal model for exploration of pathophysiology and therapy based on genomic determinants.

Increased circulating malondialdehyde-modified LDL in the patients with familial combined hyperlipidemia and its relation with the hepatic lipase activity

Familial combined hyperlipidemia (FCHL) is characterized by elevated levels of serum total cholesterol (TC), triglyceride (TG), or both. The increased incidence of coronary artery diseases (CAD) in the patients with FCHL is believed to be caused by circulating atherogenic lipoproteins associated with the complex phenotype. Recent establishment of sensitive detection system for malondialdehyde-modified (MDA)-LDL, which is one of oxidized lipoproteins, showed its increased circulating level in the patients with CAD. In order to know the atherogenic lipoproteins resulted from the dyslipidemia observed in FCHL, we measured the serum MDA-LDL level in the patients. The circulating MDA-LDL level and the ratio of MDA-LDL and LDL-C in FCHL were significantly higher (P<0.05) than those in control, which are adjusted about the age, serum TC, LDL-C and HDL-C levels, respectively. Furthermore, the circulating MDA-LDL level and the ratio of MDA-LDL and LDL-C were negatively correlated (R=-0.635, P<0.01 and R=-0.702, P<0.01, respectively) with hepatic lipase (HL) activity in FCHL. The serum MDA-LDL level and the ratio of MDA-LDL and LDL-C were in the subjects with T/T genotypes in the HL C-514T polymorphism were significantly increased compared to those with C/C genotype, respectively. The subjects with T/T genotype showed the activities to 65 and 79% of those in the subjects with C/C genotype in male and female, respectively. The intima-media thickness (IMT) of carotid artery was significantly higher (P<0.05) in the subjects with T/T genotype than those with C/C genotype in male. These findings indicate that the circulating MDA-LDL level is possibly contributing the atherogenic process in FCHL, and the common HL polymorphism might be a determinant of the serum level of oxidized LDL in the patients with FCHL.

Genome-wide scan for quantitative trait loci influencing LDL size and plasma triglyceride in familial hypertriglyceridemia

Small, dense LDLs and hypertriglyceridemia, two highly correlated and genetically influenced risk factors, are known to predict for risk of coronary heart disease. The objective of this study was to perform a whole-genome scan for linkage to LDL size and triglyceride (TG) levels in 26 kindreds with familial hypertriglyceridemia (FHTG). LDL size was estimated using gradient gel electrophoresis, and genotyping was performed for 355 autosomal markers with an average heterozygosity of 76% and an average spacing of 10.2 centimorgans (cMs). Using variance components linkage analysis, one possible linkage was found for LDL size [logarithm of odds (LOD) = 2.1] on chromosome 6, peak at 140 cM distal to marker F13A1 (closest marker D6S2436). With adjustment for TG and/or HDL cholesterol, the LOD scores were reduced, but remained in exactly the same location. For TG, LOD scores of 2.56 and 2.44 were observed at two locations on chromosome 15, with peaks at 29 and 61 cM distal to marker D15S822 (closest markers D15S643 and D15S211, respectively). These peaks were retained with adjustment for LDL size and/or HDL cholesterol. These findings, if confirmed, suggest that LDL particle size and plasma TG levels could be caused by two different genetic loci in FHTG.

Determinants of low HDL levels in familial combined hyperlipidemia

In familial combined hyperlipidemia (FCHL), affected family members frequently have reduced levels of HDL cholesterol, in addition to elevated levels of total cholesterol and/or triglycerides (TGs). In the present study, we focused on those determinants that are important regulators of HDL cholesterol levels in FCHL, and measured postheparin plasma activities of hepatic lipase (HL), lipoprotein lipase, cholesterol ester transfer protein, and phospholipid transfer protein (PLTP) in 228 subjects from 49 FCHL families. In affected family members (n = 88), the levels of HDL cholesterol, HDL2 cholesterol, HDL3 cholesterol, and apolipoprotein A-I were lower than in unaffected family members (n = 88) or spouses (n = 52). The main change was the reduction of HDL2 cholesterol by 25.4% in affected family members (P < 0.001 vs. unaffected family members; P = 0.003 vs. spouses). Affected family members had higher HL activity than unaffected family members (P = 0.001) or spouses (P = 0.013). PLTP activity was higher in affected than unaffected family members (P = 0.025). In univariate correlation analysis, a strong negative correlation was observed between HL activity and HDL2 cholesterol (r = -0.339, P < 0.001). Multivariate regression analysis demonstrated that gender, HL activity, TG, and body mass index have independent contributions to HDL2 cholesterol levels. We suggest that in FCHL, TG enrichment of HDL particles and enhanced HL activity lead to the reduction of HDL cholesterol and HDL2 cholesterol.

Hepatic lipase: a marker for cardiovascular disease risk and response to therapy

PURPOSE OF REVIEW

Hepatic lipase plays a key role in the metabolism of pro-atherogenic and anti-atherogenic lipoproteins affecting their plasma level as well as their physico-chemical properties. However, controversial evidence exists concerning whether hepatic lipase is pro or anti-atherogenic. The goal of this review is to summarize recent evidence that connects the enzyme to cardiovascular disease. The potential impact of genetic determinants of hepatic lipase activity in modulating both the development of coronary and carotid atherosclerosis will be discussed based on hepatic lipase proposed roles in lipoprotein metabolism.

RECENT FINDINGS

Twenty to 30% of individual variation of hepatic lipase activity is accounted for by the presence of a common polymorphism in the promoter region (-514 C to T) of the hepatic lipase gene (LIPC). This polymorphism, via its impact on hepatic lipase synthesis and activity, appears to contribute to (1) individual susceptibility to cardiovascular disease: the presence of the T allele (low hepatic lipase activity) may carry a marginally increased risk of atherosclerosis; (2) carotid plaque composition and individual susceptibility to cerebrovascular events: the presence of the C allele (high hepatic lipase activity) is associated with increased carotid intima-media thickness and abundance of macrophages in the carotid plaque (unstable plaque); and (3) response of cardiovascular disease patients to lipid-lowering therapy: patients with the CC genotype have the greatest clinical benefit from intensive lipid-lowering therapy.

SUMMARY

Convincing evidence shows that hepatic lipase plays a key role in remnant lipoprotein catabolism as well as in remodeling of LDL and HDL particles. The anti or pro-atherogenic role of hepatic lipase is likely to be modulated by the concurrent presence of other lipid abnormalities (i.e. increased LDL cholesterol levels) as well as by the genetic regulation of other enzymes involved in lipoprotein metabolism. Characterization of patients by their LIPC genotype will contribute to a better definition of individual risk of coronary and cerebrovascular events, specifically in patients with qualitative (small, atherogenic LDL and low HDL2 cholesterol) rather than quantitative lipid abnormalities for whom the routine lipid profile may underestimate the risk of coronary and cerebrovascular disease.

Visceral obesity attenuates the effect of the hepatic lipase -514C>T polymorphism on plasma HDL-cholesterol levels in French-Canadian men

The dyslipidemic state of visceral obesity is characterized by increased plasma triglyceride (TG) levels, low HDL-cholesterol concentrations and alterations in LDL composition and concentration. A functional, non-coding -514C>T single nucleotide polymorphism (SNP) of the hepatic lipase gene (LIPC) has been related to variation in HDL-cholesterol concentrations.

OBJECTIVES

To investigate the hypotheses that the LIPC -514C>T polymorphism may be associated with a deteriorated lipoprotein-lipid profile and that environmental factor, such as abdominal obesity, alters this association.

METHODS

A total of 235 French-Canadian men from the greater Quebec City area were assigned into three groups on the basis of their LIPC -514C>T SNP, including 149 CC homozygotes, 75 CT heterozygotes, and 11 TT homozygotes.

RESULTS

In the present study, the highest values of BMI, waist circumference, and accumulation of visceral adipose tissue (VAT) were observed among TT homozygotes (p<0.05). After adjustment for age and BMI, TT homozygotes still showed higher plasma apolipoprotein (apo) AI and HDL-TG concentrations than the two other groups (p<0.05). When the two genotype groups (CC vs CT/TT) were further divided on the basis of VAT accumulation using a cut-off point of 130 cm(2) (high vs low) it appears that irrespective of the genotype subjects with low VAT had higher HDL(2)-cholesterol concentrations (p<0.0001). However, lean carriers of the T allele had higher plasma HDL(2)-cholesterol levels than lean CC homozygotes. The beneficial effect of the T allele on plasma HDL(2)-cholesterol levels was abolished in the presence of visceral obesity (VAT>130 cm(2)).

CONCLUSION

In summary, the presence of visceral obesity attenuates the impact of the LIPC -514C>T polymorphism on plasma HDL(2)-cholesterol levels.

Overexpression of apoC-I in apoE-null mice: severe hypertriglyceridemia due to inhibition of hepatic lipase

Apolipoprotein C-I (apoC-I) has been proposed to act primarily via interference with apoE-mediated lipoprotein uptake. To define actions of apoC-I that are independent of apoE, we crossed a moderately overexpressing human apoC-I transgenic, which possesses a minimal phenotype in the WT background, with the apoE-null mouse. Surprisingly, apoE-null/C-I mice showed much more severe hyperlipidemia than apoE-null littermates in both the fasting and non-fasting states, with an almost doubling of cholesterol, primarily in IDL+LDL, and a marked increase in triglycerides; 3-fold in females to 260 +/- 80 mg/dl and 14-fold in males to 1409 +/- 594 mg/dl. HDL lipids were not significantly altered but HDL were apoC-I-enriched and apoA-II-depleted. Production rates of VLDL triglyceride were unchanged as was the clearance of post-lipolysis remnant particles. Plasma post-heparin hepatic lipase and lipoprotein lipase levels were undiminished as was the in vitro hydrolysis of apoC-I transgenic VLDL. However, HDL from apoC-I transgenic mice had a marked inhibitory effect on hepatic lipase activity, as did purified apoC-I. LPL activity was minimally affected. Atherosclerosis assay revealed significantly increased atherosclerosis in apoE-null/C-I mice assessed via the en face assay. Inhibition of hepatic lipase may be an important mechanism of the decrease in lipoprotein clearance mediated by apoC-I.

A novel allele in the promoter of the hepatic lipase is associated with increased concentration of HDL-C and decreased promoter activity

Hepatic lipase (HL) is a lipolytic enzyme involved in the metabolism of plasma lipoproteins, especially HDLs. Association of the polymorphisms in the promoter region of the LIPC gene to post-heparin plasma HL activity and the plasma HDL-C concentration has been investigated thoroughly, but to date little is known about this in the Chinese. In the present study, we analyzed the polymorphisms in the promoter region of LIPC gene in Chinese patients with coronary artery disease (CAD) using denaturing high performance liquid chromatography (DHPLC) and DNA sequencing. As the result, a novel single nucleotide polymorphism -586T-to-C was identified and no linkage of this variant with other polymorphisms in the promoter was found. Compared with the nonsymptomatic control subjects, excess of carriers of the -586T/C substitution were detected in the CAD patients (43% vs. 31%, chi(2) = 4.597, degree of freedom = 2, P = 0.032). The -586C allele carriers in the CAD patients had a significantly higher HDL-C level than the noncarriers (1.13 +/- 0.24 mmol/l vs. 0.91 +/- 0.14 mmol/l, P < 0.05). To test the functionality of this substitution, luciferase-reporter assays was performed in HepG2 cells. Promoter activity of the -586C construct was decreased 2-fold than the -586T construct. Our studies suggest that a T-to-C substitution at -586 of the LIPC promoter is associated with a lowered HL activity and that this variation may contribute to the increased plasma HDL-C concentration in the Chinese.

Hepatic lipase: a pro- or anti-atherogenic protein?

Hepatic lipase (HL) plays a role in the metabolism of pro- and anti-atherogenic lipoproteins affecting their plasma level and composition. However, there is controversy regarding whether HL accelerates or retards atherosclerosis. Its effects on different lipoprotein classes show that, potentially, HL may promote as well as decrease atherogenesis. Studies in animals with genetically modulated HL expression show that it depends on the model used whether HL acts pro- or anti-atherogenic. In humans, HL activity seems to correlate inversely with atherosclerosis in (familial) hypercholesterolemia, and positively in hypertriglyceridemia. In normolipidemia, HL activity is weakly associated with coronary artery disease (CAD). Genetically low or absent HL activity is usually associated with increased CAD risk, especially if plasma lipid transport is impaired due to other factors. Since HL promotes the uptake of lipoproteins and lipoprotein-associated lipids, HL may affect intracellular lipid content. We hypothesize that the prime role of HL is to maintain, in concert with other factors (e.g., lipoprotein receptors), intracellular lipid homeostasis. This, and the uncertainties about its impact on human atherosclerosis, makes it difficult to predict whether HL is a suitable target for intervention to lower CAD risk. First, the physiological meaning of changes in HL activity under different conditions should be clarified.