Body mass index and hepatic lipase gene (LIPC) polymorphism jointly influence postheparin plasma hepatic lipase activity

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.

Differential metabolic and multi-tissue transcriptomic responses to fructose consumption among genetically diverse mice

Understanding how individuals react differently to the same treatment is a major concern in precision medicine. Metabolic challenges such as the one posed by high fructose intake are important determinants of disease mechanisms. We embarked on studies to determine how fructose affects differential metabolic dysfunctions across genetically dissimilar mice, namely, C57BL/6 J (B6), DBA/2 J (DBA) and FVB/NJ (FVB), by integrating physiological and gene regulatory mechanisms. We report that fructose has strain-specific effects, involving tissue-specific gene regulatory cascades in hypothalamus, liver, and white adipose tissues. DBA mice showed the largest numbers of genes associated with adiposity, congruent with their highest susceptibility to adiposity gain and glucose intolerance across the three tissues. In contrast, B6 and FVB mainly exhibited cholesterol phenotypes, accompanying the largest number of adipose genes correlating with total cholesterol in B6, and liver genes correlating with LDL in FVB mice. Tissue-specific network modeling predicted strain-and tissue-specific regulators such as Fgf21 (DBA) and Lss (B6), which were subsequently validated in primary hepatocytes. Strain-specific fructose-responsive genes revealed susceptibility for human diseases such that genes in liver and adipose tissue in DBA showed strong enrichment for human type 2 diabetes and obesity traits. Liver and adipose genes in FVB were mostly related to lipid traits, and liver and adipose genes in B6 showed relevance to most cardiometabolic traits tested. Our results show that fructose induces gene regulatory pathways that are tissue specific and dependent on the genetic make-up, which may underlie interindividual variability in cardiometabolic responses to high fructose consumption.

Associations of High-Density Lipoprotein Particle and High-Density Lipoprotein Cholesterol With Alcohol Intake, Smoking, and Body Mass Index - The INTERLIPID Study

BACKGROUND

Recently, high-density lipoprotein particles (HDL-P) have been found to be more strongly inversely associated with coronary artery disease (CAD) risk than their counterpart, HDL cholesterol (HDL-C). Given that lifestyle is among the first targets in CAD prevention, we compared the associations of HDL-P and HDL-C with selected lifestyle factors. Methods and Results: We examined 789 Japanese participants of the INTERLIPID Study: men (n=386) and women (n=403) aged 40-59 years in 1996-1998. Participants treated for dyslipidemias were excluded. Lifestyle factors included alcohol intake, smoking amount, and body mass index (BMI). Multivariable linear regression was used for cross-sectional analyses of these factors with HDL-P, HDL-C, HDL-P size subclasses (small, medium and large) and mean HDL-P size. In men, higher alcohol intake was associated with higher HDL-P and higher HDL-C. The associations of alcohol, however, were strongest with HDL-P. A higher smoking amount tended to be associated with lower HDL-P and HDL-C. In contrast, BMI was not associated with HDL-P, but was strongly inversely associated with HDL-C. While alcohol intake favored larger mean HDL-P size, smoking and BMI favored a lipid profile with smaller HDL-P subclasses and overall smaller mean HDL-P size. Similar, but generally weaker results were observed in women.

CONCLUSIONS

Although both HDL-P and HDL-C are parameters of HDL, they have different associations with alcohol, smoking and BMI.

Overnutrition, ectopic lipid and the metabolic syndrome

The metabolic syndrome is a constellation of metabolic risk factors including atherogenic dyslipidemia (elevated serum triglycerides, reduced high-density lipoprotein (HDL) cholesterol), elevated blood pressure, dysglycemia (insulin resistance and elevated serum glucose), a pro-inflammatory state, and a prothrombotic state. Most persons with metabolic syndrome are obese, and usually have abdominal obesity. Generally, obesity is a reflection of overnutrition. A current view is that when adipose tissue fails to store all excess nutrients as triglyceride, lipid begins to accumulate in various tissues (eg, muscle, liver, pancreas, and heart). This accumulation is called ectopic lipid. Various mechanisms have been proposed whereby ectopic lipid is detrimental in different tissues; these derangements induce metabolic risk factors. The foundation of the metabolic syndrome thus appears to be overnutrition, that is, more nutrient intake than can be safely disposed by lipid oxidation. Excess dietary carbohydrate also induces ectopic lipid. Of interest, less than half of obese individuals develop metabolic syndrome. Through various mechanisms they adapt to overnutrition so as to minimize lipid overload in tissues, and consequently, prevent the syndrome.

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.

Interactions of several single nucleotide polymorphisms and high body mass index on serum lipid traits

The interactions between single nucleotide polymorphisms (SNPs) and high body mass index (BMI) on serum lipid profiles are limited. This study was undertaken to detect the interactions of 10 SNPs and high BMI on serum lipid traits in an isolated population. A total of 978 normal BMI (< 24 kg/m2) and 751 high BMI (≥ 24 kg/m2) subjects of Bai Ku Yao were randomly selected from our previous stratified randomized cluster samples. Genotypes of rs2066715, rs1044925, low density lipoprotein receptor (LDL-R) Ava||, rs2070895, rs2000813, rs1801133, rs3757354, rs505151, rs2016520, and rs5888 SNPs were determined by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing. The interactions were detected by factorial design covariance analysis. The genotypic and allelic frequencies of rs2070895 and rs505151 were different between normal and high BMI subjects, the genotypic frequency of rs2000813 and allelic frequency of rs3757354 were also different between normal and high BMI subjects (P < 0.01). The levels of total cholesterol (TC), apolipoprotein (Apo) A1 (rs2066715); TC, low-density lipoprotein cholesterol (LDL-C), ApoA1, ApoB, and ApoA1/ApoB (rs2070895); triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and ApoA1 (rs2000813); TC, HDL-C, LDL-C, ApoA1, and ApoB (rs1801133); HDL-C and ApoA1 (rs3757354) in normal BMI subjects were different among the genotypes (P < 0.01). The levels of LDL-C, ApoB, and ApoA1/ApoB (rs2066715); HDL-C, ApoA1, ApoB, and ApoA1/ApoB (rs2070895); TC, HDL-C, ApoA1, and ApoB (rs2000813); TC, TG, HDL-C, LDL-C, ApoA1, and ApoB (rs1801133); TC, TG, and ApoB (rs3757354); TG (rs505151); TG and ApoA1 and ApoB (rs2016520); and TC, HDL-C, LDL-C, ApoA1, and ApoB (rs5888) in high BMI subjects were also different among the genotypes (P < 0.01). The SNPs of rs2066715 (LDL-C and ApoA1/ApoB); rs2070895 (TC, LDL-C, ApoA1, and ApoB); rs2000813 (ApoB); rs1801133 (TC, TG, and LDL-C); rs3757354 (TC and TG); rs505151 (TG, HDL-C, ApoB, and ApoA1/ApoB); rs2016520 (TG and ApoA1/ApoB); and rs5888 (TG, ApoA1, and ApoB) interacted with high BMI to influence serum lipid levels (P < 0.01). The differences in serum lipid levels between normal and high BMI subjects might partly result from different interactions of several SNPs and high BMI.

Positive association of the hepatic lipase gene polymorphism c.514C > T with estrogen replacement therapy response

Background

Hepatic lipase (HL), an enzyme present in the hepatic sinusoids, is responsible for the lipolysis of lipoproteins. Human HL contains four polymorphic sites: G-250A, T-710C, A-763G, and C-514T single-nucleotide polymorphism (SNPs). The last polymorphism is the focus of the current study. The genotypes associated with the C-514T polymorphism are CC (normal homozygous - W), CT (heterozygous - H), and TT (minor-allele homozygous - M). HL activity is significantly impaired in individuals of the TT and CT genotypes. A total of 58 post-menopausal women were studied. The subjects were hysterectomized women receiving hormone replacement therapy consisting of 0.625 mg of conjugated equine estrogen once a day. The inclusion criteria were menopause of up to three years and normal blood tests, radiographs, cervical-vaginal cytology, and densitometry. DNA was extracted from the buccal and blood cells of all 58 patients using a commercially available kit (GFX^® - Amersham-Pharmacia, USA).

Results

Statistically significant reductions in triglycerides (t = 2.16; n = 58; p = 0.03) but not in total cholesterol (t = 0.14; n = 58; p = 0.89) were found after treatment. This group of good responders were carriers of the T allele; the CT and TT genotypes were present significantly more frequently than in the group of non-responders (p = 0.02 or p = 0.07, respectively). However, no significant difference in HDL-C (t = 0.94; n = 58; p = 0.35) or LDL-C (t = -0.83; n = 58; p = 0.41) was found in these patients.

Conclusions

The variation in lipid profile associated with the C-514T polymorphism is significant, and the T allele is associated with the best response to ERT.

Mouse hepatic lipase alleles with variable effects on lipoprotein composition and size

The structural features responsible for the activities of hepatic lipase (HL) can be clarified by in vivo comparisons of naturally occurring variants. The coding sequence of HL from C57BL/6J (B6) and SPRET/EiJ (SPRET) mice differs by four amino acids (S106N, A156V, L416V, S480T); however, these changes are not predicted to influence HL function. To test for allelic effects, we generated SPRET-HL transgenics with physiological levels of HL mRNA and HL activity that was parallel in female transgenics and about 70% higher in male transgenics, toward tri-[3H]oleate, compared with B6 controls. We found no correlation between activity levels and plasma lipids. However, significant allelic effects on plasma lipids were observed. Compared with B6-HL, SPRET-HL mediated reductions in total cholesterol (TC) and VLDL-, LDL- and HDL-cholesterol and HDL-triglyceride (TG) in fed males, and SPRET-HL decreased total TG and VLDL- and HDL-TG levels in fasted males. Fasted female transgenics had reduced TC compared with controls. We also found allele and sex effects on lipoprotein particle size. Male transgenic mice had increased VLDL and decreased LDL size, and female transgenic mice had decreased HDL size compared with control animals. These findings demonstrate highly divergent effects of naturally occurring HL coding sequence variants on lipid and lipoprotein metabolism.

Polymorphisms in the hepatic lipase gene affect plasma HDL-cholesterol levels in a Turkish population

We investigated the effects of single nucleotide polymorphisms (SNPs) of the hepatic lipase gene (LIPC) on plasma HDL-cholesterol (HDL-C) levels in Turks, a population with low levels of HDL-C. All exons and six evolutionarily conserved regions from 28 Turkish subjects were sequenced. We found 51 SNPs, nine of which were novel. Those 51 SNPs and SNPs from the National Center for Biotechnology Information dbSNP were evaluated by bioinformatics approaches. The population frequencies and linkage disequilibrium among SNPs from HapMap were combined with results from transcriptional factor prediction tools and the literature to select SNPs for genotyping. We found that five tagging LIPC SNPs, two reported here for the first time, were significantly associated with plasma HDL-C levels in both men and women (n = 2,612). These results were replicated in a separate Turkish cohort (n = 1,164). Plasma HDL-C levels were higher in subjects homozygous for the minor alleles of rs4775041, rs1800588 (-514C>T), and rs11858164 and lower in subjects homozygous for the minor alleles of rs11856322 and rs2242061. These SNPs seemed to have independent and additive effects on plasma HDL-C levels (1.5-5.2 mg/dl). Hepatic lipase activity in a subset (n = 260) of the main cohort was also significantly associated with all five SNPs. Thus, five LIPC SNPs, two novel, are associated with plasma HDL-C levels and hepatic lipase activity in two cohorts of Turkish subjects.

Diagnostic value of post-heparin lipase testing in detecting common genetic variants in the LPL and LIPC genes

Post-heparin lipoprotein lipase and hepatic lipase activities are used to identify primary disorders of triglyceride and HDL-cholesterol metabolism. Their ability to identify common variants in the lipoprotein lipase (LPL) and hepatic lipase (LIPC) genes is unclear. To investigate the ability of lipase testing to detect common lipase gene variants, we included 183 patients who had undergone post-heparin lipase testing and genotyped the LPL D9N, N291S, PvuII, HindIII, and S447X and the LIPC-514CT, V73M, V133V, and N193S polymorphisms. Allele frequencies were compared with 163 controls. Polymorphisms with different allele frequencies in patients and controls or influencing lipids, were analyzed further. The diagnostic value of post-heparin lipase testing was assessed using logistic regression and receiver operating characteristic curves. We found that lipase activities did not predict the LPL D9N and N291S polymorphisms, but predicted the LPL S447X and LIPC-514CT polymorphisms. Adjusted for covariates, the area under the receiver operating characteristic curves was 0.643, 0.478, 0.686, and 0.657 for LPL D9N, N291S S447X and LIPC-514CT, respectively. On the basis of these findings, we conclude that high-LPL and low-HL activities associate with the LPL S447X and LIPC-514CT polymorphisms, but low-LPL activity was not related to LPL polymorphisms. Overall, the discriminative ability of post-heparin lipase tests in identifying carriers of common variants in the LPL and LIPC genes was limited. This indicates that conclusions on the genetic causes of lipase activities outside of the normal range should be drawn with caution.

Down-regulation of hepatic lipase expression by elevation of cAMP in human hepatoma but not adrenocortical cells

Expression of hepatic lipase (HL) in the liver is reduced during prolonged fasting. This effect is mainly mediated via catecholamines, which signal through elevation of Ca(i)(2+) as well as cAMP. We have studied the effect of cAMP on HL expression in cell culture. Overnight incubation of HepG2 cells with 10-300microM 8-bromo-cyclic AMP resulted in a dose-dependent, up to 50% reduction in secretion of HL, but had no effect on secretion of alpha(1)-antitrypsin or overall protein synthesis. HL mRNA levels were decreased 1.5 fold, as determined by semi-quantitative and real-time RT-PCR. In HepG2 cells transiently transfected with human HL (-685/+13) or rat HL (-446/+9) promoter-reporter constructs, cAMP induced a similar dose-dependent suppression of HL promoter activity. cAMP responsiveness in HepG2 cells was mediated by a conserved 10-bp response element at -45/-36, that represents a potential binding site for CCAAT/enhancer-binding protein beta (C/EBPbeta). cAMP reduced expression of the 45kDa C/EBPbeta protein and binding of C/EBPbeta to the proximal promoter region of the human HL gene by 50%, as determined by immunoblotting and chromatin immunoprecipitation assay, respectively. In human H295R adrenocortical cells, cAMP failed to suppress HL promoter activity, and only slightly reduced C/EBPbeta expression. We conclude that the fall in HL expression during prolonged fasting may be mediated through elevation of cAMP and lowering of C/EBPbeta expression.

Longitudinal changes in triglycerides according to ANGPTL4[E40K] genotype and longitudinal body weight change in the atherosclerosis risk in communities study

PURPOSE

Allelic variation in the adipokine angiopoietin-like 4 gene (ANGPTL4[E40K]) has been cross-sectionally associated with triglycerides, but the effects of genotype, or the interaction between genotype and body weight, on longitudinal triglyceride change have not been studied.

METHODS

Body weight, triglycerides, and ANGPTL4[E40K] genotype were determined at baseline (1987-1989) and at 3 follow-up exams (1990-1992, 1993-1995, 1996-1998) in 7,939 white ANGPTL4[E40K] G allele homozygotes and 344 A allele carriers. Changes in body weight and triglycerides were characterized as the difference between exam 4 and baseline measurements.

RESULTS

ANGPTL4[E40K] A allele carriers had triglyceride concentrations that were 15 to 18 mg/dL lower than G allele homozygotes at all exams (P<0.0001). Triglycerides increased in both genotype groups over the 9-year period (+19.1+/-0.9 and +16.2+/-4.1 mg/dL in GG and GA/AA, respectively; P difference, 0.48). Weight gain was associated with increased triglycerides to a comparable degree in both genotype groups (+5.5+/-0.3 and +4.3+/-0.9 mg/dL per 2-kg increase in body weight in GG and GA/AA, respectively, p interaction=0.30).

CONCLUSIONS

Differences in triglyceride concentrations between ANGPTL4[E40K] A allele carriers and G allele homozygotes are maintained over time, but the degree of increase in triglycerides was similar between groups and was not modified by body weight changes.

The -250G>A promoter variant in hepatic lipase associates with elevated fasting serum high-density lipoprotein cholesterol modulated by interaction with physical activity in a study of 16,156 Danish subjects

CONTEXT

Hepatic lipase plays a pivotal role in the metabolism of high-density lipoprotein (HDL) and low-density lipoprotein by involvement in reverse cholesterol transport and the formation of atherogenic small dense low-density lipoprotein.

OBJECTIVES

The objective was to investigate the impact of variants in LIPC on metabolic traits and type 2 diabetes in a large sample of Danes. Because behavioral factors influence hepatic lipase activity, we furthermore examined possible gene-environment interactions in the population-based Inter99 study.

DESIGN

The LIPC -250G>A (rs2070895) variant was genotyped in the Inter99 study (n = 6070), the Anglo-Danish-Dutch Study of Intensive Treatment in People with Screen Detected Diabetes in Primary Care Denmark screening cohort of individuals with risk factors for undiagnosed type 2 diabetes (n = 8662), and in additional type 2 diabetic patients (n = 1,064) and glucose-tolerant control subjects (n = 360).

RESULTS

In the Inter99 study, the A allele of rs2070895 associated with a 0.057 mmol/liter [95% confidence interval (CI) 0.039-0.075] increase in fasting serum HDL-cholesterol (HDL-c) (P = 8 x 10(-10)) supported by association in the Anglo-Danish-Dutch Study of Intensive Treatment in People with Screen Detected Diabetes in Primary Care study [0.038 mmol/liter per allele (95% CI 0.024-0.053); P = 2 x 10(-7)). The allelic effect on HDL-c was modulated by interaction with self-reported physical activity (P(interaction) = 0.002) because vigorous physically active homozygous A-allele carriers had a 0.30 mmol/liter (95% CI 0.22-0.37) increase in HDL-c compared with homozygous G-allele carriers.

CONCLUSIONS

We validate the association of LIPC promoter variation with fasting serum HDL-c and present data supporting an interaction with physical activity implying an increased effect on HDL-c in vigorous physically active subjects carrying the -250 A allele. This interaction may have potential implications for public health and disease prevention.

Genetic variation in the hepatic lipase gene and the risk of coronary heart disease among US diabetic men: potential interaction with obesity

AIMS/HYPOTHESIS

The -514 C to T polymorphism of the hepatic lipase gene (LIPC) has been associated with lowered LIPC activity and elevated HDL-cholesterol concentrations. Previous findings on the association of this polymorphism with the risk of CHD are inconsistent. Moreover, data on this association among diabetic patients are limited. We investigated the association of the LIPC polymorphism with CHD risk among US diabetic men and evaluated whether this association was modified by adiposity status.

SUBJECTS AND METHODS

The case group consisted of 220 diabetic men who were recruited from the Health Professionals Follow-up Study (years 1986-2000) and were free of cardiovascular disease at baseline, but subsequently developed CHD. A total of 641 diabetic men from the same study but without cardiovascular disease constituted the control group.

RESULTS

No overall association between the LIPC polymorphism and CHD risk was observed. However, we did observe a significant interaction between this polymorphism and BMI in association with CHD risk. Among obese men, after adjustment for age, duration of diabetes and major lifestyle factors, the CT or TT genotype was associated with an increased CHD risk compared with the CC genotype (odds ratio [OR] 2.52, 95% CI 1.08-5.90); the corresponding ORs (95% CI) were 0.99 (0.58, 1.69) for overweight men (25< or =BMI <30 kg/m(2)) and 0.37 (0.17, 0.79) for lean men (BMI <25 kg/m(2)) (p for interaction 0.001). Stratified analyses by waist circumference (tertiles) showed a similar pattern of interaction (adjusted p for interaction 0.023).

CONCLUSION/INTERPRETATION

These data suggest that obesity may modify the association between the LIPC C(-514)T polymorphism and CHD risk among diabetic men.

One third of the variability in HDL-cholesterol level in a large dyslipidaemic population is predicted by age, sex and triglyceridaemia: The Paris La Pitié Study

OBJECTIVE

The objective of this study was to identify key determinants of high-density lipoprotein-cholesterol (HDL-C) level, including subclinical inflammation and insulin resistance, and to determine the prevalence of a low HDL-C phenotype in dyslipidaemic patients at high cardiovascular risk.

METHODS

In a cross-sectional study, we assessed the prevalence of low HDL-C phenotypes in 14 667 dyslipidaemic patients attending our specialised lipid clinic and evaluated the potential relationships between HDL-C level and 16 clinical and biological parameters.

RESULTS

In univariate analysis, women exhibited higher plasma concentrations of HDL-C as compared with men. Levels of triglycerides, fasting blood glucose, uric acid, waist circumference, body mass index, high sensitivity C-reactive protein (hs-CRP), insulin resistance (as HOMA-IR index) and smoking were all negatively correlated with HDL-C, whereas age was positively correlated with HDL-C levels. Moderate drinkers (10-30 g/day) displayed higher HDL-C concentrations as compared with abstinent subjects; in contrast, consumption of more than 30 g alcohol/day was associated with a further non-significant elevation of HDL-C levels as compared to moderate drinkers. Multivariate analysis identified eight independent correlates of HDL-C. Age, sex and TG accounted for 37% of variability in HDL-C; modifiable factors including waist circumference, alcohol consumption and smoking, in addition to HOMA-IR and hs-CRP, accounted for an additional 5% of the variability in HDL-C. Using a cut-off of 40 mg/dL (1.03 mmol/L) for men and 50 mg/dL (1.29 mmol/L) for women, 33% and 28% of men and women displayed low levels of HDL-C.

CONCLUSION

Eight independent determinants of HDL-C account for 41% of variability in HDL-C in our dyslipidaemic population. Three of them, i.e. age, sex and degree of triglyceridaemia accounted for more than one third of such variability. The high prevalence of low HDL-C phenotypes in dyslipidaemic patients at elevated cardiovascular risk emphasises the need for both lifestyle and pharmacological strategies of intervention to raise HDL-C.

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.

New Insights Into the Regulation of HDL Metabolism and Reverse Cholesterol Transport

The metabolism of high-density lipoproteins (HDL), which are inversely related to risk of atherosclerotic cardiovascular disease, involves a complex interplay of factors regulating HDL synthesis, intravascular remodeling, and catabolism. The individual lipid and apolipoprotein components of HDL are mostly assembled after secretion, are frequently exchanged with or transferred to other lipoproteins, are actively remodeled within the plasma compartment, and are often cleared separately from one another. HDL is believed to play a key role in the process of reverse cholesterol transport (RCT), in which it promotes the efflux of excess cholesterol from peripheral tissues and returns it to the liver for biliary excretion. This review will emphasize 3 major evolving themes regarding HDL metabolism and RCT. The first theme is that HDL is a universal plasma acceptor lipoprotein for cholesterol efflux from not only peripheral tissues but also hepatocytes, which are a major source of cholesterol efflux to HDL. Furthermore, although efflux of cholesterol from macrophages represents only a tiny fraction of overall cellular cholesterol efflux, it is the most important with regard to atherosclerosis, suggesting that it be specifically termed macrophage RCT. The second theme is the critical role that intravascular remodeling of HDL by lipid transfer factors, lipases, cell surface receptors, and non-HDL lipoproteins play in determining the ultimate metabolic fate of HDL and plasma HDL-c concentrations. The third theme is the growing appreciation that insulin resistance underlies the majority of cases of low HDL-c in humans and the mechanisms by which insulin resistance influences HDL metabolism. Progress in our understanding of HDL metabolism and macrophage reverse cholesterol transport will increase the likelihood of developing novel therapies to raise plasma HDL concentrations and promote macrophage RCT and in proving that these new therapeutic interventions prevent or cause regression of atherosclerosis in humans.

Interactions between the -514C->T polymorphism of the hepatic lipase gene and lifestyle factors in relation to HDL concentrations among US diabetic men

BACKGROUND

Low plasma HDL-cholesterol concentrations are a hallmark of diabetic dyslipidemia. A common polymorphism (-514C-->T) of the hepatic lipase gene (LIPC), which accounts for up to 30% of the variation in hepatic lipase activity, has been associated with low hepatic lipase activity and high HDL-cholesterol concentrations.

OBJECTIVE

We examined the association between this polymorphism and plasma HDL-cholesterol concentrations and evaluated whether this association was modified by adiposity and dietary fat intake.

DESIGN

We followed men aged 40-75 y who participated in the Health Professionals Follow-Up Study in 1986. Among 18 159 men who returned blood samples by 1994, 780 had confirmed type 2 diabetes at blood drawing or during follow-up to 1998 and were free of cardiovascular disease at blood drawing.

RESULTS

After adjustment for age, smoking, alcohol consumption, fasting status, glycated hemoglobin concentration, physical activity, and body mass index, HDL-cholesterol concentrations were significantly higher in men with the C/T or T/T genotype than in those with the C/C genotype (adjusted x: 40.9 and 38.8 mg/dL, respectively; P = 0.01). We observed significant LIPC -514 polymorphism x body mass index and LIPC -514 polymorphism x saturated fat intake interactions for HDL-cholesterol concentrations (P = 0.003 for both). The T allele was associated with higher HDL-cholesterol concentrations only in men who were not overweight or who had higher saturated fat intake.

CONCLUSION

Our study suggests that the effects of -514C-->T of the LIPC gene on HDL concentrations were modified by saturated fat intake and obesity.

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.

Metabolic syndrome: therapeutic considerations

The metabolic syndrome is a constellation of metabolic risk factors for atherosclerotic cardiovascular disease (ASCVD) occurring in one individual. There are five cardiovascular risk factors that accompany the metabolic syndrome: atherogenic dyslipidemia [elevated apolipoprotein B (apo B), elevated triglyceride, small low-density lipoprotein (LDL) particles, and low high-density lipoprotein (HDL)cholesterol], elevated blood pressure, elevated glucose, a prothrombotic state, and a proinflammatory state. The likelihood of an individual developing metabolic syndrome is enhance by underlying risk factors, notably, obesity, insulin resistance, lack of physical activity, advancing age, and hormonal factors (e.g., androgens and corticosteroids). Besides being at higher risk for ASCVD, persons with the metabolic syndrome are at increased risk for type 2 diabetes. Persons with the metabolic syndrome deserve management in the clinical setting to reduce the risk for both ASCVD and type 2 diabetes. The two major therapeutic strategies for treatment of affected persons are modification of the underlying risk factors and separate drug treatment of the particular metabolic risk factors when appropriate. First-line therapy for underlying risk factors is therapeutic lifestyle changes, i.e., weight loss in obese persons, increased physical activity, and anti-atherogenic diet. These changes will improve all of the metabolic risk factors. Whether use of drugs to reduce insulin resistance is effective, safe, and cost-effective before the onset of diabetes awaits the results of more clinical research. Turning to individual risk components, for atherogenic dyslipidemia, drug therapies that promote lowering of apo B and raise HDL cholesterol will be needed for higher risk patients. Treatment of categorical hypertension with drugs has become standard practice. When hyperglycemia reaches the diabetic level, glucose-lowering agents will become necessary when dietary control is no longer effective, and reduction of a prothrombotic state with low-dose aspirin may be indicated in higher-risk patients.

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.

What is the contribution of obesity to the metabolic syndrome?

Many prospective studies show that obesity is accompanied by increased risk for cardiovascular disease. Obesity affects metabolism of lipids and glucose, regulation of blood pressure, thrombotic and fibrinolytic processes, and inflammatory reactions. Multiple aberrations exist in each of these systems; obesity acting alone probably is not sufficient to produce full-blown metabolic syndrome. There must be other factors, including genetic and aging factors. It is difficult to sort out all pathogenic factors that link obesity to cardiovascular disease risk. It is worthwhile to investigate individually the components of the obesity-induced metabolic syndrome for their atherogenic potential, because out of that investigation likely will come new targets for clinical or public health intervention to reduce the risk for cardiovascular disease.

Ethnic differences in hepatic lipase and HDL in Japanese, black, and white Americans: role of central obesity and LIPC polymorphisms

Hepatic lipase activity (HLA) is a determinant of HDL levels, and a polymorphism in the hepatic lipase gene (LIPC) promoter (C-514T) has been hypothesized to account for higher HDL in blacks and Japanese compared with whites. To determine whether the polymorphism contributes to ethnic differences in HDL, we compared LIPC allele frequencies and HLA in Japanese American (JA; n = 84), black American (BA; n = 94), and white American (WA; n = 110) men and women. The LIPC polymorphism was associated with HLA in all cohorts (BA, P = 0.012; JA, P = 0.008; WA, P = 0.009). WA men had 49% and 58% higher HLA than BA and JA men, respectively (both P < 0.05), yet no differences in HLA were found between the women. The higher HLA in the WA men remained after adjustment for the LIPC polymorphism's effect on HLA (P = 0.037) but was erased after adjustment for waist-to-hip-ratio (P = 0.46). Although the WA men had lower HDL and HDL(3) than the JA and BA men (all P < 0.05), there were no differences in HDL(2), implying that variance in HLA may not underlie the ethnic differences in HDL levels. These results suggest that 1) the LIPC promoter polymorphism contributes to variation in HLA and HDL(2) in the three ethnic groups; 2) WA men had higher HLA than BA and JA men, related to ethnic differences in central adiposity but not LIPC allele frequency; and 3) the higher HLA in WA men did not contribute to the ethnic differences in HDL, as the differences in HDL were made up entirely of differences in HDL(3) and not HDL(2).

The interactive effects of hepatic lipase gene promoter polymorphisms with sex and obesity on high-density-lipoprotein cholesterol levels in Taiwanese–Chinese

OBJECTIVES

Hepatic lipase (HL) is involved in the metabolism of several lipoproteins and plays a key role in reverse cholesterol transport. The aim of the current study was to test the statistical association between two HL gene promoter polymorphisms (HL-514C/T and HL-250G/A) and lipoprotein profiles in a Taiwanese-Chinese population.

METHODS

A sample population of 716 Taiwanese-Chinese individuals was analyzed. DNA was extracted from the blood and genotypes were determined by polymerase chain reaction, restriction enzyme digestion, and agarose gel electrophoresis.

RESULTS

Analysis of the data revealed that these two polymorphisms are in strong linkage disequilibrium (D/D(max)=0.97, P<0.001). A significantly lower total cholesterol/HDL-C ratio was noted for carriers with the -514T and -250A alleles compared to non-carriers (P=0.007 and 0.004, respectively). A significant trend of the association was also found on the high levels of high-density-lipoprotein cholesterol (HDL-C) among carriers with the -514T and -250A alleles as opposed to that of non-carriers (P=0.030 and 0.023, respectively). Multivariate analysis has demonstrated that the effects of HL-514C/T and HL-250G/A polymorphisms on HDL-C levels were not affected by subjects' sex, body mass index, plasma triglyceride levels and the cholesterol ester transfer protein gene TaqIB polymorphism. Subgroup analysis on each sex has revealed that the two studied polymorphisms were significantly associated with HDL-C levels among males but not significant in women. The same association between obese and non-obese men was not consistent. The P-value of the respective polymorphisms on HDL-C levels were 0.012 and 0.002 among obese men, but not significant among non-obese men.

CONCLUSION

Analysis of our data revealed an independent association between the HL gene promoter polymorphisms and HDL-C levels in Taiwanese-Chinese. The data also suggests that the HL-514C/T and HL-250G/A polymorphisms interact with sex and obesity on HDL-C levels. The findings give clues for identifying high risk population in preventive medicine and clinical diagnosis. The subsequent impacts on treatment profiles and prognosis were derived from this study.

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.

Mechanisms of HDL lowering in insulin resistant, hypertriglyceridemic states: the combined effect of HDL triglyceride enrichment and elevated hepatic lipase activity

Hypertriglyceridemia, low plasma concentrations of high density lipoproteins (HDL) and qualitative changes in low density lipoproteins (LDL) comprise the typical dyslipidemia of insulin resistant states and type 2 diabetes. Although isolated low plasma HDL-cholesterol (HDL-c) and apolipoprotein A-I (apo A-I, the major apolipoprotein component of HDL) can occur in the absence of hypertriglyceridemia or any other features of insulin resistance, the majority of cases in which HDL-c is low are closely linked with other clinical features of insulin resistance and hypertriglyceridemia. We and others have postulated that triglyceride enrichment of HDL particles secondary to enhanced CETP-mediated exchange of triglycerides and cholesteryl ester between HDL and triglyceride-rich lipoproteins, combined with the lipolytic action of hepatic lipase (HL), are driving forces in the reduction of plasma HDL-c and apoA-I plasma concentrations. The present review focuses on these metabolic alterations in insulin resistant states and their important contributions to the reduction of HDL-c and HDL-apoA-I plasma concentrations.

Atorvastatin dose-dependently decreases hepatic lipase activity in type 2 diabetes: effect of sex and the LIPC promoter variant

OBJECTIVE

Hepatic lipase (HL) is involved in the metabolism of several lipoproteins and may contribute to the atherogenic lipid profile in type 2 diabetes. Little is known about the effect of cholesterol synthesis inhibitors on HL activity in relation to sex and the hepatic lipase gene, the LIPC promoter variant in type 2 diabetes. Therefore, we studied the effect of atorvastatin 10 mg (A10) and 80 mg (A80) on HL activity in 198 patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Patients (aged 45-75 years, without manifest coronary artery disease, total cholesterol 4.0-8.0 mmol/l, and fasting triglycerides [TG] 1.5-6.0 mmol/l) were included in a double-blind, randomized, placebo-controlled trial for 30 weeks (Diabetes Atorvastatin Lipid Intervention study).

RESULTS

HL activity at baseline was significantly higher in our population compared with an age-matched control group without type 2 diabetes (406 +/- 150 vs. 357 +/- 118 units/l). HL activity in men versus women (443 +/- 158 vs. 358 +/- 127 units/l), in carriers of the LIPC C/C allele versus carriers of the T/T allele (444 +/- 142 vs. 227 +/- 96 units/l), and in Caucasians versus blacks (415 +/- 150 vs. 260 +/- 127 units/l) all differed significantly (P < 0.001). Atorvastatin dose-dependently decreased HL (A10, -11%; A80, -22%; both P < 0.001). Neither sex nor the LIPC C-->T variation influenced the effect of atorvastatin on HL activity.

CONCLUSIONS

Sex, LIPC promoter variant, and ethnicity significantly contribute to the baseline variance in HL activity. Atorvastatin treatment in diabetic dyslipidemia results in a significant dose-dependent decrease in HL activity, regardless of sex or the LIPC promoter variant.

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.

Sources of variability in genetic association studies: insights from the analysis of hepatic lipase (LIPC)

Genetic association studies have been widely used to identify loci that influence plasma lipoprotein concentrations, but few of the associations reported have proved consistently reproducible across different study populations. This lack of consistency is a widely recognized limitation of association studies, and is often ascribed to inadequate statistical power, population substructure, and population-specific linkage disequilibrium. However, few studies have assessed the causes of variability underlying a given genotype-phenotype association. We have examined two possible sources of variability in the association between the -514 polymorphism in hepatic lipase (LIPC) and plasma HDL-C concentrations. First, we compared the association between this polymorphism and hepatic lipase activity in four populations. A single copy of the -514C allele was associated with a 10 mmol.hr(-1).l(-1) increase in hepatic lipase activity in white American and Turkish men but only approximately 5 mmol.hr(-1).l(-1) in Chinese and African-American men. Second, we tested the effects of a stanozolol-induced increase in hepatic lipase activity on plasma HDL-C concentrations in men with normal (< 150mg/dl) or elevated (150-300mg/dl) levels of plasma triglyceride. The increase in hepatic lipase activity was similar in the two groups, but the resulting decline in HDL-C levels was significantly greater in normolipidemic men. These data suggest that the effect of a polymorphism on gene expression can vary among individuals, and that the resulting phenotype may be further modified by interactions with other factors. Three novel LIPC polymorphisms were identified in the study (-1596insC, -2740A>G, and -2880G>C).

Effects of gender, hepatic lipase gene polymorphism and type 2 diabetes mellitus on hepatic lipase activity in Chinese

Genetic variation in the hepatic lipase (HL) gene (LIPC) promoter is an important determinant of HL activity in Caucasians. As HL activity is increased in patients with type 2 diabetes mellitus, we have investigated whether the -514 C-to-T polymorphism acted independently of type 2 diabetes to regulate HL activity. The frequency of this polymorphism and its effect on plasma HL activity and lipids were examined in 203 Chinese patients with type 2 diabetes and 205 controls. The frequency of the T allele was 0.343 and 0.376 in male and female diabetic patients, respectively, compared with 0.371 and 0.372 in male and female controls. The effect of LIPC genotype on HL activity was similar between men and women, and between diabetic patients and non-diabetic controls, with the lowest HL activity being found in those subjects with the TT genotype. On multivariate analysis, gender, LIPC genotype, the presence of type 2 diabetes and body mass index were independent predictors of HL activity, accounting for 22, 9, 5 and 3%, respectively, of the variance in HL activity (whole model adjusted R(2)=0.39, P<0.0001). The T allele was associated with higher high-density lipoprotein in the controls but not in the diabetic patients, and no associations were found between LIPC genotype and low-density lipoprotein subfractions in either groups. In conclusion, despite the higher frequency of the T allele in Chinese than in Caucasians, gender was the best predictor for HL activity, with LIPC gene polymorphism and type 2 diabetes making relatively smaller contributions to the variation in HL activity.

Hepatic lipase promoter activity is reduced by the C-480T and G-216A substitutions present in the common LIPC gene variant, and is increased by Upstream Stimulatory Factor

The common -216G-->A and -480C-->T substitutions in the promoter region of the human hepatic lipase (LIPC) gene show high allelic association, and are correlated with decreased hepatic lipase activity and increased high-density lipoprotein cholesterol levels. To test the functionality of these substitutions, CAT-reporter assays were performed in HepG2 cells. LIPC (-650/+48) but not (-650/+61) promoter constructs showed transcriptional activity. LIPC (-650/+48) constructs with both -216A and -480T exhibited significantly lower promoter activity (-45%) than the wild-type form. Activities of -289/+48 constructs were not significantly affected by the -216G-->A substitution. The -480C/T site lies within a binding region for Upstream Stimulatory Factor (USF). Gel-shift assays showed that the binding affinity of USF protein for HL specific oligonucleotides was decreased four-fold by the -480C-->T substitution. However, promoter activity of the -650/+48 constructs was not significantly affected by the -480C-->T substitution alone. Co-transfection of HepG2 cells with USF(43) cDNA yielded a similar dose-dependent increase in activity of all -650/+48 constructs; the absolute difference in promoter activity increased but the relative difference between the variant promoter forms was maintained. Our studies demonstrate that the common LIPC promoter variation is functional, which explains the association of the -480T allele with a lower hepatic lipase activity in man.

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

Low activity of hepatic lipase (HL) has been associated with high levels of triglycerides and high density lipoproteins, but the association of the HL promoter variants with insulin sensitivity has not been investigated. Therefore, in this study, the relationship of the G-250A promoter variant of the HL gene to the rates of insulin-stimulated glucose uptake measured by the hyperinsulinemic euglycemic clamp was investigated in 110 control subjects (82 men and 28 women, aged 50.7+/-7.6 [mean+/-SD] years, body mass index 26. 1+/-3.6 kg/m(2)) and in 105 first-degree relatives (65 men and 40 women, aged 47.8+/-16.0 years, body mass index 26.9+/-5.3 kg/m(2)) of 34 families with familial combined hyperlipidemia (FCHL). The A-250 allele of the HL promoter was associated with low rates of insulin-stimulated whole-body nonoxidative glucose disposal in control subjects (41.1+/-12.7 micromol. kg(-1). min(-1) in subjects with the G-250G genotype, 36.9+/-13.1 micromol. kg(-1). min(-1) in subjects with the G-250A genotype, and 29.9+/-13.5 micromol. kg(-1). min(-1) in subjects with the A-250A genotype; P=0.012 adjusted for age and sex) and with low rates of insulin-stimulated whole-body glucose oxidation in FCHL family members (16.7+/-4.2 versus 15.0+/-4. 4 versus 14.1+/-4.4 micromol. kg(-1). min(-1), P=0.024). In addition, the A-250 allele was associated with high levels of fasting insulin (P=0.047), very low density lipoprotein cholesterol (P=0.007), and total (P=0.009) and very low density lipoprotein (P=0.005) triglycerides in control subjects and with high levels of low density lipoprotein triglycerides (P=0.001) in FCHL family members (n=340). We conclude that the G-250A promoter variant of the HL gene is associated with dyslipidemia and insulin resistance. Mechanisms via which this polymorphism could affect insulin sensitivity remain to be elucidated.

Effect of weight loss with reduction of intra-abdominal fat on lipid metabolism in older men

How weight loss improves lipid levels is poorly understood. Cross-sectional studies have suggested that accumulation of fat in intra-abdominal stores (IAF) may lead to abnormal lipid levels, increased hepatic lipase (HL) activity, and smaller low density lipoprotein (LDL) particle size. To determine what effect loss of IAF would have on lipid parameters, 21 healthy older men underwent diet-induced weight loss. During a period of weight stability before and after weight loss, subjects underwent studies of body composition, lipids, measurement of postheparin lipoprotein and HL lipase activities, cholesteryl ester transfer protein activity, and insulin sensitivity (Si). After an average weight loss of 10%, reductions in fat mass, IAF, and abdominal s.c. fat were seen, accompanied by reductions in levels of triglyceride, very low density lipoprotein cholesterol, apolipoprotein B, and HL activity. High density lipoprotein-2 cholesterol and Si increased. In those subjects with pattern B LDL at baseline, LDL particle size increased. Cholesteryl ester transfer protein activity did not change. Changes in IAF and Si correlated with a decrease in HL activity (although not independently of each other). In summary, in men undergoing diet-induced weight loss, only loss of IAF was found to be associated with a reduction in HL, which is associated with beneficial effects on lipid levels.

A hepatic lipase gene promoter polymorphism attenuates the increase in hepatic lipase activity with increasing intra-abdominal fat in women

High hepatic lipase (HL) activity is associated with an atherogenic lipoprotein profile of small, dense LDL particles and lower HDL(2)-C. Intra-abdominal fat (IAF) is positively associated with HL activity. A hepatic lipase gene (LIPC) promoter variant (G-->A(-250)) is associated with lower HL activity, higher HDL(2)-C, and less dense LDL particles. To determine whether the LIPC promoter polymorphism acts independently of IAF to regulate HL, 57 healthy, premenopausal women were studied. The LIPC promoter A allele was associated with significantly lower HL activity (GA/AA=104+/-34 versus GG=145+/-57 nmoles x mL(-1) x min(-1), P=0.009). IAF was positively correlated with HL activity (r=0.431, P<0.001). Multivariate analysis revealed a strong relationship between both the LIPC promoter genotype (P=0. 001) and IAF (P<0.001) with HL activity. The relationship between IAF and HL activity for carriers and noncarriers of the A allele was curvilinear with the carriers having a lower apparent maximum level of plasma HL activity compared with noncarriers (138 versus 218 nmoles x mL(-1) x min(-1), P<0.001). In addition, the LIPC A allele was associated with a significantly higher HDL(2)-C (GA/AA=16+/-7 versus GG=11+/-5 mg/dL, P=0.003). We conclude that the LIPC promoter A allele attenuates the increase in HL activity due to IAF in premenopausal women.

Absence of association between genetic variation in the LIPC gene promoter and plasma lipoproteins in three Canadian populations

The promoter sequence variant -480T in the hepatic lipase gene (LIPC) has been shown to be significantly associated with low post-heparin hepatic lipase activity. Some studies have also found that the -480T variant is associated with elevation in plasma HDL cholesterol. We tested for associations of LIPC -480T with plasma lipoprotein traits in samples taken from three distinct Canadian populations: 657 Alberta Hutterites, 328 Ontario Oji-Cree and 210 Keewatin Inuit. Plasma HL activity was not available for analyses. The LIPC -480T allele frequencies in these three groups, respectively, were 0.219, 0.527 and 0.383, and the prevalence of LIPC -480T/T homozygotes was, respectively, 0.042, 0.274 and 0.167. No significant association was found between LIPC -480T and plasma HDL cholesterol or apolipoprotein AI concentration, after adjusting for covariates including gender and body mass index. There was no consistent relationship between the population mean plasma HDL cholesterol concentration and the population LIPC -480T frequency. Our findings are consistent with the idea that the common promoter variation in LIPC, which has been reported to be associated with variation in post heparin HL activity and HDL triglyceride concentration, is not always associated with variation in plasma HDL cholesterol concentration, possibly due to yet unspecified environmental or genetic factors.

Hepatic lipase (LIPC) promoter polymorphism in men with coronary artery disease. Allele frequency and effects on hepatic lipase activity and plasma HDL-C concentrations

Hepatic lipase is an important determinant of plasma HDL concentration and LDL subclass distribution and may therefore influence susceptibility to coronary artery disease (CAD). To assess the effect of genetic variation in hepatic lipase activity on CAD susceptibility, we determined the frequency of the -514T allele of hepatic lipase in white men with CAD and in controls who did not have CAD. In men with CAD, postheparin plasma hepatic lipase activity was 15% to 20% lower in heterozygotes and 30% lower in homozygotes for the -514T allele. Allele frequencies were similar in cases and controls, however, and were consistent with Hardy-Weinberg expectation in both groups. This finding was confirmed in a second group comprising cases with premature symptomatic CAD and controls who were free of disease. These data indicate that a primary decrease in hepatic lipase activity of as much as 30% does not influence susceptibility to CAD in white men.

Hepatic lipase: new insights from genetic and metabolic studies

Hepatic lipase catalyses the hydrolysis of triglycerides and phospholipids in all major classes of lipoproteins. Genetic deficiency of this enzyme is associated with a unique plasma lipoprotein profile, characterized by hypertriglyceridemia and elevated concentrations of intermediate density lipoproteins and HDL. Recent studies have identified common polymorphisms in the hepatic lipase gene that are associated with low hepatic lipase activity and increased concentrations of large HDL. Association studies using these polymorphisms are elucidating the effects of variation in hepatic lipase activity on plasma lipoprotein concentrations and susceptibility to coronary atherosclerosis.