Familial combined hyperlipidemia is associated with upstream transcription factor 1 (USF1)

Gene-gene interaction between APOA5 and USF1: two candidate genes for the metabolic syndrome

OBJECTIVE

The metabolic syndrome, a major cluster of risk factors for cardiovascular diseases, shows increasing prevalence worldwide. Several studies have established associations of both apolipoprotein A5 (APOA5) gene variants and upstream stimulatory factor 1 (USF1) gene variants with blood lipid levels and metabolic syndrome. USF1 is a transcription factor for APOA5.

METHODS

We investigated a possible interaction between these two genes on the risk for the metabolic syndrome, using data from the German population-based KORA survey 4 (1,622 men and women aged 55-74 years). Seven APOA5 single nucleotide polymorphisms (SNPs) were analyzed in combination with six USF1 SNPs, applying logistic regression in an additive model adjusting for age and sex and the definition for metabolic syndrome from the National Cholesterol Education Program's Adult Treatment Panel III (NCEP (AIII)) including medication.

RESULTS

The overall prevalence for metabolic syndrome was 41%. Two SNP combinations showed a nominal gene-gene interaction (p values 0.024 and 0.047). The effect of one SNP was modified by the other SNP, with a lower risk for the metabolic syndrome with odds ratios (ORs) between 0.33 (95% CI = 0.13-0.83) and 0.40 (95% CI = 0.15-1.12) when the other SNP was homozygous for the minor allele. Nevertheless, none of the associations remained significant after correction for multiple testing.

CONCLUSION

Thus, there is an indication of an interaction between APOA5 and USF1 on the risk for metabolic syndrome.

Causes and metabolic consequences of Fatty liver

Type 2 diabetes and cardiovascular disease represent a serious threat to the health of the population worldwide. Although overall adiposity and particularly visceral adiposity are established risk factors for these diseases, in the recent years fatty liver emerged as an additional and independent factor. However, the pathophysiology of fat accumulation in the liver and the cross-talk of fatty liver with other tissues involved in metabolism in humans are not fully understood. Here we discuss the mechanisms involved in the pathogenesis of hepatic fat accumulation, particularly the roles of body fat distribution, nutrition, exercise, genetics, and gene-environment interaction. Furthermore, the effects of fatty liver on glucose and lipid metabolism, specifically via induction of subclinical inflammation and secretion of humoral factors, are highlighted. Finally, new aspects regarding the dissociation of fatty liver and insulin resistance are addressed.

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.

Allelic variants of upstream transcription factor 1 associate with carotid artery intima-media thickness: the Cardiovascular Risk in Young Finns study

BACKGROUND

Polymorphisms of the upstream transcription factor 1 (USF1) have been associated with familial combined hyperlipidemia and coronary heart disease. The impact of this gene on subclinical atherosclerosis is unknown. Associations of 3 allelic variants of the USF1 gene and their haplotypes with carotid artery intima - media thickness (IMT), carotid artery compliance (CAC) and brachial artery flow mediated dilatation (FMD) were studied in a population of Finnish healthy young adults.

METHODS AND RESULTS

The study population comprised 2,281 individuals participating in the Cardiovascular Risk in Young Finns study. IMT, CAC and FMD values were measured by ultrasound examination. Genotypes were analysed using the 5' nuclease assay. A significant difference in IMT was found for usf1s1 (rs3737787) and usf1s8 (rs2516838) genotypes (p-values 0.046 and 0.021, respectively). Moreover, there was a significant difference between groups in haplotype 1 and haplotype 2 for IMT (p-values 0.011 and 0.028 respectively). In multivariate stepwise linear regression models adjusted by age, sex, body mass index, systolic and diastolic blood pressures, smoking, C-reactive protein, glucose, high- and low-density lipoprotein-cholesterols and triglycerides there were significant associations for the usf1s1 minor genotype AA to predict low IMT (p=0.038) and usf1s8 minor genotype GG to predict high IMT (p=0.003). There was also a significant association for haplotype 2 to predict low IMT in the otherwise similar multivariate model (p=0.006). No associations were found for polymorphisms and CAC, FMD or serum lipids.

CONCLUSIONS

The rs2516838 and rs3737787 polymorphisms of USF1 influence the carotid artery IMT, which is a new finding.

Isolated populations and complex disease gene identification

Isolated populations can be useful for the identification of genes underlying common complex diseases.

The utility of genetically isolated populations (population isolates) in the mapping and identification of genes is not only limited to the study of rare diseases; isolated populations also provide a useful resource for studies aimed at improved understanding of the biology underlying common diseases and their component traits. Well characterized human populations provide excellent study samples for many different genetic investigations, ranging from genome-wide association studies to the characterization of interactions between genes and the environment.

Upstream transcription factor 1 (USF1) in risk of type 2 diabetes: association study in 2000 Dutch Caucasians

Type 2 diabetes shares substantial genetic and phenotypic overlap with familial combined hyperlipidemia. Upstream stimulatory factor 1 (USF1), a well-established susceptibility gene for familial combined hyperlipidemia, is postulated to be such a shared genetic determinant. We evaluated two established variants in familial combined hyperlipidemia (rs2073658 and rs3737787) for association with type 2 diabetes in two Dutch case-control samples (N=2011). The first case-control sample comprised 501 subjects with type 2 diabetes from the Breda cohort and 920 healthy blood bank donors of Dutch Caucasian origin. The second case-control sample included 211 subjects with type 2 diabetes, and 379 normoglycemic controls. SNP rs2073658 and SNP rs3737787 were in perfect linkage disequilibrium. In the first case-control sample, prevalence of the major allele was higher in patients than in controls (75% versus 71%, OR=1.25, p=0.018). A similar effect-size and -direction was observed in the second case-control sample (76% versus 72%, OR=1.22, p=0.16). A combined analysis strengthened the evidence for association (OR=1.23, p=0.006). Notably, the increased risk for type 2 diabetes could be ascribed to the major allele, and its high frequency translated to a substantial population attributable risk of 14.5%. In conclusion, the major allele of rs2073658 in the USF1 gene is associated with a modestly increased risk to develop type 2 diabetes in Dutch Caucasians, with considerable impact at the population level.

Clinical and laboratory assessment of cardiovascular risk in children: Guidelines for screening, evaluation, and treatment

The early lesions of atherosclerosis begin in childhood and are related to antecedent cardiovascular disease (CVD) risk factors. Environmental and genetic factors (eg, diet, obesity, exercise, and certain inherited dyslipidemias) influence progression of such lesions. Identification of youth at risk for atherosclerosis includes an integrated assessment of these predisposing factors. Treatment starts with a diet low in total and saturated fat and cholesterol, use of water-soluble fiber, plant stanols and plant sterols, weight control, and exercise. Drug therapy, for example, with inhibitors of hydroxymethylglutaryl-CoA reductase, bile acid sequestrants, and cholesterol absorption inhibitors, can be considered in those with a positive family history of premature CVD and low-density lipoprotein cholesterol >160 mg/dL after dietary and hygienic measures. Candidates for drug therapy often include those with familial hypercholesterolemia, familial combined hyperlipidemia, the metabolic syndrome, polycystic ovarian syndrome, type 1 diabetes, and the nephrotic syndrome. Such dietary and drug therapy appears safe and efficacious. Early identification and treatment of youth with CVD risk factors and dyslipidemia are likely to retard the atherosclerotic process. Optimal detection and treatment of high-risk children either from the general population or from families with premature CVD will require a comprehensive universal screening and evaluation program.

Biochemical and structural characterization of apolipoprotein A-I binding protein, a novel phosphoprotein with a potential role in sperm capacitation

The physiological changes that sperm undergo in the female reproductive tract rendering them fertilization-competent constitute the phenomenon of capacitation. Cholesterol efflux from the sperm surface and protein kinase A (PKA)-dependent phosphorylation play major regulatory roles in capacitation, but the link between these two phenomena is unknown. We report that apolipoprotein A-I binding protein (AI-BP) is phosphorylated downstream to PKA activation, localizes to both sperm head and tail domains, and is released from the sperm into the media during in vitro capacitation. AI-BP interacts with apolipoprotein A-I, the component of high-density lipoprotein involved in cholesterol transport. The crystal structure demonstrates that the subunit of the AI-BP homodimer has a Rossmann-like fold. The protein surface has a large two compartment cavity lined with conserved residues. This cavity is likely to constitute an active site, suggesting that AI-BP functions as an enzyme. The presence of AI-BP in sperm, its phosphorylation by PKA, and its release during capacitation suggest that AI-BP plays an important role in capacitation possibly providing a link between protein phosphorylation and cholesterol efflux.

Association analysis of allelic variants of USF1 in coronary atherosclerosis

OBJECTIVE

USF1 regulates the transcription of more than 40 cardiovascular related genes and is well established as a gene associated with familial combined hyperlipidemia, a condition increasing the risk for coronary heart disease. No detailed data, however, exists on the impact of this gene to the critical outcome at the tissue level: different types of atherosclerotic lesions.

METHODS AND RESULTS

We analyzed the USF1 in 2 autopsy series of altogether 700 middle-aged men (the Helsinki Sudden Death Study) with quantitative morphometric measurements of coronary atherosclerosis. SNP rs2516839, tagging common USF1 haplotypes, associated with the presence of several types of atherosclerotic lesions, particularly with the proportion of advanced atherosclerotic plaques (P=0.02) and area of calcified lesions (P<0.001) of the coronary arteries. Importantly, carriers of risk alleles of rs2516839 also showed a 2-fold risk for sudden cardiac death (genotype TT versus CC; OR 2.10, 95% CI 1.17 to 3.75, P=0.04). The risk effect of rs2516839 was present also in aorta samples of the men.

CONCLUSIONS

Our findings in this unique study sample suggest that USF1 contributes to atherosclerosis, the pathological arterial wall phenotype resulting in coronary heart disease and in its most dramatic consequence-sudden cardiac death.

A novel promoter polymorphism in the human gene GNAS affects binding of transcription factor upstream stimulatory factor 1, Galphas protein expression and body weight regulation

OBJECTIVES

Body weight regulation is under complex control involving the central nervous system and peripheral pathways. The beta-adrenoceptor Galphas protein system plays an important role in heart rate regulation and lipid mobilization suggesting a key role for the stimulatory G protein Galphas in body weight regulation.

METHODS

We sequenced the whole GNAS promoter to identify a functional variant which results in altered Galphas expression. We genotyped 110 participants of a randomized placebo-controlled weight loss trial who were under a low calorie diet and were additionally treated with either placebo or 15 mg sibutramine daily for 54 weeks and associated the respective alleles with regard to treatment outcome using an intention-to-treat analysis.

RESULTS

A G>A transition at position -1211 the human GNAS promoter (minor allele frequency=0.36) was identified resulting in altered upstream stimulatory factor 1 transcription factor binding, promoter activity, Galphas expression, and lipolysis. Under a low calorie diet -1211GG genotypes lost significantly more weight compared with A-allele carriers (placebo group: 1211GG, 7.5+/-0.4 versus -1211A, 4.5+/-0.3 kg, P=0.020). Sibutramine was effective only in A-allele carriers whereas GG genotypes showed no additional weight loss under sibutramine but showed the strongest increases in resting heart rate (8.5 bpm; 95% confidence interval: 2.7-14.21 bpm; P=0.005) and systolic blood pressure (9.1 mmHg, 95% confidence interval: 3.1-15.1; P=0.004) compared with placebo.

CONCLUSIONS

Determination of GNAS promoter alleles may identify obese individuals who lose weight easily under lifestyle changes alone but also those who benefit from adjunct sibutramine therapy.

Translating molecular discoveries into new therapies for atherosclerosis

Atherosclerosis is characterized by the thickening of the arterial wall and is the primary cause of coronary artery disease and cerebrovascular disease, two of the most common causes of illness and death worldwide. Clinical trials have confirmed that certain lipoproteins and the renin-angiotensin-aldosterone system are important in the pathogenesis of atherosclerotic cardiovascular disease, and that interventions targeted towards these are beneficial. Furthermore, efforts to understand how risk factors such as high blood pressure, dysregulated blood lipids and diabetes contribute to atherosclerotic disease, as well as to understand the molecular pathogenesis of atherosclerotic plaques, are leading to new targets for therapy.

Variations in DNA elucidate molecular networks that cause disease

Identifying variations in DNA that increase susceptibility to disease is one of the primary aims of genetic studies using a forward genetics approach. However, identification of disease-susceptibility genes by means of such studies provides limited functional information on how genes lead to disease. In fact, in most cases there is an absence of functional information altogether, preventing a definitive identification of the susceptibility gene or genes. Here we develop an alternative to the classic forward genetics approach for dissecting complex disease traits where, instead of identifying susceptibility genes directly affected by variations in DNA, we identify gene networks that are perturbed by susceptibility loci and that in turn lead to disease. Application of this method to liver and adipose gene expression data generated from a segregating mouse population results in the identification of a macrophage-enriched network supported as having a causal relationship with disease traits associated with metabolic syndrome. Three genes in this network, lipoprotein lipase (Lpl), lactamase beta (Lactb) and protein phosphatase 1-like (Ppm1l), are validated as previously unknown obesity genes, strengthening the association between this network and metabolic disease traits. Our analysis provides direct experimental support that complex traits such as obesity are emergent properties of molecular networks that are modulated by complex genetic loci and environmental factors.

Association of F11 receptor gene polymorphisms with central obesity and blood pressure

OBJECTIVES

F11 receptor, also known as junctional adhesion molecule-1, in the autonomic nervous system is implicated in the development of hypertension in spontaneous hypertensive rats. We investigated the association of single nucleotide polymorphisms (SNPs) in the F11 receptor gene (F11R) with hypertension and central obesity in Hong Kong Chinese.

METHODS

Seven tagging SNPs were identified in the HapMap database. Genotyping was performed using Sequenom MassArray in 263 hypertensive subjects and 393 normotensive controls, of whom 263 matched the cases in age and sex.

RESULTS

When subjects on anti-hypertensive medication were excluded, rs790056 and rs2774276 were associated with lower systolic blood pressure (TT:124.8 +/- 18.3 mmHg vs. TC + CC: 120.2 +/- 15.5 mmHg, P = 0.004 and CC: 124.7 +/- 18.5 mmHg vs. CG+GG: 120.5 +/- 15.1 mmHg, P = 0.007 respectively). Comparing 213 subjects with central obesity with 213 controls matched for sex and age, rs2481084 and rs3737787 were associated with lower odds of central obesity (odds ratio = 0.516, P = 0.002 and odds ratio = 0.540, P = 0.005 respectively). All these associations remained significant after correction for multiple testing. Analysis of statistically similar SNPs suggested that the causative variants for systolic blood pressure were located in F11R, whilst those for central obesity could be due to causative variants in the transcription factor 1 gene immediately upstream.

CONCLUSIONS

F11 receptor plays a role in blood pressure regulation, not only in rats but also in man. The link between F11 receptor and central obesity merits further investigation.

USF1 gene variants contribute to metabolic traits in men in a longitudinal 32-year follow-up study

AIMS/HYPOTHESIS

Genetic variants of upstream transcription factor 1 (USF1) have previously been associated with dyslipidaemias in family studies. Our aim was to further address the role of USF1 in metabolic syndrome and cardiovascular traits at the population level in a large Swedish male cohort (n=2,322) with multiple measurements for risk factors during 32 years of follow-up.

METHODS

Participants, born in 1920-1924, were examined at 50, 60, 70 and 77 years of age. The follow-up period for cardiovascular events was 1970-2002. We genotyped three haplotype tagging polymorphisms capturing the major allelic variants of USF1.

RESULTS

SNP rs2774279 was associated with the metabolic syndrome. The minor allele of rs2774279 was less common among individuals with metabolic syndrome than among healthy controls [p=0.0029 when metabolic syndrome was defined according to the National Cholesterol Education Program Adult Treatment Panel III; p=0.0073 when defined according to the International Diabetes Federation (IDF)]. The minor allele of rs2774279 was also associated with lower BMI, lower fasting glucose values and higher HDL-cholesterol concentrations in longitudinal analyses. With SNP rs2073658, a borderline association with metabolic syndrome was observed (p=0.036, IDF), the minor allele being the risk-increasing allele. The minor allele of rs2073658 also associated with higher total and LDL-cholesterol, apolipoprotein B-100 and lipoprotein(a) concentrations in longitudinal analyses. Importantly, these trends with respect to the allelic variants prevailed throughout the follow-up time of three decades.

CONCLUSIONS/INTERPRETATION

Our results suggest that USF1 variants associate with the metabolic syndrome at population level and influence the cardiovascular risk factors throughout adulthood in a consistent, longitudinal manner.

Tissue-specific stable isotope measurements of postprandial lipid metabolism in familial combined hyperlipidaemia

OBJECTIVE

The metabolic defects underlying familial combined hyperlipidaemia (FCHL) are not clearly understood. We used stable isotope techniques combined with tissue-specific measurements in adipose tissue and forearm muscle to investigate fatty acid handling by these tissues in the fasting and postprandial states.

RESULTS

Patients were insulin resistant as shown by higher glucose and insulin concentrations and lower muscle glucose extraction than controls. Plasma triacylglycerol (TAG) concentrations were higher in patients. Adipose tissue TAG extraction was not lower in patients than controls, although TAG clearance was lower, probably representing saturation. Following a test meal, patients showed a greater increase in chylomicron-TAG concentrations. There were no differences between FCHL patients and controls in postprandial suppression of non-esterified fatty acid (NEFA) concentrations or postprandial NEFA release, but patients had greater trapping of exogenous fatty acids in adipose tissue. 3-Hydroxybutyrate concentrations were lower in patients indicative of decreased hepatic fatty acid oxidation.

CONCLUSIONS

In this group of patients with FCHL, the major defect appeared to be overproduction of TAG by the liver due to decreased fatty acid oxidation, with fatty acids directed to TAG synthesis. We found no evidence of decreased lipoprotein lipase action or impaired fatty acid re-esterification in adipose tissue.

Body mass index is associated with USF1 haplotype in Korean premenopausal women

The upstream stimulatory factor 1 (USF1) gene has been shown to play an essential role as the cause of familial combined hyperlipidemia, and there are several association studies on the relationship between USF1 and metabolic disorders. In this study, we analyzed two single nucleotide polymorphisms in USF1 rs2073653 (306A>G) and rs2516840 (1748C>T) between the case (dyslipidemia or obesity) group and the control group in premenopausal females, postmenopausal females, and males among 275 Korean subjects. We observed a statistically significant difference in the GC haplotype between body mass index (BMI) > or =25 kg/m2) and BMI <25 kg/m2 groups in premenopausal females ( chi2=4.23, p=0.04). It seems that the USF1 GC haplotype is associated with BMI in premenopausal Korean females.

Whole-genome maps of USF1 and USF2 binding and histone H3 acetylation reveal new aspects of promoter structure and candidate genes for common human disorders

Transcription factors and histone modifications are crucial regulators of gene expression that mutually influence each other. We present the DNA binding profiles of upstream stimulatory factors 1 and 2 (USF1, USF2) and acetylated histone H3 (H3ac) in a liver cell line for the whole human genome using ChIP-chip at a resolution of 35 base pairs. We determined that these three proteins bind mostly in proximity of protein coding genes transcription start sites (TSSs), and their bindings are positively correlated with gene expression levels. Based on the spatial and functional relationship between USFs and H3ac at protein coding gene promoters, we found similar promoter architecture for known genes and the novel and less-characterized transcripts human mRNAs and spliced ESTs. Furthermore, our analysis revealed a previously underestimated abundance of genes in a bidirectional conformation, where USFs are bound in between TSSs. After taking into account this promoter conformation, the results indicate that H3ac is mainly located downstream of TSS, and it is at this genomic location where it positively correlates with gene expression. Finally, USF1, which is associated to familial combined hyperlipidemia, was found to bind and potentially regulate nuclear mitochondrial genes as well as genes for lipid and cholesterol metabolism, frequently in collaboration with GA binding protein transcription factor alpha (GABPA, nuclear respiratory factor 2 [NRF-2]). This expands our understanding about the transcriptional control of metabolic processes and its alteration in metabolic disorders.

Identifying genes for coronary artery disease: An idea whose time has come

BACKGROUND

Coronary artery disease (CAD) remains the number one killer in the western world. Genetics accounts for greater than 50% of the risk for CAD. Genetic screening and early prevention in individuals identified as being at increased risk could dramatically reduce the prevalence of CAD, thus necessitating the identification of genes predisposing to CAD. Studies of genes identified by the candidate gene approach have not been replicated due, in part, to inadequate sample size. Genome-wide scan association studies have been limited by the use of thousands of markers rather than the hundreds of thousands required, and by the use of hundreds of individuals rather than the thousands required. Replication of positive findings in an independent population is essential. To detect a minor allele frequency of 5% or greater with an odds ratio for risk of 1.3 or greater and 90% power, an estimated 14,000 (9000 affected and 5000 control) subjects are required.

METHODS

The Affymetrix GeneChip Human Mapping 500K Array Set (Affymetrix Inc, USA) provides a marker every 6000 base pairs as required, and is being used to genotype 1000 cases of premature CAD and 1000 normal subjects, followed by replication in 8000 affected individuals and 4000 control subjects. The phenotype is confirmed or excluded by coronary arteriograms by catheterization or multislice computed tomography.

RESULTS

Since 2005, more than 800 million genotypes have been performed and analyses performed on 500 control subjects and 500 affected individuals. Several thousand significant single nucleotide polymorphisms and 130 clusters associated with CAD have been identified.

CONCLUSIONS

This is the first genome-wide scan using the 500,000 marker set in a case-control association study for CAD genes. Several genes associated with CAD appear promising.

TCF7L2 is associated with high serum triacylglycerol and differentially expressed in adipose tissue in families with familial combined hyperlipidaemia

AIMS/HYPOTHESIS

Common DNA variants of the transcription factor 7-like 2 gene (TCF7L2) are associated with type 2 diabetes. Familial combined hyperlipidaemia (FCHL) is characterised by hypertriacylglycerolaemia, hypercholesterolaemia, or both. Additionally, disturbances in glucose metabolism are commonly seen in FCHL. Therefore, we hypothesised that TCF7L2 may contribute to the genetic susceptibility for this common dyslipidaemia.

METHODS

We investigated the effect of the TCF7L2 variants, rs7903146 and rs12255372, on FCHL and its component traits triacylglycerol (TG), total cholesterol (TC) and apolipoprotein B (ApoB) in 759 individuals from 55 Mexican families. As a replication sample, 719 individuals from 60 Finnish FCHL families were analysed. We also used quantitative RT-PCR to evaluate the transcript levels of TCF7L2 in 47 subcutaneous fat biopsies from unrelated Mexican FCHL and normolipidaemic participants.

RESULTS

Significant evidence for association was observed for high TG for the T alleles of rs7903146 and rs12255372 (p = 0.005 and p = 0.01) in Mexican FCHL families. No evidence for association was observed for FCHL, TC, ApoB or glucose in Mexicans. When testing rs7903146 and rs12255372 for replication in Finnish FCHL families, these single nucleotide polymorphisms were associated with TG (p = 0.01 and p = 0.007). Furthermore, we observed statistically significant decreases in the mRNA levels (p = 0.0002) of TCF7L2 in FCHL- and TG-affected individuals. TCF7L2 expression was not altered by the SNP genotypes.

CONCLUSIONS/INTERPRETATION

These data show that rs7903146 and rs12255372 are significantly associated with high TG in FCHL families from two different populations. In addition, significantly decreased expression of TCF7L2 was observed in TG- and FCHL-affected individuals.

Apolipoprotein AII is a regulator of very low density lipoprotein metabolism and insulin resistance

Apolipoprotein AII (apoAII) transgenic (apoAIItg) mice exhibit several traits associated with the insulin resistance (IR) syndrome, including IR, obesity, and a marked hypertriglyceridemia. Because treatment of the apoAIItg mice with rosiglitazone ameliorated the IR and hypertriglyceridemia, we hypothesized that the hypertriglyceridemia was due largely to overproduction of very low density lipoprotein (VLDL) by the liver, a normal response to chronically elevated insulin and glucose. We now report in vivo and in vitro studies that indicate that hepatic fatty acid oxidation was reduced and lipogenesis increased, resulting in a 25% increase in triglyceride secretion in the apoAIItg mice. In addition, we observed that hydrolysis of triglycerides from both chylomicrons and VLDL was significantly reduced in the apoAIItg mice, further contributing to the hypertriglyceridemia. This is a direct, acute effect, because when mouse apoAII was injected into mice, plasma triglyceride concentrations were significantly increased within 4 h. VLDL from both control and apoAIItg mice contained significant amounts of apoAII, with approximately 4 times more apoAII on apoAIItg VLDL. ApoAII was shown to transfer spontaneously from high density lipoprotein (HDL) to VLDL in vitro, resulting in VLDL that was a poorer substrate for hydrolysis by lipoprotein lipase. These results indicate that one function of apoAII is to regulate the metabolism of triglyceride-rich lipoproteins, with HDL serving as a plasma reservoir of apoAII that is transferred to the triglyceride-rich lipoproteins in much the same way as VLDL and chylomicrons acquire most of their apoCs from HDL.

USF1 Gene Variants, Cardiovascular Risk, and Mortality in European Americans

Objective— A common haplotype of the upstream transcription factor 1 gene ( USF1 ) has been associated with decreased susceptibility to familial combined hyperlipidemia (FCHL) and, paradoxically, with increased risk of cardiovascular disease (CVD) and all-cause mortality.

Methods and Results— We assessed associations between USF1 tagSNPs, CVD risk factors, and aging-related phenotypes using data from 2 large population-based cohorts, Coronary Artery Risk Development in Young Adults (CARDIA) and the Cardiovascular Health Study (CHS), comprising younger and older adults, respectively. In CARDIA, each additional copy of the FCHL low-risk allele was associated with 2.4 mg/dL lower levels of LDL cholesterol ( P =0.01) and decreased risk of subclinical atherosclerosis as assessed by coronary artery calcium (odds ratio 0.79; 95%CI 0.63 to 0.98). Whereas there was little association between USF1 genotype and metabolic or CVD traits in older adults from CHS, the USF1 low-risk dyslipidemia allele was associated with higher plasma C-reactive protein and interleukin (IL)-6 levels and with increased risk of mortality, particularly attributable to noncardiovascular causes.

Conclusions— There appears to be a complex and possibly age-dependent relationship between USF1 genotype, atherosclerosis phenotypes, and CVD risk. USF1 may influence mortality through pathways distinct from atherosclerosis. Alternatively, linkage disequilibrium with neighboring polymorphisms in other genes such as F11R may be responsible for the observed USF1 genotype–phenotype associations in older adults.

European guidelines on cardiovascular disease prevention in clinical practice: executive summary. Fourth Joint Task Force of the European Society of Cardiology and other societies on cardiovascular disease prevention in clinical practice (constituted by representatives of nine societies and by invited experts)

Other experts who contributed to parts of the guidelines: Edmond Walma, Schoonhoven (The Netherlands), Tony Fitzgerald, Dublin (Ireland), Marie Therese Cooney, Dublin (Ireland), Alexandra Dudina, Dublin (Ireland) European Society of Cardiology (ESC) Committee for Practice Guidelines (CPG):, Alec Vahanian (Chairperson) (France), John Camm (UK), Raffaele De Caterina (Italy), Veronica Dean (France), Kenneth Dickstein (Norway), Christian Funck-Brentano (France), Gerasimos Filippatos (Greece), Irene Hellemans (The Netherlands), Steen Dalby Kristensen (Denmark), Keith McGregor (France), Udo Sechtem (Germany), Sigmund Silber (Germany), Michal Tendera (Poland), Petr Widimsky (Czech Republic), José Luis Zamorano (Spain)

Document reviewers: Irene Hellemans (CPG Review Coordinator) (The Netherlands), Attila Altiner (Germany), Enzo Bonora (Italy), Paul N. Durrington (UK), Robert Fagard (Belgium), Simona Giampaoli(Italy), Harry Hemingway (UK), Jan Hakansson (Sweden), Sverre Erik Kjeldsen (Norway), Mogens Lytken Larsen (Denmark), Giuseppe Mancia (Italy), Athanasios J. Manolis (Greece), Kristina Orth-Gomer (Sweden), Terje Pedersen (Norway), Mike Rayner (UK), Lars Ryden (Sweden), Mario Sammut (Malta), Neil Schneiderman (USA), Anton F. Stalenhoef (The Netherlands), Lale Tokgözoglu (Turkey), Olov Wiklund (Sweden), Antonis Zampelas (Greece)

USF1 Contributes to High Serum Lipid Levels in Dutch FCHL Families and U.S. Whites With Coronary Artery Disease

Objective— Familial combined hyperlipidemia (FCHL) characterized by high serum total cholesterol and/or triglycerides (TGs) is a common dyslipidemia predisposing to coronary artery disease (CAD). Recently, the upstream transcription factor 1 ( USF1 ) was linked and associated with FCHL and TGs in Finnish FCHL families. Here we examined the previously associated rs3737787 SNP in extended Dutch FCHL families (n=532) and in a cohort of US subjects who underwent diagnostic coronary angiography (n=1533).

Methods and Results— In males of the Dutch FCHL families, we observed significant sex-dependent associations between the common allele of rs3737787 and FCHL, TGs, and related metabolic traits ( P =0.02 to 0.006). In the U.S. Whites, sex-dependent associations with TGs and related metabolic traits were observed for the common allele of rs3737787 in males ( P =0.04 to 0.02) and rare allele in females ( P =0.05 to 0.002). This intriguing relationship was further supported by the highly significant genotype x sex interactions observed for TGs in the Dutch and TGs and body mass index (BMI) in U.S. White subjects with CAD ( P =0.0005 to 0.00004).

Conclusion— These data show that USF1 influences several cardiovascular risk factors in a sex-dependent manner in Dutch FCHL families and U.S. Whites with CAD. A significant interaction between sex and genotype was shown to affect TGs and BMI.

Thioredoxin and thioredoxin-binding protein-2 in cancer and metabolic syndrome

Thioredoxin (TRX), a small redox-active multifunctional protein, acts as a potent antioxidant and a redox regulator in signal transduction. TRX expression is elevated in various types of human cancer. Overexpression of TRX introduces resistance to anti-cancer drugs or radiation-induced apoptosis; however, there is no evidence that the incidence of cancer is frequent in TRX-transgenic mice or that the administration of recombinant human TRX enhances tumor growth. Plasma/serum level of TRX is a good marker for oxidative stress-induced various disorders, including metabolic syndrome. Thioredoxin-binding protein-2 (TBP-2), which was originally identified as a negative regulator of TRX, acts as a growth suppressor and a regulator in lipid metabolism. TBP-2 expression is downregulated in various types of human cancer. TBP-2 deficiency induces lipid dysfunction and a phenotype resembling Reye syndrome. Thus, TRX and TBP-2 play important roles in the pathophysiology of cancer and metabolic syndrome by direct interaction or by independent mechanisms.

USF1 recruits histone modification complexes and is critical for maintenance of a chromatin barrier

The insulator element at the 5' end of the chicken beta-globin locus acts as a barrier, protecting transgenes against silencing effects of adjacent heterochromatin. We showed earlier that the transcription factor USF1 binds within the insulator and that this site is important for generating in adjacent nucleosomes histone modifications associated with active chromatin and, by inference, with barrier function. To understand the mechanism of USF1 action, we have characterized USF1-containing complexes. USF1 interacts directly with the histone H4R3-specific methyltransferase PRMT1. USF1, PRMT1, and the histone acetyltransferases (HATs) PCAF and SRC-1 form a complex with both H4R3 histone methyltransferase and HAT activities. Small interfering RNA downregulation of USF1 results in localized loss of H4R3 methylation, and other histone modifications associated with euchromatin, at the insulator. A dominant negative peptide that interferes with USF1 binding to DNA causes silencing of an insulated reporter construct, indicating abolition of barrier function. These results show that USF1 plays a direct role in maintaining the barrier, supporting a model in which the insulator works as a barrier by maintaining a local environment of active chromatin.

Important differences between human and mouse APOE gene promoters: limitation of mouse APOE model in studying Alzheimer's disease

Apolipoprotein E (ApoE), encoded by the apolipoprotein E gene (APOE), plays an important role in the pathogenesis of Alzheimer's disease (AD). The APOE epsilon4 variant is strongly associated with AD. APOE promoter polymorphisms have also been reported to associate with higher AD risk. Mouse models of APOE expression have long been used to study the pathogenesis of AD. Elucidating the role of the APOE gene in AD requires understanding of how its regulation differs between mouse and human APOE genes, and how the differences influence AD risk. We compared the structure and function of both the human APOE gene promoter (hAPOEP) and mouse APOE gene promoter (mAPOEP) regions. Homology is less than 40% at 180 bp or more upstream of the two species' transcription start site (TSS, +1). Functional analysis revealed both similarities and important differences between the two sequences, significantly affected by human versus rodent cell line origin. We likewise probed nuclear extracts from several cell lines of different origins (astrocytic, glial, and neuronal) and mouse brain with specific hAPOEP and mAPOEP fragments. Each fragment shared DNA-protein interactions with the other but, notably, also bound distinct factors, demonstrated by gel shift and southwestern analyses. We determined possible identities for these distinct factors. These results suggest that regulation of mouse and human APOE genes may be sufficiently unique to justify the use of both the human APOE promoter sequence in transgenic rodent models and non-rodent AD models for studying factors involved in AD pathogenesis.

The role of junctional adhesion molecules in vascular inflammation

Junctional adhesion molecules (JAMs) of the immunoglobulin superfamily are important in the control of vascular permeability and leukocyte transmigration across endothelial-cell surfaces, by engaging in homophilic, heterophilic and lateral interactions. Through their localization on the endothelial-cell surface and expression by platelets, JAMs contribute to adhesive interactions with circulating leukocytes and platelets. Antibody-blocking studies and studies using genetically modified mice have implicated these functions of JAMs in the regulation of leukocyte recruitment to sites of inflammation and ischaemia-reperfusion injury, in growth-factor-mediated angiogenesis, atherogenesis and neointima formation. The comparison of different JAM-family members and animal models, however, shows that the picture remains rather complex. This Review summarizes recent progress and future directions in understanding the role of JAMs as 'gate keepers' in inflammation and vascular pathology.

Common ABCA1 variants, HDL levels, and cellular cholesterol efflux in subjects with familial low HDL

HDL promotes cholesterol efflux from peripheral cells via ABCA1 in the first step of reverse cholesterol transport (RCT). We investigated whether the early steps of RCT were disturbed in subjects with familial low HDL and an increased risk for early atherosclerosis. Cholesterol efflux from monocyte-derived macrophages to lipid-free apolipoprotein A-I (apoA-I; %) was measured in 22 patients with familial low HDL without Tangier disease mutations and in 21 healthy controls. In addition, we defined the different alleles of ABCA1 using single-nucleotide polymorphism haplotypes and measured ABCA1 and ABCG1 mRNA transcript levels in cholesterol-loaded macrophages. Similar ABCA1-mediated cholesterol efflux levels were observed for macrophages derived from control subjects and from low-HDL subjects. However, when efflux of cholesterol was estimated as cholesterol efflux to apoA-I (%)/relative ABCA1 mRNA expression level, cholesterol removal was significantly (P = 0.001) lower in the low-HDL group. Cholesterol-loaded macrophages from low-HDL subjects showed significantly increased levels of ABCA1 mRNA but not of ABCG1 mRNA and were more often carriers of the rare ABCA1 alleles L158 and R219K. These results suggest that defective ABCA1 function in cholesterol-loaded macrophages is one potential contributor to the impaired RCT process and the increased coronary heart disease risk in subjects with familial low HDL.

Associations between USF1 gene variants and cardiovascular risk factors in the Quebec Family Study

Cardiovascular (CVD) risk factors are under the influence of environmental and genetic factors. Human upstream transcription factor 1 gene (USF1) encodes for a transcription factor, which modulates the expression of genes involved in lipid and carbohydrate metabolic pathways. The aim of this study was to test the hypothesis that USF1 gene variants are associated with CVD risk factors in the Quebec Family Study (QFS). USF1 has been sequenced in 20 QFS subjects with high plasma apolipoprotein B100 (APOB) levels (>1.14 g/l) and small, dense low-density lipoprotein (LDL) particles (> or =250.7 Angstroms and < or =255.9 Angstroms), as well as in five subjects with larger LDL particles. Ten variants were identified in non-coding regions of USF1. Two of these polymorphisms (intron 7 c.561-100 G>A, and exon 11 c.*187 C>T) as well as the c.-56 A>G polymorphism, were genotyped and analyzed in 760 subjects from QFS. Association studies showed that women with c.561-100 A/A and c.*187 T/T genotypes had more favorable adiposity indices (<0.04). In summary, significant associations between relatively common USF1 genetic variants and CVD risk factors were observed in French Canadians.

Genetic variation in thioredoxin interacting protein (TXNIP) is associated with hypertriglyceridaemia and blood pressure in diabetes mellitus

AIMS

Thioredoxin interacting protein (TXNIP) is an attractive candidate gene for diabetes or diabetic dyslipidaemia, since TXNIP is the strongest glucose-responsive gene in pancreatic B-cells, TXNIP deficiency in a mouse model is associated with hyperlipidaemia and TXNIP is located in the 1q21-1q23 chromosomal Type 2 diabetes mellitus (DM) locus. We set out to investigate whether metabolic effects of TXNIP that were previously reported in a murine model are also relevant in human Type 2 DM.

METHODS

The frequency distribution of a 3' UTR single nucleotide polymorphism (SNP) in TXNIP was investigated in subjects with normal glucose tolerance (NGT; n = 379), impaired glucose tolerance (IGT; n = 228) and Type 2 DM (n = 230). Metabolic data were used to determine the effect of this SNP on parameters associated with lipid and glucose metabolism.

RESULTS

The frequency of the TXNIP variation did not differ between groups, but within the group of diabetic subjects, carriers of the TXNIP-T variant had 1.6-fold higher triglyceride concentrations (P = 0.015; n = 136) and a 5.5-mmHg higher diastolic blood pressure (P = 0.02; n = 212) than homozygous carriers of the common C-allele, whereas in non-diabetic subjects fasting glucose was 0.26 mmol/l lower (P = 0.002; n = 478) in carriers of the T-allele. Moreover, a significant interaction between plasma glucose concentrations and TXNIP polymorphism on plasma triglycerides was observed (P = 0.012; n = 544).

CONCLUSION

This is the first report to implicate TXNIP in a human disorder of energy metabolism, Type 2 diabetes. The effect of TXNIP on triglycerides is influenced by plasma glucose concentrations, suggesting that the biological relevance of TXNIP variations may be particularly relevant in recurrent episodes of hyperglycaemia.

Characterization of the Basal promoter element of human organic cation transporter 2 gene

Human organic cation transporter 2 (hOCT2; SLC22A2) is abundantly expressed in the kidney, and it plays important roles in the renal tubular secretion of cationic drugs. Although the transport characteristics of hOCT2 have been studied extensively, there is no information available for the transcriptional regulation of hOCT2. The present study was undertaken to identify the cis-element and trans-factor for basal expression of hOCT2. The transcription start site was located 385 nucleotides above the translation start site by using 5'-rapid amplification of cDNA ends. An approximately 4-kilobase fragment of the hOCT2 promoter region was isolated and the promoter activities were measured in the renal epithelial cell line LLC-PK1. A deletion analysis suggested that the region spanning -91 to -58 base pairs was essential for basal transcriptional activity. This region lacked a TATA-box but contained a CCAAT box and an E-box. Electrophoretic mobility shift assays showed that specific DNA/protein complexes were present in the E-box but not in the CCAAT box, and supershift assays revealed that upstream stimulatory factor 1 (USF-1), which belongs to the basic helix-loop-helix-leucine zipper family of transcription factors, bound to the E-box. Mutation of the E-box resulted in a decrease in hOCT2 promoter activity, and overexpression of USF-1 enhanced the hOCT2 promoter activity in a dose-dependent manner. This article reports the first characterization of the hOCT2 promoter and shows that USF-1 functions as a basal transcriptional regulator of the hOCT2 gene via the E-box.

High Frequency of a Retinoid X Receptor γ Gene Variant in Familial Combined Hyperlipidemia That Associates With Atherogenic Dyslipidemia

OBJECTIVE

The genetic background of familial combined hyperlipidemia (FCHL) has not been fully clarified. Because several nuclear receptors play pivotal roles in lipid metabolism, we tested the hypothesis that genetic variants of nuclear receptors contribute to FCHL.

METHODS AND RESULTS

We screened all the coding regions of the PPARalpha, PPARgamma2, PPARdelta, FXR, LXRalpha, and RXRgamma genes in 180 hyperlipidemic patients including 60 FCHL probands. Clinical characteristics of the identified variants were evaluated in other 175 patients suspected of coronary disease. We identified PPARalpha Asp140Asn and Gly395Glu, PPARgamma2 Pro12Ala, RXRgamma Gly14Ser, and FXR -1g->t variants. Only RXRgamma Ser14 was more frequent in FCHL (15%, P<0.05) than in other primary hyperlipidemia (4%) and in controls (5%). Among patients suspected of coronary disease, we identified 9 RXRgamma Ser14 carriers, who showed increased triglycerides (1.62+/-0.82 versus 1.91+/-0.42 [mean+/-SD] mmol/L, P<0.05), decreased HDL-cholesterol (1.32+/-0.41 versus 1.04+/-0.26, P<0.05), and decreased post-heparin plasma lipoprotein lipase protein levels (222+/-85 versus 149+/-38 ng/mL, P<0.01). In vitro, RXRgamma Ser14 showed significantly stronger repression of the lipoprotein lipase promoter than RXRgamma Gly14.

CONCLUSION

These findings suggest that RXRgamma contributes to the genetic background of FCHL.

Comparative genomic and functional analyses reveal a novel cis-acting PTEN regulatory element as a highly conserved functional E-box motif deleted in Cowden syndrome

Germline mutations in PTEN, encoding a phosphatase on 10q23, cause Cowden syndrome (CS) and Bannayan-Riley-Ruvalcaba syndrome (BRRS). Approximately, 10% of CS-related PTEN mutations occur in the PTEN promoter and 11% of BRRS-related mutations include large deletions, often favoring the gene's 5' end (exon 1, promoter). In order to better understand the mechanism(s) underlying the deregulation of PTEN in these syndromes, it is important that functional cis-regulatory elements be identified. We employed a comparative genomic approach combined with molecular genetic techniques to identify a highly conserved sequence upstream of the PTEN promoter, sharing 80% sequence identity among Homo sapiens, Mus musculus and Rattus norvegicus. Within this region, we identified a canonical E-box sequence (CACGTG) located at position -2181 to -2176, approximately 800 bp upstream of the PTEN core promoter and more than 1.1 kb upstream of its minimal promoter region (located at -958 to -821). In vitro assays suggest that this motif is recognized by members of the basic region-helix-loop-helix-leucine-zipper (bHLH-LZ) transcription factor family, USF1 and USF2, and reporter assays indicate that this novel E-box is involved in mediating PTEN transcriptional activation. Four of 30 CS/CS-like patients, without previously identified PTEN mutations, were found with germline deletions of the E-box element. Of the four, three had deletions stretching to exon 1, but not 3' of it; importantly, one classic CS patient harbored a germline deletion localizing to this E-box region, further affirming the role of this element in PTEN's regulation and deregulation, and its contribution to the pathogenesis of CS.

In vitro analysis of DNA-protein interactions by proximity ligation

Protein-binding DNA sequence elements encode a variety of regulated functions of genomes. Information about such elements is currently in a state of rapid growth, but improved methods are required to characterize the sequence specificity of DNA-binding proteins. We have established an in vitro method for specific and sensitive solution-phase analysis of interactions between proteins and nucleic acids in nuclear extracts, based on the proximity ligation assay. The reagent consumption is very low, and the excellent sensitivity of the assay enables analysis of as few as 1-10 cells. We show that our results are highly reproducible, quantitative, and in good agreement with both EMSA and predictions obtained by using a motif finding software. This assay can be a valuable tool to characterize in-depth the sequence specificity of DNA-binding proteins and to evaluate effects of polymorphisms in known transcription factor binding sites.

Apolipoprotein E polymorphism influences lipid phenotypes in Chinese families with familial combined hyperlipidemia

BACKGROUND

Apolipoprotein E (apoE) polymorphism is associated with changes in the lipoprotein profile of individuals with familial combined hyperlipidemia (FCHL), but its effects on the lipoprotein profiles of members of Chinese families with FCHL remain uncertain.

METHODS AND RESULTS

43 FCHL families (n=449) and 9 normolipidemic families (n=73) were recruited to assess the influence of apoE polymorphism on plasma lipids. The relative frequency of the epsilon4 allele in affected and unaffected FCHL relatives, spouses and normolipidemic members was 13.8%, 5.3%, 9.1% and 6.8%, respectively, with a significantly higher frequency in affected FCHL relatives, compared with unaffected FCHL relatives or normolipidemic members (p=0.0002 or p=0.029). In FCHL relatives, the apoE4 subset (E4/4 and E4/3) exhibited significantly higher levels of apoB, total cholesterol and low-density lipoprotein-cholesterol (LDL-C) than did the apoE3 (E3/3) subset, especially in women (all p<0.05), and there was significant elevation of LDL-C concentrations in men only (p<0.05). In men, the apoE2 (E3/2) subset indicated a decreased level of apoB and increased apoA1 compared with those in the apoE3 subset (p<0.05).

CONCLUSIONS

ApoE polymorphism appears to be associated with variance of the lipoprotein phenotype in Chinese families with FCHL.

Personalized genomic medicine: a future prerequisite for the prevention of coronary artery disease

Within the next 10-15 years, medicine will be personalized in large part on the basis of the individual's genomic variants. Coronary artery disease remains the number one cause of morbidity and mortality in the Western world and is predicted to become the number one cause worldwide by 2010. It has been stated that treating the risk factors of coronary artery disease has made it a preventable disease that should be eliminated in the 21st century. It is postulated that about 50% of susceptibility to coronary artery disease is genetic, involving known and occult risk factors. Thus, comprehensive prevention will require identification of genetic susceptibility. The recent technology of a chip with 500,000 DNA markers makes genome-wide scanning to identify the genes contributing to coronary artery disease possible. Multislice CT will provide the high-throughput coronary arteriograms required for this research and for prevention in asymptomatic individuals with a family history of heart disease.

Metabolic syndrome prevalence and characteristics in Greek adults with familial combined hyperlipidemia

Familial combined hyperlipidemia (FCH) is closely related with metabolic syndrome (MetSyn), and coronary artery disease (CAD) is positively associated to MetSyn and FCH. In this study, we evaluated the prevalence of MetSyn and its components between patients with FCH and a control group. We also investigated the role of MetSyn and diabetes mellitus (DM) on the incidence of CAD within the FCH group. Our study population consisted of 463 male and 243 female patients with FCH who were not receiving any hypolipidemic treatment, and 1128 men and 1154 women who came from the same geographical region. The prevalence of MetSyn was 42% and 19.8% among FCH subjects and controls, respectively, whereas MetSyn increased with age in both groups. The prevalence of CAD was 15.3% in the FCH group. Moreover, after dividing FCH patients into 3 subgroups, with and without MetSyn and with DM, CAD prevailed at a percentage of 15.2%, 11.1%, and 26.5%, respectively. However, statistically significant differences in the prevalence of CAD were observed only between FCH subjects with DM compared with the other 2 subgroups, even when an adjustment for age, sex, and smoking was conducted. People with FCH and MetSyn differed in several anthropometric, biochemical, and clinical characteristics, compared with the non-MetSyn subgroup of FCH. MetSyn is more prevalent in the FCH than in the control group. Among subjects with FCH, only DM was significantly associated with an increase in the prevalence of CAD in this subgroup compared with FCH individuals with or without MetSyn.

High-throughput single-nucleotide polymorphisms genotyping: TaqMan assay and pyrosequencing assay

Single-nucleotide polymorphisms (SNPs) are DNA sequence variations that occur at a single base in the genome sequence. SNPs are valuable markers for identifying genes responsible for susceptibility to common diseases, and in some cases, they are the causes of human diseases. A genetic study of a complex disease usually involves a case-control association study that requires genotyping of a large number of SNPs in hundreds of patients (cases) and matched controls. A significant difference of the allele frequency or genotypic frequency of a SNP between the two populations is considered to be the evidence for the association between the SNP and disease. A key to a fast and effective case-control association study requires high-throughput genotyping of SNPs. Two assays-the TaqMan SNP genotyping assay and the pyrosequencing assay-have been developed for this purpose and proven to be particularly useful. Here, we present the operative protocol, clarify the key technical issues, and highlight certain cautionary notes for high throughput SNP genotyping using TaqMan and pyrosequencing assays.

Cis and trans regulation of hepcidin expression by upstream stimulatory factor

Hepcidin is the presumed negative regulator of systemic iron levels; its expression is induced in iron overload, infection, and inflammation, and by cytokines, but is suppressed in hypoxia and anemia. Although the gene is exquisitely sensitive to changes in iron status in vivo, its mRNA is devoid of prototypical iron-response elements, and it is therefore not obvious how it may be regulated by iron flux. The multiplicity of effectors of its expression also suggests that the transcriptional circuitry controlling the gene may be very complex indeed. In delineating enhancer elements within both the human and mouse hepcidin gene promoters, we show here that members of the basic helix-loop-helix leucine zipper (bHLH-ZIP) family of transcriptional regulators control hepcidin expression. The upstream stimulatory factor 2 (USF2), previously linked to hepcidin through gene ablation in inbred mice, appears to exert a polar or cis-acting effect, while USF1 may act in trans to control hepcidin expression. In mice, we found variation in expression of both hepcidin genes, driven by these transcription factors. In addition, c-Myc and Max synergize to control the expression of this hormone, supporting previous findings for the role of this couple in regulating iron metabolism. Transcriptional activation by both USF1/USF2 and c-Myc/Max heterodimers occurs through E-boxes within the promoter. Site-directed mutagenesis of these elements rendered the promoter unresponsive to USF1/USF2 or c-Myc/Max. Dominant-negative mutants of USF1 and USF2 reciprocally attenuated promoter transactivation by both wild-type USF1 and USF2. Promoter occupancy by the transcription factors was confirmed by DNA-binding and chromatin immunoprecipitation assays. Taken together, it would appear that synergy between these members of the bHLH-ZIP family of transcriptional regulators may subserve an important role in iron metabolism as well as other pathways in which hepcidin may be involved.

Serum lipids in the GENECARD study of coronary artery disease identify quantitative trait loci and phenotypic subsets on chromosomes 3q and 5q

Coronary artery disease (CAD) and dyslipidemia have strong genetic components. Heterogeneity complicates evaluating genetics of complex diseases such as CAD; incorporating disease-related phenotypes may help reduce heterogeneity. We hypothesized that incorporating lipoproteins in a study of CAD would increase the power to map genes, narrow linkage peaks, identify phenotypic subsets, and elucidate the contribution of established risk factors to genetic results. We performed ordered subset analysis (OSA) and quantitative trait linkage (QTL) using serum lipoproteins and microsatellite markers in 346 families with early-onset CAD. OSA defined homogeneous subsets and calculated lod scores across a chromosome after ranking families by mean lipoprotein values. QTL used variance components analysis. We found significantly increased linkage to chromosome 3q13 (LOD 5.10, p = 0.008) in families with higher HDL cholesterol, lower LDL and total cholesterol, lower triglycerides, and fewer CAD risk factors, possibly due to a concentrated non-lipoprotein-related genetic effect. OSA identified linkage on chromosome 5q34 in families with higher cholesterol, possibly representing a hereditary lipoprotein phenotype. Multiple QTLs were identified, with the strongest for: total cholesterol on chromosome 5q14 (LOD 4.3); LDL on 20p12 (LOD 3.97); HDL on 3p14 (LOD 1.65); triglycerides on 18q22 (LOD 1.43); and HDL/TC ratio on 3q27-28 (LOD 2.06). Our findings suggest the presence of etiologic heterogeneity in families with early-onset CAD, potentially due to differential effects of lipoprotein phenotypes. Candidate genes are under investigation.

Association analysis of adiponectin and somatostatin polymorphisms on BTA1 with growth and carcass traits in Angus cattle

This study tested positional candidate genes adiponectin (ADIPOQ) and somatostatin (SST) for effects on carcass traits in a commercially relevant cattle population. Both genes are located within a region of BTA1 previously reported to harbour quantitative trait loci (QTL) that affect marbling, quality grade, yield grade, ribeye area and weaning weight in Bos taurus x Bos indicus crosses. Except for the first intron of ADIPOQ, both genes, including over 2 kb upstream of the promoters, were sequenced in five registered Angus sires to identify polymorphisms. A variable copy duplication and three single nucleotide polymorphisms (SNPs) in ADIPOQ and one SNP in SST were genotyped and tested for association with 19 traits in a 14-generation pedigree of 1697 registered Angus artificial insemination sires representing all the major USA lineages of the breed. Linear models that parameterized predicted genetic merits in terms of allele substitution effects were fit by weighted least squares, and goodness-of-fit tests were employed to differentiate causal mutations or polymorphisms in strong linkage disequilibrium (LD) with causal mutations from markers in weak LD with QTL. We confirmed the presence of QTL affecting marbling, ribeye muscle area and fat thickness in the vicinity of SST and ADIPOQ on BTA1 in Angus; excluded SST as underlying the ribeye muscle area QTL; and excluded ADIPOQ as underlying the marbling score QTL. However, association analysis provides very limited information about QTL location and has little intrinsic value when performed in the absence of linkage or LD analysis using flanking marker data to localize the QTL effect relative to positional candidate genes.

The involvement of upstream stimulatory factor 1 in Dutch patients with familial combined hyperlipidemia

Recently, the upstream stimulatory factor 1 gene (USF1) was proposed as a candidate gene for familial combined hyperlipidemia (FCH). In this study, we examined the previously identified risk haplotype of USF1 with respect to FCH and its related phenotypes in 36 Dutch FCH families. The diagnosis of FCH was based on both the traditional diagnostic criteria and a nomogram. The two polymorphisms, USF1s1 and USF1s2, were in complete linkage disequilibrium. No association was found for the individual single nucleotide polymorphisms (SNPs) with FCH defined by the nomogram (USF1s1, P = 0.53; USF1s2, P = 0.53), whereas suggestive associations were found when using the traditional diagnostic criteria for FCH (USF1s1, P = 0.08; USF1s2, P = 0.07). USF1 was associated with total cholesterol (USF1s1, P = 0.05; USF1s2, P = 0.04) and apolipoprotein B (USF1s1, P = 0.06; USF1s2, P = 0.04). Small dense LDL showed a suggestive association (USF1s1, P = 0.10; USF1s2, P = 0.09). The results from the haplotype analyses supported the results obtained for the individual SNPs. In conclusion, the previously identified risk haplotype of USF1 showed a suggestive association with FCH and contributed to the related lipid traits in our Dutch FCH families.

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.