Uric acid is predictive of cardiovascular mortality and sudden cardiac death in subjects referred for coronary angiography

BACKGROUND AND AIMS

High serum uric acid (SUA) is suggested to be causally involved in the pathogenesis of vascular disease. The present study aimed to investigate whether SUA independently predicts all-cause mortality, cardiovascular mortality and sudden cardiac death in subjects scheduled for coronary angiography.

METHODS AND RESULTS

We studied participants of the LUdwigshafen RIsk and Cardiovascular health (LURIC) study. A total of 3245 individuals were included in the analysis. There was a follow-up for all-cause mortality, cardiovascular mortality, and sudden cardiac death with a mean (±standard deviation) duration of 7.3 (±2.3) years. Sex-specific quartiles of SUA were established and multivariate statistical models were used. A total of 730 deaths occurred during the follow-up. Among these, 473 (64.8%) were accounted for by cardiovascular diseases. Sudden cardiac death occurred in 184 (25.2%) cases. Adjusting for sex and age subjects in the fourth SUA quartile had increased all-cause (hazard ratio (HR) = 1.68, p < 0.001) and cardiovascular (HR = 2.00, p < 0.001) mortality compared to individuals in the first quartile. Furthermore, high SUA was a risk factor for sudden cardiac death (HR = 2.27, p < 0.001). These associations remained significant including cardiovascular risk factors and the severity of coronary atherosclerosis as covariates in the models. After additional adjustment for medication use statistical significance for the association between the SUA quartiles and all-cause mortality disappeared.

CONCLUSION

High SUA independently indicates increased risk for cardiovascular and sudden cardiac death in subjects referred for coronary angiography.

Fluvastatin/fenofibrate vs. simvastatin/ezetimibe in patients with metabolic syndrome: different effects on LDL-profiles

BACKGROUND

Patients with metabolic syndrome (MS) and type 2 diabetes (T2DM) show increased risk for coronary artery disease. Lipoprotein metabolism is characterized by elevated triglycerides (TG), low high-density lipoprotein cholesterol (HDL-C) and predominance of atherogenic small, dense low-density lipoprotein (sdLDL), while low-density lipoprotein (LDL) cholesterol is only slightly elevated.

METHODS

Multicentre, randomized, open-label cross-over study investigating the effect of combination of fluvastatin/fenofibrate (80/200 mg) (F&F) on LDL-subfractions compared with combination of simvastatin/ezetimibe (20/10 mg) (S&E) in patients with MS/T2DM.

RESULTS

Seventy-five patients were randomized, 69 completed the study and LDL-subfractions of 56 patients were analysed. Thirty-eight out of 56 patients (68%) showed a profile dominated by sdLDL. In these, TG and total cholesterol (TC) were elevated compared with non-sdLDL patients. In all patients, reduction of TC and LDL cholesterol (LDL-C) by S&E was stronger than by F&F. The increase of HDL-C was stronger with S&E in the non-sdLDL group, whereas in the sdLDL group, there was no difference between treatments. In non-sdLDL patients, there was no effect on TG or LDL-radius. However, in the sdLDL group, F&F was more effective in reducing TG and increased LDL radius, whereas S&E reduced LDL radius even further.

CONCLUSIONS

S&E is more efficient in reducing TC and LDL-C. This is also true for HDL-C increase in non-sdLDL patients. However, in patients with sdLDL, F&F was more efficient in reducing TG and increasing LDL radius.

Genetic variants and haplotypes of lipoprotein associated phospholipase A2 and their influence on cardiovascular disease (The Ludwigshafen Risk and Cardiovascular Health Study)

BACKGROUND

There is increasing evidence that lipoprotein-associated phospholipase A2 (LpPLA2) is associated with cardiovascular disease. However, it is still unclear whether LpPLA2 is simply a marker or has a causal role as either a pro- or anti-atherogenic factor.

METHODS

We analyzed the association of five polymorphisms (-1357G>A, -403T>C, Arg92His, Ile198Thr, Ala379Val) and related haplotypes at the PLA2G7 locus with angiographic coronary artery disease (CAD), plasma LpPLA2 activity, and long-term survival in 3234 patients scheduled for coronary angiography.

RESULTS

The promoter variant -403C and His(92) were associated with a decrease and Val(379) with an increase in plasma LpPLA2 activity. Both coding variants revealed a clear gene-dose effect. Interestingly, the rare Thr(198) allele, which was not associated with any change in plasma LpPLA2 activity, was more frequent in subjects without CAD (P = 0.009), with an adjusted odds ratio for CAD of 0.69 (95% CI: 0.49-0.96; P = 0.029). None of the analyzed variants showed any robust association with all-cause or cardiovascular mortality.

CONCLUSION

Irrespective of the significant association between some variants with plasma LpPLA2 activity, it is still unclear whether these polymorphisms or haplotypes are associated with the risk and outcome of cardiovascular disease in Caucasians.

Covalent Linkage of Apolipoprotein E to Albumin Nanoparticles Strongly Enhances Drug Transport into the Brain

Drug delivery to the brain is becoming more and more important but is severely restricted by the blood-brain barrier. Nanoparticles coated with polysorbates have previously been shown to enable the transport of several drugs across the blood-brain barrier, which under normal circumstances is impermeable to these compounds. Apolipoprotein E was suggested to mediate this drug transport across the blood-brain barrier. In the present study, apolipoprotein E was coupled by chemical methods to nanoparticles made of human serum albumin (HSA-NP). Loperamide, which does not cross the blood-brain barrier but exerts antinociceptive effects after direct injection into the brain, was used as model drug. Apolipoprotein E was chemically bound via linkers to loperamide-loaded HSA-NP. This preparation induced antinociceptive effects in the tail-flick test in ICR mice after i.v. injection. In contrast, nanoparticles linked to apolipoprotein E variants that do not recognize lipoprotein receptors failed to induce these effects. These results indicate that apolipoprotein E attached to the surface of nanoparticles facilitates transport of drugs across the blood-brain barrier, probably after interaction with lipoprotein receptors on the brain capillary endothelial cell membranes.

Helicobacter pylori seropositive subjects do not show a pronounced systemic inflammatory response even in the presence of the interleukin-1 receptor antagonist gene polymorphism

The aim of this analysis was to evaluate the effects of the presence of the IL-1RA gene polymorphism and H. pylori infection on markers of a systemic inflammatory response taking into account virulence markers of this infection. Serum concentrations of interleukin (IL)-6, IL-8, and tumour-necrosis factor (TNF)-alpha of 479 occasional blood donors were not statistically significantly higher in subjects having antibodies against H. pylori, or more specifically against CagA and VacA, and being homozygous for the pro-inflammatory IL-1RN*2 allele compared to others after adjustment for covariates. The findings suggest that the possible pro-inflammatory effect of the IL-1RN*2 allele in combination with H. pylori infection is limited to the mucosal level.

The PlA1/A2 polymorphism of platelet glycoprotein IIIa is not associated with the risk of type 2 diabetes. The Ludwigshafen Risk and Cardiovascular Health study

AIMS/HYPOTHESIS

The PlA1/A2 polymorphism of platelet glycoprotein IIIa (GPIIIa) has been implicated in the pathogenesis of type 2 diabetes. We studied this polymorphism in a homogenous, extensively phenotyped cohort using the candidate gene approach.

METHODS

The PlA1/A2 polymorphism was determined in 1051 patients with type 2 diabetes and in 2247 individuals without type 2 diabetes.

RESULTS

In patients with type 2 diabetes, genotype frequencies were as follows: PlA1/A1 71.4%, PlA1/A2 26.0%, and PlA2/A2 2.7%. In individuals without type 2 diabetes, genotype frequencies were 71.6%, 25.7% and 2.8%, respectively. The PlA2 allele was not associated with fasting and postprandial glucose, glycated haemoglobin, insulin, proinsulin, C-peptide and calculated indices of insulin resistance or pancreatic beta cell function. The PlA2 allele was also not significantly associated with angiographic CHD (adjusted odds ratio [OR] 1.13; 95% CI, 0.93-1.39) or with a history of previous myocardial infarction (adjusted OR 1.09; 95% CI, 0.87-1.37).

CONCLUSIONS/INTERPRETATION

The GPIIIa PlA1/A2 polymorphism is not associated with type 2 diabetes, glucose metabolism, angiographic CHD or myocardial infarction.

Association between the A-2518G polymorphism in the monocyte chemoattractant protein-1 gene and insulin resistance and Type 2 diabetes mellitus

AIMS/HYPOTHESIS

The molecular mechanisms of obesity-related insulin resistance are incompletely understood. Macrophages accumulate in adipose tissue of obese individuals. In obesity, monocyte chemoattractant protein-1 (MCP-1), a key chemokine in the process of macrophage accumulation, is overexpressed in adipose tissue. MCP-1 is an insulin-responsive gene that continues to respond to exogenous insulin in insulin-resistant adipocytes and mice. MCP-1 decreases insulin-stimulated glucose uptake into adipocytes. The A-2518G polymorphism in the distal regulatory region of MCP-1 may regulate gene expression. The aim of this study was to investigate the impact of this gene polymorphism on insulin resistance.

METHODS

We genotyped the Ludwigshafen Risk and Cardiovascular Health (LURIC) cohort ( n=3307). Insulin resistance, estimated by homeostasis model assessment, and Type 2 diabetes were diagnosed in 803 and 635 patients respectively.

RESULTS

Univariate analysis revealed that plasma MCP-1 levels were significantly and positively correlated with WHR ( p=0.011), insulin resistance ( p=0.0097) and diabetes ( p<0.0001). Presence of the MCP-1 G-2518 allele was associated with decreased plasma MCP-1 ( p=0.017), a decreased prevalence of insulin resistance (odds ratio [OR]=0.82, 95% CI: 0.70-0.97, p=0.021) and a decreased prevalence of diabetes (OR=0.80, 95% CI: 0.67-0.96, p=0.014). In multivariate analysis, the G allele retained statistical significance as a negative predictor of insulin resistance (OR=0.78, 95% CI: 0.65-0.93, p=0.0060) and diabetes (OR=0.80, 95% CI: 0.66-0.96, p=0.018).

CONCLUSIONS/INTERPRETATION

In a large cohort of Caucasians, the MCP-1 G-2518 gene variant was significantly and negatively correlated with plasma MCP-1 levels and the prevalence of insulin resistance and Type 2 diabetes. These results add to recent evidence supporting a role for MCP-1 in pathologies associated with hyperinsulinaemia.

Qualitative Effect of Fenofibrate and Quantitative Effect of Atorvastatin on LDL Profile in Combined Hyperlipidemia with dense LDL

INTRODUCTION

The association of elevated plasma triglyceride concentrations, decreased HDL-cholesterol, and dense LDL (dLDL) is referred to as the atherogenic lipoprotein phenotype. dLDL particularly plays a role in the metabolic syndrome and type 2 diabetes and may be one of the factors responsible for the increased risk for coronary artery disease in these patients. The effect of fenofibrate and atorvastatin on the LDL subfraction profile in patients with combined hyperlipidemia and a preponderance of dLDL was studied in a sequential design.

METHODS

Six male patients with combined hyperlipidemia and dLDL received 160 mg/die supra-bioavailable fenofibrate. After a washout phase of 8 weeks all patients received 10 mg/die atorvastatin for another 8 weeks. At baseline, after fenofibrate, and after atorvastatin treatment LDL subfractions were analyzed by equilibrium density gradient ultracentrifugation.

RESULTS

Treatment with atorvastatin and fenofibrate reduced serum cholesterol by 30 % and 21 % (p = 0.046) (p-values for differences between treatment groups), triglycerides by 32 % and 45 %, LDL cholesterol by 28 % and 16 %, and increased HDL cholesterol by 3 % and 6 %, respectively. Atorvastatin and fenofibrate treatment resulted in the following changes of apoB and LDL subfractions: LDL-1 (1.019 - 1.031 kg/L) - 31 % and + 15 % (p = 0.028); LDL-2 (1.031 - 1.034 kg/L) - 14 % and + 57 % (p = 0.028); LDL-3 (1.034 - 1.037 kg/L) - 20 % and + 30 % (p = 0.028); LDL-4 (1.037 - 1.040 kg/L) - 25 % and - 6 %; LDL-5 (1.040 - 1.044 kg/L) - 29 % and - 38 %; and LDL-6 (1.044 - 1.063 kg/L) - 39 % and - 55 % (p = 0.028). As a consequence, fenofibrate reduced LDL density significantly (p = 0.028 versus atorvastatin).

CONCLUSIONS

Atorvastatin decreased all LDL-subfractions to a similar extent (quantitative effect) whereas fenofibrate reduced predominantly dLDL and changed the LDL profile towards medium dense LDL-particles (qualitative effect). Since medium dense LDL have a higher affinity to the LDL-receptor fenofibrate may have a higher antiatherogenic potential than assessed by the reduction of total LDL-cholesterol and triglycerides alone.

Haplotypes of the cholesteryl ester transfer protein gene predict lipid-modifying response to statin therapy

Cholesteryl ester transfer protein (CETP) plays a central role in high-density lipoprotein (HDL) metabolism. Single nucleotide polymorphisms (SNPs) and haplotypes in the CETP gene were determined in 98 patients with untreated dyslipidemias and analyzed for associations with plasma CETP and plasma lipids before and during statin treatment. Individual CETP SNPs and haplotypes were both significantly associated with CETP enzyme mass and activity. However, only certain CETP haplotypes, but not individual SNPs, significantly predicted the magnitude of change in HDL cholesterol (HDL-C) and triglycerides. After adjusting for covariates and multiple testing, the TTCAAA haplotype showed a gene-dose effect in predicting the HDL-C increase (P=0.03), while the TTCAAAGGG and AAAGGG haplotypes predicted a decrease in triglycerides (P=0.04 both). This is the first study to demonstrate that SNP haplotypes derived from allelic SNP combinations in the CETP gene were more informative than single SNPs in predicting the response to lipid-modifying therapy with statins.

Apolipoprotein E3Basel: new insights into a highly conserved protein region

BACKGROUND

Apolipoprotein E is important for the receptor-mediated uptake of triglyceride-rich lipoproteins. Mutations in the gene encoding apolipoprotein E may cause a reduced uptake of these lipoproteins. Particular apolipoprotein E mutations have been also found to be associated with nephrologic, neurologic, and even ophthalmologic diseases. Hence, a continuously expanding role in biology is being attributed to this protein.

DESIGN

Randomly selected volunteers from of a large Swiss cohort were genotyped for the common apolipoprotein E isoforms (apolipoprotein E2, apolipoprotein E3, apolipoprotein E4).

RESULTS

In one of the volunteers, a novel C-to-T mutation causing an alanine-to-valine substitution (A106V, designated apolipoprotein E3Basel) was discovered. Alanine at residue 106 is highly conserved between mammalian species and is located in the immediate vicinity of the 112C/R polymorphism (apolipoprotein E4). Recombinant apolipoprotein E3Basel, expressed in the baculovirus system, displayed no detectable reduction in its low density lipoprotein (LDL) receptor- and heparin-binding activities. Despite normal binding functions, apolipoprotein E3Basel might cause modifications in the lipoprotein pattern. In the index case, plasma triglycerides were elevated and in two further apolipoprotein E3Basel-carriers, cholesterol, phospholipid, apolipoprotein CIII levels, LDL-cholesterol/apoB-100- and VLDL-triglyceride/VLDL-cholesterol-ratios were higher compared with apolipoprotein E3Basel-noncarriers when pair-matched for age and gender. One of the four apolipoprotein E3Basel-carriers from the index family had a personal history of Alzheimer's disease.

CONCLUSIONS

Alanine at amino acid position 106 is highly conserved but not crucial in the receptor-mediated uptake of lipoprotein particles. Nevertheless, amino acid position 106 might be involved in the apolipoprotein E-dependent regulation of the lipoprotein lipase that hydrolyzes triglycerides and in the development of Alzheimer's disease.

Apolipoprotein E (apoE) uptake and distribution in mammalian cell lines is dependent upon source of apoE and can be monitored in living cells

As part of investigations of the cellular uptake of apolipoprotein E (apoE) relevant to Alzheimer's disease we have found that different preparations of apoE are handled differently by cells expressing the LDL-receptor. Comparing recombinant, cellular and native apoE, complexed with different preparations of lipid we find that only cellular and native apoE enter a vesicular compartment. Some, but not all of these apoE containing vesicles are lysosomes. In order to further examine the intracellular fate of apoE we demonstrate that apoE-Enhanced green fluorescent protein chimeric protein can be taken up from medium by recipient cells and tracked within these cells for extended periods.

Coronary artery disease and dyslipidemia within Europe: genetic variants in lipid transport gene loci in German subjects with premature coronary artery disease

Fifteen polymorphisms in six lipid transport genes were studied in a German population for relationships with dyslipidemia and coronary artery disease (CAD), to investigate a possible genetic basis for the marked differences in mortality rates from coronary heart disease within Europe. In other populations these polymorphisms have all been associated with CAD or with phenotypes known to predispose to CAD. The apoAI PstI polymorphism (P<0.005) and the lipoprotein lipase Ser(447)-Ter mutation (P<0.005) were associated with plasma triglyceride concentrations. Additionally, the apoAI PstI polymorphism (P<0.05), the apoB XbaI polymorphism (P<0.05) and apoE phenotypes (P<0.05) were associated with plasma cholesterol concentrations. However, none of the allele frequencies of the polymorphisms studied were related to the presence, or absence, of coronary artery disease. Associations between five polymorphisms representing four lipid transport gene loci and dyslipidemia were demonstrated in this German population. It is possible that predisposition to dyslipidemia in Germany involves a particular selection of polymorphic loci, which are different from those identified in other European countries.

Homocysteine and methylenetetrahydrofolate reductase genotype: association with risk of coronary heart disease and relation to inflammatory, hemostatic, and lipid parameters

AIM

It has been suggested that homocysteine (tHcy) levels and methylenetetrahydrofolate reductase (MTHFR) genotype are primary risk factors for coronary heart disease (CHD). We performed a case-control study to investigate whether tHcy levels and MTHFR genotype (677 C-->T mutation and 1298 A-->C mutation) are associated with CHD under special consideration of the possibility for confounding.

METHODS

German speaking patients aged 40-68 years who underwent coronary angiography at the University of Ulm between April 1996 and November 1997 and who had at least one coronary stenosis greater than 50% were included in the study. Controls were sampled from voluntary blood donors and were matched for sex and age. tHcy levels were measured by high performance liquid chromatography and MTHFR genotype by means of polymerase chain reaction. In addition, C-reactive protein, fibrinogen, plasma viscosity, leukocytes, HDL-cholesterol and Lp(a) were determined.

RESULTS

Overall, 312 patients and 479 controls were enrolled in the study (response in patients 78%, in controls 84%). Mean tHcy value was 9.43 micromol/l in CHD patients and 8.91 micromol/l in controls (P=0.145). Prevalence of 677TT-polymorphism was 9.9% in patients and 10.4% in controls (P=0.295). Prevalence of 1298CC-polymorphism was 9.7% in patients and 13.8% in controls (P=0.346). There was a clear association of tHcy-values, but not of 677TT- or 1298CC-genotype with conventional CHD risk factors. After adjustment for these risk factors no increased risk for CHD could be associated with increased tHcy-values, with 677TT or 1298CC-genotype, or with their combination. Also no statistically significant relationships of these parameters to inflammatory, rheologic or hemostatic parameters or lipids were detectable.

CONCLUSION

These results do not confirm an independent relationship of tHcy values and MTHFR genotype with risk of CHD in the population studied.

Effects of apolipoprotein A-I genetic variations on plasma apolipoprotein, serum lipoprotein and glucose levels

The present authors investigated the individual and combined associations of the apolipoprotein (apo) A-I -75 bp and +83 bp polymorphisms with plasma lipid, lipoprotein and apolipoprotein levels in 734 Caucasian men and women. The frequency of the A allele at position -75 bp (G-->A) was 0.14 in women and 0.17 in men. The frequencies for the rare M2 allele at position +83 bp and/or 84 bp (C-->T and G-->A, respectively) were 0.04 and 0.05 in women and men, respectively. In women, the A allele was associated with significantly higher levels of apo B (P = 0.016), total cholesterol (TC) (P = 0.005), low-density lipoprotein cholesterol (LDL-C) (P = 0.018) and TC:high-density lipoprotein (HDL) ratio (P = 0.026) compared to the G/G subjects. In men, no significant associations were detected between the -75 bp polymorphism and any lipid trait examined. The M2 allele for the +83 bp polymorphism was significantly associated in men with higher levels of apo A-I (P = 0.002) and TC (P = 0.046). In women, a significant effect was observed for TC (P = 0.036), with M2+/- subjects having lower levels than M2+/+ subjects. Significant linkage disequilibrium (P = 0.037) between the apo A-I -75 bp and +83 bp polymorphisms was detected. Women carrying both rare alleles (G/A M2+/-) had significantly higher TC:HDL ratios (P = 0.031) compared to the other haplotypes. In men, significant differences were observed for apo A-I (P = 0.021) and TC (P = 0.044), with carriers of the G/G M2+/- haplotype having the highest values compared to other genotype combinations. In conclusion, the -75 bp (G/A) polymorphism appears to have a significant effect on levels of apo B, plasma TC and LDL-C in women, while the +83 bp polymorphism seems to affect the apo A-I levels in men, and the plasma cholesterol levels in both genders.

The significance of genetic polymorphisms in modulating the response to lipid-lowering drugs

The response to lipid-lowering drugs is modified by a number of factors like age, gender, concomitant disease and genetic determinants. Even within homogenous groups of patients, individual responses vary greatly. Until now, no clinical or biochemical parameter exists which predicts whether a subject will respond well to a particular lipid-lowering drug or, in the extreme case, will develop adverse, life-threatening effects (e.g., myositis or rhabdomyolysis). The recent advances in the human genome project promises to have a great impact on our understanding of lipid and lipoprotein metabolism and of the individual response to lipid-lowering drugs. Monogenetic disorders of the lipid metabolism produce severe clinical phenotypes, such as Tangier disease, but have a minor role in the evaluation of cardiovascular risk in the general population. On the other hand, several polymorphisms in genes involved in lipoprotein metabolism (e.g., apolipoprotein E) are associated with the plasma levels of lipoproteins, explaining a substantial fraction of the variance of LDL or HDL concentrations. In combination, the knowledge of these polymorphisms, further variants yet to be discovered and variants within the genes involved in the metabolism of lipid-lowering drugs will in the future allow these drugs to be selected according to the patients needs and thus increase both efficacy and cost-effectiveness of lipid-lowering regimes.

Fluvastatin lowers atherogenic dense low-density lipoproteins in postmenopausal women with the atherogenic lipoprotein phenotype

BACKGROUND

Although HMG-CoA reductase inhibitors (HMGRIs) are effective lipid-lowering agents, it remains controversial whether these agents also lower dense LDL (dLDL), a predominance of which is considered to contribute to the atherogenicity of the metabolic syndrome.

METHODS AND RESULTS

In a multicenter, double-blind, randomized, placebo-controlled study, we determined the effect of the HMGRI fluvastatin on lipids, apolipoproteins, and LDL subfractions (by equilibrium density gradient ultracentrifugation). A total of 52 postmenopausal women with combined hyperlipidemia and increased dLDL were treated with either fluvastatin 40 mg/d (n=35) or placebo (n=17). After 12 weeks' treatment, significant reductions (P<0.001) in total cholesterol (-19%), IDL cholesterol (-35%), LDL cholesterol (-23%), apolipoprotein B (-21%), and apolipoprotein B in dLDL (-42%) were apparent among fluvastatin recipients. No significant changes in triglycerides or HDL cholesterol were observed. The effect of fluvastatin on dLDL was correlated with baseline values. There was no consistent relationship, however, between the effect of fluvastatin on triglycerides and the decrease in dLDL.

CONCLUSIONS

Fluvastatin lowers total and LDL cholesterol and the concentration of dLDL. This profile may contribute to an antiatherogenic effect for fluvastatin that is greater than expected on the basis of changes in lipids and apolipoproteins.

Characterization of transgenic mice expressing apolipoprotein E4(C112R) and apolipoprotein E4(L28P; C112R)

Apolipoprotein E (ApoE), which is genetically polymorphic, is a constituent of different lipoproteins. Two variants, ApoE4(C112R) and ApoE4(L28P; C112R) have been linked to the risk of developing Alzheimer's disease. Transgenic mice carrying ApoE4(C112R) (AD71) and ApoE4(L28P; C112R) (AD61) were generated and compared to wild-type mice. The use of glial fibrillary acidic protein as promoter led to transgene expression mainly in glial cells but also in neurons. Transgene protein levels were approximately three-and-a-half-fold that of endogenous ApoE in the glial fibrillary acidic protein-ApoE4(C112R) (AD71) and nearly twofold in the glial fibrillary acidic protein-ApoE4(L28P; C112R) (AD61) mouse lines. Neither transgenic mouse differed from wild-type in cognitive tests at the age of approximately one-and-a-half years. The locomotor activity of AD61 mice was similar to controls, whereas AD71 mice exhibited a clearly reduced level of motor activity. Immunohistological and biochemical brain protein analyses revealed no difference between strains.Thus, in the absence of morphological changes over-expression of ApoE4(C112R) on a background of endogenous mouse ApoE, may result in behavioral deficits while for the ApoE4(L28P; C112R) transgene higher expression might be required or some compensatory mechanisms might protect these animals from the behavioral abnormalities.

Common genetic variants that relate to disorders of lipid transport in Spanish subjects with premature coronary artery disease

Fifteen common polymorphic variants at six loci (apolipoproteins AI, B, CIII and E, hepatic lipase and lipoprotein lipase) involved in plasma lipid transport have been studied in 210 northern Spanish men, of whom 98 had proven coronary artery disease. The other 112 men were clinically free from coronary artery disease and acted as controls. The genotypes were investigated for relationships with plasma lipid and lipoprotein levels, as well as for the presence of coronary artery disease. As expected, the mean levels of plasma triacylglycerols (triglycerides) and lipoprotein (a) and the number of smokers were significantly higher in the disease group, and high-density lipoprotein (HDL)-cholesterol was significantly lower. Surprisingly, plasma cholesterol and low-density lipoprotein cholesterol were not different between the two groups. With regard to the common mutations, plasma triacylglycerol levels were related to the HindIII variants of lipoprotein lipase (P<0.05), to the apolipoprotein CIII variant (C3175G in exon 4) and to the apolipoprotein AI XmnI polymorphisms (P<0.05 and P<0.02 respectively). The apolipoprotein E variants were related to plasma cholesterol (P<0.05), HDL-cholesterol (P<0.02), plasma triacylglycerols (P<0.05) and the triacylglycerol/HDL ratio (P<0.01). Only the three-codon insertion/deletion variants of the apolipoprotein B signal peptide region discriminated between the two groups with or without arterial disease (P=0.02). The possible functional effects of these common mutations are discussed.

Apolipoprotein E1 Baden (Arg(180)-->Cys). A new apolipoprotein E variant associated with hypertriglyceridemia

Apolipoprotein (apo) E mediates the removal of chylomicron and very low density lipoprotein remnants from plasma. It is polymorphic in sequence and the products of the three common alleles (epsilon 2, epsilon 3, epsilon 4) differ from one another in their binding to lipoprotein receptors. ApoE2 is defective in binding and homozygosity for apoE2 is associated with type III hyperlipoproteinemia (HLP). Other rare isoforms of apoE have been found to be associated either with dominant type III HLP or with the development of hypertriglyceridemia. We identified a 42 year-old hypertriglyceridemic woman with an apoE phenotype 3/1. Restriction isotyping using AflIII/HaeII resulted in an apparent apoE genotype 3/2, suggesting that the mutation occurred in an epsilon 2 allele. DNA sequence analysis revealed a C-->T point mutation at the first position of the codon for amino acid residue 180 of the mature apoE. This predicted a change Arg(180)-->Cys. The mutation altered a recognition site for the endonuclease HaeII, which allowed us rapidly to screen for this mutation. In relatives of the proband, apoE1 Baden was consistently associated with hypertriglyceridemia. Similar to other apoE variants linked to hypertriglyceridemia, the Arg(180)-->Cys mutation is located within the lipid binding domain of apoE. We therefore suggest that apoE1 Baden may cause hypertrigylceridemia, possibly by inhibiting the hydrolysis of triglycerides associated with very low density lipoproteins.

Identification of an apolipoprotein(e) variant associated with type III hyperlipoproteinaemia in an indigenous Australian

As a result of testing for lipid and apolipoprotein(e) (apo E) phenotype status of an indigenous Australian community, an apo E variant associated with type III hyperlipoproteinaemia has been identified. Apo E phenotype was determined by analysis of VLDL by isoelectric focusing, and genotype on DNA amplified by polymerase chain reaction, using two different restriction enzyme isotyping assays. Phenotypes and genotypes were discordant in samples from two subjects and an abnormal-sized restriction fragment was also observed in their genotyping gel patterns. DNA sequencing studies revealed this was due to a single nucleotide deletion, 3817delC, at amino acid 136 on apo E. This resulted in a new reading frame and the premature termination of the apo E protein due to a stop codon (TGA) at nucleotide 4105. The variant apo E null allele showed a recessive mode of inheritance and, in combination with the E2 allele, resulted in the type III hyperlipoproteinaemic phenotype but when inherited with the E4 allele had no marked effect on plasma lipids.

Low density lipoprotein (LDL) subfractions during pregnancy: accumulation of buoyant LDL with advancing gestation

Pregnancy is accompanied by changes in the maternal lipoprotein metabolism that may serve to satisfy the nutritional demands of the fetus. In this study lipoprotein metabolism was investigated in 23 women during normal pregnancy in the first, second, and third trimesters and in 15 healthy nonpregnant women with regular menstrual cycles. Lipid and apolipoprotein concentrations were measured in total plasma, very low density, intermediate density, low density (LDL), and high density lipoproteins, and in each of six LDL subfractions. During early pregnancy, triglycerides, and dense LDL were higher than in the nonpregnant state. With advancing gestation, triglycerides increased and the distribution of apolipoprotein B-100-containing lipoproteins became increasingly dominated by the accumulation of very low density and intermediate density lipoproteins and buoyant, triglyceride-rich LDL. This is the first study that investigates LDL subfractions in pregnancy using a method that strictly separates LDL subfractions by virtue of density. The accumulation of buoyant, triglyceride-rich lipoproteins may be related to the down-regulation of maternal lipase activities by placental hormones. As a consequence, the metabolic changes of late pregnancy may result in an increased flux of lipoprotein-derived lipids to the placenta, which, with advancing gestation, increasingly expresses receptors with a high affinity for triglyceride-rich lipoproteins.

Type I hyperlipoproteinemia due to a novel loss of function mutation of lipoprotein lipase, Cys(239)-->Trp, associated with recurrent severe pancreatitis

Lipoprotein lipase (LPL) is the major enzyme responsible for the hydrolysis of triglyceride-rich lipoproteins in plasma. The purpose of this study was to examine the molecular pathogenesis of type I hyperlipoproteinemia in a patient suffering from recurrent severe pancreatitis. Apolipoprotein (apo) CII concentration was normal as well as apo CII-activated LPL in an in vitro assay. In postheparin plasma neither LPL mass nor activity was detectable, whereas hepatic lipase activity was normal. Direct sequencing of all 10 exons of the LPL gene revealed that the patient was homozygous for a hitherto unknown mutation in exon 6, Cys(239)-->Trp. The mutation prevents the formation of the second disulfide bridge of LPL, which is an essential part of the lid covering the catalytic center. Consequently, misfolded LPL is rapidly degraded within the cells, causing the absence of LPL immunoreactive protein in the plasma of this patient. In conclusion, we have identified a novel loss of function mutation in the LPL gene (Cys(239)-->Trp) of a patient with type I hyperlipoproteinemia suffering from severe recurrent pancreatitis. After initiation of heparin therapy (10,000 U/day sc), the patient experienced no more episodes of pancreatitis, although heparin therapy did not affect serum triglyceride levels.

Differential effects of apolipoprotein E isoforms on phosphorylation at specific sites on tau by glycogen synthase kinase-3 beta identified by nano-electrospray mass spectrometry

Previously published data have shown an allele-specific variation in the in vitro binding of apolipoprotein E (apoE) to tau, which prompted the hypothesis that apoE binding may protect tau from phosphorylation, apoE3 being more efficient than apoE4. We have, therefore, investigated the effects of apoE on tau phosphorylation in vitro by the proline-directed kinase, glycogen synthase kinase (GSK)-3 beta. The phosphopeptide maps of tau alone, of tau with apoE3 and of tau with apoE4 were very similar. When apoE2 was present a further four spots were evident. Additionally, of the 15 peptides phosphorylated in the presence or absence of apoE, subtle differences, some isoform-specific, in the relative amounts of phosphorylation were observed.

Increased production of HDL ApoA-I in homozygous familial defective ApoB-100

Familial defective apolipoprotein (apo) B-100 (FDB) is a frequent cause of hypercholesterolemia. Hypercholesterolemia in homozygous FDB is less severe than in homozygotes for familial hypercholesterolemia. Recently, we showed decreased low density lipoprotein (LDL) apoB-100 fractional catabolism and decreased production of LDL due to an enhanced removal of apoE-containing precursors in a patient with homozygous FDB. The effects of defective apoB-100 on high density lipoprotein (HDL) metabolism are unknown. We studied HDL apoA-I metabolism in this FDB patient and in 6 control subjects by using (2)H(3)-L-leucine as a tracer. ApoA-I levels were normal in all study subjects. However, the fractional catabolic rate and the production rate of apoA-I were increased, by 79% and 70%, respectively, in FDB; the fractional catabolic rate of apoA-I in FDB was 0.34 day(-1) compared with 0.19+/-0.03 day(-1) in normal controls. The production rate of apoA-I in FDB was 18.4 mg. kg(-1). d(-1) compared with 10.8+/-2.3 mg. kg(-1). d(-1) in controls. Thus, we have shown for the first time that defective apoB-100 may influence HDL kinetics. The increase in total HDL turnover might enhance reverse cholesterol transport and could contribute to the seemingly benign clinical course of FDB compared with that of familial hypercholesterolemia.

Molecular basis of type III hyperlipoproteinemia in Germany

Type III hyperlipoproteinemia (HLP) is usually associated with homozygosity for apolipoprotein (apo) E2 (Arg112 --> Cys, Arg158 --> Cys). This common apo E isoform is defective in its binding to lipoprotein receptors. However, other rare mutations in the apo epsilon gene may also, in part dominantly, predispose to the disease. In order to assess the prevalence of rare apo E variants and mutations in the apo epsilon gene in Germany, we examined apo epsilon genotypes by restriction isotyping (RI) and apo E phenotypes by isoelectric focusing (IEF) in 107 German patients with type III HLP. Concordance between apo epsilon genotype and apo E phenotype was observed in 101 subjects (94.4%). Six individuals (5.6%) had genotypes and phenotypes other than E2/2. One subject was apparently homozygous for apo E2 by IEF, but heterozygous for epsilon3/2 by RI. Sequencing of the apo epsilon gene disclosed a hitherto undescribed point mutation (TGG --> TGA) at the third position of the codon for amino acid 20 (Trp), introducing a premature termination codon. This is the first study demonstrating that in the German population type III HLP is mainly associated with homozygosity for apo E2 (Arg112 --> Cys, Arg158 --> Cys) and that discrepancies between apo epsilon genotype and apo E phenotype are rare in this genetic condition.

Antagonistic effects of vitamin D and parathyroid hormone on lipoprotein lipase in cultured adipocytes

The effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) (calcitriol) and parathyroid hormone (PTH) on synthesis and secretion of lipoprotein lipase (LPL) were studied in 3T3-L1 adipocytes. Expression of the vitamin D receptor was demonstrated by saturation kinetics with radiolabeled calcitriol. Incubation with calcitriol (10(-8) M) for up to 4 d resulted in a time-dependent significant increase in heparin-releasable LPL activity (LPLa) accompanied by a significant increase in LPL mRNA. In contrast, incubation with intact (1-84) PTH (10(-6) to 10(-9) M) produced a time- and dose-dependent significant decrease in LPLa, but no change in LPL mRNA. The effect of PTH (24-h incubation, 10(-8) M) could be prevented by the calcium channel blocker verapamil. Coincubation with both calcitriol and PTH at equimolar concentration (10(-8) M) resulted in an increase in LPLa and LPL mRNA. These data indicate an antagonistic role for calcitriol and PTH in the regulation of LPL, possibly mediated by intracellular calcium, which may contribute to the alterations in lipoprotein metabolism occurring in uremia.

The lipoprotein lipase HindIII polymorphism: association with total cholesterol and LDL-cholesterol, but not with HDL and triglycerides in 342 females

BACKGROUND

Lipoprotein lipase (LPL) is the rate-limiting enzyme in the hydrolysis of core triglycerides in chylomicrons and VLDL.

METHODS

We investigated the association between the HindIII polymorphism of the LPL gene and fasting glucose, lipid, and lipoprotein concentrations in 683 Caucasians. We first stabilized the study subjects, using an 8-day diet and exercise intervention program before obtaining blood samples. The use of this standardization period reduced the variance of all glucose and lipid concentrations.

RESULTS

In our study, the HindIII allele frequencies for females and males were 0.29 and 0.34 for H- and 0.71 and 0.66 for H+, respectively. We found in females, but not in males, a significant association between the HindIII genotype and total cholesterol (P = 0.007) and LDL-cholesterol (P = 0.018), with females homozygous for the rare H- allele having the lowest, heterozygotes (H-/+) having intermediate, and women homozygous for the common H+ allele having the highest of each of these lipid traits. With regard to triglycerides, HDL-cholesterol, and glucose, no significant effect of the HindIII genotype was noted in either gender.

CONCLUSIONS

These results suggest that in a gender-specific manner, the rare LPL HindIII H- allele has a cholesterol-lowering and, therefore, potentially cardioprotective effect compared with the common H+ allele.

Mutations in the apolipoprotein (apo) B-100 receptor-binding region: detection of apo B-100 (Arg3500-->Trp) associated with two new haplotypes and evidence that apo B-100 (Glu3405-->Gln) diminishes receptor-mediated uptake of LDL

BACKGROUND

Ligand-defective apolipoprotein (apo) B-100 is a major cause of hypercholesterolemia. For many years, apo B-100 (Arg3500-->Gln) has been the only mutation known to cause ligand-defective apo B-100.

METHODS

Using temperature gradient gel electrophoresis, we screened 297 unrelated individuals with LDL-cholesterol >1.55 g/L and triglycerides <2.0 g/L for sequence variants of the putative LDL receptor-binding domain of apo B-100.

RESULTS

We found apo B-100 (Arg3500-->Gln) in 21 individuals (7.1%). When extrapolated to the general population, this corresponds to the highest prevalence of apo B-100 (Arg3500-->Gln) reported to date. Furthermore, we identified three unrelated carriers (1%) of a silent substitution (CTG-->CTA) affecting the codon for leucine3350, four carriers (1.3%) of apo B-100 (Glu3405-->Gln), and two subjects (0.7%) with apo B-100 (Arg3500-->Trp). apo B-100 (Arg3500-->Trp) was assigned to two different, previously unknown haplotypes. The binding, uptake, and degradation of apo B-100 (Arg3500-->Trp) was lower than that of normal LDL, but higher than with apo B-100 (Arg3500-->Gln), implying that the substitution of Trp3500 for Arg may cause less severe reduction of binding than the substitution of Gln. LDL from individuals heterozygous for apo B-100 (Glu3405-->Gln) bound to LDL receptors at the same rate as normal LDL, but was taken up and degraded at significantly reduced rates, suggesting that domains of apo B-100 involved in binding and uptake do not completely overlap.

CONCLUSIONS

In Germany, apo B-100 (Arg3500-->Gln) may be more frequent than previously assumed. Both apo B-100 (Arg3500-->Trp) and apo B-100 (Glu3405-->Gln) may contribute to the phenotype of ligand-defective LDL. These variants will be missed if screening is confined to apo B-100 (Arg3500-->Gln) only.

Competition of Abeta amyloid peptide and apolipoprotein E for receptor-mediated endocytosis

The genetic polymorphism of apolipoprotein E (apoE) is associated with the age of onset and relative risk of Alzheimer's disease (AD). In contrast to apoE3, the wild type allele, apoE4 confers an increased risk of late-onset AD. We demonstrate that the beta-amyloid peptide isoforms Abeta (1-28), Abeta (1-40), and Abeta (1-43) compete for the cellular metabolism of apoE3 and apoE4 containing beta-very low density lipoproteins. An antibody raised against Abeta (1-28) cross-reacted with recombinant apoE. Epitope mapping revealed positive amino acid clusters as common epitopes of Abeta (13 through 17; HHQKL) and apoE (residues 144 through 148; LRKRL), both regions known to be heparin binding domains. Abeta in which amino acids 13 through 17 (HHQKL) were replaced by glycine (GGQGL) failed to compete with the cellular uptake of apoE enriched betaVLDL. These observations indicate that Abeta and apoE are taken up into cells by a common pathway involving heparan sulfate proteoglycans.

Detection of mutations in the apolipoprotein CII gene by denaturing gradient gel electrophoresis. Identification of the splice site variant apolipoprotein CII-Hamburg in a patient with severe hypertriglyceridemia

Familial apolipoprotein (apo) CII deficiency is a rare autosomal recessive inborn error of metabolism clinically resembling lipoprotein lipase deficiency. A number of mutations of the apo CII gene are known to date; they are located in the promoter region, the coding exons, or in the splice junctions. We present a simple assay based on PCR and denaturing gradient gel electrophoresis, which allows scanning of the promoter, the entire coding sequence, and the splice junctions of the apo CII gene for sequence variants. All gene fragments are amplified using a common PCR protocol and are examined for mutations on a single gradient gel. Using this method and direct sequencing, we identified homozygosity for a donor splice-site mutation in the second intron, previously designated apo CII-Hamburg, as the genetic cause of apo CII deficiency in a 9-year-old boy presenting with chylomicronemia, eruptive xanthoma, and pancreatitis. In addition, the method allowed us to detect all of six different other known mutations of the apo CII gene. We conclude, therefore, that our assay is highly sensitive; in addition, it is easy to perform and may facilitate the differential diagnosis of disorders of lipoprotein metabolism at the genetic level.

Apolipoprotein E2 (Arg136 --> Cys) mutation in the receptor binding domain of apoE is not associated with dominant type III hyperlipoproteinemia

Using apoE phenotyping by immunoblotting and apoE genotyping we identified four heterozygous carriers of a rare apolipoprotein (apo) E2 variant, apoE2 (Arg136 --> Cys). ApoE2 (Arg136 --> Cys) was not distinct from apoE2 (Arg158 --> Cys) by phenotyping, but produced a unique pattern of bands on CfoI restriction typing of a 244 bp apoE gene fragment. Two of the four apoE2 (Arg136 --> Cys)/3 heterozygotes had elevated triglycerides, two were normolipidemic. The composition of very low density lipoproteins (VLDL) was normal in each of the four apoE2 (Arg136 --> Cys) carriers, regardless of the triglyceride concentrations. None of the apoE2 (Arg136 --> Cys) carriers displayed a broad beta-band and none revealed beta-migrating particles in the VLDL. The two hypertriglyceridemic carriers of apoE2 (Arg136 --> Cys) were, therefore, classified as having type IV rather than type III hyperlipoproteinemia. LDL receptor binding activities were studied using recombinant apoE loaded to dimyristoylphosphatidylcholine (DMPC) vesicles and to VLDL and from an apoE-deficient individual. LDL receptor binding of apoE2 (Arg136 --> Cys) was 14% of apoE3 and was thus higher than that of apoE2 (Arg158 --> Cys). Both apoE2 (Arg136 --> Cys) and apoE2 (Arg158 --> Cys) displayed substantial heparin binding (61 and 53% of apoE3, respectively). As the dominant apoE variants known so far are characterized by more pronounced reductions of heparin binding, we suggest that apoE2 (Arg136 --> Cys) is not associated with dominant expression of type III hyperlipoproteinemia. These findings lend support to the concept that apoE variants predisposing to dominant type III hyperlipoproteinemia differ from recessive mutations by a more severe defect in heparin binding.

Mutations at the lipoprotein lipase gene locus in subjects with diabetes mellitus, obesity and lipaemia

1. The common association of obesity, diabetes mellitus and hyperlipidaemia may have a primary aetiological basis. Insulin resistance has been postulated as a possible cause, but defects in the plasma transport of triacylglycerol or fatty acids could also be primary determinants. 2. We have therefore studied 18 patients with diabetes mellitus, obesity and severe hypertriglyceridaemia for defects of a key protein involved in the clearance of plasma triacylglycerols, lipoprotein lipase. 3. DNA was prepared from leucocytes of 18 patients with the above syndrome, and exons encoding lipoprotein lipase were amplified by PCR. The products were sequenced using the dideoxy chain-termination method. 4. Eight of the subjects were found to possess genetic variants at the lipoprotein lipase gene locus. These were: (a) G579-->A, V108V; (b) G818-->A, G188E; (c) C829-->T, R192; (d) A1127-->G, N291S; (e) C1308-->G, F351L; (f) C1338-->A, T361T; and (g) C1595-->G, S447. Three of these, (c), (e) and (f), have not hitherto been described. Variant (f), appears to be a population polymorphism whose allele frequency in normolipidaemic diabetics was found to be 0.12 (162 chromosomes studied). The others are all rare at frequencies of < 0.01 and may contribute to the phenotype by impairing clearance of plasma triacylglycerols. 5. We conclude that genetic variants at the lipoprotein lipase locus occur commonly in subjects with this syndrome (four out of 18 subjects with probably functional mutants) and may affect the individual's response to obesity and diabetes mellitus for the development of lipaemia.

Functioning thoracic paraganglioma: association with Von Hippel-Lindau syndrome

Functioning thoracic paraganglioma (pheochromocytoma) is unusual and therefore suggestive of a pathogenesis distinct from that of sporadic adrenal pheochromocytoma. To determine whether the pheochromocytoma-associated syndromes Von Hippel-Lindau disease (VHL) and multiple endocrine neoplasia type 2 (MEN 2) play a role in the development of thoracic functioning paragangliomas, germline DNA from five unselected patients with this rare tumor was analyzed for mutations in the genes that predispose to VHL and MEN 2. Genetic investigations and further clinical data revealed that three had VHL, with two different germline mutations of the vhl gene, but no individual was affected by MEN 2. Two of the three patients with VHL did not show any additional VHL-associated lesions. This result suggests that VHL should be considered in the differential diagnosis of thoracic pheochromocytoma, as such a diagnosis carries further important implications for the patient and family. Conversely, in patients suspected of a catecholamine-secreting tumor and known VHL, thoracic localization should be considered if an adrenal pheochromocytoma cannot be detected.

Construction and functional characterization of recombinant fusion proteins of human lipoprotein lipase and apolipoprotein CII

The hydrolysis of triacylglycerols of chylomicrons and very low density lipoproteins by lipoprotein lipase (LPL) requires the presence of apolipoprotein (apo) CII as a cofactor. To obtain further information on the interaction of apo CII and LPL, we generated two fusion proteins consisting of the complete LPL molecule and the mature form of apo CII. The cDNAs of both proteins were either connected directly or by a segment encoding a 16-amino-acid linker peptide. The fused cDNAs were stably expressed in human embryonic kidney (HEK) 293 cells and the enzymic properties of the recombinant proteins were examined. The fusion proteins hydrolysed both emulsified long-chain (lipase) triacyglycerol substrate and a water-soluble short-chain (esterase) fatty acid ester substrate (p-nitrophenylbutyrate), regardless of whether or not they contained the linker peptide. In the absence of exogenous apo CII, the fusion proteins had up to 3.5-times higher basal activity than wild-type LPL. Similar to wild-type LPL, the fusion proteins were inhibited by 1 M NaCl, however less than wild-type LPL. A polyclonal antibody specific for apo CII impaired their ability to hydrolyse triacylglycerol emulsions. A similar effect was seen when the tetrapeptide KGEE was used as inhibitor, which corresponds to the carboxy-terminal four amino acids of apo CII.