D609-phosphatidylcholine-specific phospholipase C inhibitor attenuates thapsigargin-induced sodium influx in human lymphocytes

Previously, we reported that the phosphatidylcholine-specific phospholipase C (PC-PLC) inhibitor tricyclodecan-9-yl xanthogenate (D609) potentiates thapsigargin-induced Ca(2+) influx in human lymphocytes. In the present study we examined the effect of D609 on the thapsigargin-induced Na(+) entry. We found that the early phase of the thapsigargin-induced increase in the intracellular Na(+) concentration (approx. 1-2 min after stimulation) was attenuated after preincubation of lymphocytes with D609. By contrast, thapsigargin-induced Na(+) influx was not affected in the presence butan-1-ol, which inhibits phosphatidylcholine-specific phospholipase D (PC-PLD). The thapsigargin-induced Na(+) influx could be mimicked by PC-PLC exogenously added to the lymphocyte suspension, whereas addition of PC-PLD had no effect. In addition, thapsigargin stimulated formation of the physiological PC-PLC products, diacylglycerol. Cell-permeable diacylglycerol analogue, dioctanoyl-glycerol (DOG), produced time- and concentration-dependent increase in the intracellular Na(+) concentration. Both thapsigargin- and DOG-induced Na(+) increases were not affected in the presence of Na(+)/H(+) antiport inhibitor, HOE609, or Na(+)/Ca(2+) antiport inhibitor, dimethylthiourea, as well as in the presence of Co(2+) and Ni(2+), which block store-operated Ca(2+) entry. By contrast, markedly reduced thapsigargin- and DOG-induced Na(+) influx were noted in the presence of flufenamic acid, which blocks the non-selective cation current (I(CRANC)). In conclusion, our results suggest that diacylglycerol released due to the PC-PLC activation contributes to the thapsigargin-induced Na(+) entry.

[Knowledge about stroke among the German population]

BACKGROUND AND OBJECTIVE

Modern stroke therapy requires patients to correctly identify stroke symptoms and seek immediate hospital admission. US studies showed that only 57% of the population knew at least one stroke symptom. This is the first study about stroke knowledge among German populations.

METHODS

Using a cross-sectional questionnaire survey, 300 working-age participants of the PROCAM study, the Prospective Cardiovascular Münster Study, and 95 senior citizens of the Augsburg Study, a follow-up project of the MONICA survey 1989/90, were asked about stroke symptoms and what to do if they occur. Good knowledge about stroke was defined as knowing at least two stroke symptoms and calling the emergency medical system or seeking immediate hospital admission in case of symptoms.

RESULTS

Participation rate in the PROCAM study was 90%, while all senior citizens took part. The mean age of the working population was 41.2 years, the mean age of the retired population was 72.8 years. 35% of the working and 24.5% of the retired participants knew at least two stroke symptoms. Urgent hospital admission was selected by 78.2% of the occupational but only 41.5% of the retired participants. Good stroke knowledge was demonstrated by nearly a third of the workers but less than 10% of the elderly. Among the occupational population, being a white-collar worker or knowing someone with a stroke was a significant predictor of good stroke knowledge. Among senior citizens higher age and current smoking status were significant predictors.

CONCLUSION

Our study shows significant information deficits about stroke in our population: education needs to be geared especially towards the elderly.

Detection of missense mutations in the genes for lipoprotein lipase and hepatic triglyceride lipase in patients with dyslipidemia undergoing coronary angiography

Coronary events have a close association with a low HDL/hypertriglyceridemia (LHDL/HTG) phenotype. As enzymes that hydrolyze triglyceride-rich lipoproteins are associated with a modulation of both HDL cholesterol and triglycerides, we have tested the hypothesis that mutations in the genes encoding lipoprotein lipase (LPL) or hepatic lipase (HTGL) may contribute to the formation of coronary atherosclerosis and, thus, of coronary heart disease (CHD). The entire coding and boundary regions of LPL and HTGL genes were analyzed by direct sequencing in 20 patients with both LHDL/HTG and diagnosed CHD. In the LPL gene six different polymorphisms were identified with same frequencies observed in the general population. In the HTGL gene, besides several polymorphisms, we identified three missense mutations: Asn37His, Val73Met, and Ser267Phe. Population screening using allele specific PCR identified Val73Met as a polymorphism while the two others were absent from 100 control individuals. One of the mutations (Ser267Phe) is known to cause HTGL deficiency and is associated with type III hyperlipoproteinemia. Since this dyslipoproteinemia meets the criteria of LHDL/HTG, it is intriguing to speculate that missense mutations in HTGL may play a role in the pathogenesis of this atherogenic phenotype.

Phospholipase A(2) is involved in thapsigargin-induced sodium influx in human lymphocytes

Previously, we reported that emptying of intracellular Ca(2+) pools with endoplasmatic Ca(2+)-ATP-ase inhibitor thapsigargin leads to the Na(+) influx in human lymphocytes (M. Tepel et al., 1994, J. Biol. Chem. 269, 26239-26242). In the present study we examined the mechanism underlying the thapsigargin-induced Na(+) entry. We found that the thapsigargin-induced increase in Na(+) concentration was effectively inhibited by three structurally unrelated phospholipase A(2) (PLA(2)) inhibitors, p-bromophenacyl bromide, 3-(4-octadecyl)-benzoylacrylic acid (OBAA), and bromoenol lactone (BEL). The thapsigargin-induced Na(+) influx could be mimicked by PLA(2) exogenously added to the lymphocyte suspension. In addition, thapsigargin stimulated formation of arachidonic acid (AA), the physiological PLA(2) product. AA induced Na(+) entry in a time- and concentration-dependent fashion. Both, thapsigargin-induced Na(+) influx and AA liberation were completely inhibited in the presence of tyrosine kinase inhibitor genistein but not in the absence of extracellular Ca(2+). Collectively, these data show that thapsigargin-induced Na(+) entry is associated with tyrosine kinase-dependent stimulation of PLA(2).

Effects of testosterone suppression in young men by the gonadotropin releasing hormone antagonist cetrorelix on plasma lipids, lipolytic enzymes, lipid transfer proteins, insulin, and leptin

We investigated in a pilot study the effect of testosterone suppression on lipoprotein metabolism, insulin, and leptin in 10 men who were treated either with cetrorelix, an antagonist of gonadotropin releasing hormone, or with placebo (P). Group C + C (n = 4) was treated with 10 mg cetrorelix as daily subcutaneous injections for five days and with a subsequent injection of 60 mg cetrorelix depot. Group C + P (n = 3) received 10 mg cetrorelix as daily intramuscular injections for five days and a subsequent injection of placebo depot. Group P + P (n = 3) received placebo both as daily and depot injections. Treatment with cetrorelix reversibly suppressed testosterone to castrate levels for three weeks in group C + C and for one week in group C + P. Compared to baseline, treatment with cetrorelix increased serum levels of apolipoprotein (apo) A-I, HDL subclass LpA-I, insulin, and leptin. In the group P + P, treatment with placebo was not associated with any change of these parameters. Compared to baseline and group P + P, treatment with cetrorelix in groups C + C and C + P did not lead to considerable or consistent changes in the plasma activities of lecithin:cholesterol acyltransferase (LCAT), phospholipid transfer protein (PLTP), cholesteryl ester transfer protein (CETP), lipoprotein lipase, and hepatic lipase (HL). Only the pooled data of groups C + C and C + P unraveled small but statistically significant decreases of HL and CETP activities in response to cetrorelix. In conclusion, the small or absent effects of cetrorelix on LCAT, CETP, PLTP, LPL, and HL indicate that testosterone regulates HDL levels by other metabolic pathways. The increases of insulin and leptin in response to cetrorelix suggest that testosterone influences HDL metabolism also via obesity and insulin resistance. These effects, however, are rather in contrast to the HDL raising effect of suppressed testosterone.

Aberrant oxidation of the cholesterol side chain in bile acid synthesis of sterol carrier protein-2/sterol carrier protein-x knockout mice

Peroxisomal beta-oxidation plays an important role in the metabolism of a wide range of substrates, including various fatty acids and the steroid side chain in bile acid synthesis. Two distinct thiolases have been implicated to function in peroxisomal beta-oxidation: the long known 41-kDa beta-ketothiolase identified by Hashimoto and co-workers (Hijikata, M., Ishii, N., Kagamiyama, H., Osumi, T., and Hashimoto, T. (1987) J. Biol. Chem. 262, 8151-8158) and the recently discovered 60-kDa SCPx thiolase, that consists of an N-terminal domain with beta-ketothiolase activity and a C-terminal moiety of sterol carrier protein-2 (SCP2, a lipid carrier or transfer protein). Recently, gene targeting of the SCP2/SCPx gene has shown in mice that the SCPx beta-ketothiolase is involved in peroxisomal beta-oxidation of 2-methyl-branched chain fatty acids like pristanic acid. In our present work we have investigated bile acid synthesis in the SCP2/SCPx knockout mice. Specific inhibition of beta-oxidation at the thiolytic cleavage step in bile acid synthesis is supported by our finding of pronounced accumulation in bile and serum from the knockout mice of 3alpha,7alpha, 12alpha-trihydroxy-27-nor-5beta-cholestane-24-one (which is a known bile alcohol derivative of the cholic acid synthetic intermediate 3alpha,7alpha,12alpha-trihydroxy-24-keto-cholestano yl-coenzyme A). Moreover, these mice have elevated concentrations of bile acids with shortened side chains (i.e. 23-norcholic acid and 23-norchenodeoxycholic acid), which may be produced via alpha- rather than beta-oxidation. Our results demonstrate that the SCPx thiolase is critical for beta-oxidation of the steroid side chain in conversion of cholesterol into bile acids.

c-erbB-2/EGFR as dominant heterodimerization partners determine a motogenic phenotype in human breast cancer cells

Separate mechanisms for oncogenesis and metastasis have been postulated. We show here that prolonged and invasive cell migration, a key mechanism in cancer metastasis, is linked to c-erbB-2 signaling. Cell lines with c-erbB-2 and EGFR expression and transphosphorylation activity display a high transendothelial invasiveness in an endothelial-extracellular matrix model mimicking a capillary vessel wall in vitro. Tyrosine-phosphorylated c-erbB-2 receptors and EGFR are localized predominantly in areas of the cell with high membrane extension activity. On the molecular level, there is a subtle cross talk between the transmembrane signaling molecule c-erbB-2 and the actin cytoskeleton at multiple levels, including the generation of the second messenger PIP2 and the mobilization of the actin-regulatory protein gelsolin. Our data strongly suggest that c-erbB-2, especially in a heterodimer with EGFR, is closely involved in signaling pathways, inducing alterations in cell morphology that are required for a human breast cancer cell to become motile and conceivably metastatic.

Systemic inflammatory parameters in patients with atherosclerosis of the coronary and peripheral arteries

Plasma concentration of markers of inflammation are increased in patients with atherosclerosis. However, it is unclear whether the pattern and magnitude of this increase vary with the site and extent of disease. In 147 patients undergoing semiquantitative coronary angiography, we measured the acute-phase reactants C-reactive protein (CRP) or serum amyloid A (SAA); the proinflammatory cytokine interleukin 6 (IL-6); the active and total fractions of the anti-inflammatory cytokine transforming growth factor-beta (TGF-beta); the macrophage activation marker neopterin; and the infection marker procalcitonin. Compared with 62 patients without either coronary artery disease (CAD) or peripheral artery disease (PAD), 57 patients with CAD but no PAD showed greater median CRP (0. 4 versus 0.2 mg/dL, P=0.004) and IL-6 (3.8 versus 1.6 pg/mL, P=0. 007) levels and a lower level of active-TGF-beta (57 versus 100 ng/mL, P=0.038). Moreover, CRP, IL-6, and neopterin levels showed a positive and the active TGF-beta level a negative correlation with the extent of coronary atherosclerosis. Compared with these 57 patients with CAD alone, 15 patients with PAD and CAD had higher median levels of SAA (17 versus 7 mg/mL, P=0.008), IL-6 (12 versus 4 pg/mL, P=0.002), neopterin (14 versus 11 mg/dL, P=0.006), and total TGF-beta (11834 versus 6417 ng/L, P=0.001). However, these strong univariate associations of markers of inflammation and atherosclerosis were lost in multivariate analysis once age, sex, and high density lipoprotein cholesterol or fibrinogen were taken into account. Increased plasma levels of CRP, SAA, IL-6, TGF-beta, neopterin, and procalcitonin constitute an inflammatory signature of advanced atherosclerosis and are correlated with the extent of disease but do not provide discriminatory diagnostic power over and above established risk factors.

D-dimers in relation to the severity of arteriosclerosis in patients with stable angina pectoris after myocardial infarction

BACKGROUND

Plasma concentrations of D-dimers show the extent of intravascular fibrinolysis of cross-linked fibrin. Higher concentrations of D-dimers are found in the plasma of arteriosclerosis patients with increased fibrin metabolism. The present study was performed in order to investigate whether there is a relationship between the severity of arteriosclerosis and fibrinolytic activity indicated by plasma levels of D-dimer.

METHODS

The study populations consisted of 1112 men and 299 women with stable angina pectoris, on average 36+/-5.6 days after a myocardial infarction, as well as 326 men and 138 women with no clinical signs of cardiovascular disease. In addition to cardiological and angiological examinations, the lipid status and levels of fibrinogen, plasma viscosity, F 1+2, plasminogen, plasminogen activator inhibitor-1, D-dimer, and C-reactive protein of the participants were determined.

RESULTS

The plasma concentration of D-dimers increases with age, both in the group with coronary artery disease and in the control group, with the female gender showing consistently higher concentrations in both groups. D-dimers correlate with other parameters of the lipid and coagulation systems, which explains 32.0% and 39.2% of the variance in D-dimer values in men and women, respectively. A significant increase in the level of D-dimers can be found in participants with generalized arteriosclerosis, with a left ventricular ejection fraction </=40% as well as those with left-ventricular aneurysm.

CONCLUSION

This study indicates that there is increased fibrinolytic activity in patients with severe arteriosclerosis. This finding gives further support to the hypothesis that D-dimer concentration is dependent on the amount of fibrin associated with arteriosclerotic thrombi. However, because of the low specificity and wide overlap of D-dimer values between patients and controls, enhanced D-dimer values are of limited relevance above and beyond other lipid metabolism risk indicators for coronary artery disease or coronary artery disease and peripheral arterial occlusive disease.

Effects of lovastatin on progression of non-dilated and dilated coronary segments and on restenosis in patients after PTCA. The cholesterol lowering atherosclerosis PTCA trial (CLAPT)

OBJECTIVES

The Cholesterol Lowering Atherosclerosis PTCA Trial (CLAPT) is a prospective, randomized trial with blinded angiographic end-points to assess the effect of 2-year's treatment with lovastatin initiated 4 weeks prior to PTCA, compared to usual care on non-dilated coronary segments and on dilated coronary lesions in male patients with total cholesterol between 200 and 300 mg. dl(-1)who underwent elective PTCA.

METHODS AND RESULTS

Two hundred and twenty six patients were randomized 4 weeks prior to PTCA to special care (diet plus lovastatin n=112) or usual care (diet; n=114). One hundred and ninety-nine patients underwent PTCA at baseline and were finally included in the study. Quantitative coronary angiographic assessment was performed on blinded cinefilms at baseline (PTCA) and repeated after 4 and 24 months in 91% and 81% of the patients. The primary end-point was a change in the mean segment diameter of non-dilated segments. The mean lovastatin dose was 33 mg. day(-1). Total- and LDL-cholesterol decreased by 21% and 29% in the special care group and by 7% and 11% in the usual care patients. After 2 years, the mean segment diameter of non-dilated segments decreased by 0.03 mm in the usual care group and 0.004 mm in the special care group (P=0.27). The decrease in the mean segment diameter of dilated lesions was 0.17 mm (usual care) and 0.06 mm (special care) (P=0.04) after 4 months; 0.16 mm (usual care) and 0. 002 mm (special care) after 24 months, respectively (P=0.05). In both groups, the mean segment diameter of dilated lesions increased between 4 and 24 months after PTCA compared to a decrease in mean segment diameter of non-dilated segments (P<0.05). Restenosis (>50% diameter stenosis at follow-up) occurred in 28.4% of usual care and 22.2% of special care patients (P=0.17).

CONCLUSIONS

Lovastatin reduced the progression of dilated lesions in men with elective PTCA. Independent of treatment allocation, the dilated lesions regressed and the non-dilated segments progressed during the study follow-up. Four weeks of pre-treatment with lovastatin did not influence the rate of restenosis. Lovastatin had no statistically significant effect on non-dilated segments.

Increased lipoprotein(a) is an important risk factor for venous thromboembolism in childhood

BACKGROUND

Serum levels of lipoprotein(a) [Lp(a)] are determined largely by genetic variation in the gene encoding for apolipoprotein(a) [apo(a)], the specific protein component of Lp(a) that is very homologous to plasminogen. High plasma levels of Lp(a) increase the risk for premature atherosclerotic vessel diseases. We investigated the little-characterized role of Lp(a) as a risk factor for venous thromboembolic diseases, alone and in conjunction with established thrombophilic risk factors of proteins regulating blood coagulation and fibrinolysis.

METHODS AND RESULTS

Serum levels of Lp(a) and lipids, protein C, protein S, and antithrombin, as well as the size of apo(a) isoforms and the presence of the factor V:Q(506) mutation, were determined in 186 consecutively admitted children from neonates to 18 years old with a history of venous thrombosis and in 186 age- and disease-matched control subjects. Children with a history of venous thrombosis had a significantly higher median Lp(a) level (19 versus 4.4 mg/dL) than control subjects. The risk for thromboembolic events in children with Lp(a) levels in the upper quartile, ie, >30 mg/dL, was 7.2 (95% CI, 3.7 to 14.5). The size of apo(a) isoforms was inversely related to Lp(a) levels and to the risk for thromboembolic events. Compared with the highest quartile of the apo(a) size distribution, the lowest quartile was associated with a risk of 8.2. In addition, multivariate statistical analysis gives evidence that the factor V:Q(506) mutation (OR/CI, 2.8/1.6 to 4.9), protein C (OR/CI, 6.5/2.1 to 19), and antithrombin deficiency (OR/CI, 10.4/1.2 to 90) were independent risk factors of childhood venous thrombosis. Coincidence of elevated Lp(a) with factor V:Q(506) mutation or deficiencies of protein C or antithrombin further increased the risk for thromboembolic events to 8.4.

CONCLUSIONS

Lp(a) >30 mg/dL is a risk factor for venous thromboembolism in childhood. Lp(a) measurements should be included in the screening of causal factors in children with venous thromboembolic events.

Na(+)/Ca(2+) exchange inhibitors modulate thapsigargin-induced Ca(2+) and Na(+) influx in human lymphocytes

Thapsigargin has been shown the elevate intracellular Na(+) concentration in human lymphocytes, but mechanisms underlying thapsigargin-induced Na(+) entry are little understood. In the present study we investigated thapsigargin-induced changes in cytosolic free Na(+) and Ca(2+) concentration in human lymphocytes after inhibition of the Na(+)/Ca(2+) exchange with two structurally unrelated compounds, dimethylthiourea ad bepridil. The intracellular Na(+) increase induced by 5 microM thapsigargin was significantly enhanced in the presence of 5 mM dimethylthiourea or 40 microM bepridil. In contrast, both compounds significantly decreased the thapsigargin-induced intracellular Ca(2+) elevation. No effect of dimethylthiourea or bepridil on thapsigargin-induced Ca(2+) influx was observed in the absence of extracellular Na(+). These observations are consistent with the hypothesis that thapsigargin stimulates Na(+)/Ca(2+ )exchange in human lymphocytes. However, Na(+)/Ca(2+) exchange does not mediate Na(+) influx in human lymphocytes.

Tangier disease is caused by mutations in the gene encoding ATP-binding cassette transporter 1

Tangier disease (TD) was first discovered nearly 40 years ago in two siblings living on Tangier Island. This autosomal co-dominant condition is characterized in the homozygous state by the absence of HDL-cholesterol (HDL-C) from plasma, hepatosplenomegaly, peripheral neuropathy and frequently premature coronary artery disease (CAD). In heterozygotes, HDL-C levels are about one-half those of normal individuals. Impaired cholesterol efflux from macrophages leads to the presence of foam cells throughout the body, which may explain the increased risk of coronary heart disease in some TD families. We report here refining of our previous linkage of the TD gene to a 1-cM region between markers D9S271 and D9S1866 on chromosome 9q31, in which we found the gene encoding human ATP cassette-binding transporter 1 (ABC1). We also found a change in ABC1 expression level on cholesterol loading of phorbol ester-treated THP1 macrophages, substantiating the role of ABC1 in cholesterol efflux. We cloned the full-length cDNA and sequenced the gene in two unrelated families with four TD homozygotes. In the first pedigree, a 1-bp deletion in exon 13, resulting in truncation of the predicted protein to approximately one-fourth of its normal size, co-segregated with the disease phenotype. An in-frame insertion-deletion in exon 12 was found in the second family. Our findings indicate that defects in ABC1, encoding a member of the ABC transporter superfamily, are the cause of TD.

Apolipoprotein A-I (R151C)Paris is defective in activation of lecithin: cholesterol acyltransferase but not in initial lipid binding, formation of reconstituted lipoproteins, or promotion of cholesterol efflux

ApoA-I(R151)Paris is a natural apolipoprotein (apo) A-I variant that is associated with low levels of high-density lipoprotein cholesterol (HDL-cholesterol) and the partial deficiency of lecithin:cholesterol acyl-transferase (LCAT) in the plasma of heterozygous carriers. We compared the abilities of recombinant normal apoA-I and recombinant apoA-I(R151C)Paris to clear an emulsion of dimyristoylphosphatidylcholine (DMPC), to form reconstituted lipoproteins with dipalmitoylphosphatidylcholine (DPPC), to activate LCAT, and to promote efflux of biosynthetic cholesterol from porcine aortic smooth muscle cells (SMCs) or of exogenous cholesterol from lipid-loaded mouse peritoneal macrophages. Recombinant apoA-I(R151C)Paris occurred in monomeric and dimeric forms at a ratio of 60:40. Normal apoA-I and apoA-I(R151C)Paris cleared DMPC emulsions at equal rates. Both isoforms associated completely with DPPC during cholate dialysis. Normal apoA-I formed one single particle with a mean diameter of 9.3 nm, whereas apoA-I(R151)Paris gave rise to three particles with mean diameters of 9.3 nm (containing 74% of apoA-I), 10.6 nm, and 12.1 nm, respectively. Compared to normal apoA-I, apoA-I(R151C)Paris had a reduced LCAT-cofactor activity with a 60% lower Vmax/Km ratio due to a 50% higher affinity constant, Km. During incubations for 10 min and 360 min, normal apoA-I/DPPC complexes and apoA-I(R151C)Paris/DPPC complexes were equally efficient in releasing biosynthetic cholesterol from SMCs. In the lipid-free form, apoA-I(R151C)Paris induced normal hydrolysis of cholesteryl esters and normal cholesterol efflux from lipid-loaded mouse-peritoneal macrophages. In conclusion, in addition to its ability to form homo- and heterodimers, apoA-I(R151C)Paris is characterized by defective LCAT-cofactor activity but by normal lipid binding and cholesterol-efflux-promoting abilities.

High risk strategies for atherosclerosis

Calculating a person's chances of developing coronary heart disease (CHD) is not simple, as many risk factors interact in a complex fashion. Thus many markers, though significant in univariate comparisons, are no longer so when multivariate analysis is performed. Those factors contributing independently to risk can be identified only in prospective investigations such as the Münster Heart (PROCAM) or the Framingham studies. In the Münster Heart study, follow-up of middle-aged men for eight years identified the following nine independent risk variables: age, smoking history, personal history of angina pectoris, family history of myocardial infarction, systolic blood pressure, raised plasma low density lipoprotein cholesterol (LDL-C), low plasma high density lipoprotein cholesterol, raised fasting plasma triglyceride and presence of diabetes mellitus. These have been used to generate an algorithm for prediction of first coronary events which is available in interactive fashion on the internet'. Large trials have shown that lowering LDL-C reduces the risk of CHD, and diminishes CHD morbidity and mortality in persons without prior evidence of coronary atherosclerosis (primary prevention). This is even more the case in patients with such evidence (secondary prevention). It appears that lowering of LDL-C also reduces all-cause mortality in secondary prevention.

Stability and binding properties of wild-type and c17s mutated human sterol carrier protein 2

The temperature- and solvent-induced denaturation of both the SCP2 wild-type and the mutated protein c71s were studied by CD measurements at 222 nm. The temperature-induced transition curves were deconvoluted according to a two-state mechanism resulting in a transition temperature of 70.5 degrees C and 59.9 degrees C for the wild-type and the c71s, respectively, with corresponding values of the van't Hoff enthalpies of 183 and 164 kJ/mol. Stability parameters characterizing the guanidine hydrochloride denaturation curves were also calculated on the basis of a two-state transition. The transitions of the wild-type occurs at 0.82 M GdnHCl and that of the c71s mutant at 0.55 M GdnHCl. These differences in the half denaturation concentration of GdnHCl reflect already the significant stability differences between the two proteins. A quantitative measure are the Gibbs energies DeltaG(0)(D)(buffer) at 25 degrees C of 15.5 kJ/mol for the wild-type and 8.0 kJ/mol for the mutant. We characterized also the alkyl chain binding properties of the two proteins by measuring the interaction parameters for the complex formation with 1-O-Decanyl-beta-D-glucoside using isothermal titration microcalorimetry. The dissociation constants, K(d), for wild-type SCP2 are 335 microM at 25 degrees C and 1.3 mM at 35 degrees C. The corresponding binding enthalpies, DeltaH(b), are -21. 5 kJ/mol at 25 degrees C and 72.2 kJ/mol at 35 degrees C. The parameters for the c71s mutant at 25 degrees C are K(d)=413 microM and DeltaH(b)=16.6 kJ/mol. These results suggest that both SCP2 wild-type and the c71s mutant bind the hydrophobic compound with moderate affinity.

Associations of obesity markers, insulin, and sex hormones with HDL-cholesterol levels in Turkish and German individuals

Turkish men and women have about 20% lower mean levels of HDL-C and apoA-I than German individuals. To obtain some information on the metabolic basis of this difference, we compared anthropometric data as well as serum levels of leptin, insulin, testosterone (T), estradiol (E2), and sex hormone binding globuline (SHBG) in 289 German and 120 Turkish men as well as in 108 German and 182 Turkish women aged 20-60. Individuals who smoke, take hormones, have overt diabetes mellitus, BMI > 30 kg/m2, triglycerides > 400 mg/dl, or LDL-cholesterol > 200 mg/dl were excluded. In both sexes, Turks had significantly lower levels of HDL-C, apoA-I, Lp(a), and SHBG than Germans. Moreover, German men had a larger waist circumference, lower levels of E2 and a lower ratio of T/SHBG. German women also had a lower BMI, smaller waist circumference, lower insulin levels and higher T levels. Mean values of age, waist-hip-ratio (WHR), leptin, triglycerides, LDL-C, and apoB did not differ significantly among Germans and Turks. Upon univariate analysis HDL-C had inverse correlations with BMI, waist circumference, WHR, leptin, and insulin as well as positive correlations with SHBG in both sexes. Upon multivariate analysis, most of the different levels of HDL-C and apoA-I between Germans and Turks were explained by ethnicity, independently of obesity markers, insulin, and sex hormones.

The biologic lower detection limit of six ultrasensitive PSA assays

BACKGROUND

The benefit of monitoring patients with prostate cancer (PCA) by ultrasensitive measurement of prostate specific antigen (PSA) is frequently discussed. Usually, the analytic lower detection limit of an ultrasensitive assay is determined by the manufacturer. As the analytic lower detection limit does not take into account interfering factors of human serum, the biologic lower detection limit, which is defined as PSA concentration detected in PSA-free human serum, plus 3 standard deviations, is of greater interest.

MATERIALS AND METHODS

We investigated the biologic lower detection limit of six ultrasensitive PSA assays. Sera from 15 men with bladder cancer after radical cystoprostatectomy and from 30 healthy women were applied. Hence, we expected no PSA of prostatic origin.

RESULTS

The biologic lower detection limit obtained using these sera was up to 30 fold higher (men, 0.29-0.63 ng/ml; women, 0.03-0.69 ng/ml) than the analytic lower detection limit (0.01-0.09 ng/ml).

CONCLUSIONS

PSA measurement in sera obtained from men without prostate and women results in PSA values above the ultrasensitive range. Therefore, advantages provided by ultrasensitive PSA measurement in monitoring PCA patients after radical prostatectomy are limited.

An ecological study of determinants of coronary heart disease rates: a comparison of Czech, Bavarian and Israeli men

BACKGROUND

The large differences in cardiovascular disease rates between Eastern and Western Europe have largely developed over the last few decades, and are only partly explained by classical risk factors. This study was set up to identify other potential determinants of these differences.

METHODS

This was an ecological study comparing random samples of men aged 45-64 years selected from three cities representing populations with different rates of cardiovascular mortality: Pardubice (Czech Republic), Augsburg (Bavaria, Germany), and Jerusalem (Israel). In total, 191 (response rate 70%), 153 (70%) and 162 (62%) men, respectively, participated. All centres followed the same study protocol. Lifestyle, anthropometry and biochemical risk factors were assessed by identical questionnaires, standardized medical examination, and central analyses of fasting blood samples.

RESULTS

The mortality rates in the study populations, as well as the prevalence of coronary heart disease in study samples, were highest in Czech, intermediate in Bavarian and low in Israeli men. This pattern was replicated across the three samples by mean blood pressure (P < 0.001), cigarette smoking (not significant), triglycerides (P < 0.05), fibrinogen or D-dimer levels (P < 0.05). On the other hand, the prevalence of diabetes and obesity were similar; total and high density lipoprotein (HDL)-cholesterol, apolipoprotein B, lipoprotein (Lp(a)) and glucose did not differ between Czech and Bavarian men; and Czechs had particularly low levels of serum insulin and factor VIIc. Israelis had low fasting glucose and total cholesterol, as well as HDL-cholesterol levels and a high Lp(a) (each P < 0.001) compared with the two other samples. Striking differences were found for plasma homocysteine (10.5 in Czechs versus 8.9 mumol/l in Bavarians, P < 0.001) and for alpha-carotene (geometric mean in Czechs 16, Bavarians 21 and Israelis 30 micrograms/l), beta-carotene (60, 110 and 102 micrograms/l), and lycopene (84, 177 and 223 micrograms/l), respectively; all P-values < 0.001). Adjustment for obesity or smoking did not change these estimates. There were no differences in the levels of tocopherol and retinol.

CONCLUSIONS

Czech men had high levels of blood pressure, triglycerides, fibrinogen and D-dimer but many other traditional risk factors, as well as indicators of metabolic disorders and vitamins A and E, did not differ between the study samples. The low levels of carotenoids and high concentrations of homocysteine in Czech men seem to reflect their low dietary intakes of fruit and vegetables. The results provide indirect support for the importance of dietary factors in the East-West morbidity and mortality divide.

Strategies for the assessment of genetic coronary artery disease risk

In atherosclerotic diseases, genetic factors have a substantial influence on the age of onset and the frequency and severity of clinical symptoms, as well as response to therapy. In myocardial infarctions occurring at young age, genetics may be the leading causative factor. Despite such a prominent role of genetics in the pathophysiology of atherosclerosis clinical risk assessment and therapeutic decision making are still based on classical risk factors. In this paper we analyse the reasons for the current lack of predictive power of genetics-based algorithms and we speculate why future developments might open the door to a role for genetics in the clinical management of atherosclerosis.

Obesity, mortality and cardiovascular disease in the Münster Heart Study (PROCAM)

In the Münster Heart Study (PROCAM), 16,288 men aged 40.6 +/- 11.3 years (mean +/- S.D.) and 7328 women aged 36.0 +/- 12.3 years were enrolled between 1979 and 1991. Mean body mass indices (BMIs) were 25.6 +/- 3.3 and 23.8 +/- 4.1 kg/m2 in men and women, respectively. There was a graded and continuous positive interaction in both men and women between BMI, age and serum total cholesterol, low density lipoprotein (LDL) cholesterol, and blood pressure (both systolic and diastolic). High density lipoprotein (HDL) cholesterol tended to increase with age, but decreased in graded fashion with increases in BMI in both sexes. Triglyceride increased with BMI in both sexes and with age in women, but decreased in the older age groups of overweight and obese men. Though fasting blood glucose increased with age and BMI in both sexes, the increase was more marked in women. Among the 10,856 men aged 36-65 years at study entry, 313 deaths occurred within a follow-up period of 7.1 +/- 2.4 years. Among these men, increased mortality was seen at high BMIs in both smokers and non-smokers and was caused by coronary heart disease (CHD). Increased mortality at low BMI was seen in smokers but not in non-smokers and was due to an increase in cancer deaths. The BMI-associated increase in CHD death was completely accounted for by the factors contained in the Münster Heart Study (PROCAM) risk algorithm, indicating that the effect of overweight and obesity on CHD is mediated via other risk factors.

Effects of a frequent apolipoprotein E isoform, ApoE4Freiburg (Leu28-->Pro), on lipoproteins and the prevalence of coronary artery disease in whites

Different isoforms of apoE modulate the concentrations of plasma lipoproteins and the risk for atherosclerosis. A novel apoE isoform, apoE4Freiburg, was detected in plasma by isoelectric focusing because its isoelectric point is slightly more acidic than that of apoE4. ApoE4Freiburg results from a base exchange in the APOE4 gene that causes the replacement of a leucine by a proline at position 28. Analysis of the allelic frequencies in whites in southwestern Germany revealed that this isoform is frequent among control subjects (10:4264 alleles) and is even more frequent in patients with coronary artery disease (21:2874 alleles; P=0.004; adjusted odds ratio, 3.09; 95% confidence interval, 1.20 to 7.97). ApoE4Freiburg affects serum lipoproteins by lowering cholesterol, apoB, and apoA-I compared with apoE4 (P<0.05). Our 4 apoE4Freiburg homozygotes suffered from various phenotypes of hyperlipoproteinemia (types IIa, IIb, IV, and V). In vitro binding studies excluded a binding defect of apoE4Freiburg, and in vivo studies excluded an abnormal accumulation of chylomicron remnants. ApoE4Freiburg and apoE4 accumulated to a similar extent in triglyceride-rich lipoproteins. HDLs, however, contained about 40% less apoE4Freiburg than apoE4. In conclusion, our data indicate that apoE4Freiburg exerts its possible atherogenic properties by affecting the metabolism of triglyceride-rich lipoproteins and HDL.

The LQT syndromes--current status of molecular mechanisms

Our knowledge on the molecular genetics of inherited cardiac arrhythmias is very recent in comparison to the advances of genetics achieved in other inherited cardiac disorders. This is related to the high mortality and early disease onset of these arrhythmias resulting in mostly small nucleus families. Thus, traditional genetic linkage studies that are based on the genetic information obtained from large multi-generation families were made difficult. In 1991, the first chromosomal locus for congenital long-QT (LQT) syndrome was identified on chromosome 11p15.5 (LQT1 locus) by linkage analysis. Meanwhile, the disease-causing gene at the LQT1 locus (KCNQ1), a gene encoding a K+ channel subunit of the IKs channel, and three other, major genes, all encoding cardiac ion channel components, have been identified. Taken together, LQT syndrome turned out to be a heterogeneous channelopathy. Moreover, the power of linkage studies to reveal the genetic causes of the LQT syndrome was also important to identify unknown but fundamental channel components that contribute to the ion currents tuning ventricular repolarization. In-vitro expression of the altered ion channel genes demonstrated in each case that the altered ion channel function produces prolongation of the action potential and thus the increasing propensity to ventricular tachyarrhythmias. Since these ion channels are pharmacological targets of many antiarrhythmic (and other) drugs, individual and potentially deleterious drug responses may be related to genetic variation in ion channel genes. Very recently, also in acquired LQT syndrome, which is a frequent clinical disorder in cardiology a genetic basis has been proposed in part since mutations in LQT genes have been specifically found. The discovery of ion channel defects in LQT syndrome represents the major achievement in our understanding and implies potential therapeutic options. The knowledge of the genomic structure of the LQT genes now offers the possibility to detect the underlying genetic defect in 80-90% of all patients. With this specific information, containing the type of ion channel (Na+ versus K+ channel) and electrophysiological alteration by the mutation (loss-of-function versus change-of-function mutation), gene-directed, elective drug therapies have been initiated in genotyped LQT patients. Based on preliminary data, that were supported by in vitro studies, this approach may be useful in recompensating the characteristic phenotypes in some LQT patients. Mutation detection is a new diagnostic tool which may become of more increasing importance in patients with a normal QTc or just a borderline prolongation of the QTc interval at presentation. These patients represent approximately 40% of all familial cases. Moreover, LQT3 syndrome and idiopathic ventricular fibrillation are allelic disorders and genetically overlap. In both mutations in the LQT3 gene SCN5A encoding the Na+ channel alpha-subunit for INa have been reported. Thus, the clinical nosology of inherited arrhythmias may be reconsidered after elucidation of the underlying molecular bases. Meanwhile, genotype-phenotype correlations in large families are on the way to evaluate intergene, interfamilial, and intrafamilial differences in the clinical phenotype reflecting gene specific, gene-site specific, and individual consequences of a given mutation. LQT syndrome is phenotypically heterogeneous due to the reduced penetrance and variable expressivity associated with the mutations. This paper discusses the current data on molecular genetics and genotype-phenotype correlations and the implications for diagnosis and treatment.

Phytanic acid is ligand and transcriptional activator of murine liver fatty acid binding protein

Branched-chain phytanic acid is metabolized in liver peroxisomes. Sterol carrier protein 2/sterol carrier protein x (SCP2/SCPx) knockout mice, which develop a phenotype with a deficiency in phytanic acid degradation, accumulate dramatically high concentrations of this fatty acid in serum (Seedorf at al. 1998. Genes Dev. 12: 1189-1201) and liver. Concomitantly, a 6.9-fold induction of liver fatty acid binding protein (L-FABP) expression is observed in comparison to wild-type animals fed standard chow, possibly mediated by the peroxisome proliferator-activated receptor alpha (PPARalpha). Cytosolic transport of phytanic acid to either peroxisomal membranes or to the nucleus for activation of PPARalpha may be mediated by L-FABP, which gives rise to the question whether phytanic acid is a transactivator of this protein. Here we show first that phytanic acid binds to recombinant L-FABP with high affinity. Then the increase of the in vivo phytanic acid concentration by phytol feeding to mice results in a 4-fold induction of L-FABP expression in liver, which is in the order of that attained with bezafibrate, a known peroxisome proliferator. Finally to test in vitro whether this induction is conferred by phytanic acid, we cotransfected HepG2 cells with an expression plasmid for murine PPARalpha and a CAT-reporter gene with 176 bp of the murine L-FABP promoter, containing the peroxisome proliferator responsive element (PPRE). After incubation with phytanic acid, we observed a 3.2-fold induction of CAT expression. These findings, both in vivo and in vitro, demonstrate that phytanic acid is a transcriptional activator of L-FABP expression and that this effect is mediated via PPARalpha.

Depletion of pre beta 1LpA1 and LpA4 particles by mast cell chymase reduces cholesterol efflux from macrophage foam cells induced by plasma

Exposure of the LpA1-containing particles present in HDL3 and plasma to a minimal degree of proteolysis by the neutral protease chymase from exocytosed rat mast cell granules (granule remnants) leads to a reduction in the high-affinity component of cholesterol efflux from macrophage foam cells. In this study, we demonstrate for the first time, a role for mast cell chymase in the depletion of the lipid-poor minor components of HDL that are specifically involved in reverse cholesterol transport as initial acceptors of cellular cholesterol. Thus, addition of proteolytically active granule remnants or human skin chymase to cholesterol-loaded macrophages of mouse or human origin incubated with human apoA1, ie, a system in which prebeta1LpA1 is generated, resulted in a sharp reduction in the high-affinity cholesterol efflux promoted by apoA1. As determined by nondenaturing 2-dimensional polyacrylamide gradient gel electrophoresis, the granule remnants effectively depleted the prebeta1LpA1, but not the alphaLpA1, in HDL3 and in plasma during incubation at 37 degrees C for <1 hour. Incubation of plasma with granule remnants for 1 hour also led to near disappearance of the LpA4-1 and LpA4-2 particles, but did not affect the distribution of the apoA2-containing lipoproteins present in the plasma. We conclude that the reduced ability of granule remnant-treated HDL3 and granule remnant-treated plasma to induce cholesterol efflux from macrophage foam cells is caused by selective depletion by mast cell chymase of quantitatively minor A1- and A4-containing subpopulations of HDL. Because these particles, ie, prebeta1LpA1 and LpA4, are efficient acceptors of cholesterol from cell surfaces, their depletion by mast cells may block the initiation of reverse cholesterol transport in vivo and thereby favor foam cell formation in the arterial intima, the site of atherogenesis.

In vivo kinetics of human apolipoprotein A-I variants in rabbits

BACKGROUND

Genetic variants of human apolipoprotein (apo) A-I, the major protein component of high-density lipoprotein (HDL), with a single amino acid substitution have been reported, and some of these result in very low plasma HDL-cholesterol (C) levels. Examining the kinetics of radiolabelled apolipoprotein is a straightforward technique for determining its metabolism in vivo. In this study, we investigated the in vivo kinetics of several human apo A-I variants, which we had identified previously, in rabbits.

MATERIALS AND METHODS

Apo A-I variants from heterozygous carriers of Lys-107-->0, Lys-107-->Met, Pro-3-->Arg, Pro-4-->Arg, Pro-165-->Arg and Glu-198-->Lys and the corresponding normal apo A-I were purified and then radioiodinated with 131I and 125I. A kinetic study of apo A-I variants was performed in normolipidaemic rabbits after simultaneous injection of the two isotopes that had been incorporated into HDL. The fractional catabolic rate (FCR) was calculated from the radioactive decay curve.

RESULTS

Acidic mature (negatively charged) apo A-I variants caused by a single amino acid substitution (Lys-107-->0, and Lys-107-->Met) were catabolized faster (FCR, 1.931 +/- 0.539 per day vs. 1.636 +/- 0.460 per day, P </= 0.01 using the Wilcoxon signed-rank test) and basic mature (positively charged) apo A-I variants (Pro-3-->Arg, Pro-4-->Arg, Pro-165-->Arg and Glu-198-->Lys) were catabolized more slowly (FCR 1.470 +/- 0.380 per day vs. 1.654 +/- 0.430 per day, P </= 0.01) than the corresponding normal mature apo A-I in vivo in rabbits. In addition, an inverse linear relationship was observed between the deviation in the FCR of variant human apo A-I from that of normal human apo A-I and the number of electric charges that the apo A-I variant carried (r = -0. 90, k = -0.188, P = 0.0003), as assessed by a linear regression analysis, suggesting that the electric charge of apo A-I variants may determine, at least in part, its in vivo kinetics in rabbits.

CONCLUSIONS

Genetic variants of apo A-I with a single amino acid substitution show abnormal kinetics, and the electric charge of a apo A-I variant could contribute to determining its kinetics in vivo in this xenologous model.

Multiple dysfunctions of two apolipoprotein A-I variants, apoA-I(R160L)Oslo and apoA-I(P165R), that are associated with hypoalphalipoproteinemia in heterozygous carriers

ApoA-I(R160L)Oslo and apoA-I(P165R) are naturally occurring apolipoprotein (apo) A-I variants that are associated with low HDL-cholesterol in heterozygous carriers. We characterized the capacity of these variants to bind lipid, to activate lecithin:cholesterol acyltransferase (LCAT), and to promote efflux of biosynthetic cholesterol from porcine aortic smooth muscle cells (SMCs) or exogenous cholesterol from lipid-loaded mouse peritoneal macrophages. During cholate dialysis, normal apoA-I and both variants associated completely with dipalmitoylphosphatidylcholine (DPPC) and formed rLpA-I of identical size. However, both apoA-I(P165R) and apoA-I(R160L)Oslo showed a reduced capacity to clear a turbid emulsion of dimyristoylphosphatidylcholine (DMPC). Compared to normal apoA-I, the LCAT-cofactor activity of apoA-I(P165R) and apoA-I(R160L)Oslo as defined by the ratio of Vmax to appKm was reduced significantly by 62% and 29%, respectively (here and throughout the text, the apparent Km is given as Michaelis-Menten kinetics do not take particle binding into account and therefore would result in errors with an interfacial enzyme such as LCAT; Vmax estimates are not affected by this error). ApoA-I/DPPC complexes induced biphasic cholesterol efflux from SMCs with a fast and a slow efflux component. Compared to rLpA-I reconstituted with wild type apoA-I, rLpA-I with apoA-I(P165R) or apoA-I(R160L)Oslo were significantly less effective in promoting cholesterol efflux from SMCs in incubations of 10 min duration but equally effective in incubations of 6 h duration. Lipid-free apoA-I did not induce efflux of biosynthetic cholesterol from SMCs but induced hydrolysis of cholesteryl esters and cholesterol efflux from acetyl-LDL-loaded mouse peritoneal macrophages. In the lipid-free form, both apoA-I variants promoted normal cholesterol efflux from murine peritoneal macrophages. We conclude that amino acid residues arginine 160 and proline 165 of apoA-I contribute to the formation of a domain that is very important for initial lipid binding and contributes to LCAT-activation and promotion of initial cholesterol efflux but not to the stabilization of preformed rLpA-I.

Hypochromic red cells and reticulocyte haemglobin content as markers of iron-deficient erythropoiesis in patients undergoing chronic haemodialysis

BACKGROUND

In patients on chronic haemodialysis, because of a non-specific increase in serum ferritin, iron deficiency may be overlooked leading to failure of erythropoietin treatment. A reticulocyte haemglobin content < 26 pg and a percentage of hypochromic red cells > 2.5 have been proposed as markers of iron-deficient erythropoiesis in such subjects, but it is unclear which parameter is superior.

METHODS

We measured haematocrit, reticulocyte haemglobin content, ferritin and the percentage of hypochromic red cells over 10-150 days in 36 chronic haemodialysis patients in a university hospital. Transferrin saturation was also measured in a subset of 25 patients; iron deficiency was defined as a transferrin saturation < 15%.

RESULTS

The diagnostic sensitivity and specificity of a reticulocyte haemoglobin content < 26 pg in detecting iron deficiency were 100% and 73% respectively, compared with 91% and 54% for a percentage of hypochromic red cells > 2.5. Paradoxical reticulocyte haemglobin concentrations occurred on follow-up in five patients receiving 4000 U erythropoietin per haemodialysis (HD). In three patients, reticulocyte haemglobin content exceeded 26 pg despite a persistent lack of iron. In a fourth, iron gluconate (62.5 mg i.v./HD) increased transferrin saturation to 27% and reduced the percentage of hypochromic red cells from 12 to 4, while reticulocyte haemglobin remained > 30 pg. In the final patient, iron gluconate increased transferrin saturation from 8 to 30% and reduced the percentage of hypochromic red cells from 40 to below 5, but reticulocyte haemglobin content remained < or = 26 pg throughout.

CONCLUSIONS

The reticulocyte haemglobin content is superior to the percentage of hypochromic red cells in detecting iron deficiency in haemodialysis patients.

Phytanic acid activates the peroxisome proliferator-activated receptor alpha (PPARalpha) in sterol carrier protein 2-/ sterol carrier protein x-deficient mice

We showed recently that a targeted null mutation in the murine sterol carrier protein 2-/sterol carrier protein x-gene (Scp2) leads to defective peroxisomal catabolism of 3,7,11, 15-tetramethylhexadecanoic acid (phytanic acid), peroxisome proliferation, hypolipidemia, and enhanced hepatic expression of several genes that have been demonstrated to be transcriptionally regulated by the peroxisome proliferator-activated receptor alpha (PPARalpha). As a broad range of fatty acids activates PPARalpha in vitro, we examined whether the latter effects could be because of phytanic acid-induced activation of this transcription factor. Dietary phytol supplementation was used to modulate the concentration of phytanic acid in C57Bl/6 and Scp2 (-/-) mice. We found that the serum concentrations of phytanic acid correlated well with the expression of genes encoding peroxisomal beta-oxidation enzymes and liver fatty acid-binding protein, which have all been demonstrated to contain functionally active peroxisome proliferator response elements in their promoter regions. In accordance with these findings, a stimulating effect on acyl-CoA oxidase gene expression was also observed after incubation of the rat hepatoma cell line MH1C1 with phytanic acid. Moreover, reporter gene studies revealed that phytanic acid induces the expression of a peroxisome proliferator response element-driven chloramphenicol transferase reporter gene comparable with strong peroxisome proliferators. In addition, the ability of phytanic acid to act as an inductor of PPARalpha-dependent gene expression corresponded with high affinity binding of this dietary branched chain fatty acid to recombinant PPARalpha. We conclude that phytanic acid can be considered as a bona fide physiological ligand of murine PPARalpha.

Factor V Leiden mutation is a risk factor for cerebral venous thrombosis: a case-control study of 55 patients

BACKGROUND AND PURPOSE

Different coagulation disorders have been associated with cerebral venous thrombosis (CVT). Until now, fewer than 50 patients have been reported with CVT and the factor V Leiden (FVL) mutation. Although the prevalence of FVL-positive patients with CVT ranged from 10% to 25%, it was as low as 0.5% to 3% in the control groups. Most other studies had not systematically searched for concomitant risk factors or previous thromboembolic events. To better define the relevance of the FVL mutation in conjunction with additional risk factors in CVT, we conducted the present case-control study.

METHODS

Fifty-five patients with CVT were compared with 272 healthy controls. A standardized interview regarding established risk factors for venous thrombosis and the patients' and their families' histories for thromboembolic events was performed. The presence of the FVL mutation was determined by polymerase chain reaction on DNA obtained from peripheral blood leukocytes.

RESULTS

Of 55 patients, 8 (14.5%) were heterozygous for the FVL mutation compared with 17 of 272 controls (6.25%). The relative risk for the presence of FVL was 2.55 (95% confidence interval, 1.04 to 6.26; P=0.04). Additional risk factors for CVT were frequently found in both the presence and absence of FVL. Recurrence of venous thromboembolic events was more frequent in patients with the FVL mutation (5 of 8 patients, 62.5%) than in those without this anomaly (8 of 47 patients, 17%; P<0.005).

CONCLUSIONS

Our study confirms the FVL mutation as the most relevant hereditary risk factor for CVT. Coexisting risk factors are usually involved in the initiation of CVT. Patients with the FVL mutation are at an increased risk for recurrent venous thrombosis.

Smoking, lipoproteins and coronary heart disease risk. Data from the Münster Heart Study (PROCAM)

AIMS

The mechanism of the increase in coronary heart disease risk associated with smoking is unclear, but may partly be due to smoking-related changes in intermediate risk factors such as lipid levels, fibrinogen and blood pressure. We therefore examined the distribution of these variables among smokers and non-smokers in the Münster Heart Study.

METHODS

20696 men, aged 41.7+/-2.7 years (mean +/- SD) and 10212 women, aged 37.0+/-2.6 years, were enrolled between 1978 and 1995. Thirty-two percent of women and 36% of men smoked. Compared to non-smokers, mean levels of low density lipoprotein cholesterol, total cholesterol, triglycerides and fibrinogen were increased, respectively, by 1.4%, 0.9%, 15% and 12.1% in male and by 2.0%, 5.5%, 12% and 3.4% in female smokers. Mean high density lipoprotein cholesterol levels, body mass index and blood pressure were reduced, respectively, by 6.4%, 3.8%, and 2% in male, and by 6.7% 1.2% and 2% in female smokers. In the subgroup of 4639 men aged 40 to 65 with 8 years of follow-up, the coronary event rate (definite myocardial infarction, sudden cardiac death) in cigarette smokers was more than twice that of non-smokers with otherwise identical risk factors.

CONCLUSION

In the Münster Heart Study, smoking was associated with adverse changes in lipids (of greater magnitude in women), and fibrinogen (of greater magnitude in men). However, these changes explained only a small part of the smoking-related increase in coronary heart disease risk.

Diagnosis and management of new cardiovascular risk factors

Independent risk factors for coronary heart disease (CHD) can best be identified by means of long-term prospective epidemiological studies. These factors should not be viewed in isolation, but as part of a complex governing a person's global risk of CHD. In the Münster Heart Study (PROCAM), 8-year follow up of a cohort of middle-aged men has led to the identification of nine variables which independently contribute to CHD risk: age, smoking history, personal history of angina pectoris, family history of myocardial infarction (MI), presence of diabetes mellitus, systolic blood pressure and the levels of low density lipoprotein (LDL) cholesterol, high density lipoprotein cholesterol and triglyceride. An algorithm based on these risk factors may be used to calculate an individual's risk of fatal or non-fatal MI and is available in interactive fashion on the website of the International Task Force for Prevention of Coronary Heart Disease at www.chd-taskforce.com. Treatment goals for LDL cholesterol depend on a person's level of risk: for persons with a small increase in risk 160 mg x dl(-1), for those with a moderate increase in risk 135 mg x dl(-1) and for those at high risk, including those with a history of CHD (secondary prevention) 100 mg x dl(-1). Intervention trials indicate that lowering of LDL cholesterol for 5 years produces much of the benefit predicted from the epidemiological data. The place of newer risk markers such as Lp(a), homocysteine, and parameters of clotting and inflammation in risk prediction and management remains to be determined.

Overexpression and accumulation of apolipoprotein E as a cause of hypertriglyceridemia

The molecular mechanisms of hypertriglyceridemia (HTG), a common lipid metabolic disorder in humans, often of genetic origin, are not well understood. In studying the effect of apolipoprotein (apo) E on the metabolism of triglyceride-rich lipoproteins, we found that expressing high plasma levels of human apoE3 in transgenic mice lacking endogenous mouse apoE caused HTG. These transgenic animals had 3-fold higher plasma triglyceride levels, higher very low density lipoproteins (VLDL), and lower high density lipoproteins than did nontransgenics. Removing one or both low density lipoprotein receptor alleles in the apoE3-overexpressing mice caused severe HTG (8-11-fold over nontransgenics) and increased VLDL and decreased low and high density lipoproteins, and apoE3-enriched VLDL were markedly depleted in apoC-II. At least two mechanisms could explain HTG associated with apoE3 overexpression: stimulated VLDL triglyceride production and impaired VLDL lipolysis. The apoE3 mice with HTG had a 50% increase in hepatic VLDL triglyceride production. Furthermore, overexpression of apoE (E2, E3, or E4) in cultured hepatocytes (McA-RH7777 cells) correlated positively with secretion of VLDL into the medium. However, apoE3 overexpression-associated HTG was only partially explained by VLDL overproduction, as lipoprotein lipase-mediated VLDL lipolysis was also decreased 20-86% depending on apoE3 levels, most likely by displacing or masking apoC-II on the particles. In human subjects, HTG correlated positively with increased VLDL triglyceride and plasma and VLDL apoE levels. However, plasma and VLDL apoE correlated negatively with VLDL apoC-II levels and lipoprotein lipase-mediated VLDL lipolysis. Thus, optimal expression of apoE is crucial for normal metabolism of triglyceride-rich lipoproteins, and overexpression and/or accumulation of apoE may contribute to HTG by stimulating VLDL triglyceride production and by impairing VLDL lipolysis. The apoE3-overexpressing mice will be useful for studying the pathophysiology of this disorder.