Associations of HDL phospholipids and paraoxonase activity with coronary heart disease in postmenopausal women

A low high-density lipoprotein-cholesterol (HDL-C) is an established indicator for increased risk of coronary heart disease (CHD). Multiple functional relationships between HDL and CHD have been discussed. We tested the clinical relevance of some of these relationships in a cross-sectional coronary angiography (CA) study of 87 post-menopausal women between 48 and 73 years. In addition to established cardiovascular risk factors we measured concentrations of phosphatidylcholine (PC) and sphingomyelin (SPM) in HDL as indirect markers of cholesterol efflux capacity, the serum activity of the paraoxonase (PON) as a measure of the antioxidative capacity and serum concentrations of insulin/C-peptide and C-reactive protein (CRP) as indirect markers of insulin sensitivity and inflammation, respectively. Upon multivariate analysis of data from 55 women with angiographically assessed CHD differed from 32 women with angiographically excluded CHD, HDL-SPM had the strongest association with the presence of CHD among all HDL-related parameters. It was also the only HDL-related parameter which had a significant and independent correlation with the number of coronary stenoses. As HDL-SPM was previously shown to correlate with cholesterol efflux capacity of plasma, we conclude that reduced cholesterol efflux capacity is an important factor accounting for the inverse association between HDL-cholesterol and CHD.

[Clinical aspects and molecular genetics of the Jervell- and Lange-Nielsen Syndrome]

In contrast to the Romano-Ward (R-W) syndrome, the Jervell and Lange-Nielsen (J-LN) syndrome is an autosomal recessive inherited disease characterized by QT-prolongation in the electrocardiogram (ECG) and recurrent syncopal attacks which are also typical for the R-W syndrome, but also by congenital deafness. Recently, defect alleles in the genes for KCNQ1 and KCNE1 have been identified in patients with the J-LN syndrome. These genes may be causative for the R-W syndrome as well but in J-LN patients, they are only present in the homozygote or compound heterozygote form. In the present paper, we review the clinical and genetic similarities and differences of the J-LN and the R-W syndrome as well as the diagnostic and therapeutic management of these patients and their family members.

Association of the GPIa C807T and GPIIIa PlA1/A2 polymorphisms with premature myocardial infarction in men

Aims Recent studies have reported an association between the platelet glycoprotein (GP) Ia C807T polymorphism and myocardial infarction, whereas other studies have reported contradictory results concerning the platelet GPIIIa PlA1/A2 polymorphism. In most of these studies the patients were older than 45 years. Thus we decided to examine both genotypes in 287 men who had their first myocardial infarction before age 45, and a group of 138 healthy controls. Methods and Results The frequency of T807 allele carriers was similar among myocardial infarction patients and among controls (54.6% vs 62.3%; odds ratio (OR) 0.73; 95% confidence interval (CI), 0.47-1.12). The frequency of PlA2 carriers was higher in cases than in controls (26.5% vs 15.2%; OR 1.65; CI, 1.09-2.54). After performing a logistic regression analysis, taking into account other cardiovascular risk factors, this difference did not remain significant. The combination of the risk alleles of both genotypes had no major effect on the myocardial infarction risk. Conclusions The GPIIIa PlA2 allele is not independently associated with the risk of premature myocardial infarction. The T807 allele of the GPIa gene alone or in combination with the PlA2 allele had no major effect on premature myocardial infarction risk.

Effects of dietary fatty acids on the composition and oxidizability of low-density lipoprotein

OBJECTIVE

The objective of this study was to compare the effects of dietary monounsaturated fatty acids (MUFA), n-6 and n-3 polyunsaturated fatty acids (PUFA) on LDL composition and oxidizability.

DESIGN, SETTING AND SUBJECTS

Sixty-nine healthy young volunteers, students at a nearby college, were included. Six subjects withdrew because of intercurrent illness and five withdrew because they were unable to comply with the dietary regimen.

INTERVENTIONS

The participants received a 2-week wash-in diet rich in saturated fatty acids (SFA) followed by diets rich in refined olive oil, rapeseed oil or sunflower oil for 4 weeks. Intakes of vitamin E and other antioxidants did not differ significantly between the diets.

RESULTS

At the end of the study, LDL oxidizability was lowest in the olive oil group (lag time: 72.6 min), intermediate in the rapeseed oil group (68.2 min) and highest in the sunflower oil group (60.4 min, P<0.05 for comparison of all three groups). Despite wide variations in SFA intake, the SFA content of LDL was not statistically different between the four diets (25.8-28.5% of LDL fatty acids). By contrast, the PUFA (43.5%-60.5% of LDL fatty acids) and MUFA content of LDL (13.7-29.1% of LDL fatty acids) showed a wider variability dependent on diet.

CONCLUSIONS

Enrichment of LDL with MUFA reduces LDL susceptibility to oxidation. As seen on the rapeseed oil diet this effect is independent of a displacement of higher unsaturated fatty acids from LDL. Evidence from this diet also suggests that highly unsaturated n-3 fatty acids in moderate amounts do not increase LDL oxidizability when provided in the context of a diet rich in MUFA.

Lowering of HDL cholesterol in post-menopausal women by tibolone is not associated with changes in cholesterol efflux capacity or paraoxonase activity

Low HDL cholesterol increases the risk of coronary heart disease. Treatment of postmenopausal women with tibolone lowers HDL cholesterol. We elucidated the consequences of this unwanted side effect in a randomized, double-blind study, where 12 women received 2.5 mg tibolone per day and 6 women, placebo. Blood samples were collected on days -1 (i.e. baseline), 28, 56, and 84 for the analysis of various parameters of lipid metabolism and HDL function. Compared to placebo, treatment with tibolone led to statistically significant decreases of HDL cholesterol (-22% to -32%), apoA-I (-14% to -22%), and HDL subclass LpA-I (-30% to -40%) but to no significant changes in apoA-II and HDL subclass LpA-I,A-II. These changes were not associated with statistically significant changes in the activity of plasma to release 3H-cholesterol from radiolabeled fibroblasts or in the serum activity of the anti-oxidative enzyme paraoxonase/arylesterase. There were no significant changes in either serum levels of triglycerides, LDL cholesterol, apoB, and leptin, or in LDL size. We conclude that changes in insulin do not contribute to the lowering of HDL cholesterol by tibolone. Despite decreased HDL cholesterol, putatively anti-atherogenic activities of HDL remained unchanged.

The human ABCG4 gene is regulated by oxysterols and retinoids in monocyte-derived macrophages

Here we report the induction of gene expression of ABCG4, a member of the ABC transporter subfamily G, from human macrophages by oxysterols and retinoids, agonists of the nuclear receptors LXR and RXR. The cloned ABCG4 transcript has a size of 3.5 kb and contains an open reading frame which encodes a polypeptide of 646 amino acids. Structurally, the putative ABC transporter protein consists of a nucleotide binding fold followed by a cluster of six transmembrane-spanning domains and thus conforms to the group of half-size ABC transporters. Among the human ABC transporter subfamily G members the novel transporter shows highest protein sequence homology and identity to ABCG1 (84 and 72%, respectively). Analysis of the genomic organization demonstrates that the ABCG4 gene is composed of at least 14 exons which extend across a region of 12.6 kb in size on chromosome 11q23.3. Based on its structural features and an LXR/RXR-responsive regulation similar to the cellular lipid export protein ABCA1, we conclude that ABCG4 may be involved in macrophage lipid homeostasis.

Association of serum apolipoprotein A-I (but not high-density lipoprotein cholesterol) with healed myocardial infarction in men independent of serum insulin and C-peptide

Low serum levels of high-density lipoprotein (HDL) cholesterol or apolipoprotein A-I and high serum levels of insulin increase the risk of coronary heart disease (CHD) and can indicate insulin resistance. We tested the strength, independence, and interactions of associations between HDL cholesterol (or apolipoprotein A-I), insulin (or C-peptide), glucose, and CHD in 95 male nondiabetic patients with CHD who were <60 years old, in 92 probands from the PROCAM study, and in 61 non-cardiologic patients; all subjects were matched by age, body mass index, and smoking habits. Systemic hypertension (odds radio [OR] 2.8, 95% confidence intervals [CI] 1.6 to 4.8), high serum levels of glucose (OR 2.3, 95% CI 1.6 to 4.8), insulin (OR 2.1, 95% CI 1.3 to 3.6), and C-peptide (OR 4.1, 95% CI 2.2 to 7.5) as well as low serum levels of HDL cholesterol (OR 2.0, 95% CI 1.1 to 3.5) or apolipoprotein A-I (OR 3.9, 95% CI 2.1 to 7.1) had significant associations with CHD. At multivariate analysis, systolic blood pressure, glucose, apolipoprotein A-I, and C-peptide, but not HDL cholesterol and insulin, had consistent independent associations with CHD. Thus, the combined measurement of apolipoprotein A-I and C-peptide may improve the identification of nondiabetic patients at increased risk for CHD.

Suppression of endothelial cell apoptosis by high density lipoproteins (HDL) and HDL-associated lysosphingolipids

Apoptotic cell death following injury of vascular endothelium is assumed to play an important role in the pathogenesis of atherosclerosis. In this report, we demonstrate that high density lipoproteins (HDL), a major anti-atherogenic lipoprotein fraction, protect endothelial cells against growth factor deprivation-induced apoptosis. HDL blocked the mitochondrial pathway of apoptosis by inhibiting dissipation of mitochondrial potential (Deltapsi(m)), generation of reactive oxygen species, and release of cytochrome c into the cytoplasm. As a consequence, HDL prevented activation of caspases 9 and 3 and apoptotic alterations of the plasma membrane such as increase of permeability and translocation of phosphatidylserine. Treatment of endothelial cells with HDL induced activation of the protein kinase Akt, an ubiquitous transducer of anti-apoptotic signals, and led to phosphorylation of BAD, a major Akt substrate. Suppression of Akt activity both by wortmannin and LY-294002 or by a dominant negative Akt mutant abolished the anti-apoptotic effect of HDL. Two bioactive lysosphingolipids present in HDL particles, sphingosylphosphorylcholine and lysosulfatide, fully mimicked the survival effect of HDL by blocking the mitochondrial pathway of apoptosis and potently activating Akt. In conclusion, the present study identifies HDL as a carrier of endogenous endothelial survival factors and suggests that inhibition of endothelial apoptosis by HDL-associated lysosphingolipids may represent an important and novel aspect of the anti-atherogenic activity of HDL.

Differential secretion of atrial and brain natriuretic peptide in critically ill patients

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are cardiac hormones with natriuretic, vasorelaxant, and aldosterone-inhibiting properties. We analyzed the plasma of 178 critically ill patients for ANP, BNP, aldosterone, and serum sodium concentration, as well as serum and urine osmolality and sodium filtration fraction. Mean plasma concentrations of ANP and BNP were increased in critically ill patients compared with healthy controls (ANP, 14.3 +/- 5.8 pmol/L versus 8.8 +/- 3.2 pmol/L, P < 0.05; BNP, 26.2 +/- 10.7 pmol/L versus 4.6 +/- 2.8 pmol/L, P < 0.0001). The relative increases in ANP concentrations were comparable in all diseases. BNP concentrations, by contrast, showed a wider variation. The largest BNP concentrations were observed in patients who underwent cardiac surgical procedures and in patients with subarachnoid hemorrhage. ANP, but not BNP, was correlated with aldosterone levels (r = 0.4, P < 0.001), serum sodium (r = 0.42, P < 0.001), sodium filtration fraction (r = 0.3, P < 0.001), serum osmolality (r = 0.25, P < 0.01), urinary osmolality (r = -0.24, P < 0.01), and central venous pressure (r = 0.22, P < 0.01). ANP and BNP concentrations were increased in critically ill patients; however, this did not correlate with the severity of illness or mortality. Our data support a regulatory role for ANP in the maintenance of water and electrolyte balance. The physiologic role of BNP, by contrast, is less clear. ANP and BNP are not predictors for the severity of illness and mortality in critically ill patients.

Accumulation of cardiolipin and lysocardiolipin in fibroblasts from Tangier disease subjects

Tangier disease (TD) is an inherited disorder of lipid metabolism characterized by very low high density lipoprotein (HDL) plasma levels, cellular cholesteryl ester accumulation and reduced cholesterol excretion in response to HDL apolipoproteins. Molecular defects in the ATP binding cassette transporter 1 (ABCA1) have recently been identified as the cause of TD. ABCA1 plays a key role in the translocation of cholesterol across the plasma membrane, and defective ABCA1 causes cholesterol storage in TD cells. Not only cholesterol efflux, but also phospholipid efflux was shown to be impaired in TD cells. By use of thin layer chromatography, high performance liquid chromatography and time-of-flight secondary ion mass spectrometry, we characterized the cellular phospholipid content in fibroblasts from three homozygous TD patients. The cellular content of the major phospholipids was not found to be significantly altered in TD fibroblasts. However, the two phospholipids cardiolipin and lysocardiolipin, which make up minute amounts in normal cells, were at least 3-5-fold enriched in fibroblasts from TD subjects. A structurally closely related phospholipid (lysobisphosphatidic acid) has recently been shown to be enriched in Niemann-Pick type C, another lipid storage disorder. Altogether these data may indicate that the role of these phospholipids is a regulatory one rather than that of a bulk mediator of cholesterol solubilization in sterol trafficking and efflux.

ATP binding cassette transporter ABCA1 modulates the secretion of apolipoprotein E from human monocyte-derived macrophages

Apolipoprotein E (apoE) produced by macrophages in the arterial wall protects against atherosclerosis, but the regulation of its secretion by these cells is poorly understood. Here we investigated the contribution of the adenosine triphosphate binding cassette transporters ABCA1 and ABC8 to the secretion of apoE from either primary human monocyte-derived macrophages (HMDM) or human THP1 macrophages. During incubations of up to 6 h, apoE secretion from both THP1 macrophages and HMDM was stimulated by 8-Br-cAMP, which activates ABCA1 expression. The putative ABCA1 inhibitor glyburide and antisense oligonucleotides directed against ABCA1 mRNA significantly reduced apoE secretion from THP1 macrophages and HMDM. Antisense oligonucleotides directed against ABC8 mRNA also inhibited apoE secretion, although this inhibition was less pronounced and consistent than in the case of ABCA1. ApoE secretion from HMDM of ABCA1-deficient patients with Tangier disease was also decreased. ApoE mRNA expression was not affected by inhibition of ABCA1 or ABC8 in normal HMDM or the lack of functional ABCA1 in HMDM from Tangier disease patients. Inhibition of ABCA1 in HMDM prevented the occurrence of anti-apoE-immunoreactive granular structures in the plasma membrane. We conclude that ABCA1 and, to a lesser extent, ABC8 both promote secretion of apoE from human macrophages.

The role of PPAR alpha in obesity

Obesity is a rapidly increasing health problem in all developed countries. Overweight rarely occurs in isolation but as part of a complex pattern of metabolic abnormalities ("metabolic syndrome" or "syndrome X") consisting of hyperlipidemia, hypoalphalipoproteinemia, type II diabetes and atherosclerosis. The disorder is considerably influenced by genetic, behavioural and nutritional factors. Recent data indicate that a group of closely related nuclear receptors, the peroxisome proliferator-activated receptors (PPARs), may be involved in the metabolic changes ultimately leading to obesity. This review summarises the latest developments in the PPAR field, with particular emphasis being placed on the physiological function of PPAR alpha during various nutritional states, and the possible role of PPAR alpha in obesity.

Plasma fibrinogen in relation to the severity of arteriosclerosis in patients with stable angina pectoris after myocardial infarction

BACKGROUND

Authors both of retrospective and of prospective studies have demonstrated that there is a relationship between concentration of fibrinogen in plasma and the angiographically determined severity of coronary heart disease (CHD).

OBJECTIVE

To determine the relevance of the plasma fibrinogen concentration for the severity of CHD, particularly in cases with additional arteriosclerotic changes in the extracranial arteries supplying the brain [cerebrovascular disease (CVD)], in the pelvic/leg arteries [peripheral occlusive arterial disease (POAD)], or in both.

PATIENTS AND METHODS

In a retrospective cross-sectional survey the cardiological and angiographical status of a total of 1112 male and 299 female patients with stable angina pectoris after sustained myocardial infarction and an age-matched control group of 326 male and 138 female subjects with no clinical symptoms of CHD was determined, together with measurements of plasma fibrinogen, dynamic plasma viscosity and D-dimers.

RESULTS

More than two-thirds of the patients with arteriosclerosis had plasma fibrinogen concentrations in the uppermost tertile of the control range (men > 2.75; women > 2.83 g/l). Plasma fibrinogen concentration was correlated to the severity of CHD (for men r = 0.173, P < 0.001; for women r= 0.144, P < 0.013). Patients with generalized arteriosclerosis had higher plasma fibrinogen concentrations than did those suffering from CHD only (for men, control 2.65 +/- 0.51, CHD 3.07 +/- 0.73, CHD plus POAD 3.17 +/- 0.77 and CHD plus POAD plus CVD 3.45 +/- 0.78 g/l; for women, control 2.69 +/- 0.44, CHD 3.25 +/- 0.67, CHD plus POAD 3.19 +/- 0.77, CHD plus POAD plus CVD 3.60 +/- 0.84 g/l). Multivariate analysis showed that C-reactive protein, D-dimers and dynamic plasma viscosity accounted for 48.2% (for men) and 49.4% (for women) of the variance in plasma fibrinogen concentration.

CONCLUSIONS

Our findings demonstrate that there is not only a correlation between plasma fibrinogen concentration and the severity of CHD, but also a correlation to the incidence of additional POAD or CVD.

[Obesity and cardiovascular risk]

PROBANDS AND METHOD: In the Prospective Cardiovascular Münster (PROCAM) Study, 16,288 men aged 40.5 +/- 11.3 years (mean +/- SD) and 7,328 women aged 35.8 +/- 12.3 years were enrolled between 1979 and 1991.

RESULTS

Mean body mass indices (BMI) were 25.6 +/- 3.3 kg/m2 and 23.8 +/- 4.1 kg/m2 in men and women, respectively. There was a graded positive interaction in both men and women between BMI and age-standardized levels of serum total cholesterol, low density lipoprotein cholesterol, triglycerides, fasting blood glucose, uric acid, and blood pressure (both systolic and diastolic). High density lipoprotein cholesterol tended to decrease with increases in BMI in both sexes. In the subgroup of male participants aged 40-65 years without a prior history of myocardial infarction or stroke in an 8-year follow-up 258 major coronary events were observed. Although incidences of major coronary events increased with increase in relative body weight in a multiple logistic function analysis BMI did not independently contribute to cardiovascular risk, indicating that the effect of overweight on coronary heart disease is mediated via other risk factors.

High density lipoproteins induce cell cycle entry in vascular smooth muscle cells via mitogen activated protein kinase-dependent pathway

In this study we found that HDL acts as a potent and specific mitogen in vascular smooth muscle cells (VSMC) by stimulating entry into S-phase and DNA synthesis in a time- and concentration-dependent manner, induction of cyclins D1, E, and A, as well as activation of cyclin D-dependent kinases as inferred from phosphorylation of the retinoblastoma protein (pRb). Moreover, HDL induced activation of the mitogen-activated protein kinase pathway including Raf-, MEK-1, and ERK1/2, as well as the expression of proto-oncogen c-fos, which is controlled by ERK1/2. PD98059, an inhibitor of MEK-1 blocked the mitogenic activity of HDL and cyclin D1 expression. HDL-induced VSMC proliferation, cell cycle progression, cyclin D1 expression, and activation of the Raf-1/MEK-1/ERK1/2 cascade were blocked by preincubation of cells with pertussis toxin indicating involvement of trimeric G-protein. By contrast, none of these responses was inhibited by the protein kinase C inhibitor, GF109203X. The mitogenic effects of native HDL were not mimicked by apo A-I, reconstituted HDL containing apo A-I, or cholesterol-containing liposomes. In conclusion, HDL possesses an intrinsic property to induce G-protein- and MAP-kinase-dependent proliferation and cell cycle progression in VSMC. The strong and specific mitogenic effect of HDL should be taken into account, when therapeutic strategies to elevate the plasma level of these lipoproteins are developed.

Interleukin-6 promoter polymorphism (--174 G/C) in Caucasian German patients with systemic lupus erythematosus

BACKGROUND

A biallelic polymorphism (--174 G/C) within the interleukin-6 (IL-6) promoter reportedly has functional importance through the modulation of IL-6 expression in vitro and in vivo.

METHODS

We performed a population-based case-control study to analyse the association of the --174 G/C polymorphism with disease susceptibility and clinical manifestations in 211 German patients with systemic lupus erythematosus (SLE).

RESULTS

There were no significant differences in allelic and genotypic frequencies between patients and healthy controls. Comparing patients with various disease manifestations, we found an association of the --174 G allele with discoid skin lesions (Pc=0.034) and anti-histone antibodies (Pc=0.009).

CONCLUSIONS

The IL-6 promoter polymorphism --174 G/C does not contribute significantly to disease susceptibility, but predisposes to distinct clinical and immunological features. A genetically determined high IL-6 response may have a pathogenic role under these conditions.

Clinical value of electrocardiographic parameters in genotyped individuals with familial long QT syndrome

Rate corrected QT interval (QTc) and QT dispersion (QTd) have been suggested as markers of an increased propensity to arrhythmic events and efficacy of therapy in patients with long QT syndrome (LQTS). To evaluate whether QTc and QTd correlate to genetic status and clinical symptoms in LQTS patients and their relatives, ECGs of 116 genotyped individuals were analyzed. JTc and QTc were longest in symptomatic patients (n = 28). Both QTd and JTd were significantly higher in symptomatic patients than in asymptomatic (n = 29) or unaffected family members (n = 59). The product of QTd/JTd and QTc/JTc was significantly different among all three groups. Both dispersion and product put additional and independent power on identification of mutation carriers when adjusted for sex and age in a logistic regression analysis. Thus, symptomatic patients with LQTS show marked inhomogenity of repolarization in the surface ECG. QT dispersion and QT product might be helpful in finding LQTS mutation carriers and might serve as additional ECG tools to identify asymptomatic LQTS patients.

Pro and con: high-density lipoprotein, triglycerides, and other lipid subfractions are the future of lipid management

Risk assessment limited to low-density lipoprotein cholesterol (LDL-C) levels fails to identify a substantial proportion of individuals at risk for coronary artery disease. Data from the Prospective Cardiovascular Münster (PRO-CAM) study indicate that triglyceride levels and high-density lipoprotein cholesterol levels are important determinants of risk irrespective of LDL-C level. Risk is most accurately predicted using an algorithm incorporating multiple risk factors, as shown by the multiple logistic function analysis using the independent risk variables identified on multivariate analysis in PROCAM. It remains unclear what effect statin therapy to decrease LDL-C has in individuals with risk associated with factors other than elevated LDL-C. Such individuals might derive preferential benefit from treatments targeting such risk factors.

Changes in hemostasis during treatment of hypertriglyceridemia with a diet rich in monounsaturated and n-3 polyunsaturated fatty acids in comparison with a low-fat diet

High levels of fibrinogen, factor (F) VIIc, plasminogen activator inhibitor-1 (PAI-1), and plasma viscosity are associated with an increased coronary risk. As positive correlations of these parameters with triglycerides have been shown, the increased coronary risk associated with high levels of triglycerides may be assumed to be due to alterations within the hemostatic system. To reduce the coronary risk to which hypertriglyceridemic patients are exposed, dietary treatment is recommended; the optimal composition of such a diet is, however, a matter of debate. With regard to the effects on hemostasis, we compared in a sequential approach two diets for treatment of 25 nonobese male patients (age, mean+/-S.D., 40.4+/-8.7 years) with fasting triglycerides >2.3 mmol/l. The first diet (high fat) was rich in monounsaturated fatty acids (MUFA) and marine n-3 polyunsaturated fatty acids (PUFA), whereas the second diet (low-fat) was rich in complex carbohydrates and dietary fiber. The high-fat diet induced a significant lowering of FIIc, FIXc, FXc, FVIIc, FVIIa, FXIIa, PAI-1, plasma viscosity, and platelet activity, but led to an increase in fibrinogen, whereas the low-fat diet lowered FXIIc values and induced a nonsignificant decrease in fibrinogen. Probands on this diet had a slightly higher FVIIa and platelet activity than those on the high-fat diet. However, as all changes appeared to be within the normal range of each hemostatic parameter, it remains to be clarified whether the likely beneficial effects of the high-fat diet on most hemostatic factors are outweighed by the small increase in fibrinogen levels.

Endogenous apolipoprotein E modulates cholesterol efflux and cholesteryl ester hydrolysis mediated by high-density lipoprotein-3 and lipid-free apolipoproteins in mouse peritoneal macrophages

We investigated the effect of endogenous apolipoprotein (apo) E synthesis in mouse peritoneal macrophages on cholesterol efflux and intracellular cholesteryl ester hydrolysis mediated by high-density lipoprotein-3 (HDL3) and lipid-free apolipoproteins (apo). After loading with acetylated LDL (acLDL) peritoneal macrophages from wild-type (apoE(+/+)) and apoE-deficient (apoE(-/-)) mice were incubated with medium alone or with liposomes, HDL3, lipid-free apoA-I, or lipid-free apoE3. Cholesterol and cholesteryl esters in the cells and culture media were quantified by HPLC. Incubation of apoE(+/+) or apoE(-/-) macrophages for 18 h with medium alone or with liposomes did not cause significant changes in cellular cholesterol. Addition of HDL3, apoA-I, or apoE3 to the medium led to significant cholesterol efflux, which was less efficient in apoE(-/-) macrophages than in apoE(+/+) macrophages. HDL and lipid-free apolipoproteins were more effective in reducing the cellular content of cholesteryl esters of apoE(+/+) macrophages than of apoE(-/-) macrophages, suggesting that endogenous apoE stimulates cholesteryl ester hydrolysis. The difference in the mass of cholesteryl esters was more pronounced for cholesteryl arachidonate and linoleate than for cholesteryl oleate or palmitate. Furthermore, in [(14)C]arachidonate labeling experiments cholesterol arachidonate hydrolysis was higher in apoE(+/+) macrophages than in apoE(-/-) macrophages in the presence of cholesterol efflux mediated by HDL3 or apoA-I. In contrast, in the absence of cholesterol efflux cholesterol arachidonate synthesis was higher in apoE(+/+) macrophages than in apoE-/- macrophages. Taken together, our data suggest that endogenous apoE stimulates cholesterol efflux and intracellular cholesteryl ester hydrolysis mediated by HDL3 and lipid-free apolipoproteins in mouse peritoneal macrophages. This may contribute to the antiatherogenic effect of apoE.

Effects of diets containing olive oil, sunflower oil, or rapeseed oil on the hemostatic system

Various studies have already shown that the fatty acid composition of dietary fat has different effects on hemostasis and platelet function. However, knowledge on this topic is incomplete. In the present study, fifty-eight healthy students received either a 4-week rapeseed oil [high content of monounsaturated fatty acids (MUFA) and high n-3/n-6 PUFA ratio], an olive oil (high content of MUFA, low n-3/n-6 PUFA ratio) or a sunflower oil (low content of MUFA, low n-3/n-6 PUFA ratio) diet. In each group, effects on hemostatic parameters were compared with a wash-in diet rich in saturated fatty acids with respect to intermediate-time effects on the hemostatic system and platelet function. With the olive oil diet, a reduction of coagulation factors VIIc, XIIc, XIIa, and Xc was found, whereas sunflower oil led to lower values of coagulation factors XIIc, XIIa, and IXc. In all study groups levels of plasmin-alpha2-antiplasmin were lower in week 4 than at baseline. Lower fibrinogen binding on platelets was found after the sunflower oil diet, whereas expression of CD62 and spontaneous platelet aggregation were slightly higher after the olive oil diet. However, given the major differences in the fatty acid compositions of the diets, the differences between the groups with respect to hemostasis tended to be small. Therefore, the clinical significance of the present findings remains to be evaluated.

Atherosclerosis in apolipoprotein E-deficient mice is decreased by the suppression of endogenous sex hormones

To elucidate the influence of gonadotropins, endogenous sex hormones and testosterone on atherosclerosis, 4-week-old male and female apoE-deficient mice received either 100 microg subcutaneous injections of the gonadotropin-releasing hormone (GnRH) antagonist Cetrorelix every 48 hours or a subcutaneous implantation of a permeable silastic tube with 35 mg of testosterone. Control mice received either subcutaneous injections of saline, a silastic implant with saline, or no treatment. The animals were sacrificed after eight weeks of treatment; blood was obtained by cardiac puncture and the aorta was taken out and prepared. The suppression of testosterone led to an increase in atherosclerosis in both the sinus aortae and the ascending aorta despite increases of cholesterol in male and decreases of HDL cholesterol in female mice. Treatment with testosterone led to small but significant increases of cholesterol levels and atherosclerotic lesions in male mice. Female mice showed no change in lipids and fewer atherosclerotic lesions. In conclusion, the suppression of gonadotropins appears to have a moderate anti-atherogenic effect. The effect of testosterone appears to be either neutral or opposed by gonadotropins.

Lipoprotein(a) further increases the risk of coronary events in men with high global cardiovascular risk

OBJECTIVES

This prospective population study was conducted to assess the role of elevated lipoprotein(a) [Lp(a)] as a coronary risk factor.

BACKGROUND

The role of elevated Lp(a) as a risk factor for coronary heart disease is controversial. In addition, little attention has been paid to the interaction of Lp(a) with other risk factors.

METHODS

A total of 788 male participants of the Prospective Cardiovascular Münster (PROCAM) study aged 35 to 65 years were followed for 10 years. Both Lp(a) and traditional cardiovascular risk factors (e.g., age, low density lipoprotein [LDL] cholesterol, high density lipoprotein [HDL] cholesterol, triglycerides, systolic blood pressure, cigarette smoking, diabetes mellitus, angina pectoris, and family history of myocardial infarction) were evaluated in 44 men who suffered from myocardial infarction, and in 744 men who survived without major coronary events or stroke. A multiple logistic function algorithm was used to estimate global cardiovascular risk by the combined effects of traditional risk factors.

RESULTS

Overall, the risk of a coronary event in men with an Lp(a) > or =0.2 g/liter was 2.7 times that of men with lower levels (95% confidence interval [CI]: 1.4 to 5.2). This increase in risk was most prominent in men with LDL cholesterol level > or =4.1 mmol/liter (relative risk [RR]: 2.6; 95% CI: 1.2 to 5.7), with HDL cholesterol < or =0.9 mmol/liter (RR 8.3; 95% CI: 2.0 to 35.5), with hypertension (RR 3.2; 95% CI: 1.4 to 7.2), or within the two highest global risk quintiles (relative risk: 2.7; 95% CI: 1.3 to 5.7).

CONCLUSIONS

Lp(a) increases the coronary risk, especially in men with high LDL cholesterol, low HDL cholesterol, hypertension and/or high global cardiovascular risk.

Genomic sequence and structure of the human ABCG1 (ABC8) gene

The human ATP-binding cassette half transporter G1 (hABCG1) may play a role in cholesterol transport in macrophages. Using RACE assays we determined the structure of this gene. The hABCG1 gene spans more than 97 kb comprising 20 exons, 20 kb and 5 exons more than hitherto described. Four of the novel exons are upstream and one is downstream of previous exon 1, and they are predicted to encode at least five novel transcripts. We also detected two separate promoters, upstream of exons 1 and 5, respectively. The region 650 bp upstream of exon 1 was predicted to contain putative binding sites for SP1 and nuclear factor kappaB (NF-kappaB), but no sterol response elements (SREs) or retinoid X receptor (RXR) binding sites. The region 650 bp upstream of exon 5 contained 19 possible SP1 binding sites, one possible SRE, two possible NF-kappaB, and two putative RXR binding sites. Nevertheless, both promoters responded in macrophages to stimulation by hydroxycholesterol and retinoic acid.

Accumulation of RhoA, RhoB, RhoG, and Rac1 in fibroblasts from Tangier disease subjects suggests a regulatory role of Rho family proteins in cholesterol efflux

Tangier disease (TD) is an inherited disorder of lipid metabolism characterized by very low high density lipoprotein (HDL) plasma levels, cellular cholesteryl ester accumulation and reduced cholesterol excretion in response to HDL apolipoproteins. Molecular defects in the ATP binding cassette transporter 1 (ABCA1) have recently been identified as the cause of TD. ABCA1 plays a key role in the translocation of cholesterol across the plasma membrane, and defective ABCA1 causes cholesterol storage in TD cells. However, the exact relationship of many of the biochemical and morphological abnormalities in TD to ABCA1 is unknown. Since small GTP-binding proteins are important regulators of many cellular functions, we characterized these proteins in normal and TD fibroblasts using the [alpha-32P]GTP overlay technique and Western blotting of SDS and isoelectric focusing gels. Our results indicate that GTP-binding proteins of the Rho family (RhoA, RhoB, RhoG, Rac-1) are enriched in fibroblasts from TD patients. The accumulation of small G proteins may have potential implications for the TD phenotype and the regulation of cholesterol excretion in TD cells.

High density lipoproteins and arteriosclerosis. Role of cholesterol efflux and reverse cholesterol transport

High density lipoprotein (HDL) cholesterol is an important risk factor for coronary heart disease, and HDL exerts various potentially antiatherogenic properties, including the mediation of reverse transport of cholesterol from cells of the arterial wall to the liver and steroidogenic organs. Enhancement of cholesterol efflux and of reverse cholesterol transport (RCT) is considered an important target for antiatherosclerotic drug therapy. Levels and composition of HDL subclasses in plasma are regulated by many factors, including apolipoproteins, lipolytic enzymes, lipid transfer proteins, receptors, and cellular transporters. In vitro experiments as well as genetic family and population studies and investigation of transgenic animal models have revealed that HDL cholesterol plasma levels do not necessarily reflect the efficacy and antiatherogenicity of RCT. Instead, the concentration of HDL subclasses, the mobilization of cellular lipids for efflux, and the kinetics of HDL metabolism are important determinants of RCT and the risk of atherosclerosis.

Activation of phosphatidylinositol-specific phospholipase C by HDL-associated lysosphingolipid. Involvement in mitogenesis but not in cholesterol efflux

Our earlier studies demonstrated that high-density lipoproteins (HDLs) stimulate multiple signaling pathways, including activation of phosphatidylcholine-specific phospholipases C and D (PC-PLs) and phosphatidylinositol-specific phospholipase C (PI-PLC). However, only activation of PC-PLs was linked to the HDL-induced cholesterol efflux. In the study presented here, the role of HDL-induced PI-PLC activation was studied. In human skin fibroblasts, HDL potently induced PI-PLC as inferred from enhanced phosphatidylinositol bisphosphate (PtdInsP(2)) turnover and Ca(2+) mobilization. The major protein component of HDL, apo A-I, did not induce PtdInsP(2) turnover or Ca(2+) mobilization in these cells. Both HDL and apo A-I promoted cellular cholesterol efflux, whereas only HDL induced fibroblast proliferation. Inhibition of PI-PLC with U73122 or blocking intracellular Ca(2+) elevation with Ni(2+) or EGTA markedly reduced the extent of HDL-induced cell proliferation but had no effect on cholesterol efflux. In fibroblasts from patients with Tangier disease which are characterized by defective cholesterol efflux, neither HDL-induced PtdInsP(2) breakdown and Ca(2+) mobilization nor cell proliferation was impaired. HDL-induced fibroblast proliferation, PtdInsP(2) turnover, and Ca(2+) mobilization were fully mimicked by the lipid fraction isolated from HDL. Analysis of this fraction with high-performance liquid chromatography (HPLC) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS) revealed that the PI-PLC-inducing activity is identical with two bioactive lysosphingolipids, namely, lysosulfatide (LSF) and sphingosylphosphorylcholine (SPC). Like native HDL, LSF and SPC induced PtdInsP(2) turnover, Ca(2+) mobilization, and fibroblast proliferation. However, both compounds did not promote cholesterol efflux. In conclusion, two agonist activities are carried by HDL. Apo A-I stimulates phosphatidylcholine breakdown and thereby facilitates cholesterol efflux, whereas LSF and SPC trigger PI-PLC activation and thereby stimulate cell proliferation.

Prevention of coronary heart disease by raising high-density lipoprotein cholesterol?

Consistent with several potentially anti-atherogenic activities of high-density lipoproteins in vitro, low plasma levels of high-density lipoprotein cholesterol are associated with an increased risk of coronary heart disease. In addition to genes, lifestyle factors (e.g. smoking, being overweight and physical inactivity) strongly affect plasma high-density lipoprotein cholesterol levels. Moreover, a low level of high-density lipoprotein cholesterol interacts with other risk factors. Raising of high-density lipoprotein cholesterol by either adjustments of lifestyle or drug intervention as well as elimination of additional risk factors are thus thought to affect coronary risk. Here, we summarize the outcomes of observational and interventional studies as well as genetic and experimental research which have recently much advanced our understanding of the function and regulation of high-density lipoprotein metabolism. We conclude from the data that changes in the kinetics and functionality of high-density lipoprotein rather than changes in plasma high-density lipoprotein cholesterol levels per se will affect the anti-atherogenicity of therapeutic interference with high-density lipoprotein metabolism.

Short-term prognostic value of lipid measurements in patients with angina pectoris. The ECAT Angina Pectoris Study Group: European Concerted Action on Thrombosis and Disabilities

We studied the role of various markers of lipid metabolism, hemostasis and inflammation in a two year follow-up of 3,000 patients with angina pectoris, during which time 106 patients experienced myocardial infarction or sudden coronary death. Low levels of high density lipoprotein (HDL) cholesterol and of apolipoprotein (apo) A-I were most strongly associated with increased coronary risk. The relative risk per standard deviation increase was 0.68 for HDL cholesterol (95% confidence interval 0.55 to 0.84) and 0.66 for apoA-I (0.54 to 0.81). These associations were independent of other coronary risk factors, other lipid measurements, hemostatic factors, and C-reactive protein (CRP). The associations of total and LDL cholesterol, triglycerides, apoB, and lipoprotein(a) with coronary events were not independent of HDL cholesterol or hemostatic factors. We conclude that HDL cholesterol or apoA-I, hemostatic risk factors, and CRP are important prognostic markers of coronary events in secondary prevention.

Risk for diabetes mellitus in middle-aged Caucasian male participants of the PROCAM study: implications for the definition of impaired fasting glucose by the American Diabetes Association. Prospective Cardiovascular Münster

The criteria of the American Diabetes Association and the WHO for the diagnosis of diabetes mellitus are controversially discussed. In a prospective population study, we evaluated the data of 3,737 men, aged 36-60 yr, without diabetes mellitus and with fasting serum glucose levels less than 7 mmol/L at entry into the study who had at least 1 repeat examination during a follow-up of 4-10 yr. During a mean follow-up of 6.3 yr, 200 men developed diabetes mellitus. They differed significantly from 3,537 men by body mass index, fasting serum levels of glucose, high density lipoprotein cholesterol, and family history positive for diabetes mellitus. Receiver operating curve analysis revealed that a glucose level of 5.72 mmol/L was the best discriminatory cut-off. Upon global risk estimation by multiple logistic function (MLF) analysis, 69.6% of all diabetes mellitus incidences occurred in the highest quintile as defined by the MLF algorithm. The relative risk of a men in this quintile was 8.7 compared to that in the residual population. The performance of risk assessment by MLF as estimated by the area under the receiver operator characteristic curve was similar to fasting glucose levels. Global risk estimation by multiple risk factors does not improve the prediction of diabetes mellitus by fasting glucose in middle-aged men. The lower discriminatory cut-off of 5.72 mmol/L glucose may help to reduce the previously reported discordance between impaired fasting glucose (American Diabetes Association) and impaired glucose tolerance (WHO) in diagnosis of the prediabetic state.

Treatment of hypertriglyceridemia by two diets rich either in unsaturated fatty acids or in carbohydrates: effects on lipoprotein subclasses, lipolytic enzymes, lipid transfer proteins, insulin and leptin

BACKGROUND

There is lack of agreement on which dietary regimen is most suitable for treatment of hypertriglyceridemia, especially if high triglyceride concentrations are not due to obesity or alcohol abuse. We compared the effects on blood lipids of a diet high in total and unsaturated fat with a low-fat diet in patients with triglyceride concentrations of > 2.3 mmol/l.

METHODS

Nineteen non-obese male outpatients with triglycerides ranging from 2.30 to 9.94 mmol/l received two consecutive diets for 3 weeks each: first a modified high-fat diet (39% total fat, 8% SFA, 15% monounsaturated fatty acids, 1.6% marine n-3 polyunsaturated fatty acids), and then a low-fat diet (total fat 28%, carbohydrates 54%).

RESULTS

The high-fat diet significantly decreased triglycerides (-63%), total cholesterol (-22%), VLDL cholesterol (-54%), LDL cholesterol ( 16%), total apoC-III (-27%), apoC-III in apoB containing lipoproteins (apoC-III LpB; -31%) and in HDL (apoC-III nonLpB; -29%), apoE in serum (-33%) and apoB-containing lipoproteins (nonHDL-E; -42%), LpA-I (-16%), insulin (-36%), and leptin (-26%) and significantly increased the means of HDL cholesterol (+8%), LDL size (+6%), lipoprotein lipase (LPL, +11%), hepatic lipase (+13%), and lecithin: cholesterol acyltransferase (LCAT, +2%). The subsequent low-fat diet increased triglycerides (+63%), VLDL cholesterol (+19%), apoC-III (+23%), apoC-III LpB (+44%) apoC-III nonLpB (+17%), apoE (+29%) and nonHDL-E (+43%), and decreased HDL cholesterol (-12%), LPL (-3%), and LCAT (-3%). Changes in triglycerides correlated with changes in LPL activity and insulin levels.

CONCLUSIONS

In hypertriglyceridemic patients, a modified diet rich in mono- and n-3 polyunsaturated fatty acids is more effective than a carbohydrate-rich low-fat diet in correcting the atherogenic lipoprotein phenotype.

Risk for diabetes mellitus in middle-aged Caucasian male participants of the PROCAM study: implications for the definition of impaired fasting glucose by the American Diabetes Association. Prospective Cardiovascular Münster

The criteria of the American Diabetes Association and the WHO for the diagnosis of diabetes mellitus are controversially discussed. In a prospective population study, we evaluated the data of 3,737 men, aged 36-60 yr, without diabetes mellitus and with fasting serum glucose levels less than 7 mmol/L at entry into the study who had at least 1 repeat examination during a follow-up of 4-10 yr. During a mean follow-up of 6.3 yr, 200 men developed diabetes mellitus. They differed significantly from 3,537 men by body mass index, fasting serum levels of glucose, high density lipoprotein cholesterol, and family history positive for diabetes mellitus. Receiver operating curve analysis revealed that a glucose level of 5.72 mmol/L was the best discriminatory cut-off. Upon global risk estimation by multiple logistic function (MLF) analysis, 69.6% of all diabetes mellitus incidences occurred in the highest quintile as defined by the MLF algorithm. The relative risk of a men in this quintile was 8.7 compared to that in the residual population. The performance of risk assessment by MLF as estimated by the area under the receiver operator characteristic curve was similar to fasting glucose levels. Global risk estimation by multiple risk factors does not improve the prediction of diabetes mellitus by fasting glucose in middle-aged men. The lower discriminatory cut-off of 5.72 mmol/L glucose may help to reduce the previously reported discordance between impaired fasting glucose (American Diabetes Association) and impaired glucose tolerance (WHO) in diagnosis of the prediabetic state.

High-density lipoproteins inhibit fibrinogen binding on adenosine diphosphate-activated monocytes

High levels of fibrinogen and low levels of high-density lipoprotein (HDL) cholesterol were reported to be risk factors for coronary heart disease. CD11b/CD18, a fibrinogen-binding protein, is expressed on the surface of monocytes, which play a crucial role in the formation of atherosclerotic lesions. In the present study, we investigate the effects of antibodies against CD11b and CD18, as well as HDL3 and low-density lipoprotein (LDL) cholesterol on fibrinogen binding on monocytes. We find that binding of fibrinogen on monocytes activated with adenosine diphosphate (ADP) was reduced to 66.0+/-8.3% (mean +/- SD) in the presence of anti-CD11b antibodies (12.5 microg/ml; P < or = 0.02) and to 54.5+/-4.9% in the presence of anti-CD18 antibodies (20 microg/ml; P < or = 0.01), respectively. Fibrinogen binding on Cytochalasin-B-activated monocytes was reduced to 79.8+/-6.0% in the presence of anti-CD18 (20 microg/ml; P < or = 0.05). Incubation of ADP-activated monocytes with HDL3 (0.5 g/l) led to a lowering of fibrinogen binding to 65.0+/-6.6% (P < or = 0.05). No effect of HDL3 on fibrinogen binding was seen on Cytochalasin-B-activated monocytes. A slight, non-significant stimulatory effect of LDL on fibrinogen binding on ADP-activated but not on Cytochalasin-B-activated monocytes was additionally observed. Neither incubation with HDL3 or with LDL had a significant influence on ADP-activated cellular binding of anti-CD11b or anti-CD18 antibodies. The inhibition of fibrinogen binding on monocytes in the presence of HDL3 is a major new finding of this study. Since inhibition of fibrinogen binding in the presence of HDL might impair both monocyte recruitment to the arterial wall and foam cells formation, our findings suggests a novel mechanism by which HDL may prevent development of arteriosclerosis.

Phase II trial of cyclophosphamide, leucovorin, 5-fluorouracil 24-hour infusion and tamoxifen in pancreatic cancer

Leucovorin modulates the cytotoxic effects of 5-fluorouracil (5-FU) in the treatment of cancer. 24-hour infusion of 5-FU has been shown to enhance antitumor activity in colorectal cancer compared to bolus infusion. According to experimental data cyclophosphamide and tamoxifen may enhance the effectiveness of leucovorin and 5-FU. A phase II trial was initiated to evaluate the effect of a combination of low-dose cyclophosphamide (C), leucovorin (L), 5-FU (F) and tamoxifen (T) (CLFT) in advanced pancreatic cancer. Fifty patients were treated monthly with 300 mg/m2 cyclophosphamide and weekly with 500 mg/m2 leucovorin followed by a 24-hour infusion of 2000 mg/m2 5-FU and tamoxifen 20 mg bid. Three patients had a partial response (6%), two a minor response (4%) and 32 (64%) no change of disease. The median survival time was 8.5 months for all patients, the median time to progression of disease was 4.6 months and the 1-year survival rate was 28%. CLFT was fairly well tolerated. These data suggest that biochemical modulation of 24-hour infusional 5-FU with leucovorin together with cyclophosphamide and tamoxifen has some positive effects in the treatment of pancreatic cancer.

Acceleration of reverse cholesterol transport

A low level of high-density lipoprotein (HDL) cholesterol is an important risk factor for coronary heart disease. Levels of HDL cholesterol and composition of HDL subclasses in plasma are regulated by many factors, including apolipoproteins, lipolytic enzymes, lipid transfer proteins, receptors, and cellular transporters. Reverse transport of cholesterol from cells of the arterial wall to the liver is an important mechanism by which HDL exerts its anti-atherogenic properties. Enhancement of reverse cholesterol transport is considered as a potential target for anti-atherosclerotic drug therapy. It is suggested, however, that the serum level of HDL cholesterol does not necessarily reflect the efficacy of reverse cholesterol transport.

Involvement of phospholipase D in store-operated calcium influx in vascular smooth muscle cells

In non-excitable cells, sustained intracellular Ca2+ increase critically depends on influx of extracellular Ca2+. Such Ca2+ influx is thought to occur by a 'store-operated' mechanism, i.e. the signal for Ca2+ entry is believed to result from the initial release of Ca2+ from inositol 1,4,5-trisphosphate-sensitive intracellular stores. Here we show that the depletion of cellular Ca2+ stores by thapsigargin or bradykinin is functionally linked to a phosphoinositide-specific phospholipase D (PLD) activity in cultured vascular smooth muscle cells (VSMC), and that phosphatidic acid formed via PLD enhances sustained calcium entry in this cell type. These results suggest a regulatory role for PLD in store-operated Ca2+ entry in VSMC.

Molecular genetics of arrhythmias--a new paradigm

The molecular genetic background of inherited cardiac arrhythmias has only recently been uncovered. This late development in comparison to other inherited cardiac disorders has partly been due to the high mortality and early disease onset of these arrhythmias resulting in mostly small nucleus families. Thus, traditional genetic linkage studies, which are based on the genetic information obtained from large multi-generation families, were made difficult. Inherited arrhythmogenic disorders can be divided into 'primary electrical disorders' (e.g., long-QT [LQT] syndrome) in which a detectable, organic heart disease is not evident, and into inherited diseases of the myocardial structure (e.g., hypertrophic cardiomyopathies) in which the arrhythmias occur combined with the structural alterations. To date, all inherited arrhythmogenic disorders in which the causative genes have been identified turned out to be channelopathies, since the genes encode channel subunits that regulate important ion currents that tune the cardiac action potential. The discovery of the genetic bases of the LQT syndrome became a new methodologic paradigm; because with the use of 'classical' genetic linkage strategies (named [positional] candidate strategies) not only the causative genes have been found, but moreover, functional components with a previously unknown but fundamental role for a normal repolarization process were discovered. Disease mutations turned out to be not only a family-specific event with a distinct phenotype and the potential of an additional diagnostic tool, but also, when expressed in heterologous expression systems, characterize the defective ion channel in a topological way and lead to a more specific understanding of ion channel function. Most, if not all, primary electrical cardiac disorders show a high genetic diversity. For the LQT syndromes, sixth disease loci and the responsible gene have been recently discovered (so-called locus or genetic heterogeneity). Within all disease genes, the mutations are spread over the entire gene (allelic heterogeneity); in addition, more than one disease mutation may be present. This complexity requires, at least, complete mutation analysis of all LQT genes before medical advice should be given. Meanwhile, genotype-phenotype correlations in large families are being used to evaluate intergene, interfamilial and intrafamilial differences in the clinical phenotype, reflecting gene specific, gene-site specific and individual consequences of a given mutation. A widespread phenotypic heterogeneity even within mutation carriers in the same family raises the importance of modifying factors and genes that are mostly unknown to date. The reduced penetrance and variable expressivity associated with the LQT mutations remain still to be explained. First insights into the complex actions of mutations are being extracted, from expression data; these preliminary results may lead to potential implications for a specific (gene-site directed) therapy. This paper discusses the current data on molecular genetics and genotype-phenotype correlations in LQT syndrome and related disorders and the potential implications for diagnosis and treatment.

Cholesterol efflux from normal and Tangier disease fibroblasts into normal, high-density lipoprotein-deficient, and apolipoprotein E-deficient plasmas

Tangier disease (TD) fibroblasts have defective cholesterol release in the presence of lipid-free apolipoproteins. We compared normolipidemic probands and patients with apolipoprotein A-I (apoA-I) deficiency, apoE deficiency, or TD in terms of the plasma capacity to induce the efflux of [3H]-cholesterol from normal and TD fibroblasts and to esterify this cell-derived cholesterol. Compared with normal fibroblasts, TD fibroblasts released a significantly smaller fraction of [3H]-cholesterol into normal, high-density lipoprotein (HDL)-deficient, and apoE-deficient plasmas. Supplementation of apoE-deficient plasma with exogenous apoE normalized the cholesterol efflux from normal cells but did not fully restore the reduced cholesterol efflux from TD fibroblasts. Compared with control plasma, HDL- and apoE-deficient plasmas had a significantly reduced activity to esterify cell-derived cholesterol. Cholesterol derived from TD fibroblasts was less available for esterification in either patient or normal plasmas than cholesterol derived from normal cells. The esterification defect of TD cell-derived cholesterol was more pronounced in patient plasmas than in control plasma. We conclude that (1) apoA-I and, to a lesser degree, apoE are important determinants of the cholesterol efflux and esterification capacity of plasma, (2) TD fibroblasts have a reduced capacity to release cholesterol into the plasma, and (3) TD cell-derived cholesterol is less available for esterification in plasma than cholesterol from normal fibroblasts. The absence of distinct apoA-I- or apoE-containing subclasses aggravates the defective efflux and esterification of cholesterol derived from TD cells.

Primary prevention of coronary heart disease: from controversy to consensus

In recent years, interest has tended to focus on prevention of coronary events in high-risk groups, particularly those with established coronary heart disease. While this is understandable, it has led to a lack of emphasis on primary prevention. Yet it is only by means of primary or even pri-mordial prevention that a substantial reduction in coronary mortality on a population level will be achieved. This becomes clear when we consider that half of all persons who suffer a first myocardial infarction will die within the first month thereafter. Nevertheless, major progress has been made in primary prevention. Reliable risk algorithms have been constructed in Europe (PROCAM) and the U.S., and preliminary analyses on both sides of the Atlantic indicate that these algorithms can be useful applied to populations which are geographically and ethnically distinct from those in which they were derived. A notable trend in recent years is the increasing recognition of the metabolic syndrome with its key components of abdominal obesity, hypertriglyceridemia hypertension, low HDL-C, small, dense LDL, insulin resistance and hyperinsulinemia as being perhaps the most common and dangerous metabolic abnormality of all. Newer risk markers are being evaluated. The position of homocysteine remains unclear. Despite a strong association of elevated homocysteine with risk in case-control studies, prospective investigations have been less convincing. Evidence is beginning to accumulate from cross-sectional and prospective studies that markers of inflammation such as C-reactive peptide may improve our ability to predict risk of coronary events. While these data are encouraging, results of further studies must be awaited before the true place of these markers can be determined. The same can be said of many genetic markers of risk. Though a very large number of association studies have indicated links between a variety of genetic markers and coronary risk, these effects have tended to disappear after controlling for epigenetic and confounding factors and with increasing sample sizes. Finally, much attention is being devoted to non-invasive imaging of the coronary arteries. Such methods hold much promise as a screening test to exclude coronary stenosis in low-risk individuals. However, the measurement of calcium content of the arterial wall by EBCT has yet to prove its usefulness as a predictor of coronary events.

C-reactive protein and the severity of atherosclerosis in myocardial infarction patients with stable angina pectoris

BACKGROUND

Recent findings provide evidence for the importance of inflammatory processes in the pathogenesis of atherosclerosis. C-reactive protein was elevated in patients with peripheral artery disease, coronary heart disease and myocardial infarction compared to normal subjects.

METHODS

In 1112 male and 299 female survivors of myocardial infarction (mean age +/- SD, men, 50.4 +/- 9.5, women, 56.1 +/- 9.3), we investigated whether plasma C-reactive protein concentration is associated with the severity of coronary heart disease and generalized pre-clinical or clinically manifest arteriopathy. The control group consisted of 326 male and 138 female individuals matched for age without clinical symptoms of coronary disease. The severity of arteriosclerotic changes was determined for the extra-cranial brain-supplying arteries, abdominal aorta, pelvis and leg arteries. In myocardial infarction patients coronary angiography was performed. Laboratory analyses included determination of C-reactive protein, fibrinogen, D-dimer, HDL-cholesterol, LDL-cholesterol and triglycerides.

RESULTS

The following ranking of C-reactive protein concentrations was found: controls < or = patients after myocardial infarction without atherosclerosis < or = patients with myocardial infarction and pre-clinical atherosclerosis < or = patients with myocardial infarction and clinically manifest atherosclerosis. Additionally, our data showed a significant association between C-reactive protein concentrations and the angiographically detected degree of coronary heart disease.

CONCLUSIONS

As C-reactive protein is a marker of inflammatory processes, our results in patients with clinically manifest and early pre-clinical atherosclerosis support the hypothesis that inflammatory processes in the vessel wall participate in atherogenesis. Moreover, they support the hypothesis of a causal relationship between an acute phase reaction and the pathogenesis of atherosclerosis in coronary arteries and other parts of the arterial vessel system.

Genotype/phenotype relationships in HNF-4alpha/MODY1: haploinsufficiency is associated with reduced apolipoprotein (AII), apolipoprotein (CIII), lipoprotein(a), and triglyceride levels

Hepatocyte nuclear factor (HNF)-4alpha is a transcription factor that plays an important role in regulation of gene expression in pancreatic beta-cells and in the liver. Heterozygous mutations in the HNF-4alpha gene are responsible for maturity-onset diabetes of the young 1 (MODY1), which is characterized by pancreatic beta-cell-deficient insulin secretion. HNF-4alpha is a major transcriptional regulator of many genes expressed in the liver. However, no liver defect has been identified in individuals with HNF-4alpha mutations. In this study, we have identified HNF-4alpha target genes that are mainly expressed in the liver, including alpha1-antitrypsin, alpha1-antichymotrypsin, alpha-fetal protein, ceruloplasmin, IGF binding protein 1, transferrin, apolipoprotein(AI) [apo(AI)], apo(AII), apo(B), and apo(CIII). Serum levels of these proteins and Lp(a) and triglycerides were measured in 24 members of the HNF-4alpha/MODY1 RW pedigree (Q268X mutation), including 12 diabetic patients with HNF-4alpha mutations (D-HNF4+/-), 6 nondiabetic subjects with HNF-4alpha mutations (N-HNF4+/-), 6 normal relatives (N-HNF4+/+), 6 unrelated normal matched control subjects (N-HNF4+/+), and 12 matched diabetic (non-MODY1-5) patients (D-HNF4+/+). Serum levels of apo(AII), apo(CIII), lipoprotein(a) [Lp(a)], and triglyceride were significantly reduced in HNF4+/- subjects (26.9, 19.8, 12.1, and 72.1 mg/dl, respectively) compared with HNF4+/+ subjects (37.4, 26.5, 45.2, and 124.2 mg/dl, respectively) (P = 0.00001, P = 0.01, P = 0.00006, and P = 0.000003, respectively). This reduction was not found when apo(AII), apo(CIII), Lp(a), and triglyceride levels were compared in D-HNF4+/- versus N-HNF4+/- or in D-HNF4+/+ versus N-HNF4+/+ subjects, which indicates that HNF-4alpha haploinsufficiency rather than hyperglycemia is the primary cause of decreased serum protein and triglyceride concentrations. Furthermore, we determined that genetic or environmental modifiers other than HNF-4alpha do not appear to contribute to the observed decrease of HNF-4alpha-regulated serum proteins. This study demonstrates that a heterozygous HNF-4alpha mutation leads to an HNF-4alpha-dependent hepatocyte secretory defect of liver-specific proteins.