A common functional polymorphism in the promoter region of the microsomal triglyceride transfer protein gene influences plasma LDL levels

Microsomal triglyceride transfer protein (MTP) is required for the assembly and cellular secretion of apolipoprotein B (apoB) -containing lipoproteins from the liver and intestine. The secretion pattern of apoB-containing lipoproteins is likely to influence the VLDL and LDL levels in plasma. By initial opportunistic screening for polymorphic sites in the regulatory region of the MTP gene by gene sequencing in 20 healthy male subjects, a common functional G/T polymorphism was detected 493 bp upstream from the transcriptional start point. There was differential binding of unique nuclear proteins at this site, as shown by electrophoretic mobility shift assay. The G variant seemed to bind two or three nuclear proteins that do not bind to the T variant. Expression studies with minimal promoter constructs linked to the chloramphenicol acetyltransferase reporter and transfected into HepG2 cells revealed marked enhancement of transcriptional activity with the T variant. The prevalence of the MTP promoter genotypes was investigated in a group of 184 healthy, middle-aged white men; the frequency of homozygosity for the MTP -493 T variant was .06 and the allele frequency of MTP -493T was .25 in the population. These homozygous subjects had a 22% lower LDL cholesterol concentration than did heterozygotes or subjects homozygous for the MTP -493 G variant (2.9+/-0.6 versus 3.7+/-0.8 mmol/L, P<.05). Analysis of apoB and triglyceride contents in VLDL subfractions revealed a markedly changed balance within the VLDL population. Subjects homozygous for the MTP -493 T variant had fewer but more lipid-rich VLDL particles, thereby arguing for an effect of MTP expression on the hepatic secretion of triglyceride-rich, apoB-containing lipoproteins. This common genetic variation of the MTP promoter is likely to have important implications for cardiovascular disease.

Effects of a cardioselective beta-blocker on postprandial triglyceride-rich lipoproteins, low density lipoprotein particle size and glucose-insulin homeostasis in middle-aged men with modestly increased cardiovascular risk

Beta-adrenergic receptor-blocking agents are commonly used for treatment of hypertension, angina pectoris and arrhythmias and as secondary prevention after myocardial infarction. The modest protection against myocardial infarction conferred by these compounds in primary-preventive studies has suggested that beneficial effects of beta-blockade are counteracted by known adverse influences on lipid and glucose metabolism. As most beta-blockers increase plasma triglycerides and decrease the high density lipoprotein (HDL) cholesterol concentration, a randomized, double-blind, cross-over study was conducted to evaluate whether a 12-week treatment with metoprolol (100 mg o.d.) or placebo affected the metabolism of postprandial triglyceride-rich lipoproteins in 15 middle-aged men with a modestly increased cardiovascular risk. Metoprolol treatment significantly increased the postprandial responses of very low density lipoprotein (VLDL) and VLDL remnants to a mixed meal-type of oral fat tolerance test. The effect was particularly prominent for larger (Svedberg flotation rate (Sf) > 400 and Sf 60-400) particle species (P < 0.001 in repeated measures ANOVA), whereas the smaller (Sf 20-60) particles were less affected (P < 0.05). The changes in the postprandial responses of the different VLDL species were mainly related to an effect on the fasting plasma concentrations, with limited or no influences on VLDL catabolism during the postprandial state. In contrast, metoprolol treatment did not significantly influence the postprandial responses of chylomicrons and chylomicron remnants. Notably, the enhanced fasting and postprandial triglyceridaemia during metoprolol treatment was neither accompanied by a rise in fasting or postprandial free fatty acid concentrations, nor by alterations of the glucose and insulin responses to a standard oral glucose challenge. The ensuing shift in the LDL particle size distribution towards smaller particles was limited (fraction small LDL: metoprolol 22.8 +/- 15.7% versus placebo 19.3 +/- 15.0%, P < 0.05). In conclusion, metoprolol treatment primarily enhances fasting and postprandial triglyceridaemia in middle-aged men by increasing the basal hepatic production of VLDL.

Effects of recombinant apolipoprotein A-I(Milano) on aortic atherosclerosis in apolipoprotein E-deficient mice

BACKGROUND

We previously reported marked inhibitory effects of recombinant apolipoprotein (apo) A-I(Milano)/phospholipid complex (A-I[Milano]/PC) on neointimal lesions in balloon-injured iliofemoral arteries of hypercholesterolemic rabbits. In this study, we tested the hypothesis that apo A-I(Milano)/PC would inhibit aortic atherosclerosis in apo E-deficient mice.

METHODS AND RESULTS

Thirty-five apo E-deficient mice fed a high-cholesterol diet were included in the study. Control mice were killed at 20 (n=8) or 25 (n=7) weeks. Treated mice received 18 injections of either 40 mg/kg apo A-I(Milano)/PC (n=15) or PC only (n=5) intravenously every other day from 20 weeks until death at 25 weeks. Aortic atherosclerosis was identified with Sudan IV staining. Lipid and macrophage contents of the aortic sinus plaques were measured after oil-red O and Mac-1 antibody staining, respectively, and quantified with computed morphometry. In control mice, from 20 to 25 weeks, aortic atherosclerosis increased by 59% (11 +/- 1% versus 17 +/- 5% of the aortic surface, P=.002), and lipid content increased by 45% (22 +/- 8% versus 32 +/- 6% of plaque area, P=.02) without a significant change in macrophage content (10.8 +/- 2% versus 13.2 +/- 6%). Compared with 20-week-old untreated control mice, PC only-treated mice at 25 weeks demonstrated a 32% increase in aortic atherosclerosis (11 +/- 1% versus 15 +/- 4%, P=.01) and an increase in lipid content (22 +/- 8% versus 47 +/- 3%, P<.0001) without a change in macrophage content (10.8 +/- 2% versus 11 +/- 2%). In comparison with 20-week-old untreated control mice, 25-week-old apo A-I(Milano)/PC-treated mice demonstrated no increase in aortic atherosclerosis (11 +/- 1% versus 10 +/- 4%, P=NS), a 40% reduction in lipid content (22 +/- 8% versus 13 +/- 8%, P=.01), and a 46% reduction in macrophage content (10.8 +/- 2% versus 5.8 +/- 2.9%; P=.03). Serum cholesterol levels were markedly elevated in all groups and did not change significantly with apo A-I(Milano)/PC or PC only. In vitro, apo A-I(Milano)/PC stimulated cholesterol efflux from cholesterol-loaded FU5AH hepatoma cell lines in a dose-dependent manner, whereas PC only or PC-free apo A-I(Miano) had no effect.

CONCLUSIONS

Recombinant A-I(Milano)/PC prevented progression of aortic atherosclerosis and reduced lipid and macrophage content of plaques in apo E-deficient mice despite severe hypercholesterolemia. Thus, A-I(Milano)/PC may have a role in inhibiting progression and promoting stabilization of atherosclerosis.

Alimentary lipemia enhances the membrane expression of platelet P-selectin without affecting other markers of platelet activation

The present study was conducted to determine whether alimentary lipemia alters platelet activity in vivo. Normolipidemic volunteers were given a fatty meal and platelet function was assessed before, and 3 and 6 h after the meal. Platelet aggregability and secretion was determined using whole blood flow cytometry (expression of platelet P-selectin and fibrinogen binding), filtragometry ex vivo (reflecting platelet aggregability in vivo) and by measurements of platelet specific products in plasma (beta-thromboglobulin and platelet factor 4). Plasma triglycerides increased from 0.8 (0.6:1.1; median, 25th and 75th percentiles) to 1.7 (1.0:2.3) mmol/l at 3 h and returned to baseline after 6 h (P < 0.001, one-way ANOVA). Apo B-100 and apo B-48 were both markedly increased 3 h postprandially in the Sf 60-400 fraction (large VLDLs, P < 0.001 for both), whereas the Sf 20-60 (small VLDLs) and Sf 12-20 fractions (IDL) did not change. The platelet function assessments revealed that the percentage of platelets expressing P-selectin increased by 40% (5%; 64%) after 3 h and by 51% (- 7%; 85%) 6 h postprandially in unstimulated samples (P < 0.05 for both). In samples stimulated by ADP in vitro P-selectin expression increased by 45% (6%; 58%) after 3 h and by 30% (12%; 58%) (P<0.01 for both) after 6 h at 0.1 microM. Platelet P-selectin expression was less influenced at higher ADP concentrations. The plasma levels of beta-thromboglobulin (approximately 20 ng/ml) and platelet factor 4 (approximately 0.3 ng/ml) were not affected by the fat load. Flow cytometric analyses of fibrinogen binding and filtragometry measurements also failed to reveal any postprandial alterations. The present finding of enhanced platelet P-selectin expression suggests that platelets are mildly sensitized postprandially. Whether this is of importance for thrombus formation and atherosclerosis needs to be studied further.

Progression of coronary artery disease in young male post-infarction patients is linked to disturbances of carbohydrate and lipoprotein metabolism and to impaired fibrinolytic function

AIMS

To assess determinants of coronary artery disease progression in men with previous myocardial infarction.

METHODS AND RESULTS

A total of 102 unselected non-diabetic Swedish men (age 40.4 +/- 3.6, range 23-44 years) entered the study 3-6 months after a first myocardial infarction. The programme included metabolic and haemostatic investigations and routine coronary angiography at baseline, followed by re-angiography 5 years later. Of the original cohort, 76 patients underwent a second angiogram. Separate semiquantitative scoring systems were used for diffuse coronary atherosclerosis and distinct stenoses in 15 proximal coronary segments. Smoking, global severity of coronary atherosclerosis and presence of multi-vessel disease at baseline (P < 0.001) characterized patients with severe progression of both diffuse and focal lesions. Higher plasma levels of low density lipoprotein cholesterol (P < 0.01) and low density lipoprotein triglycerides (P < 0.05), a lower plasma high density lipoprotein2 cholesterol level (P < 0.05) and higher plasma plasminogen activator inhibitor-1 activity (P < 0.05), together with a high baseline stenosis score (P < 0.001) characterized patients with severe progression of coronary atherosclerosis. On the other hand, more pronounced fasting and post-prandial glycaemia (P < 0.05), together with higher plasma plasminogen activator inhibitor-1 activity (P < 0.01) characterized severe progressors with respect to coronary stenosis. Multivariate analysis identified the presence of multi-vessel disease as an independent predictor of progression of both coronary atherosclerosis (P = 0.008) and stenoses (P = 0.007), whereas a high low density lipoprotein triglyceride level (P < 0.01) was independently related to progression of coronary atherosclerosis and a high fasting glucose level (P = 0.02) to progression of coronary stenoses.

CONCLUSION

Disturbances in carbohydrate and lipoprotein metabolism and impaired fibrinolytic function are associated with progression of coronary artery disease in young male post-infarction patients.

Platelet activity in vivo in hyperlipoproteinemia--importance of combined hyperlipidemia

Platelet hyperactivity in vitro is found in patients with isolated hypercholesterolemia. It is, however, less well established if platelet activity in vivo is enhanced, and if there are differences between various types of hyperlipoproteinemia. Platelet function in vivo was studied at rest and during mental stress in men with isolated hypercholesterolemia (phenotype IIa; n = 21) or combined hyperlipidemia (phenotype IIb; n = 29), and age-matched normolipidemic controls (n = 41). The urinary excretion of 11-dehydrothromboxane B2 was elevated in patients compared to controls (IIa, p <0.05; IIb, p <0.001), and higher in type IIb than in IIa patients (p <0.05). Platelet secretion, assessed as plasma beta-thromboglobulin levels, was higher in type IIb patients compared to controls (p <0.01) and type IIa patients (p <0.05) during mental stress. The urinary excretion of beta-thromboglobulin was also elevated in type IIb patients compared to controls (p <0.05). Platelet aggregability at rest, as measured by filtragometry ex vivo was, however, reduced in both patient groups compared to controls (p <0.05). No correlations were found between plasma lipoprotein levels and markers of platelet function in vivo. Type IIb patients had higher plasma fibrinogen levels and higher leukocyte counts than controls (p <0.05 and p <0.001) and type IIa patients (p <0.05 and p = 0.06). Thromboxane excretion was positively related to fibrinogen levels and leukocyte counts (p <0.01 for both). Preliminary data regarding serum TNF-alpha also indicated an elevation of this inflammatory cytokine in type IIb patients (p <0.05 vs controls). In conclusion, thromboxane generation and platelet secretion in vivo are enhanced in patients with hypercholesterolemia, and particularly so among patients with concomitant elevation of plasma triglycerides. The mechanism is unknown, but inflammatory mediators may be involved. The present findings are of interest in relation to the role of triglycerides in coronary artery disease.

Transient triglyceridemia in healthy normolipidemic men increases cellular processing of large very low density lipoproteins by fibroblasts in vitro

Exaggerated and prolonged postprandial triglyceridemia is a characteristic of patients with precocious coronary heart disease. Although large very low density lipoprotein (VLDL) particles accumulate during alimentary lipemia, the biological properties of the postprandial VLDL remain unknown. In the present study, an intravenous infusion of a chylomicron-like emulsion was given to healthy normolipidemic men to examine the effects of transient triglyceridemia in vivo on compositional and cell biological characteristics of VLDL. The postinfusion large(Svedberg flotation rate (Sf) (60-400) VLDL was found to have increased capacity to inhibit low density lipoprotein (LDL) binding to the LDL-receptor and a greater ability to suppress the 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity of cultured fibroblasts compared to VLDL isolated from fasting plasma. These alterations in cellular interactions were accompanied by increases in the number of apolipoprotein (apo) E, C-I, and C-III molecules per large VLDL particle and loss of apoC-II, compositional changes similar to those observed after an oral fat load. The increase in number of apoE molecules per large VLDL particle correlated positively and significantly with the increase in the capacity of large VLDL to inhibit LDL binding to the LDL receptor (r = 0.76, P = 0.01, n = 10). In contrast, the composition of the small (Sf 20-60) VLDL particles did not change significantly, nor was the LDL receptor-mediated processing of these particles altered consistently. These observations indicate that large VLDL particles that accumulate during alimentary lipemia undergo compositional changes that render them more prone to cellular binding and uptake.

Helicobacter pylori seropositivity is not associated with inflammatory parameters, lipid concentrations and degree of coronary artery disease

OBJECTIVES

To determine the prevalence of chronic infection with Helicobacter pylori (HP) in patients with established coronary artery disease (CAD) and in healthy controls. Furthermore, to investigate whether HP infection is associated with inflammatory parameters, lipid concentrations and degree and progression of CAD.

DESIGN

A case-control study combined with a prospective angiographic study.

SETTING

Stockholm Metropolitan Area, Sweden.

PATIENTS AND METHODS

A material consisting of 92 young men aged 40.9 +/- 3.2 (mean +/- SD) years, with previous myocardial infarction and documented coronary atherosclerosis, and 95 healthy sex-matched controls, aged 43.2 +/- 3.0 (mean +/- SD) years, with similar socio-economic status and ethnic background was analysed for the prevalence of HP seropositivity, plasma concentrations of the inflammatory parameters fibrinogen, tumour necrosis factor alpha and orosomucoid, and serum concentrations of lipids. The impact of HP seropositivity on degree and progression of CAD, as assessed by quantitative coronary angiography, was also determined.

RESULTS

The study population of mainly Scandinavian origin had a low prevalence of HP seropositivity in comparison with previously published European populations. No significant increase in HP seropositivity was found in patients compared with controls (42.2 vs. 32.6%). Furthermore, HP infection was not associated with increased levels of inflammatory parameters, lipid concentrations or with degree of angiographically determined CAD at baseline, or progression of CAD and clinical events over 5 years.

CONCLUSIONS

HP infection is not associated with inflammatory parameters and lipid concentrations and could not be confirmed as a risk factor for CAD.

Evidence for a role of tumor necrosis factor alpha in disturbances of triglyceride and glucose metabolism predisposing to coronary heart disease

Elevated plasma levels of triglyceride-rich lipoproteins, a decreased high-density lipoprotein (HDL) cholesterol concentration, hyperinsulinemia, and impaired fibrinolytic function frequently aggregate in patients with premature coronary heart disease (CHD). Experimental studies suggest that the cytokine tumor necrosis factor alpha (TNFalpha) produced by adipocytes plays a part in the regulation of triglyceride and glucose metabolism. The present study examined whether TNFalpha is implicated in these metabolic and fibrinolytic disturbances in young postinfarction patients. TNFalpha levels were determined in two groups of young (age <45 years) male postinfarction patients (n = 92 and 60) and in matched, population-based control subjects (n = 63). Plasma TNFalpha was higher in patients than in controls (4.1 +/- 1.6 v2.5 +/- 0.4 pg/mL, P < .0001). In hyperlipidemic patients, TNFalpha levels correlated significantly with the concentrations of very-low-density lipoprotein (VLDL) triglyceride and cholesterol and negatively with HDL cholesterol. Treatment with bezafibrate decreased VLDL triglycerides and increased HDL cholesterol, but did not affect TNFalpha levels. The TNFalpha concentration also correlated significantly with fasting glucose and proinsulin concentrations, as well as glucose and proinsulin levels after glucose ingestion. In contrast, no relations were found with the insulin level or degree of insulin resistance. The present results provide clinical evidence for a basic role of TNFalpha in hypertriglyceridemia, glucose intolerance, and the etiology of premature CHD.

Adipose tissue secretion of plasminogen activator inhibitor-1 in non-obese and obese individuals

High plasma plasminogen activator inhibitor-1 (PAI-1) activity is a frequent finding in obesity, and both PAI-1 and obesity are risk factors for cardiovascular disease. To study the mechanisms underlying increased PAI-1 levels in obese individuals, gene expression and secretion of PAI-1 were measured in human abdominal subcutaneous adipose tissue. A total of 32 obese, otherwise healthy subjects and 10 never-obese healthy subjects with a body mass index (BMI) of 42.6 +/- 1.2 and 24.3 +/- 1.9 kg/m2 (mean +/- SEM), respectively, were investigated. Plasma PAI-1 activity, adipose tissue PAI-1 secretion and adipocyte PAI-1 mRNA levels were increased seven-fold (p < 0.0001), sixfold (p < 0.0001) and twofold (p < 0.05), respectively, in the obese group. There were clear associations between adipose tissue secretion of PAI-1 and PAI-1 mRNA levels on the one hand and fat cell volume on the other (r = 0.68, p < 0.0001 and r = 0.51, p < 0.01, respectively, in the obese group). PAI-1 mRNA levels were also related to the amount of PAI-1 secreted among obese individuals (r = 0.31, p = 0.09). It is concluded that adipose tissue secretes significant amounts of PAI-1, that PAI-1 secretion from adipose tissue is increased in obesity, and that PAI-1 secretion is related to the lipid content and cell volume of fat cells. Plasma PAI-1 activity is elevated in obesity, at least in part due to increased gene expression in adipocytes, which, in turn, enhances PAI-1 secretion from adipose tissue.

Very-low-density lipoprotein response element in the promoter region of the human plasminogen activator inhibitor-1 gene implicated in the impaired fibrinolysis of hypertriglyceridemia

Hypertriglyceridemia and impaired fibrinolytic function are linked to coronary heart disease and other atherothrombotic disorders. Triglyceride-rich lipoproteins may attenuate fibrinolysis by increasing the plasma levels of plasminogen activator inhibitor-1 (PAI-1). Furthermore, a common 4/5 guanosine (4G/5G) polymorphism in the promoter region of the PAI-1 gene has been indicated to influence plasma PAI-1 activity and to be involved in an allele-specific response to triglycerides. Herein we show by transfection assays that VLDLs induce transcription of the human PAI-1 promoter in endothelial cells. A VLDL response element (VLDLRE) is located to residues -672 to -657 in the promoter region by electromobility shift assay, methylation interference, and DNase I footprinting, and its activity is shown to be influenced by the common 4G/5G polymorphism located adjacent to and upstream of the binding site of a VLDL-inducible transcription factor. These findings may provide a molecular explanation to the link between VLDL and PAI-1 activity elevation in plasma and to the interaction between the 4G/5G polymorphism and plasma triglycerides.

Effect of bezafibrate treatment over five years on coronary plaques causing 20% to 50% diameter narrowing (The Bezafibrate Coronary Atherosclerosis Intervention Trial [BECAIT])

Recent reports indicate that most coronary events originate from plaques causing <50% diameter stenosis. A subgroup analysis of the Bezafibrate Coronary Atherosclerosis Intervention Trial (BECAIT) data was undertaken to determine the effects of bezafibrate in relation to baseline narrowing. BECAIT included 92 male postacute myocardial infarction patients <45 years of age. Each received double-blind treatment with bezafibrate (200 mg 3 times daily) or placebo for 5 years, together with a low-fat diet. Coronary angiography was performed at baseline and after 2 and 5 years. The mean minimum lumen diameter of lesions causing 20% to <50% diameter stenosis at baseline did not narrow over 5 years in the bezafibrate group and decreased by 0.15 mm in the placebo group (p <0.05). In segments with > or =50% diameter stenosis at baseline, no change was seen in either of the 2 groups. In the analysis including only segments with 20% to <50% stenosis at baseline, coronary events were seen in 7 of 40 patients with a progression in minimum lumen diameter of more than the median value and in 3 of 41 patients with a change less than the median value. Thus, bezafibrate had a preferential effect in slowing the progression of narrowings causing <50% stenosis at baseline in young men followed up for a 5-year period after acute myocardial infarction.

The way ahead in the management of unstable coronary artery disease

Recent knowledge of the composition of coronary plaques is briefly reviewed, including factors that are considered to be responsible for the provocation of instability. Based on this information, possibilities for the early detection of threatening instability and measures to prevent destabilization of coronary plaques and to counteract thrombus formation are discussed.

Chylomicron/chylomicron remnant turnover in humans: evidence for margination of chylomicrons and poor conversion of larger to smaller chylomicron remnants

The size of cholesterol-rich lipoprotein particles is a strong determinant of whether they may be deposited in the arterial wall and by this become potentially atherogenic. This study deals with the in vivo transformation of larger-sized chylomicrons and chylomicron remnants to smaller-sized remnants. Twelve healthy men aged 22 to 45 years were given a fatty meal to which retinyl palmitate (RP) had been added. Plasmapheresis was performed 4 1/2 h after meal intake to isolate approximately 400 ml plasma. The RP-rich plasma was re-injected to the subject 24 h later. The RP content was determined in whole plasma and in Svedberg flotation rate fractions (Sf) > 400, Sf 60-400 and Sf 20-60. A compartmental model was developed for the kinetic analysis. Lipoprotein fractions showed minimal signs of aggregation, thus arguing for well-preserved postprandial lipoproteins. Approximately a fourth [23% (4-68%)] of the RP-containing lipoproteins in the Sf > 400 pool was converted to smaller species (Sf 60-400). Conversion of material from the Sf 60-400 to the Sf 20-60 fraction could not be detected. In a second study a large bolus dose of a triglyceride emulsion (Intralipid) was injected to subjects shortly after the RP-labeled plasma to investigate the endothelial binding of the chylomicron/chylomicron remnants. RP material in the Sf > 400 fraction rapidly returned to plasma, arguing for margination of chylomicrons, whereas the corresponding effect was minimal in the Sf 60-400 and Sf 20-60 fractions. The formation of small chylomicron remnants from the larger chylomicron/chylomicron remnant species is limited and large chylomicron/chylomicron remnants are not evenly distributed in plasma, rather they show signs of being marginated to the vascular endothelium.

Retardation of coronary atherosclerosis: the Bezafibrate Coronary Atherosclerosis Intervention Trial (BECAIT) and other angiographic trials

A large number of both primary and secondary preventive trials suggest that treatment of elevated plasma lipids may reduce the frequency of coronary heart disease (CHD) events. Meta-analyses indicate that for every 10% reduction of cholesterol, CHD mortality is lowered by 13% and all-cause mortality by 10%. Experience from several angiographic trials also suggests that coronary atherosclerosis can be retarded, and in some instances limited regression induced, by low-density lipoprotein (LDL)-cholesterol reduction and/or high-density lipoprotein (HDL)-cholesterol elevation. Coronary angiographic studies have shown that although the effects on retardation/regression of altherogenic lesions have been small, with luminal diameter changes of around 0.10 mm, the effects on clinical events were more substantial, with reductions of the order of 50%. There is also evidence that it is the mild and moderate lesions that are of particular concern with respect to the occurrence of clinical coronary events. The progression of atherosclerosis and the occurrence of coronary events are probably not exclusively dependent on a lowering of LDL-cholesterol concentrations. Analyses from the Monitored Atherosclerosis Regression Study (MARS), the Cholesterol Lowering Atherosclerotic Study (CLAS), and the Programs on the Surgical Control of the Hyperlipidaemias (POSCH) indicate that triglyceride-rich lipoproteins may also be of importance for the progression of mild/moderate lesions in subjects treated with cholesterol-lowering regimens. Recently, the results of the 5-year Bezafibrate Coronary Atherosclerosis Intervention Trial (BECAIT) demonstrated that bezafibrate significantly retarded the progression of coronary atheroma and coronary events in young male survivors of myocardial infarction, as assessed by changes in minimum lumen diameter. This positive outcome is most likely due to the beneficial treatment effects on the levels of serum triglycerides (-31%), plasma fibrinogen (-12%), and HDL cholesterol (+9%). The results of the BECAIT on progression of coronary atherosclerosis are comparable with those of two recent angiographic trials with HMG-CoA reductase inhibitors, the Multicenter Anti-Atheroma Study (MAAS), and the Regression Growth Evaluation Statin Study (REGRESS), despite different lipid and metabolic effects. BECAIT is the first controlled angiographic study to show that a fibrate can significantly retard the progression of coronary atherosclerosis. The exact mechanisms by which this occurs remain to be elucidated. However, the results of BECAIT illustrate the importance of factors other than LDL cholesterol in the progression of coronary atherosclerosis.

Mortality prediction in diabetic patients with myocardial infarction: experiences from the DIGAMI study

OBJECTIVES

We analysed predictors of 1-year mortality following acute myocardial infarction in patients with diabetes mellitus by applying uni- and multivariate statistics on the DIGAMI cohort.

BACKGROUND

Diabetic patients with acute myocardial infarction have a poor prognosis. This may depend on a poor metabolic control, a hypothesis that was tested in DIGAMI, a prospective randomised study. In this trial institution of immediate intensive insulin treatment reduced 1-year mortality by 30%.

METHODS

We recruited 620 diabetic patients with acute myocardial infarction, 314 of whom served as controls, while the remaining 306 patients were treated with an acute insulin-glucose infusion followed by multidose subcutaneous insulin.

RESULTS

Age, previous myocardial damage, duration of the diabetes and previous insulin therapy were significantly related to 1-year mortality, while conventional risk factors lacked independent prognostic weight. Female sex was not linked to mortality when controlling for the confounding effects of other predictors. One of the strongest predictors of a fatal outcome, in particular during the hospital phase, was blood glucose at hospital admission. Beta-blockade appeared to exert a striking, independent secondary-preventive effect.

CONCLUSIONS

It seems that good metabolic control and not conventional risk factors is of major importance for diabetic patients sustaining acute myocardial infarction. Also treatment with beta-blockade seems to be of special importance in this category of patients.

Alterations of VLDL composition during alimentary lipemia

Apoliprotein (apo) B-100-containing very low density lipoprotein (VLDL) particles secreted from the liver accumulate in plasma during alimentary lipemia. To determine whether changes of VLDL composition occur in the postprandial state that may render these lipoproteins more atherogenic, apoE, C-I, C-II, and C-III, and lipids (triglycerides, phospholipids, and cholesterol) were measured in Svedberg flotation (Sf) 60-400 (large) and Sf 20-60 (small) VLDL before and after an oral fat load. Ten normotriglyceridemic (NTG) and three hypertriglyceridemic (HTG) healthy men were given a fat-rich mixed meal (1,000 kCal with 60.2 E% from fat). Triglyceride-rich lipoproteins were isolated by density gradient ultracentrifugation from plasma samples obtained before (fasting) and at 2-h intervals after the meal. VLDL was then separated from chylomicrons and their remnants by immunoaffinity chromatography using monoclonal antibodies 4G3 and 5E11, recognizing apoB-100, but not apoB-48 epitopes. Large and small VLDL isolated from the NTG group were enriched with apoE and C-I, and cholesterol, but depleted of apoC-II in the postprandial state, whereas the apoC-III, triglyceride, and phospholipid contents were essentially unchanged. The compositional changes of VLDL in HTG subjects were similar but more pronounced compared with NTG subjects. We conclude that postprandial lipemia in healthy men induces transient compositional alterations of VLDL that link these lipoprotein species to the formation of atherosclerosis.

Secondary preventive potential of lipid-lowering drugs. The Bezafibrate Coronary Atherosclerosis Intervention Trial (BECAIT)

Current experience from coronary angiographic trials using different treatment regimens such as lifestyle changes, resins, nicotinic acid and statins, shows that progression of atheroma can be retarded, and that regression can sometimes be induced, by a marked lowering of LDL-cholesterol. Young post-myocardial infarction patients, however, usually exhibit a multiplicity of metabolic risk factors with dyslipidaemias, predominantly hypertriglyceridaemia, and disturbances of glucose-insulin homeostasis and of the haemostatic system. These factors, together coupled with coronary angiographic data showing that the degree of dyslipidaemia is related to the extent and degree of coronary atherosclerosis, and the fact that rapid progression of coronary atherosclerosis was foreseen in this group of patients, resulted in the initiation of the Bezafibrate Coronary Atherosclerosis Intervention Trial (BECAIT) in 1985. BECAIT was a 5-year, double-blind, placebo-controlled study of bezafibrate (200 mg three times daily) and dietary intervention in dyslipidaemic male survivors of myocardial infarction below 45 years of age. The angiographic analysis included 81 patients (42 bezafibrate and 39 placebo) who underwent baseline and at least one post-treatment angiogram, at 2 and 5 years. Changes in mean minimum lumen diameter indicated that there was 0.13 mm less (95% Cl: 0.10; 0.15) disease progression in focal lesions in the bezafibrate group than in the placebo group (P = 0.049). Parallel, but non-statistically significant, treatment effects were observed for mean segment diameter and percent stenosis. Three patients treated with bezafibrate and 11 patients in the placebo group suffered coronary events during the course of the trial (P = 0.02 logrank test). The angiographic effects of bezafibrate were accompanied by statistically significant reductions in serum cholesterol and triglycerides. Furthermore, plasma fibrinogen levels were significantly reduced and HDL-cholesterol concentration increased but there was no net change in LDL-cholesterol. These findings show that bezafibrate slowed the progression of focal coronary atherosclerosis to a degree that is comparable to that achieved with the statins in angiographic trials such as MAAS and REGRESS. Bezafibrate also reduced the occurrence of coronary events in young post-infarction victims. Like BECAIT, analyses of data from the NHLBI type II study, CLAS, POSCH and MARS provide evidence for the role of triglyceride-rich lipoproteins in the progression of coronary artery disease. Retardation of progression of atherosclerosis and a reduction in coronary events is, therefore, possible without reducing LDL-cholesterol.

High-density lipoprotein: relations to metabolic parameters and severity of coronary artery disease

The regulation of plasma high-density lipoprotein (HDL) cholesterol level by the joint influence of plasma lipoprotein lipids, lipoprotein lipase (LPL), hepatic lipase (HL), cholesteryl ester transfer protein (CETP), oral glucose tolerance, and postload plasma insulin and proinsulin levels was investigated in young postinfarction patients and healthy population-based control subjects. In addition, the association between HDL cholesterol and the number and severity of coronary stenoses previously reported in this cohort of young postinfarction patients was further investigated by analyzing the determinants and angiographic relations of HDL subclasses measured by gradient gel electrophoresis. The following parameters showed significant univariate relations with HDL cholesterol level in the patient group: very-low-density lipoprotein (VLDL) cholesterol and triglyceride, low-density lipoprotein (LDL) triglyceride, and postload plasma insulin concentrations, preheparin plasma LPL mass, and postheparin plasma HL activity. In the control group, significant correlations with HDL cholesterol concentration in addition to those noted among the patients were found for body mass index (BMI), LDL cholesterol level, postload plasma intact proinsulin concentration, and LPL activity in postheparin plasma. In contrast to the patients, no significant relations were noted for postload plasma insulin level and preheparin plasma LPL mass. Multiple stepwise regression analysis showed that 42% of the variability of HDL cholesterol in the patients could be accounted for by VLDL cholesterol concentration (29%), LDL triglyceride level (7%), and postheparin plasma HL activity (8%), whereas the corresponding figure in controls was 35% (VLDL cholesterol concentration [9%] and postheparin plasma HL activity [26%]. The strength of the relationships of HDL cholesterol and HDL subclasses to the coronary stenosis score was similar and statistically significant (r = .25 to .36). When the metabolic parameters that correlated with HDL cholesterol and HDL subclass concentrations in univariate analysis were used as covariates, all relations to the coronary stenosis score disappeared. This clearly indicates that the influence of triglyceride-rich lipoproteins and lipolytic enzymes needs to be considered when assessing the association between HDL cholesterol and coronary artery disease (CAD).