Transforming growth factor-beta: the key to understanding lipoprotein(a)?

Functional impact of sequence variation in the promoter region of TGFB1

Pathological deregulation of the transforming growth factor, beta 1 (TGFB1) pathway has been implicated in the development of several major diseases, including cancers. Regulatory variation in the TGFB1 gene may lead to altered TGFB1 expression and activity, and thus, modulate an individual's susceptibility to disease. Here, we performed a study of the functional relevance of cis-acting regulatory variation in the proximal promoter region of the TGFB1 gene. In a previous study, 9 promoter polymorphisms were identified in the 2kb region upstream of the transcription start site and 9 distinct promoter haplotypes were inferred from a panel of individuals from 5 distinct continental population groups. Following experimental validation, we found that the 2 major haplotypes significantly influenced TGFB1 transcriptional activity in an allele-specific manner and that 3 of the SNPs (-1886G>A, -509C>T and -1550DEL/AGG) altered DNA-protein complex formation. Though the biological relevance of these findings remains to be verified, our study suggests that polymorphisms in the TGFB1 promoter could indeed influence gene expression and potentially contribute to the pathogenesis of TGFB1 related diseases.

Polymorphisms of TGF-beta1 in cystic fibrosis patients

There is a significant phenotypic variance among cystic fibrosis (CF) patients. Due to the role of TGF-beta1 in fibrotic processes we investigated its role in CF pathogenesis. TGF-beta 1 codons 10 and 25 were genotyped in 118 Czech CF patients and 268 controls by PCR-ARMS. Difference between CF and controls was found at codon 10, lower frequency of T/T homozygotes, and codon 25, higher frequency of G/C heterozygotes. We did not prove the association of TGF-beta1 polymorphisms and lung function in CF, however, the TT (codon 10)/GG (codon 25) genotype was preferentially associated with CF-related liver disease and diabetes. Independent of the TGF-beta1 genotype, production of cytokine was higher in patients than in controls with the notable exception of very low levels in Burkholderia cepacia complex colonized patients. In CF, both extremes, highest or lowest TGF-beta 1 production, were associated with impaired lung function.

Association Between Plasma Lipoprotein(a) Concentration and Restenosis After Stent Implantation

BACKGROUND

The plasma concentration of lipoprotein (a) [Lp(a)] is associated with atherosclerotic and thrombotic vascular diseases. The aim of the present study was to evaluate the association between plasma Lp(a) concentration and in-stent restenosis.

METHODS AND RESULTS

One hundred and 9 patients with successful elective coronary stent implantation underwent follow-up angiography at 24+/-6 weeks. Restenosis after stent implantation occurred in 38 patients. Univariate analysis showed that the reference diameter of the lesion was smaller in the restenosis group (2.93+/-0.29 mm) than in the no-restenosis group (3.21+/-0.43 mm) (p < 0.05). The lesion was longer in the restenosis group (14.2+/-5.3 mm) than in the no-restenosis group (11.6+/-4.9 mm) (p < 0.05). Plasma Lp(a) concentrations in the restenosis group (30.5+/-23.9 mg/dl) were higher than in the no-restenosis group (16.9+/-11.1 mg/dl) (p < 0.01). Other lipid concentrations were similar in both groups. Among the plasma Lp(a) concentrations, the rate of restenosis (71.4%) in the high Lp(a) group (> 40 mg/dl) (n = 14) was greater compared with the other groups: 33.3% in the intermediate Lp(a) group (10-40 mg/dl) (n = 54), and 24.4% in the low Lp(a) group (< 10 mg/dl) (n = 41) (p < 0.01). The late loss (0.57+/-0.53 mm) in the low Lp(a) group was significantly less than the other groups: 0.88+/-0.47 mm in the intermediate Lp(a) group, and 1.08+/-0.56 mm in the high Lp(a) group (p < 0.05). In a multivariate regression model, plasma Lp(a) concentration remained significant as an independent predictor of restenosis in patients undergoing stent implantation (p = 0.020 odds ratio (OR) 1.37 95%conficence interval (CI) 1.050-1.793), although the reference diameter (p = 0.025 OR 0.23 95%CI 0.061-0.830) and lesion length (p = 0.021 OR 1.12 95%CI 1.017-1.232) were related to stent restenosis.

CONCLUSIONS

Plasma Lp(a) concentration is an independent predictor of stent restenosis.

Concerted effect of transforming growth factor-β, cyclin inhibitor p21, and c-mycon smooth muscle cell proliferation

Increased aortic smooth muscle cell (SMC) proliferation is a key event in the pathogenesis of atherosclerosis. Transforming growth factor-β (TGF-β) is one of the potent inhibitors of SMC proliferation. The purpose of this study was 1) to explore the effect of TGF-β inhibition on proliferation of SMC and expression of growth regulatory molecules like p21 and c- myc and 2) to determine whether restoration of cell cycle regulatory molecules normalizes the altered proliferation. To test the role of TGF-β in SMC proliferation, using antisense plasmid DNA, we inhibited TGF-β gene from aortic SMC, which resulted in a significant increase ( P < 0.03) in proliferation (studied by quantifying new DNA synthesis with [3H]thymidine uptake assay). In TGF-β-altered SMC (TASMC), the mRNA expression (studied by RT-PCR) of c- myc was increased whereas that of the cyclin inhibitor p21 was completely inhibited. Using p21 sense plasmid DNA, we transfected p21 gene in TASMC, which restored p21 mRNA and protein expression and decreased proliferation ( P < 0.002) in TASMC. Similar treatment with c- myc antisense oligonucleotides significantly ( P < 0.001) decreased the proliferation of TASMC. TASMC also exhibited alteration in morphological changes in SMC but returned to normal with treatment of p21 and TGF-β sense plasmid DNA. Two-dimensional gel electrophoresis analysis of SMC and TASMC demonstrated differential expression of proteins relevant to cellular proliferation and atherosclerosis. This study uniquely analyzes the effect of TGF-β at the molecular level on proliferation of SMC and on cell cycle regulatory molecules, implicating their potential role in the pathogenesis of atherosclerosis.

Transforming growth factor beta and atherosclerosis: so far, so good for the protective cytokine hypothesis

The role of the anti-inflammatory cytokine transforming growth factor beta (TGF-beta) in atherosclerosis has been the subject of considerable debate for a decade. In the early 1990s, we postulated that TGF-beta played an important role in maintaining normal vessel wall structure and that loss of this protective effect contributed to the development of atherosclerosis. We termed this the protective cytokine hypothesis. This proposal was slow to gain broad acceptance, however, because at that time there were little data available on the role of TGF-beta during the development of atherosclerosis but much information about its role during trauma-induced neointima formation. Because TGF-beta apparently aggravates neointima formation, both by inhibiting endothelial regeneration and by promoting fibrosis, it was difficult to accept that its presence might ameliorate the superficially similar atherogenesis process. But several recent studies revealed beyond doubt the fact that TGF-beta protects against lipid lesion formation, at least in mouse models of atherosclerosis. Therefore, two important questions remain. First, is the role of TGF-beta in vascular biology similar in humans and in mice? Secondly, how important, compared with defects in thrombosis or lipoprotein metabolism, is the protective role of TGF-beta during atherogenesis?

Circulating transforming growth factor-beta1, lipoprotein(a) and cellular adhesion molecules in angiographically assessed coronary artery disease

Transforming growth factor-beta1 (TGF-beta1) is involved in different physiological and pathological processes, including atherogenesis. High plasma lipoprotein(a) (Lp(a)) concentration is an established independent risk factor that may interfere with the plasmin-mediated TGF-beta1 activation. Both Lp(a) and TGF-beta1 are thought to influence the expression of cellular adhesion molecules (CAMs), also involved in the process of atherogenesis. Whereas many studies confirmed the association between high plasma Lp(a) levels and coronary artery disease (CAD), conflicting results were obtained in different studies in which the changes of TGF-beta1 and CAM concentrations in CAD patients were investigated. The aim of this case-control study was to explore the association of circulating TGF-beta1, Lp(a) and CAMs (intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin) levels with the occurrence and severity of angiographically assessed coronary artery disease. Plasma TGF-beta1, Lp(a), ICAM-1, VCAM-1 and E-selectin concentrations were measured in 100 patients with angiographically assessed CAD and 100 healthy blood donors matched according to age and gender. Lp(a) and TGF-beta1 were significantly higher in patients than in healthy controls (p < 0.001 and p < 0.01, respectively), but no significant correlation between the TGF-beta1 and Lp(a) values was found. The CAM concentrations obtained in CAD patients did not differ significantly as compared with the corresponding values in the controls. None of the measured parameters were influenced by the severity of CAD.

Lipoprotein(a) promotes smooth muscle cell proliferation and dedifferentiation in atherosclerotic lesions of human apo(a) transgenic rabbits

Elevated plasma lipoprotein(a) [Lp(a)] levels constitute an independent risk factor for the development of atherosclerosis. However, the mechanism underlying Lp(a) atherogenicity is unclear. Recently, we demonstrated that Lp(a) may potentially be proatherogenic in transgenic rabbits expressing human apolipoprotein(a) [apo(a)]. In this study, we further investigated atherosclerotic lesions of transgenic rabbits by morphometry and immunohistochemistry. On a cholesterol diet, human apo(a) transgenic rabbits had more extensive atherosclerotic lesions of the aorta, carotid artery, iliac artery, and coronary artery than did nontransgenic littermate rabbits as defined by increased intimal lesion area. Enhanced lesion development in transgenic rabbits was characterized by increased accumulation of smooth muscle cells, that was often associated with the Lp(a) deposition. To explore the possibility that Lp(a) may be involved in the smooth-muscle cell phenotypic modulation, we stained the lesions using a panel of monoclonal antibodies against smooth-muscle myosin heavy-chain isoforms (SM1, SM2, and SMemb) and basic transcriptional element binding protein-2 (BTEB2). We found that a large number of smooth muscle cells located in the apo(a)-containing areas of transgenic rabbits were positive for SMemb and BTEB2, suggesting that these smooth muscle cells were either immature or in the state of activation. In addition, transgenic rabbits showed delayed fibrinolytic activity accompanied by increased plasma plasminogen activator inhibitor-1. We conclude that Lp(a) may enhance the lesion development by mediating smooth muscle cell proliferation and dedifferentiation possibly because of impaired fibrinolytic activity.

Impact of apolipoprotein(a) phenotypes on long-term renal transplant survival

The long-term success of renal transplantation is limited because of chronic rejection (CR), which shows histologic parallels to atherosclerosis. Lipoprotein(a) [Lp(a)] is an independent risk factor for atherosclerosis, but its role in CR has not been investigated. Plasma levels of Lp(a) are determined mainly by the inherited isoform (phenotype) of apolipoprotein(a) [apo(a)] and show an inverse correlation with the molecular weight of apo(a). Apo(a) isoforms were identified in frozen sera of 327 patients who received a renal transplant during 1982 to 1992. Long-term graft survival in recipients with high molecular weight (HMW) or low molecular weight (LMW) apo(a) phenotypes were compared retrospectively. Mean (95% confidence interval) transplant survival was 12.8 yr (range, 11.9 to 13.6 yr) in patients with HMW and 11.9 yr (range, 10.8 to 13.1 yr) in patients with LMW apo(a) phenotypes (P = 0.2065). In patients who were 35 yr or younger at the time of transplantation, mean transplant survival was more than 3 yr longer in recipients with HMW apo(a) phenotypes compared with those with LMW apo(a) phenotypes (13.2 yr [range, 12.1 to 14.4 yr] versus 9.9 yr (range, 8.5 to 11.5 yr); P = 0.0156). In a Cox's proportional hazards regression model, the presence of LMW phenotypes-but not gender, immunosuppression, or HLA mismatches-in young patients was associated with a statistically significant risk of CR (P = 0.0434). These retrospective data indicate that young renal transplant recipients with LMW apo(a) phenotypes have a significantly shorter long-term graft survival, regardless of the number of HLA mismatches, gender, or immunosuppressive treatment.

Suppressing thrombin generation is compatible with the development of atherosclerosis in mice

Thrombin has been proposed to play a key role in the development of atherosclerosis, both by promoting fibrin deposition into the atherosclerotic vessel wall and also by signalling through thrombin receptors. Unfortunately, mice homozygous for a deletion of the prothrombin gene (FII) die in utero, making a direct assessment of the role of thrombin during atherogenesis difficult. We have assessed the contribution of thrombin-dependent processes to vascular lipid lesion formation in the atherosclerosis-prone apolipoprotein E (ApoE)-deficient mice by inhibiting thrombin generation with warfarin. ApoE-/- mice were treated with warfarin at a dose that increased the prothrombin time (PT) more than 10-fold (250-375 microg/kg body weight/day) for 12 weeks from the age of 12 weeks onwards. The extent and composition of the vascular lipid lesions that developed were assessed using oil red O to measure neutral lipid in the vessel wall and quantitative immunofluoresence to measure fibrin(ogen) levels as well as macrophage and smooth muscle cell numbers. Mice treated with warfarin developed lesions both in the aortic sinus and the descending aorta to the same degree as mice receiving no treatment (28,351+/-350 microm2/mouse treated with warfarin versus 27,952+/-750 micro2/control mouse; P = .86). However, the amount of fibrin(ogen) deposited in the vessel wall was decreased by more than 60% (34+/-11 arbitrary units in warfarin treated mice versus 92+/-11 arbitrary units in control mice; P < .01). Staining of macrophage and for smooth muscle cell markers was unaltered by treatment with warfarin. We conclude that suppressing thrombin generation does not alter the development of vascular lipid lesions in mice with a severe disorder of lipid metabolism, despite a marked reduction in fibrin(ogen) deposition.

Lipids, cardiovascular disease and atherosclerosis in systemic lupus erythematosus

Systemic lupus erythematosus is commonly associated with early onset cardiovascular disease and is often associated with hyperlipidaemia. This review examines the evidence for an increased prevalence of both CHD and hyperlipidaemia in SLE and mechanisms by which autoimmunity in SLE could accelerate the progression of atheroma. It postulates how lipid lowering therapies used in cardiological disease might help reduce the incidence of CHD in SLE.

Distinct patterns of transforming growth factor-beta isoform and receptor expression in human atherosclerotic lesions. Colocalization implicates TGF-beta in fibrofatty lesion development

BACKGROUND

Some animal studies suggest that transforming growth factor-beta (TGF-beta) protects vessels from atherosclerosis by preventing intima formation, but others indicate a role in vessel proteoglycan accumulation and lipoprotein retention. To distinguish between these possibilities in humans, immunohistochemical studies were performed examining the coexpression of TGF-beta isoforms and the TGF-beta receptors ALK-5 and TbetaR-II in aorta during the various stages of atherosclerotic lesion development.

METHODS AND RESULTS

The spatial relationships between TGF-beta1, TGF-beta3, ALK-5, and TbetaR-II expression were compared in aortic segments from 21 subjects. Nonatherosclerotic intima contained predominantly TGF-beta1, low concentrations of TbetaR-II, and barely detectable amounts of ALK-5. In contrast, fatty streaks/fibrofatty lesions contained high concentrations of both TGF-beta isoforms. Smooth muscle cells (SMCs), macrophages, and foam cells of macrophage and SMC origin contributed to these high levels. These lesions also contained high, colocalized concentrations of ALK-5 and TbetaR-II. Despite fibrous plaques containing TGF-beta1, its receptors were at detection limits. We found no evidence for truncated TbetaR-II expression in either normal intima or the various atherosclerotic lesions.

CONCLUSIONS

TGF-beta appears to be most active in lipid-rich aortic intimal lesions. The findings support the hypothesis that TGF-beta contributes primarily to the pathogenesis of lipid-rich atherosclerotic lesions by stimulating the production of lipoprotein-trapping proteoglycans, inhibiting smooth muscle proliferation, and activating proteolytic mechanisms in macrophages.

Expression of type VIII collagen after cholesterol diet and injury in the rabbit model of atherosclerosis

This study presents an analysis of the expression of type VIII collagen mRNA in response to cholesterol diet and balloon injury in the rabbit iliac artery. The design of the animal experiments was as follows: 28 male New Zealand White rabbits were divided into the 3 different treatment groups. Group 1 received regular chow; group 2 was fed with a 1% cholesterol diet for 6 weeks and normal chow for 5 weeks; and group 3 underwent balloon injury, then 6 weeks of a 1% cholesterol diet, which was followed by 5 weeks of normal chow. The expression pattern of type VIII collagen mRNA was compared with that of the fibrillar collagen types I and III, transforming growth factor-beta1, a factor known to exert the most potent stimulatory effect on collagen synthesis in vitro, and matrix metalloproteinase 1, a collagen-degrading enzyme. The cholesterol diet resulted in an upregulation of type VIII collagen, fibrillar collagens, transforming growth factor-beta1, and matrix metalloproteinase I in the adventitia. Although the number of type VIII collagen mRNA-expressing cells in the media increased, no significant difference in overall expression levels was detectable by northern blot analysis. The ratio of medial smooth muscle cells expressing type VIII collagen mRNA to those expressing type I and type III collagen mRNA (CVIII:CI:CIII) changed from 1:1.88:0.03 in the normal media to 1:0.78:0.29. When cholesterol feeding was preceded by balloon injury, type VIII collagen mRNA expression concomitant with the fibrillar collagens was further upregulated over and above that level reported after cholesterol diet alone. In general, low levels of transforming growth factor-beta1 mRNA correlated with high expression of matrix metalloproteinase I. Our study indicates that a cholesterol diet resulted in a balanced reorganization of the collagen composition but did not result in marked collagen accumulation. This may provide an extracellular environment that favors migration and proliferation processes during early atherogenesis. It also demonstrates that type VIII collagen is highly expressed and deposited at later stages, and this may be linked to processes such as tissue reorganization during vascular repair and plaque stabilization.

Lipoprotein(a) and dietary proteins: casein lowers lipoprotein(a) concentrations as compared with soy protein

BACKGROUND

Substitution of soy protein for casein in the diet decreases LDL cholesterol and increases HDL cholesterol. How the 2 proteins affect lipoprotein(a) [Lp(a)], an independent risk factor for coronary artery disease, is unknown.

OBJECTIVE

We compared the effects of dietary soy protein and casein on plasma Lp(a) concentrations.

DESIGN

Nine normolipidemic men were studied initially while consuming their habitual, self-selected diets, and then, in a crossover design, while consuming 2 liquid-formula diets containing either casein or soy protein. The dietary periods lasted 45 d (n = 7) or 33 d (n = 2). Fasting total cholesterol, LDL-cholesterol, HDL-cholesterol, triacylglycerol, and Lp(a) concentrations were measured throughout.

RESULTS

After 30 d of each diet, the mean concentration of Lp(a) was not significantly different after the soy-protein and self-selected diets. However, Lp(a) decreased by an average of 50% (P < 0.001) after the casein diet as compared with concentrations after both the soy-protein and self-selected diets. Two weeks after subjects switched from the self-selected to the soy-protein diet, Lp(a) increased by 20% (P = 0.065), but subsequently decreased to baseline. In contrast, the switch to the casein diet did not cause an increase in Lp(a), but instead a continuing decrease in mean concentrations to 65% below baseline (P < 0.0002). Total cholesterol, LDL cholesterol, and HDL cholesterol were significantly lower > or =30 d after both the casein and soy-protein diets than after the self-selected diet (P < 0.001). HDL cholesterol was 11% higher after the soy-protein diet than after the casein diet (P < 0.002), but LDL cholesterol, total cholesterol, and triacylglycerol were not significantly different after the casein and soy-protein diets.

CONCLUSION

These findings indicate that soy protein may have an Lp(a)-raising effect, potentially detrimental to its use in antiatherogenic diets.

Did grandma give you heart disease? The new battle against coronary artery disease

Atherosclerosis/coronary artery disease (CAD) is largely a result of genetically linked dyslipidemias that can often be identified in clinical practice. Expression of these genetic traits is highly individual and can be affected by environmental factors such as diet and exercise. By understanding the heterogeneity of CAD, it becomes clear that all patients cannot be optimally managed with the same therapeutic regimen. Whereas elevated low-density lipoprotein (LDL) cholesterol is strongly correlated with CAD risk, reduction of LDL cholesterol alone is not an adequate strategy in many cases. Patients with the small, dense LDL of the atherogenic lipoprotein profile (pattern B) experience a 3-fold increased risk of CAD, and pattern B is also correlated with the development of type 2 diabetes. Likewise, elevated lipoprotein(a) increases atherosclerotic risk, particularly in the presence of other risk factors, and is predictive of CAD risk in both women and men. Recent data show that the routine lipid profile--total cholesterol, triglycerides, LDL cholesterol, and high-density lipoprotein (HDL) cholesterol--does not detect the most common inherited dyslipidemias. Newer, more sophisticated tests, such as gradient gel electrophoresis, can detect disease-relevant lipidemic details, e.g., LDL subclass pattern, LDL particle diameter, and LDL subregions. Although these testing procedures are more expensive, their cost must be weighed against the potential lifelong cost of sometimes expensive drug treatment that may be avoided based on the results of such tests. Thus, by attending to the implications of family history, the interactions of genetic, metabolic, and environmental factors, and utilizing more targeted testing procedures, physicians can match the patient's disorder with specifically effective therapy while maintaining a cost-effective approach to disease management.

Functional food science and the cardiovascular system

Cardiovascular disease has a multifactorial aetiology, as is illustrated by the existence of numerous risk indicators, many of which can be influenced by dietary means. It should be recalled, however, that only after a cause-and-effect relationship has been established between the disease and a given risk indicator (called a risk factor in that case), can modifying this factor be expected to affect disease morbidity and mortality. In this paper, effects of diet on cardiovascular risk are reviewed, with special emphasis on modification of the plasma lipoprotein profile and of hypertension. In addition, dietary influences on arterial thrombotic processes, immunological interactions, insulin resistance and hyperhomocysteinaemia are discussed. Dietary lipids are able to affect lipoprotein metabolism in a significant way, thereby modifying the risk of cardiovascular disease. However, more research is required concerning the possible interactions between the various dietary fatty acids, and between fatty acids and dietary cholesterol. In addition, more studies are needed with respect to the possible importance of the postprandial state. Although in the aetiology of hypertension the genetic component is definitely stronger than environmental factors, some benefit in terms of the development and coronary complications of atherosclerosis in hypertensive patients can be expected from fatty acids such as alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid. This particularly holds for those subjects where the hypertensive mechanism involves the formation of thromboxane A2 and/or alpha 1-adrenergic activities. However, large-scale trials are required to test this contention. Certain aspects of blood platelet function, blood coagulability, and fibrinolytic activity are associated with cardiovascular risk, but causality has been insufficiently proven. Nonetheless, well-designed intervention studies should be initiated to further evaluate such promising dietary components as the various n-3 and n-6 fatty acids and their combination, antioxidants, fibre, etc. for their effect on processes participating in arterial thrombus formation. Long-chain polyenes of the n-3 family and antioxidants can modify the activity of immunocompetent cells, but we are at an early stage of examining the role of immune function on the development of atherosclerotic plaques. Actually, there is little, if any, evidence that dietary modulation of immune system responses of cells participating in atherogenesis exerts beneficial effects. Although it seems feasible to modulate insulin sensitivity and subsequent cardiovascular risk factors by decreasing the total amount of dietary fat and increasing the proportion of polyunsaturated fatty acids, additional studies on the efficacy of specific fatty acids, dietary fibre, and low-energy diets, as well as on the mechanisms involved are required to understand the real function of these dietary components. Finally, dietary supplements containing folate and vitamins B6 and/or B12 should be tested for their potential to reduce cardiovascular risk by lowering the plasma level of homocysteine.

Elevated plasma lipoprotein(a) is associated with coronary artery disease in patients with chronic stable angina pectoris

OBJECTIVES

We sought to assess the relation between plasma lipoprotein(a) [Lp(a)] levels, clinical variables and angiographic coronary artery disease (CAD) in patients with chronic stable angina.

BACKGROUND

The relation between plasma Lp(a) levels and the severity and extent of angiographic CAD has not been studied in well characterized patients with stable angina pectoris.

METHODS

We investigated clinical variables, lipid variables and angiographic scores in 129 consecutive white patients (43 women) undergoing coronary angiography for chronic stable angina.

RESULTS

Plasma Lp(a) levels were significantly higher in patients with than in those without significant angiographic stenoses (> or =70%) (372 mg/liter [interquartile range 87 to 884] vs. 105 mg/liter [interquartile range 56 to 366], respectively, p=0.002). This difference remained significant when patients with mild or severe angiographic disease were compared with those with completely normal coronary arteries (312 mg/liter [interquartile range 64 to 864] vs. 116 mg/liter [interquartile range 63 to 366], respectively, p=0.02). However, subset analysis indicated that this difference achieved statistical significance only in women. Multiple logistic regression analysis indicated that Lp(a) concentration was independently predictive of significant angiographic stenoses (adjusted odds ratio [OR] 9.1, 95% confidence interval [CI] 2.0 to 42.1, p=0.006) and remained true even after exclusion of patients receiving lipid-lowering treatment (n=27) (OR 10.4, 95% CI 1.1 to 102.9, p=0.05). Lp(a) also had independent predictive value in a similar analysis using mild or severe angiographic disease as the outcome variable (OR 11.8, 95% CI 1.5 to 90.8, p=0.02).

CONCLUSIONS

Our results indicate that elevated plasma Lp(a) is an independent risk factor for angiographic CAD in chronic stable angina and may have particular significance in women.

Plasma concentrations of Lp(a) lipoprotein and TGF-beta1 are altered in preeclampsia

This study was performed to investigate the possible association between preeclampsia and the plasma concentrations of Lp(a) lipoprotein and TGF-beta1 in a large series of patients. Additionally, correlation between the concentrations of these molecules and the severity of preeclampsia or fetal growth retardation was evaluated. Following clinical examination and biochemical analyses, both electroimmunoassay and RIA technique were used for quantitative determinations of plasma Lp(a) lipoprotein. ELISA technique was used to measure the active form of TGF-beta1 in plasma of pregnant normotensive and preeclamptic women. We examined 154 women with preeclampsia (preeclampsia group) and 76 healthy, pregnant normotensive women (control group). The preeclampsia group was further divided into the following subgroups: mild preeclampsia, severe preeclampsia and preeclampsia with fetal growth retardation. Plasma levels of Lp(a) lipoprotein were lower in the total preeclampsia group as well as in all preeclampsia subgroups (5.45+/-7.41, 5.58+/-8.02, 5.08+/-5.38, and 4.32+/-5.28 mg/dl in the total preeclampsia group, and in subgroups with mild preeclampsia, severe preeclampsia, and preeclampsia with fetal growth retardation, respectively) than in the control group (7.84+/-9.26 mg/dl) as determined by quantitative electroimmunoassay. Corresponding results were obtained with a radioimmunoassay (166.03+/-200.2 U/l in the total preeclampsia group vs. 229.18+/-257.7 U/l in controls). There was good correlation between the two methods used for Lp(a) lipoprotein measurement. The differences between controls and the total preeclampsia group as well as each preeclampsia subgroup were statistically significant by a non-parametric test (one-way Kruskal-Wallis test). Plasma concentrations of the active form of TGF-beta1 were increased in all preeclampsia subgroups as well as in the total group (5.63+/-1.68 ng/ml) compared to controls (4.67+/-1.33 ng/ml). This increase in TGF-beta1 was statistically highly significant. Plasma concentrations of Lp(a) lipoprotein and the active form of TGF-beta1 did not differ significantly between the preeclampsia subgroups. The outcome of this study may suggest involvement of both parameters in the pathophysiology of preeclampsia and may substantiate the notion of a multifactorial etiology of the disease.

Hypertriglyceridemia and elevated lipoprotein(a) are risk factors for major coronary events in middle-aged men

Cardiovascular risk factors were analyzed in 4,849 male participants, aged 40 to 65 years, in an 8-year follow-up of the Münster Heart Study (Prospective Cardiovascular Münster Study; PROCAM). One hundred eighty-one definite nonfatal myocardial infarctions, 49 fatal myocardial infarctions, and 28 sudden cardiac deaths were observed. Multiple logistic function analysis confirmed that age, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, systolic blood pressure, cigarette smoking, diabetes mellitus, angina pectoris, and family history of myocardial infarction were important cardiovascular risk factors. Interestingly, this analysis revealed a significant and independent association between serum levels of triglycerides and the incidence of major coronary events. The relation between lipoprotein(a) [Lp(a)] levels and the occurrence of major coronary events was analyzed in a subgroup of 878 men. Thirty-three probands with major coronary events had significantly higher geometric mean levels of Lp(a) than 828 men who did not experience major coronary events (0.09 vs 0.05 g/L; p <0.011). Thus, in addition to established risk for factors, serum levels of triglycerides and Lp(a) are sensitive indicators of increased risk major coronary events.