Association of serum C3 levels with the risk of myocardial infarction

Plasma levels of complement C3 is associated with development of hypertension: a longitudinal cohort study

Hypertension has been associated with raised plasma levels of complement factor 3 and 4 (C3 and C4). The nature of this association is unclear. This population-based longitudinal study explored whether C3 or C4 is associated with development of hypertension. Blood pressure and plasma levels of C3 and C4 were determined in 2178 healthy men, aged 35-50 years, initially without treatment for hypertension. Incidence of hypertension and blood pressure increase over 15.7 (+/-2.2) years follow-up was studied in relation to C3 and C4 at baseline. Among men with initially normal blood pressure (<160/95 mm Hg), incidence of hypertension (>or=160/95 mm Hg or treatment) was 32, 42, 37 and 47%, respectively, for men with C3 in the first, second, third and fourth quartile (trend: P=0.001). This relationship remained significant after adjustment for confounding factors. Among men without blood pressure treatment, systolic BP increase (mean+standard error, adjusted for age, initial blood pressure and follow-up time) was 17.5+0.8, 19.6+0.9, 19.8+0.8 and 20.8+0.8 mm Hg, respectively, in the C3 quartiles (trend: P=0.004). C3 was not associated diastolic blood pressure at follow-up. Although C4 was associated with blood pressure at the baseline examination, there was no relationship between C4 and development of hypertension or future blood pressure increase. It is concluded that C3 in plasma is associated with future blood pressure increase and development of hypertension.

The third component of the complement (C3) is a marker of the risk of atherogenesis

AIM

The aim of this study was to assess the association between the third component of the complement (C3) and other risk factors of coronary heart disease.

METHODS AND RESULTS

We evaluated 1200 individuals aged 25-74 years (600 men and 600 women). A strong relationship was shown between serum C3 and both body mass index (BMI, P<0.01) and fibrinogen (P<0.01). We found a significant, independent correlation with: platelet count (P<0.01), insulin level (P<0.01), triglycerides (P<0.01), low-density lipoprotein (LDL) cholesterol (P<0.01), and an inverse correlation with cigarette smoking (P<0.01).

CONCLUSIONS

A high concentration of C3 is a marker of a profile at risk of atherogenesis.

Expression of complement regulators and receptors on human NT2-N neurons--effect of hypoxia and reoxygenation

Complement activation can cause tissue damage in cerebral stroke by the release of biologically potent activation products and impaired function of regulatory proteins. We investigated the constitutive and hypoxia-reoxygenation-dependent expression of complement receptor 1 (CD35), membrane cofactor protein (CD46), decay-accelerating factor (CD55), protectin (CD59), and complement C3a and C5a receptors (C3aR and C5aR) on human NT2-N neurons. The effect of hypoxia-reoxygenation on C3d-deposition on neurons and endothelial cells was also investigated. NT2-N neurons were examined by cellular enzyme-linked immunosorbent assay and immunofluorescence microscopy. Endothelial cells were examined by flow cytometry. Three hours 1% or 0.1% hypoxia and 21h reoxygenation with 50% AB-serum were used to investigate the effect of hypoxia-reoxygenation on regulators and C3d-deposition. NT2-N neurons expressed significant amounts of CD59 (Clone H19/Clone BRIC229: p=0.000006/p=0.000003), CD46 (p=0.00006), CD55 (p=0.003) and C3aR (p=0.00003). CD35 and C5aR were not significantly expressed. There were no effects of hypoxia-reoxygenation on any of the regulators or receptors after 1% hypoxia and reoxygenation. However, CD55 (p=0.02) was down-regulated after 0.1% hypoxia and subsequent reoxygenation with AB-serum. There were no difference observed in the C3d-deposition during hypoxia-reoxygenation in either neurons or endothelial cells. In conclusion, human NT2-N neurons constitutively express C3aR, CD46, CD55 and, in particular, CD59. The cells may respond to locally produced C3a and, at the same time, be well protected against complement attack. Although severe hypoxia-reoxygenation may down-regulate CD55 expression, it does not seem to influence C3d-deposition.

Complement C3 and C-Reactive Protein Are Elevated in South Asians Independent of a Family History of Stroke

BACKGROUND AND PURPOSE

Complement components are emerging risk factors for cardiovascular disease. In this study, we examined the relation among C3, C-reactive protein (CRP), factor B, and features of the insulin resistance (IR) syndrome in 143 first-degree relatives of South Asian subjects with ischemic stroke, 141 South Asian controls, and 121 white controls.

METHODS

C3, CRP (high-sensitivity assay), and factor B levels were measured by ELISAs, and their relation to features of the IR syndrome were assessed. Data are presented as geometric mean (95% CI).

RESULTS

There was no significant difference in the levels of C3 between South Asian relatives (1.25 [1.21, 1.29] g/L) and South Asian controls (1.20 [1.15, 1.24] g/L, P=0.2). Levels in both South Asian groups were significantly higher than in white controls (0.95 [0.92, 0.98] g/L; P<0.001 for both comparisons). These differences remained significant after adjustment for covariates. Similarly, levels of CRP were not different between the 2 South Asian groups, but levels in both South Asian groups, after adjustment for covariates, were significantly higher than in white controls. There was no difference in the levels of factor B among the 3 groups. South Asian subjects with elevated C3 levels clustered risk factors associated with IR to a greater extent than those with high CRP.

CONCLUSIONS

These results suggest that South Asians have a greater level of chronic subclinical inflammation than do whites, independent of a family history of stroke. In addition, C3 is more likely to cluster with features of the IR syndrome compared with CRP in South Asians.

[Relationship between nutritional status and some inflammatory markers]

INTRODUCTION

Obesity is well known risk factor of metabolic complications and CVD. On the other hand, CRP as a marker of inflammation has lately aroused huge interest as predictor of cardiovascular risk.

OBJECTIVE

The objective of the study was to determine whether the nutritional status parameters were related to some inflammatory markers and what was the extent of such relation.

METHOD

The study involved 220 patients, 40.5 +/- 14.5 years old, who referred to Nutrition Clinic of the Institute of Hygiene in order to get a dietetic advice or nutritional medical therapy. Nutritional status was assessed by BMI (kg/m2), calculated from measured values of body weight and height, the waist measurement and body fat percentage according to WHO recommendations. Biochemical parameters and inflammatory markers were measured from blood samples collected after a twelve-hour fast.

RESULTS

The subjects were categorized into quartiles of BMI (kg/m2) and % body fat. The inflammatory markers followed the increase of BMI and % body fat, as odds ratio (95% CI) of elevated level of CRP was observed to be highest in the fourth quartiles of BMI [1.55 [(OR = 0.731 - 3.296] as well as in the fourth quartile of % body fat - 1.34 [(OR = 0.598 - 3.009)]. This was confirmed by analysis of linear correlation which resulted in r = 0.148 for BMI (p < 0.05) and r = 0.164 (p < 0.05) for fat percentage. In addition, there was highly significant positive correlation between fibrinogen level, C3 and BMI (p < 0.01), and body fat (p < 0.01).

CONCLUSION

The results showed that determination of inflammatory markers should become a routine screening procedure in all patients with elevated anthropometric parameters in order to prevent the consequences of atherosclerosis as quickly as possible.

Adipose tissue metabolism, diabetes and vascular disease--lessons from in vivo studies

There is an epidemic of obesity, insulin resistance and cardiovascular disease. Adipose tissue plays a major metabolic role and produces hormones with important physiological effects. In vitro studies remove regulatory factors, such as blood flow, making results difficult to interpret, and animal studies cannot necessarily be extrapolated to humans. Fortunately, adipose tissue can be studied in vivo with microdialysis, adipose tissue vein cannulation, measurement of blood flow using 133Xenon washout, stable isotope tracers and biopsies. In vivo studies have shown that adipose tissue is an efficient buffer against the postprandial flux of non-esterified fatty acids (NEFA) in the circulation, protecting other tissues. When there is excess adipose tissue, this buffering effect may be impaired. The postprandial blood flow response is also reduced, potentially causing an atherogenic lipid profile and atheroma. A systems biology approach, combining in vivo techniques with genomics, proteomics and metabolomics, will clarify links between adipose tissue and vascular disease.

Effects of C-reactive protein and the third and fourth components of complement (C3 and C4) on incidence of atrial fibrillation

Although C-reactive protein (CRP) is a major cardiovascular risk factor, its association with atrial fibrillation (AF) remains controversial. This study explored whether the CRP-related incidence of AF is modified by serum markers of inflammation in a population-based cohort with follow-up data. Serum CRP and 2 components of the complement system (C3 and C4) were determined in 1,011 healthy patients (25 to 64 years old). The incidence of AF was compared between groups defined by levels of CRP, C3, and C4. The follow-up time was 4 years. A high complement level was defined as either C3 or C4 in the top quartile. High CRP was associated with high complement components. An increased CRP level was associated with an increased incidence of AF. The complement components modified these associations. After risk factor adjustment, those with high CRP and high complement components had a significantly higher risk of AF (relative risk 3.0, 95% confidence interval 2.0 to 4.2) than those with normal CRP and low complement levels. In the absence of a high complement level, a high CRP level was not significantly associated with AF (relative risk 1.1, 95% confidence interval 1.0 to 1.4). In conclusion, high CRP levels are associated with high serum levels of complement components. These proteins increase the CRP-related incidence of AF. In the absence of elevated complement components, no statistically confirmed association was found between a high CRP level and AF.

Weight gain in relation to plasma levels of complement factor 3: results from a population-based cohort study

AIMS/HYPOTHESIS

Mice that are deficient for complement factor 3 (C3) have shown resistance to weight gain, despite increased food intake. Cross-sectional studies of humans have reported correlations between C3 and obesity. This longitudinal study explored whether C3 predicts a large weight gain in middle-aged men.

METHODS

Plasma concentrations of C3 and complement factor 4 (C4) were measured in 2,706 non-diabetic healthy men aged between 38 and 50 years, who were re-examined after a mean period of 6.1 years.

RESULTS

After adjustments for initial weight, age, height and follow-up time, the odds of incurring large weight gain (75th percentile, > or =3.8 kg) were 1.00 (reference), 0.96 (95% CI:0.7-1.2), 1.1 (CI:0.9-1.5) and 1.4 (CI:1.1-1.8), respectively, among men with C3 levels in the first, second, third and fourth quartiles (p for trend=0.01) respectively. This relationship remained significant after further adjustments for lifestyle factors (physical inactivity, alcohol, smoking), metabolic factors (glucose or homeostasis model assessment values, cholesterol, triglycerides), inflammatory markers (fibrinogen, haptoglobin, ceruloplasmin, orosomucoid, alpha1-antitrypsin) and for C4. C4 was associated with weight gain after adjustments for initial weight, height, follow-up time and lifestyle factors, but not after adjustments for C3.

CONCLUSIONS/INTERPRETATION

C3 is a risk factor for incurring large weight gain in middle-aged men.

Metformin reduces C-reactive protein but not complement factor C3 in overweight patients with Type 2 diabetes mellitus

AIMS

To determine the influence of metformin treatment on plasma C-reactive protein (CRP) and complement factor C3.

METHODS

A double-blind, placebo-controlled trial of metformin in patients with poorly controlled Type 2 diabetes mellitus and body mass index > 25 kg/m2. CRP and C3 were analysed in stored plasma samples by in-house ELISAs. Patients attended two baseline visits before randomization and subsequently attended at 3, 6, 12 and 24 weeks post randomization. All patients gave informed consent according to a protocol approved by the Leeds Teaching Hospitals Research Ethics Committee.

RESULTS

Baseline CRP in the patients randomized to placebo [1.33 (0.79, 2.25) mg/l] and metformin [1.24 (0.89, 1.71) mg/l] were similar (P = 0.8). Baseline CRP correlated with baseline C3 (r = 0.366) and HbA1c (r = 0.327). The difference in ratios of CRP levels at each visit to baseline between placebo- (n = 16) and metformin-treated (n = 26) subjects was significantly different at the 12-week (P = 0.002) and 24-week (P = 0.03) visits. The difference in CRP ratios between the two treatment groups remained significant after accounting for glycaemic control at both visits (P = 0.001 and P = 0.003, respectively). Baseline C3 was correlated with CRP. Baseline C3 was lower in the placebo-treated group [0.97 (0.88, 1.05) mg/ml] compared with the metformin-treated group [1.09 (1.02, 1.17) mg/ml, P = 0.03]. There was no difference in the mean change in C3 at any visit from baseline between placebo- and metformin-treated groups.

CONCLUSION

Metformin may have a specific interaction with mechanisms involved in CRP synthesis or secretion, not directly related to improved insulin sensitivity and dampening of chronic inflammation.

Upregulation of the immune system in primary hypercholesterolaemia: effect of atorvastatin therapy

OBJECTIVES

High levels of plasma high sensitivity C-reactive protein (CRP), sensitive to therapy with statins, have been described in hypercholesterolaemia. In vitro evidence shows that CRP activates the complement system, which, in turn, leads to an increased expression of ICAM-1. Our objectives were to verify whether primary hypercholesterolaemia (PHC) is associated with an upregulation of the inflammatory/immune response, and whether this is sensitive to atorvastatin.

METHODS AND RESULTS

We examined the levels of sICAM-1, C3, C4 complement fractions in 48 patients with PHC, with (CAD group) or without (No-CAD group) coronary artery disease (CAD) in comparison with a group of 48 healthy controls. The two patient groups were studied before and after atorvastatin therapy. Both hypercholesterolaemic groups showed higher mean values of sICAM-1, C3 and C4 (P < 0.0001) when compared with the controls. The two groups of patients responded differently to atorvastatin therapy. After 3 months, the C3 levels normalized in both groups of patients (P < 0.02 compared with basal values); C4 was greatly reduced only in the CAD group (P < 0.01). After 12 months of therapy, in CAD group C3 mean levels were still significantly lower than baseline values (P < 0.01); a further decrease in the C4 values (P < 0.05 with respect to levels after 3 months of therapy) and also a substantial reduction in sICAM-1 values (P < 0.001 with respect to basal values) were observed.

CONCLUSIONS

High plasma values of C3 and C4 in PHC cluster with high values of sICAM-1, distinguish subjects with CAD and could be used to monitor the anti-inflammatory effect of statin therapy in these patients.

Complement component C5a predicts future cardiovascular events in patients with advanced atherosclerosis

AIMS

Complement activation occurs in atherosclerotic lesions, and particularly complement component C5a exerts potent chemotactic and proinflammatory effects. However, it is yet unknown, whether plasma levels of C5a may predict cardiovascular risk. The aim of this study was to examine whether plasma levels of the complement component C5a may predict cardiovascular risk in patients with advanced atherosclerosis.

METHODS AND RESULTS

We studied 173 patients with symptomatic peripheral artery disease (median age 72, 82 male). Cardiovascular risk profile, levels of the complement factor C5a, and other non-specific inflammatory parameters [high sensitivity C-reactive protein, serum amyloid A (SAA), and fibrinogen] were obtained at baseline, and patients were followed for median 22 months [interquartile range (IQR) 13-27] for the occurrence of major adverse cardiovascular events (MACE: myocardial infarction, percutaneous coronary interventions, coronary artery bypass graft, carotid revascularization, stroke, and death). We observed 65 MACE in 49 patients (28%). Cumulative event rates (95% confidence interval (CI)) within quartiles of C5a at 24 months were 16 (5-27), 26 (13-39), 36 (21-51), and 37% (23-51), respectively (P=0.0077). Adjusted hazard ratios for the occurrence of a first MACE according to increasing quartiles of C5a were 1.81, 2.23, and 2.66, respectively, as compared to the lowest quartile (P=0.038), irrespective of the level of other inflammatory parameters.

CONCLUSION

Complement activation, indicated by the elevation of C5a, seems to be associated with increased cardiovascular risk in patients with advanced atherosclerosis. Clinically, determination of C5a may add to the predictive value of other non-specific inflammatory parameters.

Effects of weight loss and risk factor treatment in subjects with elevated serum C3, an inflammatory predictor of myocardial infarction

BACKGROUND

Serum C3 is an inflammatory predictor of myocardial infarction and a covariate of fasting insulin and several endogenous risk factors. This study was performed to ascertain whether risk factor control may reduce elevated C3 concentrations.

METHODS

After traditional risk factor and C3 assessment in 1100 unselected men aged 55-64 years, 238 men with persistently elevated C3 levels (>=1.19 g/l, high tertile) were randomised into 2 groups: 43 controls, who were referred to their general practitioner, and 195 subjects who were intensively treated with diet, and anti-hypertensive or antidiabetic drugs according to specific indications, without anti-dyslipidemic drugs.

RESULTS

After three months in the treated subjects significant decrements of body weight, blood pressure, blood glucose and serum lipids were obtained, with stable C3 levels (while in controls a 3.3% increase occurred, P=0.02). The factors associated with a C3 decrement >5% were a high baseline C3 level, a recent acute inflammation, physical activity, belonging to the treated group, and a significant reduction in body weight, triglycerides or blood glucose. However, in multivariate analysis only an elevated baseline C3 (P<0.0001), a weight loss >2% (P=0.0009) and physical activity (P=0.02) remained independently associated with a C3 decrement >5% (R(2)=0.14).

CONCLUSIONS

Only weight loss and physical activity, but not traditional risk factor lowering, could independently induce a significant C3 decrease. Thus, C3 elevation is associated with, but probably not caused by, traditional risk factors.

Cross-sectional study of complement C3 as a coronary risk factor among men and women

In the present study, we examined (i) whether C3 (complement C3) was an independent marker of prevalent CHD (coronary heart disease), and (ii) which preferential associations existed between C3 and some cardiovascular risk factors when jointly analysed with CRP (C-reactive protein) and fibrinogen. In a cohort of 756 unselected adults, 39% of whom had the metabolic syndrome, C3 and other risk variables were evaluated in a cross-sectional manner. In a logistic regression model for the likelihood of CHD, a significant OR (odds ratio) of 3.5 [95% CI (confidence intervals), 1.27 and 9.62)] for C3 was obtained after adjustment for smoking status, TC (total cholesterol) and usage of statins. A similar model, also comprising systolic blood pressure, with a cut-off point of >or=1.6 g/l C3 exhibited a 1.9-fold risk (95% CI, 1.01 and 3.58) compared with individuals below the cut-off point. Both analyses displayed an adjusted OR of 1.37 for each S.D. increment in C3. The significant relationship of C3 with a likelihood of CHD also proved to be independent of CRP. In multiple linear regression models, associations were tested for each acute-phase protein with measures of obesity, fasting insulin, triacylglycerols (triglycerides), TC, HDL (high-density lipoprotein)-cholesterol, physical activity, smoking status, diagnosis of metabolic syndrome and family income. When both genders were combined, C3 was independently associated with serum triacylglycerols, waist circumference, BMI (body mass index) and TC. CRP was independently associated with waist circumference, TC, family income (inversely) and physical activity, and fibrinogen with BMI, TC, smoking status and metabolic syndrome. In summary, elevated levels of complement C3 are associated with an increased likelihood of CHD independent of standard risk factors and regardless of the presence of acute coronary events, suggesting that C3 might be actively involved in coronary atherothrombosis. Unlike CRP and fibrinogen, C3 was preferentially associated with waist girth and serum triacylglycerols.

Complement C3 is a risk factor for the development of diabetes: a population-based cohort study

Cross-sectional studies have reported strong correlations between plasma levels of complement C3, insulin, and glucose. This prospective study explored whether elevated levels of C3, C4, and other inflammation-sensitive plasma proteins (ISPs; fibrinogen, orosomucoid, alpha1-antitrypsin, haptoglobin, and ceruloplasmin) are associated with the development of diabetes. Plasma proteins were measured in 2,815 nondiabetic healthy men, age 38-50 years, who were reexamined after a mean follow-up of 6.1 years. Diabetes development (n = 123) was studied in relation to baseline levels of plasma proteins. After adjusting for age, screening year, and glucose at baseline, the odds ratio (95% CI) for developing diabetes was 1.00, 2.4 (1.1-5.3), 2.9 (1.4-6.0), and 5.6 (2.8-10.9), respectively, for men with C3 in the 1st, 2nd, 3rd, and 4th quartiles (trend: P < 0.00001). Fibrinogen, haptoglobin, C4, and the number of elevated ISPs were also related to future diabetes in this model. Only C3 was significantly associated with diabetes development after further adjustments for potential confounders, including BMI, insulin, and other inflammatory markers. We concluded that the risk of developing diabetes is related to levels of complement C3.

Association of high serum concentration of the third component of complement (C3) with pre-existing severe coronary artery disease and new vascular events in women

Atherosclerosis is an inflammatory disease. The complement system plays an important role in the atherosclerotic process. However, lesser data is available on the possible role of C3 as a risk factor for atherosclerosis. Therefore, in a follow up study we determined C3 levels in 266 patients with pre-existing severe coronary artery disease (CAD) and compared their serum C3 concentrations with the cause of the disease. We investigated whether C3 levels predict the major complications of severe CAD during a 5-year long follow up period in patients, who have received an aorto-coronary bypass graft surgery. C3 concentrations were elevated in the patients with severe CAD compared to 182 healthy controls, and women had higher C3 concentrations than men. Pathological C3 levels (C3> or =1.8 g/L) were able to predict major complications of atherosclerosis (death by cardiac events, new acute myocardial infarction, stroke, carotid surgery and peripheral arterial disease) that developed during the follow up period only in women (OR: 4.1, 95% C.I. 1.23-13.61, p = 0.0249) independent of other risk factors for atherosclerosis. Our data supports the assumption that high C3 indicates the progression of atherosclerosis as a special marker of chronic inflammation.

Statin drugs do not affect serum complement activation in vitro

Statin drugs prevent coronary heart disease through anti-inflammatory mechanisms in addition to the well-known reduction of low-density lipoproteins. The complement system plays an essential role in the inflammatory response and has been postulated to be modified by statins. A direct role for statins in complement activation, however, has not been previously investigated. We therefore studied the effect of statins on in vitro complement activation. Pravastatin, atorvastatin and the active metabolite of the latter, ortho-hydroxy atorvastatin, were added to normal human serum and incubated for 1 h in the absence or presence of aggregated immunoglobulin (classical pathway activation) or cobra venom factor (alternative pathway activation). The degree of complement activation, as detected by specific complement-activation products for the classical pathway (C1rs-C1-inhibitor complexes), the combined classical and lectin pathway (C4bc), the alternative pathway (C3bBbP) and the final common pathway (C3bc and TCC), was not affected by pre-incubation of the serum with any of the statins. Statins do not affect complement activation directly, but indirect effects in vivo may well be operative.

Acylation-stimulating protein precursor proteins in adipose tissue in human obesity

Recent reports have suggested a link between acylation-stimulating protein (ASP) and complement C3 with obesity, insulin resistance, coronary artery disease, and hyperlipidemia. Our aim was to examine the mRNA expression of C3 and other factors related to ASP production (such as factor B and adipsin) in adipose tissue. The influence of gender and obesity was examined in subcutaneous (SC) and omental (OM) tissues from 16 males and 16 females with body mass index (BMI) from 20 to 54 kg/m(2). The results demonstrate that factor B mRNA expression is higher in males than females in both SC and OM tissues. In female SC tissue, C3 and adipsin mRNA decrease with increasing BMI (r = 0.557, P =.025 and r = 0.717 P =.002, respectively), with no change in factor B. By contrast, in males there was a pronounced increase in C3, adipsin, and factor B in OM tissue with increasing BMI (r = 0.759 P =.001, r = 0.650 P =.006, and r = 0.568 P =.022, respectively). Of note, however, in both men and women there was a marked increase in the OM/SC ratio of C3 and adipsin with increasing BMI. These results suggest that in female SC adipose tissue, there is downregulation of factors related to ASP production in obesity, perhaps to limit further expansion of adipose tissue. In males, there is increased expression in OM tissue. In addition, relative OM/SC expression increases with obesity and these changes may contribute to the development of visceral adipose tissue.

A comparison of acute phase proteins and traditional risk factors as markers of combined plaque and intima-media thickness and plaque density in carotid and femoral arteries

OBJECTIVES

To test the hypothesis that some acute phase proteins may be better independent predictors of objective measures of arterial wall impairment than traditional risk factors.

DESIGN

Cross-sectional study.

MATERIALS AND METHODS

C-reactive protein (CRP), fibrinogen, C3 complement and traditional risk factors were measured in 288 men aged 55-64 years, randomly chosen from the local registry lists. By ultrasound assessment of the bifurcations of carotid and femoral arteries, maximum combined plaque/intima-media thickness (CPIMTmax) and mean plaque density (MPD, in a grey scale from 0 to 255) were also measured.

RESULTS

In multivariate analysis only traditional risk factors remained associated with the overall CPIMTmax: smoking (r = 0.35, p < 0.0001), cholesterol (r = 0.23, p = 0.0001), age (r = 0.22, p = 0.0002), glucose (r = 0.18, p = 0.002) and systolic blood pressure (r = 0.13, p = 0.02). However, with regard to carotid disease only, fibrinogen was the strongest covariate of CPIMT (r = 0.18, p = 0.002). The overall MPD was independently associated with CRP (r = 0.25, p = 0.0008), physical activity (r = 0.19, p = 0.009), triglycerides (r = -0.18, p = 0.02) and body mass index (r = 0.15, p = 0.04). CRP was mainly associated with femoral MPD, while triglycerides were the major (inverse) covariate of carotid MPD.

CONCLUSIONS

Traditional risk factors are the main determinants of CPIMTmax, although fibrinogen seems to play a role in carotids. CRP was associated with high density femoral plaques. Finally, no acute phase protein was independently associated with low density, potentially vulnerable, plaques.

Critical review of acylation-stimulating protein physiology in humans and rodents

In the last few years, there has been increasing interest in the physiological role of acylation-stimulating protein (ASP). Recent studies in rats and mice, in particular in C3 (-/-) mice that are ASP deficient, have advanced our understanding of the role of ASP. Of note, the background strain of the mice influences the phenotype of delayed postprandial triglyceride clearance in ASP-deficient mice. Administration of ASP in all types of lean and obese mice studied to date, however, enhances postprandial triglyceride clearance. On the other hand, regardless of the background strain, ASP-deficient mice demonstrate reduced body weight, reduced leptin and reduced adipose tissue mass, suggesting that ASP deficiency results in protection against development of obesity. In humans, a number of studies have examined the relationship between ASP, obesity, diabetes and dyslipidemia as well as the influence of diet, exercise and pharmacological therapy. While many of these studies have small subject numbers, interesting observations may help us to better understand the parameters that may influence ASP production and ASP action. The aim of the present review is to provide a comprehensive overview of the recent literature on ASP, with particular emphasis on those studies carried out in rodents and humans.

Different associations of C-reactive protein, fibrinogen and C3 with traditional risk factors in middle-aged men

BACKGROUND

Some acute phase proteins are associated with both ischemic events and traditional risk factors. Since they are strongly interrelated, each of them partly reflects the characteristics of other proteins. This study was carried out to ascertain the specific preferential associations of some acute phase proteins with traditional risk factors for atherosclerotic disease.

METHODS

High-sensitivity C-reactive protein, fibrinogen and C3-complement were assessed in 288 unselected men aged 55-64 years. Three multiple linear regression analyses were performed, in which each of the three acute phase proteins was considered the dependent variable of both traditional risk factors and the other two proteins.

RESULTS

The three acute phase proteins strongly correlated with each other. Moreover, C-reactive protein was independently associated with triglycerides (P<0.0001), age (P=0.0130), body mass index (P=0.0179), and acute (P=0.0280) and chronic (P=0.0582) inflammations (R2=0.17). Fibrinogen was associated with alcohol consumption (inversely, P=0.0001) and smoking (P=0.0598) (R2=0.06). Finally, C3 was associated with insulin (P<0.0001), cholesterol (P=0.0001), sedentarity (P=0.0028), glucose (P=0.0077), and systolic blood pressure (P=0.0124) (R2=0.28).

CONCLUSIONS

When simultaneously studied in multivariate analysis, acute phase proteins have different preferential associations with traditional risk factors, a probable consequence of their involvement in different cellular activations and metabolic processes.

Postprandial increase of complement component 3 in normolipidemic patients with coronary artery disease: effects of expanded-dose simvastatin

Plasma concentrations of the third complement component (C3) predict the risk of myocardial infarction. Because chylomicrons stimulate C3 production by adipocytes in vitro, we investigated plasma C3 changes in vivo after an oral fat load. Thirty-seven subjects (20 normolipidemic patients with coronary artery disease [CAD] and 17 healthy control subjects) underwent an oral fat load (50 g/m(2)). C3 was measured at baseline and at 2-hour intervals after fat intake for 10 hours. The effects of lipid lowering by simvastatin were evaluated in 16 patients. Fasting plasma C3 was 1.06+/-0.26 and 0.90+/-0.12 g/L in CAD patients and control subjects, respectively. Fasting C3 was correlated with several parameters associated with insulin resistance. The best determinant of fasting C3 was waist circumference (adjusted R(2)=0.48, beta=0.71, P<0.001); the addition of postprandial triglyceridemia to the model improved it (adjusted R(2)=0.63). Plasma C3 levels at 2, 4, and 6 hours after fat ingestion were significantly higher than fasting levels in patients and control subjects. C3 increased maximally to 1.39+/-0.33 g/L in patients and to 1.11+/-0.18 g/L in control subjects (P<0.01 for patients versus control subjects). Total postprandial triglyceridemia was the best determinant of maximal C3 increase (adjusted R(2)=0.47, beta=0.70; P<0.001). Treatment with simvastatin decreased fasting and postprandial C3 by 6% and 39%, respectively (P<0.05 for both versus no treatment). Postprandial plasma C3 concentrations increase in CAD patients and control subjects. Fasting C3 is associated with waist circumference, but postprandial C3 increment is associated with postprandial lipemia. Fasting and postprandial C3 concentrations decrease after treatment with simvastatin.

Comparative study of Helicobacter pylori infection in guinea pigs and mice - elevation of acute-phase protein C3 in infected guinea pigs

Eighteen Dunkin-Hartley guinea pigs and 50 NMRI mice were inoculated with Helicobacter pylori and the infection followed by culture, histopathology, antibody response, and plasma levels of the acute-phase proteins albumin, C3, and transferrin for up to 7 weeks. The immune response to H. pylori surface proteins was studied by an enzyme immunoassay (EIA) and Western immunoblot and the plasma levels of albumin, C3, and transferrin were analyzed by single radial immunodiffusion. Guinea pigs had a more severe gastritis and a higher EIA immune response than NMRI mice. Serum C3 levels were elevated in infected guinea pigs after 3 and 7 weeks indicating a systemic inflammatory response and a possible link between H. pylori infection and extragastric manifestations such as vasculitis associated with atherosclerosis. Serum cholesterol levels were analyzed in guinea pigs at 7 weeks and indicated a higher level in H. pylori-infected than in control animals, but this difference was not statistically significant.

A critical evaluation of the putative role of C3adesArg (ASP) in lipid metabolism and hyperapobetalipoproteinemia

The acylation stimulating protein, ASP is a small, basic serum protein capable of stimulating triglyceride synthesis in cultured fibroblasts and adipocytes. Sequence analysis of ASP has shown that ASP is identical to C3adesArg the inactive fragment of the complement anaphylatoxin peptide, C3a. It has been proposed that C3adesArg (ASP) can be generated by mature adipocytes secreting the three complement proteins: complement protein C3, factor B and factor D (adipsin). There have also been indications that adipocytes may express a specific C3adesArg (ASP)-receptor that is distinct from the recently cloned C3a-receptor. This suggests that C3adesArg (ASP) acts as an adipocyte autocrine and that it plays a central role in the metabolism of adipose tissue. Based on these observations a hypothesis for the etiology of hyperapobetalipoproteinemia (hyperapoB) has been proposed. Hyperapobetalipoproteinemia (hyperapoB), is a familial lipoprotein disorder characterized by increased hepatic secretion of very low density lipoprotein (VLDL) and low density lipoprotein (LDL) particles. If C3adesArg (ASP) function in the adipose tissue is impaired, a reduced rate of triglyceride synthesis will follow, generating an increased flux of fatty acids to the liver. In response to an increased flow of fatty acids, the liver will increase its production of VLDL particles yielding the phenotype of hyperapoB. This review critically assesses this hypothesis and the potential role of C3adesArg (ASP) as a major determinant for triglyceride synthesis in the light of data collected in vitro and in vivo.

Genetic deficiency of acylation stimulating protein (ASP(C3ades-Arg)) does not cause hyperapobetalipoproteinemia in mice

The acylation stimulating protein (ASP) is a 76-amino acid peptide that has been proposed as a potent mediator of triglyceride synthesis and, when functionally impaired, as a major cause of hyperapobetalipoproteinemia (HyperapoB). Purification and sequence analysis of ASP from human sera have revealed that ASP is identical to the complement C3-derived activation peptide C3ades-Arg. Because C3 is the precursor for C3ades-Arg and therefore ASP, a deficiency in C3 would be predicted to result in a phenotype characteristic of HyperapoB. To test this hypothesis in vivo, the current study was undertaken in which ASP(C3ades-Arg)-deficient mice were used as a model system. No significant differences were found in the triglyceride, cholesterol, or free fatty acid concentrations in the plasma of fasted normal and ASP(C3ades-Arg)-deficient animals. In addition, plasma lipoprotein analyses indicated that the very low density lipoprotein, low density lipoprotein, and high density lipoprotein cholesterol and triglyceride concentrations as well as the apolipoprotein B-48 and B-100 levels were not significantly different in the plasma of ASP(C3ades-Arg)-deficient and wild type mice. Furthermore, when challenged with an oral fat load, the ASP(C3ades-Arg)-deficient mice showed no impaired ability to clear triglycerides and free fatty acids from their circulation when compared with their wild-type littermates. Collectively, these results indicate that ASP(C3ades-Arg) deficiency does not cause HyperapoB in mice and that the physiological importance of impaired ASP(C3ades-Arg) function as a cause of hyperapobetalipoproteinemia needs to be reevaluated.

Complement activation in patients with acute myocardial infarction treated with streptokinase

Twenty patients with acute myocardial infarction (AMI) treated with streptokinase (SK) and 11 patients with AMI not treated with SK were clinically and echocardiographically evaluated in the intensive coronary care unit (ICCU). Blood samples, in which complement components C4d, C5b-9, and Bb were measured, were taken immediately after arrival of the patient at the ICCU, 1 hour after SK infusion, and 24 hours later from the SK group, and similar time-matched samples were taken from the control group. The classic, alternative, and common complement pathways were found to be activated in AMI, but this activation was statistically significant only in the SK-treated group. Activation was not related to the site of the AMI nor to the extent of its damage, as assessed by Killip class and ejection fraction. However, in the SK-treated group and even more so in non-SK group, the C5b-9 increment was significantly higher in patients diagnosed with reperfusion, based on ST-segment recovery of > or =50% reduction from the peak ST-segment level. There was little change in complement levels when reperfusion did not occur. Detection of reperfusion without coronary angiography would have important practical clinical implications, and complement activation may predict its occurrence. However, more studies of this phenomenon are needed.

Serum complement and familial combined hyperlipidemia

Familial combined hyperlipidemia (FCHL) is one of the most common inherited lipid disorders. Resistance of adipocytes to the effects of acylation stimulating protein (ASP) may contribute to ineffective triglyceride synthesis and thereby prolonged postprandial lipemia and increased fatty acid flux to the liver seen in FCHL patients. Interestingly, ASP is identical to C3a-desArg, fragment of the third component of complement. We examined the relationships between serum levels of complement components C3 and C4 and markers of lipid and glucose metabolism in 11 large FCHL families (n = 53). Median serum C3 levels were 38% higher in affected compared to non-affected male FCHL family members (1.90 g/l vs. 1.38, P = 0.0027). The strongest correlations were observed between serum complement C3 and apolipoprotein B levels, reaching 0.77 in males. These relations were not confounded by obesity or impaired glucose tolerance. In conclusion, serum levels of the main complement components C3 and C4 correlated significantly with serum lipid levels. Further studies are needed to clarify the importance of disturbances in the complement system on the pathogenesis of FCHL and other lipid disorders.

Apolipoprotein E and complement C3 polymorphism and their role in the response to gemfibrozil and low fat low cholesterol therapy

Three different allelic variants of apolipoprotein E determine, in concert with other gene products, the levels of plasma lipoproteins. Recently, cleavage products of the complement C3 molecule have also been implicated in determining plasma triacylglycerol concentrations. This study presents data of an ongoing study to dissect the role of the apolipoprotein E gene locus in the response to low fat/low cholesterol diet combined with gemfibrozil treatment. In addition, for the first time, the significance of C3 allelic variants to such hypolipidaemic therapy response was analysed. To this end data from 81 obese hyperlipoproteinaemic patients (Fredrickson type II/A and B and type IV and V) confirmed the usefulness of the combined gemfibrozil/diet treatment and unveiled apolipoprotein E allele group specific therapy responses. The mean changes of lipid properties due to combined treatment was 15% for total cholesterol, 48% for triacylglycerols and 28% for atherogenic index. Division into hyperlipidaemia types according to Fredrickson and subgrouping into E2, E3 and E4 groups (apolipoprotein E2/2 and 2/3, apolipoprotein E3/3 and apolipoprotein E4/2 and 4/3 phenotype groups respectively) exposed pronounced differences from these mean changes, suggesting substantial influence of apolipoprotein E variants on this therapy. We observed triacylglycerol reductions of from 17% in type IIA-apolipoprotein E3 group patients up to 78% in the type IV and V-apolipoprotein E2 group. Thus it might be concluded the apolipoprotein E genotyping aides therapy success prediction. Although, low sample number in some subgroups obscures significance in this pilot study, significant therapy success emerges for the E3 and E4 group in type IV and V hyperlipidaemia and type IIB-apolipoprotein E3 homozygous patients can be predicted to respond better than apolipoprotein E2 carriers. Finally, we present evidence that positive changes of lipid properties are also determined by the "fast" complement C3 allel (C3-F). Patients with complement factor C3-FS pattern respond better to treatment than patients with C3-SS configuration. In summary these data endorse the genotyping of apolipoprotein E alleles to predict maximal success of "fibrate" treatment. In addition they argue strongly for further assessment of the involvement of complement C3 allelic variations in lipid homeostasis.