Serum amyloid A: high-density lipoproteins interaction and cardiovascular risk

SAA1 gene polymorphisms in osteoporosis patients

Background: Serum amyloid A (SAA1) is an apolipoprotein that maintains glucose and lipid homeostasis. Its polymorphisms are associated with risks of myocardial infarction and coronary artery disease (CAD). Methods: However, little is known about the associations of these polymorphisms with susceptibility to osteoporosis, which we evaluated in this hospital-based case–control study involving 300 osteoporosis patients and 350 controls. Three single-nucleotide polymorphisms (SNPs) (rs183978373, rs12218, and rs10832915) were genotyped using MALDI TOF MS. Results: There were no differences in the rs183978373 and rs12218 polymorphisms between the osteoporosis group and controls. The SAA1 gene rs10832915 polymorphism increased the risk of osteoporosis in our Chinese population. The genotypes of the rs10832915 polymorphism were not significantly associated with clinical parameters (age, body mass index (BMI), high- and low-density lipoprotein (LDL), total cholesterol (TC), and T-score). Haplotype analysis revealed that the ATT haplotype had a significant correlation with a decreased risk of osteoporosis. Conclusion: In conclusion, the SAA1 rs10832915 polymorphism and its haplotypes are associated with osteoporosis, but this finding should be confirmed in large well-designed studies.

High-Density Lipoprotein from Chronic Kidney Disease Patients Modulates Polymorphonuclear Leukocytes

The anti-inflammatory properties of high-density lipoproteins (HDL) are lost in uremia. These HDL may show pro-inflammatory features partially as a result of changed protein composition. Alterations of polymorphonuclear leukocytes (PMNLs) in chronic kidney disease (CKD) may contribute to chronic inflammation and high vascular risk. We investigated if HDL from uremic patients is related to systemic inflammation by interfering with PMNL function. PMNL apoptosis was investigated by assessing morphological features and DNA content. CD11b surface expression was quantified by flow cytometry. Oxidative burst was measured via cytochrome c reduction assay. Chemotaxis was assessed by using an under-agarose migration assay. We found that HDL from CKD and hemodialysis (HD) patients significantly attenuated PMNL apoptosis, whereas HDL isolated from healthy subjects had no effect on PMNL apoptosis. The use of signal transduction inhibitors indicated that uremic HDL exerts anti-apoptotic effects by activating pathways involving phosphoinositide 3-kinase and extracellular-signal regulated kinase. Healthy HDL attenuated the surface expression of CD11b, whereas HDL from CKD and HD patients had no effect. All tested isolates increased the stimulation of oxidative burst, but did not affect PMNL chemotactic movement. In conclusion, HDL may contribute to the systemic inflammation in uremic patients by modulating PMNL functions.

Protein markers of dysfunctional HDL in scavenger receptor class B type I deficient mice

Background

Scavenger receptor class B type I (SR-BI) plays a key role in high density lipoproteins (HDL) metabolism. SR-BI deficiency in mice results in enhanced susceptibility to atherosclerosis with abnormal large, cholesterol enriched, and functional impaired HDL. This study was to characterize the protein markers of dysfunctional HDL in SR-BI deficient (SR-BI^−/−) mice and to test if the defective of HDL might be affected by probucol treatment.

Methods

Shotgun proteomics and 2-D gel electrophoresis were performed to examine the profile of HDL protein and distribution of HDL particles isolated from SR-BI^−/− mice. HDL’s cell-function, paraoxonase 1 (PON1) and myeloperoxidase activity were assessed. The mice were treated with 1.2 mg/g/day probucol for 6 weeks and the impact on HDL protein markers was analyzed. The differential proteins were quantified by Western blotting.

Results

The relative amount of protein in SR-BI^−/− HDL was decreased by about 25% compared to that in HDL from wild type (WT) mice. Compared to WT HDL, relative protein abundance of representative apoAI and PON1 in SR-BI^−/− HDL were significantly reduced, whereas acute-phase protein serum amyloid A (SAA) and apoAIV, proteinase inhibitor proteins α-1-antitrypsin (A1AT) were increased. The distribution of plasma apoAI-containing HDL particles in SR-BI^−/− mice was also dramatically altered, although plasma apoAI level was no difference. The protein alterations were accompanied with dysfunction of SR-BI^−/− HDL, evidenced by impaired cholesterol homeostasis in macrophages, and reduced anti-oxidative and anti-inflammatory effects. Probucol treatment of SR-BI^−/− mice could restored the relative contents of critical proteins including apoAI, PON1, SAA, apoAIV and A1AT on HDL, and improve HDL dysfunction despite decreased HDL-C level.

Conclusion

SR-BI deficiency leading to dysfunctional HDL is closely related to alteration of HDL protein, suggesting that identification of apoAI, PON1, SAA, apoAIV, and A1AT may serve as the valuable protein markers for diagnosis and therapeutics of dysfunctional HDL-related metabolic diseases.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1502-y) contains supplementary material, which is available to authorized users.

Association of plasma pentraxin-3 levels with coronary risk factors and the lipid profile: a cross-sectional study in Japanese patients with stable angina pectoris

The aim of this study was to evaluate the relationships among the traditional risk factors, lipid profile, and pentraxin-3 in stable angina (SAP). Plasma pentraxin-3 and serum LDL, HDL, and high-sensitivity CRP levels were measured in 163 SAP and 28 non-coronary artery disease (CAD) patients. Their relationships with five risk factors, hypertension (HT), dyslipidemia (DL), diabetes mellitus (DM), obesity (body mass index: BMI > 25 kg/m²), and high age (> 75 years), were evaluated. No significant difference was observed in the pentraxin-3 level between patients in SAP and in non-CAD [2.1 (1.4-3.5) ng/ml versus off 2.6 (1.6-3.8) ng/ml, P = 0.56). In SAP patients, pentraxin-3 levels decreased with more risk factors, according to the number of 3 traditional risk factors (HT, DL, and DM) and the number of 5 expanded risk factors (HT, DL, DM, obesity, and high age) (P for trend = 0.01 and 0.05, respectively). Pentraxin-3 showed a positive association with HDL (rs = 0.229; P = 0.050) and an inverse association with LDL (rs = - 0.224; P = 0.045). On multiple logistic regression, the number of 3 traditional risk factors was a significant predictor of pentraxin-3 levels (odds ratio = 0.444; 95% confidence interval  0.205-0.963, P = 0.040) in SAP patients. In SAP patients, the cardiovascular risk factor burden remained a negative impact on pentraxin-3 levels after multivariate analysis, suggesting that they have distinct roles in atherosclerosis.Trial registration: UMIN000023837.

HDL in CKD-The Devil Is in the Detail

The picture of HDL cholesterol (HDL-C) as the "good" cholesterol has eroded. This is even more surprising because there exists strong evidence that HDL-C is associated with cardiovascular disease (CVD) in the general population as well as in patients with impairment of kidney function and/or progression of CKD. However, drugs that dramatically increase HDL-C have mostly failed to decrease CVD events. Furthermore, genetic studies took the same line, as genetic variants that have a pronounced influence on HDL-C concentrations did not show an association with cardiovascular risk. For many, this was not surprising, given that an HDL particle is highly complex and carries >80 proteins and several hundred lipid species. Simply measuring cholesterol might not reflect the variety of biologic effects of heterogeneous HDL particles. Therefore, functional studies and the involvement of HDL components in the reverse cholesterol transport, including the cholesterol efflux capacity, have become a further focus of study during recent years. As also observed for other aspects, CKD populations behave differently compared with non-CKD populations. Although clear disturbances have been observed for the "functionality" of HDL particles in patients with CKD, this did not necessarily translate into clear-cut associations with outcomes.

Pharmacological Intervention to Modulate HDL: What Do We Target?

The cholesterol concentrations of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) have traditionally served as risk factors for cardiovascular disease. As such, novel therapeutic interventions aiming to raise HDL cholesterol have been tested in the clinical setting. However, most trials led to a significant increase in HDL cholesterol with no improvement in cardiovascular events. The complexity of the HDL particle, which exerts multiple physiological functions and is comprised of a number of subclasses, has raised the question as to whether there should be more focus on HDL subclass and function rather than cholesterol quantity. We review current data regarding HDL subclasses and subclass-specific functionality and highlight how current lipid modifying drugs such as statins, cholesteryl ester transfer protein inhibitors, fibrates and niacin often increase cholesterol concentrations of specific HDL subclasses. In addition this review sets out arguments suggesting that the HDL3 subclass may provide better protective effects than HDL2.

Relations of GlycA and lipoprotein particle subspecies with cardiovascular events and mortality: A post hoc analysis of the AIM-HIGH trial

BACKGROUND

The Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides and Impact on Global Health Outcomes trial showed no incremental benefit of extended-release niacin (ERN) therapy added to simvastatin in subjects with cardiovascular disease (CVD).

OBJECTIVES

To examine the effects of ERN treatment on lipoprotein particles and GlycA, a new marker of systemic inflammation, and their relations with incident CVD events including mortality.

METHODS

GlycA and very low-density lipoprotein, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) particle subclasses were quantified by nuclear magnetic resonance spectroscopy using available stored baseline (n = 2754) and 1-year in-trial (n = 2581) samples. Associations with CVD events and all-cause mortality were assessed using multivariable Cox proportional hazards regression adjusted for age, sex, diabetes, treatment assignment, and lipoproteins.

RESULTS

Compared to placebo, ERN treatment lowered very low-density lipoprotein and LDL and increased HDL particle concentrations, increased LDL and HDL particle sizes (all P < .0001), but did not affect GlycA. Baseline and in-trial GlycA levels were associated with increased risk of CVD events: hazard ratio (HR) per SD increment, 1.17 (95% confidence interval [CI], 1.06-1.28) and 1.13 (1.02-1.26), respectively. However, none of the lipoprotein particle classes or subclasses was associated with incident CVD. By contrast, all-cause mortality was significantly associated with both GlycA (baseline HR: 1.46 [1.22-1.75]; in-trial HR: 1.41 [1.24-1.60]) and low levels of small HDL particles (baseline HR: 0.69 [0.56-0.86]; in-trial HR: 0.69 [0.56-0.86]).

CONCLUSIONS

This Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides and Impact on Global Health Outcomes trial post hoc substudy indicates that inflammation, as indexed by GlycA, is unaffected by ERN treatment but is significantly associated with the residual risk of CVD and death in patients treated to low levels of LDL cholesterol.

Serum amyloid A enrichment impairs the anti-inflammatory ability of HDL from diabetic nephropathy patients

AIMS

Impaired anti-inflammatory ability of high-density lipoprotein (HDL) has been demonstrated in patients with type-2 diabetes mellitus (T2DM). However, whether HDL from patients with diabetic nephropathy (DN) suffers additional damage remains unknown. This study compared the anti-inflammatory capacities of HDL from healthy controls, T2DM patients with normal renal function, and T2DM patients with DN.

MATERIALS AND METHODS

HDL was isolated from healthy controls (n=33) and T2DM patients with normal renal function (n=21), chronic kidney disease (CKD) (n=27), and end-stage renal disease (ESRD) (n=27). Human peripheral blood mononuclear cells (PBMCs) from healthy volunteers were pretreated with HDL (100μg/mL) for 1h, then incubated with lipopolysaccharide (LPS) (50ng/mL) for 24h. The anti-inflammatory ability of HDL was measured as the secretion of TNF-α in LPS-activated monocytes.

RESULTS

The anti-inflammatory ability of HDL was gradually impaired as kidney function declined. Serum amyloid A (SAA) concentration in HDL^DN significantly increased and was positively correlated with the impaired anti-inflammatory ability of HDL (Pearson r=0.315, P=0.006). Furthermore, HDL supplemented with SAA significantly increased TNF-α release from PBMCs compared with that from control HDL.

CONCLUSIONS

These findings identified an impaired anti-inflammatory capacity of HDL from DN patients, which might be attributable to SAA enrichment.

Association of Serum Amyloid A with Kidney Outcomes and All-Cause Mortality in American Indians with Type 2 Diabetes

BACKGROUND

Serum amyloid A (SAA) induces inflammation and apoptosis in kidney cells and is found to be causing the pathologic changes that are associated with diabetic kidney disease (DKD). Higher serum SAA concentrations were previously associated with increased risk of end-stage renal disease (ESRD) and death in persons with type 2 diabetes and advanced DKD. We explored the prognostic value of SAA in American Indians with type 2 diabetes without DKD or with early DKD.

METHODS

SAA concentration was measured in serum samples obtained at the start of follow-up. Multivariate proportional hazards models were employed to examine the magnitude of the risk of ESRD or death across tertiles of SAA concentration after adjustment for traditional risk factors. The C statistic was used to assess the additional predictive value of SAA relative to traditional risk factors.

RESULTS

Of 256 participants (mean ± SD glomerular filtration rate [iothalamate] = 148 ± 45 mL/min, and median [interquartile range] urine albumin/creatinine = 39 [14-221] mg/g), 76 developed ESRD and 125 died during a median follow-up period of 15.2 and 15.7 years, respectively. After multivariable proportional hazards regression, participants in the 2 highest SAA tertiles together exhibited a 53% lower risk of ESRD (hazard ratio [HR] 0.47, 95% CI 0.29-0.78), and a 30% lower risk of death (HR 0.70, 95% CI 0.48-1.02), compared with participants in the lowest SAA tertile, although the lower risk of death was not statistically significant. Addition of SAA to the ESRD model increased the C statistic from 0.814 to 0.815 (p = 0.005).

CONCLUSIONS

Higher circulating SAA concentration is associated with a reduced risk of ESRD in American Indians with type 2 diabetes.

Protective effect of HDL on NADPH oxidase-derived super oxide anion mediates hypoxia-induced cardiomyocyte apoptosis

Cardiovascular diseases are the leading cause of death of death in Taiwan. Atherosclerosis can lead to serious problems, including heart attack, stroke, or even death. Coronary heart disease (CHD) occurs when plaque builds up in the coronary arteries to cause the ischemic heart disease which will enhance myocardial remodeling and also induce myocardial hypoxia. High density lipoprotein (HDL) has been proposed to have cardio-protective effects. Under hypoxic conditions (1%O₂ for 24hr), in H9c2 cells, reactive oxygen species (ROS) is induced which leads to cardiomyocyte apoptosis and cardiac dysfunction. Therefore, the present study described the protective effect of HDL on hypoxia-induced cardiomyocyte damage. We investigated the NADPH oxidase-produced ROS-related signaling pathways and apoptosis in cardiomyocytes under hypoxia conditions. Results showed that the ROS mediated cardiac damage might occur via AT1 and PKC activation. Furthermore, hypoxia downregulated the survival protein (p-AKT^ser473) and anti-apoptotic protein (BCL₂), whereas pro-apoptotic protein, Bax and caspase 3 were upregulated. These detrimental effects by ROS and apoptosis were prevented by HDL pretreatment. Our findings revealed the underlying molecular mechanism by which HDL suppresses the hypoxia-induced cardiomyocyte dysfunction. Further, we elucidated the role of HDL on preventing hypoxia induced cardiomyocyte apoptosis is mediated through the inhibition of NADPH oxidase-derived ROS.

Lipid testing in infectious diseases: possible role in diagnosis and prognosis

INTRODUCTION

Acute infections lead to significant alterations in metabolic regulation including lipids and lipoproteins, which play a central role in the host immune response. In this regard, several studies have investigated the role of lipid levels as a marker of infection severity and prognosis.

SCOPE OF REVIEW

We review here the role of lipids in immune response and the potential mechanisms underneath. Moreover, we summarize studies on lipid and lipoprotein alterations in acute bacterial, viral and parasitic infections as well as their diagnostic and prognostic significance. Chronic infections (HIV, HBV, HCV) are also considered.

RESULTS

All lipid parameters have been found to be significantly dearranged during acute infection. Common lipid alterations in this setting include a decrease of total cholesterol levels and an increase in the concentration of triglyceride-rich lipoproteins, mainly very low-density lipoproteins. Also, low-density lipoprotein cholesterol, apolipoprotein A1, low-density lipoprotein cholesterol and apolipoprotein-B levels decrease. These lipid alterations may have prognostic and diagnostic role in certain infections.

CONCLUSION

Lipid testing may be of help to assess response to treatment in septic patients and those with various acute infections (such as pneumonia, leptospirosis and others). Diagnostically, new onset of altered lipid levels should prompt the clinician to test for underlying infection (such as leishmaniasis).

HDL cholesterol: reappraisal of its clinical relevance

Background

While several lines of evidence prove that elevated concentrations of low-density lipoproteins (LDL) causally contribute to the development of atherosclerosis and its clinical consequences, high-density lipoproteins are still widely believed to exert atheroprotective effects. Hence, HDL cholesterol (HDL-C) is in general still considered as “good cholesterol”. Recent research, however, suggests that this might not always be the case and that a fundamental reassessment of the clinical significance of HDL-C is warranted.

Method

This review article is based on a selective literature review.

Results

In individuals without a history of cardiovascular events, low concentrations of HDL-C are inversely associated with the risk of future cardiovascular events. This relationship may, however, not apply to patients with metabolic disorders or manifest cardiovascular disease. The classical function of HDL is to mobilise cholesterol from extrahepatic tissues for delivery to the liver for excretion. These roles in cholesterol metabolism as well as many other biological functions of HDL particles are dependent on the number as well as protein and lipid composition of HDL particles. They are poorly reflected by the HDL-C concentration. HDL can even exert negative vascular effects, if its composition is pathologically altered. High serum HDL-C is therefore no longer regarded protective. In line with this, recent pharmacological approaches to raise HDL-C concentration have not been able to show reductions of cardiovascular outcomes.

Conclusion

In contrast to LDL cholesterol (LDL-C), HDL-C correlates with cardiovascular risk only in healthy individuals. The calculation of the ratio of LDL-C to HDL-C is not useful for all patients. Low HDL-C should prompt examination of additional metabolic and inflammatory pathologies. An increase in HDL-C through lifestyle change (smoking cessation, physical exercise) has positive effects and is recommended. However, HDL-C is currently not a valid target for drug therapy.

[Clinical importance of HDL cholesterol]

BACKROUND

Each year 16-17 million determinations of high-density lipoprotein cholesterol (HDL-C) are conducted and interpreted in Germany. Recently acquired data have led to a fundamental reassessment of the clinical significance of HDL-C.

METHOD

This review article is based on a selective literature search.

RESULTS

Low HDL‑C levels usually indicate an increased cardiovascular risk, particularly in primary prevention but the epidemiological relationship between HDL‑C and the risk is complex. The HDL plays a role in the back transport and excretion of cholesterol; however, the biological functions of HDL are dependent on the protein and lipid composition, which is not reflected by the HDL‑C concentration. If the composition of HDL is pathologically altered it can also exert negative vascular effects.

CONCLUSION

Compared with low-density lipoprotein cholesterol (LDL-C), HDL‑C is of secondary importance for cardiovascular risk stratification and the calculation of the LDL-C:HDL‑C ratio is not useful for all patients. Low HDL‑C levels should prompt a search for additional metabolic and inflammatory pathologies. An increase in HDL‑C through lifestyle changes (e.g. smoking cessation and physical exercise) has positive effects and is recommended; however, HDL‑C is currently not a valid target for drug therapy.

A Novel Protein Glycan-Derived Inflammation Biomarker Independently Predicts Cardiovascular Disease and Modifies the Association of HDL Subclasses with Mortality

BACKGROUND

Evidence suggests that systemic inflammation may adversely impact HDL function. In this study we sought to evaluate the independent and incremental predictive performance of GlycA-a novel serum inflammatory biomarker that is an aggregate measure of enzymatically glycosylated acute phase proteins-and HDL subclasses on adverse events in a retrospective observational study of a secondary prevention population and to understand a priori defined potential interactions between GlycA and HDL subclasses.

METHODS

GlycA and HDL subclasses were measured using proton nuclear magnetic resonance spectroscopy in 7617 individuals in the CATHGEN (CATHeterization GENetics) cardiac catheterization biorepository.

RESULTS

GlycA was associated with presence [odds ratio (OR) 1.07 (1.02-1.13), P = 0.01] and extent [OR 1.08 (1.03, 1.12) P < 0.0005] of coronary artery disease and with all-cause mortality [hazard ratio (HR) 1.34 (1.29-1.39), P < 0.0001], cardiovascular mortality [1.37 (1.30-1.45), P < 0.0001] and noncardiovascular mortality [1.46 (1.39-1.54) P < 0.0001] in models adjusted for 10 cardiovascular risk factors. GlycA and smaller HDL subclasses had independent but opposite effects on mortality risk prediction, with smaller HDL subclasses being protective [HR 0.69 (0.66-0.72), P < 0.0001]. There was an interaction between GlycA and smaller HDL subclasses-increasing GlycA concentrations attenuated the inverse association of smaller HDL subclasses with mortality. Adding GlycA and smaller HDL subclasses into the GRACE (Global Registry of Acute Coronary Events) and Framingham Heart Study Risk Scores improved mortality risk prediction, discrimination and reclassification.

CONCLUSIONS

These findings highlight the interaction of systemic inflammation and HDL with clinical outcomes and may increase precision for clinical risk assessment in secondary prevention populations.

Different relationship between ANGPTL3 and HDL components in female non-diabetic subjects and type-2 diabetic patients

Background

Angiopoietin-like protein 3 (ANGPTL3) is a major lipoprotein regulator and shows positive correlation with high-density lipoprotein-cholesterol (HDL-c) in population studies and ANGPTL3 mutated subjects. However, no study has looked its correlation with HDL components nor with HDL function in patients with type 2 diabetes mellitus (T2DM).

Methods

We studied 298 non-diabetic subjects and 300 T2DM patients who were randomly recruited in the tertiary referral centre. Plasma levels of ANGPTL3 were quantified by ELISA. Plasma samples were fractionated to obtain HDLs. HDL components including apolipoprotein A-I (apoA-I), triglyceride, serum amyloid A (SAA), phospholipid and Sphingosine-1-phosphate were measured. HDLs were isolated from female controls and T2DM patients by ultracentrifugation to assess cholesterol efflux against HDLs. A Pearson unadjusted correlation analysis and a linear regression analysis adjusting for age, body mass index and lipid lowering drugs were performed in male or female non-diabetic participants or diabetic patients, respectively.

Results

We demonstrated that plasma level of ANGPTL3 was lower in female T2DM patients than female controls although no difference of ANGPTL3 levels was detected between male controls and T2DM patients. After adjusting for confounding factors, one SD increase of ANGPTL3 (164.6 ng/ml) associated with increase of 2.57 mg/dL cholesterol and 1.14 μg/mL apoA-I but decrease of 47.07 μg/L of SAA in HDL particles of non-diabetic females (p < 0.05 for cholesterol and SAA; p < 0.0001 for apoA-I). By contrast, 1-SD increase of ANGPTL3 (159.9 ng/ml) associated with increase of 1.69 mg/dl cholesterol and 1.25 μg/mL apoA-I but decrease of 11.70 μg/L of SAA in HDL particles of female diabetic patients (p < 0.05 for cholesterol; p < 0.0001 for apoA-I; p = 0.676 for SAA). Moreover, one SD increase of ANGPTL3 associated with increase of 2.11 % cholesterol efflux against HDLs in non-diabetic females (p = 0.071) but decrease of 1.46 % in female T2DM patients (p = 0.13) after adjusting for confounding factors.

Conclusions

ANGPTL3 is specifically correlated with HDL-c, apoA-I, SAA and HDL function in female non-diabetic participants. The decrease of ANGPTL3 level in female T2DM patients might contribute to its weak association to HDL components and function. ANGPTL3 could be considered as a novel therapeutic target for HDL metabolism for treating diabetes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0450-1) contains supplementary material, which is available to authorized users.

Liver disease alters high-density lipoprotein composition, metabolism and function

High-density lipoproteins (HDL) are important endogenous inhibitors of inflammatory responses. Functional impairment of HDL might contribute to the excess mortality experienced by patients with liver disease, but the effect of cirrhosis on HDL metabolism and function remain elusive. To get an integrated measure of HDL quantity and quality, we assessed several metrics of HDL function using apolipoprotein (apo) B-depleted sera from patients with compensated cirrhosis, patients with acutely decompensated cirrhosis and healthy controls. We observed that sera of cirrhotic patients showed reduced levels of HDL-cholesterol and profoundly suppressed activities of several enzymes involved in HDL maturation and metabolism. Native gel electrophoresis analyses revealed that cirrhotic serum HDL shifts towards the larger HDL2 subclass. Proteomic assessment of isolated HDL identified several proteins, including apoA-I, apoC-III, apoE, paraoxonase 1 and acute phase serum amyloid A to be significantly altered in cirrhotic patients. With regard to function, these alterations in levels, composition and structure of HDL were strongly associated with metrics of function of apoB-depleted sera, including cholesterol efflux capability, paraoxonase activity, the ability to inhibit monocyte production of cytokines and endothelial regenerative activities. Of particular interest, cholesterol efflux capacity appeared to be strongly associated with liver disease mortality. Our findings may be clinically relevant and improve our ability to monitor cirrhotic patients at high risk.

Serum- and HDL3-serum amyloid A and HDL3-LCAT activity are influenced by increased CVD-burden

BACKGROUND

High density lipoproteins (HDL) protect against cardiovascular disease (CVD). However, increased serum amyloid-A (SAA) related inflammation may negate this property. This study investigated if SAA was related to CVD-burden.

METHODS

Subjects referred to the rapid chest pain clinic (n = 240) had atherosclerotic burden assessed by cardiac computerised tomography angiography. Subjects were classified as: no-CVD (n = 106), non-obstructive-CVD, stenosis<50% (n = 58) or moderate/significant-CVD, stenosis ≥50% (n = 76). HDL was subfractionated into HDL2 and HDL3 by rapid-ultracentrifugation. SAA-concentration was measured by ELISA and lecithin cholesterol acyltransferase (LCAT) activity measured by a fluorimetric assay.

RESULTS

We illustrated that serum-SAA and HDL3-SAA-concentration were higher and HDL3-LCAT-activity lower in the moderate/significant-CVD-group, compared to the no-CVD and non-obstructive-CVD-groups (percent differences: serum-SAA, +33% & +30%: HDL3-SAA, +65% and +39%: HDL3-LCAT, -6% & -3%; p < 0.05 for all comparisons). We also identified a positive correlation between serum-SAA and HDL3-SAA (r = 0.698; p < 0.001) and a negative correlation between HDL3-SAA and HDL3-LCAT-activity (r = -0.295; p = 0.003), while CVD-burden positively correlated with serum-SAA (r = 0.150; p < 0.05) and HDL3-SAA (r = 0.252; p < 0.001) and negatively correlated with HDL3-LCAT-activity (r = -0.182; p = 0.006). Additionally, multivariate regression analysis adjusted for age, gender, CRP and serum-SAA illustrated that HDL3-SAA was significantly associated with modifying CVD-risk of moderate/significant CVD-risk (p < 0.05).

CONCLUSION

This study has demonstrated increased SAA-related inflammation in subjects with moderate/significant CVD-burden, which appeared to impact on the antiatherogenic potential of HDL. We suggest that SAA may be a useful biomarker to illustrate increased CVD-burden, although this requires further investigation.