| BackgroundSubstantial epidemiological studies have demonstrated that high-density lipoprotein cholesterol (HDL-C) level is a strong, independent, and inverse risk factor for coronary heart disease (CHD). As a result, HDL-C is gaining increasing interests as a research target. There continues to be an emphasis on HDL-C level in nearly all clinical trials of lipid-modifying therapies. However, the simple measurement of HDL-C levels may not always be reflective of HDL functionality of promoting cholesterol efflux, reducing oxidation, attenuating vascular inflammation and improving vascular endothelial function. HDL-C is a complex heterogeneous mixture of particles consisting of lipids and proteins, and proteins determines its functional properties, rather than the circulating HDL-C level. ApoA-I in HDL has been identified as being responsible for reverse cholesterol transport and reverse atherosclerosis, and paraoxonase1in HDL has been found to have anti-oxidant properties. Several recent studies have provided evidence that HDL exerts pro-inflammatory properties and loses its protective functions in the context of CHD. These findings are supported by the studies indicating that inflammation generates dysfunctional or even pro-atherogenic forms of HDL by promoting phospholipid depletion and enrichment with pro-inflammatory proteins such as serum amyloid A protein (SAA) or complement component3. The composition changes promoting the conversion of anti-inflammatory HDL to pro-inflammatory HDL in CHD have not been fully identified.In our laboratory, we have preformed a preliminary study and identified12differential expressed proteins in HDL fraction between the CHD patients and the controls by proteomic methods, which was a relative quantification and based on small sample (n=10/group). To compare the protein composition of HDL particles in CHD patients and controls, SAA, component5(C5), apoliprotein C-I (apoC-I) were selected and quantified by ELISA in this study.In the first section of our study, plasma SAA was showed to be increased in CHD patients and elevated levels of SAA was independently associated with CHD risks. Many studies have demonstrated that high expression of SAA may contribute to atherogenesis. However, the relationships between SAA gene polymorphisms and atherosclerosis remain unclear. Carotid intima-media thickness (cIMT) is strongly associated with atherosclerosis. Only the SAA1and SAA2genes encode acute-phase SAAs (SAA1and SAA2proteins), so a lot of research focuses on them. Recently, Carty et al.[8] reported an association of SAA gene polymorphisms and HDL, plasma SAA and total CVD. However, the relationship between the genetic polymorphisms of SAA1/2and HDL level, SAA level and carotid cIMT in Chinese Han subjects is incompletely understood.Part1:Changes of apoC-I, SAA Levels in HDL Fraction of Coronary Heart Disease PatientsObjectivesTo compare the difference of the levels of apoC-I, SAA and C5in HDL isolated form CHD patients and controls; and the levels of apoC-I and SAA in plasma of CHD patients and controls.MethodsBetween July2011and July2012,300patients without lipids-lowing drugs (including statins) were enrolled in the FuWai Hospital, dividing into three groups:stable coronary artery disease group (SCAD, n=65), acute coronary syndromes group (ACS n=115), and control group (n=120). HDL was isolated by ultracentrifugation from plasma. Enzyme linked immunosorbent assay (ELISA) was used to detect the levels of apoC-1, SAA and C5in plasma and HDL fraction.Results1. Compared with controls, the level of apoC-I was significantly decreased in HDL isolated from ACS and SCAD patients (36.08±9.96μg/mL vs.37.4±10.33μg/mL vs.45.18±7.42μg/mL, P<0.001). The difference was still exist when adjusted by potential confounding factors (F=18.58, P<0.001). The level of log(HDL-SAA) was significantly higher in ACS group and SCAD group than the control group (1.53±0.60vs.1.32±0.43vs.1.16±0.38, P<0.001). The significance was still exist after adjustment for confounding factors (F=18.58, P<0.001). There was no significant difference in HDL-C5in the three groups (2.44±0.65ng/mL vs.2.38±0.59ng/mL vs.2.46±0.69ng/mL, P=0.872). 2. Compared with controls, the level of apoC-I in plasma was increased in ACS patients and SCAD patients (22.62±13.86μg/mL vs.24.10±12.48μg/mL vs.9.37±6.3μg/mL,P=0.028). The level of log(plasma-SAA) was significantly higher in ACS group and SCAD group than the control group (1.08±0.63vs.0.89±0.50vs.0.72±0.41, P<0.001) independently after adjusting confounding factors.3. The level of plasma-SAA was significantly correlated with HDL-SAA in all subjects (r=0.80,P<0.001).Part2:Influence of SAA genetic polymorphism on AtherosclerosisObjectivesThe aim of the present study was to observe the distribution of SAA1/SAA2gene in Han Chinese population; to explore the relationship between SAA1/SAA2gene polymorphisms and cIMT as well as SAA and HDL levels in plasma in Han Chinese subjects.Methods611Han Chinese subjects were recruited in the FuWai Hospital. Five SNPs (rs11603089, rs1520887, rs2468844, rs7130337, rs7113375) were genotyped by MGB-Taqman probes. HDL was isolated by ultracentrifugation from plasma. ELISA was used to detect the levels of SAA in plasma and in HDL in282subjects. B-mode ultrasound of the carotid IMT were measured in298subjects. A dominant model was defined as follow:common allele homozygotes coded as1, and heterozygotes and recessive allele homozyotes coded as2.Results1. The variations of rs11603089, rs1520887, rs2468844, rs7130337, rs7113375were25.3%, rs1520887, rs2468844, rs7130337and rs7113375, respectively. Except rs7130337, all the genotype distribution did not deviate significantly from Hardy-Weinberg expectations.2.SAA2-rs7113375was associated with lower HDL levels (1.00±0.24mmol/L vs.1.14±0.31mmol/L, P=0.004) in a dominant model and the difference remained significant after multivariate adjustment (P=0.12, P=0.003).3. SAA2-rs7113375was found to be significantly associated with higher SAA levels in plasma and HDL fraction in a dominant model (P=0.012and P=0.018, respectively), and the difference remained significant after multivariate adjustment (standardized β=0.20, P<0.001, and standardized β=0.18, P<0.001respectively).4. The SNP SAA2-rs7113375was associated with higher carotid IMT in a dominant model (0.86±0.21vs.1.03±0.28, P<0.001), and the difference remained significant after multivariate adjustment (standardized β=-0.24, P<0.001).Conclusions1. The HDL proteome displays a pro-atherogenic profile that might compromise the protective effects of HDL in CHD patients. Enrichment of SAA has a potential relevance to the pro-inflammatory properties of HDL, and apoC-I was decreased. Therefore, proteomic measurement of HDL particles could aid in detecting special HDL-associated proteins and, in turn, in evaluating the risk of cardiovascular events and identifying a more appropriate therapeutic target than simple HDL-C levels.2. The plasma-SAA was significantly correlated with the HDL-SAA, the increasement of plasma-SAA has a potential relevance to the pro-inflammatory properties of HDL, and might evaluate the risk of cardiovascular events and be identified as a therapeutic target.3. The polymorphisms of SAA2gene were associated with cIMT in a large cohort of Han Chinese subjects, and rs7113375was associated with higher cIMT. The polymorphisms of SAA2gene could aid in evaluating the risk of atherosclerosis and cardiovascular events.4. SAA2-rs113375was found to be significantly associated with higher SAA levels in plasma and HDL fraction. |
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