SEARCH

SEARCH BY CITATION

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES
  9. Supporting Information

Objective

The purpose of this study was to explore whether nontraditional risk factors, such as apolipoprotein C-III (Apo C-III) and its corresponding Apo B lipoprotein (Lp) subclasses, contribute to the risk of cardiovascular disease in rheumatoid arthritis (RA) patients.

Methods

Apolipoprotein and lipoproteins were measured in 152 RA patients by immunoturbidimetric procedures, electroimmunoassay, and immunoprecipitation. Patients had a coronary artery calcium (CAC) score assessed at baseline and at year 3. Differences in the CAC scores between baseline and year 3 were calculated and dichotomized at 0, where patients with a difference score >0 were denoted as progressors and the rest were denoted as nonprogressors. Differences between means were tested with a 2-sided independent Student's t-test with Satterthwaite's adjustment. Proportion differences were tested with a chi-square test. Multiple logistic regression was performed to assess the relationship between apolipoprotein and lipoprotein levels and the dichotomized CAC score.

Results

Progressors accounted for almost 60% of the cohort. Progressors had significantly higher levels of triglycerides, very low-density lipoprotein (VLDL) cholesterol, total cholesterol/high-density lipoprotein (HDL), triglycerides/HDL, Apo B, LpA-II:B:C:D:E, LpB:C, Apo B/Apo A-I, Apo C-III, and Apo C-III–heparin precipitate than the nonprogressors. After adjusting for age, sex, statin use (yes/no), and hypertension (yes/no), significant risk factors of progressors were total cholesterol, triglycerides, VLDL cholesterol, LDL cholesterol, Apo B, LpB:C, Apo C-III, and Apo B/Apo A-I.

Conclusion

Apo C-III–containing Apo B lipoprotein subclasses were found to be significantly elevated in progressors compared to nonprogressors. Many of these same lipoproteins were found to be associated with an increase in CAC scores among progressors. These lipoproteins may be considered new risk factors for progression of atherosclerosis in RA patients.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES
  9. Supporting Information

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease characterized by progressive joint deformity and disability, affecting approximately 2.1 million adult Americans (1). Numerous recent studies have shown an increased risk for both subclinical atherosclerosis and for cardiovascular (CV) events in RA populations compared to control populations (2–4). Furthermore, it has been estimated that one-third to one-half of RA-related mortality is due to CV disease (3, 5). Traditional CV risk factors have not accounted for the increased prevalence or incidence of CV disease in RA patients (6). Growing evidence indicates that atherosclerosis is an inflammatory disorder, the pathogenic features of which overlap significantly with that of rheumatoid synovial inflammation (3, 7, 8). Therefore, it has been suggested that chronic inflammation is responsible for the increased risk of CV disease in patients with RA.

However, inflammatory pathways intersect significantly with metabolic pathways that convey CV risk. For example, in both clinical and preclinical studies, infusion of tumor necrosis factor α, a key inflammatory modulator in RA pathogenesis, induces both insulin resistance and a proatherogenic lipid profile (9). Disentangling the individual contributions of aberrant inflammatory versus aberrant metabolic pathways to CV risk can be difficult in clinical cohort studies, particularly since CV risk factors have been measured and defined relatively crudely in many studies (6, 9, 10). One example of this is in lipid biology, wherein most clinical studies of RA report serum levels of lipoproteins using the traditional classification by density gradient (e.g., high-density lipoprotein [HDL], low-density lipoprotein [LDL], and very low-density lipoprotein [VLDL]). However, this classification does not convey information on lipoprotein function, which is determined primarily by apolipoproteins, the protein components of plasma lipoproteins.

Apolipoprotein-defined lipoproteins consist of 2 major lipoprotein classes characterized by apolipoprotein A (Apo A-I + Apo A-II) and Apo B as their major protein components. Each of the major apolipoproteins can have several minor apolipoprotein peptides binding to it, such as a cluster of Apo C (Apo C-I, Apo C-II, and Apo C-III), Apo D, and Apo E. The Apo A–containing lipoprotein of high-density properties consists of 3 lipoprotein subclasses referred to as: lipoprotein A-I (LpA-I), LpA-II, and LpA-I:A-II. There are 5 major Apo B lipoprotein subclasses, including: LpB, LpB:E, LpB:C, LpB:E + LpB:C:E, and LpA-II:B:C:D:E. The Apo A-I and Apo B–containing lipoprotein subclasses differ not only in their apolipoprotein composition, but also in their metabolic and atherogenic properties (11, 12).

Studies from this and other laboratories have characterized the metabolic and atherogenic role of Apo C-III, a minor component of the Apo C cluster of polypeptides occurring in triglyceride-rich Apo B–containing lipoproteins. Apo C-III, in both the lipoprotein form (Apo C-III–rich VLDL) and Apo C-III alone, increases adhesion of human monocytes to vascular endothelial cells via up-regulation of vascular cell adhesion molecule 1 and intercellular cell adhesion molecule 1 (13, 14). Furthermore, Apo C-III induces insulin resistance in endothelial cells and reduces production of the potent vasodilator nitric oxide.

Regarding its atherogenic properties, Apo C-III inhibits lipoprotein lipase activity (15) and interferes with the binding of Apo B–containing lipoproteins to hepatic B/E receptors (16). In clinical studies, higher levels of Apo C-III alone or bound to Apo-B–containing lipoproteins were associated with insulin resistance and dyslipidemic profiles, including hypertriglyceridemia (17, 18). Moreover, Apo C-III levels have been linked in multiple studies to increased risk for progression of atherosclerosis and for CV events (19–23).

The recognition of Apo C-III as a link between atherogenicity and inflammation suggests that this minor apolipoprotein could play a role in the accelerated atherosclerosis observed in RA patients. The objective of this study, therefore, was to explore whether Apo C-III and its corresponding Apo-B–containing lipoprotein subclasses contribute to the prevalence or progression of atherosclerosis in a well-characterized RA population.

Significance & Innovations

  • This is the first time apolipoproteins have been measured in a prospective cohort of rheumatoid arthritis (RA) patients.

  • Apolipoprotein-defined lipoproteins proved to be independent risk factors for cardiovascular disease in RA patients.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES
  9. Supporting Information

RA patients.

Participants consisted of 195 patients with RA enrolled in the Evaluation of Subclinical Cardiovascular Disease and Predictors of Events in Rheumatoid Arthritis (ESCAPE RA) study, a cohort study of the prevalence, progression, and risk factors for subclinical CV disease in men and women with RA (24). Enrollment in ESCAPE RA required a diagnosis of RA for 6 months, fulfillment of the American College of Rheumatology 1987 criteria for the classification of RA, and age 45–84 years (25). Prevalent CV disease at baseline (defined as self-reported physician-diagnosed myocardial infarction, heart failure, coronary artery revascularization, angioplasty, peripheral arterial disease or procedures, pacemaker or defibrillator devices, and current atrial fibrillation) was excluded. Additional exclusions included weight exceeding 300 pounds (due to imaging equipment restrictions) and a computed tomography (CT) scan of the chest within 6 months prior to enrollment (to limit radiation exposure). Participants were recruited from among patients followed at the Johns Hopkins Arthritis Center and by referral from local rheumatologists. The study was approved by the Johns Hopkins Hospital Institutional Review Board. All participants provided written consent prior to enrollment occurring from October 2004 through May 2006. During the study, 5 participants had a nonfatal cardiac event.

Measurement of coronary artery calcium (CAC) events.

All 195 participants underwent cardiac multidetector row CT scanning at the baseline visit (visit 1) using methodology described previously (26). CAC was quantified using the Agatston method (27). The results of the analysis of the baseline CAC scores have been published previously (24). Of these 195 participants, 152 returned for a repeat cardiac CT scan at visit 3, approximately 30 months after the baseline visit. The current analysis consists of these 152 participants who had 2 CAC measurements.

Baseline covariate assessment.

Information on demographics, smoking, and family history was collected at the baseline visit (visit 1) by questionnaire. Resting blood pressure (BP) was measured 3 times in the seated position, and the average of the last 2 measurements was used in the analysis. Hypertension was defined by systolic BP 140 mm Hg, diastolic BP 90 mm Hg, or antihypertensive medication use. Diabetes mellitus was defined as a fasting serum glucose 126 mg/dl or use of antidiabetic medications. Physical activity was assessed using a modified 7-Day Physical Activity Recall questionnaire. Prescription and over-the-counter medications used in the preceding 2 weeks were documented from containers supplied by the participant.

RA-specific covariates.

At the baseline visit, 44 joints were examined by a single trained assessor for swelling, tenderness, deformity, and surgical replacement or fusion. RA disease duration was calculated based on self-report from time of physician diagnosis. RA activity was calculated using the Disease Activity Score for 28 joints (DAS28) with high-sensitivity C-reactive protein (CRP) (28). Functional limitation was assessed with the Stanford Health Assessment Questionnaire (29). Current and past use of glucocorticoids and biologic and nonbiologic disease-modifying antirheumatic drugs (DMARDs) were ascertained by interviews. Single-view, anteroposterior radiographs of the hands and feet were obtained and scored for radiographic damage of RA by using the modified Sharp/van der Heijde score (30) by a single trained radiologist blinded to patient characteristics. For 5 subjects with incomplete radiographic assessments, the missing score (hand or foot) was imputed from the available data based on a regression equation using data from the remaining subjects in the cohort.

Laboratory assessments.

Fasting sera and plasma were collected at the baseline visit, separated by centrifugation, and stored at −70°C. CRP level and interleukin-6 (IL-6) were measured as previously described (31). The RA autoantibodies, rheumatoid factor (RF) and anti–cyclic citrullinated peptide (anti-CCP) antibodies, were defined as positive at concentrations of 60 and ≥40 units, respectively.

Lipids, apolipoproteins, and lipoprotein subclasses.

Density-defined lipoprotein classes, including total cholesterol, triglycerides, and HDL cholesterol, were measured as previously described (32, 33). VLDL cholesterol and LDL cholesterol were calculated according to the Friedewald formula (34). Apo A-I, Apo B, and Apo C-III were quantified by the immunoturbidimetric procedure of Riepponen et al (35) using corresponding monospecific polyclonal antisera generated in this laboratory. Apo C-III bound to Apo A-I–containing lipoproteins (Apo C-III–heparin soluble [HS]) and to Apo B–containing lipoproteins (Apo C-III–heparin precipitate [HP]) were measured by electroimmunoassay in HS and HP fractions, respectively (11). The ratio of Apo C-III–HS/Apo C-III–HP is denoted as Apo C-III-Ratio, or just Apo C-III-R.

Apolipoprotein-defined lipoprotein subclasses were measured as follows: 1) LpA-I and LpA-I:A-II according to the procedure by März et al (36) and 2) LpB, LpB:C, LpB:E, LpB:C:E, and LpA-II:B:C:D:E by sequential immunoprecipitation as previously described. The antisera to Apo A-II, Apo E, and Apo C-III were prepared according to a previously described procedure (37). The concentrations of the LpB, LpB:C, LpB:E + LpB:C:E, and LpA-II:B:C:D:E subclasses were expressed in terms of their Apo B content (Table 1).

Table 1. Baseline levels of lipids, apolipoproteins, and apolipoprotein-containing subclasses in 152 patients with RA who had CAC progression or nonprogression*
 Progressors (ΔCAC >0)Nonprogressors (ΔCAC ≤0)
  • *

    Values are the mean ± SD. Two-sampled independent Satterthwaite's t-tests were performed on continuous data, and 2-sampled proportion tests were performed on categorical data. Chi-square test was performed on categorical data with more than 2 levels. RA = rheumatoid arthritis; CAC = coronary artery calcification; VLDL = very low-density lipoprotein; HDL = high-density lipoprotein; Apo = apolipoprotein; Lp = lipoprotein; HS = heparin soluble; HP = heparin precipitate.

  • P < 0.001.

  • P < 0.01.

  • §

    P < 0.05.

Total cholesterol200 ± 39.89191.159 ± 40.22
Log2 (triglycerides)6.98 ± 0.746.58 ± 0.63
Log2 (VLDL cholesterol)4.63 ± 0.694.25 ± 0.63
LDL cholesterol122.21 ± 33.27112.41 ± 33.82
HDL cholesterol51.54 ± 18.7555.88 ± 18.50
Apo B100.65 ± 15.8793.22 ± 15.33
LpA-II:B:C:D:E17.37 ± 7.9214.65 ± 6.43§
LpBE + LpB:C:E11.61 ± 4.7110.85 ± 4.08
LpB61.39 ± 7.2359.42 ± 8.00
LpB:C10.28 ± 4.098.31 ± 4.41
Apo A-I140.88 ± 22.73145.34 ± 20.27
LpA-I34.11 ± 4.4734.29 ± 4.29
LpA-I:A-II106.77 ± 19.27111.05 ± 17.35
Apo C-III10.38 ± 4.178.97 ± 2.99§
Apo C-III–HS7.23 ± 2.646.60 ± 2.11
Apo C-III–HP3.11 ± 1.602.57 ± 1.02§
Apo C-III–Ratio2.56 ± 0.872.70 ± 0.73
Apo B/Apo A-I0.73 ± 0.170.63 ± 0.13
Total cholesterol/HDL4.37 ± 1.803.70 ± 1.25
Triglycerides/HDL3.65 ± 4.762.29 ± 1.81§

Statistical analysis.

The numerical difference in CAC scores between visits 1 and 3 was calculated, thus creating a new variable, denoted as ΔCAC, which was dichotomized at 0. Individuals with ΔCAC >0 were denoted as “progressors,” while those with ΔCAC ≤0 were denoted as “nonprogressors.” Distributions of the continuous variables were examined and, if needed, log2 transformed in order to meet the normality assumption. Given the broad range of apolipoprotein variability, we standardized all their values with a Z transformation.

Means were compared between progressors and nonprogressors through a 2-sampled t-test with the Satterthwaite adjustment. Proportion differences between categorical groups were tested with a chi-square test. To assess the association between apolipoprotein and lipoprotein levels and the dichotomized dependent variable, ΔCAC, multiple logistical regression was performed to obtain both a crude odds ratio (OR) and an adjusted OR. The adjusted OR contained adjustments for sex, age, statin use, hypertension, smoking status, body mass index (BMI), DMARD use, biologic agent use, and steroid use. In all tests a nominal alpha level of 0.05 was considered statistically significant. Due to the hierarchical nature of the apolipoproteins, we chose not to adjust for multiple comparisons.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES
  9. Supporting Information

Demographic and RA characteristics in progressors and nonprogressors.

Progression of CAC (▵CAC >0) occurred in 89 (59%) of the 152 study participants between visits 1 and 3. The cutoff of 0 for CAC progression was arbitrary; however, sensitivity analysis revealed that changing the cutoff to 20 did not have an effect on any of the following results. Baseline demographic and RA characteristics, as well as conventional CV risk factors, in the progressors and nonprogressors are shown in Table 2. Progressors were older on average and more likely to be women. Hypertension, statin use, systolic BP, and homocysteine levels were higher in the progressors, as was the Framingham risk score. None of the measures of RA disease activity (DAS28, swollen joint count or tender joint count, CRP level, or IL-6 level) or of disease severity (RF, CCP, and Sharp/van der Heijde score) differed between the 2 groups. Likewise, use of disease-modifying treatments for RA (hydroxychloroquine, methotrexate, or biologic agents) did not differ significantly between the 2 groups. There were not enough diabetic patients to allow for adequate statistical adjustment in this cohort.

Table 2. Baseline characteristics of 152 patients with RA who had CAC progression or nonprogression*
 Progressors, ΔCAC >0 (n = 89)Nonprogressors, ΔCAC ≤0 (n = 63)
  • *

    Values are the mean ± SD unless otherwise indicated. Two-sampled independent Satterthwaite's t-tests were performed on continuous data. Two-sampled proportion tests were performed on categorical data. Chi-square test was performed on categorical data with more than 2 levels. RA = rheumatoid arthritis; CAC = coronary artery calcification; BMI = body mass index; DAS28 = Disease Activity Score in 28 joints; CRP = C-reactive protein; TJC = tender joint count; SJC = swollen joint count; HAQ = Health Assessment Questionnaire; IL-6 = interleukin-6; RF = rheumatoid factor; CCP = cyclic citrullinated peptide; BP = blood pressure.

  • P < 0.05.

  • P < 0.01.

  • §

    P < 0.001.

Female sex, no. (%)47 (53)47 (63)
Age, years61 ± 8.357.13 ± 8.2
BMI, kg/m227.81 ± 4.8827.96 ± 5.18
Prednisone, no. (%)31 (35)24 (38)
Plaquenil, no. (%)20 (22)18 (29)
Methotrexate, no. (%)52 (58)46 (73)
Biologic agents, no. (%)40 (45)27 (43)
Hypertension, no. (%)54 (61)24 (39)
Statin, no. (%)20 (22)5 (8)
DAS283.57 ± 1.053.68 ± 1.01
Log2(CRP + 1)1.99 ± 1.302.06 ± 1.35
Log2(TJC + 1), range 0–442.60 ± 1.482.79 ± 1.42
Log2(SJC + 1), range 0–422.68 ± 1.042.71 ± 1.09
Log2(HAQ + 1)0.66 ± 0.570.77 ± 0.52
Log2(IL-6 + 1)2.32 ± 1.012.14 ± 1.13
RF positive, no. (%)56 (63)33 (52)
CCP positive, no. (%)60 (68)40 (63)
Diabetes mellitus, no. (%)  
 Normal glucose (0)63 (71)54 (86)
 Impaired fasting glucose (1)17 (19)9 (14)
 Untreated diabetes mellitus (2)1 (1)0 (0)
 Treated diabetes mellitus (3)8 (9)0 (0)
Smoking, no. (%)  
 Never37 (42)30 (48)
 Former42 (47)28 (44)
 Current10 (11)5 (8)
Homocysteine9.96 ± 2.968.60 ± 2.21§
Systolic BP, mm Hg128.34 ± 16.91121.90 ± 17.49
Diastolic BP, mm Hg76.12 ± 9.1273.55 ± 8.68
Metabolic syndrome, no. (%)14 (16)4 (6)
Framingham risk score0.09 ± 0.070.05 ± 0.07

Levels of lipids, apolipoproteins, and lipoproteins in CAC progressors and nonprogressors.

Baseline plasma concentrations of lipids, apolipoproteins, and lipoproteins for the progressors and nonprogressors are shown in Table 1. Among the density-defined lipoprotein classes, levels of triglycerides and VLDL cholesterol, as well as the ratios of total cholesterol/HDL and triglycerides/HDL, were significantly higher in progressors than nonprogressors. Among the Apo B and Apo B–containing lipoprotein subclasses, progressors exhibited significantly higher levels of Apo B, LpA-II:B:C:D:E, LpB:C, and Apo B/Apo A-I than nonprogressors. There were no significant differences in levels of Apo A or Apo A–containing lipoprotein subclasses between progressors and nonprogressors. However, among Apo C-III and Apo C-III–containing lipoprotein subclasses, progressors exhibited significantly higher levels of Apo C-III and of Apo C-III bound to Apo B–containing lipoproteins (Apo C-III–HP) than nonprogressors.

Variables associated with progression of CAC.

The crude and adjusted ORs are presented in Table 3. The crude OR included: triglycerides, VLDL cholesterol, Apo B, LpA-II:B:C:D:E, LpB:C, Apo C-III, Apo C-III–HP, and triglycerides/HDL as being statistically significant. After adjusting the crude OR for age, sex, hypertension status, BMI, smoking, the use of statins, DMARDs, biologic agents, and steroids (Table 3), the following remained significantly associated with progression of CAC: triglycerides, VLDL cholesterol, Apo B, LpA-II:B:C:D:E, and LpB:C. Total cholesterol and LDL cholesterol became significantly associated after adjustment; however, triglycerides/HDL ratio and Apo C-III–HP lost significance from the adjustment. Supplementary Table 1 (available in the online version of this article at http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)2151-4658) displays the upper triangle of the Spearman's covariance matrix across the lipids, apolipoproteins, and lipoproteins. Due to the hierarchical biochemical nature of these peptides, they exhibit strong covariance. For example, Apo A-I has a correlation of 0.78 with LpA-I and of 0.99 with LpA-I:A-II. This is due to the fact that both LpA-I and LpA-I:A-II are members of the Apo A class.

Table 3. Crude and adjusted ORs for progressors vs. nonprogressors per SD increase in lipids, apolipoproteins, and lipoproteins*
 OR (95% CI)Adjusted OR (95% CI)
  • *

    Adjusting for age, sex, statin, hypertension, smoking, disease-modifying antirheumatic drugs, steroids, biologic agents, and body mass index. OR = odds ratio; 95% CI = 95% confidence interval; VLDL = very low-density lipoprotein; HDL = high-density lipoprotein; Apo = apolipoprotein; Lp = lipoprotein; HS = heparin soluble; HP = heparin precipitate.

  • P < 0.05.

  • P < 0.001.

  • §

    P < 0.01.

Total cholesterol1.25 (0.90–1.77)1.62 (2.62–1.05)
Triglycerides2.17 (1.33–3.86)2.05 (3.99–1.17)
VLDL cholesterol1.83 (1.24–2.87)§1.71 (2.84–1.11)
LDL cholesterol1.36 (0.96–1.95)1.44 (2.08–1.02)
HDL cholesterol0.79 (0.56–1.10)0.85 (1.24–0.57)
Apo B1.69 (1.18–2.50)§1.91 (3.19–1.22)
LpA-II:B:C:D:E1.50 (1.06–2.21)1.6 (2.61–1.03)
LpB:E+LpB:C:E1.19 (0.86–1.66)1.19 (1.75–0.82)
LpB1.31 (0.94–1.87)1.45 (2.23–0.98)
LpB:C1.68 (1.17–2.48)§1.69 (2.71–1.11)
Apo A-I0.81 (0.58–1.13)0.82 (1.31–0.5)
LpA-I0.96 (0.69–1.33)1.06 (1.69–0.67)
LpAI:A-II0.79 (0.56–1.10)0.79 (1.25–0.49)
Apo C-III1.59 (1.07–2.53)1.29 (1.96–0.89)
Apo C-III–HS1.32 (0.93–1.95)1.14 (1.63–0.82)
Apo C-III–HP1.64 (1.09–2.68)1.29 (2–0.87)
Apo C-III–Ratio0.84 (0.60–1.18)0.93 (1.26–0.68)
Apo B/Apo A-I0.94 (1.30–0.68)1.02 (1.5–0.7)
Total cholesterol/HDL0.85 (1.14–0.63)0.94 (1.33–0.66)
Triglycerides/HDL0.95 (1.36–0.66)§1.01 (1.65–0.7)

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES
  9. Supporting Information

The recent recognition of Apo C-III as a link between atherogenesis and inflammation has offered opportunity to explore whether this minor apolipoprotein plays a role in the accelerated atherosclerosis in RA patients. Since various classes of lipoproteins have different metabolic and atherogenic properties, based in large part on their apolipoprotein content, the corresponding subclasses of these lipoproteins were measured. To our knowledge, this is the first time subclasses of these lipoproteins were measured in patients with RA (11, 12). Using change in CAC over 3 years as a measure of progression of coronary atherosclerosis, we observed no statistically significant differences in baseline levels of Apo A-I, or of levels of LpA-I and LpA-I:A-II subclasses, between progressors and nonprogressors. Among Apo B–containing lipoprotein subclasses, there were also no baseline differences in the levels of cholesterol-rich LpB and LpB:E+LpB:C:E between progressors and nonprogressors. However, the levels of triglyceride-rich and Apo C-III–containing LpB:C and LpA-II:B:C:D:E subclasses were found to be significantly higher in progressors compared to nonprogressors. The levels of lipid and apolipoprotein constituents of these 2 subclasses, including triglycerides, VLDL cholesterol, Apo B, and Apo C-III–HP, were also significantly associated with CAC progression.

This recognition of Apo C-III–rich LpB:C and LpA-II:B:C:D:E subclasses as potential novel risk factors for progression of atherosclerosis in RA patients could be explained by the dual characteristics of Apo C-III as a major contributor to the atherogenicity of Apo B–containing lipoproteins on one hand and as an independent contributor to inflammatory processes on the other. We and others have shown in several clinical studies that Apo C-III–containing Apo B lipoproteins are independent risk factors for CV disease (19–23). The marked atherogenicity of LpB:C subclass reflects the metabolic properties of this lipoprotein subclass. Under normal metabolic conditions, the efficient lipolytic degradation of LpB:C particles results in low plasma concentrations of this lipoprotein. However, even a slight impairment in the formation and/or degradation of LpB:C, further exacerbated by the lack of binding activity to B/E receptors (16), results not only in increased plasma levels and residence time, but also in an enhanced uptake of these lipoprotein particles by macrophages (12, 38, 39). Due to a low affinity for lipoprotein lipase, LpA-II:B:C:D:E has a prolonged residence time in the circulation (40); although this subclass may be taken up by B/E receptors, its uptake by macrophages seems to be higher than that of LpB or LpB:E subclasses.

Kawakami and Yoshida have shown that Apo C-III itself rather than other apolipoproteins and lipids present in Apo C-III–rich VLDL caused the pro-adhesive effect (14, 41). Furthermore, lipids extracted from Apo C-III–containing VLDL did not increase monocytic adhesion. Since a number of previous studies have emphasized the role of lipid moieties as carriers of lipoprotein atherogenicity, Kawakami and Yoshida have clearly established that an apolipoprotein, such as Apo C-III, is a distinct contributor to inflammation and atherosclerosis.

If, indeed, LpB:C and LpA-II:B:C:D:E subclasses are to be considered as novel risk factors for progression of atherosclerosis in RA patients, their abnormal concentrations become targets for normalization. One may briefly speculate about the potential of available pharmacologic agents for affecting, if not normalizing, the levels of Apo C-III–containing LpB:C and LpA-II:B:C:D:E. At the present time, the main goal of therapeutic interventions has been to positively affect not only inflammatory mediators but especially lipid profiles as the most characteristic risk factors of CV disease in RA (9, 42, 43). Due to their well-established lipid-lowering effects and antiinflammatory properties, statins have been recommended and used almost exclusively in the therapeutic studies.

It should be emphasized that none of these studies dealt with the effects of statins on CV disease mortality of RA patients. In one of these studies, referred to as Trial of Atorvastatin in Rheumatoid Arthritis, 116 RA patients were randomized in a double-blind placebo-controlled study to atorvastatin (40 mg/day) or placebo as an adjunct to DMARD therapy (44). After 6 months of treatment, the levels of total cholesterol, triglycerides, and LDL cholesterol were significantly decreased, but there was no change in the levels of HDL cholesterol. More importantly, the DAS28 European League Against Rheumatism response was achieved in 18 (31%) of 58 patients on atorvastatin and 6 (10%) of 58 allocated to placebo. As concluded by the authors, atorvastatin can only mediate a modest outcome by clinically apparent antiinflammatory effects. In another study, based on 29 RA patients, atorvastatin (20 mg/day) significantly reduced arterial stiffness and the levels of total cholesterol and LDL cholesterol, but serum inflammatory markers remained unchanged (45). In a pilot study, treatment of 20 RA patients with atorvastatin (80 mg/day) for 12 weeks significantly reduced the levels of total cholesterol and LDL cholesterol, but had no significant effect on triglyceride levels (46). In a separate study of 20 RA patients, simvastatin (20 mg/day) and, separately, ezetimibe (10 mg/day) significantly reduced the levels of total cholesterol and LDL cholesterol, but not the triglycerides levels after 6 weeks of treatment. In addition, both simvastatin and ezetimibe reduced DAS28 scores, inflammatory markers, and aortic pulse valve velocity to a similar extent in RA patients (47). As stated by the authors, it still remains unanswered whether a reduction of arterial stiffness and improvement in endothelial dysfunction results in improved CV outcome in RA patients.

In the present study, only 25 or 16% of the total 152 RA patients were treated with statins; among this relatively small group of patients, 20 were progressors and only 5 were nonprogressors. There were no differences in the level of total cholesterol and total cholesterol–rich LpB subclass between progressors and nonprogressors receiving statins. However, the CAC progressors were characterized by higher levels of triglycerides, Apo B, Apo C-III–HP, LpB:C, LpB:E+LpB:C:E, and LpA-II:B:C:D:E than nonprogressors, indicating the prevalence of triglycerides and Apo C-III–containing Apo B lipoproteins as the major contributors to the acceleration of atherosclerosis in RA patients. While statins are very effective drugs in reducing the levels of total cholesterol–rich LpB and LpB:E subclasses, they seem to be less effective in lowering triglyceride-rich and Apo C-III–containing LpB:C, LpB:E+ LpB:C:E, and LpA-II:B:C:D:E subclasses (39, 48–50). In that respect, it has been shown in a recent study that fenofibrates displayed more antiinflammatory and antidyslipidemic activity than statins in RA patients (51).

The main weaknesses of this study are the relatively small number of progressors and nonprogressors, a short time interval (3 years) for following the number of progressors and nonprogressors, and a lack of a non-RA control group.

The strength of this study is that it has shown for the first time that Apo C-III–containing Apo B lipoproteins are risk factors for the progression of atherosclerosis in patients with RA. The next step would include confirmation of these results in another RA population, as well as a comparison to non-RA controls, and evaluation of the effects of a statin-fibrate combination on CV morbidity and mortality in RA patients.

AUTHOR CONTRIBUTIONS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES
  9. Supporting Information

All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be submitted for publication. Mr. Knowlton had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study conception and design. Knowlton, Centola, Giles, Bathon, Alaupovic.

Acquisition of data. Knowlton, Giles, Bathon, Alaupovic.

Analysis and interpretation of data. Knowlton, Wages, Giles, Bathon, Quiroga, Alaupovic.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES
  9. Supporting Information
  • 1
    Lawrence RC, Helmick CG, Arnett FC, Deyo RA, Felson DT, Giannini EH, et al. Estimates of the prevalence of arthritis and selected musculoskeletal disorders in the United States. Arthritis Rheum 1998; 41: 77899.
  • 2
    Wolfe F, Freundlich B, Straus WL. Increase in cardiovascular and cerebrovascular disease prevalence in rheumatoid arthritis. J Rheumatol 2003; 30: 3640.
  • 3
    Solomon DH, Karlson EW, Rimm EB, Cannuscio CC, Mandl LA, Manson JE, et al. Cardiovascular morbidity and mortality in women diagnosed with rheumatoid arthritis. Circulation 2003; 107: 13037.
  • 4
    Nicola PJ, Maradit-Kremers H, Roger VL, Jacobsen SJ, Crowson CS, Ballman KV, et al. The risk of congestive heart failure in rheumatoid arthritis: a population-based study over 46 years. Arthritis Rheum 2005; 52: 41220.
  • 5
    Reilly PA, Cosh JA, Maddison PJ, Rasker JJ, Silman AJ. Mortality and survival in rheumatoid arthritis: a 25-year prospective study of 100 patients. Ann Rheum Dis 1990; 49: 3639.
  • 6
    Del Rincon ID, Williams K, Stern MP, Freeman GL, Escalante A. High incidence of cardiovascular events in a rheumatoid arthritis cohort not explained by traditional cardiac risk factors. Arthritis Rheum 2001; 44: 273745.
  • 7
    Pasceri V, Yeh ET. A tale of two diseases: atherosclerosis and rheumatoid arthritis. Circulation 1999; 100: 21246.
  • 8
    Snow MH, Mikuls TR. Rheumatoid arthritis and cardiovascular disease: the role of systemic inflammation and evolving strategies of prevention. Curr Opin Rheumatol 2005; 17: 23441.
  • 9
    Toms TE, Symmons DP, Kitas GD. Dyslipidaemia in rheumatoid arthritis: the role of inflammation, drugs, lifestyle and genetic factors. Curr Vasc Pharmacol 2010; 8: 30126.
  • 10
    Myasoedova E, Crowson CS, Kremers HM, Fitz-Gibbon PD, Therneau TM, Gabriel SE. Total cholesterol and LDL levels decrease before rheumatoid arthritis. Ann Rheum Dis 2010; 69: 13104.
  • 11
    Alaupovic P. Apolipoprotein composition as the basis for classifying plasma lipoproteins: characterization of ApoA- and ApoB-containing lipoprotein families. Prog Lipid Res 1991; 30: 10538.
  • 12
    Alaupovic P. The concept of apolipoprotein-defined lipoprotein families and its clinical significance. Curr Atheroscler Rep 2003; 5: 45967.
  • 13
    Kawakami A, Aikawa M, Alcaide P, Luscinskas FW, Libby P, Sacks FM. Apolipoprotein CIII induces expression of vascular cell adhesion molecule-1 in vascular endothelial cells and increases adhesion of monocytic cells. Circulation 2006; 114: 6817.
  • 14
    Kawakami A, Aikawa M, Libby P, Alcaide P, Luscinskas FW, Sacks FM. Apolipoprotein CIII in apolipoprotein B lipoproteins enhances the adhesion of human monocytic cells to endothelial cells. Circulation 2006; 113: 691700.
  • 15
    Wang CS, McConathy WJ, Kloer HU, Alaupovic P. Modulation of lipoprotein lipase activity by apolipoproteins: effect of apolipoprotein C-III. J Clin Invest 1985; 75: 38490.
  • 16
    Clavey V, Lestavel-Delattre S, Copin C, Bard JM, Fruchart JC. Modulation of lipoprotein B binding to the LDL receptor by exogenous lipids and apolipoproteins CI, CII, CIII, and E. Arterioscler Thromb Vasc Biol 1995; 15: 96371.
  • 17
    Blackett PR, Blevins KS, Quintana E, Stoddart M, Wang W, Alaupovic P, et al. ApoC-III bound to apoB-containing lipoproteins increase with insulin resistance in Cherokee Indian youth. Metabolism 2005; 54: 1807.
  • 18
    Florez H, Mendez A, Casanova-Romero P, Larreal-Urdaneta C, Castillo-Florez S, Lee D, et al. Increased apolipoprotein C-III levels associated with insulin resistance contribute to dyslipidemia in normoglycemic and diabetic subjects from a triethnic population. Atherosclerosis 2006; 188: 13441.
  • 19
    Blankenhorn DH, Alaupovic P, Wickham E, Chin HP, Azen SP. Prediction of angiographic change in native human coronary arteries and aortocoronary bypass grafts: lipid and nonlipid factors. Circulation 1990; 81: 4706.
  • 20
    Alaupovic P, Mack WJ, Knight-Gibson C, Hodis HN. The role of triglyceride-rich lipoprotein families in the progression of atherosclerotic lesions as determined by sequential coronary angiography from a controlled clinical trial. Arterioscler Thromb Vasc Biol 1997; 17: 71522.
  • 21
    Sacks FM, Alaupovic P, Moye LA, Cole TG, Sussex B, Stampfer MJ, et al. VLDL, apolipoproteins B, CIII, and E, and risk of recurrent coronary events in the Cholesterol and Recurrent Events (CARE) trial. Circulation 2000; 102: 188692.
  • 22
    Gervaise N, Garrigue MA, Lasfargues G, Lecomte P. Triglycerides, apo C3 and Lp B:C3 and cardiovascular risk in type II diabetes. Diabetologia 2000; 43: 7038.
  • 23
    Lee SJ, Campos H, Moye LA, Sacks FM. LDL containing apolipoprotein CIII is an independent risk factor for coronary events in diabetic patients. Arterioscler Thromb Vasc Biol 2003; 23: 8538.
  • 24
    Giles JT, Szklo M, Post W, Petri M, Blumenthal RS, Lam G, et al. Coronary arterial calcification in rheumatoid arthritis: comparison with the Multi-Ethnic Study of Atherosclerosis. Arthritis Res Ther 2009; 11: R36.
  • 25
    Arnett FC, Edworthy SM, Bloch DA, McShane DJ, Fries JF, Cooper NS, et al. The American Rheumatism Association 1987 revised criteria for the classification of rheumatoid arthritis. Arthritis Rheum 1988; 31: 31524.
  • 26
    Carr JJ, Nelson JC, Wong ND, McNitt-Gray M, Arad Y, Jacobs DR Jr, et al. Calcified coronary artery plaque measurement with cardiac CT in population-based studies: standardized protocol of Multi-Ethnic Study of Atherosclerosis (MESA) and Coronary Artery Risk Development in Young Adults (CARDIA) study. Radiology 2005; 234: 3543.
  • 27
    Agatston AS, Janowitz WR, Hildner FJ, Zusmer NR, Viamonte M Jr, Detrano R. Quantification of coronary artery calcium using ultrafast computed tomography. J Am Coll Cardiol 1990; 15: 82732.
  • 28
    Prevoo ML, van 't Hof MA, Kuper HH, van Leeuwen MA, van de Putte LB, van Riel PL. Modified disease activity scores that include twenty-eight–joint counts: development and validation in a prospective longitudinal study of patients with rheumatoid arthritis. Arthritis Rheum 1995; 38: 448.
  • 29
    Wolfe F, Kleinheksel SM, Cathey MA, Hawley DJ, Spitz PW, Fries JF. The clinical value of the Stanford Health Assessment Questionnaire Functional Disability Index in patients with rheumatoid arthritis. J Rheumatol 1988; 15: 14808.
  • 30
    Van der Heijde D. How to read radiographs according to the Sharp/van der Heijde method. J Rheumatol 2000; 27: 2613.
  • 31
    Nettleton JA, Steffen LM, Mayer-Davis EJ, Jenny NS, Jiang R, Herrington DM, et al. Dietary patterns are associated with biochemical markers of inflammation and endothelial activation in the Multi-Ethnic Study of Atherosclerosis (MESA). Am J Clin Nutr 2006; 83: 136979.
  • 32
    Wang CS, Alaupovic P, Gregg RE, Brewer HB Jr. Studies on the mechanism of hypertriglyceridemia in Tangier disease: determination of plasma lipolytic activities, k1 values and apolipoprotein composition of the major lipoprotein density classes. Biochim Biophys Acta 1987; 920: 919.
  • 33
    Warnick GR, Albers JJ. A comprehensive evaluation of the heparin-manganese precipitation procedure for estimating high density lipoprotein cholesterol. J Lipid Res 1978; 19: 6576.
  • 34
    Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 1972; 18: 499502.
  • 35
    Riepponen P, Marniemi J, Rautaoja T. Immunoturbidimetric determination of apolipoproteins A-1 and B in serum. Scand J Clin Lab Invest 1987; 47: 73944.
  • 36
    Marz W, Trommlitz M, Gross W. Differential turbidimetric assay for subpopulations of lipoproteins containing apolipoprotein A-I. J Clin Chem Clin Biochem 1988; 26: 5738.
  • 37
    Hilpert KF, West SG, Kris-Etherton PM, Hecker KD, Simpson NM, Alaupovic P. Postprandial effect of n-3 polyunsaturated fatty acids on apolipoprotein B-containing lipoproteins and vascular reactivity in type 2 diabetes. Am J Clin Nutr 2007; 85: 36976.
  • 38
    Koren E, Koscec M, Corder C, Knight-Gibson C, Lee D, Alaupovic P. Differential atherogenicity of complex apo B-containing lipoprotein particles [abstract]. Atherosclerosis 1994; 109: 2178.
  • 39
    Alaupovic P, Heinonen T, Shurzinske L, Black DM. Effect of a new HMG-CoA reductase inhibitor, atorvastatin, on lipids, apolipoproteins and lipoprotein particles in patients with elevated serum cholesterol and triglyceride levels. Atherosclerosis 1997; 133: 12333.
  • 40
    Alaupovic P, Knight-Gibson C, Wang CS, Downs D, Koren E, Brewer HB Jr, et al. Isolation and characterization of an apoA-II-containing lipoprotein (LP-A-II:B complex) from plasma very low density lipoproteins of patients with Tangier disease and type V hyperlipoproteinemia. J Lipid Res 1991; 32: 919.
  • 41
    Kawakami A, Yoshida M. Apolipoprotein CIII links dyslipidemia with atherosclerosis. J Atheroscler Thromb 2009; 16: 611.
  • 42
    Gazi IF, Boumpas DT, Mikhailidis DP, Ganotakis ES. Clustering of cardiovascular risk factors in rheumatoid arthritis: the rationale for using statins. Clin Exp Rheumatol 2007; 25: 10211.
  • 43
    Giles JT, Post W, Blumenthal RS, Bathon JM. Therapy insight: managing cardiovascular risk in patients with rheumatoid arthritis. Nat Clin Pract Rheumatol 2006; 2: 3209.
  • 44
    McCarey DW, McInnes IB, Madhok R, Hampson R, Scherbakov O, Ford I, et al. Trial of Atorvastatin in Rheumatoid Arthritis (TARA): double-blind, randomised placebo-controlled trial. Lancet 2004; 363: 201521.
  • 45
    Van Doornum S, McColl G, Wicks IP. Atorvastatin reduces arterial stiffness in patients with rheumatoid arthritis. Ann Rheum Dis 2004; 63: 15715.
  • 46
    Charles-Schoeman C, Khanna D, Furst DE, McMahon M, Reddy ST, Fogelman AM, et al. Effects of high-dose atorvastatin on antiinflammatory properties of high density lipoprotein in patients with rheumatoid arthritis: a pilot study. J Rheumatol 2007; 34: 145964.
  • 47
    Maki-Petaja KM, Booth AD, Hall FC, Wallace SM, Brown J, McEniery CM, et al. Ezetimibe and simvastatin reduce inflammation, disease activity, and aortic stiffness and improve endothelial function in rheumatoid arthritis. J Am Coll Cardiol 2007; 50: 8528.
  • 48
    Alaupovic P, Attman PO, Knight-Gibson C, Mulec H, Weiss L, Samuelsson O. Effect of fluvastatin on apolipoprotein-defined lipoprotein subclasses in patients with chronic renal insufficiency. Kidney Int 2006; 69: 186571.
  • 49
    Nowakowska Fortuna E, Herlitz H, Saeed A, Attman PO, Jensen G, Alaupovic P, et al. Lipoprotein abnormalities in patients with atherosclerotic renovascular disease. Kidney Blood Press Res 2011; 34: 3119.
  • 50
    Schweitzer M, Tessier D, Vlahos WD, Leiter L, Collet JP, McQueen MJ, et al. A comparison of pravastatin and gemfibrozil in the treatment of dyslipoproteinemia in patients with non-insulin-dependent diabetes mellitus. Atherosclerosis 2002; 162: 20110.
  • 51
    Goto M. A comparative study of anti-inflammatory and antidyslipidemic effects of fenofibrate and statins on rheumatoid arthritis. Mod Rheumatol 2010; 20: 23843.

Supporting Information

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES
  9. Supporting Information

Additional Supporting Information may be found in the online version of this article.

FilenameFormatSizeDescription
ACR_21646_sm_Suppltable1.doc67KSupplementary Table 1

Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.