Author + information
- Received February 2, 2006
- Revision received April 20, 2006
- Accepted April 23, 2006
- Published online July 18, 2006.
- Joseph B. Muhlestein, MD, FACC⁎,†,⁎ (, )
- Heidi T. May, MSPH⁎,
- Jonathan R. Jensen, BS⁎,
- Benjamin D. Horne, PhD, MPH⁎,
- Richard B. Lanman, MD‡,
- Farangis Lavasani, FNP⁎,
- Robert L. Wolfert, PhD‡,
- Robert R. Pearson, BS⁎,
- H. Daniel Yannicelli, MD§ and
- Jeffrey L. Anderson, MD, FACC⁎,†
- ↵⁎Reprint requests and correspondence:
Dr. J. Brent Muhlestein, LDS Hospital Cardiovascular Department, 8th Avenue and C Street, Salt Lake City, Utah 84143.
Objectives The primary objective was to determine the effect of statin-fibrate combination therapy on inflammatory biomarkers in patients with diabetes.
Background Atherosclerosis is a long-term, chronic inflammatory disease that is exacerbated in patients with diabetes.
Methods Patients (n = 300) with type II diabetes, mixed dyslipidemia (2 or more of low-density lipoprotein ≥100 mg/dl, triglycerides ≥200 mg/dl, or high-density lipoprotein <40 mg/dl), and no history of coronary heart disease were randomly assigned to receive simvastatin 20 mg, fenofibrate 160 mg, or a combination of simvastatin 20 mg and fenofibrate 160 mg daily. At 12 weeks after randomization, we measured levels of high-sensitivity C-reactive protein (hsCRP) and lipoprotein-associated phospholipase A2(Lp-PLA2).
Results At 12 weeks, median hsCRP was significantly reduced (−14.6%, p = 0.004) from baseline, but the effect did not differ between treatments. The effect was greatest among patients with baseline hsCRP levels >2.0 mg/l (fenofibrate = −18.9%, p = 0.002 vs. baseline; simvastatin = −24.8%, p < 0.0001; combination = −27.3%, p = 0.002). Likewise, median Lp-PLA2levels in the overall study population were significantly reduced (−16.8%, p < 0.0001), and the effect did not differ among treatments. This effect also was greatest among patients with increased baseline levels of Lp-PLA2greater than the median of 320.9 ng/ml (fenofibrate = −41.3%, p < 0.0001; simvastatin = −47.5%, p < 0.0001; combination = −46.8%, p < 0.0001).
Conclusions Simvastatin, fenofibrate, and combination therapy each lowered hsCRP and Lp-PLA2. These anti-inflammatory effects were most pronounced among patients with increased baseline levels. Combination therapy was no more effective than either form of monotherapy. (The DIACOR Study; http://www.clinicaltrials.gov/ct/show/NCT00309712?order=1)
Diabetes mellitus confers a 2- to 4-fold increase in cardiovascular risk compared with the general population (1). Although microvascular complications of diabetes result in increased rates of morbidity, macrovascular complications, including coronary artery disease, often cause death (2). Cardiovascular disease and diabetes are both associated with elevated levels of inflammatory biomarkers, including C-reactive protein (CRP) (3). C-reactive protein is the most well-studied inflammatory marker of atherothrombotic risk (4) and is incremental to the Framingham Risk Score (5). Lipoprotein-associated phospholipase A2(Lp-PLA2) is a newer inflammatory biomarker that has been proposed to be more specific to vascular inflammation.
Statin and fibrate therapy have been shown to variably lower levels of CRP (6,7), as well as levels of Lp-PLA2(8). However, the influence of a statin and fibrate combination on levels of inflammatory markers requires further investigation (9,10). Therefore, among patients with type II diabetes, we assessed the effect of statin, fibrate, and combination therapy on inflammatory biomarkers in the DIACOR (Diabetes and Combined Lipid Therapy Regimen) study.
Patients with a clinical diagnosis of type II diabetes mellitus and biochemical evidence of mixed dyslipidemia were considered for enrollment in the study. The study protocol was approved by the institutional review board, and all patients provided written informed consent. Patients meeting prescreening criteria were required to undergo washout if currently receiving lipid therapy. A complete list of inclusion/exclusion criteria is found in Table 1.
We undertook a single-center, randomized, double-blind, and placebo-controlled 12-week study. Those participants satisfying all inclusion/exclusion criteria were assigned randomly to receive 1 of 3 daily oral treatments: simvastatin 20 mg taken in the evening/fenofibrate placebo taken in the morning with food, fenofibrate 160 mg taking in the morning with food/simvastatin placebo taken in the evening, or simvastatin 20 mg taken in the evening and fenofibrate 160 mg taken in the morning with food. Coordinators, investigators, statistical personnel, and patients remained blinded to patient treatment assignment.
Follow-up visits were scheduled 6 and 12 weeks after randomization, where assessment of adverse events and 12-h fasting laboratory measurements were made. A creatine kinase was drawn if the patient complained of any muscle aches at those visits or at any time throughout the study period.
Laboratory samples were analyzed in an Intermountain Healthcare laboratory (LDS Hospital, Salt Lake City, Utah, or McKay Dee Hospital, Ogden, Utah). Total cholesterol and triglycerides were quantified using dry-slide measurement on the VITROS 950 Analyzer (Ortho Clinical Diagnostics, Raritan, New Jersey). High-density lipoprotein cholesterol (HDL-C) was measured with the same instrument after treatment with VITROS HDL-Cholesterol Magnetic Reagent (Ortho Clinical Diagnostics); low-density lipoprotein cholesterol (LDL-C) was calculated from the total cholesterol and triglyceride measurements.
The concentration of high-sensitivity C-reactive protein (hsCRP) was determined using an immunoturbidimetric assay on the Hitachi 917 analyzer (Roche Diagnostics, Indianapolis, Indiana), using reagents and calibrators from Denka Seiken (Niigata, Japan). This assay has a sensitivity of 0.03 mg/l. The day-to-day variability of the assay at concentrations of 0.91 mg/l, 3.07 mg/l, and 13.38 mg/l are 2.81%, 1.61%, and 1.1%, respectively. Any patient with an hsCRP >10 mg/l was excluded from the analysis. We measured Lp-PLA2by using the PLAC test (diaDexus, Inc., San Francisco, California), and testing was performed at diaDexus, Inc., as described in the package insert, a modification of the originally published protocol (11).
This study was designed to provide an 80% power to detect a 20% difference in achievement of the primary study end point (percent of patients achieving triglyceride levels of <200 mg/dl after 12 weeks of treatment, which results are not described here) among study treatments with 100 patients in each group. Analysis was performed blinded by assigning each patient a letter (A, B, or C) that corresponded to their treatment group using the intention-to-treat model. Descriptive statistics were used to summarize characteristics of the study population and biomarker measurements. For evaluations of concentrations of triglycerides, hsCRP, and Lp-PLA2, these variables were transformed using the natural logarithm to normalize the distributions before within-group analyses. Differences in baseline and 12-week levels were evaluated using the paired ttest. The effect of study therapy on mean percent reduction from baseline levels of lipids, hsCRP, and Lp-PLA2was analyzed using analysis of variance and the Tukey’s HSD test. Pearson’s correlation coefficient was used to determine correlations among percent change at 12 weeks for hsCRP, Lp-PLA2, and individual lipid parameters. Two-tailed p values are presented, with 0.05 designated as nominally significant.
Table 2summarizes the baseline characteristics of the overall study population (n = 300) and also among each treatment group. Overall, significant changes between baseline and 12 weeks were found in median levels of hsCRP: 2.11 and 1.81 mg/l (−14.6%, p = 0.004); of Lp-PLA2: 320.9 and 229.4 ng/ml (−33.2%, p < 0.0001); of triglycerides: 260.0 and 160.0 mg/dl (−36.2%, p < 0.0001); in mean levels of total cholesterol: 228.7 and 176.9 mg/dl (−21.6%, p < 0.0001); of LDL-C: 137.9 and 101.9 mg/dl (−23.2%, p < 0.0001); of HDL-C: 36.6 and 40.3 mg/dl (+11.3%, p < 0.0001); and of non–HDL-C: 192.1 and 136.2 (−27.6%, p < 0.0001), respectively. Table 3shows levels of hsCRP, Lp-PLA2, and lipids at baseline and 12 weeks with their percent change by treatment group. Table 4displays comparisons of absolute changes among treatment groups for their ability to modify lipids, hsCRP, and Lp-PLA2. No significant difference in effect on either inflammatory marker was noted between treatment groups. For those missing 12-week information (n = 10), analysis using 6-week information was performed and did not alter the results.
For those with increased levels of baseline hsCRP (>2.0 mg/l, n = 141), the median percent change within each treatment arm was greater and highly significant (Fig. 1).For these patients, median hsCRP levels within each treatment at baseline and 12 weeks were fenofibrate = 4.05 and 2.79 mg/l, simvastatin = 3.88 and 2.83 mg/l, and combination = 3.98 and 2.93 mg/l, respectively. Likewise, the percent reduction of Lp-PLA2was greatest among those with baseline levels greater than the median of 320.9 (n = 137) (Fig. 2).For patients with Lp-PLA2greater than the median, median levels at baseline and 12 weeks were fenofibrate = 459.3 and 237.9 ng/ml, simvastatin = 434.9 and 231.9 ng/ml, and combined = 439.1 and 228.2 ng/ml, respectively.
The percent change of hsCRP was not correlated with the percent change of Lp-PLA2or any lipids. A decrease in Lp-PLA2was significantly correlated with a decrease in total cholesterol (r = 0.46, p < 0.001), LDL-C (r = 0.35, p < 0.001), and non–HDL-C (r = 0.45, p < 0.001) with simvastatin but not with fenofibrate or combination therapy (Fig. 3).No other treatments correlated significantly with inflammatory markers and lipids.
Clinical adverse events were similar among all treatment groups. There were no cases of rhabdomyolysis, clinical myopathy (creatine kinase >10 upper limit of control), persistent myalgias, or adverse liver-related events, even among those subjects who dropped out of the study (n = 19). No serious drug-related clinical adverse events were noted throughout the study.
In this double-blind, placebo-controlled randomized study of 300 dyslipidemic patients with type II diabetes, we observed highly significant modifications in plasma concentrations of Lp-PLA2, total cholesterol, LDL-C, HDL-C, triglycerides, and non–HDL-C in addition to a trend toward reduction of hsCRP by the combination therapy of simvastatin and fenofibrate. Combination therapy was not more effective in modifying levels of hsCRP and Lp-PLA2than either simvastatin or fenofibrate monotherapy; however, it was superior in reducing total cholesterol, LDL-C, and non–HDL-C concentrations compared with fenofibrate and in reducing triglyceride levels compared with simvastatin.
Four points contribute to the clinical relevance and importance of this study. 1) The magnitude of reduction by fenofibrate, simvastatin, and combination therapy was greatest when concentrations of hsCRP and Lp-PLA2were increased >2.0 mg/l and the median value of 320.9 ng/ml, respectively. 2) The ability of fenofibrate to lower hsCRP was comparable with simvastatin and combination therapy. 3) Reductions of hsCRP were not correlated with any other lipid parameter or Lp-PLA2by any treatment. 4) Reduction of Lp-PLA2was significantly correlated with reductions in total cholesterol, LDL-C, and non–HDL-C by simvastatin. The extent of correlation to the reduction of LDL is similar to that reported by Albert et al. (12) in the PRINCE (Effect of Statin Therapy on C-Reactive Protein Levels: The Pravastatin Inflammation/CRP Evaluation) study.
The important reported relationship between hyperlipidemia, chronic inflammation, and cardiovascular risk, as demonstrated by the strong association among concomitant reductions in lipids (LDL-C to <70 mg/dl) and inflammatory markers (hsCRP to <2 mg/l) and cardiovascular risk (13), deserves further investigation, as also does the potentially vascular specific inflammatory marker and direct vascular toxin Lp-PLA2. Little is known regarding the effect of combination therapy on inflammatory biomarkers, including hsCRP, but particularly for Lp-PLA2. Koh et al. (9) examined the effect of atorvastatin, fenofibrate, and the combination of atorvastatin and fenofibrate on hsCRP in patients with hyperlipidemia. Our study, as well as the study by Koh et al. (9), found all therapies reduced hsCRP levels from baseline; however, the magnitude of the reduction was similar among all therapies. Our study is the first to report reductions of Lp-PLA2by combination therapy. As with hsCRP, all treatments significantly reduced Lp-PLA2concentrations from baseline to 12 weeks, with reductions being similar among treatments. Why there was no greater effect on these inflammatory markers from combination compared with either monotherapy is not known. Although statins and fibrates have different mechanisms of action in relationship to lipid metabolism, it is possible that they both exert a similar non–dose-responsive effect on inflammation. Therefore, the combination therapy would have no greater effect than either monotherapy.
Among type II diabetic patients with mixed dyslipidemia, fenofibrate, simvastatin, and combination therapy, the use of each lowered hsCRP and Lp-PLA2. Of interest, combination therapy was no more effective than either form of monotherapy. These anti-inflammatory effects were most pronounced among patients with elevated baseline inflammation levels. Likewise, combination therapy significantly altered lipid concentrations, with combination therapy exerting a greater positive combined effect on total cholesterol, triglycerides, and non–HDL-C than either monotherapy.
Supported by Abbott Laboratories, Inc., Abbott Park, Illinois; in-kind support of Merck & Co., Inc., Horsham, Pennsylvania, and diaDexus Inc., San Francisco, California. Dr. Yannicelli is employed by Abbott Laboratories, and Dr. Wolfert and Dr. Lanman are employed by diaDexus.
- Abbreviations and Acronyms
- C-reactive protein
- high-density lipoprotein cholesterol
- high-sensitivity C-reactive protein
- low-density lipoprotein cholesterol
- lipoprotein-associated phospholipase A2
- Received February 2, 2006.
- Revision received April 20, 2006.
- Accepted April 23, 2006.
- American College of Cardiology Foundation
- American Heart Association
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