Design and Participants
The study was performed in a prospective, randomized design. In order to minimize the effect of seasonal changes on 25-hydroxyvitamin D levels, the study was conducted between October 2008 and March 2009. All of the patients enrolled in the study were living in Ankara, where these months are considered to be winter, with little exposure to ultraviolet light.
The study population consisted of 134 hyperlipidemic patients who had not previously been treated with lipid lowering medications. Patients with a fasting low-density lipoprotein-cholesterol (LDL-C) > 100 mg/dL after 6 weeks of National Cholesterol Education Program (NCEP) diet were considered hyperlipidemic and enrolled in the study . Patients were randomized in a 1:1 ratio to rosuvastatin 10 mg (Crestor) or fluvastatin 80 mg XL (Lescol XL) during the trial. Eligible subjects underwent a comprehensive medical assessment including documentation of the detailed history, physical examination, and measurement of the essential laboratory variables. Exclusion criteria were alcoholism (>20 g/day alcohol), malignancy (all types of malignancy including basal cell carcinoma), hypercalcemia, hypocalcemia, and hyperparathyroidism. Patients who were on phosphorus-calcium modifying drugs before and after treatment were excluded. Patients who were already receiving fibrate or other statins were also excluded.
According to NCEP ATP III guideline, rosuvastatin (10 mg) (Crestor) or fluvastatin 80 mg XL (Lescol XL) were given to the subjects as primary or secondary prevention. Lipid parameters, 25-hydroxyvitamin D, renal and liver function tests, electrolytes, bone alkaline phosphatase (B-ALP) were obtained at the baseline and after 8 weeks of treatment. The Local Ethics Committee approved the study, and all patients gave informed consent.
Fasting blood samples were obtained by the venipuncture of the large antecubital veins of the studied patients without stasis, after a 12-h fast. The samples were then centrifuged immediately; the serum and plasma (EDTA) were separated and stored at −80°C. In order to avoid variation, all samples were studied on the same day and the same kit.
The measurements of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) employing the routine procedures were performed at 37°C on a Konelab analyzer (Konelab 60İ, Thermo Scientific, Vantaa, Finland) with commercial test kits from Thermo Scientific following the IFCC reference methods. The serum creatinine was measured with the alkaline picrate (Jaffe) method (Lot No: C092, Konelab).
Serum cholesterol (Lot No: B540, Konelab) levels were measured by cholesterol oxidase without triglyceride blank. The measurement range is 0.2–15.0 mmol/L and extended measuring range after secondary dilution is 0.2–45.0 mmol/L. The within run and betweenday CV (Coefficient of variation) are 1.1–2.0%, respectively, at 3.9 mmol/L and 0.9–0.9% at 6.3 mmol/L.
Triglyceride (Lot No: C186, Konelab) levels were measured with enzymatic (glycerol phosphate oxidase and peroxidase) colorimetric method. The measurement range is 0.05–11.0 mmol/L and extended measuring range after secondary dilution is 0.05–55.0 mmol/L. The within run and betweenday CV are 1.0–2.5%, respectively, at 1.10 mmol/L and 1.0–2.5% at 2.84 mmol/L.
Low-density lipoprotein-cholesterol (Lot No: C435, Konelab) were measured with the homogeneous enzymatic colorimetric test, where in the presence of magnesium ions, a sugar compound markedly reduced the enzymatic reaction for the cholesterol measurement in VLDL and chylomicrons. The combination of a sugar compound with detergent enables the selective determination of LDL-cholesterol in serum. The measurement range is 0.09–11.0 mmol/L and extended measuring range after secondary dilution is 0.09–33.0 mmol/L. The within run and betweenday CV are 1.1–1.1%, respectively, at 2.64 mmol/L and 0.9–1.3% at 4.86 mmol/L.
HDL-C (Lot No: C136, Konelab) were measured with the homogeneous enzymatic colorimetric test, where in the presence of magnesium, dextran sulfate selectively forms water-soluble complexes with LDL, VLDL, and chylomicrons, which are resistant to PEG (Polyethylene glycol) modified enzymes. The concentration of HDL-cholesterol is determined enzymatically by cholesterol oxidase coupled with PEG. The measurement range is 0.16–2.80 mmol/L and extended measuring range after secondary dilution is 0.16–8.40 mmol/L. The within run and betweenday CV are 0.5–1.6%, respectively, at 1.26 mmol/L and 0.6–1.7% at 2.40 mmol/L.
Osteocalcin was measured with Immulite 1000 (Siemens Healthcare Diagnostics IL, USA) by using osteocalcin kit (Catalog No: LKON1). Serum 25-hydroxyvitamin D and B-ALP levels were measured by RIA. 25OH-VIT.D3-RIA-CT kit (Catolog No: KIP1961) (Biosource, Neville, Belgium) was used. Bone alkaline phosphatase level was measured by Ostease IRMA kit (Immunotech, Beckman Coulter, Inc. Fullerton, CA, USA).
Distribution of the continuous variables was determined by the Kolmogorov–Smirnov test. Continuous variables with normal distribution were expressed as mean ± SD. Variables with skew distribution are expressed as median (minimum–maximum), and categorical variables are expressed as percentage. Pearson chi-square test or Fischer test were performed for the comparison of categorical variables. The paired sample t-test was used to compare normally distributed variables, and the Wilcoxon rank-sum test for skew distributed variables. Pearson or Spearman analysis, where appropriate, was used to identify correlations between study parameters. For all statistics, a two-sided P value < 0.05 was considered to be statistically significant. All analyses were performed with SPSS 10.0 for Windows (SPSS Inc., Chicago, IL, USA).