Statins And Biomarkers In Claudicants With Peripheral Arterial Disease: Cross-sectional Study

This exploratory substudy of The Iron (Fe) and Atherosclerosis Study (FeAST) compared baseline inflammatory markers, including cytokines, C-reactive protein (CRP), and ferritin, in subjects with peripheral arterial disease (PAD) taking statins with subjects with PAD who were not taking statins. Inflammatory markers in the serum of 47 subjects with PAD not taking statins and a healthy cohort of 21 medication-free men were compared with 53 PAD subjects taking statins at entry to the FeAST.

Healthy subjects demonstrated lower levels of tumor necrosis factor (TNF)-R1, interleukin-6 (IL-6), and CRP. TNF-α R1 averaged 2.28 ng/mL versus 3.52 ng/mL, p  =  .0025; IL-6 averaged 4.24 pg/mL versus16.61 pg/mL, p  =  .0008; and CRP averaged 0.58 mg/dL versus 0.92 mg/dL, p  =  .0192. A higher level of IL-6 was observed in PAD statin takers versus PAD subjects not taking statins: 19.47 pg/mL versus 13.24 pg/mL, p  =  .0455. As expected, total cholesterol and low-density lipoprotein levels were lower in the statin-treated group, p  =  .0006 and p  =  .0001, respectively. No significant differences in inflammatory cytokines were detected for varying doses of simvastatin. Additionally, no significant differences in inflammatory biomedical markers were found in subjects with PAD alone compared with those with concomitant coronary artery disease (CAD).

Unexpectedly, serum inflammatory cytokine IL-6 levels were significantly higher in PAD subjects receiving statins. There was no difference in measured inflammatory markers in PAD subjects with concomitant CAD.

Cytokine signatures in atherosclerotic claudicants

BACKGROUND

Iron accumulation and inflammation may affect atherosclerosis. This study intended to define a cytokine signature in atherosclerotic claudicants and to determine whether reduction in serum ferritin by phlebotomy influenced this pattern.

METHODS

Ninety-one subjects with peripheral vascular disease (PVD; mean age, 67 years) were recruited from the VA Cooperative Iron and Atherosclerosis Study (FeAST) testing the hypothesis that ferritin reduction to 25 ng/ml may ameliorate atherosclerosis. Cytokines TNF-a, IL-2, IL-6, and IL-10 were analyzed by enzyme amplified sensitivity assay (EASIA). Fasting iron and cholesterol panels, complete blood count, C-reactive protein (CRP), uric acid, fibrinogen, glucose, and hemoglobin A1c levels were also quantified. Values were compared with "healthy" controls (n = 21; mean age, 56 years). After randomization of PVD to phlebotomy (intervention group [IG], n = 44) or control (nonintervention group [NG], n = 47), analyses were compared at 6 and 12 months using t test, Wilcoxon rank sum test, chi-square, and robust MM regression.

FINDINGS

Age, glucose, and hemoglobin A1c were higher in PVD compared with healthy controls (P < 0.01), whereas serum iron (P < 0.01) and percentage of transferrin saturation (P < 0.05) were lower. Tumor necrosis factor-alpha (TNF-alpha; P < 0.05), IL-6 (P < 0.01), and CRP (P < 0.05) levels were higher in the PVD group, whereas IL-10 was lower (P < 0.01). At 6 months post phlebotomy, ferritin levels were reduced (P < 0.01), although ferritin levels were reduced less in smokers. IL-6 and fibrinogen, CRP and ferritin levels correlated positively. At 6 and 12 months, subjects with TNF-alpha (n= 15) and IL-6 (n = 10) levels in the upper 25th percentile were reduced by phlebotomy.

INTERPRETATION

An inflammatory cytokine signature exists in atherosclerosis. Elevated levels of TNF-alpha and IL-6, reportedly associated with recurrent and future myocardial infarction, were reduced by phlebotomy. The utility of the iron/inflammatory hypotheses will ultimately relate to clinical outcomes obtained prospectively by the FeAST trial.

Effect of thyroidectomy on 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced lipid peroxidation

Thyroid hormones have been implicated in the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Therefore, the effects of methimazole (MMI) and propylthiouracil (PTU) induced hypothyroidism and surgical thyroidectomy on several toxic manifestations of TCDD were investigated. Female rats were treated with MMI (0.50 mg/kg) for 10 or 28 days, or PTU (5.0 mg/kg) for 10 days. Other animals were surgically thyroidectomized. The animals received TCDD (100 micrograms/kg) orally or the corn oil vehicle 6 days prior to sacrifice. MMI and PTU decreased serum thyroxine (T4) levels by 27-33% while surgical thyroidectomy decreased T4 levels by 66%. TCDD alone decreased T4 levels by 67%, and similar effects occurred in MMI and PTU treated animals. TCDD produced a 9% increase in serum triiodothyronine (T3) concentrations, and neither MMI or PTU treatment for 10 days modified this effect. Neither antithyroid drug prevented TCDD induced weight loss. TCDD administration resulted in over a 300% increase in hepatic malondialdehyde (MDA) content and a 60% decrease in glutathione peroxidase activity. Neither antithyroid compound affected TCDD-induced alterations in these two parameters. TCDD enhanced MDA content by 220% and inhibited glutathione peroxidase activity by 39% in surgically thyroidectomized rats. Thus, only severe hypothyroidism produced by surgical thyroidectomy was able to partially prevent the effects of TCDD on hepatic MDA content and glutathione peroxidase activity.

Glutathione peroxidase and reactive oxygen species in TCDD-induced lipid peroxidation

Previous studies have shown that high doses of TCDD induce hepatic lipid peroxidation and inhibit selenium dependent glutathione peroxidase (GSH-Px) activity. The dose dependent effects of TCDD on hepatic lipid peroxidation (malondialdehyde content) and GSH-Px activity were determined. A dose as low as 1 microgram/kg induced hepatic lipid peroxidation and inhibited GSH-Px. Based on the use of scavengers of reactive oxygen species, lipid peroxidation (malondialdehyde formation) by hepatic microsomes from both control and TCDD-treated rats appears to be due primarily to H2O2. The results indicate that superoxide, hydroxyl radical and singlet oxygen are also involved. The differences in the reactive oxygen species involved in microsomal lipid peroxidation between control and TCDD treated animals appear to be quantitative rather than qualitative. A 5.9-fold greater rate of malondialdehyde (MDA) formation by microsomes from TCDD treated animals occurred as compared to controls, while livers of TCDD rats had an MDA content that was 5.0-fold greater than the controls. These differences may be due in part to an enhanced production of H2O2 as well as a decrease in the activity of selenium dependent glutathione peroxidase which metabolizes H2O2.