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Impact of cardiac magnetic resonance on endothelial function in type 2 diabetic patients
Atherosclerosis 239 (2015) 131e136
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Impact of cardiac magnetic resonance on endothelial function in type 2 diabetic patients Guangda Xiang a, *, Lin Xiang a, Honglin He b, Junxia Zhang a, Jing Dong a a b
Department of Endocrinology, Wuhan General Hospital of Guangzhou Command, Wuluo Road 627, Wuhan 430070, Hubei, China Department of Radiology, Wuhan General Hospital of Guangzhou Command, Wuluo Road 627, Wuhan 430070, Hubei, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 24 July 2014 Received in revised form 30 November 2014 Accepted 9 December 2014 Available online 13 January 2015
Objectives Recent studies have shown that cardiac magnetic resonance (CMR) scanning is associated with cellular DNA damage. The aim of the present study was to assess the impact of CMR scanning on endothelial function in Chinese men with type 2 diabetes. Methods A randomized, single-blind, parallelgroup study was conducted in 60 Chinese men with type 2 diabetes treated with or without CMR (CMR and sham CMR group), and the changes of endothelial function before and after CMR were compared. High-resolution ultrasound was used to measure flow-mediated endothelium-dilation (FMD) of the brachial artery. Results The FMD in CMR group at Day 1 after CMR was 3.60%, which was significantly lower than that (3.85%) in sham CMR group (p < 0.001). The levels of C-reactive protein (CRP), thiobarbituric acid-reactive substances (TBARS), tumor necrosis factor alpha (TNF-a) and interleukin-6(IL-6) in CMR group were significantly higher than those in sham CMR group at Day 1 (p < 0.001). But these characteristics did not differ between two groups at baseline, Day 2 and Day 3 (p > 0.05). Linear correlation and multiple regression analyses showed that CRP, TBARS, TNF-a and IL-6 were associated with FMD in the CMR group (p < 0.01). Conclusions The present data showed that CMR scanning can reversibly suppress endothelial function, probably through the increased production of oxygen-derived free radicals and inflammatory reactions in Chinese men with type 2 diabetes, indicating that CMR should be used with caution in order to avoid unnecessary damage to the endothelium. Clinical Trial Registration URL: https://register.clinicaltrials.gov/, Unique Identifier: NCT02001753. © 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: Cardiac magnetic resonance Endothelial function Type 2 diabetes Oxidative stress
Magnetic resonance (MR) imaging is an established clinical diagnostic tool with the number of systems installed world-wide approaching 4000 [1]. By using a static and a gradient magnetic field in combination with a radiofrequency field, MR provides excellent contrast among different tissues of the body including the brain, musculoskeletal system, and heart. Although long-term effects on human health from exposure to strong static magnetic
Abbreviation: BMI, Body mass index; CMR, cardiac magnetic resonance; CRP, Creactive protein; FMD, flow-mediated vasodilation; FBG, fasting blood glucose; GTN, glyceryl trinitrate; HDL-C, high-density lipoprotein cholesterol; HbA1c, haemoglobinA1c; IL-6, interleukin-6; LDL-C, low-density lipoprotein cholesterol; MR, magnetic resonance; 2h-BG, postprandial 2 h glucose; TC, total cholesterol; TG, triglyceride; TBARS, thiobarbituric acid reactive substances; TNF-a, tumor necrosis factor-alpha; UAER, urinary albumin excretion rate; WHO, World Health Organization. * Corresponding author. E-mail addresses: [email protected] (G. Xiang), Xianglin832010@ hotmail.com (L. Xiang), [email protected] (H. He), [email protected] (J. Zhang), [email protected] (J. Dong). http://dx.doi.org/10.1016/j.atherosclerosis.2014.12.028 0021-9150/© 2014 Elsevier Ireland Ltd. All rights reserved.
fields seem unlikely [2], acute effects such as vertigo, nausea, change in blood pressure, reversible arrhythmia [3], and neurobehavioural effects have been documented from occupational exposure to 1.5 T [4]. Cardiac magnetic resonance (CMR) is a noninvasive tool that provides high-resolution, three-dimensional images of the heart; CMR requires some of the strongest and fastest switching electromagnetic gradients available in MR, exposing patients to the highest administered energy levels accepted by the controlling authorities [5]. Studies focusing on the experimental teratogenic [6e10] or carcinogenic [11e13] effects of MR have revealed conflicting results. Since CMR is emerging as one of the fastest growing new fields of broad MR application [14], it is of particular concern that a recent in vitro study with CMR sequences has reported CMRinduced DNA damage in white blood cells up to 24 h after exposure to 1.5 T CMR [5]. Moreover, one in vivo study showed that contrast CMR scanning in daily clinical routine is associated with increased lymphocyte DNA damage [15]. However, to date, no data are available on the relationship between CMR and endothelial
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dysfunction, especially in diabetic conditions. Therefore, the aim of the present study was to assess the impact of routine CMR scanning on endothelial function in Chinese men with type 2 diabetes.
1. Subjects and methods 1.1. Subjects From Dec. 2013 to Feb. 2014, the newly diagnosed Chinese type 2 diabetic men, who had been referred to our hospital for diabetic evaluation, were identified as potentially eligible subjects (540 cases). The type 2 diabetes was diagnosed according to the World Health Organization (WHO) 1999 criteria. Of them, a total of 60 eligible Chinese type 2 diabetic men, aged 40e65 years old (mean 54 ± 7 years old), were included in this study. Patients with clinical angiopathy including micro- and macroangiopathy as well as hypertension were excluded from this study. Microangiopathy included nephropathy [urinary albumin excretion rate (UAER) > 20 mg/min], retinopathy (at least one microaneurysm or hemorrhage or exudates in either eye), and neuropathy (pain in the extremities, paresthesias, absent tendon reflexes, and/or absent vibration sensation); and macroangiopathy included coronary artery disease (myocardial infarction, ischemia electrocardiogram changes, and angina), cerebrovascular disease (transient ischemic attack or stroke), and peripheral vascular disease (the abolition of one or more peripheral arterial pulses, and/or intermittent claudication, and/or a past history of revascularization of the lower limbs). The recruited patients were all required to have an office blood pressure (BP) < 140/90 mm Hg, which was measured by a trained nurse. After at least a 5-min rest, two successive readings were taken from the right arm using a mercury manometer with a 12-cm by 33.5-cm cuff. During the same period, 28 healthy men (all from the medical staff in our hospital), who had had a normal glucose tolerance, were selected as control subjects. Subjects who were obese [body mass index (BMI) > 30 kg/m2], or smokers, or had malignant neoplasms, renal or liver diseases, or endocrinological diseases other than diabetes were excluded from the study. In addition, no patients were taking any drugs, such as oestrogen supplements, thyroxine, diuretics, diabetic medications, antihypertensive and hypolipidaemic drugs. All subjects enrolled in the study gave their informed consent. The study protocol was in agreement with the guidelines of the ethics committee at our hospital. Two to three days before the beginning of the study, advice on a standard, well-balanced, controlled diet was given to all the eligible subjects. Diabetic patients were then scheduled to undertake a 4-day randomized, single-blind, parallel-group trial of investigations with or without CMR scanning. The patients were divided randomly into two groups, 30 cases in each group (the CMR group and sham CMR group). In the CMR group, CMR scanning for evaluation of left ventricular mass was performed at 8e10 AM; in the sham CMR group, all subjects remained in the supine position in the same MR machine scanner at 8e10 AM and the patients were not subjected to the pulse sequences of a typical examination. Our previous studies showed that oxidative stress and inflammation as well as blood glucose are associated with endothelial dysfunction [16e19], therefore, the examinations of vascular function, blood glucose, oxidative stress, and inflammation were performed at 1 day (baseline) before and at 1 day (Day 1), 2 days (Day 2), 3 days (Day 3) after the CMR procedure for the CMR group or the sham CMR procedure for the without CMR group. Only a one-time examination was performed for the healthy controls at baseline.
2. Methods 2.1. CMR scanning The CMR imaging was performed on a 1.5-T Magnetom Avanto scanner (Siemens, Erlangen, Germany) for the CMR group. Serial contiguous short-axis cines were acquired from the vertical long axis and horizontal long axis of the left ventricle [electrocardiogram gated, steady-state free precession imaging (true fast imaging with steady-state precession), with the short-axis imaging parameters being a repetition time of 2.5 ms, echo time of 1.1 ms, flip angle of 60 , and slice thickness of 6 mm]. Regarding the procedure for the sham CMR group, the patients only stayed in the scanner for the same length of time as subjects in the CMR group. 2.2. Brachial artery ultrasonography Brachial artery ultrasonography was performed noninvasively, as previously described by us [16,17]. High resolution ultrasonography was used to measure arterial diameter changes in response to reactive hyperemia (with increased flow producing an endothelium-dependent stimulus to vasodilation; flow-mediated vasodilation, FMD) and to glyceryl trinitrate (GTN, an endothelium-independent vasodilator; GTN-induced dilation; 128XP/10 with a 7.0 MHz linear array transducer: Acuson, Mountain View, CA, USA). The intra- and interobserver variability in our laboratory for repeated measurements of artery diameter are 0.09 ± 0.10 and 0.08 ± 0.13 mm, respectively. The coefficients of variation for the FMD measurements over time are 6.8e8.2%. 2.3. Laboratory methods Venous blood was collected after a 12-h fast at baseline for all individuals and at Day 1, Day 2 and Day 3 after the CMR or sham CMR procedure for diabetic patients. Measurements of serum lipids, serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglyceride and high-density lipoprotein cholesterol (HDL-C) were measured enzymatically. Creatinine was measured enzymatically. Blood glucose including fasting blood glucose (FBG) and postprandial 2-h glucose (2-h BG) was measured by a glucose oxidase procedure. HaemoglobinA1c (HbA1c) was measured by high-performance liquid chromatography. The Creactive protein (CRP) concentration was measured by using the CRP (Latex) ultrasensitive assay. Nitrite and nitrate, stable metabolites of NO, were measured using methods reported by Xiang et al. [18]. The plasma lipid peroxide content was determined using thiobarbituric acid reactive substances (TBARS) as markers [18,19]. Briefly, 2.0 mL of trichloroacetic acid-thiobarbituric acid-HCl reagent was added to 1.0 mL of sample and vortexed. To minimize peroxidation during the assay procedure, butylated hydroxytoluene was added to the thiobarbituric acid reagent mixture. The results were expressed as malondialdehyde equivalent content (nmol MDA/mL plasma). Interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-a) were measured using high-sensitivity commercial ELISA kits. The urinary albumin excretion rate (UAER) was measured by a radioimmunoassay. The intra-assay coefficients of variation for these assays were 1e2% (TC, HDL-C, blood glucose, and CRP), 2e3% (LDL-C and nitrite/nitrate), 2e4% (UAER and TBARS), 5.3%e6.9% (TNF-a and IL-6). 3. Statistical methods As expected from our previous study [19], the standard deviation (SD) for FMD was about 0.75, and the expected absolute error
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(d) is 0.2 in this study. Therefore, at least, 56 patients in total should be recruited in the present study. Because we wanted to achieve more solid conclusion, the initial plan of recruiting 88 patients was registered. However, only 60 patients were recruited in this study because of the lack of finance. The statistical analyses were performed according to the intention-to-treat principle on data from all patients who underwent randomization. For the differences between CMR and sham CMR group, the unpaired t-test was used and other comparisons of data between two groups were also performed using the Student's unpaired t-test. In the case of vascular function, blood glucose, TBARS, and nitrite/nitrate levels, etc., where repeated measures were taken, one-way analysis of variance with post hoc testing (Scheffe's test) was used. For the regression or correlation analysis, we ignored the parameters of Day 2 and Day 3, and changes from baseline to Day 1 for each physiologic factor were calculated and paired t-test for changes was used. Correlations between changes in vascular reactivity and changes in other parameters during follow-up were examined using Pearson's method. Multiple stepwise regression analysis was performed in the follow up period, which included changes in baseline vessels, baseline flow, IL-6, TNF-a, CRP, TBARS, nitrite/nitrate, FBG, 2h-BG, diastolic blood pressure (DBP), systolic blood pressure (SBP), and pulse rate as independent variables. Statistical significance was defined as p < 0.05. UAER concentrations were log-transformed before analysis, and were reported as median values and ranges. All analyses were carried out by using the statistical package SPSS 12.0 (SPSS, Inc., Chicago, IL, USA). This study was registered with ClinicalTrials. gov, number NCT02001753.
4. Results The clinical characteristics and biochemical as well as brachial artery ultrasonography results of the diabetic and control subjects are summarized in Table S (Supplementary Data). Compared with the control group, the BMI, DBP, SBP, TC, LDL-C, TG, IL-6, TNF-a, CRP, TBARS, FBG, 2h-BG, and HbA1c were significantly greater (p < 0.05), but HDL-C and FMD were markedly less (p < 0.01). The GTNinduced dilation, basal arterial diameter, and increase in blood flow during the reactive hyperemia were not significantly different between the two groups (Supplementary Data, Table). There were eight study dropouts (CMR group: 2 cases at Day 2
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and 1 case at Day 3; sham CMR group: 3 cases at Day 2 and 2 cases at Day 3) during the follow-up period; 52 patients completed the 3day follow-up study (Fig. 1). There were no significant differences between the CMR group and the sham CMR group with respect to
Table 1 Brachial arterial data and biochemical characteristics before and after the CMR or sham CMR procedure (x±s).
sham CMR group No. of subjects Baseline vessel (mm) Baseline flow (mL/min) FMD (%) GTN-induced dilation (%) IL-6 (pg/mL) TNF-a(pg/mL) CRP (mg/L) TBARS (nmol/mL) Nitrite/nitrate (umol/L) FBG (mmol/L) 2h-BG (mmol/L) SBP (mmHg) DBP (mmHg) Pulse rate (beats/min) CMR group No. of subjects Baseline vessel (mm) Baseline flow (ml/min) FMD (%) GTN-induced dilation (%) IL-6 (pg/mL) TNF-a(pg/mL) CRP (mg/L) TBARS (nmol/mL) Nitrite/nitrate (umol/L) FBG (mmol/L) 2h-BG (mmol/L) SBP (mmHg) DBP (mmHg) Pulse rate (beats/min)
Baseline
Day 1
Day 2
Day 3
30 3.79 ± 0.71 81.1 ± 31.6 3.90 ± 0.59 21.81 ± 2.99
30 3.78 ± 0.71 80.4 ± 33.9 3.85 ± 0.71 20.52 ± 2.82
27 3.80 ± 0.67 80.8 ± 32.5 3.86 ± 0.64 21.11 ± 2.77
25 3.79 ± 0.66 82.1 ± 32.1 3.87 ± 0.76 20.36 ± 2.82
2.53 ± 0.67 2.54 ± 0.82 2.47 ± 0.41 2.58 ± 0.79 60.7 ± 10.3 8.90 ± 1.39 13.42 ± 4.22 116.4 ± 7.7 76.8 ± 6.1 70.5 ± 7.8
2.54 ± 0.67 2.52 ± 0.72 2.52 ± 0.50 2.55 ± 0.78 61.2 ± 9.7 9.03 ± 1.45 13.64 ± 4.15 115.0 ± 9.5 77.5 ± 7.0 71.2 ± 8.8
2.53 ± 0.68 2.50 ± 0.68 2.48 ± 0.49 2.57 ± 0.74 61.3 ± 11.2 8.89 ± 1.28 15.02 ± 4.56 114.5 ± 9.7 77.0 ± 6.6 70.7 ± 7.9
2.60 ± 0.69 2.51 ± 0.83 2.54 ± 0.60 2.53 ± 0.73 60.4 ± 9.6 8.95 ± 1.42 13.17 ± 5.11 114.6 ± 9.3 76.6 ± 6.7 71.4 ± 8.0
30 3.75 ± 0.65 79.2 ± 31.1 3.93 ± 0.63 19.69 ± 2.86
30 3.79 ± 0.62 80.3 ± 30.1 3.60 ± 0.55**y 20.15 ± 2.56
28 3.78 ± 0.70 79.5 ± 29.7 3.89 ± 0.58 19.73 ± 2.80
27 3.77 ± 0.68 80.3 ± 31.5 3.95 ± 0.49 19.55 ± 2.74
2.58 ± 0.70 2.49 ± 0.76 2.44 ± 0.53 2.56 ± 0.63 60.7 ± 10.8 8.94 ± 1.58 13.74 ± 3.98 116.4 ± 8.22 77.6 ± 6.9 71.5 ± 8.0
3.08 ± 0.66**y 3.03 ± 0.62**y 2.57 ± 0.48* 2.84 ± 0.70**y 61.5 ± 11.5 8.74 ± 1.36 14.14 ± 4.16 114.1 ± 7.56 76.8 ± 6.3 71.7 ± 7.6
2.60 ± 0.70 2.52 ± 0.72 2.50 ± 0.43 2.55 ± 0.71 61.1 ± 9.7 9.11 ± 1.29 13.94 ± 4.25 115.2 ± 7.58 77.1 ± 5.8 70.8 ± 7.9
2.69 ± 0.70 2.58 ± 0.70 2.49 ± 0.45 2.55 ± 0.65 60.3 ± 9.6 8.92 ± 1.37 13.55 ± 4.18 114.3 ± 7.33 77.3 ± 6.0 71.1 ± 8.4
C-reactive protein, CRP; flow-mediated vasodilation, FMD; fasting blood glucose, FBG; glyceryl trinitrate, GTN; interleukin-6, IL-6; postprandial 2 h glucose, 2h-BG; thiobarbituric acid reactive substances, TBARS; tumor necrosis factor-alpha, TNF-a. *p < 0.05, **p < 0.001, compared with baseline. yp < 0.001, compared with the sham CMR group at the same time point.
Screened for eligibility (n=540) Excluded (n=480) Not meeting inclusion criteria (n=410) Refused to participate (n=63) Other reasons (n=7)
Recruited and randomized (n=60) Allocated to the CMR (N=30) Study dropout (n=3)(2 at day 2 and 1 at day 3 because of the time constraint)
Allocated to the sha sham CMR (N=30) Study dropout (n=5)(3 at day 2 and 2 at day 3 because of the time constraint)
27 patients completed plet the study
25 Patients completed mpl the study
Fig. 1. Flow diagram of the study. CMR ¼ cardiac magnetic resonance.
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Fig. 2. Effects of CMR and sham CMR on FMD. This graph illustrates the effect of CMR (rhombus) or sham CMR (squares) intervention on FMD. CMR significantly decreases FMD at Day 1 after CMR scanning compared with sham CMR (*p < 0.001). Data are expressed as mean ± SEM.
baseline characteristics including endothelial function, inflammation, blood pressure, blood glucose, etc. (Table 1). The FMD decreased significantly at Day 1 (3.60 ± 0.55%) after the CMR procedure from baseline (3.93 ± 0.63%) in the CMR group (p < 0.001), and then returned to baseline at Day 2 (3.89 ± 0.58%) and Day 3 (3.95 ± 0.49%). However, we found no significant differences in FMD changes within the sham CMR group (p > 0.05). Compared to the sham CMR group (3.85 ± 0.71% at Day 1), the FMD at Day 1 was significantly lower in the CMR group (p < 0.001), however, the differences were not significant at other time points between two groups (p > 0.05) (Fig. 2). The groups did not differ significantly with respect to the other brachial ultrasound results including baseline vessels, baseline flow, and GTN-induced dilation
(p > 0.05; Table 1). Table 1 also shows the oxidative stress and inflammation reaction in response to the CMR or sham CMR procedure in type 2 diabetic patients. The intervention with CMR was found to significantly increase the levels of oxidative stress marker (TBARS) and inflammation markers (CRP，TNF-a and IL-6) (p < 0.001) at Day 1 from baseline and then returned to baseline at Day 2 and 3 in the CMR group, while these were not the cases within the sham CMR group. Compared to the sham CMR group, the levels of TBARS, CRP, TNF-a and IL-6 were dramatically higher at Day 1 after the CMR procedure in the CMR group (p < 0.001), and there were not differences between the two groups at other different time points (p > 0.05). In addition, the CMR procedure and sham CMR also did not have any significant effect on blood pressure, blood glucose, nitrite/nitrate, or heart rate. To reveal the possible causes of CMR-induced FMD changes, linear correlation and multiple stepwise regression analyses were performed between the changes of blood pressure (DBP and SBP), blood glucose (FBG and 2h-BG), oxidative stress (TBARS and nitrite/ nitrate), inflammation (CRP, TNF-a, and IL-6), pulse rate, and vascular reactivity (FMD and GNT-induced arterial dilation) from baseline to Day 1. According to linear correlation analysis, only TBARS, CRP, TNF-a, and IL-6 were found to be inversely associated with FMD in the CMR group (Fig. 3; p < 0.001). In multiple stepwise regression model, the changes of baseline vessel, baseline flow, DBP, SBP, pulse rate, FBG, 2h-BG, TBARS, nitrite/nitrate, CRP, TNF-a, and IL-6 from baseline to Day 1 were entered (forward) at the beginning of the procedure. Of those, TBARS, CRP, TNF-a, and IL-6 were found to be independently associated with change of FMD levels (all p < 0.05) (Table 2). These associations based on linear correlation and multiple stepwise regression models were not found in the sham CMR group (p > 0.05).
Fig. 3. Pearson's analysis to evaluate correlation of the changes of FMD with the changes of other risk factors during the follow up in CMR group. A: The changes of FMD is negatively related with the changes of TBARS (r ¼ 0.498, p < 0.001) B: The changes of FMD is negatively associated with the changes of TNF-a (r ¼ 0.452, p < 0.001) C: The changes of FMD is negatively correlated with the changes of IL-6 (r ¼ 0.475, p < 0.001) D: The changes of FMD is negatively associated with the changes of CRP (r ¼ - 0.248, p ¼ 0.005).
G. Xiang et al. / Atherosclerosis 239 (2015) 131e136 Table 2 Multiple stepwise regression analysis (forward) with changes of FMD level during the follow up period as dependent variable in CMR group. Variables
b
SE
p
Baseline vessels (mm) Baseline flow (mL/min) CRP (mg/L) SBP (mm Hg) DBP (mm Hg) pulse rate (beats/min) TBARS (nmol/mL) Nitrite/nitrate (umol/L) FBG (mmol/L) 2h-BG (mmol/L) IL-6 (pg/mL) TNF-a (pg/mL)
0.07 0.09 0.24 0.12 0.10 0.05 0.46 0.08 0.11 0.09 0.45 0.57
0.49 0.54 0.09 0.13 0.11 0.35 0.08 0.14 0.09 0.26 0.14 0.09
0.585 0.836 0.042 0.104 0.133 0.671 <0.001 0.268 0.095 0.247 0.005 <0.001
b, regression coefficient; SE, standard error; C-reactive protein, CRP; flow-mediated vasodilation, FMD; fasting blood glucose, FBG; interleukin-6, IL-6; postprandial 2 h glucose, 2h-BG; thiobarbituric acid reactive substances, TBARS; tumor necrosis factor-alpha, TNF-a.
5. Discussion In this study, we explored the changes of endothelial function, oxidative stress, as well as inflammation before and after a clinical routine CMR scan in patients with newly diagnosed Chinese men type 2 diabetes. The results showed a reversible FMD reduction below baseline at Day 1 after the CMR procedure, which strongly depended on the magnitude of oxidative stress and inflammation, suggesting that oxidative stress and inflammation may be important factors in endothelial dysfunction induced by CMR scanning. Although many experimental in vitro and in vivo studies have suggested DNA damage after exposure to MR imaging [6e13,15], here, we present the first in vivo results documenting that routine clinical CMR scanning is associated with increased endothelial dysfunction. Why would the endothelial function in diabetic patients be impaired after CMR scanning? The underlying mechanisms are unclear. No differences in clinical characteristics, such as FBG, 2hBG, blood pressure, and creatinine, were found among the different follow up days after the CMR procedure, indicating that the impaired endothelial function cannot be explained by these classic cardiovascular risk factors alone. The possible explanations are as follows: (1) FMD has been shown to be mediated by the endothelium-derived relaxing factor, which is identified as NO [20]. Previous studies have established that oxygen-derived free radicals interfere with or destroy FMD by inactivating NO in normal vessels [21,22]. Recently, some studies have documented that plasma TBARS, a marker of oxygen-derived free radicals, is negatively related to the FMD of the brachial conduit artery [18,23]. In the present study, we found that the TBARS levels increase markedly at Day 1 after CMR, which is inversely associated with FMD during the follow-up days. Indeed, one study has documented that MR can induce oxidative stress [24], which is consistent with our present data. (2) Increased levels of inflammation biomarkers, such as CRP, IL-6 and TNF-a, have been recently considered as potential contributors to inflammatory diseases including atherosclerosis as well as markers of cardiovascular risk [25,26]. Our present data showed that CRP, IL-6 and TNF-a levels increased significantly at Day 1 after CMR, and were inversely associated with FMD. Therefore, inflammation may partially contribute to the impaired endothelial function after CMR in diabetic subjects. (3) Some studies have revealed that MR scanning exerts genotoxic effects in white blood cells and lymphocytes [6e13,15]. In the clinic, CMR imaging requires some of the strongest and fastest switching electromagnetic gradients [5]. In fact, the field gradient generated during MR scanning includes
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extremely low frequencies (ELF), which have been classified by the International Agency for Research on Cancer (IARC) as a possible human carcinogen (group 2B) [27] based on a large body of literature on the genotoxic effects of ELF magnetic fields [28e31]. These effects of CMR may have partially contributed to the observed endothelial dysfunction. Of note, observations in several subsets of patients seem to suggest increased sensitivities to MRI exposure, as a higher susceptibility for DNA damage by MR imaging has been found in the lymphocytes of patients with Turner's syndrome [32]. In the present study, we analyzed Chines men diabetic patients; thus, inappropriate examinations should be avoided and CMR should be used with caution in order to avoid unnecessary endothelial damage in Chinese men diabetic conditions. Some limitations should be mentioned here. Firstly, the plasma lipid peroxide content was determined using TBARS as marker of oxidative stress. According to the manufacture instructions, plasma is not suitable sample for TBARS. Secondly, the possibility cannot be excluded that patients undergoing sham CMR did not realize the difference from the CMR procedure. Thirdly, we applied rigorous inclusion criteria to recruit patients in this study. The applicability of this study finding to general patient population is not clear. Finally, the small sample size and generalizability to non-Chinese population are also the limitations of this study. In conclusion, the present data showed that CMR can reversibly impair endothelial function, probably through the increased production of oxygen-derived free radicals and inflammatory reactions in type 2 diabetes. The confirmation of impact of CMR on endothelial function in general patient population warrants long-term follow-up studies based on representative cohorts. Author's contributions Guangda Xiang performed research design; Lin Xiang and Honglin He conducted the CMR and sham CMR procedure and data collection; Junxia Zhang took charge of the conduct of the study and manuscript writing; Jing Dong collected data. Disclosures None. Acknowledgments The program was supported by National Foundation of Natural Science (81370896), and Natural Science Foundation of Hubei Province (number 2011CDA002 and number 2009CDB427 as well as number 2013CFB432). Dr Guangda Xiang is the guarantor of the work, and as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.atherosclerosis.2014.12.028. References [1] M.K. Stehling, R. Bowtell, P. Reimer, Long-term outlook for MRI appears positive, Diagn Imaging 17 (1995) 3le41. [2] A. Kangarlu, P. Robitaille, Biological effects and health implications in magnetic resonance imaging, Concepts Magn. Reson 12 (2000) 321e359. [3] G. Franco, R. Perduri, A. Murolo, Health effects of occupational exposure to static magnetic fields used in magnetic resonance imaging: a review, Med. Lav. 99 (2008) 16e28.
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Impact of cardiac magnetic resonance on endothelial function in type 2 diabetic patients Guangda Xiang a, *, Lin Xiang a, Honglin He b, Junxia Zhang a, Jing Dong a a b
Department of Endocrinology, Wuhan General Hospital of Guangzhou Command, Wuluo Road 627, Wuhan 430070, Hubei, China Department of Radiology, Wuhan General Hospital of Guangzhou Command, Wuluo Road 627, Wuhan 430070, Hubei, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 24 July 2014 Received in revised form 30 November 2014 Accepted 9 December 2014 Available online 13 January 2015
Objectives Recent studies have shown that cardiac magnetic resonance (CMR) scanning is associated with cellular DNA damage. The aim of the present study was to assess the impact of CMR scanning on endothelial function in Chinese men with type 2 diabetes. Methods A randomized, single-blind, parallelgroup study was conducted in 60 Chinese men with type 2 diabetes treated with or without CMR (CMR and sham CMR group), and the changes of endothelial function before and after CMR were compared. High-resolution ultrasound was used to measure flow-mediated endothelium-dilation (FMD) of the brachial artery. Results The FMD in CMR group at Day 1 after CMR was 3.60%, which was significantly lower than that (3.85%) in sham CMR group (p < 0.001). The levels of C-reactive protein (CRP), thiobarbituric acid-reactive substances (TBARS), tumor necrosis factor alpha (TNF-a) and interleukin-6(IL-6) in CMR group were significantly higher than those in sham CMR group at Day 1 (p < 0.001). But these characteristics did not differ between two groups at baseline, Day 2 and Day 3 (p > 0.05). Linear correlation and multiple regression analyses showed that CRP, TBARS, TNF-a and IL-6 were associated with FMD in the CMR group (p < 0.01). Conclusions The present data showed that CMR scanning can reversibly suppress endothelial function, probably through the increased production of oxygen-derived free radicals and inflammatory reactions in Chinese men with type 2 diabetes, indicating that CMR should be used with caution in order to avoid unnecessary damage to the endothelium. Clinical Trial Registration URL: https://register.clinicaltrials.gov/, Unique Identifier: NCT02001753. © 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: Cardiac magnetic resonance Endothelial function Type 2 diabetes Oxidative stress
Magnetic resonance (MR) imaging is an established clinical diagnostic tool with the number of systems installed world-wide approaching 4000 [1]. By using a static and a gradient magnetic field in combination with a radiofrequency field, MR provides excellent contrast among different tissues of the body including the brain, musculoskeletal system, and heart. Although long-term effects on human health from exposure to strong static magnetic
Abbreviation: BMI, Body mass index; CMR, cardiac magnetic resonance; CRP, Creactive protein; FMD, flow-mediated vasodilation; FBG, fasting blood glucose; GTN, glyceryl trinitrate; HDL-C, high-density lipoprotein cholesterol; HbA1c, haemoglobinA1c; IL-6, interleukin-6; LDL-C, low-density lipoprotein cholesterol; MR, magnetic resonance; 2h-BG, postprandial 2 h glucose; TC, total cholesterol; TG, triglyceride; TBARS, thiobarbituric acid reactive substances; TNF-a, tumor necrosis factor-alpha; UAER, urinary albumin excretion rate; WHO, World Health Organization. * Corresponding author. E-mail addresses: [email protected] (G. Xiang), Xianglin832010@ hotmail.com (L. Xiang), [email protected] (H. He), [email protected] (J. Zhang), [email protected] (J. Dong). http://dx.doi.org/10.1016/j.atherosclerosis.2014.12.028 0021-9150/© 2014 Elsevier Ireland Ltd. All rights reserved.
fields seem unlikely [2], acute effects such as vertigo, nausea, change in blood pressure, reversible arrhythmia [3], and neurobehavioural effects have been documented from occupational exposure to 1.5 T [4]. Cardiac magnetic resonance (CMR) is a noninvasive tool that provides high-resolution, three-dimensional images of the heart; CMR requires some of the strongest and fastest switching electromagnetic gradients available in MR, exposing patients to the highest administered energy levels accepted by the controlling authorities [5]. Studies focusing on the experimental teratogenic [6e10] or carcinogenic [11e13] effects of MR have revealed conflicting results. Since CMR is emerging as one of the fastest growing new fields of broad MR application [14], it is of particular concern that a recent in vitro study with CMR sequences has reported CMRinduced DNA damage in white blood cells up to 24 h after exposure to 1.5 T CMR [5]. Moreover, one in vivo study showed that contrast CMR scanning in daily clinical routine is associated with increased lymphocyte DNA damage [15]. However, to date, no data are available on the relationship between CMR and endothelial
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dysfunction, especially in diabetic conditions. Therefore, the aim of the present study was to assess the impact of routine CMR scanning on endothelial function in Chinese men with type 2 diabetes.
1. Subjects and methods 1.1. Subjects From Dec. 2013 to Feb. 2014, the newly diagnosed Chinese type 2 diabetic men, who had been referred to our hospital for diabetic evaluation, were identified as potentially eligible subjects (540 cases). The type 2 diabetes was diagnosed according to the World Health Organization (WHO) 1999 criteria. Of them, a total of 60 eligible Chinese type 2 diabetic men, aged 40e65 years old (mean 54 ± 7 years old), were included in this study. Patients with clinical angiopathy including micro- and macroangiopathy as well as hypertension were excluded from this study. Microangiopathy included nephropathy [urinary albumin excretion rate (UAER) > 20 mg/min], retinopathy (at least one microaneurysm or hemorrhage or exudates in either eye), and neuropathy (pain in the extremities, paresthesias, absent tendon reflexes, and/or absent vibration sensation); and macroangiopathy included coronary artery disease (myocardial infarction, ischemia electrocardiogram changes, and angina), cerebrovascular disease (transient ischemic attack or stroke), and peripheral vascular disease (the abolition of one or more peripheral arterial pulses, and/or intermittent claudication, and/or a past history of revascularization of the lower limbs). The recruited patients were all required to have an office blood pressure (BP) < 140/90 mm Hg, which was measured by a trained nurse. After at least a 5-min rest, two successive readings were taken from the right arm using a mercury manometer with a 12-cm by 33.5-cm cuff. During the same period, 28 healthy men (all from the medical staff in our hospital), who had had a normal glucose tolerance, were selected as control subjects. Subjects who were obese [body mass index (BMI) > 30 kg/m2], or smokers, or had malignant neoplasms, renal or liver diseases, or endocrinological diseases other than diabetes were excluded from the study. In addition, no patients were taking any drugs, such as oestrogen supplements, thyroxine, diuretics, diabetic medications, antihypertensive and hypolipidaemic drugs. All subjects enrolled in the study gave their informed consent. The study protocol was in agreement with the guidelines of the ethics committee at our hospital. Two to three days before the beginning of the study, advice on a standard, well-balanced, controlled diet was given to all the eligible subjects. Diabetic patients were then scheduled to undertake a 4-day randomized, single-blind, parallel-group trial of investigations with or without CMR scanning. The patients were divided randomly into two groups, 30 cases in each group (the CMR group and sham CMR group). In the CMR group, CMR scanning for evaluation of left ventricular mass was performed at 8e10 AM; in the sham CMR group, all subjects remained in the supine position in the same MR machine scanner at 8e10 AM and the patients were not subjected to the pulse sequences of a typical examination. Our previous studies showed that oxidative stress and inflammation as well as blood glucose are associated with endothelial dysfunction [16e19], therefore, the examinations of vascular function, blood glucose, oxidative stress, and inflammation were performed at 1 day (baseline) before and at 1 day (Day 1), 2 days (Day 2), 3 days (Day 3) after the CMR procedure for the CMR group or the sham CMR procedure for the without CMR group. Only a one-time examination was performed for the healthy controls at baseline.
2. Methods 2.1. CMR scanning The CMR imaging was performed on a 1.5-T Magnetom Avanto scanner (Siemens, Erlangen, Germany) for the CMR group. Serial contiguous short-axis cines were acquired from the vertical long axis and horizontal long axis of the left ventricle [electrocardiogram gated, steady-state free precession imaging (true fast imaging with steady-state precession), with the short-axis imaging parameters being a repetition time of 2.5 ms, echo time of 1.1 ms, flip angle of 60 , and slice thickness of 6 mm]. Regarding the procedure for the sham CMR group, the patients only stayed in the scanner for the same length of time as subjects in the CMR group. 2.2. Brachial artery ultrasonography Brachial artery ultrasonography was performed noninvasively, as previously described by us [16,17]. High resolution ultrasonography was used to measure arterial diameter changes in response to reactive hyperemia (with increased flow producing an endothelium-dependent stimulus to vasodilation; flow-mediated vasodilation, FMD) and to glyceryl trinitrate (GTN, an endothelium-independent vasodilator; GTN-induced dilation; 128XP/10 with a 7.0 MHz linear array transducer: Acuson, Mountain View, CA, USA). The intra- and interobserver variability in our laboratory for repeated measurements of artery diameter are 0.09 ± 0.10 and 0.08 ± 0.13 mm, respectively. The coefficients of variation for the FMD measurements over time are 6.8e8.2%. 2.3. Laboratory methods Venous blood was collected after a 12-h fast at baseline for all individuals and at Day 1, Day 2 and Day 3 after the CMR or sham CMR procedure for diabetic patients. Measurements of serum lipids, serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglyceride and high-density lipoprotein cholesterol (HDL-C) were measured enzymatically. Creatinine was measured enzymatically. Blood glucose including fasting blood glucose (FBG) and postprandial 2-h glucose (2-h BG) was measured by a glucose oxidase procedure. HaemoglobinA1c (HbA1c) was measured by high-performance liquid chromatography. The Creactive protein (CRP) concentration was measured by using the CRP (Latex) ultrasensitive assay. Nitrite and nitrate, stable metabolites of NO, were measured using methods reported by Xiang et al. [18]. The plasma lipid peroxide content was determined using thiobarbituric acid reactive substances (TBARS) as markers [18,19]. Briefly, 2.0 mL of trichloroacetic acid-thiobarbituric acid-HCl reagent was added to 1.0 mL of sample and vortexed. To minimize peroxidation during the assay procedure, butylated hydroxytoluene was added to the thiobarbituric acid reagent mixture. The results were expressed as malondialdehyde equivalent content (nmol MDA/mL plasma). Interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-a) were measured using high-sensitivity commercial ELISA kits. The urinary albumin excretion rate (UAER) was measured by a radioimmunoassay. The intra-assay coefficients of variation for these assays were 1e2% (TC, HDL-C, blood glucose, and CRP), 2e3% (LDL-C and nitrite/nitrate), 2e4% (UAER and TBARS), 5.3%e6.9% (TNF-a and IL-6). 3. Statistical methods As expected from our previous study [19], the standard deviation (SD) for FMD was about 0.75, and the expected absolute error
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(d) is 0.2 in this study. Therefore, at least, 56 patients in total should be recruited in the present study. Because we wanted to achieve more solid conclusion, the initial plan of recruiting 88 patients was registered. However, only 60 patients were recruited in this study because of the lack of finance. The statistical analyses were performed according to the intention-to-treat principle on data from all patients who underwent randomization. For the differences between CMR and sham CMR group, the unpaired t-test was used and other comparisons of data between two groups were also performed using the Student's unpaired t-test. In the case of vascular function, blood glucose, TBARS, and nitrite/nitrate levels, etc., where repeated measures were taken, one-way analysis of variance with post hoc testing (Scheffe's test) was used. For the regression or correlation analysis, we ignored the parameters of Day 2 and Day 3, and changes from baseline to Day 1 for each physiologic factor were calculated and paired t-test for changes was used. Correlations between changes in vascular reactivity and changes in other parameters during follow-up were examined using Pearson's method. Multiple stepwise regression analysis was performed in the follow up period, which included changes in baseline vessels, baseline flow, IL-6, TNF-a, CRP, TBARS, nitrite/nitrate, FBG, 2h-BG, diastolic blood pressure (DBP), systolic blood pressure (SBP), and pulse rate as independent variables. Statistical significance was defined as p < 0.05. UAER concentrations were log-transformed before analysis, and were reported as median values and ranges. All analyses were carried out by using the statistical package SPSS 12.0 (SPSS, Inc., Chicago, IL, USA). This study was registered with ClinicalTrials. gov, number NCT02001753.
4. Results The clinical characteristics and biochemical as well as brachial artery ultrasonography results of the diabetic and control subjects are summarized in Table S (Supplementary Data). Compared with the control group, the BMI, DBP, SBP, TC, LDL-C, TG, IL-6, TNF-a, CRP, TBARS, FBG, 2h-BG, and HbA1c were significantly greater (p < 0.05), but HDL-C and FMD were markedly less (p < 0.01). The GTNinduced dilation, basal arterial diameter, and increase in blood flow during the reactive hyperemia were not significantly different between the two groups (Supplementary Data, Table). There were eight study dropouts (CMR group: 2 cases at Day 2
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and 1 case at Day 3; sham CMR group: 3 cases at Day 2 and 2 cases at Day 3) during the follow-up period; 52 patients completed the 3day follow-up study (Fig. 1). There were no significant differences between the CMR group and the sham CMR group with respect to
Table 1 Brachial arterial data and biochemical characteristics before and after the CMR or sham CMR procedure (x±s).
sham CMR group No. of subjects Baseline vessel (mm) Baseline flow (mL/min) FMD (%) GTN-induced dilation (%) IL-6 (pg/mL) TNF-a(pg/mL) CRP (mg/L) TBARS (nmol/mL) Nitrite/nitrate (umol/L) FBG (mmol/L) 2h-BG (mmol/L) SBP (mmHg) DBP (mmHg) Pulse rate (beats/min) CMR group No. of subjects Baseline vessel (mm) Baseline flow (ml/min) FMD (%) GTN-induced dilation (%) IL-6 (pg/mL) TNF-a(pg/mL) CRP (mg/L) TBARS (nmol/mL) Nitrite/nitrate (umol/L) FBG (mmol/L) 2h-BG (mmol/L) SBP (mmHg) DBP (mmHg) Pulse rate (beats/min)
Baseline
Day 1
Day 2
Day 3
30 3.79 ± 0.71 81.1 ± 31.6 3.90 ± 0.59 21.81 ± 2.99
30 3.78 ± 0.71 80.4 ± 33.9 3.85 ± 0.71 20.52 ± 2.82
27 3.80 ± 0.67 80.8 ± 32.5 3.86 ± 0.64 21.11 ± 2.77
25 3.79 ± 0.66 82.1 ± 32.1 3.87 ± 0.76 20.36 ± 2.82
2.53 ± 0.67 2.54 ± 0.82 2.47 ± 0.41 2.58 ± 0.79 60.7 ± 10.3 8.90 ± 1.39 13.42 ± 4.22 116.4 ± 7.7 76.8 ± 6.1 70.5 ± 7.8
2.54 ± 0.67 2.52 ± 0.72 2.52 ± 0.50 2.55 ± 0.78 61.2 ± 9.7 9.03 ± 1.45 13.64 ± 4.15 115.0 ± 9.5 77.5 ± 7.0 71.2 ± 8.8
2.53 ± 0.68 2.50 ± 0.68 2.48 ± 0.49 2.57 ± 0.74 61.3 ± 11.2 8.89 ± 1.28 15.02 ± 4.56 114.5 ± 9.7 77.0 ± 6.6 70.7 ± 7.9
2.60 ± 0.69 2.51 ± 0.83 2.54 ± 0.60 2.53 ± 0.73 60.4 ± 9.6 8.95 ± 1.42 13.17 ± 5.11 114.6 ± 9.3 76.6 ± 6.7 71.4 ± 8.0
30 3.75 ± 0.65 79.2 ± 31.1 3.93 ± 0.63 19.69 ± 2.86
30 3.79 ± 0.62 80.3 ± 30.1 3.60 ± 0.55**y 20.15 ± 2.56
28 3.78 ± 0.70 79.5 ± 29.7 3.89 ± 0.58 19.73 ± 2.80
27 3.77 ± 0.68 80.3 ± 31.5 3.95 ± 0.49 19.55 ± 2.74
2.58 ± 0.70 2.49 ± 0.76 2.44 ± 0.53 2.56 ± 0.63 60.7 ± 10.8 8.94 ± 1.58 13.74 ± 3.98 116.4 ± 8.22 77.6 ± 6.9 71.5 ± 8.0
3.08 ± 0.66**y 3.03 ± 0.62**y 2.57 ± 0.48* 2.84 ± 0.70**y 61.5 ± 11.5 8.74 ± 1.36 14.14 ± 4.16 114.1 ± 7.56 76.8 ± 6.3 71.7 ± 7.6
2.60 ± 0.70 2.52 ± 0.72 2.50 ± 0.43 2.55 ± 0.71 61.1 ± 9.7 9.11 ± 1.29 13.94 ± 4.25 115.2 ± 7.58 77.1 ± 5.8 70.8 ± 7.9
2.69 ± 0.70 2.58 ± 0.70 2.49 ± 0.45 2.55 ± 0.65 60.3 ± 9.6 8.92 ± 1.37 13.55 ± 4.18 114.3 ± 7.33 77.3 ± 6.0 71.1 ± 8.4
C-reactive protein, CRP; flow-mediated vasodilation, FMD; fasting blood glucose, FBG; glyceryl trinitrate, GTN; interleukin-6, IL-6; postprandial 2 h glucose, 2h-BG; thiobarbituric acid reactive substances, TBARS; tumor necrosis factor-alpha, TNF-a. *p < 0.05, **p < 0.001, compared with baseline. yp < 0.001, compared with the sham CMR group at the same time point.
Screened for eligibility (n=540) Excluded (n=480) Not meeting inclusion criteria (n=410) Refused to participate (n=63) Other reasons (n=7)
Recruited and randomized (n=60) Allocated to the CMR (N=30) Study dropout (n=3)(2 at day 2 and 1 at day 3 because of the time constraint)
Allocated to the sha sham CMR (N=30) Study dropout (n=5)(3 at day 2 and 2 at day 3 because of the time constraint)
27 patients completed plet the study
25 Patients completed mpl the study
Fig. 1. Flow diagram of the study. CMR ¼ cardiac magnetic resonance.
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Fig. 2. Effects of CMR and sham CMR on FMD. This graph illustrates the effect of CMR (rhombus) or sham CMR (squares) intervention on FMD. CMR significantly decreases FMD at Day 1 after CMR scanning compared with sham CMR (*p < 0.001). Data are expressed as mean ± SEM.
baseline characteristics including endothelial function, inflammation, blood pressure, blood glucose, etc. (Table 1). The FMD decreased significantly at Day 1 (3.60 ± 0.55%) after the CMR procedure from baseline (3.93 ± 0.63%) in the CMR group (p < 0.001), and then returned to baseline at Day 2 (3.89 ± 0.58%) and Day 3 (3.95 ± 0.49%). However, we found no significant differences in FMD changes within the sham CMR group (p > 0.05). Compared to the sham CMR group (3.85 ± 0.71% at Day 1), the FMD at Day 1 was significantly lower in the CMR group (p < 0.001), however, the differences were not significant at other time points between two groups (p > 0.05) (Fig. 2). The groups did not differ significantly with respect to the other brachial ultrasound results including baseline vessels, baseline flow, and GTN-induced dilation
(p > 0.05; Table 1). Table 1 also shows the oxidative stress and inflammation reaction in response to the CMR or sham CMR procedure in type 2 diabetic patients. The intervention with CMR was found to significantly increase the levels of oxidative stress marker (TBARS) and inflammation markers (CRP，TNF-a and IL-6) (p < 0.001) at Day 1 from baseline and then returned to baseline at Day 2 and 3 in the CMR group, while these were not the cases within the sham CMR group. Compared to the sham CMR group, the levels of TBARS, CRP, TNF-a and IL-6 were dramatically higher at Day 1 after the CMR procedure in the CMR group (p < 0.001), and there were not differences between the two groups at other different time points (p > 0.05). In addition, the CMR procedure and sham CMR also did not have any significant effect on blood pressure, blood glucose, nitrite/nitrate, or heart rate. To reveal the possible causes of CMR-induced FMD changes, linear correlation and multiple stepwise regression analyses were performed between the changes of blood pressure (DBP and SBP), blood glucose (FBG and 2h-BG), oxidative stress (TBARS and nitrite/ nitrate), inflammation (CRP, TNF-a, and IL-6), pulse rate, and vascular reactivity (FMD and GNT-induced arterial dilation) from baseline to Day 1. According to linear correlation analysis, only TBARS, CRP, TNF-a, and IL-6 were found to be inversely associated with FMD in the CMR group (Fig. 3; p < 0.001). In multiple stepwise regression model, the changes of baseline vessel, baseline flow, DBP, SBP, pulse rate, FBG, 2h-BG, TBARS, nitrite/nitrate, CRP, TNF-a, and IL-6 from baseline to Day 1 were entered (forward) at the beginning of the procedure. Of those, TBARS, CRP, TNF-a, and IL-6 were found to be independently associated with change of FMD levels (all p < 0.05) (Table 2). These associations based on linear correlation and multiple stepwise regression models were not found in the sham CMR group (p > 0.05).
Fig. 3. Pearson's analysis to evaluate correlation of the changes of FMD with the changes of other risk factors during the follow up in CMR group. A: The changes of FMD is negatively related with the changes of TBARS (r ¼ 0.498, p < 0.001) B: The changes of FMD is negatively associated with the changes of TNF-a (r ¼ 0.452, p < 0.001) C: The changes of FMD is negatively correlated with the changes of IL-6 (r ¼ 0.475, p < 0.001) D: The changes of FMD is negatively associated with the changes of CRP (r ¼ - 0.248, p ¼ 0.005).
G. Xiang et al. / Atherosclerosis 239 (2015) 131e136 Table 2 Multiple stepwise regression analysis (forward) with changes of FMD level during the follow up period as dependent variable in CMR group. Variables
b
SE
p
Baseline vessels (mm) Baseline flow (mL/min) CRP (mg/L) SBP (mm Hg) DBP (mm Hg) pulse rate (beats/min) TBARS (nmol/mL) Nitrite/nitrate (umol/L) FBG (mmol/L) 2h-BG (mmol/L) IL-6 (pg/mL) TNF-a (pg/mL)
0.07 0.09 0.24 0.12 0.10 0.05 0.46 0.08 0.11 0.09 0.45 0.57
0.49 0.54 0.09 0.13 0.11 0.35 0.08 0.14 0.09 0.26 0.14 0.09
0.585 0.836 0.042 0.104 0.133 0.671 <0.001 0.268 0.095 0.247 0.005 <0.001
b, regression coefficient; SE, standard error; C-reactive protein, CRP; flow-mediated vasodilation, FMD; fasting blood glucose, FBG; interleukin-6, IL-6; postprandial 2 h glucose, 2h-BG; thiobarbituric acid reactive substances, TBARS; tumor necrosis factor-alpha, TNF-a.
5. Discussion In this study, we explored the changes of endothelial function, oxidative stress, as well as inflammation before and after a clinical routine CMR scan in patients with newly diagnosed Chinese men type 2 diabetes. The results showed a reversible FMD reduction below baseline at Day 1 after the CMR procedure, which strongly depended on the magnitude of oxidative stress and inflammation, suggesting that oxidative stress and inflammation may be important factors in endothelial dysfunction induced by CMR scanning. Although many experimental in vitro and in vivo studies have suggested DNA damage after exposure to MR imaging [6e13,15], here, we present the first in vivo results documenting that routine clinical CMR scanning is associated with increased endothelial dysfunction. Why would the endothelial function in diabetic patients be impaired after CMR scanning? The underlying mechanisms are unclear. No differences in clinical characteristics, such as FBG, 2hBG, blood pressure, and creatinine, were found among the different follow up days after the CMR procedure, indicating that the impaired endothelial function cannot be explained by these classic cardiovascular risk factors alone. The possible explanations are as follows: (1) FMD has been shown to be mediated by the endothelium-derived relaxing factor, which is identified as NO [20]. Previous studies have established that oxygen-derived free radicals interfere with or destroy FMD by inactivating NO in normal vessels [21,22]. Recently, some studies have documented that plasma TBARS, a marker of oxygen-derived free radicals, is negatively related to the FMD of the brachial conduit artery [18,23]. In the present study, we found that the TBARS levels increase markedly at Day 1 after CMR, which is inversely associated with FMD during the follow-up days. Indeed, one study has documented that MR can induce oxidative stress [24], which is consistent with our present data. (2) Increased levels of inflammation biomarkers, such as CRP, IL-6 and TNF-a, have been recently considered as potential contributors to inflammatory diseases including atherosclerosis as well as markers of cardiovascular risk [25,26]. Our present data showed that CRP, IL-6 and TNF-a levels increased significantly at Day 1 after CMR, and were inversely associated with FMD. Therefore, inflammation may partially contribute to the impaired endothelial function after CMR in diabetic subjects. (3) Some studies have revealed that MR scanning exerts genotoxic effects in white blood cells and lymphocytes [6e13,15]. In the clinic, CMR imaging requires some of the strongest and fastest switching electromagnetic gradients [5]. In fact, the field gradient generated during MR scanning includes
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extremely low frequencies (ELF), which have been classified by the International Agency for Research on Cancer (IARC) as a possible human carcinogen (group 2B) [27] based on a large body of literature on the genotoxic effects of ELF magnetic fields [28e31]. These effects of CMR may have partially contributed to the observed endothelial dysfunction. Of note, observations in several subsets of patients seem to suggest increased sensitivities to MRI exposure, as a higher susceptibility for DNA damage by MR imaging has been found in the lymphocytes of patients with Turner's syndrome [32]. In the present study, we analyzed Chines men diabetic patients; thus, inappropriate examinations should be avoided and CMR should be used with caution in order to avoid unnecessary endothelial damage in Chinese men diabetic conditions. Some limitations should be mentioned here. Firstly, the plasma lipid peroxide content was determined using TBARS as marker of oxidative stress. According to the manufacture instructions, plasma is not suitable sample for TBARS. Secondly, the possibility cannot be excluded that patients undergoing sham CMR did not realize the difference from the CMR procedure. Thirdly, we applied rigorous inclusion criteria to recruit patients in this study. The applicability of this study finding to general patient population is not clear. Finally, the small sample size and generalizability to non-Chinese population are also the limitations of this study. In conclusion, the present data showed that CMR can reversibly impair endothelial function, probably through the increased production of oxygen-derived free radicals and inflammatory reactions in type 2 diabetes. The confirmation of impact of CMR on endothelial function in general patient population warrants long-term follow-up studies based on representative cohorts. Author's contributions Guangda Xiang performed research design; Lin Xiang and Honglin He conducted the CMR and sham CMR procedure and data collection; Junxia Zhang took charge of the conduct of the study and manuscript writing; Jing Dong collected data. Disclosures None. Acknowledgments The program was supported by National Foundation of Natural Science (81370896), and Natural Science Foundation of Hubei Province (number 2011CDA002 and number 2009CDB427 as well as number 2013CFB432). Dr Guangda Xiang is the guarantor of the work, and as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.atherosclerosis.2014.12.028. References [1] M.K. Stehling, R. Bowtell, P. Reimer, Long-term outlook for MRI appears positive, Diagn Imaging 17 (1995) 3le41. [2] A. Kangarlu, P. Robitaille, Biological effects and health implications in magnetic resonance imaging, Concepts Magn. Reson 12 (2000) 321e359. [3] G. Franco, R. Perduri, A. Murolo, Health effects of occupational exposure to static magnetic fields used in magnetic resonance imaging: a review, Med. Lav. 99 (2008) 16e28.
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