Synthesis and evaluation of a 68Ga-labeled spermine derivative for tumor PET imaging.

BACKGROUND: The polyamine transporter system (PTS), which renders it a promising target for tumor therapy and imaging applications, facilitates the transmembrane transport of polyamines. We reported a novel derivative of spermine labeled with gallium-68 ([68Ga]Ga-NOTA-Spermine) for the imaging of the PTS in mouse models of tumor. RESULTS: The radiochemical yield of [68Ga]Ga-NOTA-Spermine was determined to be 64-69 %, demonstrating exceptional stability and radiochemical purity (>98 %). Cellular uptake experiments revealed that A549 cells exhibited peak uptake of [68Ga]Ga-NOTA-Spermine at 90 min (15.4 % ± 0.68 %). Biodistribution analysis demonstrated significant accumulation of [68Ga]Ga-NOTA-Spermine in kidneys and liver, while exhibiting low uptake levels in muscle, brain, and bones. Furthermore, Micro-PET/CT scans conducted on A549 tumor-bearing mouse models indicated substantial uptake of [68Ga]Ga-NOTA-Spermine, with maximum tumor/muscle (T/M) ratios reaching 3.71. CONCLUSION: These results suggest that [68Ga]Ga-NOTA-Spermine holds potential as a PET imaging agent for tumors with high levels of PTS.

A new 68Ga-labeled ornithine derivative for PET imaging of ornithine metabolism in tumors.

Ornithine metabolism plays a vital role in tumorigenesis. For cancer cells, ornithine is mainly used as a substrate for ornithine decarboxylase (ODC) for the synthesis of polyamines. The ODC as a key enzyme of polyamine metabolism has become an important target for cancer diagnosis and treatment. To non-invasively detect the levels of ODC expression in malignant tumors, we have synthesized a novel 68Ga-labeled ornithine derivative ([68Ga]Ga-NOTA-Orn). The synthesis time of [68Ga]Ga-NOTA-Orn was about 30 min with a radiochemical yield of 45-50% (uncorrected), and the radiochemical purity was > 98%. [68Ga]Ga-NOTA-Orn was stable in saline and rat serum. Cellular uptake and competitive inhibition assays using DU145 and AR42J cells demonstrated that the transport pathway of [68Ga]Ga-NOTA-Orn was similar to that of L-ornithine, and it could interact with the ODC after transporting into the cell. Biodistribution and micro-positron emission tomography (Micro-PET) imaging studies showed that [68Ga]Ga-NOTA-Orn exhibited rapid tumor uptake and was rapidly excreted through the urinary system. All above results suggested that [68Ga]Ga-NOTA-Orn is a novel amino acid metabolic imaging agent with great potential of tumor diagnosis.

Effects of high temperature and high humidity stress on the negative feedback regulation of hippocampus on HPA axis in rats.

OBJECTIVE: To investigate the negative feedback regulation from rat hippocampus on hypothalamic-pituitary-adrenal (HPA) axis under high temperature and high humidity stress. METHODS: Thirty (30) SD male rats were randomly divided into three groups: control group, high temperature and high humidity group, drug intervention group. The rats in control group were kept in the environment with temperature of 24 ± 1°C and humidity of 50 ± 5%, without any stimulation. The rats in the other groups were exposed to high temperature and high humidity environment for 4 h each day, with temperature of 35±1 °C and humidity of 85±5%. The rats in drug intervention group were intragastrically administered with the glucocorticoid receptor antagonist mifepristone. The administration was continued for 3 weeks. After 3 weeks, the serum levels of corticotropin releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and corticosterone (CORT) were detected by ELISA.The protein and mRNA levels of corticosteroid receptors (MR), glucocorticoid receptors (GR) and inducible nitric oxide synthase (iNOS), transient receptor potential vanilloid 1 (TRPV1) and 11ß-hydroxysteroid dehydrogenase 1 (11ß-HSD1) in hippocampus were determined by immunohistochemistry and in situ hybridization, respectively. The apoptosis of hippocampal cells was examined with TUNEL apoptosis staining. RESULTS: After stimulation with high temperature and high humidity stress for 3 weeks, the serum levels of CRH, ACTH and CORT in the high temperature and high humidity group were significantly increased compared to that of control group; the levels of these indicators in drug intervention group were decreased compared to that of high temperature and high humidity group (P<0.05). In high temperature and high humidity group, the protein and mRNA levels of MR, GR, iNOS in hippocampus of rats were significantly increased compared with that of control group (p<0.05); and the levels of these indicators in drug intervention group were lower than that of high temperature and high humidity group (p<0.05). In addition, compared with the control group, the TRPV1 protein level in hippocampus of rats in high temperature and high humidity group was not significantly changed (p>0.05), while the TRPV1 mRNA level was significantly increased (p<0.05). Neither the protein nor mRNA levels of 11ß-HSD1 showed significant difference compared to control group (p>0.05). The apoptosis of hippocampus cells in the high temperature and high humidity group was significantly increased compared with that of control group (p<0.05); and it was lower in the drug intervention group than that of in high temperature and high humidity group while the result was not significant (p>0.05). CONCLUSION: High temperature and high humidity stress may up-regulate the local expression of iNOS in hippocampus and decrease the activity of glucocorticoids (GC) receptor, then the effective binding of GR-GC would be decreased and the negative feedback regulation of hippocampus on HPA axis would be inhibited. The glucocorticoid receptor antagonist can improve the negative feedback regulation of hippocampus on HPA axis in rat.

Total Lesion Glycolysis Estimated by a Radiomics Model From CT Image Alone.

PURPOSE: In this study, total lesion glycolysis (TLG) on positron emission tomography images was estimated by a trained and validated CT radiomics model, and its prognostic ability was explored among lung cancer (LC) and esophageal cancer patients (EC). METHODS: Using the identical features between the combined and thin-section CT, the estimation model of SUVsum (summed standard uptake value) was trained from the lymph nodes (LNs) of LC patients (n = 1239). Besides LNs of LC patients from other centers, the validation cohorts also included LNs and primary tumors of LC/EC from the same center. After calculating TLG (accumulated SUVsum of each individual) based on the model, the prognostic ability of the estimated and measured values was compared and analyzed. RESULTS: In the training cohort, the model of 3 features was trained by the deep learning and linear regression method. It performed well in all validation cohorts (n = 5), and a linear regression could correct the bias from different scanners. Additionally, the absolute biases of the model were not significantly affected by the evaluated factors whether they included LN metastasis or not. Between the estimated natural logarithm of TLG (elnTLG) and the measured values (mlnTLG), significant difference existed among both LC (n = 137, bias = 0.510 ± 0.519, r = 0.956, P<0.001) and EC patients (n = 56, bias = 0.251± 0.463, r = 0.934, P<0.001). However, for both cancers, the overall shapes of the curves of hazard ratio (HR) against elnTLG or mlnTLG were quite alike. CONCLUSION: Total lesion glycolysis can be estimated by three CT features with particular coefficients for different scanners, and it similar to the measured values in predicting the outcome of cancer patients.

Phantom and clinical assessment of small pulmonary nodules using Q.Clear reconstruction on a silicon-photomultiplier-based time-of-flight PET/CT system.

To evaluate the quantification accuracy of different positron emission tomography-computed tomography (PET/CT) reconstruction algorithms, we measured the recovery coefficient (RC) and contrast recovery (CR) in phantom studies. The results played a guiding role in the partial-volume-effect correction (PVC) for following clinical evaluations. The PET images were reconstructed with four different methods: ordered subsets expectation maximization (OSEM), OSEM with time-of-flight (TOF), OSEM with TOF and point spread function (PSF), and Bayesian penalized likelihood (BPL, known as Q.Clear in the PET/CT of GE Healthcare). In clinical studies, SUVmax and SUVmean (the maximum and mean of the standardized uptake values, SUVs) of 75 small pulmonary nodules (sub-centimeter group: < 10 mm and medium-size group: 10-25 mm) were measured from 26 patients. Results show that Q.Clear produced higher RC and CR values, which can improve quantification accuracy compared with other methods (P < 0.05), except for the RC of 37 mm sphere (P > 0.05). The SUVs of sub-centimeter fludeoxyglucose (FDG)-avid pulmonary nodules with Q.Clear illustrated highly significant differences from those reconstructed with other algorithms (P < 0.001). After performing the PVC, highly significant differences (P < 0.001) still existed in the SUVmean measured by Q.Clear comparing with those measured by the other algorithms. Our results suggest that the Q.Clear reconstruction algorithm improved the quantification accuracy towards the true uptake, which potentially promotes the diagnostic confidence and treatment response evaluations with PET/CT imaging, especially for the sub-centimeter pulmonary nodules. For small lesions, PVC is essential.

Does the beta regularization parameter of bayesian penalized likelihood reconstruction always affect the quantification accuracy and image quality of positron emission tomography computed tomography?

PURPOSE: This study aims to provide a detailed investigation on the noise penalization factor in Bayesian penalized likelihood (BPL)-based algorithm, with the utilization of partial volume effect correction (PVC), so as to offer the suitable beta value and optimum standardized uptake value (SUV) parameters in clinical practice for small pulmonary nodules. METHODS: A National Electrical Manufacturers Association (NEMA) image-quality phantom was scanned and images were reconstructed using BPL with beta values ranged from 100 to 1000. The recovery coefficient (RC), contrast recovery (CR), and background variability (BV) were measured to assess the quantification accuracy and image quality. In the clinical assessment, lesions were categorized into sub-centimeter (<10 mm, n = 7) group and medium size (10-30 mm, n = 16) group. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured to evaluate the image quality and lesion detectability. With PVC was performed, the impact of beta values on SUVs (SUVmax, SUVmean, SUVpeak) of small pulmonary nodules was evaluated. Subjective image analysis was performed by two experienced readers. RESULTS: With the increasing of beta values, RC, CR, and BV decreased gradually in the phantom work. In the clinical study, SNR and CNR of both groups increased with the beta values (P < 0.001), although the sub-centimeter group showed increases after the beta value reached over 700. In addition, highly significant negative correlations were observed between SUVs and beta values for both lesion-size groups before the PVC (P < 0.001 for all). After the PVC, SUVpeak measured from the sub-centimeter group was no significantly different among different beta values (P = 0.830). CONCLUSION: Our study suggests using SUVpeak as the quantification parameter with PVC performed to mitigate the effects of beta regularization. Beta values between 300 and 400 were preferred for pulmonary nodules smaller than 30 mm.

Sodium-fluoride PET-CT for the non-invasive evaluation of coronary plaques in symptomatic patients with coronary artery disease: a cross-correlation study with intravascular ultrasound.

OBJECTIVES: The aim of this study was to evaluate the 18F-sodium fluoride (18F-NaF) coronary uptake compared to coronary intravascular ultrasound (IVUS) in patients with symptomatic coronary artery disease. BACKGROUND: 18F-NaF PET enables the assessment of vascular osteogenesis by interaction with surface hydroxyapatite, while IVUS enables both identification and quantification of intra-plaque components. METHODS: Forty-four patients with symptomatic coronary artery disease were included in this prospective controlled trial, 32 of them (30 patients with unstable angina and 2 patients with stable angina), representing the final study cohort, got additional IVUS. All patients underwent cardiac 18F-NaF PET/CT and IVUS within 2 days. 18F-NaF maximum tissue-to-blood ratios (TBRmax) were calculated for 69 coronary plaques and correlated with IVUS plaque classification. RESULTS: Significantly increased 18F-NaF uptake ratios were observed in fibrocalcific lesions (meanTBRmax = 1.42 ± 0.28), thin-cap atheroma with spotty calcifications (meanTBRmax = 1.32 ± 0.23), and thick-cap mixed atheroma (meanTBRmax = 1.28 ± 0.38), while fibrotic plaques showed no increased uptake (meanTBRmax = 0.96 ± 0.18). The 18F-NaF uptake ratio was consistently higher in atherosclerotic lesions with severe calcification (meanTBRmax = 1.34 ± 0.22). The regional 18F-NaF uptake was most likely localized in the border region of intensive calcification. Coronary lesions with positive 18F-NaF uptake showed some increased high-risk anatomical features on IVUS in comparison to 18F-NaF negative plaques. It included a significant severe plaque burden (70.1 ± 13.8 vs. 61.0 ± 13.8, p = 0.01) and positive remodeling index (1.03 ± 0.08 vs. 0.99 ± 0.07, p = 0.05), as well as a higher percentage of necrotic tissue (37.6 ± 13.3 vs. 29.3 ± 15.7, p = 0.02) in positive 18F-NaF lesions. CONCLUSIONS: 18F-NaF coronary uptake may provide a molecular insight for the characterization of coronary atherosclerotic lesions. Specific regional uptake is needed to be determined by histology.

13N-Ammonia PET/CT Detection of Myocardial Perfusion Abnormalities in Beagle Dogs After Local Heart Irradiation.

Our objective was to determine the potential value of 13N-ammonia PET/CT myocardial perfusion imaging (MPI) for early detection of myocardial perfusion changes induced by radiation damage. Methods: Thirty-six Beagle dogs were randomly divided into a control group (n = 18) or an irradiation group (n = 18). The latter underwent local irradiation to the left ventricular anterior cardiac wall with a single dose of 20 Gy, whereas the former received sham irradiation. All dogs underwent 13N-ammonia PET/CT MPI 1 wk before irradiation and at 3, 6, and 12 mo after sham or local irradiation. One week after undergoing 13N-ammonia PET/CT MPI, the irradiation group underwent coronary angiography. Six randomly selected dogs from each group were sacrificed and used to detect pathologic cardiac injury at 3, 6, and 12 mo after irradiation. Results: Compared with the control group and baseline, the irradiation group showed significantly increased perfusion in the irradiated area of the heart at 3 mo after irradiation, perfusion reduction at 6 mo after irradiation, and a perfusion defect at 12 mo after irradiation. There was no significant difference in the left ventricular ejection fraction between the control and irradiation groups at baseline or at 3 mo after irradiation. The irradiation group showed a reduction of left ventricular ejection fraction compared with the control group at 6 mo (50.0% ± 8.1% vs. 59.3% ± 4.1%, P = 0.016) and 12 mo (47.2% ± 6.7% vs. 57.4% ± 3.3%, P = 0.002) after irradiation. No coronary stenosis was observed in the irradiation group. Regional wall motion abnormalities appeared in the irradiated area at 6 mo after irradiation, and its extent was enlarged at 12 mo after irradiation. Pathologic changes were observed; radiation-induced myocardial tissue damage and microvascular fibrosis in the irradiated area progressively increased over time. Conclusion:13N-ammonia PET/CT MPI can dynamically detect myocardial perfusion changes together with global and regional left ventricular dysfunction induced by irradiation and may be a valuable method for monitoring radiation-induced heart disease.

Detection of Myocardial Metabolic Abnormalities by 18F-FDG PET/CT and Corresponding Pathological Changes in Beagles with Local Heart Irradiation.

OBJECTIVE: To determine the efficacy of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in the detection of radiation-induced myocardial damage in beagles by comparing two pre-scan preparation protocols as well as to determine the correlation between abnormal myocardial FDG uptake and pathological findings. MATERIALS AND METHODS: The anterior myocardium of 12 beagles received radiotherapy locally with a single X-ray dose of 20 Gy. 18F-FDG cardiac PET/CT was performed at baseline and 3 months after radiation. Twelve beagles underwent two protocols before PET/CT: 12 hours of fasting (12H-F), 12H-F followed by a high-fat diet (F-HFD). Regions of interest were drawn on the irradiation and the non-irradiation fields to obtain their maximal standardized uptake values (SUVmax). Then the ratio of the SUV of the irradiation to the non-irradiation fields (INR) was computed. Histopathological changes were identified by light and electron microscopy. RESULTS: Using the 12H-F protocol, the average INRs were 1.18 ± 0.10 and 1.41 ± 0.18 before and after irradiation, respectively (p = 0.021). Using the F-HFD protocol, the average INRs were 0.99 ± 0.15 and 2.54 ± 0.43, respectively (p < 0.001). High FDG uptake in irradiation field was detected in 33.3% (4/12) of 12H-F protocol and 83.3% (10/12) of F-HFD protocol in visual analysis, respectively (p = 0.031). The pathology of the irradiated myocardium showed obvious perivascular fibrosis and changes in mitochondrial vacuoles. CONCLUSION: High FDG uptake in an irradiated field may be related with radiation-induced myocardial damage resulting from microvascular damage and mitochondrial injury. An F-HFD preparation protocol used before obtaining PET/CT can improve the sensitivity of the detection of cardiotoxicity associated with radiotherapy.

Cinnamaldehyde prevents endothelial dysfunction induced by high glucose by activating Nrf2.

BACKGROUND/AIMS: It is well documented that hyperglycemia-induced oxidative stress is an important causative factor of endothelial dysfunction. Cinnamaldehyde (CA) is a key flavor compound in cinnamon essential oil that can enhance the antioxidant defense against reactive oxygen species (ROS) by activating NF-E2-related factor 2 (Nrf2), which has been shown to have a cardiovascular protective effect, but its role in endothelial dysfunction induced by high glucose is unknown. METHODS: Dissected male C57BL/6J mouse aortic rings and HUVECs were cultured in normal glucose(NG 5.5 mM) or high glucose(HG 30.0 mM) DMEM treatment with or without CA (10 µM). RESULTS: Treatment with CA protected the endothelium relaxation, inhibited ROS generation and preserved nitric oxide (NO) levels in the endothelium of mouse aortas treated with high glucose . CA up-regulated Nrf2 expression, promoted its translocation to the nucleus'and increased HO-1, NQO1, Catalase and Gpx1 expression under high glucose condition. The increased level of nitrotyrosine in HUVECs under high glucose was also attenuated by treatment with CA. Dihydroethidium (DHE) and DAF-2DA staining indicated that CA inhibited the ROS generation and preserved the NO levels in HUVECs, but these effects were reversed by Nrf2-siRNA in high glucose conditions. CONCLUSION: Our results indicated that CA protected endothelial dysfunction under high glucose conditions and this effect was mediated by Nrf2 activation and the up-regulation of downstream target proteins. CA administration may represent a promising intervention in diabetic patients who are at risk for vascular complications.

[Protection and mechanism of shenqi compound for diabetic angiopathy model rats].

OBJECTIVE: To investigate the protective effect and mechanism of Shenqi Compound on diabetic angiopathy modeled rats. METHODS: Totally 18 SD rats were randomized into 3 groups, i.e., the normal control group, the diabetic mellitus (DM) group, and Shenqi Compound group, 6 in each group. The DM rat model was established by feeding high-fat diet (to induce hyperlipidemia) +intraperitoneal injection of small dose streptozotocin (STZ). Shenqi Compound was given to rats in the Shenqi Compound group at the daily dose of 2 g/kg. Equal volume of normal saline was given to rats in the model group and the normal control group by gastrogavage. All treatment was lasted for 12 weeks. Then 2-D and ultrasonic integrated backscatter technique were used to evaluate structural and functional changes of abdominal aorta in the progression of diabetic macroangiopathy. The fibrosis degree of the aorta vessel and myocardium capillaries were observed by using HE and Masson trichrome staining. The tension of the aortic vascular ring was determined. The transforming growth factor beta (TGF-beta) mRNA expression was detected by real time PCR (RT-PCR). The protein expression of TGF-beta, collagen I, collagen III, connective tissue growth factor (CTGF), and phosphorylation P38 MAPK were detected by Western blot. RESULTS: Compared with the normal control group, abdominal aortic systolic inner diameter, diastolic inner diameter, Peterson elastic modulus, stiffness index, and backscatter integral significantly increased; the rangeability of integral backscatter and the extension coefficient of cross section significantly decreased in the DM group (all P < 0.05). After 12 weeks aforesaid indices were obviously improved in the Shenqi Compound group (P < 0.05). Results of HE and Masson staining showed that the fibrosis degree of the aorta vessel and myocardium capillaries was obviously alleviated in rats of the Shenqi Compound group (P < 0.05). Results of the aortic vascular ring tension showed that acetylcholine induced vasodilatation and maximum diastolic percent were obviously elevated in the Shenqi Compound group (P < 0.05). Compared with the normal control group, the mRNA expression of TGF-beta, and the protein expression of TGF-beta, collagen I, and collagen III, and phosphorylation of P38 MAPK all significantly increased in the DM group (P < 0.05). Compared with the DM group, the mRNA expression of TGF-beta, and the protein expression of TGF-beta, collagen I, and collagen III, and phosphorylation of P38 MAPK all decreased (P < 0.05). CONCLUSIONS: Shenqi Compound could effectively improve the arterial function in diabetic marcoangiopathy and microvascular dysfunction. The mechanism might be due to the down-regulating the expression of TGF-beta, and further suppressing the phosphorylation of P38 MAPK, reducing the synthesis of collagen I and collagen III, therefore, ameliorating arterial and myocardial interstitial fibrosis.

TRPV1 activation prevents high-salt diet-induced nocturnal hypertension in mice.

High dietary salt-caused hypertension is associated with increasing reactive oxygen species generation and reduced nitric oxide (NO) bioavailability. Transient receptor potential vanilloid type 1 (TRPV1), a specific receptor for capsaicin, is proposed to be involved in Dahl salt-sensitive hypertension, as determined in acute or short-term experiments. However, it remains unknown whether activation of TRPV1 by dietary capsaicin could prevent the vascular oxidative stress and hypertension induced by a high-salt diet. Here, we report that consumption of a high-salt diet blunted endothelium-dependent relaxation in mesenteric resistance arteries and elevated nocturnal blood pressure in mice. These effects were associated with increased superoxide anion generation and reduced NO levels in mesenteric vessels in mice on a high-salt diet. However, chronic administration of capsaicin reduced the high-salt diet-induced endothelial dysfunction and nocturnal hypertension in part by preventing the generation of superoxide anions and NO reduction of mesenteric arteries through vascular TRPV1 activation. Our findings provide new insights into the role of TRPV1 channels in the long-term regulation of blood pressure in response to high-salt intake. TRPV1 activation through chronic dietary capsaicin may represent a promising lifestyle intervention in populations with salt-sensitive hypertension.

Uncoupling protein 2 ablation exacerbates high-salt intake-induced vascular dysfunction.

BACKGROUND: Salt-induced vascular dysfunction in which underlying mechanisms involve reactive oxygen species (ROS)-mediated reduction of nitric oxide (NO) bioavailability has been well documented. Uncoupling protein 2 (UCP2) has been implicated in the vascular protection, specifically by decreasing ROS production. However, it is unclear how UCP2 affects vascular function in salt-loaded mice. METHODS: UCP2-deficient (UCP2(-/-)) and wild-type (WT) mice were placed on either a normal-salt (NS, 0.5%) or a high-salt (HS, 8%) diet for 24 weeks. Blood pressure (BP), mesenteric arterial reactivity, superoxide production, and NO bioavailability in the intact vessels were measured in each group. RESULTS: UCP2(-/-) mice on a HS diet had a higher BP than those on a NS diet (P < 0.01). However, BP in WT mice was not different between the NS and HS diet group. Phenylephrine (PE)-induced contraction was enhanced while acetylcholine (ACh)-elicited relaxation was impaired in mesenteric resistance arteries from the HS diet-fed WT mice. Importantly, the enhanced contraction and impaired relaxation were both further exacerbated in UCP2(-/-) mice. Similarly, the HS diet led to a moderate increase in superoxide production and a comparable decrease in NO availability in both aortas and mesenteric resistance vessels, and these effects were also remarkably enhanced in UCP2(-/-) mice. CONCLUSIONS: These findings suggest that UCP2 plays an important role in preventing salt-sensitive hypertension, which may be achieved by suppressing superoxide production and reserving NO bioavailability in blood vessels.

Resveratrol prevents hyperglycemia-induced endothelial dysfunction via activation of adenosine monophosphate-activated protein kinase.

Endothelial dysfunction secondary to persistent hyperglycemia plays a key role in the development of type 2 diabetic vascular disease. The aim of the present study was to examine the protective effect of resveratrol against hyperglycemia-induced endothelial dysfunction. In cultured human umbilical vein endothelial cells (HUVECs), resveratrol (10-100 microM) concentration dependently enhanced phosphorylation of endothelial nitric oxide synthesis (eNOS) at Ser1177 and nitric oxide (NO) production. In addition, resveratrol can increase the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) at Thr172 and suppress high glucose-induced generation of superoxide anion. In mouse aortic rings, resveratrol (1-100 microM) elicited endothelium-dependent vasodilatations and alleviated high glucose-mediated endothelial dysfunction. All these beneficial effects of resveratrol on the endothelium were abolished by pharmacological antagonism of AMPK by compound C. These results provide new insight into the protective properties of resveratrol against endothelial dysfunction caused by high glucose, which is attributed to the AMPK mediated reduction of superoxide level.