scholarly journals Therapeutic Potential of Sunitinib in Ameliorating Endothelial Dysfunction in Type 2 Diabetic Rats

Pharmacology ◽  
2021 ◽  
pp. 1-7
Author(s):  
Ali Mahdi ◽  
Tong Jiao ◽  
Yahor Tratsiakovich ◽  
Bernhard Wernly ◽  
Jiangning Yang ◽  
...  
Keyword(s):  
Endothelial Dysfunction ◽  
Endothelial Function ◽  
Wistar Rats ◽  
Microvascular Complications ◽  
Mesenteric Arteries ◽  
Tyrosine Kinase Receptor ◽  
Gk Rats ◽  
Glucose Levels ◽  
Arterial Blood

<b><i>Introduction:</i></b> Sunitinib, a multi-targeted tyrosine kinase receptor inhibitor used to treat renal-cell carcinoma and gastrointestinal stromal tumor, was recently shown to have a beneficial effect on metabolism in type 2 diabetes (T2D). Endothelial dysfunction is a key factor behind macro- and microvascular complications in T2D. The effect of sunitinib on endothelial function in T2D remains, however, unclear. We therefore tested the hypothesis that sunitinib ameliorates endothelial dysfunction in T2D. <b><i>Methods:</i></b> Sunitinib (2 mg/kg/day, by gavage) was administered to T2D Goto-Kakizaki (GK) rats for 6 weeks, while water was given to GK and Wistar rats as controls. Hemodynamic, inflammatory, and metabolic parameters as well as endothelial function were measured. <b><i>Results:</i></b> Systolic, mean arterial blood pressures, plasma tumor necrosis factor α levels, kidney weight to body weight (BW) ratio, and glucose levels were higher, while BW was lower in GK rats than in Wistar rats. Six-week treatment with sunitinib in GK rats did not affect these parameters but suppressed the increase in glucose levels. Endothelium-dependent relaxations were reduced in both aortas and mesenteric arteries isolated from GK as compared to Wistar rats, which was markedly reversed in both types of arteries from GK rats treated with sunitinib. <b><i>Conclusions:</i></b> This study demonstrates that sunitinib has a glucose-lowering effect and ameliorates endothelial dysfunction in both conduit and resistance arteries of GK rats.

scholarly journals Altered Purinergic Receptor Sensitivity in Type 2 Diabetes-Associated Endothelial Dysfunction and Up4A-Mediated Vascular Contraction

2018 ◽  
Vol 19 (12) ◽  
pp. 3942 ◽  
Author(s):  
Ali Mahdi ◽  
Tong Jiao ◽  
Yahor Tratsiakovich ◽  
Jiangning Yang ◽  
Claes-Göran Östenson ◽  
...  
Keyword(s):  
Endothelial Dysfunction ◽  
Endothelial Function ◽  
Vascular Function ◽  
Purinergic Receptor ◽  
Purinergic Signaling ◽  
Mesenteric Arteries ◽  
Vascular Contraction ◽  
Gk Rats ◽  
Vasoconstrictor Response

Purinergic signaling may be altered in diabetes accounting for endothelial dysfunction. Uridine adenosine tetraphosphate (Up4A), a novel dinucleotide substance, regulates vascular function via both purinergic P1 and P2 receptors (PR). Up4A enhances vascular contraction in isolated arteries of diabetic rats likely through P2R. However, the precise involvement of PRs in endothelial dysfunction and the vasoconstrictor response to Up4A in diabetes has not been fully elucidated. We tested whether inhibition of PRs improved endothelial function and attenuated Up4A-mediated vascular contraction using both aortas and mesenteric arteries of type 2 diabetic (T2D) Goto Kakizaki (GK) rats vs. control Wistar (WT) rats. Endothelium-dependent (EDR) but not endothelium-independent relaxation was significantly impaired in both aortas and mesenteric arteries from GK vs. WT rats. Non-selective inhibition of P1R or P2R significantly improved EDR in aortas but not mesenteric arteries from GK rats. Inhibition of A1R, P2X7R, or P2Y6R significantly improved EDR in aortas. Vasoconstrictor response to Up4A was enhanced in aortas but not mesenteric arteries of GK vs. WT rats via involvement of A1R and P2X7R but not P2Y6R. Depletion of major endothelial component nitric oxide enhanced Up4A-induced aortic contraction to a similar extent between WT and GK rats. No significant differences in protein levels of A1R, P2X7R, and P2Y6R in aortas from GK and WT rats were observed. These data suggest that altered PR sensitivity accounts for endothelial dysfunction in aortas in diabetes. Modulating PRs may represent a potential therapy for improving endothelial function.

scholarly journals Altered Glucose and Insulin Responses to Brain Medullary Thyrotropin-Releasing Hormone (TRH)-Induced Autonomic Activation in Type 2 Diabetic Goto-Kakizaki Rats

Endocrinology ◽  
2005 ◽  
Vol 146 (12) ◽  
pp. 5425-5432 ◽  
Author(s):  
Yan Ao ◽  
Natalie Toy ◽  
Moon K. Song ◽  
Vay Liang W. Go ◽  
Hong Yang
Keyword(s):  
Insulin Secretion ◽  
Blood Glucose ◽  
Wistar Rats ◽  
Mrna Levels ◽  
Gk Rats ◽  
Glucose Levels ◽  
Blood Glucose Levels ◽  
Autonomic Activation ◽  
Insulin Responses

Insulin secretion is impaired in type 2 diabetes (T2D). The insulin and glucose responses to central autonomic activation induced by excitation of brain medullary TRH receptors were studied in T2D Goto-Kakizaki (GK) rats. Blood glucose levels in normally fed, pentobarbital-anesthetized GK and nondiabetic Wistar rats were 193 and 119 mg/100 ml in males and 214 and 131 mg/100 ml in females. Intracisternal injection (ic) of the stable TRH analog RX 77368 (10 ng) induced significantly higher insulin response in both genders of overnight-fasted GK rats compared with Wistar rats and slightly increased blood glucose in female Wistar rats but significantly decreased it from 193 to 145 mg/100 ml in female GK rats. RX 77368 (50 ng) ic induced markedly greater glucose and relatively weaker insulin responses in male GK rats than Wistar rats. Bilateral vagotomy blocked ic RX 77368-induced insulin secretion, whereas adrenalectomy abolished its hyperglycemic effect. In adrenalectomized male GK but not Wistar rats, ic RX 77368 (50 ng) dramatically increased serum insulin levels by 6.5-fold and decreased blood glucose levels from 154 to 98 mg/100 ml; these changes were prevented by vagotomy. GK rats had higher basal pancreatic insulin II mRNA levels but a lower response to ic RX 77368 (50 ng) compared with Wistar rats. These results indicate that central-vagal activation-induced insulin secretion is susceptible in T2D GK rats. However, the dominant sympathetic-adrenal response to medullary TRH plays a suppressing role on vagal-mediated insulin secretion. This unbalanced vago-sympathetic activation by medullary TRH may contribute to the impaired insulin secretion in T2D.

Involvement of NO and MEK/ERK pathway in enhancement of endothelin-1-induced mesenteric artery contraction in later-stage type 2 diabetic Goto-Kakizaki rat

2009 ◽  
Vol 296 (5) ◽  
pp. H1388-H1397 ◽  
Author(s):  
Takayuki Matsumoto ◽  
Keiko Ishida ◽  
Naoaki Nakayama ◽  
Tsuneo Kobayashi ◽  
Katsuo Kamata
Keyword(s):  
Mesenteric Artery ◽  
Wistar Rats ◽  
Molecular Mechanisms ◽  
Mesenteric Arteries ◽  
No Production ◽  
Erk Pathway ◽  
Gk Rats ◽  
Protein Expressions ◽  
Type 2 Diabetic

Endothelin (ET)-1 is a likely candidate for a key role in diabetic vascular complications. However, no abnormalities in the vascular responsiveness to ET-1 have been identified in the chronic stage of type 2 diabetes. Our goal was to look for abnormalities in the roles played by ET receptors (ETA and ETB) in the mesenteric artery of the type 2 diabetic Goto-Kakizaki (GK) rat and to identify the molecular mechanisms involved. Using mesenteric arteries from later-stage (32–38 wk old) individuals, we compared the ET-1-induced contraction and the relaxation induced by the selective ETB receptor agonist IRL1620 between GK rats and control Wistar rats. Mesenteric artery ERK activity and the protein expressions for ET receptors and MEK were also measured. In GK rats (vs. age-matched Wistar rats), we found as follows. 1) The ET-1-induced contraction was greater and was attenuated by BQ-123 (ETA antagonist) but not by BQ-788 (ETB antagonist). In the controls, BQ-788 augmented this contraction. 2) Both the relaxation and nitric oxide (NO) production induced by IRL1620 were reduced. 3) ET-1-induced contraction was enhanced by NG-nitro-l-arginine (l-NNA; NO synthase inhibitor) but suppressed by sodium nitroprusside (NO donor). 4) The enhanced ET-1-induced contraction was reduced by MEK/ERK pathway inhibitors (PD-98059 or U0126). 5) ET-1-stimulated ERK activation was increased, as were the ETA and MEK1/2 protein expressions. 6) Mesenteric ET-1 content was increased. These results suggest that upregulation of ETA, a defect in ETB-mediated NO signaling, and activation of the MEK/ERK pathway together represent a likely mechanism mediating the hyperreactivity to ET-1 examined in this study.

scholarly journals GLP-1 Agonists Liraglutide Improved Vascular Endothelial Function in Type 2 Diabetes Rats

2020 ◽  
Vol 2 (2) ◽  
pp. 46-55
Author(s):  
Li X ◽  
Wu W ◽  
Wang Y ◽  
Zhang X ◽  
Feng X ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Type 2 Diabetes ◽  
Type 2 Diabetes Mellitus ◽  
Endothelial Dysfunction ◽  
Endothelial Function ◽  
Mesenteric Arteries ◽  
Vascular Endothelial ◽  
Vascular Endothelial Dysfunction ◽  
Vascular Endothelial Function

Objective: Liraglutide (LIRA), a Glucagon-like peptide-1 (GLP-1) receptor agonist, showed potential vascular protective effects with the mechanism remained incompletely understood. Therefore, this study aimed to investigate whether LIRA exerts its effect on vascular endothelial function in rats with type 2 diabetes mellitus (T2DM) via caveolin-1/ endothelial oxide synthase (eNOS) expression. Methods: T2DM rats were used as study subjects and randomly divided into four groups: 1) Veh group, 2) Veh+LIRA group, 3) T2DM group, and 4) T2DM+LIRA group. All rats received either saline or LIRA 0.2 mg/kg (by i.p. injection) per day for 4 weeks. After the model was successfully established, vascular endothelial function was determined the effect of vasodilator to mesenteric artery rings. Immunofluorescence and western blot were performed to understand the molecular mechanism. Cultured HUVECs with small interfering RNA (siRNA) under high glucose (HG), NO concentration, and western blot were performed to understand the molecular mechanism between LIRA and vascular endothelial function. Results: Based on our results, the LIRA reduced hyperglycemia and ameliorated vascular endothelial dysfunction in type 2 diabetic mice. LIRA activated eNOS phosphorylation, suppressing oxidative stress and enhancing endothelium-dependent vasorelaxation of mesenteric arteries. Besides, from its anti-oxidative capacity, LIRA activated eNOS to dilate the mesenteric arteries via the downregulation of Cav-1. Conclusion: LIRA ameliorates vascular endothelial dysfunction in rats with type 2 diabetes mellitus via anti-oxidative and activated eNOS by downregulated Cav-1.

scholarly journals Endothelial dysfunction precedes hypertension in diet-induced insulin resistance

1998 ◽  
Vol 275 (3) ◽  
pp. R788-R792 ◽  
Author(s):  
Prasad V. G. Katakam ◽  
Michael R. Ujhelyi ◽  
Margarethe E. Hoenig ◽  
Allison Winecoff Miller
Keyword(s):  
Insulin Resistance ◽  
Endothelial Dysfunction ◽  
Serum Insulin ◽  
Serum Glucose ◽  
Mesenteric Arteries ◽  
Control Group ◽  
Sprague Dawley ◽  
Insulin Resistant ◽  
Glucose Levels

The insulin-resistant (IR) syndrome may be an impetus for the development of hypertension (HTN). Unfortunately, the mechanism by which this could occur is unclear. Our laboratory and others have described impaired endothelium-mediated relaxation in IR, mildly hypertensive rats. The purpose of the current study is to determine if HTN is most likely a cause or result of impaired endothelial function. Sprague-Dawley rats were randomized to receive a fructose-rich diet for 3, 7, 10, 14, 18, or 28 days or were placed in a control group. The control group received rat chow. After diet treatment, animals were instrumented with arterial cannulas, and while awake and unrestrained, their blood pressure (BP) was measured. Subsequently, endothelium-mediated relaxation to acetylcholine was determined (in vitro) by measuring intraluminal diameter of phenylephrine-preconstricted mesenteric arteries (∼250 μM). Serum insulin levels were significantly elevated in all groups receiving fructose feeding compared with control, whereas there were no differences in serum glucose levels between groups. Impairment of endothelium-mediated relaxation starts by day 14 [mean percent maximal relaxation (Emax): 69 ± 10% of baseline] and becomes significant by day 18 (Emax: 52 ± 11% of baseline; P < 0.01). However, the mean BP (mmHg) does not become significantly elevated until day 28 [BP: 132 ± 1 ( day 28) vs. 116 ± 3 (control); P < 0.05]. These findings demonstrate that both IR and endothelial dysfunction occur before HTN in this model and suggest that endothelial dysfunction may be a mechanism linking insulin resistance and essential HTN.

Fenofibrate improves endothelial function in the brachial artery and forearm resistance arterioles of statin-treated Type 2 diabetic patients

2010 ◽  
Vol 118 (10) ◽  
pp. 607-615 ◽  
Author(s):  
Sandra J. Hamilton ◽  
Gerard T. Chew ◽  
Timothy M.E. Davis ◽  
Gerald F. Watts
Keyword(s):  
Endothelial Dysfunction ◽  
Endothelial Function ◽  
Statin Therapy ◽  
Brachial Artery ◽  
Ldl Cholesterol ◽  
Density Lipoprotein ◽  
Diabetic Patients ◽  
Type 2 Diabetic Patients ◽  
Type 2 Diabetic

Dyslipidaemia contributes to endothelial dysfunction and CVD (cardiovascular disease) in Type 2 diabetes mellitus. While statin therapy reduces CVD in these patients, residual risk remains high. Fenofibrate corrects atherogenic dyslipidaemia, but it is unclear whether adding fenofibrate to statin therapy lowers CVD risk. We investigated whether fenofibrate improves endothelial dysfunction in statin-treated Type 2 diabetic patients. In a cross-over study, 15 statin-treated Type 2 diabetic patients, with LDL (low-density lipoprotein)-cholesterol <2.6 mmol/l and endothelial dysfunction [brachial artery FMD (flow-mediated dilatation) <6.0%] were randomized, double-blind, to fenofibrate 145 mg/day or matching placebo for 12 weeks, with 4 weeks washout between treatment periods. Brachial artery FMD and endothelium-independent NMD (nitrate-mediated dilatation) were measured by ultrasonography at the start and end of each treatment period. PIFBF (post-ischaemic forearm blood flow), a measure of microcirculatory endothelial function, and serum lipids, lipoproteins and apo (apolipoprotein) concentrations were also measured. Compared with placebo, fenofibrate increased FMD (mean absolute 2.1±0.6 compared with −0.3±0.6%, P=0.04), but did not alter NMD (P=0.75). Fenofibrate also increased maximal PIFBF {median 3.5 [IQR (interquartile range) 5.8] compared with 0.3 (2.1) ml/100 ml/min, P=0.001} and flow debt repayment [median 1.0 (IQR 3.5) compared with −1.5 (3.0) ml/100 ml, P=0.01]. Fenofibrate lowered serum cholesterol, triacylgycerols (triglycerides), LDL-cholesterol, apoB-100 and apoC-III (P≤0.03), but did not alter HDL (high-density lipoprotein)-cholesterol or apoA-I. Improvement in FMD was inversely associated with on-treatment LDL-cholesterol (r=−0.61, P=0.02) and apoB-100 (r=−0.54, P=0.04) concentrations. Fenofibrate improves endothelial dysfunction in statin-treated Type 2 diabetic patients. This may relate partly to enhanced reduction in LDL-cholesterol and apoB-100 concentrations.

scholarly journals Clinacanthus nutans Leaves Extract Reverts Endothelial Dysfunction in Type 2 Diabetes Rats by Improving Protein Expression of eNOS

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Ahmad Khusairi Azemi ◽  
Siti Safiah Mokhtar ◽  
Aida Hanum Ghulam Rasool
Keyword(s):  
Type 2 Diabetes ◽  
Endothelial Dysfunction ◽  
Endothelial Function ◽  
Protein Expression ◽  
Diabetic Rats ◽  
Organ Bath ◽  
Aortic Endothelium ◽  
Clinacanthus Nutans ◽  
Enos Protein

Diabetes mellitus is associated with endothelial dysfunction; it causes progressive vascular damage resulting from an impaired endothelium-dependent vasorelaxation. In the diabetes state, presence of hyperglycemia and insulin resistance predisposes to endothelial dysfunction. Clinacanthus nutans, widely used as a traditional medicine for diabetes is reported to have hypoglycemic, hypolipidemic, antioxidant, and anti-inflammatory properties. However, the possibility of C. nutans affecting the vascular endothelial function in diabetes remains unclear. This study was aimed at evaluating the effects of C. nutans methanolic leaves extract (CNME) on endothelial function in a type 2 diabetes (T2DM) rat model. Sixty male Sprague-Dawley rats were divided into five groups (n=12 per group): nondiabetic control, nondiabetic treated with four weeks of CNME (500 mg/kg/daily), untreated diabetic rats, diabetic treated with metformin (300 mg/kg/daily), and diabetic treated with CNME (500 mg/kg/daily). T2DM was induced by a single intraperitoneal injection of low-dose streptozotocin (STZ) to rats fed with high-fat diet (HFD). Endothelial-dependent and endothelial-independent relaxations and contractions of the thoracic aorta were determined using the organ bath. Aortic endothelial nitric oxide synthase (eNOS) expression was determined using Western blotting. Endothelial-dependent relaxation was reduced in diabetic rats. Both diabetic groups treated with CNME or metformin significantly improved the impairment in endothelium-dependent vasorelaxation; this was associated with increased expression of aortic eNOS protein. CNME- and metformin-treated groups also reduced aortic endothelium-dependent and aortic endothelium-independent contractions in diabetics. Both of these diabetic-treated groups also reduced blood glucose levels and increased body weight compared to the untreated diabetic group. In conclusion, C. nutans improves endothelial-dependent vasodilatation and reduces endothelial-dependent contraction, thus ameliorating endothelial dysfunction in diabetic rats. This may occur due to its effect on increasing eNOS protein expression.

scholarly journals Endothelial Dysfunction: A Contributor to Adverse Cardiovascular Remodeling and Heart Failure Development in Type 2 Diabetes beyond Accelerated Atherogenesis

2020 ◽  
Vol 9 (7) ◽  
pp. 2090 ◽  
Author(s):  
Aleksandra Gamrat ◽  
Michał A. Surdacki ◽  
Bernadeta Chyrchel ◽  
Andrzej Surdacki
Keyword(s):  
Heart Failure ◽  
Type 2 Diabetes ◽  
Endothelial Dysfunction ◽  
Microvascular Complications ◽  
Cardiovascular Remodeling ◽  
Lv Dysfunction ◽  
Lv Remodeling ◽  
No Bioavailability ◽  
Lv Diastolic Dysfunction

Endothelial dysfunction, associated with depressed nitric oxide (NO) bioavailability, is a well-recognized contributor to both accelerated atherogenesis and microvascular complications in type 2 diabetes (DM). However, growing evidence points to the comorbidities-driven endothelial dysfunction within coronary microvessels as a key player responsible for left ventricular (LV) diastolic dysfunction, restrictive LV remodeling and heart failure with preserved ejection fraction (HFpEF), the most common form of heart failure in DM. In this review we have described: (1) multiple cellular pathways which may link depressed NO bioavailability to LV diastolic dysfunction and hypertrophy; (2) hemodynamic consequences and prognostic effects of restrictive LV remodeling and combined diastolic and mild systolic LV dysfunction on cardiovascular outcomes in DM and HFpEF, with a focus on the clinical relevance of endothelial dysfunction; (3) novel therapeutic strategies to improve endothelial function in DM. In summary, beyond associations with accelerated atherogenesis and microvascular complications, endothelial dysfunction supplements the multiple interwoven pathways affecting cardiomyocytes, endothelial cells and the extracellular matrix with consequent LV dysfunction in DM patients. The association amongst impaired endothelial function, reduced coronary flow reserve, combined LV diastolic and discrete systolic dysfunction, and low LV stroke volume and preload reserve—all of which are adverse outcome predictors—is a dangerous constellation of inter-related abnormalities, underlying the development of heart failure. Nevertheless, the relevance of endothelial effects of novel drugs in terms of their ability to attenuate cardiovascular remodeling and delay heart failure onset in DM patients remains to be investigated.

Previous gestational diabetes impairs long-term endothelial function in a mouse model of complicated pregnancy

2010 ◽  
Vol 299 (3) ◽  
pp. R862-R870 ◽  
Author(s):  
Joanna L. Stanley ◽  
Sowndramalingam Sankaralingam ◽  
Philip N. Baker ◽  
Sandra T. Davidge
Keyword(s):  
Endothelial Dysfunction ◽  
Gestational Diabetes ◽  
Mouse Model ◽  
Endothelial Function ◽  
Fluorescence Intensity ◽  
Mean Fluorescence Intensity ◽  
Mesenteric Arteries ◽  
Superoxide Production ◽  
Increased Risk

Women who develop gestational diabetes mellitis (GDM) display endothelial dysfunction up to 1 yr after pregnancy, despite a return to normoglycemia. It is unknown whether this dysfunction was preexisting or whether GDM pregnancy leads to long-term endothelial dysfunction. A mouse model that spontaneously develops GDM ( Lepr db/+) was used to determine whether the endothelial dysfunction that develops during GDM is evident in later life. Heterozygous and wild-type (WT) controls were allowed to litter once, then age to 9–10 mo, and were compared with virgin controls. Vascular function of small mesenteric arteries was assessed using wire myography. Concentration response curves to the thromboxane A2mimetic U46619 and the endothelium-dependent vasodilator methacholine were constructed. Superoxide production and peroxynitrite formation was also measured. Mice with previous GDM displayed blood glucose concentrations similar to previously pregnant WT mice (8.0 ± 0.1 vs. 7.1 ± 0.3 mmol/l, P > 0.05). Arteries from mice with previous GDM displayed increased sensitivity to U46619 (EC50 5.2 ± 0.7 vs. 45.2 ± 1.0 nmol/l, P < 0.01) and impaired endothelium-dependent relaxation compared with WT controls (29 ± 8 vs. 58 ± 16 percent relaxation, P < 0.05). This was associated with increased superoxide production (93.3 ± 2.3 vs. 64.6 ± 1.6 mean fluorescence intensity, P < 0.001) and increased peroxynitrite formation (173.5 ± 11.0 vs. 57.4 ± 16.2 mean fluorescence intensity, P < 0.01) compared with virgin controls. In summary, endothelial dysfunction was evident in mice with previous GDM compared with previously healthy pregnant mice or virgin controls. These data suggest that GDM affects endothelial function and may contribute to an increased risk of cardiovascular disease.

Metformin normalizes endothelial function by suppressing vasoconstrictor prostanoids in mesenteric arteries from OLETF rats, a model of type 2 diabetes

2008 ◽  
Vol 295 (3) ◽  
pp. H1165-H1176 ◽  
Author(s):  
Takayuki Matsumoto ◽  
Eri Noguchi ◽  
Keiko Ishida ◽  
Tsuneo Kobayashi ◽  
Nobuhiro Yamada ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Type 2 Diabetes ◽  
Endothelial Function ◽  
Mesenteric Arteries ◽  
Oletf Rats ◽  
Diabetes Model ◽  
Amp Activated Protein Kinase ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

We previously reported that in mesenteric arteries from aged Otsuka Long-Evans Tokushima fatty (OLETF) rats (a type 2 diabetes model) endothelium-derived hyperpolarizing factor (EDHF)-type relaxation is impaired while endothelium-derived contracting factor (EDCF)-mediated contraction is enhanced (Matsumoto T, Kakami M, Noguchi E, Kobayashi T, Kamata K. Am J Physiol Heart Circ Physiol 293: H1480–H1490, 2007). Here we investigated whether acute and/or chronic treatment with metformin might improve this imbalance between the effects of the above endothelium-derived factors in mesenteric arteries isolated from OLETF rats. In acute studies on OLETF mesenteric arteries, ACh-induced relaxation was impaired and the relaxation became weaker at high ACh concentrations. Both metformin and 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside [AICAR, an AMP-activated protein kinase (AMPK) activator that is also activated by metformin] 1) diminished the tendency for the relaxation to reverse at high ACh concentrations and 2) suppressed both ACh-induced EDCF-mediated contraction and ACh-stimulated production of prostanoids (thromboxane A2 and PGE2). In studies on OLETF arteries from chronically treated animals, metformin treatment (300 mg·kg−1·day−1 for 4 wk) 1) improved ACh-induced nitric oxide- or EDHF-mediated relaxation and cyclooxygenase (COX)-mediated contraction, 2) reduced EDCF-mediated contraction, 3) suppressed production of prostanoids, and 4) reduced superoxide generation. Metformin did not alter the protein expressions of endothelial nitric oxide synthase (eNOS), phospho-eNOS (Ser1177), or COX-1, but it increased COX-2 protein. These results suggest that metformin improves endothelial functions in OLETF mesenteric arteries by suppressing vasoconstrictor prostanoids and by reducing oxidative stress. Our data suggest that within the timescale studied here, metformin improves endothelial function through this direct mechanism, rather than by improving metabolic abnormalities.

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