The effect of vanadyl treatment on vascular responsiveness of streptozotocin-diabetic rats

Mediating macrophage immunity with wogonin in mice with vascular inflammation

Vascular inflammation may induce a number of diseases, including organ damage or failure, heart attack and stroke. The present study aimed to investigate the use of wogonin, a compound extracted from herbs, to mediate inflammatory reactions in vascular inflammation. Wogonin was loaded in a well‑characterized polymeric biomaterial carrier. In mice with streptozotocin‑induced vascular inflammation, wogonin treatment regulated the production of inflammatory cytokines, including interleukin‑6, tumor necrosis factor‑α and granulocyte macrophage colony‑stimulating factor. To understand the impact of wogonin on major immune cells, macrophages were treated with wogonin in vitro. It was determined that wogonin did not affect macrophage viability, and that wogonin regulated the relative ratio of M1 versus M2 macrophages. In addition, in co‑culture, wogonin decreased inflammatory cytokine production and regulated the activation of macrophage surface markers including CD80, CD86 and CD40. Results from the present study may aid in our understanding of the effects of wogonin in regulating inflammation, especially its effects on macrophages.

6-Gingerol alleviates exaggerated vasoconstriction in diabetic rat aorta through direct vasodilation and nitric oxide generation

The aim of the present study is to investigate the effect and potential mechanism of action of 6-gingerol on alterations of vascular reactivity in the isolated aorta from diabetic rats. Male Wistar rats were divided into two experimental groups, control and diabetics. Diabetes was induced by a single intraperitoneal injection of streptozotocin (50 mg kg⁻¹), and the rats were left for 10 weeks to develop vascular complications. The effect of in vitro incubation with 6-gingerol (0.3–3 μM) on the vasoconstrictor response of the isolated diabetic aortae to phenylephrine and the vasodilator response to acetylcholine was examined. Effect of 6-gingerol was also examined on aortae incubated with methylglyoxal as an advanced glycation end product (AGE). To investigate the mechanism of action of 6-gingerol, the nitric oxide synthase inhibitor Nω-nitro-l-arginine methyl ester hydrochloride (100 μM), guanylate cyclase inhibitor methylene blue (5 μM), calcium-activated potassium channel blocker tetraethylammonium chloride (10 mM), and cyclooxygenase inhibitor indomethacin (5 μM) were added 30 minutes before assessing the direct vasorelaxant effect of 6-gingerol. Moreover, in vitro effects of 6-gingerol on NO release and the effect of 6-gingerol on AGE production were examined. Results showed that incubation of aortae with 6-gingerol (0.3–10 μM) alleviated the exaggerated vasoconstriction of diabetic aortae to phenylephrine in a concentration-dependent manner with no significant effect on the impaired relaxatory response to acetylcholine. Similar results were seen in the aortae exposed to methylglyoxal. In addition, 6-gingerol induced a direct vasodilation effect that was significantly inhibited by Nω-nitro-l-arginine methyl ester hydrochloride and methylene blue. Furthermore, 6-gingerol stimulated aortic NO generation but had no effect on AGE formation. In conclusion, 6-gingerol ameliorates enhanced vascular contraction in diabetic aortae, which may be partially attributed to its ability to increase the production of NO and stimulation of cyclic guanosine monophosphate.

Assessment of antidiabetogenic potential of fermented soybean extracts in streptozotocin-induced diabetic rat

Most of the available drugs for the treatment of diabetes mellitus (DM) produce detrimental side effects, which has prompted an ongoing search for plant with the antidiabetic potential. The present study investigated the effect of soybean extracts fermented with Bacillus subtilis MORI, fermented soybean extracts (BTD-1) was investigated in streptozotocin (STZ)-induced diabetic rats. The possible effects of BTD-1 against hyperglycemia and free radical-mediated oxidative stress was investigated by assaying the plasma glucose level and the activity of enzymatic antioxidants, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and malondialdehyde (MDA). A significant increase in the levels of both plasma glucose and reactive oxygen species (ROS) was observed in the diabetic rats when compared to normal control group. After administration of BTD-1 (500 and 1000 mg/kg/day), the elevated plasma glucose level was significantly reduced while the plasma insulin level and the activities of SOD, GSH-Px, CAT and MDA were significantly increased. The results suggest that administration of BTD-1 can inhibit hyperglycemia and free radical-mediated oxidative stress. The administration of BTD-1 also inhibited the contractile response by norepinephrine (10(-10)-10(-5) M) in the presence of endothelium, and caused significant relaxation by carbachol (10(-8)-10(-5) M) in rat aorta. These findings indicate that BTD-1 improves vascular functions on STZ-induced diabetic rats. Therefore, subchronic administration of BTD-1 could prevent the functional changes in vascular reactivity in STZ-induced diabetic rats. The collective findings support that administration of BTD-1 may prevent some diabetes-related changes in vascular reactivity directly and/or indirectly due to its hypoglycaemic effect and inhibition of production of ROS.

Effect of phenolic acids on functions of rat aorta, vas deferens and on metabolic changes in streptozotocin-induced diabetes

Objectives:

This study aimed to investigate the effects of antioxidant treatment on streptozotocin (STZ)-induced diabetic metabolic and smooth muscle (SM) complications in rats.

Materials and Methods:

Threeweeks after STZ injection (i.v.), vehicle, p-OH benzoic (p-OHBA), protocatechic (PA) and gallic acids (GA) were separately administered (10 mg/kg each, i.p.) to the rats everyday for 3 weeks. Metabolic functions were observedregularly. The rats in all groups were sacrificed andaorta and Vas deferens were dissected. Theresponses of isolated organs to agonists (acetylcholine and phenylephrine) were recorded.

Results:

Protocatechic acid prevented increase in food consumption and feces output significantly. The responses of isolated organs to agonists increased in the STZ-diabetic rats. The test drugs either prevented, exacerbated or didnot affect the SMchanges in the STZ-diabetic rats.

Conclusions:

It was concluded that p-OHBA, PA and GA may cause effects independently of their antioxidant effect and/or of diabeticcomplications. They may exhibit pro-oxidant activities in the experimental conditions applied.

Mechanisms responsible for the vascular effect of aqueous Trigonella foenum-graecum leaf extract in diabetic rats

BACKGROUND AND OBJECTIVE

Since a beneficial vascular effect of aqueous leaf extract of Trigonella foenum-graecum (TFG) has previously been reported, this study was conducted to evaluate the underlying mechanisms, including the role of nitric oxide (NO) and cyclooxygenase pathways, in diabetic rats.

MATERIALS AND METHODS

Male Wistar rats were divided into control, extract-treated control, diabetic, and extract-treated diabetic groups. Diabetes was induced by a single i.p. injection of streptozotocin (STZ; 60 mg/kg). Treatment groups received TFG extract (200 mg/kg; ip.) every other day for 1 month. Contractile reactivity of the thoracic aorta to KCl and noradrenaline (NA) and relaxation response to acetylcholine (ACh) were determined. For determination of the participation of NO and prostaglandins in the relaxation response to ACh, aortic rings were incubated for 30 min before the experiment with N-nitro-l-arginine methyl ester (L-NAME) and/or indomethacin (INDO).

RESULTS

The diabetic state significantly increased the maximum contractile response to KCl and NA (P < 0.01-0.005) and reduced the maximum relaxation due to ACh (P < 0.01) as compared to controls and treatment with TFG extract in the diabetic group significantly improved these changes relative to the untreated diabetic group (P < 0.05). With L-NAME pretreatment, no significant difference between diabetic and extract-treated diabetic groups was found out. On the other hand, there was a significant difference between these two groups following INDO pretreatment (P < 0.05).

CONCLUSION

Intraperitoneal administration of aqueous leaf extract of TFG for one month could improve some functional indices of the vascular system in the diabetic state and endothelium-derived prostaglandins are essential in this respect.

Effect of salvianolic acid A on vascular reactivity of streptozotocin-induced diabetic rats

AIMS

The present study aims to evaluate the beneficial effect of salvianolic acid A (SAA) on the alterations in vascular reactivity of streptozotocin (STZ)-induced diabetic rats.

MAIN METHODS

Diabetes was induced by a single intraperitoneal injection of STZ (60 mg/kg). Following 16 weeks of SAA treatment (1 mg/kg/day), thoracic aortic rings of rats were mounted in organ baths. Contractile responses to noradrenaline (NA) and KCl and relaxant responses to acetylcholine (ACh) and sodium nitroprusside (SNP) were assessed.

KEY FINDINGS

Loss of weight, hyperglycemia, elevated content of malondialdehyde (MDA) and decline of total antioxidant capacity (TAC) were observed in diabetic rats. SAA could reverse these metabolic and biochemical abnormalities. Compared to the control, the maximum contraction (E(max)) to NA, but not sensitivity (pD(2)), increased significantly in diabetic aortas, which was prevented by SAA treatment. However, the response of rat aortas to KCl (E(max) and pD(2)) was not altered either in diabetic group or SAA treatment compared with that of normal control group. We also observed the significant decrease in relaxation to ACh rather than SNP in diabetic group compared with controls, and SAA treatment could revert the ACh response.

SIGNIFICANCE

It is concluded that oral administration of SAA can significantly improve glucose metabolism and inhibit oxidative injury as well as protect against impaired vascular responsiveness in STZ-induced diabetic rats.

Mechanisms underlying quercetin-induced vasorelaxation in aorta of subchronic diabetic rats: an in vitro study

In this study, the mechanisms involved in vasorelaxant effect of the flavonoid quercetin was investigated in isolated aortic rings from streptozotocin (STZ)-diabetic rats. After 4 weeks, addition of quercetin (0.1 microM-1 mM) caused a significant dose-dependent relaxation of noradrenaline (NA)- and KCl-preconstricted rings in both control and diabetic groups with a significant inter-group difference of P<0.01. Furthermore, both nitro-L-arginine-methyl ester (L-NAME, 100 microM) and indomethacin (10 microM) markedly attenuated the vasorelaxant responses following quercetin application. Meanwhile, endothelium removal significantly attenuated the quercetin-induced vasorelaxation. It is concluded that the quercetin can relax the preconstricted rings of aorta in subchronic STZ-diabetic rats through nitric oxide- and -prostaglandin-mediated pathways, which themselves could be considered as endothelium-dependent.

Protective effect of enalapril on vascular reactivity of the rat aorta

Cardiovascular complications are the major cause of morbidity and mortality in patients with diabetes mellitus (DM). Strategies that interrupt the renin-angiotensin system have been shown to reduce the ensuing threatening risk factors. The present study was carried out to investigate the effect of subchronic administration of enalapril on the aortic reactivity of streptozotocin (STZ)-diabetic rats. For this purpose, STZ-diabetic rats received enalapril (10 and 20 mg/kg ip) daily for 2 months. Contractile responses to phenylephrine (PE) and relaxation responses to acetylcholine (Ach) and isosorbide dinitrate (ISD) were obtained from aortic rings. Concentration-response curves from enalapril-treated diabetic (ED) rats to PE were attenuated as compared to vehicle-treated diabetics (VD), especially at a dose of 20 mg/kg for enalapril. In addition, endothelium-dependent relaxation responses induced by Ach was significantly higher in ED rats as compared to diabetic ones. The endothelium-independent relaxation responses for ISD were also found not to be significantly different among the groups. Therefore, subchronic treatment of diabetic rats with enalapril in a dose-dependent manner could prevent the functional changes in vascular reactivity in diabetic rats.

Endothelium-dependent and -independent effect of aqueous extract of garlic on vascular reactivity on diabetic rats

Garlic has been well known for its protective effects against cardiovascular disease. In this study, the effect of aqueous extract of garlic on the vascular reactivity of thoracic aorta from streptozotocin (STZ)-diabetic rats was investigated in the presence and absence of endothelium. Although, 8-weeks of treatment with garlic extract had no significant effect on the concentration of serum glucose, but it significantly attenuated the abnormality in vascular reactivity to noradrenaline (NA) and acetylcholine (Ach). In addition, the endothelium-independent relaxation response to isosorbide dinitrate (ISD) was not affected by diabetes or garlic treatment. The results suggest that garlic treatment of STZ-diabetic rats can prevent the development of abnormal contractility through an endothelium-dependent and -independent mechanism.

Beneficial effect of aqueous garlic extract on the vascular reactivity of streptozotocin-diabetic rats

The present study evaluated the beneficial effect of aqueous extract of garlic (Allium sativum L.; 100mg/kg/day) on the alterations in vascular reactivity of streptozotocin-diabetic rats. After 8 weeks of treatment, thoracic aortic rings of rats were mounted in organ baths and contractile responses to phenylephrine and relaxant responses to acetylcholine and isosorbide dinitrate were assessed. Induction of diabetes significantly increased contractile responses to phenylephrine and impaired endothelium-dependent relaxations to acetylcholine in aortic rings, but did not change endothelium-independent relaxation to isosorbide dinitrate. Garlic administration significantly improved the impaired endothelium-dependent relaxations and decreased the enhanced contractile response to phenylephrine in diabetic rats. It is concluded that intraperitoneal administration of aqueous garlic extract can improve endothelial dysfunction in insulin-dependent model of uncontrolled diabetes.

Effect of 5-aminoimidazole-4-carboxamide riboside (AICA-r) on isolated thoracic aorta responses in streptozotocin-diabetic rats

Diabetes mellitus alters the vascular responsiveness to several vasoconstrictors and vasodilators. 5-amino-4-imidazole-carboxamide riboside (AICA-r), a nucleoside corresponding to AICA-ribotide and an intermediate of the de novo pathway of purine biosynthesis, was recently proposed as a new insulinotropic tool in non-insulin-dependent diabetes mellitus. The aim of the present study was to define whether AICA-r affects altered vascular responsiveness to vasoconstrictors and vasodilators in the thoracic aorta of neonatal streptozotocin (STZ)-diabetic rats. The results of this study indicate that a 1-month treatment with AICA-r significantly increases the body weight in diabetic rats; significantly decreases the blood glucose level of diabetic rats (from 302+/-47 to 135+/-11 mg/dL, p<0.001); does not significantly affect the fast, slow, and total components of responses to noradrenaline in all the experimental groups; reverses the increased Emax values of noradrenaline in diabetic rats to near-control values; reverses the completely abolished responses of acetylcholine (pD2 and percent relaxation) in diabetic rats to control values; and reverses the decreased pD2 values of sodium nitroprussiate in diabetic rats to control values. In conclusion, AICA-r treatment in neonatal STZ-diabetic rats improved increased blood glucose levels, accelerated weight gain, reversed endothelial dysfunction, and normalized vascular responses.

The effects of chronic L-arginine treatment on vascular responsiveness of streptozotocin-diabetic rats

In this study, the protective effects of L-arginine treatment in vivo on vascular reactivity of streptozotocin (STZ)-induced 12-week-old diabetic rats were examined. Loss of weight, polydipsia, polyphagia, hyperglycemia, hypoinsulinemia, and elevated levels of plasma cholesterol and triglyceride were observed in diabetic rats. L-arginine treatment (1 mg/mL in drinking water) did not significantly affect these metabolic and biochemical abnormalities. Plasma malondialdehyde (MDA) levels in untreated diabetic rats were also significantly higher than untreated controls. However, L-arginine treatment prevented the increase in MDA level of plasma of diabetic rats. Contractile responses, but not sensitivity to noradrenaline (NA), were significantly increased in diabetic rats compared to controls. Treatment of diabetic rats with L-arginine completely prevented the increase in NA responses. Relaxation response to acetylcholine (ACh), but not to sodium nitroprusside (SNP), in diabetic aorta has been found to be significantly decreased as compared with controls. However, there were no significant differences in pD2 values of acetylcholine in either of the groups. L-arginine treatment increased the ACh responses to the control level. All effects of L-arginine on vascular reactivity were found to be specific for diabetic rats and not controls. These results suggest that functional abnormalities occurred in aorta from diabetic rat might at least in part result from L-arginine deficiency, and the lipid peroxidation-lowering effect of L-arginine may account for its protective effect on vascular reactivity of diabetic rats.

Vanadate treatment normalizes exaggerated vascular smooth muscle responses in the obese Zucker rat

The effect of oral vanadate treatment on isometric tension responses were examined in aortic rings isolated from obese and lean Zucker rats. Rats from both strains that were either maintained on food ad libitum or pair-fed were included to serve as controls. Higher plasma insulin and glucose levels and exaggerated aortic tension responses to endothelin-1, methoxamine, and KCl observed in obese Zucker rats were normalized in vanadate treated, but not pair-fed, rats. These data suggest that abnormal vascular responses in obese Zucker rats can be normalized by vanadate treatment in a manner at least partly independent of food intake.

Renal arterial reactivity to potassium, noradrenaline, and neuropeptide Y and association with urinary albumin excretion in the diabetic rat

A changed vasomotor reactivity of renal arteries may lead to defect autoregulation of renal hemodynamics with damage of diabetic kidneys. Eleven streptozotocin-induced diabetic male Wistar rats were daily treated with insulin in order to achieve a blood glucose of 21 mmol/L. Seventeen age and gender-matched rats served as controls. After 50 days, the kidneys were rapidly removed, arteria renalis and the first branches of the intrarenal arteries were dissected free. The arterial reactivity was tested with a sensitive in vitro method. The reactivity to noradrenaline was tested by cumulative application (10(-9) to 3 x 10(-4) M) before and after a single concentration of neuropeptide Y (NPY). Potassium (60 mM) and noradrenaline induced a strong contraction of all arteries with similar response in diabetic and control rats. The effect of noradrenaline after NPY was unchanged in renal vessels of control rats, whereas it was diminished in intrarenal vessels for both diabetic and control rats. Similarly, a diminished response was found for renal arteries in diabetic rats, an effect which was related to the level of blood glucose (r = 0.62, 2p = 0.04). The urinary excretion rate of albumin in the diabetic rats was related to the largest noradrenaline induced contraction (r = 0.71, 2p = 0.01) of renal but not of intrarenal arteries. In conclusion, there was no difference in potassium and noradrenaline evoked contractions in renal and intrarenal arteries in diabetic and control rats. NPY decreased the contractile response to noradrenaline. The high blood glucose slightly increased this effect of NPY.

Antioxidant and triglyceride-lowering effects of vitamin E associated with the prevention of abnormalities in the reactivity and morphology of aorta from streptozotocin-diabetic rats. Antioxidants in Diabetes-Induced Complications (ADIC) Study Group

In this study, we evaluated the effects of vitamin E on the vascular reactivity and structure of thoracic aorta from streptozotocin (STZ)-diabetic rats. Plasma glucose, cholesterol, and triglyceride concentrations in rats were increased markedly by STZ-diabetes. The thiobarbituric acid (TBA) reactivity level as an index of lipid peroxidation was higher in both plasma and aorta of STZ-diabetic rats compared with controls. The rings of thoracic aorta with or without endothelium were mounted in organ chambers for measurement of isometric tension and were contracted by a single dose (10-5 mol/L) and then cumulative doses of noradrenaline ([NA] 10(-9) to 10(-5) mol/L). Pretreatment with methylene blue (MB) or removal of the endothelium resulted in a similar degree of enhancement in NA-induced contraction of control rings. STZ-diabetes increased the fast and slow components of NA-induced contraction in all experiments. The maximal contractile response of aorta to NA was also augmented by STZ-diabetes, whereas the sensitivity (pD2) remained unaltered. STZ-diabetes resulted in significant increases in the maximum contractile response and sensitivity of aorta to KCl. STZ-diabetic rats showed a significant reduction in the percentage of endothelial response (PER). A group of diabetic rats was treated from the time of diabetes induction with a 0.5% dietary supplement of vitamin E. Vitamin E supplementation of STZ-diabetic rats eliminated accumulation of lipid peroxides and returned plasma triglycerides toward normal levels. Diabetes-induced abnormal contractility and endothelial dysfunction were significantly but not completely prevented by vitamin E treatment. The endothelium-independent relaxation response to sodium nitroprusside (SNP) was not affected by diabetes or vitamin E treatment. Electron microscopic examination of thoracic aorta revealed that normal tissue organization was disrupted in STZ-diabetic rats, and that vitamin E treatment can protect the morphological integrity of aorta against STZ-diabetes. The results suggest the following: (1) The increased triglycerides/lipid peroxides may be an important reason for morphological or functional disruption of endothelium and enhanced activation of contractile mechanisms of vascular smooth muscle in STZ-diabetic rats. Both contribute to an increased responsiveness of diabetic aorta to vasoconstrictor agents. (2) Vitamin E treatment of STZ-diabetic rats can prevent the development of abnormal contractility and structure and endothelial dysfunction in aorta. (3) The triglyceride- and/or lipid peroxidation-lowering effect of vitamin E may be crucial for the protective effect of this vitamin on the vasculature.

Duration-dependent changes in calcium responsiveness in the alloxan-diabetic rat intestine

Disturbances of the gastrointestinal tract that are common in diabetes mellitus seem to be related to intestinal motility. In experimental models of diabetes, decreased calcium sensitivity has been demonstrated in various smooth muscles including those in the gastrointestinal tract. The main purpose of the present study was to examine further the calcium sensitivity in diabetic rat intestine and to understand if changes in the calcium sensitivity occur at an earlier stage of the disease. For this purpose, the effects of potassium and calcium were evaluated on nondepolarized and depolarized duodenum from rats with alloxan diabetes for 1 and 8 weeks and their age-matched controls. To evaluate the calcium sensitivity in rat duodenum, apparent affinity constants (pD2 values) and intrinsic activities (alpha E values) were calculated for every experimental conditions examined in this study. Both values (pD2 and alpha E) for the effects of potassium and calcium on the nondepolarized and depolarized duodenum, respectively, were not changed in 1-week diabetic rats. In contrast, intrinsic activities for the effects of potassium and calcium were found to be significantly decreased (p < 0.001) in the nondepolarized and depolarized duodenum from rats with alloxan diabetes for 8 weeks, whereas apparent affinity constants were not altered in this case. Taking into consideration all these experimental findings, the decreased calcium sensitivity in gastrointestinal tract seems to be closely related to decreased calmodulin levels and may occur at a later stage of diabetes as a linkage to long-term gastrointestinal complications.

Effect of insulin treatment on smooth muscle calmodulin levels in rats with long-term streptozotocin-diabetes

Altered responses to several agonists have been reported in various smooth muscles from experimentally-diabetic animals suggesting a defective contractile process of smooth muscle. Recently, decreased smooth muscle calmodulin levels have been reported in streptozotocin-diabetic rats. However, the effectiveness of insulin on the decreased calmodulin levels in diabetic rats has not been questioned. Therefore, the present study was designed to examine the effect of insulin on smooth muscle calmodulin levels from streptozotocin-diabetic rats. Calmodulin levels of the smooth muscle were measured by a radioimmunoassay technique. Streptozotocin diabetes caused a significant decrease in tissue calmodulin levels of smooth muscles. Insulin therapy for 20 days did not correct the changes in calmodulin levels of rat smooth muscles, although it normalised blood glucose in streptozotocin-diabetic rats. These findings suggest that the altered smooth muscle calmodulin may contribute the defective contractile responses in diabetes and these changes may be resistant to insulin therapy.