Arthrospira (Spirulina) platensis Attenuates Dextran Sulfate Sodium-induced Colitis in Mice by Suppressing Key Pro-inflammatory Cytokines.

Background/Aims: Therapies aimed at modulating cytokines have been used to treat inflammatory illnesses, such as inflammatory bowel disease. On the other hand, patients may become intolerant, refractory, or present with several side effects. Arthrospira (Spirulina) platensis (SPI) is a blue-green microalga with bioactive molecules that have been evaluated to treat inflammatory diseases. On the other hand, few studies have examined their effects on the production of specific cytokines and the intestinal architecture in dextran sulfate sodium (DSS)-induced colitis. Therefore, this study examined the effects of a treatment using SPI in a murine model of intestinal inflammation. Methods: All mice (C57BL/6 male) were evaluated daily for their food and water intake, bodyweight variations, and clinical signs of disease. Colon inflammation was induced by exposure to DSS for 6 consecutive days. SPI was given orally at 50, 100, and 250 mg/kg/day. ELISA was performed to assess the production of cytokines. Myeloperoxidase and nitric oxide were also investigated. The level of microscopic damage was assessed by staining colon sections with hematoxylin and eosin. Results: SPI attenuated the DSS-induced inflammation, with improvements in the clinical signs and a decrease in the production of inflammatory cytokines, such as tumor necrosis factor-α and interferon-γ. In addition, particularly at 250 mg/kg, SPI attenuated the severity of colitis by modulating the level of mucosal and submucosal cell infiltration, which preserved the epithelial barrier. Conclusions: SPI may be an alternative source of bioactive molecules with immunomodulatory properties, and has great potential to be used in the treatment of inflammatory diseases.

Glucose lowering effect of montbretin A in Zucker Diabetic Fatty rats.

Diabetes is an increasingly prevalent disease state with a global impact. It is important that effective and cost-efficient methods be developed to treat this disease state. Zucker diabetic fatty rats, an animal model of type 2 diabetes, were treated with montbretin A (MbA), a selective human pancreatic α-amylase inhibitor, isolated from the corms of the Crocosmia crocosmiiflora plant that may have potential as a glucose-lowering agent. The study purpose was to determine if MbA was an orally effective treatment for diabetes. The effect of MbA was compared to a current clinical treatment modality, acarbose that is associated with gastrointestinal side effects known to affect patient compliance. MbA and acarbose were administered daily in the drinking water. Body weight and fluid intake were measured daily to calculate dose consumption. Plasma glucose levels were determined twice weekly in both the fed and fasted state. At termination samples were collected to assess increased risk of secondary complications related to diabetes and oxidative stress. There was no effect of either MbA or acarbose treatment on insulin levels. Plasma glucose levels were significantly lower following MbA treatment in the ZT group which persisted throughout the study period (day 49: 12.1 ± 1.2 mM). However, while there was an initial decrease in plasma glucose levels in the acarbose-treated fatty group, this effect was not sustained (day 49: 20.6 ± 1.3 mM) through to termination. MbA improved the oxidative status of the fatty diabetic animals as well as attenuated markers for increased risk of cardiovascular complications associated with diabetes. This study demonstrated that, at a lower dose as compared to acarbose (10 mg/kg/day), chronic oral administration of MbA (7.5 mg/kg/day) was an effective glucose-lowering agent in the treatment of type 2 diabetes.

Combined metoprolol and ascorbic acid treatment prevents intrinsic damage to the heart during diabetic cardiomyopathy.

Metabolic disturbances and oxidative stress have been highlighted as potential causative factors for the development of diabetic cardiomyopathy. The ß-blocker metoprolol is known to improve function in the diabetic rat heart and ameliorates the sequelae associated with oxidative stress, without lowering oxidative stress. The antioxidant ascorbic acid is known to improve function in the diabetic rat heart. We tested whether a combination of ascorbic acid and metoprolol treatment would improve function further than each drug individually. Control and streptozotocin-induced diabetic Wistar rats were treated with metoprolol (15 mg·(kg body mass)(-1)·day(-1), via an osmotic pump) and (or) ascorbic acid (1000 mg·(kg body mass)(-1)·day(-1), via their drinking water). To study the effect of treatment on the development of dysfunction, we examined time points before (5 weeks diabetic) and after (7 weeks diabetic) development of overt systolic dysfunction. Echocardiography and working-heart-perfusion were used to assess cardiac function. Blood and tissue samples were collected to assess the severity of disease and oxidative stress. While both drugs improved function, only ascorbic acid had effects on oxidative damage. Combination treatment had a more pronounced improvement in function. Our ß-blocker + antioxidant treatment strategy focused on oxidative stress, not diabetes specifically; therefore, it may prove useful in other diseases where oxidative stress contributes to the pathology.

The effects of phentolamine on fructose-fed rats.

Metabolic syndrome (MS) is a combination of medical disorders that increase the risk of developing cardiovascular disease and diabetes. MS is associated with obesity, increased blood pressure, hyperlipidemia, and hyperglycemia. This study was designed to investigate the pharmacological profile of phentolamine, a nonselective α adrenergic receptor antagonist, in the prevention of increased blood pressure in fructose-fed rats. Phentolamine prevented the fructose-induced increase in systolic blood pressure without affecting insulin sensitivity and major metabolic parameters. The levels of plasma noradrenaline and angiotensin II, 2 proposed contributors to the development of fructose-induced elevated blood pressure, were examined. Neither noradrenaline nor angiotensin II levels were affected by phentolamine treatment. Since overproduction of nitric oxide has been shown to lead to an elevation in peroxynitrite, the role of oxidative stress, a proposed mechanism of fructose-induced elevated blood pressure and insulin resistance, was examined by measuring plasma levels of total nitrate/nitrite. Plasma nitrate/nitrite was significantly elevated in all fructose-fed animals, regardless of treatment with phentolamine. Another proposed contributor toward fructose-induced MS is an elevation in uric acid levels. In this experiment, plasma levels of uric acid were found to be increased by dietary fructose and were unaffected by phentolamine treatment.

Testosterone-dependent increase in blood pressure is mediated by elevated Cyp4A expression in fructose-fed rats.

Endothelial dysfunction and increased blood pressure following insulin resistance play an important role in the development of secondary cardiovascular complications. The presence of testosterone is essential for the development of endothelial dysfunction and increased blood pressure. Testosterone regulates the synthesis of vasoconstrictor eicosanoids such as 20-hydroxyeicosatetranoic acid (20-HETE). In a series of studies, we examined: (1) the role of the androgen receptor in elevating blood pressure and (2) the effects of Cyp4A-catalyzed 20-HETE synthesis on vascular reactivity and blood pressure in fructose-fed rats. In the first study, intact and castrated male rats were made insulin resistant by feeding fructose for 9 weeks following which their superior mesenteric arteries (SMA) were isolated and examined for changes in endothelium-dependent relaxation in the presence and absence of 1-aminobenzotriazole (ABT) and N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS), which are inhibitors of 20-HETE synthesis. In another study, male rats were treated with either ABT or the androgen receptor blocker, flutamide, following which changes in insulin sensitivity, blood pressure, and vascular Cyp4A expression were measured. In the final study, HET0016, which is a more selective inhibitor of 20-HETE synthesis, was used to confirm our earlier findings. Treatment with HET0016 or ABT prevented or ameliorated the increase in blood pressure. Gonadectomy or flutamide prevented the increase in both the Cyp4A and blood pressure. Furthermore, both ABT and DDMS improved relaxation only in the intact fructose-fed rats. Taken together our results suggest that in the presence of testosterone, the Cyp4A/20-HETE system plays a key role in elevating the blood pressure secondary to insulin resistance.

Renal expression of arachidonic acid metabolizing enzymes and RhoA/Rho kinases in fructose insulin resistant hypertensive rats.

Fructose feeding has been shown to induce insulin resistance and hypertension. Renal protein expression for the cytochrome P (CYP) 450 arachidonic acid metabolizing enzymes has been shown to be altered in other models of diet-induced hypertension. Of special interest is CYP4A, which produces the potent vasoconstrictor, 20-hydroxyeicosatetraenoic acid and CYP2C, which catalyzes the formation of the potent dilators epoxyeicosatrienoic acids as well as soluble epoxide hydrolase (sEH) which metabolizes the latter to dihydroxyeicosatrienoic acids. The RhoA/Rho kinase (ROCK) signaling pathway is downstream of arachidonic acid and is reported to mediate metabolic-cardio-renal dysfunctions in some experimental models of insulin resistance and diabetes. The aim of the present study was to determine the expression of CYP4A, CYP2C23, CYP2C11, sEH, RhoA, ROCK-1, ROCK-2, and phospho-Lin-11/Isl-1/Mec-3 kinase (LIMK) in kidneys of fructose-fed (F) rats. Male Wistar rats were fed a high fructose diet for 8 weeks. Body weight, systolic blood pressure, insulin sensitivity, and renal expression of the aforementioned proteins were assessed. No change was observed in the body weight of F rats; however, euglycemia and hyperinsulinemia implicating impaired glucose tolerance and significant elevation in systolic blood pressure were observed. Renal expression of CYP4A and CYP2C23 was significantly increased while that of CYP2C11 and sEH was not changed in F rats. Equal expression for RhoA in both control and F rats and an enhanced level of ROCK-1 and ROCK-2 constitutively activate 130 kDa cleavage fragments as well as phospho-LIMK. These data suggest that the kidneys could be actively participating in the pathogenesis of insulin resistance-induced hypertension through the arachidonic acid CYP 450-RhoA/Rho kinase pathway(s).

The fructose-fed rat: a review on the mechanisms of fructose-induced insulin resistance and hypertension.

The metabolic syndrome is an important public health concern that predisposes individuals to the development of cardiovascular disease and/or Type 2 diabetes. The fructose-fed rat is an animal model of acquired systolic hypertension that displays numerous features of the metabolic syndrome. This animal model is used to study the relationship between insulin resistance/compensatory hyperinsulinemia and the development of hypertension. Several mechanisms have been proposed to mediate the link between insulin resistance and hypertension. In this review, we have addressed the role of sympathetic nervous system overactivation, increased production of vasoconstrictors, such as endothelin-1 and angiotensin II, and prostanoids in the development of hypertension in fructose-fed rats. The roles of nitric oxide, impaired endothelium-dependent relaxation and sex hormones in the pathogenesis of the fructose-fed induced hypertensive rats have also been highlighted. More recently, increased formation of reactive oxygen species and elevated levels of uric acid have been reported to contribute to fructose-induced hypertension.

Role of inducible nitric oxide synthase in induction of RhoA expression in hearts from diabetic rats.

AIMS: Recent studies from our laboratory demonstrated that increased expression of the small GTP-binding protein RhoA and activation of the RhoA/rho kinase (ROCK) pathway play an important role in the contractile dysfunction associated with diabetic cardiomyopathy in hearts from streptozotocin (STZ)-induced diabetic rats. Nitric oxide (NO) has been reported to be a positive regulator of RhoA expression in vascular smooth muscle, and we have previously found that the expression of inducible NO synthase (iNOS) is increased in hearts from STZ-diabetic rats. Therefore, in this study, we investigated the hypothesis that induction of iNOS positively regulates RhoA expression in diabetic rat hearts. METHODS AND RESULTS: To determine whether NO and iNOS could increase RhoA expression in the heart, cardiomyocytes from non-diabetic rats were cultured in the presence of the NO donor sodium nitroprusside (SNP) or lipopolysaccharide (LPS) in the absence and presence of the selective iNOS inhibitor, N(6)-(1-iminoethyl)-l-lysine dihydrochloride (L-NIL). In a second study, 1 week after induction of diabetes with STZ, rats were treated with L-NIL (3 mg/kg/day) for 8 more weeks to determine the effect of iNOS inhibition in vivo on RhoA expression and cardiac contractile function. Expression of iNOS was elevated in cardiomyocytes isolated from diabetic rat hearts. Both SNP and LPS increased RhoA expression in non-diabetic cardiomyocytes. The LPS-induced elevation in RhoA expression was accompanied by an increase in iNOS expression and prevented by L-NIL. Treatment of diabetic rats with L-NIL led to a significant improvement in left ventricular developed pressure and rates of contraction and relaxation concomitant with normalization of total cardiac nitrite levels, RhoA expression, and phosphorylation of the ROCK targets LIM (Lin-11, Isl-1, Mec-3) kinase and ezrin/radixin/moesin. CONCLUSION: These data suggest that iNOS is involved in the increased expression of RhoA in diabetic hearts and that one of the mechanisms by which iNOS inhibition improves cardiac function is by preventing the upregulation of RhoA and its availability for activation.

Cardiac expression of adiponectin and its receptors in streptozotocin-induced diabetic rats.

Adiponectin can improve both glucose metabolism and insulin resistance via the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. Activated AMPK phosphorylates a variety of intracellular proteins, including acetyl coenzyme A carboxylase (ACC) that is involved in fatty acid oxidation. Adenosine monophosphate-activated protein kinase increases glucose transport by stimulating the translocation of glucose transporter 4 (GLUT4) to the sarcolemma in the heart. Adiponectin exerts its effect through adiponectin receptors, which are predominantly expressed in the liver and skeletal muscle. It is unknown whether the cardiac expression of adiponectin and its receptors is changed in diabetic rats. In the present study, we investigated the protein expression of adiponectin and its receptors in streptozotocin (STZ)-induced diabetic rat hearts. We also explored whether the levels of AMPK, ACC, and GLUT4 will be altered with the changed adiponectin and its receptors in STZ diabetic rat hearts. Plasma and cardiac adiponectin levels were measured by radioimmunoassay. Plasma and cardiac interleukin 6 and plasma tumor necrosis factor alpha (TNF-alpha) were assayed by enzyme-linked immunosorbent assay. Cardiac adiponectin receptors, AMPK-alpha, ACC, GLUT4, and TNF-alpha were analyzed by Western blot in control and STZ diabetic rats. The plasma adiponectin level was decreased, but the cardiac protein expression of adiponectin receptor 1 was increased in diabetic rats. There was no difference in the cardiac adiponectin level and the cardiac adiponectin receptor 2 protein expression between control and diabetic rats. The phosphorylation of AMPK-alpha and protein expression of GLUT4 were decreased, but the phosphorylation of ACC was unchanged in diabetic rat hearts. Plasma and cardiac levels of interleukin 6 and TNF-alpha were increased in diabetic rats. In conclusion, STZ-induced diabetes up-regulates adiponectin receptors in the heart. Despite an increase in cardiac adiponectin receptor 1 expression, there is an increased cardiac inflammatory response and a decreased GLUT4 protein expression associated with a reduction in circulating adiponectin.

Endothelin-1 blockade prevents COX2 induction and TXA2 production in the fructose hypertensive rat.

Feeding rats with a high fructose diet results in insulin resistance and hypertension. Fructose-hypertensive rats (FHR) have increased vascular levels of endothelin-1 (ET-1) and thromboxane (TXA2). We have previously shown that chronic treatment with either the dual endothelin receptor blocker, bosentan, or the thromboxane synthase inhibitor, dazmegrel, prevented fructose-induced increases in blood pressure, suggesting that both ET-1 and TXA2 play important roles in the development of hyperinsulinemia/insulin resistance-associated hypertension. In this study, we investigated the potential interrelationship between ET-1 and TXA2 in the development of fructose-induced hypertension in vivo. Male Wistar rats were fed on a high fructose diet for 9 weeks. Either bosentan or dazmegrel treatment (daily by oral gavage) was initiated 3 weeks after the start of fructose feeding for a total duration of 6 weeks. At the end of drug treatment, blood and aorta were collected from each animal. Plasma thromboxane B2 (TXB2), a stable TXA2 metabolite, increased significantly in FHR and was reduced to control level by both chronic bosentan and dazmegrel treatment. Protein expression of cyclooxygenase 2 (COX2) was elevated significantly in FHR aortas and treatment with bosentan and dazmegrel corrected these changes. These results indicate that the actions of ET-1 in the aorta of FHR may be mediated through COX2-derived TXA2. Bosentan may prevent the development of hypertension in fructose-fed rats through inhibition of COX2 induction and subsequently the reduction in plasma TXA2.

Acute inhibition of Rho-kinase improves cardiac contractile function in streptozotocin-diabetic rats.

OBJECTIVE: The purpose of the present study was to determine whether increased activation of the RhoA/Rho-kinase (ROCK) pathway occurs in diabetic cardiomyopathy and whether acute inhibition of this pathway improves contractile function of the diabetic heart. METHODS: Male Wistar rats were made diabetic with streptozotocin. Twelve to fourteen weeks later, the effects of acute administration of the ROCK inhibitors Y-27632 and H-1152 on cardiac contractile function were measured both in vitro, in isolated working hearts, and in vivo, using echocardiography. Changes in the expression and activity of RhoA, and the effect of ROCK inhibition on changes in the phosphorylation of the downstream target of ROCK, LIM kinase 2, and on actin polymerization in diabetic hearts were also determined. RESULTS: Perfusion of isolated working hearts from diabetic rats with Y-27632 or H-1152 acutely improved left ventricle developed pressure and the rates of contraction and relaxation. Acute administration of H-1152 also significantly improved the percent fraction shortening, an index of left ventricle contractility, in vivo in diabetic rats. The expression and activity of RhoA in cardiomyocytes from diabetic rats were significantly increased, as was the phosphorylation of LIM kinase 2. This was associated with an increase in actin polymerization (the F-actin to G-actin ratio). Both the increase in LIM kinase 2 phosphorylation and actin polymerization were attenuated by ROCK inhibition. CONCLUSIONS: These data suggest that activation of the RhoA/ROCK signaling pathway plays a critical role in the development of diabetic cardiomyopathy, and that ROCK is an excellent therapeutic target in the treatment of this condition.

Effects of endothelin receptor blockade on hypervasoreactivity in streptozotocin-diabetic rats: vessel-specific involvement of thromboxane A2.

Increased vasoconstrictor response to norepinephrine (NE) and endothelin (ET)-1 in arteries from diabetic animals is ameliorated by chronic endothelin receptor blockade with bosentan and was absent in endothelium-denuded arteries, suggesting the involvement of ET-1 and an endothelium-derived contracting factor such as thromboxane A2 (TxA2). To examine this possibility, we determined the effects of acute blockade of ET receptors or inhibition of TxA2 synthesis on the vascular function of superior mesenteric arteries (SMA) and renal arteries (RA) isolated from nondiabetic and 11-week streptozotocin (STZ) diabetic rats chronically treated with either bosentan or vehicle. Both in vitro incubation with bosentan and a selective ETA receptor blocker, BQ123, eradicated the increase in NE contractile responses in diabetic SMA. Additionally, in vitro incubation with the thromboxane synthase inhibitor, dazmegrel, abrogated the exaggerated NE and ET-1 contractile responses in diabetic SMA. Conversely, in RA, no significant acute effect of bosentan, BQ123, nor dazmegrel on vascular responses to NE was observed. Dazmegrel incubation attenuated the maximum contractile responses to ET-1 in diabetic RA; however, these responses in diabetic RA remained significantly greater than those of other groups. Diabetic RA but not SMA exhibited an enhanced contractile response to the TxA2 analogue U46619, which was corrected by chronic bosentan treatment. Immunohistochemical analyses in diabetic SMA revealed an increase in ETA receptor level that was normalized by chronic bosentan treatment. These data indicate that an interaction between ET-1 and TxA2 may be involved in mediating the exaggerated vasoconstrictor responses in diabetic arteries. Furthermore, the underlying mechanisms appear to be vessel specific.

Differences in plasma homocysteine levels between Zucker fatty and Zucker diabetic fatty rats following 3 weeks oral administration of organic vanadium compounds.

PURPOSE: Recently, our laboratory group has reported that rats with Type 1 diabetes have decreased plasma homocysteine and cysteine levels compared to non-diabetic controls and that organic vanadium treatment increased plasma homocysteine concentrations to non-diabetic concentrations. However, to date, no studies have been done investigating the effects of organic vanadium compounds on plasma homocysteine and its metabolites in Type 2 diabetic animal model. These studies examined the effect of organic vanadium compounds [bis(maltolato)oxovanadium(IV) and bis(ethylmaltolato)oxovanadium(IV); BMOV and BEOV] administered orally on plasma concentrations of homocysteine and its metabolites (cysteine and cysteinylglycine) in lean, Zucker fatty (ZF) and Zucker diabetic fatty (ZDF) rats. ZF rats are a model of pre-diabetic Type 2 diabetes characterized by hyperinsulinemia and normoglycemia. The ZDF rat is a model of Type 2 diabetes characterized by relative hypoinsulinemia and hyperglycemia. METHODS: Zucker lean and ZF rats received BMOV in the drinking water at a dose of 0.19 +/- 0.02 mmol/kg/day. Lean and ZDF rats received BEOV by oral gavage daily at dose of 0.1 mmol/kg. The treatment period for both studies was 21 days. At termination, animals were fasted overnight (approximately 16 h) and blood samples were collected by cardiac puncture for determination of plasma glucose, insulin and homocysteine levels. Plasma homocysteine and its metabolites levels were determined using high-pressure liquid chromatography. Plasma glucose was determined using a Glucose Analyzer 2. Plasma insulin levels were determined by radioimmunoassay. Plasma triglycerides were determined by an enzymatic assay methodology. RESULTS: ZF (n = 4) and ZDF (n = 10) rats had significantly lower plasma homocysteine as compared to their respective lean groups (ZF 0.78 +/- 0.1 micromol/L vs. Zucker lean 2.19 +/- 0.7 micromol/L; ZDF 1.71 +/- 0.2 micromol/L vs. Zucker lean 3.02 +/- 0.3 micromol/L; p < 0.05). BMOV treatment in ZF rats restored plasma homocysteine levels to those observed in lean untreated rats (ZF treated: 2.04 +/- 0.2 micromol/L; lean 2.19 +/- 0.7 micromol/L). There was a modest effect of BMOV treatment on plasma glucose levels in ZF rats. BEOV treatment significantly decreased the elevated plasma glucose levels in the ZDF rats (lean 7.9 +/- 0.1 mmol/L; lean + vanadium 7.7 +/- 0.2 mmol/L; ZDF 29.9 +/- 0.4 mmol/L; ZDF + vanadium 17.4 +/- 0.3 mmol/L, p < 0.05). Organic vanadium treatment reduced cysteine levels in both ZF and ZDF rats. No differences in total plasma cysteinylglycine concentrations were observed. CONCLUSION: Plasma homocysteine levels are significantly reduced in a pre-diabetic model of Type 2 diabetes, which was restored to lean levels upon vanadium treatment; however, this restoration of plasma homocysteine levels was not seen in ZDF Type 2 diabetic rats following vanadium treatment. In the latter case vanadium treatment may not have totally overcome the insulin resistance seen in these animals.

Chronic estrogen treatment reduces vaso-constrictor responses in insulin resistant rats.

Previous experiments have shown that chronic estrogen treatment via subcutaneous implants prevented insulin-induced blood pressure elevation and increased insulin sensitivity in ovariectomized female rats. In vitro vascular studies were performed using isolated mesenteric arteries to determine the effect of chronic estrogen and insulin treatments on vascular responses to vasoconstrictor agents. Female Wistar rats were assigned to the following groups: sham-operated, sham-operated plus insulin, sham-operated plus insulin plus estrogen, ovariectomized, ovariectomized plus insulin, and ovariectomized plus insulin plus estrogen. Chronic insulin and estrogen treatments were initiated with subcutaneous placement of insulin implants (2 U/d) and 17beta-estradiol implants (0.5 mg/pellet, 60 day release) at the back of the neck. After 8 weeks of treatment, mesenteric arteries were isolated for assessment of constrictor responses to norepinephrine and the thromboxane A2 analogue U46619 in the presence or absence of the endothelium. The results show that chronic estrogen treatment attenuated the vascular constrictor responses to norepinephrine and U46619 only in endothelium intact vessels. Incubation with insulin did not significantly affect norepinephrine-induced vascular smooth muscle contraction. The study provides evidence that the mechanism by which estrogen prevents insulin-induced blood pressure elevation in insulin-treated ovariectomized rats is by influencing endothelium-derived vasoactive factors such as thromboxane A2.

Chronic estrogen treatment modifies insulin-induced insulin resistance and hypertension in ovariectomized rats.

BACKGROUND: Gender differences have been found in the development of hypertension. The role of estrogen in the association between hyperinsulinemia/insulin resistance and hypertension was investigated in an insulin-induced, insulin-resistant, and hypertensive model. METHODS: Ovariectomized or sham operated female Wistar rats were chronically treated with insulin and/or estrogen via subcutaneous implants (insulin, 2 U/day; 17beta-estradiol 0.5 mg/pellet, 60-day release). Systolic blood pressure was monitored at weeks 0, 3, and 6. At week 7, an oral glucose tolerance test was performed. RESULTS: Ovariectomy resulted in the development of insulin resistance and blood pressure elevation in chronically insulin-treated female rats. Chronic estrogen treatment prevented the elevation in blood pressure and the development of insulin resistance. CONCLUSION: The results indicate that chronic estrogen treatment modifies the insulin-induced hypertension by increasing insulin sensitivity in ovariectomized rats.

Synthesis and characterization of dual function vanadyl, gallium and indium curcumin complexes for medicinal applications.

Novel bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin) complexes with the formula, ML(3), where M is Ga(III) or In(III), or of the formula, ML(2) where M is [VO](2+), have been synthesized and characterized by mass spectrometry, infrared and absorption spectroscopies, and elemental analysis. A new ligand, bis[4-acetyl-3-hydroxyphenyl]-1,6-heptadiene-3,5-dione (diacetylbisdemethoxycurcumin, DABC) was similarly characterized; an X-ray structure analysis was performed. Vanadyl complexes tested in an acute i.p. testing protocol in STZ-diabetic rats showed a lack of insulin enhancing potential. Vanadyl complexes were, however, more cytotoxic than were the ligands alone in standard MTT (3-[4,5-dimethylthiazole-2-yl]ate, -2,5-diphenyl-tetrazolium bromide) cytotoxicity testing, using mouse lymphoma cells. With the exception of DABC, that was not different from VO(DABC)(2), the complexes were not significantly different from one another, with IC(50) values in the 5-10 microM range. Gallium and indium curcumin complexes had IC(50) values in the same 5-10 microM range; whereas Ga(DAC)(3) and In(DAC)(3) (where DAC=diacetylcurcumin) were much less cytotoxic (IC(50)=20-30 microM). Antioxidant capacity was decreased in VO(DAC)(2), Ga(DAC)(3), and In(DAC)(3), compared to vanadyl, gallium and indium curcumin, corroborating the importance of curcumin's free phenolic OH groups for scavenging oxidants, and correlated with reduced cytotoxic potential.

Vanadium complexes with mixed O,S anionic ligands derived from maltol: synthesis, characterization, and biological studies.

Four mixed O,S binding bidentate ligand precursors derived from maltol (3-hydroxy-2-methyl-4-pyrone) have been chelated to vanadium to yield new bis(ligand)oxovanadium(IV) and tris(ligand)vanadium(III) complexes. The four ligand precursors include two pyranthiones, 3-hydroxy-2-methyl-4-pyranthione, commonly known as thiomaltol (Htma), and 2-ethyl-3-hydroxy-4-pyranthione, commonly known as ethylthiomaltol (Hetma), as well as two pyridinethiones, 3-hydroxy-2-methyl-4(H)-pyridinethione (Hmppt) and 3-hydroxy-1,2-dimethyl-4-pyridinethione (Hdppt). Vanadium complex formation was confirmed by elemental analysis, mass spectrometry, and IR and EPR (where possible) spectroscopies. The X-ray structure of oxobis(thiomaltolato)vanadium(IV),VO(tma)(2), was also determined; both cis and trans isomers were isolated in the same asymmetric unit. In both isomers, the two thiomaltolato ligands are arranged around the base of the square pyramid with the V=O linkage perpendicular; the vanadium atom is slightly displaced from the basal plane [V(1) = 0.656(3) A, V(2) = 0.664(2) A]. All of the new complexes were screened for insulin-enhancing effectiveness in streptozotocin-induced diabetes in rats, and VO(tma)(2) was profiled metabolically for urinary vanadium and ligand clearance by GFAAS and ESIMS, respectively. The new vanadium complexes did not lower blood glucose levels acutely, possibly because of rapid dissociation and excretion.

Coordination chemistry and insulin-enhancing behavior of vanadium complexes with maltol C6H6O3 structural isomers.

Syntheses of vanadium complexes using the naturally occurring ligands isomaltol (Hima) and allomaltol (Hama), as well as a newly synthesized, potentially tetradentate diaminodipyrone [H(2)(en(ama)(2)], are reported. Complete characterization of the resulting compounds [trans-VO(ima)(2)(H(2)O), VO(ama)(2), V(ima)(3), V(ama)(3) and VO(en(ama)(2))], including X-ray crystallography analyses for trans-VO(ima)(2)(H(2)O) and V(ima)(3), are presented herein. Potentiometric titrations (25 degrees C, I = 0.16 M NaCl) were used to measure stability constants in the V(IV)-Hima system; these data were compared to previous data collected on the V(IV)-L (L = Hma, Hama) systems. The in vivo efficacy of these compounds to lower the blood glucose levels of STZ-diabetic rats was tested; all but VO(en(ama)(2)) produced significant decreases in plasma glucose levels. The results were compared to those of the benchmark compound BMOV [VO(ma)(2), bis(maltolato)oxovanadium(IV)], a known insulin-enhancing agent.

Comparison of anti-hyperglycemic effect amongst vanadium, molybdenum and other metal maltol complexes.

A wide variety of vanadium-containing complexes have been tested, both in vivo and in vitro, as possible therapeutic agents for the oral treatment of type 2 diabetes mellitus. None so far has surpassed bis(maltolato)oxovanadium(IV) (BMOV) for glucose- and lipid-lowering in an orally available formulation. Ligand choice is clearly an important factor in pharmacological efficacy of vanadium compounds as insulin enhancing agents. In this study, we kept the ligand and dose the same, varying instead the metal ion bound to the maltolato ligand in a series of binary complexes of neutral charge. A requirement for vanadyl ion as the metal ion of choice was apparent; no other metal ion tested served as a suitable substitute. Amongst [MoO(2)](2+), Co(II), Cu(II), Cr(III), and Zn(II), only [MoO(2)](2+) and Co(II) showed any hypoglycemic activity at the ED(50) dose for bis(maltolato)oxovanadium(IV), 0.6 mmolkg(-1) by oral gavage in streptozotocin (STZ)-diabetic rats within 72 h of administration of compound.

Effects of three and eight weeks oral administration of bis(maltolato)oxovanadium(IV) on plasma homocysteine and cysteine levels in streptozotocin-induced diabetic rats.

BACKGROUND: Diabetes mellitus is one of the leading causes of illness and death in North America. Cardiovascular diseases are a common secondary complication in the diabetic population. One of the important risk factors identified for the development of cardiovascular disease is an elevation in the sulfur amino acid, homocysteine. Although the exact mechanism(s) that underlie the relationship between elevated plasma homocysteine levels and cardiovascular disease remain unclear, it has been suggested that endothelial dysfunction produced by modestly elevated blood homocysteine concentrations may account for an increased risk of both arterial and venous occlusive disease. OBJECTIVES: The present study examined the effects of three- and eight-weeks bis(maltolato)oxovanadium(IV) (BMOV) treatment on plasma concentrations of homocysteine and cysteine in both control and streptozotocin (STZ) diabetic rats. METHODS: Diabetes was induced in male Wistar rats by a single intravenous injection of STZ (60 mg/kg) in normal saline. Control animals received normal saline only. Animals were further randomized into treated and untreated groups. Treated animals received BMOV orally, dissolved in tap water, while untreated animals only received tap water. Three or eight weeks postinduction of diabetes, blood samples were obtained by cardiac puncture from the animals. Plasma harvested from each blood sample was used to determine glucose, insulin, homocysteine and cysteine concentrations. RESULTS: There was a significant decrease in plasma homocysteine levels in the diabetic (three- and eight-week study) groups compared with their respective controls (three-week study: diabetic group 3.1+/-0.7 mumol/L and control group 6.1+/-0.7 mumol/L; eight-week study: diabetic group 4.3+/-0.5 mumol/L and control group 6.9+/-1.0 mumol/L). Plasma cysteine levels were significantly decreased in the diabetic and diabetic treated groups (eight-week study) compared with their respective control groups (diabetic group 90.2+/-32.3 mumol/L and control group 177.9+/-36.7 mumol/L). BMOV treatment restored plasma homocysteine concentrations in diabetic animals to concentrations found in nondiabetic animals. CONCLUSIONS: Taken together, these findings suggest that STZ-induced diabetes may result in decreased plasma homocysteine and cysteine levels and that BMOV treatment may increase plasma homocysteine concentrations to nondiabetic concentrations. These results may provide further insight on how this insulin-enhancing/mimetic agent modifies plasma homocysteine metabolism.