Vanadate induces normolipidemia and a reduction in the levels of hepatic lipogenic enzymes in obese Zucker rat

Vanadium: Risks and possible benefits in the light of a comprehensive overview of its pharmacotoxicological mechanisms and multi-applications with a summary of further research trends

BACKGROUND

Vanadium (V) is an element with a wide range of effects on the mammalian organism. The ability of this metal to form organometallic compounds has contributed to the increase in the number of studies on the multidirectional biological activity of its various organic complexes in view of their application in medicine.

OBJECTIVE

This review aims at summarizing the current state of knowledge of the pharmacological potential of V and the mechanisms underlying its anti-viral, anti-bacterial, anti-parasitic, anti-fungal, anti-cancer, anti-diabetic, anti-hypercholesterolemic, cardioprotective, and neuroprotective activity as well as the mechanisms of appetite regulation related to the possibility of using this element in the treatment of obesity. The toxicological potential of V and the mechanisms of its toxic action, which have not been sufficiently recognized yet, as well as key information about the essentiality of this metal, its physiological role, and metabolism with certain aspects on the timeline is collected as well. The report also aims to review the use of V in the implantology and industrial sectors emphasizing the human health hazard as well as collect data on the directions of further research on V and its interactions with Mg along with their character.

RESULTS AND CONCLUSIONS

Multidirectional studies on V have shown that further analyses are still required for this element to be used as a metallodrug in the fight against certain life-threatening diseases. Studies on interactions of V with Mg, which showed that both elements are able to modulate the response in an interactive manner are needed as well, as the results of such investigations may help not only in recognizing new markers of V toxicity and clarify the underlying interactive mechanism between them, thus improving the medical application of the metals against modern-age diseases, but also they may help in development of principles of effective protection of humans against environmental/occupational V exposure.

The vital role of ATP citrate lyase in chronic diseases

Chronic or non-communicable diseases are the leading cause of death worldwide; they usually result in long-term illnesses and demand long-term care. Despite advances in molecular therapeutics, specific biomarkers and targets for the treatment of these diseases are required. The dysregulation of de novo lipogenesis has been found to play an essential role in cell metabolism and is associated with the development and progression of many chronic diseases; this confirms the link between obesity and various chronic diseases. The main enzyme in this pathway-ATP-citrate lyase (ACLY), a lipogenic enzyme-catalyzes the critical reaction linking cellular glucose catabolism and lipogenesis. Increasing lines of evidence suggest that the modulation of ACLY expression correlates with the development and progressions of various chronic diseases such as neurodegenerative diseases, cardiovascular diseases, diabetes, obesity, inflammation, and cancer. Recent studies suggest that the inhibition of ACLY activity modulates the glycolysis and lipogenesis processes and stimulates normal physiological functions. This comprehensive review aimed to critically evaluate the role of ACLY in the development and progression of different diseases and the effects of its downregulation in the prevention and treatment of these diseases.

Alternative therapies for diabetes and its cardiac complications: role of vanadium

It is now well known that a cardiomyopathic state accompanies diabetes mellitus. Although insulin injections and conventional hypoglycemic drug therapy have been of invaluable help in reducing cardiac damage and dysfunction in diabetes, cardiac failure continues to be a common cause of death in the diabetic population. The use of alternative medicine to maintain health and treat a variety of diseases has achieved increasing popularity in recent years. The goal of alternative therapies in diabetic patients has been to lower circulating blood glucose levels and thereby treat diabetic complications. This paper will focus its discussion on the role of vanadium on diabetes and the associated cardiac dysfunction. Careful administration of a variety of forms of vanadium has produced impressive long-lasting control of blood glucose levels in both Type 1 and Type 2 diabetes in animals. This has been accompanied by, in many cases, a complete correction of the diabetic cardiomyopathy. The oral delivery of vanadium as a vanadate salt in the presence of tea has produced particularly impressive hypoglycemic effects and a restoration of cardiac function. This intriguing approach to the treatment of diabetes and its complications, however, deserves further intense investigation prior to its use as a conventional therapy for diabetic complications due to the unknown long-term effects of vanadium accumulation in the heart and other organs of the body.

Alternative therapies for diabetes and its cardiac complications: role of vanadium

It is now well known that a cardiomyopathic state accompanies diabetes mellitus. Although insulin injections and conventional hypoglycemic drug therapy have been of invaluable help in reducing cardiac damage and dysfunction in diabetes, cardiac failure continues to be a common cause of death in the diabetic population. The use of alternative medicine to maintain health and treat a variety of diseases has achieved increasing popularity in recent years. The goal of alternative therapies in diabetic patients has been to lower circulating blood glucose levels and thereby treat diabetic complications. This paper will focus its discussion on the role of vanadium on diabetes and the associated cardiac dysfunction. Careful administration of a variety of forms of vanadium has produced impressive long-lasting control of blood glucose levels in both Type 1 and Type 2 diabetes in animals. This has been accompanied by, in many cases, a complete correction of the diabetic cardiomyopathy. The oral delivery of vanadium as a vanadate salt in the presence of tea has produced particularly impressive hypoglycemic effects and a restoration of cardiac function. This intriguing approach to the treatment of diabetes and its complications, however, deserves further intense investigation prior to its use as a conventional therapy for diabetic complications due to the unknown long-term effects of vanadium accumulation in the heart and other organs of the body.

Nicotine attenuates spatial learning deficits induced by sodium metavanadate

Learning can be severely impaired as a consequence of exposure to environmental pollutants. Vanadium (V), a metalloid which is widely distributed in the environment, has been shown to exert toxic effects on a variety of biological systems including the nervous system. However, studies exploring the impact of vanadium on learning are limited. Herein, we investigated the effects of oral administration of sodium metavanadate (SMV) (15, 20 and 25mg/kg/day for 2weeks) on spatial learning using Morris water maze (MWM). Our results showed that pre-training administration of sodium metavanadate impaired learning in Morris water maze. Analyzing the role of cholinergic system in SMV-induced learning deficit, we found that bilateral intra-hippocampal infusion of nicotine (1μg/side) during training could significantly diminish the SMV-induced learning impairment. We next examined the expression of choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) as cholinergic markers in CA1 region of hippocampus as well as in medial septal area (MSA). Our molecular analyses showed that vanadium administration decreased ChAT and VAChT protein expression, an effect that was attenuated by nicotine. Altogether, our results confirmed the toxic effects of SMV on spatial acquisition, while also pointing to the neuroprotective effects of nicotine on SMV-induced impairments in learning capabilities. These findings might open a new avenue for the prevention of vanadium adverse effects on spatial learning and memory through activation of cholinergic signaling pathway.

Effects of luminal ATPase inhibitors on electrogenic ion transport in rat distal colon

BACKGROUND

The involvement of transport proteins, other than chloride channels, expressed in the luminal membrane of epithelial cells in regulated chloride secretion in native colon remains poorly understood. There are at least two distinct ATPases expressed in the apical membrane of rat colonocytes. They can be distinguished by their different sensitivity to the vanadium-derived compound orthovanadate. The objective was to study the effects of luminal ATPase inhibitors on regulated chloride secretion using elecrophysiological and pharmacological approaches.

MATERIALS AND METHODS

Unstripped rat distal colon segments were mounted in Ussing chambers. Potential difference, transepithelial resistance, and short-circuit current across unstripped colon segments were monitored with a dual voltage/current clamp.

RESULTS

Luminal application of VO4(3-) did not alter baseline electrical values in rat distal colon but dose-dependently inhibited forskolin-stimulated Isc. Luminal ouabain (1 mm) did not blunt the response to the cAMP agonist. The inhibitory effect of luminal VO4(3-) occurred at a site distal to cAMP generation and was rather specific for the cyclic nucleotide-dependent signaling pathway, because the response to the Ca2+ agonist carbachol was largely preserved.

CONCLUSION

VO4(3-) inhibits cAMP-stimulated Cl- secretion in rat distal colon at a site distal to cAMP generation without altering intestinal permeability. Ouabain-sensitive luminal K+-ATPases do not seem to contribute to forskolin-stimulated electrogenic ion transport. These findings may suggest new therapeutic targets for secretory diarrhea.

Combined treatment of sodium orthovanadate and Momordica charantia fruit extract prevents alterations in lipid profile and lipogenic enzymes in alloxan diabetic rats

Momordica charantia Linn., commonly called bitter gourd, is a medicinal plant used in the Ayurvedic system of medicine for treating various diseases including diabetes mellitus. Sodium orthovanadate (SOV) is also well-known insulin mimetic and an antidiabetic compound. Our laboratory has been using reduced doses of SOV along with administration of herbal extracts to alloxan diabetic rats and has established this combination as a good antihyperglycemic agent. The present study was undertaken to investigate the effects of treatment of Momordica fruit extract (MFE) and sodium orthovanadate, separately and in combination, on serum and tissue lipid profile and on the activities of lipogenic enzymes in alloxan induced diabetic rats. The results show that there was a significant (p < 0.01) increase in serum total lipids, triglycerides and total cholesterol levels after 21 days of alloxan diabetes. In the liver and kidney of diabetic rats the levels of total lipids and triglycerides also increased significantly (p < 0.01) while levels of total cholesterol decreased significantly (p < 0.01 and p < 0.05, respectively). The lipogenic enzymes showed decreased activity in the diabetic liver, while in kidney they showed an increased activity. When compared with the controls these changes were significant. The treatment of alloxan diabetic rats with MFE and SOV prevented these alterations and maintained all parameters near control values. Most effective prevention was however observed in a combined treatment of Momordica with a reduced dose of SOV (0.2%). The results suggest that Momordica fruit extract and SOV exhibit hypolipidemic as well as hypoglycemic effect in diabetic rats and their effect is pronounced when administered in combination.

Effect of oxovanadium(IV) complexes on nondiabetic and streptozotocin-diabetic rats

The effects of vanadium complexes with organic ligands, [VO(phen)2]SO4.3H2O, [VO(bpy)2]SO4.2H2O, and [VOCl2(Hmcp)2H2O], on blood glucose and plasma lipid levels were studied in nondiabetic and streptozotocin-diabetic rats and compared to that of [VO(mal)2] (the reference compound). The present results provide evidence that the compounds examined possess lower toxicity than [VO(mal)2]. One of the compounds examined, viz. [VO(bpy)2]SO4.2H2O, decreases, statistically significantly, the glucose level and a second one, viz. [VOCl2(Hmcp)2H2O], decreases, also significantly, the total cholesterol level.

Effect of sodium orthovanadate treatment on cardiovascular function in the hyperinsulinemic, insulin-resistant obese Zucker rat

We recently demonstrated that oral vanadate treatment ameliorates exaggerated vasoconstriction in aortic tissue from the hyperinsulinemic/insulin resistant obese Zucker rat. It has been suggested that changes in large artery contractility might contribute to the development of hypertension in this strain. Thus we examined the effect of vanadate treatment (0.5 mg/ml, p.o.) on conductance and resistance vessel function as well as blood pressure (BP) in Zucker rats. Vasoconstrictor responses to endothelin-1 (ET-1) and methoxamine and vasodilator responses to acetylcholine in the aorta and perfused mesenteric vascular bed served as indices of conductance and resistance function, respectively. Separate groups were treated with insulin (12 mU/kg/min, s.c.) to determine its role in the actions of vanadate. Vanadate treatment reduced (2.5-fold; p < 0.05) elevated plasma insulin levels and abolished exaggerated aortic vasoconstriction in obese rats. Vasoconstrictor responses in the mesenteric bed, however, were similar between obese and lean rats, and were unaffected by vanadate. Vanadate did not affect elevated BP in obese rats and actually increased BP in the lean group. Insulin treatment per se failed to affect vasomotor function or BP in either strain, and acetylcholine-evoked relaxation was similar in all groups. We conclude that whereas vanadate overcomes exaggerated central artery contractility in obese Zucker rats, it fails to affect resistance vessel function or BP in this strain, and might conversely elevate BP in normotensive lean control rats. The vascular actions of vanadate in obese rats appear to occur independent of changes in plasma insulin or endothelial function.

Effects of vanadium on activity and learning in rats

The effects of vanadate administration on activity and learning were assessed in rats. Four groups of adult male rats were given by gavage 0, 4.1, 8.2, and 16.4 mg/kg/day of sodium metavanadate for eight consecutive weeks. Three weeks after the cessation of the treatment, general motor activity of all animals was measured in an open-field. Rats were also tested for two-way shock avoidance learning in an automatic reflex conditioner. At the end of the testing period, rats were killed and vanadium concentration was determined in a number of tissues. Vanadium exposure caused an observable but not significant effect on body weight gain, while a persistent presence of vanadium was observed in all tissues measured. The results of the behavioral testing show that oral vanadate administration resulted in significant reductions in both general activity and learning.

Vanadium salts as insulin substitutes: mechanisms of action, a scientific and therapeutic tool in diabetes mellitus research

Vanadium and its compounds exhibit a wide variety of insulin-like effects. In this review, these effects are discussed with respect to the treatment of type I and type II diabetes in animal models, in vitro actions, antineoplastic role, treatment of IDDM and NIDDM patients, toxicity, and the possible mechanism(s) involved. Newly established CytPTK plays a major role in the bioresponses of vanadium. It has a molecular weight of approximately 53 kDa and is active in the presence of Co2+ rather than Mn2+. Among the protein-tyrosine kinase blockers, staurosporine is found to be a potent inhibitor of CytPTK but a poor inhibitor of InsRTK. Vanadium inhibits PTPase activity, and this in turn enhances the activity of protein tyrosine kinases. Our data show that inhibition of PTPase and protein tyrosine kinase activation has a major role in the therapeutic efficacy of vanadium in treating diabetes mellitus.