Therapeutic properties of VO(dmpp)2 as assessed by in vitro and in vivo studies in type 2 diabetic GK rats

A Non-Toxic Binuclear Vanadium(IV) Complex as Insulin Adjuvant Improves the Glycemic Control in Streptozotocin-Induced Diabetic Rats

Diabetes mellitus (DM) complications are a burden to health care systems due to the associated consequences of poor glycemic control and the side effects of insulin therapy. Recently. adjuvant therapies, such as vanadium compounds, have gained attention due to their potential to improve glucose homeostasis in patients with diabetes. In order to determine the anti-diabetic and antioxidant effects of the oxidovanadium(IV) complex (Et3NH)2[{VO(OH}2)(ox)2(µ-ox)] or Vox2), rats with streptozotocin (STZ)-induced diabetes were treated with 30 and 100 mg/kg of Vox2, orally administered for 12 days. Vox2 at 100 mg/kg in association with insulin caused a 3.4 times decrease in blood glucose in STZ rats (424 mg/dL), reaching concentrations similar to those in the normoglycemic animals (126 mg/dL). Compared to insulin alone, the association with Vox2 caused an additional decrease in blood glucose of 39% and 65% at 30 and 100 mg/kg, respectively, and an increased pancreatic GSH levels 2.5 times. Vox2 alone did not cause gastrointestinal discomfort, diarrhea, and hepatic or renal toxicity and was not associated with changes in blood glucose level, lipid profile, or kidney or liver function. Our results highlight the potential of Vox2 in association with insulin in treating diabetes.

Vanadium Compounds with Antidiabetic Potential

Over the last four decades, vanadium compounds have been extensively studied as potential antidiabetic drugs. With the present review, we aim at presenting a general overview of the most promising compounds and the main results obtained with in vivo studies, reported from 1899-2023. The chemistry of vanadium is explored, discussing the importance of the structure and biochemistry of vanadate and the impact of its similarity with phosphate on the antidiabetic effect. The spectroscopic characterization of vanadium compounds is discussed, particularly magnetic resonance methodologies, emphasizing its relevance for understanding species activity, speciation, and interaction with biological membranes. Finally, the most relevant studies regarding the use of vanadium compounds to treat diabetes are summarized, considering both animal models and human clinical trials. An overview of the main hypotheses explaining the biological activity of these compounds is presented, particularly the most accepted pathway involving vanadium interaction with phosphatase and kinase enzymes involved in the insulin signaling cascade. From our point of view, the major discoveries regarding the pharmacological action of this family of compounds are not yet fully understood. Thus, we still believe that vanadium presents the potential to help in metabolic control and the clinical management of diabetes, either as an insulin-like drug or as an insulin adjuvant. We look forward to the next forty years of research in this field, aiming to discover a vanadium compound with the desired therapeutic properties.

The antihyperglycemic and hypolipidemic activities of a sulfur-oxidovanadium(IV) complex

This study describes the synthesis, characterization, and biological activity of a new class of antidiabetic oxidovanadium(IV)-complexes with S₂O₂ coordination mode. The target complex 3,6-dithio-1,8-octanediolatooxidovanadium(IV), abbreviated as ([V^IVO(octd)]), where octd = 3,6-dithio-1,8-octanediol, is formed from the reaction between the 3,6-dithio-1,8-octanediol and vanadyl sulfate (V^IVOSO₄). The effects of treatment with ([V^IVO(octd)] on blood glucose, lipidic profile, body weight, food intake, water intake, urinary volume, glycogen levels, and biomarkers for liver toxicity were investigated using a streptozotocin (STZ)-induced diabetic Wistar rats model. The results have shown that the [V^IVO(octd)] complex caused a significant decrease in blood glucose (247.6 ± 19.3 mg/dL vs 430.1 ± 37.6 mg/dL diabetic group, p < 0.05), triglycerides (TG, 50%) and very low-density cholesterol (VLDL-C, 50%) levels in STZ-diabetic rats after 3 weeks of treatment. The [V^IVO(octd)] has shown antihyperglycemic activity in diabetic rats as well as a reduction in elevated lipid levels. Time-dependent studies using EPR and ⁵¹V NMR spectroscopy of [V^IVO(octd)] were done in aqueous solutions to determine the complex stability and species present in the oral gavage solution used for complex administration. The spectroscopic studies have shown that the antidiabetic/hypolipidemic activity could be attributed to [V^IVO(octd)], vanadium species resulting from redox processes, the hydrolysis of [V^IVO(octd)] and its decomposition products, or some combination of these factors. In summary, the oxidovanadium(IV) complex containing the S₂O₂ donor ligand has desirable antidiabetic properties eliminating the symptoms of Diabetes mellitus and its comorbidities.

Heteroleptic oxidovanadium(IV)-malate complex improves glucose uptake in HepG2 and enhances insulin action in streptozotocin-induced diabetic rats

Diabetes mellitus, a complex and heterogeneous disease associated with hyperglycemia, is a leading cause of mortality and reduces life expectancy. Vanadium complexes have been studied for the treatment of diabetes. The effect of complex [VO(bpy)(mal)]·H₂O (complex A) was evaluated in a human hepatocarcinoma (HepG2) cell line and in streptozotocin (STZ)-induced diabetic male Wistar rats conditioned in seven groups with different treatments (n = 10 animals per group). Electron paramagnetic resonance and ⁵¹V NMR analyses of complex A in high-glucose Dulbecco's Modified Eagle Medium (DMEM) revealed the oxidation and hydrolysis of the oxidovanadium(IV) complex over a period of 24 h at 37 °C to give low-nuclearity vanadates "V1" (H₂VO₄^-), "V2" (H₂V₂O₇^2-), and "V4" (V₄O₁₂^4-). In HepG2 cells, complex A exhibited low cytotoxic effects at concentrations 2.5 to 7.5 μmol L^-1 (IC₅₀ 10.53 μmol L^-1) and increased glucose uptake (2-NBDG) up to 93%, an effect similar to insulin. In STZ-induced diabetic rats, complex A at 10 and 30 mg kg^-1 administered by oral gavage for 12 days did not affect the animals, suggesting low toxicity or metabolic impairment during the experimental period. Compared to insulin treatment alone, complex A (30 mg kg^-1) in association with insulin was found to improve glycemia (30.6 ± 6.3 mmol L^-1 vs. 21.1 ± 8.6 mmol L^-1, respectively; p = 0.002), resulting in approximately 30% additional reduction in glycemia. The insulin-enhancing effect of complex A was associated with low toxicity and was achieved via oral administration, suggesting the potential of complex A as a promising candidate for the adjuvant treatment of diabetes.

Study of DNA Interaction and Cytotoxicity Activity of Oxidovanadium(V) Complexes with ONO Donor Schiff Base Ligands

Two new oxidovanadium(V) complexes, (HNEt3)[VVO2L] (1) and [(VVOL)2μ-O] (2), have been synthesized using a tridentate Schiff base ligand H2L [where H2L = 4-((E)-(2-hydroxy-5-nitrophenylimino)methyl)benzene-1,3-diol] and VO(acac)2 as starting metal precursor. The ligand and corresponding metal complexes are characterized by physicochemical (elemental analysis), spectroscopic (FT-IR, UV–Vis, and NMR), and spectrometric (ESI–MS) methods. X-ray crystallographic analysis indicates the anion in salt 1 features a distorted square-pyramidal geometry for the vanadium(V) center defined by imine-N, two phenoxide-O, and two oxido-O atoms. The interaction of the compounds with CT–DNA was studied through UV–Vis absorption titration and circular dichroism methods. The results indicated that complexes showed enhanced binding affinity towards DNA compared to the ligand molecule. Finally, the in vitro cytotoxicity studies of H2L, 1, and 2 were evaluated against colon cancer (HT-29) and mouse embryonic fibroblast (NIH-3T3) cell lines by MTT assay. The results demonstrated that the compounds manifested a cytotoxic potential comparable with clinically referred drugs and caused cell death by apoptosis.

Chemistry of mixed-ligand oxidovanadium(IV) complexes of aroylhydrazones incorporating quinoline derivatives: Study of solution behavior, theoretical evaluation and protein/DNA interaction

A series of eight hexacoordinated mixed-ligand oxidovanadium(IV) complexes [VO(L^x)(L^N-N)] (1-8), where L^x = L¹ - L⁴ are four differently substituted ONO donor aroylhydrazone ligands and L^N-N are N,N-donor bases like 2,2'-bipyridine (bipy) (1, 3, 5 and 7) and 1,10-phenanthroline (phen) (2, 4, 6 and 8), have been reported. All synthesized complexes have been characterized by various physicochemical techniques and molecular structures of 1 and 6 were determined by X-ray crystallography. With a view to evaluate the biological activity of the V^IVO species, the behavior of the systems V^IVO²⁺/L^x, V^IVO²⁺/L^x/bipy and V^IVO²⁺/L^x/phen was studied as a function of pH in a mixture of H₂O/DMSO 50/50 (v/v). DFT calculations allowed finding out the relative stability of the tautomeric forms of the ligands, and predicting the structure of vanadium complexes and their EPR parameters. To study their interaction with proteins, firstly the ternary systems V^IVO²⁺/L^1,2 with 1-methylimidazole, which is a good model for histidine binding, were examined. Subsequently the interaction of the complexes with lysozyme (Lyz), cytochrome c (Cyt) and bovine serum albumin (BSA) was studied. The results indicate that the complexes showed moderate binding affinity towards BSA, while no interaction takes place with lysozyme and cytochrome c. This could be explained with the higher number of accessible coordinating and polar residues for BSA than for Lyz and Cyt. Further, the complexes were also evaluated for their DNA binding propensity through UV-vis absorption titration and fluorescence spectral studies. These results were consistent with BSA binding affinity and showed moderate binding affinity towards CT-DNA.

Metabolic effects of VO(dmpp)2– anex vivo1H-HRMAS NMR study to unveil its pharmacological properties

VO(dmpp)₂ameliorates liver metabolic profile of obese pre-diabetic Zucker rats after 4 weeks of treatment, as demonstrated byex vivo¹H-HRMAS NMR study.

Integrated ESI-MS/EPR/computational characterization of the binding of metal species to proteins: vanadium drug–myoglobin application

An integrated strategy based on ESI-MS spectrometry, EPR spectroscopy and docking/QM computational methods is applied to the systems formed by V^IVO²⁺ ions and four potential V^IVOL₂ drugs and myoglobin. This approach is generizable to other metals and proteins.

Vanadium: History, chemistry, interactions with α-amino acids and potential therapeutic applications

In the last 30 years, since the discovery that vanadium is a cofactor found in certain enzymes of tunicates and possibly in mammals, different vanadium-based drugs have been developed targeting to treat different pathologies. So far, the in vitro studies of the insulin mimetic, antitumor and antiparasitic activity of certain compounds of vanadium have resulted in a great boom of its inorganic and bioinorganic chemistry. Chemical speciation studies of vanadium with amino acids under controlled conditions or, even in blood plasma, are essential for the understanding of the biotransformation of e.g. vanadium antidiabetic complexes at the physiological level, providing clues of their mechanism of action. The present article carries out a bibliographical research emphaticizing the chemical speciation of the vanadium with different amino acids and reviewing also some other important aspects such as its chemistry and therapeutical applications of several vanadium complexes.

Synthesis, structure, solution behavior, reactivity and biological evaluation of oxidovanadium(iv/v) thiosemicarbazone complexes

The synthesis and characterization of an oxidovanadium(iv) [VIVO(L)(acac)] (1) and of two dioxidovanadium(v) [VVO2(L')] (2) and [VVO2(L)] (2a) complexes of the Schiff base formed from the reaction of 4-(p-fluorophenyl) thiosemicarbazone with pyridine-2-aldehyde (HL) are described. The oxidovanadium(iv) species [VIVO(L)(acac)] (1) was synthesized by the reaction of VIVO(acac)2 with the thiosemicarbazone HL in refluxing ethanol. The recrystallization of [VIVO(L)(acac)] (1) in DMF, CH3CN or EtOH gave the same product i.e. the dioxidovanadium(v) complex [VVO2(L)] (2a); however, upon recrystallization of 1 in DMSO a distinct compound [VVO2(L')] (2) was formed, wherein the original ligand L- is transformed to a rearranged one, L'-. In the presence of DMSO the ligand in complex 1 is found to undergo methylation at the carbon centre attached to imine nitrogen (aldimine) and transformed to the corresponding VVO2-species through in situ reaction. The synthesized HL and the metal complexes were characterized by elemental analysis, IR, UV-Vis, NMR and EPR spectroscopy. The molecular structure of [VVO2(L')] (2) was determined by single crystal X-ray crystallography. The methylation of various other ligands and complexes prepared from different vanadium precursors under similar reaction conditions was also attempted and it was confirmed that the imine methylation observed is both ligand and metal precursor specific. Complexes 1 and 2 show in vitro insulin-like activity against insulin responsive L6 myoblast cells, higher than VIVO(acac)2, with complex 1 being more potent. In addition, the in vitro cytotoxicity studies of HL, and of complexes 1 and 2 against the MCF-7 and Vero cell lines were also done. The ligand is not cytotoxic and complex 2 is significantly more cytotoxic than 1. DAPI staining experiments indicate that an increase in the time of incubation and an increase of concentration of the complexes lead to the increase in cell death.

Lupinus mutabilis Extract Exerts an Anti-Diabetic Effect by Improving Insulin Release in Type 2 Diabetic Goto-Kakizaki Rats

Lupinus mutabilis (LM) is a legume part of Bolivian traditional diet that has a nutraceutical property reducing blood glucose levels. The prevalence of type 2 diabetes is increasing worldwide thus; the search for novel anti-diabetic drugs is needed. Based on its traditional use, we evaluated the anti-diabetic effect of LM in the spontaneously diabetic Goto-Kakizaki (GK) rat, a model of type 2 diabetes and in Wistar (W) rats as healthy control. LM seeds hydroethanolic extract, analyzed by gas chromatography-mass spectrometry and high-performance liquid chromatography-high resolution mass spectrometry, is a complex mixture of volatile and non-volatile components. A single oral administration of LM extract (2000 mg/kg b.w.) improved glucose tolerance during the oral glucose tolerance test (OGTT) (30–120 min) in GK and W rats (p < 0.0001). The long-term treatment with LM (1000 mg/kg b.w.), for 21 days, improved the area under the curve (AUC) of glucose during OGTT at day 20, in both GK (p < 0.01) and W rats (p < 0.01). The HbA1c (GK rats, p < 0.05 and W rats, p < 0.0001) and the non-fasting glucose (GK rats, p < 0.05) were also reduced. LM increased both serum insulin levels (2.4-fold in GK rats and 2.5-fold W rats), and the glucose-induced (16.7 mM glucose) insulin release in isolated islets from treated animals (6.7-fold in GK rats, and 6.6-fold in W rats). Moreover, LM (10 mg/mL) stimulated in vitro glucose induced (16.7 mM glucose) insulin release in batch incubated GK and W rat islets (p < 0.0001). In perifused GK rat islets, insulin release in 16.7 mM glucose was increased 95.3-fold compared to untreated islets (p < 0.0001), while no significant differences were found in perifused W rat islets. The LM mechanism of action, evaluated using inhibitory compounds of the insulin secretion pathway, showed that LM-dependent insulin secretion was reduced 42% by diazoxide (p < 0.001), 70% by nifedipine (p < 0.001), 86.7% by H89 (p < 0.0001), 70.8% by calphostine-C (p < 0.0001) and 93% by pertussis toxin (p < 0.0001). A similar effect was observed in W rats islets. Our findings provide evidence that LM has an anti-diabetic effect through stimulation of insulin release. The effect is-dependent on L-type calcium channel, protein kinase A and C systems, and G protein-coupled exocytosis and is partially mediated by K-ATP channels.

Bis(picolinato) complexes of vanadium and zinc as potential antidiabetic agents: synthesis, structural elucidation and in vitro insulin-mimetic activity study

The studied vanadium(iv), vanadium(v) and zinc(ii) complexes show inhibition of the free fatty acid release from rat adipocytes.

Vanadium and zinc complexes of 5-cyanopicolinate and pyrazine derivatives: synthesis, structural elucidation and in vitro insulino-mimetic activity study

Inhibition of free fatty acid release from rat adipocytes was observed for vanadium(iv), vanadium(v) and zinc(ii) complexes.

Vanadium(IV)-chlorodipicolinate inhibits 3T3-L1 preadipocyte adipogenesis by activating LKB1/AMPK signaling pathway

Our previous studies demonstrated that vanadium(IV) complex with 4-chlorodipicolinic acid (VOdipic-Cl) alleviates lipid abnormalities in streptozotocin (STZ)-induced diabetic rats. However, the molecular mechanisms are not fully understood. In the present study, the effect of VOdipic-Cl on adipogenesis and mechanisms of action in 3T3-L1 preadipocytes were investigated. The 3T3-L1 preadipocytes were induced to differentiate in the presence or absence of VOdipic-Cl for 8days. The cells were determined for proliferation, differentiation, lipid accumulation as well as the protein expressions of molecular targets that are involved in fatty acid synthesis. The results demonstrated that VOdipic-Cl at concentrations ranging from 2.5μM to 10μM reduced the intracellular lipid content by 10%, 22% and 30% compared to control. VOdipic-Cl down-regulated the expression of peroxisome proliferator-activated receptor (PPARγ), CCAAT element binding protein a (C/EBPα), sterol regulatory element binding protein 1c (SREBP-1c), fatty acid synthase (FAS) and fatty acid-binding protein 4 (FABP4) and activated the phosphorylation of acetyl coenzyme A carboxylase (ACC), adenosine monophosphate-activated protein kinase (AMPK) and liver kinase B1 (LKB1) in a dose-dependent manner. Further studies showed that AMPK small interfering RNA (siRNA) markedly up-regulated PPARγ, C/EBPα, FAS and FABP4 expression in the presence of VOdipic-Cl, respectively. When LKB1 was silenced with siRNA, the effect of VOdipic-Cl on AMPK phosphorylation was diminished. Taken together, these results suggested that VOdipic-Cl can inhibit 3T3-L1 preadipocyte differentiation and adipogenesis through activating the LKB1/AMPK-dependent signaling pathway. These findings raise the possibility that VOdipic-Cl may be a promising therapy in treatment of obesity.

Water soluble heterometallic potassium-dioxidovanadium(V) complexes as potential antiproliferative agents

Two water soluble heterometallic potassium–dioxidovanadium polymers, [KVO2(L1)]n (1) and [KVO2(L2)(H2O)]n (2) [H2L1= (2,3-dihydroxybenzylidene)-2-hydroxybenzohydrazide and H2L2=(2,3-dihydroxybenzylidene)benzohydrazide], have been synthesized and characterized by IR, NMR, elemental analysis and single crystal X-ray diffraction. The antiproliferative potentials of 1 and 2 were examined towards human colorectal carcinoma (HCT116), and lung (A549) and breast (MCF7) adenocarcinoma cell lines. 1 exhibits a high cytotoxic activity against colorectal carcinoma cells (HCT116), with IC50 lower than those for cisplatin.

In vitro effects of bis(1,2-dimethyl-3-hydroxy-4-pyridinonato)oxidovanadium(IV), or VO(dmpp)2, on insulin secretion in pancreatic islets of type 2 diabetic Goto-Kakizaki rats

Vanadium compounds have been explored as therapy of diabetes, and most studies have focussed on insulin mimetic effects, i.e. reducing hyperglycemia by improving glucose sensitivity and thus glucose uptake in sensitive tissues. We have recently shown that bis(1,2-dimethyl-3-hydroxy-4-pyridinonato)oxidovanadium(IV), VO(dmpp)2, has promising effects when compared to another vanadium compound, bis(maltolato)oxidovanadium(IV), BMOV, and insulin itself, in isolated adipocytes and in vivo in Goto-Kakizaki (GK) rats, an animal model of hereditary type 2 diabetes (T2D).We now have investigated in GK rats whether VO(dmpp)2 also modulates another important defect in T2D, impaired insulin secretion. VO(dmpp)2, but not BMOV, stimulated insulin secretion from isolated GK rat pancreatic islets at high, 16.7mM, but not at low–normal, 3.3 mM, glucose concentration. Mechanistic studies demonstrate that the insulin releasing effect of VO(dmpp)2 is due to its interaction with several steps in the stimulus-secretion coupling for glucose, including islet glucose metabolism and K-ATP channels, L-type Ca2+ channels, modulation by protein kinases A and C, as well as the exocytotic machinery. In conclusion, VO(dmpp)2 exhibits properties of interest for treatment of the insulin secretory defect in T2D, in addition to its well-described insulin mimetic activity.

Vanadium compounds in medicine

Vanadium is a transition metal that, being ubiquitously distributed in soil, crude oil, water and air, also found roles in biological systems and is an essential element in most living beings. There are also several groups of organisms which accumulate vanadium, employing it in their biological processes. Vanadium being a biological relevant element, it is not surprising that many vanadium based therapeutic drugs have been proposed for the treatment of several types of diseases. Namely, vanadium compounds, in particular organic derivatives, have been proposed for the treatment of diabetes, of cancer and of diseases caused by parasites. In this work we review the medicinal applications proposed for vanadium compounds with particular emphasis on the more recent publications. In cells, partly due to the similarity of vanadate and phosphate, vanadium compounds activate numerous signaling pathways and transcription factors; this by itself potentiates application of vanadium-based therapeutics. Nevertheless, this non-specific bio-activity may also introduce several deleterious side effects as in addition, due to Fenton's type reactions or of the reaction with atmospheric O2, VCs may also generate reactive oxygen species, thereby introducing oxidative stress with consequences presently not well evaluated, particularly for long-term administration of vanadium to humans. Notwithstanding, the potential of vanadium compounds to treat type 2 diabetes is still an open question and therapies using vanadium compounds for e.g. antitumor and anti-parasitic related diseases remain promising.

Synthesis and crystal structure of the two-dimensional coordination compound potassium oxo-bis(hydroxylamido)-pyridine-2, 3-dicarboxylato-vanadate(V)

The crystal structure of the title compound, K2[VO(C7H3O4N)(NH2O)2(H2O)]2, is composed of KO9 and VO5N2 polyhedra connected through pyridine-2,3-dicarboxylate (2,3-dipicolinate) bridges. The VO5N2 coordination polyhedron is a pentagonal bipyramid, with hydroxylamido and dipicolinato ligands being bidentate. The axial positions are occupied by the terminal oxo ligand and one oxygen atom from a deprotonated carboxylate group. The oxygen atoms from hydroxylamido and the nitrogen atoms belonging either to the pyridine ring or to the hydroxylamido occupy the equatorial positions and form an approximate pentagonal plane. The irregular KO9 polyhedra are linked, sharing edges and planes to form infinite chains. These chains are linked by the dipicolinate bridges to form layers. The distorted VO5N2 polyhedron is grafted on to the layer by the dipicolinate carboxylate O atom. Adjacent layers are connected through N–H···O hydrogen bonds to form a three-dimensional supramolecular structure.

Thirty years through vanadium chemistry

The relevance of vanadium in biological systems is known for many years and vanadium-based catalysts have important industrial applications, however, till the beginning of the 80s research on vanadium chemistry and biochemistry did not receive much attention from the scientific community. The understanding of the broad bioinorganic implications resulting from the similarities between phosphate and vanadate(V) and the discovery of vanadium dependent enzymes gave rise to an enormous increase in interest in the chemistry and biological relevance of vanadium. Thereupon the last 30years corresponded to a period of enormous research effort in these fields, as well as in medicinal applications of vanadium and in the development of catalysts for use in fine-chemical synthesis, some of these inspired by enzymatic active sites. Since the 80s my group in collaboration with others made contributions, described throughout this text, namely in the understanding of the speciation of vanadium compounds in aqueous solution and in biological fluids, and to the transport of vanadium compounds in blood plasma and their uptake by cells. Several new types of vanadium compounds were also synthesized and characterized, with applications either as prospective therapeutic drugs or as homogeneous or heterogenized catalysts for the production of fine chemicals. The developments made are described also considering the international context of the evolution of the knowledge in the chemistry and bioinorganic chemistry of vanadium compounds during the last 30years. This article was compiled based on the Vanadis Award presentation at the 9th International Vanadium Symposium.