Is the hypoglycemic action of vanadium compounds related to the suppression of feeding?

The Deficits of Insulin Signal in Alzheimer's Disease and the Mechanisms of Vanadium Compounds in Curing AD

Vanadium is a well-known essential trace element, which usually exists in oxidation states in the form of a vanadate cation intracellularly. The pharmacological study of vanadium began with the discovery of its unexpected inhibitory effect on ATPase. Thereafter, its protective effects on β cells and its ability in glucose metabolism regulation were observed from the vanadium compound, leading to the application of vanadium compounds in clinical trials for curing diabetes. Alzheimer's disease (AD) is the most common dementia disease in elderly people. However, there are still no efficient agents for treating AD safely to date. This is mainly because of the complexity of the pathology, which is characterized by senile plaques composed of the amyloid-beta (Aβ) protein in the parenchyma of the brain and the neurofibrillary tangles (NFTs), which are derived from the hyperphosphorylated tau protein in the neurocyte, along with mitochondrial damage, and eventually the central nervous system (CNS) atrophy. AD was also illustrated as type-3 diabetes because of the observations of insulin deficiency and the high level of glucose in cerebrospinal fluid (CSF), as well as the impaired insulin signaling in the brain. In this review, we summarize the advances in applicating the vanadium compound to AD treatment in experimental research and point out the limitations of the current study using vanadium compounds in AD treatment. We hope this will help future studies in this field.

Targeting Breast Cancer and Their Stem Cell Population through AMPK Activation: Novel Insights

Despite some significant advancements, breast cancer has become the most prevalent cancer in the world. One of the main reasons for failure in treatment and metastasis has been attributed to the presence of cancer initiating cells-cancer stem cells. Consequently, research is now being focussed on targeting cancer cells along with their stem cell population. Non-oncology drugs are gaining increasing attention for their potent anticancer activities. Metformin, a drug commonly used to treat type 2 diabetes, is the best example in this regard. It exerts its therapeutic action by activating 5' adenosine monophosphate-activated protein kinase (AMPK). Activated AMPK subsequently phosphorylates and targets several cellular pathways involved in cell growth and proliferation and the maintenance of stem-like properties of cancer stem cells. Therefore, AMPK is emerging as a target of choice for developing effective anticancer drugs. Vanadium compounds are well-known PTP inhibitors and AMPK activators. They find extensive applications in treatment of diabetes and obesity via PTP1B inhibition and AMPK-mediated inhibition of adipogenesis. However, their role in targeting cancer stem cells has not been explored yet. This review is an attempt to establish the applications of insulin mimetic vanadium compounds for the treatment of breast cancer by AMPK activation and PTP1B inhibition pathways.

Alzheimer's Disease and Diabetes Mellitus in Comparison: The Therapeutic Efficacy of the Vanadium Compound

Alzheimer’s disease (AD) is an intractable neurodegenerative disease that leads to dementia, primarily in elderly people. The neurotoxicity of amyloid-beta (Aβ) and tau protein has been demonstrated over the last two decades. In line with these findings, several etiological hypotheses of AD have been proposed, including the amyloid cascade hypothesis, the oxidative stress hypothesis, the inflammatory hypothesis, the cholinergic hypothesis, et al. In the meantime, great efforts had been made in developing effective drugs for AD. However, the clinical efficacy of the drugs that were approved by the US Food and Drug Association (FDA) to date were determined only mild/moderate. We recently adopted a vanadium compound bis(ethylmaltolato)-oxidovanadium (IV) (BEOV), which was originally used for curing diabetes mellitus (DM), to treat AD in a mouse model. It was shown that BEOV effectively reduced the Aβ level, ameliorated the inflammation in brains of the AD mice, and improved the spatial learning and memory activities of the AD mice. These finding encouraged us to further examine the mechanisms underlying the therapeutic effects of BEOV in AD. In this review, we summarized the achievement of vanadium compounds in medical studies and investigated the prospect of BEOV in AD and DM treatment.

Prenatal and postnatal exposure to vanadium and the immune function of children

BACKGROUND

The immunotoxicity induced by vanadium exposure have been reported in some toxicology researches. However, evidence from population-based epidemiological studies was lacking.

METHODS

This study was conducted to assess the associations between prenatal and postnatal exposure to vanadium and immune function of children. A total of 407 pre-school aged children were followed, whose peripheral blood was collected for T lymphocyte subsets and inflammatory cytokines analysis, as well as vanadium concentration measurement. Maternal urine samples were also collected to measure vanadium concentration. We used generalized linear models to evaluate the associations of maternal and children vanadium concentration with children's immune function. Stratification analysis was further conducted to explore the potential gender-specific effects.

RESULTS

The geometric means of vanadium concentration in maternal urine and children plasma were 0.85 and 1.12 μg/L, respectively. Maternal urinary vanadium was inversely associated with the percentage of CD3⁺CD4⁺ cells [-5.53 % (-10.38 %, -0.41 %)] and absolute counts of CD3⁺ cells [-2.43 % (-5.05 %, 0.25 %)], and we only observed significant negative associations in males when stratifying by fetal gender. Children plasma vanadium was also associated with reduced absolute counts of CD3⁺ cells [-5.25 % (-9.57 %, -0.73 %)], but gender-specific effects were not observed. No significant associations of vanadium exposure with cytokines were found.

CONCLUSIONS

Prenatal and postnatal exposure to vanadium had suppressive impacts on childhood cellular immune. Further studies are needed to confirm our findings.

Metforminium Decavanadate (MetfDeca) Treatment Ameliorates Hippocampal Neurodegeneration and Recognition Memory in a Metabolic Syndrome Model

The consumption of foods rich in carbohydrates, saturated fat, and sodium, accompanied by a sedentary routine, are factors that contribute to the progress of metabolic syndrome (MS). In this way, they cause the accumulation of body fat, hypertension, dyslipidemia, and hyperglycemia. Additionally, MS has been shown to cause oxidative stress, inflammation, and death of neurons in the hippocampus. Consequently, spatial and recognition memory is affected. It has recently been proposed that metformin decavanadate (MetfDeca) exerts insulin mimetic effects that enhance metabolism in MS animals; however, what effects it can cause on the hippocampal neurons of rats with MS are unknown. The objective of the work was to evaluate the effect of MetfDeca on hippocampal neurodegeneration and recognition memory in rats with MS. Administration of MetfDeca for 60 days in MS rats improved object recognition memory (NORt). In addition, MetfDeca reduced markers of oxidative stress and hippocampal neuroinflammation. Accompanied by an increase in the density and length of the dendritic spines of the hippocampus of rats with MS. We conclude that MetfDeca represents an important therapeutic agent to treat MS and induce neuronal and cognitive restoration mechanisms.

Sodium metavanadate treatment improves glycogen levels in multiple tissues in a model of metabolic syndrome caused by chronic cadmium exposure in Wistar rats

Cadmium, one of the more hazardous environmental contaminants, has been proposed as a metabolic disruptor. Vanadium has emerged as a possible treatment for metabolic diseases. Both metals are important in public health. We aimed to investigate whether vanadium treatment is effective against metabolic disturbances caused by chronic exposure to the lowest-observable adverse effect level of cadmium. Male Wistar rats were exposed to cadmium (32.5 ppm) in drinking water for 3 months. Metabolic complications such as overweight, visceral adipose gain, hyperglycemia, impaired glucose tolerance, and dyslipidemia were detected, and low glycogen levels and steatosis were observed in the tissues. Then, the control and treated animals were subdivided and treated with a solution of 5 μM NaVO₃/kg/twice a week for 2 months. The control-NaVO₃ group did not show zoometric or metabolic changes. A strong interaction of NaVO₃ treatment over cadmium metabolic disruption was observed. The vanadium accumulation diminished cadmium concentration in tissues. Also, vanadium interaction improved glucose homeostasis. The major effect was observed on glycogen synthesis, which was fully recovered in all tissues analyzed. Additionally, vanadium treatment prevented overweight and visceral fat accumulation, improving BMI and the percentage of fat. However, NaVO₃ treatment did not have an effect on dyslipidemia or steatosis. In conclusion, this work shows that vanadium administration has a strong effect against metabolic disturbances caused by chronic cadmium exposure, observing powerful interaction on glucose homeostasis.

Vanadium and insulin: Partners in metabolic regulation

Since the 1970s, the biological role of vanadium compounds has been discussed as insulin-mimetic or insulin-enhancer agents. The action of vanadium compounds has been investigated to determine how they influence the insulin signaling pathway. Khan and coworkers proposed key proteins for the insulin pathway study, introducing the concept "critical nodes". In this review, we also considered critical kinases and phosphatases that participate in this pathway, which will permit a better comprehension of a critical node, where vanadium can act: a) insulin receptor, insulin receptor substrates, and protein tyrosine phosphatases; b) phosphatidylinositol 3'-kinase, 3-phosphoinositide-dependent protein kinase and mammalian target of rapamycin complex, protein kinase B, and phosphatase and tensin homolog; and c) insulin receptor substrates and mitogen-activated protein kinases, each node having specific negative modulators. Additionally, leptin signaling was considered because together with insulin, it modulates glucose and lipid homeostasis. Even in recent literature, the possibility of vanadium acting against metabolic diseases or cancer is confirmed although the mechanisms of action are not well understood because these critical nodes have not been systematically investigated. Through this review, we establish that vanadium compounds mainly act as phosphatase inhibitors and hypothesize on their capacity to affect kinases, which are critical to other hormones that also act on common parts of the insulin pathway.

Trace Elements, PPARs, and Metabolic Syndrome

Metabolic syndrome (MetS) is a constellation of metabolic derangements, including central obesity, insulin resistance, hypertension, glucose intolerance, and dyslipidemia. The pathogenesis of MetS has been intensively studied, and now many factors are recognized to contribute to the development of MetS. Among these, trace elements influence the structure of proteins, enzymes, and complex carbohydrates, and thus an imbalance in trace elements is an independent risk factor for MetS. The molecular link between trace elements and metabolic homeostasis has been established, and peroxisome proliferator-activated receptors (PPARs) have appeared as key regulators bridging these two elements. This is because on one hand, PPARs are actively involved in various metabolic processes, such as abdominal adiposity and insulin sensitivity, and on the other hand, PPARs sensitively respond to changes in trace elements. For example, an iron overload attenuates hepatic mRNA expression of Ppar-α; zinc supplementation is considered to recover the DNA-binding activity of PPAR-α, which is impaired in steatotic mouse liver; selenium administration downregulates mRNA expression of Ppar-γ, thereby improving lipid metabolism and oxidative status in the liver of high-fat diet (HFD)-fed mice. More importantly, PPARs' expression and activity are under the control of the circadian clock and show a robust 24 h rhythmicity, which might be the reasons for the side effects and the clinical limitations of trace elements targeting PPARs. Taken together, understanding the casual relationships among trace elements, PPARs' actions, and the pathogenesis of MetS is of great importance. Further studies are required to explore the chronopharmacological effects of trace elements on the diurnal oscillation of PPARs and the consequent development of MetS.

Mini review-vanadium-induced neurotoxicity and possible targets

Vanadium, a transition metal, ubiquitous in nature is known to have therapeutic effect as well as toxic effect. It is known to possess antidiabetic, antitumor and antiparasitic activity. However, on long term exposure, it produces neurotoxicity which may result in memory impairment. The possible mechanism known to cause neurotoxicity suggested is oxidative stress and inflammation of neuronal cells. The present review has focused on discussing the role of protein P38 mitogen-activated protein kinase and oxidative stress as possible targets to treat vanadium-induced neurotoxicity.

Vanadium in Biosphere and Its Role in Biological Processes

Ultra-trace elements or occasionally beneficial elements (OBE) are the new categories of minerals including vanadium (V). The importance of V is attributed due to its multifaceted biological roles, i.e., glucose and lipid metabolism as an insulin-mimetic, antilipemic and a potent stress alleviating agent in diabetes when vanadium is administered at lower doses. It competes with iron for transferrin (binding site for transportation) and with lactoferrin as it is secreted in milk also. The intracellular enzyme protein tyrosine phosphatase, causing the dephosphorylation at beta subunit of the insulin receptor, is inhibited by vanadium, thus facilitating the uptake of glucose inside the cell but only in the presence of insulin. Vanadium could be useful as a potential immune-stimulating agent and also as an antiinflammatory therapeutic metallodrug targeting various diseases. Physiological state and dose of vanadium compounds hold importance in causing toxicity also. Research has been carried out mostly on laboratory animals but evidence for vanadium importance as a therapeutic agent are available in humans and large animals also. This review examines the potential biochemical and molecular role, possible kinetics and distribution, essentiality, immunity, and toxicity-related study of vanadium in a biological system.

Vanadium(IV)-chlorodipicolinate alleviates hepatic lipid accumulation by inducing autophagy via the LKB1/AMPK signaling pathway in vitro and in vivo

Numerous studies have demonstrated that vanadium compounds are able to improve lipemia and triglyceridemia in both humans and animals. However, the molecular mechanism remains elusive. The present study was conducted to investigate the anti-hyperlipidemic effect of vanadium(IV) complex with 4-chlorodipicolinic acid (VOdipic-Cl)-induced autophagy on hepatic lipid accumulation. To explore the possible underlying mechanisms, primary rat hepatocytes, human hepatoma cell line HepG2, and liver tissue from C57BL/6 mice fed a high-fat diet (HFD) were used. In vitro, cultured primary rat hepatocytes were treated with palmitate (0.25, 0.5 and 0.75 mM) prior to VOdipic-Cl (50, 100, and 200 μM) for 24 h, respectively. In vivo, C57BL/6 mice were fed with high-fat diet for 16 weeks. VOdipic-Cl (10 mg V/kg body weight) was given by daily gavage for 4 weeks. In vitro results showed that VOdipic-Cl significantly inhibited lipid droplet formation by increasing the level of conversion and punctuation of microtubule-associated proteins light chain 3 (LC3) in a dose-dependent manner, and activated liver kinase B-1 (LKB1) and adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. Confocal microscopy images also showed that VOdipic-Cl induced sequestration of lipid droplets (LDs) by autophagy. In vivo, VOdipic-Cl attenuated the increase in serum and liver triglyceride levels in the mice fed with high-fat diet, while significantly increased autophagy induction and activated LKB1 and AMPK phosphorylation in the liver. Taken together, these results suggest that VOdipic-Cl reduces hepatic lipid accumulation by inducing autophagy via the activation of LKB1/AMPK-dependent signaling pathway.

Direct imaging of how lanthanides break the normal evolution of plants

After rare earth elements [REE(III)] are anchored outside of the plasma membrane, REE(III) break plant evolution to initiate leaf cell endocytosis, which finally affects plant growth. However, the molecule for anchoring REE(III) in the acidic environment outside of the plasma membrane is not clear, which is crucial for exploring the mechanism of REE(III) breaking plant evolution. Here, lanthanum(III) [La(III)] and terbium(III) [Tb(III)] were respectively served as a representative of REE(III) without and with f electrons, and Arabidopsis was served as a representative of plants, cellular and molecular basis for arabinogalactan proteins (AGP) anchoring REE(III) outside of the plasma membrane was investigated. By using interdisciplinary methods, when REE(III) initiated leaf cell phagocytosis, we observed the increase in the expression of AGP and their migration to the outside of the plasma membrane. In the acidic environment outside of the plasma membrane, Tb(III) formed more stable Lewis acid-base [REE(III)-AGP] complexes with a higher apparent binding constant (1.51 × 10^-6) than La(III) (1.24 × 10^-6). In REE(III)-AGP complexes, the bond lengths of REE(III)-O were in normal range and H-bonds were strong H-bonds. The formation of REE(III)-AGP complexes sequentially disturbed the secondary and tertiary structure of AGP, which were enhanced with increasing the concentration of REE(III), and Tb(III) caused stronger structural changes than La(III). Hence, AGP could be molecules for anchoring REE(III) outside of the plasma membrane. The results of this study are direct imaging of how lanthanides break the normal evolution of plants, and can serve as an important guidance for investigating mechanism of lanthanides in organisms.

Synthesis and anti-diabetic activity of new N,N-dimethylphenylenediamine-derivatized nitrilotriacetic acid vanadyl complexes

Vanadium compounds are promising anti-diabetic agents. However, reducing the metal toxicity while keeping/improving the hypoglycemic effect is still a big challenge towards the success of anti-diabetic vanadium drugs. To improve the therapeutic potency using the anti-oxidative strategy, we synthesized new N,N-dimethylphenylenediamine (DMPD)-derivatized nitrilotriacetic acid vanadyl complexes ([VO(dmada)]). The in vitro biological evaluations revealed that the DMPD-derivatized complexes showed improved antioxidant capacity and lowered cytotoxicity on HK-2 cells than bis(maltolato)oxidovanadium (IV) (BMOV). In type II diabetic mice, [VO(p-dmada)] (0.15mmolkg^-1/day) exhibited better hypoglycemic effects than BMOV especially on improving glucose tolerance and alleviating the hyperglycemia-induced liver damage. These insulin enhancement effects were associated with increased expression of peroxisome proliferator-activated receptor α and γ (PPARα/γ) in fat, activation of Akt (v-Akt murine thymoma viral oncogene)/PKB (protein kinase-B) in fat and liver, and inactivation of c-Jun NH₂-terminal protein kinases (JNK) in liver. Moreover, [VO(p-dmada)] showed no tissue toxicity at the therapeutic dose in diabetic mice and the oral acute toxicity (LD50) was determined to be 1640mgkg^-1. Overall, the experimental results indicated that [VO(p-dmada)] can be a potent insulin enhancement agent with improved efficacy-over- toxicity index for further drug development. In addition, the results on brain Tau phosphorylation suggested necessary investigation on the effects of vanadyl complexes on the pathology of the Alzheimer's disease in the future.

Synthesis, characterization and anti-diabetic therapeutic potential of novel aminophenol-derivatized nitrilotriacetic acid vanadyl complexes

In the present work, we synthesized three novel aminophenol-derivatized nitrilotriacetic acid vanadyl complexes (VOohpada, VOmhpada, VOphpada) using the strategy of rational incorporation of antioxidant groups in ligand in order to balance the side effects with the therapeutic properties. The complexes were characterized by IR, UV-VIS, ESI-MS and elemental analysis. The biological evaluations in vitro revealed that the position of the hydroxyl group of aminophenol moiety regulated the antioxidant activity of the complexes as well as the cytotoxicity on HK-2 cells. The vanadyl complex of p-hydroxyl aminophenol derivative (VOphpada) exhibited better antioxidant activity and lower cytotoxicity than other analogs. In type II diabetic db/db mice, VOphpada (0.1 mmol/kg/day) effectively reduced blood glucose level, improved glucose tolerance, and alleviated stresses induced by hyperglycemia and hyperlipidemia. VOphpada treatment significantly increased expression of PPARα and γ, activated Akt, and inactivated JNK in muscle and adipose tissues. The insulin enhancement effects of VOphpada were observed more potent than BMOV. Moreover, VOphpada decreased the level of kidney injury molecule-1 marker (KIM-1), suggesting a potentially lower renal toxicity. In overall, the present results suggest VOphpada as a novel hypoglycemic agent with improved efficacy-over-toxicity index.

Vanadyl sulfate treatment stimulates proliferation and regeneration of beta cells in pancreatic islets

We examined the effects of vanadium sulfate (VOSO4) treatment at 5 and 10 mg/kg for 30 days on endocrine pancreas activity and histology in nondiabetic and STZ-induced diabetic rats. In diabetic group, blood glucose levels significantly increased while insulinemia level markedly decreased. At the end of treatment, VOSO4 at a dose of 10 mg/Kg normalized blood glucose level in diabetic group, restored insulinemia, and significantly improved insulin sensitivity. VOSO4 also increased in a dose-dependent manner the number of insulin immunopositive beta cells in pancreatic islets of nondiabetic rats. Furthermore, in the STZ-diabetic group, the decrease in the number of insulin immunopositive beta cells was corrected to reach the control level mainly with the higher dose of vanadium. Therefore, VOSO4 treatment normalized plasma glucose and insulin levels and improved insulin sensitivity in STZ-experimental diabetes and induced beta cells proliferation and/or regeneration in normal or diabetic rats.