Vanadyl acetylacetonate upregulates PPARγ and adiponectin expression in differentiated rat adipocytes

Mechanism of Metal Complexes in Alzheimer's Disease

Alzheimer's disease (AD) is a kind of neurodegenerative diseases characterized by beta-amyloid deposition and neurofibrillary tangles and is also the main cause of dementia. According to statistics, the incidence of AD is constantly increasing, bringing a great burden to individuals and society. Nonetheless, there is no cure for AD, and the available drugs are very limited apart from cholinesterase inhibitors and N-Methyl-D-aspartic acid (NMDA) antagonists, which merely alleviate symptoms without delaying the progression of the disease. Therefore, there is an urgent need to develop a medicine that can delay the progression of AD or cure it. In recent years, increasing evidence suggests that metal complexes have the enormous potential to treat AD through inhibiting the aggregation and cytotoxicity of Aβ, interfering with the congregation and hyperphosphorylation of tau, regulating dysfunctional synaptic and unbalanced neurotransmitters, etc. In this review, we summarize the current metal complexes and their mechanisms of action for treating AD, including ruthenium, platinum, zinc, vanadium, copper, magnesium, and other complexes.

Insulin Receptor Substrates Regulation and Clinical Responses Following Vanadium-Enriched Yeast Supplementation in Obese Type 2 Diabetic Patients: a Randomized, Double-Blind, Placebo-Controlled Clinical Trial

Increasing evidence suggests that organic vanadium compounds are bioavailable and safe therapeutic agents with insulin-mimetic and insulin-enhancing features. The objective of the current study was to examine the effect of vanadium-enriched yeast (VEY) supplementation on the gene expression level of insulin receptor substrates and clinical manifestations of obese type 2 diabetic mellitus (T2DM) patients. In this randomized, double-blind, placebo-controlled clinical trial, 44 obese T2DM patients were randomly allocated into either VEY (0.9 mg/day vanadium pentoxide) or placebo group for 12 weeks. The mRNA expression level of protein tyrosine phosphatase 1B (PTP1B), phosphatase and tensin homolog (PTEN), mitogen-activated protein kinase (MAPK), ribosomal protein S6 kinase (S6K), and nuclear factor kappa-light-chain-enhancer of activated B cells (NFƘB) genes in the peripheral blood mononuclear cells, serum levels of metabolic parameters, anthropometric indices, as well as the quality of life, and dietary intake were collected at pre- and post-intervention phases. Analysis of covariance was performed to obtain the corresponding effect size. Results showed that VEY administration significantly decreased anthropometric indices and glycemic parameters and increased insulin sensitivity after adjusting for potential covariates (p < 0.05), in comparison to the placebo group. Additionally, VEY supplementation was significantly effective on MAPK, PTP1B, and NFƘB gene expression level, compared to the placebo group. No significant changes were noticed for dietary intake, quality of life, and lipid profile in the VEY group, compared to the placebo group. Overall, VEY supplementation can be considered as a promising safe adjunct therapy for improving anthropometric indices and glycemic parameters in T2DM patients.

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.

An Adequate Supply of Bis(ethylmaltolato)oxidovanadium(IV) Remarkably Reversed the Pathological Hallmarks of Alzheimer's Disease in Triple-Transgenic Middle-Aged Mice

Alzheimer's disease (AD) is a complex and progressive neurodegenerative disease with impaired synapse, imbalanced mineral metabolism, protein mis-folding and aggregation. Bis(ethylmaltolato)oxidovanadium(IV) (BEOV), an organic bioactive vanadium compound with low toxicity and high bioavailability, has been studied as therapeutic agent against tuberculosis and diabetes. However, its neuroprotective effects have rarely been reported. Therefore, in this study, the potential application of BEOV in intervening AD cognitive dysfunction and neuropathology was evaluated. Both low- and high-dose of BEOV (0.2 mmol/L and 1.0 mmol/L) supplementation for 2 months improved the spatial learning and memory deficits of the triple-transgenic AD (3 × Tg AD) mice and mitigated the loss of synaptic proteins and synaptic dysfunction. By inhibiting the expression of amyloid-β precursor protein and β-secretase, and the phosphorylation of tau protein at Ser262, Ser396, Ser404, and Ser202/Thr205 residues, BEOV reduced the amyloid-β deposition and neurofibrillary tangle formation in AD mouse brains and primarily cultured neurons. Further analysis of the brain ionome revealed that BEOV supplementation could significantly affect the concentrations of a variety of metals, most of which, including several AD risk metals, showed reduced levels, particularly with a high-dose intake. Additionally, the elemental correlation network identified both conserved and specific elemental correlations, implying a highly complex and dynamic crosstalk between vanadium and other elements during long-term BEOV supplementation. Overall, our results suggest that BEOV is effective in AD intervention via both ameliorating the disease related pathology and regulating metal homeostasis.

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.

Bis(ethylmaltolato)oxidovanadium (IV) attenuates amyloid-beta-mediated neuroinflammation by inhibiting NF-κB signaling pathway via a PPARγ-dependent mechanism

Neuroinflammation plays a pivotal role in the pathophysiology of neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. During brain neuroinflammation, activated microglial cells resulting from amyloid-beta (Aβ) overload trigger toxic proinflammatory responses. Bis(ethylmaltolato)oxidovanadium (BEOV) (IV), an important vanadium compound, has been reported to have anti-diabetic, anti-cancer, and neuroprotective effects, but its anti-inflammatory property has rarely been investigated. In the present study, the inhibitory effects of BEOV on neuroinflammation were revealed in both Aβ-stimulated BV2 microglial cell line and APPswe/PS1E9 transgenic mouse brain. BEOV administration significantly decreased the levels of tumor necrosis factor-α, interleukin-6, interleukin-1β, inducible nitric oxide synthase, and cyclooxygenase-2 both in the hippocampus of APPswe/PS1E9 mice and in the Aβ-stimulated BV2 microglia. Furthermore, BEOV suppressed the Aβ-induced activation of nuclear factor-κB (NF-κB) signaling and upregulated the protein expression level of peroxisome proliferator-activated receptor gamma (PPARγ) in a dose-dependent manner. PPARγ inhibitor GW9662 could eliminate the effect of BEOV on Aβ-induced NF-κB activation and proinflammatory mediator production. Taken altogether, these findings suggested that BEOV ameliorates Aβ-stimulated neuroinflammation by inhibiting NF-κB signaling pathway through a PPARγ-dependent mechanism.

Combination of bis (α-furancarboxylato) oxovanadium (IV) and metformin improves hepatic steatosis through down-regulating inflammatory pathways in high-fat diet-induced obese C57BL/6J mice

The effects of the combination of bis (α-furancarboxylato) oxovanadium (IV) (BFOV) and metformin (Met) on hepatic steatosis were investigated in high-fat diet-induced obese C57BL/6J mice (HFC57 mice) for 6 weeks. Oral glucose tolerance test was performed to evaluate glucose metabolism. Moreover, blood and hepatic biochemical and histological indices were detected. Besides, Affymetrix-GeneChip analysis and Western blot of the liver were performed. Comparing to the monotherapy group, BFOV + Met showed more effective improvement in glucose metabolism, which decreased the fasting blood glucose, insulin levels and improved insulin sensitivity in HFC57 mice. BFOV + Met significantly decreased serum ALT and AST activities and reduced hepatic triglyceride content and iNOS activities, accompanied by ameliorating intrahepatic fat accumulation and hepatocellular vacuolation. Enhanced hepatic insulin signalling transduction and attenuated inflammation pathway were identified as the major pathways in the BFOV + Met group. BFOV + Met significantly down-regulated the protein expression levels of MMPs, NF-κB, iNOS and up-regulated phosphorylation of AKT and AMPK levels. We concluded that a combination of BFOV and metformin ameliorates hepatic steatosis in HFC57 mice via alleviating hepatic inflammation and enhancing insulin signalling pathway, suggesting that the combination of BFOV and metformin is a potential treatment for hepatic steatosis.

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.

Selenium, Zinc, Chromium, and Vanadium Levels in Serum, Hair, and Urine Samples of Obese Adults Assessed by Inductively Coupled Plasma Mass Spectrometry

The objective of this study was to investigate of selenium (Se), zinc (Zn), chromium (Cr), and vanadium (V) levels in blood serum, hair, and urine of adult obese patients. A total of 199 lean and 196 obese subjects were enrolled in the study. Serum, hair, and urinary metal and metalloid analysis were performed by inductively coupled plasma mass spectrometry at NexION 300D (PerkinElmer Inc., USA). The results established that obese subjects were characterized by 47% and 30% lower serum Cr and V levels compared with controls, respectively, whereas serum Se levels exceeded control values by 9%. In contrast, hair Cr, Se, and V content in obese subjects exceeded the control values by 51%, 21%, and 50%, respectively. In turn, hair Zn levels were found to be significantly lower by 11% compared with the lean control values. In urine, the levels of V and Zn were found to be 30% and 18% higher in obese patients. Prevalence of hypertension in obese subjects was associated with a trend for impaired Se and Zn levels. In a regression model adjusted for age, gender, hypertension, atherosclerosis, and glucose intolerance, serum Cr, V, and hair Zn were inversely associated with body mass index (BMI), whereas hair Se was considered as the positive predictor. Our data allow proposing that the observed alterations may at least partially contribute to metabolic disturbances in obesity. In turn, monitoring of Se exposure in a well-nourished adult population is required to reduce its potential contribution to obesity.

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.

Bis(ethylmaltolato)oxidovanadium (IV) mitigates neuronal apoptosis resulted from amyloid-beta induced endoplasmic reticulum stress through activating peroxisome proliferator-activated receptor γ

Neuronal apoptosis caused by amyloid-beta (Aβ) overproduction is one of the most important pathological features in Alzheimer's disease (AD). Endoplasmic reticulum (ER) stress induced by Aβ overload plays a critical role in this process. Bis(ethylmaltolato)oxidovanadium (IV) (BEOV), a vanadium compound which had been regarded as peroxisome proliferator-activated receptor γ (PPARγ) agonist, was reported to exert an antagonistic effect on ER stress. In this study, we tested whether BEOV could ameliorate the Aβ-induced neuronal apoptosis by inhibiting ER stress. It was observed that BEOV treatment ameliorated both tunicamycin-induced and/or Aβ-induced ER stress and neurotoxicity in a dose-dependent manner through downgrading ER stress-associated and apoptosis-associated proteins in primary hippocampal neurons. Consistent with in vitro results, BEOV also reduced ER stress and inhibited neuronal apoptosis in hippocampi and cortexes of transgenic AD model mice. Moreover, by adopting GW9662 and salubrinal, the inhibitor of PPARγ and hyperphosphorylated eukaryotic translation initiation factor 2α, respectively, we further confirmed that BEOV alleviated Aβ-induced ER stress and neuronal apoptosis in primary hippocampal neurons by activating PPARγ. Taken together, these results provided scientific evidences to support the concept that BEOV ameliorates Aβ-induced ER stress and neuronal apoptosis through activating PPARγ.

The Protective Effect of Vanadium on Cognitive Impairment and the Neuropathology of Alzheimer's Disease in APPSwe/PS1dE9 Mice

Alzheimer's disease (AD) is a widely distributed neurodegenerative disease characterized clinically by cognitive deficits and pathologically by formation of amyloid-β (Aβ) plaque and neurofibrillary tangles (NFTs) in the brain. Vanadium is a biological trace element that has a function to mimic insulin for diabetes. Bis(ethylmaltolato) oxidovanadium (IV) (BEOV) has been reported to have a hypoglycemic property, but its effect on AD remains unclear. In this study, BEOV was supplemented at doses of 0.2 and 1.0 mmol/L to the AD model mice APPSwe/PS1dE9 for 3 months. The results showed that BEOV substantially ameliorated glucose metabolic disorder as well as synaptic and behavioral deficits of the AD mice. Further investigation revealed that BEOV significantly reduced Aβ generation by increasing the expression of peroxisome proliferator-activated receptor gamma and insulin-degrading enzyme and by decreasing β-secretase 1 in the hippocampus and cortex of AD mice. BEOV also reduced tau hyperphosphorylation by inhibiting protein tyrosine phosphatase-1B and regulating the pathway of insulin receptor/insulin receptor substrate-1/protein kinase B/glycogen synthase kinase 3 beta. Furthermore, BEOV could enhance autophagolysosomal fusion and restore autophagic flux to increase the clearance of Aβ deposits and phosphorylated tau in the brains of AD mice. Collectively, the present study provides solid data for revealing the function and mechanism of BEOV on AD pathology.

Bis(ethylmaltolato)oxidovanadium(iv) inhibited the pathogenesis of Alzheimer's disease in triple transgenic model mice

Vanadium compounds have been reported to mimic the anti-diabetes effects of insulin on rodent models, but their effects on Alzheimer's disease (AD) have rarely been explored. In this paper, 9-month-old triple transgenic AD model mice (3×Tg-AD) received bis(ethylmaltolato)oxidovanadium(iv) (BEOV) at doses of 0.2 mmol L^-1 (68.4 μg mL^-1) and 1.0 mmol L^-1 (342 μg mL^-1) for 3 months. BEOV at both doses was found to improve contextual memory and spatial learning in AD mice. It also improved glucose metabolism and protected neuronal synapses in the AD brain, as evidenced respectively by ¹⁸F-labeled fluoro-deoxyglucose positron emission tomography (¹⁸F-FDG-PET) scanning and by transmission electron microscopy. Inhibitory effects of BEOV on β-amyloid (Aβ) plaques and neuronal impairment in the cortex and hippocampus of fluorescent AD mice were visualized three-dimensionally by applying optical clearing technology to brain slices before confocal laser scanning microscopy. Western blot analysis semi-quantitatively revealed the altered levels of Aβ₄₂ in the brains of wildtype, AD, and AD treated with 0.2 and 1.0 mmol L^-1 BEOV mice (70.3%, 100%, 83.2% and 56.8% in the hippocampus; 82.4%, 100%, 66.9% and 42% in the cortex, respectively). The mechanism study showed that BEOV increased the expression of peroxisome proliferator-activated receptor γ (PPARγ) (140%, 100%, 142% and 160% in the hippocampus; 167%, 100%, 124% and 133% in the cortex) to inactivate the JAK2/STAT3/SOCS-1 pathway and to block the amyloidogenesis cascade, thus attenuating Aβ-induced insulin resistance in AD models. BEOV also reduced protein tyrosine phosphatase 1B (PTP1B) expression (74.8%, 100%, 76.5% and 53.8% in the hippocampus; 71.8%, 100%, 94.2% and 81.8% in cortex) to promote insulin sensitivity and to stimulate the PI3K/Akt/GSK3β pathway, subsequently reducing tau hyperphosphorylation (phosphorylated tau396 levels were 51.1%, 100%, 56.1% and 50.2% in the hippocampus; 22.2%, 100%, 36.1%, and 24% in the cortex). Our results suggested that BEOV reduced the pathological hallmarks of AD by targeting the pathways of PPARγ and PTP1B in 3×Tg AD mice.

Effect of Epigallo-Catechin-3-Gallate on Lipid Metabolism Related Gene Expression and Yolk Fatty Acid Profiles of Laying Hens Exposed to Vanadium

As the understanding of the pathways involved in such effect are quite limited, we investigated the gene pathways that modulate lipid metabolism in layers and the fatty acid profiles of the yolk of layers that were challenged with dietary vanadium (V) and supplemented with epigallo-catechin-3-gallate (EGCG). For this purpose, a total of 120 hens were divided into four groups which were fed the following experimental diets for a period of 8 weeks: control (basal diet), V10 (control + 10 mg/kg V), EGCG130 (V10 + 130 mg/kg EGCG), and EGCG217 (V10 + 217 mg/kg EGCG). Blood total cholesterol, triglyceride, glucose, and very low-density lipoprotein-cholesterol concentration were lower in V10, EGCG130, and EGCG217 groups compared to the control group, while total cholesterol and triglyceride content in blood were lower in the EGCG217 group than in V10 group (P < 0.05). Hens consumed V10 diet had the highest triglyceride content in liver among treatments, whereas EGCG130 and EGCG217 groups had lower values when compared to those observed in the control group (P < 0.01). Dietary inclusion of V increased yolk polyunsaturated fatty acid (PUFA) and total unsaturated fatty acid (UFA) content compared to the control group (P < 0.05), whereas the addition of either 130 or 217 mg/kg EGCG in V containing diet resulted in similar yolk PUFA and UFA contents with those observed in the control group. Treatment with V alone upregulated the expression of hepatic fatty acid synthase (FAS) and sterol-regulator element-binding protein 1 (SREBP1), while EGCG downregulated FAS and SREBP1 expressions in contrast to V10 treatments (P < 0.01). Liver gene expression peroxisome proliferator-activated receptor gamma (PPARγ) was lower in the V10 than in the control group while EGCG inclusion groups upregulated their expression (P < 0.05). In conclusion, the data gathered in this study indicate that dietary V and EGCG alter the layers' lipid metabolism and fat deposition pattern in egg yolk, which might be associated with their modulatory effect on lipogenesis-related gene (FAS, SREBP1, and PPARγ) expression.

Vanadyl acetylacetonate attenuates Aβ pathogenesis in APP/PS1 transgenic mice depending on the intervention stage

VAC treatment caused different Grp75 responses before and after Aβ plaque formation.

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.

Anti-diabetic vanadyl complexes reduced Alzheimer's disease pathology independent of amyloid plaque deposition

Association of Alzheimer's disease (AD) with cerebral glucose hypometabolism, likely due to impairments of insulin signaling, has been reported recently, with encouraging results when additional insulin is provided to AD patients. Here, we tested the potential effects of the anti-diabetic vanadium, vanadyl (IV) acetylacetonate (VAC), on AD in vitro and in vivo models. The experimental results showed that VAC at sub-micromolar concentrations improved the viability of neural cells with or without increased β-amyloid (Aβ) burden; and in APP/PS1 transgenic mice, VAC treatment (0.1 mmol kg^-1 d^-1) preserved cognitive function and attenuated neuron loss, but did not reduce brain Aβ plaques. Further studies revealed that VAC attenuated Aβ pathogenesis by (i) activation of the PPARγ-AMPK signal transduction pathway, leading to improved glucose and energy metabolism; (ii) up-regulation of the expression of glucose-regulated protein 75 (Grp75), thus suppressing p53-mediated neuronal apoptosis under Aβ-related stresses; and (iii) decreasing toxic soluble Aβ peptides. Overall, our work suggested that vanadyl complexes may have great potential for effective therapeutic treatment of AD.

Vanadyl complexes discriminate between neuroblastoma cells and primary neurons by inducing cell-specific apoptotic pathways

Vanadium compounds have arisen as potential therapeutic agent for the treatment of cancers over the past decades. A few studies suggested that vanadyl complexes may discriminate between the cancerous and the normal cells. Here, we reported the investigation on the pro-apoptotic effect and the underlying mechanism of bis(acetylacetonato) oxovanadium(IV) ([VO(acac)₂]) on SH-SY5Y neuroblastoma cells in comparison with that of mouse primary cortex neurons. The experimental results revealed that [VO(acac)₂] showed about 10-fold higher cytotoxicity (IC50 ~16 μM) on the neuroblastoma cells than on normal neurons (IC50 ~250 μM). Further analysis indicated that the vanadyl complex suppressed the growth of neuroblastoma cells via different pathways depending on its concentration. It induced a special cyclin D-mediated and p53-independent cell apoptosis at <50 μM but cell cycle arrests at >50 μM. In contrast, [VO(acac)₂] promoted cell viability of primary neurons in the concentration range of 0-150 μM; while [VO(acac)₂] at hundreds of μM would cause neuronal death possibly via the reactive oxygen species (ROS)-mediated signal pathways. The extraordinary discrimination between neuroblastoma cells and primary neurons suggests potential application of vanadyl complexes for therapeutic treatment of neuroblastoma. In addition, the p53-independent apoptotic pathways induced by vanadyl complexes may provide new insights for future discovery of new anticancer drugs overcoming the chemo-resistance due to p53 mutation.

SHORT CHAIN FATTY ACIDS UPREGULATE ADIPOKINE PRODUCTION IN TYPE 2 DIABETES-DERIVED HUMAN ADIPOCYTES

PURPOSE

Short chain fatty acids (SCFAs) play a major regulatory role in adipocyte function and metabolism. The aim of this study was to investigate the effects of SCFAs on adiponectin and leptin expression in adipocytes, and also to determine whether the effects of SCFA treatment in visceral adipocytes obtained from healthy subjects are different relative to the effects in adipocytes from patients with type 2 diabetes.

MATERIALS AND METHODS

Human pericardiac preadipocytes and human pericardiac preadipocytes type 2 diabetes were differentiated into adipocytes for 21 days in 48-well plates. After differentiation, two kinds of mature adipocytes, human pericardiac adipocytes (HPAd) and human pericardiac adipocytes-type 2 diabetes (HPAd-T2D) were incubated with or without 1 mM of acetic acid (AA), butyrate acid (BA), and propionic acid (PA). After 48 hours of incubation, intracellular lipid accumulation was measured using oil red staining. In addition, mRNA levels of adiponectin, leptin and Peroxisome Proliferator-Activated Receptor γ (PPARγ) were determined by Real-Time PCR system.

RESULTS

In HPAd, SCFA supplementation did not inhibit lipid accumulation. By contrast, both AA (p<0.01) and PA (p<0.01) significantly inhibited lipid accumulation in HPAd-T2D. Regarding mRNA levels of adiponectin, no significant changes were found in HPAd, while all three types of SCFAs significantly increased (p<0.05) adiponectin expression in HPAd-T2D. Leptin mRNA expression levels were significantly increased by treatment with all three types of SCFAs in both HPAd (p<0.05) and HPAd-T2D (p<0.05).

CONCLUSION

SCFAs inhibited lipid droplet accumulation and increased mRNA expression of adiponectin and leptin in T2D-derived adipocytes.

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.

Dietary protein-induced hepatic IGF-1 secretion mediated by PPARγ activation

Dietary protein or amino acid (AA) is a crucial nutritional factor to regulate hepatic insulin-like growth factor-1 (IGF-1) expression and secretion. However, the underlying intracellular mechanism by which dietary protein or AA induces IGF-1 expression remains unknown. We compared the IGF-1 gene expression and plasma IGF-1 level of pigs fed with normal crude protein (CP, 20%) and low-protein levels (LP, 14%). RNA sequencing (RNA-seq) was performed to detect transcript expression in the liver in response to dietary protein. The results showed that serum concentrations and mRNA levels of IGF-1 in the liver were higher in the CP group than in the LP group. RNA-seq analysis identified a total of 1319 differentially expressed transcripts (667 upregulated and 652 downregulated), among which the terms “oxidative phosphorylation”, “ribosome”, “gap junction”, “PPAR signaling pathway”, and “focal adhesion” were enriched. In addition, the porcine primary hepatocyte and HepG2 cell models also demonstrated that the mRNA and protein levels of IGF-1 and PPARγ increased with the increasing AA concentration in the culture. The PPARγ activator troglitazone increased IGF-1 gene expression and secretion in a dose dependent manner. Furthermore, inhibition of PPARγ effectively reversed the effects of the high AA concentration on the mRNA expression of IGF-1 and IGFBP-1 in HepG2 cells. Moreover, the protein levels of IGF-1 and PPARγ, as well as the phosphorylation of mTOR, significantly increased in HepG2 cells under high AA concentrations. mTOR phosphorylation can be decreased by the mTOR antagonist, rapamycin. The immunoprecipitation results also showed that high AA concentrations significantly increased the interaction of mTOR and PPARγ. In summary, PPARγ plays an important role in the regulation of IGF-1 secretion and gene expression in response to dietary protein.

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.

Local vanadium release from a calcium sulfate carrier accelerates fracture healing

This study evaluated the efficacy of using calcium sulfate (CaSO4 ) as a carrier for intramedullary delivery of an organic vanadium salt, vanadyl acetylacetonate (VAC) after femoral fracture. VAC can act as an insulin-mimetic and can be used to accelerate fracture healing in rats. A heterogenous mixture of VAC and CaSO4 was delivered to the fracture site of BB Wistar rats, and mechanical testing, histomorphometry, micro-computed tomography (micro-CT) were performed to measure healing. At 4 weeks after fracture, maximum torque to failure, effective shear modulus, and effective shear stress were all significantly higher (p < 0.05) in rats treated with 0.25 mg/kg VAC-CaSO4 as compared to carrier control rats. Histomorphometry found a 71% increase in percent cartilage matrix (p < 0.05) and a 64% decrease in percent mineralized tissue (p < 0.05) at 2 weeks after fracture in rats treated with 0.25 mg/kg of VAC-CaSO4 . Micro-CT analyses at 4 weeks found a more organized callus structure and higher trending maximum connected z-ray. fraction for VAC-CaSO4 groups. Evaluation of radiographs and serial histological sections at 12 weeks did not show any evidence of ectopic bone formation. As compared to previous studies, CaSO4 was an effective carrier for reducing the dose of VAC required to accelerate femoral fracture healing in rats.

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

Vanadium compounds exhibit effective hypoglycemic activity in both type I and type II diabetes mellitus. However, there was one argument that the hypoglycemic action of vanadium compounds could be attributable to the suppression of feeding-one common toxic aspect of vanadium compounds. To clarify this question, we investigated in this work the effect of a vanadyl complex, BSOV (bis((5-hydroxy-4-oxo-4H-pyran-2-yl)methyl-2-hydroxy-benzoatato) oxovanadium (IV)), on diabetic obese (db/db) mice at a low dose (0.05 mmol/kg/day) when BSOV did not inhibit feeding. The experimental results showed that this dose of BSOV effectively normalized the blood glucose level in diabetic mice without affecting the body weight growth. Western blotting assays on the white adipose tissue of db/db mice further indicated that BSOV treatment significantly improved expression of peroxisome proliferator-activated receptor γ (PPARγ) and activated AMP-activated protein kinase (AMPK). In addition, vanadium treatment caused a significant suppression of phosphorylation of c-Jun N-terminal protein kinase (JNK), which plays a key role in insulin-resistance in type II diabetes. This is the first evidence that the mechanism of insulin enhancement action involves interaction of vanadium compounds with JNK. Overall, the present work indicated that vanadium compounds exhibit antidiabetic effects irrelevant to food intake suppression but by modulating the signal transductions of diabetes and other metabolic disorders.

Modulation of adiponectin as a potential therapeutic strategy

Adiponectin is produced predominantly by adipocytes and plays an important role in metabolic and cardiovascular homeostasis through its insulin-sensitizing actions and anti-inflammatory and anti-atherogenic properties. Recently, it has been observed that lower levels of adiponectin can substantially increase the risk of developing type 2 diabetes, metabolic syndrome, atherosclerosis, and cardiovascular disease in patients who are obese. Circulating adiponectin levels are inversely related to the inflammatory process, oxidative stress, and metabolic dysregulation. Intensive lifestyle modifications and pharmacologic agents, including peroxisome proliferator-activated receptor-γ or α agonists, some statins, renin-angiotensin-aldosterone system blockers, some calcium channel blockers, mineralocorticoid receptor blockers, new β-blockers, and several natural compounds can increase adiponectin levels and suppress or prevent disease initiation or progression, respectively, in cardiovascular and metabolic disorders. Therefore, it is important for investigators to have a thorough understanding of the interventions that can modulate adiponectin. Such knowledge may lead to new therapeutic approaches for diseases such as type 2 diabetes, metabolic syndrome, cardiovascular disease, and obesity. This review focuses on recent updates regarding therapeutic interventions that might modulate adiponectin.