Oxidovanadium(IV) sulfate-induced glucose uptake in HepG2 cells through IR/Akt pathway and hydroxyl radicals

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.

Effects of VO2 nanoparticles on human liver HepG2 cells: Cytotoxicity, genotoxicity, and glucose and lipid metabolism disorders

The rapid development of smart materials stimulates the production of vanadium dioxide (VO₂) nanomaterials. This significantly increases the population exposure to VO₂ nanomaterials via different pathways, and thus urges us to pay more attentions to their biosafety. Liver is the primary accumulation organ of nanomaterials in vivo, but the knowledge of effects of VO₂ nanomaterials on the liver is extremely lacking. In this work, we comprehensively evaluated the effects of a commercial VO₂ nanoparticle, S-VO₂, in a liver cell line HepG2 to illuminate the potential hepatic toxicity of VO₂ nanomaterials. The results indicated that S-VO₂ was cytotoxic and genotoxic to HepG2 cells, mainly by inhibiting the cell proliferation. Apoptosis was observed at higher dose of S-VO₂, while DNA damage was detected at all tested concentrations. S-VO₂ particles were internalized by HepG2 cells and kept almost intact inside cells. Both the particle and dissolved species of S-VO₂ contributed to the observed toxicities. They induced the overproduction of ROS, and then caused the mitochondrial dysfunction, ATP synthesis interruption, and DNA damages, consequently arrested the cell cycle in G2/M phase and inhibited the proliferation of HepG2 cells. The S-VO₂ exposure also resulted in the upregulations of glucose uptake and lipid content in HepG2 cells, which were attributed to the ROS production and autophagy flux block, respectively. Our findings offer valuable insights into the liver toxicity of VO₂ nanomaterials, benefiting their safely practical applications.

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-dependent activation of glucose transport in adipocytes by catecholamines is not mediated via adrenoceptor stimulation or monoamine oxidase activity

BACKGROUND

Benzylamine and methylamine activate glucose uptake in adipocytes. For tyramine, this effect has even been extended to cardiomyocytes.

AIM

To investigate the effects of catecholamines and other amines on glucose uptake.

METHODS

A screening compared 25 biogenic amines on 2-deoxyglucose (2-DG) uptake activation in rat adipocytes. Pharmacological approaches and transgenic mouse models were then used to decipher the mode of action of several hits.

RESULTS

In rat adipocytes, insulin stimulation of 2-DG uptake was reproduced with catecholamines. 100 µmol/L or 1 mmol/L adrenaline, noradrenaline, dopamine and deoxyepinephrine, maximally activated hexose transport only when sodium orthovanadate was added at 100 µmol/L. Such activation was similar to that already reported for benzylamine, methylamine and tyramine, well-recognized substrates of semicarbazide-sensitive amine oxidase (SSAO) and monoamine oxidase (MAO). Several, but not all, tested agonists of β-adrenoreceptors (β-ARs) also activated glucose transport while α-AR agonists were inactive. Lack of blockade by α- and β-AR antagonists indicated that catecholamine-induced 2-DG uptake was not mediated by AR stimulation. Adipocytes from mice lacking β1-, β2- and β3-ARs (triple KO) also responded to millimolar doses of adrenaline or noradrenaline by activating hexose transport in the presence of 100 µmol/L vanadate. The MAO blocker pargyline, and SSAO inhibitors did not block the effects of adrenaline or noradrenaline plus vanadate, which were blunted by antioxidants.

CONCLUSION

Catecholamines exert unexpected insulin-like actions in adipocytes when combined with vanadium. For limiting insulin resistance by activating glucose consumption at least in fat stores, we propose that catecholamine derivatives combined with vanadium can generate novel complexes that may have low toxicity and promising anti-diabetic properties.

Kinetic Studies of Sodium and Metforminium Decavanadates Decomposition and In Vitro Cytotoxicity and Insulin- Like Activity

The kinetics of the decomposition of 0.5 and 1.0 mM sodium decavanadate (NaDeca) and metforminium decavanadate (MetfDeca) solutions were studied by 51V NMR in Dulbecco’s modified Eagle’s medium (DMEM) medium (pH 7.4) at 25 °C. The results showed that decomposition products are orthovanadate [H2VO4]− (V1) and metavanadate species like [H2V2O7]2− (V2), [V4O12]4− (V4) and [V5O15]5− (V5) for both compounds. The calculated half-life times of the decomposition reaction were 9 and 11 h for NaDeca and MetfDeca, respectively, at 1 mM concentration. The hydrolysis products that presented the highest rate constants were V1 and V4 for both compounds. Cytotoxic activity studies using non-tumorigenic HEK293 cell line and human liver cancer HEPG2 cells showed that decavanadates compounds exhibit selectivity action toward HEPG2 cells after 24 h. The effect of vanadium compounds (8–30 μM concentration) on the protein expression of AKT and AMPK were investigated in HEPG2 cell lines, showing that NaDeca and MetfDeca compounds exhibit a dose-dependence increase in phosphorylated AKT. Additionally, NaDeca at 30 µM concentration stimulated the glucose cell uptake moderately (62%) in 3T3-L1 adipocytes. Finally, an insulin release assay in βTC-6 cells (30 µM concentration) showed that sodium orthovanadate (MetV) and MetfDeca enhanced insulin release by 0.7 and 1-fold, respectively.

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.

Sodium Orthovanadate Changes Fatty Acid Composition and Increased Expression of Stearoyl-Coenzyme A Desaturase in THP-1 Macrophages

Vanadium compounds are promising antidiabetic agents. In addition to regulating glucose metabolism, they also alter lipid metabolism. Due to the clear association between diabetes and atherosclerosis, the purpose of the present study was to assess the effect of sodium orthovanadate on the amount of individual fatty acids and the expression of stearoyl-coenzyme A desaturase (SCD or Δ⁹-desaturase), Δ⁵-desaturase, and Δ⁶-desaturase in macrophages. THP-1 macrophages differentiated with phorbol 12-myristate 13-acetate (PMA) were incubated in vitro for 48 h with 1 μM or 10 μM sodium orthovanadate (Na₃VO₄). The estimation of fatty acid composition was performed by gas chromatography. Expressions of the genes SCD, fatty acid desaturase 1 (FADS1), and fatty acid desaturase 2 (FADS2) were tested by qRT-PCR. Sodium orthovanadate in THP-1 macrophages increased the amount of saturated fatty acids (SFA) such as palmitic acid and stearic acid, as well as monounsaturated fatty acids (MUFA)-oleic acid and palmitoleic acid. Sodium orthovanadate caused an upregulation of SCD expression. Sodium orthovanadate at the given concentrations did not affect the amount of polyunsaturated fatty acids (PUFA) such as linoleic acid, arachidonic acid, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA). In conclusion, sodium orthovanadate changed SFA and MUFA composition in THP-1 macrophages and increased expression of SCD. Sodium orthovanadate did not affect the amount of any PUFA. This was associated with a lack of influence on the expression of FADS1 and FADS2.

Comparative assessment of metal-specific adipogenic activity in zinc and vanadium-citrates through associated gene expression

Diabetes mellitus comprises a group of metabolic abnormalities due to insulin deficiency and/or resistance. Obesity contributes to diabetes, with a strong causal relationship existing between diabetes and insulin resistance, especially in patients with Diabetes mellitus II. Adipocytes emerge as key constituents of adipose tissue physiology. In their pre-mature form to mature state transformation, adipocytes fully exemplify one of the key adipogenic actions of insulin. Poised to a) gain insight into adipogenesis leading to antidiabetic factors, and b) investigate adipogenesis through careful examination of insulin contributions to interwoven mechanistic pathways, a systematic comparative study was launched involving well-defined metal-citrates (zinc and vanadium), the chemical reactivity of which was in line with their chemistry under physiological conditions. Selection of the specific compounds was based on their common aqueous coordination chemistry involving the physiological chelator citric acid. Cellular maturation of pre-adipocytes to their mature form was pursued in the presence-absence of insulin and employment of closely linked genetic targets, key to adipocyte maturation (Peroxisome proliferator-activated receptor gamma (PPAR-γ), Glucose transporter 1,3,4 (GLUT 1,3,4), Adiponectin (ADIPOQ), Glucokinase (GCK), and Insulin receptor (INS-R)). The results show a) distinct adipogenic biological profiles for the metalloforms involved in a dose-, time- and nature-dependent manner, and b) metal ion-specific adipogenic response-signals at the same or higher level than insulin toward all selected targets. Collectively, the foundations have been established for future exploitation of the distinct metal-specific adipogenic factors contributing to the functional maturation of adipose tissue and their use toward hyperglycemic control in Diabetes mellitus.

Vanadyl Sulfate Effects on Systemic Profiles of Metabolic Syndrome in Old Rats with Fructose-Induced Obesity

BACKGROUND

Currently, energy obtained from hypercaloric diets has been part of the obesity and type 2 diabetes mellitus (T2DM) epidemics from childhood to old age. Treatment alternatives have been sought from plants, minerals, and trace elements with metabolic effects. Vanadyl sulfate (VS) has been investigated as a hypoglycemic compound in animal and human studies showing effective insulin-mimetic properties. This characteristic encompasses several molecules that have beneficial pleiotropic effects. The aim was to determine the antiobesity, hypoglycemic, and hypolipidemic effects of VS on fructose-induced metabolic syndrome in aged rats.

MATERIAL AND METHODS

Five groups of male Wistar rats were made, each with six rats: two groups with normal diet (ND) and three with high-fructose diet (HFD). The first ND group was treated with saline solution (SS), the second with VS; treatment for HFD groups was in the first group with SS, second with VS, and third with metformin. Weight, body mass index (BMI), blood glucose, and lipidic profile were measured; water, food, fructose and energy consumption were also determined. All parameters were compared among groups.

RESULTS AND DISCUSSION

Although obese rats treated with VS presented anorexia, oligodipsia, and a marked weight loss in the first two weeks. They recovered food and water intake in the third week with a slow recovery of some weight weeks later. VS normalized blood glucose level and decreased triglyceride and insulin levels in obese rats. These results suggest that vanadyl sulfate shows antiobesity, hypoglycemic, and hypolipidemic properties in old obese rats and could be useful as an alternative, additional, and potent preventive treatment for obesity and T2DM control in elderly obese and poorly controlled diabetic patients.

CONCLUSION

VS could play an important role in the treatment of metabolic syndrome, contributing to a decrease in obesity and T2DM, through different ways, such as euglycemia, satiety, weight loss, and lipid profile optimization, among others. However, more research is needed to confirm this suggestion.

Mechanism of insulin-like effect of chromium(III) ions on glucose uptake in C2C12 mouse myotubes involves ROS formation

Chromium is considered a trace element which improves glucose tolerance, but mechanism accounting for this insulin-like action is not recognized. The main purpose of this study was to examine the role of reactive oxygen species (ROS) in chromium and insulin stimulated glucose transport using antioxidants. Effect of chromium ions on phosphatases, enzymes involved in inhibition of insulin signaling was also investigated. Experiments were performed in vitro on C2C12 mouse myotubes. ROS level was measured with the use of confocal microscope and 2',7' dichlorodihydrofluorescein diacetate (DCFH-DA). Glucose metabolism was assayed by the measurement of 2-[³H]-deoxyglucose uptake. Cr³⁺ ions and insulin treatment caused significant increase of ROS formation and also stimulated glucose uptake in C2C12 cells in concentration dependent manner. Antioxidants (L-ascorbic acid and N-acetyl cysteine 100μM) and DPI (diphenyleneiodonium-NADPH oxidase inhibitor, 10μM) abolished insulin- and Cr-inducted glucose transport. Our results confirm the hypothesis that the ROS are integral part of insulin signaling pathway and that the insulin mimetic effect of Cr³⁺ ions depends on the antioxidant status of the cells. Surprisingly, chromium treatment resulted in increased activity of membrane phosphatases.