Sodium tungstate: Is it a safe option for a chronic disease setting, such as diabetes?

Anticancer Metallocenes and Metal Complexes of Transition Elements from Groups 4 to 7

With the progression in the field of bioinorganic chemistry, the role of transition metal complexes as the most widely used therapeutics is becoming a more and more attractive research area. The complexes of transition metals possess a great variety of attractive pharmacological properties, including anticancer, anti-inflammatory, antioxidant, anti-infective, etc., activities. Transition metal complexes have proven to be potential alternatives to biologically active organic compounds, especially as antitumor agents. The performance of metal coordination compounds in living systems is anticipated to differ generally from the action of non-metal-containing drugs and may offer unique diagnostic and/or therapeutic opportunities. In this review, the rapid development and application of metallocenes and metal complexes of elements from Groups 4 to 7 in cancer diagnostics and therapy have been summarized. Most of the heavy metals discussed in the current review are newly discovered metals. That is why the use of their metal-based compounds has attracted a lot of attention concerning their organometallic and coordination chemistry. All of this imposes more systematic studies on their biological activity, biocompatibility, and toxicity and presupposes further investigations.

Polyoxometalates Impact as Anticancer Agents

Polyoxometalates (POMs) are oxoanions of transition metal ions, such as V, Mo, W, Nb, and Pd, forming a variety of structures with a wide range of applications. Herein, we analyzed recent studies on the effects of polyoxometalates as anticancer agents, particularly their effects on the cell cycle. To this end, a literature search was carried out between March and June 2022, using the keywords "polyoxometalates" and "cell cycle". The effects of POMs on selected cell lines can be diverse, such as their effects in the cell cycle, protein expression, mitochondrial effects, reactive oxygen species (ROS) production, cell death and cell viability. The present study focused on cell viability and cell cycle arrest. Cell viability was analyzed by dividing the POMs into sections according to the constituent compound, namely polyoxovanadates (POVs), polyoxomolybdates (POMos), polyoxopaladates (POPds) and polyoxotungstates (POTs). When comparing and sorting the IC₅₀ values in ascending order, we obtained first POVs, then POTs, POPds and, finally, POMos. When comparing clinically approved drugs and POMs, better results of POMs in relation to drugs were observed in many cases, since the dose required to have an inhibitory concentration of 50% is 2 to 200 times less, depending on the POMs, highlighting that these compounds could become in the future an alternative to existing drugs in cancer therapy.

Sodium Tungstate (NaW) Decreases Reactive Oxygen Species (ROS) Production in Cells: New Cellular Antioxidant

Diabetic nephropathy (DN) is the leading cause of end-stage renal failure worldwide. Hyperglycemia generates reactive oxygen species (ROS), contributing to diabetic complications, especially in DN. Sodium Tungstate (NaW) is an effective antidiabetic agent for short and long-term treatments of both type 1 and type 2 diabetes models. In this study, we evaluated the effect of NaW on ROS production in bovine neutrophils incubated with platelet-activating factor (PAF) and in HK-2 cells induced by high glucose or H₂O₂. In addition, we evaluated the effect on iNOS expression in the type 1 diabetic rat model induced with streptozotocin (STZ). NaW inhibited ROS production in PAF-induced bovine neutrophils, and human tubular cells (HK-2) were incubated in high glucose or H₂O₂. In addition, NaW inhibited iNOS expression in glomeruli and tubular cells in the type 1 diabetic rat. This study demonstrates a new role for NaW as an active antioxidant and its potential use in treating DN.

Decavanadate and metformin-decavanadate effects in human melanoma cells

Decavanadate is a polyoxometalate (POMs) that has shown extensive biological activities, including antidiabetic and anticancer activity. Importantly, vanadium-based compounds as well as antidiabetic biguanide drugs, such as metformin, have shown to exert therapeutic effects in melanoma. A combination of these agents, the metformin-decavanadate complex, was also recognized for its antidiabetic effects and recently described as a better treatment than the monotherapy with metformin enabling lower dosage in rodent models of diabetes. Herein, we compare the effects of decavanadate and metformin-decavanadate on Ca²⁺-ATPase activity in sarcoplasmic reticulum vesicles from rabbit skeletal muscles and on cell signaling events and viability in human melanoma cells. We show that unlike the decavanadate-mediated non-competitive mechanism, metformin-decavanadate inhibits Ca²⁺-ATPase by a mixed-type competitive-non-competitive inhibition with an IC₅₀ value about 6 times higher (87 μM) than the previously described for decavanadate (15 μM). We also found that both decavanadate and metformin-decavanadate exert antiproliferative effects on melanoma cells at 10 times lower concentrations than monomeric vanadate. Western blot analysis revealed that both, decavanadate and metformin-decavanadate increased phosphorylation of extracellular signal-regulated kinase (ERK) and serine/threonine protein kinase AKT signaling proteins upon 24 h drug exposure, suggesting that the anti-proliferative activities of these compounds act independent of growth-factor signaling pathways.

Regulatory Effects of Functional Soluble Dietary Fiber from Saccharina japonica Byproduct on the Liver of Obese Mice with Type 2 Diabetes Mellitus

Though the relationship between dietary fiber and physical health has been investigated widely, the use of dietary fiber from marine plants has been investigated relatively rarely. The Saccharina japonica byproducts after the production of algin contain a large amount of insoluble polysaccharide, which will cause a waste of resources if ignored. Soluble dietary fiber (SDF)prepared from waste byproducts of Saccharina japonica by alkaline hydrolysis method for the first time had a wrinkled microscopic surface and low crystallinity, which not only significantly reduced liver index, serum levels of aspartate aminotransferase (AST) and alanine amiotransferase (ALT), and liver fat accumulation damage to the livers of obese diabetic mice, but also activated the PI3K/AKT signaling pathway to increase liver glycogen synthesis and glycolysis. By LC-MS/MS employing a Nexera UPLC tandem QE high-resolution mass spectrometer, the 6 potential biomarker metabolites were screened, namely glycerophosphocholine (GPC), phosphocholine (PCho), pantothenic acid, glutathione (GSH), oxidized glutathione (GSSG), and betaine; several pathways of these metabolites were associated with lipid metabolism, glycogen metabolism, and amino acid metabolism in the liver were observed. This study further provided a detailed insight into the mechanisms of SDF from Saccharina japonica byproducts in regulating the livers of obese mice with type 2 diabetes and laid a reliable foundation for the further development and utilization of Saccharina japonica.

Multipollutant, longitudinal analysis of the association between urinary tungsten and incident diabetes in a rural population

BACKGROUND

Cross-sectional studies suggest tungsten (W) exposure may be associated with diabetes. We assessed longitudinal associations between urinary W and fasting glucose, 2-hour glucose, insulin resistance (HOMA-IR), β-cell function (HOMA-β), and incident type 2 diabetes.

METHODS

We used data from 1,609 Hispanic and non-Hispanic White adults with 20 to 74 years of age residing in rural Colorado and participating in the San Luis Valley Diabetes Study. Urinary metal exposure values were measured at baseline and natural log-transformed. We assessed longitudinal associations between urinary W and continuous outcome measures using linear-mixed effect models and associations with incident diabetes using Fine and Gray competing risks regression models (competing event = all-cause mortality). The main adjustment set of covariates included: age, sex, ethnicity, education, smoking status, hypertension, body mass index, caloric intake, alcohol intake, and urinary creatinine levels. Secondary models were further adjusted for arsenic, cadmium, and lead exposures. We assessed whether sex or ethnicity were effect modifiers.

RESULTS

At baseline, the median W concentration was 0.22 μg/L (interquartile range = 0.20, 0.59). In the main cross-sectional analyses, lnW levels were significantly associated with 3% higher lnHOMA-IR (95% CI = 1 to 5). In the main longitudinal models, lnW was significantly associated with 1% higher natural log-transformed fasting glucose (95% CI = <1 to 1), 3% higher natural log-transformed HOMA-IR (95% CI = 2 to 5), and 28% higher incident diabetes (subdistribution hazard ratio=1.28, 95% CI = 1.09 to 1.50). Results remained significant when further adjusting for other metals. We observed evidence for effect modification by sex and ethnicity.

CONCLUSION

Urinary W was longitudinally associated with adverse metabolic health indicators.

Gluconeogenic Enzymes in β-Cells: Pharmacological Targets for Improving Insulin Secretion

Pancreatic β-cells express the gluconeogenic enzymes glucose 6-phosphatase (G6Pase), fructose 1,6-bisphosphatase (FBP), and phosphoenolpyruvate (PEP) carboxykinase (PCK), which modulate glucose-stimulated insulin secretion (GSIS) through their ability to reverse otherwise irreversible glycolytic steps. Here, we review current knowledge about the expression and regulation of these enzymes in the context of manipulating them to improve insulin secretion in diabetics. Because the regulation of gluconeogenic enzymes in β-cells is so poorly understood, we propose novel research avenues to study these enzymes as modulators of insulin secretion and β-cell dysfunction, with especial attention to FBP, which constitutes an attractive target with an inhibitor under clinical evaluation at present.