Ultrastructural Analysis of In Vivo Hypoglycemiant Effect of Two Polyoxometalates in Rats with Streptozotocin-Induced Diabetes

Polyoxidovanadates a new therapeutic alternative for neurodegenerative and aging diseases

Aging is a natural phenomenon characterized by a progressive decline in physiological integrity, leading to a deterioration of cognitive function and increasing the risk of suffering from chronic-degenerative diseases, including cardiovascular diseases, osteoporosis, cancer, diabetes, and neurodegeneration. Aging is considered the major risk factor for Parkinson's and Alzheimer's disease develops. Likewise, diabetes and insulin resistance constitute additional risk factors for developing neurodegenerative disorders. Currently, no treatment can effectively reverse these neurodegenerative pathologies. However, some antidiabetic drugs have opened the possibility of being used against neurodegenerative processes. In the previous framework, Vanadium species have demonstrated a notable antidiabetic effect. Our research group evaluated polyoxidovanadates such as decavanadate and metforminium-decavanadate with preventive and corrective activity on neurodegeneration in brain-specific areas from rats with metabolic syndrome. The results suggest that these polyoxidovanadates induce neuronal and cognitive restoration mechanisms. This review aims to describe the therapeutic potential of polyoxidovanadates as insulin-enhancer agents in the brain, constituting a therapeutic alternative for aging and neurodegenerative diseases.

The Effects of Chromium and Vanadium on Biomarkers of Carbohydrate and Lipid Metabolism in Workers Exposed to Coal Fly Ash

Chromium (Cr) and vanadium (V) are micronutrients playing a role in carbohydrate and lipid metabolism but can be toxic at high concentrations, especially in specific forms. The study documents the effect of Cr and V concentrations on glucose and lipid metabolism in workers exposed to coal fly ash. We quantified selected metals (Cr, V) in the blood and serum of workers from a thermal power plant in Kosovo and compared them with the reference biological values. We determined fasting serum glucose and lipid profiles using a biochemical analyzer Synchron CX7 (Beckman Coulter). We quantified blood and serum Cr and V by inductively coupled plasma mass spectrometry. We also evaluated the association between carbohydrate and lipid metabolism biomarkers (glucose, cholesterol, and triglycerides) and co-exposure to coal fly ash. Power plant workers had significantly higher blood Cr and V levels (p < 0.0001) and significantly lower serum Cr and V levels (p < 0.0001) than the controls. We also found statistically significant (p < 0.0001) correlations between high blood Cr levels and low glucose/blood Cr ratios as well as between high serum Cr levels and low glucose/serum Cr ratios. Finally, in power plant workers, high blood V levels significantly correlated with low triglycerides/blood V and cholesterol/blood V ratios (p < 0.0001), while high serum V levels correlated with low cholesterol/serum V ratios (p = 0.005). Based on these findings, we concluded that the glucose/Cr, triglycerides/V and cholesterol/V ratios should be considered when evaluating carbohydrate and lipid metabolism disorders in occupationally-exposed workers.

In Vitro Antibacterial Susceptibility of Different Pathogens to Thirty Nano-Polyoxometalates

Due to their unique properties, nano-polyoxometalates (POMs) can be alternative chemotherapeutic agents instrumental in designing new antibiotics. In this research, we synthesized and characterized “smart” nanocompounds and validated their antibacterial effects in order to formulate and implement potential new drugs. We characterized thirty POMs in terms of antibacterial activity–structure relationship. The antibacterial effects of these compounds are directly dependent upon their structure and the type of bacterial strain tested. We identified three POMs that presented sound antibacterial activity against S. aureus, B. cereus, E. coli, S. enteritidis and P. aeruginosa strains. A newly synthesized compound K₆[(VO)SiMo₂W₉O₃₉]·11H₂O (POM 7) presented antibacterial activity only against S. aureus (ATCC 6538P). Twelve POMs exerted antibacterial effects against both Gram-positive and Gram-negative strains. Only one POM (a cluster derivatized with organometallic fragments) exhibited a stronger effect compared to amoxicillin. New studies in terms of selectivity and specificity are required to clarify these extremely important aspects needed to be considered in drug design.

Polyoxometalates in Biomedicine: Update and Overview

BACKGROUND

Polyoxometalates (POMs) are negatively charged metal-oxo clusters of early transition metal ions in high oxidation states (e.g., WVI, MoVI, VV). POMs are of interest in the fields of catalysis, electronics, magnetic materials and nanotechnology. Moreover, POMs were shown to exhibit biological activities in vitro and in vivo, such as antitumor, antimicrobial, and antidiabetic.

METHODS

The literature search for this peer-reviewed article was performed using PubMed and Scopus databases with the help of appropriate keywords.

RESULTS

This review gives a comprehensive overview of recent studies regarding biological activities of polyoxometalates, and their biomedical applications as promising anti-viral, anti-bacterial, anti-tumor, and anti-diabetic agents. Additionally, their putative mechanisms of action and molecular targets are particularly considered.

CONCLUSION

Although a wide range of biological activities of Polyoxometalates (POMs) has been reported, they are to the best of our knowledge not close to a clinical trial or a final application in the treatment of diabetes or infectious and malignant diseases. Accordingly, further studies should be directed towards determining the mechanism of POM biological actions, which would enable fine-tuning at the molecular level, and consequently efficient action towards biological targets and as low toxicity as possible. Furthermore, biomedical studies should be performed on solutionstable POMs employing physiological conditions and concentrations.

In vivo toxicity evaluation of two polyoxotungstates with potential antidiabetic activity using Wistar rats as a model system

Study of the in vivo hypoglycemic effect, hepatotoxicity and nephrotoxicity of a donut-shaped polyanion salt (NH₄)₁₄[Na@P₅W₃₀O₁₁₀]·31H₂O {NaP5W30} and its Ag-containing derivative K₁₄[Ag@P₅W₃₀O₁₁₀]·22H₂O·6KCl {AgP5W30}.

Vanadium in Biological Action: Chemical, Pharmacological Aspects, and Metabolic Implications in Diabetes Mellitus

Vanadium compounds have been primarily investigated as potential therapeutic agents for the treatment of various major health issues, including cancer, atherosclerosis, and diabetes. The translation of vanadium-based compounds into clinical trials and ultimately into disease treatments remains hampered by the absence of a basic pharmacological and metabolic comprehension of such compounds. In this review, we examine the development of vanadium-containing compounds in biological systems regarding the role of the physiological environment, dosage, intracellular interactions, metabolic transformations, modulation of signaling pathways, toxicology, and transport and tissue distribution as well as therapeutic implications. From our point of view, the toxicological and pharmacological aspects in animal models and humans are not understood completely, and thus, we introduced them in a physiological environment and dosage context. Different transport proteins in blood plasma and mechanistic transport determinants are discussed. Furthermore, an overview of different vanadium species and the role of physiological factors (i.e., pH, redox conditions, concentration, and so on) are considered. Mechanistic specifications about different signaling pathways are discussed, particularly the phosphatases and kinases that are modulated dynamically by vanadium compounds because until now, the focus only has been on protein tyrosine phosphatase 1B as a vanadium target. Particular emphasis is laid on the therapeutic ability of vanadium-based compounds and their role for the treatment of diabetes mellitus, specifically on that of vanadate- and polioxovanadate-containing compounds. We aim at shedding light on the prevailing gaps between primary scientific data and information from animal models and human studies.

Treatment With Naringenin Elevates the Activity of Transcription Factor Nrf2 to Protect Pancreatic β-Cells From Streptozotocin-Induced Diabetes in vitro and in vivo

Chronic hyperglycemia and unusually high oxidative stress are the key contributors for diabetes in humans. Since nuclear factor E2-related factor 2 (Nrf2) controls the expression of antioxidant- and detoxification genes, it is hypothesized that targeted activation of Nrf2 using phytochemicals is likely to protect pancreatic β-cells, from oxidative damage, thereby mitigates the complications of diabetes. Naringenin is one such activator of Nrf2. However, it is currently not known whether the protective effect of naringenin against streptozotocin (STZ) induced damage is mediated by Nrf2 activation. Hence, the potential of naringenin to activate Nrf2 and protect pancreatic β-cells from STZ-induced damage in MIN6 cells is studied. In MIN6 cells, naringenin could activate Nrf2 and its target genes GST and NQO1, thereby inhibit cellular apoptosis. In animals, administration of 50 mg/kg body weight naringenin, for 45 days, significantly decreased STZ-induced blood glucose levels, normalized the lipid profile, and augmented the levels of antioxidants in pancreatic tissues. Immunohistochemical analysis measuring the number of insulin-positive cells in pancreas showed restoration of insulin expression similar to control animals. Furthermore, naringenin promoted glycolysis while inhibiting gluconeogenesis. In conclusion, naringenin could be a good anti-diabetic agent, which works by promoting Nrf2 levels and by decreasing cellular oxidative stress.

Toxicity evaluation of two polyoxotungstates with anti-acetylcholinesterase activity

A toxicity evaluation of two Keggin-type heteropolytungstates, K₇[Ti₂PW₁₀O₄₀]·6H₂O and K₆H[SiV₃W₉O₄₀]·3H₂O, with different inhibitory potencies toward acetylcholinesterase activity (IC₅₀ values of 1.04×10^-6 and 4.80×10^-4mol/L, respectively) was performed. Wistar albino rats were orally treated with single doses (5 and 50mg/kg) of both investigated compounds. The biochemical parameters of renal (serum urea and creatinine) and liver function (direct and total bilirubin, alanine transaminase, and aspartate aminotransferase) were determined after 24h and 14days. A histopathological analysis of liver tissue was carried out 14days after the polyoxotungstate administration. Both applied doses of the investigated compounds did not induce statistically significant alterations of the renal function markers. However, the polyoxotungstate treatment caused an increase in the activities of serum alanine transaminase and aspartate aminotransferase in a time- and concentration-dependent manner, although statistically significant changes in bilirubin concentrations were not observed. Furthermore, the detected hepatotoxic effect was confirmed by histhopathological analysis that suggested some reversible liver tissue damage two weeks after the treatment, especially in the case of K₆H[SiV₃W₉O₄₀]·3H₂O. Accordingly, the toxicity of these two polyoxotungstates with anti-acetylcholinesterase effect cannot be considered as a severe one, but their potential clinical application would require a more complex toxicological study.