inorganics Article Kinetic Studies of Sodium and Metforminium Decavanadates Decomposition and In Vitro Cytotoxicity and Insulin- Like Activity Aniela M. Silva-Nolasco 1,2, Luz Camacho 2 , Rafael Omar Saavedra-Díaz 1, Oswaldo Hernández-Abreu 1 , Ignacio E. León 3 and Irma Sánchez-Lombardo 1,* 1 Centro de Investigación de Ciencia y Tecnología Aplicada de Tabasco, División Académica de Ciencias Básicas (CICTAT), Universidad Juárez Autónoma de Tabasco, Carretera Cunduacán-Jalpa km. 1 Col. La Esmeralda, Cunduacán 86690, Tabasco, Mexico; [email protected] (A.M.S.-N.); [email protected] (R.O.S.-D.); [email protected] (O.H.-A.) 2 Laboratorio de Nutrición Experimental, Instituto Nacional de Pediatría, Ciudad de Mexico 04530, Mexico; [email protected] 3 Centro de Química Inorgánica CEQUINOR (CONICET, UNLP), Bv 120 1465, La Plata 1900, Argentina; [email protected] * Correspondence: [email protected] Received: 22 October 2020; Accepted: 2 December 2020; Published: 8 December 2020 Abstract: 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 2 4 are orthovanadate [H2VO4]− (V1) and metavanadate species like [H2V2O7] − (V2), [V4O12] − (V4) 5 and [V5O15] − (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. Keywords: polyoxometalates; decavanadate; cytotoxicity; insulin-like activity; diabetes therapy; vanadium biochemistry; vanadium speciation 1. Introduction Polyoxometalates (POMs) have several applications in biology and medicine. Interactions between the highly charged POM molecules and biological molecules frequently occur through hydrogen-bonding and electrostatic interactions [1]. Moreover, POMs have shown pharmacological activities in vitro and in vivo, such as antitumor, antimicrobial, and antidiabetic [2,3]. Their roles in biological systems are non-functional or functional kind of interactions with biomolecules [4], like the tungstate cluster that helps to solve the X-ray structure of ribosome [5] or the insulin-like properties of the decavanadates [6]. Inorganics 2020, 8, 67; doi:10.3390/inorganics8120067 www.mdpi.com/journal/inorganics InorganicsInorganics2020, 208,20 67, 8, x FOR PEER REVIEW 2 of 202 of 20 the tungstate cluster that helps to solve the X-ray structure of ribosome [5] or the insulin-like Inproperties recent years,of the decavanadates several organic [6] and. inorganic decavanadate compounds have been synthesized, exhibitingIn a rece wident years structural, several supramolecular organic and inorganic diversity decavanadate in one, two compound or three dimensionss have been synthesized [7–9]. However,, the interactionexhibiting a of wide decavanadates structural supramolecular with biological diversity targets in under one, physiologicaltwo or three dimensions conditions are[7–9] scarce. However, the interaction of decavanadates with biological targets under physiological conditions are reported since the decavanadate anion can be formed at vanadium concentrations up to 0.1 mM and in scarce reported since the decavanadate anion can be formed at vanadium concentrations up to 0.1 the pH range of 2–6 [10], and some organic decavanadates compounds are water-insoluble [11]. mM and in the pH range of 2–6 [10], and some organic decavanadates compounds are water-insoluble In[11] biological. studies, buffer solutions are extensively used, although just a few studies have addressedIn thebiological speciation studies of, thebuffer decomposition solutions are extensively products ofused, the although decavanadate just a few compounds studies have in such reactionaddress media.ed the The speciation decomposition of the decomposition of the decameric products species of at the neutral decavanadate pH can becompounds followed byin 51suchV NMR showingreaction a decrease media. T inhe thedecomposition peaks associated of the decameric with the threespecies magnetic at neutral independent pH can be followed vanadium by 51V nuclei of theNMR decavanadate showing a VdecreaseA,VB and in the VC peaks(Figure associated1), albeit with an increasethe three ofmagnetic the signals independent for the metavanadatevanadium nuclei of the decavanadate VA, VB and VC (Figure 1), albeit an increase of the signals for the2 peak [H2VO4]− (V1) and the appearance of the orthovanadates species signals like [H2V2O7] − (V2), metavanadate4 peak [H2VO5 4]− (V1) and the appearance of the orthovanadates species signals like [V4O12] − (V4) and [V5O15] − (V5)[12–14]. Moreover, monomeric vanadate is always present in [H2V2O7]2− (V2), [V4O12]4− (V4) and [V5O15]5− (V5) [12–14]. Moreover, monomeric vanadate is always decavanadate solutions at neutral pH [15]. The decavanadate decomposition rate is faster in acid than present in decavanadate solutions at neutral pH [15]. The decavanadate decomposition rate is faster in basic solutions [16,17]. In the latter, the reaction proceeds via base-dependent or base-independent in acid than in basic solutions [16,17]. In the latter, the reaction proceeds via base-dependent or base- paths,independent and it depends paths, on and the it depends counterions on the present counterions in the present solution in the [17 solution]. [17]. O O 6- O O VC VC O O O O O O O O V VA V O O O B O O B O O VB VA VB V V V O O - OH - O O- O O O O O O O OH OH OH VC VC O O O a) b) c) O O - O O O- O- O O O V O V O - NH+ V V O N NH2 O O O O - O + - O V NH2 NH2 O V V V O O O O O O- O O- V - O d) e) O f) 6− 6 - - FigureFigure 1. Schematic 1. Schematic structure structure ofof (a) decavanadate decavanadate anion anion [V10 [VO2810]O, 28(b]) −orthovanadate,(b) orthovanadate [H2VO4] [H(V12),VO 4] metavanadate species like (c) [H2V2O7]2− (V2), (d2) [V4O12]4− (V4), (e) [V5O4 15]5− (V5) and (f) diprotonated5 (V1), metavanadate species like (c) [H2V2O7] − (V2), (d) [V4O12] − (V4), (e) [V5O15] − (V5) and (f) diprotonatedmetformin (Metf). metformin (Metf). VanadiumVanadium speciation speciation is is complicated complicated underunder physiological conditions conditions,, many many known known forms forms of of vanadium V4+ and V5+ species have been shown to readily interconvert through redox and hydrolytic vanadium V4+ and V5+ species have been shown to readily interconvert through redox and hydrolytic reactions, and it is, therefore, difficult to determine which are the active species [18]. Additionally, in reactions, and it is, therefore, difficult to determine which are the active species [18]. Additionally, biological studies, the active vanadium species will depend on the sample preparation and handling, in biologicalthat is, whether studies, the the compounds active vanadium were dissolved species in will media depend or buffer on the before sample addition preparation to the cell and culture handling, that is,and whether for how thelong compounds the complexes were have dissolved been in solution in media before or buaddffinger beforealiquots addition to the medium to the [19] cell. culture and for howMetabolic long the diseases complexes like diabetes have been mellitus in solution type 2 before(DM2) adding and cancer aliquots are tonon the-communicable medium [19 ]. Metabolicdiseases (NCD) diseases that have like diabetesbecome one mellitus of the typemajor 2health (DM2) hazard andscancer of the aremodern non-communicable world [20]. diseasesCarcinogenesis (NCD) that occurs have when become normal one cells of thereceive major genetic health “hits” hazards, after ofwhich the a modern full neoplastic world [20]. Carcinogenesisphenotype occursof growth, when invasion, normal cellsand receivemetastasis genetic develops. “hits”, Diabetes after which may ainfluence full neoplastic this process phenotype of growth,through invasion, chronic inflammation, and metastasis endogenous develops. or Diabetesexogenous may hyperinsulinemia, influence this or process hyperglycemia through, but chronic potential biologic links between the two diseases are incompletely understood [21]. The development inflammation, endogenous or exogenous hyperinsulinemia, or hyperglycemia, but potential biologic links between the two diseases are incompletely understood [21]. The development of innovative therapeutic modalities [22] that increase the effectiveness of clinical drugs like cis-platin or metformin hydrochloride and arrest their chemoresistance or side effects is a topic trend for scientists. In this context, AMP-activated kinase (AMPK) signaling has become a promising therapeutic target in hepatocellular