Publications by authors named "Fátima Regina Mena Barreto Silva"

77 Publications

Synthesis of a novel glibenclamide-pioglitazone hybrid compound and its effects on glucose homeostasis in normal and insulin-resistant rats.

Bioorg Chem 2021 Sep 7;114:105157. Epub 2021 Jul 7.

Universidade Federal de Santa Catarina, Departamento de Bioquímica - Centro de Ciências Biológicas, Campus Universitário, Trindade, CEP: 88040-900 - Florianópolis, SC, Brazil. Electronic address:

A new library of hybrid compounds that combine the functional parts of glibenclamide and pioglitazone was designed and developed. Compounds were screened for their antihyperglycemic effects on the glucose tolerance curve. This approach provided a single molecule that optimizes the pharmacological activities of two drugs used for the treatment of diabetes mellitus type 2 (DM2) and that have distinct biological activities, potentially minimizing the adverse effects of the original drugs. From a total of 15 compounds, 7 were evaluated in vivo; the compound 2; 4- [2- (2-phenyl-4-oxo-1,3-thiazolidin-3-yl) ethyl] benzene-1-sulfonamide (PTEBS) was selected to study its mechanism of action on glucose and lipid homeostasis in acute and chronic animal models related to DM2. PTEBS reduced glycemia and increased serum insulin in hyperglycemic rats, and elevated in vitro insulin production from isolated pancreatic islets. This compound increased the glycogen content in hepatic and muscular tissue. Moreover, PTEBS stimulated the uptake of glucose in soleus muscle through a signaling pathway similar to that of insulin, stimulating translocation and protein synthesis of glucose transporter 4 (GLUT4). PTEBS was effective in increasing insulin sensitivity in resistance rats by stimulating increased muscle glucose uptake, among other mechanisms. In addition, this compound reduced total triglycerides in a tolerance test to lipids and reduced advanced glycation end products (AGES), without altering lactate dehydrogenase (LDH) activity. Thus, we suggest that PTEBS may have similar effects to the respective prototypes, which may improve the therapeutic efficacy of these molecules and decrease adverse effects in the long-term.
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http://dx.doi.org/10.1016/j.bioorg.2021.105157DOI Listing
September 2021

Biological activity of 2α,3β,23-trihydroxyolean-12-ene on glucose homeostasis.

Eur J Pharmacol 2021 Sep 10;907:174250. Epub 2021 Jun 10.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil. Electronic address:

We studied the effect and the mechanisms of action of 2α,3β,23-trihydroxyolean-12-ene (THO), from Croton heterodoxus Baill. (Euphorbiaceae), in glucose uptake in hyperglycemic rats. The effect of in vivo pretreatment with THO in hyperglycemic rats was analyzed. The in vitro effects of THO were observed in adipocytes and in adipose tissue. THO reduced glycemia, in part by increasing serum insulin and augmenting the disposal of glucose as glycogen in hepatocytes but did not change the serum concentration of glucagon-like peptide-1. THO increased glucose uptake in adipocytes and in adipose tissue by a mechanism dependent on phosphatidylinositol 3-kinase vesicular traffic and on the process of vesicle fusion at the plasma membrane in regions containing cholesterol, indicating the involvement of glucose transporter-4 (GLUT4). This triterpene may act solely via the activation and translocation of GLUT4 (rather than via nuclear actions, such as upregulation of GLUT4 synthesis), since THO did not alter the amount of GLUT4 mRNA or the content of GLUT4. Consistent with these data, the stimulatory effect of this triterpene on the quantity of GLUT4 in the membrane fraction was dependent upon p38 phosphorylation. In this experimental model, orally administered 10 mg/kg THO did not modulate extracellular serum lactate dehydrogenase. In conclusion, THO decreases hyperglycemia by increasing serum insulin and hepatic glycogen content. The THO mechanism of action on adipose tissue for glucose uptake is suggested to be via GLUT4 translocation stimulation mediated by a p38-dependent mechanism. THO is a potential antihyperglycemic agent that acts in a target tissue for glucose homeostasis.
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http://dx.doi.org/10.1016/j.ejphar.2021.174250DOI Listing
September 2021

Estradiol and 1α,25(OH) vitamin D share plasma membrane downstream signal transduction through calcium influx and genomic activation in immature rat testis.

Theriogenology 2021 Sep 30;172:36-46. Epub 2021 May 30.

Laboratório de Hormônios & Transdução de Sinais, Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil. Electronic address:

The aim of this study was to investigate the rapid response pathway and gene and protein expression profiles of the rat testis in response to estradiol (E) and 1α,25(OH) vitamin D (1,25-D), to understand how they mediate their effects on the first spermatogenic wave. To do this, we compared the effects of 1,25-D and E on calcium(Ca) uptake and the involvement of estrogen receptors (ESR) in their rapid responses. Additionally, we studied the downstream signal transduction effects of 1,25-D and E on cyclin A1/B1 and cellular cycle protein expression. As previously observed for 1,25-D, E also increased Ca uptake in immature rat testes via voltage-dependent Ca channels, Ca-dependent chloride channels and via the activation of protein kinase C, protein kinase A and mitogen-activated protein kinase kinase (MEK). Elevated aromatase expression by testes was observed in the presence of 1,25-D and both hormones decreased ESR mRNA expression. Furthermore, 1,25-D and E diminished cyclin A1 mRNA expression, but E did not affect cyclin B1 mRNA levels. Consistent with these findings, the immunocontent of cyclin A1 and B1 in the testes was also increased by 1,25-D and E. 1,25-D increased expressions of the p16 and p53 proteins, supporting the anti-proliferative and pro-apoptotic properties of 1,25-D while E also augmented p16. Data indicate that both hormones trigger rapid responses at the plasma membrane that may control the expression of gene and proteins related to cell cycle regulation, and thereby modulate spermatogenesis.
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http://dx.doi.org/10.1016/j.theriogenology.2021.05.030DOI Listing
September 2021

Triterpene betulin may be involved in the acute effects of pulp and paper mill effluent on testis physiology in zebrafish.

Toxicol In Vitro 2021 Jun 17;73:105147. Epub 2021 Mar 17.

Universidade Federal de Santa Catarina, Departamento de Bioquímica, Centro de Ciências Biológicas, Florianópolis, SC, Brazil. Electronic address:

Pulp and paper mill effluent can cause changes in the morphology and energy metabolism in the zebrafish (Danio rerio) testis. Betulin, a naturally occurring triterpene is commonly present in this type of effluent and is suspected of being involved in these effects. The aim of this study was to compare the effects pulp and paper mill effluent and betulin on various aspects of testicular physiology in the zebrafish. This included the in vitro effects of effluent and betulin on testicular lactate content and lactate dehydrogenase (LDH) activity. In addition, the effects of betulin on glucose uptake, glycogen, alanine aminotransferase (ALT), reactive oxygen and nitrogen species formation and oxidative damage in the testes were determined. Furthermore, we compared the effects and mechanism of action of betulin and effluent on calcium homeostasis in testes. In vitro exposure to both effluent and betulin decreased lactate and calcium influx, possibly due to the activation of the sodium‑calcium exchanger (NCX) pump. Additionally, betulin-treated testes had higher reactive oxygen species (ROS) and reduced glutathione (GSH) content, as well as increased glutathione transferase (GST) activity and a tendency towards decreased catalase (CAT) activity. Thus, this study shows that alterations in testis physiology caused by the pulp and paper mill effluent in the testis may be due in part to the actions of betulin.
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http://dx.doi.org/10.1016/j.tiv.2021.105147DOI Listing
June 2021

Cytotoxicity of glucoevatromonoside alone and in combination with chemotherapy drugs and their effects on Na,K-ATPase and ion channels on lung cancer cells.

Mol Cell Biochem 2021 Apr 18;476(4):1825-1848. Epub 2021 Jan 18.

Programa de Pós-Graduação Em Farmácia, Centro de Ciências da Saúde, Universidade Federal de Santa Catarina, Florianópolis, SC, 88040-900, Brazil.

Cardiac glycosides (CGs) are useful drugs to treat cardiac illnesses and have potent cytotoxic and anticancer effects in cultured cells and animal models. Their receptor is the Na,K ATPase, but other plasma membrane proteins might bind CGs as well. Herein, we evaluated the short- and long-lasting cytotoxic effects of the natural cardenolide glucoevatromonoside (GEV) on non-small-cell lung cancer H460 cells. We also tested GEV effects on Na,K -ATPase activity and membrane currents, alone or in combination with selected chemotherapy drugs. GEV reduced viability, migration, and invasion of H460 cells spheroids. It also induced cell cycle arrest and death and reduced the clonogenic survival and cumulative population doubling. GEV inhibited Na,K-ATPase activity on A549 and H460 cells and purified pig kidney cells membrane. However, it showed no activity on the human red blood cell plasma membrane. Additionally, GEV triggered a Cl-mediated conductance on H460 cells without affecting the transient voltage-gated sodium current. The administration of GEV in combination with the chemotherapeutic drugs paclitaxel (PAC), cisplatin (CIS), irinotecan (IRI), and etoposide (ETO) showed synergistic antiproliferative effects, especially when combined with GEV + CIS and GEV + PAC. Taken together, our results demonstrate that GEV is a potential drug for cancer therapy because it reduces lung cancer H460 cell viability, migration, and invasion. Our results also reveal a link between the Na,K-ATPase and Clion channels.
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http://dx.doi.org/10.1007/s11010-020-04040-xDOI Listing
April 2021

Pyriproxyfen induces intracellular calcium overload and alters antioxidant defenses in Danio rerio testis that may influence ongoing spermatogenesis.

Environ Pollut 2021 Feb 23;270:116055. Epub 2020 Nov 23.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil. Electronic address:

We investigated the in vitro effects of pyriproxyfen on ionic balance in the testis of the zebrafish by measuring Ca influx. In vivo pyriproxyfen treatment was carried out to study oxidative stress, and conduct morphological analysis of the testis and liver. Whole testes were incubated in vitro with/without pyriproxyfen (10, 10 or 10 M; 30 min) and Ca influx determined. To study pyriproxyfen's mechanism of action, inhibitors/activators of ionic channels or pumps/exchangers, protein kinase inhibitors or a calcium chelator were added 15 min before the addition of Ca and pyriproxyfen. We evaluated the in vivo effects of 7 day exposure to waterborne pyriproxyfen (10 M) on reactive oxygen species (ROS) formation, lipid peroxidation, and reduced glutathione content (GSH), glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT) and γ-glutamyltransferase (GGT) activity. Morphological analyses of the testis and liver were carried out after in vivo exposure of D. rerio to pyriproxyfen. Pyriproxyfen increased Ca influx by opening the voltage-dependent T-type channels (T-type VDCC), inhibiting sarco/endoplasmic reticulum Ca-ATPase (SERCA) and the NCX exchanger (forward mode) and by mobilizing calcium from stores. The involvement of potassium channels and protein kinase C (PKC) was also demonstrated in pyriproxyfen-induced intracellular calcium elevation. In vivo pyriproxyfen treatment of D. rerio increased lipid peroxidation, decreased GSH content and increased GST activity in testes, in addition to increasing the number and size of spermatogonia cysts and inducing hepatocyte basophilia and dilation of blood vessels in the liver. The toxicity of pyriproxyfen is mediated by calcium overload, increased lipid peroxidation, and a diminished antioxidant capacity in the testis, due to GSH depletion, and altered spermatogenesis. The development of high basophilia in the liver suggests that pyriproxyfen may have estrogenic activity, possibly acting as an endocrine-disruptor. These findings indicate that these alterations may contribute to pyriproxyfen toxicity and spermatogenesis disruption.
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http://dx.doi.org/10.1016/j.envpol.2020.116055DOI Listing
February 2021

Dibutyl phthalate rapidly alters calcium homeostasis in the gills of Danio rerio.

Chemosphere 2020 Nov 17;258:127408. Epub 2020 Jun 17.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, CEP: 88040-900, Florianópolis, Santa Catarina, Brazil. Electronic address:

This study investigates the impacts of exposure to an environment Ca challenge and the mechanism of action of dibutyl phthalate (DBP) on Ca influx in the gills of Danio rerio. In vitro profile of Ca influx in gills was verified through the basal time-course. Fish were exposed to low, normal and high Ca concentrations (0.02, 0.7 and 2 mM) for 12 h. So, gills were morphologically analysed and ex vivoCa influx at 30 and 60 min was determined. For the in vitro studies, gills were treated for 60 min with DBP (1 pM, 1 nM and 1 μM) with/without blockers/activators of ionic channels, Ca chelator, inhibitors of ATPases, ionic exchangers and protein kinase C to study the mechanism of DBP-induced Ca influx. Exposure to high environmental Ca augmented Ca influx when compared to fish exposed to normal and low Ca concentrations. Additionally, histopathological changes were observed in the gills of fish maintained for 12 h in low and high Ca. In vitro exposure of gills to DBP (1 pM) disturbed Ca homeostasis. DBP stimulated Ca influx in gills through the transitory receptor potential vanilloid 1 (TRPV1), and reverse-mode Na/Ca exchanger (NCX) activation, protein kinase C and K channels and sarco/endoplasmic reticulum Ca-ATPase (SERCA). These data suggest that in vivo short-term exposure of gills to low and high Ca leads to Ca influx and histopathological changes. Additionally, the DBP-induced rapid Ca influx is mediated by TRPV1, NCX activation with the involvement of PKC, K-channels and SERCA, thereby altering Ca homeostasis.
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http://dx.doi.org/10.1016/j.chemosphere.2020.127408DOI Listing
November 2020

A Brazilian pulp and paper mill effluent disrupts energy metabolism in immature rat testis and alters Sertoli cell secretion and mitochondrial activity.

Anim Reprod 2020 Jun 26;17(2):e20190116. Epub 2020 Jun 26.

Departamento de Bioquímica, Universidade Federal de Santa Catarina, Florianópolis, SC, Brasil.

Our objective was to investigate whether the pulp and paper mill industry effluent could affect the testis and Sertoli cells in a fast exposure period. For this, the present study was carried out in immature rats at 10-day-old. Testis treated with 4% effluent for 1 h presented changes in energy metabolism in terms of a decrease in lactate content and glucose uptake. Elevation in GSH content, as an antioxidant defense mechanism, was also detected. Sertoli cells treated with 4% effluent for 1 hour showed alterations in the mitochondrial metabolism that favor the decoupling of oxidative phosphorylation and the generation of oxygen reactive species and also a time and concentration-dependent delay secretion of acidic vesicles. Our results showed that pollutants present in the pulp and paper mill effluents, in a short time of exposure, are capable of inducing alterations in important metabolic functions in the testis and in Sertoli cells that are crucial for the correct progression of spermatogenesis and fertility.
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http://dx.doi.org/10.1590/1984-3143-AR2019-0116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7375872PMC
June 2020

Cellular target of isoquercetin from Passiflora ligularis Juss for glucose uptake in rat soleus muscle.

Chem Biol Interact 2020 Oct 18;330:109198. Epub 2020 Jul 18.

Universidade Federal de Santa Catarina, Departamento de Bioquímica - Centro de Ciências Biológicas, Campus Universitário, Bairro Trindade, Cx. Postal 5069, CEP: 88040-970, Florianópolis, SC, Brazil. Electronic address:

Quercetin 3-O-beta-d-glucopyranoside (isoquercetin) is one of the most frequent metabolites of the Passiflora ligularis Juss. The purpose of this study was to investigate the effect of the aqueous extract and ethanol fraction from P. ligularis Juss leaves on glycaemia and the mechanism of action of isoquercetin on glucose uptake. In the glucose tolerance test, the aqueous extract and ethanol fraction from P. ligularis Juss (125 mg/kg to 500 mg/kg o. g.) reduced glycaemia and increased the hepatic and muscular glycogen content. Phytochemical analysis evidenced the dominant presence of isoquercetin in the extract and fraction from leaves of P. ligularis Juss. Isoquercetin mediates the stimulatory effect on glucose uptake independent of insulin receptor activation but, involve PI3K, MAPK, MEK/ERK pathways and de novo protein synthesis to GLUT-4 translocation. Overall findings revealed that isoquercetin and aqueous extract and ethanol fraction of P. ligularis Juss leaves might be a promising functional food or medicine for the treatment or prevention of diabetes.
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http://dx.doi.org/10.1016/j.cbi.2020.109198DOI Listing
October 2020

Guanosine Neuroprotective Action in Hippocampal Slices Subjected to Oxygen and Glucose Deprivation Restores ATP Levels, Lactate Release and Glutamate Uptake Impairment: Involvement of Nitric Oxide.

Neurochem Res 2020 Sep 14;45(9):2217-2229. Epub 2020 Jul 14.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Trindade, Florianópolis, SC, 88040-900, Brazil.

Stroke is a major cause of disability and death worldwide. Oxygen and glucose deprivation (OGD) in brain tissue preparations can reproduce several pathological features induced by stroke providing a valuable ex vivo protocol for studying the mechanism of action of neuroprotective agents. Guanosine, an endogenous guanine nucleoside, promotes neuroprotection in vivo and in vitro models of neurotoxicity. We previously showed that guanosine protective effect was mimicked by inhibition of nitric oxide synthases (NOS) activity. This study was designed to investigate the involvement of nitric oxide (NO) in the mechanisms related to the protective role of guanosine in rat hippocampal slices subjected to OGD followed by reoxygenation (OGD/R). Guanosine (100 μM) and the pan-NOS inhibitor, L-NAME (1 mM) afforded protection to hippocampal slices subjected to OGD/R. The presence of NO donors, DETA-NO (800 μM) or SNP (5 μM) increased reactive species production, and abolished the protective effect of guanosine or L-NAME against OGD/R. Guanosine or L-NAME treatment prevented the impaired ATP production, lactate release, and glutamate uptake following OGD/R. The presence of a NO donor also abolished the beneficial effects of guanosine or L-NAME on bioenergetics and glutamate uptake. These results showed, for the first time, that guanosine may regulate cellular bioenergetics in hippocampal slices subjected to OGD/R injury by a mechanism that involves the modulation of NO levels.
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http://dx.doi.org/10.1007/s11064-020-03083-2DOI Listing
September 2020

Role of bisphenol A on calcium influx and its potential toxicity on the testis of Danio rerio.

Ecotoxicol Environ Saf 2020 Oct 18;202:110876. Epub 2020 Jun 18.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, CEP: 88040-900, Florianópolis, Santa Catarina, Brazil. Electronic address:

This study investigated the acute in vitro effect of low-concentration bisphenol A (BPA) on calcium (Ca) influx in zebrafish (Danio rerio) testis and examined whether intracellular Ca was involved in the effects of BPA on testicular toxicity. In vitro studies on Ca influx were performed in the testes after incubation with BPA for 30 min. Inhibitors were added 15 min before the addition of Ca and BPA to testes to study the mechanism of action of BPA. The involvement of intracellular calcium from stores on lactate dehydrogenase (LDH) release and on triacylglycerol (TAG) content were carried out after in vitro incubation of testes with BPA for 1 h. Furthermore, gamma-glutamyl transpeptidase (GGT) and aspartate aminotransferase (AST) activities were analyzed in the liver at 1 h after in vitro BPA incubation of D. rerio. Our data show that the acute in vitro treatment of D. rerio testes with BPA at very low concentration activates plasma membrane ionic channels, such as voltage-dependent calcium channels and calcium-dependent chloride channels, and protein kinase C (PKC), which stimulates Ca influx. In addition, BPA increased cytosolic Ca by activating inositol triphosphate receptor (IPR) and inhibiting sarco/endoplasmic reticulum calcium ATPase (SERCA) at the endoplasmic reticulum, contributing to intracellular Ca overload. The protein kinases, PKC, MEK 1/2 and PI3K, are involved in the mechanism of action of BPA, which may indicate a crosstalk between the non-genomic initiation effects mediated by PLC/PKC/IPR signaling and genomic responses of BPA mediated by the estrogen receptor (ESR). In vitro exposure to a higher concentration of BPA caused cell damage and plasma membrane injury with increased LDH release and TAG content; both effects were dependent on intracellular Ca and mediated by IPR. Furthermore, BPA potentially induced liver damage, as demonstrated by increased GGT activity. In conclusion, in vitro effect of BPA in a low concentration triggers cytosolic Ca overload and activates downstream protein kinases pointing to a crosstalk between its non-genomic and genomic effects of BPA mediated by ESR. Moreover, in vitro exposure to a higher concentration of BPA caused intracellular Ca-dependent testicular cell damage and plasma membrane injury. This acute toxicity was reinforced by increased testicular LDH release and GGT activity in the liver.
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http://dx.doi.org/10.1016/j.ecoenv.2020.110876DOI Listing
October 2020

Acute exposure to bis(2-ethylhexyl)phthalate disrupts calcium homeostasis, energy metabolism and induces oxidative stress in the testis of Danio rerio.

Biochimie 2020 Aug 15;175:23-33. Epub 2020 May 15.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, CEP: 88040-900, Florianópolis, Santa Catarina, Brazil. Electronic address:

Bis(2-ethylhexyl)phthalate (BEHP) negatively affects testicular functions in different animal species, disturbing reproductive physiology and male fertility. The present study investigated the in vitro acute effect of BEHP on the mechanism of action of ionic calcium (Ca) homeostasis and energy metabolism. In addition, the effect of BEHP on oxidative stress was studied in vitro and in vivo in the testis of Danio rerio (D. rerio). Testes were treated in vitro for 30 min with 1 μM BEHP for Ca influx measurements. Testes were also incubated with 1 μM BEHP for 1 h (in vitro) or 12 h (in vivo) for the measurements of lactate content, C-deoxy-d-glucose uptake, lactate dehydrogenase (LDH) and gamma-glutamyl transpeptidase (GGT) activity, total reactive oxygen species (ROS) production and lipid peroxidation. In addition, the effect of BEHP (1 μM) on GGT, glutamic oxaloacetic transferase (GOT) and glutamic pyruvic transferase (GPT) activity in the liver was evaluated after in vivo treatment for 12 h. BEHP disturbs the Ca balance in the testis when given acutely in vitro. BEHP stimulated Ca influx occurs through L-type voltage-dependent Ca channels (L-VDCC), transitory receptor potential vaniloid (TRPV1) channels, reverse-mode Na/Ca exchanger (NCX) activation and inhibition of sarco/endoplasmic reticulum Ca-ATPase (SERCA). BEHP affected energy metabolism in the testis by decreasing the lactate content and LDH activity. In vitro and in vivo acute effects of BEHP promoted oxidative stress by increasing ROS production, lipid peroxidation and GGT activity in the testis. Additionally, BEHP caused liver damage by increasing GPT activity.
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http://dx.doi.org/10.1016/j.biochi.2020.05.002DOI Listing
August 2020

Crosstalk in the non-classical signal transduction of testosterone and retinol in immature rat testes.

Steroids 2020 01 14;153:108522. Epub 2019 Oct 14.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, Trindade, CEP: 88040-900 Florianópolis, SC, Brazil; Núcleo de Bioeletricidade Celular (NUBIOCEL), Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, Trindade, CEP: 88040-900 Florianópolis, SC, Brazil. Electronic address:

This study aimed to investigate the effects of the interaction between testosterone and retinol on the rapid responses of cultured Sertoli cells obtained from 10-day-old immature rat testes. Non-classical actions of testosterone and retinol were investigated, and the activities of L-type voltage-dependent calcium channels (L-VDCC) and voltage-dependent potassium channels (Kv) were determined by measuring Ca influx in whole testis. Additionally, the effects of testosterone and retinol on these channels were studied in primary culture of Sertoli cells using the patch-clamp technique. Ca influx was used to observe a dose-response curve on tissues treated with retinol and/or testosterone for 2 min (10, 10 and 10 M and 10 and 10 M), and a concentration of 10 M was selected to investigate the mechanism of action of testosterone and retinol on rapid responses. Participation of the L-VDCC and Kv channels was investigated using nifedipine and tetraethylammonium chloride (TEA) inhibitors, respectively. Both, testosterone and retinol act through non-classical mechanisms, stimulating Ca influx in immature rat testes. The response to testosterone was abolished by nifedipine and TEA, whereas the effects of retinol were partially blocked by nifedipine and completely inhibited by TEA. Retinol amplified the testosterone-induced effect on Ca influx in the testes, suggesting a crosstalk between rapid responses (calcium influx) and cell repolarization via activation of Kv channels. Whole-cell electrophysiology data demonstrated that testosterone and retinol increased voltage-dependent potassium currents (Kv) in Sertoli cells; inhibition of these responses by TEA confirmed the involvement of TEA-sensitive K channels in these effects. Taken together, we demonstrate, for the first time, crosstalk between testosterone and retinol that is mediated by a non-classical mechanism involving the L-VDCC-triggered cell depolarization and activation of repolarization by Kv currents in Sertoli cells. These ionic modulations play a physiological role in Sertoli cells and male fertility via stimulation of secretory activities.
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http://dx.doi.org/10.1016/j.steroids.2019.108522DOI Listing
January 2020

Astragalin augments basal calcium influx and insulin secretion in rat pancreatic islets.

Cell Calcium 2019 06 28;80:56-62. Epub 2019 Mar 28.

Universidade Federal de Santa Catarina, Departamento de Bioquímica - Centro de Ciências Biológicas, Campus Universitário, BairroTrindade, Cx. Postal 5069, CEP: 88040-970, Florianópolis, SC, Brazil. Electronic address:

Astragalin is a flavonol glycoside with several biological activities, including antidiabetic properties. The objective of this study was to investigate the effects of astragalin on glycaemia and insulin secretion, in vivo, and on calcium influx and insulin secretion in isolated rat pancreatic islets, ex vivo. Astragalin (1 and 10 mg / kg) was administered by oral gavage to fasted Wistar rats and serum glucose and plasma insulin were measured. Isolated pancreatic islets were used to measure basal insulin secretion and calcium influx. Astragalin (10 mg/ kg) decreased glycaemia and increased insulin secretion significantly at 15-180 min, respectively, in the glucose tolerance test. In isolated pancreatic cells, astragalin (100 μM) stimulated calcium influx through a mechanism involving ATP-dependent potassium channels, L-type voltage-dependent calcium channels, the sarcoendoplasmic reticulum calcium transport ATPase (SERCA), PKC and PKA. These findings highlight the dietary coadjuvant, astragalin, as a potential insulin secretagogue that may contribute to glucose homeostasis.
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http://dx.doi.org/10.1016/j.ceca.2019.03.009DOI Listing
June 2019

New ionic targets of 3,3',5'-triiodothyronine at the plasma membrane of rat Sertoli cells.

Biochim Biophys Acta Biomembr 2019 04 9;1861(4):748-759. Epub 2019 Jan 9.

Departamento de Bioquímica - Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, Trindade, Cx. Postal 5069, CEP: 88040-970 Florianópolis, SC, Brazil; Núcleo de Bioeletricidade Celular (NUBIOCEL) - Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, Trindade, Cx. Postal 5069, CEP: 88040-970 Florianópolis, SC, Brazil. Electronic address:

The functions of Sertoli cells, which structurally and functionally support ongoing spermatogenesis, are effectively modulated by thyroid hormones, amongst other molecules. We investigated the mechanism of action of rT on calcium (Ca) uptake in Sertoli cells by means of in vitro acute incubation. In addition, we performed electrophysiological recordings of potassium efflux in order to understand the cell repolarization, coupled to the calcium uptake triggered by rT. Our results indicate that rT induces nongenomic responses, as a rapid activation of whole-cell potassium currents in response to rT occurred in <5 min in Sertoli cells. In addition, the rT metabolite, T, also exerted a rapid effect on calcium uptake in immature rat testis and in Sertoli cells. rT also modulated calcium uptake, which occurred within seconds via the action of selective ionic channels and the Na/K ATPase pump. The rapid response of rT is essentially triggered by calcium uptake and cell repolarization, which appear to mediate the secretory functions of Sertoli cells.
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http://dx.doi.org/10.1016/j.bbamem.2019.01.002DOI Listing
April 2019

Sulfonyl(thio)urea derivative induction of insulin secretion is mediated by potassium, calcium, and sodium channel signal transduction.

J Cell Physiol 2019 07 11;234(7):10138-10147. Epub 2018 Nov 11.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, Florianópolis, Brazil.

Aim: To investigate the mechanism of action of sulfonyl(thio)urea derivative (SD) on glycemia and on insulin secretion in pancreatic islets.

Methods: Wistar rats were divided into hyperglycemic control group, rats received 4 g/kg body weight glucose plus sitagliptin 10 mg/kg (p.o.); hyperglycemic plus SD 10 mg/kg (p.o.); hyperglycemic plus SD plus sitagliptin. Blood was collected before glucose overloading (zero time), and at 15, 30, 60, and 180 min after glucose, from the afore mentioned groups for glycemia and glucagon-like peptide 1 (GLP-1) measurements and intestinal disaccharidases activity. Pancreatic islets were isolated for the calcium influx and insulin secretion in in vitro studies.

Results: SD reduced glycemia and increased GLP-1 secretion, while inhibited sucrase and lactase activity. This SD (1.0 and 10.0 µM) stimulated calcium influx in a similar percentile to that of glibenclamide, and in a nonsynergic manner. In addition, the trigger effect of SD on calcium influx was through the K -ATP-dependent channels, and partially by activating voltage-dependent K channels and voltage-dependent calcium channels. Furthermore, SD-stimulated Na and Ca entry, induced by the transient receptor potential ankyrin 1 and by modulation of Na /Ca exchange. The activation of these pathways by SD culminated in in vitro insulin secretion, reinforcing the critical role of K -ATP channels in the secretagogue effect of SD.

Conclusions: SD diminish glycemia by inducing GLP-1 secretion and inhibiting disaccharidases. To our knowledge, this is the first report of an insulin secretagogue effect of SD that is mediated by potassium and calcium, as well as sodium, signal transduction.
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http://dx.doi.org/10.1002/jcp.27680DOI Listing
July 2019

Experimentally-induced maternal hypothyroidism alters enzyme activities and the sensorimotor cortex of the offspring rats.

Mol Cell Endocrinol 2018 12 18;478:62-76. Epub 2018 Jul 18.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil. Electronic address:

In this study, we used an experimental model of congenital hypothyroidism to show that deficient thyroid hormones (TH) disrupt different neurochemical, morphological and functional aspects in the cerebral cortex of 15-day-old offspring. Our results showing decreased glutamine synthetase (GS) activity and Ca overload in the cerebral cortex of hypothyroid pups suggest misregulated glutamate metabolism associated with developmentally induced TH deficiency. The C-MeAIB accumulation indicates upregulated System A activity and glutamine uptake by neurons. Energy metabolism in hypothyroid cortical slices was preserved, as demonstrated by unaltered glucose metabolism. We also found upregulated acetylcholinesterase activity, depleting acetylcholine from the synaptic cleft, pointing to disrupted cholinergic system. Increased reactive oxygen species (ROS) generation, lipid peroxidation, glutathione (GSH) depletion, which were associated with glutathione peroxidase, superoxide dismutase and gamma-glutamyltransferase downregulation suggest redox imbalance. Disrupted astrocyte cytoskeleton was evidenced by downregulated and hyperphosphorylated glial fibrillary acidic protein (GFAP). Morphological and structural characterization of the sensorimotor cerebral cortex (SCC) showed unaltered thickness of the SCC. However, decreased size of neurons on the layers II & III and IV in the right SCC and increased NeuN positive neurons in specific SCC layers, suggest that they are differently affected by the low TH levels during neurodevelopment. Hypothyroid pups presented increased number of foot-faults in the gridwalk test indicating affected motor functions. Taken together, our results show that congenital hypothyroidism disrupts glutamatergic and cholinergic neurotransmission, Ca equilibrium, redox balance, cytoskeleton integrity, morphological and functional aspects in the cerebral cortex of young rats.
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http://dx.doi.org/10.1016/j.mce.2018.07.008DOI Listing
December 2018

Fern-9(11)-ene-2α,3β-diol Action on Insulin Secretion under Hyperglycemic Conditions.

Biochemistry 2018 07 11;57(26):3894-3902. Epub 2018 Jun 11.

Departamento de Bioquímica, Centro de Ciências Biológicas , Universidade Federal de Santa Catarina , Florianópolis , SC 88040-900 , Brazil.

The objective of this study was to investigate the effect and the mechanism of action of fernenediol as an insulin secretagogue. Wistar rats were treated with 0.1, 1, and 10 mg/kg fernenediol before inducing hyperglycemia by oral glucose. The glycaemia, insulin, LDH, calcium, and hepatic glycogen were analyzed. Considering the intestine and pancreas as targets for the triterpene action, the duodenum was used to verify the influence of fernenediol on intestinal glycosidases. Additionally, pancreatic islets were used for studies of C-deoxyglucose uptake and the influx of Ca in hyperglycemic media with/without fernenediol in the presence/absence of an inhibitor/activator of K channels, glibenclamide, diazoxide, nifedipine, calcium chelator (BAPTA-AM), and H-89 and ST, the inhibitors of the PKA and PKC enzymes. Fernenediol significantly reduced glycaemia, potentiated glucose-induced insulin secretion, and stimulated liver glycogen deposition in hyperglycemic rats after an in vivo treatment without changing intestinal disaccharidases activities and showing no influence on intestinal glucose absorption. Also, it stimulated the glucose uptake and calcium influx in pancreatic islets. The involvement of voltage-dependent L-type calcium channels and ATP-dependent potassium channels and the release of calcium from intracellular stores are mandatory for the stimulatory effect of fernenediol on calcium influx. Fernenediol did not change PKA and PKC activities or modify calcium levels. This triterpene is a potent antihyperglycemic agent with a strong insulin secretagogue effect on glycogen accumulation as well. As a whole, this compound presents significant perspectives as a future new drug for the treatment of insulin resistance and/or diabetes.
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http://dx.doi.org/10.1021/acs.biochem.8b00302DOI Listing
July 2018

The potent insulin secretagogue effect of betulinic acid is mediated by potassium and chloride channels.

Arch Biochem Biophys 2018 06 25;648:20-26. Epub 2018 Apr 25.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil. Electronic address:

Betulinic acid (BA) has been described as an insulin secretagogue which may explain its potent antihyperglycemic effect; however, the exact role of BA as an insulinogenic agent is not clear. The aim of this study was to investigate the mechanism of BA on calcium influx and static insulin secretion in pancreatic islets isolated from euglycemic rats. We found that BA triggers calcium influx by a mechanism dependent on ATP-dependent potassium channels and L-type voltage-dependent calcium channels. Additionally, the voltage-dependent and calcium-dependent chloride channels are also involved in the mechanism of BA, probably due to an indirect stimulation of calcium entry and increased intracellular calcium. Additionally, the downstream activation of PKC, which is necessary for the effect of BA on calcium influx, is involved in the full stimulatory response of the triterpene. BA stimulated the static secretion of insulin in pancreatic islets, indicating that the abrupt calcium influx may be a key step in its secretagogue effect. As such, BA stimulates insulin secretion through the activation of electrophysiological mechanisms, such as the closure of potassium channels and opening of calcium and chloride channels, inducing cellular depolarization associated with metabolic-biochemical effects, in turn activating PKC and ensuring the secretion of insulin.
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http://dx.doi.org/10.1016/j.abb.2018.04.015DOI Listing
June 2018

Exposure to a Brazilian pulp mill effluent impacts the testis and liver in the zebrafish.

Comp Biochem Physiol C Toxicol Pharmacol 2018 Apr 27;206-207:41-47. Epub 2018 Feb 27.

Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada. Electronic address:

While many studies have shown that pulp mill effluents can affect ovarian physiology in fish, far fewer studies have considered the effects in males. We conducted a lab study to examine the effects of effluent from a Brazilian pulp and paper mill on hepatic and testicular morphology and various aspects of testicular physiology in the zebrafish Danio rerio. Males were exposed to lab water (control) or 4% effluent for 14 days. Effluent exposure did not affect testis size as measured by the gonadosomatic index, but contributed to morphological changes in the seminiferous tubules. The number of cysts with histopathological changes was elevated in effluent-exposed fish and the number of cysts containing spermatids was significantly reduced. The testis of effluent exposed fish had reduced levels of lactate, elevated lactate dehydrogenase activity, increased levels of reactive oxygen species and reduced levels of phosphorylated P38 mitogen-activated protein kinase (pP38 MAPK). Separate studies showed that the addition of lactate to testicular tissue incubated in vitro increased the activation of P38 MAPK. Effluent exposure also increased vacuolization, necrosis, apoptosis, hyperemia, and fat infiltration of the hepatocytes. Collectively, we provide evidence of short term effects of pulp mill effluent on testicular and hepatic physiology and biochemistry in the zebrafish.
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http://dx.doi.org/10.1016/j.cbpc.2018.02.005DOI Listing
April 2018

Acute effect of bisphenol A: Signaling pathways on calcium influx in immature rat testes.

Reprod Toxicol 2018 04 21;77:94-102. Epub 2018 Feb 21.

Laboratório de Hormônios & Transdução de Sinais, Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil. Electronic address:

We investigated the acute effect of low concentrations of BPA on calcium influx and the mechanism of action of BPA in this rapid response in the rat testis. BPA increased calcium influx at 1 pM and 1 nM at 300 s of incubation, in a similar manner to that of estradiol. At 1 pM, BPA stimulated calcium influx independently of classical estrogen receptors, consistent with a G-protein coupled receptor. This effect also involves the modulation of ionic channels, such as K, TRPV1 and Cl channels. Furthermore, BPA is able to modulate calcium from intracellular storages by inhibiting SERCA and activating IP receptor/Ca channels at the endoplasmic reticulum and activate kinase proteins, such as PKA and PKC. The rapid responses of BPA on calcium influx could, in turn, trigger a cross talk by MEK and p38 activation and also mediate genomic responses.
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http://dx.doi.org/10.1016/j.reprotox.2018.02.009DOI Listing
April 2018

Brain bioenergetics in rats with acute hyperphenylalaninemia.

Neurochem Int 2018 07 14;117:188-203. Epub 2018 Feb 14.

Laboratório de Erros Inatos do Metabolismo, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil. Electronic address:

Phenylketonuria (PKU) is a disorder of phenylalanine (Phe) metabolism caused by deficient phenylalanine hydroxylase (PAH) activity. The deficiency results in increased levels of Phe and its metabolites in fluids and tissues of patients. PKU patients present neurological signs and symptoms including hypomyelination and intellectual deficit. This study assessed brain bioenergetics at 1 h after acute Phe administration to induce hyperphenylalaninemia (HPA) in rats. Wistar rats were randomized in two groups: HPA animals received a single subcutaneous administration of Phe (5.2 μmol/g) plus p-Cl-Phe (PAH inhibitor) (0.9 μmol/g); control animals received a single injection of 0.9% NaCl. In cerebral cortex, HPA group showed lower mitochondrial mass, lower glycogen levels, as well as lower activities of complexes I-III and IV, ATP synthase and citrate synthase. Higher levels of free Pi and phospho-AMPK, and higher activities of LDH, α-ketoglutarate dehydrogenase and isocitrate dehydrogenase were also reported in cerebral cortex of HPA animals. In striatum, HPA animals had higher LDH (pyruvate to lactate) and isocitrate dehydrogenase activities, and lower activities of α-ketoglutarate dehydrogenase and complex IV, as well as lower phospho-AMPK immunocontent. In hippocampus, HPA rats had higher mRNA expression for MFN1 and higher activities of α-ketoglutarate dehydrogenase and isocitrate dehydrogenase, but decreased activities of pyruvate dehydrogenase and complexes I and IV. In conclusion, our data demonstrated impaired bioenergetics in cerebral cortex, striatum and hippocampus of HPA rats.
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http://dx.doi.org/10.1016/j.neuint.2018.01.001DOI Listing
July 2018

Reverse T interacts with αvβ3 integrin receptor and restores enzyme activities in the hippocampus of hypothyroid developing rats: Insight on signaling mechanisms.

Mol Cell Endocrinol 2018 07 16;470:281-294. Epub 2017 Nov 16.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil; Programa de Pós-Graduação em Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil. Electronic address:

In the present study we provide evidence that 3,3',5'-triiodothyronine (reverse T, rT) restores neurochemical parameters induced by congenital hypothyroidism in rat hippocampus. Congenital hypothyroidism was induced by adding 0.05% propylthiouracil in the drinking water from gestation day 8 and continually up to lactation day 15. In the in vivo rT exposure, hypothyroid 12-day old pups were daily injected with rT (50 ng/kg body weight) or saline until day 14. In the ex vivo rT treatment, hippocampal slices from 15-day-old hypothyroid pups were incubated for 30 min with or without rT (1 nM). We found that ex vivo and/or in vivo exposure to rT failed in restoring the decreased C-glutamate uptake; however, restored the phosphorylation of glial fibrillary acidic protein (GFAP), Ca influx, aspartate transaminase (AST), glutamine synthetase (GS) and gamma-glutamate transferase (GGT) activities, as well as glutathione (GSH) levels in hypothyroid hippocampus. In addition, rT improved C-2-deoxy-D-glucose uptake and lactate dehydrogenase (LDH) activity. Receptor agonists/antagonists (RGD peptide and AP-5), kinase inhibitors of p38MAPK, ERK1/2, CaMKII, PKA (SB239063, PD98059, KN93 and H89, respectively), L-type voltage-dependent calcium channel blocker (nifedipine) and intracellular calcium chelator (BAPTA-AM) were used to determine the mechanisms of the nongenomic rT action on GGT activity. Using molecular docking analysis, we found rT interaction with αvβ3 integrin receptors, nongenomically activating signaling pathways (PKA, CaMKII, p38MAPK) that restored GGT activity. We provide evidence that rT is an active TH metabolite and our results represent an important contribution to elucidate the nonclassical mechanism of action of this metabolite in hypothyroidism.
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http://dx.doi.org/10.1016/j.mce.2017.11.013DOI Listing
July 2018

Editorial: Natural Compounds and Their Derivatives as a Source of Promising Drugs for Diabetes and Insulin Resistance.

Curr Drug Targets 2017 ;18(6):618

Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Bioquímica, Cx. Postal 5069 - CEP: 88040-970, Bairro Trindade, Florianópolis, Brazil.

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http://dx.doi.org/10.2174/138945011806170330194537DOI Listing
February 2019

Interactions between oestrogen and 1α,25(OH)-vitamin D signalling and their roles in spermatogenesis and spermatozoa functions.

Basic Clin Androl 2017 8;27:10. Epub 2017 May 8.

INRA, OeReCa, Normandie University, UNICAEN, 14000 Caen, France.

Oestrogens and 1α,25(OH)-vitamin D (1,25-D) are steroids that can provide effects by binding to their receptors localised in the cytoplasm and in the nucleus or the plasma membrane respectively inducing genomic and non-genomic effects. As confirmed notably by invalidation of the genes, coding for their receptors as tested with mice with in vivo and in vitro treatments, oestrogens and 1,25-D are regulators of spermatogenesis Moreover, some functions of ejaculated spermatozoa as viability, DNA integrity, motility, capacitation, acrosome reaction and fertilizing ability are targets for these hormones. The studies conducted on their mechanisms of action, even though not completely elicited, have allowed the demonstration of putative interactions between their signalling pathways that are worth examining more closely. The present review focuses on the elements regulated by oestrogens and 1,25-D in the testis and spermatozoa as well as the interactions between the signalling pathways of both hormones.
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http://dx.doi.org/10.1186/s12610-017-0053-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5421336PMC
May 2017

1,25(OH)2 vitamin D3 signalling on immature rat Sertoli cells: gamma-glutamyl transpeptidase and glucose metabolism.

J Cell Commun Signal 2017 Sep 3;11(3):233-243. Epub 2017 Feb 3.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, Bairro Trindade, Cx Postal 5069, Florianópolis, Santa Catarina, CEP: 88040-970, Brazil.

1α,25-Dihydroxyvitamin D (1,25-D) is critical for the maintenance of normal male reproduction since reduced fertility is observed in vitamin D-deficient rats. Gamma-glutamyl transpeptidase (GGT) is a membrane-bound enzyme that is localized on Sertoli cells and catalyses the transfer of the gamma-glutamyl residues to an amino acid or peptide acceptor. Sertoli cells are also responsible for providing nutrients, as lactate, to the development of germ cells. The aim of this study was to investigate the effect and the mechanism of action of 1,25-D on GGT on Sertoli cell functions from 30-day-old immature rat testis. Results demonstrated that 1,25-D stimulates GGT activity at Sertoli cells plasma membrane through a PKA-dependent mechanism of action, which was not dependent of active de novo protein synthesis. The hormone increases glucose uptake, as well as lactate production and release by Sertoli cells without altering the reactive oxygen species (ROS) generation. In addition, 1,25-D did not change reduced glutathione (GSH) amount or oxygen consumption, and diminished Sertoli cell death. These findings demonstrate that 1,25-D stimulatory effect on GGT activity, glucose uptake, LDH activity and lactate production seem to be an important contribution of Sertoli cells for germ cells nutrition and for a full and active ongoing spermatogenesis.
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http://dx.doi.org/10.1007/s12079-016-0367-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5559392PMC
September 2017

In vivo inhibition of tumor progression by 5 hydroxy-1,4-naphthoquinone (juglone) and 2-(4-hydroxyanilino)-1,4-naphthoquinone (Q7) in combination with ascorbate.

Biochem Biophys Res Commun 2016 09 24;477(4):640-646. Epub 2016 Jun 24.

Department of Biochemistry, Universidade Federal de Santa Catarina (UFSC), Florianópolis, SC, Brazil. Electronic address:

The purpose of the study was to obtain further in vivo data of antitumor effects and mechanisms triggered by juglone and Q7 in combination with ascorbate. The study was done using Ehrlich ascites tumor-bearing mice. Treatments were intraperitoneal every 24 h for 9 days. Control group was treated with excipient. Previous tests selected the doses of juglone and Q7 plus ascorbate (1 and 100 mg/kg, respectively). Samples of ascitic fluid were collected to evaluate carbonyl proteins, GSH and activity of antioxidant enzymes such as catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase. Hypoxia inducible factor HIF-1α, GLUT1, proteins driving cell cycle (p53, p16 and cyclin A) and apoptosis (poly-ADP-polymerase PARP, Bax and Bcl-xL) were assessed by western blot. Tumor cells were categorized by the phase of cell cycle using flow cytometry and type of cell death using acridine orange/ethidium bromide. A glucose uptake assessment was performed by liquid scintillation using Ehrlich tumor cells cultured with (14)C-deoxyglucose. Treatments caused increased protein carbonylation and activity of antioxidant enzymes and decreased levels of GSH, HIF-1α, GLUT1 and glucose uptake in tumor cells. They also caused increased number of tumor cells in G1, p53 and p16 activation and decreased cyclin A, but only when combined with ascorbate. Apoptosis was induced mostly when treatments were done with ascorbate, causing PARP and Bax cleavage, and increased Bax/Bcl-xL ratio. Juglone and Q7 in combination with ascorbate caused inhibition of tumor progress in vivo by triggering apoptosis and cell cycle arrest associated with oxidative stress, suppression of HIF-1 and uncoupling of glycolytic metabolism.
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http://dx.doi.org/10.1016/j.bbrc.2016.06.113DOI Listing
September 2016

Mechanism of Action of Novel Glibenclamide Derivatives on Potassium and Calcium Channels for Insulin Secretion.

Curr Drug Targets 2017 ;18(6):641-650

Departamento de Bioquimica, Centro de Ciencias Biologicas, UFSC. Campus Universitario, Bairro Trindade, Cx Postal 5069, CEP: 88040-970 - Florianopolis, Santa Catarina, Brazil.

Glibenclamide is widely used and remains a cornerstone and an effective antihyperglycemic drug. After the casual discovery of its hypoglycemic potential, this compound was introduced for diabetes treatment. However, the long-term side effects reveal that glibenclamide should be replaced by new molecules able to maintain the health of β-cells, protecting them from hyperstimulation/hyperexcitability, hyperinsulinemia, functional failure and cell death. The aim of this review was to highlight the main mechanism of action of glibenclamide and the influence of its derivatives, such as acylhydrazones, sulfonamides and sulfonylthioureas on β-cells potassium and calcium channels for insulin secretion as well as the contribution of these new compounds to restore glucose homeostasis. Furthermore, the role of glibenclamide-based novel structures that promise less excitability of β-cell in a long-term treatment with effectiveness and safety for diabetes therapy was discussed.
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http://dx.doi.org/10.2174/1389450117666160615084752DOI Listing
April 2018

Bis-Pyrano Prenyl Isoflavone Improves Glucose Homeostasis by Inhibiting Dipeptidyl Peptidase-4 in Hyperglycemic Rats.

J Cell Biochem 2017 01 13;118(1):92-103. Epub 2016 Jun 13.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, Trindade, Cx. Postal 5069, CEP: 88040-970, Florianópolis, Santa Catarina, Brazil.

Isoflavones widely distributed in plants prevent diabetes. This study investigated the in vivo and in vitro effect of 3',4'-dihydroxy-6″,6″,6″',6″'-tetramethylbis(pyrano[2″,3″:5,6::2″',3″':7,8]isoflavone (bis-pyrano prenyl isoflavone) on glucose homeostasis in hyperglycemic rats. The ethyl acetate fraction from aerial parts of Polygala molluginifolia that contain isoflavones was assayed on glucose tolerance, on in vitro maltase activity and on protein glycation. The isoflavone bis-pyrano prenyl isolated from this fraction was investigated on glucose homeostasis. The in vivo action of the isoflavone exhibits an anti-hyperglycemic effect by improving glucose tolerance, augmenting the liver glycogen, inhibiting maltase activity, and stimulating glucagon-like peptide-1 (GLP-1) and insulin secretion. The in vitro isoflavone inhibits dipeptidyl peptidase-4 (DPP-4) activity since the glucose tolerance was improved in the presence of the isoflavone as much as sitagliptin, an inhibitor of DPP-4. However, the co-incubation with isoflavone and sitagliptin exhibited an additive anti-hyperglycemic action. The isoflavone increased the GLP-1 faster than the positive hyperglycemic group, which shows that the intestine is a potential target. Thus, to clarify the main site of action in which isoflavone improves glucose balance, the in vitro mechanism of action of this compound was tested in intestine using calcium influx as a trigger for the signal pathways for GLP-1 secretion. The isoflavone stimulates calcium influx in intestine and its mechanism involves voltage-dependent calcium channels, phospholipase C, protein kinase C, and stored calcium contributing for GLP-1 secretion. In conclusion, the isoflavone regulates glycaemia by acting mainly in a serum target, the DPP-4 inhibitor. Furthermore, the long-term effect of isoflavone prevents protein glycation. J. Cell. Biochem. 118: 92-103, 2017. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/jcb.25614DOI Listing
January 2017

Triterpene derivative: A potential signaling pathway for the fern-9(11)-ene-2α,3β-diol on insulin secretion in pancreatic islet.

Life Sci 2016 Jun 22;154:58-65. Epub 2016 Apr 22.

Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil. Electronic address:

Aim: Triterpenes and their derivatives influence on carbohydrate metabolism. In vivo and in vitro treatment investigated the effect of the natural triterpene fern-9(11)-ene-2α,3β-diol (1), isolated from Croton heterodoxus, and a derivative triterpene (2) on glucose homeostasis.

Main Methods: The antidiabetic effect of the crude extract from C. heterodoxus leaves, the natural triterpene (1) as well as the derivative triterpene (2) were assayed on glucose tolerance. The effect and the mechanism of action on in vivo treatment with triterpene 2 on glycaemia and insulin secretion were studied. In addition, in vitro studies investigated the mechanism of triterpene 2 on glucose uptake and calcium influx on insulin secretion in pancreatic islets.

Key Findings: The results show the extract slightly reduced the glycaemia when compared with hyperglycemic group. However, the presence of the substituent electron-withdrawing 4-nitrobenzoyl group in the A-ring of triterpene 2 powered the serum glucose lowering compared to triterpene 1. In addition, in vivo treatment with triterpene 2 significantly increased the insulin secretion induced by glucose and stimulated the glucose uptake and calcium influx in pancreatic islet. The effect of triterpene on calcium influx was completely inhibited by diazoxide, nifedipine and stearoylcarnitine treatment.

Significance: The stimulatory effect of triterpene 2 on glucose uptake, calcium influx, regulation of potassium (K(+)-ATP) and calcium (L-VDCCs) channels activity as well as the pathway of PKC highlights the mechanism of action of the compound in pancreatic islets on insulin secretion and glucose homeostasis. In addition, this compound did not induce toxicity in this experimental condition.
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http://dx.doi.org/10.1016/j.lfs.2016.04.027DOI Listing
June 2016
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