Evaluation of cardiac effects of angiotensin 1-7 in an animal model of hyperthyroidism.

A hipótese do presente estudo é que as ações cardioprotetoras da Angiotensina1-7 (Ang1-7) consigam atenuar os efeitos cardíacos dos hormônios tireoidianos. Ratos selvagens ou transgênicos que superexpressam Ang1-7 foram induzidos ao hipertireoidismo por injeções intraperitoneais de triiodotironina (T3) (7µg/100g/dia). Parâmetros de morfologia e função cardíaca foram avaliados, bem como os componentes do Sistema-Renina-Angiotensina no coração. Os elevados níveis de Ang1-7 nos animais transgênicos atenuaram os efeitos tróficos do T3 e o hiperdinamismo cardíaco, além de promover a melhora da função cardíaca. Os animais hipertireoideos apresentaram aumento da Angiotensina II, do receptor AT1 e da atividade da ECA2 no coração. In vitro, o tratamento com Ang1-7 (1000nM) foi capaz de impedir o aumento da área de superfície celular em cultura primária de cardiomiócitos neonatos tratados com T3 (10nM) por 24 horas. Sendo assim, estes dados demonstram, pela primeira vez na literatura, ações cardioprotetoras da Ang1-7 frente às ações cardíacas e hipertróficas do T3.The aim of this study is to verify if Angiotensin1-7 (Ang1-7) may influence the cardiovascular effects induced by thyroid hormone. Wild or Transgenic rats that constitutively overexpress Ang1-7 (TGR-L3292) received intraperitoneal injections of T3 (7µg/100g/day) for 14 days in order to develop hyperthyroidism. Cardiac morphology, function parameters and RAS components were evaluated in the heart. High levels of Ang1-7 attenuated cardiac hypertrophy and hemodynamic parameters induced by T3. Ang1-7 treatment improved the cardiac function of hyperthyroid animals. Moreover, high levels of T3 increased Angiotensin II levels, AT1 receptor and ACE2 activity in the heart. Anti-hypertrophic effects of Ang1-7 were also observed in vitro. Ang1-7 treatment (1000nM) prevented the increase in cell surface area in primary cultures of neonatal cardiomyocytes treated with T3 (10nM) for 24 hours. For the first time, cardioprotective actions of Ang1-7 were observed in the heart of hyperthyroid animals

Role of Angiotensin-(1-7) and PI3K/Akt/FOXO and PI3K/Akt/mTOR signaling pathway in thyroid hormone-induced cardiomyocytic hypertrophy.

Elevados níveis de hormônios tireoidianos (HT), como aqueles encontrados no hipertireoidismo, induzem a hipertrofia das células musculares cardíacas, a qual se confirma experimentalmente in vivo e in vitro. Resultados prévios do nosso grupo de pesquisa demonstraram que elevados níveis plasmáticos do peptídeo Angiotensina-(1-7) (Ang-(1-7)) inibem a hipertrofia cardíaca induzida pelos HT em ratos. Entretanto, os mecanismos moleculares envolvidos nessas ações da Ang-(1-7) ainda não foram totalmente elucidados e mais estudos são necessários. Neste contexto, o presente estudo teve como objetivo avaliar o possível envolvimento das vias de sinalização PI3K/Akt/mTOR e PI3K/Akt/FOXO para a deflagração desse efeito anti-hipertrófico promovido pela Ang-(1-7). Para isso, culturas primárias de cardiomiócitos obtidas a partir de ratos neonatos foram preparadas e tratadas com triiodotironina (T3) e/ou Ang-(1-7). Os resultados obtidos por diferentes técnicas experimentais mostraram significativa ação anti-hipertrófica da Ang-(1-7) frente às ações tróficas do T3 in vitro, ocorrendo mediante a ativação do receptor MAS. Em relação aos mecanismos moleculares, o tratamento com T3 ou Ang-(1-7) levou ao aumento da Akt fosforilada, indicando a ativação dessa quinase, assim como da proteína downstream mTOR. Por outro lado, embora o T3 não influencie na atividade de FOXO3, o tratamento com Ang-(1-7) resultou na ativação desta proteína, evidenciada por uma redução na sua forma inativa (p-FOXO3), bem como por seu maior acúmulo nuclear. A ativação de FOXO3 mostrou-se ser fundamental para os efeitos anti-hipertróficos da Ang-(1-7). Como consequência ao aumento de FOXO3, foi observada maior expressão das enzimas antioxidantes (superóxido dismutase e catalase) e menor concentração de espécies reativas de oxigênio (EROs) nas células tratadas com Ang-(1-7). Além disso, uma outra contribuição interessante deste estudo foi a observação de uma regulação negativa nos níveis do receptor AT1 e do peptídeo Angiotensina II (Ang II) frente ao tratamento com Ang-(1-7) nos cardiomiócitos. Em conjunto, esses resultados sugerem um novo mecanismo anti-hipertrófico da Ang-(1-7) frente às ações do T3, o que pode vir a contribuir para o estudo de futuros alvos terapêuticos.High levels of thyroid hormone (TH), such as found in hyperthyroidism, induce a hypertrophic phenotype in cardiac muscle cells, which is experimentally confirmed in vivo and in vitro conditions. Previous results from our group demonstrated that the upregulation of Angiotensin-(1-7) peptide (Ang-(1-7)) is able to prevent the TH-induced cardiac hypertrophy. However, the molecular mechanisms involved in these Ang-(1-7) effects have not been fully elucidated and further studies are needed. In this context, the present study aimed to evaluate the possible involvement of the PI3K/Akt/mTOR and PI3K/Akt/FOXO signaling pathways in the Ang-(1-7) antihypertrophic effect. Primary cultures of cardiomyocytes obtained from neonatal Wistar rats were prepared and treated with triiodothyronine (T3) and/or Ang-(1-7). The results showed a significative antihypertrophic effect of Ang-(1-7) against the trophic actions of T3 in vitro, which has been confirmed by different experimental approaches and occurs through the activation of MAS receptor. Regarding molecular mechanisms, treatment with T3 or Ang-(1-7) led to increased phosphorylated Akt (serine 473 and threonine 308) in cardiomyocytes, indicating the activation of this kinase, as well as the downstream protein mTOR. On the other hand, although T3 does not influence the FOXO3 activity, treatment with Ang-(1-7) resulted in its activation, evidenced by reduction in its inactive form (p-FOXO3), as well as by greater nuclear accumulation of this protein, which proved to be essential for the Ang-(1-7) antihypertrophic effect. In addition, as consequence of increased FOXO3, high expression of antioxidant enzymes (superoxide dismutase and catalase) and low reactive oxygen species (ROS) concentration were observed in cells treated with Ang-(1-7). Interestingly, a negative regulation of AT1 receptor and Angiotensin II (Ang II) levels were detected in cells treated with Ang-(1-7). Together, these results suggest a new antihypertrophic mechanism of Ang-(1-7) in T3-induced cardiomyocyte hypertrophy, which may contribute to the study of future therapeutic targets

Hypoglycaemic activity of Bauhinia holophylla through GSK3-β inhibition and glycogenesis activation

Context: Bauhinia L. species, including Bauhinia holophylla (Bong.) Steud. (Fabaceae), have traditionally been used to treat diabetes. Bauhinia is a complex botanical genus, and the indiscriminate use of the diverse Bauhinia species is reflected in the experimental divergence of their medicinal potential. Objective: The hypoglycaemic and hypolipidaemic effects, molecular mechanism of action and phytochemical properties of an authentic extract of B. holophylla leaves were evaluated. Materials and methods: A phytochemical study of a 70% EtOH extract was performed using FIA-ESI-IT-MS/MSn and HPLC-PAD-ESI-IT-MS. The extract (200 or 400 mg/kg b.w.) was administered for 14 days to streptozotocin-induced diabetic Swiss mice. Glucose tolerance and insulin sensitivity, blood parameters, gene and protein expression, and the in vivo and in vitro inhibition of intestinal glucosidases were assessed. Results: HPLC-PAD-ESI-IT-MS analysis identified flavonoid derivatives of quercetin, myricetin, luteolin and kaempferol. Treatment with 400 mg/kg of the extract reduced blood glucose (269.0 ± 32.4 mg/dL vs. 468.0 ± 32.2 mg/dL for diabetic animals), improved glucose tolerance, decreased cholesterol and triglyceride levels, and increased the mRNA expression of proteins involved in glucogenesis in the liver and muscle, such as PI3-K/Akt, GS, GSK3-β (ser-9), AMPK and Glut4. The activity of intestinal maltase was inhibited in vitro (IC50: 43.0 µg/mL for the extract compared to 516.4 µg/mL for acarbose) and in vivo. Discussion and conclusions: Treatment with B. holophylla was associated with a marked hypoglycaemic effect through the stimulation of glycogenesis and inhibition of gluconeogenesis and intestinal glucose absorption, without increasing basal insulinaemia