RESUMO
AIM: Thyroid hormones regulate metabolic response. While triiodothyronine (T3) is usually considered to be the active form of thyroid hormone, one form of diiodothyronine (3,5-T2) exerts T3-like effects on energy consumption and lipid metabolism. 3,5-T2 also improves glucose tolerance in rats and 3,5-T2 levels correlate with fasting glucose in humans. Presently, however, little is known about mechanisms of 3,5-T2 effects on glucose metabolism. Here, we set out to compare effects of T3, 3,5-T2 and another form of T2 (3,3-T2) in a mouse model of diet-induced obesity and determined effects of T3 and 3,5-T2 on markers of classical insulin sensitization to understand how diiodothyronines influence blood glucose. METHODS: Cell- and protein-based assays of thyroid hormone action. Assays of metabolic parameters in mice. Analysis of transcript and protein levels in different tissues by qRT-PCR and Western blot. RESULTS: T3 and 3,5-T2 both reduce body weight, adiposity and body temperature despite increased food intake. 3,3'-T2 lacks these effects. T3 and 3,5-T2 reduce blood glucose levels, whereas 3,3'-T2 worsens glucose tolerance. Neither T3 nor 3,5-T2 affects markers of insulin sensitization in skeletal muscle or white adipose tissue (WAT), but both reduce hepatic GLUT2 glucose transporter levels and glucose output. T3 and 3,5-T2 also induce expression of mitochondrial uncoupling proteins (UCPs) 3 and 1 in skeletal muscle and WAT respectively. CONCLUSIONS: 3,5-T2 influences glucose metabolism in a manner that is distinct from insulin sensitization and involves reductions in hepatic glucose output and changes in energy utilization.
Assuntos
Glicemia/efeitos dos fármacos , Di-Iodotironinas/farmacologia , Resistência à Insulina , Animais , Dieta Hiperlipídica , Metabolismo Energético/efeitos dos fármacos , Células Hep G2 , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Obesidade , Tri-Iodotironina/farmacologiaRESUMO
AIM: This study aimed at evaluating whether thyroid hormone treatment could improve glycaemia and insulin response in alloxan-induced diabetic rats by altering cytokine expression in the skeletal muscle and epididymal white adipose tissue (eWAT) as well as altering inflammatory cell infiltration in eWAT. METHODS: Diabetes mellitus (DM) was induced in male Wistar rats by alloxan injection, and a subset of the diabetic rats was treated with T3 (1.5 µg per 100 g body weight) for a 28-day period (DT3 ). Cytokines were measured in serum (MILIplex assay kit) as well as in soleus and EDL skeletal muscles and eWAT by Western blotting. Thyroid function was evaluated by morphological, molecular and biochemical parameters. Cardiac function was assessed by measuring heart rate, blood pressure, maximal rate of pressure development (dp/dtmax ) and decline (dp/dtmin ) as well as the contractility index (CI). Sixty rats were used in the study. RESULTS: Diabetic rats exhibited decreased thyroid function and increased inflammatory cytokines in serum, soleus muscle and eWAT. T3 treatment decreased glycaemia and improved insulin sensitivity in diabetic animals. These alterations were accompanied by decreased TNF-alpha and IL-6 content in soleus muscle and eWAT, and inflammatory cell infiltration in eWAT. T3 treatment did not affect cardiac function of diabetic rats. CONCLUSIONS: The present data provide evidence that T3 treatment reduces glycaemia and improves insulin sensitivity in diabetic rats, and that at least part of this effect could result from its negative modulation of inflammatory cytokine expression.
Assuntos
Tecido Adiposo/imunologia , Citocinas/imunologia , Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Experimental/imunologia , Insulina/sangue , Músculo Esquelético/imunologia , Tri-Iodotironina/administração & dosagem , Tecido Adiposo/efeitos dos fármacos , Aloxano , Animais , Glicemia/metabolismo , Diabetes Mellitus Experimental/induzido quimicamente , Inflamassomos/imunologia , Mediadores da Inflamação/imunologia , Resistência à Insulina , Masculino , Músculo Esquelético/efeitos dos fármacos , Ratos Wistar , Resultado do Tratamento , Tri-Iodotironina/farmacologiaRESUMO
Erythropoietin (EPO) has been well characterized as a renal glycoprotein hormone regulating red blood cell production by inhibiting apoptosis of erythrocyte progenitors in hematopoietic tissues. EPO exerts regulatory effects in cardiac and skeletal muscles. Duchenne muscular dystrophy is a lethal degenerative disorder of skeletal and cardiac muscle. In this study, we tested the possible therapeutic beneficial effect of recombinant EPO (rhEPO) in dystrophic muscles in mdx mice. Total strength was measured using a force transducer coupled to a computer. Gene expression for myostatin, transforming growth factor-β1 (TGF-β1), and tumor necrosis factor-α (TNF-α) was determined by quantitative real time polymerase chain reaction. Myostatin expression was significantly decreased in quadriceps from mdx mice treated with rhEPO (rhEPO=0.60±0.11, control=1.07±0.11). On the other hand, rhEPO had no significant effect on the expression of TGF-β1 (rhEPO=0.95±0.14, control=1.05±0.16) and TNF-α (rhEPO=0.73±0.20, control=1.01±0.09). These results may help to clarify some of the direct actions of EPO on skeletal muscle.
Assuntos
Animais , Masculino , Regulação para Baixo/efeitos dos fármacos , Eritropoetina/uso terapêutico , Expressão Gênica/efeitos dos fármacos , Distrofia Muscular de Duchenne/tratamento farmacológico , Miostatina/metabolismo , Proteínas Recombinantes/uso terapêutico , Modelos Animais de Doenças , Distrofina/deficiência , Camundongos Endogâmicos mdx , Força Muscular/efeitos dos fármacos , Músculo Esquelético/metabolismo , Distrofia Muscular de Duchenne/metabolismo , Miostatina/genética , Fenótipo , Reação em Cadeia da Polimerase em Tempo Real , Fator de Crescimento Transformador beta1/genética , Fator de Crescimento Transformador beta1/metabolismo , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Erythropoietin (EPO) has been well characterized as a renal glycoprotein hormone regulating red blood cell production by inhibiting apoptosis of erythrocyte progenitors in hematopoietic tissues. EPO exerts regulatory effects in cardiac and skeletal muscles. Duchenne muscular dystrophy is a lethal degenerative disorder of skeletal and cardiac muscle. In this study, we tested the possible therapeutic beneficial effect of recombinant EPO (rhEPO) in dystrophic muscles in mdx mice. Total strength was measured using a force transducer coupled to a computer. Gene expression for myostatin, transforming growth factor-ß1 (TGF-ß1), and tumor necrosis factor-α (TNF-α) was determined by quantitative real time polymerase chain reaction. Myostatin expression was significantly decreased in quadriceps from mdx mice treated with rhEPO (rhEPO = 0.60 ± 0.11, control = 1.07 ± 0.11). On the other hand, rhEPO had no significant effect on the expression of TGF-ß1 (rhEPO = 0.95 ± 0.14, control = 1.05 ± 0.16) and TNF-α (rhEPO = 0.73 ± 0.20, control = 1.01 ± 0.09). These results may help to clarify some of the direct actions of EPO on skeletal muscle.
Assuntos
Regulação para Baixo/efeitos dos fármacos , Eritropoetina/uso terapêutico , Expressão Gênica/efeitos dos fármacos , Distrofia Muscular de Duchenne/tratamento farmacológico , Miostatina/metabolismo , Proteínas Recombinantes/uso terapêutico , Animais , Modelos Animais de Doenças , Distrofina/deficiência , Masculino , Camundongos Endogâmicos mdx , Força Muscular/efeitos dos fármacos , Músculo Esquelético/metabolismo , Distrofia Muscular de Duchenne/metabolismo , Miostatina/genética , Fenótipo , Reação em Cadeia da Polimerase em Tempo Real , Fator de Crescimento Transformador beta1/genética , Fator de Crescimento Transformador beta1/metabolismo , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Myoglobin acts as an oxygen store and a reactive oxygen species acceptor in muscles. We examined myoglobin mRNA in rat cardiac ventricle and skeletal muscles during the first 42 days of life and the impact of transient neonatal hypo- and hyperthyroidism on the myoglobin gene expression pattern. Cardiac ventricle and skeletal muscles of Wistar rats at 7-42 days of life were quickly removed, and myoglobin mRNA was determined by Northern blot analysis. Rats were treated with propylthiouracil (5-10 mg/100 g) and triiodothyronine (0.5-50 µg/100 g) for 5, 15, or 30 days after birth to induce hypo- and hyperthyroidism and euthanized either just after treatment or at 90 days. During postnatal (P) days 7-28, the ventricle myoglobin mRNA remained unchanged, but it gradually increased in skeletal muscle (12-fold). Triiodothyronine treatment, from days P0-P5, increased the skeletal muscle myoglobin mRNA 1.5- to 4.5-fold; a 2.5-fold increase was observed in ventricle muscle, but only when triiodothyronine treatment was extended to day P15. Conversely, hypothyroidism at P5 markedly decreased (60%) ventricular myoglobin mRNA. Moreover, transient hyperthyroidism in the neonatal period increased ventricle myoglobin mRNA (2-fold), and decreased heart rate (5%), fast muscle myoglobin mRNA (30%) and body weight (20%) in adulthood. Transient hypothyroidism in the neonatal period also permanently decreased fast muscle myoglobin mRNA (30%) and body weight (14%). These results indicated that changes in triiodothyronine supply in the neonatal period alter the myoglobin expression program in ventricle and skeletal muscle, leading to specific physiological repercussions and alterations in other parameters in adulthood.
Assuntos
Hipertireoidismo/metabolismo , Hipotireoidismo/metabolismo , Músculo Esquelético/metabolismo , Miocárdio/metabolismo , Mioglobina/genética , RNA Mensageiro/metabolismo , Animais , Animais Recém-Nascidos , Antitireóideos , Pressão Sanguínea , Northern Blotting , Expressão Gênica , Frequência Cardíaca , Ventrículos do Coração/metabolismo , Hipertireoidismo/induzido quimicamente , Hipotireoidismo/induzido quimicamente , Masculino , Mioglobina/metabolismo , Tamanho do Órgão , Propiltiouracila , Distribuição Aleatória , Ratos Wistar , Espécies Reativas de Oxigênio , Tri-IodotironinaRESUMO
Myoglobin acts as an oxygen store and a reactive oxygen species acceptor in muscles. We examined myoglobin mRNA in rat cardiac ventricle and skeletal muscles during the first 42 days of life and the impact of transient neonatal hypo- and hyperthyroidism on the myoglobin gene expression pattern. Cardiac ventricle and skeletal muscles of Wistar rats at 7-42 days of life were quickly removed, and myoglobin mRNA was determined by Northern blot analysis. Rats were treated with propylthiouracil (5-10 mg/100 g) and triiodothyronine (0.5-50 µg/100 g) for 5, 15, or 30 days after birth to induce hypo- and hyperthyroidism and euthanized either just after treatment or at 90 days. During postnatal (P) days 7-28, the ventricle myoglobin mRNA remained unchanged, but it gradually increased in skeletal muscle (12-fold). Triiodothyronine treatment, from days P0-P5, increased the skeletal muscle myoglobin mRNA 1.5- to 4.5-fold; a 2.5-fold increase was observed in ventricle muscle, but only when triiodothyronine treatment was extended to day P15. Conversely, hypothyroidism at P5 markedly decreased (60%) ventricular myoglobin mRNA. Moreover, transient hyperthyroidism in the neonatal period increased ventricle myoglobin mRNA (2-fold), and decreased heart rate (5%), fast muscle myoglobin mRNA (30%) and body weight (20%) in adulthood. Transient hypothyroidism in the neonatal period also permanently decreased fast muscle myoglobin mRNA (30%) and body weight (14%). These results indicated that changes in triiodothyronine supply in the neonatal period alter the myoglobin expression program in ventricle and skeletal muscle, leading to specific physiological repercussions and alterations in other parameters in adulthood.
Assuntos
Animais , Masculino , Hipertireoidismo/metabolismo , Hipotireoidismo/metabolismo , Músculo Esquelético/metabolismo , Miocárdio/metabolismo , Mioglobina/genética , RNA Mensageiro/metabolismo , Animais Recém-Nascidos , Antitireóideos , Pressão Sanguínea , Northern Blotting , Expressão Gênica , Frequência Cardíaca , Ventrículos do Coração/metabolismo , Hipertireoidismo/induzido quimicamente , Hipotireoidismo/induzido quimicamente , Mioglobina/metabolismo , Tamanho do Órgão , Propiltiouracila , Distribuição Aleatória , Ratos Wistar , Espécies Reativas de Oxigênio , Tri-IodotironinaRESUMO
AIM: Investigate, in healthy sedentary rats, the potential mechanisms involved on the effects of beta hydroxy beta methylbutyrate (HMB) supplementation upon the glycaemic homeostasis, by evaluating the insulin sensitivity in liver, skeletal muscle, and white adipose tissue. METHODS: Rats were supplemented with either beta hydroxy beta methylbutyrate (320 mg kg(-1) BW) or saline by gavage for 4 weeks. After the experimental period, the animals were subjected to the glucose tolerance test (GTT) and plasma non-esterified fatty acids (NEFA) concentration measurements. The soleus skeletal muscle, liver and white adipose tissue were removed for molecular (western blotting and RT-PCR) and histological analysis. RESULTS: The beta hydroxy beta methylbutyrate supplemented rats presented: (i) higher ratio between the area under the curve (AUC) of insulinaemia and glycaemia during glucose tolerance test; (ii) impairment of insulin sensitivity on liver and soleus skeletal muscle after insulin overload; (iii) reduction of glucose transporter 4 (GLUT 4) total and plasma membrane content on soleus; (iv) increased hormone-sensitive lipase (HSL) mRNA and protein expression on white adipose tissue and plasma NEFA levels and (v) reduction of fibre cross-sectional area of soleus muscle. CONCLUSION: The data altogether indicate that beta hydroxy beta methylbutyrate supplementation impairs insulin sensitivity in healthy sedentary rats, which, in the long-term, could lead to an increased risk of developing type 2 diabetes.
Assuntos
Suplementos Nutricionais/toxicidade , Resistência à Insulina/fisiologia , Músculo Esquelético/efeitos dos fármacos , Valeratos/toxicidade , Tecido Adiposo/efeitos dos fármacos , Animais , Western Blotting , Teste de Tolerância a Glucose , Transportador de Glucose Tipo 4/metabolismo , Fígado/efeitos dos fármacos , Masculino , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase em Tempo RealRESUMO
Thyroid hormone (TH) activates PI3K and Akt, leading to glucose uptake in rat skeletal muscle cells and proliferation of insulinoma cells, respectively. However, TH actions on pancreatic beta cells have been little explored, which lead us to evaluate the TH eff ects on proinsulin gene expression, and the involvement of PI3K/Akt/GSK-3ß signaling pathway, and a transcriptional factor for insulin (PDX-1). INS-1E cells were sorted into 3 groups: control and TH-depleted treated or not with T3 for 30 min. Cells were also previously treated with actinomycin D (ActD), cycloheximide (CHX), wortmannin or Akt inhibitor. Proinsulin mRNA expression was evaluated by real time PCR, and pGSK-3ß and PDX-1 protein content was analyzed by Western blotting. TH depletion decreased proinsulin mRNA content, which was restored after acute T3 treatment. ActD, CHX and wortmannin, but not Akt inhibitor, prevented the rapid stimulatory eff ect of T3 on proinsulin mRNA expression. TH depletion did not affect the phosphorylated GSK-3ß and PDX-1 protein content; but T3 treatment led to an increase in the content of these proteins. These data indicate that T3 acutely increases proinsulin mRNA expression, by mechanisms which depends on the activation of PI3K, but not of Akt, and may involve the inactivation of GSK-3ß by phosphorylation. Since GSK-3ß enhances PDX-1 degradation rate, the GSK-3ß inactivation could explain the increase of PDX-1 content in T3-treated cells. Considering that PDX-1 is one of the most important transcriptional factors for proinsulin gene expression, its enhancement may underlie the increased proinsulin mRNA content acutely induced by T3.
Assuntos
Regulação da Expressão Gênica/efeitos dos fármacos , Quinase 3 da Glicogênio Sintase/metabolismo , Proteínas de Homeodomínio/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proinsulina/biossíntese , Transativadores/metabolismo , Tri-Iodotironina/farmacologia , Animais , Linhagem Celular Tumoral , Cicloeximida/farmacologia , Dactinomicina/farmacologia , Ativação Enzimática/efeitos dos fármacos , Ativação Enzimática/genética , Regulação da Expressão Gênica/genética , Quinase 3 da Glicogênio Sintase/genética , Glicogênio Sintase Quinase 3 beta , Proteínas de Homeodomínio/genética , Inibidores da Síntese de Ácido Nucleico/farmacologia , Fosfatidilinositol 3-Quinases/genética , Fosforilação/efeitos dos fármacos , Fosforilação/genética , Proinsulina/genética , Inibidores da Síntese de Proteínas/farmacologia , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Ratos , Transativadores/genéticaRESUMO
The amino acid arginine (Arg) is a recognized secretagogue of growth hormone (GH), and has been shown to induce GH gene expression. Arg is the natural precursor of nitric oxide (NO), which is known to mediate many of the effects of Arg, such as GH secretion. Arg was also shown to increase calcium influx in pituitary cells, which might contribute to its effects on GH secretion. Although the mechanisms involved in the effects of Arg on GH secretion are well established, little is known about them regarding the control of GH gene expression. We investigated whether the NO pathway and/or calcium are involved in the effects of Arg on GH gene expression in rat isolated pituitaries. To this end, pituitaries from approximately 170 male Wistar rats (~250 g) were removed, divided into two halves, pooled (three hemi-pituitaries) and incubated or not with Arg, as well as with different pharmacological agents. Arg (71 mM), the NO donor sodium nitroprusside (SNP, 1 and 0.1 mM) and a cyclic guanosine monophosphate (cGMP) analogue (8-Br-cGMP, 1 mM) increased GH mRNA expression 60 min later. The NO acceptor hemoglobin (0.3 µM) blunted the effect of SNP, and the combined treatment with Arg and L-NAME (a NO synthase (NOS) inhibitor, 55 mM) abolished the stimulatory effect of Arg on GH gene expression. The calcium channel inhibitor nifedipine (3 µM) also abolished Arg-induced GH gene expression. The present study shows that Arg directly induces GH gene expression in hemi-pituitaries isolated from rats, excluding interference from somatostatinergic neurons, which are supposed to be inhibited by Arg. Moreover, the data demonstrate that the NOS/NO signaling pathway and calcium mediate the Arg effects on GH gene expression.
Assuntos
Animais , Masculino , Ratos , Arginina/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Hormônio do Crescimento/genética , Hipófise/efeitos dos fármacos , Relação Dose-Resposta a Droga , Hormônio do Crescimento/metabolismo , Óxido Nítrico Sintase/efeitos dos fármacos , Óxido Nítrico Sintase/genética , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico/genética , Óxido Nítrico/metabolismo , Hipófise/metabolismo , Ratos Wistar , Transdução de SinaisRESUMO
The amino acid arginine (Arg) is a recognized secretagogue of growth hormone (GH), and has been shown to induce GH gene expression. Arg is the natural precursor of nitric oxide (NO), which is known to mediate many of the effects of Arg, such as GH secretion. Arg was also shown to increase calcium influx in pituitary cells, which might contribute to its effects on GH secretion. Although the mechanisms involved in the effects of Arg on GH secretion are well established, little is known about them regarding the control of GH gene expression. We investigated whether the NO pathway and/or calcium are involved in the effects of Arg on GH gene expression in rat isolated pituitaries. To this end, pituitaries from approximately 170 male Wistar rats (~250 g) were removed, divided into two halves, pooled (three hemi-pituitaries) and incubated or not with Arg, as well as with different pharmacological agents. Arg (71 mM), the NO donor sodium nitroprusside (SNP, 1 and 0.1 mM) and a cyclic guanosine monophosphate (cGMP) analogue (8-Br-cGMP, 1 mM) increased GH mRNA expression 60 min later. The NO acceptor hemoglobin (0.3 µM) blunted the effect of SNP, and the combined treatment with Arg and L-NAME (a NO synthase (NOS) inhibitor, 55 mM) abolished the stimulatory effect of Arg on GH gene expression. The calcium channel inhibitor nifedipine (3 µM) also abolished Arg-induced GH gene expression. The present study shows that Arg directly induces GH gene expression in hemi-pituitaries isolated from rats, excluding interference from somatostatinergic neurons, which are supposed to be inhibited by Arg. Moreover, the data demonstrate that the NOS/NO signaling pathway and calcium mediate the Arg effects on GH gene expression.