Assuntos
Fármacos Antiobesidade/uso terapêutico , Cirurgia Bariátrica , Diabetes Mellitus Tipo 2/etiologia , Desenho de Fármacos , Obesidade/tratamento farmacológico , Obesidade/cirurgia , Fármacos Antiobesidade/química , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/fisiopatologia , Diabetes Mellitus Tipo 2/cirurgia , Humanos , Obesidade/complicações , Obesidade/fisiopatologia , Resultado do Tratamento , Redução de PesoRESUMO
It is unclear how hepatic glucocorticoid receptor (GR) function and hypothalamic-pituitary-adrenal axis tone contribute to the diabetic state and in particular whole-body glucose fluxes. We have previously demonstrated that long-term exposure to hepatic GR inhibition lowers glucose levels in ob/ob mice (J Pharmacol Exp Ther 2005;314:191). The purpose of this study was to determine the effects of a novel GR antagonist (A-348441) on whole-body glucose fluxes in a model of insulin resistance, the Zucker fatty (fa/fa) rat. After an overnight fast, euglycemic-hyperinsulinemic clamp studies were performed 2 hours after single oral dosing as follows: (1) A-348441 at 100 mg/kg or (2) vehicle. Furthermore, effects of 1 week of treatment with either vehicle or A-348441 (3, 10, 30, or 100 mg/kg PO, once per day) were investigated in separate groups of rats fasted overnight and given a final dose of their respective compound, followed 2 hours later by a euglycemic-hyperinsulinemic clamp. One week after catheter implantation, body weight returned to presurgery levels, with no difference between groups. A single, 100-mg/kg dose of A-348441 significantly increased glucose infusion rate 4-fold (P < .05) and reduced endogenous glucose production by 37% (P < .05) but did not change glucose disposal. After 1 week of sub-long-term dosing, fasting glucose levels were reduced dose-dependently with A-348441 vs vehicle (-8%, not significant; -14%, -20%, and -25%, P < .05, at 3, 10, 30, and 100 mg/kg, respectively) with no observed hypoglycemia or change in fasting insulin levels. A-348441 increased the glucose infusion rates after 1-week treatment by 1.3-, 5.7-, 7.3-, and 6.4-fold (P < .05). Endogenous glucose production was decreased (-25%, -44%, -50%, and -61%, P < .05), whereas glucose disposal was increased (29% and 13%, not significant; 23% and 34%, P < .05), with A-348441. In summary, single-dose treatment with the liver-selective GR antagonist A-348441 decreases glucose production with no effect on glucose disposal or fasting glucose levels. After 1 week of treatment with A-348441, (1) there was no effect on body weight, (2) fasting glucose levels decreased, (3) both glucose disposal and glucose infusion rate increased during clamping, and (4) endogenous glucose production was greatly reduced. In addition, hepatic glucose production was highly correlated with fasting glucose levels (r = 0.97). In conclusion, these results indicate that A-348441 increases insulin sensitivity at both the liver and peripheral tissues, leading toward a normalization of the insulin resistant state. Furthermore, with 1-week vs single-dose liver-selective glucocorticoid antagonism, we have determined that the peripheral effect is secondary to the primary event of reduced hepatic glucose production. The approach of inhibiting the hepatic GR may be an advantageous treatment paradigm for individuals with type 2 diabetes mellitus.
Assuntos
Ácidos Cólicos/farmacologia , Estrona/análogos & derivados , Glucose/metabolismo , Resistência à Insulina , Fígado/metabolismo , Receptores de Glucocorticoides/antagonistas & inibidores , Animais , Glicemia/análise , Relação Dose-Resposta a Droga , Estrona/farmacologia , Insulina/sangue , Ratos , Ratos ZuckerRESUMO
A liver-selective glucocorticoid (GC) receptor antagonist (A-348441) was used to determine the effect of reduced hepatic GC signaling on hepatic glucose production. Fasted conscious dogs were studied in the presence (GRA, n = 6) or absence (CON, n = 6) of the intraduodenally administered GC receptor antagonist (100 mg/kg). All dogs were maintained on a pancreatic clamp and in a euglycemic state for 7 hours to ensure that any changes in glucose metabolism were the direct result of the effects of A-348441, which was given at the start of a 5-hour experimental period. In the GRA group, the arterial plasma insulin level was 4.6 +/- 0.7 and 4.8 +/- 0.6 microU/mL during the basal and the last 30 minutes of the experimental periods, respectively. In the CON group, it was 4.0 +/- 0.3 and 4.5 +/- 0.5 microU/mL in the 2 periods, respectively. The arterial plasma glucagon level was 49 +/- 4 and 46 +/- 3 pg/mL in the 2 periods in the GRA group, and 45 +/- 3 and 42 +/- 3 pg/mL in the CON group. Net hepatic glucose balance progressively decreased in the GRA group from 1.31 +/- 0.18 to 0.49 +/- 0.30 mg/kg per minute, whereas in the CON group, net hepatic glucose balance was 1.17 +/- 0.09 and 1.43 +/- 0.18 mg/kg per minute during the basal and last 30 minutes of the experimental periods, respectively. No significant change in net renal or gut glucose balance or nonhepatic glucose uptake was observed in either group. This study demonstrates that the GC receptor plays an important role in the regulation of basal hepatic glucose production and represents a significant potential therapeutic target.
Assuntos
Glucose/biossíntese , Fígado/metabolismo , Receptores de Glucocorticoides/antagonistas & inibidores , Animais , Glicemia/análise , Ácidos Cólicos/administração & dosagem , Ácidos Cólicos/farmacologia , Cães , Estrona/administração & dosagem , Estrona/análogos & derivados , Estrona/farmacologia , Glucagon/sangue , Técnica Clamp de Glucose , CinéticaRESUMO
The net contribution of endothelin type A (ET(A)) and type B (ET(B)) receptors in blood pressure regulation in humans and experimental animals, including the conscious mouse, remains undefined. Thus we assessed the role of ET(A) and ET(B) receptors in the control of basal blood pressure and also the role of ET(A) receptors in maintaining the hypertensive effects of systemic ET(B) blockade in telemetry-instrumented mice. Mean arterial pressure (MAP) and heart rate were recorded continuously from the carotid artery and daily (24 h) values determined. At baseline, MAP ranged from 99 +/- 1 to 101 +/- 1 mmHg and heart rate ranged between 547 +/- 15 and 567 +/- 19 beats/min (n = 6). Daily oral administration of the ET(B) selective antagonist A-192621 [10 mg/kg twice daily] increased MAP to 108 +/- 1 and 112 +/- 2 mmHg on days 1 and 5, respectively. Subsequent coadministration of the ET(A) selective antagonist atrasentan (5 mg/kg twice daily) in conjunction with A-192621 (10 mg/kg twice daily) decreased MAP to baseline values on day 6 (99 +/- 2 mmHg) and to below baseline on day 8 (89 +/- 3 mmHg). In a separate group of mice (n = 6) in which the treatment was reversed, systemic blockade of ET(B) receptors produced no hypertension in animals pretreated with atrasentan, underscoring the importance of ET(A) receptors to maintain the hypertension produced by ET(B) blockade. In a third group of mice (n = 10), ET(A) blockade alone (atrasentan; 5 mg/kg twice daily) produced an immediate and sustained decrease in MAP to values below baseline (baseline values = 101 +/- 2 to 103 +/- 2 mmHg; atrasentan decreased pressure to 95 +/- 2 mmHg). Thus these data suggest that ET(A) and ET(B) receptors play a physiologically relevant role in the regulation of basal blood pressure in normal, conscious mice. Furthermore, systemic ET(B) receptor blockade produces sustained hypertension in conscious telemetry-instrumented mice that is absent in mice pretreated with an ET(A) antagonist, suggesting that ET(A) receptors maintain the hypertension produced by ET(B) blockade.
Assuntos
Pressão Sanguínea/efeitos dos fármacos , Antagonistas do Receptor de Endotelina B , Hipertensão/fisiopatologia , Receptor de Endotelina A/efeitos dos fármacos , Animais , Atrasentana , Relação Dose-Resposta a Droga , Frequência Cardíaca/efeitos dos fármacos , Hipertensão/induzido quimicamente , Camundongos , Camundongos Endogâmicos C57BL , Pirrolidinas/farmacologia , TelemetriaRESUMO
RNA interference (RNAi) is an exciting new tool to effect acute in vivo knockdown of genes for pharmacological target validation. Testing the application of this technology to metabolic disease targets, three RNAi delivery methods were compared in two frequently utilized preclinical models of obesity and diabetes, the diet-induced obese (DIO) and B6.V-Lep
RESUMO
Atrasentan, an endothelin antagonist, would have beneficial effects on metabolic responses in a model of insulin resistance. Zucker lean or fatty rats were maintained either on regular (lean and fatty control, n = 12) or atrasentan-treated water (5 mg/kg/d, fatty atrasentan, n = 13) for 6 weeks. There was no significant difference in water intake and body weight with the atrasentan-treated group compared with fatty controls. Although atrasentan had no effect on 3-hour fasting glucose levels, it reduced fasting insulin levels between weeks 2 and 4 of treatment by 53% (fatty control vs fatty atrasentan, P < .01). Atrasentan decreased the incremental area under the plasma glucose response curve ( Delta AUC) after a nutritionally complete meal tolerance test (MTT), by 28% in the atrasentan-treated group compared with fatty controls ( P < .05), and decreased the MTT-induced insulin Delta AUC by 63% in treated animals compared with the fatty control group ( P < .01). In addition, atrasentan significantly decreased the MTT-induced glucose-insulin index Delta AUC by 58% in treated rats compared with fatty controls ( P < .01). In summary, in the Zucker fatty rat, atrasentan significantly reduces (1) 3-hour fasting insulin levels at 4 weeks, (2) glucose and insulin MTT-induced Delta AUCs, and (3) the MTT-induced glucose-insulin index Delta AUC. These results demonstrate an improvement in hyperinsulinemia as well as in glucose tolerance and insulin sensitivity with chronic endothelin antagonism in a model of insulin resistance and suggest that chronic endothelin antagonism may have benefits in the treatment of insulin resistance and/or diabetes.
Assuntos
Antagonistas do Receptor de Endotelina A , Pirrolidinas/farmacologia , Animais , Área Sob a Curva , Atrasentana , Glicemia/análise , Endotelina-1/sangue , Ácidos Graxos não Esterificados/sangue , Insulina/sangue , Resistência à Insulina , Ratos , Ratos ZuckerRESUMO
Glucocorticoids amplify endogenous glucose production in type 2 diabetes by increasing hepatic glucose output. Systemic glucocorticoid blockade lowers glucose levels in type 2 diabetes, but with several adverse consequences. It has been proposed, but never demonstrated, that a liver-selective glucocorticoid receptor antagonist (LSGRA) would be sufficient to reduce hepatic glucose output (HGO) and restore glucose control to type 2 diabetic patients with minimal systemic side effects. A-348441 [(3b,5b,7a,12a)-7,12-dihydroxy-3-{2-[{4-[(11b,17b)-17-hydroxy-3-oxo-17-prop-1-ynylestra-4,9-dien-11-yl] phenyl}(methyl)amino]ethoxy}cholan-24-oic acid] represents the first LSGRA with significant antidiabetic activity. A-348441 antagonizes glucocorticoid-up-regulated hepatic genes, normalizes postprandial glucose in diabetic mice, and demonstrates synergistic effects on blood glucose in these animals when coadministered with an insulin sensitizer. In insulin-resistant Zucker fa/fa rats and fasted conscious normal dogs, A-348441 reduces HGO with no acute effect on peripheral glucose uptake. A-348441 has no effect on the hypothalamic pituitary adrenal axis or on other measured glucocorticoid-induced extrahepatic responses. Overall, A-348441 demonstrates that an LSGRA is sufficient to reduce elevated HGO and normalize blood glucose and may provide a new therapeutic approach for the treatment of type 2 diabetes.
Assuntos
Glicemia/metabolismo , Ácidos Cólicos/farmacologia , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Estrona/análogos & derivados , Glucose/metabolismo , Fígado/metabolismo , Receptores de Glucocorticoides/antagonistas & inibidores , Células 3T3 , Adipócitos/metabolismo , Animais , Biotransformação/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Ácidos Cólicos/metabolismo , Diabetes Mellitus Tipo 2/sangue , Cães , Sinergismo Farmacológico , Estrona/metabolismo , Estrona/farmacologia , Glucocorticoides/farmacologia , Glutamato-Amônia Ligase/metabolismo , Hipoglicemiantes/farmacologia , Masculino , Camundongos , Obesidade/metabolismo , Prednisolona/farmacologia , Ratos , Ratos Zucker , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Rosiglitazona , Tiazolidinedionas/farmacologia , Tirosina Transaminase/metabolismoRESUMO
The role of endothelin-B (ET(B)) receptors in circulatory homeostasis is ambiguous, reflecting vasodilator and constrictor effects ascribed to the receptor and diuretic and natriuretic responses that could oppose the hypertensive effects of ET excess. With the use of conscious, telemetry-instrumented cynomolgus monkeys, we characterized the hypertension produced by ET(B) blockade and the role of ET(A) receptors in mediating this response. Mean arterial pressure (MAP) and heart rate (HR) were measured 24 h/day for 24 days under control conditions and during administration of the ET(B)-selective antagonist A-192621 (0.1, 1.0, and 10 mg/kg bid, 4 days/dose) followed by coadministration of the ET(A) antagonist atrasentan (5 mg/kg bid) + A-192621 (10 mg/kg bid) for another 4 days. High-dose ET(B) blockade increased MAP from 79 +/- 3 (control) to 87 +/- 3 and 89 +/- 3 mmHg on the first and fourth day, respectively; HR was unchanged, and plasma ET-1 concentration increased from 2.1 +/- 0.3 pg/ml (control) to 7.24 +/- 0.99 and 11.03 +/- 2.37 pg/ml. Atrasentan + A-192621 (10 mg/kg) decreased MAP from hypertensive levels (89 +/- 3) to 75 +/- 2 and 71 +/- 4 mmHg on the first and fourth day, respectively; plasma ET-1 and HR increased to 26.64 +/- 3.72 and 28.65 +/- 2.89 pg/ml and 113 +/- 5 (control) to 132 +/- 5 and 133 +/- 7 beats/min. Thus systemic ET(B) blockade produces a sustained hypertension in conscious nonhuman primates, which is mediated by ET(A) receptors. These data suggest an importance clearance function for ET(B) receptors, one that influences arterial pressure homeostasis indirectly by reducing plasma ET-1 levels and minimizing ET(A) activation.
Assuntos
Antagonistas dos Receptores de Endotelina , Hipertensão/fisiopatologia , Receptores de Endotelina/fisiologia , Animais , Antineoplásicos/farmacologia , Atrasentana , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Estado de Consciência , Endotelina-1/sangue , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Homeostase , Hipertensão/induzido quimicamente , Macaca fascicularis , Masculino , Pirrolidinas/farmacologia , Receptor de Endotelina A , Receptor de Endotelina B , TelemetriaRESUMO
Endothelins (ETs), 21-amino-acid peptides involved in the pathogenesis of various diseases, bind to ET(A) and ET(B) receptors to initiate their effects. Based on the same core structure, we have developed four small-molecule ET receptor antagonists, ABT-627, ABT-546, A-182086 and A-192621, which exhibit difference in selectivity for ET(A) and ET(B) receptors. In this report, we compare the potency and selectivity of these four antagonists in inhibiting (125)I-labelled ET-1 binding to cloned human ET(A) and ET(B) receptors, and in blocking ET-1-induced functional responses (arachidonic acid release and phosphatidylinositol hydrolysis).
Assuntos
Antagonistas dos Receptores de Endotelina , Vasodilatadores/farmacologia , Animais , Ácido Araquidônico/metabolismo , Atrasentana , Ligação Competitiva , Células CHO , Linhagem Celular , Cricetinae , Endotelina-1/metabolismo , Endotelina-1/farmacologia , Humanos , Hidrólise , Radioisótopos do Iodo/metabolismo , Fosfatidilinositóis/metabolismo , Pirrolidinas/farmacologia , Receptor de Endotelina A , Receptor de Endotelina B , Receptores de Endotelina/genética , Receptores de Endotelina/metabolismo , Sulfonamidas/farmacologia , TransfecçãoRESUMO
Endothelins (ETs), 21-amino-acid peptides involved in the pathogenesis of various diseases, bind to ET(A) and ET(B) receptors to initiate their effects. Based on the same core structure, we have developed four small-molecule ET receptor antagonists, ABT-627 (atrasentan), ABT-546, A-182086 and A-192621, which exhibit differences in selectivity for ET(A) and ET(B) receptors. In this report, we compare the efficacy, potency and pharmacokinetic properties of these four antagonists, including potency in inhibiting ET-1- or Sarafotoxin 6c-induced vessel constriction in isolated arteries and efficacy in antagonizing ET-1-, big ET-1- or Sarafotoxin 6c-induced pressor responses in rats.
Assuntos
Antagonistas dos Receptores de Endotelina , Endotélio Vascular/efeitos dos fármacos , Músculo Liso Vascular/efeitos dos fármacos , Pirrolidinas/farmacologia , Vasodilatadores/farmacologia , Análise de Variância , Animais , Aorta , Atrasentana , Cães , Relação Dose-Resposta a Droga , Endotelina-1/farmacologia , Feminino , Humanos , Técnicas In Vitro , Macaca fascicularis , Masculino , Pirrolidinas/farmacocinética , Coelhos , Ratos , Ratos Sprague-Dawley , Receptor de Endotelina A , Receptor de Endotelina B , Sulfonamidas/farmacocinética , Sulfonamidas/farmacologia , Vasoconstritores/farmacologia , Vasodilatadores/farmacocinética , Venenos de Víboras/farmacologiaRESUMO
Asthma is a chronic respiratory disease that is characterized by airway inflammation, bronchoconstriction and the influx of pro-inflammatory cells, mostly eosinophils in the lung tissue and bronchoalveolar space. Amongst the many physiopathological roles attributed to endothelins (ETs), one is to modulate pulmonary functions. It is established that Balb/c mice develop allergen-induced Th(2)-cytokine gene expression, airway inflammation and hyper-responsiveness whereas C57Bl/6 mice are much less reactive. In the present study, we investigated the roles of ETs in these two murine models of allergic asthma (AA). Mice were sensitized and challenged with either saline (S) and/or ovalbumin (O) over 6 weeks (groups S/S and O/O) and treated chronically with ABT-627 or its vehicle. Twenty-four hours after the last sensitization, challenged mice developed a marked airway inflammatory response characterized by the accumulation of total inflammatory cells (a 21-fold increase) in the bronchoalveolar space, similar in both mouse strains. The increase in eosinophils was marked in both groups, representing 98% of total cell count in O/O versus <1% in S/S. Macrophages were also increased 3-fold in both strains. ABT-627 did reduce the accumulation of macrophages in both stains (36 to 53%) whereas it blocked by 76% the influx of eosinophils in Balb/c but not in C57Bl/6 mice. These results show that ET(A)-receptor antagonism is more effective against O/O-induced AA in Balb/c mice, even though both strains were associated with the same increase in key pro-inflammatory cells in the bronchoalveolar space. It is unclear whether this is due to a lack or a disproportionate expression of ET(A) receptors in these two murine strains, or in post-receptor transduction modulation, or different regulation of ET receptors in various pulmonary cells, after sensitization and challenge.
Assuntos
Antineoplásicos/uso terapêutico , Asma/tratamento farmacológico , Antagonistas dos Receptores de Endotelina , Pirrolidinas , Animais , Asma/imunologia , Atrasentana , Líquido da Lavagem Broncoalveolar/imunologia , Eosinófilos/imunologia , Contagem de Leucócitos , Contagem de Linfócitos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Modelos Animais , Receptor de Endotelina A , Especificidade da EspécieRESUMO
Acute pulmonary air embolism (APAE) injures the vascular endothelium in the lung and results in pulmonary hypertension (PH). Endothelins (ETs), a family of potent vasoactive peptides, are known to be associated with PH of various aetiologies. We evaluated the effects of ABT-627, a selective ET(A) receptor (ET(A)-R) antagonist in a rat model of APAE over 3 h. APAE rats developed a higher right ventricular systolic pressure (RVSP), lower mean arterial blood pressure (MABP), and had lower PaO(2). At 3 h, arterial plasma levels of ET-1 were increased. ABT-627-treated controls showed no effects. However, ABT-627 significantly lowered RVSP during APAE, abolished the short recovery phase (within 10-25 min) of MABP without affecting the subsequent lowering of MABP, and improved oxygen saturation in APAE rats. These results show that ET(A)-R subtype is involved in the pathogenesis of APAE since a blockade of this receptor subtype attenuated the cardiopulmonary deterioration and improved blood gas exchanges in rats with this disease.
Assuntos
Antagonistas dos Receptores de Endotelina , Embolia Pulmonar/tratamento farmacológico , Pirrolidinas/uso terapêutico , Doença Aguda , Animais , Atrasentana , Embolia Aérea/tratamento farmacológico , Embolia Aérea/metabolismo , Endotelina-1/sangue , Endotelina-3/genética , Expressão Gênica , Pulmão/metabolismo , Masculino , Modelos Animais , Oxigênio/sangue , Embolia Pulmonar/metabolismo , Ratos , Ratos Sprague-Dawley , Receptor de Endotelina A , Receptor de Endotelina B , Receptores de Endotelina/genética , Receptores de Endotelina/metabolismoRESUMO
The role of protein-tyrosine phosphatase 1B (PTP1B) in diabetes was investigated using an antisense oligonucleotide in ob/ob and db/db mice. PTP1B antisense oligonucleotide treatment normalized plasma glucose levels, postprandial glucose excursion, and HbA(1C). Hyperinsulinemia was also reduced with improved insulin sensitivity. PTP1B protein and mRNA were reduced in liver and fat with no effect in skeletal muscle. Insulin signaling proteins, insulin receptor substrate 2 and phosphatidylinositol 3 (PI3)-kinase regulatory subunit p50alpha, were increased and PI3-kinase p85alpha expression was decreased in liver and fat. These changes in protein expression correlated with increased insulin-stimulated protein kinase B phosphorylation. The expression of liver gluconeogenic enzymes, phosphoenolpyruvate carboxykinase, and fructose-1,6-bisphosphatase was also down-regulated. These findings suggest that PTP1B modulates insulin signaling in liver and fat, and that therapeutic modalities targeting PTP1B inhibition may have clinical benefit in type 2 diabetes.