RESUMEN
Because polyphenols may have beneficial effects on dyslipidemia, which accelerates atherosclerosis in diabetes, we examined the effect of polyphenols on hepatocellular AMP-activated protein kinase (AMPK) activity and lipid levels, as well as hyperlipidemia and atherogenesis in type 1 diabetic LDL receptor-deficient mice (DMLDLR(-/-)). In HepG2 hepatocytes, polyphenols, including resveratrol (a major polyphenol in red wine), apigenin, and S17834 (a synthetic polyphenol), increased phosphorylation of AMPK and its downstream target, acetyl-CoA carboxylase (ACC), and they increased activity of AMPK with 200 times the potency of metformin. The polyphenols also prevented the lipid accumulation that occurred in HepG2 cells exposed to high glucose, and their ability to do so was mimicked and abrogated, respectively, by overexpression of constitutively active and dominant-negative AMPK mutants. Furthermore, treatment of DMLDLR(-/-) mice with S17834 prevented the decrease in AMPK and ACC phosphorylation and the lipid accumulation in the liver, and it also inhibited hyperlipidemia and the acceleration of aortic lesion development. These studies 1) reveal that inactivation of hepatic AMPK is a key event in the pathogenesis of hyperlipidemia in diabetes, 2) point to a novel mechanism of action of polyphenols to lower lipids by activating AMPK, and 3) emphasize a new therapeutic avenue to benefit hyperlipidemia and atherosclerosis specifically in diabetes via activating AMPK.
Asunto(s)
Aterosclerosis/prevención & control , Diabetes Mellitus Experimental/complicaciones , Flavonoides/administración & dosificación , Lípidos/sangre , Complejos Multienzimáticos/metabolismo , Fenoles/administración & dosificación , Proteínas Serina-Treonina Quinasas/metabolismo , Receptores de LDL/deficiencia , Proteínas Quinasas Activadas por AMP , Acetil-CoA Carboxilasa/metabolismo , Animales , Apigenina/farmacología , Benzopiranos/administración & dosificación , Carcinoma Hepatocelular , Línea Celular Tumoral , Diabetes Mellitus Experimental/tratamiento farmacológico , Activación Enzimática/efectos de los fármacos , Glucosa/farmacología , Humanos , Hipolipemiantes/administración & dosificación , Metabolismo de los Lípidos/efectos de los fármacos , Hígado/efectos de los fármacos , Hígado/metabolismo , Neoplasias Hepáticas , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Fosforilación , Polifenoles , Receptores de LDL/fisiología , Resveratrol , Estilbenos/administración & dosificaciónRESUMEN
Arachidonic acid metabolites, some of which may activate thromboxane A(2) receptors (TPr) and contribute to the development of diabetes complications, including nephropathy, are elevated in diabetes. This study determined the effect of blocking TPr with S18886 or inhibiting cyclooxygenase with aspirin on oxidative stress and the early stages of nephropathy in streptozotocin-induced diabetic apolipoprotein E(-/-) mice. Diabetic mice were treated with S18886 (5 mg . kg(-1) . day(-1)) or aspirin (30 mg . kg(-1) . day(-1)) for 6 weeks. Neither S18886 nor aspirin affected hyperglycemia or hypercholesterolemia. There was intense immunohistochemical staining for nitrotyrosine in diabetic mouse kidney. In addition, a decrease in manganese superoxide dismutase (MnSOD) activity was associated with an increase in MnSOD tyrosine-34 nitration. Tyrosine nitration was significantly reduced by S18886 but not by aspirin. Staining for the NADPH oxidase subunit p47(phox), inducible nitric oxide synthase, and 12-lipoxygenase was increased in diabetic mouse kidney, as were urine levels of 12-hydroxyeicosatetraenoic acid and 8-iso-prostaglandin F(2alpha). S18886 attenuated all of these markers of oxidant stress and inflammation. Furthermore, S18886 significantly attenuated microalbuminuria in diabetic mice and ameliorated histological evidence of diabetic nephropathy, including transforming growth factor-beta and extracellular matrix expression. Thus, in contrast to inhibiting cyclooxygenase, blockade of TPr may have therapeutic potential in diabetic nephropathy, in part by attenuating oxidative stress.
Asunto(s)
Apolipoproteínas E/deficiencia , Diabetes Mellitus Experimental/complicaciones , Diabetes Mellitus Experimental/metabolismo , Naftalenos/farmacología , Estrés Oxidativo/efectos de los fármacos , Propionatos/farmacología , Proteinuria/metabolismo , Receptores de Tromboxanos/antagonistas & inhibidores , Animales , Apolipoproteínas E/genética , Araquidonato 12-Lipooxigenasa/metabolismo , Aspirina/farmacología , Femenino , Eliminación de Gen , Enfermedades Renales/tratamiento farmacológico , Enfermedades Renales/patología , Ratones , NADPH Oxidasas , Naftalenos/uso terapéutico , Óxido Nítrico Sintasa de Tipo II , Fosfoproteínas/metabolismo , Propionatos/uso terapéutico , Proteinuria/complicaciones , Proteinuria/tratamiento farmacológico , Receptores de Tromboxanos/metabolismoRESUMEN
BACKGROUND: S18886 is an orally active thromboxane A2 (TXA2) receptor (TP) antagonist in clinical development for use in secondary prevention of thrombotic events in cardiovascular disease. We previously showed that S18886 inhibits atherosclerosis in apolipoprotein E-deficient (apoE(-/-)) mice by a mechanism independent of platelet-derived TXA2. Atherosclerosis is accelerated by diabetes and is associated with increased TXA(2) and other eicosanoids that stimulate TP. The purpose of this study was to determine whether S18886 lessens the enhanced atherogenesis in diabetic apoE(-/-) mice. METHODS AND RESULTS: Diabetes mellitus was induced in apoE(-/-) mice with streptozotocin and was treated or not with S18886 (5 mg.kg(-1).d(-1)). After 6 weeks, aortic lesion area was increased >4-fold by diabetes in apoE(-/-) mice, associated with similar increases in serum glucose and cholesterol. S18886 largely prevented the diabetes-related increase in lesion area without affecting the hyperglycemia or hypercholesterolemia. S18886 prevented deterioration of endothelial function and endothelial nitric oxide synthase expression, as well as increases in intimal markers of inflammation associated with diabetes. In human aortic endothelial cells in culture, S18886 also prevented the induction of vascular cell adhesion molecule-1 and prevented the decrease in endothelial nitric oxide synthase expression caused by high glucose. CONCLUSIONS: The TP antagonist inhibits inflammation and accelerated atherogenesis caused by diabetes, most likely by counteracting effects on endothelial function and adhesion molecule expression of eicosanoids stimulated by the diabetic milieu.
Asunto(s)
Apolipoproteínas E/deficiencia , Aterosclerosis/prevención & control , Diabetes Mellitus Experimental/complicaciones , Angiopatías Diabéticas/prevención & control , Naftalenos/farmacología , Propionatos/farmacología , Receptores de Tromboxano A2 y Prostaglandina H2/antagonistas & inhibidores , Animales , Cruzamientos Genéticos , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones NoqueadosRESUMEN
The antidiabetic drug metformin stimulates AMP-activated protein kinase (AMPK) activity in the liver and in skeletal muscle. To better understand the role of AMPK in the regulation of hepatic lipids, we studied the effect of metformin on AMPK and its downstream effector, acetyl-CoA carboxylase (ACC), as well as on lipid content in cultured human hepatoma HepG2 cells. Metformin increased Thr-172 phosphorylation of the alpha subunit of AMPK in a dose- and time-dependent manner. In parallel, phosphorylation of ACC at Ser-79 was increased, which was consistent with decreasing ACC activity. Intracellular triacylglycerol and cholesterol contents were also decreased. These effects of metformin were mimicked or completely abrogated by adenoviral-mediated expression of a constitutively active AMPKalpha or a kinase-inactive AMPKalpha, respectively. An insulin-resistant state was induced by exposing cells to 30 mm glucose as indicated by decreased phosphorylation of Akt and its downstream effector, glycogen synthase kinase 3alpha/beta. Under these conditions, the phosphorylation of AMPK and ACC was also decreased, and the level of hepatocellular triacylglycerols increased. The inhibition of AMPK and the accumulation of lipids caused by high glucose concentrations were prevented either by metformin or by expressing the constitutively active AMPKalpha. The kinase-inactive AMPKalpha increased lipid content and blocked the ability of metformin to decrease lipid accumulation caused by high glucose concentrations. Taken together, these results indicate that AMPKalpha negatively regulates ACC activity and hepatic lipid content. Inhibition of AMPK may contribute to lipid accumulation induced by high concentrations of glucose associated with insulin resistance. Metformin lowers hepatic lipid content by activating AMPK, thereby mediating beneficial effects in hyperglycemia and insulin resistance.
Asunto(s)
Hipoglucemiantes/metabolismo , Resistencia a la Insulina/fisiología , Metabolismo de los Lípidos , Hígado/metabolismo , Metformina/metabolismo , Complejos Multienzimáticos/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Quinasas Activadas por AMP , Acetil-CoA Carboxilasa/metabolismo , Línea Celular Tumoral , Activación Enzimática , Glucosa/metabolismo , Glucógeno Sintasa Quinasa 3/metabolismo , Glucógeno Sintasa Quinasa 3 beta , Humanos , Insulina/metabolismo , Hígado/citología , Complejos Multienzimáticos/genética , Proteínas Serina-Treonina Quinasas/genética , Subunidades de Proteína/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-akt , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismoRESUMEN
Diabetic nephropathy is associated with increased urinary albumin and reduce kallikrein excretion. Increased activity of the renal kallikrein-kinin system has been suggested as one of the possible mechanisms underlying diabetic hyperfiltration. The present study shown that kallikrein-kinin system is progressively increased in the diabetic-pregnant rats at 7, 14, 21 days; 48 and 7 days after pregnancy (P<0.05 vs Control). However, this increase during diabetic pregnancy did not reached the levels of control pregnancy. On the other hand albumin excretion shown a significant and progressive renal damage in the diabetic state. These findings suggest that the diabetic pregnancy could impair the renal hemodynamic, but, on the other side could modulate the vasodilatador system at pregnancy in the attempt protect the fetus.
Asunto(s)
Femenino , Humanos , Animales , Embarazo , Diabetes Mellitus Experimental/patología , Nefropatías Diabéticas/patología , Calicreínas/orina , Embarazo en Diabéticas/patología , Presión Sanguínea , Diabetes Mellitus Experimental/fisiopatología , Nefropatías Diabéticas/fisiopatología , Embarazo en Diabéticas/fisiopatología , Ratas WistarRESUMEN
Diabetic nephropathy is associated with increased urinary albumin and reduce kallikrein excretion. Increased activity of the renal kallikrein-kinin system has been suggested as one of the possible mechanisms underlying diabetic hyperfiltration. The present study shown that kallikrein-kinin system is progressively increased in the diabetic-pregnant rats at 7, 14, 21 days; 48 and 7 days after pregnancy (P<0.05 vs Control). However, this increase during diabetic pregnancy did not reached the levels of control pregnancy. On the other hand albumin excretion shown a significant and progressive renal damage in the diabetic state. These findings suggest that the diabetic pregnancy could impair the renal hemodynamic, but, on the other side could modulate the vasodilatador system at pregnancy in the attempt protect the fetus. (AU)