RESUMO
We evaluated the potential for a monoclonal antibody antagonist of the glucagon receptor (Ab-4) to maintain glucose homeostasis in type 1 diabetic rodents. We noted durable and sustained improvements in glycemia which persist long after treatment withdrawal. Ab-4 promoted ß-cell survival and enhanced the recovery of insulin+ islet mass with concomitant increases in circulating insulin and C peptide. In PANIC-ATTAC mice, an inducible model of ß-cell apoptosis which allows for robust assessment of ß-cell regeneration following caspase-8-induced diabetes, Ab-4 drove a 6.7-fold increase in ß-cell mass. Lineage tracing suggests that this restoration of functional insulin-producing cells was at least partially driven by α-cell-to-ß-cell conversion. Following hyperglycemic onset in nonobese diabetic (NOD) mice, Ab-4 treatment promoted improvements in C-peptide levels and insulin+ islet mass was dramatically increased. Lastly, diabetic mice receiving human islet xenografts showed stable improvements in glycemic control and increased human insulin secretion.
Assuntos
Anticorpos Monoclonais/farmacologia , Diabetes Mellitus Experimental/terapia , Células Secretoras de Glucagon/efeitos dos fármacos , Hipoglicemiantes/farmacologia , Células Secretoras de Insulina/efeitos dos fármacos , Receptores de Glucagon/antagonistas & inibidores , Animais , Glicemia/metabolismo , Peptídeo C/metabolismo , Linhagem da Célula/efeitos dos fármacos , Transdiferenciação Celular/efeitos dos fármacos , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Experimental/imunologia , Diabetes Mellitus Experimental/patologia , Diabetes Mellitus Tipo 1/genética , Diabetes Mellitus Tipo 1/imunologia , Diabetes Mellitus Tipo 1/patologia , Diabetes Mellitus Tipo 1/terapia , Expressão Gênica , Glucagon/antagonistas & inibidores , Glucagon/metabolismo , Células Secretoras de Glucagon/metabolismo , Células Secretoras de Glucagon/patologia , Humanos , Insulina/metabolismo , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patologia , Ilhotas Pancreáticas/metabolismo , Ilhotas Pancreáticas/fisiologia , Transplante das Ilhotas Pancreáticas , Camundongos , Camundongos Endogâmicos NOD , Tamanho do Órgão/efeitos dos fármacos , Receptores de Glucagon/genética , Receptores de Glucagon/metabolismo , Resultado do TratamentoRESUMO
Dermal fibroblasts are an essential population of skin cells. They are not only responsible for synthesis and remodelling of the extracellular matrix of the dermis, but also communicate with other skin cells via autocrine and paracrine interactions. Skin-associated dermal adipocytes reside below the reticular dermis. Strong lipolysis is observed during the regression of dermal adipocytes. However, the nature of the local intercellular crosstalk in which lipids released by dermal adipocytes affecting the metabolism of adjacent skin fibroblasts has not yet been examined. With the use of a series of novel mouse models that allow us to manipulate adipocytes, we demonstrate that dermal adipocytes can modulate the structure of the dermis through regulating extracellular matrix production in dermal fibroblasts. Fatty acids released by dermal adipocytes are involved in this process. Our observations offer new in vivo insights into the role of dermal adipocyte-derived lipids in influencing metabolism of adjacent local cells in the skin through a paracrine effect in the microenvironment of the dermal adipocyte.
Assuntos
Adipócitos/metabolismo , Matriz Extracelular/metabolismo , Fibroblastos/metabolismo , Comunicação Parácrina , Tecido Adiposo Branco/citologia , Tecido Adiposo Branco/metabolismo , Animais , Microambiente Celular , Colágeno/genética , Colágeno Tipo I/genética , Cadeia alfa 1 do Colágeno Tipo I/genética , Colágeno Tipo III/genética , Células do Cúmulo , Dieta Hiperlipídica , Ácidos Graxos/metabolismo , Feminino , Expressão Gênica , Lipólise , Masculino , Camundongos , Pele/citologiaRESUMO
Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a class of antidiabetic drug used for the treatment of diabetes. These drugs are thought to lower blood glucose by blocking reabsorption of glucose by SGLT2 in the proximal convoluted tubules of the kidney. To investigate the effect of inhibiting SGLT2 on pancreatic hormones, we treated perfused pancreata from rats with chemically induced diabetes with dapagliflozin and measured the response of glucagon secretion by alpha cells in response to elevated glucose. In these type 1 diabetic rats, glucose stimulated glucagon secretion by alpha cells; this was prevented by dapagliflozin. Two models of type 2 diabetes, severely diabetic Zucker rats and db/db mice fed dapagliflozin, showed significant improvement of blood glucose levels and glucose disposal, with reduced evidence of glucagon signaling in the liver, as exemplified by reduced phosphorylation of hepatic cAMP-responsive element binding protein, reduced expression of phosphoenolpyruvate carboxykinase 2, increased hepatic glycogen, and reduced hepatic glucose production. Plasma glucagon levels did not change significantly. However, dapagliflozin treatment reduced the expression of the liver glucagon receptor. Dapagliflozin in rodents appears to lower blood glucose levels in part by suppressing hepatic glucagon signaling through down-regulation of the hepatic glucagon receptor.
Assuntos
Compostos Benzidrílicos/farmacologia , Diabetes Mellitus Experimental/tratamento farmacológico , Glucagon/metabolismo , Glucosídeos/farmacologia , Hipoglicemiantes/farmacologia , Transdução de Sinais/efeitos dos fármacos , Animais , Glicemia/efeitos dos fármacos , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Regulação para Baixo/efeitos dos fármacos , Células Secretoras de Glucagon/efeitos dos fármacos , Células Secretoras de Glucagon/metabolismo , Glucose/metabolismo , Túbulos Renais Proximais/efeitos dos fármacos , Túbulos Renais Proximais/metabolismo , Masculino , Camundongos , Ratos , Ratos Sprague-Dawley , Ratos Zucker , Roedores/metabolismo , Transportador 2 de Glucose-Sódio/metabolismoRESUMO
Insulin monotherapy can neither maintain normoglycemia in type 1 diabetes (T1D) nor prevent the long-term damage indicated by elevated glycation products in blood, such as glycated hemoglobin (HbA1c). Here we find that hyperglycemia, when unaccompanied by an acute increase in insulin, enhances itself by paradoxically stimulating hyperglucagonemia. Raising glucose from 5 to 25 mM without insulin enhanced glucagon secretion â¼two- to fivefold in InR1-G9 α cells and â¼18-fold in perfused pancreata from insulin-deficient rats with T1D. Mice with T1D receiving insulin treatment paradoxically exhibited threefold higher plasma glucagon during hyperglycemic surges than during normoglycemic intervals. Blockade of glucagon action with mAb Ac, a glucagon receptor (GCGR) antagonizing antibody, maintained glucose below 100 mg/dL and HbA1c levels below 4% in insulin-deficient mice with T1D. In rodents with T1D, hyperglycemia stimulates glucagon secretion, up-regulating phosphoenolpyruvate carboxykinase and enhancing hyperglycemia. GCGR antagonism in mice with T1D normalizes glucose and HbA1c, even without insulin.
Assuntos
Anticorpos Monoclonais/uso terapêutico , Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Experimental/patologia , Diabetes Mellitus Tipo 1/tratamento farmacológico , Diabetes Mellitus Tipo 1/patologia , Insulina/uso terapêutico , Receptores de Glucagon/imunologia , Animais , Anticorpos Monoclonais/farmacologia , Glicemia/metabolismo , Diabetes Mellitus Experimental/sangue , Diabetes Mellitus Tipo 1/sangue , Feminino , Glucagon/metabolismo , Humanos , Camundongos , Camundongos Endogâmicos NOD , Comunicação Parácrina/efeitos dos fármacos , Ratos , Ratos ZuckerRESUMO
To determine the role of glucagon action in diet-induced and genetic type 2 diabetes (T2D), we studied high-fat-diet-induced obese (DIO) and leptin receptor-defective (LepR(-/-)) rodents with and without glucagon receptors (GcgRs). DIO and LepR(-/-),GcgR(+/+) mice both developed hyperinsulinemia, increased liver sterol response element binding protein 1c, and obesity. DIO GcgR(+/+) mice developed mild T2D, whereas LepR(-/-),GcgR(+/+) mice developed severe T2D. High-fat-fed (HFF) glucagon receptor-null mice did not develop hyperinsulinemia, increased liver sterol response element binding protein 1c mRNA, or obesity. Insulin treatment of HFF GcgR(-/-) to simulate HFF-induced hyperinsulinemia caused obesity and mild T2D. LepR(-/-),GcgR(-/-) did not develop hyperinsulinemia or hyperglycemia. Adenoviral delivery of GcgR to GcgR(-/-),LepR(-/-) mice caused the severe hyperinsulinemia and hyperglycemia of LepR(-/-) mice to appear. Spontaneous disappearance of the GcgR transgene abolished the hyperinsulinemia and hyperglycemia. In conclusion, T2D hyperglycemia requires unsuppressible hyperglucagonemia from insulin-resistant α cells and is prevented by glucagon suppression or blockade.
Assuntos
Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/patologia , Células Secretoras de Glucagon/patologia , Hiperglicemia/complicações , Hiperglicemia/patologia , Insulina/farmacologia , Animais , Glicemia/metabolismo , Temperatura Corporal/efeitos dos fármacos , Peso Corporal/efeitos dos fármacos , Linhagem Celular , Ceramidas/farmacologia , Cricetinae , Dieta , Modelos Animais de Doenças , Comportamento Alimentar/efeitos dos fármacos , Glucagon/metabolismo , Células Secretoras de Glucagon/efeitos dos fármacos , Células Secretoras de Glucagon/metabolismo , Hiperglicemia/sangue , Hiperinsulinismo/sangue , Hiperinsulinismo/complicações , Hiperinsulinismo/patologia , Insulina/sangue , Insulina/genética , Células Secretoras de Insulina/efeitos dos fármacos , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patologia , Lipogênese/efeitos dos fármacos , Masculino , Camundongos Endogâmicos C57BL , RNA Mensageiro/sangue , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Receptores de Glucagon/metabolismoRESUMO
Glucagon plays important roles in normal glucose homeostasis and in metabolic abnormalities, particularly diabetes. Glucagon excess, rather than insulin deficiency, is essential for the development of diabetes for several reasons. Glucagon increases hepatic glucose and ketone production, the catabolic features of insulin deficiency. Hyperglucagonaemia is present in every form of diabetes. Beta cell destruction in glucagon receptor null mice does not cause diabetes unless mice are administered adenovirus encoding the glucagon receptor. In rodent studies the glucagon suppressors leptin and glucagon receptor antibody suppressed all catabolic manifestations of diabetes during insulin deficiency. Insulin prevents hyperglycaemia; however, insulin monotherapy cannot cure diabetes such that non-diabetic glucose homeostasis is achieved. Glucose-responsive beta cells normally regulate alpha cells, and diminished insulin action on alpha cells will favour hypersecretion of glucagon by the alpha cells, thus altering the insulin:glucagon ratio. Treating diabetes by suppression of glucagon, with leptin or antibody against the glucagon receptor, normalised glucose level (without glycaemic volatility) and HbA1c. Glucagon suppression also improved insulin sensitivity and glucose tolerance. If these results can be translated to humans, suppression of glucagon action will represent a step forward in the treatment of diabetes. This review summarises a presentation given at the 'Novel data on glucagon' symposium at the 2015 annual meeting of the EASD. It is accompanied by two other reviews on topics from this symposium (by Mona Abraham and Tony Lam, DOI: 10.1007/s00125-016-3950-3 , and by Russell Miller and Morris Birnbaum, DOI: 10.1007/s00125-016-3955-y ) and an overview by the Session Chair, Isabel Valverde (DOI: 10.1007/s00125-016-3946-z ).
Assuntos
Diabetes Mellitus/metabolismo , Diabetes Mellitus/patologia , Glucagon/metabolismo , Animais , Hemoglobinas Glicadas/metabolismo , Humanos , Insulina/metabolismo , CamundongosRESUMO
Although insulin monotherapy prevents death from ketoacidosis, it does not prevent either the hyperglycemic surges or the hypoglycemic plunges of glucose levels that plague the majority of patients with type 1 diabetes. However, significant improvements have occurred with the combination of continuous insulin delivery matched by continuous glucose monitoring, but the technology is not available for all patients, requires extensive education, is expensive and moreover, while much better than standard care, it almost never reduces haemoglobin A1c (HbA1c ) to below 6%. This may indicate that an improved diabetes therapy involving antagonism of glucagon action will for the first time control glucose levels to normal and eradicate the long-term complications of diabetes. Although one can never predict that results in animals will be reproduced in humans, the available evidence suggests that patients with type 1 and type 2 diabetes may expect far superior control of the metabolic abnormalities without the need for significant monitoring of glucose, a very important but expensive part of any insulin regimen.
Assuntos
Diabetes Mellitus Tipo 1/tratamento farmacológico , Diabetes Mellitus Tipo 2/tratamento farmacológico , Glucagon/antagonistas & inibidores , Hipoglicemiantes/uso terapêutico , HumanosRESUMO
To determine unambiguously if suppression of glucagon action will eliminate manifestations of diabetes, we expressed glucagon receptors in livers of glucagon receptor-null (GcgR(-/-)) mice before and after ß-cell destruction by high-dose streptozotocin. Wild type (WT) mice developed fatal diabetic ketoacidosis after streptozotocin, whereas GcgR(-/-) mice with similar ß-cell destruction remained clinically normal without hyperglycemia, impaired glucose tolerance, or hepatic glycogen depletion. Restoration of receptor expression using adenovirus containing the GcgR cDNA restored hepatic GcgR, phospho-cAMP response element binding protein (P-CREB), and phosphoenol pyruvate carboxykinase, markers of glucagon action, rose dramatically and severe hyperglycemia appeared. When GcgR mRNA spontaneously disappeared 7 d later, P-CREB declined and hyperglycemia disappeared. In conclusion, the metabolic manifestations of diabetes cannot occur without glucagon action and, once present, disappear promptly when glucagon action is abolished. Glucagon suppression should be a major therapeutic goal in diabetes.
Assuntos
Diabetes Mellitus Experimental/metabolismo , Glucagon/metabolismo , Insulina/deficiência , Fígado/metabolismo , Adenoviridae , Animais , Glicemia , Cromatografia Gasosa , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Primers do DNA/genética , Ensaio de Imunoadsorção Enzimática , Vetores Genéticos/genética , Immunoblotting , Espectrometria de Massas , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Reação em Cadeia da Polimerase em Tempo Real , Receptores de Glucagon/genética , Receptores de Glucagon/metabolismoRESUMO
The glucagon receptor (GCGR) in the kidney is expressed in nephron tubules. In humans and animal models with chronic kidney disease, renal GCGR expression is reduced. However, the role of kidney GCGR in normal renal function and in disease development has not been addressed. Here, we examined its role by analyzing mice with constitutive or conditional kidney-specific loss of the Gcgr. Adult renal Gcgr knockout mice exhibit metabolic dysregulation and a functional impairment of the kidneys. These mice exhibit hyperaminoacidemia associated with reduced kidney glucose output, oxidative stress, enhanced inflammasome activity, and excess lipid accumulation in the kidney. Upon a lipid challenge, they display maladaptive responses with acute hypertriglyceridemia and chronic proinflammatory and profibrotic activation. In aged mice, kidney Gcgr ablation elicits widespread renal deposition of collagen and fibronectin, indicative of fibrosis. Taken together, our findings demonstrate an essential role of the renal GCGR in normal kidney metabolic and homeostatic functions. Importantly, mice deficient for kidney Gcgr recapitulate some of the key pathophysiological features of chronic kidney disease.
Assuntos
Receptores de Glucagon , Insuficiência Renal Crônica , Humanos , Animais , Camundongos , Receptores de Glucagon/metabolismo , Regulação para Baixo , Camundongos Knockout , Rim/metabolismo , Homeostase/fisiologia , LipídeosRESUMO
Partial leptin reduction can induce significant weight loss, while weight loss contributes to partial leptin reduction. The cause-and-effect relationship between leptin reduction and weight loss remains to be further elucidated. Here, we show that FGF21 and the glucagon-like peptide 1 receptor (GLP-1R) agonist liraglutide rapidly induced a reduction in leptin. This leptin reduction contributed to the beneficial effects of GLP-1R agonism in metabolic health, as transgenically maintaining leptin levels during treatment partially curtailed the beneficial effects seen with these agonists. Moreover, a higher degree of leptin reduction during treatment, induced by including a leptin neutralizing antibody with either FGF21 or liraglutide, synergistically induced greater weight loss and better glucose tolerance in diet-induced obese mice. Furthermore, upon cessation of either liraglutide or FGF21 treatment, the expected immediate weight regain was observed, associated with a rapid increase in circulating leptin levels. Prevention of this leptin surge with leptin neutralizing antibodies slowed down weight gain and preserved better glucose tolerance. Mechanistically, a significant reduction in leptin induced a higher degree of leptin sensitivity in hypothalamic neurons. Our observations support a model that postulates that a reduction of leptin levels is a necessary prerequisite for substantial weight loss, and partial leptin reduction is a viable strategy to treat obesity and its associated insulin resistance.
Assuntos
Leptina , Liraglutida , Animais , Camundongos , Leptina/metabolismo , Liraglutida/farmacologia , Obesidade , Redução de Peso , Glucose/metabolismo , Receptor do Peptídeo Semelhante ao Glucagon 1/metabolismoRESUMO
Adipogenin (Adig) is an evolutionarily conserved microprotein and is highly expressed in adipose tissues and testis. Here, we identify Adig as a critical regulator for lipid droplet formation in adipocytes. We determine that Adig interacts directly with seipin, leading to the formation of a rigid complex. We solve the structure of the seipin/Adig complex by Cryo-EM at 2.98Å overall resolution. Surprisingly, seipin can form two unique oligomers, undecamers and dodecamers. Adig selectively binds to the dodecameric seipin complex. We further find that Adig promotes seipin assembly by stabilizing and bridging adjacent seipin subunits. Functionally, Adig plays a key role in generating lipid droplets in adipocytes. In mice, inducible overexpression of Adig in adipocytes substantially increases fat mass, with enlarged lipid droplets. It also elevates thermogenesis during cold exposure. In contrast, inducible adipocyte-specific Adig knockout mice manifest aberrant lipid droplet formation in brown adipose tissues and impaired cold tolerance.
RESUMO
In nonobese diabetic mice with uncontrolled type 1 diabetes, leptin therapy alone or combined with low-dose insulin reverses the catabolic state through suppression of hyperglucagonemia. Additionally, it mimics the anabolic actions of insulin monotherapy and normalizes hemoglobin A1c with far less glucose variability. We show that leptin therapy, like insulin, normalizes the levels of a wide array of hepatic intermediary metabolites in multiple chemical classes, including acylcarnitines, organic acids (tricarboxylic acid cycle intermediates), amino acids, and acyl CoAs. In contrast to insulin monotherapy, however, leptin lowers both lipogenic and cholesterologenic transcription factors and enzymes and reduces plasma and tissue lipids. The results imply that leptin administration may have multiple short- and long-term advantages over insulin monotherapy for type 1 diabetes.
Assuntos
Diabetes Mellitus Tipo 1/tratamento farmacológico , Insulina/deficiência , Leptina/uso terapêutico , Adenilato Quinase/metabolismo , Animais , Glicemia/metabolismo , Diabetes Mellitus Tipo 1/sangue , Implantes de Medicamento , Regulação da Expressão Gênica , Glucagon/sangue , Insulina/administração & dosagem , Insulina/uso terapêutico , Leptina/administração & dosagem , Fígado/enzimologia , Metaboloma , Camundongos , Camundongos Endogâmicos NOD , Fosforilação , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas Recombinantes/uso terapêutico , Triglicerídeos/sangueRESUMO
The G protein-coupled receptor 84 (GPR84), a medium-chain fatty acid receptor, has garnered attention because of its potential involvement in a range of metabolic conditions. However, the precise mechanisms underlying this effect remain elusive. Our study has shed light on the pivotal role of GPR84, revealing its robust expression and functional significance within brown adipose tissue (BAT). Mice lacking GPR84 exhibited increased lipid accumulation in BAT, rendering them more susceptible to cold exposure and displaying reduced BAT activity compared with their WT counterparts. Our in vitro experiments with primary brown adipocytes from GPR84-KO mice revealed diminished expression of thermogenic genes and reduced O2 consumption. Furthermore, the application of the GPR84 agonist 6-n-octylaminouracil (6-OAU) counteracted these effects, effectively reinstating the brown adipocyte activity. These compelling in vivo and in vitro findings converge to highlight mitochondrial dysfunction as the primary cause of BAT anomalies in GPR84-KO mice. The activation of GPR84 induced an increase in intracellular Ca2+ levels, which intricately influenced mitochondrial respiration. By modulating mitochondrial Ca2+ levels and respiration, GPR84 acts as a potent molecule involved in BAT activity. These findings suggest that GPR84 is a potential therapeutic target for invigorating BAT and ameliorating metabolic disorders.
Assuntos
Adipócitos Marrons , Cálcio , Receptores Acoplados a Proteínas G , Animais , Camundongos , Adipócitos Marrons/metabolismo , Tecido Adiposo Marrom/metabolismo , Cálcio/metabolismo , Ácidos Graxos/metabolismo , Camundongos Endogâmicos C57BL , Transdução de Sinais , Termogênese/genética , Receptores Acoplados a Proteínas G/metabolismo , Mitocôndrias/metabolismo , Mitocôndrias/fisiologiaRESUMO
The disease progression of the metabolic syndrome is associated with prolonged hyperlipidemia and insulin resistance, eventually giving rise to impaired insulin secretion, often concomitant with hypoadiponectinemia. As an adipose tissue derived hormone, adiponectin is beneficial for insulin secretion and ß cell health and differentiation. However, the down-stream pathway of adiponectin in the pancreatic islets has not been studied extensively. Here, along with the overall reduction of endocrine pancreatic function in islets from adiponectin KO mice, we examine PPARα and HNF4α as additional down-regulated transcription factors during a prolonged metabolic challenge. To elucidate the function of ß cell-specific PPARα and HNF4α expression, we developed doxycycline inducible pancreatic ß cell-specific PPARα (ß-PPARα) and HNF4α (ß-HNF4α) overexpression mice. ß-PPARα mice exhibited improved protection from lipotoxicity, but elevated ß-oxidative damage in the islets, and also displayed lowered phospholipid levels and impaired glucose-stimulated insulin secretion. ß-HNF4α mice showed a more severe phenotype when compared to ß-PPARα mice, characterized by lower body weight, small islet mass and impaired insulin secretion. RNA-sequencing of the islets of these models highlights overlapping yet unique roles of ß-PPARα and ß-HNF4α. Given that ß-HNF4α potently induces PPARα expression, we define a novel adiponectin-HNF4α-PPARα cascade. We further analyzed downstream genes consistently regulated by this axis. Among them, the islet amyloid polypeptide (IAPP) gene is an important target and accumulates in adiponectin KO mice. We propose a new mechanism of IAPP aggregation in type 2 diabetes through reduced adiponectin action.
Assuntos
Diabetes Mellitus Tipo 2 , Células Secretoras de Insulina , Animais , Camundongos , Adiponectina/genética , Adiponectina/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Insulina/metabolismo , Células Secretoras de Insulina/metabolismo , PPAR alfa/genética , PPAR alfa/metabolismoRESUMO
Adiponectin is a secretory protein, primarily produced in adipocytes. However, low but detectable expression of adiponectin can be observed in cell types beyond adipocytes, particularly in kidney tubular cells, but its local renal role is unknown. We assessed the impact of renal adiponectin by utilizing male inducible kidney tubular cell-specific adiponectin overexpression or knockout mice. Kidney-specific adiponectin overexpression induces a doubling of phosphoenolpyruvate carboxylase expression and enhanced pyruvate-mediated glucose production, tricarboxylic acid cycle intermediates and an upregulation of fatty acid oxidation (FAO). Inhibition of FAO reduces the adiponectin-induced enhancement of glucose production, highlighting the role of FAO in the induction of renal gluconeogenesis. In contrast, mice lacking adiponectin in the kidney exhibit enhanced glucose tolerance, lower utilization and greater accumulation of lipid species. Hence, renal adiponectin is an inducer of gluconeogenesis by driving enhanced local FAO and further underlines the important systemic contribution of renal gluconeogenesis.
Assuntos
Adiponectina , Gluconeogênese , Rim , Animais , Masculino , Camundongos , Adiponectina/genética , Adiponectina/metabolismo , Gluconeogênese/genética , Gluconeogênese/fisiologia , Glucose/metabolismo , Rim/metabolismo , Fígado/metabolismo , Camundongos Knockout , Ácido Pirúvico/metabolismoRESUMO
Despite their high degree of effectiveness in the management of psychiatric conditions, exposure to antipsychotic drugs, including olanzapine and risperidone, is frequently associated with substantial weight gain and the development of diabetes. Even before weight gain, a rapid rise in circulating leptin concentrations can be observed in most patients taking antipsychotic drugs. To date, the contribution of this hyperleptinemia to weight gain and metabolic deterioration has not been defined. Here, with an established mouse model that recapitulates antipsychotic drug-induced obesity and insulin resistance, we not only confirm that hyperleptinemia occurs before weight gain but also demonstrate that hyperleptinemia contributes directly to the development of obesity and associated metabolic disorders. By suppressing the rise in leptin through the use of a monoclonal leptin-neutralizing antibody, we effectively prevented weight gain, restored glucose tolerance, and preserved adipose tissue and liver function in antipsychotic drug-treated mice. Mechanistically, suppressing excess leptin resolved local tissue and systemic inflammation typically associated with antipsychotic drug treatment. We conclude that hyperleptinemia is a key contributor to antipsychotic drug-associated weight gain and metabolic deterioration. Leptin suppression may be an effective approach to reducing the undesirable side effects of antipsychotic drugs.
Assuntos
Antipsicóticos , Doenças Metabólicas , Humanos , Camundongos , Animais , Antipsicóticos/efeitos adversos , Leptina/metabolismo , Obesidade/metabolismo , Aumento de PesoRESUMO
To determine whether adipocyte storage capacity influences the onset and severity of type 2 diabetes and other components of the metabolic syndrome, we made normal and db/db mice resistant to obesity by overexpressing leptin receptor-b on the aP2-Lepr-b promoter. On a 4% diet, these mice have no phenotype, but on a 60% fat diet, they resist diet-induced obesity because constitutive adipocyte-specific overexpression of Lepr-b prevents obesity via the antilipogenic autocrine/paracrine action of leptin on adipocytes. After 8 months on the same 60% fat diet, body fat of transgenic mice was 70% below WT controls. Cardiac and liver fat was elevated in the transgenics, and their hyperinsulinemia was more marked, suggesting greater insulin resistance. The aP2-Lepr-b transgene also prevented obesity in db/db mice; at 10 weeks of age their body fat was half that of the db/db mice. This lack of obesity was attributable to reduced expression of sterol regulatory element binding protein-1c and its target lipogenic enzymes in adipose tissue and a 6-fold increase in Pref-1 mRNA. Severe diabetes was present in transgenics at 4 weeks of age, 10 weeks before db/db controls. Echocardiographic evidence of cardiomyopathy appeared at 10 weeks, weeks before the db/db mice. Histologically, loss of beta cells and myocardial fibrosis was present in the transgenic group at least 6 weeks before the db/db mice. These results suggest that the expression level of genes that regulate the adipogenic response to overnutrition profoundly influences the age of onset and severity of diet-induced type 2 diabetes and co-morbidities.
Assuntos
Adipogenia/genética , Diabetes Mellitus Tipo 2/genética , Predisposição Genética para Doença/genética , Síndrome Metabólica/genética , Obesidade/genética , Receptores para Leptina/genética , Adipócitos/metabolismo , Tecido Adiposo/metabolismo , Animais , Proteínas de Ligação ao Cálcio , Cardiomiopatias/genética , Cardiomiopatias/patologia , Glucagon/análise , Glucagon/metabolismo , Insulina/análise , Insulina/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/genética , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Camundongos , Camundongos Transgênicos , Pâncreas/química , Pâncreas/metabolismo , Regiões Promotoras Genéticas , RNA Mensageiro/análise , RNA Mensageiro/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 1/genética , Proteína de Ligação a Elemento Regulador de Esterol 1/metabolismo , TransgenesRESUMO
Terminally ill insulin-deficient rodents with uncontrolled diabetes due to autoimmune or chemical destruction of beta-cells were made hyperleptinemic by adenoviral transfer of the leptin gene. Within approximately 10 days their severe hyperglycemia and ketosis were corrected. Despite the lack of insulin, moribund animals resumed linear growth and appeared normal. Normoglycemia persisted 10-80 days without other treatment; normal physiological conditions lasted for approximately 175 days despite reappearance of moderate hyperglycemia. Inhibition of gluconeogenesis by suppression of hyperglucagonemia and reduction of hepatic cAMP response element-binding protein, phoshoenolpyruvate carboxykinase, and peroxisome proliferator-activated receptor-gamma-coactivator-1alpha may explain the anticatabolic effect. Up-regulation of insulin-like growth factor 1 (IGF-1) expression and plasma levels and increasing IGF-1 receptor phosphorylation in muscle may explain the increased insulin receptor substrate 1, PI3K, and ERK phosphorylation in skeletal muscle. These findings suggest that leptin reverses the catabolic consequences of total lack of insulin, potentially by suppressing glucagon action on liver and enhancing the insulinomimetic actions of IGF-1 on skeletal muscle, and suggest strategies for making type 1 diabetes insulin-independent.
Assuntos
Diabetes Mellitus Tipo 1/metabolismo , Insulina/deficiência , Aloxano/farmacologia , Animais , Complicações do Diabetes/metabolismo , Diabetes Mellitus Tipo 1/induzido quimicamente , Regulação para Baixo , Glucagon/metabolismo , Insulina/metabolismo , Fator de Crescimento Insulin-Like I/metabolismo , Fígado/metabolismo , Camundongos , Ratos , Fator de Transcrição STAT3/metabolismo , Transdução de Sinais , Estreptozocina/farmacologiaRESUMO
Iron overload is positively associated with diabetes risk. However, the role of iron in adipose tissue remains incompletely understood. Here, we report that transferrin-receptor-1-mediated iron uptake is differentially required for distinct subtypes of adipocytes. Notably, adipocyte-specific transferrin receptor 1 deficiency substantially protects mice from high-fat-diet-induced metabolic disorders. Mechanistically, low cellular iron levels have a positive impact on the health of the white adipose tissue and can restrict lipid absorption from the intestine through modulation of vesicular transport in enterocytes following high-fat diet feeding. Specific reduction of adipocyte iron by AAV-mediated overexpression of the iron exporter Ferroportin1 in adult mice effectively mimics these protective effects. In summary, our studies highlight an important role of adipocyte iron in the maintenance of systemic metabolism through an adipocyte-enterocyte axis, offering an additional level of control over caloric influx into the system after feeding by regulating intestinal lipid absorption.
Assuntos
Adipócitos , Tecido Adiposo , Adipócitos/metabolismo , Tecido Adiposo/metabolismo , Animais , Dieta Hiperlipídica , Ferro/metabolismo , Lipídeos , Camundongos , Obesidade/metabolismoRESUMO
Adiponectin is essential for the regulation of tissue substrate utilization and systemic insulin sensitivity. Clinical studies have suggested a positive association of circulating adiponectin with healthspan and lifespan. However, the direct effects of adiponectin on promoting healthspan and lifespan remain unexplored. Here, we are using an adiponectin null mouse and a transgenic adiponectin overexpression model. We directly assessed the effects of circulating adiponectin on the aging process and found that adiponectin null mice display exacerbated age-related glucose and lipid metabolism disorders. Moreover, adiponectin null mice have a significantly shortened lifespan on both chow and high-fat diet. In contrast, a transgenic mouse model with elevated circulating adiponectin levels has a dramatically improved systemic insulin sensitivity, reduced age-related tissue inflammation and fibrosis, and a prolonged healthspan and median lifespan. These results support a role of adiponectin as an essential regulator for healthspan and lifespan.