RESUMO
Exenatide, a glucagon-like peptide-1 receptor agonist, induces insulin secretion. Its role in insulin clearance has not been adequately examined. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes hepatic insulin clearance to maintain insulin sensitivity. Feeding C57BL/6J mice a high-fat diet down-regulates hepatic Ceacam1 transcription to cause hyperinsulinemia, insulin resistance, and hepatic steatosis, as in Ceacam1 null mice (Cc1-/- ). Thus, we tested whether exenatide regulates Ceacam1 expression in high-fat diet-fed mice and whether this contributes to its insulin sensitizing effect. Exenatide (100 nM) induced the transcriptional activity of wild-type Ceacam1 promoter but not the constructs harboring block mutations of peroxisome proliferator-activated receptor response element and retinoid X receptor alpha, individually or collectively, in HepG2 human hepatoma cells. Chromatin immunoprecipitation analysis demonstrated binding of peroxisome proliferator-activated receptor gamma to Ceacam1 promoter in response to rosiglitazone and exenatide. Consistently, exenatide induced Ceacam1 messenger RNA expression within 12 hours in the absence but not in the presence of the glucagon-like peptide-1 receptor antagonist exendin 9-39. Exenatide (20 ng/g body weight once daily intraperitoneal injection in the last 30 days of feeding) restored hepatic Ceacam1 expression and insulin clearance to curb diet-induced metabolic abnormalities and steatohepatitis in wild-type but not Cc1-/- mice fed a high-fat diet for 2 months. Conclusion: Exenatide promotes insulin clearance in parallel with insulin secretion to prevent chronic hyperinsulinemia and the resulting hepatic steatosis, and this contributes to its insulin sensitizing effect. Our data further highlight the relevance of physiologic insulin metabolism in maintaining insulin sensitivity and normal lipid metabolism. (Hepatology Communications 2018;2:35-47).
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AIMS/HYPOTHESIS: The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes insulin clearance. Mice with global null mutation (Cc1 -/-) or with liver-specific inactivation (L-SACC1) of Cc1 (also known as Ceacam1) gene display hyperinsulinaemia resulting from impaired insulin clearance, insulin resistance, steatohepatitis and obesity. Because increased lipolysis contributes to the metabolic phenotype caused by transgenic inactivation of CEACAM1 in the liver, we aimed to further investigate the primary role of hepatic CEACAM1-dependent insulin clearance in insulin and lipid homeostasis. To this end, we examined whether transgenic reconstitution of CEACAM1 in the liver of global Cc1 -/- mutant mice reverses their abnormal metabolic phenotype. METHODS: Insulin response was assessed by hyperinsulinaemic-euglycaemic clamp analysis and energy balance was analysed by indirect calorimetry. Mice were overnight-fasted and refed for 7 h to assess fatty acid synthase activity in the liver and the hypothalamus in response to insulin release during refeeding. RESULTS: Liver-based rescuing of CEACAM1 restored insulin clearance, plasma insulin level, insulin sensitivity and steatohepatitis caused by global deletion of Cc1. It also reversed the gain in body weight and total fat mass observed with Cc1 deletion, in parallel to normalising energy balance. Mechanistically, reversal of hyperphagia appeared to result from reducing fatty acid synthase activity and restoring insulin signalling in the hypothalamus. CONCLUSIONS/INTERPRETATION: Despite the potential confounding effects of deleting Cc1 from extrahepatic tissues, liver-based rescuing of CEACAM1 resulted in full normalisation of the metabolic phenotype, underscoring the key role that CEACAM1-dependent hepatic insulin clearance pathways play in regulating systemic insulin sensitivity, lipid homeostasis and energy balance.
Assuntos
Antígeno Carcinoembrionário/metabolismo , Fígado Gorduroso/metabolismo , Hiperinsulinismo/metabolismo , Fígado/metabolismo , Animais , Antígeno Carcinoembrionário/genética , Metabolismo Energético/genética , Metabolismo Energético/fisiologia , Ácido Graxo Sintases/genética , Ácido Graxo Sintases/metabolismo , Fígado Gorduroso/genética , Hiperinsulinismo/genética , Resistência à Insulina/genética , Resistência à Insulina/fisiologia , Lipólise/genética , Lipólise/fisiologia , Masculino , CamundongosRESUMO
AIMS/HYPOTHESIS: Cc2 -/- mice lacking the gene encoding the carcinoembryonic-antigen-related cell adhesion molecule 2 (Cc2 [also known as Ceacam2]) exhibit hyperphagia that leads to obesity and insulin resistance. This starts at 2 months of age in female mice. Male mutants maintain normal body weight and insulin sensitivity until the last age previously examined (7-8 months), owing to increased sympathetic tone to white adipose tissue and energy expenditure. The current study investigates whether insulin resistance develops in mutant male mice at a later age and whether this is accompanied by changes in insulin homeostasis. METHODS: Insulin response was assessed by insulin and glucose tolerance tests. Energy balance was analysed by indirect calorimetry. RESULTS: Male Cc2 -/- mice developed overt metabolic abnormalities at about 9 months of age. These include elevated global fat mass, hyperinsulinaemia and insulin resistance (as determined by glucose and insulin intolerance, fed hyperglycaemia and decreased insulin signalling pathways). Pair-feeding experiments showed that insulin resistance resulted from hyperphagia. Indirect calorimetry demonstrated that older mutant male mice had compromised energy expenditure. Despite increased insulin secretion caused by Cc2 deletion, chronic hyperinsulinaemia did not develop in mutant male mice until about 9 months of age, at which point insulin clearance began to decline substantially. This was probably mediated by a marked decrease in hepatic CEACAM1 expression. CONCLUSIONS/INTERPRETATION: The data demonstrate that at about 9 months of age, Cc2 -/- male mice develop a reduction in energy expenditure and energy imbalance which, combined with a progressive decrease in CEACAM1-dependent hepatic insulin clearance, causes chronic hyperinsulinaemia and sustained age-dependent insulin resistance. This represents a novel mechanistic underpinning of age-related impairment of hepatic insulin clearance.
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Antígenos CD/metabolismo , Moléculas de Adesão Celular/metabolismo , Resistência à Insulina/fisiologia , Insulina/metabolismo , Animais , Antígenos CD/genética , Moléculas de Adesão Celular/genética , Metabolismo Energético/genética , Metabolismo Energético/fisiologia , Hiperinsulinismo/genética , Hiperinsulinismo/metabolismo , Resistência à Insulina/genética , Masculino , Camundongos , Camundongos MutantesRESUMO
Impairment of insulin clearance is being increasingly recognized as a critical step in the development of insulin resistance and metabolic disease. The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes insulin clearance. Null deletion or liver-specific inactivation of Ceacam1 in mice causes a defect in insulin clearance, insulin resistance, steatohepatitis, and visceral obesity. Immunohistological analysis revealed reduction of hepatic CEACAM1 in obese subjects with fatty liver disease. Thus, we aimed to determine whether this occurs at the hepatocyte level in response to systemic extrahepatic factors and whether this holds across species. Northern and Western blot analyses demonstrate that CEACAM1 mRNA and protein levels are reduced in liver tissues of obese individuals compared to their lean age-matched counterparts. Furthermore, Western analysis reveals a comparable reduction of CEACAM1 protein in primary hepatocytes derived from the same obese subjects. Similar to humans, Ceacam1 mRNA level, assessed by quantitative RT-PCR analysis, is significantly reduced in the livers of obese Zucker (fa/fa, ZDF) and Koletsky (f/f) rats relative to their age-matched lean counterparts. These studies demonstrate that the reduction of hepatic CEACAM1 in obesity occurs at the level of hepatocytes and identify the reduction of hepatic CEACAM1 as a common denominator of obesity across multiple species.
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The pathogenesis of human non-alcoholic fatty liver disease (NAFLD) remains unclear, in particular in the context of its relationship to insulin resistance and visceral obesity. Work on the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) in mice has resolved some of the related questions. CEACAM1 promotes insulin clearance by enhancing the rate of uptake of the insulin-receptor complex. It also mediates a negative acute effect of insulin on fatty acid synthase activity. This positions CEACAM1 to coordinate the regulation of insulin and lipid metabolism. Fed a regular chow diet, global null mutation of Ceacam1 manifest hyperinsulinemia, insulin resistance, obesity, and steatohepatitis. They also develop spontaneous chicken-wire fibrosis, characteristic of non-alcoholic steatohepatitis. Reduction of hepatic CEACAM1 expression plays a significant role in the pathogenesis of diet-induced metabolic abnormalities, as bolstered by the protective effect of hepatic CEACAM1 gain-of-function against the metabolic response to dietary fat. Together, this emphasizes that loss of hepatic CEACAM1 links NAFLD to insulin resistance and obesity.
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Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) regulates insulin sensitivity by promoting hepatic insulin clearance and mediating suppression of fatty acid synthase activity. Feeding C57BL/6J male mice with a high-fat (HF) diet for 3-4 weeks triggered a >60% decrease in hepatic CEACAM1 levels to subsequently impair insulin clearance and cause systemic insulin resistance and hepatic steatosis. This study aimed at investigating whether lipolysis drives reduction in hepatic CEACAM1 and whether this constitutes a key mechanism leading to diet-induced metabolic abnormalities. Blocking lipolysis with a daily intraperitoneal injection of nicotinic acid in the last two days of a 30-day HF feeding regimen demonstrated that white adipose tissue (WAT)-derived fatty acids repressed hepatic CEACAM1-dependent regulation of insulin and lipid metabolism in 3-month-old male C57BL/6J mice. Adenoviral-mediated CEACAM1 redelivery countered the adverse metabolic effect of the HF diet on insulin resistance, hepatic steatosis, visceral obesity, and energy expenditure. It also reversed the effect of HF diet on inflammation and fibrosis in WAT and liver. This assigns a causative role for lipolysis-driven decrease in hepatic CEACAM1 level and its regulation of insulin and lipid metabolism in sustaining systemic insulin resistance, hepatic steatosis, and other abnormalities associated with excessive energy supply.
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Adipócitos/metabolismo , Antígeno Carcinoembrionário/fisiologia , Ácidos Graxos/metabolismo , Hepatócitos/metabolismo , Tecido Adiposo Branco/efeitos dos fármacos , Tecido Adiposo Branco/metabolismo , Tecido Adiposo Branco/patologia , Animais , Células Cultivadas , Dieta Hiperlipídica/efeitos adversos , Metabolismo Energético , Fibrose , Resistência à Insulina , Metabolismo dos Lipídeos , Masculino , Camundongos Endogâmicos C57BL , Niacina/farmacologia , Obesidade/etiologia , Obesidade/metabolismoRESUMO
High fat diet reduces the expression of CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1), a transmembrane glycoprotein that promotes insulin clearance and down-regulates fatty acid synthase activity in the liver upon its phosphorylation by the insulin receptor. Because peroxisome proliferator-activated receptor α (PPARα) transcriptionally suppresses CEACAM1 expression, we herein examined whether high fat down-regulates CEACAM1 expression in a PPARα-dependent mechanism. By activating PPARα, the lipid-lowering drug fenofibrate reverses dyslipidemia and improves insulin sensitivity in type 2 diabetes in part by promoting fatty acid oxidation. Despite reducing glucose-stimulated insulin secretion, fenofibrate treatment does not result in insulin insufficiency. To examine whether this is mediated by a parallel decrease in CEACAM1-dependent hepatic insulin clearance pathways, we fed wild-type and Pparα-/- null mice a high fat diet supplemented with either fenofibrate or Wy14643, a selective PPARα agonist, and examined their effect on insulin metabolism and action. We demonstrated that the decrease in insulin secretion by fenofibrate and Wy14643 is accompanied by reduction in insulin clearance in wild-type but not Pparα-/- mice, thereby maintaining normoinsulinemia and insulin sensitivity despite continuous high fat intake. Intact insulin secretion in L-CC1 mice with protected hepatic insulin clearance and CEACAM1 levels provides in vivo evidence that insulin secretion responds to changes in insulin clearance to maintain physiologic insulin and glucose homeostasis. These results also emphasize the relevant role of hepatic insulin extraction in regulating insulin sensitivity.
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Fenofibrato/farmacologia , Resistência à Insulina , Insulina/metabolismo , PPAR alfa/agonistas , Animais , Antígeno Carcinoembrionário/genética , Antígeno Carcinoembrionário/metabolismo , Secreção de Insulina , Camundongos , Camundongos Knockout , PPAR alfa/genética , PPAR alfa/metabolismo , Pirimidinas/farmacologiaRESUMO
Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is an Ig-ITIM superfamily member that regulates integrin αIIbß3 function. We hypothesized that its twin protein, CEACAM2, exerts a similar physiologic role in murine platelets. CEACAM2-deficient mice (Cc2-/-) displayed prolonged tail bleeding times and increased volume of blood loss. Cc2-/- platelets have moderate integrin αIIbß3-mediated functional defects with impaired kinetics of platelet spreading on fibrinogen and type I collagen and delayed kinetics in the retraction of fibrin clots in vitro. This functional integrin αIIbß3 defect could not be attributed to altered integrin αIIbß3 expression. Cc2-/- platelets displayed normal 'inside-out' signaling properties as demonstrated by normal agonist-induced binding of soluble fluorescein isothiocyanate (FITC)-fibrinogen and JON/A antibody binding. This data provides direct evidence that disruption of CEACAM2 induces a moderate integrin αIIbß3-mediated platelet function defect, and that CEACAM2 is essential to maintain a normal integrin αIIbß3-mediated platelet function.
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Antígenos CD/metabolismo , Plaquetas/metabolismo , Moléculas de Adesão Celular/metabolismo , Complexo Glicoproteico GPIIb-IIIa de Plaquetas/metabolismo , Animais , Antígenos CD/genética , Tempo de Sangramento , Plaquetas/ultraestrutura , Moléculas de Adesão Celular/genética , Retração do Coágulo , Camundongos , Camundongos Knockout , Adesividade Plaquetária , Ligação Proteica , Transdução de SinaisRESUMO
Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes hepatic insulin clearance. Consistently, mice with null mutation of Ceacam1 (Cc1(-/-)) exhibit impaired insulin clearance with increased lipid production in liver and redistribution to white adipose tissue, leading to visceral obesity at 2 months of age. When the mutation is propagated on the C57/BL6J genetic background, total fat mass rises significantly with age, and glucose intolerance and systemic insulin resistance develop at 6 months of age. This study was carried out to determine the mechanisms underlying the marked increase in total fat mass in 6-month-old mutants. Indirect calorimetry analysis showed that Cc1(-/-) mice develop hyperphagia and a significant reduction in physical activity, in particular in the early hours of the dark cycle, during which energy expenditure is only slightly lower than in wild-type mice. They also exhibit increased triglyceride accumulation in skeletal muscle, due in part to incomplete fatty acid ß-oxidation. Mechanistically, hypothalamic leptin signaling is reduced, as demonstrated by blunted STAT3 phosphorylation in coronal sections in response to an intracerebral ventricular injection of leptin. Hypothalamic fatty-acid synthase activity is also elevated in the mutants. Together, the data show that the increase in total fat mass in Cc1(-/-) mice is mainly attributed to hyperphagia and reduced spontaneous physical activity. Although the contribution of the loss of CEACAM1 from anorexigenic proopiomelanocortin neurons in the arcuate nucleus is unclear, leptin resistance and elevated hypothalamic fatty-acid synthase activity could underlie altered energy balance in these mice.
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Antígeno Carcinoembrionário/genética , Antígeno Carcinoembrionário/metabolismo , Leptina/metabolismo , Obesidade/etiologia , Animais , Núcleo Arqueado do Hipotálamo/metabolismo , Moléculas de Adesão Celular/deficiência , Moléculas de Adesão Celular/genética , Moléculas de Adesão Celular/metabolismo , Metabolismo Energético , Ácidos Graxos/metabolismo , Deleção de Genes , Hiperfagia/etiologia , Hiperfagia/genética , Hiperfagia/metabolismo , Hipotálamo/metabolismo , Resistência à Insulina , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Músculo Esquelético/metabolismo , Mutação , Obesidade/genética , Obesidade/metabolismo , Pró-Opiomelanocortina/metabolismo , Transdução de Sinais , Triglicerídeos/metabolismoRESUMO
Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is expressed at high levels in the hepatocyte, consistent with its role in promoting insulin clearance in liver. CEACAM1 also mediates a negative acute effect of insulin on fatty acid synthase activity. Western blot analysis reveals lower hepatic CEACAM1 expression during fasting. Treating of rat hepatoma FAO cells with Wy14,643, an agonist of peroxisome proliferator-activated receptor α (PPARα), rapidly reduces Ceacam1 mRNA and CEACAM1 protein levels within 1 and 2 h, respectively. Luciferase reporter assay shows a decrease in the promoter activity of both rat and mouse genes by Pparα activation, and 5'-deletion and block substitution analyses reveal that the Pparα response element between nucleotides -557 and -543 is required for regulation of the mouse promoter activity. Chromatin immunoprecipitation analysis demonstrates binding of liganded Pparα toCeacam1promoter in liver lysates ofPparα(+/+), but notPparα(-/-)mice fed a Wy14,643-supplemented chow diet. Consequently, Wy14,643 feeding reduces hepatic Ceacam1 mRNA and CEACAM1 protein levels, thus decreasing insulin clearance to compensate for compromised insulin secretion and maintain glucose homeostasis and insulin sensitivity in wild-type mice. Together, the data show that the low hepatic CEACAM1 expression at fasting is mediated by Pparα-dependent mechanisms. Changes in CEACAM1 expression contribute to the coordination of fatty acid oxidation and insulin action in the fasting-refeeding transition.
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Antígenos CD/genética , Moléculas de Adesão Celular/genética , Jejum , Ácidos Graxos/metabolismo , Regulação da Expressão Gênica , Fígado/metabolismo , PPAR alfa/metabolismo , Animais , Antígenos CD/análise , Antígenos CD/metabolismo , Moléculas de Adesão Celular/análise , Moléculas de Adesão Celular/metabolismo , Células Cultivadas , Deleção de Genes , Insulina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Oxirredução , Regiões Promotoras Genéticas , RNA Mensageiro/genética , RatosRESUMO
Carcinoembryonic antigen-related cell adhesion molecule 2 (CEACAM2) regulates food intake as demonstrated by hyperphagia in mice with the Ceacam2 null mutation (Cc2(-/-)). This study investigated whether CEACAM2 also regulates insulin secretion. Ceacam2 deletion caused an increase in ß-cell secretory function, as assessed by hyperglycemic clamp analysis, without affecting insulin response. Although CEACAM2 is expressed in pancreatic islets predominantly in non-ß-cells, basal plasma levels of insulin, glucagon and somatostatin, islet areas, and glucose-induced insulin secretion in pooled Cc2(-/-) islets were all normal. Consistent with immunofluorescence analysis showing CEACAM2 expression in distal intestinal villi, Cc2(-/-) mice exhibited a higher release of oral glucose-mediated GLP-1, an incretin that potentiates insulin secretion in response to glucose. Compared with wild type, Cc2(-/-) mice also showed a higher insulin excursion during the oral glucose tolerance test. Pretreating with exendin(9-39), a GLP-1 receptor antagonist, suppressed the effect of Ceacam2 deletion on glucose-induced insulin secretion. Moreover, GLP-1 release into the medium of GLUTag enteroendocrine cells was increased with siRNA-mediated Ceacam2 down-regulation in parallel to an increase in Ca(2+) entry through L-type voltage-dependent Ca(2+) channels. Thus, CEACAM2 regulates insulin secretion, at least in part, by a GLP-1-mediated mechanism, independent of confounding metabolic factors.
Assuntos
Moléculas de Adesão Celular/deficiência , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Glucose/farmacologia , Animais , Antígenos CD/metabolismo , Canais de Cálcio Tipo L/metabolismo , Moléculas de Adesão Celular/metabolismo , Imunofluorescência , Teste de Tolerância a Glucose , Insulina/metabolismo , Secreção de Insulina , Ilhotas Pancreáticas/efeitos dos fármacos , Ilhotas Pancreáticas/metabolismo , Masculino , Camundongos , VigíliaRESUMO
CEACAM1 promotes insulin extraction, an event that occurs mainly in liver. Phenocopying global Ceacam1 null mice (Cc1(-/-) ), C57/BL6J mice fed a high-fat (HF) diet exhibited reduced hepatic CEACAM1 levels and impaired insulin clearance, followed by hyperinsulinemia, insulin resistance, and visceral obesity. Conversely, forced liver-specific expression of CEACAM1 protected insulin sensitivity and energy expenditure, and limited gain in total fat mass by HF diet in L-CC1 mice. Because CEACAM1 protein is barely detectable in white adipose tissue (WAT), we herein investigated whether hepatic CEACAM1-dependent insulin clearance pathways regulate adipose tissue biology in response to dietary fat. While HF diet caused a similar body weight gain in L-CC1, this effect was delayed and less intense relative to wild-type (WT) mice. Histological examination revealed less expansion of adipocytes in L-CC1 than WT by HF intake. Immunofluorescence analysis demonstrated a more limited recruitment of crown-like structures, and qRT-PCR analysis showed no significant rise in TNFα mRNA levels in response to HF intake in L-CC1 than WT mice. Unlike WT, HF diet did not activate TGF-ß in WAT of L-CC1 mice, as assessed by Western analysis of Smad2/3 phosphorylation. Consistently, HF diet caused relatively less collagen deposition in L-CC1 than WT mice, as shown by Trichrome staining. Coupled with reduced lipid redistribution from liver to visceral fat, lower inflammation and fibrosis could contribute to protected energy expenditure against HF diet in L-CC1 mice. The data underscore the important role of hepatic insulin clearance in the regulation of adipose tissue inflammation and fibrosis.
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Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) regulates insulin sensitivity by promoting hepatic insulin clearance. Liver-specific inactivation or global null-mutation of Ceacam1 impairs hepatic insulin extraction to cause chronic hyperinsulinemia, resulting in insulin resistance and visceral obesity. In this study we investigated whether diet-induced insulin resistance implicates changes in hepatic CEACAM1. We report that feeding C57/BL6J mice a high-fat diet reduced hepatic CEACAM1 levels by >50% beginning at 21 days, causing hyperinsulinemia, insulin resistance, and elevation in hepatic triacylglycerol content. Conversely, liver-specific inducible CEACAM1 expression prevented hyperinsulinemia and markedly limited insulin resistance and hepatic lipid accumulation that were induced by prolonged high-fat intake. This was partly mediated by increased hepatic ß-fatty acid oxidation and energy expenditure. The data demonstrate that the high-fat diet reduced hepatic CEACAM1 expression and that overexpressing CEACAM1 in liver curtailed diet-induced metabolic abnormalities by protecting hepatic insulin clearance.
Assuntos
Antígenos CD/metabolismo , Moléculas de Adesão Celular/metabolismo , Dieta Hiperlipídica , Resistência à Insulina/genética , Fígado/metabolismo , Animais , Antígenos CD/genética , Moléculas de Adesão Celular/genética , Metabolismo Energético/fisiologia , Ácidos Graxos/metabolismo , Hiperinsulinismo/genética , Hiperinsulinismo/metabolismo , Insulina/sangue , Camundongos , Camundongos TransgênicosRESUMO
The hypothalamus is the central regulator of systemic energy homeostasis, and its dysfunction can result in extreme body weight alterations. Insights into the complex cellular physiology of this region are critical to the understanding of obesity pathogenesis; however, human hypothalamic cells are largely inaccessible for direct study. Here, we developed a protocol for efficient generation of hypothalamic neurons from human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) obtained from patients with monogenetic forms of obesity. Combined early activation of sonic hedgehog signaling followed by timed NOTCH inhibition in human ESCs/iPSCs resulted in efficient conversion into hypothalamic NKX2.1+ precursors. Application of a NOTCH inhibitor and brain-derived neurotrophic factor (BDNF) further directed the cells into arcuate nucleus hypothalamic-like neurons that express hypothalamic neuron markers proopiomelanocortin (POMC), neuropeptide Y (NPY), agouti-related peptide (AGRP), somatostatin, and dopamine. These hypothalamic-like neurons accounted for over 90% of differentiated cells and exhibited transcriptional profiles defined by a hypothalamic-specific gene expression signature that lacked pituitary markers. Importantly, these cells displayed hypothalamic neuron characteristics, including production and secretion of neuropeptides and increased p-AKT and p-STAT3 in response to insulin and leptin. Our results suggest that these hypothalamic-like neurons have potential for further investigation of the neurophysiology of body weight regulation and evaluation of therapeutic targets for obesity.
Assuntos
Diferenciação Celular , Hipotálamo/metabolismo , Células-Tronco Pluripotentes Induzidas/metabolismo , Neurônios , Obesidade/metabolismo , Antígenos de Diferenciação/metabolismo , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Células Cultivadas , Células-Tronco Embrionárias/metabolismo , Células-Tronco Embrionárias/patologia , Proteínas Hedgehog/metabolismo , Humanos , Hipotálamo/patologia , Células-Tronco Pluripotentes Induzidas/patologia , Proteínas Nucleares/metabolismo , Obesidade/patologia , Pró-Opiomelanocortina/metabolismo , Fator Nuclear 1 de Tireoide , Fatores de Transcrição/metabolismoRESUMO
Transcription factor forkhead box O1 (FoxO1) regulates energy expenditure (EE), food intake, and hepatic glucose production. These activities have been mapped to specific hypothalamic neuronal populations using cell type-specific knockout experiments in mice. To parse out the integrated output of FoxO1-dependent transcription from different neuronal populations and multiple hypothalamic regions, we used transgenic mice expressing Cre recombinase from the Nkx2.1 promoter to ablate loxP-flanked Foxo1 alleles from a majority of hypothalamic neurons (Foxo1KO(Nkx2.1) mice). This strategy resulted in the expected inhibition of FoxO1 expression, but only produced a transient reduction of body weight as well as a decreased body length. The transient decrease of body weight in male mice was accompanied by decreased fat mass. Male Foxo1KO(Nkx2.1) mice show food intake similar to that in wild-type controls, and, although female knockout mice eat less, they do so in proportion to a reduced body size. EE is unaffected in Foxo1KO(Nkx2.1) mice, although small increases in body temperature are present. Unlike other neuron-specific Foxo1 knockout mice, Foxo1KO(Nkx2.1) mice are not protected from diet-induced obesity. These studies indicate that, unlike the metabolic effects of highly restricted neuronal subsets (proopiomelanocortin, neuropeptide Y/agouti-related peptide, and steroidogenic factor 1), those of neurons derived from the Nkx2.1 lineage either occur in a FoxO1-independent fashion or are compensated for through developmental plasticity.
Assuntos
Metabolismo Energético/fisiologia , Fatores de Transcrição Forkhead/metabolismo , Hipotálamo/metabolismo , Neurônios/metabolismo , Proteínas Nucleares/metabolismo , Fatores de Transcrição/metabolismo , Proteína Relacionada com Agouti/metabolismo , Animais , Peso Corporal/fisiologia , Linhagem da Célula/fisiologia , Ingestão de Alimentos/fisiologia , Feminino , Proteína Forkhead Box O1 , Fatores de Transcrição Forkhead/genética , Masculino , Camundongos , Camundongos Transgênicos , Neuropeptídeo Y/metabolismo , Proteínas Nucleares/genética , Obesidade/genética , Obesidade/metabolismo , Pró-Opiomelanocortina/metabolismo , Regiões Promotoras Genéticas , Transdução de Sinais/fisiologia , Fator Nuclear 1 de Tireoide , Fatores de Transcrição/genéticaRESUMO
Successful development of antiobesity agents requires detailed knowledge of neural pathways controlling body weight, eating behavior, and peripheral metabolism. Genetic ablation of FoxO1 in selected hypothalamic neurons decreases food intake, increases energy expenditure, and improves glucose homeostasis, highlighting the role of this gene in insulin and leptin signaling. However, little is known about potential effects of FoxO1 in other neurons. To address this question, we executed a broad-based neuronal ablation of FoxO1 using Synapsin promoter-driven Cre to delete floxed Foxo1 alleles. Lineage-tracing experiments showed that NPY/AgRP and POMC neurons were minimally affected by the knockout. Nonetheless, Syn-Cre-Foxo1 knockouts demonstrated a catabolic energy homeostatic phenotype with a blunted refeeding response, increased sensitivity to leptin and amino acid signaling, and increased locomotor activity, likely attributable to increased melanocortinergic tone. We confirmed these data in mice lacking the three Foxo genes. The effects on locomotor activity could be reversed by direct delivery of constitutively active FoxO1 to the mediobasal hypothalamus, but not to the suprachiasmatic nucleus. The data reveal that the integrative function of FoxO1 extends beyond the arcuate nucleus, suggesting that central nervous system inhibition of FoxO1 function can be leveraged to promote hormone sensitivity and prevent a positive energy balance.
Assuntos
Ingestão de Alimentos , Fatores de Transcrição Forkhead/antagonistas & inibidores , Hipotálamo/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Locomoção/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Animais , Fármacos Antiobesidade/farmacologia , Desenho de Fármacos , Ingestão de Alimentos/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Proteína Forkhead Box O1 , Fatores de Transcrição Forkhead/deficiência , Regulação da Expressão Gênica/efeitos dos fármacos , Genótipo , Hipotálamo/efeitos dos fármacos , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Knockout , Transdução de Sinais/efeitos dos fármacosRESUMO
Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes hepatic insulin clearance and endothelial survival. However, its role in the morphology of macrovessels remains unknown. Mice lacking Ceacam1 (Cc1-/-) exhibit hyperinsulinemia, which causes insulin resistance and fatty liver. With increasing evidence of an association among hyperinsulinemia, fatty liver disease, and atherosclerosis, we investigated whether Cc1-/- exhibited vascular lesions in atherogenic-prone aortae. Histological analysis revealed impaired endothelial integrity with restricted fat deposition and aortic plaque-like lesions in Cc1-/- aortae, likely owing to their limited lipidemia. Immunohistochemical analysis indicated macrophage deposition, and in vitro studies showed increased leukocyte adhesion to aortic wall, mediated in part by elevation in vascular cell adhesion molecule 1 levels. Basal aortic eNOS protein and NO content were reduced, in parallel with reduced Akt/eNOS and Akt/Foxo1 phosphorylation. Ligand-induced vasorelaxation was compromised in aortic rings. Increased NADPH oxidase activity and plasma 8-isoprostane levels revealed oxidative stress and lipid peroxidation in Cc1-/- aortae. siRNA-mediated CEACAM1 knockdown in bovine aortic endothelial cells adversely affected insulin's stimulation of IRS-1/PI 3-kinase/Akt/eNOS activation by increasing IRS-1 binding to SHP2 phosphatase. This demonstrates that CEACAM1 regulates both endothelial cell autonomous and nonautonomous mechanisms involved in vascular morphology and NO production in aortae. Systemic factors such as hyperinsulinemia could contribute to the pathogenesis of these vascular abnormalities. Cc1-/- mice provide a first in vivo demonstration of distinct CEACAM1-dependent hepatic insulin clearance linking hepatic to macrovascular abnormalities.
Assuntos
Antígenos CD/metabolismo , Aorta Torácica/metabolismo , Aorta Torácica/patologia , Antígeno Carcinoembrionário/metabolismo , Moléculas de Adesão Celular/metabolismo , Endotélio Vascular/metabolismo , Placa Aterosclerótica/metabolismo , Placa Aterosclerótica/patologia , Animais , Antígenos CD/genética , Aorta Torácica/imunologia , Antígeno Carcinoembrionário/química , Antígeno Carcinoembrionário/genética , Bovinos , Adesão Celular , Moléculas de Adesão Celular/antagonistas & inibidores , Moléculas de Adesão Celular/genética , Células Cultivadas , Endotélio Vascular/imunologia , Endotélio Vascular/patologia , Leucócitos/imunologia , Leucócitos/metabolismo , Leucócitos/patologia , Peroxidação de Lipídeos , Macrófagos/imunologia , Macrófagos/metabolismo , Macrófagos/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase Tipo III/genética , Óxido Nítrico Sintase Tipo III/metabolismo , Estresse Oxidativo , Placa Aterosclerótica/imunologia , Interferência de RNA , Transdução de Sinais , Molécula 1 de Adesão de Célula Vascular/biossíntese , Molécula 1 de Adesão de Célula Vascular/genética , Molécula 1 de Adesão de Célula Vascular/metabolismoRESUMO
FoxO1 integrates multiple metabolic pathways. Nutrient levels modulate FoxO1 acetylation, but the functional consequences of this posttranslational modification are unclear. To answer this question, we generated mice bearing alleles that encode constitutively acetylated and acetylation-defective FoxO1 proteins. Homozygosity for an allele mimicking constitutive acetylation (Foxo1(KQ/KQ)) results in embryonic lethality due to cardiac and angiogenesis defects. In contrast, mice homozygous for a constitutively deacetylated Foxo1 allele (Foxo1(KR/KR)) display a unique metabolic phenotype of impaired insulin action on hepatic glucose metabolism but decreased plasma lipid levels and low respiratory quotient that are consistent with a state of preferential lipid usage. Moreover, Foxo1(KR/KR) mice show a dissociation between weight gain and insulin resistance in predisposing conditions (high fat diet, diabetes, and insulin receptor mutations), possibly due to decreased cytokine production in adipose tissue. Thus, acetylation inactivates FoxO1 during nutrient excess whereas deacetylation selectively potentiates FoxO1 activity, protecting against excessive catabolism during nutrient deprivation.
Assuntos
Tecido Adiposo/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Glucose/metabolismo , Resistência à Insulina/genética , Metabolismo dos Lipídeos/genética , Fígado/metabolismo , Acetilação , Tecido Adiposo/embriologia , Alelos , Animais , Peso Corporal , Citocinas/metabolismo , Dieta Hiperlipídica , Proteína Forkhead Box O1 , Fatores de Transcrição Forkhead/genética , Expressão Gênica , Técnicas de Introdução de Genes , Genótipo , Homozigoto , Insulina/metabolismo , Fígado/embriologia , Camundongos , Camundongos Transgênicos , Fenótipo , Processamento de Proteína Pós-Traducional , Receptor de Insulina/metabolismo , Transdução de Sinais/genéticaRESUMO
Glucocorticoid hormones control diverse physiological processes, including metabolism and immunity, by activating the major glucocorticoid receptor (GR) isoform, GRalpha. However, humans express an alternative isoform, human (h)GRbeta, that acts as an inhibitor of hGRalpha to produce a state of glucocorticoid resistance. Indeed, evidence exists that hGRbeta contributes to many diseases and resistance to glucocorticoid hormone therapy. However, rigorous testing of the GRbeta contribution has not been possible, because rodents, especially mice, are not thought to express the beta-isoform. Here, we report expression of GRbeta mRNA and protein in the mouse. The mGRbeta isoform arises from a distinct alternative splicing mechanism utilizing intron 8, rather than exon 9 as in humans. The splicing event produces a form of beta that is similar in structure and functionality to hGRbeta. Mouse (m)GRbeta has a degenerate C-terminal region that is the same size as hGRbeta. Using a variety of newly developed tools, such as a mGRbeta-specific antibody and constructs for overexpression and short hairpin RNA knockdown, we demonstrate that mGRbeta cannot bind dexamethasone agonist, is inhibitory of mGRalpha, and is up-regulated by inflammatory signals. These properties are the same as reported for hGRbeta. Additionally, novel data is presented that mGRbeta is involved in metabolism. When murine tissue culture cells are treated with insulin, no effect on mGRalpha expression was observed, but GRbeta was elevated. In mice subjected to fasting-refeeding, a large increase of GRbeta was seen in the liver, whereas mGRalpha was unchanged. This work uncovers the much-needed rodent model of GRbeta for investigations of physiology and disease.
Assuntos
Receptores de Glucocorticoides/genética , Receptores de Glucocorticoides/metabolismo , Sequência de Aminoácidos , Animais , Western Blotting , Células COS , Chlorocebus aethiops , Clonagem Molecular , Dieta , Imunofluorescência , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/efeitos dos fármacos , Inativação Gênica/efeitos dos fármacos , Genes Dominantes/genética , Glucocorticoides/farmacologia , Íntrons/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores de Glucocorticoides/antagonistas & inibidores , Receptores de Glucocorticoides/químicaRESUMO
BACKGROUND & AIMS: The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a transmembrane glycoprotein with pleotropic functions, including clearance of hepatic insulin. We investigated the functions of the related protein CEACAM2, which has tissue-specific distribution (kidney, uterus, and crypt epithelia of intestinal tissues), in genetically modified mice. METHODS: Ceacam2-null mice (Cc2-/-) were generated from a 129/SvxC57BL/6J background. Female mice were assessed by hyperinsulinemic-euglycemic clamp analysis and indirect calorimetry and body fat composition was measured. Cc2-/- mice and controls were fed as pairs, given insulin tolerance tests, and phenotypically characterized. RESULTS: Female, but not male Cc2-/- mice exhibited obesity that resulted from hyperphagia and reduced energy expenditure. Pair feeding experiments showed that hyperphagia led to peripheral insulin resistance. Insulin action was normal in liver but compromised in skeletal muscle of female Cc2-/- mice; the mice had incomplete fatty acid oxidation and impaired glucose uptake and disposal. The mechanism of hyperphagia in Cc2-/- mice is not clear, but appears to result partly from increased hyperinsulinemia-induced hypothalamic fatty acid synthase levels and activity. Hyperinsulinemia was caused by increased insulin secretion. CONCLUSIONS: In mice, CEACAM2 is expressed by the hypothalamus. Cc2-/- mice develop obesity from hyperphagia and reduced energy expenditure, indicating its role in regulating energy balance and insulin sensitivity.