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1.
Sci Transl Med ; 15(723): eadd4897, 2023 11 22.
Artigo em Inglês | MEDLINE | ID: mdl-37992152

RESUMO

Deficiency in the adipose-derived hormone leptin or leptin receptor signaling causes class 3 obesity in individuals with genetic loss-of-function mutations in leptin or its receptor LEPR and metabolic and liver disease in individuals with hypoleptinemia secondary to lipoatrophy such as in individuals with generalized lipodystrophy. Therapies that restore leptin-LEPR signaling may resolve these metabolic sequelae. We developed a fully human monoclonal antibody (mAb), REGN4461 (mibavademab), that activates the human LEPR in the absence or presence of leptin. In obese leptin knockout mice, REGN4461 normalized body weight, food intake, blood glucose, and insulin sensitivity. In a mouse model of generalized lipodystrophy, REGN4461 alleviated hyperphagia, hyperglycemia, insulin resistance, dyslipidemia, and hepatic steatosis. In a phase 1, randomized, double-blind, placebo-controlled two-part study, REGN4461 was well tolerated with an acceptable safety profile. Treatment of individuals with overweight or obesity with REGN4461 decreased body weight over 12 weeks in those with low circulating leptin concentrations (<8 ng/ml) but had no effect on body weight in individuals with higher baseline leptin. Furthermore, compassionate-use treatment of a single patient with atypical partial lipodystrophy and a history of undetectable leptin concentrations associated with neutralizing antibodies to metreleptin was associated with noteable improvements in circulating triglycerides and hepatic steatosis. Collectively, these translational data unveil an agonist LEPR mAb that may provide clinical benefit in disorders associated with relatively low leptin concentrations.


Assuntos
Resistência à Insulina , Lipodistrofia Generalizada Congênita , Animais , Camundongos , Humanos , Leptina/uso terapêutico , Ensaios de Uso Compassivo , Receptores para Leptina/metabolismo , Lipodistrofia Generalizada Congênita/tratamento farmacológico , Obesidade/tratamento farmacológico , Anticorpos/uso terapêutico , Peso Corporal
2.
J Biol Chem ; 295(33): 11529-11541, 2020 08 14.
Artigo em Inglês | MEDLINE | ID: mdl-32554468

RESUMO

The insulinotropic actions of glucagon-like peptide 1 receptor (GLP-1R) in ß-cells have made it a useful target to manage type 2 diabetes. Metabolic stress reduces ß-cell sensitivity to GLP-1, yet the underlying mechanisms are unknown. We hypothesized that Glp1r expression is heterogeneous among ß-cells and that metabolic stress decreases the number of GLP-1R-positive ß-cells. Here, analyses of publicly available single-cell RNA-Seq sequencing (scRNASeq) data from mouse and human ß-cells indicated that significant populations of ß-cells do not express the Glp1r gene, supporting heterogeneous GLP-1R expression. To check these results, we used complementary approaches employing FACS coupled with quantitative RT-PCR, a validated GLP-1R antibody, and flow cytometry to quantify GLP-1R promoter activity, gene expression, and protein expression in mouse α-, ß-, and δ-cells. Experiments with Glp1r reporter mice and a validated GLP-1R antibody indicated that >90% of the ß-cells are GLP-1R positive, contradicting the findings with the scRNASeq data. α-cells did not express Glp1r mRNA and δ-cells expressed Glp1r mRNA but not protein. We also examined the expression patterns of GLP-1R in mouse models of metabolic stress. Multiparous female mice had significantly decreased ß-cell Glp1r expression, but no reduction in GLP-1R protein levels or GLP-1R-mediated insulin secretion. These findings suggest caution in interpreting the results of scRNASeq for low-abundance transcripts such as the incretin receptors and indicate that GLP-1R is widely expressed in ß-cells, absent in α-cells, and expressed at the mRNA, but not protein, level in δ-cells.


Assuntos
Receptor do Peptídeo Semelhante ao Glucagon 1/genética , Células Secretoras de Insulina/metabolismo , Animais , Células Cultivadas , Expressão Gênica , Receptor do Peptídeo Semelhante ao Glucagon 1/análise , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Análise de Célula Única
3.
Skelet Muscle ; 9(1): 9, 2019 04 16.
Artigo em Inglês | MEDLINE | ID: mdl-30992050

RESUMO

BACKGROUND: Critical illness myopathy (CIM) is associated with severe skeletal muscle wasting and impaired function in intensive care unit (ICU) patients. The mechanisms underlying CIM remain incompletely understood. To elucidate the biological activities occurring at the transcriptional level in the skeletal muscle of ICU patients with CIM, the gene expression profiles, potential upstream regulators, and enrichment pathways were characterized using RNA sequencing (RNA-seq). We also compared the skeletal muscle gene signatures in ICU patients with CIM and genes perturbed by mechanical loading in one leg of the ICU patients, with an aim of reducing the loss of muscle function. METHODS: RNA-seq was used to assess gene expression changes in tibialis anterior skeletal muscle samples from seven critically ill, immobilized, and mechanically ventilated ICU patients with CIM and matched control subjects. We also examined skeletal muscle gene expression for both legs of six ICU patients with CIM, where one leg was mechanically loaded for 10 h/day for an average of 9 days. RESULTS: In total, 6257 of 17,221 detected genes were differentially expressed (84% upregulated; p < 0.05 and fold change ≥ 1.5) in skeletal muscle from ICU patients with CIM when compared to control subjects. The differentially expressed genes were highly associated with gene changes identified in patients with myopathy, sepsis, long-term inactivity, polymyositis, tumor, and repeat exercise resistance. Upstream regulator analysis revealed that the CIM signature could be a result of the activation of MYOD1, p38 MAPK, or treatment with dexamethasone. Passive mechanical loading only reversed expression of 0.74% of the affected genes (46 of 6257 genes). CONCLUSIONS: RNA-seq analysis revealed that the marked muscle atrophy and weakness observed in ICU patients with CIM were associated with the altered expression of genes involved in muscle contraction, newly identified E3 ligases, autophagy and calpain systems, apoptosis, and chaperone expression. In addition, MYOD1, p38 MAPK, and dexamethasone were identified as potential upstream regulators of skeletal muscle gene expression in ICU patients with CIM. Mechanical loading only marginally affected the skeletal muscle transcriptome profiling of ICU patients diagnosed with CIM.


Assuntos
Apoptose , Autofagia , Chaperonas Moleculares/metabolismo , Contração Muscular , Músculo Esquelético/metabolismo , Doenças Musculares/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Estado Terminal , Feminino , Expressão Gênica , Humanos , Masculino , Pessoa de Meia-Idade , Chaperonas Moleculares/genética , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Debilidade Muscular/genética , Debilidade Muscular/metabolismo , Atrofia Muscular/etiologia , Atrofia Muscular/metabolismo , Doenças Musculares/etiologia , Análise de Sequência de RNA , Transcriptoma , Ubiquitina-Proteína Ligases/genética
4.
Endocrinology ; 160(5): 979-988, 2019 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-30938753

RESUMO

Plasma amino acids and their transporters constitute an important part of the feedback loop between the liver and pancreatic α-cell function, and glucagon regulates hepatic amino acid turnover. Disruption of hepatic glucagon receptor action activates the loop and results in high plasma amino acids and hypersecretion of glucagon associated with α-cell hyperplasia. In the present study, we report a technique to rescue implanted human pancreatic islets from the mouse kidney capsule. Using this model, we have demonstrated that expression of the amino acid transporter SLC38A4 increases in α-cells after administration of a glucagon receptor blocking antibody. The increase in SLC38A4 expression and associated α-cell proliferation was dependent on mechanistic target of rapamycin pathway. We confirmed increased α-cell proliferation and expression of SLC38A4 in pancreas sections from patients with glucagon cell hyperplasia and neoplasia (GCHN) with loss-of-function mutations in the glucagon receptor. Collectively, using a technique to rescue implanted human islets from the kidney capsule in mice and pancreas sections from patients with GCHN, we found that expression of SLC38A4 was increased under conditions of disrupted glucagon receptor signaling. These data provide support for the existence of a liver-human α-cell endocrine feedback loop.


Assuntos
Sistema A de Transporte de Aminoácidos/metabolismo , Células Secretoras de Glucagon/metabolismo , Glucagon/metabolismo , Transplante das Ilhotas Pancreáticas/métodos , Receptores de Glucagon/metabolismo , Adulto , Sistema A de Transporte de Aminoácidos/genética , Animais , Proliferação de Células/genética , Feminino , Células Secretoras de Glucagon/citologia , Humanos , Hiperplasia/sangue , Hiperplasia/metabolismo , Masculino , Camundongos , Pessoa de Meia-Idade , Receptores de Glucagon/genética , Transdução de Sinais , Transplante Heterólogo
5.
Proc Natl Acad Sci U S A ; 115(32): E7642-E7649, 2018 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-30038024

RESUMO

SLC30A8 encodes a zinc transporter that is primarily expressed in the pancreatic islets of Langerhans. In ß-cells it transports zinc into insulin-containing secretory granules. Loss-of-function (LOF) mutations in SLC30A8 protect against type 2 diabetes in humans. In this study, we generated a knockin mouse model carrying one of the most common human LOF mutations for SLC30A8, R138X. The R138X mice had normal body weight, glucose tolerance, and pancreatic ß-cell mass. Interestingly, in hyperglycemic conditions induced by the insulin receptor antagonist S961, the R138X mice showed a 50% increase in insulin secretion. This effect was not associated with enhanced ß-cell proliferation or mass. Our data suggest that the SLC30A8 R138X LOF mutation may exert beneficial effects on glucose metabolism by increasing the capacity of ß-cells to secrete insulin under hyperglycemic conditions.


Assuntos
Diabetes Mellitus Tipo 2/genética , Glucose/metabolismo , Células Secretoras de Insulina/metabolismo , Insulina/metabolismo , Transportador 8 de Zinco/genética , Alelos , Animais , Glicemia , Diabetes Mellitus Tipo 2/metabolismo , Modelos Animais de Doenças , Técnicas de Introdução de Genes , Humanos , Hiperglicemia/sangue , Hiperglicemia/induzido quimicamente , Hiperglicemia/metabolismo , Secreção de Insulina , Mutação com Perda de Função , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Peptídeos/farmacologia , Receptor de Insulina/antagonistas & inibidores , Receptor de Insulina/metabolismo , Transportador 8 de Zinco/metabolismo
6.
Cell Signal ; 46: 120-128, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29522819

RESUMO

Diphosphoinositol pentakisphosphate (IP7) is critical for the exocytotic capacity of the pancreatic ß-cell, but its regulation by the primary instigator of ß-cell exocytosis, glucose, is unknown. The high Km for ATP of the IP7-generating enzymes, the inositol hexakisphosphate kinases (IP6K1 and 2) suggests that these enzymes might serve as metabolic sensors in insulin secreting ß-cells and act as translators of disrupted metabolism in diabetes. We investigated this hypothesis and now show that glucose stimulation, which increases the ATP/ADP ratio, leads to an early rise in IP7 concentration in ß-cells. RNAi mediated knock down of the IP6K1 isoform inhibits both glucose-mediated increase in IP7 and first phase insulin secretion, demonstrating that IP6K1 integrates glucose metabolism and insulin exocytosis. In diabetic mouse islets the deranged ATP/ADP levels under both basal and glucose-stimulated conditions are mirrored in both disrupted IP7 generation and insulin release. Thus the unique metabolic sensing properties of IP6K1 guarantees appropriate concentrations of IP7 and thereby both correct basal insulin secretion and intact first phase insulin release. In addition, our data suggest that a specific cell signaling defect, namely, inappropriate IP7 generation may be an essential convergence point integrating multiple metabolic defects into the commonly observed phenotype in diabetes.


Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Células Secretoras de Insulina/enzimologia , Fosfotransferases (Aceptor do Grupo Fosfato)/metabolismo , Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Diabetes Mellitus Experimental , Técnicas de Silenciamento de Genes , Glucose/metabolismo , Humanos , Fosfatos de Inositol/metabolismo , Fosfatos de Inositol/fisiologia , Secreção de Insulina , Células Secretoras de Insulina/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Fosfotransferases (Aceptor do Grupo Fosfato)/genética
8.
J Clin Invest ; 127(8): 2904-2915, 2017 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-28650342

RESUMO

Atherosclerosis is a chronic inflammatory disease, and developing therapies to promote its regression is an important clinical goal. We previously established that atherosclerosis regression is characterized by an overall decrease in plaque macrophages and enrichment in markers of alternatively activated M2 macrophages. We have now investigated the origin and functional requirement for M2 macrophages in regression in normolipidemic mice that received transplants of atherosclerotic aortic segments. We compared plaque regression in WT normolipidemic recipients and those deficient in chemokine receptors necessary to recruit inflammatory Ly6Chi (Ccr2-/- or Cx3cr1-/-) or patrolling Ly6Clo (Ccr5-/-) monocytes. Atherosclerotic plaques transplanted into WT or Ccr5-/- recipients showed reduced macrophage content and increased M2 markers consistent with plaque regression, whereas plaques transplanted into Ccr2-/- or Cx3cr1-/- recipients lacked this regression signature. The requirement of recipient Ly6Chi monocyte recruitment was confirmed in cell trafficking studies. Fate-mapping and single-cell RNA sequencing studies also showed that M2-like macrophages were derived from newly recruited monocytes. Furthermore, we used recipient mice deficient in STAT6 to demonstrate a requirement for this critical component of M2 polarization in atherosclerosis regression. Collectively, these results suggest that continued recruitment of Ly6Chi inflammatory monocytes and their STAT6-dependent polarization to the M2 state are required for resolution of atherosclerotic inflammation and plaque regression.


Assuntos
Aterosclerose/sangue , Macrófagos/citologia , Monócitos/citologia , Placa Aterosclerótica/sangue , Animais , Aorta/metabolismo , Aorta/fisiologia , Aterosclerose/metabolismo , Receptor 1 de Quimiocina CX3C , Linhagem da Célula , Feminino , Hiperlipidemias/sangue , Inflamação , Macrófagos/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Monócitos/metabolismo , Fenótipo , Placa Aterosclerótica/metabolismo , Receptores CCR2/genética , Receptores CCR5/genética , Receptores de Quimiocinas/genética , Fator de Transcrição STAT6/metabolismo , Análise de Sequência de RNA , Resultado do Tratamento
9.
J Lipid Res ; 58(6): 1166-1173, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28413163

RESUMO

Angiopoietin-like (ANGPTL)3 and ANGPTL8 are secreted proteins and inhibitors of LPL-mediated plasma triglyceride (TG) clearance. It is unclear how these two ANGPTL proteins interact to regulate LPL activity. ANGPTL3 inhibits LPL activity and increases serum TG independent of ANGPTL8. These effects are reversed with an ANGPTL3 blocking antibody. Here, we show that ANGPTL8, although it possesses a functional inhibitory motif, is inactive by itself and requires ANGPTL3 expression to inhibit LPL and increase plasma TG. Using a mutated form of ANGPTL3 that lacks LPL inhibitory activity, we demonstrate that ANGPTL3 activity is not required for its ability to activate ANGPTL8. Moreover, coexpression of ANGPTL3 and ANGPTL8 leads to a far more efficacious increase in TG in mice than ANGPTL3 alone, suggesting the major inhibitory activity of this complex derives from ANGPTL8. An antibody to the C terminus of ANGPTL8 reversed LPL inhibition by ANGPTL8 in the presence of ANGPTL3. The antibody did not disrupt the ANGPTL8:ANGPTL3 complex, but came in close proximity to the LPL inhibitory motif in the N terminus of ANGPTL8. Collectively, these data show that ANGPTL8 has a functional LPL inhibitory motif, but only inhibits LPL and increases plasma TG levels in mice in the presence of ANGPTL3.


Assuntos
Proteínas Semelhantes a Angiopoietina/metabolismo , Lipase Lipoproteica/antagonistas & inibidores , Hormônios Peptídicos/metabolismo , Triglicerídeos/sangue , Motivos de Aminoácidos , Sequência de Aminoácidos , Proteína 3 Semelhante a Angiopoietina , Proteína 8 Semelhante a Angiopoietina , Proteínas Semelhantes a Angiopoietina/química , Proteínas Semelhantes a Angiopoietina/deficiência , Animais , Células CHO , Cricetinae , Cricetulus , Células HEK293 , Humanos , Hipertrigliceridemia/metabolismo , Lipase Lipoproteica/metabolismo , Camundongos , Hormônios Peptídicos/química , Hormônios Peptídicos/deficiência
10.
Proc Natl Acad Sci U S A ; 114(10): 2753-2758, 2017 03 07.
Artigo em Inglês | MEDLINE | ID: mdl-28115707

RESUMO

Inactivating mutations in the insulin receptor results in extreme insulin resistance. The resulting hyperglycemia is very difficult to treat, and patients are at risk for early morbidity and mortality from complications of diabetes. We used the insulin receptor antagonist S961 to induce severe insulin resistance, hyperglycemia, and ketonemia in mice. Using this model, we show that glucagon receptor (GCGR) inhibition with a monoclonal antibody normalized blood glucose and ß-hydroxybutyrate levels. Insulin receptor antagonism increased pancreatic ß-cell mass threefold. Normalization of blood glucose levels with GCGR-blocking antibody unexpectedly doubled ß-cell mass relative to that observed with S961 alone and 5.8-fold over control. GCGR antibody blockage expanded α-cell mass 5.7-fold, and S961 had no additional effects. Collectively, these data show that GCGR antibody inhibition represents a potential therapeutic option for treatment of patients with extreme insulin-resistance syndromes.


Assuntos
Diabetes Mellitus Experimental/genética , Glucagon/metabolismo , Resistência à Insulina/genética , Receptor de Insulina/genética , Receptores de Glucagon/genética , Ácido 3-Hidroxibutírico/metabolismo , Animais , Glicemia/genética , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Experimental/patologia , Glucagon/genética , Células Secretoras de Glucagon/metabolismo , Células Secretoras de Glucagon/patologia , Humanos , Hiperglicemia/genética , Hiperglicemia/metabolismo , Hiperglicemia/patologia , Insulina/genética , Insulina/metabolismo , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patologia , Cetose/genética , Cetose/metabolismo , Cetose/patologia , Camundongos , Mutação , Peptídeos/farmacologia , Receptores de Glucagon/antagonistas & inibidores
11.
Cell Metab ; 24(4): 608-615, 2016 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-27667665

RESUMO

Pancreatic islet cells are critical for maintaining normal blood glucose levels, and their malfunction underlies diabetes development and progression. We used single-cell RNA sequencing to determine the transcriptomes of 1,492 human pancreatic α, ß, δ, and PP cells from non-diabetic and type 2 diabetes organ donors. We identified cell-type-specific genes and pathways as well as 245 genes with disturbed expression in type 2 diabetes. Importantly, 92% of the genes have not previously been associated with islet cell function or growth. Comparison of gene profiles in mouse and human α and ß cells revealed species-specific expression. All data are available for online browsing and download and will hopefully serve as a resource for the islet research community.


Assuntos
Diabetes Mellitus Tipo 2/genética , Análise de Sequência de RNA/métodos , Análise de Célula Única/métodos , Animais , Perfilação da Expressão Gênica , Humanos , Camundongos , Transdução de Sinais/genética , Transcriptoma/genética
12.
Proc Natl Acad Sci U S A ; 113(12): 3293-8, 2016 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-26951663

RESUMO

This study provides an assessment of the Fluidigm C1 platform for RNA sequencing of single mouse pancreatic islet cells. The system combines microfluidic technology and nanoliter-scale reactions. We sequenced 622 cells, allowing identification of 341 islet cells with high-quality gene expression profiles. The cells clustered into populations of α-cells (5%), ß-cells (92%), δ-cells (1%), and pancreatic polypeptide cells (2%). We identified cell-type-specific transcription factors and pathways primarily involved in nutrient sensing and oxidation and cell signaling. Unexpectedly, 281 cells had to be removed from the analysis due to low viability, low sequencing quality, or contamination resulting in the detection of more than one islet hormone. Collectively, we provide a resource for identification of high-quality gene expression datasets to help expand insights into genes and pathways characterizing islet cell types. We reveal limitations in the C1 Fluidigm cell capture process resulting in contaminated cells with altered gene expression patterns. This calls for caution when interpreting single-cell transcriptomics data using the C1 Fluidigm system.


Assuntos
Ilhotas Pancreáticas/metabolismo , Análise de Sequência de RNA/métodos , Animais , Ilhotas Pancreáticas/citologia , Camundongos , Camundongos Endogâmicos C57BL , Fatores de Transcrição/metabolismo
13.
Endocrinology ; 156(12): 4502-10, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26406932

RESUMO

Secreted frizzled-related protein 4 (SFRP4) is an extracellular regulator of the wingless-type mouse mammary tumor virus integration site family (WNT) pathway. SFRP4 has been implicated in adipocyte dysfunction, obesity, insulin resistance, and impaired insulin secretion in patients with type 2 diabetes. However, the exact role of SFRP4 in regulating whole-body metabolism and glucose homeostasis is unknown. We show here that male Sfrp4(-/-) mice have increased spine length and gain more weight when fed a high-fat diet. The body composition and body mass per spine length of diet-induced obese Sfrp4(-/-) mice is similar to wild-type littermates, suggesting that the increase in body weight can be accounted for by their longer body size. The diet-induced obese Sfrp4(-/-) mice have reduced energy expenditure, food intake, and bone mineral density. Sfrp4(-/-) mice have normal glucose and insulin tolerance and ß-cell mass. Diet-induced obese Sfrp4(-/-) and control mice show similar impairments of glucose tolerance and a 5-fold compensatory expansion of their ß-cell mass. In summary, our data suggest that loss of SFRP4 alters body length and bone mineral density as well as energy expenditure and food intake. However, SFRP4 does not control glucose homeostasis and ß-cell mass in mice.


Assuntos
Tamanho Corporal/genética , Densidade Óssea/genética , Dieta Hiperlipídica , Ingestão de Alimentos/genética , Metabolismo Energético/genética , Células Secretoras de Insulina/metabolismo , Obesidade , Proteínas Proto-Oncogênicas/genética , Animais , Glicemia/metabolismo , Composição Corporal/genética , Comportamento Alimentar , Técnicas de Introdução de Genes , Teste de Tolerância a Glucose , Células HEK293 , Homeostase/genética , Humanos , Insulina/metabolismo , Masculino , Camundongos , Camundongos Knockout , Via de Sinalização Wnt , Microtomografia por Raio-X
14.
Proc Natl Acad Sci U S A ; 112(37): 11630-5, 2015 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-26305978

RESUMO

Angiopoietin-like protein 3 (ANGPTL3) is a circulating inhibitor of lipoprotein and endothelial lipase whose physiological function has remained obscure. Here we show that ANGPTL3 plays a major role in promoting uptake of circulating very low density lipoprotein-triglycerides (VLDL-TGs) into white adipose tissue (WAT) rather than oxidative tissues (skeletal muscle, heart brown adipose tissue) in the fed state. This conclusion emerged from studies of Angptl3(-/-) mice. Whereas feeding increased VLDL-TG uptake into WAT eightfold in wild-type mice, no increase occurred in fed Angptl3(-/-) animals. Despite the reduction in delivery to and retention of TG in WAT, fat mass was largely preserved by a compensatory increase in de novo lipogenesis in Angptl3(-/-) mice. Glucose uptake into WAT was increased 10-fold in KO mice, and tracer studies revealed increased conversion of glucose to fatty acids in WAT but not liver. It is likely that the increased uptake of glucose into WAT explains the increased insulin sensitivity associated with inactivation of ANGPTL3. The beneficial effects of ANGPTL3 deficiency on both glucose and lipoprotein metabolism make it an attractive therapeutic target.


Assuntos
Tecido Adiposo Branco/metabolismo , Angiopoietinas/metabolismo , Regulação da Expressão Gênica , Fígado/metabolismo , Proteína 3 Semelhante a Angiopoietina , Proteínas Semelhantes a Angiopoietina , Animais , Glicemia/metabolismo , Composição Corporal , AMP Cíclico/metabolismo , Ácidos Graxos/metabolismo , Feminino , Homeostase , Hormônios/metabolismo , Insulina/metabolismo , Lipase Lipoproteica/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transdução de Sinais , Distribuição Tecidual , Triglicerídeos/metabolismo
15.
J Lipid Res ; 56(7): 1296-307, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25954050

RESUMO

Humans and mice lacking angiopoietin-like protein 3 (ANGPTL3) have pan-hypolipidemia. ANGPTL3 inhibits two intravascular lipases, LPL and endothelial lipase, and the low plasma TG and HDL-cholesterol levels in ANGPTL3 deficiency reflect increased activity of these enzymes. The mechanism responsible for the low LDL-cholesterol levels associated with ANGPTL3 deficiency is not known. Here we used an anti-ANGPTL3 monoclonal antibody (REGN1500) to inactivate ANGPTL3 in mice with genetic deficiencies in key proteins involved in clearance of ApoB-containing lipoproteins. REGN1500 treatment consistently reduced plasma cholesterol levels in mice in which Apoe, Ldlr, Lrp1, and Sdc1 were inactivated singly or in combination, but did not alter clearance of rabbit (125)I-ßVLDL or mouse (125)I-LDL. Despite a 61% reduction in VLDL-TG production, VLDL-ApoB-100 production was unchanged in REGN1500-treated animals. Hepatic TG content, fatty acid synthesis, and fatty acid oxidation were similar in REGN1500 and control antibody-treated animals. Taken together, our findings indicate that inactivation of ANGPTL3 does not affect the number of ApoB-containing lipoproteins secreted by the liver but alters the particles that are made such that they are cleared more rapidly from the circulation via a noncanonical pathway(s). The increased clearance of lipolytic remnants results in decreased production of LDL in ANGPTL3-deficient animals.


Assuntos
Angiopoietinas/genética , Inativação Gênica , Lipoproteínas VLDL/metabolismo , Fígado/metabolismo , Triglicerídeos/metabolismo , Proteína 3 Semelhante a Angiopoietina , Proteínas Semelhantes a Angiopoietina , Angiopoietinas/deficiência , Angiopoietinas/imunologia , Animais , Anticorpos Monoclonais/imunologia , Apolipoproteínas E/deficiência , Colesterol/sangue , Humanos , Proteína-1 Relacionada a Receptor de Lipoproteína de Baixa Densidade , Masculino , Camundongos , Coelhos , Receptores de LDL/deficiência , Sindecana-1/deficiência , Proteínas Supressoras de Tumor/deficiência
16.
Proc Natl Acad Sci U S A ; 110(40): 16109-14, 2013 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-24043787

RESUMO

Angiopoietin-like protein (ANGPTL)8 (alternatively called TD26, RIFL, Lipasin, and Betatrophin) is a newly recognized ANGPTL family member that has been implicated in both triglyceride (TG) and glucose metabolism. Hepatic overexpression of ANGPTL8 causes hypertriglyceridemia and increased insulin secretion. Here we examined the effects of inactivating Angptl8 on TG and glucose metabolism in mice. Angptl8 knockout (Angptl8(-/-)) mice gained weight more slowly than wild-type littermates due to a selective reduction in adipose tissue accretion. Plasma levels of TGs of the Angptl8(-/-) mice were similar to wild-type animals in the fasted state but paradoxically decreased after refeeding. The lower TG levels were associated with both a reduction in very low density lipoprotein secretion and an increase in lipoprotein lipase (LPL) activity. Despite the increase in LPL activity, the uptake of very low density lipoprotein-TG is markedly reduced in adipose tissue but preserved in hearts of fed Angptl8(-/-) mice. Taken together, these data indicate that ANGPTL8 plays a key role in the metabolic transition between fasting and refeeding; it is required to direct fatty acids to adipose tissue for storage in the fed state. Finally, glucose and insulin tolerance testing revealed no alterations in glucose homeostasis in mice fed either a chow or high fat diet. Thus, although absence of ANGPTL8 profoundly disrupts TG metabolism, we found no evidence that it is required for maintenance of glucose homeostasis.


Assuntos
Dislipidemias/metabolismo , Glucose/metabolismo , Homeostase/fisiologia , Hormônios Peptídicos/deficiência , Triglicerídeos/metabolismo , Tecido Adiposo/metabolismo , Proteína 8 Semelhante a Angiopoietina , Proteínas Semelhantes a Angiopoietina , Animais , Transporte Biológico/fisiologia , Calorimetria Indireta , VLDL-Colesterol/sangue , Dislipidemias/tratamento farmacológico , Immunoblotting , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Hormônios Peptídicos/genética , Reação em Cadeia da Polimerase em Tempo Real , Análise de Sequência de DNA , Triglicerídeos/sangue
17.
Nat Cell Biol ; 14(10): 1105-12, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22983116

RESUMO

Endoplasmic reticulum (ER) stress causes pancreatic ß-cell dysfunction and contributes to ß-cell loss and the progression of type 2 diabetes. Wolfram syndrome 1 (WFS1) has been shown to be an important regulator of the ER stress signalling pathway; however, its role in ß-cell function remains unclear. Here we provide evidence that WFS1 is essential for glucose- and glucagon-like peptide 1 (GLP-1)-stimulated cyclic AMP production and regulation of insulin biosynthesis and secretion. Stimulation with glucose causes WFS1 translocation from the ER to the plasma membrane, where it forms a complex with adenylyl cyclase 8 (AC8), an essential cAMP-generating enzyme in the ß-cell that integrates glucose and GLP-1 signalling. ER stress and mutant WFS1 inhibit complex formation and activation of AC8, reducing cAMP synthesis and insulin secretion. These findings reveal that an ER-stress-related protein has a distinct role outside the ER regulating both insulin biosynthesis and secretion. The reduction of WFS1 protein on the plasma membrane during ER stress is a contributing factor for ß-cell dysfunction and progression of type 2 diabetes.


Assuntos
Adenilil Ciclases/metabolismo , Membrana Celular/metabolismo , Insulina/biossíntese , Proteínas de Membrana/metabolismo , Adenilil Ciclases/química , Animais , Membrana Celular/química , Células Cultivadas , AMP Cíclico/biossíntese , Estresse do Retículo Endoplasmático , Peptídeo 1 Semelhante ao Glucagon/farmacologia , Glucose/farmacologia , Humanos , Insulina/metabolismo , Secreção de Insulina , Células Secretoras de Insulina/metabolismo , Masculino , Proteínas de Membrana/química , Proteínas de Membrana/genética , Camundongos , Camundongos Knockout , Mutação , Ratos , Ratos Sprague-Dawley , Transdução de Sinais
18.
Nat Med ; 17(11): 1481-9, 2011 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-22037645

RESUMO

Exercise, obesity and type 2 diabetes are associated with elevated plasma concentrations of interleukin-6 (IL-6). Glucagon-like peptide-1 (GLP-1) is a hormone that induces insulin secretion. Here we show that administration of IL-6 or elevated IL-6 concentrations in response to exercise stimulate GLP-1 secretion from intestinal L cells and pancreatic alpha cells, improving insulin secretion and glycemia. IL-6 increased GLP-1 production from alpha cells through increased proglucagon (which is encoded by GCG) and prohormone convertase 1/3 expression. In models of type 2 diabetes, the beneficial effects of IL-6 were maintained, and IL-6 neutralization resulted in further elevation of glycemia and reduced pancreatic GLP-1. Hence, IL-6 mediates crosstalk between insulin-sensitive tissues, intestinal L cells and pancreatic islets to adapt to changes in insulin demand. This previously unidentified endocrine loop implicates IL-6 in the regulation of insulin secretion and suggests that drugs modulating this loop may be useful in type 2 diabetes.


Assuntos
Células Enteroendócrinas/metabolismo , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Células Secretoras de Glucagon/metabolismo , Insulina/metabolismo , Interleucina-6/metabolismo , Animais , Glicemia/metabolismo , Células Cultivadas , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/fisiopatologia , Dieta Hiperlipídica , Modelos Animais de Doenças , Células Enteroendócrinas/efeitos dos fármacos , Feminino , Células Secretoras de Glucagon/efeitos dos fármacos , Teste de Tolerância a Glucose , Humanos , Secreção de Insulina , Interleucina-6/antagonistas & inibidores , Interleucina-6/genética , Interleucina-6/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Condicionamento Físico Animal , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia
19.
Biochem Biophys Res Commun ; 410(3): 398-403, 2011 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-21672517

RESUMO

Atrial natriuretic peptide (ANP) has been shown to regulate lipid and carbohydrate metabolism providing a possible link between cardiovascular function and metabolism by mediating the switch from carbohydrate to lipid mobilization and oxidation. ANP exerts a potent lipolytic effect via cGMP-dependent protein kinase (cGK)-I mediated-stimulation of AMP-activated protein kinase (AMPK). Activation of the ANP/cGK signaling cascade also promotes muscle mitochondrial biogenesis and fat oxidation. Here we demonstrate that ANP regulates lipid metabolism and oxygen utilization in differentiated human adipocytes by activating the alpha2 subunit of AMPK. ANP treatment increased lipolysis by seven fold and oxygen consumption by two fold, both of which were attenuated by inhibition of AMPK activity. ANP-induced lipolysis was shown to be mediated by the alpha2 subunit of AMPK as introduction of dominant-negative alpha2 subunit of AMPK attenuated ANP effects on lipolysis. ANP-induced activation of AMPK enhanced mitochondrial oxidative capacity as evidenced by a two fold increase in oxygen consumption and induction of mitochondrial genes, including carnitine palmitoyltransferase 1A (CPT1a) by 1.4-fold, cytochrome C (CytC) by 1.3-fold, and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) by 1.4-fold. Treatment of human adipocytes with fatty acids and tumor necrosis factor α (TNFα) induced insulin resistance and down-regulation of mitochondrial genes, which was restored by ANP treatment. These results show that ANP regulates lipid catabolism and enhances energy dissipation through AMPK activation in human adipocytes.


Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Adipócitos/metabolismo , Fator Natriurético Atrial/fisiologia , Lipólise , Consumo de Oxigênio , Adipócitos/efeitos dos fármacos , Adipócitos/enzimologia , Fator Natriurético Atrial/farmacologia , Células Cultivadas , Ativação Enzimática , Expressão Gênica/efeitos dos fármacos , Genes Mitocondriais , Humanos , Resistência à Insulina , Metabolismo dos Lipídeos
20.
Endocrinology ; 151(7): 3115-24, 2010 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-20484464

RESUMO

Cevoglitazar is a dual agonist for the peroxisome proliferator-activated receptor (PPAR)-alpha and -gamma subtypes. Dual activation of PPARalpha and -gamma is a therapeutic approach in development for the treatment of type 2 diabetes mellitus and diabetic dyslipidemia. In this report, we show that, in addition to improving insulin sensitivity and lipid metabolism like other dual PPAR agonists, cevoglitazar also elicits beneficial effects on energy homeostasis in two animal models of obesity. In leptin-deficient ob/ob mice, administration of cevoglitazar at 0.5, 1, or 2 mg/kg for 18 d led to acute and sustained, dose-dependent reduction of food intake and body weight. Furthermore, plasma levels of glucose and insulin were normalized after 7 d of cevoglitazar treatment at 0.5 mg/kg. Plasma levels of free fatty acids and triglycerides were dose-dependently reduced. In obese and insulin-resistant cynomolgus monkeys, treatment with cevoglitazar at 50 and 500 mug/kg for 4 wk lowered food intake and body weight in a dose-dependent manner. In these animals, cevoglitazar also reduced fasting plasma insulin and, at the highest dose, reduced hemoglobin A1c levels by 0.4%. These preclinical results demonstrate that cevoglitazar holds promise for the treatment of diabetes and obesity-related disorders because of its unique beneficial effect on energy balance in addition to improving glycemic and metabolic control.


Assuntos
Fármacos Antiobesidade/uso terapêutico , Obesidade/tratamento farmacológico , PPAR alfa/agonistas , PPAR gama/agonistas , Células 3T3-L1 , Acil-CoA Oxidase/metabolismo , Animais , Fármacos Antiobesidade/química , Peso Corporal/efeitos dos fármacos , Linhagem Celular Tumoral , Ingestão de Alimentos/efeitos dos fármacos , Glicerolfosfato Desidrogenase/metabolismo , Macaca fascicularis , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Obesos , Estrutura Molecular , Obesidade/metabolismo , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa
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