RESUMO
Hydrops fetalis describes fluid accumulation in at least 2 fetal compartments, including abdominal cavities, pleura, and pericardium, or in body tissue. The majority of hydrops fetalis cases are nonimmune conditions that present with generalized edema of the fetus, and approximately 15% of these nonimmune cases result from a lymphatic abnormality. Here, we have identified an autosomal dominant, inherited form of lymphatic-related (nonimmune) hydrops fetalis (LRHF). Independent exome sequencing projects on 2 families with a history of in utero and neonatal deaths associated with nonimmune hydrops fetalis uncovered 2 heterozygous missense variants in the gene encoding Eph receptor B4 (EPHB4). Biochemical analysis determined that the mutant EPHB4 proteins are devoid of tyrosine kinase activity, indicating that loss of EPHB4 signaling contributes to LRHF pathogenesis. Further, inactivation of Ephb4 in lymphatic endothelial cells of developing mouse embryos led to defective lymphovenous valve formation and consequent subcutaneous edema. Together, these findings identify EPHB4 as a critical regulator of early lymphatic vascular development and demonstrate that mutations in the gene can cause an autosomal dominant form of LRHF that is associated with a high mortality rate.
Assuntos
Hidropisia Fetal/genética , Hidropisia Fetal/metabolismo , Mutação , Receptor EphB4/genética , Receptor EphB4/metabolismo , Animais , Células Endoteliais/metabolismo , Exoma , Feminino , Deleção de Genes , Genes Dominantes , Células HEK293 , Heterozigoto , Humanos , Vasos Linfáticos/patologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Mutação de Sentido Incorreto , Polimorfismo de Nucleotídeo ÚnicoRESUMO
AIMS/HYPOTHESIS: Glucagon-like peptide-1 (GLP-1) is an incretin hormone derived from proglucagon, which is released from intestinal L-cells and increases insulin secretion in a glucose dependent manner. GPR119 is a lipid derivative receptor present in L-cells, believed to play a role in the detection of dietary fat. This study aimed to characterize the responses of primary murine L-cells to GPR119 agonism and assess the importance of GPR119 for the detection of ingested lipid. METHODS: GLP-1 secretion was measured from murine primary cell cultures stimulated with a panel of GPR119 ligands. Plasma GLP-1 levels were measured in mice lacking GPR119 in proglucagon-expressing cells and controls after lipid gavage. Intracellular cAMP responses to GPR119 agonists were measured in single primary L-cells using transgenic mice expressing a cAMP FRET sensor driven by the proglucagon promoter. RESULTS: L-cell specific knockout of GPR119 dramatically decreased plasma GLP-1 levels after a lipid gavage. GPR119 ligands triggered GLP-1 secretion in a GPR119 dependent manner in primary epithelial cultures from the colon, but were less effective in the upper small intestine. GPR119 agonists elevated cAMP in â¼70% of colonic L-cells and 50% of small intestinal L-cells. CONCLUSIONS/INTERPRETATION: GPR119 ligands strongly enhanced GLP-1 release from colonic cultures, reflecting the high proportion of colonic L-cells that exhibited cAMP responses to GPR119 agonists. Less GPR119-dependence could be demonstrated in the upper small intestine. In vivo, GPR119 in L-cells plays a key role in oral lipid-triggered GLP-1 secretion.
Assuntos
Óleo de Milho/farmacologia , Células Enteroendócrinas/metabolismo , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Azeite de Oliva/farmacologia , Receptores Acoplados a Proteínas G/metabolismo , Animais , Células Cultivadas , AMP Cíclico/metabolismo , Células Enteroendócrinas/efeitos dos fármacos , Feminino , Masculino , Camundongos Transgênicos , Azeite de Oliva/administração & dosagem , Cultura Primária de Células , Sistemas do Segundo MensageiroRESUMO
Nuclear receptor subfamily 1, group H, member 4 (Nr1h4, FXR) is a bile acid activated nuclear receptor mainly expressed in the liver, intestine, kidney and adrenal glands. Upon activation, the primary function is to suppress cholesterol 7 alpha-hydroxylase (Cyp7a1), the rate-limiting enzyme in the classic or neutral bile acid synthesis pathway. In the present study, a novel Fxr deficient mouse line was created and studied with respect to metabolism and liver function in ageing mice fed chow diet. The Fxr deficient mice were similar to wild type mice in terms of body weight, body composition, energy intake and expenditure as well as behaviours at a young age. However, from 15 weeks of age and onwards, the Fxr deficient mice had almost no body weight increase up to 39 weeks of age mainly because of lower body fat mass. The lower body weight gain was associated with increased energy expenditure that was not compensated by increased food intake. Fasting levels of glucose and insulin were lower and glucose tolerance was improved in old and lean Fxr deficient mice. However, the Fxr deficient mice displayed significantly increased liver weight, steatosis, hepatocyte ballooning degeneration and lobular inflammation together with elevated plasma levels of ALT, bilirubin and bile acids, findings compatible with non-alcoholic steatohepatitis (NASH) and cholestasis. In conclusion, ageing Fxr deficient mice display late onset leanness associated with elevated energy expenditure and improved glucose control but develop severe NASH-like liver pathology.
Assuntos
Metabolismo Energético , Fígado Gorduroso/metabolismo , Glucose/metabolismo , Receptores Citoplasmáticos e Nucleares/deficiência , Tecido Adiposo Branco/metabolismo , Tecido Adiposo Branco/patologia , Envelhecimento , Animais , Glicemia , Composição Corporal , Peso Corporal , Tamanho Celular , Ingestão de Energia , Feminino , Metabolismo dos Lipídeos , Fígado/metabolismo , Fígado/patologia , Fígado/fisiopatologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Atividade Motora , Hepatopatia Gordurosa não Alcoólica , Tamanho do Órgão , Receptores Citoplasmáticos e Nucleares/genética , Pele/patologia , Triglicerídeos/metabolismoRESUMO
Glycerol-3-phosphate acyltransferase (GPAT) is involved in triacylglycerol (TAG) and phospholipid synthesis, catalyzing the first committed step. In order to further investigate the in vivo importance of the dominating mitochondrial variant, GPAT1, a novel GPAT1(-/-) mouse model was generated and studied. Female GPAT1(-/-) mice had reduced body weight-gain and adiposity when fed chow diet compared with littermate wild-type controls. Furthermore, GPAT1(-/-) females on chow diet showed decreased liver TAG content, plasma cholesterol and TAG levels and increased ex vivo liver fatty acid oxidation and plasma ketone bodies. However, these beneficial effects were abolished and the glucose tolerance tended to be impaired when GPAT1(-/-) females were fed a long-term high-fat diet (HFD). GPAT1-deficiency was not associated with altered whole body energy expenditure or respiratory exchange ratio. In addition, there were no changes in male GPAT1(-/-) mice fed either diet except for increased plasma ketone bodies on chow diet, indicating a gender-specific phenotype. Thus, GPAT1-deficiency does not protect against HFD-induced obesity, hepatic steatosis or whole body glucose intolerance.
Assuntos
Gorduras na Dieta/efeitos adversos , Fígado Gorduroso/etiologia , Intolerância à Glucose/etiologia , Glucose/metabolismo , Glicerol-3-Fosfato O-Aciltransferase/fisiologia , Obesidade/etiologia , Triglicerídeos/metabolismo , Animais , Colesterol/sangue , Dieta , Gorduras na Dieta/administração & dosagem , Modelos Animais de Doenças , Metabolismo Energético , Fígado Gorduroso/genética , Feminino , Intolerância à Glucose/genética , Glicerol-3-Fosfato O-Aciltransferase/genética , Homeostase , Masculino , Camundongos , Camundongos Mutantes , Mitocôndrias/enzimologia , Obesidade/genética , Triglicerídeos/análise , Aumento de PesoRESUMO
The myxoid/round cell liposarcoma oncogene TLS-CHOP belongs to a growing family of tumor type specific fusion genes generated by chromosome translocations. We have recently found that the TLS-CHOP fusion protein is localized to well-defined nuclear structures, a pattern distinct from normal TLS or CHOP cellular distribution. Since location and function are intimately coupled in the organized nucleus, the aberrant localization of the fusion protein most certainly reflects the oncogenic activities of TLS-CHOP. We have investigated the role of the functionally unknown, SYGQ-rich, TLS N-terminal in the localization of TLS-CHOP to nuclear structures. Here, we report the temperature-dependent localization of TLS-CHOP to splicing factor compartments and association with Cajal bodies. Further, mutational analysis of the N-terminal part of green fluorescent protein-tagged TLS-CHOP identifies a region within the N-terminal required for colocalization with the splicing factor SC-35.