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In this interview with Cell, Dr. Giles Yeo shares his journey into metabolism research, his strategies for engaging audiences, and the challenges of simplifying complex concepts. He also discusses the impact of social media, the advantages of podcasting, and the question he's most afraid of.
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Mídias Sociais , Humanos , Comunicação , Metabolismo , História do Século XXIRESUMO
More than one-half billion people are obese, and despite progress in genetic research, much of the heritability of obesity remains enigmatic. Here, we identify a Trim28-dependent network capable of triggering obesity in a non-Mendelian, "on/off" manner. Trim28(+/D9) mutant mice exhibit a bi-modal body-weight distribution, with isogenic animals randomly emerging as either normal or obese and few intermediates. We find that the obese-"on" state is characterized by reduced expression of an imprinted gene network including Nnat, Peg3, Cdkn1c, and Plagl1 and that independent targeting of these alleles recapitulates the stochastic bi-stable disease phenotype. Adipose tissue transcriptome analyses in children indicate that humans too cluster into distinct sub-populations, stratifying according to Trim28 expression, transcriptome organization, and obesity-associated imprinted gene dysregulation. These data provide evidence of discrete polyphenism in mouse and man and thus carry important implications for complex trait genetics, evolution, and medicine.
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Epigênese Genética , Haploinsuficiência , Proteínas Nucleares/genética , Obesidade/genética , Proteínas Repressoras/genética , Magreza/genética , Adolescente , Animais , Índice de Massa Corporal , Criança , Pré-Escolar , Humanos , Camundongos , Inquéritos Nutricionais , Polimorfismo Genético , Proteína 28 com Motivo TripartidoRESUMO
The prevalence of obesity has tripled over the past four decades, imposing an enormous burden on people's health. Polygenic (or common) obesity and rare, severe, early-onset monogenic obesity are often polarized as distinct diseases. However, gene discovery studies for both forms of obesity show that they have shared genetic and biological underpinnings, pointing to a key role for the brain in the control of body weight. Genome-wide association studies (GWAS) with increasing sample sizes and advances in sequencing technology are the main drivers behind a recent flurry of new discoveries. However, it is the post-GWAS, cross-disciplinary collaborations, which combine new omics technologies and analytical approaches, that have started to facilitate translation of genetic loci into meaningful biology and new avenues for treatment.
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Predisposição Genética para Doença/genética , Variação Genética , Genoma Humano/genética , Estudo de Associação Genômica Ampla/métodos , Obesidade/genética , Sequenciamento Completo do Genoma/métodos , Animais , Ingestão de Alimentos/genética , Interação Gene-Ambiente , Humanos , Herança Multifatorial/genética , Sobrepeso/genéticaRESUMO
Metformin, the world's most prescribed anti-diabetic drug, is also effective in preventing type 2 diabetes in people at high risk1,2. More than 60% of this effect is attributable to the ability of metformin to lower body weight in a sustained manner3. The molecular mechanisms by which metformin lowers body weight are unknown. Here we show-in two independent randomized controlled clinical trials-that metformin increases circulating levels of the peptide hormone growth/differentiation factor 15 (GDF15), which has been shown to reduce food intake and lower body weight through a brain-stem-restricted receptor. In wild-type mice, oral metformin increased circulating GDF15, with GDF15 expression increasing predominantly in the distal intestine and the kidney. Metformin prevented weight gain in response to a high-fat diet in wild-type mice but not in mice lacking GDF15 or its receptor GDNF family receptor α-like (GFRAL). In obese mice on a high-fat diet, the effects of metformin to reduce body weight were reversed by a GFRAL-antagonist antibody. Metformin had effects on both energy intake and energy expenditure that were dependent on GDF15, but retained its ability to lower circulating glucose levels in the absence of GDF15 activity. In summary, metformin elevates circulating levels of GDF15, which is necessary to obtain its beneficial effects on energy balance and body weight, major contributors to its action as a chemopreventive agent.
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Peso Corporal/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Fator 15 de Diferenciação de Crescimento/metabolismo , Metformina/farmacologia , Administração Oral , Adulto , Idoso , Animais , Glicemia/análise , Glicemia/metabolismo , Dieta Hiperlipídica , Método Duplo-Cego , Ingestão de Energia/efeitos dos fármacos , Enterócitos/citologia , Enterócitos/efeitos dos fármacos , Feminino , Receptores de Fator Neurotrófico Derivado de Linhagem de Célula Glial/antagonistas & inibidores , Receptores de Fator Neurotrófico Derivado de Linhagem de Célula Glial/deficiência , Receptores de Fator Neurotrófico Derivado de Linhagem de Célula Glial/genética , Fator 15 de Diferenciação de Crescimento/sangue , Fator 15 de Diferenciação de Crescimento/deficiência , Fator 15 de Diferenciação de Crescimento/genética , Homeostase/efeitos dos fármacos , Humanos , Intestinos/citologia , Intestinos/efeitos dos fármacos , Masculino , Metformina/administração & dosagem , Camundongos , Camundongos Obesos , Pessoa de Meia-Idade , Redução de Peso/efeitos dos fármacosRESUMO
An Amendment to this paper has been published and can be accessed via a link at the top of the paper.
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In the Editorial, Giles Yeo discusses if it is possible that the UPF concept could be doing more harm than good.
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AIMS: Pancreatic polypeptide (PP) is elevated in people with vascular risk factors such as type 2 diabetes or increased visceral fat. We investigated potential relationships between PP and microvascular and macrovascular complications of diabetes. MATERIALS AND METHODS: Animal study: Subcutaneous PP infusion for 4 weeks in high fat diet mouse model. Retinal mRNA submitted for Ingenuity Pathway Analysis. Human study: fasting PP measured in 1478 participants and vascular complications recorded over median 5.5 (IQR 4.9-5.8) years follow-up. RESULTS: Animal study: The retinal transcriptional response to PP was indicative of cellular stress and damage, and this footprint matched responses described in previously published studies of retinal disease. Of mechanistic importance the transcriptional landscape was consistent with upregulation of folliculin, a recently identified susceptibility gene for diabetic retinopathy. Human study: Adjusting for established risk factors, PP was associated with prevalent and incident clinically significant retinopathy (odds ratio (OR) 1.289 (1.107-1.501) p = 0.001; hazard ratio (HR) 1.259 (1.035-1.531) p = 0.0213), albuminuria (OR 1.277 (1.124-1.454), p = 0.0002; HR 1.608 (1.208-2.141) p = 0.0011), and macrovascular disease (OR 1.021 (1.006-1.037) p = 0.0068; HR 1.324 (1.089-1.61), p = 0.0049), in individuals with type 2 diabetes, and progression to diabetes in non-diabetic individuals (HR 1.402 (1.081-1.818), p = 0.0109). CONCLUSIONS: Elevated fasting PP is independently associated with vascular complications of diabetes and affects retinal pathways potentially influencing retinal neuronal survival. Our results suggest possible new roles for PP-fold peptides in the pathophysiology of diabetes complications and vascular risk stratification.
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Diabetes Mellitus Tipo 2 , Angiopatias Diabéticas , Retinopatia Diabética , Jejum , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/patologia , Humanos , Masculino , Feminino , Pessoa de Meia-Idade , Angiopatias Diabéticas/etiologia , Angiopatias Diabéticas/epidemiologia , Animais , Camundongos , Seguimentos , Retinopatia Diabética/etiologia , Retinopatia Diabética/epidemiologia , Retinopatia Diabética/patologia , Prognóstico , Incidência , Biomarcadores/análise , Fatores de Risco , IdosoRESUMO
An acute increase in the circulating concentration of glucocorticoid hormones is essential for the survival of severe somatic stresses. Circulating concentrations of GDF15, a hormone that acts in the brain to reduce food intake, are frequently elevated in stressful states. We now report that GDF15 potently activates the hypothalamic-pituitary-adrenal (HPA) axis in mice and rats. A blocking antibody to the GDNF-family receptor α-like receptor completely prevented the corticosterone response to GDF15 administration. In wild-type mice exposed to a range of stressful stimuli, circulating levels of both corticosterone and GDF15 rose acutely. In the case of Escherichia coli or lipopolysaccharide injections, the vigorous proinflammatory cytokine response elicited was sufficient to produce a near-maximal HPA response, regardless of the presence or absence of GDF15. In contrast, the activation of the HPA axis seen in wild-type mice in response to the administration of genotoxic or endoplasmic reticulum toxins, which do not provoke a marked rise in cytokines, was absent in Gdf15-/- mice. In conclusion, consistent with its proposed role as a sentinel hormone, endogenous GDF15 is required for the activation of the protective HPA response to toxins that do not induce a substantial cytokine response. In the context of efforts to develop GDF15 as an antiobesity therapeutic, these findings identify a biomarker of target engagement and a previously unrecognized pharmacodynamic effect, which will require monitoring in human studies.
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Fator 15 de Diferenciação de Crescimento/metabolismo , Sistema Hipotálamo-Hipofisário/metabolismo , Sistema Hipófise-Suprarrenal/metabolismo , Animais , Cisplatino/administração & dosagem , Cisplatino/farmacologia , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Receptores de Fator Neurotrófico Derivado de Linhagem de Célula Glial/metabolismo , Glucocorticoides/metabolismo , Fator 15 de Diferenciação de Crescimento/administração & dosagem , Humanos , Lipopolissacarídeos , Camundongos , Ratos , Tunicamicina/farmacologiaRESUMO
RATIONALE: Atherosclerosis is a chronic inflammatory disease. Recent studies have shown that dysfunctional autophagy in endothelial cells, smooth muscle cells, and macrophages, plays a detrimental role during atherogenesis, leading to the suggestion that autophagy-stimulating approaches may provide benefit. OBJECTIVE: Dendritic cells (DCs) are at the crossroad of innate and adaptive immune responses and profoundly modulate the development of atherosclerosis. Intriguingly, the role of autophagy in DC function during atherosclerosis and how the autophagy process would impact disease development has not been addressed. METHODS AND RESULTS: Here, we show that the autophagic flux in atherosclerosis-susceptible Ldlr-/- (low-density lipoprotein receptor-deficient) mice is substantially higher in splenic and aortic DCs compared with macrophages and is further activated under hypercholesterolemic conditions. RNA sequencing and functional studies on selective cell populations reveal that disruption of autophagy through deletion of Atg16l1 differentially affects the biology and functions of DC subsets in Ldlr-/- mice under high-fat diet. Atg16l1 deficient CD11b+ DCs develop a TGF (transforming growth factor)-ß-dependent tolerogenic phenotype and promote the expansion of regulatory T cells, whereas no such effects are seen with Atg16l1 deficient CD8α+ DCs. Atg16l1 deletion in DCs (all CD11c-expressing cells) expands aortic regulatory T cells in vivo, limits the accumulation of T helper cells type 1, and reduces the development of atherosclerosis in Ldlr-/- mice. In contrast, no such effects are seen when Atg16l1 is deleted selectively in conventional CD8α+ DCs and CD103+ DCs. Total T-cell or selective regulatory T-cell depletion abrogates the atheroprotective effect of Atg16l1 deficient DCs. CONCLUSIONS: In contrast to its proatherogenic role in macrophages, autophagy disruption in DCs induces a counter-regulatory response that maintains immune homeostasis in Ldlr-/- mice under high-fat diet and limits atherogenesis. Selective modulation of autophagy in DCs could constitute an interesting therapeutic target in atherosclerosis.
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Aorta/imunologia , Doenças da Aorta/prevenção & controle , Aterosclerose/prevenção & controle , Autofagia , Antígeno CD11b/imunologia , Comunicação Celular , Proliferação de Células , Células Dendríticas/imunologia , Ativação Linfocitária , Linfócitos T Reguladores/imunologia , Animais , Aorta/metabolismo , Aorta/patologia , Doenças da Aorta/imunologia , Doenças da Aorta/metabolismo , Doenças da Aorta/patologia , Aterosclerose/imunologia , Aterosclerose/metabolismo , Aterosclerose/patologia , Proteína 5 Relacionada à Autofagia/metabolismo , Proteínas Relacionadas à Autofagia/genética , Proteínas Relacionadas à Autofagia/metabolismo , Transplante de Medula Óssea , Antígenos CD11/genética , Antígenos CD11/metabolismo , Antígeno CD11b/metabolismo , Células Cultivadas , Células Dendríticas/metabolismo , Modelos Animais de Doenças , Feminino , Lectinas Tipo C/genética , Lectinas Tipo C/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Placa Aterosclerótica , Receptores Imunológicos/genética , Receptores Imunológicos/metabolismo , Receptores de LDL/genética , Receptores de LDL/metabolismo , Transdução de Sinais , Linfócitos T Reguladores/metabolismoRESUMO
BACKGROUND: Though it is well established that neonatal nutrition plays a major role in lifelong offspring health, the mechanisms underpinning this have not been well defined. Early postnatal accelerated growth resulting from maternal nutritional status is associated with increased appetite and body weight. Likewise, slow growth correlates with decreased appetite and body weight. Food consumption and food-seeking behaviour are directly modulated by central serotonergic (5-hydroxytryptamine, 5-HT) pathways. This study examined the effect of a rat maternal postnatal low protein (PLP) diet on 5-HT receptor mediated food intake in offspring. METHODS: Microarray analyses, in situ hybridization or laser capture microdissection of the ARC followed by RT-PCR were used to identify genes up- or down-regulated in the arcuate nucleus of the hypothalamus (ARC) of 3-month-old male PLP rats. Third ventricle cannulation was used to identify altered sensitivity to serotonin receptor agonists and antagonists with respect to food intake. RESULTS: Male PLP offspring consumed less food and had lower growth rates up to 3 months of age compared with Control offspring from dams fed a normal diet. In total, 97 genes were upregulated including the 5-HT5A receptor (5-HT5AR) and 149 downregulated genes in PLP rats compared with Controls. The former obesity medication fenfluramine and the 5-HT receptor agonist 5-Carboxamidotryptamine (5-CT) significantly suppressed food intake in both groups, but the PLP offspring were more sensitive to d-fenfluramine and 5-CT compared with Controls. The effect of 5-CT was antagonized by the 5-HT5AR antagonist SB699551. 5-CT also reduced NPY-induced hyperphagia in both Control and PLP rats but was more effective in PLP offspring. CONCLUSIONS: Postnatal low protein programming of growth in rats enhances the central effects of serotonin on appetite by increasing hypothalamic 5-HT5AR expression and sensitivity. These findings provide insight into the possible mechanisms through which a maternal low protein diet during lactation programs reduced growth and appetite in offspring.
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Apetite/fisiologia , Peso Corporal/fisiologia , Regulação da Expressão Gênica no Desenvolvimento/genética , Hipotálamo/metabolismo , Receptores de Serotonina , Animais , Dieta , Feminino , Masculino , Obesidade/metabolismo , Ratos , Receptores de Serotonina/genética , Receptores de Serotonina/metabolismo , Transcriptoma/genéticaRESUMO
Endoplasmic reticulum (ER) thiol oxidases initiate a disulfide relay to oxidatively fold secreted proteins. We found that combined loss-of-function mutations in genes encoding the ER thiol oxidases ERO1α, ERO1ß, and PRDX4 compromised the extracellular matrix in mice and interfered with the intracellular maturation of procollagen. These severe abnormalities were associated with an unexpectedly modest delay in disulfide bond formation in secreted proteins but a profound, 5-fold lower procollagen 4-hydroxyproline content and enhanced cysteinyl sulfenic acid modification of ER proteins. Tissue ascorbic acid content was lower in mutant mice, and ascorbic acid supplementation improved procollagen maturation and lowered sulfenic acid content in vivo. In vitro, the presence of a sulfenic acid donor accelerated the oxidative inactivation of ascorbate by an H(2)O(2)-generating system. Compromised ER disulfide relay thus exposes protein thiols to competing oxidation to sulfenic acid, resulting in depletion of ascorbic acid, impaired procollagen proline 4-hydroxylation, and a noncanonical form of scurvy.
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Ácido Ascórbico/metabolismo , Retículo Endoplasmático/metabolismo , Glicoproteínas/metabolismo , Oxirredutases/metabolismo , Escorbuto/etiologia , Escorbuto/metabolismo , Animais , Ácido Ascórbico/farmacologia , Células Cultivadas , Tecido Conjuntivo/metabolismo , Tecido Conjuntivo/patologia , Modelos Animais de Doenças , Dissulfetos/metabolismo , Feminino , Glicoproteínas/deficiência , Glicoproteínas/genética , Masculino , Camundongos , Camundongos Mutantes , Mutação , Oxirredução , Oxirredutases/deficiência , Oxirredutases/genética , Peroxirredoxinas/deficiência , Peroxirredoxinas/genética , Peroxirredoxinas/metabolismo , Pró-Colágeno/metabolismo , Dobramento de Proteína , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Escorbuto/genética , Escorbuto/patologia , Ácidos Sulfênicos/metabolismo , Fator de Crescimento Transformador beta/metabolismoRESUMO
An intergenic region of human chromosome 2 (2p25.3) harbors genetic variants which are among those most strongly and reproducibly associated with obesity. The gene closest to these variants is TMEM18, although the molecular mechanisms mediating these effects remain entirely unknown. Tmem18 expression in the murine hypothalamic paraventricular nucleus (PVN) was altered by changes in nutritional state. Germline loss of Tmem18 in mice resulted in increased body weight, which was exacerbated by high fat diet and driven by increased food intake. Selective overexpression of Tmem18 in the PVN of wild-type mice reduced food intake and also increased energy expenditure. We provide evidence that TMEM18 has four, not three, transmembrane domains and that it physically interacts with key components of the nuclear pore complex. Our data support the hypothesis that TMEM18 itself, acting within the central nervous system, is a plausible mediator of the impact of adjacent genetic variation on human adiposity.
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Apetite/genética , Peso Corporal/genética , Proteínas de Membrana/metabolismo , Obesidade/genética , Animais , Masculino , Proteínas de Membrana/genética , Camundongos , Camundongos Knockout , Núcleo Hipotalâmico Paraventricular/metabolismo , Proteínas de Transporte VesicularRESUMO
OBJECTIVE: Myelosuppression is a life-threatening complication of thiopurine therapy, and the incidence of thiopurine-induced myelosuppression is higher in East Asians than in Europeans. We investigated genetic factors associated with thiopurine-induced leukopenia in patients with IBD. DESIGN: A genome-wide association study (GWAS) was conducted in thiopurine-treated patients with IBD, followed by high-throughput sequencing of genes identified as significant in the GWAS or those involved in thiopurine metabolism (n=331). Significant loci associated with thiopurine-induced leukopenia were validated in two additional replication cohorts (n=437 and n=330). Functional consequences of FTO (fat mass and obesity-associated) variant were examined both in vitro and in vivo. RESULTS: The GWAS identified two loci associated with thiopurine-induced leukopenia (rs16957920, FTO intron; rs2834826, RUNX1 intergenic). High-throughput targeted sequencing indicated that an FTO coding variant (rs79206939, p.A134T) linked to rs16957920 is associated with thiopurine-induced leukopenia. This result was further validated in two replication cohorts (combined p=1.3×10-8, OR=4.3). The frequency of FTO p.A134T is 5.1% in Koreans but less than 0.1% in Western populations. The p.A134T variation reduced FTO activity by 65% in the nucleotide demethylase assay. In vivo experiments revealed that Fto-/- and Fto+/- mice were more susceptible to thiopurine-induced myelosuppression than wild-type mice. CONCLUSIONS: The results suggest that the hypomorphic FTO p.A134T variant is associated with thiopurine-induced leukopenia. These results shed light on the novel physiological role of FTO and provide a potential pharmacogenetic biomarker for thiopurine therapy.
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Dioxigenase FTO Dependente de alfa-Cetoglutarato/genética , Azatioprina/efeitos adversos , Imunossupressores/efeitos adversos , Doenças Inflamatórias Intestinais/tratamento farmacológico , Leucopenia/induzido quimicamente , Mercaptopurina/efeitos adversos , Polimorfismo de Nucleotídeo Único , Adolescente , Adulto , Idoso , Animais , Azatioprina/uso terapêutico , Estudos de Casos e Controles , Estudos de Coortes , Feminino , Marcadores Genéticos , Estudo de Associação Genômica Ampla , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Imunossupressores/uso terapêutico , Doenças Inflamatórias Intestinais/genética , Leucopenia/genética , Masculino , Mercaptopurina/uso terapêutico , Camundongos , Camundongos Knockout , Pessoa de Meia-Idade , República da Coreia , Análise de Sequência de DNA , Adulto JovemRESUMO
At one level, obesity is clearly a problem of simple physics, a result of eating too much and not expending enough energy. The more complex question, however, is why do some people eat more than others? Studies of human and mouse genetics over the past two decades have uncovered a number of pathways within the brain that play a key role in the control of food intake. A prime example is the leptin-melanocortin pathway, which we now know greatly contributes to mammalian appetitive behaviour. However, genetic disruption of this pathway remains rare and does not represent the major burden of the disease that is carried by those of us with 'common obesity'. In recent years, genome-wide association studies have revealed more than 100 different candidate genes linked to BMI, with most (including many components of the melanocortin pathway) acting in the central nervous system and influencing food intake. So while severe disruption of the melanocortin pathway results in severe obesity, subtle variations in these genes influence where you might sit in the normal distribution of BMI. As we now enter this 'post-genomics' world, can this new information influence our treatment and management of obese patients?
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Obesidade/etiologia , Animais , Índice de Massa Corporal , Cães , Ingestão de Alimentos , Estudo de Associação Genômica Ampla , Humanos , Hipotálamo/metabolismo , Melanocortinas/genéticaRESUMO
AIMS/HYPOTHESIS: Intra-islet and gut-islet crosstalk are critical in orchestrating basal and postprandial metabolism. The aim of this study was to identify regulatory proteins and receptors underlying somatostatin secretion though the use of transcriptomic comparison of purified murine alpha, beta and delta cells. METHODS: Sst-Cre mice crossed with fluorescent reporters were used to identify delta cells, while Glu-Venus (with Venus reported under the control of the Glu [also known as Gcg] promoter) mice were used to identify alpha and beta cells. Alpha, beta and delta cells were purified using flow cytometry and analysed by RNA sequencing. The role of the ghrelin receptor was validated by imaging delta cell calcium concentrations using islets with delta cell restricted expression of the calcium reporter GCaMP3, and in perfused mouse pancreases. RESULTS: A database was constructed of all genes expressed in alpha, beta and delta cells. The gene encoding the ghrelin receptor, Ghsr, was highlighted as being highly expressed and enriched in delta cells. Activation of the ghrelin receptor raised cytosolic calcium levels in primary pancreatic delta cells and enhanced somatostatin secretion in perfused pancreases, correlating with a decrease in insulin and glucagon release. The inhibition of insulin secretion by ghrelin was prevented by somatostatin receptor antagonism. CONCLUSIONS/INTERPRETATION: Our transcriptomic database of genes expressed in the principal islet cell populations will facilitate rational drug design to target specific islet cell types. The present study indicates that ghrelin acts specifically on delta cells within pancreatic islets to elicit somatostatin secretion, which in turn inhibits insulin and glucagon release. This highlights a potential role for ghrelin in the control of glucose metabolism.
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Grelina/farmacologia , Células Secretoras de Glucagon/efeitos dos fármacos , Células Secretoras de Insulina/efeitos dos fármacos , Células Secretoras de Somatostatina/efeitos dos fármacos , Transcriptoma/genética , Animais , Cálcio/metabolismo , Glucagon/metabolismo , Células Secretoras de Glucagon/metabolismo , Insulina/metabolismo , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/efeitos dos fármacos , Ilhotas Pancreáticas/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Células Secretoras de Somatostatina/metabolismoRESUMO
AIMS/HYPOTHESIS: Ageing is a major risk factor for development of metabolic diseases such as type 2 diabetes. Identification of the mechanisms underlying this association could help to elucidate the relationship between age-associated progressive loss of metabolic health and development of type 2 diabetes. We aimed to determine molecular signatures during ageing in the endocrine pancreas. METHODS: Global gene transcription was measured in pancreatic islets isolated from young and old rats by Ilumina BeadChip arrays. Promoter DNA methylation was measured by Sequenom MassArray in 46 genes that showed differential expression with age, and correlations with expression were established. Alterations in morphological and cellular processes with age were determined by immunohistochemical methods. RESULTS: Age-related changes in gene expression were found at 623 loci (>1.5-fold, false discovery rate [FDR] <5%), with a significant (FDR < 0.05) enrichment in genes previously implicated in islet-cell function (Enpp1, Abcc8), type 2 diabetes (Tspan8, Kcnq1), inflammatory processes (Cxcl9, Il33) and extracellular matrix organisation (Col3a1, Dpt). Age-associated transcriptional differences negatively correlated with promoter DNA methylation at several loci related to inflammation, glucose homeostasis, cell proliferation and cell-matrix interactions (Il33, Cxcl9, Gpr119, Fbp2, Col3a1, Dpt, Spp1). CONCLUSIONS/INTERPRETATION: Our findings suggest that a significant proportion of pancreatic islets develop a low-grade 'chronic' inflammatory status with ageing and this may trigger altered functional plasticity. Furthermore, we identified changes in expression of genes previously linked to type 2 diabetes and associated changes in DNA methylation that could explain their age-associated dysregulation. These findings provide new insights into key (epi)genetic signatures of the ageing process in islets.
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Envelhecimento/fisiologia , Diabetes Mellitus Tipo 2/etiologia , Inflamação/genética , Ilhotas Pancreáticas/metabolismo , Envelhecimento/genética , Animais , Quimiocina CXCL9/genética , Colágeno Tipo III/genética , Metilação de DNA/genética , Diabetes Mellitus Tipo 2/metabolismo , Epigênese Genética/genética , Inflamação/metabolismo , Canal de Potássio KCNQ1/genética , Masculino , Diester Fosfórico Hidrolases/genética , Pirofosfatases/genética , Ratos , Receptores de Sulfonilureias/genética , Tetraspaninas/genéticaRESUMO
Transcription factors of the nuclear factor one (NFI) family play a pivotal role in the development of the nervous system. One member, NFIX, regulates the development of the neocortex, hippocampus, and cerebellum. Postnatal Nfix(-/-) mice also display abnormalities within the subventricular zone (SVZ) lining the lateral ventricles, a region of the brain comprising a neurogenic niche that provides ongoing neurogenesis throughout life. Specifically, Nfix(-/-) mice exhibit more PAX6-expressing progenitor cells within the SVZ. However, the mechanism underlying the development of this phenotype remains undefined. Here, we reveal that NFIX contributes to multiple facets of SVZ development. Postnatal Nfix(-/-) mice exhibit increased levels of proliferation within the SVZ, both in vivo and in vitro as assessed by a neurosphere assay. Furthermore, we show that the migration of SVZ-derived neuroblasts to the olfactory bulb is impaired, and that the olfactory bulbs of postnatal Nfix(-/-) mice are smaller. We also demonstrate that gliogenesis within the rostral migratory stream is delayed in the absence of Nfix, and reveal that Gdnf (glial-derived neurotrophic factor), a known attractant for SVZ-derived neuroblasts, is a target for transcriptional activation by NFIX. Collectively, these findings suggest that NFIX regulates both proliferation and migration during the development of the SVZ neurogenic niche.
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Movimento Celular , Proliferação de Células , Ventrículos Laterais/embriologia , Fatores de Transcrição NFI/fisiologia , Células-Tronco Neurais/fisiologia , Neurogênese , Animais , Feminino , Fator Neurotrófico Derivado de Linhagem de Célula Glial/metabolismo , Interneurônios/fisiologia , Ventrículos Laterais/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fatores de Transcrição NFI/genética , Fatores de Transcrição NFI/metabolismo , Neuroglia/fisiologia , Bulbo Olfatório/embriologia , Bulbo Olfatório/metabolismo , Nicho de Células-TroncoRESUMO
The strongest BMI-associated GWAS locus in humans is the FTO gene. Rodent studies demonstrate a role for FTO in energy homeostasis and body composition. The phenotypes observed in loss of expression studies are complex with perinatal lethality, stunted growth from weaning, and significant alterations in body composition. Thus understanding how and where Fto regulates food intake, energy expenditure, and body composition is a challenge. To address this we generated a series of mice with distinct temporal and spatial loss of Fto expression. Global germline loss of Fto resulted in high perinatal lethality and a reduction in body length, fat mass, and lean mass. When ratio corrected for lean mass, mice had a significant increase in energy expenditure, but more appropriate multiple linear regression normalisation showed no difference in energy expenditure. Global deletion of Fto after the in utero and perinatal period, at 6 weeks of age, removed the high lethality of germline loss. However, there was a reduction in weight by 9 weeks, primarily as loss of lean mass. Over the subsequent 10 weeks, weight converged, driven by an increase in fat mass. There was a switch to a lower RER with no overall change in food intake or energy expenditure. To test if the phenotype can be explained by loss of Fto in the mediobasal hypothalamus, we sterotactically injected adeno-associated viral vectors encoding Cre recombinase to cause regional deletion. We observed a small reduction in food intake and weight gain with no effect on energy expenditure or body composition. Thus, although hypothalamic Fto can impact feeding, the effect of loss of Fto on body composition is brought about by its actions at sites elsewhere. Our data suggest that Fto may have a critical role in the control of lean mass, independent of its effect on food intake.
Assuntos
Composição Corporal/genética , Ingestão de Alimentos/genética , Metabolismo Energético/genética , Oxigenases de Função Mista/genética , Obesidade , Oxo-Ácido-Liases/genética , Dioxigenase FTO Dependente de alfa-Cetoglutarato , Animais , Peso Corporal/genética , Desenvolvimento Embrionário/genética , Regulação da Expressão Gênica no Desenvolvimento , Células Germinativas/metabolismo , Homeostase , Humanos , Masculino , Camundongos , Obesidade/genética , Obesidade/metabolismoRESUMO
SNPs in the first intron of FTO (fat mass and obesity associated) are strongly associated with human obesity. While it is not yet formally established that this effect is mediated through the actions of the FTO protein itself, loss of function mutations in FTO or its murine homologue Fto result in severe growth retardation, and mice globally overexpressing FTO are obese. The mechanisms through which FTO influences growth and body composition are unknown. We describe a role for FTO in the coupling of amino acid levels to mammalian target of rapamycin complex 1 signaling. These findings suggest that FTO may influence body composition through playing a role in cellular nutrient sensing.