RESUMO
Obesity and insulin resistance are risk factors for the pathogenesis of type 2 diabetes (T2D). Here, we report that hepatic TGF-ß1 expression positively correlates with obesity and insulin resistance in mice and humans. Hepatic TGF-ß1 deficiency decreased blood glucose levels in lean mice and improved glucose and energy dysregulations in diet-induced obese (DIO) mice and diabetic mice. Conversely, overexpression of TGF-ß1 in the liver exacerbated metabolic dysfunctions in DIO mice. Mechanistically, hepatic TGF-ß1 and Foxo1 are reciprocally regulated: fasting or insulin resistance caused Foxo1 activation, increasing TGF-ß1 expression, which, in turn, activated protein kinase A, stimulating Foxo1-S273 phosphorylation to promote Foxo1-mediated gluconeogenesis. Disruption of TGF-ß1âFoxo1âTGF-ß1 looping by deleting TGF-ß1 receptor II in the liver or by blocking Foxo1-S273 phosphorylation ameliorated hyperglycemia and improved energy metabolism in adipose tissues. Taken together, our studies reveal that hepatic TGF-ß1âFoxo1âTGF-ß1 looping could be a potential therapeutic target for prevention and treatment of obesity and T2D. ARTICLE HIGHLIGHTS: Hepatic TGF-ß1 levels are increased in obese humans and mice. Hepatic TGF-ß1 maintains glucose homeostasis in lean mice and causes glucose and energy dysregulations in obese and diabetic mice. Hepatic TGF-ß1 exerts an autocrine effect to promote hepatic gluconeogenesis via cAMP-dependent protein kinase-mediated Foxo1 phosphorylation at serine 273, endocrine effects on brown adipose tissue action, and inguinal white adipose tissue browning (beige fat), causing energy imbalance in obese and insulin-resistant mice. TGF-ß1âFoxo1âTGF-ß1 looping in hepatocytes plays a critical role in controlling glucose and energy metabolism in health and disease.
Assuntos
Diabetes Mellitus Experimental , Diabetes Mellitus Tipo 2 , Metabolismo Energético , Gluconeogênese , Animais , Camundongos , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Metabolismo Energético/genética , Proteína Forkhead Box O1/genética , Proteína Forkhead Box O1/metabolismo , Gluconeogênese/genética , Glucose/metabolismo , Resistência à Insulina , Fígado/metabolismo , Camundongos Endogâmicos C57BL , Obesidade/metabolismo , Fator de Crescimento Transformador beta1/farmacologiaRESUMO
Gain-of-function mutations in the gene encoding the phosphatidylinositol-3-OH kinase catalytic subunit p110δ (PI3Kδ) result in a human primary immunodeficiency characterized by lymphoproliferation, respiratory infections and inefficient responses to vaccines. However, what promotes these immunological disturbances at the cellular and molecular level remains unknown. We generated a mouse model that recapitulated major features of this disease and used this model and patient samples to probe how hyperactive PI3Kδ fosters aberrant humoral immunity. We found that mutant PI3Kδ led to co-stimulatory receptor ICOS-independent increases in the abundance of follicular helper T cells (TFH cells) and germinal-center (GC) B cells, disorganized GCs and poor class-switched antigen-specific responses to immunization, associated with altered regulation of the transcription factor FOXO1 and pro-apoptotic and anti-apoptotic members of the BCL-2 family. Notably, aberrant responses were accompanied by increased reactivity to gut bacteria and a broad increase in autoantibodies that were dependent on stimulation by commensal microbes. Our findings suggest that proper regulation of PI3Kδ is critical for ensuring optimal host-protective humoral immunity despite tonic stimulation from the commensal microbiome.
Assuntos
Linfócitos B/fisiologia , Microbioma Gastrointestinal/imunologia , Centro Germinativo/fisiologia , Mutação/genética , Fosfatidilinositol 3-Quinases/genética , Linfócitos T Auxiliares-Indutores/fisiologia , Animais , Autoanticorpos/sangue , Células Cultivadas , Classe I de Fosfatidilinositol 3-Quinases/genética , Modelos Animais de Doenças , Proteína Forkhead Box O1/genética , Proteína Forkhead Box O1/metabolismo , Humanos , Imunidade Humoral/genética , Switching de Imunoglobulina/genética , Síndromes de Imunodeficiência/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismoRESUMO
Although many functions of activating transcription factor 4 (ATF4) are identified, a role of ATF4 in the hypothalamus in regulating energy homeostasis is unknown. Here, we generated adult-onset agouti-related peptide neuron-specific ATF4 knockout (AgRP-ATF4 KO) mice and found that these mice were lean, with improved insulin and leptin sensitivity and decreased hepatic lipid accumulation. Furthermore, AgRP-ATF4 KO mice showed reduced food intake and increased energy expenditure, mainly because of enhanced thermogenesis in brown adipose tissue. Moreover, AgRP-ATF4 KO mice were resistant to high-fat diet-induced obesity, insulin resistance, and liver steatosis and maintained at a higher body temperature under cold stress. Interestingly, the expression of FOXO1 was directly regulated by ATF4 via binding to the cAMP-responsive element site on its promoter in hypothalamic GT1-7 cells. Finally, Foxo1 expression was reduced in the arcuate nucleus (ARC) of the hypothalamus of AgRP-ATF4 KO mice, and adenovirus-mediated overexpression of FOXO1 in ARC increased the fat mass in AgRP-ATF4 KO mice. Collectively, our data demonstrate a novel function of ATF4 in AgRP neurons of the hypothalamus in energy balance and lipid metabolism and suggest hypothalamic ATF4 as a potential drug target for treating obesity and its related metabolic disorders.
