RESUMEN
OBJECTIVE: Type 1 diabetes (T1D) is an autoimmune disease caused by the destruction of pancreatic ß-cells producing insulin. Both T1D patients and animal models exhibit gut microbiota and mucosa alterations, although the exact cause for these remains poorly understood. We investigated the production of key cytokines controlling gut integrity, the abundance of segmented filamentous bacteria (SFB) involved in the production of these cytokines, and the respective role of autoimmune inflammation and hyperglycaemia. DESIGN: We used several mouse models of autoimmune T1D as well as mice rendered hyperglycaemic without inflammation to study gut mucosa and microbiota dysbiosis. We analysed cytokine expression in immune cells, epithelial cell function, SFB abundance and microbiota composition by 16S sequencing. We assessed the role of anti-tumour necrosis factor α on gut mucosa inflammation and T1D onset. RESULTS: We show in models of autoimmune T1D a conserved loss of interleukin (IL)-17A, IL-22 and IL-23A in gut mucosa. Intestinal epithelial cell function was altered and gut integrity was impaired. These defects were associated with dysbiosis including progressive loss of SFB. Transfer of diabetogenic T-cells recapitulated these gut alterations, whereas induction of hyperglycaemia with no inflammation failed to do so. Moreover, anti-inflammatory treatment restored gut mucosa and immune cell function and dampened diabetes incidence. CONCLUSION: Our results demonstrate that gut mucosa alterations and dysbiosis in T1D are primarily linked to inflammation rather than hyperglycaemia. Anti-inflammatory treatment preserves gut homeostasis and protective commensal flora reducing T1D incidence.
Asunto(s)
Bacterias/aislamiento & purificación , Diabetes Mellitus Tipo 1/complicaciones , Disbiosis/etiología , Microbioma Gastrointestinal , Mucosa Intestinal/microbiología , Mucosa Intestinal/patología , Animales , Citocinas/metabolismo , Diabetes Mellitus Tipo 1/metabolismo , Diabetes Mellitus Tipo 1/microbiología , Modelos Animales de Enfermedad , Células Epiteliales/metabolismo , Células Epiteliales/patología , Hiperglucemia/etiología , Inflamación/etiología , Mucosa Intestinal/metabolismo , RatonesRESUMEN
The gut-brain peptide neuromedin U (NMU) decreases food intake and body weight and improves glucose tolerance. Here, we characterized NMU as an enteropeptide and determined how it impacts glucose excursion. NMU was expressed predominantly in the proximal small intestine, and its secretion was triggered by ingestion of a mixed meal. Although a single peripheral injection of NMU in C57BL/6NRj mice prevented the rise of glycemia upon an oral but not an intraperitoneal load of glucose, it unexpectedly prevented insulin secretion, only slightly improved peripheral insulin sensitivity, and barely reduced intestinal glucose absorption. Interestingly, peripheral administration of NMU abrogated gastric emptying. NMU receptors 1 and 2 were detected in pyloric muscles and NMU was able to directly induce pyloric contraction in a dose-dependent manner ex vivo in isometric chambers. Using a modified glucose tolerance test, we demonstrate that improvement of oral glucose tolerance by NMU was essentially, if not exclusively, because of its impact on gastric emptying. Part of this effect was abolished in vagotomized (VagoX) mice, suggesting implication of the vagus tone. Accordingly, peripheral injection of NMU was associated with increased number of c-FOS-positive neurons in the nucleus of the solitary tract, which was partly prevented in VagoX mice. Finally, NMU kept its ability to improve oral glucose tolerance in obese and diabetic murine models. Together, these data demonstrate that NMU is an enteropeptide that prevents gastric emptying directly by triggering pylorus contraction and indirectly through vagal afferent neurons. This blockade consequently reduces intestinal nutrient absorption and thereby results in an apparent improved tolerance to oral glucose challenge.-Jarry, A.-C., Merah, N., Cisse, F., Cayetanot, F., Fiamma, M.-N., Willemetz, A., Gueddouri, D., Barka, B., Valet, P., Guilmeau, S., Bado, A., Le Beyec, J., Bodineau, L., Le Gall, M. Neuromedin U is a gut peptide that alters oral glucose tolerance by delaying gastric emptying via direct contraction of the pylorus and vagal-dependent mechanisms.
Asunto(s)
Glucemia/efectos de los fármacos , Vaciamiento Gástrico/efectos de los fármacos , Glucosa/metabolismo , Neuropéptidos/farmacología , Péptidos/farmacología , Píloro/efectos de los fármacos , Nervio Vago/efectos de los fármacos , Animales , Peso Corporal/efectos de los fármacos , Ingestión de Alimentos/efectos de los fármacos , Microbioma Gastrointestinal/efectos de los fármacos , Prueba de Tolerancia a la Glucosa/métodos , Masculino , Ratones , Ratones Endogámicos C57BLRESUMEN
Metabolic diseases such as obesity and type 2 diabetes are recognized as independent risk factors for hepatocellular carcinoma (HCC). Hyperinsulinemia, a hallmark of these pathologies, is suspected to be involved in HCC development. The molecular adapter growth factor receptor binding protein 14 (Grb14) is an inhibitor of insulin receptor catalytic activity, highly expressed in the liver. To study its involvement in hepatocyte proliferation, we specifically inhibited its liver expression using a short hairpin RNA strategy in mice. Enhanced insulin signaling upon Grb14 inhibition was accompanied by a transient induction of S-phase entrance by quiescent hepatocytes, indicating that Grb14 is a potent repressor of cell division. The proliferation of Grb14-deficient hepatocytes was cell-autonomous as it was also observed in primary cell cultures. Combined Grb14 down-regulation and insulin signaling blockade using pharmacological approaches as well as genetic mouse models demonstrated that Grb14 inhibition-mediated hepatocyte division involved insulin receptor activation and was mediated by the mechanistic target of rapamycin complex 1-S6K pathway and the transcription factor E2F1. In order to determine a potential dysregulation in GRB14 gene expression in human pathophysiology, a collection of 85 human HCCs was investigated. This revealed a highly significant and frequent decrease in GRB14 expression in hepatic tumors when compared to adjacent nontumoral parenchyma, with 60% of the tumors exhibiting a reduced Grb14 mRNA level. CONCLUSION: Our study establishes Grb14 as a physiological repressor of insulin mitogenic action in the liver and further supports that dysregulation of insulin signaling is associated with HCC. (Hepatology 2017;65:1352-1368).
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/genética , Carcinoma Hepatocelular/fisiopatología , Diabetes Mellitus Tipo 2/fisiopatología , Neoplasias Hepáticas/fisiopatología , Receptor de Insulina/metabolismo , Animales , Carcinoma Hepatocelular/epidemiología , Carcinoma Hepatocelular/metabolismo , Línea Celular Tumoral , Proliferación Celular/genética , Células Cultivadas , Diabetes Mellitus Tipo 2/epidemiología , Diabetes Mellitus Tipo 2/metabolismo , Modelos Animales de Enfermedad , Regulación hacia Abajo , Hepatocitos/citología , Hepatocitos/metabolismo , Humanos , Neoplasias Hepáticas/epidemiología , Neoplasias Hepáticas/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Distribución Aleatoria , Sensibilidad y EspecificidadRESUMEN
Since glucose is the principal energy source for most cells, many organisms have evolved numerous and sophisticated mechanisms to sense glucose and respond to it appropriately. In this context, cloning of the carbohydrate responsive element binding protein has unraveled a critical molecular link between glucose metabolism and transcriptional reprogramming induced by glucose. In this review, we detail major findings that have advanced our knowledge of glucose sensing.
Asunto(s)
Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/metabolismo , Metabolismo Energético , Glucosa/metabolismo , Transducción de Señal , Tejido Adiposo/metabolismo , Tejido Adiposo/patología , Animales , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patología , Ácidos Grasos/metabolismo , Humanos , Resistencia a la Insulina , Hígado/metabolismo , Hígado/patología , Neoplasias/metabolismo , Neoplasias/patología , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Enfermedad del Hígado Graso no Alcohólico/patología , Isoformas de ProteínasRESUMEN
The importance of B-isoform of leptin receptor (LEPR-B) signaling in the hypothalamus, pancreas, or liver has been well characterized, but in the intestine, a unique site of entry for dietary nutrition into the body, it has been relatively ignored. To address this question, we characterized a mouse model deficient for LEPR-B specifically in intestinal epithelial cells (IECs). (IEC)LEPR-B-knockout (KO) and wild-type (WT) mice were generated by Cre-Lox strategy and fed a normal or high-fat diet (HFD). The analyses of the animals involved histology and immunohistochemistry of intestinal mucosa, indirect calorimetric measurements, whole-body composition, and expression and activities of nutrient transporters. (IEC)LEPR-B-KO mice exhibited a 2-fold increase in length of jejunal villi and have normal growth on a normal diet but were less susceptible (P<0.01) to HFD-induced obesity. No differences occurred in energy intake and expenditure between (IEC)LEPR-B-WT and -KO mice, but (IEC)LEPR-B-KO mice fed an HFD showed increased excreted fats (P<0.05). Activities of the Na(+)/glucose cotransporter SGLT-1 and GLUT2 were unaffected in LEPR-B-KO jejunum, while GLUT5-mediated fructose transport and PepT1-mediated peptide transport were substantially reduced (P<0.01). These data demonstrate that intestinal LEPR-B signaling is important for the onset of diet-induced obesity. They suggest that intestinal LEPR-B could be a potential per os target for prevention against obesity.
Asunto(s)
Dieta Alta en Grasa/efectos adversos , Proteínas Facilitadoras del Transporte de la Glucosa/metabolismo , Transportador de Glucosa de Tipo 2/metabolismo , Mucosa Intestinal/metabolismo , Obesidad/etiología , Receptores de Leptina/fisiología , Simportadores/metabolismo , Animales , Western Blotting , Composición Corporal , Peso Corporal , Proliferación Celular , Células Cultivadas , Ingestión de Energía , Femenino , Proteínas Facilitadoras del Transporte de la Glucosa/genética , Transportador de Glucosa de Tipo 2/genética , Transportador de Glucosa de Tipo 5 , Técnicas para Inmunoenzimas , Mucosa Intestinal/patología , Leptina/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Transportador de Péptidos 1 , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Simportadores/genéticaRESUMEN
[This corrects the article DOI: 10.1016/j.jhepr.2023.100878.].
RESUMEN
Cancer cells integrate multiple biosynthetic demands to drive unrestricted proliferation. How these cellular processes crosstalk to fuel cancer cell growth is still not fully understood. Here, we uncover the mechanisms by which the transcription factor Carbohydrate responsive element binding protein (ChREBP) functions as an oncogene during hepatocellular carcinoma (HCC) development. Mechanistically, ChREBP triggers the expression of the PI3K regulatory subunit p85α, to sustain the activity of the pro-oncogenic PI3K/AKT signaling pathway in HCC. In parallel, increased ChREBP activity reroutes glucose and glutamine metabolic fluxes into fatty acid and nucleic acid synthesis to support PI3K/AKT-mediated HCC growth. Thus, HCC cells have a ChREBP-driven circuitry that ensures balanced coordination between PI3K/AKT signaling and appropriate cell anabolism to support HCC development. Finally, pharmacological inhibition of ChREBP by SBI-993 significantly suppresses in vivo HCC tumor growth. Overall, we show that targeting ChREBP with specific inhibitors provides an attractive therapeutic window for HCC treatment.
Asunto(s)
Carcinoma Hepatocelular , Neoplasias Hepáticas , Humanos , Carcinoma Hepatocelular/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Neoplasias Hepáticas/metabolismo , Transducción de Señal , Carcinogénesis , Proliferación Celular , Línea Celular TumoralRESUMEN
Background & Aims: O-GlcNAcylation is a reversible post-translational modification controlled by the activity of two enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). In the liver, O-GlcNAcylation has emerged as an important regulatory mechanism underlying normal liver physiology and metabolic disease. Methods: To address whether OGT acts as a critical hepatic nutritional node, mice with a constitutive hepatocyte-specific deletion of OGT (OGTLKO) were generated and challenged with different carbohydrate- and lipid-containing diets. Results: Analyses of 4-week-old OGTLKO mice revealed significant oxidative and endoplasmic reticulum stress, and DNA damage, together with inflammation and fibrosis, in the liver. Susceptibility to oxidative and endoplasmic reticulum stress-induced apoptosis was also elevated in OGTLKO hepatocytes. Although OGT expression was partially recovered in the liver of 8-week-old OGTLKO mice, hepatic injury and fibrosis were not rescued but rather worsened with time. Interestingly, weaning of OGTLKO mice on a ketogenic diet (low carbohydrate, high fat) fully prevented the hepatic alterations induced by OGT deletion, indicating that reduced carbohydrate intake protects an OGT-deficient liver. Conclusions: These findings pinpoint OGT as a key mediator of hepatocyte homeostasis and survival upon carbohydrate intake and validate OGTLKO mice as a valuable model for assessing therapeutical approaches of advanced liver fibrosis. Impact and Implications: Our study shows that hepatocyte-specific deletion of O-GlcNAc transferase (OGT) leads to severe liver injury, reinforcing the importance of O-GlcNAcylation and OGT for hepatocyte homeostasis and survival. Our study also validates the Ogt liver-deficient mouse as a valuable model for the study of advanced liver fibrosis. Importantly, as the severe hepatic fibrosis of Ogt liver-deficient mice could be fully prevented upon feeding on a ketogenic diet (i.e. very-low-carbohydrate, high-fat diet) this work underlines the potential interest of nutritional intervention as antifibrogenic strategies.
RESUMEN
In recent years, a substantial body of evidence has accumulated to support the notion that signaling pathways known to be important during embryonic development play important roles in regulating self-renewing tissues and tumorigenesis. In this context, Notch signaling is now recognized as essential for maintaining progenitor/ stem cell population as well as for regulating cell lineage differentiation in the normal intestinal mucosa. Many studies have also showed that Notch signaling is constitutively activated in colorectal cancer and its inhibition is able to suppress the cell growth and sensitize cancer cells to treatment-induced apoptosis. Therefore, discovery of the role of γ-secretase in the Notch signaling activation has prompted intensive research on the potential use of γ-secretase inhibitors in the treatment of colon cancer. This chapter reviews the current understanding and research findings of the role of Notch signaling in intestinal homeostasis and colorectal cancer and discusses the possible Notch targeting approaches as novel molecular therapy for intestinal cancer.
Asunto(s)
Neoplasias Intestinales/metabolismo , Neoplasias Intestinales/patología , Receptores Notch/metabolismo , Animales , Humanos , Transducción de SeñalRESUMEN
OBJECTIVE: A common feature of metabolic diseases is their association with chronic low-grade inflammation. While enhanced gut permeability and systemic bacterial endotoxin translocation have been suggested as key players of this metaflammation, the mechanistic bases underlying these features upon the diabesity cascade remain partly understood. METHODS: Here, we show in mice that, independently of obesity, the induction of acute and global insulin resistance and associated hyperglycemia, upon treatment with an insulin receptor (IR) antagonist (S961), elicits gut hyperpermeability without triggering systemic inflammatory response. RESULTS: Of note, S961-treated diabetic mice display major defects of gut barrier epithelial functions, such as increased epithelial paracellular permeability and impaired cell-cell junction integrity. We also observed in these mice the early onset of a severe gut dysbiosis, as characterized by the bloom of pro-inflammatory Proteobacteria, and the later collapse of Paneth cells antimicrobial defense. Interestingly, S961 treatment discontinuation is sufficient to promptly restore both the gut microbial balance and the intestinal barrier integrity. Moreover, fecal transplant approaches further confirm that S961-mediated dybiosis contributes at least partly to the disruption of the gut selective epithelial permeability upon diabetic states. CONCLUSIONS: Together, our results highlight that insulin signaling is an indispensable gatekeeper of intestinal barrier integrity, acting as a safeguard against microbial imbalance and acute infections by enteropathogens.
Asunto(s)
Diabetes Mellitus Experimental , Microbioma Gastrointestinal , Resistencia a la Insulina , Animales , Disbiosis/metabolismo , Disbiosis/microbiología , Microbioma Gastrointestinal/fisiología , Inflamación/metabolismo , RatonesRESUMEN
TxNIP (Thioredoxin-interacting protein) is considered as a potential drug target for type 2 diabetes. Although TxNIP expression is correlated with hyperglycemia and glucotoxicity in pancreatic ß cells, its regulation in liver cells has been less investigated. In the current study, we aim at providing a better understanding of Txnip regulation in hepatocytes in response to physiological stimuli and in the context of hyperglycemia in db/db mice. We focused on regulatory pathways governed by ChREBP (Carbohydrate Responsive Element Binding Protein) and FoxO1 (Forkhead box protein O1), transcription factors that play central roles in mediating the effects of glucose and fasting on gene expression, respectively. Studies using genetically modified mice reveal that hepatic TxNIP is up-regulated by both ChREBP and FoxO1 in liver cells and that its expression strongly correlates with fasting, suggesting a major role for this protein in the physiological adaptation to nutrient restriction.
RESUMEN
OBJECTIVE: The intestinal epithelial barrier (IEB) restricts the passage of microbes and potentially harmful substances from the lumen through the paracellular space, and rupture of its integrity is associated with a variety of gastrointestinal disorders and extra-digestive diseases. Increased IEB permeability has been linked to disruption of metabolic homeostasis leading to obesity and type 2 diabetes. Interestingly, recent studies have uncovered compelling evidence that the AMP-activated protein kinase (AMPK) signaling pathway plays an important role in maintaining epithelial cell barrier function. However, our understanding of the function of intestinal AMPK in regulating IEB and glucose homeostasis remains sparse. METHODS: We generated mice lacking the two α1 and α2 AMPK catalytic subunits specifically in intestinal epithelial cells (IEC AMPK KO) and determined the physiological consequences of intestinal-specific deletion of AMPK in response to high-fat diet (HFD)-induced obesity. We combined histological, functional, and integrative analyses to ascertain the effects of gut AMPK loss on intestinal permeability in vivo and ex vivo and on the development of obesity and metabolic dysfunction. We also determined the impact of intestinal AMPK deletion in an inducible mouse model (i-IEC AMPK KO) by measuring IEB function, glucose homeostasis, and the composition of gut microbiota via fecal 16S rRNA sequencing. RESULTS: While there were no differences in in vivo intestinal permeability in WT and IEC AMPK KO mice, ex vivo transcellular and paracellular permeability measured in Ussing chambers was significantly increased in the distal colon of IEC AMPK KO mice. This was associated with a reduction in pSer425 GIV phosphorylation, a marker of leaky gut barrier. However, the expression of tight junction proteins in intestinal epithelial cells and pro-inflammatory cytokines in the lamina propria were not different between genotypes. Although the HFD-fed AMPK KO mice displayed suppression of the stress polarity signaling pathway and a concomitant increase in colon permeability, loss of intestinal AMPK did not exacerbate body weight gain or adiposity. Deletion of AMPK was also not sufficient to alter glucose homeostasis or the acute glucose-lowering action of metformin in control diet (CD)- or HFD-fed mice. CD-fed i-IEC AMPK KO mice also presented higher permeability in the distal colon under homeostatic conditions but, surprisingly, this was not detected upon HFD feeding. Alteration in epithelial barrier function in the i-IEC AMPK KO mice was associated with a shift in the gut microbiota composition with higher levels of Clostridiales and Desulfovibrionales. CONCLUSIONS: Altogether, our results revealed a significant role of intestinal AMPK in maintaining IEB integrity in the distal colon but not in regulating glucose homeostasis. Our data also highlight the complex interaction between gut microbiota and host AMPK.
Asunto(s)
Proteínas Quinasas Activadas por AMP/genética , Proteínas Quinasas Activadas por AMP/metabolismo , Colon/metabolismo , Glucosa/metabolismo , Homeostasis , Animales , Bacterias/clasificación , Bacterias/genética , Diabetes Mellitus Tipo 2/metabolismo , Dieta Alta en Grasa/efectos adversos , Modelos Animales de Enfermedad , Células Epiteliales/metabolismo , Heces/microbiología , Microbioma Gastrointestinal , Mucosa Intestinal/metabolismo , Masculino , Metformina/farmacología , Ratones , Ratones Noqueados , Obesidad/metabolismo , Permeabilidad/efectos de los fármacos , ARN Ribosómico 16SRESUMEN
The Wnt/ß-catenin pathway plays a pivotal role in liver structural and metabolic homeostasis. Wnt activity is tightly regulated by the acyltransferase Porcupine through the addition of palmitoleate. Interestingly palmitoleate can be endogenously produced by the stearoyl-CoA desaturase 1 (SCD1), a lipogenic enzyme transcriptionally regulated by insulin. This study aimed to determine whether nutritional conditions, and insulin, regulate Wnt pathway activity in liver. An adenoviral TRE-Luciferase reporter was used as a readout of Wnt/ß-catenin pathway activity, in vivo in mouse liver and in vitro in primary hepatocytes. Refeeding enhanced TRE-Luciferase activity and expression of Wnt target genes in mice liver, revealing a nutritional regulation of the Wnt/ß-catenin pathway. This effect was inhibited in liver specific insulin receptor KO (iLIRKO) mice and upon wortmannin or rapamycin treatment. Overexpression or inhibition of SCD1 expression regulated Wnt/ß-catenin activity in primary hepatocytes. Similarly, palmitoleate added exogenously or produced by SCD1-mediated desaturation of palmitate, induced Wnt signaling activity. Interestingly, this effect was abolished in the absence of Porcupine, suggesting that both SCD1 and Porcupine are key mediators of insulin-induced Wnt/ß-catenin activity in hepatocytes. Altogether, our findings suggest that insulin and lipogenesis act as potential novel physiological inducers of hepatic Wnt/ß-catenin pathway.
Asunto(s)
Insulina/metabolismo , Vía de Señalización Wnt/efectos de los fármacos , beta Catenina/efectos de los fármacos , Aciltransferasas/metabolismo , Animales , Ácidos Grasos Monoinsaturados/farmacología , Hepatocitos/metabolismo , Lipogénesis/efectos de los fármacos , Hígado/metabolismo , Hígado/patología , Masculino , Proteínas de la Membrana/metabolismo , Ratones , Ratones Endogámicos C57BL , Estearoil-CoA Desaturasa/genética , Estearoil-CoA Desaturasa/metabolismo , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/metabolismo , Vía de Señalización Wnt/fisiología , beta Catenina/metabolismoRESUMEN
BACKGROUND & AIMS: Notch downstream targets are fundamental to intestinal cell lineage commitment and are suggested as therapeutic targets for colon cancer cells. However, the role of endogenous Notch signaling through receptor-ligand interaction, and effects of its longer term down-regulation on intestinal homeostasis, are unclear. METHODS: To address these issues, the gene encoding protein O-fucosyltransferase 1, an enzyme required for Notch ligand binding and thus activation of all Notch receptors, was deleted in the mouse intestinal and colonic epithelium, through Villin-Cre-mediated recombination. RESULTS: Pofut1 deletion inactivated Notch signaling, giving rise to smaller but viable mice. These mice exhibited a large increase in all intestinal secretory cell lineages, which accumulated in the crypts, resulting in crypt hyperplasia. Although proliferating cells were largely reduced in the colon, the transit amplifying compartment was maintained in the upper crypts of the intestinal mucosa. By 9 months, these perturbations in cell maturation altered mucus-associated gut microbiota and caused chronic intestinal inflammation, with evidence of bacterial translocation to the mesenteric lymph nodes, macrophage, and T-lymphocyte infiltration, and Th1/Th17 immune response. Dysplastic foci were also observed in Pofut1-deficient small intestine with occasional progression to tumor formation. CONCLUSIONS: Mucus hypersecretion upon Pofut1 inactivation is accompanied by alteration of the mucus-associated flora, which likely contributes to the development of enterocolitis. Therefore, these data identify important potential complications in strategies to target Notch signaling in therapeutic approaches to colon cancer.
Asunto(s)
Enterocolitis/metabolismo , Fucosiltransferasas/metabolismo , Mucosa Intestinal/metabolismo , Receptores Notch/metabolismo , Transducción de Señal , Animales , Traslocación Bacteriana , Fraccionamiento Celular , Enterocolitis/patología , Proteínas de Unión a Ácidos Grasos/metabolismo , Fucosiltransferasas/genética , Silenciador del Gen , Proteínas del Grupo de Alta Movilidad/metabolismo , Mucosa Intestinal/microbiología , Mucosa Intestinal/patología , Ligandos , Ganglios Linfáticos/microbiología , Ratones , Ratones Transgénicos , Factor de Transcripción SOX9 , Técnicas de Cultivo de Tejidos , Factores de Transcripción/metabolismo , Galactósido 2-alfa-L-FucosiltransferasaRESUMEN
Thioredoxin interacting protein (TxNIP), which strongly responds to glucose, has emerged as a central mediator of glucotoxicity in pancreatic ß cells. TxNIP is a scaffold protein interacting with target proteins to inhibit or stimulate their activity. Recent studies reported that high glucose stimulates the interaction of TxNIP with the inflammasome protein NLRP3 (NLR family, pyrin domain containing 3) to increase interleukin-1 ß (IL1ß) secretion by pancreatic ß cells. To better understand the regulation of TxNIP by glucose in pancreatic ß cells, we investigated the implication of O-linked ß-N-acetylglucosamine (O-GlcNAcylation) in regulating TxNIP at the posttranslational level. O-GlcNAcylation of proteins is controlled by two enzymes: the O-GlcNAc transferase (OGT), which transfers a monosaccharide to serine/threonine residues on target proteins, and the O-GlcNAcase (OGA), which removes it. Our study shows that TxNIP is subjected to O-GlcNAcylation in response to high glucose concentrations in ß cell lines. Modification of the O-GlcNAcylation pathway through manipulation of OGT or OGA expression or activity significantly modulates TxNIP O-GlcNAcylation in INS1 832/13 cells. Interestingly, expression and O-GlcNAcylation of TxNIP appeared to be increased in islets of diabetic rodents. At the mechanistic level, the induction of the O-GlcNAcylation pathway in human and rat islets promotes inflammasome activation as evidenced by enhanced cleaved IL1ß. Overexpression of OGT in HEK293 or INS1 832/13 cells stimulates TxNIP and NLRP3 interaction, while reducing TxNIP O-GlcNAcylation through OGA overexpression destabilizes this interaction. Altogether, our study reveals that O-GlcNAcylation represents an important regulatory mechanism for TxNIP activity in ß cells.
RESUMEN
Colorectal cancer (CRC) is associated with metabolic and redox perturbation. The mitochondrial transporter uncoupling protein 2 (UCP2) controls cell proliferation in vitro through the modulation of cellular metabolism, but the underlying mechanism in tumors in vivo remains unexplored. Using murine intestinal cancer models and CRC patient samples, we find higher UCP2 protein levels in tumors compared to their non-tumoral counterparts. We reveal the tumor-suppressive role of UCP2 as its deletion enhances colon and small intestinal tumorigenesis in AOM/DSS-treated and ApcMin/+ mice, respectively, and correlates with poor survival in the latter model. Mechanistically, UCP2 loss increases levels of oxidized glutathione and proteins in tumors. UCP2 deficiency alters glycolytic pathways while promoting phospholipid synthesis, thereby limiting the availability of NADPH for buffering oxidative stress. We show that UCP2 loss renders colon cells more prone to malignant transformation through metabolic reprogramming and perturbation of redox homeostasis and could favor worse outcomes in CRC.
Asunto(s)
Carcinogénesis/genética , Neoplasias Colorrectales/metabolismo , Lipogénesis , NADP/metabolismo , Estrés Oxidativo , Proteína Desacopladora 2/metabolismo , Anciano , Anciano de 80 o más Años , Animales , Carcinogénesis/metabolismo , Colon/metabolismo , Colon/patología , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología , Glucólisis , Humanos , Intestino Delgado/metabolismo , Intestino Delgado/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Persona de Mediana Edad , Proteína Desacopladora 2/genéticaRESUMEN
Impaired adipose tissue insulin signalling is a critical feature of insulin resistance. Here we identify a pathway linking the lipolytic enzyme hormone-sensitive lipase (HSL) to insulin action via the glucose-responsive transcription factor ChREBP and its target, the fatty acid elongase ELOVL6. Genetic inhibition of HSL in human adipocytes and mouse adipose tissue results in enhanced insulin sensitivity and induction of ELOVL6. ELOVL6 promotes an increase in phospholipid oleic acid, which modifies plasma membrane fluidity and enhances insulin signalling. HSL deficiency-mediated effects are suppressed by gene silencing of ChREBP and ELOVL6. Mechanistically, physical interaction between HSL, independent of lipase activity, and the isoform activated by glucose metabolism ChREBPα impairs ChREBPα translocation into the nucleus and induction of ChREBPß, the isoform with high transcriptional activity that is strongly associated with whole-body insulin sensitivity. Targeting the HSL-ChREBP interaction may allow therapeutic strategies for the restoration of insulin sensitivity.
Asunto(s)
Adipocitos/metabolismo , Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/metabolismo , Resistencia a la Insulina , Insulina/metabolismo , Esterol Esterasa/metabolismo , Tejido Adiposo/metabolismo , Animales , Biomarcadores , Elongasas de Ácidos Grasos/genética , Elongasas de Ácidos Grasos/metabolismo , Expresión Génica , Glucosa/metabolismo , Resistencia a la Insulina/genética , Fluidez de la Membrana/genética , Ratones , Ratones Transgénicos , Mapeo de Interacción de Proteínas , Mapas de Interacción de Proteínas , Transducción de SeñalRESUMEN
Although the mechanisms by which glucose regulates insulin secretion from pancreatic ß-cells are now well described, the way glucose modulates gene expression in such cells needs more understanding. Here, we demonstrate that MondoA, but not its paralog carbohydrate-responsive element-binding protein, is the predominant glucose-responsive transcription factor in human pancreatic ß-EndoC-ßH1 cells and in human islets. In high-glucose conditions, MondoA shuttles to the nucleus where it is required for the induction of the glucose-responsive genes arrestin domain-containing protein 4 (ARRDC4) and thioredoxin interacting protein (TXNIP), the latter being a protein strongly linked to ß-cell dysfunction and diabetes. Importantly, increasing cAMP signaling in human ß-cells, using forskolin or the glucagon-like peptide 1 mimetic Exendin-4, inhibits the shuttling of MondoA and potently inhibits TXNIP and ARRDC4 expression. Furthermore, we demonstrate that silencing MondoA expression improves glucose uptake in EndoC-ßH1 cells. These results highlight MondoA as a novel target in ß-cells that coordinates transcriptional response to elevated glucose levels.
Asunto(s)
Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/metabolismo , Regulación de la Expresión Génica , Glucosa/metabolismo , Células Secretoras de Insulina/metabolismo , Insulina/metabolismo , Sistemas de Mensajero Secundario , Transporte Activo de Núcleo Celular/efectos de los fármacos , Animales , Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/antagonistas & inhibidores , Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/genética , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Línea Celular , AMP Cíclico/metabolismo , Exenatida , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Incretinas/farmacología , Secreción de Insulina , Células Secretoras de Insulina/efectos de los fármacos , Péptidos y Proteínas de Señalización Intracelular/genética , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Ratones Endogámicos C57BL , Ratones Noqueados , Persona de Mediana Edad , Péptidos/farmacología , Interferencia de ARN , Sistemas de Mensajero Secundario/efectos de los fármacos , Tiorredoxinas/genética , Tiorredoxinas/metabolismo , Técnicas de Cultivo de Tejidos , Ponzoñas/farmacologíaRESUMEN
With the identification of ChREBP in 2001, our interest in understanding the molecular control of carbohydrate sensing has surged. While ChREBP was initially studied as a master regulator of lipogenesis in liver and fat tissue, it is now clear that ChREBP functions as a central metabolic coordinator in a variety of cell types in response to environmental and hormonal signals, with wide implications in health and disease. Celebrating its sweet sixteenth birthday, we review here the current knowledge about the function and regulation of ChREBP throughout usual and less explored tissues, to recapitulate ChREBP's role as a whole-body glucose sensor.