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1.
Cell ; 177(5): 1217-1231.e18, 2019 05 16.
Artículo en Inglés | MEDLINE | ID: mdl-31006530

RESUMEN

The intestinal microbiota produces tens of thousands of metabolites. Here, we used host sensing of small molecules by G-protein coupled receptors (GPCRs) as a lens to illuminate bioactive microbial metabolites that impact host physiology. We screened 144 human gut bacteria against the non-olfactory GPCRome and identified dozens of bacteria that activated both well-characterized and orphan GPCRs, including strains that converted dietary histidine into histamine and shaped colonic motility; a prolific producer of the essential amino acid L-Phe, which we identified as an agonist for GPR56 and GPR97; and a species that converted L-Phe into the potent psychoactive trace amine phenethylamine, which crosses the blood-brain barrier and triggers lethal phenethylamine poisoning after monoamine oxidase inhibitor administration. These studies establish an orthogonal approach for parsing the microbiota metabolome and uncover multiple biologically relevant host-microbiota metabolome interactions.


Asunto(s)
Bacterias/crecimiento & desarrollo , Colon/microbiología , Microbioma Gastrointestinal/fisiología , Interacciones Microbiota-Huesped/fisiología , Receptores Acoplados a Proteínas G/metabolismo , Animales , Células HEK293 , Humanos , Ratones
2.
Cell ; 172(1-2): 234-248.e17, 2018 01 11.
Artículo en Inglés | MEDLINE | ID: mdl-29307489

RESUMEN

The transition from the fed to the fasted state necessitates a shift from carbohydrate to fat metabolism that is thought to be mostly orchestrated by reductions in plasma insulin concentrations. Here, we show in awake rats that insulinopenia per se does not cause this transition but that both hypoleptinemia and insulinopenia are necessary. Furthermore, we show that hypoleptinemia mediates a glucose-fatty acid cycle through activation of the hypothalamic-pituitary-adrenal axis, resulting in increased white adipose tissue (WAT) lipolysis rates and increased hepatic acetyl-coenzyme A (CoA) content, which are essential to maintain gluconeogenesis during starvation. We also show that in prolonged starvation, substrate limitation due to reduced rates of glucose-alanine cycling lowers rates of hepatic mitochondrial anaplerosis, oxidation, and gluconeogenesis. Taken together, these data identify a leptin-mediated glucose-fatty acid cycle that integrates responses of the muscle, WAT, and liver to promote a shift from carbohydrate to fat oxidation and maintain glucose homeostasis during starvation.


Asunto(s)
Glucemia/metabolismo , Ácidos Grasos/metabolismo , Gluconeogénesis , Homeostasis , Leptina/metabolismo , Inanición/metabolismo , Tejido Adiposo Blanco/metabolismo , Alanina/metabolismo , Animales , Insulina/sangre , Leptina/sangre , Lipólisis , Hígado/metabolismo , Masculino , Mitocondrias/metabolismo , Ratas , Ratas Sprague-Dawley
3.
Cell ; 160(4): 745-758, 2015 Feb 12.
Artículo en Inglés | MEDLINE | ID: mdl-25662011

RESUMEN

Impaired insulin-mediated suppression of hepatic glucose production (HGP) plays a major role in the pathogenesis of type 2 diabetes (T2D), yet the molecular mechanism by which this occurs remains unknown. Using a novel in vivo metabolomics approach, we show that the major mechanism by which insulin suppresses HGP is through reductions in hepatic acetyl CoA by suppression of lipolysis in white adipose tissue (WAT) leading to reductions in pyruvate carboxylase flux. This mechanism was confirmed in mice and rats with genetic ablation of insulin signaling and mice lacking adipose triglyceride lipase. Insulin's ability to suppress hepatic acetyl CoA, PC activity, and lipolysis was lost in high-fat-fed rats, a phenomenon reversible by IL-6 neutralization and inducible by IL-6 infusion. Taken together, these data identify WAT-derived hepatic acetyl CoA as the main regulator of HGP by insulin and link it to inflammation-induced hepatic insulin resistance associated with obesity and T2D.


Asunto(s)
Acetilcoenzima A/metabolismo , Resistencia a la Insulina , Hígado/metabolismo , Paniculitis/metabolismo , Tejido Adiposo Blanco/química , Adolescente , Animales , Diabetes Mellitus Tipo 2 , Dieta Alta en Grasa , Glucosa/metabolismo , Humanos , Hiperglucemia , Interleucina-6/análisis , Lipólisis , Masculino , Ratones , Obesidad/metabolismo , Ratas Sprague-Dawley
4.
Nature ; 579(7798): 279-283, 2020 03.
Artículo en Inglés | MEDLINE | ID: mdl-32132708

RESUMEN

Although it is well-established that reductions in the ratio of insulin to glucagon in the portal vein have a major role in the dysregulation of hepatic glucose metabolism in type-2 diabetes1-3, the mechanisms by which glucagon affects hepatic glucose production and mitochondrial oxidation are poorly understood. Here we show that glucagon stimulates hepatic gluconeogenesis by increasing the activity of hepatic adipose triglyceride lipase, intrahepatic lipolysis, hepatic acetyl-CoA content and pyruvate carboxylase flux, while also increasing mitochondrial fat oxidation-all of which are mediated by stimulation of the inositol triphosphate receptor 1 (INSP3R1). In rats and mice, chronic physiological increases in plasma glucagon concentrations increased mitochondrial oxidation of fat in the liver and reversed diet-induced hepatic steatosis and insulin resistance. However, these effects of chronic glucagon treatment-reversing hepatic steatosis and glucose intolerance-were abrogated in Insp3r1 (also known as Itpr1)-knockout mice. These results provide insights into glucagon biology and suggest that INSP3R1 may represent a target for therapies that aim to reverse nonalcoholic fatty liver disease and type-2 diabetes.


Asunto(s)
Glucagón/farmacología , Gluconeogénesis/efectos de los fármacos , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Hígado/efectos de los fármacos , Acetilcoenzima A/metabolismo , Tejido Adiposo/efectos de los fármacos , Animales , Diabetes Mellitus Tipo 2/fisiopatología , Activación Enzimática/efectos de los fármacos , Glucagón/sangre , Receptores de Inositol 1,4,5-Trifosfato/genética , Lipasa/metabolismo , Lipólisis/efectos de los fármacos , Lipólisis/genética , Ratones Noqueados , Mitocondrias/efectos de los fármacos , Enfermedad del Hígado Graso no Alcohólico/fisiopatología , Oxidación-Reducción/efectos de los fármacos
5.
Proc Natl Acad Sci U S A ; 119(10): e2122287119, 2022 03 08.
Artículo en Inglés | MEDLINE | ID: mdl-35238637

RESUMEN

SignificanceMetformin is the most commonly prescribed drug for the treatment of type 2 diabetes mellitus, yet the mechanism by which it lowers plasma glucose concentrations has remained elusive. Most studies to date have attributed metformin's glucose-lowering effects to inhibition of complex I activity. Contrary to this hypothesis, we show that inhibition of complex I activity in vitro and in vivo does not reduce plasma glucose concentrations or inhibit hepatic gluconeogenesis. We go on to show that metformin, and the related guanides/biguanides, phenformin and galegine, inhibit complex IV activity at clinically relevant concentrations, which, in turn, results in inhibition of glycerol-3-phosphate dehydrogenase activity, increased cytosolic redox, and selective inhibition of glycerol-derived hepatic gluconeogenesis both in vitro and in vivo.


Asunto(s)
Complejo IV de Transporte de Electrones/antagonistas & inhibidores , Gluconeogénesis , Guanidinas/farmacología , Hipoglucemiantes/farmacología , Metformina/farmacología , Fenformina/farmacología , Animales , Glucosa/metabolismo , Glicerol/metabolismo , Glicerolfosfato Deshidrogenasa/antagonistas & inhibidores , Hígado/efectos de los fármacos , Hígado/metabolismo , Oxidación-Reducción , Piridinas/farmacología
6.
Diabetologia ; 66(3): 567-578, 2023 03.
Artículo en Inglés | MEDLINE | ID: mdl-36456864

RESUMEN

AIMS/HYPOTHESIS: Athletes exhibit increased muscle insulin sensitivity, despite increased intramuscular triacylglycerol content. This phenomenon has been coined the 'athlete's paradox' and is poorly understood. Recent findings suggest that the subcellular distribution of sn-1,2-diacylglycerols (DAGs) in the plasma membrane leading to activation of novel protein kinase Cs (PKCs) is a crucial pathway to inducing insulin resistance. Here, we hypothesised that regular aerobic exercise would preserve muscle insulin sensitivity by preventing increases in plasma membrane sn-1,2-DAGs and activation of PKCε and PKCθ despite promoting increases in muscle triacylglycerol content. METHODS: C57BL/6J mice were allocated to three groups (regular chow feeding [RC]; high-fat diet feeding [HFD]; RC feeding and running wheel exercise [RC-EXE]). We used a novel LC-MS/MS/cellular fractionation method to assess DAG stereoisomers in five subcellular compartments (plasma membrane [PM], endoplasmic reticulum, mitochondria, lipid droplets and cytosol) in the skeletal muscle. RESULTS: We found that the HFD group had a greater content of sn-DAGs and ceramides in multiple subcellular compartments compared with the RC mice, which was associated with an increase in PKCε and PKCθ translocation. However, the RC-EXE mice showed, of particular note, a reduction in PM sn-1,2-DAG and ceramide content when compared with HFD mice. Consistent with the PM sn-1,2-DAG-novel PKC hypothesis, we observed an increase in phosphorylation of threonine1150 on the insulin receptor kinase (IRKT1150), and reductions in insulin-stimulated IRKY1162 phosphorylation and IRS-1-associated phosphoinositide 3-kinase activity in HFD compared with RC and RC-EXE mice, which are sites of PKCε and PKCθ action, respectively. CONCLUSIONS/INTERPRETATION: These results demonstrate that lower PKCθ/PKCε activity and sn-1,2-DAG content, especially in the PM compartment, can explain the preserved muscle insulin sensitivity in RC-EXE mice.


Asunto(s)
Resistencia a la Insulina , Ratones , Animales , Resistencia a la Insulina/fisiología , Proteína Quinasa C-theta/metabolismo , Proteína Quinasa C-epsilon/metabolismo , Cromatografía Liquida , Fosfatidilinositol 3-Quinasas/metabolismo , Ratones Endogámicos C57BL , Espectrometría de Masas en Tándem , Insulina/metabolismo , Músculo Esquelético/metabolismo , Triglicéridos/metabolismo , Ceramidas/metabolismo
7.
Cell ; 135(5): 813-24, 2008 Nov 28.
Artículo en Inglés | MEDLINE | ID: mdl-19041747

RESUMEN

N-acylphosphatidylethanolamines (NAPEs) are a relatively abundant group of plasma lipids of unknown physiological significance. Here, we show that NAPEs are secreted into circulation from the small intestine in response to ingested fat and that systemic administration of the most abundant circulating NAPE, at physiologic doses, decreases food intake in rats without causing conditioned taste aversion. Furthermore, (14)C-radiolabeled NAPE enters the brain and is particularly concentrated in the hypothalamus, and intracerebroventricular infusions of nanomolar amounts of NAPE reduce food intake, collectively suggesting that its effects may be mediated through direct interactions with the central nervous system. Finally, chronic NAPE infusion results in a reduction of both food intake and body weight, suggesting that NAPE and long-acting NAPE analogs may be novel therapeutic targets for the treatment of obesity.


Asunto(s)
Regulación del Apetito , Fosfatidiletanolaminas/fisiología , Amidas , Animales , Peso Corporal , Grasas de la Dieta/metabolismo , Endocannabinoides , Etanolaminas , Hipotálamo/metabolismo , Intestino Delgado/metabolismo , Ratones , Ratones Obesos , Actividad Motora , Obesidad/metabolismo , Ácidos Palmíticos/metabolismo , Fosfatidiletanolaminas/sangre , Proteínas Proto-Oncogénicas c-fos/metabolismo , Ratas , Espectrometría de Masas en Tándem
8.
Proc Natl Acad Sci U S A ; 117(13): 7347-7354, 2020 03 31.
Artículo en Inglés | MEDLINE | ID: mdl-32179679

RESUMEN

Weight loss by ketogenic diet (KD) has gained popularity in management of nonalcoholic fatty liver disease (NAFLD). KD rapidly reverses NAFLD and insulin resistance despite increasing circulating nonesterified fatty acids (NEFA), the main substrate for synthesis of intrahepatic triglycerides (IHTG). To explore the underlying mechanism, we quantified hepatic mitochondrial fluxes and their regulators in humans by using positional isotopomer NMR tracer analysis. Ten overweight/obese subjects received stable isotope infusions of: [D7]glucose, [13C4]ß-hydroxybutyrate and [3-13C]lactate before and after a 6-d KD. IHTG was determined by proton magnetic resonance spectroscopy (1H-MRS). The KD diet decreased IHTG by 31% in the face of a 3% decrease in body weight and decreased hepatic insulin resistance (-58%) despite an increase in NEFA concentrations (+35%). These changes were attributed to increased net hydrolysis of IHTG and partitioning of the resulting fatty acids toward ketogenesis (+232%) due to reductions in serum insulin concentrations (-53%) and hepatic citrate synthase flux (-38%), respectively. The former was attributed to decreased hepatic insulin resistance and the latter to increased hepatic mitochondrial redox state (+167%) and decreased plasma leptin (-45%) and triiodothyronine (-21%) concentrations. These data demonstrate heretofore undescribed adaptations underlying the reversal of NAFLD by KD: That is, markedly altered hepatic mitochondrial fluxes and redox state to promote ketogenesis rather than synthesis of IHTG.


Asunto(s)
Dieta Cetogénica/métodos , Hígado Graso/dietoterapia , Enfermedad del Hígado Graso no Alcohólico/dietoterapia , Composición Corporal , Citrato (si)-Sintasa/metabolismo , Ácidos Grasos/metabolismo , Ácidos Grasos no Esterificados/metabolismo , Femenino , Humanos , Insulina/metabolismo , Resistencia a la Insulina/fisiología , Lipoproteínas VLDL/metabolismo , Hígado/metabolismo , Masculino , Persona de Mediana Edad , Mitocondrias/metabolismo , Obesidad/metabolismo , Sobrepeso/patología , Oxidación-Reducción , Piruvato Carboxilasa/metabolismo , Triglicéridos/metabolismo
9.
Proc Natl Acad Sci U S A ; 117(14): 8166-8176, 2020 04 07.
Artículo en Inglés | MEDLINE | ID: mdl-32188779

RESUMEN

Multiple insulin-regulated enzymes participate in hepatic glycogen synthesis, and the rate-controlling step responsible for insulin stimulation of glycogen synthesis is unknown. We demonstrate that glucokinase (GCK)-mediated glucose phosphorylation is the rate-controlling step in insulin-stimulated hepatic glycogen synthesis in vivo, by use of the somatostatin pancreatic clamp technique using [13C6]glucose with metabolic control analysis (MCA) in three rat models: 1) regular chow (RC)-fed male rats (control), 2) high fat diet (HFD)-fed rats, and 3) RC-fed rats with portal vein glucose delivery at a glucose infusion rate matched to the control. During hyperinsulinemia, hyperglycemia dose-dependently increased hepatic glycogen synthesis. At similar levels of hyperinsulinemia and hyperglycemia, HFD-fed rats exhibited a decrease and portal delivery rats exhibited an increase in hepatic glycogen synthesis via the direct pathway compared with controls. However, the strong correlation between liver glucose-6-phosphate concentration and net hepatic glycogen synthetic rate was nearly identical in these three groups, suggesting that the main difference between models is the activation of GCK. MCA yielded a high control coefficient for GCK in all three groups. We confirmed these findings in studies of hepatic GCK knockdown using an antisense oligonucleotide. Reduced liver glycogen synthesis in lipid-induced hepatic insulin resistance and increased glycogen synthesis during portal glucose infusion were explained by concordant changes in translocation of GCK. Taken together, these data indicate that the rate of insulin-stimulated hepatic glycogen synthesis is controlled chiefly through GCK translocation.


Asunto(s)
Hígado Graso/patología , Glucoquinasa/metabolismo , Glucosa/metabolismo , Glucógeno Hepático/biosíntesis , Hígado/metabolismo , Animales , Dieta Alta en Grasa/efectos adversos , Modelos Animales de Enfermedad , Hígado Graso/etiología , Técnicas de Silenciamiento del Gen , Glucoquinasa/genética , Glucosa/administración & dosificación , Glucosa-6-Fosfato/análisis , Glucosa-6-Fosfato/metabolismo , Humanos , Hiperglucemia/etiología , Hiperglucemia/patología , Hiperinsulinismo/etiología , Hiperinsulinismo/patología , Insulina/metabolismo , Resistencia a la Insulina , Hígado/patología , Masculino , Metabolómica , Fosforilación , Ratas
10.
Nature ; 534(7606): 213-7, 2016 06 09.
Artículo en Inglés | MEDLINE | ID: mdl-27279214

RESUMEN

Obesity, insulin resistance and the metabolic syndrome are associated with changes to the gut microbiota; however, the mechanism by which modifications to the gut microbiota might lead to these conditions is unknown. Here we show that increased production of acetate by an altered gut microbiota in rodents leads to activation of the parasympathetic nervous system, which, in turn, promotes increased glucose-stimulated insulin secretion, increased ghrelin secretion, hyperphagia, obesity and related sequelae. Together, these findings identify increased acetate production resulting from a nutrient-gut microbiota interaction and subsequent parasympathetic activation as possible therapeutic targets for obesity.


Asunto(s)
Acetatos/metabolismo , Encéfalo/fisiología , Microbioma Gastrointestinal/fisiología , Células Secretoras de Insulina/metabolismo , Síndrome Metabólico/metabolismo , Animales , Dieta Alta en Grasa , Ghrelina/metabolismo , Glucosa/metabolismo , Hiperfagia/metabolismo , Insulina/metabolismo , Secreción de Insulina , Obesidad/metabolismo , Sistema Nervioso Parasimpático/fisiología , Ratas
11.
Int J Mol Sci ; 22(9)2021 Apr 30.
Artículo en Inglés | MEDLINE | ID: mdl-33946157

RESUMEN

The metabolic ratios lactate/pyruvate and ß-hydroxybutyrate/acetoacetate are considered valuable tools to evaluate the in vivo redox cellular state by estimating the free NAD+/NADH in cytoplasm and mitochondria, respectively. The aim of the current study was to validate a gas-chromatography mass spectrometry method for simultaneous determination of the four metabolites in plasma and liver tissue. The procedure included an o-phenylenediamine microwave-assisted derivatization, followed by liquid-liquid extraction with ethyl acetate and silylation with bis(trimethylsilyl)trifluoroacetamide:trimethylchlorosilane 99:1. The calibration curves presented acceptable linearity, with a limit of quantification of 0.001 mM for pyruvate, ß-hydroxybutyrate and acetoacetate and of 0.01 mM for lactate. The intra-day and inter-day accuracy and precision were within the European Medicines Agency's Guideline specifications. No significant differences were observed in the slope coefficient of three-point standard metabolite-spiked curves in plasma or liver and water, and acceptable recoveries were obtained in the metabolite-spiked samples. Applicability of the method was tested in precision-cut liver rat slices and also in HepG2 cells incubated under different experimental conditions challenging the redox state. In conclusion, the validated method presented good sensitivity, specificity and reproducibility in the quantification of lactate/pyruvate and ß-hydroxybutyrate/acetate metabolites and may be useful in the evaluation of in vivo redox states.


Asunto(s)
Ácido 3-Hidroxibutírico/metabolismo , Acetoacetatos/metabolismo , Cromatografía de Gases y Espectrometría de Masas , Lactatos/metabolismo , Piruvatos/metabolismo , Ácido 3-Hidroxibutírico/análisis , Ácido 3-Hidroxibutírico/sangre , Acetoacetatos/análisis , Acetoacetatos/sangre , Animales , Femenino , Cromatografía de Gases y Espectrometría de Masas/métodos , Células Hep G2 , Humanos , Lactatos/análisis , Lactatos/sangre , Límite de Detección , Hígado/química , Hígado/metabolismo , Oxidación-Reducción , Piruvatos/análisis , Piruvatos/sangre , Ratas Wistar
12.
J Lipid Res ; 61(12): 1565-1576, 2020 12.
Artículo en Inglés | MEDLINE | ID: mdl-32907986

RESUMEN

Microsomal triglyceride transfer protein (MTTP) deficiency results in a syndrome of hypolipidemia and accelerated NAFLD. Animal models of decreased hepatic MTTP activity have revealed an unexplained dissociation between hepatic steatosis and hepatic insulin resistance. Here, we performed comprehensive metabolic phenotyping of liver-specific MTTP knockout (L-Mttp-/-) mice and age-weight matched wild-type control mice. Young (10-12-week-old) L-Mttp-/- mice exhibited hepatic steatosis and increased DAG content; however, the increase in hepatic DAG content was partitioned to the lipid droplet and was not increased in the plasma membrane. Young L-Mttp-/- mice also manifested normal hepatic insulin sensitivity, as assessed by hyperinsulinemic-euglycemic clamps, no PKCε activation, and normal hepatic insulin signaling from the insulin receptor through AKT Ser/Thr kinase. In contrast, aged (10-month-old) L-Mttp-/- mice exhibited glucose intolerance and hepatic insulin resistance along with an increase in hepatic plasma membrane sn-1,2-DAG content and PKCε activation. Treatment with a functionally liver-targeted mitochondrial uncoupler protected the aged L-Mttp-/- mice against the development of hepatic steatosis, increased plasma membrane sn-1,2-DAG content, PKCε activation, and hepatic insulin resistance. Furthermore, increased hepatic insulin sensitivity in the aged controlled-release mitochondrial protonophore-treated L-Mttp-/- mice was not associated with any reductions in hepatic ceramide content. Taken together, these data demonstrate that differences in the intracellular compartmentation of sn-1,2-DAGs in the lipid droplet versus plasma membrane explains the dissociation of NAFLD/lipid-induced hepatic insulin resistance in young L-Mttp-/- mice as well as the development of lipid-induced hepatic insulin resistance in aged L-Mttp-/- mice.


Asunto(s)
Proteínas Portadoras/genética , Membrana Celular/metabolismo , Diglicéridos/metabolismo , Técnicas de Inactivación de Genes , Resistencia a la Insulina , Hígado/metabolismo , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Animales , Ratones , Enfermedad del Hígado Graso no Alcohólico/genética , Enfermedad del Hígado Graso no Alcohólico/patología
13.
FASEB J ; 33(7): 8174-8185, 2019 07.
Artículo en Inglés | MEDLINE | ID: mdl-30922125

RESUMEN

The connection between adipose glucocorticoid action and whole-body metabolism is incompletely understood. Thus, we generated adipose tissue-specific glucocorticoid receptor-knockout (Ad-GcR-/-) mice to explore potential mechanisms. Ad-GcR-/- mice had a lower concentration of fasting plasma nonesterified fatty acids and less hepatic steatosis. This was associated with increased protein kinase B phosphorylation and increased hepatic glycogen synthesis after an oral glucose challenge. High-fat diet (HFD)-fed Ad-GcR-/- mice were protected against the development of hepatic steatosis and diacylglycerol-PKCε-induced impairments in hepatic insulin signaling. Under hyperinsulinemic-euglycemic conditions, hepatic insulin response was ∼10-fold higher in HFD-fed Ad-GcR-/- mice. Insulin-mediated suppression of adipose lipolysis was improved by 40% in Ad-GcR-/- mice. Adipose triglyceride lipase expression was decreased and insulin-mediated perilipin dephosphorylation was increased in Ad-GcR-/- mice. In metabolic cages, food intake decreased by 3 kcal/kg per hour in Ad-GcR-/- mice. Therefore, physiologic adipose glucocorticoid action appears to drive hepatic lipid accumulation during stressors such as fasting. The resultant hepatic insulin resistance prevents hepatic glycogen synthesis, preserving glucose for glucose-dependent organs. Absence of adipose glucocorticoid action attenuates HFD-induced hepatic insulin resistance; potential explanations for reduction in hepatic steatosis include reductions in adipose lipolysis and food intake.-Abulizi, A., Camporez, J.-P., Jurczak, M. J., Høyer, K. F., Zhang, D., Cline, G. W., Samuel, V. T., Shulman, G. I., Vatner, D. F. Adipose glucocorticoid action influences whole-body metabolism via modulation of hepatic insulin action.


Asunto(s)
Tejido Adiposo/metabolismo , Glucocorticoides/metabolismo , Resistencia a la Insulina , Insulina/metabolismo , Lipólisis , Hígado/metabolismo , Animales , Grasas de la Dieta/efectos adversos , Grasas de la Dieta/farmacología , Glucocorticoides/genética , Insulina/genética , Errores Innatos del Metabolismo/genética , Errores Innatos del Metabolismo/metabolismo , Ratones , Ratones Noqueados , Receptores de Glucocorticoides/deficiencia , Receptores de Glucocorticoides/genética , Receptores de Glucocorticoides/metabolismo
14.
Nature ; 513(7519): 559-63, 2014 Sep 25.
Artículo en Inglés | MEDLINE | ID: mdl-25043024

RESUMEN

Macrophages have an important role in the maintenance of tissue homeostasis. To perform this function, macrophages must have the capacity to monitor the functional states of their 'client cells': namely, the parenchymal cells in the various tissues in which macrophages reside. Tumours exhibit many features of abnormally developed organs, including tissue architecture and cellular composition. Similarly to macrophages in normal tissues and organs, macrophages in tumours (tumour-associated macrophages) perform some key homeostatic functions that allow tumour maintenance and growth. However, the signals involved in communication between tumours and macrophages are poorly defined. Here we show that lactic acid produced by tumour cells, as a by-product of aerobic or anaerobic glycolysis, has a critical function in signalling, through inducing the expression of vascular endothelial growth factor and the M2-like polarization of tumour-associated macrophages. Furthermore, we demonstrate that this effect of lactic acid is mediated by hypoxia-inducible factor 1α (HIF1α). Finally, we show that the lactate-induced expression of arginase 1 by macrophages has an important role in tumour growth. Collectively, these findings identify a mechanism of communication between macrophages and their client cells, including tumour cells. This communication most probably evolved to promote homeostasis in normal tissues but can also be engaged in tumours to promote their growth.


Asunto(s)
Ácido Láctico/metabolismo , Macrófagos/metabolismo , Macrófagos/patología , Neoplasias/metabolismo , Neoplasias/patología , Animales , Arginasa/genética , Arginasa/metabolismo , Carcinoma Pulmonar de Lewis/patología , Comunicación Celular/efectos de los fármacos , División Celular/efectos de los fármacos , Medios de Cultivo Condicionados/química , Medios de Cultivo Condicionados/farmacología , Femenino , Glucólisis , Homeostasis , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Ácido Láctico/farmacología , Masculino , Melanoma Experimental/patología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , ARN Mensajero/análisis , ARN Mensajero/genética , Solubilidad , Regulación hacia Arriba/efectos de los fármacos , Factor A de Crecimiento Endotelial Vascular/genética , Factor A de Crecimiento Endotelial Vascular/metabolismo
15.
Nature ; 510(7506): 542-6, 2014 Jun 26.
Artículo en Inglés | MEDLINE | ID: mdl-24847880

RESUMEN

Metformin is considered to be one of the most effective therapeutics for treating type 2 diabetes because it specifically reduces hepatic gluconeogenesis without increasing insulin secretion, inducing weight gain or posing a risk of hypoglycaemia. For over half a century, this agent has been prescribed to patients with type 2 diabetes worldwide, yet the underlying mechanism by which metformin inhibits hepatic gluconeogenesis remains unknown. Here we show that metformin non-competitively inhibits the redox shuttle enzyme mitochondrial glycerophosphate dehydrogenase, resulting in an altered hepatocellular redox state, reduced conversion of lactate and glycerol to glucose, and decreased hepatic gluconeogenesis. Acute and chronic low-dose metformin treatment effectively reduced endogenous glucose production, while increasing cytosolic redox and decreasing mitochondrial redox states. Antisense oligonucleotide knockdown of hepatic mitochondrial glycerophosphate dehydrogenase in rats resulted in a phenotype akin to chronic metformin treatment, and abrogated metformin-mediated increases in cytosolic redox state, decreases in plasma glucose concentrations, and inhibition of endogenous glucose production. These findings were replicated in whole-body mitochondrial glycerophosphate dehydrogenase knockout mice. These results have significant implications for understanding the mechanism of metformin's blood glucose lowering effects and provide a new therapeutic target for type 2 diabetes.


Asunto(s)
Gluconeogénesis/efectos de los fármacos , Glicerolfosfato Deshidrogenasa/antagonistas & inhibidores , Metformina/farmacología , Mitocondrias/enzimología , Animales , Glucemia/análisis , Glucemia/biosíntesis , Células Cultivadas , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Diabetes Mellitus Tipo 2/enzimología , Diabetes Mellitus Tipo 2/metabolismo , Glicerolfosfato Deshidrogenasa/deficiencia , Glicerolfosfato Deshidrogenasa/genética , Glicerolfosfato Deshidrogenasa/metabolismo , Humanos , Hipoglucemiantes/farmacología , Insulina/metabolismo , Secreción de Insulina , Ácido Láctico/metabolismo , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Ratones Noqueados , Oxidación-Reducción/efectos de los fármacos , Ratas , Ratas Sprague-Dawley
16.
J Physiol ; 597(15): 3885-3903, 2019 08.
Artículo en Inglés | MEDLINE | ID: mdl-31206703

RESUMEN

KEY POINTS: Oestrogen has been shown to play an important role in the regulation of metabolic homeostasis and insulin sensitivity in both human and rodent studies. Insulin sensitivity is greater in premenopausal women compared with age-matched men, and metabolism-related cardiovascular diseases and type 2 diabetes are less frequent in these same women. Both female and male mice treated with oestradiol are protected against obesity-induced insulin resistance. The protection against obesity-induced insulin resistance is associated with reduced ectopic lipid content in liver and skeletal muscle. These results were associated with increased insulin-stimulated suppression of white adipose tissue lipolysis and reduced inflammation. ABSTRACT: Oestrogen has been shown to play an important role in the regulation of metabolic homeostasis and insulin sensitivity in both human and rodent studies. Overall, females are protected against obesity-induced insulin resistance; yet, the mechanisms responsible for this protection are not well understood. Therefore, the aim of the present work was to evaluate the underlying mechanism(s) by which female mice are protected against obesity-induced insulin resistance compared with male mice. We studied male and female mice in age-matched or body weight-matched conditions. They were fed a high-fat diet (HFD) or regular chow for 4 weeks. We also studied HFD male mice treated with oestradiol or vehicle. Both HFD female and HFD male mice treated with oestradiol displayed increased whole-body insulin sensitivity, associated with reduction in ectopic hepatic and muscle lipid content compared to HFD male mice. Reductions in ectopic lipid content in these mice were associated with increased insulin-stimulated suppression of white adipose tissue (WAT) lipolysis. Both HFD female and HFD male mice treated with oestradiol also displayed striking reductions in WAT inflammation, represented by reductions in plasma and adipose tissue tumour necrosis factor α and interleukin 6 concentrations. Taken together these data support the hypothesis that HFD female mice are protected from obesity-induced insulin resistance due to oestradiol-mediated reductions in WAT inflammation, leading to improved insulin-mediated suppression of WAT lipolysis and reduced ectopic lipid content in liver and skeletal muscle.


Asunto(s)
Estrógenos/farmacología , Resistencia a la Insulina , Interleucina-6/metabolismo , Caracteres Sexuales , Tejido Adiposo Blanco/efectos de los fármacos , Tejido Adiposo Blanco/metabolismo , Animales , Peso Corporal , Línea Celular , Células Cultivadas , Dieta Alta en Grasa/efectos adversos , Estrógenos/metabolismo , Femenino , Lipólisis , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Factor de Necrosis Tumoral alfa/metabolismo
17.
Hepatology ; 68(6): 2197-2211, 2018 12.
Artículo en Inglés | MEDLINE | ID: mdl-29790582

RESUMEN

Pharmacologic inhibition of acetyl-CoA carboxylase (ACC) enzymes, ACC1 and ACC2, offers an attractive therapeutic strategy for nonalcoholic fatty liver disease (NAFLD) through simultaneous inhibition of fatty acid synthesis and stimulation of fatty acid oxidation. However, the effects of ACC inhibition on hepatic mitochondrial oxidation, anaplerosis, and ketogenesis in vivo are unknown. Here, we evaluated the effect of a liver-directed allosteric inhibitor of ACC1 and ACC2 (Compound 1) on these parameters, as well as glucose and lipid metabolism, in control and diet-induced rodent models of NAFLD. Oral administration of Compound 1 preferentially inhibited ACC enzymatic activity in the liver, reduced hepatic malonyl-CoA levels, and enhanced hepatic ketogenesis by 50%. Furthermore, administration for 6 days to high-fructose-fed rats resulted in a 20% reduction in hepatic de novo lipogenesis. Importantly, long-term treatment (21 days) significantly reduced high-fat sucrose diet-induced hepatic steatosis, protein kinase C epsilon activation, and hepatic insulin resistance. ACCi treatment was associated with a significant increase in plasma triglycerides (approximately 30% to 130%, depending on the length of fasting). ACCi-mediated hypertriglyceridemia could be attributed to approximately a 15% increase in hepatic very low-density lipoprotein production and approximately a 20% reduction in triglyceride clearance by lipoprotein lipase (P ≤ 0.05). At the molecular level, these changes were associated with increases in liver X receptor/sterol response element-binding protein-1 and decreases in peroxisome proliferator-activated receptor-α target activation and could be reversed with fenofibrate co-treatment in a high-fat diet mouse model. Conclusion: Collectively, these studies warrant further investigation into the therapeutic utility of liver-directed ACC inhibition for the treatment of NAFLD and hepatic insulin resistance.


Asunto(s)
Acetil-CoA Carboxilasa/metabolismo , Resistencia a la Insulina , Hígado/metabolismo , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Triglicéridos/sangre , Acetil-CoA Carboxilasa/antagonistas & inhibidores , Animales , Ácidos Grasos no Esterificados/sangre , Cetonas/metabolismo , Lipogénesis , Lipoproteínas VLDL/sangre , Masculino , Análisis de Flujos Metabólicos , PPAR alfa/agonistas , Ratas Sprague-Dawley , Receptores Citoplasmáticos y Nucleares/metabolismo
18.
Biochem J ; 475(6): 1063-1074, 2018 03 20.
Artículo en Inglés | MEDLINE | ID: mdl-29483297

RESUMEN

Exposure to the toxins methylene cyclopropyl acetic acid (MCPA) and methylene cyclopropyl glycine (MCPG) of unripe ackee and litchi fruit can lead to hypoglycemia and death; however, the molecular mechanisms by which MCPA and MCPG cause hypoglycemia have not been established in vivo To determine the in vivo mechanisms of action of these toxins, we infused them into conscious rodents and assessed rates of hepatic gluconeogenesis and ketogenesis, hepatic acyl-CoA and hepatic acetyl-CoA content, and hepatocellular energy charge. MCPG suppressed rates of hepatic ß-oxidation as reflected by reductions in hepatic ketogenesis, reducing both short- and medium-chain hepatic acyl-CoA concentrations. Hepatic acetyl-CoA content decreased, and hepatic glucose production was inhibited. MCPA also suppressed ß-oxidation of short-chain acyl-CoAs, rapidly inhibiting hepatic ketogenesis and hepatic glucose production, depleting hepatic acetyl-CoA content and ATP content, while increasing other short-chain acyl-CoAs. Utilizing a recently developed positional isotopomer NMR tracer analysis method, we demonstrated that MCPA-induced reductions in hepatic acetyl-CoA content were associated with a marked reduction of hepatic pyruvate carboxylase (PC) flux. Taken together, these data reveal the in vivo mechanisms of action of MCPA and MCPG: the hypoglycemia associated with ingestion of these toxins can be ascribed mostly to MCPA- or MCPG-induced reductions in hepatic PC flux due to inhibition of ß-oxidation of short-chain acyl-CoAs by MCPA or inhibition of both short- and medium-chain acyl-CoAs by MCPG with resultant reductions in hepatic acetyl-CoA content, with an additional contribution to hypoglycemia through reduced hepatic ATP stores by MCPA.


Asunto(s)
Ciclopropanos , Glicina/análogos & derivados , Hipoglucemia/inducido químicamente , Animales , Gluconeogénesis/efectos de los fármacos , Glucosa/metabolismo , Hipoglucemia/patología , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Oxidación-Reducción/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Transducción de Señal/efectos de los fármacos
19.
Proc Natl Acad Sci U S A ; 113(24): E3423-30, 2016 06 14.
Artículo en Inglés | MEDLINE | ID: mdl-27247419

RESUMEN

A key sensor of cellular energy status, AMP-activated protein kinase (AMPK), interacts allosterically with AMP to maintain an active state. When active, AMPK triggers a metabolic switch, decreasing the activity of anabolic pathways and enhancing catabolic processes such as lipid oxidation to restore the energy balance. Unlike oxidative tissues, in which AMP is generated from adenylate kinase during states of high energy demand, the ornithine cycle enzyme argininosuccinate synthetase (ASS) is a principle site of AMP generation in the liver. Here we show that ASS regulates hepatic AMPK, revealing a central role for ureagenesis flux in the regulation of metabolism via AMPK. Treatment of primary rat hepatocytes with amino acids increased gluconeogenesis and ureagenesis and, despite nutrient excess, induced both AMPK and acetyl-CoA carboxylase (ACC) phosphorylation. Antisense oligonucleotide knockdown of hepatic ASS1 expression in vivo decreased liver AMPK activation, phosphorylation of ACC, and plasma ß-hydroxybutyrate concentrations. Taken together these studies demonstrate that increased amino acid flux can activate AMPK through increased AMP generated by ASS, thus providing a novel link between protein catabolism, ureagenesis, and hepatic lipid metabolism.


Asunto(s)
Proteínas Quinasas Activadas por AMP/metabolismo , Argininosuccinato Sintasa/biosíntesis , Regulación Enzimológica de la Expresión Génica/fisiología , Metabolismo de los Lípidos/fisiología , Hígado/metabolismo , Urea/metabolismo , Animales , Activación Enzimática , Ratas , Ratas Sprague-Dawley
20.
Diabetologia ; 61(12): 2598-2607, 2018 12.
Artículo en Inglés | MEDLINE | ID: mdl-29721633

RESUMEN

AIMS/HYPOTHESIS: The progressive loss of beta cell function is part of the natural history of type 2 diabetes. Autopsy studies suggest that this is, in part, due to loss of beta cell mass (BCM), but this has not been confirmed in vivo. Non-invasive methods to quantify BCM may contribute to a better understanding of type 2 diabetes pathophysiology and the development of therapeutic strategies. In humans, the localisation of vesicular monoamine transporter type 2 (VMAT2) in beta cells and pancreatic polypeptide cells, with minimal expression in other exocrine or endocrine pancreatic cells, has led to its development as a measure of BCM. We used the VMAT2 tracer [18F]fluoropropyl-(+)-dihydrotetrabenazine to quantify BCM in humans with impaired glucose tolerance (prediabetes) or type 2 diabetes, and in healthy obese volunteers (HOV). METHODS: Dynamic positron emission tomography (PET) data were obtained for 4 h with metabolite-corrected arterial blood measurement in 16 HOV, five prediabetic and 17 type 2 diabetic participants. Eleven participants (six HOV and five with type 2 diabetes) underwent two abdominal PET/computed tomography (CT) scans for the assessment of test-retest variability. Standardised uptake value ratio (SUVR) was calculated in pancreatic subregions (head, body and tail), with the spleen as a reference region to determine non-specific tracer uptake at 3-4 h. The outcome measure SUVR minus 1 (SUVR-1) accounts for non-specific tracer uptake. Functional beta cell capacity was assessed by C-peptide release following standard (arginine stimulus test [AST]) and acute insulin response to the glucose-enhanced AST (AIRargMAX). Pearson correlation analysis was performed between the binding variables and the C-peptide AUC post-AST and post-AIRargMAX. RESULTS: Absolute test-retest variability (aTRV) was ≤15% for all regions. Variability and overlap of SUVR-1 was measured in all groups; HOV and participants with prediabetes and with type 2 diabetes. SUVR-1 showed significant positive correlations with AIRargMAX (all groups) in all pancreas subregions (whole pancreas p = 0.009 and pancreas head p = 0.009; body p = 0.019 and tail p = 0.023). SUVR-1 inversely correlated with HbA1c (all groups) in the whole pancreas (p = 0.033) and pancreas head (p = 0.008). SUVR-1 also inversely correlated with years since diagnosis of type 2 diabetes in the pancreas head (p = 0.049) and pancreas tail (p = 0.035). CONCLUSIONS/INTERPRETATION: The observed correlations of VMAT2 density in the pancreas and pancreas regions with years since diagnosis of type 2 diabetes, glycaemic control and beta cell function suggest that loss of BCM contributes to deficient insulin secretion in humans with type 2 diabetes.


Asunto(s)
Diabetes Mellitus Tipo 2/metabolismo , Páncreas/metabolismo , Tomografía de Emisión de Positrones/métodos , Proteínas de Transporte Vesicular de Monoaminas/metabolismo , Femenino , Humanos , Células Secretoras de Insulina/metabolismo , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad
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