Resistencia a insulina en el músculo esquelético: conexión con la obesidad

Insulin resistance is an important contributor to the pathogenesis of type 2 diabetes and obesity is a risk factor for its development, due in part to the fact that adipose tissue secretes proteins called adipokines that may influence insulin sensitivity. Among these molecules, TNFa has been proposed as a link between obesity and insulin resistance because TNFa is overexpressed in adipose tissues of obese animals and humans, and obese mice lacking either TNFa or its receptor show protection for developing insulin resistance. The direct exposure to TNFa induced a state of insulin resistance on glucose uptake in myocytes and brown adipocytes, due to the activation of pro-inflammatory pathways that impair insulin-signaling at the level of the IRS proteins. In this regard the residue Ser307 in IRS-1 has been identified as a site for TNFa-inhibitory effects in myotubes, with being p38MAPK and IKK involved in the phosphorylation of this residue. Conversely, serine phosphorylation of IRS-2 mediated by TNFa activation of MAPKs was the mechanism found in brown adipocytes. The phosphatase PTP1B acts as a physiological negative regulator of insulin signaling by dephosphorylating the phosphotyrosine residues of the insulin receptor and IRS-1, and PTP1B expression is increased in muscle and white adipose tissue of obese and diabetic humans and rodents. Moreover, up-regulation of PTP1B expression has recently been found in cells treated with TNFa. Accordingly, myocytes and primary brown adipocytes deficient on PTP1B are protected against insulin resistance by this cytokine. Furthermore, down-regulation of PTP1B activity is also possible by the use of pharmacological agonists of nuclear receptors that restored insulin sensitivity in the presence of TNFa. In conclusion, the lack of PTP1B in muscle and brown adipocytes increase insulin sensitivity and glucose uptake and could confer protection against insulin resistance induced by adipokines.Key Words: Glucose uptake, LXR, PTP1B, TNFa, IL-6.Entre las complicaciones asociadas a la Obesidad, tiene una especial relevancia el desarrollo de resistencia a la insulina, siendo el primer eslabón de una amplia patología conocida como diabetes tipo 2. La Obesidad se considera como un estado crónico de inflamación de baja intensidad, como indican los niveles circulantes elevados de moléculas proinflamatorias. Se ha propuesto al TNFa como el nexo de unión entre adiposidad y desarrollo de resistencia a insulina ya que la mayoría de los pacientes con diabetes tipo 2 son obesos y tienen aumentada la expresión de TNFa en sus adipocitos, y los animales obesos deleccionados para la función del TNFa o su receptor no desarrollan resistencia a insulina. Las citocinas proinflamatorias producidas por los adipocitos y/o macrófagos activan quinasas de estrés, proinflamatorias y factores de transcripción que actúan sobre los tejidos periféricos (entre ellos el músculo y el propio tejido adiposo) produciendo resistencia a la acción de la insulina, que es un defecto en la señalización a varios niveles. En concreto, el TNFa activa la quinasa p38MAPK que fosforila en residuos de serina a los IRSs, bloqueando su fosforilación en tirosina en respuesta a la insulina, tanto en adipocitos marrones como en miocitos. Muy recientemente hemos observado que la fosfatasa PTP1B también está implicada en la resistencia a insulina por TNFa en ambos modelos. En la clínica se está utilizando actualmente el tratamiento con tiazolidindionas en pacientes con diabetes tipo 2. Otros agonistas de receptores nucleares empiezan a aparecer en la bibliografía como potenciales sensibilizadores a acción de la insulina, entre ellos el LXR, que puede antagonizar la señalización proinflamatoria en los propios adipocitos y/o en el músculo.Palabras clave: Transporte de glucosa, LXR, PTP1B, TNFa, IL-6

Skeletal muscle myogenesis is regulated by G protein-coupled receptor kinase 2

This is a pre-copyedited, author-produced pdf of an article accepted for publication in Journal of Molecular Cell Biology following peer review. The version of record Journal of Molecular Cell Biology 6.4 (2014) is available online at: http://dx.doi.org/10.1093/jmcb/mju025G protein-coupled receptor kinase 2 (GRK2) is an important serine/threonine-kinase regulating different membrane receptors and intracellular proteins. Attenuation of Drosophila Gprk2 in embryos or adult flies induced a defective differentiation of somatic muscles, loss of fibers, and a flightless phenotype. In vertebrates, GRK2 hemizygous mice contained less but more hypertrophied skeletal muscle fibers than wild-type littermates. In C2C12 myoblasts overexpression of a GRK2 kinase-deficient mutant (K220R) caused precocious differentiation of cells into immature myotubes, which were wider in size and contained more fused nuclei, while GRK2 overexpression blunted differentiation. Moreover, p38MAPK and Akt pathways were activated at an earlier stage and to a greater extent in K220R-expressing cells or upon kinase downregulation, while the activation of both kinases was impaired in GRK2- overexpressing cells. The impaired differentiation and fewer fusion events promoted by enhanced GRK2 levels were recapitulated by a p38MAPK mutant, which was able to mimic the inhibitory phosphorylation of p38MAPK by GRK2, whereas the blunted differentiation observed in GRK2-expressing clones was rescued in the presence of a constitutively active upstream stimulator of the p38MAPK pathway. These results suggest that balanced GRK2 function is necessary for a timely and complete myogenic process.This work was supported by Grants BFU2008-04043 (to M.L. and S.F.-V.), SAF2012-3618 (to S.F.-V.), and SAF2011-23800 (to F.M.) from Ministerio de Economía y Competitividad, Spain; S2010/BMD-2332 (INDISNET) from Comunidad de Madrid, Spain (to F.M.); CIBER de Diabetes y Enfermedades Metabólicas Asociadas and The Cardiovascular Network (RD06- 0014/0037 and RD12/0042/0012) from Ministerio Sanidad y Consumo-Instituto Carlos III, Spain (to F.M.); UAM-Banco de Santander (to C.M.); BFU2010-14884 (to M.R.-G.). S.F.-V. is recipient of a ‘Miguel Servet’ tenure track program (CP10/00438) co-financed by the European Regional Development Fund (ERDF). We also acknowledge the support of COST Action BM0602 from the European Commission (to M.L.) and institutional support from Fundación Ramón Arece

Association Between Preexisting Versus Newly Identified Atrial Fibrillation and Outcomes of Patients With Acute Pulmonary Embolism

Background Atrial fibrillation (AF) may exist before or occur early in the course of pulmonary embolism (PE). We determined the PE outcomes based on the presence and timing of AF. Methods and Results Using the data from a multicenter PE registry, we identified 3 groups: (1) those with preexisting AF, (2) patients with new AF within 2 days from acute PE (incident AF), and (3) patients without AF. We assessed the 90-day and 1-year risk of mortality and stroke in patients with AF, compared with those without AF (reference group). Among 16 497 patients with PE, 792 had preexisting AF. These patients had increased odds of 90-day all-cause (odds ratio [OR], 2.81; 95% CI, 2.33-3.38) and PE-related mortality (OR, 2.38; 95% CI, 1.37-4.14) and increased 1-year hazard for ischemic stroke (hazard ratio, 5.48; 95% CI, 3.10-9.69) compared with those without AF. After multivariable adjustment, preexisting AF was associated with significantly increased odds of all-cause mortality (OR, 1.91; 95% CI, 1.57-2.32) but not PE-related mortality (OR, 1.50; 95% CI, 0.85-2.66). Among 16 497 patients with PE, 445 developed new incident AF within 2 days of acute PE. Incident AF was associated with increased odds of 90-day all-cause (OR, 2.28; 95% CI, 1.75-2.97) and PE-related (OR, 3.64; 95% CI, 2.01-6.59) mortality but not stroke. Findings were similar in multivariable analyses. Conclusions In patients with acute symptomatic PE, both preexisting AF and incident AF predict adverse clinical outcomes. The type of adverse outcomes may differ depending on the timing of AF onset.info:eu-repo/semantics/publishedVersio

Higher COVID-19 pneumonia risk associated with anti-IFN-α than with anti-IFN-ω auto-Abs in children

We found that 19 (10.4%) of 183 unvaccinated children hospitalized for COVID-19 pneumonia had autoantibodies (auto-Abs) neutralizing type I IFNs (IFN-alpha 2 in 10 patients: IFN-alpha 2 only in three, IFN-alpha 2 plus IFN-omega in five, and IFN-alpha 2, IFN-omega plus IFN-beta in two; IFN-omega only in nine patients). Seven children (3.8%) had Abs neutralizing at least 10 ng/ml of one IFN, whereas the other 12 (6.6%) had Abs neutralizing only 100 pg/ml. The auto-Abs neutralized both unglycosylated and glycosylated IFNs. We also detected auto-Abs neutralizing 100 pg/ml IFN-alpha 2 in 4 of 2,267 uninfected children (0.2%) and auto-Abs neutralizing IFN-omega in 45 children (2%). The odds ratios (ORs) for life-threatening COVID-19 pneumonia were, therefore, higher for auto-Abs neutralizing IFN-alpha 2 only (OR [95% CI] = 67.6 [5.7-9,196.6]) than for auto-Abs neutralizing IFN-. only (OR [95% CI] = 2.6 [1.2-5.3]). ORs were also higher for auto-Abs neutralizing high concentrations (OR [95% CI] = 12.9 [4.6-35.9]) than for those neutralizing low concentrations (OR [95% CI] = 5.5 [3.1-9.6]) of IFN-omega and/or IFN-alpha 2

Protein-tyrosine phosphatase 1B-deficient myocytes show increased insulin sensitivity and protection against tumor necrosis factor-α-induced insulin resistance

Protein-tyrosine phosphatase (PTP)1B is a negative regulator of insulin signaling and a therapeutic target for type 2 diabetes. In this study, we have assessed the role of PTP1B in the insulin sensitivity of skeletal muscle under physiological and insulin-resistant conditions. Immortalized myocytes have been generated from PTP1B-deficient and wild-type neonatal mice. PTP1B-/- myocytes showed enhanced insulin-dependent activation of insulin receptor autophosphorylation and downstream signaling (tyrosine phosphorylation of insulin receptor substrate [IRS]-1 and IRS-2, activation of phosphatidylinositol 3-kinase, and serine phosphorylation of AKT), compared with wild-type cells. Accordingly, PTP1B-/- myocytes displayed higher insulin-dependent stimulation of glucose uptake and GLUT4 translocation to the plasma membrane than wildtype cells. Treatment with tumor necrosis factor-α (TNF-α) induced insulin resistance on glucose uptake, impaired insulin signaling, and increased PTP1B activity in wild-type cells. Conversely, the lack of PTP1B confers protection against insulin resistance by TNF-α in myocyte cell lines and in adult male mice. Wild-type mice treated with TNF-α developed a pronounced hyperglycemia along the glucose tolerance test, accompanied by an impaired insulin signaling and increased PTP1B activity in muscle. However, mice lacking PTP1B maintained a rapid clearance of glucose and insulin sensitivity and displayed normal muscle insulin signaling regardless the presence of TNF-α. © 2007 by the American Diabetes Association.M.L. has received grant BFU2005-03054 from Ministry of Education and Science (MEC), Spain. A.M.V. has received grant BFU2005-01615 from MEC. I.N.-V. and C.d.A. have received fellowships from MEC. S.F.-V. was a recipient of a contract Juan de la Cierva from MEC.Peer Reviewe

Role of G protein-coupled receptor kinase 2 (GRK2) in insulin resistance and obesity

Resumen del trabajo presentado al XXXIV Congreso de la Sociedad Española de Bioquímica y Biología Molecular, celebrado en Barcelona del 5 al 8 de septiembre de 2011.Prevalence of obesity has reached epidemic scope in industrialized countries and it currently stands as a risk factor for the development of common metabolic disorders as insulin resistance and T2D. Nowadays, GRK2 has been recognized as an integrative node regulating a variety of transduction pathways including the insulin signaling cascade. We have recently reported that GRK2 plays a relevant physiological role in the modulation of insulin responses in vivo. In cultured adipocytes and myocytes, increased GRK2 levels inhibit insulin-stimulated glucose uptake and signaling by a mechanism involving the formation of dynamic GRK2/IRS1 complexes. This work also uncovers a role for GRK2 in the regulation of adiposity since GRK2+/- mice were resistant to diet and age-induced obesity (Garcia-Guerra et al., 2010). We further evaluated the potential contribution of brown fat to the leaner phenotype of GRK2+/- mice. Our results indicate that GRK2 modulate white and brown fat lipid metabolism. GRK2+/- adult mice exhibited increased energy expenditure and a lower RER, consistently with a less deteriorated BAT morphology. Indeed, decreased GRK2 protein levels were associated with higher core body temperature and a better thermogenic capacity. In addition, we detect a negative effect of GRK2 in the metabolism and differentiation of cultured brown adipocytic cells, further supporting the hypothesis that the lean phenotype of GRK2 +/- mice clearly involves a role for this kinase in BAT function. In summary, our data identify GRK2 as an important negative regulator of insulin effects and point at GRK2 inhibition as a potential tool for the enhancement of brown fat activity, which may have important therapeutic implications for the treatment of obesity and associated metabolic disorders.Peer Reviewe

Contribucion del TNF-alfa a la insulinorresistencia asociada a la obesidad

Insulin resistance is an important contributor to the pathogenesis of type 2 diabetes, and obesity is a risk factor for its development, due in part to the fact that adipose tissue secretes proteins called adipokines, that may influence insulin sensitivity. Among these molecules, TNF-á has been proposed as a link between obesity and insulin resistance because TNF-á is overexpressed in adipose tissues of obese animals and humans, and obese mice lacking either TNF-á or its receptor show protection for developing insulin resistance. The direct exposure to TNF-á induced a state of insulin resistance on glucose uptake in myocytes and brown adipocytes, due to the activation of pro-inflammatory pathways that impair insulin- signaling at the level of the IRS proteins. In this regard the residue Ser307 in IRS-1 has been identified as a site for TNF-á-inhibitory effects in myotubes, with p38MAPK and IKK being involved in the phosphorylation of this residue. Conversely, serine phosphorylation of IRS-2 mediated by TNF-á activation of MAPKs was the mechanism found in brown adipocytes. The phosphatase PTP1B acts as a physiological negative regulator of insulin signaling by dephosphorylating the phosphotyrosine residues of the insulin receptor and IRS-1, and PTP1B expression is increased in muscle and white adipose tissue of obese and diabetic humans and rodents. Moreover, up-regulation of PTP1B expression was recently found in cells treated with TNF-á. Accordingly, myocytes and primary brown adipocytes deficient on PTP1B are protected against insulin resistance by this cytokine. Furthermore, down-regulation of PTP1B activity is also possible by the use of pharmacological agonists of nuclear receptors that restore insulin sensitivity in the presence of TNF-á. In conclusion, the lack of PTP1B in muscle and brown adipocytes increases insulin sensitivity and glucose uptake and could confer protection against insulin resistance induced by adipokines.Entre las complicaciones asociadas a la Obesidad, tiene una especial relevancia el desarrollo de resistencia a la insulina, siendo el primer eslabon de una amplia patologia conocida como diabetes tipo 2. La Obesidad se considera como un estado cronico de inflamacion de baja intensidad, como indican los niveles circulantes elevados de moleculas proinflamatorias. Se ha propuesto al TNF-ƒ¿ como el nexo de union entre adiposidad y desarrollo de resistencia a insulina ya que la mayoria de los pacientes con diabetes tipo 2 son obesos y tienen aumentada la expresion de TNF-ƒ¿ en sus adipocitos, y los animales obesos deleccionados para la funcion del TNF-ƒ¿ o su receptor no desarrollan resistencia a insulina. Las citocinas proinflamatorias producidas por los adipocitos y/o macrofagos activan quinasas de estres, proinflamatorias y factores de transcripcion que actuan sobre los tejidos perifericos (entre ellos el musculo, asi como el propio tejido adiposo) produciendo resistencia a la accion de la insulina, que es un defecto en la senalizacion a varios niveles. En concreto, el TNF-ƒ¿ activa la quinasa p38MAPK que fosforila en residuos de serina a los IRSs, bloqueando su fosforilacion en tirosina en respuesta a la insulina, tanto en adipocitos marrones como en miocitos. Muy recientemente hemos observado que la fosfatasa PTP1B tambien esta implicada en la resistencia a insulina por TNF-ƒ¿ en ambos modelos. En la Clinica se esta utilizando actualmente el tratamiento con tiazolidindionas en pacientes con diabetes tipo 2. Otros agonistas de receptores nucleares empiezan a aparecer en la bibliografia como potenciales sensibilizadores a accion de la insulina, entre ellos el LXR, que puede antagonizar la senalizacion proinflamatoria tanto en los propios adipocitos como en el musculo

Skeletal muscle myogenesis is regulated by G protein-coupled receptor kinase 2, GRK2

Resumen del póster presentado al XXXIV Congreso de la Sociedad Española de Bioquímica y Biología Molecular, celebrado en Barcelona del 5 al 8 de septiembre de 2011.GRK2 is the more ubiquitous G protein-coupled receptor kinase isoform and, additionally to its role in GPCR desensitization, it has been implicated in the modulation of different intracellular signalling pathways. Recently, GRK2 has been identified as a novel inactivating kinase of p38MAPK that interferes with 3T3L1 differentiation. Therefore, a possible role for GRK2 in the differentiation of myocytic cells remains to be explored. In this regard, the main objective was to investigate the contribution of GRK2 to myogenesis.We analyzed myoblast C2C12 differentiation and cell cycle protein expression. In this issue we generated stable cell lines that overexpressed wild-type GRK2 or GRK2 catalytically-deficient mutant (K220R). Overexpression of wild-type GRK2 impaired the myoblast fusion and the expression of myogenic markers. These cells were unable to activate not only p38MAPK but also Akt pathways. However, cells overexpressing GRK2 kinasedeficient mutant differentiated in the same way as wild-type cells. We also analyzed the skeletal muscle phenotypic and functional differences between Wt and GRK2 hemizygous animals. GRK2+/- mice exhibited increased muscle fibber size and less number of fibbers compared to Wt animals. Furthermore, we also observed that this hypertrophy is consistent with increased glucose clearance into skeletal muscle in 9-month-old GRK2+/- mice, suggesting that the muscle of these animals preserved its functionality better than Wt mice during the elderly. We conclude that GRK2 inactivation leads to increased Akt and p38MAPK signalling improving skeletal muscle differentiation. Our data identify GRK2 as a negative regulator of skeletal muscle myogenesis, which uncovers an important new function in the signalling networks of this protein.Peer reviewe

GRK2 contribution to the regulation of energy expenditure and brown fat function

Obesity is a major health problem and an important risk factor for the development of multiple disorders. Previous studies in our laboratory have revealed that down-regulation of GRK2 decreases age-related adiposity, but the physiological and molecular mechanisms underlying this outcome remain unclear. We evaluate whether the lean phenotype results from a direct effect of GRK2 on energy homeostasis. The study of white adipose tissue (WAT) in wild-type (WT) and GRK2 +/- littermates showed a reduced expression of lipogenic enzymes and enhanced lipolytic rate in adult GRK2 +/- mice. Moreover, hemizygous mice display higher energy expenditure and lower respiratory exchange ratio. Analysis of brown adipose tissue (BAT) from adult GRK2 +/- mice showed a less deteriorated morphology associated with age compared to WT, which is correlated with a higher basal core temperature. BAT from young GRK2 +/- mice showed an increase in gene expression of thermogenesis-related genes. Accordingly, hemizygous mice displayed better thermogenic capacity and exhibited a more oxidative phenotype in both BAT and WAT than WT littermates. Overexpression of GRK2 in brown adipocytes corroborated the negative effect of this kinase in BAT function and differentiation. Collectively, our data point to GRK2 inhibition as a potential tool for the enhancement of brown fat activity, which may have important therapeutic implications for the treatment of obesity and associated metabolic disorders. © FASEB.Peer Reviewe

G Protein-coupled receptor kinase 2 (GRK2): A novel modulator of insulin resistance

G protein-coupled receptor kinase 2 (GRK2) is emerging as a key, integrative node in many signalling pathways. Besides its canonical role in the modulation of the signalling mediated by many G protein-coupled receptors (GPCR), this protein can display a very complex network of functional interactions with a variety of signal transduction partners, in a stimulus, cell type, or context-specific way. We review herein recent data showing that GRK2 can regulate insulin-triggered transduction cascades at different levels and that this protein plays a relevant role in insulin resistance and obesity in vivo, what uncovers GRK2 as a potential therapeutic target in the treatment of these disorders.Peer reviewe