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In skeletal muscle (SkM), a reduced mitochondrial elongate phenotype is associated with several metabolic disorders like type 2 diabetes mellitus (T2DM). However, the mechanisms contributing to this reduction in mitochondrial elongate phenotype in SkM have not been fully elucidated. It has recently been shown in a SkM cell line that toll-like receptor 4 (TLR4) contributes to the regulation of mitochondrial morphology. However, this has not been investigated in human SkM. Here we found that in human SkM biopsies, TLR4 protein correlated negatively with Opa1 (pro-mitochondrial fusion protein). Moreover, the incubation of human myotubes with LPS reduced mitochondrial size and elongation and induced abnormal mitochondrial cristae, which was prevented with the co-incubation of LPS with TAK242. Finally, T2DM myotubes were found to have reduced mitochondrial elongation and mitochondrial cristae density. Mitochondrial morphology, membrane structure, and insulin-stimulated glucose uptake were restored to healthy levels in T2DM myotubes treated with TAK242. In conclusion, mitochondrial morphology and mitochondrial cristae seem to be regulated by the TLR4 pathway in human SkM. Those mitochondrial alterations might potentially contribute to insulin resistance in the SkM of patients with T2DM.

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AIMS/HYPOTHESIS: Skeletal muscle is a key target organ for insulin's actions and is the main regulator of blood glucose. In obese individuals and animal models, there is a chronic low-grade inflammatory state affecting highly metabolic organs, leading to insulin resistance. We have described that adult skeletal muscle fibres can release ATP to the extracellular medium through pannexin-1 (PANX1) channels. Besides, it is known that high extracellular ATP concentrations can act as an inflammatory signal. Here, we propose that skeletal muscle fibres from obese mice release high levels of ATP, through PANX1 channels, promoting inflammation and insulin resistance in muscle cells. METHODS: C57BL/6J mice were fed with normal control diet (NCD) or high-fat diet (HFD) for 8 weeks. Muscle fibres were isolated from flexor digitorum brevis (FDB) muscle. PANX1-knockdown FDB fibres were obtained by in vivo electroporation of a short hairpin RNA Panx1 plasmid. We analysed extracellular ATP levels in a luciferin/luciferase assay. Gene expression was studied with quantitative real-time PCR (qPCR). Protein levels were evaluated by immunoblots, ELISA and immunofluorescence. Insulin sensitivity was analysed in a 2-NBDG (fluorescent glucose analogue) uptake assay, immunoblots and IPGTT. RESULTS: HFD-fed mice showed significant weight gain and insulin resistance compared with NCD-fed mice. IL-6, IL-1ß and TNF-α protein levels were increased in FDB muscle from obese mice. We observed high levels of extracellular ATP in muscle fibres from obese mice (197 ± 55 pmol ATP/µg RNA) compared with controls (32 ± 10 pmol ATP/µg RNA). ATP release in obese mice fibres was reduced by application of 100 µmol/l oleamide (OLE) and 5 µmol/l carbenoxolone (CBX), both PANX1 blockers. mRNA levels of genes linked to inflammation were reduced using OLE, CBX or 2 U/ml ATPase apyrase in muscle fibres from HFD-fed mice. In fibres from mice with pannexin-1 knockdown, we observed diminished extracellular ATP levels (78 ± 10 pmol ATP/µg RNA vs 252 ± 37 pmol ATP/µg RNA in control mice) and a lower expression of inflammatory markers. Moreover, a single pulse of 300 µmol/l ATP to fibres from control mice reduced insulin-mediated 2-NBDG uptake and promoted an elevation in mRNA levels of inflammatory markers. PANX-1 protein levels were increased two- to threefold in skeletal muscle from obese mice compared with control mice. Incubation with CBX increased Akt activation and 2-NBDG uptake in HFD fibres after insulin stimulation, rescuing the insulin resistance condition. Finally, in vivo treatment of HFD-fed mice with CBX (i.p. injection of 10 mg/kg each day) for 14 days, compared with PBS, reduced extracellular ATP levels in skeletal muscle fibres (51 ± 10 pmol ATP/µg RNA vs 222 ± 28 pmol ATP/µg RNA in PBS-treated mice), diminished inflammation and improved glycaemic management. CONCLUSIONS/INTERPRETATION: In this work, we propose a novel mechanism for the development of inflammation and insulin resistance in the skeletal muscle of obese mice. We found that high extracellular ATP levels, released by overexpressed PANX1 channels, lead to an inflammatory state and insulin resistance in skeletal muscle fibres of obese mice.

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Resumen Objetivo: Determinar los factores asociados a la cantidad de horas de sueño, somnolencia diurna e insomnio antes y durante un periodo de clases y exámenes. Material y métodos: Se evaluó a 384 alumnos de ambos sexos (74,1% mujeres), quienes reportaron su peso y estatura. A cada estudiante se le aplicó el Cuestionario de Insomnio y la Escala De Somnolencia de Epworth en el periodo de clases y periodo de exámenes. Resultados: Al comparar la somnolencia diurna, insomnio, latencia al sueño y cantidad de horas de sueño entre periodo de clases y exámenes se observó un incremento en la latencia al sueño (p<0,05) durante los exámenes. Al realizar la comparación según estado nutricional se observó, en el caso de las mujeres, que aquellas que presentan sobrepeso/obesidad tienen una menor cantidad de horas de sueño en ambos periodos (p<0,05); en hombres, los que presentan sobrepeso/obesidad tienen una mayor somnolencia diurna en exámenes (p<0,01). Al realizar la regresión logística tomando como variable dependiente somnolencia diurna, en mujeres se incrementa el riesgo de somnolencia diurna: OR=3,1 (IC95 % 1,1-8,8); en cambio, la ausencia de insomnio es un factor protector para somnolencia diurna: OR=0,06 (IC95 % 0,01-0,35). Conclusión: En periodo de exámenes se incrementa significativamente la latencia al sueño, en especial en mujeres; en hombres se observa una disminución de las horas de sueño. Finalmente, las mujeres presentan un mayor riesgo de somnolencia diurna; en cambio, la ausencia de insomnio es un factor protector. Ni el estado nutricional ni el consumo de cafeína se asociaron con problemas de sueño.

Abstract Objective: To determine the factors associated with sleep duration, daytime somnolence and insomnia before and after a period of classes and exams periods. Material and methods: 384students (74.1% female) were evaluated, who reported their weight and height. The insomnia questionnaire and Epworth sleepiness scale were administered to each student during class period and exams period. Results: When comparing daytime somnolence, insomnia, sleep latency and the amount of sleeping hours between classes and exam periods an increase in sleep latency (p <0.05) was observed during exams. Fewer hours of sleep were observed in both periods (p <0.05) in women with overweight / obesity. In men, those who are overweight / obese show a higher daytime somnolence during exam periods (p <0.01). By performing the logistic regression analysis using daytime somnolence as a dependent variable, being a woman increases the risk of daytime somnolence (OR = 3.1, 95 % CI 1.1 to 8.8), whereas the absence of insomnia is a protective factor for daytime somnolence (OR = 0.06, 95 % CI 0.01 to 0.35). Conclusion: Sleep latency is significantly increased during exam period, especially in women; in men a decrease is observed in sleep hours. Finally, women present high risk of diurnal somnolence, in difference the absence of insomnia is a protective factor, however the nutritional status and caffeine intake was not associated with sleeping problems.

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The aim of the study was to characterize the anthropometric profile and somatotype of a sample of 50 players table tennis competitive with an average age 21.6 (± 3.1) years belonging to the Chilean team and institutions of higher education in the region of Valparaiso. The evaluation was conducted under the protocol marking the International Society for the Advancement of Kinanthropometry (ISAK) for the measurement procedure 25 restricted profile variables described by Drinkwater, Norton and Olds. Order to determine the body composition, fat, muscle, bone, skin and tissue residual was considered, using the equations proposed by Kerr. The body shape is characterized through somatotype method proposed by Carter. The sample was divided into 4 groups; Chilean Selection, Traditional Private Universities, State Universities and Private Universities Traditional Nontraditional. Regarding body composition; the Chilean team has the highest values of muscle tissue (45.6 ± 1.7%) and the lowest values of adipose tissue (25.2 ± 1.8%), also presenting lesser value in the Σ 6 skinfolds (mm) . The results showed no significant differences between groups in the aforementioned variables. In general somatotype compared by analyzing SANOVA no significant differences between groups (p = 0.409) was observed. The results show a biotype with such a characterization of endo-mesomorph with average values (4,1-4,9-1,8). This study provides updated data biotypological reference for this sport that can be used for decision-making.

El objetivo del estudio fue caracterizar el perfil antropometrico y el somatotipo de una muestra de 50 jugadores de tenis de mesa de nivel competitivo con un promedio de edad 21,6 (± 3,1) anos pertenecientes a la seleccion chilena e instituciones de educacion superior de la region de Valparaiso. La evaluacion se realizo bajo el protocolo de marcaje de la International Society for the Advancement of Kinanthropometry (ISAK) para el procedimiento de medicion de 25 variables de perfil restringido descrito por Drinkwater1, Norton & Olds2. Con el objetivo de determinar la composicion corporal, se considero el tejido adiposo, muscular, oseo, residual y de piel, utilizando las ecuaciones propuestas por Kerr3. La forma corporal se caracterizo a traves del metodo del somatotipo propuesto por Carter4. La muestra se distribuyo en cuatro grupos: seleccion chilena, universidades privadas tradicionales, universidades estatales tradicionales y universidades privadas no tradicionales. Respecto a la composicion corporal; la seleccion chilena presenta los mayores valores de tejido muscular (45,6 ± 1,7%) y los menores valores de tejido adiposo (25,2 ± 1,8%), presentando tambien menor valor en la Σ seis pliegues (mm). Los resultados no evidenciaron diferencias significativas entre los grupos en las variables antes mencionadas. En la comparacion general del somatotipo a traves del analisis SANOVA no se aprecian diferencias significativas entre los grupos (p = 0,409). Los resultados obtenidos muestran un biotipo con una caracterizacion de tipo endo-mesomorfo con valores promedio de (4,1-4,9-1,8). Este estudio aporta datos biotipologicos actualizados de referencia para este deporte que pueden ser utilizados para la toma de decisiones.

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