RESUMO
Fibroblast growth factor 21 (FGF21) is a pleiotropic peptide hormone that is considered a myokine playing a role in a variety of endocrine functions, including regulation of glucose transport and lipid metabolism. Although FGF21 has been associated with glucose metabolism in skeletal muscle cells, its cellular mechanism in adult skeletal muscle fibers glucose uptake is poorly understood. In the present study, we found that FGF21 induced a dose-response effect, increasing glucose uptake in skeletal muscle fibers from flexor digitorum brevis muscle of mice, evaluated using the fluorescent glucose analog 2-NBDG (300 µM) in single living fibers. This effect was prevented by the use of either Cytochalasin B (5 µM) or Indinavir (100 µM), both antagonists of GLUT4 activity. The use of PI3K inhibitors such as Wortmannin (100 nM) and LY294002 (50 µM) completely prevented the FGF21-dependent glucose uptake. In fibers electroporated with the construct encoding GLUT4myc-eGFP chimera and stimulated with FGF21 (100 ng/mL), a strong sarcolemmal GLUT4 label was detected. This effect promoted by FGF21 was demonstrated to be dependent on atypical PKC-ζ, by using selective PKC inhibitors. FGF21 at low concentrations potentiated the effect of insulin on glucose uptake but at high concentrations, completely inhibited the uptake in the presence of insulin. These results suggest that FGF21 regulates glucose uptake by a mechanism mediated by GLUT4 and dependent on atypical PKC-ζ- in skeletal muscle.
RESUMO
Objetivo. Describir la respuesta del balance simpático-parasimpático después una semana de entrenamiento de volumen aeróbico en ciclistas de ruta. Métodos. El estudio fue basado en un diseño transversal no experimental. Una muestra no aleatoria de cinco ciclistas hombres. Todos participan en la categoría «Todo Competidor» del circuito nacional (27.0±1.9 años, 170.0±6.6cm, 66.0±4.3kg). Los sujetos fueron evaluados durante seis días con un entrenamiento aeróbico (108.4±49.5km por día). Cada día se les midió el balance autonómico a través del cociente baja frecuencia/alta frecuencia, en reposo e inmediatamente posterior al entrenamiento. Resultados. Los valores del intervalo RR (1205.9 ± 35.2-993.7 ± 61.2 basal y postentrenamiento respectivamente) muestran diferencia significativa (p<0.05). Los valores del cociente baja frecuencia/alta frecuencia (0.861±0.090-3.067±0.590 basal y postentrenamiento respectivamente) reflejan que existe una activación del balance autonómico inmediatamente terminado el entrenamiento (p<0.05). La potencia de la HF del balance autonómico (2567±697-926±367 basal y postentrenamiento respectivamente) refleja una disminución significativa apenas termina el entrenamiento y comienza la recuperación (p<0.05). Conclusiones. Los resultados de este estudio muestran un aumento significativo en la respuesta del balance autonómico del cociente baja frecuencia/alta frecuencia posterior al entrenamiento. Además, una disminución significativa de la potencia de la banda de alta frecuencia durante la recuperación que puede implicar aumento de la actividad de la respuesta parasimpática. Estos cambios podrían ayudar al control y diseño de programas de entrenamiento de forma individualizada para el ciclismo en ruta, además de ser una herramienta barata y no invasiva (AU)
Objetivo. Descrever a resposta do balanço simpático-parassimpático após uma semana de treino de volume aeróbico em ciclistas de estrada. Métodos. O estudo foi baseado num design não experimental. Amostra não-aleatória de cinco homens ciclistas. Todos participam na categoria «Todos os competidores» do circuito nacional (27±1.9 anos, 170±6.6cm, 66±4.3kg). Os indivíduos foram avaliados por seis dias com o treino de resistencia (108.4±49.5 km por dia). Cada dia era medido o balanço autonómico através da razão baixa frequencia/alta frequencia, em repouso e imediatamente após o treino. Resultados. Os valores do intervalo RR (1205.9±35.2 para 993.7±61.2 para o início do estudo e o pós-treino, respetivamente) mostram diferença significativa (p<0.05). Os valores da razão baixa frequencia/alta frequencia (0.861 ± 0.09-3.067 ± 0.59 para o início do estudo e 0 pós-treino, respetivamente) mostram que existe uma ativação do balanço autonómico imediatamente após o treino (p<0.05). A potencia alta frequencia do balanço autonómico (2.567±697-926±367 no início do estudo e pós-treino, respetivamente), reflete uma diminuição significativa logo após o treinamento e o início da recuperação (p<0.05). Conclusões. Os resultados deste estudo mostraram um aumento significativo na resposta do balanço autonómico da relação baixa frequencia/alta frequencia após o treino. Por outro lado, uma diminuição significativa na potencia banda de alta frequencia durante a recuperação pode envolver o aumento da atividade da resposta parassimpática. Essas mudanças poderiam ajudar a controlar e desenhar os programas de treino individualmente para ciclismo de estrada, além de ser uma ferramenta barata e não invasiva (AU)
Objective. To describe the response of the sympathetic-parasympathetic balance after a week of aerobic training volume in road cyclists. Methods. The study was based on a non experimental transectional design. A non-random sample of five cyclists men. All participates in category «All competitors» of the national circuit (27.0±1.9 years, 170.0±6.6cm, 66.0±4.3kg). Subjects were evaluated for six days with aerobic training (108.4±49.5km per day). Each day the autonomic balance through the ratio LF/HF was measured, at rest and immediately after training. Results. Mean values of RR (1205.9±35.2 to 993.7±61.2 at baseline and post-training respectively) interval show significant difference (p<0.05). The values of the ratio Low Frequency/High Frequency (0.861±0.090 to 3.067±0.59 at baseline and post-training respectively) show that there is an activation of the autonomic balance immediately completed the training (p<0.05). The High Frequency power of autonomic balance (2567±697 to 926±367 at baseline and post-training respectively), shows a significant decline straight after training and start recovery (p<0.05). Conclusions. The results of this study show a significant increase in the response of the autonomic balance of the ratio Low Frequency/High Frequency after training. Furthermore, a significant decrease in power of the High Frequency band during recovery may involve and increased activity of the parasympathetic response. These changes can help to the control and design of individual training programs for road cycling as well as being an inexpensive and non-invasive tool (AU)
