Efeitos agudos da terapia de fotobiomodulação sobre a glicemia e a concentração de glicogênio muscular de ratos

Abstract

Photobiomodulation (PBM) has many effects on the energetic metabolism of musculoskeletal tissue, such as increased glycogen synthesis. However, these effects can systemic, such as glycemic control. The primary objective was to evaluate the effects of photobiomodulation (PBM) by LEDs (light-emitting diodes) on glycemic levels and muscle glycogen concentration in non-diabetic rats. The secondary objectives were to evaluate the acute effects of 4 doses of PBM (dose-response: sham, 10 J/cm2, 30 J/cm2, 60 J/cm2) on glycemic levels in rats over 6 hours (time-response: pre irradiation,1 hour, 3 hours, 6 hours) after irradiation; and to evaluate the acute effects of dose-response of PBM on muscle glycogen levels in rats after 24 hours of irradiation.Finally, to correlate glycemic modulations with muscle glycogen concentrations after applying 4 different doses of PBM. Twenty-four Wistar rats were randomly and equally allocated to four groups: sham (placebo therapy), PBM 10J/cm2, PBM 30J/cm2, and FBM 60 J/cm2. The animals fasted for 6 hours. Feeding was interrupted immediately before PBM. Evaluations of glucose level were performed at pre-irradiation times (immediately before PBM), 1h, 3h and 6h. Muscle glycogen synthesis was measured 24 hours after PBM. PBM used an arrangement of 69 LEDs (light-emitting diodes) with 35 reds (630 ± 10 nm) and 34 infrared (850 ± 20 nm); 114 mW/cm2 for 90 s (10J/cm2), 270s (30J/cm2), 540s (60J/cm2) applied to the back, gluteus, and hind limbs of the animals. The 10J/cm2 group showed lower glycemic variability over 6 hours (5.92 mg/dL) compared to the sham (13.03 mg/dL), 30J/cm2 (7.77 mg/dL) and PBM 60 J/cm2 (9.07 mg/dL) groups. The PBM groups had the highest increase in muscle glycogen (10 J/cm2 > 60 J/cm2 > 30 J/cm2 > sham), characterizing a three-phase dose-response to PBM. There was a strong negative correlation between glycemic variability over 6h and muscle glycogen concentration for 10J/cm2 (r= -0.94; p<0.001) followed by 30 J/cm2 (r= -0.84; p<0.001) and 60J/cm2 (r= -0.73; p<0.006). The results suggest that PBM can play a very important role in the control of glycemic levels, and its possible mechanism of action is the induction of greater muscle glycogen synthesis independent of physical exercise.