No Mitochondrial Related Transcriptional Changes in Human Skeletal Muscle after Local Heat Application.

The purpose of the study is to determine the impact of local heating on skeletal muscle transcriptional response related to mitochondrial biogenesis and mitophagy. Twelve healthy subjects (height, 176.0 ± 11.9 cm; weight, 83.6 ± 18.3 kg; and body composition, 19.0 ± 7.7% body fat) rested in a semi-reclined position for 4 h with a heated thermal wrap (HOT) around one thigh and a wrap without temperature regulation (CON) around the other (randomized). Skin temperature, blood flow, intramuscular temperature, and a skeletal muscle biopsy from the vastus lateralis were obtained after the 4 h intervention. Skin temperature via infrared thermometer and thermal camera was higher after HOT (37.3 ± 0.7 and 36.7 ± 1.0 °C, respectively) than CON (34.8 ± 0.7, 35.2 ± 0.8 °C, respectively, p < 0.001). Intramuscular temperature was higher in HOT (36.3 ± 0.4 °C) than CON (35.2 ± 0.8 °C, p < 0.001). Femoral artery blood flow was higher in HOT (304.5 ± 12.5 mL‧min-1) than CON (272.3 ± 14.3 mL‧min-1, p = 0.003). Mean femoral shear rate was higher in HOT (455.8 ± 25.1 s-1) than CON (405.2 ± 15.8 s-1, p = 0.019). However, there were no differences in any of the investigated genes related to mitochondrial biogenesis (PGC-1α, NRF1, GAPBA, ERRα, TFAM, VEGF) or mitophagy (PINK-1, PARK-2, BNIP-3, BNIP-3L) in response to heat (p > 0.05). These data indicate that heat application alone does not impact the transcriptional response related to mitochondrial homeostasis, suggesting that other factors, in combination with skeletal muscle temperature, are involved with previous observations of altered exercise induced gene expression with heat.

Influence of Local Muscle Cooling on Mitochondrial-Related Gene Expression at Rest.

The purpose of this study was to determine the impact of localized cooling of the skeletal muscle during rest on mitochondrial related gene expression. Thermal wraps were applied to the vastus lateralis of each limb of 12 participants. One limb received a cold application (randomized) (COLD), while the other did not (RT). Wraps were removed at the 4 h time point and measurements of skin temperature, blood flow, and intramuscular temperature were taken prior to a muscle biopsy. RT-qPCR was used to measure expression of genes associated with mitochondrial development. Skin and muscle temperatures were lower in COLD than RT (p < 0.05). Femoral artery diameter was lower in COLD after 4 h (0.62 ± 0.05 cm, to 0.60 ± 0.05 cm, p = 0.018). Blood flow was not different in COLD compared to RT (259 ± 69 mL·min-1 vs. 275 ± 54 mL·min-1, p = 0.20). PGC-1α B and GABPA expression was higher in COLD relative to RT (1.57-fold, p = 0.037 and 1.34-fold, p = 0.006, respectively). There was no difference (p > 0.05) in the expression of PGC-1α, NT-PGC-1α, PGC-1α A, TFAM, ESRRα, NRF1, GABPA, VEGF, PINK1, PARK 2, or BNIP3-L. The impact of this small magnitude of difference in gene expression of PGC-1α B and GABPA without alterations in other genes are unknown. There appears to be only limited impact of local muscle cooling on the transcriptional response related to mitochondrial development.