Matthew Heesch

Effects of post-exercise recovery in a cold environment on muscle glycogen, PGC-1α, and downstream transcription factors.

PURPOSE The purpose of this investigation was to determine the impact of post-exercise environmental cold exposure on muscle glycogen, PGC-1α, and downstream transcription factors. METHODS Eight males cycled for 1h and recovered in either 7 °C (cold) or 20 °C (room temp) environment for 4h. Muscle biopsies were obtained pre, post, and 4h post exercise for the analysis of muscle glycogen and mRNA. During recovery participants consumed 1.8 g kg⁻¹ of body weight of an oral dextrose solution immediately following the post biopsy and 2h into recovery. Blood samples were obtained post exercise and at 30, 60, 120, 150, 180, and 240 min post exercise for the analysis of serum glucose and insulin AUC. RESULTS Oxygen uptake was lower during room temp than during cold recovery (0.40 ± 0.05 L x min⁻¹ vs. 0.80 ± 0.12 L x min⁻¹; p<0.01). There was no effect of temperature on muscle glycogen recovery or glucose AUC. However, insulin AUC was greater during the room temp trial compared to the cold trial (5139 ± 1412 vs. 4318 ± 1272, respectively; p=0.025). PGC-1α gene expression was higher (p=0.029), but ERRα and NRF2 were lower (p=0.019 and p=0.046, respectively) after recovery in the cold. There were no differences in NRF1 (p=.173) or TFAM (p=0.694). CONCLUSIONS This investigation shows no effect of a cold recovery environment on glycogen re-synthesis but does demonstrate reduced ERRα and NRF2 mRNA despite elevations in PGC-1α mRNA when recovery post-exercise takes place in a cold environment.

Human Skeletal Muscle mRNA Response to a Single Hypoxic Exercise Bout

BACKGROUND The ability to physically perform at high altitude may require unique strategies to acclimatize before exposure. The effect of acute hypoxic exposure on the metabolic response of the skeletal muscle may provide insight into the value of short-term preacclimatization strategies. OBJECTIVE To determine the human skeletal muscle response to a single acute bout of exercise in a hypoxic environment on metabolic gene expression. METHODS Eleven recreationally active male participants (24 ± 4 years, 173 ± 20 cm, 82 ± 12 kg, 15.2 ± 7.1% fat, 4.0 ± 0.6 L/min maximal oxygen consumption) completed two 1-hour cycling exercise trials at 60% of peak power followed by 4 hours of recovery in ambient environmental conditions (975 m) and at normobaric hypoxic conditions simulating 3000 m in a randomized counterbalanced order. Muscle biopsies were obtained from the vastus lateralis before exercise and 4 hours after exercise for real-time polymerase chain reaction analysis of select metabolic genes. RESULTS Gene expression of hypoxia-inducible factor 1 alpha, cytochrome c oxidase subunit 4, peroxisome proliferator-activated receptor gamma coactivator 1 alpha, hexokinase, phosphofructokinase, mitochondrial fission 1, and mitofusin-2 increased with exercise (P < .05) but did not differ with hypoxic exposure (P > .05). Optic atrophy 1 did not increase with exercise or differ between environmental conditions (P > .05). CONCLUSIONS The improvements in mitochondrial function reported with intermittent hypoxic training may not be explained by a single acute hypoxic exposure, and thus it appears that a longer period of preacclimatization than a single exposure may be required.

Effects of exercise in a cold environment on transcriptional control of PGC-1α

Peroxisome proliferator-activated receptor-α coactivator-1α (PGC-1α) mRNA is increased with both exercise and exposure to cold temperature. However, transcriptional control has yet to be examined during exercise in the cold. Additionally, the need for environmental cold exposure after exercise may not be a practical recovery modality. The purpose of this study was to determine mitochondrial-related gene expression and transcriptional control of PGC-1α following exercise in a cold compared with room temperature environment. Eleven recreationally trained males completed two 1-h cycling bouts in a cold (7°C) or room temperature (20°C) environment, followed by 3 h of supine recovery in standard room conditions. Muscle biopsies were taken from the vastus lateralis preexercise, postexercise, and after a 3-h recovery. Gene expression and transcription factor binding to the PGC-1α promoter were analyzed. PGC-1α mRNA increased from preexercise to 3 h of recovery, but there was no difference between trials. Estrogen-related receptor-α (ERRα), myocyte enhancer factor-2 (MEF2A), and nuclear respiratory factor-1 (NRF-1) mRNA were lower in cold than at room temperature. Forkhead box class-O (FOXO1) and cAMP response element-binding protein (CREB) binding to the PGC-1α promoter were increased postexercise and at 3 h of recovery. MEF2A binding increased postexercise, and activating transcription factor 2 (ATF2) binding increased at 3 h of recovery. These data indicate no difference in PGC-1α mRNA or transcriptional control after exercise in cold versus room temperature and 3 h of recovery. However, the observed reductions in the mRNA of select transcription factors downstream of PGC-1α indicate a potential influence of exercise in the cold on the transcriptional response related to mitochondrial biogenesis.

Irisin and Fibronectin Type III Domain-Containing 5 Responses to Exercise in Different Environmental Conditions: 1051 Board #230 May 31 3

Fibronectin type III domain-containing 5 (FNDC5) is a skeletal muscle membrane-bound precursor to the myokine irisin. Irisin is involved in stimulating adipose tissue to become more metabolically active in order to produce heat. The purpose of this study was to determine the effects of exercise in a hot (33 °C), cold (7 °C), and room temperature (RT, 20 °C) environment on the skeletal muscle gene expression of FNDC5 and the plasma concentrations of irisin. Twelve recreationally trained males completed three separate, 1 h cycling bouts at 60% of Wmax in a hot, cold, and RT environment followed by three hours of recovery at room temperature. Blood samples were taken from the antecubital vein and muscle biopsies were taken from the vastus lateralis pre-, post-, and 3 h post-exercise. Plasma concentrations of irisin did not change from pre- (9.23 ± 2.68 pg·mL−1) to post-exercise (9.6 ± 0.2 pg·mL−1, p = 0.068), but did decrease from post-exercise to 3 h post-exercise (8.9 ± 0.5 pg·mL−1, p = 0.047) regardless of temperature. However, when plasma volume shifts were considered, no differences were found in irisin (p = 0.086). There were no significant differences between trials for irisin plasma concentrations (p > 0.05). No significant differences in FNDC5 were observed between the hot, cold, or RT or pre-, post-, or 3 h post-exercise time points (p > 0.05). These data indicate that the temperature in which exercise takes place does not influence FNDC5 transcription or circulating irisin in a human model.

Exercise-Induced Interleukin-6 and Metabolic Responses in Hot, Temperate, and Cold Conditions

The purpose of this study was to determine the effects of exercise in hot, cold, and temperate environments on plasma interleukin-6 (IL-6). Eleven recreationally trained males (age 5 25 ¡ 4 years, height 5 178 ¡ 5 cm, weight 5 79.4 ¡ 13.5 kg, body fat 5 14.7 ¡ 3.6%, VO2 peak 5 54.6 ¡ 11.5 ml kg 21 min) performed a 1 hr cycling bout in hot (33 C̊), cold (7 C̊), and temperate (20 C̊) environments at 60% of Wmax followed by 3 hr of supine recovery in temperate conditions. Expired gases were measured every 15 min during exercise and once every hour during recovery. Heart rate was continuously measured throughout the trials. Blood samples were obtained from the antecubital vein pre-exercise, immediately post-exercise, and 3 hr post-exercise. Blood samples were analyzed for plasma concentrations of IL-6 using a commercial ELISA kit. Plasma IL-6 concentrations were significantly higher immediately post-exercise (14.8 ¡ 1.6 pg ml, p 5 0.008) and 3 hr post-exercise (14.8 ¡ 0.9 pg ml, p 5 0.018) compared to pre-exercise (11.4 ¡ 2.4 pg ml), across all trials. There were no differences in plasma IL-6 concentrations (p 5 0.207) between temperature conditions. Oxygen consumption and heart rate were higher and respiratory exchange ratio was lower in the hot compared to other conditions (p , 0.05). These data indicate that the temperature in which exercise occurs does not affect acute plasma IL-6 response despite differences in metabolic state.