Initiating aerobic exercise with low glycogen content reduces markers of myogenesis but not mTORC1 signaling

Abstract

Background The effects of low muscle glycogen on molecular markers of protein synthesis and myogenesis before and during aerobic exercise with carbohydrate ingestion is unclear. The purpose of this study was to determine the effects of initiating aerobic exercise with low muscle glycogen on mTORC1 signaling and markers of myogenesis. Methods Eleven men completed two cycle ergometry glycogen depletion trials separated by 7-d, followed by randomized isocaloric refeeding for 24-h to elicit low (LOW; 1.5 g/kg carbohydrate, 3.0 g/kg fat) or adequate (AD; 6.0 g/kg carbohydrate, 1.0 g/kg fat) glycogen. Participants then performed 80-min of cycle ergometry (64 ± 3% VO2peak) while ingesting 146 g carbohydrate. mTORC1 signaling (Western blotting) and gene transcription (RT-qPCR) were determined from vastus lateralis biopsies before glycogen depletion (baseline, BASE), and before (PRE) and after (POST) exercise. Results Regardless of treatment, p-mTORC1Ser2448, p-p70S6KSer424/421, and p-rpS6Ser235/236 were higher (P < 0.05) POST compared to PRE and BASE. PAX7 and MYOGENIN were lower (P < 0.05) in LOW compared to AD, regardless of time, while MYOD was lower (P < 0.05) in LOW compared to AD at PRE, but not different at POST. Conclusion Initiating aerobic exercise with low muscle glycogen does not affect mTORC1 signaling, yet reductions in gene expression of myogenic regulatory factors suggest that muscle recovery from exercise may be reduced.

Serum Branched-Chain Amino Acid Metabolites Increase in Males When Aerobic Exercise Is Initiated with Low Muscle Glycogen

“…Greater increases in these indirect markers of myofibrillar protein breakdown substantiates our hypothesis that exercising with low muscle glycogen accelerates muscle protein loss by increasing the body's reliance on BCAA for energy production. As a result, BCAA, to support muscle protein synthesis and anabolic signaling during and in recovery from exercise is diminished when aerobic exercise is initiated with low glycogen [10,11,[13][14][15].…”

“…Greater increases in these metabolites in LOW compared to AD in the current study further suggest an increased reliance on BCAA of oxidative purposes when glycogen availability is limited. Alterations in use of BCAA oxidation with low glycogen availability likely contributed to reductions in markers of myogenesis, PAX7, MYOD, and MYOGENIN within the skeletal muscle of these same participants [15]. Indeed, low glucose availability in cell culture and mouse models was shown to increase BCAA catabolism and impair cellular growth [38].…”

“…This results in lower rates of muscle protein synthesis [10,11] and blunts activation of the mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway [13,14]. Furthermore, we recently reported reductions in the gene expression of myogenic markers when aerobic exercise was initiated with low versus adequate glycogen stores [15]. While these data indicate a potential reduction in the anabolic response to aerobic exercise when muscle glycogen content is low, the specific mechanism suppressing the anabolic state is unclear.…”

Advanced Artificial Intelligence and Big Data Algorithm in Aerobics Formation Transformation Route Simulation Research

“…Aerobic exercise AF with low glycogen leads to molecular changes that promote enhanced fat oxidation. Aerobics has a rigid teaching method AF that cannot keep up with the times [2]. Aerobic formation on transformation route simulation research tests has been developed due to a desire to make fitness testing in a team-sport situation more accessible and more cost-effective.…”

Circulating and skeletal muscle microRNA profiles are more sensitive to sustained aerobic exercise than energy balance in males

“…Failure to match energy intake to expenditure results in negative energy balance and reduced muscle glycogen content (Hennigar et al., 2021; Jacobs et al., 1983; Margolis, Crombie et al., 2014). Low energy and glycogen availability following periods of physical activity blunts muscle anabolism and markers of muscle regeneration (Areta et al., 2014; Hector et al., 2015; Hector et al., 2018; Margolis, Wilson et al., 2021), produces negative protein balance (Margolis et al., 2016; Margolis, Murphy et al., 2014; Pasiakos et al., 2013) and alters substrate metabolism (Karl et al., 2017; Margolis et al., 2019; Margolis, Karl et al., 2021; Margolis, Wilson et al., 2021). The underlying mechanisms mediating these effects of low energy and glycogen availability remain largely unknown.…”