Author(s): TAKAHASHI, Y., KOGIN, K., KANESHIMA, N., OYANAGI, Y., WANG, W., INABA, T., Institution: THE UNIVERSITY OF TOKYO, Country: JAPAN, Abstract-ID: 531

INTRODUCTION:
Mitochondria are responsible for energy production in cells. Altering the quantity and function of mitochondria in skeletal muscles contributes to improved exercise capacity and metabolic health. In recent years, ketone bodies have gained attention as signaling molecules potentially involved in metabolic adaptations. One study reported that chronic administration of ketone bodies increased the protein levels of certain mitochondrial components in the skeletal muscle (Monsalves-Alvarez et al. 2020). Conversely, it has also been reported that post-exercise ketone body intake reduces the active form of AMP-activated protein kinase (AMPK), which is known to promote mitochondrial biogenesis, in skeletal muscles (Vandoorne et al. 2017; Takahashi et al. 2025). As the combined effect of ketone body intake and training on skeletal muscle mitochondrial adaptation remains unproven, we investigated the effects of ketone monoester ((R)-3-hydroxybutyl (R)-3-hydroxybutyrate, KE) intake with endurance training on the protein levels of mitochondrial components.
METHODS:
Male Institute of Cancer Research mice aged 10 weeks were divided into four groups: a sedentary-control group (Sed-Con, n = 10), a sedentary-KE group (Sed-KE, n = 9), a training-control group (Tr-Con, n = 10), and a training-KE group (Tr-KE, n = 10). All mice orally administered either KE (2.0 g/kg body weight [BW]) solution or an isocaloric control (triolein, 1.11 g/kg BW) solution. The training groups underwent treadmill running at a speed of 25 m/min for 60 minutes. Administrations and training sessions were conducted five times a week for four weeks. The training groups received the solution immediately after running. We harvested the soleus muscle (SOL), which is predominantly composed of slow-twitch fibers, and the plantaris muscle (PLA), which is predominantly composed of fast-twitch fibers. We measured the maximal activity of citrate synthase (CS), a widely used quantitative indicator of mitochondrial content, and protein levels of oxidative phosphorylation (OXPHOS) complexes in the SOL and PLA.
RESULTS:
In both SOL and PLA, a significant positive main effect of training on maximal CS activities were observed (p < 0.05 in SOL; p < 0.01 in PLA). Meanwhile, no significant main effect of KE intake was observed on maximal CS activity in either muscle. Regarding OXPHOS complex proteins, there was a significant negative main effect of KE intake on complex II protein levels in SOL (p < 0.05). In PLA, significant positive main effects of training were observed in complex I and IV protein levels (p < 0.05). However, there were no significant main effect of KE intake was observed in OXPHOS complex proteins. These results suggest that long-term ketone body intake combined with endurance training may partially influence changes in mitochondrial OXPHOS protein levels in skeletal muscle predominantly composed of slow-twitch fibers.
CONCLUSION:
These results suggest that chronic ketone body intake combined with endurance training may influence changes in mitochondrial OXPHOS protein levels in skeletal muscle.