Time-restricted feeding during the inactive phase abolishes the daily rhythm in mitochondrial respiration in rat skeletal muscle.
Level 5 - mechanism / opinion, no new human data
Animal research (rodent study)
PubMed 35032416 · doi:10.1096/fj.202100707R
What was done
Rats were assigned to one of three feeding regimens: ad libitum (AL) feeding, time-restricted feeding (TRF) restricted to the active (dark) phase, or TRF restricted to the inactive (light) phase. Researchers evaluated soleus muscle mitochondrial respiration, expression of genes related to mitochondrial biogenesis and dynamics (fission/fusion), metabolite and lipid profiles (via metabolomics and lipidomics), and respiratory exchange ratio (RER).
What was found
The abstract reports qualitative changes without specific numerical values. Rats on AL or dark-phase TRF maintained a daily rhythm in muscle mitochondrial oxidative phosphorylation capacity. In contrast, inactive-phase (light-fed) TRF abolished this respiratory rhythm and led to lower overall 24-hour respiration. Light-fed rats also altered expression of mitochondrial biogenesis and fission/fusion genes, lost rhythmic levels of alpha-ketoglutarate and citric acid, and gained rhythmic variations in triglyceride levels. While RER shifted completely with food intake, locomotor activity and mitochondrial respiration did not fully realign, creating a circadian mismatch.
Why it matters
These findings identify skeletal muscle mitochondrial disruption and metabolic misalignment as potential physiological mechanisms explaining the heightened risk of type 2 diabetes observed in shift workers eating during normal resting periods.
Limits
The study was conducted exclusively in a rat model, and exact sample sizes are not provided in the abstract. Findings in nocturnal rodents eating during their light phase cannot be directly extrapolated to human shift workers without clinical verification.
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- context Mitochondria produce more ATP in the morning than at any other time of day.