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Sleep, an essential biological state, involves significant reductions in physical activity, sensory awareness, and interaction with the environment. This complex physiological process is primarily regulated by specific brain regions, notably the hypothalamus and pons, which govern the sleep-wake cycle or circadian rhythm.
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Through-the-Wall Blood Sampling Method to Minimize Sleep Disruption in Clinical Settings
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Through-the-Wall Blood Sampling Method to Minimize Sleep Disruption in Clinical Settings

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Metabolic flexibility during sleep.

Simeng Zhang1, Yoshiaki Tanaka2, Asuka Ishihara3

  • 1International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, Japan.

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During sleep, the body

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Area of Science:

  • Metabolic Physiology
  • Sleep Science
  • Nutritional Biochemistry

Background:

  • Metabolic flexibility, the body's ability to switch fuel sources, is crucial for energy homeostasis.
  • During fasting periods like sleep, substrate oxidation is expected to shift from carbohydrates to fats, lowering the respiratory quotient (RQ).
  • Previous assumptions about substrate utilization during sleep lacked detailed temporal resolution.

Purpose of the Study:

  • To investigate the dynamics of substrate oxidation, measured by respiratory quotient (RQ), during overnight fasting.
  • To identify factors influencing RQ patterns during sleep, including sex, age, and metabolic flexibility.
  • To explore the potential of RQ during sleep as an indicator of early metabolic inflexibility.

Main Methods:

  • Utilized whole-room indirect calorimetry with high temporal resolution to monitor gas exchange.
  • Analyzed respiratory quotient (RQ) trends throughout the sleep period in non-obese young adults.
  • Compared RQ patterns between sexes, age groups, and individuals with varying degrees of metabolic flexibility.

Main Results:

  • Contrary to expectations, RQ did not continuously decrease but showed a transient decrease followed by an increase before awakening.
  • The nadir of RQ occurred earlier in women than in men.
  • Metabolically inflexible men and older individuals exhibited a blunted decrease in RQ during sleep.
  • Significant inter-individual differences in RQ became apparent during sleep.

Conclusions:

  • Sleep substrate oxidation patterns are more complex than previously assumed, with RQ dynamics varying by sex and age.
  • A blunted RQ decrease during sleep is associated with metabolic inflexibility and aging.
  • Sleep-derived RQ patterns may offer insights into the early stages of metabolic inflexibility and related health risks.