Diet-Habit Linkage: High-Fat Diet Disrupts Circadian Rhythms

📖 Literature Information and Abstract Translation

Daily changes in neuronal activities of the dorsal motor nucleus of the vagus under standard and high-fat diet

Chrobok L, Klich JD, Jeczmien-Lazur JS, Pradel K, Palus-Chramiec K, Sanetra AM, Piggins HD, Lewandowski MH. Daily changes in neuronal activities of the dorsal motor nucleus of the vagus under standard and high-fat diet. J Physiol. 2022 Feb;600(4):733-749.

🔗 DOI, PubMed, Google Scholar

✅ Prerequisite knowledge: What is a circadian rhythm?
- A mechanism that oscillates 24-hour rhythmic signals to form a circadian rhythm.
- Also known as a biological clock.
🌍 Reference site >>> site.

🔑 Key points
- We recently discovered that the dorsal vagal complex exhibits autonomous circadian clock properties.
- The dorsal motor nucleus of the vagus (DMV) is the executive part of this complex, which is the source of parasympathetic innervation of the gastrointestinal tract.
- Here, we reveal daily changes in neuronal activities of the rat DMV, including firing rate, intrinsic excitability, and synaptic input (all peaking in the late night).
- Furthermore, we revealed that short-term high-fat diet disrupts these daily rhythms, increasing fluctuations in firing rate while blunting the responsiveness of the DMV to feeding cues.
- These results deepen our understanding of the daily control of parasympathetic outflow and provide evidence for its dependence on a high-fat diet.

[Background/Objective] While the suprachiasmatic nucleus (SCN) functions as the brain's master circadian clock, circadian clock genes are also rhythmically expressed in several other brain regions, allowing for local temporal control of physiology and behavior. Recently, we found that the hindbrain dorsal vagal complex has strong circadian clock functions, with the area postrema and the nucleus of the solitary tract showing the most robust clock properties. Whether the DMV, the executive part of this complex, also shows daily changes has not been widely studied. The DMV is the source of vagal efferent motor neurons that control gastric motility and emptying, consequently influencing meal size and energy homeostasis.

[Methods-Results] We combined multichannel electrophysiology and patch-clamp recording to understand the effects of time of day and diet on DMV cells. We found that DMV neurons show increased spontaneous activity, excitability, and responsiveness to metabolic neuromodulators in the late hours of the day, which parallels an increase in synaptic input to these neurons. While high-fat diets generally attenuate circadian rhythms, we found that high-fat diet intake paradoxically amplifies the daily fluctuations in DMV neuronal activity, while blunting the responsiveness of neurons to metabolic neuromodulators.

[Conclusion] We revealed for the first time that DMV neuronal activity changes depending on the time of day, and this temporal change is regulated by diet. These findings provide clear implications for our understanding of the daily control of vagal release and parasympathetic outflow.

✅ Figure. Schematic diagram showing the daily enhancement of food intake regulation: It is thought that if these daily rhythms are disrupted at any point in the food intake regulation mechanism, food intake patterns will be disrupted, affecting energy homeostasis. NTS, nucleus of the solitary tract; DMV, dorsal motor nucleus of the vagus; GLP-1, glucagon-like peptide-1. 📕 Journal review (open access): Page, 2021 >>>
doi.

🌱 So What?: What did I find interesting?

I am a person with a great interest in the techniques of habit formation.
I am so enthusiastic that I even created a specialized magazine within note to explore habit formation techniques, and recently, I formulated, executed, and achieved results on a plan for habits to 'prevent overeating'.

There is a composition regarding diet and habits that many people hold.
That is the composition of 'habituation' to 'prevent overeating'.
However, this paper showed that the exact opposite is also powerful.
'preventing overeating' for 'habituation'.
Binge eating high-fat foods disrupts circadian rhythms.
Taking a leap, it is thought that when circadian rhythms are disrupted, the function of doing 'fixed things' at 'fixed times' declines. This is because the circadian rhythm is a biological clock that signals 'fixed times.' Even if you try to align with a broken clock that points to different times every time, it is unlikely to lead to habituation.
Conversely, being able to preserve circadian rhythms may enhance the 'ability to form habits'. If so, 'preventing overeating' directly leads to enhancing the 'ability to form habits'.

'Diet'-'Habit', this was not a unidirectional relationship, but a relationship that mutually links to form a spiral loop.
That spiral loop extends in both positive and negative directions.
I used 'habituation' to 'prevent overeating', but that was simultaneously enhancing my ability to form habits.
One good thing is often connected to another good thing yet to be seen.
So, it is okay not to know all the butterfly effects.
Let's do one certain good thing right in front of us.
That is what I thought.

Things and the world are given to me along with the parts of my body, not by natural geometry, but in a living connection that can be compared to, or rather is identical to, the connection that exists between the parts of my body itself.
Maurice Merleau-Ponty, 'Phenomenology of Perception'

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