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CASE-047: Gut microbes and the host's hunger and mood: a lower-level collective that can drive the person

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Properties8
StatusActive
Standingdocumented
Kindspecimen
Tagsecology, agency, emotion-and-affect
Linedistributed-agency
SupportsCLAIM-166 — A lower-level collective within the composite person, such as the gut microbiome, can at times drive higher-level behaviour and even experience: the routes exist and the effects are causal in rodents, while the human evidence is modest
IllustratesCLAIM-166 — A lower-level collective within the composite person, such as the gut microbiome, can at times drive higher-level behaviour and even experience: the routes exist and the effects are causal in rodents, while the human evidence is modest
Reported inLIT-903 — From gut microbiota to host appetite: gut microbiota-derived metabolites as key regulators, LIT-915 — One Giant Leap from Mouse to Man: The Microbiota–Gut–Brain Axis in Mood Disorders and Translational Challenges Moving towards Human Clinical Trials, NOTE-703 — Forssten et al. — One Giant Leap from Mouse to Man, NOTE-706 — Han et al. — From gut microbiota to host appetite

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The case

A person’s gut hosts a microbial community that produces short-chain fatty acids, bile-acid derivatives, indoles and proteins such as ClpB, which mimics a host satiety peptide. These signal through gut hormones, the immune system and the vagus nerve. In rodents:

  • colonizing germ-free animals changes their stress responses;
  • transplanting microbiota from depressed humans partly transfers depressive-like behaviour.

In humans:

  • some probiotic trials reduce subjective stress in healthy volunteers;
  • strains with strong animal records have failed in trials;
  • delivered microbial metabolites (propionate) acutely reduce food intake.

The details and grades are in NOTE-706 and NOTE-703.

What it can show

  • Drive from below that is not a single part. The source is a community whose own drive profile (TERM-051) is likely diffuse.
  • Drive that changes with time. Hunger and mood vary, and the microbiome’s contribution varies with diet and state.
  • Membership in question. The holobiont reading (LIT-709) and the threshold criterion (CLAIM-157) bear on whether these microbes are part of the person.

As a documented case it shows only what the evidence does: routes, and causal effects in animals. That the owner’s own hunger and mood are driven this way is the claim (CLAIM-166), not the case.

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