I don't understand enough about the physiology and kinetics of butyrate delivery to the cells, but there are clearly some positive and negative factors.
- Enhanced MCT expression (as mentioned above)
- Greater colonic concentration of butyrate, duh
- Lower pH (a very prominent factor)
- Longer time in contact with cells
- The converse of above
- Accumulation of Carboxylic acids, for example a derivative of cinnamon would do this. I think a lot of plant compounds may do this to those with inflammatory disease processes. The intestinal epithelium (not the lumen to my knowledge) has a microbial specialists or rather a few that metabolize cinnamic acid, so I suspect many with ME/CFS may be sensitive to cinnamon. Cinnamic acid probably also has a role in modulating the immune response through its effect melanin which modifies the effects of UVB since cinnamic acid inhibits the synthesis of melanin in skin. (yet another built in way that our microbes participate in the immune response)
- The presence of monocarboxylates (pyruvate and L-lactate, propionate, acetate). So the accumulation of other SCFA's MAY have a deleterious effect in terms of inhibiting butyrate uptake. Perhaps this is why LAG may be too harsh for many given its ability to increase acetate concentrations paired with insufficiency of the butyrate synthesizers...or something like this.