In theory you could supplement with L-tryptophan which is metabolized into indole which then raises GLP-1 production within enteroendocrine cells.
https://www.sciencedirect.com/science/article/pii/S221112471...
https://www.sciencedirect.com/science/article/pii/S221112471...
> Indole increased GLP-1 release during short exposures, but it reduced secretion over longer periods.