GCG and Alzheimer disease: Moreover, prebiotic fructooligosaccharides (FOSs) as dietary supplements ameliorated cognitive deficits and pathological changes in the APPSWE/PS1DeltaE9 Tg mice and increased the levels of synapsin I and synaptic plasticity markers, postsynaptic density protein 95, and decreased the phosphorylated level of c-Jun N-terminal kinase, indicating that FOS can modulate the gut microbiota-glucagon-like peptide-1 (GLP-1)/GLP-1 receptor (GLP-1R) pathway to play a beneficial role in AD (Sun et al., 2019a).