Fig. 6

The reduction of short-chain fatty acids by fiber deficiency is critical for cognitive impairment. A–C The serum levels of acetate, propionate, and butyrate were decreased in mice with the fiber deficiency diet (FD) for 15 weeks (n = 6). D–I The parameters of the gut-brain axis were examined in GPR41^−/− and GPR43^−/− mice. D Protein expression levels of occludin and ZO-1 in the colon (n = 5). The object location (E), temporal order memory (F), and nest-building (G) tests were performed (n = 8–10). E Percentage of time spent with the object in the novel place to total object exploration time. F The discrimination ratio. G Untore nestler weight (amount of untore nesting material). H, I Protein levels of pCaMKII/CaMKII and SYN in the hippocampus (n = 6). J–S The parameters of the gut-brain axis in FD mice with SCFAs supplementation (FDS). The object location (J), temporal order memory (K), and nest building (L) tests were performed (n = 15). J Percentage of time spent with the object in the novel place to total object exploration time. K The discrimination ratio. L Untore nestler weight. M, N Protein expression levels of SYN and PSD95 in the hippocampus (n = 6). O The mRNA expression of pro-inflammatory cytokines, TNFα, IL-1β, and IL-6 in the hippocampus (n = 5). P Alcian blue-stained colonic sections were showing the mucus layer (arrows). Opposing black arrows with shafts delineate the mucus layer that was measured. Scale bar: 50 μm. Q The quantification of the colonic mucus layer was statistically analyzed (2 sections per animal, n = 5). R Quantitation of colonic Reg3γ by RT-PCR (n = 6). S Protein expression levels of occludin and ZO-1 in the colon (n = 5). Values are mean ± SEM. *p < 0.05 vs. wild-type (WT) or control (Con) groups. ^#p < 0.05 vs. fiber deficiency (FD) group