Markedly elevated formaldehyde in the cecum of APP/PS1 transgenic mouse model of Alzheimer’s disease

Abstract:

[Objective] Intestinal microbiota affects the function of central nervous system through the “microbiota-gut-brain axis”. Alzheimer’s disease (AD) is considered being related with the microbiota in the intestines. Concentrations of endogenous formaldehyde are positively correlated to the cognitive impairment of AD inpatients. Therefore, we compared the concentration of intestinal formaldehyde between APP/PS1 transgenic mouse model of Alzheimer’s disease and C57BL/6J wildtype mice. [Methods] Take different sections of duodenum, small intestine, cecum, and colon of APP/PS1 transgenic mice (n=8) and those of C57BL/6J wildtype mice (n=9), respectively. Measure the concentrations of formaldehyde in the digestion contents and intestinal walls with HPLC coupled with 2,4-dinitrophenylhydrazine (DNPH) absorptions. [Results] The levels of the cecum formaldehyde in the digestion contents from APP/PS1 transgenic mice were significantly (P=0.036) higher than those from C57BL/6J wildtype mice, but no significant (P>0.05) difference could be observed in the small intestine and colon. Formaldehyde in walls of duodenum, cecum and colon were not significantly different except for the small intestine. That is, the concentration of formaldehyde was observably elevated in small intestinal wall though the change approached to the significant (P=0.052) different. For APP/PS1 mice, the concentration of formaldehyde in cecum either digestion content or wall exhibited the highest, compared with the other intestinal sections. [Conclusion] Intestinal microbiota is one of the important sources producing formaldehyde. The elevated concentrations of formaldehyde in the cecum digestion contents and small intestinal wall of APP/PS1 transgenic AD mice suggested that dysmetabolism of formaldehyde in the intestinal microbiota may be related to age-related cognitive impairment.