Lifestyle choices, external environment, aging, and other factors influence the synthesis of
melatonin. Although the physiological functions of
melatonin have been widely studied in relation to specific organs, the systemic effects of endogenous
melatonin reduction has not been reported. This study evaluates the systemic changes and possible pathogenic risks in an endogenous
melatonin reduction (EMR) mouse model deficient in the rate limiting
enzyme in
melatonin production,
arylalkylamine N-acetyltransferase (Aanat) gene. Using this model, we identified a new relationship between
melatonin,
Alzheimer's disease (AD), and gut microbiota. Systematic changes were evaluated using multi-omics analysis.
Fecal microbiota transplantation (FMT) was performed to examine the role of gut microbiota in the pathogenic risks of EMR. EMR mice exhibited a pan-metabolic disorder, with significant transcriptome changes in 11 organs, serum metabolome alterations as well as microbiota
dysbiosis. Microbiota
dysbiosis was accompanied by increased gut permeability along with gut and systemic
inflammation. Correlation analysis revealed that systemic
inflammation may be related to the increase of Ruminiclostridium_5 relative abundance. 8-month-old EMR mice had AD-like phenotypes, including Iba-1 activation, A β
protein deposition and decreased spatial memory ability. Moreover, EMR mice showed decreased anti stress ability, under high-fat diet, EMR mice had greater
body weight and more obvious hepatic steatosis compared with WT group. FMT improved gut permeability, systemic
inflammation, and AD-related phenotypes, while reducing
obesity in EMR mice. Our findings suggest EMR causes systemic changes mediated by gut microbiota
dysbiosis, which may be a pathogenic factor for AD and
obesity, we further proved the gut microbiota is a potential target for the prevention and treatment of AD and
obesity.