Circadian rhythm disruption aggravates high-fat diet-induced NAFLD through gut microbiota alterations in mice.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is closely associated with gut microbiota dysbiosis, and circadian rhythm disruption (CRD) has been reported to aggravate metabolic disorders. However, the contribution of gut microbiota alterations to CRD-associated deterioration of NAFLD remains incompletely understood. OBJECTIVE: This study aimed to investigate the effects of CRD on gut microbiota alterations and hepatic metabolic abnormalities in high-fat diet (HFD)-induced NAFLD mice, and to explore whether microbiota modulation could influence CRD-associated disease progression. METHODS: Male C57BL/6J mice were divided into three groups: normal diet with normal light-dark cycle (ND-LD), HFD with normal light-dark cycle (HFD-LD), and HFD with disrupted light-dark cycle (HFD-CRD). Food intake, locomotor activity, and body weight were monitored. After 14 weeks, samples were collected following euthanasia. The remaining HFD-LD mice were further divided into two groups: fecal microbiota donor and normal light-dark cycle with saline gavage (LD-NS). The remaining HFD-CRD mice were assigned to either disrupted light-dark cycle with saline gavage (CRD-NS) or disrupted light-dark cycle with fecal microbiota transplantation (CRD-FMT). After another 14 weeks, samples were again collected following euthanasia. Serum biochemical parameters, liver histology, inflammatory markers, and gut microbiota composition based on 16S rRNA sequencing were analyzed. RESULTS: HFD induced NAFLD, while CRD exacerbated metabolic dysfunction, liver injury, and gut microbiota alterations. Over time, the impact of CRD on glucose metabolism and liver injury diminished. CRD further altered gut microbiota in NAFLD mice, reducing microbial diversity and increasing pro-inflammatory taxa. FMT from HFD-LD donors partially reshaped gut microbiota composition of CRD mice and attenuated several CRD-associated metabolic and hepatic abnormalities, although its effects on body weight and glucose metabolism were limited. CONCLUSION: These findings suggest that gut microbiota alterations contribute to CRD-associated aggravation of HFD-induced NAFLD, although further studies are required to identify specific microbial mediators.