Bupleuri Radix ameliorates MASLD induced by high-fat diet and circadian disruption in rats: Involvement of the NR1D1-SREBF1/CYP7A1 circadian-metabolic axis.

Abstract

<p>ETHNOPHARMACOLOGICAL RELEVANCE: Metabolic dysfunction-associated steatotic liver disease (MASLD) is closely linked to circadian rhythm disruption (CRD). While the biological clock coordinates metabolic homeostasis, the rhythmic signaling coupling lipid and bile acid metabolism remains unclear. Bupleuri Radix (BR; Bupleurum chinense DC.) is a traditional Chinese medicine widely used for liver-related disorders and known for its liver-soothing effect. However, whether its bioactive fractions can modulate the "circadian-metabolic coupling" process in MASLD has not yet been elucidated. AIM OF THE STUDY: This study aimed to evaluate the protective effects of BR against high-fat diet (HFD)- and CRD-induced MASLD in rats and to explore its potential mechanisms through integrated multi-omics analysis. MATERIALS AND METHODS: A rat model of MASLD was established by combining HFD feeding with CRD. Subsequently, BR fractions with different polarities were orally administered for 6 weeks. Biphenyldicarboxylate (BIC) and melatonin (MT) served as positive controls. Biochemical profiling, behavioral testing, histopathology, liver metabolomics, transcriptomics, and targeted bile acid analysis were performed. Diurnal gene expression was assessed at ZT05 and ZT17 by RT-qPCR. RESULTS: Different polarity fractions of BR improved HFD&nbsp;+&nbsp;CRD-induced MASLD phenotypes to varying extents. Among them, BR-L showed more pronounced regulatory effects on circadian hormone disturbances, particularly MT and CORT. Multi-omics integration revealed that BR-L remodeled glycerophospholipid metabolism and bile acid homeostasis, centering on the Nr1d1-Srebf1-Cyp7a1 regulatory axis. BR-L restored the rhythmic oscillation of Nr1d1 and synchronized downstream lipid and bile acid metabolic gene rhythms. Correlation analysis further suggested Nr1d1 as a key node linking circadian and metabolic regulation. CONCLUSION: The bioactive fractions of BR exert protective effects against HFD&nbsp;+&nbsp;CRD-induced MASLD. In particular, BR-L may act by restoring Nr1d1-associated rhythmic coordination of lipid and bile acid metabolism. This study provides a chronopharmacological perspective for the ethnopharmacological application of BR in metabolic liver diseases.</p>