Oligosaccharides and small molecule components of Sijunzi decoction modulate the gut microbiota-bile acid axis to synergistically alleviate spleen deficiency syndrome.

Abstract

ETHNOPHARMACOLOGICAL RELEVANCE: Sijunzi decoction (SJZD) is a classical formula in traditional Chinese medicine (TCM) used for the clinical treatment of spleen deficiency syndrome (SDS), and the non-polysaccharides of SJZD (SJZD-NPS) are important pharmacological substances. However, the effective substances of SJZD-NPS and their mechanism against SDS remains unclear to date. AIM OF THE STUDY: This study aimed to elucidate the effects of the oligosaccharides (SJZD-OGS) and small molecule components (SJZD-SMC) in SJZD-NPS on SDS rats, and to systematically reveal their differences and mechanisms in alleviating SDS. MATERIALS AND METHODS: Oligosaccharides (SJZD-OGS) and small molecule components (SJZD-SMC) derived from SJZD-NPS were prepared based on a pre-established separation method, and a multi-factor modeling method was carried out to establish the rat model of SDS, followed by treatment with SJZD and its components. Pharmacodynamic indicators were evaluated to assess the effects of SJZD and its components on gastrointestinal function. 16S rRNA gene sequencing was used to characterize gut microbiota composition. Gas chromatography-mass spectrometry (GC-MS) and targeted metabolomics were employed to determine the changes of short-chain fatty acids (SCFAs) and bile acids (BAs). Meanwhile, western blotting was conducted to detect the expression of proteins related to BA metabolism. RESULTS: SJZD and its components improved gastrointestinal hormone secretion and intestinal barrier function in SDS rats. Specifically, SJZD-OGS mainly restored intestinal barrier function, while SJZD-SMC mainly regulated gastrointestinal hormone levels. Furthermore, SJZD and SJZD-NPS could improve the structural disturbance of gut microbiota induced by SDS, with key bacterial genera co-regulated, including Ruminococcus and norank_f_Muribaculaceae. Notably, the regulatory effects of SJZD-OGS and SJZD-SMC on gut microbiota differed. SJZD-OGS primarily promoted the colonization of beneficial bacteria in the intestine, such as the increase in the abundance of Bifidobacterium, Akkermansia, Enterorhabdus, and Adlercreutzia, while SJZD-SMC primarily inhibited the growth of harmful bacteria, such as the decrease in the abundance of Staphylococcus, norank_f_Oscillospiraceae, and norank_f_Muribaculaceae. Additionally, SJZD and its components were able to balance the production and absorption of SCFAs, an effect mainly attributed to the prebiotic-like effects of SJZD-OGS on gut microbiota. Meanwhile, targeted BA metabolomics and immunoblotting results further revealed that SJZD and its components restored the BA enterohepatic circulation disorder, which was associated with the regulation of gut microbiota and activation of the FXR-FGF15 pathway. CONCLUSION: The study confirmed that both SJZD-OGS and SJZD-SMC derived from SJZD-NPS are pharmacological active substances that contribute to the amelioration of SDS. They could restore gastrointestinal dysfunction and gut microbiota-bile acid axis disorders caused by SDS.