Herb Pair of Aurantii Fructus Immaturus–Atractylodis Macrocephalae Rhizoma Alleviates Slow‐Transit Constipation in Rats by Regulating Mitophagy and Modulating Gut Microbiota

ABSTRACT Background Slow transit constipation (STC) is a prevalent functional gastrointestinal disorder that significantly affects people's quality of life. Aurantii Fructus Immaturus (Zhishi, ZS) and Atractylodis Macrocephalae Rhizoma (Baizhu, BZ) are a classic herbal pair in traditional Chinese medicine (TCM) for regulating spleen‐stomach function, respectively recognized for their properties of “replenishing qi and fortifying the spleen” and “dispersing stagnation and promoting digestion”. This study aimed to elucidate the mechanisms by which ZSBZ ameliorates STC through regulating mitophagy in ICCs and restructuring gut microbiota composition. Methods A rat model of STC was established by oral gavage administration of loperamide hydrochloride (3 mg/kg·day). The therapeutic effects of ZSBZ were evaluated by assessing rat body weight, 6‐h fecal number, fecal water content, and intestinal transit rate. Histopathological changes in the colon were observed using hematoxylin–eosin (HE) staining and Alcian blue‐periodic acid Schiff (AB‐PAS) staining. The ultrastructure of colon tissues was observed by transmission electron microscopy (TEM). Immunohistochemistry (IHC) was used to detect the expression of c‐Kit, SCF, and autophagy‐related markers (p62, Beclin1, and LC3II/I) in colon tissues. The expression levels of α‐KGDHC and PDH were measured by ELISA. Combined with biochemical assays for SOD, MDA, respiratory chain complexes I and II, and ATP levels, a comprehensive assessment of cellular mitochondrial oxidative stress status and energy metabolism function was performed. Flow cytometry was used to quantify intracellular Ca 2+ concentration and mitochondrial membrane potential (MMP) in cells isolated from colonic tissues. Mitophagy‐related protein and mRNA expression were analyzed by Western blotting and reverse transcription quantitative polymerase chain reaction (RT‐qPCR). Apoptosis in rat colonic tissues was detected using TUNEL assay. Gut microbiota composition was analyzed by 16S rRNA gene sequencing, and its metabolic functional potential was predicted. Results Our results showed that ZSBZ significantly ameliorated defecation function and enhanced intestinal motility in a rat model of STC. Histopathological and ultrastructural analyses revealed that ZSBZ effectively restored colonic mucosal damage, increased goblet cell numbers, and attenuated mitochondrial swelling with cristae disruption in ICCs of STC rats. Meanwhile, ZSBZ improved mitochondrial dysfunction by reducing MDA levels and increasing SOD activity in colonic tissues. Furthermore, ZSBZ improved mitochondrial energy metabolism by increasing ATP content, restoring respiratory chain complex I and II activities, and elevating α‐KGDHC and PDH activities, thereby reversing the decline in mitochondrial membrane potential and the increase in intracellular Ca 2+ concentration in cells isolated from colonic tissues. Mechanistically, ZSBZ attenuated excessive mitophagy in colonic ICCs by downregulating autophagy‐related genes and proteins, restoring p62 expression, and suppressing the elevated mRNA and protein expression of the mitophagy‐related markers PINK1 and Parkin. In addition, 16S rRNA gene sequencing demonstrated that ZSBZ reshaped the gut microbiota in STC rats, characterized by a decreased abundance of Proteobacteria and an increased abundance of Bacteroidota . KEGG functional prediction further indicated that ZSBZ regulated mitochondrial metabolism‐related pathways, possibly contributing to the amelioration of colonic dysmotility. Conclusion ZSBZ significantly alleviated constipation symptoms in STC rats. The mechanism may involve inhibition of excessive mitophagy in ICCs and restructuring of gut microbiota composition. This study provides compelling theoretical support for ZSBZ as a therapeutic strategy against STC and offers novel insights into intestinal motility restoration in humans.