Integrated gut microbiota and serum pharmacochemistry reveal the mechanisms of wine steaming in alleviating rhubarb diarrhea

Background: Long-term use of rhubarb (RH) can cause adverse gastrointestinal reactions (such as diarrhea), whereas RH steaming with wine (PRH) can alleviate RH-induced diarrhea. However, the potential material basis and mechanisms by which wine steaming alleviates diarrhea caused by RH remain unclear.

Purpose: To reveal the potential material basis and underlying mechanisms of wine steaming in alleviating diarrhea caused by RH from the perspective of small intestinal flora and immune function.

Methods: The major anthraquinone/anthrone components were detected using high-performance liquid chromatography (HPLC). Constipation model mice were replicated using loperamide hydrochloride and were administered RH and PRH for six consecutive weeks. Histopathological observation (duodenum, jejunum, and ileum) was performed using hematoxylin-eosin (HE) staining, and the serum levels of inflammatory cytokines, immunoglobulin G (IgG), and immunoglobulin A (IgA) were examined. CD4⁺, CD8⁺, and Treg cells counts in peripheral blood were determined using flow cytometry; The protein expression of Toll-like receptor 4 (TLR4) and nuclear factor kappa-B (NF-κB) was determined using immunohistochemistry (IHC) and western blot (WB). The small intestine contents and feces were analyzed by 16 S rRNA sequencing and the contents of short chain fatty acids (SCFAs) in feces were determined using gas chromatography-mass spectrometry (GC-MS). Ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) was used to analyze the blood absorption compounds and endogenous metabolites.

Results: The levels of the major anthraquinone/anthrone components were decreased in PRH. RH and PRH both increased the wet fecal weight at 12 h (WFW-12) and fecal water rate (FWR), alleviated the dry and black fecal morphology, and relieved small intestine injuries in the second week. In the fourth week, although RH and PRH alleviated the abnormal levels of indicators in the model mice (fecal water rate, immune cells percentage, and TLR4/NF-κB expression), minor small intestinal damage was observed. Compared to that at the fourth week, RH and PRH increased the levels of WFW-12, FWR, inflammatory cytokines, and TLR4/NF-κB expression, and decreased the levels of IgG/IgA and immune cells with extended administration (sixth week). Further, damage to the small intestine worsened (severe ileal damage) and different degrees of loose stools were observed in RH- and PRH-administered mice in the sixth week. Compared with those in the control group, the levels of WFW-12, FWR, inflammatory cytokines, TLR4/NF-κB expression, IgG/IgA, and immune cell percentage were significantly different in the RH-H and PRH-H mice at the sixth week (except for CD8⁺in PRH-H). Further, RH and PRH disturbed the gut microbiota (GM) (Lactobacillus and Dubosiella decreased, Aerococcus and Corynebacterium increased) and obviously reduced the content of SCFAs (acetic acid, butyric acid, and isobutyric acid). However, almost all the results indicated a lower impact of PRH than that of RH. Metabolic pathways mainly involved in glycerophospholipid metabolism were identified along with a total of 21 blood absorption components, including anthraquinones, anthrones, flavanols, and tannins. The correlation analysis showed a positive correlation of pathogenic bacteria (Aerococcus and Corynebacterium) with inflammatory cytokines, TLR4/NF-κB, LysoPC(20:0/0:0), and PE (16:0/20:4(8Z,11Z,14Z,17Z)) and a negative correlation with immune cells and SCFAs (acetic acid and isobutyric acid); however, the opposite results were observed for beneficial bacteria (Lactobacillus and Dubosiella).

Conclusion: Overall, PRH can alleviate RH-induced diarrhea by recovering the GM imbalance and abnormal levels of GM-mediated SCFAs, alleviating the decrease in cellular immune function and abnormal expression of TLR4/NF-κB, thereby suppressing the release of inflammatory factors, possibly, through its lower content of anthraquinones. This study explored for the first time the processing mechanism of wine steaming in alleviating RH-induced diarrhea from the aspects of small intestinal flora and small intestinal immune function.