Functional constipation (FC) is a gastrointestinal disorder with high incidence, and it seriously affects patients’ physical and mental health. Several studies have shown that the gut microbiome is associated with FC, but these studies have produced inconsistent findings, with few reflecting the relationship between the gut microbiome and metabolites. This study used 16S rRNA microbial genomics and non-target metabolome based on liquid chromatography–mass spectrometry to analyze the gut microbiota composition and serum metabolic profiles of 30 FC patients and 28 healthy individuals. We found that patients with FC and healthy individuals have different gut microbiota structures and serum metabolic profiles. FC patients had more Bacteroides and butyrate-producing bacteria (Roseburia, Faecaliberium, Butyriccoccus). The upstream products of host arginine biosynthesis (2-oxoglutaric acid, L-glutamic acid, N-acetylornithine, and L-ornithine) were significantly reduced in FC patients’ serum metabolites. In summary, our study describes the gut microbiome and serum metabolome of patients with functional constipation. It reveals that functional constipation may be associated with increased Bacteroidetes and downregulation of upstream products of host arginine biosynthesis, which may be potential markers for diagnosing functional constipation.

Immunoglobulin A (IgA), as the most secreted immunoglobulin in the intestine, plays an irreplaceable role in mucosal immunity regulation. Previous studies have indicated that Lactobacillus showed strain specificity in stimulating the secretion of IgA through intestinal mucosal lymphocytes. The reason for this phenomenon is not clear. The current studies have been aimed at exploring the effect of a strain on the secretion of IgA in the host’s intestine, but the mechanism behind it has not been seriously studied. Based on this, we selected five strains of Lactobacillus fermentum isolated from different individuals to determine whether there are intraspecific differences in stimulating the secretion of IgA from the intestinal mucosa. It was found that IgA concentrations in different intestinal segments and faeces induced by L. fermentum were different. 12-1 and X6L1 strains increased the secretion of IgA by the intestine significantly. In addition, different strains of L. fermentum were also proven to have different effects on the host gut microbiota but no significant effects on IgA-coated microbiota. Besides, it was speculated that different strains of L. fermentum may act on different pathways to stimulate IgA in a non-inflammatory manner. By explaining the differences of IgA secretion in the host’s intestine tract stimulated by different strains of L. fermentum, it is expected to provide a theoretical basis for the stimulation of intestinal secretion of IgA by Lactobacillus and a new direction for exploring the relationship between Lactobacillus and human immunity.

Background: Steroid 5α-reductase type II (SRD5A2) is an enzyme that plays a significant role in steroid metabolism. It is mainly located in the endoplasmic reticulum membrane and can convert testosterone (T) into more active dihydrotestosterone (DHT). It plays a critical role in gender differentiation and androgen physiology, and is implicated in tumorigenesis and progression. It has been reported in various types of tumors. Among the most common gastrointestinal malignancies, colorectal cancer (CRC) imposes a significant global health burden. Nevertheless, the expression profile and clinical significance of SRD5A2 in CRC are poorly characterized, and its precise functional role requires further investigation. This study aimed to investigate the expression profile, prognostic significance, biological functions, and potential mechanisms of SRD5A2 in CRC. Methods: This retrospective cohort study included 180 patients with CRC. Tissue microarrays (TMAs) were constructed and subjected to SRD5A2 immunohistochemistry (IHC), and H-scores were used to stratify patients into high- and low-expression groups for clinicopathological and overall survival (OS) analyses. Univariate and multivariate Cox regression analyses, as well as subgroup Kaplan-Meier analyses, were performed to evaluate the prognostic value and stability of SRD5A2. In vitro, SRD5A2 knockdown was performed in CRC cells, followed by assays of cell viability, migration, invasion, and apoptosis. Epithelial-mesenchymal transition (EMT)-related proteins, classical oncogenic signaling pathways, and metabolic homeostasis were further evaluated by western blotting (WB), glucose consumption, adenosine triphosphate (ATP), and reactive oxygen species (ROS) assays. Results: SRD5A2 expression was significantly upregulated in CRC tissues compared with paired distal normal mucosa (P<0.001). High SRD5A2 expression was associated with adverse clinicopathological features and significantly shorter OS (P<0.001). Multivariate Cox regression analysis further showed that high SRD5A2 expression remained independently associated with poorer OS. Subgroup Kaplan-Meier analyses demonstrated that this adverse prognostic association was generally maintained across several T-, N-, and M-based strata. In vitro, SRD5A2 knockdown suppressed cell proliferation, migration, and invasion, while promoting apoptosis. Mechanistically, SRD5A2 silencing reversed EMT-related molecular changes, suppressed the MAPK/ERK, JNK, NF-κB, and AKT/mTOR pathways, reduced glucose consumption and intracellular ATP levels, and increased intracellular ROS levels. Conclusions: SRD5A2 is upregulated in CRC tissues, and its high expression is related to aggressive clinicopathological features and poor OS. Multivariable survival analysis further suggests that SRD5A2 may serve as an independent prognostic factor in CRC. Functional experiments suggest that SRD5A2 has a pro-tumorigenic effect. Preliminary mechanistic analyses further suggest that SRD5A2 may exert its pro-tumorigenic effects through EMT-related molecular changes, activation of classical oncogenic signaling pathways, and maintenance of metabolic homeostasis.