Background: Polyamines are essential for cell growth and beneficial for intestinal maturation. To evaluate the effects of putrescine on alleviating intestinal atrophy and underlying molecular mechanisms, both in vivo feeding trial and in vitro cell culture were conducted. Weanling pigs were fed a diet supplemented with 0, 0.1%, 0.2% or 0.3% putrescine dihydrochloride, whereas porcine intestinal epithelial cells (IPEC-J2) were challenged with lipopolysaccharide (LPS) in the presence of 200 μmol/L putrescine. Results: Dietary supplementation with 0.2% putrescine dihydrochloride decreased the incidence of diarrhea with an improvement in intestinal integrity. Inhibition of ornithine decarboxylase activity decreased the proliferation and migration of IPEC-J2 cells, and this effect was alleviated by the supplementation with putrescine. The phosphorylation of extracellular signal regulated kinase and focal adhesion kinase was enhanced by putrescine. LPS increased the expression of inflammatory cytokines [tumor necrosis factor α (TNF-α), interleukin 6 (IL-6) and IL-8], and inhibited cell proliferation and migration in IPEC-J2 cells. Adding exogenous putrescine suppressed the expression of TNF-α, IL-6 and IL-8, and recovered cell migration and proliferation in LPS-treated IPEC-J2 cells. Dietary putrescine supplementation also reduced the mRNA levels of TNF-α, IL-6 and IL-8 and their upstream regulator nuclear receptor kappa B p65 subunit in the jejunal mucosa of piglets. Conclusions: Dietary supplementation with putrescine mitigated mucosal atrophy in weanling piglets through improving anti-inflammatory function and suppressing inflammatory response. Our results have important implications for nutritional management of intestinal integrity and health in weanling piglets and other neonates.

The gut microbiota constitutes a complex ecosystem, comprising trillions of microbes that have co-evolved with their host over hundreds of millions of years. Over the past decade, a growing body of knowledge has underscored the intricate connections among diet, gut microbiota, and human health. Bioactive polysaccharides (BPs) from natural sources like medicinal plants, seaweeds, and fungi have diverse biological functions including antioxidant, immunoregulatory, and metabolic activities. Their effects are closely tied to the gut microbiota, which metabolizes BPs into health-influencing compounds. Understanding how BPs and gut microbiota interact is critical for harnessing their potential health benefits. This review provides an overview of the human gut microbiota, focusing on its role in metabolic diseases like obesity, type II diabetes mellitus, non-alcoholic fatty liver disease, and cardiovascular diseases. It explores the basic characteristics of several BPs and their impact on gut microbiota. Given their significance for human health, we summarize the biological functions of these BPs, particularly in terms of immunoregulatory activities, blood sugar, and hypolipidemic effect, thus providing a valuable reference for understanding the potential benefits of natural BPs in treating metabolic diseases. These properties make BPs promising agents for preventing and treating metabolic diseases. The comprehensive understanding of the mechanisms by which BPs exert their effects through gut microbiota opens new avenues for developing targeted therapies to improve metabolic health.

Bacillus licheniformis (B. Licheniformis) has been considered to be an effective probiotic to maintain gut health and boost productivity in the pig industry, but there is no complete understanding of its mechanisms. We determined whether weaned piglets exposed to BL−S6 (probiotic) had altered intestinal barrier function or microbiota composition. In our study, 108 weaned piglets (54 barrows and 54 gilts) were divided equally into three groups, each with six pens and six piglets/pen, and fed a basal diet supplemented without or with antibiotic (40 g/t of Virginiamycin and 500 g/t of Chlortetracycline) or probiotic (1000 g/t of B. Licheniformis) for a 14-day trial. On day 14, one piglet was chosen from each pen to collect blood and intestinal samples. Compared with the control group, dietary supplementation with a probiotic promoted body weight (BW) gain and average daily gains (ADG) while reducing diarrhea incidence (p < 0.05). Probiotics enhanced superoxidase dismutase (SOD) activity and decreased malondialdehyde (MDA) levels in serum (p < 0.05), and increased the level of mRNA expression of SOD1, Nrf2, and HO-1 (p < 0.05) in the jejunum mucosa. Moreover, supplementation with probiotics improved intestinal mucosal integrity as evidenced by higher villus heights and a higher ratio of villus heights to crypt depths (duodenum and jejunum) and higher mRNA and protein levels of occludin and ZO-1 in jejunum mucosa (p < 0.05). The intestinal sIgA levels (p < 0.05) were elevated in the probiotic group, and that of serum immunoglobulin A (IgA) tended to be higher (p = 0.09). Furthermore, weaning piglets who were given probiotics had a better balance of the cecum microbiota, with lactobacillus abundance increased and clostridium_sensu_stricto_1 abundance decreased. In conclusion, dietary supplementation with the probiotic BL−S6 promoted intestinal integrity, which was associated, in part, with modulating intestinal barrier function and microbial diversity in weaned piglets; it may offer a promising alternative to antibiotics to prevent diarrhea.

Our previous study found that soybean isoflavones in soybean meal play an important role in improving growth performance and antioxidant capacity in pigs. However, it is still unknown whether long-term supplementation with daidzein, an active molecule deglycosylated from daidzin, in a corn–soybean meal diet can enhance growth performance in pigs. Thus, in the present study, an animal trial was carried out to investigate the effects of dietary supplementation with daidzein on the growth performance and antioxidant capacity of pigs. A total of 80 weaned piglets (40 barrows and 40 females) were assigned to 4 treatments with 5 pens per treatment and 4 piglets per pen and fed a diet supplemented with 0, 25, 50 and 100 mg/kg daidzein for a 72-day trial. In addition, porcine intestinal epithelial cells (IPEC-J2) were used as an in vitro model to explore the underlying antioxidant mechanisms of daidzein. IPEC-J2 cells were treated with 0.6 mM hydrogen peroxide (H₂O₂) in the presence or absence of 40 μM daidzein. The results showed that adding 50 mg/kg of daidzein to the diet significantly improved body weight on day 72, average daily gain (ADG) during days 0 to 72 and plasma superoxide dismutase (SOD) activity on day 42 (P < 0.05). Treatment with 0.6 mM H₂O₂ for 1 h significantly decreased cell viability and catalase (CAT) activity and increased intracellular reactive oxygen species (ROS) levels and malondialdehyde (MDA) content (P < 0.05), while pretreatment with 40 μM daidzein prevented the decrease in cell viability and CAT activity and the increase in intracellular ROS levels and MDA content caused by H₂O₂ (P < 0.05). In addition, H₂O₂ stimulation significantly suppressed the expression of nuclear factor erythroid-2-related factor 2 (Nrf2), CAT, occludin and zonula occludens-1 (ZO-1), while pretreatment with daidzein preserved the expression of Nrf2, CAT and occludin in H₂O₂-stimulated IPEC-J2 cells (P < 0.05). In conclusion, our results suggested that long-term dietary supplementation with 50 mg/kg daidzein improved growth performance in pigs and was beneficial to the antioxidant capacity of pigs. Daidzein exerted protective effects against H₂O₂-induced oxidative stress in IPEC-J2 cells and the underlying mechanism may be related to the activation of the Nrf2 signaling pathway.