In biological responses, fatty acids (FA) are absorbed and metabolized in the form of substrates for energy production. The molecular structures (number of double bonds and chain length) and composition of dietary FA impact digestion, absorption and metabolism, and the biological roles of FA. Recently, increasing evidence indicates that FA are essentially utilized as an energy source and are signaling molecules that exert physiological activity of gut microbiota and immune responses. In addition, FA could serve as natural ligands for orphan G protein-coupled receptors (GPCR), also called free fatty acid receptors (FFAR), which intertwine metabolic and immune systems via multiple mechanisms. The present review explores the recent findings on FA absorption and its impact on gut health, particularly addressing the mechanism by which dietary FA potentially influences intestinal microbiota and epithelial functions. Also, this work attempts to uncover research ideas for devising future strategies for manipulating the composition of dietary FA to regulate gut health and support a normal immune system for metabolic and immune disorders.

This study investigated the effects of dietary C. butyricum ZJU-F1 on the apparent digestibility of nutrients, intestinal barrier function, immune response, and microflora of weaned piglets, with the aim of providing a theoretical basis for the application of Clostridium butyricum as an alternative to antibiotics in weaned piglets. A total of 120 weanling piglets were randomly divided into four treatment groups, in which piglets were fed a basal diet supplemented with antibiotics (CON), Bacillus licheniformis (BL), Clostridium butyricum ZJU-F1 (CB), or Clostridium butyricum and Bacillus licheniformis (CB-BL), respectively. The results showed that CB and CB-BL treatment increased the intestinal digestibility of nutrients, decreased intestinal permeability, and increased intestinal tight junction protein and mucin expression, thus maintaining the integrity of the intestinal epithelial barrier. CB and CB-BL, as exogenous probiotics, were also found to stimulate the immune response of weaned piglets and improve the expression of antimicrobial peptides in the ileum. In addition, dietary CB and CB-BL increased the proportion of Lactobacillus. The levels of butyric acid, propionic acid, acetic acid, and total acid were significantly increased in the ceca of piglets fed CB and CB-BL. Furthermore, we validated the effects of C. butyricum ZJU-F1 on the intestinal barrier function and immune response in vitro and found C. butyricum ZJU-F1 improved intestinal function and enhanced the TLR-2-MyD88-NF-κB signaling.

Animal antimicrobial peptides (AMPs), known as broad-spectrum and high-efficiency antibacterial activity, are important effector molecules in innate immune system. AMPs not only have antimicrobial, antiviral and antitumor effects but also exhibit important effects in vivo, such as anti-inflammatory response, recruiting immune cells, promoting epithelial damage repair, and promoting phagocytosis of bacteria. However, research on the application of AMPs is incomplete and controversial. This review mainly introduces the classification of AMPs, biological functions, as well as the mechanisms of action, expression rules, and nutrition regulation from three perspectives, aiming to provide important information for the application of AMPs.

Dysregulation of the gut microbiota often leads to immune‐related disorders, indigestion, or diarrhea. Here, Jiaxing Black (JXB) pig, a local Chinese pig breed known for its great tolerance and digestibility of nutrients, was employed for a metagenomic and transcriptomic integrative analysis to reveal the gut microbiota‐genes and gut microbiota‐pathway interactions. A total of 452 differentially expressed genes, and 174 phyla were found between the JXB and the Duroc × Landrace × Yorkshire (DLY) pigs. Detailed analysis revealed that the differences in colon gene expression signatures between the JXB and DLY are mainly enriched in metabolic and inflammatory responses, with Lactobacillus and Lachnospiraceae enriched in DLY and JXB, respectively. Notably, Pacebacteria, Streptophyta, and Aerophobetes were found to participate in the PI3K‐Akt mediated immune response in both pig breeds; however, they only accelerated the metabolism in the intestines of JXB pigs. Moreover, the host could regulate microbe metabolism and immune response by Ig‐like domain‐containing protein and ITIH2, PAEP, and TDRD9, respectively. Taken together, our results revealed both common and breed‐specific regulations of host genes by gut microbiota in two pig breeds.

Summary: Faecal Microbiota Transplantation (FMT) is considered as a promising technology to fight against obesity. Wild boar has leanermuscle and less fat in comparison to the domestic pig, which were thought to be related with microbiota. To investigate the function and mechanism of the wild boar microbiota on obesity, we first analysed the wild boar microbiota composition via 16S rDNA sequencing, which showed that Firmicutes and Proteobacteria were the dominant bacteria. Then, we established a high‐fat diet (HFD)‐induced obesity model, and transfer low and high concentrations of wild boar faecal suspension in mice for 9 weeks. The results showed that FMT prevented HFD‐induced obesity and lipid metabolism disorders, and altered the jejunal microbiota composition especially increasing the abundance of the Lactobacillus and Romboutsia , which were negatively correlated with obesity‐related indicators. Moreover, we found that the anti‐obesity effect of wild boar faecal suspension was associated with jejunal N6‐methyladenosine (m ⁶ A) levels. Overall, these results suggest that FMT has a mitigating effect on HFD‐induced obesity, which may be due to the impressive effects of FMT on the microbial composition and structure of the jejunum. These changes further alter intestinal lipid metabolism and m ⁶ A levels to achieve resistance to obesity.