Plant essential oils combined with organic acids restored lipopolysaccharide-induced leaky intestine via gut microbial modulation in weaned piglets

Intestine derived lipopolysaccharide (LPS) is closely related to systemic inflammation and disorders, yet little is known about its roles in the weanling stress of piglets and its potential as a nutritional intervention target. This study aimed to investigate the potential of essential oils (EO) and organic acids (OA) in mitigating weaning stress in piglets by modulating the circulation of intestine derived LPS. Seventy-two 21-day-old weaned piglets with body weight of 8.12±0.168 kg were randomly divided into a control group (CON) and an experimental group, each consisting of six pens with six piglets per pen, and were fed either a basal diet or a basal diet supplemented with 3 kg/t OA+500 g/t EO (EO+OA). On the 14th day of the feeding trial, 12 weaned piglets were randomly selected from the CON group, and 6 piglets were selected from the experimental group. Based on diet composition and stress treatment, these 18 piglets were divided into the following three groups: 1) CON group. Piglets were fed a basal diet and received an intraperitoneal injection of saline as a control. 2) LPS group. Piglets were fed a basal diet and received an intraperitoneal injection of LPS (100 μg/kg body weight) to induce stress. 3) EO+OA+LPS group. Piglets were fed a basal diet supplemented with EO and OA and received an intraperitoneal injection of LPS (100 μg/kg body weight) to induce stress. The results showed that EO+OA significantly ameliorated the oxidative imbalance and inflammation disorder induced by LPS in piglets' serum and intestine by inhibiting the activation of the Toll-like receptor 4 (TLR4)/Nuclear factor-kappa B (NF-κB)/mitogen-activated protein kinase (MAPK) signaling pathway. Furthermore, compared to the LPS group, supplementation with EO+OA restored LPS-induced reductions in Bcl-2 protein expression in the piglets' intestines (P<0.05) and mitigated morphological damage; it also enhanced both the protein expression and relative gene expression of the tight junction proteins Occludin and Claudin-1 (P<0.05), and reduced the plasma diamine oxidase activity (DAO) and LPS content (P<0.05). Compared to the CON group, supplementation with EO+OA altered the composition of the intestinal microbiota, increasing beneficial bacteria relative abundance (Faecalibacterium) (P<0.05) and decreasing harmful bacteria relative abundance [Rikenellaceae_RC9_gut_group (P<0.01), Negativibacillus (P<0.05)]. Further analysis revealed that plasma LPS content in piglets was negatively correlated with the relative abundance of Faecalibacterium (r=-0.662, P=0.021), Akkermansia (r=-0.492, P=0.031), and average daily gain (ADG) (r=-0.912, P=0.041). Plasma LPS content was also positively correlated with the plasma inflammatory factors interleukin (IL)-1β (r=0.591, P=0.021), IL-6 (r=0.623, P=0.021), IL-12 (r =561, P=0.031) contents, and the relative abundance of Negativibacillus (r=0.712, P=0.041). In summary, the addition of EO+OA prevents the leakage of intestine derived LPS into the circulation by improving intestinal integrity and microbiota composition, thereby enhancing antioxidant and anti-inflammatory abilities and growth performance of weaned piglets.