Abstract
BackgroundThe recent identification of the endocannabinoid system in the gastrointestinal tract suggests a role in controlling intestinal inflammation. In addition, the gut chemosensing system has therapeutic applications in the treatment of gastrointestinal diseases and inflammation due to the presence of a large variety of receptors. The purposes of this study were to investigate the presence of markers of the endocannabinoid system and the chemosensing system in the pig gut and, second, to determine if thymol modulates these markers. One hundred sixty 28-day-old piglets were allocated into one of 5 treatment groups (n = 32 per treatment): T1 (control), T2 (25.5 mg thymol/kg feed), T3 (51 mg thymol/kg feed), T4 (153 mg thymol/kg feed), and T5 (510 mg thymol/kg feed). After 14 days of treatment, piglets were sacrificed (n = 8), and then duodenal and ileal mucosal scrapings were collected. Gene expression of cannabinoid receptors (CB1 and CB2), transient receptor potential vanilloid 1 (TRPV1), the olfactory receptor OR1G1, diacylglycerol lipases (DGL-α and DGL-β), fatty acid amine hydrolase (FAAH), and cytokines was measured, and ELISAs of pro-inflammatory cytokines levels were performed.ResultsmRNAs encoding all markers tested were detected. In the duodenum and ileum, the CB1, CB2, TRPV1, and OR1G1 mRNAs were expressed at higher levels in the T4 and T5 groups compared to the control group. The level of the FAAH mRNA was increased in the ileum of the T4 group compared to the control. Regarding the immune response, the level of the tumor necrosis factor (TNF-α) mRNA was significantly increased in the duodenum of the T5 group, but this increase was not consistent with the protein level.ConclusionsThese results indicate the presence of endocannabinoid system and gut chemosensing markers in the piglet gut mucosa. Moreover, thymol modulated the expression of the CB1, CB2, TRPV1, and OR1G1 mRNAs in the duodenum and ileum. It also modulated the mRNA levels of enzymes involved in the biosynthesis and degradation of endocannabinoid molecules. Based on these findings, the effects of thymol on promoting gut health are potentially mediated by the activation of these receptors.
Highlights
The recent identification of the endocannabinoid system in the gastrointestinal tract suggests a role in controlling intestinal inflammation
The level of the cannabinoid receptor 1 (CB1) mRNA was significantly increased in the duodenum of the T5 group (P = 0.0209) and in the ileum of the T4 and T5 groups (P = 0.0054) compared to the control group
Differences in the levels of the fatty acid amine hydrolase (FAAH) mRNA were not observed in the duodenum, while mRNA levels were significantly increased in the ileum of the T4 group compared to the control group (P = 0.0028)
Summary
The recent identification of the endocannabinoid system in the gastrointestinal tract suggests a role in controlling intestinal inflammation. The ECS controls a variety of gastrointestinal (GI) functions: it is presumed to regulate GI motility via the enteric nervous system (ENS) [11], to inhibit the secretion of pro-inflammatory cytokines and to attenuate the lipopolysaccharide (LPS)-induced increase in GI transit [12]. CB1 receptors are colocalized with acetylcholine transferase, which is a marker for cholinergic neurons This observation supports the role of endocannabinoids as inhibitors of intestinal motility and secretion by inhibiting cholinergic neurotransmission [10]. For all these reasons, dysregulation of the ECS clearly plays a role in intestinal disorders, including irritable bowel disease (IBD), irritable bowel syndrome, and obesity [13]
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