Capsaicin Improves Lipid Metabolism Disorders Caused by LPS-Induced Immune Stress in Weaned Piglets

The purpose of this study was to investigate the effect of capsaicin (CAP) on lipid metabolism in weaned piglets and its related mechanisms. Twenty-four weaned piglets with an initial body weight of 9.00 ± 0.30 kg were randomly divided into three groups, with eight replicates in each group. The control (CON) and lipopolysaccharide (LPS) groups were fed a basal diet, while the LPS and capsaicin group (LCA) received the basal diet supplemented with 4 mg/kg pure capsaicin (delivered via 800 mg/kg additive) for 35 days. About 4 h before sampling, piglets in the LPS and LCA groups were intraperitoneally injected with LPS at a dose of 100 μg/kg body weight, while those in the CON group were intraperitoneally injected with the same dose of normal saline. In this study, we found that the addition of 800 mg/kg CAP to the diet of piglets significantly reduced the accumulation of serum triglyceride (TG), non-esterified fatty acids (NEFA), and liver fat, and that CAP up-regulates expression of genes and proteins in the PPARα pathway, consistent with enhanced fatty acid oxidation. The intervention with 4 mg/kg CAP was also found to down-regulate cholesterol synthesis precursors (such as mevalonate, MVA), reduce pro-inflammatory phospholipids (such as phosphatidic acid-phosphatidylcholine, PA-PC), and modulate bile acid metabolism, thereby beneficially regulating blood lipid profiles (TC, TG, LDL-C) and disrupting the "lipid metabolism-inflammation" interaction cycle. Furthermore, CAP promoted fatty acid β-oxidation and bile acid metabolism by activating the TRPV1 channel, which alleviated hepatic lipid accumulation. These findings indicated that CAP has potential application value in improving lipid metabolism, intestinal health, and immune function in weaned piglets. However, its long-term safety and dose-dependent effects require further investigation.