Dose-Dependent Effects of Conjugated Linoleic Acid on Hepatic Anti-Inflammatory Activity in Mice

Conjugated linoleic acid (CLA) exerts anti-inflammatory and antioxidant bioactivities, yet its optimal hepatic anti-inflammatory dosage under lipopolysaccharide (LPS) stimulation remains unclear. This study aimed to screen the effective dietary CLA dose against LPS-triggered liver inflammation in mice. Twenty-four male mice were divided into four groups (n = 6): normal diet (ND), ND+0.5% CLA, ND+1% CLA and ND+2% CLA. After 49 days of feeding, all mice received LPS injection and were sacrificed 24 h later. Serum and liver tissues were collected to detect pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), the oxidative stress marker malondialdehyde (MDA), antioxidant indices (superoxide dismutase, SOD and total antioxidant capacity, TAC), hepatic inflammatory gene mRNA and liver histopathology. The 1% CLA group exhibited lower serum and hepatic pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) and the oxidative stress marker MDA, higher SOD and TAC (p < 0.01), and reduced hepatic inflammatory infiltration. All CLA treatments downregulated hepatic CXCL1 mRNA and upregulated peroxisome proliferator-activated receptor γ (PPARγ) mRNA (p < 0.05). In conclusion, 1% dietary CLA elicited optimal anti-inflammatory effects in this acute LPS-induced liver inflammation model, while 1% and 2% CLA showed comparable antioxidant effects. This study was a short-term acute inflammation mouse model. The tissue distribution and lipid metabolic profile of CLA were not examined, and the CLA mixed isomers were used. Moreover, the PPARγ pathway was inferred based solely on mRNA levels, and further in-depth verification is still needed.