Effects of Supplementing the Diets of Mice With Different Concentrations of Conjugated Linoleic Acid on the Anti‐Inflammatory Function of the Mammary Gland

ABSTRACT

In this study, we evaluated the impact of the dietary addition of different concentrations of conjugated linoleic acid (CLA) on the antioxidant capacity and anti‐inflammatory effects of serum and breast tissue in mice. Twenty‐four ICR mice (BW = 37.79 ± 2.17 g) at 7 days of pregnancy were divided into four groups ( n  = 6 per group): a control (CN) group, which was fed a normal diet, and three groups fed a normal diet supplemented with 0.5% CLA, 1% CLA, or 2% CLA. Each mouse had free access to food and water. After 49 days of feeding, mice were injected with lipopolysaccharide (LPS) to induce inflammation, and 24 h later, the experimental animals were anesthetized by intraperitoneal injection of pentobarbital sodium (40–50 mg/kg). After achieving deep anesthesia, blood was collected from the posterior orbital venous plexus. Subsequently, an excessive dose of pentobarbital sodium (total dose of 150–200 mg/kg) was administered to euthanize the animals. After confirming the cessation of breathing and heartbeat, breast tissues were collected for analysis. The expression levels of antioxidant and inflammatory factors in serum and mammary gland tissues were measured by ELISA, and the mRNA expression levels of mammary inflammatory factors were further quantified by RT‐PCR. Parts of the tissue samples were retained for histopathological observation. The results showed that compared with the control treatment, CLA supplementation significantly increased both the total antioxidant capacity (T‐AOC) and the levels of superoxide dismutase (SOD), with the 1% CLA group exhibiting the most pronounced increase ( p  < 0.001). The contents of interleukin 1β (IL‐1β), tumor necrosis factor (TNF‐α) and interleukin 6 (IL‐6), decreased significantly, with the lowest levels in the 1% CLA group ( p  < 0.001). Both MDA and GPx levels showed significant decline, with the lowest levels in the 1% CLA group ( p  < 0.001). The relative expression of the PPAR‐γ gene ( p  < 0.05) was significantly higher in the 2% CLA group than in the CN group, and the 1% CLA group showed certain promoting effect. Compared with the CN group, the relative expression levels of the TNF‐α and IL‐8 genes were significantly decreased in the 1% CLA group ( p  < 0.05). Histopathological analysis revealed that the mammary acinar structure of mice in the 1% CLA group remained intact, with minimal inflammatory infiltration in the acinar lumen. In conclusion, the dietary addition of CLA exerted marked antioxidant and anti‐inflammatory effects in the serum and mammary gland tissues of mice, with the best results observed with the 1% supplementation level. This study focuses on the dose optimization of CLA, and the results provide a foundational dose reference for the translational application of CLA in dairy cow farming.