3'-Sialyllactose Prevents Atherosclerosis by Attenuating Chronic Inflammation via the Gut-Immune-Cardiovascular Axis in LDLR -/- Mice.

3'-sialyllactose (3'-SL) has demonstrated potential in regulating glycolipid metabolism and improving intestinal immunity, thereby exhibiting anti-atherosclerotic (AS) properties. However, the mechanism by which 3'-SL exerts its anti-AS effects through the regulation of inflammatory signaling via intestinal immunity remains unknown. Herein, 40 male low-density lipoprotein receptor knockout (LDLR -/-) mice were randomized into five groups: normal diet (ND), high-cholesterol diet (HCD), and three 3'-SL groups (low dose SLL, medium dose SLM, high dose SLH). After 12 weeks, atherosclerotic plaque formation, serum lipids including total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and inflammatory cytokines including interleukin-6 (IL-6), interleukin-1β (IL-1β), interleukin-10 (IL-10) were measured. Multi-omics analyses (gut microbiota 16S sequencing, colonic transcriptomics, and metabolomics) were performed. Compared with the HCD group, 3'-SL L intervention dose-dependently and significantly reduced aortic lipid deposition in LDLR -/- mice, lowered serum TG and LDL levels, increased HDL, while markedly decreasing pro-inflammatory cytokines IL-6 and IL-1β and elevating the anti-inflammatory cytokine IL-10. Using the SLM group as representative for mechanistic exploration, it was found that 3'-SL reshaped the gut microbiota structure, significantly increasing the abundance of beneficial Akkermansia and reducing the Firmicutes/Bacteroidetes ratio, thereby restoring microbial balance. Integrated multi-omics analysis further revealed that 3'-SL drove colonic transcriptomic-metabolic reprogramming, with enriched key pathways mainly involving immune regulation (e.g., Ccl2, Il2ra) and lipid metabolism (e.g., Kng1, C6). Differential metabolites showed significant correlations with immune- and cardiovascular-related genes. Among these, Ccl2 (MCP-1), as a key molecule linking gut immune signals to coronary artery pathology, was suppressed in expression, which may directly reduce the recruitment of monocytes/macrophages into the subendothelial space, thereby inhibiting the initiation of atherosclerosis. Collectively, 3'-SL exhibits significant preventive effects against chronic inflammation in LDLR -/- mice with HCD-induced atherosclerosis. These effects are mediated through synergistic regulation of metabolic, inflammatory, and microbial pathways along the gut microbiota-immune-cardiovascular axis. This axis integrates gut microbial metabolism, immune responses, and transcriptional signaling changes, revealing novel targets for the prebiotic 3'-SL in preventing atherosclerosis. It provides robust preclinical evidence for nutritional intervention strategies targeting the gut microbiota.