Previous studies have shown that trans fatty acids (TFA) are associated with several chronic diseases, the gut microbiota is directly influenced by dietary components and linked to chronic diseases. Our research investigated the effects of elaidic acid (EA), a typical TFA, on the gut microbiota to understand the underlying mechanisms of TFA-related chronic diseases. 16S rDNA gene sequencing on faecal samples from Sprague-Dawley rats were performed to explore the composition change of the gut microbiota by EA gavage for 4 weeks. The results showed that the intake of EA increased the abundance of well-documented harmful bacteria, such as Proteobacteria, Anaerotruncus, Oscillibacter and Desulfovibrionaceae. Plus, EA induced translocation of lipopolysaccharides (LPS) and the above pathogenic bacteria, disrupted the intestinal barrier, led to gut-liver axis derangement and TLR4 pathway activation in the liver. Overall, EA induced intestinal barrier damage and regulated TLR4-MyD88-NF-κB/MAPK pathways in the liver of SD rats, leading to the activation of NLRP3 inflammasome and inflammatory liver damage.

Elaidic acid (EA) stimulation can lead to endoplasmic reticulum stress (ERS), accompanied by a large release of Ca²⁺, and ultimately the activation of NLRP3 inflammasome in Kupffer cells (KCs). Mitochondrial instability or dysfunction may be the key stimulating factors to activate NLRP3 inflammasome, and sustained Ca²⁺ transfer can result in mitochondrial dysfunction. We focused on KCs to explore the damage to mitochondria by EA. After EA stimulation, cells produced an oxidative stress (OS) response with a significant increase in ROS release. Immunoprecipitation experiments and the addition of inhibitors revealed that the increase in the level of intracellular Ca²⁺ led to Ca²⁺ accumulation in the mitochondrial matrix via mitochondria-associated membranes (MAMs). This was accompanied by a significant release of mROS, loss of MMP and ATP, and a significant increase in mitochondrial permeability transition pore opening, ultimately leading to mitochondrial instability. These findings confirmed the mechanism that EA induced mitochondrial Ca²⁺ imbalance in KCs via MAM, ultimately leading to mitochondrial dysfunction. Meanwhile, EA induced OS and the decrease of MMP and ATP in rat liver, and significant lesions were found in liver mitochondria. Swelling of the inner mitochondrial cristae and mitochondrial vacuolization occurred, with a marked increase in lipid droplets.