Lipid-lowering Effect of Thermally Inactivated Bacillus sp. DU-106 on High-fat C. elegans

This study explored the lipid-lowering efficacy of thermally inactivated Bacillus sp. DU-106 (TIDU-106) on Caenorhabditis elegans. A high-fat model of C. elegans was developed using a high-glucose induction method with a concentration of 10 mmol/L. To evaluate the effects of TIDU-106 on high-fat Caenorhabditis elegans, concentrations of 2.5, 5.0, and 10 mg/mL were applied, assessing their impact on lifespan, locomotion, egg-laying capability, levels of reactive oxygen species (ROS), resistance to stress, activity of antioxidant enzymes, expression of genes related to lipid metabolism, and fat accumulation. Initial investigations in wild-type worms led to the selection of 5.0 mg/mL and 10 mg/mL concentrations of TIDU-106 for further examination of its lipid-lowering properties in gene-deficient worms. The results demonstrated that TIDU-106 treatment significantly increased the maximum lifespan of high-fat worms by 35.11%, 43.84%, and 45.63% with varying doses (2.5, 5.0, 10 mg/mL) (P<0.05). These enhancements were accompanied by improved locomotion, a higher egg-laying capacity, and a decreased both in ROS levels and mitochondrial membrane potential. Additionally, treatment with TIDU-106 resulted in increased levels of superoxide dismutase, catalase, and glutathione peroxidase, coupled with a decrease in malondialdehyde levels. Notably, TIDU-106 was found to modulate key signaling pathways related to lipid-lowering, including the SREBP signaling pathway, the insulin/IGF-1 signaling pathway, the nuclear receptor signaling pathway, and the AMPK signaling pathway, as well as key genes such as mdt-15, sbp-1, fat-5, fat-7, daf-2, daf-16, skn-1, sod-3, sir-2.1, aak-2, nhr-49, acs-2, and kat-1. Specifically, after the administration of TIDU-106, there was a significant reduction in triglyceride levels in fat-5, fat-5/fat-6, fat-7, and daf-16 mutant worms (P<0.05), with daf-2, sir-2.1, and aak-2 mutants exhibiting no significant alterations (P>0.05). Above findings revealed the potential of TIDU-106 to mitigate fat deposition, boost resistance to oxidative stress, and increase antioxidant enzyme activity, thereby emphasizing its promising lipid-lowering effects in high-fat C. elegans models.