Myricanol modulates PPARγ/ACSL1/SCD1 metabolic signaling pathway to promote mitochondria biogenesis and fatty acid β-oxidation in high-fat diet-induced obese mice

Abstract

Ethnopharmacological relevance: The bark of Myrica rubra (Lour.) Siebold & Zucc (MR). is a natural remedy commonly used in China and other Asian nations because of its antioxidant, antiinflammation and antibacterial activities. Myricanol is the main lipid-lowering compounds in the bark of MR. The effects of myricanol on alleviating hyperlipidemia have rarely been reported. No study has investigated the role of the ACSL-SCD axis in the management of hyperlipidemia in vivo.

Aim of the study: This study employed a high-fat diet (HFD)-induced hyperlipidemic C57BL/6J mouse model to explore the lipid-lowering effects and underlying mechanisms of myricanol through the ACSL1-SCD1 axis.

Materials and methods: An olive oil and lard mixture was used to establish a hyperlipidemic C57BL/6J mouse model. Rosiglitazone (RSG) a peroxisome proliferator-activated receptor γ (PPARγ) agonist, and ACSL inhibitor was used as a positive control. After 8 weeks of high-fat modeling, the mice were randomly divided into the M group, RSG group (0.4 ml, 0.78 mg/kg RSG solution daily), low-dose myricanol group (MYL, 100 mg/kg), and high-dose myricanol group (MYH, 150 mg/kg). After 25 days of treatment, the lipid-lowering effects of myricanol were evaluated by measuring serum lipid levels and histopathological observation. Western blotting, metabolomics, 16S rRNA sequencing, RNA sequencing, ELISA, immunofluorescence staining, double-fluorescence labeling and cellular thermal shift assay (CETSA) were used to explore the underlying mechanisms.

Results: Only 7 days of myricanol treatment significantly reduced body weight in obese mice. Myricanol normalized serum levels of TC, TG, HDL-C, and LDL-C; reduced lipid droplet accumulation in hepatocytes; and decreased the epididymal fat volume in mice. Mechanistic studies revealed that myricanol upregulated the expression of ACSL1, PPARγ, CYP7A1, SCD1, ACLY, and SREBF1 in the mouse liver. Additionally, myricanol increased the expression of PPARγ, CPT1A, ACC1, ACSL1, APOE4, and SREBF1 in the mouse epididymal fat. Multimodal omics analyses indicated that the lipid-lowering activity of myricanol was partially mediated by modulating the gut microbiota, such as that of Monoglobus and Lachnospiraceae bacterium 28-4; regulating the interferon (IFN) pathway and IFN-stimulated genes; and influencing the expression of miRNAs such as miR-203b-3p, miR-205-5p, and miR-184-3p. Cellular thermal shift assay, molecular docking, and ELISA confirmed that myricanol directly bound to ACSL1 and decreased the concentrations of ACSL1 and SCD1 in mouse serum. Intriguingly, myricanol promoted mitochondrial biogenesis in a time- and dose-dependent manner and increased ketone body and acetyl-CoA levels in obese mice.

Conclusion: This study reveals a novel cellular mechanism through which myricanol reduces lipid levels via the PPARγ/ACSL1/SCD1 signaling pathway. Myricanol also promotes mitochondrial biogenesis and fatty acid β-oxidation; therefore, it holds great promise as a phytotherapeutic agent for hyperlipidemia.

Keywords: Fatty acid β-oxidation; Hyperlipidemia; Mitochondria biogenesis; Multimodal omics; Myricanol; PPARγ/ACSL1/SCD1 signaling pathway.