Isoliquiritigenin Ameliorates High-Fat Diet-Induced Obesity in Mice by Activating Brown Adipose Tissue

Abstract

Brown adipose tissue (BAT) is a critical regulator of non-shivering thermogenesis and energy expenditure, offering significant potential for addressing obesity and associated metabolic disorders. Isoliquiritigenin (ISL), a natural flavonoid, has shown promising therapeutic effects in lipid metabolism-related diseases. This study aimed to explore the effects of ISL on lipid metabolism and obesity using a high-fat-diet (HFD)-induced obesity model in mice. Mice were subjected to an HFD and treated with ISL via gavage. The results demonstrated that ISL treatment significantly reduced HFD-induced weight gain and upregulated the expression of key thermogenic genes, suggesting enhanced BAT activity and thermogenesis. In vitro experiments using C3H10-T1/2 cells further supported these findings, as ISL treatment markedly increased the expression of UCP1 and PPARGC1a, which are critical regulators of thermogenesis. To elucidate the molecular mechanisms underlying ISL's effects, we conducted a transcriptomic analysis of BAT from ISL-treated mice. Pathway enrichment analysis revealed that differentially expressed genes were predominantly associated with metabolic processes, including the tricarboxylic acid (TCA) cycle, oxidative phosphorylation, and fatty acid degradation. These pathways are integral to energy metabolism and thermogenesis, providing mechanistic insights into ISL's anti-obesity effects. Additionally, ISL treatment significantly downregulated the expression of NNAT and SGK1, genes implicated in lipid metabolism and energy homeostasis. These findings suggest that ISL modulates BAT function by regulating the expression of these genes, thereby influencing lipid deposition and thermogenic capacity. In summary, this study suggests that ISL treatment has the potential to mitigate HFD-induced obesity by promoting BAT thermogenesis and modulating lipid metabolism. The molecular mechanisms involve the regulation of key metabolic pathways and genes, such as NNAT and SGK1, highlighting ISL's potential as a therapeutic agent for obesity and related metabolic disorders.

Keywords: brown adipose tissue; high-fat diet; isoliquiritigenin; obesity; thermogenesis.

Figure 1

ISL protects against dietary obesity. (A) Representative images of mice at the end of the treatment. (B) Representative images of the BAT. (C) The body weight (n = 6). (D) Adipose weight-to-body weight ratio (n = 6). ** p < 0.01.

Figure 2

ISL treatment inhibits the expression of adipogenic genes. (A) H&E staining of BAT following ISL treatment (n = 3). (B) The mRNA levels of FABP4, ADIPOQ, PPARG, and C/EBPa in the BAT (n = 3). (C,D) The protein levels of C/EBPa, FASN, PPARG, FABP4, ATGL, and GLUT4 in BAT (n = 3). * p < 0.05, ** p < 0.01.

Figure 3

ISL treatment enhanced the expression of mitochondrial biogenesis and thermogenesis-related genes and proteins. (A) The mRNA levels of UCP1, UCP2, PPARGC1a, and PRDM16 in the BAT (n = 3). (B) Representative UCP1 staining of BAT (n = 3). (C,D) The protein levels of PPARGC1a, UCP1, and CKB in BAT (n = 3). * p < 0.05, ** p < 0.01.

Figure 4

ISL treatment enhanced the expression of thermogenesis-related genes and proteins in C3H10-T1/2 cells. (A) CCK-8 assay was performed to evaluate the effect of different concentrations of ISL on the viability of C3H10-T1/2 cells (n = 6). (B) Oil red O staining. (C) The mRNA levels of UCP1, UCP2, and PPARGC1a (n = 3). (D,E) The protein levels of UCP1 and PPARGC1a (n = 3). * p < 0.05, ** p < 0.01.

Figure 5

ISL treatment alters transcriptome in BAT. (A) Differential gene clustering heat map. (B) Differential comparison volcano map. (C) Differentially expressed mRNA statistics (upregulated and downregulated). (D) GO analysis of DEGs. (E) Enrichment barplot for KEGG pathway analysis. (F) Enrichment barplot for Reactome pathway analysis. (G) GSEA enrichment analysis of citrate cycle (TCA cycle), oxidative phosphorylation, and fatty acid degradation from the control and ISL-treated groups.

Figure 6

Comparative analysis of gene expression levels in BAT: RNA-Seq versus qRT-PCR results (n = 3). (A) NNAT. (B) PBLD1. (C) RARRES2. (D) SGK1. (E) CCDC80. (F) IMPHD1. * p < 0.05, ** p < 0.01.