Lactucin and lactucopicrin ameliorate obesity in high-fat diet fed mice by promoting white adipose tissue browning through the activation of the AMPK/SIRT1/PGC-1α pathway

Abstract

Lactucin and lactucopicrin are the characteristic lipid-lowering active components found in Cichorium glandulosum. However, their effects and underlying mechanisms in obesity remain unclear. In the present study, C57BL/6J mice were simultaneously subjected to a high-fat diet (HFD) and treated with drugs to investigate the impacts of lactucin and lactucopicrin on HFD-induced obese mice. The results demonstrated that in HFD obese mice, lactucin and lactucopicrin significantly decreased body weight and the weights of adipose tissues, improved serum metabolic parameters, and increased the content of irisin. Regarding the intermediate metabolites of intestinal flora, which are closely associated with white adipose tissue (WAT) browning, lactucin and lactucopicrin treatment led to a reduction in the levels of 12-α-OH/non-12-α-OH bile acids (BAs) and also tended to enhance the levels of short-chain fatty acids (SCFAs). qRT-PCR results indicated that lactucin and lactucopicrin treatment elevated the expression levels of genes related to beige fat markers, thermogenesis, mitochondrial biogenesis, and lipolysis in WAT, as well as those of thermogenesis and lipolysis genes in brown adipose tissue (BAT). Western blot analysis revealed that lactucin and lactucopicrin up-regulated the expression of uncoupling protein 1 (UCP1), the core protein in thermogenesis, in both WAT and BAT. Moreover, they also up-regulated the expression levels of AMP-activated kinase (AMPK), sirtuin 1 (SIRT1), and PPARγ coactivator 1-alpha (PGC-1α), which are key pathway proteins involved in WAT browning. Furthermore, 16S rRNA sequencing results showed that in HFD obese mice, lactucin and lactucopicrin improved the composition and function of the intestinal microbiota. In conclusion, lactucin and lactucopicrin may promote WAT browning by activating the AMPK/SIRT1/PGC-1α pathway, thereby ameliorating obesity in HFD mice.