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The mammalian target of rapamycin (mTOR)-sterol regulatory element-binding proteins (SREBPs) signaling promotes lipogenesis. However, mTOR inhibitors also displayed a significant side effect of hyperlipidemia. Thus, it is essential to develop mTOR-specific inhibitors to inhibit lipogenesis. Here, we screened the endogenous inhibitors of mTOR, and identified that FKBP38 as a vital regulator of lipid metabolism. FKBP38 decreased the lipid content in vitro and in vivo via suppression of the mTOR/P70S6K/SREBPs pathway. 3,5,6,7,8,3ʹ,4ʹ-Heptamethoxyflavone (HMF), a citrus flavonoid, was found to target FKBP38 to suppress the mTOR/P70S6K/SREBPs pathway, reduce lipid level, and potently ameliorate hyperlipidemia and insulin resistance in high fat diet (HFD)-fed mice. Our findings suggest that pharmacological intervention by targeting FKBP38 to suppress mTOR/P70S6K/SREBPs pathway is a potential therapeutic strategy for hyperlipidemia, and HMF could be a leading compound for development of anti-hyperlipidemia drugs., Graphical abstract FKBP38 suppresses mTOR/P70S6K/SREBPs signaling and lipid level. HMF targets FKBP38 to ameliorate HFD-induced hyperlipidemia via suppressing mTOR/P70S6K/SREBPs pathway.Image 1

This study aims to investigate whether magnolol (MG), a natural neolignane compound, can prevent AD induced by beta-amyloid (Aβ) and the possible mechanisms involved. MG dose-dependently reduces Aβ deposition, toxicity and memory impairment caused by Aβ in transgenic C. elegans. More importantly, these effects are reversed by GW9662, a selective peroxisome proliferator-activated receptor-γ (PPAR-γ) antagonist. MG is more effective in enhancing PPAR-γ luciferase levels than honokiol (HK). Meanwhile, MG has the potential to bind with the ligand binding domain of PPAR-γ (PPAR-γ-LBD). As expected, MG inhibited the luciferase activity of NF-κB and its target genes of inflammatory cytokines, and this effect was blocked by GW9662. The luciferase activity of Nrf2-ARE expression can be activated by MG and decreased Aβ-induced reactive oxygen species (ROS). The target gene LXR of PPAR-γ is activated by MG, which upregulates ApoE and promotes microglia phagocytosis and the degradation of Aβ, and these effects were also reversed by GW9662. In summary, MG can attenuate Aβ-induced AD and the underlying mechanism is the reduction of inflammation and promotion of phagocytosis and degradation of Aβ, which is dependent on PPAR-γ.

Carnosic acid (CA), from rosemary, a food additive used for long history in western countries, reduces triglyceride, cholesterol and glucose levels. However, the detailed mechanisms contributing to these effects remain unclear. Here we investigate the potential mechanism of how CA regulates lipid metabolism. Using reporter cell lines, we found CA inhibited SREBPs activity, using radioactive isotope labeling, we found CA impeded de novo lipid synthesis, using gene silencing and inhibitors, we investigated the possible mechanism of how CA affects SREBPs stability. In hepatocytes, CA reduces the nuclear abundance of SREBPs and downregulates their target genes, thereby inhibiting the de novo biosynthesis of both fatty acids and cholesterol. Furthermore, in western type diet-induced obese mice, CA alleviates hyperlipidemia, fatty liver and insulin resistance by suppressing SREBPs target gene expression in the liver. Our results indicate that CA promotes the degradation of mature form of SREBPs via the 26S proteasome. To our knowledge, this study is the first to describe a small molecule that strongly reduces mature SREBPs.