Mechanism of Huanglian Zhimu Decoction in improving hepatic lipid deposition in type 2 diabetes based on lipidomics and transcriptomics.

ETHNOPHARMACOLOGICAL SIGNIFICANCE

Huanglian Zhimu decoction (HLZMD), a classical formulation in traditional Chinese medicine, has historically been utilized in the management of diabetes. However, its therapeutic efficacy and the underlying mechanisms in the context of T2DM, particularly in relation to hepatic lipid dysregulation, have yet to be systematically investigated.

AIM OF THE STUDY

To explore the potential therapeutic effects and molecular mechanisms of HLZMD on T2DM.

MATERIALS AND METHODS

Initially, a T2DM model was established in spontaneously diabetic Goto-Kakizaki (GK) rats through high-fat diet induction. To elucidate the molecular mechanisms underlying the therapeutic effects of HLZMD, an integrative approach combining hepatic lipidomic profiling and transcriptomic sequencing was employed to identify HLZMD-responsive pathways. Furthermore, the expression levels of key proteins within the PDE4D/cAMP/PKA signaling pathway were quantified via western blotting in both rat liver tissues and palmitic acid-stimulated HepG2 cells. To validate the pathway specificity, pharmacological inhibition experiments were performed using roflumilast, a selective PDE4D antagonist. Lastly, the chemical composition of HLZMD was characterized through ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS), and molecular docking analysis was conducted to predict potential active components interacting with PDE4D.

RESULTS

In vivo experiments demonstrated that HLZMD significantly ameliorated fasting blood glucose levels and hepatic steatosis in T2DM rats. Lipidomic analysis further revealed that HLZMD effectively restored the homeostasis of diacylglycerols (DG), triglycerides (TG), sterols (ST), sphingolipids (SP), and glycerophospholipids (GP) in the liver. Integrative analyses incorporating lipidomics, transcriptomics, and western blotting suggested that HLZMD-mediated hepatic lipid modulation may be attributed to the regulation of the PDE4D/cAMP/PKA signaling pathway. In vitro, HLZMD treatment resulted in a significant reduction in extracellular glucose concentrations as well as intracellular TC and TG levels. Concurrently, HLZMD markedly upregulated the expression of PDE4D, SIRT1, and PPARγ proteins while downregulating the expression of cAMP, phosphorylated PKA (p-PKA/PKA), and phosphorylated hormone-sensitive lipase (p-HSL/HSL). Notably, pharmacological inhibition with roflumilast, a selective PDE4D antagonist, partially reversed the HLZMD-induced reduction in lipid deposition, supporting the specificity of this pathway in mediating HLZMD's effects. Furthermore, UPLC-Q-TOF-MS identified 80 chemical constituents in HLZMD. Molecular docking analysis predicted that 21 of these compounds may exhibit direct binding affinity for PDE4D, potentially modulating the cAMP/PKA signaling cascade.

CONCLUSION

This study is the first to provide evidence that HLZMD exerts its pharmacological effects through multi-component interactions with PDE4D, thereby modulating the cAMP/PKA signaling pathway. This regulatory mechanism contributes to the reduction of hepatic lipid accumulation, attenuation of hepatic insulin resistance, and restoration of glucose and lipid metabolic homeostasis.