Ginsenoside Rb1 and berberine synergistically protect against type 2 diabetes mellitus via GDF15/HAMP pathway throughout the liver lobules: Insights from spatial transcriptomics analysis

Type 2 diabetes mellitus (T2DM) is a significant public health issue with high morbidity and mortality. Ginsenoside Rb1 (Rb1) and berberine (BBR), the main bioactive compounds of Panax ginseng and Coptis chinensis, respectively, are known for their hypoglycemic effects. Nevertheless, the synergistic effects and underlying mechanism of Rb1 and BBR on T2DM remain unclear. In this study, we utilized a leptin receptor-deficient (db/db) mouse model to investigate the protective effects of their combination treatment. Our findings demonstrated that the combined use of Rb1 and BBR at a 1:4 ratio had more pronounced effects than the first-line anti-diabetic drug metformin on reducing the weight ratio of white adipose tissue, ameliorating insulin resistance, and improving glucose and lipid metabolism. Using spatial transcriptomics, we revealed that metformin treatment improved gluconeogenesis and lipogenesis only in the periportal zone, while the combination treatment induced improvements throughout the liver lobule, with distinct key targets across different zones, thus underscoring a more comprehensive modulation of hepatic metabolism. This may be the key reason why this combination therapy demonstrated superior protective effects against T2DM. Additionally, the reversed expression of the key callback gene hepcidin (HAMP) and its regulator growth differentiation factor 15 (GDF15) following the combination therapy across all zones, along with validation experiments, further suggested that GDF15/HAMP pathway might be a key mechanism underlying the beneficial effects of Rb1 and BBR against T2DM. This study also indicates a path toward innovative drug cocktails for treating T2DM, offering a holistic approach to regulate the entire liver lobule metabolism.