The antidiabetic effect of safflower yellow by regulating the GOAT/ghrelin/GHS-R1a/cAMP/TRPM2 pathway

Safflower yellow (SY), derived from Carthamus tinctorius L., is a valuable natural edible pigment that exhibits anti-type 2 diabetes mellitus (T2DM) efficacy; however, its mechanism of action is unclear, which hinders its effective use. In this study, we examined the impact of SY on glucose metabolism and insulin secretion both in vivo and in vitro and elucidated the possible underlying mechanism. First, molecular docking demonstrated a strong binding affinity between SY and ghrelin O-acyltransferase (GOAT) protein, which was validated by a cell heat transfer assay (CETSA) and drug affinity response target stability (DARTS) in MIN6 cells. In MIN6 cells, SY increased insulin secretion and showed time- and dose-dependent inhibition of GOAT expression and acyl ghrelin (AG) secretion without affecting the overall levels of ghrelin. Furthermore, ELISA revealed that SY enhanced high glucose (HG)-induced insulin secretion, and immunofluorescence revealed the co-localization of GOAT and ghrelin in MIN6 cells, which was suppressed by SY treatment. The mechanism analysis by Western blot demonstrated that SY downregulated the protein levels of GOAT and GHS-R1a in MIN6 cells while increasing HG-stimulated cAMP and activation of transient receptor potential melastatin 2 (TRPM2). In in vivo experiments, the intraperitoneal injection of SY significantly improved pathological damage to the pancreas, glucose tolerance, and insulin resistance in a mouse model of high-fat diet (HFD)/streptozotocin (STZ)-induced T2DM in a dose-dependent manner. SY enhanced insulin secretion by inhibiting the GOAT/ghrelin system in vivo. In conclusion, we demonstrated that SY exhibits an observable protective effect on diabetes through the GOAT/ghrelin/GHS-R1a/cAMP/TRPM2 pathway. Our findings provide a basis for further investigation of the hypoglycemic mechanism of SY and its potential for further development and utilization.