Deoxycalyxin A exerts hypoglycemic effects through activating TGR5-induced GLP-1 secretion via TGR5/PKA/MEK/ERK pathway.

Abstract

Type 2 diabetes mellitus (T2DM) is a heterogeneous metabolic disorder characterized by insulin resistance and progressive β cell dysfunction. Deoxycalyxin A (DCA), a unique diarylheptanoid-chalcone hybrid isolated from Alpinia katsumadai, was identified as a novel stimulator of GLP 1 secretion in both STC-1 (EC50: 10.7 μM) and NCI-H716 (EC50: 13.4 μM) cells. Oral administration of DCA (40 and 80 mg/kg) in db/db mice significantly reduced fasting blood glucose, ameliorated glucose intolerance and insulin resistance by enhancing endogenous GLP-1 secretion, and lowered the total serum cholesterol levels. Mechanistic study demonstrated that DCA identify the TGR5 receptor, which induces a significant increase in intracellular cyclic AMP (cAMP) levels, which activates PKA with subsequent sequential phosphorylation of MEK1/2 and ERK activation, ultimately enhancing GLP-1 secretion. Our findings identify DCA as a novel TGR5 agonist to stimulate GLP-1 secretion via the TGR5/PKA/MEK/ERK pathway, which has the potential to be developed as a promising antidiabetic lead with a distinct mechanism of action.