Glucagon-like peptide 1 (GLP-1) is an incretin hormone produced in gut L-cells, which regulates postprandial glucose-dependent insulin secretion, also known as the incretin effect. GLP-1 secretion may be reduced in type 2 diabetes mellitus, impacting on glycaemic regulation. Thus, methods to enhance endogenous GLP-1 secretion by use of natural GLP-1 secretagogues may improve glucose control in diabetes. Gypenosides (GYP) extracted from the plant Gynostemma Pentaphyllum (Jiaogulan) are known for their glucose-lowering effects both in vitro and in vivo , although their effect on GLP-1 secretion is unknown. Our results showed that GYP enhanced cell viability and significantly upregulated antioxidant gene Nrf2, Cat and Ho-1 expression. GYP did not affect glucokinase expression but downregulated proglucagon gene expression over 24h, although, cellular GLP-1 content was unchanged. Prohormone convertase 1 (Pcsk1) gene expression was unchanged by GYP over 24h, although protein levels were significantly downregulated, while prohormone convertase 2 (Pcsk2) mRNA and protein levels were significantly upregulated. Acute exposure to gypenosides enhanced calcium uptake and GLP-1 release from GLUTag cells both at low and high glucose concentrations. These results suggest that anti-diabetic properties of gypenosides are partly linked to their ability to stimulate GLP-1 secretion. Gypenosides enhance antioxidant gene expression and may protect L-cells from excess oxidative stress. ### Competing Interest Statement The authors have declared no competing interest. * GLP-1 : Glucagon-like peptide-1 GYP : Gypenosides T2DM : Type 2 diabetes mellitus Ncx : Sodium/Calcium exchange channel Sglt1 : Sodium/glucose cotransporter 1 Gcg : Glucagon Gck : Glucokinase Pc1 : Prohormone convertase-1 Pc2 : Prohormone convertase-2 Nrf2 : Nuclear factor erythroid 2-related factor 2 NFkb1 : Nuclear factor Kappa b1 Cat : Catalase Ho-1 : Heme oxygenase-1 MTT : 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide
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