A Novel Insulin Receptor-Binding Protein from Momordica charantia Enhances Glucose Uptake and Glucose Clearance in Vitro and in Vivo through Triggering Insulin Receptor Signaling Pathway

作者：Lo Hsin Yi; Ho Tin Yun; Li Chia Cheng; Chen Jaw Chyun; Liu Jau Jin; Hsiang Chien Yun^*

来源：Journal of Agricultural and Food Chemistry, 2014, 62(36): 8952-8961.

DOI：10.1021/jf5002099

• Momordica charantia
• diabetes
• insulin receptor-binding protein
• glucose homeostasis

Diabetes, a common metabolic disorder, is characterized by hyperglycemia. Insulin is the principal mediator of glucose homeostasis. In a previous study, we identified a trypsin inhibitor, named Momordica charantia insulin receptor (IR)-binding protein (mcIRBP) in this study, that might interact with IR. The physical and functional interactions between mcIRBP and IR were clearly analyzed in the present study. Photo-cross-linking coupled with mass spectrometry showed that three regions (17-21, 34-40, and 59-66 residues) located on mcIRBP physically interacted with leucine-rich repeat domain and cysteine-rich region of IR. IR-binding assay showed that the binding behavior of mcIRBP and insulin displayed a cooperative manner. After binding to IR, mcIRBP activated the kinase activity of IR by (5.87 +/- 0.45)-fold, increased the amount of phospho-IR protein by (1.31 +/- 0.03)-fold, affected phosphoinositide-3-kinase/Akt pathways, and consequently stimulated the uptake of glucose in 3T3-L1 cells by (1.36 +/- 0.12)-fold. Intraperitoneal injection of 2.5 nmol/kg mcIRBP significantly decreased the blood glucose levels by 20.9 +/- 3.2% and 10.8 +/- 3.6% in normal and diabetic mice, respectively. Microarray analysis showed that mcIRBP affected genes involved in insulin signaling transduction pathway in mice. In conclusion, our findings suggest that mcIRBP is a novel IRBP that binds to sites different from the insulin-binding sites on IR and stimulates both the glucose uptake in cells and the glucose clearance in mice.

• 出版日期2014-9-10
• 单位中国医科大学