Comparison of incretin immunoassays with or without plasma extraction: Incretin secretion in Japanese patients with type 2 diabetes
Article first published online: 4 JUL 2011
© 2011 Asian Association for the Study of Diabetes and Blackwell Publishing Asia Pty Ltd
Journal of Diabetes Investigation
Volume 3, Issue 1, pages 70–79, February 2012
Total views since publication: 59
How to Cite
Yabe, D., Watanabe, K., Sugawara, K., Kuwata, H., Kitamoto, Y., Sugizaki, K., Fujiwara, S., Hishizawa, M., Hyo, T., Kuwabara, K., Yokota, K., Iwasaki, M., Kitatani, N., Kurose, T., Inagaki, N. and Seino, Y. (2012), Comparison of incretin immunoassays with or without plasma extraction: Incretin secretion in Japanese patients with type 2 diabetes. Journal of Diabetes Investigation, 3: 70–79. doi: 10.1111/j.2040-1124.2011.00141.x
- Issue published online: 20 FEB 2012
- Article first published online: 4 JUL 2011
- Received 23 March 2011; revised 12 May 2011; accepted 13 May 2011
Aims/Introduction: The effectiveness of incretin-based therapies in Asian type 2 diabetes requires investigation of the secretion and metabolism of glucose-dependent insulinotropic polypepide (GIP) and glucagon-like peptide 1 (GLP-1). Plasma extractions have been suggested to reduce variability in intact GLP-1 levels among individuals by removing interference that affects immunoassays, although no direct demonstration of this method has been reported. We have evaluated the effects of ethanol and solid-phase extractions on incretin immunoassays. We determined incretin levels during meal tolerance tests in Japanese patients with type 2 diabetes and characterized predictors for incretin secretion.
Materials and Methods: Japanese patients with type 2 diabetes (23 anti-diabetic drug-naïve and 18 treated with sulfonylurea [SU] alone) were subjected to meal tolerance tests, and incretin levels were determined by immunoassays with or without extraction.
Results: Intact GLP-1 levels determined by an intact GLP-1 immunoassay with ethanol and solid-phase extractions were lower than those determined without extraction. Intact GLP-1 levels determined by the extractions were highly correlated with each other, much more so than the levels with and without extraction. Total GLP-1 was unaffected by extractions, showing that extractions remove interference only in the case of intact GLP-1. Incretin secretion after meal ingestion was similar between drug-naïve and SU-treated patients. Fasting and postprandial GLP-1 levels were correlated positively with fasting free fatty acids and negatively with dipeptidyl peptidase-4 activity.
Conclusions: Ethanol and solid-phase extractions remove interference for intact GLP-1 immunoassay. SU showed little effect on incretin secretion. GLP-1 and GIP secretion were predicted by different factors. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00141.x, 2012)