GIP (human) is a 42-amino acid incretin secreted by K cells of the duodenum and jejunum. GIP (human) can bind to GIPR to activate the AC-cAMP-PKA pathway, promoting insulin secretion in a glucose-dependent manner, while regulating lipid metabolism, bone formation, and inflammatory responses. GIP (human) can be used in research related to type 2 diabetes, obesity, and metabolic syndrome[1-4].
In vitro, mature adipocytes differentiated from human subcutaneous preadipocytes were treated with GIP (0.1-10nM) for 1-24h, which induced IL-6, IL-1β, and IL-1Ra mRNA expression[5]. Human subcutaneous preadipocyte-derived mature adipocytes treated with GIP (1nM) for 1-6h showed upregulation of calcitonin gene-related peptide-I (CGRP-I) mRNA expression and increased CGRP-I protein secretion[6]. HEK293T cells transfected with human GIP receptor were treated with GIP (0.01-1000nM) for 0-12h, resulting in a dose-dependent increase in intracellular cAMP levels[7].
In vivo, male NIH Swiss mice aged 12-14 weeks received a single intraperitoneal co-injection of glucose and GIP (50nmol/kg), GIP significantly reduced individual blood glucose values and blood glucose AUC[8].
References:
[1] Baggio LL, Drucker DJ. Biology of incretins: GLP-1 and GIP. Gastroenterology. 2007 May;132(6):2131-57.
[2] Meier JJ, Nauck MA, Schmidt WE, et al. Gastric inhibitory polypeptide: the neglected incretin revisited. Regul Pept. 2002 Jul 15;107(1-3):1-13.
[3] Miyachi A, Murase T, Yamada Y, et al. Quantitative analytical method for determining the levels of gastric inhibitory polypeptides GIP1-42 and GIP3-42 in human plasma using LC-MS/MS/MS. J Proteome Res. 2013 Jun 7;12(6):2690-9.
[4] Gabe MBN, van der Velden WJC, Smit FX, et al. Molecular interactions of full-length and truncated GIP peptides with the GIP receptor - A comprehensive review. Peptides. 2020 Mar;125:170224.
[5] Timper K, Grisouard J, Sauter NS, et al. Glucose-dependent insulinotropic polypeptide induces cytokine expression, lipolysis and insulin resistance in human adipocytes. Am J Physiol Endocrinol Metab. 2013;304:E1-E13.
[6] Timper K, Grisouard J, Radimerski T, et al. Glucose-dependent insulinotropic polypeptide(GIP) induces calcitonin gene-related peptide-I and procalcitonin production in human adipocytes. J Clin Endocrinol Metab. 2011 Feb;96(2):E297-E303.
[7] Chang CL, Cai JJ, Lo C, et al. Adaptive selection of an incretin gene in Eurasian populations. Genome Res. 2011 Jan;21(1):21-32.
[8] Perry RA, Craig SL, Ng MT, et al. Characterisation of glucose-dependent insulinotropic polypeptide receptor antagonists in rodent pancreatic beta cells and mice. Clin Med Insights Endocrinol Diabetes. 2019;12:1-9.