Abstract
AIMS/HYPOTHESIS: Glucose-dependent insulinotropic polypeptide (GIP) and xenin, regulatory gut hormones secreted from enteroendocrine K cells, exert important effects on metabolism. In addition, xenin potentiates the biological actions of GIP. The present study assessed the actions and therapeutic utility of a (DAla2)GIP/xenin-8-Gln hybrid peptide, in comparison with the parent peptides (DAla2)GIP and xenin-8-Gln.METHODS: Following confirmation of enzymatic stability, insulin secretory activity of (DAla2)GIP/xenin-8-Gln was assessed in BRIN-BD11 beta cells. Acute and persistent glucose-lowering and insulin-releasing effects were then examined in vivo. Finally, the metabolic benefits of twice daily injection of (DAla2)GIP/xenin-8-Gln was determined in high-fat-fed mice.RESULTS: All peptides significantly (p <0.05 to p <0.001) enhanced in vitro insulin secretion from pancreatic clonal BRIN-BD11 cells, with xenin (and particularly GIP)-related signalling pathways, being important for this action. Administration of (DAla2)GIP or (DAla2)GIP/xenin-8-Gln in combination with glucose significantly (p <0.05) lowered blood glucose and increased plasma insulin in mice, with a protracted response of up to 4 h. All treatments elicited appetite-suppressive effects (p <0.05), particularly (DAla2)GIP/xenin-8-Gln and xenin-8-Gln at elevated doses of 250 nmol/kg. Twice-daily administration of (DAla2)GIP/xenin-8-Gln or (DAla2)GIP for 21 days to high-fat-fed mice returned circulating blood glucose to lean control levels. In addition, (DAla2)GIP/xenin-8-Gln treatment significantly (p <0.05) reduced glycaemic levels during a 24 h glucose profile assessment. Neither of the treatment regimens had an effect on body weight, energy intake or circulating insulin concentrations. However, insulin sensitivity was significantly (p <0.001) improved by both treatments. Interestingly, GIP-mediated glucose-lowering (p <0.05) and insulin-releasing (p <0.05 to p <0.01) effects were substantially improved by (DAla2)GIP and (DAla2)GIP/xenin-8-Gln treatment. Pancreatic islet and beta cell area (p <0.001), as well as pancreatic insulin content (p <0.05), were augmented in (DAla2)GIP/xenin-8-Gln-treated mice, related to enhanced proliferation and decreased apoptosis of beta cells, whereas (DAla2)GIP evoked increases (p <0.05 to p <0.01) in islet number.CONCLUSIONS/INTERPRETATION: These studies highlight the clear potential of GIP/xenin hybrids for the treatment of type 2 diabetes.
Original language | English |
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Pages (from-to) | 541-552 |
Number of pages | 12 |
Journal | Diabetologia |
Volume | 60 |
Issue number | 3 |
Early online date | 21 Dec 2016 |
DOIs | |
Publication status | Published (in print/issue) - 31 Mar 2017 |
Keywords
- GIP
- Glucose
- Glucose homeostasis
- Glucose-dependent insulinotropic polypeptide
- High-fat feeding
- Hybrid
- Insulin secretion
- Xenin
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Peter Flatt
- School of Biomedical Sciences - Professor of Biological & Biomedical Sciences
- Faculty Of Life & Health Sciences - Full Professor
Person: Academic
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Victor Gault
- School of Biomedical Sciences - Professor of Experimental Medicine
- Faculty Of Life & Health Sciences - Associate Dean (Research and Innovation)
Person: Academic