%0 PDF %T Design and Engineering of New Glucagon Like Peptide-1 Analogues. %A Pamuk Turner, Diren. %8 2017-04-18 %R http://localhost/files/hd76sb041 %X Abstract: ABSTRACT Diabetes mellitus (DM) is a chronic disease that manifests itself with impaired control of blood glucose levels and affects hundreds of millions of individuals worldwide. Among various types of DM, Type II diabetes is the most prevalent. In addition to conventional therapies for diabetes, increasing knowledge of the pathology of the disease has led to new leads for drug targets. Recent studies have revealed that glucagon like peptide (GLP-1), an incretin hormone, has a significant effect in lowering blood glucose levels without serious side effects. A naturally occurring analog of GLP-1, Exenedin-4 (Byetta®), is an approved compound for diabetes. It stimulates insulin secretion in a glucose-dependent manner, and prevents and reverses the destruction of pancreatic β-cells. We have synthesized new analogs of GLP-1 using two different strategies. First, we synthesized a lipidated GLP-1 analog with a flexible linker that can anchor itself in cell membranes. Restriction of GLP-1 to the membrane could increase the effective concentration of the peptide around the GLP-1 receptor (GLP-1R); resulting in a more efficient binding and activation of downstream signals. Our results showed that lipidated construct had the same efficacy as the GLP-1, however it exhibited less potency. Nevertheless this construct includes a number of sites for optimization, which may allow for enhanced activity. We have also investigated longer lasting analogues of GLP-1 by installing unnatural amino acids at the sites that are susceptible to proteolysis. Using β-amino acid substitutions at the hydrolytic site, we intended to overcome protease degradation caused by dipeptidyl peptidase-IV (DPP-IV) enzyme. In addition to using well-known side chains of glutamic acid (Glu) and leucine (Leu), we also introduced a fluorinated amino acid with a hexafluoroleucine side chain. We describe a novel and efficient synthesis of β-hexafluoroleucine along with its use in other systems. Our results indicate that βGLP-1 analogues had similar efficacies as GLP-1, but showed diminished activities. Protease stability assays for β-Glu and β-Leu substituted analogs have revealed that they were more stable than GLP-1, which holds promise for overall insulinotropic effects of these molecules in vivo. Our strategies for designing longer lasting analogues of GLP-1 have been successful to create ligands with similar efficacy for GLP-1R, although stimulation of signal transduction has not been sufficiently achieved. Due to their efficient binding to the cognate receptor, GLP-1 analogues described in this study may still yet exhibit improved glucose lowering properties in vivo. Moreover, using these constructs as models, further modifications can be made to engineer superior GLP-1 analogues.; Thesis (Ph.D.)--Tufts University, 2011.; Submitted to the Dept. of Chemistry.; Advisor: Krishna Kumar.; Committee: Clay Bennett, Elena Rybak-Akimova, and David Kaplan.; Keywords: Chemistry, and Biochemistry. %[ 2022-10-11 %9 Text %~ Tufts Digital Library %W Institution