{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/315995"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/315995","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"Characterisation and pharmacological regulation of GLP-1-mediated glucose homeostasis","abstract":"Type 2 diabetes mellitus (T2DM) is characterised by the hormonal imbalance of insulin and glucagon, leading to dysfunctional glucose homeostasis. Glucagon-like peptide 1 (GLP-1), which is an incretin hormone, activates the predominantly Gαs-coupled glucagon-like peptide 1 receptor (GLP-1R), which is a class B G protein-coupled receptor (GPCR), to mediate glucose homeostasis. It does so by promoting glucose stimulated insulin secretion (GSIS) in the pancreatic β cells and inhibiting glucagon secretion in the pancreatic α cells. Given its proven clinical efficacy in reducing long term blood glucose level, GLP-1-based treatments, such as exenatide and liraglutide, have been widely used in T2DM patients. However, in contrast to the well-studied phenomenon of how GLP-1 enhances GSIS, the mechanism of how GLP-1 regulates glucagon secretion is still unclear. Therefore, the aim of this work is to shed new lights on how GLP-1 mediates its glucagonostatic action. To do so, the signalling properties of GLP-1 and its closely-related peptide hormones, namely oxyntomodulin (OXM), glucagon (GCG), glucose-dependent insulinotropic polypeptide (GIP), and its metabolite, GLP-1(9-36)NH2, were examined in recombinant cell lines and rodent clonal α and β cell lines using cAMP functional assaying technique. It was demonstrated that these glucagon-like peptides, including GLP-1(9-36)NH2 yet except GIP, can activate both GLP-1R and glucagon receptor (GCGR), which is struc- turally analogous to GLP-1R. Furthermore, GLP-1R, despite its very low expression in the mouse αTC1.6 cell line detected through semi-quantitative RT-PCR studies, is found to play a critical role in directly inhibiting glucagon secretion upon GLP-1 activation through performing glucagon secretion antagonism studies. More importantly, the physiologically abundant GLP-1 metabolite is discovered to play a glucagonostatic role in the mouse glucagonoma cell line via the direct actions of GLP-1R and GCGR, an observation that has not yet been documented. Therefore, this thesis provides evidence of how GLP-1 and its metabolite are actively involved in their glucagonostatic actions via direct activations of GLP-1R and GCGR. Another aim of this work is to identify viable pharmacological regulator of GLP-1- mediated glucose homeostasis through the action of positive allosteric modulator (PAM). Here, compound 249, which was identified previously as a small molecule GLP-1R PAM, was further pharmacologically validated using various signal transduction assaying techniques in recombinant cell lines. It was also demonstrated that compound 249 works independent of the cysteine-347 residue on the GLP-1R, an amino acid residue which has been previously shown to be instrumental for the actions of another GLP-1R agonist-PAMs. More importantly, compound 249 demonstrates robust potentiation of GLP-1 and OXM-augmented GSIS in the rat INS-1 832/3 insulinoma cell line and ex vivo isolated mouse islets, substantiating the potential of compound 249 to be further developed as a novel T2DM treatment. Overall this thesis presents new evidence on the direct involvement of GLP-1R on GLP-1-regulated glucagon secretion in the pancreatic α cells and illustrates compound 249 as a PAM to promote GLP-1 mediated GSIS. The findings in this thesis will be used for future design of safer and more efficacious T2DM treatments.","abstract_html":"Type 2 diabetes mellitus (T2DM) is characterised by the hormonal imbalance of insulin and glucagon, leading to dysfunctional glucose homeostasis. Glucagon-like peptide 1 (GLP-1), which is an incretin hormone, activates the predominantly Gαs-coupled glucagon-like peptide 1 receptor (GLP-1R), which is a class B G protein-coupled receptor (GPCR), to mediate glucose homeostasis. It does so by promoting glucose stimulated insulin secretion (GSIS) in the pancreatic β cells and inhibiting glucagon secretion in the pancreatic α cells. Given its proven clinical efficacy in reducing long term blood glucose level, GLP-1-based treatments, such as exenatide and liraglutide, have been widely used in T2DM patients. However, in contrast to the well-studied phenomenon of how GLP-1 enhances GSIS, the mechanism of how GLP-1 regulates glucagon secretion is still unclear. Therefore, the aim of this work is to shed new lights on how GLP-1 mediates its glucagonostatic action. To do so, the signalling properties of GLP-1 and its closely-related peptide hormones, namely oxyntomodulin (OXM), glucagon (GCG), glucose-dependent insulinotropic polypeptide (GIP), and its metabolite, GLP-1(9-36)NH2, were examined in recombinant cell lines and rodent clonal α and β cell lines using cAMP functional assaying technique. It was demonstrated that these glucagon-like peptides, including GLP-1(9-36)NH2 yet except GIP, can activate both GLP-1R and glucagon receptor (GCGR), which is struc- turally analogous to GLP-1R. Furthermore, GLP-1R, despite its very low expression in the mouse αTC1.6 cell line detected through semi-quantitative RT-PCR studies, is found to play a critical role in directly inhibiting glucagon secretion upon GLP-1 activation through performing glucagon secretion antagonism studies. More importantly, the physiologically abundant GLP-1 metabolite is discovered to play a glucagonostatic role in the mouse glucagonoma cell line via the direct actions of GLP-1R and GCGR, an observation that has not yet been documented. Therefore, this thesis provides evidence of how GLP-1 and its metabolite are actively involved in their glucagonostatic actions via direct activations of GLP-1R and GCGR. Another aim of this work is to identify viable pharmacological regulator of GLP-1- mediated glucose homeostasis through the action of positive allosteric modulator (PAM). Here, compound 249, which was identified previously as a small molecule GLP-1R PAM, was further pharmacologically validated using various signal transduction assaying techniques in recombinant cell lines. It was also demonstrated that compound 249 works independent of the cysteine-347 residue on the GLP-1R, an amino acid residue which has been previously shown to be instrumental for the actions of another GLP-1R agonist-PAMs. More importantly, compound 249 demonstrates robust potentiation of GLP-1 and OXM-augmented GSIS in the rat INS-1 832/3 insulinoma cell line and ex vivo isolated mouse islets, substantiating the potential of compound 249 to be further developed as a novel T2DM treatment. Overall this thesis presents new evidence on the direct involvement of GLP-1R on GLP-1-regulated glucagon secretion in the pancreatic α cells and illustrates compound 249 as a PAM to promote GLP-1 mediated GSIS. The findings in this thesis will be used for future design of safer and more efficacious T2DM treatments.","abstract_has_math":false,"creators":["Yeung, Ho Yan"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Ladds, Graham"],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-09-25","date_published":"2020-09-25","updated_at":"2026-07-22T22:24:21Z","subjects":["G protein-coupled receptors","Incretins","Drug discovery","Type 2 diabetes mellitus","GLP-1"],"languages":["eng"],"rights":[],"rights_urls":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/fccd6861-7d00-4f1c-b6a6-047272bd6abf/download","https://www.rioxx.net/licenses/all-rights-reserved/"],"identifier_entries":[{"key":"dc:creator.authoridentifier","label":"Author Identifier","values":["0000000173209612"],"render_values":[{"text":"0000-0001-7320-9612","href":"https://orcid.org/0000-0001-7320-9612","code":true}]}]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.63107","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Ladds, Graham"]},{"key":"dc:creator","label":"Author","values":["Yeung, Ho Yan"]},{"key":"dc:creator.authoridentifier","label":"Author Identifier","values":["0000000173209612"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2020-09-25"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/315995"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["G protein-coupled receptors","Incretins","Drug discovery","Type 2 diabetes mellitus","GLP-1"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/fccd6861-7d00-4f1c-b6a6-047272bd6abf/download","https://www.rioxx.net/licenses/all-rights-reserved/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["10.17863/CAM.63107"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/07c1887a-c4e2-40a4-8535-3234a577b76a/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Type 2 diabetes mellitus (T2DM) is characterised by the hormonal imbalance of insulin and glucagon, leading to dysfunctional glucose homeostasis. Glucagon-like peptide 1 (GLP-1), which is an incretin hormone, activates the predominantly Gαs-coupled glucagon-like peptide 1 receptor (GLP-1R), which is a class B G protein-coupled receptor (GPCR), to mediate glucose homeostasis. It does so by promoting glucose stimulated insulin secretion (GSIS) in the pancreatic β cells and inhibiting glucagon secretion in the pancreatic α cells. Given its proven clinical efficacy in reducing long term blood glucose level, GLP-1-based treatments, such as exenatide and liraglutide, have been widely used in T2DM patients. However, in contrast to the well-studied phenomenon of how GLP-1 enhances GSIS, the mechanism of how GLP-1 regulates glucagon secretion is still unclear. Therefore, the aim of this work is to shed new lights on how GLP-1 mediates its glucagonostatic action. To do so, the signalling properties of GLP-1 and its closely-related peptide hormones, namely oxyntomodulin (OXM), glucagon (GCG), glucose-dependent insulinotropic polypeptide (GIP), and its metabolite, GLP-1(9-36)NH2, were examined in recombinant cell lines and rodent clonal α and β cell lines using cAMP functional assaying technique. It was demonstrated that these glucagon-like peptides, including GLP-1(9-36)NH2 yet except GIP, can activate both GLP-1R and glucagon receptor (GCGR), which is struc- turally analogous to GLP-1R. Furthermore, GLP-1R, despite its very low expression in the mouse αTC1.6 cell line detected through semi-quantitative RT-PCR studies, is found to play a critical role in directly inhibiting glucagon secretion upon GLP-1 activation through performing glucagon secretion antagonism studies. More importantly, the physiologically abundant GLP-1 metabolite is discovered to play a glucagonostatic role in the mouse glucagonoma cell line via the direct actions of GLP-1R and GCGR, an observation that has not yet been documented. Therefore, this thesis provides evidence of how GLP-1 and its metabolite are actively involved in their glucagonostatic actions via direct activations of GLP-1R and GCGR. Another aim of this work is to identify viable pharmacological regulator of GLP-1- mediated glucose homeostasis through the action of positive allosteric modulator (PAM). Here, compound 249, which was identified previously as a small molecule GLP-1R PAM, was further pharmacologically validated using various signal transduction assaying techniques in recombinant cell lines. It was also demonstrated that compound 249 works independent of the cysteine-347 residue on the GLP-1R, an amino acid residue which has been previously shown to be instrumental for the actions of another GLP-1R agonist-PAMs. More importantly, compound 249 demonstrates robust potentiation of GLP-1 and OXM-augmented GSIS in the rat INS-1 832/3 insulinoma cell line and ex vivo isolated mouse islets, substantiating the potential of compound 249 to be further developed as a novel T2DM treatment. Overall this thesis presents new evidence on the direct involvement of GLP-1R on GLP-1-regulated glucagon secretion in the pancreatic α cells and illustrates compound 249 as a PAM to promote GLP-1 mediated GSIS. The findings in this thesis will be used for future design of safer and more efficacious T2DM treatments."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["54ca21171aa2248fc775d14478d538cb","353adac0d1ebdfd65ab16480263c3c87"]},{"key":"dc:title","label":"Title","values":["Characterisation and pharmacological regulation of GLP-1-mediated glucose homeostasis"]}]}],"canonical_facts":{"dc:contributor.advisor":["Ladds, Graham"],"dc:creator":["Yeung, Ho Yan"],"dc:creator.authoridentifier":["0000000173209612"],"dc:date.issued":["2020-09-25"],"dc:description.abstract":["Type 2 diabetes mellitus (T2DM) is characterised by the hormonal imbalance of insulin and glucagon, leading to dysfunctional glucose homeostasis. Glucagon-like peptide 1 (GLP-1), which is an incretin hormone, activates the predominantly Gαs-coupled glucagon-like peptide 1 receptor (GLP-1R), which is a class B G protein-coupled receptor (GPCR), to mediate glucose homeostasis. It does so by promoting glucose stimulated insulin secretion (GSIS) in the pancreatic β cells and inhibiting glucagon secretion in the pancreatic α cells. Given its proven clinical efficacy in reducing long term blood glucose level, GLP-1-based treatments, such as exenatide and liraglutide, have been widely used in T2DM patients. However, in contrast to the well-studied phenomenon of how GLP-1 enhances GSIS, the mechanism of how GLP-1 regulates glucagon secretion is still unclear. Therefore, the aim of this work is to shed new lights on how GLP-1 mediates its glucagonostatic action. To do so, the signalling properties of GLP-1 and its closely-related peptide hormones, namely oxyntomodulin (OXM), glucagon (GCG), glucose-dependent insulinotropic polypeptide (GIP), and its metabolite, GLP-1(9-36)NH2, were examined in recombinant cell lines and rodent clonal α and β cell lines using cAMP functional assaying technique. It was demonstrated that these glucagon-like peptides, including GLP-1(9-36)NH2 yet except GIP, can activate both GLP-1R and glucagon receptor (GCGR), which is struc- turally analogous to GLP-1R. Furthermore, GLP-1R, despite its very low expression in the mouse αTC1.6 cell line detected through semi-quantitative RT-PCR studies, is found to play a critical role in directly inhibiting glucagon secretion upon GLP-1 activation through performing glucagon secretion antagonism studies. More importantly, the physiologically abundant GLP-1 metabolite is discovered to play a glucagonostatic role in the mouse glucagonoma cell line via the direct actions of GLP-1R and GCGR, an observation that has not yet been documented. Therefore, this thesis provides evidence of how GLP-1 and its metabolite are actively involved in their glucagonostatic actions via direct activations of GLP-1R and GCGR. Another aim of this work is to identify viable pharmacological regulator of GLP-1- mediated glucose homeostasis through the action of positive allosteric modulator (PAM). Here, compound 249, which was identified previously as a small molecule GLP-1R PAM, was further pharmacologically validated using various signal transduction assaying techniques in recombinant cell lines. It was also demonstrated that compound 249 works independent of the cysteine-347 residue on the GLP-1R, an amino acid residue which has been previously shown to be instrumental for the actions of another GLP-1R agonist-PAMs. More importantly, compound 249 demonstrates robust potentiation of GLP-1 and OXM-augmented GSIS in the rat INS-1 832/3 insulinoma cell line and ex vivo isolated mouse islets, substantiating the potential of compound 249 to be further developed as a novel T2DM treatment. Overall this thesis presents new evidence on the direct involvement of GLP-1R on GLP-1-regulated glucagon secretion in the pancreatic α cells and illustrates compound 249 as a PAM to promote GLP-1 mediated GSIS. The findings in this thesis will be used for future design of safer and more efficacious T2DM treatments."],"dc:format.checksum.md5":["54ca21171aa2248fc775d14478d538cb","353adac0d1ebdfd65ab16480263c3c87"],"dc:identifier.doi":["10.17863/CAM.63107"],"dc:identifier.uri":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/07c1887a-c4e2-40a4-8535-3234a577b76a/download"],"dc:language":["eng"],"dc:publisher.institution":["University of Cambridge"],"dc:relation.isreferencedby.uri":["https://www.repository.cam.ac.uk/handle/1810/315995"],"dc:rights":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/fccd6861-7d00-4f1c-b6a6-047272bd6abf/download","https://www.rioxx.net/licenses/all-rights-reserved/"],"dc:subject":["G protein-coupled receptors","Incretins","Drug discovery","Type 2 diabetes mellitus","GLP-1"],"dc:title":["Characterisation and pharmacological regulation of GLP-1-mediated glucose homeostasis"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["Doctoral"],"dc:type.qualificationname":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-22T22:24:21Z"}