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Postpartum (PP) maternal mortality remains alarmingly high, with a rate of 32.9 per 100,000 live births in 2021 in the United States. Cardiovascular diseases, including peripartum/postpartum cardiomyopathy (PPCM) and coronary heart disease, are among the leading causes of PP morbidity and mortality. Although socioeconomic status and the level of PP care can influence the mortality rate, the underlying mechanisms leading to PPCM are not well understood. PPCM is clinically defined as (1) the development of the disease in the last month of pregnancy or within 5 months of delivery, (2) absence of pre-existing heart disease prior to the last month of pregnancy, (3) unknown cause of heart failure, and (4) left ventricular systolic dysfunction. Prognosis remains poor, with full recovery reported in only 23% of affected individuals and 50% experiencing heart failure-related mortality due to limited therapeutic options. Limited studies in both humans and mouse models of PPCM have proposed several potential mechanisms, including inflammation, viral myocarditis, autoimmune reactions, oxidative stress, and apoptosis, resulting from environmental as well as genetic factors. Studying these mechanisms in animal models, particularly those involving genetic causes, has been difficult due to the lack of severity or relevance of existing mouse models of PPCM to the human disease.

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Spatially diffuse cAMP signalling with oppositely biased GLP-1 receptor agonists in β-cells despite differences in receptor localisation

Shiqian Chen, Carolina B. Lobato, Carissa Wong, Yusman Manchanda, ... Ben Jones

Spatially diffuse cAMP signalling with oppositely biased GLP-1 receptor agonists in β-cells despite differences in receptor localisation

Internalisation of G protein-coupled receptors (GPCRs) can contribute to altered cellular responses by directing signalling from non-canonical locations, such as endosomes. If signalling processes are locally constrained, active receptors in different subcellular locations could produce different downstream effects. This phenomenon may be relevant to the optimal targeting of the glucagon-like peptide-1 receptor (GLP-1R), a type 2 diabetes and obesity target GPCR for which several ligands with varying internalisation tendency have been discovered. To investigate, we compared the signalling localisation effects of two prototypical GLP-1RAs with opposite signal bias and effects on GLP-1R trafficking: exendin-asp3 (ExD3), a full agonist that drives rapid internalisation, and exendin-phe1 (ExF1), which shows much slower internalisation. After using bioorthogonal labelling and fluorescent agonist conjugates to verify the divergent trafficking patterns of ExF1 and ExD3 in β-cell lines and primary pancreatic islets, we used live cell biosensors to monitor signalling at different subcellular locations. This revealed that cAMP/PKA/ERK signalling in β-cells is in fact distributed widely across the cell over short- (<5 min) and medium-term (up to 60 min) stimulation at pharmacological (>10 pM) concentrations, with no major differences in signal localisation that could be linked to internalised versus cell surface-bound GLP-1R. Moreover, washout experiments highlighted that, whilst fast-internalising ExD3 shows much greater accumulation and binding to GLP-1R in endosomes than slow-internalising ExF1, it is a rather inefficient driver of both cAMP production in β-cells and insulin secretion from perfused rat pancreata. These data provide a greater understanding of the cellular effects of biased GLP-1R agonism.

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Spatially diffuse cAMP signalling with oppositely biased GLP-1 receptor agonists in β-cells despite differences in receptor localisation

Shiqian Chen, Carolina B. Lobato, Carissa Wong, Yusman Manchanda, ... Ben Jones

Spatially diffuse cAMP signalling with oppositely biased GLP-1 receptor agonists in β-cells despite differences in receptor localisation

Internalisation of G protein-coupled receptors (GPCRs) can contribute to altered cellular responses by directing signalling from non-canonical locations, such as endosomes. If signalling processes are locally constrained, active receptors in different subcellular locations could produce different downstream effects. This phenomenon may be relevant to the optimal targeting of the glucagon-like peptide-1 receptor (GLP-1R), a type 2 diabetes and obesity target GPCR for which several ligands with varying internalisation tendency have been discovered. To investigate, we compared the signalling localisation effects of two prototypical GLP-1RAs with opposite signal bias and effects on GLP-1R trafficking: exendin-asp3 (ExD3), a full agonist that drives rapid internalisation, and exendin-phe1 (ExF1), which shows much slower internalisation. After using bioorthogonal labelling and fluorescent agonist conjugates to verify the divergent trafficking patterns of ExF1 and ExD3 in β-cell lines and primary pancreatic islets, we used live cell biosensors to monitor signalling at different subcellular locations. This revealed that cAMP/PKA/ERK signalling in β-cells is in fact distributed widely across the cell over short- (<5 min) and medium-term (up to 60 min) stimulation at pharmacological (>10 pM) concentrations, with no major differences in signal localisation that could be linked to internalised versus cell surface-bound GLP-1R. Moreover, washout experiments highlighted that, whilst fast-internalising ExD3 shows much greater accumulation and binding to GLP-1R in endosomes than slow-internalising ExF1, it is a rather inefficient driver of both cAMP production in β-cells and insulin secretion from perfused rat pancreata. These data provide a greater understanding of the cellular effects of biased GLP-1R agonism.

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13th
Helmholtz Diabetes Conference 
Munich, 21-23. Sep 2026                                                                                                                             

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