Liraglutide treatment reverses unconventional cellular defects in induced pluripotent stem cell-derived β cells harboring a partially functional WFS1 variant
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Aims/hypothesis
Wolfram Syndrome 1 (WS1) is a rare genetic disorder characterized by very heterogeneous clinical manifestations caused by variants of the WFS1 gene, which encodes for the Endoplasmic Reticulum (ER) protein Wolframin, involved in cellular stress response, Ca 2+ handling and autophagy. Given the central role of Wolframin, elucidating the impact of WFS1 variants on cell functions is crucial to provide an association with clinical phenotypes. Therefore, as the understanding of patient-specific defects may also help to develop targeted therapeutic approaches, here we aimed at elucidating the impact on β cell function of the c.316-1G>A mutation harboring the partially functional Wolframin that we have previously characterized, and the molecular changes following treatment with the glucagon-like peptide 1 receptor (GLP-1R) agonist liraglutide.
Methods
We previously generated patient-derived iPSCs (WFS1) and isogenic line in which the c.316-1G>A mutation was genetically corrected (WFS1 wt/757A>T ), thus performed molecular analysis, including single cell RNAseq (scRNAseq), and functional studies on iPSC-derived β cell (iBeta). Calcium flux imaging and dynamic perifusion assays were used to test glucose responsiveness of iBeta. Treatment with liraglutide was performed to investigate effects on glucose-stimulated insulin secretion (GSIS), unfolded protein response (UPR), autophagy and apoptosis.
Results
We found that both WFS1 and WFS1 wt/757A>T iBeta efficiently differentiated in vitro into pancreatic lineage, but WFS1 showed less mature endocrine phenotype, reduced glucose responsiveness and impaired insulin secretion compared to WFS1 wt/757A>T counterpart. The Ca 2+ dynamics were altered in WFS1 iBeta as Ca 2+ oscillations after glucose challenge were not synchronized mainly due to the CACNA1D and SNAP25 downmodulation. Reduced insulin secretion was correlated with a decrease in PC1/3 levels and overall increase of RGS4 expression in WFS1 iBeta, whereas secretory defects correlated with accelerated autophagic flux. While the functional residual Wolframin in WFS1 iBeta controlled short-term ER stress, prolonged insults or inflammation highlighted ineffective UPR that make the cells unable to escape apoptosis. Interestingly, treatment with liraglutide restored the Ca 2+ fluxes and secretory impairments, increasing glucose responsiveness and insulin release of WFS1 iBeta, while protecting these cells from cellular stress and inflammation-induced apoptosis.
Conclusion/interpretation
Our data highlighted alterations of key cellular pathways involved in WS1 β cell maturation and GSIS and how the pharmacological targeting of the GLP-1/GLP-1R axis was able to restore the physiologic phenotype. This study points out the need to understand the patient-specific molecular determinants associated with WFS1 variants, to design effective therapies to treat the disease.
