Periodic Reporting for period 4 - Merlin (MEtabolic Cell Reprogramming for the Recovery of Lost INsulin-Producing Cells)
Periodo di rendicontazione: 2025-03-01 al 2025-08-31
We aim at fostering the regeneration of insulin-producing beta-cells in the diabetic pancreas, by promoting the reprogramming of other islet cell-types, so-called “non-beta” cells.
This proposal was centered on the idea of manipulating metabolism within the context of insulin deficiency or beta-cell loss, to cause recovery from hyperglycemia and beta-like-cell regeneration by promoting islet cell type interconversions.
We have identified multiple circulating molecules that react to both beta-cell ablation and insulin receptor blockade, representing a repertoire of systemic signals that control the action of insulin at the whole-body level. We have observed that, surprisingly, mice containing only beta-cells in their pancreatic islets have an improved metabolic health in the absence of non-beta-cells. We have uncovered that in human islets there are fundamental metabolic differences between alpha- and beta-cells that define their functional identities. We identified a dozen patentable compounds capable of inducing insulin mRNA expression in human alpha-cells, leading to an ERC Proof of Concept grant (“REPAIR”) to evaluate their translational potential.
This proposal was centered on the idea of manipulating metabolism within the context of insulin deficiency or beta-cell loss, to cause recovery from hyperglycemia and beta-like-cell regeneration by promoting islet cell type interconversions.
We have identified multiple circulating molecules that react to both beta-cell ablation and insulin receptor blockade, representing a repertoire of systemic signals that control the action of insulin at the whole-body level. We have observed that, surprisingly, mice containing only beta-cells in their pancreatic islets have an improved metabolic health in the absence of non-beta-cells. We have uncovered that in human islets there are fundamental metabolic differences between alpha- and beta-cells that define their functional identities. We identified a dozen patentable compounds capable of inducing insulin mRNA expression in human alpha-cells, leading to an ERC Proof of Concept grant (“REPAIR”) to evaluate their translational potential.
1. As the number of beta-cells decline with diabetes progression, decades of research have shown that significant changes occur in the function, numbers and types of pancreatic endocrine cells, as well as in key blood-circulating factors. In mice, these responses can, in some cases, promote remission and recovery from diabetes by fostering beta-cell regeneration or normalization of high blood glucose levels. Unfortunately, our knowledge of these convoluted processes is fragmented and incomplete, as previous studies only provide temporal snapshots or focus only on certain physiological aspects at a time. To address this, we developed a transgenic mouse model where we can destroy different amounts of beta-cells, modelling the progressive loss of beta-cells observed in diabetes.
We successfully carried out systematic multi-omics profiling of whole-body systemic responses and physiological adaptations to decremental beta-cell mass in mice, in comparison to whole-body insulin signaling blockade using a potent insulin receptor antagonist. Multi-omics included plasma lipidomics, metabolomics, proteomics and RNAseq of miRNAs in addition to bulk RNAseq of 10 organs, all at 10 days after either the ablation of the insulin-producing pancreatic beta-cells, or insulin receptor blockade. With this novel experimental approach, we identified phenotypes and circulating molecules that are beta-cell ablation-specific, including severe whitening (lipid accumulation) of brown adipose tissue (BAT) and a variety of plasma lipids, proteins, metabolites and miRNAs.
2. Concerning the studies with human pancreatic islets, we obtained preliminary results that have started to identify key metabolic differences between human alpha- and beta-cells.
3. Our work has advanced significantly in understanding endocrine cell plasticity in the pancreas. We discovered that Ppy-expressing islet gamma-cells can also produce insulin in the absence of beta-cells, as previously reported for alpha- and delta-cells (Nat Commun., 2021). We demonstrated that adult islet cells arise from embryonic hormone-expressing cells generated at different developmental stages, with no evidence of postnatal neogenesis (Cell Rep., 2022). We showed that murine islets in vivo and human pseudoislets composed exclusively of beta-cells can sustain regulated and adaptive insulin secretion in the absence of other endocrine cell types (Nat Metab., 2024). These projects have inspired new lines of investigation, including a promising project investigating the epigenetic mechanisms driving alpha-cell plasticity.
Results have been presented at major international meetings (EASD, ISG, SSED, SFD) and several papers in high impact journals have been published or are in preparation.
We successfully carried out systematic multi-omics profiling of whole-body systemic responses and physiological adaptations to decremental beta-cell mass in mice, in comparison to whole-body insulin signaling blockade using a potent insulin receptor antagonist. Multi-omics included plasma lipidomics, metabolomics, proteomics and RNAseq of miRNAs in addition to bulk RNAseq of 10 organs, all at 10 days after either the ablation of the insulin-producing pancreatic beta-cells, or insulin receptor blockade. With this novel experimental approach, we identified phenotypes and circulating molecules that are beta-cell ablation-specific, including severe whitening (lipid accumulation) of brown adipose tissue (BAT) and a variety of plasma lipids, proteins, metabolites and miRNAs.
2. Concerning the studies with human pancreatic islets, we obtained preliminary results that have started to identify key metabolic differences between human alpha- and beta-cells.
3. Our work has advanced significantly in understanding endocrine cell plasticity in the pancreas. We discovered that Ppy-expressing islet gamma-cells can also produce insulin in the absence of beta-cells, as previously reported for alpha- and delta-cells (Nat Commun., 2021). We demonstrated that adult islet cells arise from embryonic hormone-expressing cells generated at different developmental stages, with no evidence of postnatal neogenesis (Cell Rep., 2022). We showed that murine islets in vivo and human pseudoislets composed exclusively of beta-cells can sustain regulated and adaptive insulin secretion in the absence of other endocrine cell types (Nat Metab., 2024). These projects have inspired new lines of investigation, including a promising project investigating the epigenetic mechanisms driving alpha-cell plasticity.
Results have been presented at major international meetings (EASD, ISG, SSED, SFD) and several papers in high impact journals have been published or are in preparation.
1. We have successfully progressed in the challenging task of analyzing various physiological and diabetic parameters from our graded beta-cell ablation murine model. We gained new insights into diabetes pathophysiology, pinpointing key gender differences and providing data that will help resolve longstanding questions. For example, our analysis of alpha-cells and glucagon sheds light on possible causes of diabetic hyperglucagonemia; we have started to define the thresholds of beta-cell loss that underlie glucose dysregulation and activation of key islet cell dynamics like proliferation. We have also uncovered gender-based phenotypes, like weight regulation during severe diabetes. These results could open new research avenues concerning how animals cope with varying degrees of diabetes severity. Finally, our unprecedented integrative multi-omics plasma analyses, as well as the surgical removal of BAT, has produced unexpected results concerning possible links between islets and adipose tissue in hyperglycemic mice, further illustrating the overlooked potential of dynamic interactions between circulating molecules as central players in diabetes.
2. Recently, using genetic manipulation, we showed that human alpha-cells efficiently convert into insulin-secreting cells. In exploring new ways to convert non-beta-cells, we noticed significant differences of key metabolic genes between human alpha- and beta-cells. Metabolism is pivotal in islet cell function, as it tightly links nutrient sensing/use with hormone secretion. Here, we hypothesized that modifying alpha-cell metabolism, to resemble that of beta-cells, may activate beta-cell genes, like insulin.
Our studies on human islets have uncovered fundamental metabolic differences between alpha- and beta-cells that define their functional identities. We demonstrated that beta-cells display a highly oxidative metabolic profile, in sharp contrast to alpha-cells. These features appear essential for beta-cell identity and likely underlie the limited insulin production of reprogrammed insulin-secreting human alpha-cells.
3. Adult mice can regenerate new insulin-producing cells when beta-cells are lost. We discovered that these new insulin cells were islet non-beta-cells that engaged in insulin production. We were trying to modulate this natural islet cell plasticity and wondered what would happen if we successfully forced the conversion of all non-beta-cell types. Would beta-like cells alone sustain proper insulin secretion and glucose homeostasis? It is well established that alpha-cells, delta-cells and gamma-cells closely regulate beta-cell function, so we were thrilled and astonished to observe that the absence of non-beta-cells is not detrimental to the maintenance of euglycaemia and actually conferred improved glucose tolerance and insulin sensitivity. At the islet level, non-beta-cells are dispensable for beta-cell function and their loss does not affect blood glucose homeostasis. This observation was unexpected, and therefore refutes the current view and goes straight against the ‘dogma’. Our study supports efforts aimed at fostering the regeneration of insulin-producing beta-cells in the diabetic pancreas, by promoting the reprogramming of the other islet cell-types.
2. Recently, using genetic manipulation, we showed that human alpha-cells efficiently convert into insulin-secreting cells. In exploring new ways to convert non-beta-cells, we noticed significant differences of key metabolic genes between human alpha- and beta-cells. Metabolism is pivotal in islet cell function, as it tightly links nutrient sensing/use with hormone secretion. Here, we hypothesized that modifying alpha-cell metabolism, to resemble that of beta-cells, may activate beta-cell genes, like insulin.
Our studies on human islets have uncovered fundamental metabolic differences between alpha- and beta-cells that define their functional identities. We demonstrated that beta-cells display a highly oxidative metabolic profile, in sharp contrast to alpha-cells. These features appear essential for beta-cell identity and likely underlie the limited insulin production of reprogrammed insulin-secreting human alpha-cells.
3. Adult mice can regenerate new insulin-producing cells when beta-cells are lost. We discovered that these new insulin cells were islet non-beta-cells that engaged in insulin production. We were trying to modulate this natural islet cell plasticity and wondered what would happen if we successfully forced the conversion of all non-beta-cell types. Would beta-like cells alone sustain proper insulin secretion and glucose homeostasis? It is well established that alpha-cells, delta-cells and gamma-cells closely regulate beta-cell function, so we were thrilled and astonished to observe that the absence of non-beta-cells is not detrimental to the maintenance of euglycaemia and actually conferred improved glucose tolerance and insulin sensitivity. At the islet level, non-beta-cells are dispensable for beta-cell function and their loss does not affect blood glucose homeostasis. This observation was unexpected, and therefore refutes the current view and goes straight against the ‘dogma’. Our study supports efforts aimed at fostering the regeneration of insulin-producing beta-cells in the diabetic pancreas, by promoting the reprogramming of the other islet cell-types.