Periodic Reporting for period 3 - Merlin (MEtabolic Cell Reprogramming for the Recovery of Lost INsulin-Producing Cells)
Période du rapport: 2023-09-01 au 2025-02-28
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. We previously developed transgenic mice where we elicit total (>99%) or graded controlled (between 5-90%) beta-cell ablation. These mice revealed that non-beta cells (i.e. alpha, delta and gamma-cells, which produce glucagon, somatostatin and PPY, respectively) can naturally switch to insulin production upon total or partial beta-cell damage, and lead to diabetes recovery. We have recently shown that human islet non-beta cells, from healthy or diabetic donors, also display plasticity and easily engage in regulated insulin secretion.
Can metabolic reprogramming change the identity of a given cell? By combining mouse and human islet and “pseudoislet” studies, in this project we will reveal and trigger the metabolic reprogramming of different tissues in order to reduce hyperglycemia in diabetes. What intrinsic metabolic adaptations occur in peripheral organs in response to insulin deficiency and hyperglycemia, but without autoimmunity or other complications? Can metabolic reprogramming of peripheral organs based on these adaptations suffice to decrease hyperglycemia? Spontaneous recovery from hyperglycemia (25 mM) following major beta-cell loss is well documented in mice and attributed to beta-cell replication; however, the contribution of peripheral organs to this phenomenon, and whether it happens in humans, is unknown. In stem and cancer cells, the states of stemness and malignancy are deeply tied to metabolic changes. Yet it is unclear whether shifts in the metabolism of adult differentiated cells are sufficient to reprogram gene expression of identity markers providing novel functional features. This proposal centers on the idea of manipulating metabolism within the context of insulin deficiency or beta-cell loss, to cause recovery from hyperglycemia and -cell regeneration by islet cell type interconversion.
Can metabolic reprogramming change the identity of a given cell? By combining mouse and human islet and “pseudoislet” studies, in this project we will reveal and trigger the metabolic reprogramming of different tissues in order to reduce hyperglycemia in diabetes. What intrinsic metabolic adaptations occur in peripheral organs in response to insulin deficiency and hyperglycemia, but without autoimmunity or other complications? Can metabolic reprogramming of peripheral organs based on these adaptations suffice to decrease hyperglycemia? Spontaneous recovery from hyperglycemia (25 mM) following major beta-cell loss is well documented in mice and attributed to beta-cell replication; however, the contribution of peripheral organs to this phenomenon, and whether it happens in humans, is unknown. In stem and cancer cells, the states of stemness and malignancy are deeply tied to metabolic changes. Yet it is unclear whether shifts in the metabolism of adult differentiated cells are sufficient to reprogram gene expression of identity markers providing novel functional features. This proposal centers on the idea of manipulating metabolism within the context of insulin deficiency or beta-cell loss, to cause recovery from hyperglycemia and -cell regeneration by islet cell type interconversion.
As the number of beta-cells steadily 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, due to technical challenges, 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 have undertaken a systematic and long-term characterization of multiple cell and physiological parameters, in an effort to consolidate previous knowledge and obtain new insights by simultaneous comparisons of various biological processes occurring after beta-cell loss. In particular, we are focusing on the informative potential of the panoply of blood-circulating compounds in diabetic animals. This way, we hope to better understand the organ crosstalk promoting recovery from severe beta-cell loss and identify novel diabetes diagnostic factors.
Concerning the studies with human pancreatic islets, despite difficulties in obtaining donor islets in the past year due to the lockdowns, we have progressed significantly in our optimization of key advanced analytical techniques, which are rarely used with such little amounts of tissue like pseudoislets, especially when analyzing lipids, metabolites and proteins from the same cell sample. We have also obtained preliminary results that have started to identify key metabolic differences between human alpha- and beta-cells. In line with these observations, we have greatly optimized our method for pseudoislet production and made it more suited for high-throughput experiments, like small molecule screening, where we are now able to test more than 300 different conditions in one experiment.
Concerning the studies with human pancreatic islets, despite difficulties in obtaining donor islets in the past year due to the lockdowns, we have progressed significantly in our optimization of key advanced analytical techniques, which are rarely used with such little amounts of tissue like pseudoislets, especially when analyzing lipids, metabolites and proteins from the same cell sample. We have also obtained preliminary results that have started to identify key metabolic differences between human alpha- and beta-cells. In line with these observations, we have greatly optimized our method for pseudoislet production and made it more suited for high-throughput experiments, like small molecule screening, where we are now able to test more than 300 different conditions in one experiment.
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 brown adipose tissue (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.
Beta-cell regeneration for the treatment of diabetes has become an important research focus. It includes approaches like expansion of remaining beta-cells, or generation of beta-cells from stem cells. Conversion of islet endocrine non-beta-cells into beta-like cells in situ, i.e. within the pancreas of diabetic patients, is becoming a more attractive option, as these cells have an ideal location within islets and a close functional relation to beta-cells. 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. Interestingly, recent studies in cancer and stem cells showed that metabolism can also directly control gene expression. Here, we hypothesize that modifying alpha-cell metabolism, to resemble that of beta-cells, may activate beta-cell genes, like insulin. Unfortunately, knowledge of human islet cell metabolism is scarce. Therefore, systematic analyses of human islet cell metabolism and possible links with gene expression, will improve our understanding of human islet cell function and will open novel therapeutic avenues to convert non-beta-cells into beta-cells.
Beta-cell regeneration for the treatment of diabetes has become an important research focus. It includes approaches like expansion of remaining beta-cells, or generation of beta-cells from stem cells. Conversion of islet endocrine non-beta-cells into beta-like cells in situ, i.e. within the pancreas of diabetic patients, is becoming a more attractive option, as these cells have an ideal location within islets and a close functional relation to beta-cells. 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. Interestingly, recent studies in cancer and stem cells showed that metabolism can also directly control gene expression. Here, we hypothesize that modifying alpha-cell metabolism, to resemble that of beta-cells, may activate beta-cell genes, like insulin. Unfortunately, knowledge of human islet cell metabolism is scarce. Therefore, systematic analyses of human islet cell metabolism and possible links with gene expression, will improve our understanding of human islet cell function and will open novel therapeutic avenues to convert non-beta-cells into beta-cells.