ZnT8 loss-of-function accelerates functional maturation of hESC-derived β cells and resists metabolic stress in diabetes

Abstract

Human embryonic stem cell-derived β cells (SC-β cells) hold great promise for treatment of diabetes, yet how to achieve functional maturation and protect them against metabolic stresses such as glucotoxicity and lipotoxicity remains elusive. Our single-cell RNA-seq analysis reveals that ZnT8 loss of function (LOF) accelerates the functional maturation of SC-β cells. As a result, ZnT8 LOF improves glucose-stimulated insulin secretion (GSIS) by releasing the negative feedback of zinc inhibition on insulin secretion. Furthermore, we demonstrate that ZnT8 LOF mutations endow SC-β cells with resistance to lipotoxicity/glucotoxicity-triggered cell death by alleviating endoplasmic reticulum (ER) stress through modulation of zinc levels. Importantly, transplantation of SC-β cells with ZnT8 LOF into mice with preexisting diabetes significantly improves glycemia restoration and glucose tolerance. These findings highlight the beneficial effect of ZnT8 LOF on the functional maturation and survival of SC-β cells that are useful as a potential source for cell replacement therapies.

ZnT8 Loss of Function Mutation Increases Resistance of Human Embryonic Stem Cell-Derived Beta Cells to Apoptosis in Low Zinc Condition

“…A recent study showed that genes related to beta cell maturation are upregulated in SLC30A8 KO sc-derived beta cells [ 36 ], providing a potential mechanism for the protective effect of SLC30A8 mutations. In our scRNA-seq, we also observed upregulation of PCSK2, ONECUT2, and IAPP in SLC30A8 KO cells, concordant with reported findings [ 36 ].…”

“…A recent study showed that genes related to beta cell maturation are upregulated in SLC30A8 KO sc-derived beta cells [ 36 ], providing a potential mechanism for the protective effect of SLC30A8 mutations. In our scRNA-seq, we also observed upregulation of PCSK2, ONECUT2, and IAPP in SLC30A8 KO cells, concordant with reported findings [ 36 ]. Nevertheless, in our human embryonic stem cell model of ZnT8 loss of function mutations, R138X and KO sc-beta cell clusters were neither compromised nor improved in insulin processing or glucose-stimulated secretion.…”

“…Ma et al provided an alternative interpretation for the protective effect of ZnT8 in a stem cell model: an inhibitory effect of extracellular zinc on insulin secretion [ 36 ]. This zinc would only be released from zinc-containing insulin granules, not from ZnT8 mutant beta cells.…”

“…While this study was under consideration for publication, another study reported normal differentiation of ZnT8 loss of function stem cells to beta-like cells [ 36 ].…”

Pancreatic β-cell heterogeneity in adult human islets and stem cell-derived islets

“…It is noteworthy that loss of ZnT8 has been observed to promote the maturation of hESC-dervied β-cells and protects them against cell death resulting from lipotoxicity or glucotoxicity. This is achieved by regulating zin levels, which reduces ER stress [ 178 ]. Although glucose responsive β-cells can now be generated, they still differ from adult human pancreatic β-cells in the transcriptomic profiles in which they show lower GLIS3, PCSK2, PAX6, and KCNK3 levels, in addition to lower calcium response [ 166 ].…”