VSG shifts β-cells towards mature and extreme-like states. A, UMAP plot showing refined clustering of 7183 β-cells from WT and 21,047 β-cells from db/db (VSG + PF + Sham) into four main β-cell subpopulations. Colours indicate the subpopulations identified: mature, immature, dedifferentiated and extreme-like β-cells, as well as control and intervention groups. B, Dot plot showing expression changes of key genes involved in β-cell maturity, immaturity, dedifferentiation and extreme β-cell identity in WT β-cell subclusters (top panel) and db/db (VSG + PF + Sham) β-cell subclusters (bottom panel). Color intensity shows normalized mean expression in a cell cluster; dot size indicates the percentage of cells in a cluster that express the corresponding gene. Expression is scaled per gene. C, Proportion of cells per β-cell subpopulation in WT, Sham, PF and VSG. D, RNA velocity estimates of cell transitions applied to Sham and VSG β-cells and direction of cell movement indicated as streamlines projected onto UMAP embedding (top panel). UMAP plots showing expression of key genes (Mafa, Aldh1a3, Cck) to delineate dedifferentiation from mature cells.