Figure 13.

Diagrammatic representation of intra-islet connections and regulatory signals in health and diabetes. In normoglycemia, cells are closely packed, with non-β-cells situated more peripherally and adjacent to capillaries. Secretion of insulin (green) and glucagon (purple) exert paracrine effects on α-, δ-(yellow), and β-cells. Somatostatin has inhibitory paracrine effects on all cell types (dotted lines). β-Cell products, Zn²⁺ and GABA, may affect α-cell function, and acetylcholine from α-cells may influence somatostatin secretion. In the diabetic islet, architecture is disrupted. There are less β-cells, and α-cells are increased and distributed throughout the islet. The influence of insulin on islet function is reduced but the paracrine effects of glucagon and somatostatin are likely to be increased (heavy solid and dotted lines, respectively).