Figure 3.

Model for the intra‐islet regulation of glucagon secretion from α‐cells by insulin. Normal state: In hyperglycemia, increased insulin secretion from β‐cells acts on α‐cells to suppress glucagon secretion. In hypoglycemia, decreased insulin secretion from β‐cells is sensed by α‐cells, which increases glucagon secretion. Diabetes state: In hyperglycemia, the lack of suppression of glucagon secretion because of impaired insulin secretion from β‐cells and insulin resistance in α‐cells leads to an abnormal elevation of glucagon. In hypoglycemia, the lack of decrease in insulin secretion from β‐cells, in addition to insulin insensitivity in α‐cells, results in an insufficient response in glucagon secretion.