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Islet Cell Types

The pancreas contains endocrine glands called "islets of Langerhans." A normal human pancreas contains five types of islet cells -- alpha, beta, delta, F and epsilon cells -- that respond to information from the blood supply entering the pancreas, from other islet cells and from the nervous system. This tight regulation of islet cell secretion helps the pancreas respond to changes in blood glucose and adjust the body's metabolism accordingly.

  1. Beta Cells

    • Pancreatic beta cells are the most abundant, making up 65 to 80 percent of the total islet cell population. Beta cells synthesize and secrete insulin in response to a meal, which allows muscle and the liver to absorb nutrients from the meal and replenish needed fuel reserves. The beta cells have a strong response to elevated blood glucose, so consistently high blood glucose levels increase the amount of insulin the beta cells must make. If the beta cells cannot synthesize enough insulin to compensate for the high blood glucose, diabetes will eventually develop.

    Alpha Cells

    • Alpha cells make up 15 to 20 percent of the islet cell population. These cells synthesize and secrete glucagon into the liver, where the protein hormone acts to produce glucose from the breakdown of glycogen, fat and protein while fasting. Fasting and eating a high-protein meal stimulate glucagon production and secretion from the alpha cells. Glucagon actions generally oppose those of insulin, which the beta cells synthesize as mentioned above.

    Delta Cells

    • Delta cells comprise three to 10 percent of the total islet population and tend to be located on the periphery of the islet. Delta cells synthesize and secrete somatostatin, which inhibits insulin and glucagon secretion. Chronic elevation of somatostatin is associated with diabetes since the delta cells are trying to reduce the chronically high insulin production.

    F Cells

    • F cells, also known as pancreatic polypeptide cells, make up three to five percent of all islet cells. These cells secrete pancreatic polypeptide, a hormone that reduces appetite, in response to food intake. Pancreatic polypeptide is elevated with anorexia nervosa and is reduced in conditions with increased food intake, and intravenous infusion with the hormone reduced food intake by 25 percent in a 2003 study published in the Journal of Clinical Endocrinology and Metabolism.

    Epsilon Cells

    • These recently identified cells make up less than one percent of all islet cells. Epsilon cells produce ghrelin, a hormone that increases appetite in response to fasting. A lower number of epsilon cells was associated with a higher body mass index in a 2009 study published in Diabetologia, suggesting ghrelin production is lower in these individuals. However, the role of ghrelin in food intake and metabolism is not completely understood.

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