The pancreas is an organ in the centre of the abdomen. It is made up of two compartments. These are the exocrine compartment, which contain cells that secrete enzymes into the gut to break down the food we eat, and the endocrine compartment, which contains cells that make several hormones that are secreted into the bloodstream. Cells in the endocrine compartment are organized into clusters called the Islets of Langerhans. The types of cells that are located in these islets and the hormones they make are discussed in this blog.
β (beta)-cells secrete insulin and make up the majority of cells in human islets (~55%). In type 1 diabetes, these cells are mistakenly destroyed by the immune system, leading to insulin deficiency and elevated blood glucose. That is why type 1 diabetes is classified as an autoimmune disease.
α (alpha)-cells represent the next largest population (~25%) of islet cells. These cells secrete glucagon, a hormone that counters insulin by raising blood glucose levels. Normally, insulin and glucagon work together to maintain blood glucose within an ideal “Goldilocks” range—not too low, not too high, just right. Because these cells are often preserved in diabetes, their continued glucagon secretion combined with insufficient insulin, can worsen hyperglycemia.
δ (delta)-cells make up a smaller proportion of islet cells (~10%) and secrete somatostatin, a hormone that acts on both α- and β-cells to restrict secretion of glucagon and insulin, respectively. This is important for fine-tuning any imbalances and can act as another layer of protection in cases when they are abnormally secreted in diseased conditions.
γ (gamma)-cells make up ~1% of islet cells and secrete a hormone called pancreatic polypeptide. ε (epsilon)-cells make up ≤1% and secrete a hormone called ghrelin. Although both cell types are not as commonly studied, they are best known for their roles in controlling appetite with subtle roles in regulating β-cell development and survival, and thus, insulin secretion.
Studying these islet cell types can help identify novel therapies for diabetes. For example, some researchers are studying ways to convert α-cells into β-cells. Others are focusing on coaxing stem cells to become β-like cells.
The key message is that β-cells do not work alone. They exist within a dynamic network of other islet cell types that work together to keep the body working normally.
About the author
Haiyang Huang
Haiyang is a PhD student in the Department of Physiology at the University of Toronto. His research focuses on mechanotransduction in the optimization of hPSC (human pluripotent stem cell)-derived islet differentiation. In his spare time, Haiyang enjoys performing, arranging and composing music.
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