Diabetologists in Chikkajala, Bangalore • Islets of Langerhans in the endocrine pancreas contain β (insulin - producing) and α (glucagon - producing) cells that regulate glucose homeostasis. • Pancreatic β cells may change in size, number and function during normal ageing and development. Insulin biosynthesis and secretion involves a number of steps; insulin exists in the circulation as a monomer of 6000 Da molecular weight. • Insulin secretion is biphasic: an acute fi rst phase that lasts a few minutes followed by a sustained second phase. Glucose is the main stimulator of insulin secretion, entering β cells via the GLUT - 2 transporter. • Sulphonylureas stimulate insulin secretion by binding to a component of the potassium - ATP (KATP) channel, resulting in KATP channel closure. • The incretin effect (meal - stimulated augmentation of insulin secretion) is diminished in type 2 diabetes, mainly because of reduced GLP - 1 secretion. • Insulin receptor signalling in key tissues (skeletal muscle, fat and liver) is highly complex and activates a number of second messenger steps which result in the various biological effects of insulin on glucose, lipid and protein metabolism. • Incretinmimetics (GLP - 1 agonists and DPP - 4 inhibitors) reverse the abnormalities in insulin and glucagon secretion, and may have longer term trophic effects on β cell number, structure and function.