Insulin is crucial in lowering blood sugar levels

In the 1860s, the German scientist Paul Langerhans discovered tiny patches of cells in cross-sections of pancreas tissues.  They looked like little islands, hence their name – islets of Langerhans.  These islets have a rich blood supply and consist of two type of cells – larger alpha cells and numerous smaller beta cells.  The function of these islets were unknown until the 20th century when scientists found that removing the pancreas for an animal resulted in a disease similar to human diabetes (incidentally, dogs and cats can get diabetes too).

It was isolated in the 1920s by Banting, Best & MacLeod in Canada.

Animals with their pancreas removed were treated with the “insulin” (meaning island), and this cured the animals of the diabetes.  Animal insulin was then successfully used to treat humans for many years before genetic engineering took over the production.

How insulin works in lowering blood glucose levels

Blood glucose levels above 90mg / 100ml are detected by beta cells in the pancreas, which starts insulin production & release from the pancreas into the blood plasma.  Insulin binds to receptors on muscle and liver cells, and this causes these cells to become more permeable to glucose as well as activating enzyme systems inside the cells.  Blood glucose is taken out of the blood and is converted to glycogen (a process called glycogenesis) mainly in the liver and muscle cells.

Other processes that are affected include an:

• Increased use of glucose for energy (instead of other substances like fats).
• Increased conversion of glucose into fatty acids & fats which are stored in fat cells.

These help lower blood glucose levels back below 90mg/100ml.  As the glucose levels in the blood fall, beta cells respond by reducing insulin release.

Scientists have come up with a number of synthetic insulin alternatives.  Some of these are faster acting than normal insulin, like Humalog.  Humalog insulin, often called Lispro Insulin is nearly identical to insulin released from the pancreas, but scientists swapped a couple of amino acids around on the protein chain.