| Location of the Pancreas Insulin is a hormone. And | | | | When they examined the pancreases of these dogs |
| like many hormones, insulin is a protein. Insulin is | | | | several weeks later, all of the pancreas digestive cells |
| secreted by groups of cells within the pancreas called | | | | were gone (died and were absorbed by the immune |
| islet cells. The pancreas is an organ that sits behind | | | | system) and the only thing left was thousands of |
| the stomach and has many functions in addition to | | | | pancreatic islets. They then isolated the protein from |
| insulin production. The pancreas also produces | | | | these islets and behold, they discovered insulin. Note |
| digestive enzymes and other hormones (detailed on | | | | that there are other hormones produced by different |
| another page). Carbohydrates (or sugars) are | | | | types of cells within pancreatic islets (glucagon, |
| absorbed from the intestines into the bloodstream | | | | somatostatin, etc) but insulin is produced in far |
| after a meal. Insulin is then secreted by the pancreas | | | | greater amounts under normal conditions making the |
| in response to this detected increase in blood sugar. | | | | simple approach used by Banting and Best quite |
| Most cells of the body have insulin receptors which | | | | successful. |
| bind the insulin which is in the circulation. When a cell | | | | Where Does Commercial Insulin Come From? |
| has insulin attached to its surface, the cell activates | | | | The first successful insulin preparations came from |
| other receptors designed to absorb glucose (sugar) | | | | cows (and later pigs). The pancreatic islets and the |
| from the blood stream into the inside of the cell. | | | | insulin protein contained within them were isolated |
| Pancreatic Islet Cells secrete insulin. Without insulin, | | | | from animals slaughtered for food in a similar but |
| you can eat lots of food and actually be in a state of | | | | more complex fashion than was used by our doctor |
| starvation since many of our cells cannot access the | | | | and med-student duo. The bovine (cow) and porcine |
| calories contained in the glucose very well without | | | | (pig) insulin were purified, bottled, and sold. Bovine |
| the action of insulin. This is why Type 1 diabetics who | | | | and porcine insulin worked very well (and still do!) for |
| do not make insulin can become very ill without insulin | | | | the vast majority of patients, but some could |
| shots. Insulin is a necessary hormone. Those who | | | | develop an allergy or other types of reactions to the |
| develop a deficiency of insulin must have it replaced | | | | foreign protein (a foreign protein is a protein which is |
| via shots or pumps (Type 1 Diabetes). More | | | | not native to humans). In the 1980's technology had |
| commonly, people will develop insulin resistance (Type | | | | advanced to the point where we could make human |
| 2 Diabetes) rather than a true deficiency of insulin. In | | | | insulin. The advantage would be that human insulin |
| this case, the levels of insulin in the blood are similar | | | | would have a much lower chance of inducing a |
| or even a little higher than in normal, non-diabetic | | | | reaction because it is not a foreign protein (all humans |
| individuals. However, many cells of Type 2 diabetics | | | | have the exact same insulin, so we do not "see" this |
| respond sluggishly to the insulin they make and | | | | as a foreign protein). The technology which made this |
| therefore their cells cannot absorb the sugar | | | | approach possible was the development of |
| molecules well. This leads to blood sugar levels which | | | | recombinant DNA techniques. In simple terms, the |
| run higher than normal. Occasionally Type 2 diabetics | | | | human gene which codes for the insulin protein was |
| will need insulin shots but most of the time other | | | | cloned (copied) and then put inside of bacteria. A |
| methods of treatment will work. | | | | number of tricks were performed on this gene to |
| Pancreas Secretes Insulin was the first hormone | | | | make the bacteria want to use it to constantly make |
| identified (late 1920's) which won the doctor and | | | | insulin. Big vats of bacteria now make tons of human |
| medical student who discovered it the Nobel Prize | | | | insulin. From this, pharmaceutical companies can isolate |
| (Banting and Best). They discovered insulin by tying a | | | | pure human insulin. |
| string around the pancreatic duct of several dogs. | | | | |