In the last article we looked at how the body uses negative feedback mechanisms to control the concentration of glucose in the blood. Diabetes mellitus is a condition where these feedback systems fail and blood glucose is not controlled, with potentially fatal consequences if left untreated. In this article we will look at the two types of diabetes mellitus. (Note that there is another type of diabetes called diabetes insipidus, which is a completely different condition where regulation of water balance is disrupted.)
Type 1 diabetes mellitus
Type 1 diabetes is an auto-immune condition which causes the immune system to destroy the beta cells in the pancreas. Remember that beta cells are the cells which produce insulin. Therefore in type 1 diabetes, the pancreas is not able to produce insulin. This means that blood glucose is not lowered when it is too high, and instead stays high. The term for high blood glucose is hyperglycaemia.
The disease often develops early in life. A very common treatment is for the patient to inject themselves within insulin regularly to replace the insulin which the pancreas is unable to produce. However, there is a risk of injecting too much insulin and lowering blood glucose too far (hypoglycaemia) which is also dangerous. Other treatments include an islet cell transplant or even a whole pancreas transplant. It is also important for type 1 diabetes patients to carefully regulate the glucose in their blood by controlling their diet and doing regular exercise.
Type 2 diabetes mellitus
Type 2 diabetes is a common health problem which is most often linked to lifestyle habits, although there can be a genetic predisposition in some people. In type 2 diabetes, the pancreas is normally able to produce insulin. However, the cells which have insulin receptors (e.g. liver cells) become less sensitive to insulin. The insulin is giving the signal, but the cell is not responding. Therefore the pathways that insulin are meant to activate, such as glycogenesis, are not activated and blood glucose concentration remains high. Make sure you fully understand the role of insulin in regulating blood glucose by reading the last article.
Type 2 diabetes often develops later in life. Carefully controlling the diet and doing regular exercise are important for the control of type 2 diabetes. Losing weight is also often important as there is a link to obesity and other obesity-related conditions. However there are several drugs which can help to control the condition. For example, the drug metformin is commonly used to increase insulin sensitivity and inhibit adenylate cyclase.
Here is a summary diagram showing how each type of diabetes would affect glycogenesis in liver cells.