Normal glucose regulation is dependent on a closed feedback loop relationship between the liver, peripheral tissue (muscle), and the pancreatic islet cells that secrete insulin and glucagon.
When intact, this delicate metabolic balance allows for periods of fasting without producing hypoglycemia;
- Normal functioning of beta and alpha cells in the islets of the pancreas are critical to maintaining normal glucose homeostasis. Insulin increases and glucagon falls in response to meals in healthy non-diabetic subjects.
- Beta cells are poised to release insulin in response to even a small increase in glucose. The release of insulin from beta cells also helps suppress the release of glucagon from alpha cells, providing another control for preventing elevated glucose and maintaining glucose homeostasis.
- Alpha cells perform the opposite function. They release glucagon when blood glucose levels fall in order to increase glucose output by the liver to help prevent hypoglycemia.
Below explained steps in the normalization of glucose when blood glucose levels rise during the fed state;
- With feeding, glucose enters the bloodstream.
- A rise in glucose levels is detected by the specialized beta cells in the pancreas. Beta cells respond to the rising blood glucose concentration by promptly releasing insulin.
- Insulin signals to other tissues in the body to take in glucose to be used as energy or stored for later use.
- Insulin also signals the liver to turn off glucose production.
- In the fed state, glucagon is suppressed.
- The suppression of glucagon contributes to a decrease in glucose production.
- The net result is the lowering of blood glucose concentration.
Below explained steps in the normalization of glucose when blood glucose levels fall during fasting state;
- In the fasting state (between meals, after an overnight fast, or in cases of starvation), glucose level fall.
- The alpha cells of the pancreas release glucagon.
- Glucagon directs the liver to break down stored glycogen into glucose (glycogenolysis) and to increase the formation of new glucose (gluconeogenesis) and release this glucose into the bloodstream. Thus, there is an increase in hepatic glucose production.
- There is also a decrease in insulin secretion by the beta cells of the pancreas.
- In the fasting state, insulin secretion is suppressed. The suppression of glucose uptake contributes to an increase in blood glucose.
- The net result is the rise of blood glucose concentration.
Who is a non-diabetic?
The following are the characteristics of the non-diabetic state;
- The beta cells are functioning normally, producing appropriate amounts of insulin.
- Sensitivity to insulin is normal, and insulin effectively facilitates transport of glucose into cells (e.g. muscle, fat, and liver cells).
- There is an adequate level of insulin production to meet the body’s needs.
- Glucose levels are normal, termed euglycemia.
Our future post will elaborate on the pathophysiologic evolution of type 2 diabetes in detail. It will help you to understand how type 2 diabetes evolves over the years from a healthy state individual as a result of multiple factors.