Diabetes is a disease that occurs when our body cannot properly regulate blood glucose levels. Glucose is a major nutrient for the body because it is the only source of energy for the human brain. Decreasing or increasing blood glucose levels can have serious consequences, which we will talk about below.
How is blood sugar regulated?
We will try to understand why and how diabetes develops starting with understanding how our body normally controls blood sugar (blood glucose levels).
One well-known source of glucose is glucose from food. Two other lesser known sources of glucose are: glucose obtained from glycogen storage in the liver and muscles, and glucose synthesized from other organic substances. Namely, the last two sources of glucose play the main role in controlling the level of glucose in the blood, and all the mechanisms that the body has at its disposal are aimed at balancing the supply and use of these reserves.
Once food consumption is intermittent, and glucose levels are a parameter that is required to be more or less constant, for the normal functioning of vital systems, our body, evolutionary, had no choice but to develop a series of mechanisms to even out the intermittent intake of glucose by its rapid storage following food intake, and the gradual release into circulation as it is consumed.Below we will talk about each mechanism, in the order in which they are put into action from the moment of the external intake (food) until the complete depletion of the ingested glucose.
The mechanisms of glucose level regulation, being varied in function, can be easily characterized if they are separated into two main phases:
- postprandial phase - is the phase that begins immediately after the external intake of glucose and ends with the complete assimilation of glucose from the intestine
- postabsorption phase - is the phase that follows the postprandial phase, and lasts until the intake of a new portion of glucose from the outside.
The main difference between these two phases is the following: in the postprandial phase all the mechanisms of glucose storage are activated and all the mechanisms of glucose production in the body are inhibited; in the postabsorbent phase, these mechanisms are switched in the opposite direction: storage is inhibited and glucose production is activated.
As you already know, in this phase the mechanisms of glucose storage are put into action. The main role in this phase is played by the hormone called insulin.
The first mechanism that is triggered when a new portion of glucose enters the body is insulin secretion. Insulin secretion (which is produced in the secretory cells of the pancreas) is sensitive to blood glucose. After eating, this level increases rapidly, and immediately the body reacts by secreting insulin. Keep this in mind to understand the notion of diabetes that we will talk about below.
Insulin is a hormone whose main effect is to lower glucose levels. Underlying this effect is the process of rapid storage of newly arrived glucose.
Once released into the bloodstream, insulin stops all glucose production processes (gluconeogenesis in the liver, muscles, adipose tissue (fat), etc. that we will talk about later) and activates the glucose storage process.
Glucose storage takes place mostly in: liver, musсles and adipose tissue. The choice of muscles as a deposit took place evolutionarily, for an easy to understand reason: in case of stressful situations, the muscles use only locally stored glucose. Liver glucose stores are reserved for finer regulation of basal glucose levels. Deposits in adipose tissue are long-term deposits. These deposits are the last to be replenished (after replenishing the liver and muscle deposits) and the last to be mobilized (when the other deposits are depleted).
To understand diabetes, it is important to remember the notion of insulin-sensitive tissues. These are the tissues we talked about above: the liver, the muscles and the adipose tissue. These tissues are able to alter the activity of storing and releasing glucose under the action of insulin. Below we will see how this explains the notion of diabetes.
In addition to insulin, our body secretes a hormone called glucagon, which also influences the glucose storage / production ratio. Together with insulin, this hormone ensures a fine regulation of blood sugar.
In general, glucagon is an opponent of insulin and its effects are opposite to the effects of insulin: it inhibits the storage process and activates the glucose production process. I think you already assumed that the secretion of this hormone in the postprandial phase decreases.
In this phase, which begins after glucose has been absorbed from the intestine, insulin and glucagon levels are gradually diverted in the opposite direction: insulin begins to decrease and glucagon begins to increase. In this way, glucose that was stored in the first phase under the action of insulin, is gradually released into circulation under the action of glucagon.
Hypoglycemia is a drop in blood glucose levels below normal levels. For this situation, which may follow the postabsorption phase (after the absorption of glucose from the intestine), when glucose stores have been depleted, our body has prepared a series of emergency measures that are put into action in the following order.
- decreased insulin - when blood sugar drops below normal, insulin secretion is further reduced below postprandial levels.
- increased glucagon - if the decrease in insulin fails to counteract the low level of glucose, the body secretes an even greater amount of glucagon, above the values in the postprandial phase.
- epinephrine secretion - if glucagon stores are depleted and normal glucose levels have not been reached, a hormone called epinephrine is released into the circulation. This hormone has a strong hyperglycemic effect (effect of increasing glucose levels), and is a hormone released, usually in stressful situations, when the body needs a considerable intake of glucose.
- cortisol secretion - if glucose levels are not corrected in a short time, another hormone called cortisol is released into the circulation. Cortisol raises blood glucose levels in the long run, and is a hormone of chronic stress.
What is diabetes mellitus?
Diabetes is the situation in which the body fails to put into action the mechanisms we talked about above and which aim to store glucose obtained from food.
Once these mechanisms are disrupted, glucose levels increase rapidly and uncontrollably after eating carbohydrate-containing foods, and decrease as uncontrollably if glucose intake is delayed.
Patients with this disease are practically forced to take control of glucose levels once the body is unable to exercise this control.
Controlling glucose levels includes many factors, but for now we will talk about one of the most important - the type of diabetes.
For start, I will say that diabetes is of two types - type 1 and type 2.
Understanding the difference between these two types of diabetes can be made easier if you remember those two important mechanisms we talked about above: after glucose intake the body secretes insulin and under the action of insulin certain tissues (liver, muscles and adipose tissue or tissues insulin-sensitive) begin to store glucose.
Thus, broadly speaking, the type of diabetes is defined by the mechanism that has been disrupted:
- If the first mechanism was disrupted (insulin secretion in response to glucose intake) - we are talking about type 1 diabetes.
- If the second mechanism was disrupted (glucose storage under the action of insulin in sensitive tissues) - we are talking about type 2 diabetes.
It should be noted that if in type 1 diabetes, the defect is at the level of insulin secretion, in type 2 diabetes, in addition to the deficiency of the second mechanism of regulation of blood glucose (glucose storage under the action of insulin ), to some extent is also disturbed insulin secretion. We separated these two defects, just for an easier understanding of the types of diabetes.
Understanding the link between the type of diabetes and the mechanism that has been disrupted is important for further understanding of the treatment of this disease. As mentioned above, in this disease the patient is forced to take control of the glucose level, and control is directed, of course, to the mechanism that failed in each specific situation.
How is diabetes diagnosed?
Regardless of the type of diabetes, the diagnosis can be made, if the body's inability to compensate for the glucose intake by putting in action the mechanisms mentioned above is shown. To demonstrate this inability, blood glucose levels are measured after ingesting a quantity of glucose. In patients with diabetes, blood glucose levels will rise rapidly above normal and gradually decrease as glucose is consumed by tissues. This test is called the glucose test (or oral glucose tolerance test), and is one of the main tests in the diagnosis of diabetes.
Other tests used to diagnose diabetes:
- determination of fasting blood glucose - this test involves measuring the level of fasting blood glucose. In patients with diabetes, this level will also be high.
- glycated hemoglobin test - this test is based on the fact that in case of excess blood glucose, it begins to be bound to hemoglobin, forming glycated hemoglobin. The presence of glycated hemoglobin, thus indirectly indicates a high level of glucose.
How is diabetes treated?
Based on the essence of the two types of diabetes, drug control of blood glucose in patients with diabetes is done with insulin in patients with type 1 diabetes and with drugs that increase tissue sensitivity to insulin in type 2 diabetes, such as metformin.
For both types of diabetes, of major importance are measures aimed at changing lifestyles, and especially the diet. Body weight control, meal compliance, balancing carbohydrate intake are some of these measures.