Diabetes Basics
Diabetes is a condition that we all understand a little about, or at least we think we do.... but a lot of us get stuck quite quickly once we get past the basics. These pages aim to demystify the physiology of healthy blood-glucose regulation. We'll then move onto when regulation goes wrong (eg. diabetes).
A beginners guide to how insulin and glucagon help the body use, store and regulate glucose.
Healthy Glucose Regulation
It's helpful to know what glucose regulation looks like when it's going well, before we get to stuck into when it goes wrong. In this section we'll look at glucose regulation when the endocrine system is working as expected. We'll investigate the various roles insulin plays in managing the glucose we absorb from our diets, as well as the role of Glucagon when glucose supplies are running low.
If you find visuals helpful then you can watch my animated video here.
To Much of a good thing: While the presence of at least some glucose in the blood is essential, high concentrations become toxic!
Insulin- the hormone in charge when glucose levels are high!!
Secretion
Insulin is secreted into the blood by specialist cells in the pancreas. Secretion is stimulated by the presence of glucose in the blood. Higher blood sugars lead to higher blood insulin levels.
Role one: 'Unlocking' cells for glucose
Glucose must pass into a cell before it can be broken down for energy, but it can't pass through a cell membrane without help. Insulin must first interact with the cell membrane, making it permeable to glucose. It can be helpful to think of insulin as a key, unlocking the cell to allow glucose to enter. Without insulin glucose would remain trapped in the blood, depriving the body of a source of energy!
Role two: regulating the storage of glucose
Excess glucose is taken out of the blood and stored away for later use. Most glucose is stored in the liver, although some storage in skeletal muscle and fat cells also occurs. Insulin is once again the hormone driving this process. Insulin stimulates the liver to absorb glucose from the blood, converting it into a slightly modified form, called glycogen, for storage.
Role three: Regulation of the hormone glucagon.......
Insulin acts as a 'key' unlocking the cells so glucose can enter.
Insulin promotes the uptake of glucose into the liver and muscles for storage. For storage, glucose is converted to glycogen.
Why Regulate?
Cells need a constant supply of energy
For the body's cells to function they need a steady fuel supply. Glucose is a major source of energy for cellular metabolism (activity). However, most cells cannot store glucose, therefore the body must provide them with a steady supply via the blood. There must always be at least some glucose present in the blood.
Too much of a good thing
Low blood glucose levels can be very dangerous, but excessively high glucose levels can also be hazardous too! Hyperglycaemia (high blood sugar) are associated with many short and long-term health consequences, including increased risks of stroke and heart disease. It is therefore essential that excess glucose is taken out of the blood before it can cause harm.
An inconsistent supply
While the body's need for glucose for energy is constant, the supply is not! All of us go through periods of fasting (eg. when we sleep), and during these periods new glucose is not being absorbed into the body from our diets. It is therefore essential that the body can store excess blood glucose when levels are high, and take glucose out of storage and back into the blood when glucose levels are low.
In order to conduct effective and healthy glucose regulation the body must therefore be able to do three things;
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Provide cells with a constant supply of glucose via the bloodstream.
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Remove excess glucose from the blood (storing it away for later use).
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Take glucose out of storage and back into the bloodstream when blood sugar levels are low.
Glucose is one of the bodies primary sources of energy. It is broken down inside cells to produce 'ATP', which can then bu used to power cellular metabolism.
Glucagon: what you need when your blood runs low on glucose!
Secretion
Glucagon is also secreted by the pancreas. The presence of insulin in the blood suppresses its release, so when insulin levels are high, eg. after a meal, Glucagon levels will be low. But if blood-insulin levels begin to drop (for example, when we fast), more glucagon will be able to enter the blood.
Ensuring a steady fuel supply
One of Glucagon's primary roles is to release the body's supplies of stored glucose in times of need. When Glucagon interacts with the liver and muscle cells it stimulates them to convert some of their Glycogen back to glucose, ensuring the body's cells still have a source of energy.
Not forgetting fat cells!
Glucagon will also interact with fat cells, causing them to release amino acids into the blood, which the liver can turn into ketones. Ketones are another important source of energy for cellular metabolism. They can be taken into cells and broken down for energy. However, they come with a catch... Ketones are acidic and have the potential to reduce blood pH to dangerously low levels (see Ketoacidosis for more details).
Working together!
Hopefully now the basics of regulation are starting to make some sense! Insulin and Glucagon together keep glucose levels within a healthy range ensuring the body never has to go with out a fuel supply.
Blood glucose levels increasing (after a meal) stimulates the release of Insulin from the pancreas, which in turn leads to more glucose being taken into cells & broken down for energy, and more glucose being taken into the liver the muscles (as glycogen) for storage. The net result is a reduction in blood glucose levels.
If blood glucose levels drop below optimum range (for example, overnight when were not eating) then less insulin will be secreted into the blood. High blood-insulin levels suppress the secretion of Glucagon from the pancreas, but as insulin levels reduce, some will be able to escape! Glucagon will stimulate the release of some of the stored glucose in the liver, back into the blood stream. The net result is an increase in blood glucose
Now we've gone through the basics of healthy glucose regulation we can start to look at what happens when regulation goes wrong! It's time to talk about Type one and type two diabetes!
Type One and Type Two
Diabetes
There are many forms of diabetes (eg. gestational diabetes, steroid induced diabetes etc.). The most commonly encountered and known about are of course 'type one' and 'type two'. This section aims to get you started with some of the fundamentals of the two conditions.
Oversimplified
Type one
In some ways type one diabetes is fairly simple to understand. The panaceas looses its ability to produce and secrete insulin entirely. As a result, all of the roles that insulin performs for the body will cease to occur.
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Cells will cease to be able to break down glucose for energy.
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The liver won't be able to take in excess blood glucose for storage.
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Symptoms of Ketoacidosis will begin to manifest.
In short, if a sufferer of type one diabetes doesn't get some insulin administered their in trouble!
Diabetes Type One & Two (whats the difference?)
Type Two
A sufferer of type two diabetes has a panaceas that is still capable of producing insulin, however the cells have become resistant to it's effects. As a result less glucose will be absorbed from the blood. Without carful management blood glucose levels will rise. As there is still insulin available, the effects of type two diabetes do not tend to be as immediately life threatening as those seen in type one diabetes, however the chronic effects for suffers can be very serious! (the effects of high glucose levels are covered in the next section).
Treatment will vary. For some blood glucose can be control by diet alone (consuming less sugary foods and less simple carbohydrates). Others will require medications including, in some cases, insulin, to keep their blood sugars within a healthy range.
Hypoglycemia & Hyperglycemia
Oversimplified
Hyperglycaemia (high sugars)
High blood glucose levels can have both short term and long term implications for health.
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In the short term: Glucose, in high concentrations, acts as an osmotic agent, meaning it effectively pulls water towards it. Fluid is pulled out of cells towards the high blood concentrations of glucose, and is then passed out of the body as urine. This can lead to dehydration if the sufferer doesn't drink enough to fluids to replace the loss. They may also loose essential electrolytes such as potassium with the urine, which can lead to issue's such as heart dysthymias!
HYPER & HYPOGLYCAEMIA: Diabetes (simply) explained!
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Long term: High glucose levels are 'corrosive' to the body, more or less everywhere! Much of the trouble results from damage the high glucose levels can cause to blood vessels. For example, the damage caused to blood vessels in the brain increases the risk of stroke and the the damage to the arteries supplying the heart can lead to increased risk of heart attacks (infarctions.) Other complications include damage to the kidneys, peripheral blood vessels and even the retina of the eyes!
Hypoglycaemia (low sugars)
Hypoglycaemia is often the results of medications used to control high sugars (for example insulin). The body needs a consistent supply of glucose to power the activities of its cells and when the cells are deprived of that fuel, things start to go wrong quickly!
Most of the symptoms associated with a 'hypo' result from the brain being deprived of glucose. As the brain cells begin to struggle the sufferer may initially become confused or a little agitated. If untreated this can develop into more serous complications including hallucinations and loss of consciousness! Hypoglycaemia has the potential to be life threatening!