DIABETES MELLITUS AND INSULIN

Hi, today we will be discussing about the relationship between diabetes mellitus and insulin.

We can break down food into many different types of nutrients. One of the most important nutrients our body needs is a sugar called glucose, which is the fuel that powers the cells of our body. Glucose is transported throughout the body by blood and requires careful regulation, since too much glucose in the blood can lead to disastrous consequences, such as diabetes mellitus. Read this article to learn more about the symptoms, cause, and treatment of this disease.

Let’s talk about blood glucose regulation first. The body has many ways to increase or decrease the amount of glucose in the blood. Some ways to increase blood glucose include eating a meal, synthesizing glucose from scratch, or releasing glucose from storage, while some ways to decrease blood glucose are to transport glucose into cells, which either use up glucose for energy or store it. Throughout the day, the body is constantly making slight adjustments to keep blood glucose levels at an optimal range. These slight adjustments are controlled by the hormones insulin and glucagon, but in this article, we’ll focus on insulin. Insulin is released into the bloodstream when blood glucose is high, such as after a meal. It signals to cells to take in glucose for energy or storage. It also prevents more glucose from being synthesized or released from storage. Therefore, the overall effect of insulin is to decrease blood glucose levels. Diabetes mellitus, or simply diabetes, occurs when this insulin signalling pathway is broken. Without proper functioning of insulin, blood glucose levels skyrocket. Despite glucose being a very important source of fuel for the body, too much of it in the blood is extremely damaging. In the short term, high blood glucose leads to the hallmark symptom of diabetes: glucosuria, or glucose in the urine. In fact, the term “mellitus” means “honey” in Latin to reflect this symptom of sweet-tasting urine. How does this occur?

At the kidneys, glucose is filtered out of the blood and into the urine, but is later transported back into the blood since the body does not want to lose this valuable source of fuel. This reabsorption uses proteins which have a maximum rate of transport. When there is too much glucose in the blood, more of it is filtered into the urine. Even at their maximum transport rate, the proteins cannot transport all of the glucose out of the urine, leading to glucosuria. This causes excess urination, since the presence of glucose in the urine draws in more water by osmosis. Excess thirst and dehydration are a consequence of this since more water is lost through urine. In addition, since cells cannot take up glucose for energy without insulin, the body perceives itself to be “starving”, leading to both increased appetite and fatigue. In the long term, high blood glucose damages blood vessels in the eyes and kidneys, which is why diabetes is the leading cause of adult blindness and kidney failure. High blood glucose also damages nerves, leading to loss of sensation in the feet and hands. When those areas get injured, such as from cuts or from blood vessel damage, the person does not notice the injury, leading to infections and necrosis that eventually require amputation. Most importantly, the damage to blood vessels in the heart and brain can lead to high blood pressure, stroke, and heart attacks, which account for most of the deaths in diabetic patients.

Most diabetes cases can be divided into two types based on how the insulin signalling pathway is malfunctioning. Type 1 diabetes accounts for around 10% of diabetes cases, while Type 2 makes up most of the remainder. The last few percentage points are attributed to rarer forms of diabetes that you can check out in the video description. Type 1 diabetes is caused by a lack of insulin production. In the pancreas, there are special clusters of endocrine cells called the islets of Langerhans. One type of endocrine cell in these islets is the beta cell, which produce and release insulin. In Type 1 diabetes, the beta cells are destroyed by the immune system. Therefore, the body can no longer produce insulin and blood glucose levels rise uncontrollably, leading to the symptoms mentioned earlier. Scientists believe both genetic mutations and environmental factors, such as infections, may play a role in triggering this autoimmune attack. An additional symptom of Type 1 diabetes is rapid weight loss, as fat cells, or adipocytes, begin to break down fats into another type of energy molecule known as ketone bodies. Large amounts of these ketone bodies are released into the blood, which can be taken up by other cells as an alternative source of fuel. However, ketone bodies are slightly acidic molecules, so excessive amounts of these molecules can acidify the blood. This is known as diabetic ketoacidosis, which is a life-threatening condition if untreated. However, when most people think of “diabetes”, they are probably imagining the more common Type 2 diabetes associated with obesity, ahigh sugar and fat diet, and a lack of exercise. These three lifestyle factors, as well as genetic factors, dramatically increase the risk of developing Type 2 diabetes. Unlike Type 1 diabetics, Type 2 diabetics continue to produce insulin. However, their cells have become resistant to insulin, meaning that more insulin is required to achieve the same effect of lowering blood glucose. 

To compensate for insulin’s ineffectiveness, beta cells will produce even more insulin. However, when insulin resistance becomes so severe that the insulin required by the body exceeds the maximum amount of insulin produced by beta cells, symptoms of high blood glucose begin to appear. Weight loss and diabetic ketoacidosis from fat breakdown also occur in some cases of Type 2 diabetes. Furthermore, in some cases the continued overproduction takes a toll on the beta cells, which eventually die and causes a lack of insulin production, further worsening the problem. The cause of insulin resistance is still not well understood; however, factors such as high insulin levels from excessive sugar consumption and fat around the liver and pancreas are being investigated as possible causes of insulin resistance. It is important to note that it is very difficult to “cure” diabetes as of now. Doctors are only able to make living with diabetes tolerable, as long as medications are taken and lifestyle changes occur. Current treatment depends on the type of diabetes. Since the high blood glucose of Type 1 diabetes is caused by a lack of insulin, simply administer insulin during periods of high blood glucose, such as after a meal. However, this is easier said than done. Insulin is a protein and will get degraded in the stomach if taken orally. Therefore, Type 1 diabetics must inject insulin directly into the bloodstream, usually just under the skin of their abdomen. The dose is also extremely important – too little and blood glucose levels remain high, but too much insulin will cause blood glucose levels to plummet, leading to coma or even death. On the other hand, decreasing high blood glucose in Type 2 diabetes is much more complicated. Insulin is only effective in around 30% of patients as cells are already insulin resistant, so other methods of decreasing blood glucose are required. Many diabetic drugs have been developed which target the mechanisms of blood glucose regulation mentioned in the beginning of this video. These drugs can decrease glucose absorption in the intestines after a meal, decrease synthesis of new glucose, or increase insulin sensitivity which leads to more glucose uptake by cells. For example, the drug metformin is the first line treatment to Type 2 diabetes because it can activate certain metabolic pathways to both decrease glucose synthesis and increase glucose uptake by cells by increasing insulin sensitivity. However, despite our best efforts, diabetes is the 6th leading cause of death worldwide, with 3 people dying from diabetes complications every minute. Therefore, the best treatment of diabetes is to prevent diabetes from occurring in the first place. Though no prevention method is known for Type1 diabetes, frequent exercise and a healthy diet drastically reduces the risk of the much more common Type 2 diabetes. Currently, it is estimated that 400 million adults, which is around 10% of the worldwide adult population, is living with diabetes, although this number is expected to increase in the future. If more people become aware of and avoid the lifestyle choices associated with diabetes, we can slow down or even reverse this trend. 

Furthermore, Type 2 diabetes in particular develops slowly and silently over time, leading scientists to suspect that almost half of the worldwide diabetic population is undiagnosed, which is why it is so important to educate the public about the causes and symptoms of this disease. It is also important to note that diabetes is an extremely complex and not fully understood disease that scientists are still finding new information about everyday. So if you want to learn more about diabetes, like new treatments and research, check out the links in the description below.

Thanks for reading.