Diabetes Mellitus - its different forms

When you hear the word diabetes, what do you understand about this condition? In general, many people understand that it has to do with elevated blood sugars and the need for lifestyle and medication to help maintain blood sugars as close to goal as possible. The term ‘diabetes’ comes from an ancient Greek word in which diabetes means a large release/high volume of urine. Mellitus is a term that means ‘sweet’, due to the fact that in the large volume of urine that can be a hallmark sign of diabetes, there is also a large amount of glucose, or sugar, that is present in the urine, giving it a sweet flavor. Luckily, now we have other methods of confirming a diabetes diagnosis that does not involve a taste test and instead rely on blood tests. To learn more about how to screen for diabetes, check out my instagram post here.

In this blog, I will discuss the differences between 3 main types of diabetes mellitus: Type 1 Diabetes, Type 2 Diabetes, and Gestational Diabetes. At the end, I will also mention some other types of diabetes mellitus that are important to be aware of.

Important Terms

Glucose: this is the preferred energy source of cells in the body. Glucose is also known colloquially as sugar and so often, the phrases ‘blood sugar’ and ‘blood glucose’ are used interchangeably. In order for glucose to enter cells to be used for energy, the hormone, insulin, is needed. 

Insulin: Insulin is the active part of the hormone that gets secreted by specific cells of the pancreas, called beta-cells. Insulin attaches to insulin receptors located on the surfaces of cells which triggers a cascade of signals within cells that leads to the opening of a channel on the cell surface, allowing glucose to enter and be used as energy. 

Beta-cells: Insulin producing cells of the pancreas. 

Types of Diabetes

Type 1 Diabetes

This is an autoimmune form of diabetes. Autoimmunity refers to when a person’s body, for reasons that are not yet well understood, identifies certain parts of the body and mistakenly designates them as being foreign. As with any other foreign objects in the body, the immune system that mounts an attack to destroy this foreign object. 

In Type 1 diabetes, the mistaken foreign objects are the pancreatic beta cells. These cells come under attack from the person’s own immune system and the individual loses the ability to make insulin. With loss of insulin, blood glucose levels rise.

This process can happen at any time during a person’s lifetime, which is important to note. Many people associate type 1 diabetes as a condition that shows up in childhood, however, 50% of type 1 diabetes diagnoses actually happen in adults! It is true that in children, type 1 diabetes tends to be a more aggressive destruction in the beta-cells, resulting in many of the presentations occurring as diabetic ketoacidosis, a life-threatening medical emergency. In adults, the autoimmune destruction tends to be much slower and is also why type 1 diabetes often goes mischaracterized as type 2 diabetes for years.

An important detail to be aware of related to type 1 diabetes is that event that activates the immune system and the development of different stages of type 1 diabetes: Stage 1, Stage 2, and Stage 3. 

Stage 1: This stage is when there are two or more antibodies, specific to type 1 diabetes, detected in a blood draw. However, blood glucose numbers are all normal. The 4 antibodies that are commonly screened for are: GAD65, Zinc Transporter 8, Islet antigen 2 (IA-2), and insulin autoimmune antibodies.

Stage 2: This is characterized by the presence of two or more autoantibodies but now, there is evidence of abnormal glucose levels that don’t yet qualify as diabetes-range.

Stage 3: This is characterized by the presence of two or more autoantibodies and the glucose levels are in diabetes range.

Due to the significant or absolute lack of insulin secretion, individuals with type 1 diabetes need to be on insulin therapy to help maintain the glucose levels as close to the goal range as possible to avoid complications associated with long-term dysregulated blood sugars.

Type 2 Diabetes

This type of diabetes develops due to insulin resistance. Here, especially in the early stages of the condition, there is actually an oversecretion of insulin which is evident by high levels of circulating insulin. With so much insulin, how is it then possible that the blood sugars remain high? The issue is that despite the high levels of insulin, the cells are not responding to it as they normally would. They are not inserting the channels that should allow glucose from the bloodstream into the blood and instead, are essentially ignoring or ‘resisting’ insulin’s activity. This is known as insulin resistance.

The key to understanding the development of type 2 diabetes is to understand how insulin resistance develops. Insulin resistance is something that develops slowly over time and actually precedes any signs of abnormal blood sugars for many months and even years! From a nutritional standpoint, insulin resistance develops due to the consistent overconsumption of both ultra-refined carbohydrates AND high amounts of saturated fat in the diet. This last point frequently gets overlooked and has to be part of the lifestyle intervention individuals adopt, if they are interested in improving their insulin sensitivity. 

With insulin resistance, cells are occupied with large fat droplets that result from excessive consumption of specifically saturated fat. So when insulin is released due to circulating glucose in the blood, even if it attaches to the receptors, the cells refuse to put a channel on its surface to let glucose in since it is already occupied with fat and is going to use that as energy. So what happens? The pancreas essentially freaks out and starts making more and more insulin. Insulin levels rise, but glucose levels start to go up as well, since cells are not taking in glucose. This rise in glucose then leads to pre-diabetes and, if nothing changes, will eventually lead to the onset of type 2 diabetes.

Over time, the pancreas can eventually exhaust its ability to keep up with the rate and volume of insulin it has been trying to supply to keep blood glucose levels at goal and lose beta-cells. With the loss of beta-cells, there is also a loss of insulin production and also can help explain why individuals with type 2 diabetes may eventually have to go on insulin therapy. But it is important to note how this insulin requiring state is different from type 1. Type 1 beta-cell destruction is due to an autoimmune process, whereas in type 2 diabetes, beta-cell destruction is due to being overworked and high levels of glucose. Therefore, if someone with type 2 diabetes eventually requires insulin, they did not ‘switch’ from type 2 to type 1. They still have type 2 diabetes, but now require insulin.

Gestational Diabetes

This is a form of diabetes that is unique to pregnant individuals. Pregnancy is an insulin resistant state, due to the hormones secreted from the developing placenta, mainly, human placental lactogen (hPL) and its interference with insulin’s action. In many instances, a pregnant individual’s pancreas can compensate and make enough insulin to keep blood glucose levels at goal. However, in some pregnancies, this compensation does not properly occur, resulting in glucose levels trending up.

The reason this is an issue is because glucose can freely cross the placenta whereas insulin cannot. So if there is a high level of glucose that is crossing the placenta, the developing fetus has to then secrete insulin to keep the glucose in its environment at goal. Since insulin is a growth promoting hormone, this can cause the baby to grow larger and lead to complications during delivery, such as shoulder dystocia. Additionally, if there are high levels of insulin circulating when the baby is born, and the baby is suddenly no longer in the higher sugar environment, the baby is at risk of developing hypoglycemia after birth, or very low blood sugar and may need to go to the neonatal intensive care unit after birth.

Other Important Forms of Diabetes

MODY - This stands for mature onset diabetes of the young, due to the fact that it it is a genetically passed down diabetes that is autosomal dominant and presents in childhood. It is not type 1 diabetes as there are no insulin or pancreas antibodies present. There are at least 14 different genes that can cause MODY and treatments may involve a pill or can involve insulin as well.

Post-transplant diabetes - For people who are on immune suppressant medication after organ transplantation, some of these medicines can lead to insulin resistance or decreased insulin production, leading to elevated blood sugars and eventually, diabetes mellitus.

Other Medication Induced Diabetes - There are other medicines that can cause diabetes, such as pembrolizumab, a targeted chemotherapy agent used in cancers such as melanoma. The immune system can become activated in such a way that it mistakenly attacks the beta cells of the pancreas and can cause an insulin deficient diabetes that requires insulin therapy for treatment.

Summary

Diabetes mellitus does not come in just one form, but rather, can present due to a variety of causes. Understanding what caused it is important, as it also helps guide certain medicines that can be most helpful and effective in maintaining blood sugars at goal. One thing that does unify them all in treatment is the need to focus on lifestyle measures that support both endogenous and exogenous insulin so that the cells can appropriately respond to insulin signals, use glucose appropriately, and keep blood sugars as close to goal as possible.