7.10: Diabetes
Diabetes mellitus refers to the body’s inability to manage blood sugar (glucose), which results in chronically high blood glucose, or hyperglycemia. There are different types of diabetes depending on the origin and progression of the disease, however all types have something to do with the secretion or action of insulin.
In healthy conditions, the body has a consistent hormonal mechanism for managing blood sugar homeostasis (normal, resting levels). The pancreas produces two hormones: insulin and glucagon, with opposing functions. When a person eats a meal with any amount of carbohydrates, these are broken down in the digestive system to the simplest sugar: glucose, and then released into the bloodstream. This causes the blood glucose levels to rise, and in response, the pancreas releases insulin. Insulin signals to the body’s cells to take up glucose, thus bringing the blood glucose levels back down to resting levels. All of the body’s cells have receptors for insulin, and glucose can be taken up and used for energy, or stored as glycogen or within triglycerides (fat storage). Conversely, if blood glucose levels drop - such as with fasting or exercise - the pancreas will release glucagon, which signals to the liver to break down more of its stored glycogen and release it as glucose into the bloodstream.
Type I diabetes is classified as an autoimmune disorder, in which the body’s immune system attacks and destroys the beta cells in the pancreas that produce insulin. Since the body is unable to produce adequate insulin (insulin insufficiency), hyperglycemia results and the body’s cells are unable to use glucose for energy. This can result in symptoms like unintentional weight loss and low energy, and sometimes ketoacidosis - or the overproduction of ketones - which is a byproduct of the liver breaking down fat for energy and can cause weakness, vomiting, excessive thirst and urination (CDC, 2021). Type I diabetes is usually identified in children and adolescents, however some adults may be diagnosed with a latent form of type I diabetes as well. About 5-10% of people with diabetes have type I (ElSayed et al., 2022).
Type II diabetes is thought to progress from insulin resistance in the body’s cells. Obesity is closely associated with insulin resistance, along with some genetic and immune factors that may be interrelated. Although there are likely several mechanisms in this relationship between obesity and diabetes, one of them seems to be that high levels of fat stored in adipose tissue tends to increase chronic levels of inflammation throughout the body, and this inflammation then decreases sensitivity to insulin. If the body’s cells are resistant to the insulin being produced, the pancreas creates more - causing hyperinsulinemia. Eventually, the beta cells in the pancreas may also become damaged (perhaps also due to chronic inflammation), and insulin insufficiency may result (Rohm et al., 2022). Type II diabetes accounts for 90-95% of all diabetes cases (ElSayed et al., 2022). Pre-diabetes can be diagnosed as the early stages of this process, where blood glucose is slightly higher than normal, and can also be reversed with lifestyle interventions such as nutrition, exercise, and weight management.
Gestational diabetes is similar to type II diabetes in that it is characterized by insulin resistance - this time thought to be caused by pregnancy hormones. Obesity and a family history of type II diabetes certainly increase the risk of gestational diabetes. Most cases of gestational diabetes resolve after the pregnancy is over, however there may be an increased risk of developing type II diabetes in the future (ElSayed et al., 2022).