The Dirt on Diabetes: The Basics of a Chronic Disease
Posted on 11/11/22 by Sarah Boudreau
Diabetes is a disease that’s becoming more and more common. It’s been estimated that by 2045, there will be 700 million people aged 20-75 with known diabetes—and an equal number of people with undiagnosed diabetes.
Unmanaged diabetes can have severe complications; for example, it’s the most common cause of blindness in working-age people and the most common cause of end-stage renal failure overall. It’s responsible for lower limb amputations, nerve damage, skin sores, and more. A high level of blood sugar can damage the blood vessels and nerves around the heart, increasing risk of heart disease and heart failure.
But what exactly is diabetes? Diabetes, or diabetes mellitus, is a chronic condition where blood has elevated concentrations of glucose. Diabetes occurs when the body has issues with insulin, a hormone that lowers blood glucose.
That may sound like a vague description, but that’s because there are two main types of diabetes, and each type has its own mechanism. In this blog post, we’ll talk about insulin, the two major types of diabetes, and gestational diabetes, a type of diabetes that, though it isn’t chronic, affects a significant number of pregnancies.
Insulin and the Pancreas
Before we get into the different major types of diabetes, let’s talk about the hormone at play and the organ that creates it.
The pancreas is responsible for insulin secretion. It’s a six-inch long organ located behind the stomach that consists of a head (located where the stomach meets the duodenum) and the tail, which extends across the abdomen. The pancreas contains both endocrine and exocrine gland cells, performing double duty as both an endocrine and an exocrine gland!
View of the pancreas in Human Anatomy Atlas.
Exocrine cells produce enzymes that make pancreatic juice, a digestive fluid that flows into the small intestine to help break down carbs, fats, and proteins. The pancreas also contains pancreatic islets, which produce hormones. These cell clusters include alpha cells (which synthesize glucagon) and beta cells (which synthesize insulin).
Glucagon promotes the breakdown of glycogen into glucose, the synthesis of glucose from lactic acid and noncarbohydrate molecules, and the release of glucose to the blood.
When it comes to diabetes, the focus is on insulin. Beta cells secrete insulin when blood glucose is high, signaling cells to take up glucose and convert it into energy or other substances. It also promotes protein synthesis and fat storage.
Insulin lowers glucose levels by…
- enhancing membrane transport of glucose into cells
- promoting the storage of fat in fat cells, promoting the storage of glycogen in muscle cells
- preventing the breakdown of glycogen to glucose
- preventing the conversion of amino acids to glucose.
When glucose levels drop, beta cells reduce their insulin secretion. Through glucagon and insulin, the pancreas balances the body’s blood sugar.
Type 1 diabetes is the less common of the two major types, occurring in 5-10% of diabetes cases. In type 1 diabetes, some or all beta cells are destroyed, which means that the pancreas either does not create insulin or creates too little insulin. This causes sugar to build up in the blood because it can’t be absorbed into cells.
Though researchers don’t yet know the exact cause of type 1 diabetes, it’s likely that type 1 is an autoimmune disorder, a result of the body mistakenly attacking beta cells. It’s thought that it can be triggered by viruses. Researchers have found that children who were exposed as fetuses to rubella have an increased incidence of type 1 diabetes, and RNA from viruses has been found in the pancreas of type 1 patients. It’s worth mentioning that vaccinating infants—even infants who are genetically predisposed to type 1 diabetes—does not increase the risk of type 1 diabetes.
Type 1 diabetes tends to be diagnosed early in life. Though some are diagnosed as babies and some are diagnosed even over the age of 40, it’s most common to be diagnosed with type 1 diabetes at age 13 or 14. Unlike some other diseases, most people with type 1 diabetes have no family history of the condition, though if your sibling or parent has type 1 diabetes, you’re more likely to develop it as well.
The most prominent symptoms of type 1 diabetes are thirst and excessive urination. Because of increased blood glucose, the kidneys create more urine than usual, and that in turn makes people dehydrated. This dehydration can also cause weight loss without loss of appetite.
Urine moves from the kidneys through the ureter into the bladder. Image from Human Anatomy Atlas.
One very serious complication of type 1 diabetes is diabetic ketoacidosis, or DKA. When the cells can’t use blood sugar as energy, the liver breaks down fat to use as fuel instead, which produces acids called ketones. Ketones can build to dangerous levels, and DKA can lead to coma or death.
While type 1 diabetes happens when beta cells are destroyed, type 2 diabetes occurs when cells become insulin resistant. The pancreas makes more insulin to make up for this, but eventually it can’t keep up with demand and blood sugar levels rise.
It’s thought that obesity increases the likelihood of developing type 2 diabetes because adipose tissue (aka fat tissue) alters metabolism by secreting many substances, like hormones, leptin, and cytokines. Adipose tissue also releases nonesterified fatty acids, which are associated with insulin resistance.
Other risk factors include
- High blood pressure
- High cholesterol
About one in three adult Americans has prediabetes, elevated blood sugar levels that aren’t quite elevated enough for a diabetes diagnosis. If your blood glucose is between 100 and 125 mg/dL, you have prediabetes, which increases your risk for developing type 2 diabetes. Type 2 diabetes can be prevented through lifestyle changes, like exercise and a healthy diet. In fact, exercise increases insulin sensitivity!
The symptoms of type 2 diabetes are the same as type 1 diabetes, and they tend to begin in adulthood, though they are becoming more common in children and adolescents. Symptoms often take several years to develop, but some people don’t notice symptoms at all.
Hyperosmolar hyperglycemic syndrome (HHS) is a clinical condition most commonly seen in type 2 diabetes patients, though type 1 diabetics can develop HHS. HHS occurs when blood sugar levels are extremely high, though unlike DKA, ketones are rarely present.
The kidneys allow extra glucose to leave the body through urine, which makes the body lose water. When a patient doesn’t drink enough water, the kidneys can’t offload glucose into more urine, causing a buildup of glucose in the blood. Thanks to a lack of water, the blood becomes more concentrated, which is a condition called hyperosmolarity. Blood with a high concentration of substances like glucose and salt will draw water out of the organs. Symptoms include fever, nausea, confusion, seizures, and coma. Overall, mortality is low, and HHS can be managed through aggressive hydration through an IV.
The last type of diabetes we’ll talk about today is gestational diabetes, which occurs in about 7% of all pregnancies. Unlike type 1 and type 2 diabetes, which are chronic health conditions, gestational diabetes only occurs during pregnancy; blood sugar levels typically return to normal after giving birth.
The exact mechanisms behind gestational diabetes aren’t known, but the process begins when the placenta produces hormones like cortisol, human placental lactogen, and estrogen, which block insulin from taking effect. Gestational diabetes occurs when the pancreas cannot make enough insulin to overcome the insulin resistance.
Gestational diabetes is usually diagnosed between the 24th to 28th week of pregnancy, though most patients don’t experience symptoms, and symptoms are generally mild, like increased urination. However, unmanaged gestational diabetes increases risks for other conditions.
Gestational diabetes patients are more likely to
- Develop preeclampsia, a serious blood pressure condition
- Have a C-section
- Have a miscarriage or a stillborn baby
- Develop type 2 diabetes later in life
If you have gestational diabetes, it’s more likely that your baby will
- Have hypoglycemia, or low blood pressure immediately after delivery
- Be considerably larger than normal, which can result in issues with delivery
- Have breathing problems
- Become overweight and develop type 2 diabetes later in life
All of that may seem scary, but managing gestational diabetes can mitigate those risks. Gestational diabetes is typically managed through healthy eating and exercise, though some patients require diabetes medicine while pregnant.
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