4.2: Nutrition And Diabetes Mellitus

Hormonal Regulation of Glucose

Blood glucose levels are typically lowest in the morning after an overnight fast, followed by a fluctuation in glucose levels throughout the day. Though in constant fluctuation, blood glucose levels are maintained within a homeostatic range at all times through the action of the pancreatic hormones insulin and glucagon (Figure 4.11).

Insulin and glucagon are released from the endocrine cells of the pancreas - beta cells and alpha cells, respectively. The pancreas has a rich blood supply, so these hormones are released directly into the bloodstream. Insulin is released in response to elevated blood glucose levels, such as after a meal. Insulin works to lower blood glucose levels by promoting its uptake into cells, especially in muscle and fat tissue, by stimulating the storage of excess glucose as glycogen in the liver or storage of excess glucose as fat in adipose tissue. Glucagon is released in response to low blood glucose levels, such as during fasting or in between meals. It raises blood glucose by stimulating the liver to break down glycogen stores in the liver into glucose (glycogenolysis) and to produce new glucose from noncarbohydrate sources (gluconeogenesis). While it is true that glycogen is also stored in the skeletal muscle, muscle lacks a glucagon receptor and is insensitive to glucagon. Rather, epinephrine released from the adrenal glands is important in muscle glycogenolysis and the glycogen in skeletal muscle helps fuel physical activity. Together, insulin and glucagon maintain blood glucose within a narrow, healthy range, ensuring a steady supply of energy for the body, particularly for the brain.

Diabetes Mellitus

Diabetes mellitus is a metabolic disorder that affects how the body uses glucose. It is characterized by elevated blood glucose levels, or hyperglycemia. Diabetes has become a significant global health concern, with its prevalence rising sharply over the past few decades. As of 2022, approximately 830 million people worldwide are living with diabetes—a four-fold increase since 1990 . This surge is particularly pronounced in low- and middle-income countries, where access to healthcare and treatment options may be limited. In the United States, the Centers for Disease Control and Prevention (CDC) reports that about 38.4 million people, or 11.6% of the population, have diabetes. Notably, approximately 8.7 million adults are unaware they have the condition, highlighting the importance of regular screening and early detection . Furthermore, around 97.6 million U.S. adults have prediabetes, a condition of elevated blood glucose levels that don’t yet qualify for an official diabetes diagnosis.

Figure 4.11 Blood glucose homeostasis is a balance achieved by the hormones insulin and glucagon. Insulin is released in response to high blood glucose levels, while glucagon is released in response to low blood glucose levels. “Glucose homeostasis” by Carogonz11 is licensed under the Creative Commons Attribution Share-Alike 4.0 International license. Read image transcript.

Type 1 Diabetes Mellitus

Type 1 diabetes is an autoimmune condition in which the body’s immune system mistakenly attacks and destroys the insulin-producing beta cells in the pancreas. As a result, individuals with type 1 diabetes are unable to produce sufficient insulin, leading to high blood glucose levels. This type of diabetes typically develops in childhood or adolescence, though it can occur at any age. Because insulin is essential for transporting glucose into cells for energy, people with type 1 diabetes must manage their condition through lifelong insulin therapy, either via injections or an insulin pump. Without treatment, glucose remains in the bloodstream, leading to serious complications such as nerve damage, kidney failure, and cardiovascular disease.

Type 2 Diabetes Mellitus

Type 2 diabetes is a chronic metabolic disorder characterized by insulin resistance. In this condition, the pancreas produces sufficient insulin; however, the body’s cells do not respond effectively to the insulin. Over time, it is commonly seen that the pancreas may also then produce less insulin. This form of diabetes is more common in adults but is increasingly seen in children and adolescents due to rising obesity rates and sedentary lifestyles. Risk factors include genetics, poor diet, physical inactivity, and excess body weight. Management typically involves lifestyle changes such as healthy eating, regular exercise, weight loss, and, in some cases, medication or insulin therapy. If left uncontrolled, type 2 diabetes can lead to complications similar to those seen in type 1 diabetes, including heart disease, vision problems, and nerve damage.