Basic Knowledge of Diabetes and Principles of Initial Medication: A Complete Guide from Pathogenesis to Initial Selection of Hypoglycemic Drugs

Basic Knowledge of Diabetes

What is Diabetes?

Diabetes is a common endocrine disorder caused by an absolute or relative deficiency of insulin, a hormone in the body, and decreased sensitivity of target tissue cells (i.e., effector cells acted upon by insulin, such as fat, liver, skeletal muscle, etc.) to insulin (insulin resistance), leading to disorders in the metabolism of carbohydrates, fats, and proteins. This disease is lifelong and difficult to cure completely. As the disease progresses, the metabolic disorders of the three major substances in the body worsen, leading to chronic progressive lesions in organs and tissues such as the eyes, kidneys, nerves, blood vessels, and heart. If left untreated, it can lead to diabetic cataracts and retinopathy, blindness, lower limb gangrene, uremia, cerebrovascular disease, or heart disease, ultimately endangering life.

What is Blood Sugar? What are its sources and pathways? Blood glucose is the glucose contained in the blood, referring to the concentration of glucose in the blood. Blood glucose concentration is determined by the dynamic balance of its sources and fates. Main source: Glucose produced from the digestion and absorption of starch in food. In the absence of food intake, it mainly comes from liver glycogen. Fate:

① Oxidation and decomposition in tissues and organs to supply energy;

② Synthesis of glycogen in various tissues and organs, such as the liver, muscles, and kidneys;

③ Conversion into fat for storage;

④ Conversion into other carbohydrates.

What are the functions of insulin? In a normal person, the pancreas contains islets of Langerhans, which account for 1.5% of the total pancreas. The beta cells of the islets secrete insulin. Insulin has a very wide range of effects on metabolism. Except for red blood cells, kidneys, and brain tissue, which are relatively unaffected by insulin, most other tissues are affected, particularly muscles, fat, and the liver. In short, insulin has the following functions:

① Promotes the entry of glucose from the blood into tissues such as the liver, muscles, and fat, where it is synthesized into glycogen and stored.

② Promotes the oxidation and decomposition of glucose to release energy for the body's use. Therefore, insulin can both increase glucose elimination and reduce glucose intake, thus its most significant effect is lowering blood sugar. When pancreatic beta cells are damaged or their function declines, insufficient or absent insulin secretion leads to hyperglycemia. Because blood sugar levels exceed the renal tubules' ability to absorb glucose, some glucose is excreted in the urine, resulting in diabetes.

What are the different types of diabetes? In 1996, the WHO classified diabetes into four types based on its etiology:

① Type 1 diabetes: Caused by the destruction of pancreatic beta cells, leading to an absolute lack of insulin. Patients with this type must rely on exogenous insulin to survive.

② Type 2 diabetes: Caused primarily by insulin resistance with insufficient insulin secretion, or primarily by insufficient insulin secretion with or without insulin resistance. This type accounts for more than 90% of diabetes cases.

③ Idiopathic diabetes: Drug-induced diabetes, secondary diabetes.

④ Malnutrition-related diabetes.

How does type 2 diabetes develop? Pathologically, the main causes of type 2 diabetes are:

Insufficient insulin secretion;

Insulin insensitivity (also known as insulin resistance). This condition is more common in obese patients or those with dyslipidemia. Patients with predominantly insufficient insulin secretion also have varying degrees of insulin resistance, but it is relatively mild. Their characteristic is insufficient insulin levels, and they are generally thin or of normal weight. Another type occurs when diabetes progresses to a certain stage, where both symptoms become apparent. Initially, insulin resistance is more severe, but later pancreatic function gradually declines, leading to reduced insulin secretion.

What is absolute insulin deficiency?

Generally, this refers to an absolute reduction in pancreatic beta cells, commonly seen in type 1 diabetes (due to destruction of pancreatic cells or removal of pancreatic tumors). Therefore, very little or no insulin is secreted, which is called absolute insulin deficiency.

What is relative insulin deficiency?

When a patient has normal or above-normal levels of insulin in their blood, but it cannot perform its normal physiological function, leading to diabetes, such as type 2 diabetes, this is usually called insufficient insulin secretion.

What is insulin resistance?

When the amount of insulin is not insufficient, but the body (target organs) is insensitive to insulin, meaning that insulin cannot perform its proper functions of supplying energy, transporting, and storing glucose, this is called insulin resistance. The result is elevated blood sugar, leading to diabetes.

What are the symptoms of diabetes?

The main symptoms of diabetes include polyuria, polydipsia, polyphagia, and weight loss ("the three highs and one low"), pre-meal hypoglycemia, itchy skin, susceptibility to skin infections, and decreased vision; as well as manifestations of chronic complications of diabetes such as numbness in the hands and feet, palpitations, shortness of breath, diarrhea, constipation, urinary retention (difficulty urinating), and erectile dysfunction (impotence).

What are the diagnostic criteria for diabetes?

There are various methods for detecting diabetes, but the only basis for diagnosing diabetes is venous blood glucose. Finger-prick blood glucose measured with a glucometer can be used as an indicator for diabetes detection, but not as a diagnostic basis. According to internationally unified standards, a fasting blood glucose level equal to or higher than 7.0 mmol/L, or a 2-hour postprandial blood glucose level equal to or higher than 11.1 mmol/L, is sufficient for a diagnosis of diabetes. An oral glucose tolerance test (OGTT) showing a blood glucose level equal to or higher than 11.1 mmol/L 2 hours after glucose intake can also diagnose diabetes. Principles of Hypoglycemic Drug Application