From High Blood Sugar Warning Signs to Metabolic Syndrome: Analyzing the Chain Reaction Between Abnormal Glucose and Lipid Metabolism and Insulin Resistance

Section 3 High Blood Sugar Blood sugar refers to the glucose contained in the blood, and blood sugar value represents the concentration of glucose in the blood.

2. What is the normal range of blood glucose? Carbohydrates are the basic components of blood glucose, and normal blood glucose levels are extremely important for the physiological functions of various tissues and organs in the human body. Normal blood glucose fluctuates within a certain range; fasting blood glucose should be 3.9–6.0 mmol/L, and blood glucose 2 hours after a meal should not exceed 7.8 mmol/L.

3. What is Hyperglycemia? Under normal circumstances, the human body can regulate its blood sugar levels to keep them within the normal range. Blood sugar exceeding the normal range is hyperglycemia. When blood sugar rises significantly to a certain level, such as fasting blood sugar exceeding 7.0 mmol/L or 2-hour postprandial blood sugar exceeding 11.1 mmol/L, it meets the diagnostic criteria for diabetes and is called diabetes. If blood sugar, although exceeding the normal range, is only slightly elevated and has not yet met the diagnostic criteria for diabetes, such as fasting blood sugar between 6.2 and 7.0 mmol/L, or 2-hour postprandial blood sugar between 7.8 and 11.1 mmol/L, it is medically termed impaired glucose tolerance (IGT). In a sense, this mild hyperglycemia is a warning sign of diabetes. It should be taken seriously, and preventative measures should be taken to prevent its development into diabetes. This section mainly introduces this mild hyperglycemia, which falls between the normal blood sugar range and diabetes. We will discuss diabetes in detail in Chapter 3, Section 1.

4. Can normal people experience high blood sugar? Actually, normal people can experience high blood sugar under many physiological conditions. For example, temporary high blood sugar can occur when under stress, emotional excitement, high tension, or after consuming a large amount of sugar at once; however, as the physiological state recovers, blood sugar will quickly return to the normal range.

5. Besides diabetes, what other situations can cause elevated blood sugar? We already know that although diabetes manifests as elevated blood sugar, not all elevated blood sugar is diabetes. Besides diabetes, elevated blood sugar may also occur in the following situations: (1) When liver diseases such as hepatitis and cirrhosis reduce liver glycogen reserves, a transient increase in postprandial blood sugar may occur. If the liver disease is actively treated, blood sugar can return to normal. (2) In cases of acute infection, trauma, cerebrovascular accident, burns, myocardial infarction, severe pain, etc., under stress, the secretion of insulin antagonist hormones, adrenocorticotropic hormone, adrenal medullary hormone, growth hormone (all of which have the effect of raising blood sugar) increases, while insulin secretion is relatively insufficient, causing blood sugar to rise. Blood sugar will return to normal after the stress is eliminated. (3) Hunger and decreased physical strength in patients with chronic diseases can cause impaired glucose tolerance, leading to elevated blood sugar. Actively treating chronic diseases and improving physical condition can restore blood sugar to normal. (4) Certain medications, such as glucocorticoids (dexamethasone, prednisone, etc.), oral contraceptives, thyroid hormones, niacin, and indomethacin, can cause transient hyperglycemia. Blood sugar will quickly return to normal after discontinuing the medication. (5) Some endocrine disorders, such as acromegaly, Cushing's syndrome, and hyperthyroidism, can cause secondary hyperglycemia. Blood sugar will gradually return to normal after the primary disease is effectively controlled. Therefore, if you find your blood sugar is elevated, you must rule out these factors that cause it. A clear diagnosis is the prerequisite for treatment; never take hypoglycemic drugs indiscriminately.

6. Why are pregnant women prone to hyperglycemia? After conception, women experience increased secretion of estrogen and progesterone, which act as insulin-resistant agents in the peripheral nervous system. As pregnancy progresses, the increasing levels of estrogen and progesterone prompt the body to secrete more insulin to maintain normal glucose metabolism. Due to individual differences, not everyone can compensate by secreting enough insulin, leading to insufficient insulin secretion and resulting in abnormal glucose metabolism or inadequate insulin sensitivity. Furthermore, many pregnant women consume excessive amounts of high-nutrient, high-sugar foods to ensure fetal development, while others experience significant changes in taste during pregnancy, developing a craving for fruit, sometimes even eating half a watermelon at a time. This exacerbates glucose metabolism disorders in pregnant women. These are the reasons why hyperglycemia is common during pregnancy, and many women subsequently meet the diagnostic criteria for gestational diabetes.

7. Is high blood sugar beneficial to the body? Many people wonder if high blood sugar is good for the body since glucose is essential. Actually, short-term, transient high blood sugar does not cause serious harm. Especially under stress conditions mentioned earlier, high blood sugar may even be a necessity. In such cases, high blood sugar can be considered beneficial. However, in diabetes, long-term high blood sugar causes pathological changes in various organs and tissues throughout the body, which is harmful.

Chapter Three: The Outcomes of the "Three Highs" Hypertension, hyperlipidemia, and hyperglycemia, collectively known as the "Three Highs," are common conditions among middle-aged and elderly people. While hypertension, hyperlipidemia, and hyperglycemia may seem asymptomatic on their own, they can actually cause significant harm. Most importantly, these conditions can lead to numerous other complications, many of which can seriously threaten a patient's life. You may not be very familiar with these complications of the "Three Highs"! Below, we will introduce them to you one by one.

Section 1 Metabolic Syndrome 1. Are Glucose and Lipid Metabolism Disorders, Hypertension, and Obesity Coincidentally Clustered Together? We often observe that many people simultaneously suffer from glucose metabolism disorders (impaired glucose tolerance, type 2 diabetes), lipid metabolism disorders (elevated plasma triglyceride and very low-density lipoprotein concentrations, decreased high-density lipoprotein cholesterol levels), hypertension, obesity, and other diseases. Could this be a coincidence? Although the prevalence of various metabolic disorders varies among different populations, the results of analysis across multiple populations to date are very similar: the vast majority of people either have no such diseases or have three or more of these diseases, while those with only one or two are rare. Therefore, the clustering of obesity, type 2 diabetes, impaired glucose tolerance, hypertension, and hypertriglyceridemia is not accidental. This phenomenon has gradually attracted attention. In the 1960s, Mchnert termed impaired glucose tolerance and hypertension as "affluent syndrome." In 1988, Reaven collectively termed insulin resistance, hyperinsulinemia, impaired glucose tolerance, hypertriglyceridemia, and hypertension as "Syndrome X," also known as "Reaven Syndrome." In 1989, Kaplan summarized visceral obesity, impaired glucose tolerance, hypertriglyceridemia, and hypertension-based on hyperinsulinemia-as risk factors for coronary heart disease, calling it the "Deadly Quartet." In 1991, De Fronzo named this group of metabolic cardiovascular disease syndromes "Insulin Resistance Syndrome." Australian diabetes experts use the acronym CHA-OS to name this syndrome: coronary heart disease, hypertension, hyperlipidemia, adult-onset diabetes, obesity, and stroke. Alternatively, this phenomenon is also referred to as "four highs and one low" (i.e., hypertension, hyperglycemia or impaired glucose tolerance, hyperinsulinemia, hypertriglyceridemia, and decreased high-density lipoprotein). Recently, a World Health Organization expert committee specifically discussed this syndrome and recommended the name "Metabolic Syndrome."

2. What are the clinical manifestations and characteristic factors of metabolic syndrome? Possible clinical manifestations of metabolic syndrome include: abdominal obesity, impaired glucose tolerance or type 2 diabetes, lipid metabolism disorders, hypertension, hyperuricemia and gout, premature atherosclerotic diseases (such as coronary heart disease, stroke, etc.), osteoporosis, hypercoagulable state, decreased fibrinolytic activity, decreased serum magnesium, sleep apnea syndrome, fatty liver, chronic alcoholism, growth hormone deficiency, polycystic ovary syndrome, and increased androgen levels in women. Characteristic factors of metabolic syndrome include: ① abdominal obesity; ② atherosclerotic dyslipidemia (lipid triad) (elevated triglycerides, increased small and dense low-density lipoprotein cholesterol particles, decreased high-density lipoprotein cholesterol); ③ elevated blood pressure; ④ insulin-stimulated glucose uptake resistance, hyperglycemia, hyperinsulinemia; ⑤ embolic and inflammatory states; ⑥ hyperuricemia; ⑦ coronary heart disease, cerebrovascular accident. A diagnosis of metabolic syndrome can be made when three or more of the following risk factors are present: ① Abdominal obesity: waist circumference >102 cm for men and >88 cm for women; ② Plasma triglycerides ≥3.9 mmol/L; ③ High-density lipoprotein cholesterol: <1.04 mmol/L for men and <1.3 mmol/L for women; ④ Blood pressure ≥130/85 mmHg; ⑤ Fasting blood glucose ≥6.1 mmol/L. These conditions share a common pathophysiological mechanism: insulin resistance.

3. What are the control targets for metabolic syndrome? The control targets for metabolic syndrome are shown in Table 2. Table 2: Control Targets for Metabolic Syndrome

*1999 Asia-Pacific Type 2 Diabetes Policy Group Standards; **1999 Asia-Pacific Obesity Conference Recommended Standards.

4. Types of Insulin Resistance Insulin resistance can be classified as physiological or pathological. A certain degree of insulin resistance can be observed at certain stages of a person's life, such as old age, pregnancy, and adolescence. Additionally, under certain physiological states, such as starvation, post-operative fasting or insufficient food intake, and stress, the body will exhibit a decrease in plasma insulin levels, accompanied by reduced sensitivity of peripheral tissues to insulin. Insulin resistance is a pathophysiological state that can be caused by genetics or multiple factors. It is known that the physiological function of insulin is accomplished through the binding of insulin to insulin receptors located on the cell membrane, catalyzed by a series of enzymes. Abnormalities in any step of the series of processes-from insulin synthesis, secretion, expression of insulin receptors on the cell surface, to the realization of the final physiological effect of insulin-can lead to insulin resistance.

5. Why does insulin resistance promote hypertension, diabetes, and cardiovascular disease? Insulin resistance/hyperinsulinemia can increase the excitability of the sympathetic nervous system, promote smooth muscle cell proliferation and growth, leading to vascular wall thickening, affecting the function of various blood pressure regulating factors, strengthening vascular effects, affecting vasodilation function, increasing vascular resistance, and ultimately leading to hypertension. Insulin resistance can cause impaired glucose tolerance and hyperglycemia. Long-term excessive secretion by pancreatic β cells can eventually lead to decompensation and exhaustion. For most patients with type 2 diabetes, insulin resistance is present in the early stages, and it is an important risk factor for type 2 diabetes. Insulin resistance/hyperinsulinemia can weaken the body's fibrinogenolysis function. In addition, insulin resistance/hyperinsulinemia has some direct adverse effects on the cardiovascular system, which, together with the aforementioned negative effects, contribute to the formation of atherosclerosis.

6. Metabolic obesity in individuals with normal body mass index (BMI) refers to individuals whose abdominal fat is likely to exceed the borderline risk level. These individuals are termed "metabolic obesity in individuals with normal body mass index." Although their BMI is within the normal range, they still exhibit hyperinsulinemia, insulin resistance, and a tendency towards type 2 diabetes, hypertriglyceridemia, and early-onset coronary heart disease. In fact, this group constitutes a considerable proportion of the population, and they will become "victims" of obesity-related diseases alongside those who are significantly obese. Conversely, some individuals with high BMI values ​​may have very little abdominal (visceral) fat. It is currently believed that obesity precedes insulin resistance, and central obesity is a cause of insulin resistance, or at least a significant risk factor for it. Compared to peripheral subcutaneous fat, visceral adipose tissue is less sensitive to insulin, exhibiting a certain degree of insulin resistance, which can lead to hyperinsulinemia.

7. Why do newly diagnosed diabetic patients often have many cardiovascular disease risk factors and atherosclerosis? Recent studies have shown that insulin resistance already exists in the preclinical stage of diabetes. This explains why a significant number of patients diagnosed with diabetes already have various cardiovascular disease risk factors and can show obvious signs of atherosclerosis.

8. What is the significance of microalbuminuria? Based on the amount of albumin in the urine, it can be divided into normal, microalbuminuria, and macroalbuminuria. Microalbuminuria not only serves as an independent predictor of end-stage renal failure in patients with type 1 diabetes, but it is also an important marker of atherosclerotic disease and premature death in patients with type 2 diabetes. The detection rate of microalbuminuria in diabetic patients is 32.2%; the rate is as high as 14.7% in non-diabetic individuals. Hypertension is also an important risk factor for microalbuminuria. The proportion of microalbuminuria in borderline hypertensive patients is 12%–15%, in mild to moderate hypertensive patients it is 15%–30%, and in severe hypertensive patients it exceeds 50%. Microalbuminuria is an independent high-risk factor for cardiovascular disease.