What is LDL Cholesterol?

Cholesterol often exists in the form of lipoproteins in the blood ^[1] , and low density lipoprotein (LDL) in plasma is the main carrier of endogenous cholesterol, which is bound by the low density lipoprotein on its cell membrane. (LDL-R) is degraded and transformed.

Low Density Lipoprotein Chesterol (LDL-C) is the major lipoprotein in fasting plasma, which accounts for about two-thirds of plasma lipoproteins. It is the main vehicle for transporting cholesterol to extrahepatic tissues. ^[2] .

LDL-R dysfunction can reduce the clearance of plasma LDL-C, and eventually lead to the formation of atherosclerotic plaques in the arteries. Therefore, the content of LDL-C is related to the incidence and severity of cardiovascular disease. It is considered to be the main pathogenic factor of atherosclerosis, and its concentration has a significant positive correlation with the incidence of coronary heart disease. It is also an evaluation of individual coronary heart disease. An important indicator of the occurrence of risk factors ^[1-2] .

Chinese name: Low density lipoprotein cholesterol
Foreign name: low density lipoprotein cholesterol
Short name: LDL-C

Normal value: 105-130 mg / dl
Oxidative: Easily oxidized
Pathological factors: Atherosclerosis, cardiovascular disease, etc.
Degradation mechanism: Degraded or transformed by low density lipoprotein receptor (LDL-R)

Introduction to LDL cholesterol

Low Density Lipoprotein Chesterol (LDL-C) is transformed from very low-density lipoprotein cholesterol (VLDL-C) in plasma, and its synthesis site is mainly in blood vessels, and its degradation site is in the liver ^[2] .

LDL cholesterol LDL

Low-density lipoprotein is cholesterol-rich lipoprotein, which is a kind of lipoprotein particles that carry cholesterol into peripheral tissue cells. When a normal person is fasting, 2/3 of the cholesterol in the plasma will bind to LDL, and the rest will be carried by very low density lipoprotein (VLDL) ^[3] . LDL can be oxidized to oxidized low-density lipoprotein, and oxidized low-density lipoprotein cholesterol can be commonly understood as "bad" cholesterol because elevated LDL-C levels increase the risk of coronary heart disease.

High concentration of LDL-C is a clearly independent risk factor for atherosclerosis, and its role is oxidatively modified low-density lipoprotein cholesterol (Ox-LDL-C). Preventing LDL-C from being oxidized is a key factor. When the oxidatively modified low-density lipoprotein is excessive, the cholesterol it carries accumulates on the arterial wall, which can easily cause arteriosclerosis over time. Epidemiological evidence has shown that elevated low-density lipoproteins are closely related to an increased risk of death from myocardial infarction and vascular disease ^[2] .

Low density lipoprotein cholesterol

Low-density lipoprotein cholesterol corresponds to another lipoprotein associated with cholesterol transport in the body, High Density Lipoprotein Chesterol (HDL-C). Both are related to atherosclerosis and cardiovascular disease, the former (low-density lipoprotein cholesterol) is positively related to the occurrence of disease, and the latter is one of the main risk factors for atherosclerosis, which is atherogenic lipid Protein, which is inversely related to disease occurrence. The higher the serum LDL-C level, the greater the risk of atherosclerosis. Similar to HDL-C measurement, LDL-C is also used to measure the amount of bile alcohol in LDL to indicate the level of LDL ^[2] .

LDL cholesterol reference range

Adult LDL cholesterol ranges from 2.07 to 3.37 mmol / L (80 to 130 mg / d). The newly revised "Guidelines for the Prevention and Control of Dyslipidemia in Chinese Adults" recently recommended that LDL-C <3.37 mmol (130 mg / dL) is a suitable range; 3.37 to 4.12 mmo / L (130 to 159 mg / L) is marginal elevation; The increase was 4.14 mmol / L (160 mg / d) ^[3] .

The US NCEP ATP report divides LDL-C into 5 levels for the prevention and treatment of dyslipidemia: <2.59 mmoL (100 mg / dL) is a suitable level; 2.59 ~ 3.34 mmoL (100 ~ 129 mg / dL) is a near appropriate level; 3.38 ~ 4.12 mmo / L (130 ~ 159 mg / dL) is a critical high level; 4.14 ~ 4.89 mmol / L (160 ~ 189 mg / dL) is a high level; 4.92 mmol / L (190 mg / d) is extremely high Level ^[3] .

Clinical significance of low density lipoprotein cholesterol

Pathologically elevated LDL cholesterol

Hepatic dysfunction, hepatitis, atherosclerosis, hypertension, cardiovascular disease, hyperlipoproteinemia, acute myocardial infarction, coronary heart disease, nephrotic syndrome, chronic renal failure, liver disease, and diabetes, etc. can also be seen neurologically Anorexia and pregnant women ^[4] .

Non-pathologically elevated LDL cholesterol

Unbalanced diet and excessive intake of fat;
High caused by smoking and drinking;
Excessive exercise, significantly increased during strenuous exercise;
Overweight and obese people are prone to cause high levels of LDL ^[4] .

Pathological reduction of low density lipoprotein cholesterol

Low-density lipoprotein cholesterol reduction is common in malnutrition, chronic anemia, myeloma, trauma, and severe liver disease. ^[4]

Factors Affecting LDL Cholesterol

Many factors can cause the increase of low-density lipoprotein, which can be mainly divided into non-pathological factors and pathological factors ^[5] :

LDL cholesterol non-pathological factors

(1) Unbalanced diet and excessive intake of fat;

(2) High levels caused by smoking and drinking;

(3) Overweight and obese people are prone to cause high LDL ^[5] .

LDL cholesterol pathological factors

(1) Patients with abnormal liver function and hepatitis;

(2) Atherosclerosis, hypertension, and cardiovascular disease. Low-density lipoprotein can carry cholesterol into human arterial wall cells. When low-density lipoprotein is higher than normal, excess cholesterol accumulates on the walls of blood vessels, forming atherosclerosis, and even the occurrence of coronary heart disease ^[5] .

The main hazards of LDL cholesterol

Low-density lipoprotein cholesterol forms atherosclerosis

If the concentration of LDL-C in the blood increases, it will deposit in the arterial walls of blood vessels such as the heart and brain, gradually form atherosclerotic plaques, block the corresponding blood vessels, and finally cause death such as stroke and peripheral arterial disease Disabling serious diseases ^[6] .

Coronary heart disease caused by low-density lipoprotein cholesterol

LDL and its high cholesterol (LDL-C) often cause cardio-cerebral-vascular diseases such as coronary heart disease, so some people call LDL-C "bad cholesterol". If the level of LDL-C in the blood exceeds the normal range, it will increase the risk of heart disease ^[6] .

Misunderstanding of low density lipoprotein cholesterol

1. The lower the body's cholesterol content, the better

Cholesterol is mainly divided into low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C). Higher than normal LDL-C is a "bad thing", but HDL-C higher than 3.0 is a "good thing". . High-density lipoprotein cholesterol can transport excess cholesterol in the blood to the liver, process it into bile salts, and excrete it through the biliary tract, thereby forming a specialized pathway for lipid metabolism, also known as the "reverse transport pathway" ^[7] .

2.LDL-C is the main cause of atherosclerosis

Under normal circumstances, LDL-C exists in a non-oxidized state. Non-oxidized LDL-C does not easily cause atherosclerosis (small artery wall changes like atherosclerosis). The latest edition of "Internal Medicine" has clearly stated LDL -C is oxidized to oxidized low-density lipoprotein cholesterol (Ox-LDL-C), and these oxidized LDL-C are deposited on the inner wall of blood vessels, causing atherosclerosis. If the LDL-C is regarded as a Mercedes-Benz car on the road, the oxidized LDL-C is a rusty and faulty car. HDL-C is like a trailer that clears roadblocks. If all cars are in good condition, even if there are more cars, the traffic will still be smooth, but problematic and rusty cars will definitely cause traffic jams on the road ^[7]