What are Lipoproteins? (Good and Bad Cholesterol)
Cholesterol and other fats cannot dissolve in the blood. They have to be transported to and from the special carriers called a lipoprotein. There are two kinds of lipoproteins that you need to be concerned with. Low-Density Lipoprotein or “LDL” is also known as bad cholesterol. Too much LDL can clog the arteries to your heart and increase your risk of a heart attack. High-Density Lipoprotein, or “HDL”, is also known as the “good” cholesterol.
Can Any Cholesterol Be Good For The Heart?
Certain cholesterol facts are well known. There is a general consensus that High-Density Lipoprotein (HDL) is “good cholesterol”. It transports free cholesterol from blood to the liver where it is esterified by Lecithin Cholesterol Acyl Transferase (LCAT). The apo-1 component of HDL promotes activation of LCAT and removal of free cholesterol to be deposited inside the walls of blood vessels.
HDL interacts with peripheral cells of tissues by binding of cells surface receptors via one of the HDL apoproteins A-1 and its less dense fraction contains a relatively higher concentration of apo A-1 and hence it prevents deposition in the walls of blood vessels. HDL opposes the EDRF-inhibitory effect of LDL and free cholesterol, promotes the release of prostacyclin from endothelial cells, and stabilizes circulating prostacyclin. Prostacyclin inhibits mitogen release of platelet-derived growth factor by its effects on cholesterol metabolism.
HDL indirectly has better antioxidant properties leading to antideposition effect. These functions make HDL cholesterol good cholesterol. 1-2 mg/100 ml increase in HDL is associated with a 2-4% reduction in Coronary Heart Disease (CHD) risk. Low values act as a risk factor irrespective of total cholesterol.
Several studies have been carried out to show that deficiency of HDL is a risk factor for CHD. One study in the west names PROCAM trial showed that HDL under 35mg/100 ml showed a 65% risk of CHD whereas over 35mg/100 ml the risk was 36%. Multiple Factor Intervention Trial (MRFIT) and Lipid Research Clinics Coronary Primary Prevention Trial (LRCPT) showed that HDL of more than 45mg/100 ml as a proactive role.
Helsinki heart study showed that 11% increase in HDL caused a 34% decrease in CHD. In Indian studies, Rajeev Gupta in Rajasthan showed that 23.9% of men had less than 35mg/100 ml and Reddy’s study in Delhi at AIIMS showed that 59.9% had less than 40mg/100 ml.
In India, the levels of HDL are low as compared to the West.
It is important to raise HDL cholesterol. This is possible by physical exercise, high fiber vegetarian diet, fruits, green vegetables, correction of obesity, and stopping excess alcohol consumption, smoking and tobacco products.
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