Control of Cholesterol

Introduction

Cholesterol is a fatlike, steroid alcohol with the chemical structure C27-H45-OH. It crystallizes in the form of leaflets or plates from dilute alcohol. It is commonly found in foodstuffs like animal fats and oils, milk, and yolk of egg. Cholesterol is normally present in the blood and does not cause any disease when present in normal amounts. It is also present in the bile, blood, brain tissue, liver, kidneys and the adrenal glands. However, when excess levels of cholesterol is present, it may cause conditions like coronary disease, circulatory problems and hypertension. Very high levels of cholesterol in the circulation lead to a condition known as Hypercholesterolaemia. The incidence of this condition was higher in the developed and industrialized countries, but a significant increase has been reported in the third world countries as well. It is probably due to a change in diet and lifestyle associated with development and industrialization. The incidence is also higher in the affluent groups and lower in the poorer sections of the population in all societies.





Cause and Pathogenesis

There are different types of Cholesterol like LDL(Low density Lipoprotein) Cholesterol, HDL(High Density Lipoprotein) Cholesterol (also called as good Cholesterol) etc. It is the increase in the levels of LDL Cholesterol that correlates significantly with the incidence of various diseases. Likewise, low levels of HDL Cholesterol are also associated with various diseases. The level of Triglycerides, another type of fat, is also of great significance with increased levels predisposing to disease. Excessive LDL Cholesterol levels predispose to the development of serious disorders like coronary disease, arteriosclerosis (deposits of cholesterol plaques on the blood vessels' walls, leading to their obstruction) which may lead to hypertension (elevated blood pressure), development of gallstones in the gallbladder etc. Patients with familial hypercholesterolaemia have a higher incidence of coronary disease. Studies show that there is a positive correlation between mean population plasma cholesterol concentrations and morbidity and death from coronary disease. Clinical trials have revealed that reducing elevated cholesterol levels by diet or drug therapy reduces the risk of developing cardiac disorders. Cholesterol is essential for the synthesis of vitamin D in the skin. It is also needed for the synthesis of various hormones, including the sex hormones. Cholesterol is constantly synthesized in the body, mainly in the liver and the kidneys. Most of the cholesterol present in the body is synthesized in the liver, but a proportion is also absorbed from the diet of fat-rich foodstuffs like animal fats and oils, milk, and yolk of egg. It is a precursor of bile acids and is essential for the synthesis of steroid hormones, which are vital for maintaining proper metabolism in the body and reproductive functions.





Symptoms and Signs

Elevated cholesterol levels in the body as such do not produce any major symptoms or signs, but leads to the development of serious disorders like Atherosclerotic heart disease, hypertension, peripheral vascular disease, gallstones etc. Blockage of the coronary arteries in the heart by cholesterol deposition leads to coronary insufficiency, ischaemia (decreased oxygen supply to the muscles of the heart) and this eventually results in myocardial infarction (heart attack). Cholesterol constitutes a large part of the most frequently occurring type of gallstones. Very high levels of cholesterol lead to skin changes like xanthelesma near the eyes. The lack of symptoms until the complications occur necessitates periodic monitoring of lipid profiles in all individuals.

Investigations and Diagnosis


The analysis of the lipid profile is essential in making a diagnosis. Lipid profile includes Serum Cholesterol, Serum Triglycerides, the break-up of various Cholesterol fractions like LDL, HDL and the LDL/HDL ratio, which is of significance. A serum total cholesterol level greater than 5.2 mmol/l (200 mgs/dl) is greater than the desired level. The HDL-cholesterol levels can also be measured and should be >1.55mmol/l (>60 mgs/dl). LDL Cholesterol level should be <3.36 mmol/l(<130mgs/dl).
Total Plasma Cholesterol LDL Cholesterol HDL Cholesterol
Desirable <5.20 mmol/L(<200 mgs/dl) <3.36 mmol/L(<130mgs/dl) >1.55 mmol/L(>60 mgs/dl)
Borderline 5.20-6.18 mmol/L (200-239 mgs/dl) 3.36-4.11 mmol/L (130-159 mgs/dl) 0.9-1.55 mmol/L (35-60 mgs/dl)
Undesirable >6.21mmol/L(>240 mgs/dl) >4.14mmol/L(>160 mgs/dl) <0.9 mmol/L(<35 mgs/dl)





Treatment and Prognosis

Drugs can be used to reduce the level of Serum Cholesterol in severe cases. These drugs are of several different types and include drugs like Cholestyramine, Clofibrate, Gemfibrozil and the newer agents like Lovastatin, and Simvastatin. Some of these drugs lower cholesterol levels, some lower triglyceride levels and some influence both. However, diet and exercise are the best early methods of treatment and help to prevent complications from occurring. A diet low in saturated fat supplemented with vitamins is essential for maintaining cholesterol levels. Among the fats, ingestion of foods rich in PUFA (Poly Unsaturated Fatty Acids) is preferable. Adequate exercise every day ensures that the excess lipids in the body are utilized and not deposited as cholesterol plaques in the blood vessels, thereby preventing arteriosclerosis. Check-ups for complications like hypertension, atherosclerosis, gallstones etc. should be periodically done as the incidence of these complications is high in patients with elevated cholesterol levels.

Prevention


A low-fat diet and adequate daily exercise prevents build-up of excess cholesterol levels in the body. It is necessary to avoid foodstuffs containing excessive fats, oils and animal proteins. The importance of exercise cannot be overemphasized. Also avoiding smoking, a predisposing factor to coronary artery disease, will help to reduce the incidence of complications.