There are two main types of lipid or disorders or disorders of fat metabolism. Increased levels of cholesterol are associated with premature and accelerated hardening of the arteries associated with cholesterol deposition and inflammation (atheroma). These lesions predispose to coronary artery disease of the heart and heart attacks, strokes and peripheral vascular disease. The genetic lesion is due to defective clearance of the “bad” form of cholesterol (low density lipoprotein-cholesterol or LDL) due to dysfunctional receptors of cells of the body. Children who have two copies of the bad cholesterol gene have very high levels of LDL and may have heart disease before their teenage years. Most patients have only one bad gene copy, and the disease is seen to run in the family. There is also a “good” form of cholesterol (high density lipoprotein cholesterol or HDL) which carries cholesterol from the arteries back to the liver where it is metabolized. Thus risk of heart attacks and stroke is related to both LDL and HDL levels. These levels are assayed in the Clinic on a finger prick drop of blood during the visit. Normal levels of LDL are those < 100 however levels of 120 or so may be tolerated without treatment if there are no other risk factors involved. Other risk factors include smoking, diabetes, hypertension, insulin resistance syndrome and obesity and family history of heart attacks and/or strokes. In such persons treatments are aimed to lowering LDL levels to < 100. Low fat diets may lower LDL by some 15% but the majority of LDL cholesterol is produced by the liver whatever low animal fat diet is eaten. The most frequent class of drugs used to treat high levels of LDL-cholesterol are the statins. Statins can induce muscle pains and rarely muscle inflammation, as well as liver disease. However they are usually tolerated very well. Use of statins over time, have been repeatedly shown to greatly reduce the frequency of heart attacks and strokes. Another class of agent is sometimes added to a satin to reduce that component of cholesterol absorption from the diet. Other agents are sometimes used to increase HDL levels, albeit frequent exercise and modest red wine consumption often help.
A lipid disorder frequently occurs in persons with insulin resistance and type-2 diabetes. In this disorder, the suppressive effect of insulin on liver production of triglyceride rich very low density lipoproteins or VLDL) is blunted and trigylceride (TG) levels climb while levels of the protective HDL-cholesterol decline. Hypertriglyceridemia (high TG levels) can if high enough, induce a life threatening inflammation of the pancreas (pancreatitis), fatty infiltration and inflammation of the liver (non-alcoholic steato-hepatitis or NASH) and gallbladder disease. Insulin resistance is also associated with a form of kidney disease (focal glomerulonephritis) detectable by leakage of albumin into the urine. Urinary microalbumin and liver function tests are done in the Clinic during the Clinic visit for these reasons. The dyslipidemia of insulin resistance predisposes to atheromatous diseases of the arteries like hypercholesterolemia and is thus screened for in the Clinic on a finger prick drop of blood at the time of the visit. Treatment of this disorder is to restrict the content of simple carbohydrates in the diet since they are the food substrate that TGs are formed from in the body. This diet will also induce weight loss in obese patients. The underlying insulin resistance is treated which has some benefit on dyslipidemic levels. Most patients however require additional therapy with a class of drugs named fibrates.
Mixed lipid disorders:
It is unfortunately not uncommon to find a coincidental hypercholetserolemic disorder to coexist with dyslipidemia in persons with insulin resistance or metabolic syndrome or type-2 diabetes. Since both are independent risk factors for atheromatous disease, both need to be treated independently as above. Certain combinations of drugs however have been associated with serious side effects while others recommended by the Clinic are not prone to such side effects. Coexisting hypertension and diabetes will of course need to be treated also when present.