Introduction: Lipid Profile

Abstract

Lipids and lipoproteins are risk factors for CHD. It has been demonstrated that high levels of serum total cholesterol (TC), triglycerides (TG), LDL cholesterol, very-low-density lipoprotein (VLDL), low concentration of HDL cholesterol, and increased body mass index (BMI) are significantly associated with CHD (George and Ludvik 2000). Dyslipidemia is one of the top five major risk factors leading to cardiovascular disorders. It is characterized by elevated LDL cholesterol and TG and decreased HDL cholesterol. Although there are differences in defining dyslipidemia, however, European guideline on CVD prevention in clinical practice recommends TC below 190 mg/dL (5.0 mmol/L) and an LDL cholesterol below 115 mg/dL (3.0 mmol/L) for the general population. The goals are even lower: i.e., <175 mg/dL (4.5 mmol/L) for TC and <100 mg/dL (2.6 mmol/L) for LDL cholesterol in the case of multiple disorders like CHD, other diseases of CVD, or DM (De Backer et al. 2003). Lipid abnormalities significantly contribute to the increased risk of cardiovascular disease and other morbidity in diabetics. VLDL and chylomicrons (CM) are major sources of fatty acid supply to the heart, but little is known about their metabolism in diabetic myocardium. Males and females appear to be equally susceptible to the effects of risk factors such as hypertension, increased plasma LDL cholesterol, and low levels of plasma HDL cholesterol. Estrogens have a favorable effect on lipid profile. It has been observed that they lower LDL cholesterol and elevate HDL cholesterol. Estrogens are thought to increase HDL cholesterol by reducing hepatic triglycerides’ lipase activity that catabolizes HDL cholesterol. Global studies of either gender have demonstrated that the risk of atherosclerosis is inversely related to blood levels of HDL cholesterol: the higher the level of HDL cholesterol, the lower will be the risk. It is indicated that for every 1 mg/dL rise in HDL cholesterol, the risk for developing cardiovascular disease decreases by 2–3 % (Toth 2005). HDL cholesterol helps to extract excess cholesterol deposited in blood vessel walls and deliver it back to the liver for elimination through the gastrointestinal tract. HDL cholesterol helps to keep blood vessels dilated, thereby promoting better blood flow. It also reduces blood vessel injury through its antioxidant and anti-inflammatory functions, among other effects. HDL cholesterol carries “old” cholesterol that has been discarded by cells back to the liver for recycling or excretion. The main function of LDL cholesterol is to transport cholesterol from the liver to the tissues that incorporate it into the cell membranes. The oxidation of LDL cholesterol is believed to have a central role in atherogenesis. Oxidized LDL cholesterol may be involved in atherogenesis by inducing smooth muscle cell proliferation. Acute MI is the most important consequence of coronary artery disease. Some studies have defined TG also as an independent risk factor for MI (Haffner et al. 1998). High TG value could result from the elevation of several lipoproteins such as chylomicrons, different subclasses of VLDL, or intermediate-density lipoproteins (IDL cholesterol). The risk of MI in patients with DM without a history of myocardial infarction is as high as that in patients without MI who have had a myocardial infarction. Mortality after first MI is higher in both males and females with DM. Lipid abnormalities significantly contribute to the increased risk of CVD in diabetes mellitus. Diabetes affects virtually all lipids and lipoproteins. Persons with DM typically have increased plasma concentrations of TG, low plasma concentrations of HDL cholesterol, and slightly raised plasma concentrations of LDL cholesterol. DM is also considered as an independent risk factor for cardiovascular disease (up to fivefold), and as many as 80 % of patients with type II diabetes die from cardiovascular complications (Johnson et al. 2004). Persons with high blood cholesterol levels have a higher prevalence of hypertension, and those with high blood pressure have a higher prevalence of hypercholesterolemia (O’Brien et al. 2003). Abnormalities in plasma lipoprotein metabolism play a central role in the pathogenesis of atherosclerosis, and arterial hypertension with elevated systolic or diastolic blood pressure is positively and independently associated with CHD. The risk of developing CVD associated with the presence of both hypertension and Dyslipidemia has been shown to be greater as compared to hypertension or Dyslipidemia alone (Johnson et al. 2004). Moreover, patients with these two conditions found to have three to four times higher prevalence of MI (Wald and Law 2003). Dyslipidemia causes endothelial damage and consequent loss of physiological vasomotor activity, which may be manifested as increased blood pressure. Asians experience the largest proportion of the worldwide burden of CVD. Further, Asians include several distinct ethnic subpopulations (South Asians, Chinese, etc.), who may differ in their lipid profiles. These differences may be the result of both genetic and environmental factors such as high-cholesterol carbohydrate diets, reduced physical activity, and obesity (Radhika et al. 2009). In a study it has been estimated that LDL-cholesterol, HDL-cholesterol, and TG levels are lower among Asians compared with non-Asians. Also the associations of elevated LDL cholesterol and lower levels of HDL cholesterol for the risk of AMI were found to be broadly similar among Asians and non-Asians.