Disorders of Cardiovascular System - Hyperlipidemia PDF

Disorders of arterial circulation Hyperlipidaemia Objective 8.1.1. Describe the aetiology and pathogenesis of hyperlipidaemia. Hyperlipidemia Hyperlipidemia is an excess of lipids in the blood. Lipids are classified as : a. Triglycerides b. Natural fat c. Phospholipids d. Cholestero...

Disorders of arterial circulation Hyperlipidaemia Objective 8.1.1. Describe the aetiology and pathogenesis of hyperlipidaemia. Hyperlipidemia Hyperlipidemia is an excess of lipids in the blood. Lipids are classified as : a. Triglycerides b. Natural fat c. Phospholipids d. Cholesterol Hyperlipidemia Because cholesterol and triglyceride are insoluble in plasma, they are encapsulated by a stabilizing coat of water-soluble phospholipids and proteins (called apoproteins). So now it is called lipoproteins. Lipoprotein Hyperlipidemia Lipoprotiens carry out the following functions: Transport cholesterol and triglyceride to various tissues for energy utilization Lipid deposition Steroid hormone production Bile acid formation. Hyperlipidemia Each lipoprotein contains protein and lipid. Because fats are less dense than proteins, as the proportion of triglycerides decreases, the density increases. Hyperlipidemia There are five types of lipoproteins, classified according to their densities: Chylomicrons Very–low-density lipoprotein (VLDL) Intermediate-density lipoprotein (IDL) Low-density lipoprotein (LDL) and High-density lipoprotein (HDL). Hyperlipidemia (Hypercholeserolemia) : Etiology Serum cholesterol levels may be elevated as a result of an increase in any of the lipoproteins—the chylomicrons, VLDL, IDL, LDL, or HDL. Etiology: Factors that raise blood lipid levels are: Nutrition Genetics Medications Comorbid conditions & Metabolic diseases. Hyperlipidemia (Hypercholeserolemia) : Pathogensis Primary Secondary Elevated cholesterol levels that develop Associated with other health problems and independent of other health problems or behaviours. lifestyle behaviours. Have a genetic basis. Such as : Causes include obesity with high-calorie 1. Defective synthesis of the apoproteins, intake and diabetes mellitus. 2. A lack of receptors 3. Defective receptors or 4. Defects in the handling of cholesterol in the cell that are genetically determined.  Primary Hypercholesterolemia The LDL receptor is deficient or defective in the genetic disorder known as familial hypercholesterolemia (type 2A). This autosomal dominant type of hyperlipoproteinemia results from a mutation in the gene specifying the receptor for LDL. Because most of the circulating cholesterol is removed by receptor- dependent mechanisms, blood cholesterol levels are markedly elevated in people with this disorder. Example of primary hyperlipidemia Familial hypercholesterolemia  Familial hypercholesterolemia Heterozygous Homozygous Plasma LDL range between 250 – 500 Plasma LDL may rise to 1000 mg/dL. mg/dL. Much more severely affected. Commonly have an elevated Have cutaneous xanthomas in cholesterol level from birth, they do not childhood. develop symptoms until adult life. During adult life, develop xanthomas along the tendons, and atherosclerosis appears. May experience myocardial infarction Myocardial infarction seen at a later early. age of 40 to 45 years in men. cutaneous xanthomas : skin condition in which fats build up under the surface of the skin.  Secondary Hypercholesterolemia High-calorie diets, diabetes and obesity. High calorie diets leads to : 1. increase production of VLDL 2. triglyceride elevation 3. high conversion of VLDL to LDL. Excess ingestion of cholesterol may (1) reduce the formation of LDL receptors thereby decrease LDL removal. Diets that are high in triglycerides and saturated fats: (1) increase cholesterol synthesis (2) suppress LDL receptor activity.  Secondary Hypercholesterolemia In diabetes mellitus and the metabolic syndrome, typical dyslipidemia is seen with elevation of triglycerides, low HDL, and minimal or modest elevation of LDL. 3 Other systemic disorders that can elevate lipids include hypothyroidism, nephrotic syndrome, and obstructive liver disease.