Dyslipidemia

Dyslipidemia is the number one cause of atherosclerosis, which is the accumulation of fats within the artery walls. This disease occurs when there is a high content of cholesterol, LDL (bad cholesterol) or triglycerides, in the blood. It can also mean a decrease in HDL (good cholesterol) or a mixture of either of the above.

 

Dyslipidemia is more frequently found in people with hypertension, diabetes and obesity.

 

 

Cholesterol

 

Cholesterol has many functions in the body. It is responsible for the integrity of cell membranes by giving them fluidity; it is a precursor for bile acids, steroid hormones and vitamin D.

 

If there is an internal excess or increased ingestion of cholesterol, it is deposited in tissues, especially the arteries.

 

The liver is the organ regulating cholesterol. Cholesterol is eliminated through bile acids excreted in the feces.

 

If the liver does not secrete enough bile acids, cholesterol is stored in the gall bladder. Inside the gall bladder it may precipitate (harden) causing gallstones.

 

The only source of cholesterol is found in animal food sources.

 

Lipoproteins

 

These molecules are composed of lipids and proteins. Proteins surround the lipids to enable them to become soluble in the blood. Proteins are necessary since lipids are not soluble in water and wouldn't be able to travel through the blood.

 

Lipoproteins can be obtained in two ways: by exogenous sources (diet) and by endogenous sources (synthesis by the body).

 

Five types of lipoproteins exist:

 

Chylomicrons (Have a high content of triacylglycerol and cholesterol)

 

They are assembled in the intestines from molecules aquiered from food we ingest. 

 

The main role of chylomicrons are to transport the nutrients they contain to tissues like, muscle and fat.

 

Triglycerides are used by cells to produce energy. The remains of the chylomicron travels to the liver to be degraded.

 

VLDL (Very-low-density lipoprotein)

 

VLDL are produced by the liver and once again triglycerides and cholesterol are distributed by VLDL to the rest of the body. 

 

After these lipoproteins have contact with cells and deliver the triglycerides, they become IDL (Intermediate-density lipoproteins), mainly containing cholesterol.

 

LDL (Low-density lipoprotein) 

 

When VLDL lose their lipids they travel again to the liver to be converted in LDL. LDL mainly transports cholesterol to peripheral tissues.

 

 HDL (High-density lipoproteins) 

 

The liver produces this molecule to collect cholesterol from peripheral tissues to be excreted.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Triglycerides

 

Triglycerides are mainly stored, for energy, inside adipose tissue (fat). Adipose tissue changes its fat content every 2-3 weeks. Therefore, the above means that fat is constantly being used as an energy source and you have to ingest large amounts of nutrients for fat to accumulate in your body.

 

 

Table of normal ranges for lipids

 

 

 

 

 

 

 

 

 

 

 

 

 

Symptoms

 

Dyslipidemia doesn't present any symptoms by itself, unless it is already causing complications in the body. It can be identified by a blood test.

 

Complications

 

The complications mainly occur in the vascular system; mostly in the coronary or brain arteries.

 

Atherosclerosis

 

Atherosclerosis is a disease that happens when plaques form around the walls of the arteries. Arteriosclerosis is a different disease that occurs when the artey walls thicken (see Hypertension).

 

What happens is LDL's take excess cholesterol to tissues, mainly arteries, as it travels through them. A cell called macrophage, part of the immune system, dissolves the LDL particles forming a foam that later hardens. If the immune system or the HDL do not remove the accumulation of cholesterol or lipids properly, a plaque is formed (atheroma). 

 

The plaques cause the thickening of arteries and blood flow to decrease. Finally, the arteries continue to damage causing more inflamatory processes and the arrival of macrophages. It is a cycle which continues until rupture and hemorrhages take place. Also tissues can be deprived of oxygen and nutrients causing and infarction (death of tissue). The above example is more common in the heart.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The image above shows that atherosclerosis begins to develop from the first decade of life.

 

Prevention

 

To prevent the development of atherosclerosis you need to mantain a low level of circulating LDL. Exercise and avoiding food with high content of cholesterol and saturated fats, prevents this disease.

 

La DM II, HTN, dyslipidemia and smoking contribute to the development of atherosclerosis. 

 

It is recommended to take a blood test annually, after the age of 20, to detect any abnormalities in your lipid range.

 

 

 

Bibliography:

1. CENDEISSS. Enfermedad Cardiovascular, AVC y sus Determinantes. 1 ed., San José, Costa Rica, 2005.

2. Champe, Pamela C., Richard A. Harvey, and Denise R. Ferrier. Biochemistry. Philadelphia: Lippincott/Williams & Wilkins, 2005. Capítulo 18.

3. Guyton, Arthur C., and John E. Hall. Textbook of Medical Physiology. Philadelphia: Elsevier Saunders, 2006. Capítulo 68.

4. Harrison's Principles of Internal Medicine. New York, N.Y.: McGraw-Hill, 2012. Capítulo 356.

5. MINISTERIO DE SALUD. Encuesta Multinacional de Diabetes Mellitus, Hipertensión Arterial y Factores de Riesgo Asociados. San José, 2004.International Diabetes Federation. "Costa Rica." . N.p., n.d. Web. 20 Aug. 2014. <http://www.idf.org/membership/saca/costa-rica>.