Health Effects of Lipids Part2

Atherosclerosis

Atherosclerosis involves the gradual narrowing of arteries due to the build-up of plaque. It takes years to develop and happens insidiously without people noticing it. Clinical problems develop when the obstruction is such that blood flow, and thus oxygen supply, cannot meet demands.The low oxygen supply leads to a condition called ischemia, explaining the term ischemic heart disease.Atherosclerosis occurs in many parts of the body. In the heart it may lead to ischemic heart disease, in the brain it may lead to stroke, and in areas outside the brain and heart to peripheral vascular disease also called peripheral artery disease.

Pathogenesis of atherosclerosis

The normal artery contains three layers.The inner layer is called the endothelium or intima and is in direct contact with the blood. The middle layer contains smooth muscle cells that allow blood vessels to expand or contract. The outer layer of arteries is composed mostly of connective tissue. It is commonly thought that a plaque begins to form because the endothelium becomes damaged, possibly because of elevated lipid levels in the blood, high blood pressure, or smoking. The damage causes white blood cells to stick to the endothelium. What happens is that the endothelium produces sticky molecules called adhesion molecules that capture the white blood cells.After adhesion to the endothelium, the white blood cell moves inside the wall of the artery. White blood cells that move into the blood vessel wall include T-cells and macrophages.In the vessel wall, macrophages take up lipid and become foam cells. This causes the vessel wall to gradually thicken as it fills up with lipid. As the atherosclerotic process advances, smooth muscle cells move into the intima and produce molecules such as collagen, that give the inner wall a connective tissue-like appearance.  In advancing lesions, cells die and cell debris including lipids accumulates in the central region of the plaque, called the lipid or necrotic core.It is believed that the lipids that accumulate in the atherosclerotic plaque primarily originate from LDL, which is able to penetrate the wall of the artery and become scavenged by macrophages. In turn, the macrophages become foam cells and start to produce molecules that aggravate the inflammation.

The two key in the initiation of atherosclerosis are 1)Adhesion and infiltration of immune cells into the vascular wall; 2) Entry of LDL particles into the vascular wall and formation of foam cells.The idea that lipids, especially cholesterol, are deposited in atherosclerotic lesions goes back more than 60 years, and led to the suggestion that atherosclerosis may be linked to elevated blood cholesterol. However, in the ensuing years, the hypothesis that high blood cholesterol levels contribute causally to atherosclerosis and CHD (the “lipid hypothesis”)  faced huge skepticism Even today certain groups of individuals remain in denial about the importance of (LDL) cholesterol in atherosclerosis. Within the cardiovascular research community there is a strong consensus about the role of lipids in atherosclerosis, particularly LDL. In addition to the role of lipids, there is near universal recognition for an important role of the immune system and inflammation in the development of atherosclerosis, based on experimental, clinical, and epidemiological studies (the “inflammatory hypothesis”). What is still lacking is the proof that anti-inflammatory drug therapy reduces myocardial infarctions ("heart attack"). 

Most atherosclerotic lesions are stable and do not cause any problems. In those cases, the lipid core is covered by a thick layer of materials typically found in connective tissue forming a so called fibrous cap. However, when the lesion is very inflamed, white blood cells produce molecules that gradually break down the fibrous cap. The thinning of the fibrous cap causes the plaque to become unstable and make it prone to rupture. The rupture of the plaque is very dangerous, as it triggers blood clotting (thrombosis). The blood clot can partially or completely occlude the blood vessel at the site of rupture, or it can be dislodged and travel further to block a blood vessel elsewhere.

 

 

 

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Health Effects of Lipids Part1

Dietary lipids have mainly been connected to heart disease which is also referred to as cardiovascular disease.
What is heart disease and how does it develop? What are the major risk factors for heart disease?
One the risk factors for heart disease is the cholesterol level in the blood. Cholesterol exists in our blood in two forms LDL and HDL.and one needs to be extremely concerned about ones LDL cholesterol level. This is because having high LDL cholesterol  greatly increases one risk to heart disease.
What is interesting about LDL is that it's levels can be changed by altering your diet, what is the impact of  the amount of cholesterol in your diet on your blood cholesterol level? What about consumption of saturated and unsaturated fat?
Trans fat have also been called killer fats., they used to be abundant in frying oil, pastries, fast food, certain margarines and many other processed foods.
Another hot topic is Omega-3 fatty acids numerous claims have been made about these fatty acids, particularly in their relation to heart disease.

Cardiovascular disease and coronary heart disease

Cardiovascular disease (CVD, also called heart disease) is a class of diseases that involve the heart and/or the blood vessels. The most common form of cardiovascular disease is coronary heart disease (CHD), in which the coronary arteries – the blood vessels providing blood to the heart muscle - become narrow and rigid, restricting blood flow to the heart. Coronary heart disease is also called ischemic heart disease. Another common form of cardiovascular disease is stroke, in which the arteries supplying blood to the brain become blocked and blood flow is impaired. Cardiovascular diseases are most often rooted in a process called atherosclerosis. Atherosclerosis describes the build-up of plaque in the walls of arteries, leading to narrowing of the arteries and gradual obstruction of blood flow. Other cardiovascular diseases include heart failure, diseases of the heart muscle (cardiomyopathy), heart valve problems, and arrhythmias.

Ischemic heart disease (a.k.a. coronary heart disease, CHD) is the leading cause of death in high income countries, whereas infections are the major cause of death in low income countries. It is believed that differences in abundance of infectious organisms, hygiene, medical care, and diet are responsible for the difference in death rates between high and low income countries.

Rates of coronary heart disease or ischemic heart disease differ greatly between countries. The age-standardised, disability-adjusted life year (DALY) rates from ischemic heart disease (CHD) by country (per 100,000 inhabitants, the darker the color, the higher the rates). DALY is a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability or early death. One DALY represents one lost year of "healthy" life. The sum of these DALYs across the population, or the burden of disease, can be thought of as a measurement of the gap between current health status and an ideal health situation where the entire population lives to an advanced age, free of disease and disability (Definition from WHO). Use of DALY has become increasingly popular in public health. The highest DALY rates for ischemic heart disease are observed in eastern Europe.

The age standardized ischemic heart disease (CHD) death rates per 100,000 individuals. This measure is calculated differently than the DALY but the overall picture it creates is highly similar: highest rates are observed in eastern Europe, whereas the lowest rates are observed in France and Japan.

Trends in deaths from CVD show a striking pattern. In many western and northern European countries, which originally had the highest rates of CVD, there has been a sharp decline in CVD deaths despite the growing prevalence of obesity. The decrease in CVD deaths is accounted for by a huge reduction in deaths from CHD and stroke and is largely explained by improvements in long-term and emergency medical care, combined with decreased smoking in more recent years. Behavioral adjustments towards diets and exercise are unlikely to have importantly contributed towards the decline

In contrast to western countries, there has been a substantial increase in CVD rates in eastern European countries. The extremely high rates of CVD in Eastern Europe have been linked to tobacco use, dietary behaviors, alcohol use and poor medical care

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