this is partly due to the fact thattt... i hv been doing my hbio essay! it was on familial hypercholesterolemia... i will attach it to the end of my little rant here..
apart from that.. i also had a hbio test on thursday.. went alright actually. i think better than my first hbio test which i epically screwed up. anyhow.. i also watched two hindi movies, salaam-e-ishq and also eklavya. both were really really good. ill attach some pics as well..
but im pretty much done assessment wise for two weeks :) besides the ongoing weekly chem quiz which i will be doin tmr.. all is well.
ohhk i think thats all for nows.
here are the pics:
annnd as promised.. here is my awesome essay:
Familial Hypercholesterolemia (FH) is a genetic disease which is characterised by an increase in blood cholesterol levels, consequently leading to atherosclerosis and an elevated risk of premature coronary heart disease (Maxwell et al. 2009). Treatment of FH is mainly composed of lifestyle factors which act as preventative measures against the onset of heart disease.
Cholesterol and lipid levels in the human body are regulated by lipoproteins, which are complexes of cholesterol and triglycerides that are transported around the body (Saladin 2007). Different types of lipoproteins exist, including low density lipoproteins (LDLs) and high-density lipoproteins (HDLs). These two lipoproteins have contrasting roles in cholesterol regulation within the body; LDLs deposit cholesterol around the body, and HDLs remove excess cholesterol from the body (Saladin 2007). Usually, LDLs are absorbed by receptor-mediated endocytosis, thus regulating the levels of LDLs within the blood (Saladin 2007) However, if the receptor on the endocytic cell is non-functional, it lacks the ability to recognise the LDL molecule, thus cannot ingest it into the cell; as a result, this leads to an increased concentration of LDLs within the blood. It is for this reason, that people with FH have a high blood cholesterol level. The genetic basis as to how this occurs will be discussed as follows.
FH is an inherited disease which is transmitted in an autosomal dominant manner (Fouchier 2001). The genetic basis from which the disorder arises is a variety of mutations on the LDL-receptor gene, which then leads to a multitude of defects in LDL-receptor synthesis (Fard-Esfahani et al. 2005). Consequently, this results in a deficiency of functional LDL receptors on the liver cellular surface, causing an increased concentration of LDL within the plasma (Alonso et al. 2009). Another genetic defect which can cause FH is a mutation in the gene responsible for the apolipoprotien which is required to ‘dock’ to the receptors surface (Schuster 2002). This affects the LDL concentration in the plasma as the apolipoprotien is non-functional, thus cannot recognise or attach to the receptor; consequently the LDL concentration in the plasma goes up.
A high concentration of LDLs in the blood suggests that a large amount of cholesterol is being deposited into the arteries, a condition known as atherosclerosis (Saladin 2007). In normal (non FH) people, LDL molecules bind to cells, and are then ingested by the cell. For example, LDL is ingested into hepatocytes in the liver, which requires cholesterol for the synthesis of bile acids (Schuster 2002). However, people with FH cannot process the LDL molecule due to mutations in the receptor or apolipoprotein genes, thus this regulation is not as controlled. Two of the main factors which cause atherosclerosis are high LDL plasma concentration and defective LDL receptors-both characteristics of FH. In atherosclerosis, the LDL receptors in the arterial cells are dysfunctional, thus continue to take up cholesterol even though the cell’s cholesterol requirements are met (Saladin 2007). This causes a deposit of cholesterol to build up, forming an atheroma, obstructing the lumen of the artery. This obstruction within the artery is a natural precursor to many heart conditions including myocardial infarction and angina pectoris (Smith 2000).
FH is a disease which subjects the person who has it to be predisposed to coronary heart disease. However, the incidence of heart disease in all patients is not the same. As mentioned above, the gene is inherited in an autosomal dominant manner; therefore the person with FH can be either heterozygous, or homozygous. A homozygote would produce no viable LDL receptors, whilst a heterozygote would produce half the normal amount (Saladin 2007). These production values significantly affect the incidence of myocardial infarction, due to the body’s ability to compensate to these defects. For a homozygote, the chance of heart attack in childhood is high, whilst a heterozygote is most likely to experience a heart attack by the age of 35 (Saladin 2007). Other factors which influence the formation of atheromatous plaques include anxiety, stress, obesity and bad diet. In addition, smoking, and a lack of exercise are also factors which promote the incidence of heart disease (Smith 2000). Lack of exercise increases the risk of heart disease, as it promotes LDL formation. Conversely, exercise promotes HDL formation, which lowers plasma cholesterol concentration levels, and reduces the risk of heart disease (Saladin 2007). As a result, it follows that someone who is a heterozygote, doesn’t smoke and leads a healthy lifestyle, would be unlikely to experience a heart attack.
Many preventative measures can be made when dealing with FH, along with many treatment options for coronary heart disease. As mentioned above, leading a balanced, active lifestyle delays the onset of atherosclerosis, and the resulting heart disorders which follow. Coronary heart disease can be treated in many ways, including: balloon angioplasty (whereby a catheter is introduced into the artery and the balloon inflated, such that the atheroma is either squashed or cracked, thus creating a larger lumen); laser angioplasty (whereby a laser is used to break apart and vaporise the atheroma); and coronary artery bypass surgery (whereby a section of vein or artery is used to create a bypass around the blocked section caused by the atheroma) (Saladin 2007).
FH is an inherited disease, transmitted in an autosomal dominant manner, which leads to high cholesterol level. Treatment is concerned with altering the environment of the patient to compensate for the genetic predisposition towards having heart disease.
894 words.
References
Saldin, KS 2007, Anatomy and Physiology: the unity of form and function, 4th edn. McGraw-Hill New York.
Smith, T 2000, The Human Body, Ken Fin London.
Maxwell, SJ, Molster, CM, Poke, SJ & O’Leary, P 2009, ‘Communicating Familial Hypercholesterolemia genetic information within families’, Genetic Testing and Molecular Biomarkers, vol. 13, no. 3, pp. 301-306.
Alonso, R, Defesche, JC, Tejedor, D, Castillo, S, Stef, M, Mata, N, Gomez-Enterria, P, Martinez-Faedo, C, Forga, L, Mata, P 2009, ‘Genetic diagnosis of Familial Hypercholesterolemia using a DNA-array based platform’, ClinicalBiochemsitry, vol. 42, pp. 899-903. Available from: Science Direct. [23 August 2009]
Schuster, H 2002, ‘High Risk/Priority: Familial Hypercholesterolemia-a paradigm for molecular medicine’, Atherosclerosis Supplements, vol. 2, pp. 27-32.
Fouchier, SW, Defesche JC, Umans-Eckenhausen, MAW, Kastelein, JJP 2001, ‘The molecular basis of Familial Hypercholesterolemia in The Netherlands’, Hum Genet, vol. 109, pp. 602-615
Fard-Esfahani, P, Khatami, S, Zeinali, C, Taghikhani, M, Allahyari, M 2005, ‘A modified conformation sensitive gel electrophoresis (CSGE) method for rapid and accurate detection of low density lipoprotein (LDL) receptor gene mutations in Familial Hypercholesterolemia’, Clinical Biochemistry, vol. 38, pp. 579-583. Available from: Science Direct. [24th August 2009]
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