CHAPTER ONE
INTRODUCTION
- Background of study
The heart like any other muscle in the body needs an adequate blood supply to provide oxygen so that the muscle can contract and pump blood to the rest of the body. Not only does the heart pump blood to the rest of the body, it also pumps blood to itself via the coronary arteries. These arteries originate from the base of the aorta (the major blood vessel that carries oxygenated blood from the heart) and then branch out along the surface of the heart. When the above functions are not reached, it leads to a condition called cardiac disease. Cardiac(heart) disease describes a range of conditions that affect the heart. Diseases under the heart disease umbrella include blood vessel diseases, such as coronary artery disease, heart rhythm problems (arrhythmias) and heart defects one is born with (congenital heart defects) (Kathiresan et al., 2012).
The established and proposed risk factors for cardiac diseases include age, gender, family history of cardiac disease, dyslipidemia, hypertension, diabetes mellitus, obesity,cigarette smoking, dietary pattern and increased thrombogenicity (Anderson et al., 2011). Also there is strong evidence that oxidative free radicals have a role in the development of degenerative diseases including cardiovascular diseases(Pyrola et al., 2009).
Trace elements are heavy metals that must be essentially present in body fluids in man at very low levels for metabolic processes. They are present in the body in ng quantities. Example of trace elements include zinc, coper, selenium and iodine. These trace elements may also be introduced in the body for therapeutic purposes (Arbernathy et al.,2008). Studies on the roles of trace elements in health and disease over the past 40 years have led to a good understanding of their mechanism of function and why they are essential to life.
Zinc as essential trace elements plays a critical role in the stabilization of biological membrane, protein synthesis, nucleic acid metabolism, and as a cofactor of several enzyme systems(Zuo et al., 2006). Zinc can protect membrane against unsaturated lipids and inflammatory cytokines(Henning et al., 2013). Studies have shown that abnormalities of zinc homeostasis may be associated with pathogenesis of chronic diseases. Both decrease and increase in zinc serum level were reported in ischaemic heart disease patients(Perry et al., 2007). Zinc deficiency is associated with susceptibility to oxidative stress, endothelial cell apoptosis, and atherogenesis. Investigators suggest that a decreased serum zinc concentration may increase the risk of cardiac disease(Beattie et al., 2004). Zinc depletion may affect myocardial reperfusion injury by induction of apoptosis. Zinc deficiency can alter angiotensin-conversion enzyme activity adversely and cause hypertension due to vasoconstriction. Zinc levels tend to decline with age, just as the risk for cardiac diseases increases. Some of the well-known consequences of zinc deficiency are a compromised immune system, skin conditions like dermatitis, increased susceptibility to infection and parasites, and growth failure(Zuo et al., 2016).
The transition metal copper is an essential human micronutrient for enzymes that catalyze oxidation reduction reactions (Linder and Hazegh, 2006). Copper oxidizes low density lipoprotein cholesterol, increasing its atherogenicity (Heinecke et al., 2014). Alternatively, copper may be a risk marker for inflammation rather than a risk factor for coronary heart disease directly involved in the pathogenesis of atherosclerosis. The role of copper in atherosclerosis is controversial (Salonen et al., 2012).
This trace element is involved in the structure of antioxidant enzymes such as superoxide dismutase (SOD) in the form of selenoprotein. Activity of this selenoprotein protects cardiac myocyte membranes in the myocardium against oxidative stress-mediated destruction. Moreover, Cu has a catalytic effect on oxidative stress removal through its role in catalase activity. The simultaneous presence of Cu in the structure of SOD and catalase indicates the critical role of Cu in removing oxidative stress. As such, any significant change in the status of serum Cu could lead to alterations in antioxidant enzyme activities and subsequently affect tissue susceptibility to oxidative stress(Salonen et al., 2012).
Selenium (Se) an essential trace element is crucial for many biological functions including thyroid hormone metabolism, the body’s antioxidant defense systems, the adaptive and acquired immune system and prevention of certain cancers. Serum levels of selenium are known to be positively correlated with the activity of GPx(Rotruck, 2013; Rotruck, 2012) and other antioxidant selenoproteins, which are crucial for maintenance of redox homeostasis and optimal antioxidant defense. In the chronic development of Coronary Heart Disease, reduced selenium levels thus may result in an inadequate prevention of LDL oxidation, (which is the major cause for the development of atherosclerotic plaques), through uptake by endothelial cells and macrophages(Aviram and Fuhrman, 2008).
Iodine a chemical element is the heaviest of the stable halogens. Therefore its deficiency could lead to serious complications in patients with cardiovascular diseases.
- Justification
Cardiac disease remains the major cause of premature death worldwide. About 80% of all heart disease mortality now occurs in developing countries. The prevalence of risk factors for Cardiac disease is on the increase in the developing nations of the world like Nigeria(Paradis and Chiolero, 2011). Socio-economic status (SES) is a predictor of cardiac diseases and its risk factors. However, the nature of this relationship varies dependent on the economic development of the countries(Ogden, 2012). In high income countries, the evidence points to an inverse relationship between SES and cardiac diseases risk factors in the adult population, regardless of indicators of SES used. This trend differs in low-middle-income countries and among those of lower SES in the developed countries where lower SES is a potential marker of poor health outcomes(Cai et al., 2013). In Nigeria, few reports on the association between SES and cardio-metabolic syndrome varies. High prevalence of cardiometabolic risk factors was found in high SES groups than in low SES groups(Adedoyin et al., 2013), while Mbada et al. (2011) noted a higher prevalence of obesity in the lower SES of a semi-urban Nigerian population. These few reports studied SES as an entity; however, the component of the SES driving the trend of the relationship in prevalence is worth exploring in relation to how it affects risk factors screening. Its pathogenesis still remains unclear as many researches proposed different mechanisms. However previous researches on Cardiac Diseases have shown that it occurs more in the elderly than the younger ones probably because of decline in the physiological activities during that period. The younger ones who by paradventure develop the cardiac diseases may be related to constant exposure to the risk factors associated with cardiac diseases like chronic cigarette smoking, usage of drugs, low intake of high nutritional diet that contains the essential trace elements that is required for the optimal activity of living organisms(Cai et al., 2013).
Nutrition on the other hand plays a critical role in the reduction of the risk of developing numerous cardiac diseases like hypertension, stroke, angina e.t.c. Trace elements like zinc, copper, iodine and selenium must be essentially present in body fluids in man at very low levels for metabolic processes. An inadequate supply of these trace elements are related to the development of various heart diseases (Davies and Nightingale, 2014). However, this research is done in other to give insight on the essential role of trace elements in health and its importance in reducing cardiac diseases.
- Research Question
Does cardiac disease affect the serum levels of some trace metals; zinc, copper, selenium and iodine?
- Hypothesis Testing
Null Hypothesis (): Serum trace metal levels(zinc, copper, selenium and iodine) are not affected in patients with cardiac disease.
Alternate Hypothesis(): Serum trace metal levels(zinc, copper, selenium and iodine) are affected in patients with cardiac disease.
1.5 Aim and Specific Objecives
- A) Aim
To determine the levels of some essential trace elements(Selenium, Copper, Zinc and iodine) in patients suffering from cardiac diseases.
- B) Specific Objectives
- 1. To determine the levels of trace elements(Selenium, Copper, Zinc and Iodine) in cardiac disease patients.
3 To compare the blood levels of selenium, copper, zinc and iodine in cardiac disease patients with the control subjects.
4 To determine if there is a correlation between selenium, copper, zinc and iodine in the patients suffering from cardiac disease
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