1.1 BACKGROUND OF STUDY
Hormones are chemicals produced by animals to co-ordinate their physiological activities. They acts as messengers, produced in and released from one kind of tissue to gradually stimulate or inhibit some process in a different tissue over a long period. The importance of individual hormones varies between sexes and age and a disruption of the endocrine equilibrium may result in multiple actions e.g the male hormone testosterone controls many processes from the development offoetus to libido in the adult. Alternatively, one function may be controlled by multiple hormones, e.g. the menstrual cycles involves estradiol, progesterone, follicle stimulating hormone and luteinizing hormone. Hormones are vital innormal development, maturation and physiological functioning of many vital organs and processes in the body (Annamaria, 2012).
However, like any other chemicals of natural or synthetic origin, hormones may be toxic to living organisms under certain circumstances. The toxicity may be due to an excess of its normal (physiological) action. Hormones, like other chemicals, may also exert direct toxic actions not related to their endocrine (physiological) actions (Annamaria, 2012).
Besides the endogenous corticosteroids (cortisol, cortisone) and those suspected to be endogenous (prednisone, prednisolone), there are synthetic exogenous corticosteroids (dexamethasone, betamethasone), developed because of their anti-inflammatory properties.
Estrogens, androgens, gestagens and corticosteroids are steroids which act as hormones. The parent compound from which all steroids are derived is cholesterol. The classification of steroid hormones can be done according to their biological activity and pharmacological effects which includes the sex steroids, a subset of hormones producing sex differences and reproduction such as estrogen, gestagens and androgens. The second group is the corticosteroids which are glucocorticosteroids, involves in metabolism and immune function and mineralocorticosteroids, involves in the regulation of the blood volume and electrolyte content.
They can also be classified upon their endo or exogenous origin. Steroid hormones that are biosynthetically present in the body are the endogenous hormones and they are chemical messengers from one cell (or group of cells) to another e.g (estradiol). Exogenous steroids are also called xenobiotics are foreign compounds that are naturally or synthetically produced e.gmethyltestosterone (Noppeet al., 2008).
Apart from the endogenous corticosteroids (cortisol, cortisone) and those suspected to be endogenous (prednisone, prednisolone), there are the synthetic exogenous corticosteroids ‘old’ structures. Well-known examples of these drugs with a steroids structures are tetrahydrogestrinone (THG), norbolethoneanddesoxymethyltestosterone (DMT) (Noppeet al., 2008).
Cholesterol is a waxy substance made by animal liverand also supplied in diet through animal products suchas meats, poultry, fish and dairy products. Cholesterol isneeded in the body to insulate nerves, make cellmembranes and produce certain hormones, and it is animportant lipid in some membranes. However, the bodymakes enough cholesterol, so any dietary cholesterol
isn'tneeded. Cholesterol plays a major role in human heart health but can be both good and bad. High-densitylipoprotein (HDL) is good cholesterol and low-density lipoprotein (LDL) is bad cholesterol.
Triglycerides are another fat in the bloodstream, the most common type of fat in the body. High levels oftriglycerides is also linked to heart disease and diabetes.A high triglyceride level combined with low HDL cholesterol or high LDL cholesterol seems to speed up atherosclerosis, which is the buildup of fatty deposits in artery walls that increase the risk for heart attack and stroke (Hongbao, 2006).
1.2 STATEMENT OF PROBLEM
Due to the important role of hormones in several body functions, they also have been exogenously applied to animals and humans for productivity and growth development. Focusing on the veterinary field, due to the obvious ability to improve weight gain and feed efficiency in meat producing animals, natural hormones and/or the synthetic surrogates have been used in agricultural practice for several decades by farmers and this imposes several risks on human health. Also, corticosteroids can be illegally used in animal fattening, this is because it has been described that they may have a synergetic effect when combined with anabolic steroids or agonists. (Courtheynet al., 2002; Noppeet al., 2007).
Both exogenous hormones and synthetic compounds mimicking their effects may change the endogenous balance of human body, disturbing their natural functions. Children are extremely sensitive to exogenous steroid hormones because of their low endogenous levels, small variation in their blood levels might trigger serious pubertal development effects and even future adult life problems (Aksglaedeet al., 2006; Alveset al., 2007). An unexpected advance in timing of puberty in both African-American and white American girls (Herman-Giddenset al., 1997).
In adults, an association between the risk of breast cancer and persistently elevated blood levels of oestrogen and androgen has been found in many studies (Kaakset al., 2005; Yager& Davidson, 2006). Also, data published by Swan et al., in 2007 suggested that maternal beef consumption may alter males’ testicular development in utero and adversely affect his adult reproductive capacity.
In the human diet, meat is seen as a major source of fat and especially of saturated fatty acids (SFAs), which havebeen implicated in diseases associated with modern life,mostly in developed countries. Coronary heart diseaseand arteriosclerosis are among the most importantcauses of human mortality, and are strongly associatedwith dietary intake of cholesterol and saturated fatty acids(Simopoulos, 2002, 2004). In addition, HDL is considered to be beneficial as higher levels have been correlated with reduced risk of negative cardiovascular event (American heart Association, 2007). Elevated LDL and triglycerides are considered detrimental as their increased concentration is well is well correlated with poor cardiovascular outcomes (American heart Association, 2007; Segrest, 2002).
1.3 SIGNIFICANCE OF STUDY
As regards to hormonal content, all foodstuff of animal origin contains steroids hormones and metabolites, but their concentrations vary with the kind of food, gender, age and physiological stage of the animal. (Daxenbergeret al., 2001; Poelmanset al., 2005a, 2005b). In fact meat is clearly one of the most naturally contaminated foods. (Maumeet al., 2001, 2003; Poelmanset al., 2005a). Regarding potential toxicological substances used in animal husbandry and their derivatives the US Food and Drugs Administration (FDA) concluded that ‘safety can be assured’ because they are endogenous in both food-producing animals and people.
However, to show the safety of an endogenous sex steroid, it should be demonstrated under the proposed conditions of use, the concentration of residue of the endogenous steroid in treated food-producing animals is such that the increase will not exceed this 1% permitted increase. In 1988, the Joint Food and Agricultural Organisation/World Health Organisation (FAO/WHO) Expert on Food Additives (JECFA) and the US Food and Drugs Administration (FDA) that the residues found in meat from treated animals were safe for the consumers.
The World Health Organization recommends that the daily fat intake be reduced to 30% of the total energy intake, and that saturated fats should be limited to 10% of this caloric intake. It is also advised that cholesterol intake should not exceed 300 mg per day. Dietary intake of unsaturated fatty acids (UFA) has been shown to reduce the risk of cardiovascular diseases (CVD) and possibly the incidence of some cancers, asthma and diabetes among others. In fact, clinical trials have shown that it is unnecessary to completely substitute fish or poultry for lean red meat choices to achieve desirable blood lipid profiles (Davidson et al., 1999; Hunninghakeet al., 2000).
The concentration of dexamethasone will be analyzed in order to know if the use its use is being abused in animal husbandry by local farmers and the residual concentration in meat matrix will be known at the end of this study. The lipid profile of the selected animals will also be determined.
1.4 AIM OF THE STUDY
To identify the health implication of steroid fattened livestockin Lagos market and the implication of their lipid profile for human nutrition.
1.5 OBJECTIVE OF THE STUDY
1. To determine the presence of dexamethasone (steroid) in blood samples of chicken, mutton, pork, chevon and beef.
2. To determine the Lipid profile (cholesterol, triglyceride, high density lipoprotein (HDL), low density lipoprotein (LDL) of the blood samples of the above named meat samples.