DETERMINATION OF LIPID PROFILE AND SOME BIOCHEMICAL INDICES IN PHYSICALLY ACTIVE AND SEDENTARY PREGNANT AND NON-PREGNANT WOMEN IN GIWA COMMUNITY KADUNA STATE

ABSTRACT

Lipids  and  lipoproteins are  essential  constituents of the  body and  their  activities  assist  in maintenance of the body homeostasis. Sedentary lifestyle, as predisposed by sedentary work has been shown to lead to inactivity which could lead to lipid disorders during pregnancy. Physical activity during pregnancy can reduce the risk of pregnancy induced hypertension and preeclampsia. The present study was designed to ascertain the difference in lipid profile and some biochemical indices in physically active and sedentary pregnant and non-pregnant women residing in Giwa Local Government Area Kaduna State, Nigeria.A total of 50 subjects between the ages of 16 to 45 years formed the study population, which were grouped into four; Group 1 (physically active non-pregnant women), Group 2 (Sedentary non-pregnant women), Group 3 (physically active pregnant women) Group 4 (sedentary pregnant women). The test subjects were selected among those attending ante natal clinic at the General Hospital in GiwaLocal Government area of Kaduna State, Nigeria. The study was conducted in compliance with the Declaration on the right of the Patient after approval by the Ethical Committee of the Health centers. Also, an informed consent and questionnaire was obtained from all subjects enrolled for the study.The fasting serum total cholesterol, triacylglycerol, High density lipoprotein, Low density lipoprotein, Very low density lipoprotein, serum urea and creatinine, serum electrolytes levels were analyzed using biochemical laboratory kits and readings were taking using EMP:168 biochemical analyzer.The mean ± SD for all the groups showed a statistically significant increase (p<0.05) in TC, TG, LDL-C and VLDL when compared with to control subjects (group 1), while the HDL showed a significant decrease (p<0.05) in group 4 when compared with the control

(group 1). Electrolyte (Na+, Cl-, and K+) showed no significant difference (p<0.05) in all the

groups. However, Ca+concentration was observed to be significantly (p<0.05) higher in groups 4

and 2 as compared to groups 1 and 3.HCO-

concentration showed a significant (p<0.05) increase

in groups 4, 2 and 3 as compared to group 1. A significant (p<0.05) increase was observed in serum urea from groups 3and4 while group 2 had no significant difference as compared to group

1. Serum creatinine showed a significant (p <0.05) increase in group 3and4 while group 2

showed no significant difference. The body mass index (BMI) showed a significant(p <0.05) increase in all the groups but higher in group 4 when compared to group 1. This study showed the effects of sedentary life style and the importance of physical activities during pregnancy. At  least 30minute exercise is recommended in order to reduce complications associated with pregnancy.

CHAPTER ONE

INTRODUCTION

Pregnancy represent a state of stress demanding extra energy source. Lipids serve as alternate energy supply for pregnancy sustainability (Peter, 1996). Thus high plasma level of lipids and lipoprotein cholesterol in this physiologic state is normal and has since been established in various studies in the past (Adedeji et al., 2011; Ajose et al., 2002; Jarikre et al., 2000). During pregnancy, maternal metabolism changes and must therefore satisfy the demands of the developing fetus in addition to the energy requirements of the mother (Winkler et al., 2000). The growth of the foetus is a complex process guided by an interplay between mother, placenta, and fetus. This depends on nutrients such as glucose, lipids, and amino acids (Langer, 2000).

The anabolic phase of early pregnancy result in an increased deposition of fat in maternal adipose tissue. Late pregnancy is characterized by the release of free fatty acids from adipocytes and is enhanced by both relative insulin resistance and stimulation of hormone-sensitive lipase by placental hormones (Peter, 1996). Normal pregnancy is also associated with high concentrations of oestrogens which may contribute to the rise in plasma lipids especially in the late half of pregnancy (Alvarez et al., 1996). There is a profound effect of dietary habits on the lipid metabolism in pregnancy (Di Cianni et al., 2003; Kokia et al., 1990).

Lipid profile is a panel tests used in the diagnosing, prediction and treatment of atherosclerosis. It usually consists of four tests and some calculated values. The measured tests are total cholesterol (TC), triacylglycerol (TAG), high-density lipoprotein (HDL), while the calculated values are the low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) (Ajose et al., 2002). Lipids are substances in the blood that are related to cholesterol. They are a kind of fat found in certain foods and made by the liver (Schreuder et al., 2011). Basically there are three types of lipids used in measuring total cholesterol level are:

Low-density lipoprotein, or LDL, which carries about 65% of the cholesterol in blood. Known as the “bad” cholesterol, LDL can build up in the walls of the arteries that feed the heart and brain. Along with other substances, it can form plaque—a thick, hard deposit that can clog those arteries. When this happens, the condition is known as atherosclerosis (Harville et al., 2011).

High-density lipoprotein, or HDL, carries about 30% of the cholesterol in blood. HDL is known as “good” cholesterol because it carries LDL away from the arteries and back to the liver, where it’s passed from the body. A high HDL level helps prevent heart disease, while a low HDL level increases the risk of heart attack and stroke(Schreuderetal.,2011).

Triacylglycerol are the most common type of fat. Like cholesterol, they circulate in blood but are stored in the body for extra energy. Triacylglycerol levels increase significantly after eating. A high triglyceride level combined with a low HDL or high LDL can speed up the process of plaque formation in the arteries (Woolet,2007).

Hyperlipidemia is considered to be an, increase in the fasting serum cholesterol or triglyceride levels or both. Lipid levels may be affected by diet exercise, smoking and certain medications (Elliot et al., 2002).During pregnancy, maternal physiological and hormonal changes occur that are concerned primarily with the nutrition of the growing foetus (Schreuder et al., 2011). One of the changes is the increase in the levels of total cholesterol in the blood.Maternal LDL is important  for  the  synthesis  of  placental  progesterone.  Structural  cholesterol  in  plasma membranes plays a critical role in implantation and the formation of blood vessels in the utero- placental area (Woolet,2007;Harville et al., 2011). Placental cholesterol levels changes affect transportation of molecules across the placenta and this varies with the gestational period (Wyne and Woollett 1998; Schmid et al., 2003). High density lipoprotein is involved in maintaining a balance in the placental cholesterol levels. Maternal cholesterol is thought to be transported to the foetus for development of foetal and placental tissue (Schreuder et al., 2011).In the studiesconducted by Saarelainen et al.(2006), theyrevealed that, total cholesterol levels rise with increasing gestational period. This hypercholesterolemia has been attributed to the hormonal effects of progesterone and estrogen (Alvarez et al., 1996). Studies have shown that the daily production of progesterone increases thirtyfold, while that of estrogen increases tenfold during pregnancy (Husain et al., 2006). Progesterone increases plasma levels of LDL and total cholesterol while  lowering HDL  but  oestrogen has  an opposite effect  (Nessa et  al.,  2004; Chrysohoouet al., 2004).

Various studies have shown the attribute of diet to this hypercholesterolemia during pregnancy to be insignificant (Wyne and woollett, 1998). Some studies have documented changes in maternal total cholesterol and the fractions of cholesterol. HDL increases from the second trimester and remains high throughout the rest of pregnancy in response to estrogen levels. Maternal LDL and total cholesterol increase progressively from the second semester trimester and even remain high after delivery (Chrysohoou et al., 2004; Harville et al., 2011). In the first trimester of pregnancy, cholesterol levels are thought not to change but several studies have shown that they actually fall when compared to pre-pregnancy levels. Total cholesterol levels rise in the second and peak in the third trimester (Saarelainen et al., 2006; Harville et al., 2011). The placenta is an anatomical barrier that prevents contact of the maternal and fetal blood and is composed mainly of multinucleated trophoblast (Woolet, 2007). It is thought that maternal cholesterol is able to cross the placenta and enter fetal circulation and  is taken up  in the  form of lipoproteins by the trophoblast  on  the  maternal  side  by  both  receptor  mediated  and  receptor  independent mechanisms. Studies using animal models have shown that there is a direct association between maternal and fetal total cholesterol levels (Wyne et al., 1998). According to the National Health Institution of the United Kingdom, the optimum total cholesterol levels should be less than

5.2mmol/liter irrespective of sex and age(Schmid et al., 2003).

A sedentary lifestyle is a type of lifestyle common in developed (particularly western) countries, which is characterized by sitting most of the day, in an office or at home (Varo et al., 2003). It is believed to be a factor in obesity and other disorders (Myron, 2003). Individuals who expend less than 2,000 calories per week through exercise have a higher risk of heart disease than active persons (Nelson et al., 1994).  Most Nigerians are rapidly adopting the sedentary work pattern as a result of civilization. Having a sedentary lifestyle leads to being overweight, and this can lead to diabetes or elevated blood pressure, both of which are risk factors for coronary heart disease (Nagava et al., 2001).  Due to the obvious benefits of physical fitness, there is need to assess, the lipid profile of sedentary pregnant women (in relation to physical fitness) and compare the result with that of physically active pregnant women. This will go a long way to ascertain the possible predisposition of sedentary pregnant women to coronary heart disease, hence the need of this research work.

1.1Cholesterol

The word cholesterol is coined from the Ancient Greekchole- (bile) and stereos (solid) followed by the chemicalsuffix-ol for an alcohol, is an organicmolecule. It is a sterol (or modifiedsteroid), a lipid molecule and is biosynthesized by all animal cells because it is an essential structural component of animal cell membranes that is required to maintain both membrane structural integrity and fluidity. Cholesterol enables animal cells to (a) not need a cell wall (like plants and bacteria) to protect membrane integrity/cell-viability and thus be able to (b) change shape and (c) move about (unlike bacteria and plant cells which are restricted by their cell walls) (Olson etal.,1998).

Fig. 1Chemical structure of cholesterol           Ball-and-Stick model of cholesterol

Source: (Westover et al., 2003)

In addition to its importance within cells, cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acids, and vitamin D (Hanukoglu,1992).Cholesterol is the principal  sterol  synthesized  by  animals.  All  kinds  of  cells  in  animals  can  produce  it.  In vertebrates the hepatic cells typically produce greater amounts than other cells. It  is almost completely absent among prokaryotes (bacteria and archaea), although there are some exceptions such as mycoplasma, which require cholesterol for growth (Razin and Tully,1999).

1.1.1 History of Cholesterol

François Poulletier de la Salle first identified cholesterol in solid form in gallstones in 1769. However, it was not until 1815 that chemist Michel Eugène Chevreul named the compound “cholesterine” (Olsonet al., 1998).

1.1.2 Physiology of cholesterol

Since cholesterol is essential for all animal life, each cell synthesizes it from simpler molecules, a complex 37-step process that starts with the intracellular protein enzyme 3-hydroxy-3- methylglutaryl-coenzyemA reductase (HMG-CoAR). However, normal and particularly high levels  of  fats  (including  cholesterol)  in  the  blood  circulation,  depending  on  how  they are transported within lipoproteins, and are strongly associated with the progression of atherosclerosis. For a man of about 68 kg (150 lb), typical total body-cholesterol synthesis is approximately 1 g (1,000 mg) per day, and total body content is approximately 35 g, primarily located within the  membranes of all the cells  of the body. Typical daily dietary intake of additional cholesterol for a man in the United States is 307 mg, which is above the upper limit recommended by the Dietary Guidelines Advisory Committee. (National Health and Nutrition Examination Survey, 2012).Most ingested cholesterol is esterified, and esterified cholesterol is poorly absorbed. The body also compensates for any absorption of additional cholesterol by reducing cholesterol synthesis (Lecerf et al.,2011). For these reasons, seven to ten hours after ingestion, cholesterol will show little, if any, effect on total body cholesterol content or concentrations of cholesterol in the blood. However, during the first seven hours after ingestion of cholesterol, the levels significantly increase (Duboiset al., 2007).Cholesterol is recycled. The liver excretes it in a non-esterified form (via bile) into the digestive tract. Typically about 50% of the excreted cholesterol is reabsorbed by the small bowel back into the bloodstream.

Plants make cholesterol in very small amounts. Plants manufacture phytosterols (substances chemically similar to cholesterol produced within plants), which can compete with cholesterol for reabsorption in the intestinal tract, thus potentially reducing cholesterol reabsorption. When intestinal  lining  cells  absorb phytosterols,  in  place  of cholesterol, they usually  excrete  the phytosterol molecules back into the GI tract, an important protective mechanism (John et al., 2007; Desoyeet al., 1994).

1.1.3 Functions of Cholesterol

Cholesterol is required to build and maintain membranes; it modulates membrane fluidity over the range of physiological temperatures. The hydroxyl group on cholesterol interacts with the

polarhead groups of the membranephospholipids and sphingolipids, while the bulky steroid and the hydrocarbon chain are embedded in the membrane, alongside the nonpolarfatty-acid chain of the other lipids. Through the interaction with the phospholipid fatty-acid chains, cholesterol increases membrane packing, which reduces membrane fluidity(Lewington et al., 2007). The structure of the tetracyclic ring of cholesterol contributes to the decreased fluidity of the cell membrane as the molecule is in a trans-conformation making all but the side chain of cholesterol rigid and planar. In this structural role, cholesterol reduces the permeability of the plasma membrane to neutral solutes, hydrogen ions, and sodium ions (Ohvo-Rekilä et al.,2002). Cholesterol has many physiological roles: for example it  is a precursor in the synthesis of Vitamin D and steroid hormones – cortisol, aldosterone, progesterone, estrogen and their derivatives (Butte, 2000; Simone et al., 2011). It is also structural component of the plasma cell membranes; regulating membrane fluidity over a wide range of temperature. This is because the hydroxyl group on the cholesterol molecule interacts with the phosphate groups of the membrane phospholipids, while the carboxyl groups interact with the carboxyl groups of the phospholipids (Ohvio-Rekila et  al.,  2002).  This  increases  membrane  packing  at  the  same  time  reducing membrane fluidity. Cholesterol also reduces the permeability of the membrane to neutral solutes, protons and sodium ions (Simone et al., 2011). In the cell membrane, cholesterol is important for receptor mediated endocytosis (Palinski 2009). This is particularly important in phagocytosis by cells of the immune system. Cholesterol is also important in the development of the central nervous system and is particularly important in development of the brain and spinal cord of the foetus (Palinski 2009).

Within the cell membrane, cholesterol also functions in intracellular transport, cell signaling and nerve conduction. Cholesterol is essential for the structure and function of invaginated caveolae and clathrin-coated pits, including caveola-dependent and clathrin-dependent endocytosis. The role of cholesterol in such endocytosis can be investigated by using methyl beta cyclodextrin (MβCD)  to  remove  cholesterol  from  the  plasma  membrane.Several research  revealed  that cholesterol is also implicated in cell signaling processes, assisting in the formation of lipid rafts in  the  plasma  membrane  (Ohvio-Rekila et  al.,  2002).  Lipid  raft  formation  brings  receptor proteins in close proximity with high concentrations of second messenger molecules. In many neurons, a  myelin sheath, rich in cholesterol, since it  is derived from compacted layers of

Schwann cell membrane, provides insulation for more efficient conduction of impulses (Pawlina et al.,2006).

1.1.4 Dietary sources of cholesterol

Animal fats are complex mixtures of triglycerides, with lesser amounts of phospholipids and cholesterol. As a consequence, all foods containing animal fat contain cholesterol to varying extents. Major dietary sources of cholesterol include cheese, egg yolks, beef, pork, poultry, fish, and shrimp. Human breast milk also contains significant quantities of cholesterol. (Incardona and Eaton,2000).From a dietary perspective, cholesterol is not found in significant amounts in plant sources. In addition, plant  products such as flax seeds and peanuts contain cholesterol-like compounds called phytosterols, which are believed to compete with cholesterol for absorption in the  intestines.  Phytosterols can  be  supplemented through the  use  of phytosterol-containing functional  foods  or  nutraceuticals  that  are  widely  recognized  as  having  a  proven  LDL cholesterol-lowering efficacy. (European Food Safety Authority, Journal, 2010).   Current supplemental guidelines recommend doses of phytosterols in the 1.6-3.0 grams per day range, with a recent meta-analysis demonstrating an 8.8% reduction in LDL-cholesterol at a mean dose of 2.15 gram per day. However, the benefits of a diet supplemented with phytosterol has been questioned.(Behrman and Gopaland,2004; European Food Safety Authority,2010)

1.1.5 Biosynthesis of Cholesterol in Animals

All animal cells manufacture cholesterol for their use, with relative production rates varying by cell type and organ function. About 20–25% of total daily cholesterol production occurs in the liver; other sites of higher synthesis rates include the intestines, adrenal glands, and reproductive organs. Synthesis within the body starts with one molecule of acetyl CoA and one molecule of acetoacetyl-CoA, which are hydrated to form 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) ( Berg,2002).This molecule is then reduced to mevalonate by the enzyme HMG-CoA reductase. This is the regulated, rate-limiting and irreversible step in cholesterol synthesis and is the site of action for the statin drugs (HMG-CoA reductase competitive inhibitors).

Mevalonate is then converted to 3-isopentenyl pyrophosphate in three reactions that require

ATP. Mevalonate is decarboxylated to isopentenyl pyrophosphate, which is a key metabolite for

various biological reactions. Three molecules of isopentenyl pyrophosphate condense to form farnesyl pyrophosphate through the action of geranyl transferase. Two molecules of farnesyl pyrophosphate then  condense  to  form  squalene  by  the  action  of squalene  synthase  in  the endoplasmic reticulum(Berg,2002). Oxidosqualene cyclase then cyclizes squalene to form lanosterol. Finally, lanosterol is converted to cholesterol through a 19-step process (Espenshade and Hughes2007).

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