ABSTRACT
This work was aimed at finding the effects of alcohol on some biochemical parameters. A total of one hundred and eighty (180) apparently healthy, non-hypertensive male alcoholics were used for the study. Forty (40) non-consumers of alcohol were used as control. The activity of alanine aminotransferase (ALT) in the control was 10.50±2.00 IU/L while it was 16.50±1.50 IU/L; 17.50±2.00 IU/L and 18.31±2.00 IU/L in alcoholics who showed preference for palmwine, beer and distilled spirit respectively. Also, the activity of aspartate aminotransferase (AST) in the control was 9.51±0.35 IU/L while it was 18.44±0.40 IU/L, 19.21±0.19 IU/L,
20.32±0.64 IU/L in alcoholics who showed preference for palmwine, beer and distilled spirit respectively. The ALT and AST activities of alcoholic subjects who showed preference for distilled spirit was significantly higher (p < 0.05) than those who showed preference for palmwine and beer. The activities of alcoholics who showed preference for palmwine was the lowest. Furthermore, the serum total bilirubin concentration of the alcoholics was significantly higher (p < 0.05) compared with the control. The serum total bilirubin concentrations were 18.65±2.10 μmol/l, 19.40±1.50 μmol/l and 22.75±1.60 μmol/l for alcoholics who showed preference for palmwine, beer and distilled spirit respectively. The serum total bilirubin of the control was 8.30 ± 2.00 μmol/l. The alkaline phosphatase (ALP) activity of the alcoholic subjects was significantly higher (p<0.05) compared with the control. The ALP activity of the control was 61.50 ± 30.00 IU/L while the ALP activity was 174.20±2.50 IU/L, 175.10±1.50 IU/L and 177.40±1.00 IU/L in the three categories of alcoholics who showed preference for palmwine, beer and distilled spirit respectively. Moreover, the urine total protein concentration of the alcoholics was significantly higher (p<0.05) compared with the control. Alcoholics who showed preference for distilled spirit had urine total protein of 153.96±0.43 mg/dl followed by alcoholics who showed preference for beer and palmwine who had urine total protein of 152.74±0.42 mg/dl and 151.34±0.60 mg/dl respectively. The urine total protein of the control was 56.40±0.40 mg/dl. Furthermore, the urine specific gravity, serum urea and creatinine of the alcoholics were significantly higher (p < 0.05) compared with the control. However, the plasma sodium, potassium and creatinine clearance of the alcoholics were significantly lower (p < 0.05) compared with the control. The body mass index (BMI) of the three groups of alcoholics fell within the range of 18.50 to 24.90. The blood pressure of both the alcoholic and control subjects were normal (below 140/90 mmHg). This work therefore shows that chronic alcohol use could induce both hepatic and renal dysfunctions in the alcoholics which manifested in form of adverse variations in some biochemical parameters of prognostic and diagnostic utility.
CHAPTER ONE
INTRODUCTION
Generally, alcohol designates a class of compounds that are hydroxyl derivatives of aliphatic hydrocarbons. However, in this study, the term alcohol used without additional qualifications refers specifically to ethanol. A variety of alcoholic beverages have been consumed by man in the continuing search for euphoria producing stimuli. Among some people, alcohol enjoys a high status as a social lubricant that relieves tension, gives self confidence to the inadequate, blurs the appreciation of uncomfortable realities and serves as an escape from environmental and emotional stress.
Alcohol has been loved and hated at different times by different people. Alcohol has been celebrated as healthful especially to the heart (red wine) and most pleasant to the taste buds; and then dismissed as “demon’s rum” and “devil in solution” depending on the prevalent view.
In spite of the apparent divergent and sometimes conflicting opinions about alcohol, the consensus shared by drinkers and non drinkers alike is that excessive and chronic consumption of alcohol is a disorder. Like any other chronic disorder, it develops insidiously but follows a predictable course. The first or pre-alcoholic symptomatic phase begins with the use of alcohol to relieve tensions. The second (or prodromal) phase is marked by a range of behaviours including preoccupation with alcohol, surreptitious drinking and loss of memory (Hock et al., 1992). In the third (or crucial) phase, the individual loses control over his drinking. This loss of control is the beginning of the disease process of addiction. The individual starts drinking early in the morning and stays up drinking till late in the night. Impairment in biochemical activities becomes manifest as the organs of the alcoholic begin to deteriorate. Other medical problems develop by the time the alcoholic gets into the final (chronic phase). Prolonged intoxications become the rule. Alcoholic psychosis develops, thinking is impaired, and fear and tremors become persistent (Klemin and Sherry, 1981). A previously responsible individual may be transformed into an inebriate – stereotype alcoholic.
Fear-instilling but thought- provoking terms such as the “coming epidemic”, a “miserable trap”, have been used to show concern for the potential hazard of widespread alcoholism.
In its 1978 revision of the international classification of diseases, the World Health Organization defined alcoholism as “a state, psychic and usually also physical, resulting from taking alcohol, characterised by behavioural and other responses that always include a
compulsion to take alcohol on a continuous or periodic basis in order to experience its psychic effects and sometimes to avoid the discomfort of its absence; tolerance may or may not be present. This definition emphasized the compulsive nature of drinking, the psychological and physical effects, and dependence (“discomfort of its absence”) (WHO,
1978).
The kidney and liver could be particularly vulnerable to the chemical assault resulting from alcohol abuse because they receive high percentage of the total cardiac output. Also, the liver is pivotal in intermediary metabolism; so ingested alcohol must come in contact with the liver and kidney. Alcohol could produce many of its damaging effects by the formation of dangerous, highly reactive intermediates such as acetaldehyde which may lead to glutathione depletion, free radical generation, oxidative stress and cell dysfunction.
Alcohol dehydrogenase in the presence of a hydrogen acceptor nicotinamide adenine dinucleotide (NAD) oxidizes ethanol to acetaldehyde. This is the initial obligatory biochemical event in alcohol induced hepatotoxic and nephrotoxic effects. Thus, it is important to find out in quantitative terms the effects of different types of alcohol drinks on some principal biochemical parameters of diagnostic utility.
1.1 Alcohol
1.1.1 Chemistry of Alcohol
The term ‘alcohol’ refers to a class of compounds that are hydroxy (-OH) derivatives of aliphatic hydrocarbons. There are many common alcohols – methanol or wood alcohol, isopropyl alcohol, the antifreeze diethylene glycol, and glycerine. In this study however, when the term alcohol is used without additional qualification, ethyl alcohol, a liquid also known as ethanol, is referred to. Alcohol can be considered as being derived from the corresponding alkanes by replacing the hydrogen atoms with hydroxyl groups. The hydroxyl group is the functional group of alcohols as it is responsible for their characteristic chemical properties. Monohydric alcohols contain only one hydroxyl group in each molecule. Monohydric alcohols form a homologues series with the general molecular formular CnH2n+1OH.
All alcoholic beverages arise from the process of fermentation. Indeed, ethanol, the
alcohol in beverages, is the quantitative end product of yeast glycolysis. In the presence of water, yeasts are able to convert the sugar (glucose) of plants into alcohol, as depicted by the following chemical reaction:
C6H12O6 2C2H5OH + 2CO2 Glucose + Yeast
lAcohol Carbon dioxide
A wide variety of plants have proved to be useful substrates for the action of yeast, and this is reflected by the different types of beverages used throughout the world.
1.1.2 Alcohol Production
1.1.2.1 Beer Production
Beer is generally considered to be of two types, the ale types, brewed with Saccharomyces cerevisiae and the lager type, brewed with Saccharomyces carlsbergensis. The main ingredients of beer are malted barley, the source of fermentable carbohydrates, proteins, polypeptides, minerals, and hops the primary purpose of which is to impart bitterness and the hop characteristic, but which also have anti-microbial properties, yeast and water. The basic processes for the brewing of beer include:
(a) Malting
Malting involves the mobilization and development of the enzymes formed during germination of the barley grain. The grain is permitted to germinate under controlled conditions of moisture and temperature, the starch/enzyme balance then being fixed by kilning at drying temperatures as high as 104oC
(b) Mashing
During mashing, ground malt is mixed (mashed) with hot water. This serves both to extract existing soluble compounds from the malt and to reactivate malt enzymes which complete the breakdown of starch and proteins.
(c) Wort boiling
Wort is drained from the mash tun into a copper and boiled to inactivate malt enzymes. In traditional brewing, hops are added at this stage, the humulones (α-acids) being extracted and chemically isomerized. The resulting iso-humulones have a greater solubility and contribute the characteristic bitter flavour to beer, while the ‘hop character’ is derived from essential oils. In recent years, there has been a tendency to replace hop cones with various types of hop pellets, powders or extracts including pre-isomerized hop products which may be added after fermentation. Boiling serves two other functions: reducing the
potential for microbiological problems by effectively sterilizing the wort and coagulation of proteins followed by their removal as ‘trub’. Inadequate coagulation may adversely affect the subsequent fermentation due to interference with yeast:substrate exchange processes (membrane blocking) and lead to poor quality beer.
(d) Fermentation
Fermentations are considered to be of two distinct types: the top fermentation used in production of ales, in which CO2 carries flocculated Sacch. cerevisiae to the surface of the fermenting vessel, and the bottom fermentation used in production of lagers, in which Sacch. carlsbergensis sediments to the bottom of the vessel. Differentiation on the basis of the behaviour of the yeast is, however, becoming less distinct with the increasing use of cylindro- conical fermenters and centrifuges.
(e) Maturation (Conditioning; Secondary fermentation)
Maturation may be considered to include all transformations between the end of primary fermentation and the final filtration of the beer. These include carbonation by fermentation of residual sugars, removal of excess yeast, adsorption of various non-volatiles onto the surface of the yeast and progressive change in aroma and flavour. During maturation, priming sugar may be added or amyloglucosidase used to hydrolyse dextrins.
1.1.2.2 The Production of Palm Wine
There are two main sources of palmwine namely: raphia palm particularly Raphia vinifera and Raphia hookeri; and the oil palm: Elaeis guineensis. Palmwine is an alcoholic beverage produced from the fermenting palm sap. The part tapped is the male inflorescence of a standing oil palm tree. The fermentable sugars present in palm wine are glucose, sucrose, fructose, maltose, and raffinose. The yeast species – Saccharomyces spp are responsible mainly for the conversion of the sugars in palm sap into alcohol as well as oxidative fermentation of alcohol to acetic acid.
In the fermentation of natural palm wine, lactic acid bacteria, Lactobacillus
plantarium, Leuconostoc mentseriodes and Pediococcus cerevisiae are also involved. All of them utilize meyerhof parnas pathway which results in the formation of alcohol as well as organic acids. The leuconostoc mesenteriode is a hetero-fermenter and ferments sugar to produce acetic acid., lactic acid, ethanol and carbondioxide. Lactobacillus plantarium is a homofermenter and ferments sugars to produce mainly lactic acid and small amount of
alcohol and carbondioxide. Pediococcus cerevisiae is also a homo fermenter and produces the same metabolites as Lactobacillus plantarium. Thus, the bacterial flora of palm wine contribute significantly to the fermentation of sugars to alcohol and the alcoholic constituent of palm wine varies with the species of palm tree from which the wine was tapped.
1.1.2.3 Production of Distilled Spirit
Nature alone cannot produce spirits or hard liquor by the simple process of fermentation. Yeast will continue to carry out fermentation until the alcoholic content becomes high. The process of distillation then helps to produce beverages with higher concentration of alcohol in form of distilled spirit.
1.1.3 Absorption, Distribution and Metabolism of Alcohol
1.1.3.1 Absorption
After its ingestion, alcohol is rapidly absorbed into the blood stream from the stomach and small intestines. The rate of alcohol absorption can be delayed by the presence of food or milk in the stomach. It is a common observation that when several drinks are taken on an empty stomach, a far more rapid and profound effect is observed than when an equivalent amount of alcohol is taken when there is food in the stomach.
1.1.3.2 Distribution
Alcohol gains access to all the tissues and fluids of the body. The concentrations of alcohol in the brain rapidly approach those levels in the blood because of the very rich blood supply to the brain and other organs such as the liver and the kidney. This is of obvious significance, because alcohol-induced dysfunctions in several organs depend on the concentration and duration of exposure of the organs to alcohol.
1.1.3.3 Alcohol Metabolism
Two major pathways of alcohol metabolism have been identified namely alcohol dehydrogenase pathway and microsomal ethanol oxidizing system (MEOS).
1.1.3.3.1 Alcohol Dehydrogenase Pathway
The primary pathway for alcohol metabolism involves alcohol dehydrogenase (ADH), a cytosolic enzyme that catalyzes the conversion of alcohol to acetaldehyde. This enzyme is
located mainly in the liver but small amounts are found in other organs such as the brain and stomach.
During conversion of ethanol by ADH to acetaldehyde, hydrogen ion is transferred from alcohol to the cofactor nicotinamide adenine dinucleotide (NAD+) to form NADH. As a net result, alcohol oxidation generates an excess of reducing equivalents in the liver, chiefly as NADH. The excess NADH production appears to contribute to the metabolic disorders that accompany chronic alcoholism and to both the lactic acidosis and hypoglycaemia that
frequently accompany alcohol poisoning.
1.1.3.3.2 Microsomal Ethanol Oxidizing System (MEOS)
This enzyme system, also known as the mixed function oxidase system, uses NADPH
as a cofactor in the metabolism of ethanol and consists primarily of cytochrome P450 2E1,
4A2, and 3A4. At blood concentrations below 100mg/dl (22 mmol/l), the MEOS system, which has a relatively high Km for alcohol, contributes little to the metabolism of ethanol. However when large amounts of ethanol are consumed, the alcohol dehydrogenase system
becomes saturated owing to depletion of the required cofactor, NAD+. As the concentration
of ethanol increases above 100mg/dl, there is increased contribution from the MEO system, which does not rely on NAD+ as a cofactor.
During chronic alcohol consumption MEOS activity is induced. As a result, chronic alcohol consumption results in significant increases not only in ethanol metabolism but also in the clearance of other drugs eliminated by the cytochrome P450s that constitute the MEOS system, and in the generation of the toxic by-products of cytochrome P450 reactions (toxins, free radicals H2O2). Metabolism occurs mainly via the zinc–containing enzyme alcohol dehydrogenase (ADH). Other enzyme systems, such as the microsomal ethanol oxidizing system (MEOS) or catalase system are capable of metabolising alcohol.
Oxidation of alcohol by ADH involves the transfer of hydrogen via nicotinamide adenine dinucleotide (NAD), which is converted to nicotinamide adenine dinucleotide reduced (NADH). The result of this oxidation is the metabolite acetaldehyde. The subsequent oxidation of acetaldehyde by aldehyde dehydrogenase also involves the reduction of NAD. Acetaldehyde is metabolized to acetate and this is transformed in to acetyl coenzyme A, which is then oxidized by the citric acid cycle to carbon dioxide and water. The rate limiting step in this metabolic process is the oxidation of alcohol to acetaldehyde since acetaldehyde is metabolized faster than it is formed.
1.1.4 Patterns of Alcohol Use and Abuse
Patterns of alcohol consumption may range from its occasional use to relieve emotional stress, to periodic “spree” drinking, to extreme cases where the alcoholic has little or no control over the amount of alcohol consumed. Chronic and excessive consumption of alcohol is a health and psycho-social disorder characterized by obsessive pre-occupation with alcohol and loss of control over alcohol consumption such as to lead continuously to intoxication (Johansson et al., 2003). Chronic abuse of alcohol is typically associated with physical disability, social maladjustments, emotional and occupational impairments.
The hallmarks of excessive and chronic alcohol abuse are:
1. Psychological dependence
2. Physical dependence
3. Tolerance (Martin et al., 2008).
1.1.4.1 Psychological Dependence
Psychological dependence is typically characterized by intense and uncontrollable craving for alcohol. The alcoholics’ desire for alcohol is intense, obsessive and overwhelming. The alcoholics are deeply concerned about how daily activities interfere with drinking than how drinking negatively militate against the performance of daily activities. Family, relationships, friends, profession and business are relegated to subordinate roles with full joy. Alcohol consumption becomes the driving and motivating force (Johansson et al., 2003).
1.1.4.2 Physical Dependence
Excessive and chronic consumption of alcohol produces unequivocal physical dependence, with the intensity of the syndrome associated with withdrawal directly proportional to the level of intoxication and its duration. Excessive consumption of alcohol on chronic basis directly or indirectly adversely modifies the physical and mental health of the abuser. Intermediate levels of alcohol consumption produce withdrawal symptoms typified by tremors or “shakes”, anxiety, sleeplessness and gastrointestinal upset.
Delirium tremens is one of the potentially risky withdrawal symptoms experienced by chronic abusers, when physical dependence has set in. Alcoholics that have delirium tremens suffer from restlessness, tremors, weakness, nausea and anxiety few hours after the last drink. Generally, these effects experienced by alcoholics on momentary withdrawal from alcohol serve as an impetus driving them to initiate another drinking bout in order to feel ‘normal’
again; thus, potentiating the physical dependence. The tremors could be so severe that the alcoholic on resuming drinking finds it difficult to successfully navigate beer bottle or cup to his mouth yet he craves for more alcohol.
In the early stages of this withdrawing syndrome after the onset of physical dependence, the alcoholic is hyperactive and is a victim of auditory and visual hallucinations. The alcoholics could be heard shouting that cockroaches are crawling upon them; they see red lions and they may seriously believe that they are being attacked by dangerous animals or people. They are completely disoriented.
Progressively, the alcoholic becomes weaker, agitated and confused. These syndromes coupled with exhaustion and fever are called ‘tremulus delirium’. In physical dependence the intensity of the syndromes associated with withdrawal as typified by tremulus delirium is related to the duration and level of alcohol abuse. Physical dependence could develop from ethanol induced alterations in membrane components and functions (Cargiulo, 2007).
1.1.4.3 Tolerance
Alcoholics usually exhibit increased resistance to the intoxicating effects of alcohol and are often sober at blood alcohol concentrations that could be deadly in naïve occasional drinkers. Indeed, chronic alcohol abusers can readily ingest quantities of alcohol that would severely intoxicate the occasional drinker (Chiaochicy and Shijium, 2008).
Ethanol can cross the blood- brain barrier and enter the brain quickly. Blood alcohol level is almost always directly proportional to the concentration of alcohol in brain tissue (Oscarberman and Marinkovit, 2003). However, despite increasing levels of alcohol in the blood, alcoholics usually exhibit decreasing response to the intoxicating effect of alcohol.
This phenomenon known as tolerance could be explained in part by these mechanisms: first, tolerance could develop consequent upon alterations in the absorption rate, distribution, metabolism and elimination of alcohol from the body (Rottenburg, 1986). The resultant effect of these alterations is a reduction in the duration and intensity of alcohol’s effects on the body tissues most remarkably the brain.
The second mechanism involves alterations in the properties or function of tissues rendering them less vulnerable to effects of alcohol (Wilson et al., 1984). Tolerance to alcohol could develop as a result of adaptive alterations in the central nervous system.
Alcohol changes many specific membrane dependent processes such as Na+, K+ ATPase and
adenylyl cyclase process in the cell precipitating ethanol-induced alterations in neural
functions. It has been observed that after chronic exposure to alcohol, cellular membranes often develop resistance to the fluidizing effect of alcohol (Goldstein, 1986). Ethanol-induced alterations also occur in membrane components and functions such as alterations in membrane lipids, receptors, phosphatidylinositol, GTP binding proteins, second messengers and neuro-modulator (Reynolds et al., 1990). Alterations in ion channels and transporters are also some of the ethanol induced changes in human cell membranes related to tolerance (Chastain, 2006). Putting these observations in a functional perspective, it is salient to point out the fact that these adaptive changes in membrane components are exquisite phenotypic markers for genetic predisposition to alcoholism and its attendant problems (Das et al., 2008).
1.1.5 Aetiology/Causes of Alcohol Abuse
1.1.5.1 Biochemical basis
(a) Monoaminergic System
The enzyme monoamine oxidase (MAO) is the major degradative enzyme for both catecholamines and indoleamines. It has been shown that reduced platelet monoamine oxidase concentrations are closely associated with a remarkable predisposition to alcoholism (Patsenka, 2004) and psychiatric vulnerability. It has also been proposed that a weak monoaminergic system causes predisposition to alcohol abuse (Raddtz and Parini, 1995).
Available evidence is becoming overwhelming in support of the view that sub class of alcoholics exists where genetic considerations are of etiological significance. These imposing factors appear to be reflected in low platelet monoamine oxidase (MAO). Low concentrations of platelet monoamine oxidase reflect a disturbance in the serotoninergic system (Chastain,
2006). Thus, the biochemical basis of alcoholism seems to involve combined aberrations in
some transmitter system. In essence, these aberrations have far reaching effects which are reflected in neuro-physiological, psychosocial and personality abnormalities.
(b) Tetrahydroisoquinolines
Biologically active chemicals called tetrahydroisoquinolines are formed during alcohol metabolism (Antkiewez et al., 2000). Catecholamines could also condense with aldehydes via a Pictet-Spengler reaction to form 1,4-Disubstituted tetrahydroisoquinoline (Raddatz and Parini, 1995). Tetrahydroisoquinoline such as tetrahydropapaveroline changes drinking behaviour from alcohol rejection to alcohol acceptance (Nappi and Vass, 1999).
The Picket-Spengler reaction provides a useful route for the synthesis of tefrahydrolsoquinoline (TIQ). Many tetrahydroisoquinoline are formed from dopamine and
carbonyl compounds (phenylpyruvic acids, aldehydes and ketones) two catecholamine norepinephrine or epinephrines could also react resulting in the formation of diastereomeric
Fig. 1: 1,4-disubstituted TIQ occur in form of two diastereomers and their optical isomers
Furthermore, ethanol or its first oxidation product acetaldehyde can induce catecholamines to undergo an unusual form of metabolism that results in the formation of
1,2,3,4- tetrahydroisoquinoline. Tetrahydroisoquinoline compounds have biochemical and neuropharmacological properties. They possess abilities to interact with catecholaminergic and dopaminergic systems. They also exert a potent influence on Ca2+ binding in synaptosomes in a similar manner to morphine and ethanol. T1Qs have biochemical
associations with ethanol and is deeply involved in the aetiology of alcoholism (Raddtz and
Parini, 1995).
Patsenka (2004) showed that excessive and chronic consumption of alcohol by human alcoholics could be caused by metabolic abnormalities that result in the formation of tetrahydroisoquinolines. He reasoned that because drinking generates tetrahydroisoquinolines and tetrahydroisoquinolines stimulate drinking, the positive feedback loop could be responsible for the obsessive, uncontrolled and habitual drinking by alcoholics. Thus, tetrahydroisoquinolines could be involved in the mediation of voluntary ethanol consumption habit that often degenerates to heavy intoxication, physical dependence and tolerance (Chastain, 2006).
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EFFECTS OF ALCOHOL ON SOME BIOCHEMICAL PARAMETERS OF ALCOHOLICS IN NSUKKA ENUGU STATE NIGERIA
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