Zinc and Alcohol Metabolism - Term Paper Example

Zinc and Alcohol Metabolism Zinc and Alcohol Metabolism Zinc is an important trace element in animals, plants and humans. It is essential for most biological functions as well as playing a role in up to 300 enzymes in the human body. An adult body contains 2-3 grams of zinc and are found in all body parts: cells, fluids, bones, tissues and organs. Most of the body’s zinc reserves are found in bones and muscles, while higher concentrations are found in semen and the prostate gland. Zinc is majorly present in foods rich in proteins, which is absorbed in the ileum and duodenum by the intestinal epithelium (Bolkent et al, 2006). The ileum absorbs nearly 3-4 grams of zinc per day and thus the recommended allowances, daily range from 5mg in infants to between 16 and 19 mg per day for lactating women. In addition, it is stored and used in two distinct pools: the fixed pool that is usually bound to metalloproteins, which constitutes 80-90% of body zinc. The second is the labile pool which constitutes loosely binding or free zinc, which is available for exchange by organelles and cells. This kind of pool is susceptible to depletion, especially during dietary zinc deficiency. Free zinc may be toxic to enzymes and proteins and thus the labile pool is largely bound to proteins that carry zinc. Moreover, zinc movement across organelle membranes and plasma is regulated tightly by zinc transporters. Zinc has a vast majority of functions and relates to alcohol intake through its biochemical role in metabolism of alcohol. Functions of zinc Zinc is important for cell division and growth. It is crucial, especially during pregnancy for the developing fetus because cells are dividing rapidly. Zinc helps in avoiding pre-term delivery and congenital abnormalities. Zinc is useful in activating growth-weight, height and bone development in children, infants and teenagers. Moreover, zinc plays a role in fertility. In females, it can help in the treatment of menstrual problems and alleviation of pre-menstrual syndrome associated symptoms..In males, it offers protection from infection and enlargement of the prostate gland. It also maintains mobility, sperm count and levels of testosterone at normal (Kang et al, 2008). As a component of most enzymes, it participates in synthesis as well as degradation of lipids, nucleic acids, proteins, carbohydrates and the metabolism of several other micronutrients. Zinc aids in the stabilization of the molecular structure of membranes and cellular components, and in this way contribute to cell and organ maintenance. In addition, zinc is essential in transcription of the polynucleotide and hence in the genetic expression process (Bolkent et al, 2006). Zinc, among all the minerals and vitamins has a strong effect on our immune system. It plays a crucial role in T- and B-cells, as well as innate immunity, whereby low levels of the mineral result in weakened and reduced T-cells, whose ability to recognize and fight infections is reduced. Increased zinc levels have proved to be effective in the fight of infections of diarrhoea and pneumonia. It can also decrease the severity and duration of common cold. Another function of zinc is activation of brain areas which receive and process the information from smell and taste sensors. Zinc levels in plasma and the effect of zinc on other nutrients such as manganese and copper influence taste preference and appetite. Zinc is also utilised for anorexia treatment (Kang et al, 2008). Zinc’s vitality is also evident in hair, skin and nails. It accelerates skin cells renewal. In addition, zinc creams are utilised to soothe diaper rash in babies, and in the healing of wounds and cuts. The effectiveness of zinc in acne treatment has shown a positive effect on neurodermitis and psoriasis. Zinc can also be used an anti-swelling agent that can aid in soothing the skin tissue, especially in cases of sunburn, poison ivy and blisters. Moreover, zinc is vital for healthy hair and insufficient levels of zinc can result in hair loss, early appearance of gray hair as well as dullness and thinning of hair. The retina contains zinc in high concentrations. This retinal zinc tends to decline with age and thus the development of macular degeneration that is age-related. This results in complete or partial vision loss. Zinc also offers protection against night blindness and thus aid in the prevention of cataract development (Lambert et al, 2003). Zinc is also a co-factor in thyroid function. It is a crucial mineral that aid in making thyroid releasing hormone in the brain. Signalling of the pituitary makes thyroid stimulating hormone. Additionally, zinc offers protection to proteins, enzymes and some of their specific regions against free radical attack. It can also prevent the formation of free radicals by other metals such as copper and iron. When zinc instead of copper or iron is incorporated into proteins, reactions that could otherwise generate free radicals are inhibited from occurring (Kang & Zhoul, 2005). Zinc is a vital element and its deficiency can cause many disorders such as growth retardation in children, reproductive disorders, eating disorders such as anorexia and loss of taste, low blood sugar, brain disorders, poor blood circulation, high blood cholesterol and poor bone growth. In order to treat zinc deficiency, it is crucial to eat foods with high zinc levels, such as: red meat, chicken, fish, oysters, green peas, egg yolks, peanuts, cereals and oats (Pathak et al, 2014). How zinc relates to alcohol intake Studies on zinc describe its ability for protection against damage from alcohol. Supplementation of pregnant mothers with zinc is known to reduce alcohol effects during pregnancy, including mortality and still births. Low zinc levels in adults are associated with liver damage induced by alcohol. Zinc decreases this damage through boosting the enzyme which clears alcohol. Zinc enhances anti-oxidant capability of the liver and boosts metallothionein. Lowered levels of this detoxifier lead to liver damage. Consequently, zinc is related to alcohol intake (Pathak et al, 2014). Zinc is related to alcohol intake in that chronic ingestion of alcohol alters expression of key transporters of zinc in the ileum, the alveolar epithelium and macrophages. Consequently, chronic alcohol ingestion causes a significant decrease in zinc bioavailability in the alveolar space. Alcohol induced deficiency of zinc has numerous consequences on the function of the alveolar epithelial barrier, alveolar macrophage and the innate immune function. Depletion of zinc in vitro reproduces effects on the function of the epithelial barrier and therefore supplementation with zinc directly to vitro in cells or in-vivo to human diets can aid in reversing these effects (Lambert et al, 2003). Zinc depletion from the alveolar space gives evidence that this depletion within alveolar space is a mediator in alveolar macrophage and epithelial dysfunction, which characterises the phenotype lung of an alcoholic. This renders alcoholics highly susceptible to pneumonia and acute injury of the lung. Zinc supplementation can thus decrease the incidence or severity of lung diseases in vulnerable persons. Zinc in alcohol metabolism Zinc is components of many enzymes, including alcohol dehydrogenase (ADH). All kinds of ADH contain a common domain of zinc that is formed from some amino acid residues that are specific. These serve to stabilise the molecule of oxygen in the alcohol group.ADH contains zinc and is a cytosolic enzyme present in many tissues, but the layer of the stomach mucosa and the liver contain high concentrations of ADH. This enzyme binds with two ions of zinc; one structural and the other catalytic. The catalytic ion of zinc is bound to sulphur atoms of cysteine residues and nitrogen atom of histidine residue. An acetaldehyde is fixed to zinc and the –OH group of serine residue. The structural zinc contains four ligands of deprotenated cysteine that coordinate the atom while nicotinamide ring in NAD+ is fixed close to the zinc.ADH together with NAD co-enzyme catalyzes the process of alcohol oxidation to acetylaldehyde as well as a further acetylaldehyde reduction to ethanol (Kang & Zhoul, 2005). ADH uses a zinc ion in stabilizing the alcohol oxygen, hence the increase in the acidity of the proton of the alcohol. The process encompasses the binding of a zinc atom to the substrate through the oxygen in the carbonyl group. This favours the shifting of an ion of hydride from NADH. Zinc ion stabilises electrostatically the oxygen in ethanol thereby serving to improve the acidity of the proton. The residue of histidine becomes active by general catalysis thus allowing it to accept the proton from the alcohol of the substrate. Consequently, a hydride is transferred to NAD resulting in the oxidation of the alcohol substrate to aldehyde. Thus the whole process can be summarised as hydride transfer to NAD and alcohol to aldehyde oxidation (Lambert et al, 2003). In conclusion, zinc is a vital element for all forms of life because it is a component of many enzymes which catalyze important metabolic reactions in the body, act as an antioxidant and a co-factor in thyroid function. Zinc is also essential for cell division and growth as well as plays a key role in the immune system and in the formation of strong hair and nails. Zinc is related to alcohol intake, and chronic ingestion of alcohol may change the expression of transporters of zinc in the lung and the gut, and reduce the bioavailability of zinc in the alveolar space. Supplementation of zinc in the diet can thus aid to restore zinc levels in the alveolar as well as improve immune function of the alveolar macrophage and facilitate the function of the alveolar epithelial barrier. These supplements have the potential of restoring the health of affected alcoholic lungs and consequently decrease morbidity and mortality rates due to lung injury and pneumonia. References Bolkent, S., Arda-pirincci, P., Bolkent, S., Yanardag, R., Tunali, S., & Yildirim, S. (2006). Influence of zinc sulfate intake on acute ethanol-induced liver injury in rats. World J Gastroenterol, 12 (27):4345-51. Kang, X., Song, Z., McClain, C. J., Kang, J., & Zhou, Z. (2008). Zinc supplementation enhances hepatic regeneration by preserving hepatocyte nuclear factor-4a in mice subjected to long-term ethanol administration. Am J Pathol, 172(4):916-925. Kang, Y.J., & Zhou, Z. (2005). Zinc prevention and treatment of alcoholic liver disease. Mol Aspects Med, 26(4-5):391-404. Lambert, J.C, Zhou, Z., Wang, L., Song, Z., Mcclain, C.J., & Kang, Y.J. (2003). Prevention of alterations in intestinal permeability is involved in zinc inhibition of acute ethanol-induced liver damage in mice. J Pharmacol Exp Ther, 305(3):880-6. Pathak, A., Dhawan, D., & Pathak, R. (2014). Role of zinc on ethanol metabolism in intestine of alcohol intoxicated rats. BCES, 6(14-15):33-36. Read More