Serum Zinc Level in Cirrhosis of Liver
Introduction
Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrous scar leading to progressive loss of liver function. It is most commonly caused by alcoholism and hepatitis B or C but has many other possible causes (Heidelbaugh & Bruderly 2006, pp. 756-7). Epidemiology of liver cirrhosis varies between gender, ethnic groups and geographical distribution.Prevalence Rate of Cirrhosis of the liver was approximately 1 in 679 people in USA.Average life years lost for Cirrhosis of the liver was 23.3 in North Carolina in 1994. In 2000 liver cirrhosis was the fifth leading cause of death in Mexico where as it was 12th most common cause of death in the United States (Kochanek et al. 2011, pp. 1-30).
A diagnosis of cirrhosis of the liver may be overlooked or delayed because in its early stages there generally are symptoms, such as poor appetite, fatigue, weight loss, and weakness, are vague and easily attributed to less serious conditions, such as aging and stress. Majority of patients remain symptom free until the advance stage called decompensate cirrhosis, characterized by ascites, spontaneous bacterial peritonitis, hepatic coma or Variceal bleeding from portal hypertension. The physical examination of patients with cirrhosis may reveal variety of findings that necessitate a hepatic or a gastrointestinal based work-up to determine the etiology. There is correlation observed between persistently disturbed liver function tests and biopsy-proven underlying hepatic disease, so to diagnose the cirrhosis liver biopsy should be considered when all initial and specific measures have failed to confirm (Heidelbaugh & Bruderly 2006, pp. 756-62).
The most effective treatment plan for cirrhosis of the liver uses a multifaceted approach and varies depending on the cause of the disease. Treatment plans are individualized to best fit the patient’s age, medical history, and stage of the disease. The goal of treatment is to stop or slow the progression of damage to the liver and minimize and quickly treat any complications, such as portal hypertension, esophageal varices, ascites, liver failure, hemorrhage and kidney failure. Bleeding esophageal varices are managed by endoscopic sclerotherapy or rubber band ligation. Ascites and edema are often responsive to low sodium, diuretic therapy and peritoneal paracentesis. A low protein diet and agents such as lactulose are used to manage hepatic encephalopathy. Infections such as spontaneous bacterial peritonitis must be aggressively rapidly treated with appropriate antibiotics. Coagulation disorders will sometimes respond to vitamin K and fresh frozen plasma. However liver transplantation is highly effective for the treatment of end-stage cirrhosis (Mazeaferro et al. 1996, pp.693-700).
The Zinc (Zn) is a metallic element; symbol Zn, atomic number 30 and it is a transition metal in group 12 of the periodic table (Lehto 1968, pp. 822-4). The Recommended Dietary Allowance (RDA) is 8 mg/day for women and 11 mg/day for men. Red meats, especially beef, lamb and liver have some of the highest concentrations of zinc in food (United States National Research Council 2001, pp. 442-445). Nearly two billion people in the developing world are deficient in zinc (Prasad 2003, pp. 409–10). Zinc affects growth and plays a role in the synthesis of proteins and nucleic acids, as well as in the synthesis of insulin like growth factor 1 (IGF-1) and in its effects on target tissues (MacDonald 2000, pp. 1507-8). Zinc deficiency predisposes to growth retardation, neurosensory deficit, disorders in the metabolism of several hormones and enzymes that participate in growth and bone development, wound healing retardation, skin lesions, delayed sexual maturation, and immunodeficiency (Hambridge & Krebs 2007, pp. 1101-1105). This trace element also acts as an antioxidant by means of two different mechanisms: protection against oxidation and inhibition of the production of reactive types of oxygen by transition metals, such as iron and copper, both metals linked to liver injury (Prasad 2008, pp. 354).
The low serum zinc level is common in patient with liver cirrhosis due to anorexia and reduced intake of animal proteins, increase in cytokines or hormones that may affect zinc metabolism, increase of renal loss of zinc and also portal hypertension, which are responsible for poor absorption of nutrients (Stamoulis et al. 2007, p. 1598). There is reduced liver protein synthesis in patients with cirrhosis of liver, the metallothionein (MT) is an important zinc-binding protein (formed by liver) and is involved in zinc metabolism, homeostasis and its release in number of oxidants, the released zinc will inhibit the activity of the enzymes involved in fibrogenesis (fibrosis) in the liver, all these are yet known pathophysiological mechanisms (Maret 2003, pp. 1460s-62s). Zinc is also essential for some of the neutrophil functions and it appears that zinc has a role in the maintenance of human immunity. Recent evidence suggests that thymic-dependent lymphocytes (T cells) are zinc dependent. T-helper and suppressor cells, T-effector cells and T-natural killer cells appear to be zinc dependent (McClain et al. 1986, pp. 582-9). In a study of Stamoulis et al. published by Digestive Diseases and Sciences in 2007 the prevalence of low serum zinc level in cirrhotic patients was 65.3%.
Some alterations of patients with cirrhosis may be associated with zinc deficiency: alopecia, wound healing disorders, lack of appetite, hypogeusia, gonadal growth retardation, and it is also associated with hepatic encephalopathy (Chetry & Choudhuri 2003, pp. 28–30). A study with adult patients with decompensate cirrhosis found that these patients have plasma zinc concentrations significantly lower than patients with compensated disease, and that zinc concentrations are negatively associated with fasting ammonia concentrations (Yoshida et al. 2001, pp. 349-55).
It has long been speculated that Zn has a protective effect against liver fibrosis and Zn intake in cirrhosis are based mostly on observations of reduced Zn levels in cirrhotic patients and on the beneficial effects of Zn supplementation on liver metabolism (Capocaccia et al. 1991, pp. 386–91).
Zinc serum examination is not an examination that can be routinely done in every laboratory. The zinc examination requires instrument preparation and unpractical specimen container because the validity of zinc measurement depends mainly to the successful analysis in avoiding contamination of ambient zinc (Reinhold 1975, pp. 476-500).
Therefore keeping all such important points and views in mind, the focus and aim of this study is to evaluate and assess the serum zinc level in patients with cirrhosis of liver. So far no study has been conducted on this topic in Bangladesh. As such this study will fill the gap, open new forum of discussion and will provide knowledge and information regarding the medical workup of patients with cirrhosis of liver.
Hypothesis
Serum zinc level is low in patients with cirrhosis of liver and the level is inversely related with the severity of the disease.
Aims And Objectives
General:
To observe the association of serum zinc level in cirrhosis of liver and to find out its relationship with the severity of the disease.
Specific:
· To estimate serum zinc level in patients with cirrhosis of liver (cases).
· To estimate serum zinc level in healthy control.
· To estimate serum bilirubin, serum total protein, serum albumin, prothrombin time, AST, ALT, serum glucose and serum creatinine in study subjects to diagnose cirrhosis of liver and to establish selection criteria.
· To evaluate the findings of ultrasonography of hepatobiliary system and endoscopy of upper GIT to diagnose cirrhosis of liver.
· To assess ascites and encephalopathy of the cases for scoring the severity of the disease by Child-Pugh score.
· To compare statistically the serum zinc level between cases and controls.
· To find out the relationship statistically between serum zinc level and the severity of cirrhosis of liver.
Review of Literature
Cirrhosis of Liver
Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrosis, scar tissue and regenerative nodules (lumps that occur as a result of a process in which damaged tissue is regenerated), leading to loss of liver function. It can occur at any age, has significant morbidity and is an important cause of premature death. World-wide, the most common causes of cirrhosis are chronic viral hepatitis, prolonged excessive alcohol consumption and fatty liver disease. Cirrhosis is the most common cause of portal hypertension and its associated complications (Heidelbaugh & Bruderly 2006, pp. 756-7).
The incidence of cirrhosis of liver in Bangladesh has been recorded as 2.6%. Nutritional deficiency was considered to be the important etiological factor whereas alcoholism did not appear to have any significant role. Almost all the cases (94.2%) were non-alcoholic (Islam & Khan 1975, pp. 39-40). Studies in recent past revealed Hepatitis B virus is responsible for 41 per cent of cirrhosis of liver in Bangladesh (Alam 2010, p. 1).
Causes of cirrhosis
Cirrhosis has many possible causes; sometimes more than one cause is present in the same patient. In the Western World, chronic alcoholism and hepatitis C are the most common causes.
1. Chronic viral hepatitis (B or C)
2. Alcohol
3. Non-alcoholic fatty liver disease
4. Immune
5. Primary sclerosing cholangitis
6. Autoimmune liver disease
7. Biliary
8. Primary biliary cirrhosis
9. Secondary biliary cirrhosis
10. Cystic fibrosis
11. Genetic
12. Haemochromatosis
13. Wilson’s disease
14. ?1-antitrypsin deficiency
15. Cryptogenic (unknown-15%)
16. Chronic venous outflow obstruction (Collier & Webster 2010, p. 942)
Pathophysiology
The cardinal feature of cirrhosis is an increase in fibrous tissue, progressive and widespread death of liver cells, and inflammation leading to loss of normal liver architecture. Following liver injury, stellate cells in the space of Disse are activated by cytokines produced by Kupffer cells and hepatocytes. This transforms the stellate cells into myofibroblast-like cell, capable of producing collagen, pro-inflammatory cytokines and other mediators which promote hepatocyte damage and cause tissue fibrosis.
Destruction of liver architecture causes distortion and loss of the normal hepatic vasculature with the development of portosystemic vascular shunts and the formation of nodules. Cirrhosis evolves slowly over years to decades and normally continues to progress even after removal of the etiological agent. These changes usually affect the whole liver, but can be patchy (Collier & Webster 2010, p. 943).
Classification
· Cirrhosis can be classified histologically into two types:
· Micronodular cirrhosis, characterized by small nodules about 1 mm in diameter and seen in alcoholic cirrhosis.
· Macronodular cirrhosis, characterized by larger nodules of various sizes. Areas of previous collapse of the liver architecture are evidenced by large fibrous scars (Sharlock & Dooley 2000, p.375).
Clinical features of cirrhosis of liver
Some of the following signs and symptoms may occur in the presence of cirrhosis or as a result of the complications of cirrhosis. Many are nonspecific and may occur in other diseases and do not necessarily point to cirrhosis. Likewise, the absence of any does not rule out the possibility of cirrhosis.
1. Hepatomegaly (although liver may be small)
2. Jaundice
3. Ascites
4. Circulatory changes
5. Spider talengiectasia
6. Palmar erythema
7. Cyanosis
8. Endocrine changes
9. Loss of libido
10. Hair loss
11. Men:
12. Gynaecomstia
13. Testicular atrophy
14. Impotence
15. Women:
16. Breast atrophy
17. Irregular menses
18. Amenorrhea
19. Hemorrhagic tendency
20. Bruises
21. Parpura
22. Epistaxis
23. Portal hypertension
24. Splenomegaly
25. Collateral vessels
26. Variceal bleeding
27. Hepatic (portosystemic) encephalopathy
28. Other features
29. Pigmentation
30. Digital clubbing
31. Dupytren’s contracture (Collier & Webster 2010, p. 944)
Complications of cirrhosis of liver
The clinical course of patients with advanced cirrhosis is often complicated by a number of important sequelae that are independent of the etiology of the underlying liver disease. In some people, these may be the first signs of the disease. These include—
1. Portal hypertension
2. Gastro esophageal varices
3. Splenomegaly
4. Ascites
5. Hepatic encephalopathy
6. Spontaneous bacterial peritonitis
7. Hepatorenal syndrome
8. Hepatocellular carcinoma (Chung & Podolsky 2005, p.1860)
Diagnosis of cirrhosis of liver
The gold standard for diagnosis of cirrhosis is a liver biopsy, through a percutaneous, transjugular, laparoscopic, or fine-needle approach. A biopsy is not necessary if the clinical, laboratory, and radiologic data suggests cirrhosis. Furthermore, there is a small but significant risk to liver biopsy, and cirrhosis itself predisposes for complications due to liver biopsy (Grant & Neuberger 1999).
Biochemical and Hematological findings
The following findings are typical in cirrhosis:
1. Aminotransferases – AST and ALT are moderately elevated, with AST > ALT. However, normal aminotransferases do not preclude cirrhosis.
2. Alkaline phosphatase (ALP) – usually slightly elevated.
3. Gamma-glutamyl transferase – correlates with ALP levels. Typically much higher in chronic liver disease from alcohol.
4. Bilirubin – may elevate as cirrhosis progresses.
5. Albumin – levels fall as the synthetic function of the liver declines with worsening cirrhosis since albumin is exclusively synthesized in the liver
6. Prothrombin time – increases since the liver synthesizes clotting factors.
7. Globulins – increased.
8. Serum sodium – decreased.
9. Platelet count – Rarely results in < 50,000/mL.
10. Total count of WBC- decreased with neutropenia.
Coagulation defects- the liver produces most of the coagulation factors and thus coagulopathy correlates with worsening liver disease (Heidelbaugh & Bruderly 2006, pp. 760-1).
There is now a validated and patented combination of 6 of these markers as non-invasive biomarker of fibrosis (and so of cirrhosis): FibroTest (Halfon et al. 2008, pp. 22-29).
Ultrasound of liver
It is routinely used in the evaluation of cirrhosis, where it may show a small and nodular liver in advanced cirrhosis along with increased echogenicity with irregular appearing areas. Ultrasound may also screen for Hepatocellular carcinoma, portal hypertension and Budd-Chiari syndrome (by assessing flow in the hepatic vein).
Other tests performed in particular circumstances include abdominal CT and liver/bile duct MRI (MRCP).
Endoscopic examination
Gastroscopy (endoscopic examination of the esophagus, stomach and duodenum) is performed in patients with established cirrhosis to exclude the possibility of esophageal varices.
Rarely diseases of the bile ducts, such as primary sclerosing cholangitis, can be causes of cirrhosis. Imaging of the bile ducts, such as ERCP or MRCP (MRI of biliary tract and pancreas) can show abnormalities in these patients, and may aid in the diagnosis (Heidelbaugh & Bruderly 2006, pp. 760-2).
Grading of cirrhosis of liver
The severity of cirrhosis is commonly classified with the Child-Pugh score. This score uses bilirubin, albumin, INR, presence and severity of ascites and encephalopathy to classify patients in class A, B or C; class A has a favorable prognosis, while class C is at high risk of death. It was devised in 1964 by Child and Turcotte and modified in 1973 by Pugh et al.
More modern scores, used in the allocation of liver transplants but also in other contexts, are the Model for End-Stage Liver Disease (MELD) score and its pediatric counterpart, the Pediatric End-Stage Liver Disease (PELD) score.
The hepatic venous pressure gradient, i.e., the difference in venous pressure between afferent and efferent blood to the liver, also determines severity of cirrhosis, although hard to measure. A value of 16 mm or more means a greatly increased risk of dying (Patch et al. 1999).
The Child- Pugh classification is a means of assessing the severity of liver cirrhosis.
Child-Pugh Score for Cirrhosis Mortality
| Score | 1 | 2 | 3 |
| bilirubin (?mol/L) | <34 | 34-50 | >50 |
| albumin (g/L) | >35 | 28-35 | <28 |
| PT (seconds prolonged) | <4 | 4-6 | >6 |
| encephalopathy | none | mild | marked |
| ascites | none | mild | marked |
If there is primary biliary cirrhosis or sclerosing cholangitis then bilirubin is classified as <68=1; 68-170=2; >170=3.
(To convert bilirubin in ?mol/L to mg/dL, divide by 17.)
The individual scores are summed and then grouped as:
<7 = Child’s A
7-9 = Child’s B
>9 = Child’s C
A Child’s C classification forecasts a survival of less than 12 months. (Pugh et al. 1973, p. 649)
Survival of cirrhosis
| Child-Pugh grade | Survival (%) | Hepatic deaths (%) | ||
| 1 year | 5 years | 10 years | ||
| A | 82 | 45 | 25 | 43 |
| B | 62 | 20 | 7 | 72 |
| C | 42 | 20 | 0 | 85 |
(Collier & Webster 2007, p. 945)
Epidemiology
Cirrhosis and chronic liver disease were the 10th leading cause of death for men and the 12th for women in the United States in 2001, killing about 27,000 people each year. Also, the cost of cirrhosis in terms of human suffering, hospital costs, and lost productivity is high (Anderson & Smith 2003).
Established cirrhosis has a 10-year mortality of 34-66%, largely dependent on the cause of the cirrhosis; alcoholic cirrhosis has a worse prognosis than primary biliary cirrhosis and cirrhosis due to hepatitis. The risk of death due to all causes is increased twelvefold; if one excludes the direct consequences of the liver disease, there is still a fivefold increased risk of death in all disease categories (Sørensen et al. 2003, pp. 88-93).
Little is known on modulators of cirrhosis risk, apart from other diseases that cause liver injury (such as the combination of alcoholic liver disease and chronic viral hepatitis, which may act synergistically in leading to cirrhosis). Studies have recently suggested that coffee consumption may protect against cirrhosis, especially alcoholic cirrhosis (Klatsky et al. 2006).
Zinc Metabolism
Zinc (from German: Zink), also known as spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table (Lehto 1968, pp. 822-24). It is called an ‘essential trace element’ because very small amounts of zinc are necessary for human health.
Biological role of zinc
Zinc is an essential trace element, necessary for plants, animals and microorganisms. Zinc is found in nearly 100 specific enzymes (other sources say 300), serves as structural ions in transcription factors and is stored and transferred in metallothionein. It is the second most abundant transition metal in organisms after iron and it is the only metal which appears in all enzyme classes (United States National Research Council 2001, pp. 442-454).
In proteins, Zn ions are often coordinated to the amino acid side chains of aspartic acid, glutamic acid, cysteine and histidine. In humans, zinc interacts with a wide range of organic ligands, and has roles in the metabolism of RNA and DNA, signal transduction, and gene expression. It also regulates apoptosis.
In the brain, zinc is stored in specific synaptic vesicles and can modulate brain excitability. It plays a key role in learning. However it has been called “the brain’s dark horse” since it also can be a neurotoxin, suggesting zinc homeostasis plays a critical role in normal functioning of the brain and central nervous system (Hambidge & Krebs 2007, pp. 1101-5).
Zinc is a good Lewis acid, making it a useful catalytic agent in hydroxylation and other enzymatic reactions. In blood plasma, zinc is bound to and transported by albumin (60%, low-affinity) and transferrin (10%). Since transferrin also transports iron, excessive iron reduces zinc absorption, and vice-versa (Rink & Gabriel 2000, p. 541).
Zinc may be held in metallothionein reserves within microorganisms or in the intestines or liver of animals. Metallothionein in intestinal cells is capable of adjusting absorption of zinc by 15–40%. However, inadequate or excessive zinc intake can be harmful; excess zinc particularly impairs copper absorption because metallothionein absorbs both metals (Hambidge & Krebs 2007, pp. 1101-5).
Dietary sources and daily requirement of zinc
Foods high in protein are high in zinc. Red meats, especially beef, lamb and liver have some of the highest concentrations of zinc in food. Carbohydrate, cereal, fruit and fat contain low zinc. The Recommended Dietary Allowance (RDA) is 8 mg/day for women and 11 mg/day for men (United States National Research Council 2001’ p. 442).
Absorption of zinc
Dietary zinc usually absorbed throughout the entire small intestine. Negligible absorption occurred from the caecum and colon. Zinc absorption seems to be a carrier mediated transport process. The rate and extent of zinc absorption is under the homeostatic control programmed by the zinc status of the individual. Zinc absorption is influenced by a variety of factors including dietary zinc content, metabolic demand and presence or absence of potential inhibitors of in the diets (Sandström et al. 1992).
Figure: Proposed mechanism for intestinal zinc absorption (Cousin 1979, p. 342)
Storage distribution and excretion of zinc
Zinc is present in all tissues and fluids of the body. The total body content has been calculated as 2-3 gram (30-45 mmol) in adult, of which skeletal muscle accounts for approximately 60% and bone for about 30%. Plasma zinc represents only about 0.1% of total body content; it has a rapid turnover and the level appear to be under close homeostatic control. The majority of zinc in plasma is bound to albumins which act as the transport vehicle.
Various vascular components such as erythrocytes, leucocytes and platelets may provide immediate information about zinc. Of these erythrocytes expected to give a long term indication of zinc status since their half life is 30-40 days. Platelets with a shorter half life would be more indicative of acute changes, as would be in some of the leucocytes subset (Hallberg et al. 2000, pp. 192-208).
Underwood (1977) stated that zinc absorbed from the intestine is carried to the liver and released into the peripheral circulation. In venous plasma, zinc is mostly bound to albumin to some extent transferrin and ?2 macroglobulin.
Figure: Zinc Metabolism in adult (Hallberg et al. 2000, p. 198).
The most rapid accumulation and turnover of zinc occur in pancreas, liver, kidney, spleen and prostate. The liver is the major organ involved in zinc metabolism, where the metal remains bound to metallothionein (MT). Metallothionein is unique in that, it may be synthesized de novo, depending on increased zinc status, which then serve as a storage protein for zinc, prior to its utilization in essential functions (Gordon et al. 1981, pp. 341-349).
Zinc is excreted from the body via the kidneys, skin and intestine. The intestine is the major route of zinc excretion and zinc is lost via the digestive juices & the shaded intestinal cells. Endogenous intestinal looses can range from 0.5-3.0 mg/day depending on zinc intake. Looses of zinc can be substantially increased in many diseases (Hallberg et al. 2000, pp. 192-208).
Deficiency
Zinc deficiency is usually due to insufficient dietary intake, but can be associated with malabsorption, acrodermatitis enteropathica, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy and other chronic illnesses. Symptoms of mild zinc deficiency are diverse. Clinical outcomes include depressed growth, diarrhea, impotence and delayed sexual maturation, alopecia, eye and skin lesions, impaired appetite, altered cognition, impaired host defense properties, defects in carbohydrate utilization and reproductive teratogenesis. Mild zinc deficiency depresses immunity, although excessive zinc does also (United States National Research Council 2001, pp. 442-455). The normal range of serum zinc is 700 – 1500 µg/L. The value less than 700µg/L are considered as low (Trumbo et al. 2001, pp.297-8).
Nearly two billion people in the developing world are deficient in zinc. In children it causes an increase in infection and diarrhea, contributing to the death of about 800,000 children worldwide per year (Prasad 2003, pp. 409–10).
Assessment of zinc status
Circulating levels of zinc in plasma or serum are the most widely used indices of zinc status. Although plasma zinc is decreased in severe zinc deficiency, the level can be affected by a number of conditions that are unrelated to zinc status. Other indices such as zinc level in WBC, RBC & functional indices such as taste, visual acuity and dark adaption have so far not proven useful in identifying marginal zinc deficiency in human (Hallberg et al. 2000, pp. 199-208).
Plasma zinc concentration
Zinc is an intracellular element and so only 0.01-0.02% of the body content circulates in plasma where it is highly bound to plasma proteins, particularly albumin. It is not surprising that plasma level in an individual gives limited information of body zinc status. Zinc rises after meal, interestingly falls below the baseline two hours after meal, rises on short term starvation and undergoes a diurnal rhythm. Plasma levels are also correlated with albumin levels, to which zinc is chiefly bound in plasma (Lifschitz & Henkin 1971, pp. 88-92).
Zinc in cirrhosis of liver
As liver plays an important role in zinc homeostasis and different zinc compartments have been recognized to explain Zn kinetics in humans; the liver represents a fast-exchangeable Zn pool with an important role in the metabolism of Zn and other trace elements (Echejoh et al. 2008). Whereas Kalkan et al. also identified zinc deficiency in patients with liver disease in his study published in 2002. It has long been speculated that Zn has a protective effect against liver fibrosis and Zn intake in cirrhosis are based mostly on observations of reduced Zn levels in cirrhotic patients and on the beneficial effects of Zn supplementation on liver metabolism (Capocaccia et al. 1991, pp. 386–91).
Majority of zinc deficient cirrhotic patients one belonged to rural population in the study of Ma et al. on ‘Assessment of intake inadequacy and food sources of zinc of people in China’ published in 2007. In fulminant hepatic failure and hepatic encephalopathy, biochemical parameters suggesting liver dysfunction presenting inverse correlation with serum Zn levels (Chetri et al. 2003, pp. S28-30).
As Gur et al. (1998) states that serum and hepatic Zn levels were reduced in hepatitis B virus infected patients with cirrhosis. The Zn depletion in cirrhosis has been attributed to decreased intestinal Zn absorption, increased urinary loss, malnutrition, hypoalbuminemia, portosystemic shunts, and diminished hepatic Zn extraction. Majority of the published studies have suggested that Zn absorption was reduced in cirrhotic patients. Two mechanisms were proposed for Zn malabsorption in liver cirrhosis- (1) damage of the small bowel mucosa, (2) impairment of pancreatic exocrine function accompanied by reduced synthesis of ligands such as picolinic acid in the liver (Ijuin 1998, pp. 1-5).
It has been suggested that some of the clinical features of liver cirrhosis, such as testicular atrophy, loss of body hair, night blindness, poor wound healing, poor appetite, decreased taste and smell acuity, susceptibility to infections, enhanced sensitivity to drugs, and decreased neurocognitive performances, may be related to conditioned Zn deficiency. In some cases Zn supplementation was beneficial to these patients (Grungreiff 2002, pp. 67-68). The zinc supplementation also reduces the inflammation and contributes to faster inflammation resolution, therefore further advance, modified and related studies are needed to update the data, knowledge and information regarding medical workup of patients with liver cirrhosis.
Materials and Methods
Study Design:
Case-control observational study.
Period of Study:
The study was conducted from July 2010 – June 2011.
Place of Study:
The study was carried out in the Department of Biochemistry, Dhaka Medical College in collaboration with the Department of Medicine, Dhaka Medical College Hospital and the Department of Biochemistry, Bangabandhu Seikh Mujib Medical University (BSMMU), Shahbag, Dhaka.
Study population:
Study population was the diagnosed cases of liver cirrhosis attending in department of Medicine, Dhaka Medical College Hospital, Dhaka aged 18 years and above of both male and female.
Sample:
Hundred adult subjects were selected as per selection criteria of which fifty diagnosed cases of liver cirrhosis and fifty healthy controls.
Sample Size:
Calculation:
Here, n = Sample Size
P1= Anticipated probability of exposure among cases
P2= Anticipated Probability of exposure among controls =0.5(50%)
Z?= Z value (2 tail) at a definite level of significance
= 1.96 at 95% confidence level (assumed)
Z?= Z value (1 tail) at a definite power
= 1.64 at 95% power
Using above formula, P1 = 0.6 (assuming OR = 2)
Now,
n
So, sample size should be 642. But for the convenience 100 were taken.
Sampling techniques:
Purposive consecutive sample was selected.
Selection criteria:
All study subjects were selected under the following inclusion and exclusion criteria.
Inclusion Criteria:
For cases:
Age group: 18 years and above.
Sex: Both male and female.
Diagnosed cases of cirrhosis of liver.
Diagnosis was done on the basis of
Compatible clinical history
Biochemical evidence of liver dysfunction:-
Serum bilirubin – increased
Abnormal liver enzymes (ALT, AST)
Serum total protein – reduced
Serum albumin– reduced
Prolonged prothrombin time
Radiological evidence (by ultrasound of hepatobiliary system):–
Altered liver size
Increased liver echo pattern
Portal vein diameter – increased
Evidence of ascites.
Endoscopic evidence of:–
Esophageal varices
Congestive gastropathy
Liver Biopsy – in selective cases.
For control:
Age group: 18 years and above.
Sex: Both male and female.
Subjects are apparently healthy, no acute or chronic systemic diseases.
Subjects without history of any type of hepatitis.
Subjects with normal liver function test.
Exclusion Criteria:
For both cases and control:
Patients on zinc therapy.
Patients with acute or chronic diarrhea.
Patients suffering from chronic debilitating diseases (renal failure, diabetes mellitus, malignancy).
Patients on hormonal therapy.
Pregnant woman.
Methods
This observational case control study was conducted from July 2010 to June 2011. All study subjects were selected purposively according to selection criteria. Purpose of the study was explained in detail in each subject. Written informed consent was taken. Data were collected in a pre-designed data collection sheet including particulars of the patients, history and relevant investigations. Complete physical and relevant clinical examinations were performed. Diagnosis of cirrhosis was determined on the basis of clinical, biochemical and radiological findings. Severity of liver cirrhosis was assessed by Child-Pugh score.
Collection & Preservation of Samples:
After full aseptic precaution 10ml of blood sample was collected from antecubital vein in the morning following 8 hours fasting. Before collection of blood specimen special effort was made to make the plastic wares free from metallic contamination particularly from zinc. All plastic wares used were kept immersed in detergent water for at least half an hour. Then all were washed thoroughly with tap water and were allowed to dry in air. Then all were kept immersed for 24 hours in 20% Nitric acid. After 24 hours the equipments were washed for 3 times in de-ionized water and were air dried. The air dried container were stored in a capped plastic container and used for sample collection.
Five ml of blood was transferred to de-ionized plastic test tube, centrifuged at 3500 rpm for 5 minutes. Serum was transferred to a clean polypropylene tube and preserved at -35°C until the test was carried out.
Parameters estimated were:
1. Serum zinc: Concentration was determined using Atomic Absorption Spectrophotometry (AAS).
2. Serum bilirubin
3. Serum total protein
4. Serum albumin
5. Serum aspartate aminotransferase (AST)
6. Serum alanine aminotransferase (ALT)
7. Prothrombin time
8. Serum creatinine
9. Serum glucose
Ethical issues
Ethical clearance for the study was taken from the Ethical Committee and the Department of Biochemistry, Dhaka Medical College.
Permission for the study was taken from the Department of Medicine, Dhaka Medical College Hospital and the Department of Biochemistry, Bangabandhu Seikh Mujib Medical University, Shahbag, Dhaka.
All the study subjects were thoroughly appraised about the nature purpose and implications of the study as well as entire spectrum and benefits and risk of the study.
Interests of study subjects were not compromised to safeguard their rights and health.
All the study subjects were assured of adequate treatment of any risk developed to study purpose.
Finally, written consents of all study subjects were taken free of duress and without exploiting of the subjects.
Data Analysis
After meticulous checking & rechecking all data were tabulated and processed using Statistical Package for Social Science (SPSS) version 17.0. Qualitative data were expressed as frequency and percentage and were analyzed by Chi-square test (x2 test). Quantitative variables were expressed by mean ± SD. Values of different parameters were compared to see the difference between two groups using Student’s t-test. Different Child-Pugh classes were compared by ANOVA test (F-test). Spearman’s correlation was used to correlate the serum zinc level with different CTP classes. The P-value < 0.05 was considered as statistically significant. 95% confidence limit was taken as the level of significance.
Flow Chart
Working Definitions:
Cirrhosis of Liver:
Cirrhosis of Liver is a consequence of chronic liver disease, diagnosed on the basis of compatible clinical history, abnormal liver function tests (serum bilirubin, serum total protein, serum albumin, AST, ALT, prothrombin time), ultrasound studies (altered liver size & echo pattern, signs of portal hypertension), endoscopy results (esophageal varices) and by histological examination (in selective cases) (Heidelbaugh & Bruderly 2006, pp. 756-758).
Serum Zinc Level:
The normal range of serum zinc is 700 – 1500 µg/L. The value less than 700µg/L are considered as low (Trumbo et al. 2001).
The Child- Pugh Score:
The Child- Pugh classification is a means of assessing the severity of liver cirrhosis.
Child-Pugh Score for Cirrhosis Mortality
| Score | 1 | 2 | 3 |
| Bilirubin (?mol/L) | <34 | 34-50 | >50 |
| Albumin (g/L) | >35 | 28-35 | <28 |
| PT (seconds prolonged) | <4 | 4-6 | >6 |
| Encephalopathy | none | mild | marked |
| Ascites | none | mild | marked |
If there is primary biliary cirrhosis or sclerosing cholangitis then bilirubin is classified as <68=1; 68-170=2; >170=3.
(To convert bilirubin in ?mol/L to mg/dL, divide by 17.)
The individual scores are summed and then grouped as:
<7 = Child’s A
7-9 = Child’s B
>9 = Child’s C
A Child’s C classification forecasts a survival of less than 12 months. (Pugh et al. 1973, p. 649)
Results And Observations
An observational case-control study of 50 diagnosed adult patients of cirrhosis of liver and 50 healthy control was conducted in the Department of Biochemistry, Dhaka Medical College, from July 2010 to June 2011. The fasting serum zinc level of both cases and controls were assessed. Then serum zinc level was statistically compared to observe the association with cirrhosis of liver and its relationship with the severity of the disease. The results obtained are presented bellow.
Table I
Distribution of study subjects by age
|
GroupCaseControlFrequencyPercentageFrequencyPercentage< 402142.01938.040 – 601122.01428.0> 601836.01734.0Total50100.050100.0
Table I shows the age distribution of the study subjects. Most of the subjects belonged to age group less than 40 years. In this group, 21 (42%) were case & 18 (36%) were control. Belong to the group 40 – 60 years, the frequency of case and control was 11 (22%) and 17 (34%) respectively, whereas 18 (36%) case and 15 (30%) control subjects were included in the age group of more than 60 years.
Figure I: Age distribution of case and control group
Table II
Mean age of the study subjects
| Group | Mean ± SD |
(Years)Range
(Years)tPControl
(n- 50)47.96 ± 13.2921-68-0.2560.799nsCase
(n- 50)48.72 ± 16.2818-72
Values are expressed as Mean± SD
n- Total number of subjects
t = Value obtained by Unpaired student’s t test.
P = Level of significance.
ns = Not significant (P>0.05)
Table II shows the mean age of the study subjects. In case group, the mean age was 48.72 ± 16.28 years (Range 18 – 72) and in control group, the mean age was 47.96 ± 13.29 years (Range 21 – 65). No statistically significant difference was found among the study subjects by age.
Figure II: Mean age of Case and Control
Table III
Distribution of study subjects by sex
| Sex | Case |
(n- 50)Control
(n- 50) Total
(n- 100)x2PMale31 (62.0)28 (56.0)59 (59.0)3.2400.07nsFemale19 (38.0)22 (44.0)41 (41.0)Total50 (100.0)50(100.0)100(100.0)
Figure in parenthesis indicate percentage.
X2 = Value obtained by Chi-Square test.
P = Level of significance.
ns- Not significant (P>0.05).
Table III shows the sex distribution of the study subjects. There were 31 (62%) of male and 19 (38%) of female cirrhotic patients enrolled in this study. In control group 28 (56%) were male and 22 (44%) were female. Among the total of 100 subjects, male & female were 59 (59%) and 41 (41%) accordingly. No statistically significant difference was found among the study subjects by sex.
Figure III: Distribution of study subjects by sex
Table IV
Distribution of cirrhotic patients in relation to serum zinc level
| Serum zinc level (?g/L) | |||
| Low | Normal | ||
| Frequency | Percentage | Frequency | Percentage |
| 36 | 72.0% | 14 | 28.0% |
Table IV shows the distribution of cirrhotic patients in relation to serum zinc status. Among the total of 50 patients with cirrhosis of liver the serum zinc level was low in 36 (72%) patients while remaining 14 (28%) patients had normal serum zinc level.
Figure IV: Distribution of cases in relation to serum zinc level
Table V
Mean serum zinc level in case and control
| Serum zinc level (?g/L) | Case |
(n- 50)Control
(n- 50)tPMean ± SD610.32 ± 169.60827.66 ± 267.324.8540.0001***Range183.0-938.0429.0-1830.0
Values are expressed as Mean± SD.
n- Total number of subjects.
t = Value obtained by Unpaired student’s t test.
P = Level of significance.
*** Highly significant at the 0.01 level.
Table VIII shows Mean serum zinc level in case and control. The mean serum zinc level was 610.32 ± 169.60 ?g/L in case group and it was 827.66 ± 267.32 ?g/L in control group. A statistically significant mean difference was found; indicating case group had lower serum zinc concentration than control group.
Figure V: Mean serum zinc level in case and control
Table VI
Distribution of cases in relation to CTP score
| CTP Score | Male | Female | Total |
| Group A | 2 (4.0) | 2 (4.0) | 4 (8.0) |
| Group B | 16 (32.0) | 11 (22.0) | 27 (54.0) |
| Group C | 13 (26.0) | 6 (12.0) | 19 (38.0) |
| Total | 31 (62.0) | 19 (38.0) | 50 (100.0) |
Figure in parenthesis indicate percentage.
Table VII shows Distribution of case in relation to CTP score. According to Child–Pugh score system, 4 (8%) patient were in group A and 19 (38%) were in group C. Majority of the patients i.e. 27 (54%) were remained in group B.
Figure VI: Distribution of case in relation to CTP score
Table VII
Mean serum zinc level of different CTP class
| Serum zinc (?g/dL) | Group A | Group B | Group C | F | P |
| Mean ± SD | 748.0 ± 128.49 | 644.61 ± 164.03 | 532.60 ± 156.02 | 4.401 | 0.01** |
| Range | 654.5 – 938.0 | 201.5 – 928.5 | 183.0 – 845.5 |
Values are expressed as Mean± SD.
F = Value obtained by one way ANOVA (F-test).
P = Level of significance.
** Significant (P<0.05)
Table VII shows the mean serum zinc level of cirrhotic patients according to CTP class. Here mean serum zinc level of Group A was 748.0 ± 128.49 ?g/dL (range 654.5 – 938.0) Group B was 644.61 ± 164.03 ?g/dL (range 201.5 – 928.5) and Group C was 532.60 ± 156.02 ?g/dL (range 183.0 – 845.5). A significant mean difference was found by one way ANOVA test among the groups indicating stepwise decline of serum zinc with worsening child class.
Figure VII: Mean serum zinc level of different CTP class
Figure VIII: Negative correlation of serum zinc with different CTP class
Table VIII
Correlation between serum zinc and severity of cirrhosis of liver
| Serum zinc |
VariablesCorrelation-Coefficient (r)PCTP Group A CTP Group B-0.761< 0.01**CTP Group C
r = Value obtained by Spearman rank correlation test.
P = Level of significance.
**Correlation is significant at the 0.01 level (2 tailed).
Table VIII shows correlation between serum zinc and severity of cirrhosis of liver according to CTP classification. Here Correlation-Coefficient or ‘r’-value is -0.761 which means there is strong negative correlation between serum zinc level and severity of the disease. And the relationship is statistically significant.
Discussion
The magnitude of liver disease in Bangladesh is progressively increasing. It is one of the major issues causing mortality and morbidity both in urban and rural population. It affects all age group from children to elderly people. Hepatitis B and C viruses are the commonest culprit causing cirrhosis of liver in our country. It has been observed that, even in the rural population of Bangladesh, about one-third of common people are affected by Hepatitis B virus infection sometimes in their life. About 0.5% of the population was found to posses Hepatitis C virus infection. Furthermore, due to consumption of adulterated foods, fruits, edible oils etc. may be causative factor for long term inflammation of the liver leading to chronic liver disease, cirrhosis and Hepatocellular carcinoma in a vicious cycle. Excess and fatty food intake leads to fatty liver which may progress to cirrhosis of liver in the long run. The current trend of first food culture in young generation is one of the reasons of fatty liver, which is prevailing in our country (Alam 2010).
The liver is important for the regulation of zinc homeostasis, while zinc is necessary for proper liver function. Decreased zinc levels have been implicated in both acute and chronic liver disease states, but its hepatoprotective property has not been fully elucidated (Stamoulis et al. 2007). It should be noted that zinc level is usually related to the nutritional pattern of each population. Zinc deficiency is widespread in people living in developing countries like Bangladeshi populations who consume rice-based diets (Hambridge & Krebs 2007).
Therefore keeping all such important points and views in mind, the present study was carried out to evaluate and assess the serum zinc level in patients with cirrhosis of liver. With this objective serum zinc level of adult patients with cirrhosis of liver was studied. For this reason a data collection sheet was prepared and laboratory investigations were done in all subjects for serum zinc level. All the data were filled up carefully and after plotting the results of laboratory investigation statistical analysis was done by using appropriate tests.
In the present study 59 were male and 41 were female among the total of 100 subjects. In case group 31 (62%) were male and 19 (38%) were female; in control group, 28(56%) were male and 22 (44%) were female. The mean age (Mean ± SD) of the case group was 48.72 ± 16.28 years, ranging from 18 – 72 years. In control group, it was 47.96 ± 13.29 years, ranging from 21 – 68 years. No statistically significant difference was found among the study subjects by age and sex. It is similar to the study of Ma et al. published in 2007.
This study was found a significant plasma zinc deficiency (72%) in patients with cirrhosis of liver when compared with normal control subjects in the same age group. The results of this study are compatible with Soomro et al. (2009, p. 988) who evaluated the cirrhotic patients of a tertiary care hospital in Pakistan. They found low level of zinc in 69% of cirrhotic patients. Triwikatmani et al. (2009, p. 5) found 66.7% & stamoulis et al. (2007) found 65.3% of cirrhotic patients with hypozincemia. A study in Brazil conducted by Ana et al. (2009, p. 361) showed that 43% had concentration below the normal level. That was not consistent with this study.
Mean serum zinc concentration of cirrhotic patients was 610.32±169.60 ?g/L and the mean of healthy controls was 827.66±267.32 ?g/L. A statistically significant mean difference was found; indicating case group had lower serum zinc level than control group.
In a study of Triwikatmani et al. (2009, p. 5) the mean value of zinc serum level was 637.0±248.5 ?g/L. However Yoshida et al.