Serum selenium in liver cirrhosis: correlation with markers of fibrosis

Antioxidant effects of Se-glutathione peroxidase in alcoholic liver disease

Oxidative damage induced by ethanol and its metabolites is one of the factors that fuels the development of alcoholic liver disease (ALD). Selenium (Se) is an effective cofactor for glutathione peroxidase (GPx), and has antioxidant effects that improve ALD. In patients with ALD, ethanol-induced oxidative damage inhibits the synthesis of related Se-containing proteins such as: selenoprotein P (Sepp1), albumin (ALB), and GPx in the liver, thus decreasing the overall Se level in patients. Both Se deficiency and excess can affect the expression of GPx, resulting in damage to the antioxidant defense system. This damage enhances oxidative stress by increasing the levels of reactive oxygen species (ROS) in the body, which aggravates the inflammatory response, lipid metabolism disorder, and lipid peroxidation and worsens ALD symptoms. A cascade of oxidative damages caused by ALD will deplete selenium deposition in the body, stimulate the expression of Gpx1, Sepp1, and Gpx4, and thus mobilize systemic selenoproteins, which can restore GPx activity in the hepatocytes of ALD patients, reduce the levels of reactive oxygen species and alleviate oxidative stress, the inflammatory response, lipid metabolism disorder, and lipid peroxidation, thus helping to mitigate ALD. This review provides a reference for future ALD studies that evaluate the regulation of Se levels and contributes to studies on the potential pathological mechanisms of Se imbalance in ALD.

Selenium Status in Patients with Chronic Liver Disease: A Systematic Review and Meta-Analysis

Background: The potential role of selenium in preventing chronic liver diseases remains controversial. This meta-analysis aimed to summarize the available evidence from observational studies and intervention trials that had evaluated the associations between body selenium status and chronic liver diseases. Methods: We comprehensively searched MEDLINE, Embase, Web of Science, and Cochrane Library from inception to April 2021. The study protocol was registered at PROSPERO (CRD42020210144). Relative risks (RR) for the highest versus the lowest level of selenium and standard mean differences (SMD) with 95% confidence intervals (CI) were pooled using random-effects models. Heterogeneity and publication bias were evaluated using the I² statistic and Egger’s regression test, respectively. Results: There were 50 studies with 9875 cases and 12975 population controls in the final analysis. Patients with hepatitis (SMD = −1.78, 95% CI: −2.22 to −1.34), liver cirrhosis (SMD = −2.06, 95% CI: −2.48 to −1.63), and liver cancer (SMD = −2.71, 95% CI: −3.31 to −2.11) had significantly lower selenium levels than controls, whereas there was no significant difference in patients with fatty liver diseases (SMD = 1.06, 95% CI: −1.78 to 3.89). Moreover, the meta-analysis showed that a higher selenium level was significantly associated with a 41% decrease in the incidence of significant advanced chronic liver diseases (RR = 0.59, 95% CI: 0.49 to 0.72). Conclusion: Our meta-analysis suggested that both body selenium status and selenium intake were negatively associated with hepatitis, cirrhosis, and liver cancer. However, the associations for fatty liver diseases were conflicting and need to be established in prospective trials.

Selenium and selenoprotein P in nonalcoholic fatty liver disease

Conflicting data link nonalcoholic fatty liver disease (NAFLD), a disease with no currently approved treatment, with selenium (Se) and selenoprotein P (SELENOP), a glycoprotein synthesized and primarily secreted by the hepatocytes, functioning as a Se transporter from the liver to other tissues. This review aims to summarize the evidence between Se, SELENOP, and NAFLD, which may hopefully clarify whether current data on Se and SELENOP in NAFLD warrant further investigation for their diagnostic and therapeutic potential. Most, albeit not all, experimental data show a favorable effect of Se on hepatic steatosis, inflammation, and fibrosis. It seems that Se may exert an antioxidant effect on the liver, at least partly via increasing the activity of glutathione peroxidase, whose depletion contributes to the pathogenesis of hepatic inflammation and fibrosis. Se may also affect metalloproteinases, cytokines, and growth factors participating in the pathogenesis of NAFLD and, most importantly, may induce the apoptosis of hepatic stellate cells, the key players in hepatic fibrosis. However, the association between Se or SELENOP and insulin resistance, which is a principal pathogenetic factor of NAFLD, remains inconclusive. Clinical studies on Se or SELENOP in NAFLD are conflicting, apart from those in advanced liver disease (cirrhosis or hepatocellular carcinoma), in which lower circulating Se and SELENOP are constant findings. Existing data warrant further mechanistic studies in valid animal models of human NAFLD. Prospective cohort studies and possibly randomized controlled trials are also needed to elucidate the diagnostic and therapeutic potential of Se supplementation in selected NAFLD individuals with Se deficiency.

Determination of selenium during pathogenesis of hepatic fibrosis employing hydride generation and inductively coupled plasma mass spectrometry

Serum and liver selenium levels were studied during the pathogenesis of N-nitrosodimethylamine (NDMA) induced hepatic fibrosis in rats. The degree of fibrosis was assessed with Masson’s trichrome staining and quantifying collagen content in the liver. Lipid peroxides were measured in blood and liver samples and total glutathione and glutathione peroxidase were assayed in the liver tissue to evaluate oxidative stress. Interleukin-6 (IL-6) and transforming growth factor-β1 (TGF-β1) were measured in the serum. Selenium levels were determined using inductively coupled plasma-mass spectrometry (ICP-MS) after acid digestion and hydride generation of selenium. Serial administrations of NDMA produced well-developed fibrosis and early cirrhosis in the liver with 4-fold increase of total collagen content and deposition of collagen fibers. Blood and hepatic lipid peroxides, serum IL-6 and TGF-β1 were significantly increased. There was significant reduction in hepatic glutathione and glutathione peroxidase levels. Serum and liver selenium were remarkably decreased on all the days studied. The results suggest that decreased selenium and glutathione peroxidase contribute to the impairment of cellular antioxidant defense, which in turn results in oxidative stress and trigger pathogenesis of hepatic fibrosis. The study further demonstrated that ICP-MS with hydride generation technique is a reliable and sensitive method for determination of selenium in biological samples.

Selenium deficiency is associated with insulin resistance in patients with hepatitis C virus-related chronic liver disease

The relationship between selenium (Se) deficiency and insulin resistance has not much been established in persistent hepatitis C virus (HCV) infection, although Se deficiency is often observed in patients with liver cirrhosis. We hypothesized that the decreased serum Se levels were associated with the severity of hepatic fibrosis or insulin resistance in patients with HCV-related chronic liver disease (CLD). To test the hypothesis, 52 patients with HCV-related CLD including chronic hepatitis and liver cirrhosis were enrolled in this study. The severity of hepatic fibrosis was divided into 4 categories (F(1) through F(4)) according to the new Inuyama classification. Insulin resistance was defined by the homeostasis model for assessment of insulin resistance value. Serum Se levels significantly declined in proportion to the severity of hepatic fibrosis and were positively correlated with serum albumin (r = 0.372, P = .0065) and zinc (r = 0.403, P = .0081) concentrations. Serum Se levels were also linked to glutathione peroxidase activities in the sera of the enrolled patients (r = 0.374, P = .0148). By contrast, serum Se levels were inversely correlated with the homeostasis model for assessment of insulin resistance values (r = -0.304, P = .0338). However, serum Se levels were independent of HCV genotype and loads of HCV-RNA. These findings suggest that Se deficiency was associated with the severity of hepatic fibrosis in patients with HCV-related CLD and that Se deficiency was likely to be one of the factors contributing to insulin resistance in those patients.

Selenium levels in men with liver disease in Hungary

PROJECT

We studied the relationship between selenium (Se) levels and chronic liver disease (CLD) severity and the association between socioeconomic and lifestyle factors and serum Se levels.

PROCEDURE

We performed a case-control study in Hungarian men, examining 281 patients with CLD and 778 controls. Liver function was evaluated using biochemical markers, and liver disease was verified with physical examination and blood tests. Linear regression analysis was performed to study the association of serum Se level with biochemical markers in cases and controls. In control participants we examined the relationship between Se levels and age, financial status, education, alcohol consumption, cigarette smoking, type of fat used for cooking and body mass index.

RESULTS

Serum Se levels were lower in cases (median 0.87 μmol/L (IQR: 0.77-1.03)) than in controls (median 1.08 μmol/L (IQR: 0.97-1.19)). In controls, increases in bilirubin and glutamic-oxaloacetic transaminase (GOT) were associated with decreases in Se levels. In patients with CLD, a statistically significant relationship was found between serum Se and the GOT/GPT ratio, albumin and bilirubin. Younger, better-educated controls had significantly higher, and regular smokers and heavy drinkers had significantly lower Se levels. The use of vegetable oil/fat was also associated with higher Se levels. Se level was associated with the severity of liver injury in people even in patients who did not exhibit signs and symptoms of CLD.

CONCLUSIONS

Serum Se level is strongly associated with the severity of liver damage in people with CLD from the early stage on.

Relative and combined effects of chronic alcohol consumption and HCV infection on serum zinc, copper, and selenium

In alcoholic hepatitis, Kupffer cells are activated by intestinal gram-bacteria, leading to cytokine production and free radicals release, which, enhancing cytokine secretion, create a positive feedback loop which contributes to liver inflammation. Free radicals also damage the liver in chronic hepatitis C virus (HCV) infection, a condition frequently associated to alcohol consumption. In both situations, activity of antioxidant enzymes and of its cofactors zinc (Zn), selenium (Se), and copper (Cu) is important. This study was performed to assess the relative and combined effects of chronic alcoholism and HCV infection on serum Se, Zn, and Cu, and its relation with serum malondialdehyde (MDA) and tumor necrosis factor-α, interferon-γ, and interleukins (IL) 4, 6, and 8, in 19 HCV- alcoholic patients, 12 HCV+ alcoholic patients, nine HCV+ non-alcoholic patients, and 20 controls. Serum Zn and Se were lower in both HCV+ and HCV- alcoholic patients, whereas serum Cu was lower in HCV+ individuals. Serum Zn and Se were related to liver function derangement. MDA levels were higher in alcoholics, but no relation was observed between trace elements and MDA or cytokines, so that our results do not support a relevant role of the analyzed trace elements in the pathogenesis of chronic liver disease.

Prognostic value of serum selenium levels in alcoholics

In alcoholics, exposure of Kupffer cells to intestinal-borne Gram-negative bacteria increases free radical release, which may, in turn, enhance cytokine secretion, creating a positive feedback loop, which contributes to liver inflammation. Impaired antioxidant mechanisms further aggravates this scenario. Some trace elements, such as selenium, are main cofactors of antioxidant enzymes. Some authors have found low Se levels in alcoholics in relation either with undernutrition, liver dysfunction, or intensity of alcoholism, but in general, Se supplementation has no effect on survival. In this study we measured serum Se in 16 controls and 76 alcoholics, 34 of them cirrhotics, 68 of whom were followed up for a median period of 38 months; 17 died during this period. Se levels were lower in patients than in controls and were related to prothrombin activity and nutritional status, more closely to this last parameter (stepwise logistic regression analysis). Patients who died showed lower Se values than those who survived. Se values over the median were associated with better survival, assessed by Kaplan-Meier curves and log-rank test. However, in multivariate analysis (Cox regression model), prothrombin activity displaced serum Se as a prognostic factor. We conclude that serum Se levels are low in alcoholics; these low values depend more heavily on impaired nutrition but also on liver dysfunction; although low Se levels were associated with a higher mortality, prothrombin activity displaced serum Se when survival was assessed using Cox's regression model.

Effects of selenium on histopathological and enzymatic changes in experimental liver injury of rats

The most important antioxidant aspect of selenium is its function in the active site of selenoenzyme glutathione peroxidase. Glutathione peroxidase not only allows the removal of the toxic radicals but also permits the regeneration of lipid molecules through reacylation in the cellular membrane. Thus, GSHPx may prevent the harmful effects of free radicals and may reduce the formation of the reactive metabolites of carbon tetrachloride. Carbon tetrachloride is a hepatotoxic agent which generates haloalkane radicals during its biotransformation in the liver and is widely used to make the experimental model of hepatic damage. Therefore, the aim of the present study is to investigate the possible protective role of selenium on the experimental liver cirrhosis and some enzyme activities in blood plasma from rats. While the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) were significantly increased (p < 0.05, p < 0.05 and p < 0.01, respectively), gamma-glutamyle transferase (GGT) activity was not statistically affected (p < 0.05) with carbon tetrachloride-injection. The levels of AST, ALT and GGT in carbon tetrachloride-group decreased to nearly the enzyme values in control-group after the selenium-injection but the ALP was increased (p<0.01). On the other hand, it was noticed that selenium significantly decreased the hepatic injury. In conclusion, our results showed that carbon tetrachloride caused an increase in the activities of liver enzymes in plasma and selenium application decreased the hepatic injury. Plasma levels of the liver enzymes were decreased after selenium-injections. Based upon these results, selenium may play an important role in the preventive indication of hepatic cellular injury inducted by carbon tetrachloride.

Protective effects of vitamin E on carbon tetrachloride-induced liver damage in rats

In this study we investigated whether the increase of hepatic vitamin E content by intraperitoneal administration, influences chronic liver damage induced by carbon tetrachloride (CCl(4)) in rats. Thirty adult male Wistar rats were divided into three groups. The first group was used as a control and the rats in the second group were administered CCl(4) in olive oil subcutaneously. Rats in the third group were administered intraperitoneally vitamin E (dl-alpha-tocopherol acetate, 100 mg kg(-1)). This administration was performed three times per week for five weeks. Liver samples were used for the determination of vitamin E levels, glutathione peroxidase (GSHPx) activities and histological examination. Serum levels of alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase, aspartate aminotransferase, gamma-glutamyltranspeptidase, total and conjugated bilirubin were significantly (p<0.05, p<0.01, p<0.001) higher in animals treated with CCl(4) than in the controls and had returned to normal values by the administration of vitamin E + CCl(4 ). Liver vitamin E levels were significantly (p<0.05) lower in the CCl(4) group than in the control group. However, the liver vitamin E content was significantly (p<0.01, p<0.001) increased in the vitamin E + CCl(4) injected group. On the other hand, liver GSHPx activity was not statistically different among the groups. On histological examination, vitamin E administered animals showed incomplete, but significant, prevention of liver necrosis and cirrhosis induced by CCl(4 ). these data indicate that intraperitoneally administered vitamin E has protective effects against CCl(4)-induced chronic liver damage and cirrhosis as evidenced by biochemical data and conventional histological examination.

Erythrocyte membrane lipids and serum selenium in post-viral and alcoholic cirrhosis

Erythrocyte-membrane fatty acid composition and cholesterol content were evaluated along with serum selenium in 33 patients with liver cirrhosis and in 40 normal subjects. Thirteen patients were suffering from post-viral (group V) and 20 from alcoholic (group A) cirrhosis. The aim of the study was to elucidate whether membrane lipid abnormalities in cirrhosis were linked to the aetiology of the disease or whether they were the results of the cirrhotic process itself. The patients presented a significant increase in membrane cholesterol, palmitic acid (C16:0) and saturated fatty acids (SFA), and a decrease in polyunsaturated fatty acids (PUFA) and polyunsaturated/saturated fatty acids ratio (P/S) compared with the control group. Serum selenium levels were significantly reduced. When patients were subdivided according to aetiology, the alcoholic patients showed greater lipid composition abnormalities than the viral cirrhotics (higher levels of SFA and lower PUFA and P/S), while pathologic palmitic acid, membrane cholesterol and serum selenium values were confirmed in both groups of patients. In conclusion, low serum selenium and a series of erythrocytes membrane lipid composition abnormalities would appear to be features peculiar to cirrhosis. Alcoholic cirrhotics, on the other hand, show a more deranged erythrocyte membrane lipid profile.

Determination of selenium in the serum of healthy Swiss adults and correlation to dietary intake

The serum selenium (Se) concentrations of apparently healthy 20-40 year old blood donors from different parts of Switzerland were determined by electrothermal atomic absorption spectrometry (GFAAS). Application of a rhodium/magnesium matrix-modifier resulted in improved performance in comparison with a palladium modifier. The method was validated by hydride ICP-MS and quality-controlled by independent analysis using GFAAS with palladium as matrix-modifier; no bias was detected. The serum Se concentrations for male (n = 387) and female (n = 243) subjects fell into a normal distribution with mean values and standard deviations of 96.0 +/- 13.3 micrograms/L (1.22 +/- 0.17 mumol/L) and 87.9 +/- 14.4 micrograms/L (1.11 +/- 0.18 mumol/L), respectively. These values corresponded well to the formerly estimated mean daily intakes. Small but significant differences in mean serum Se concentrations were found between genders, ethnic groups as well as geographic regions, whereas age had no influence. The overall Se status of the Swiss population is assessed as adequate, somewhat higher than in the countries adjacent to Switzerland, but lower than in the U.S.A. or Finland. There is no evidence that the Se status of the population has changed over the past 10 years. However, it appears that some Swiss population groups may have a borderline Se status.

Low selenium status in alcoholic cirrhosis is correlated with aminopyrine breath test. Preliminary effects of selenium supplementation

The relationship among impaired selenium status, lipid peroxidation, and liver function was examined in 19 hospitalized patients with severe alcoholic cirrhosis. Plasma selenium was found to be significantly lower (mean +/- SD: 54 +/- 13 micrograms/L) than in healthy controls (83 +/- 11 micrograms/L) and plasma malondialdehyde, assessed as thiobarbituric acid reactants, which reflects lipid peroxidation, was increased (2.0 +/- 1.2 mumol/L vs < 1.2 mumol/L in controls). The mean 14C aminopyrine breath test, an indicator of liver function, was lower than normal (2.7 +/- 1.9 vs 6.3 +/- 0.9% in controls) and found to be significantly correlated with plasma selenium (r = 0.59, p < 0.05). A prospective, randomized selenium supplementation trial was conducted in a group of 16 patients who received either daily 100 micrograms selenium as enriched yeast during 4 mo or a placebo. Among the 10 patients who completed the study, plasma selenium significantly increased in the supplemented group (n = 4; before: 58 +/- 10 micrograms/L, and after 101 +/- 12 micrograms/L, p < 0.01) contrary to the placebo group (n = 6, before: 47 +/- 10 micrograms/L, after: 57 +/- 9 micrograms/L, n.s.). 14C aminopyrine breath test improved in three out of four selenium-supplemented patients and in three out of six placebo patients, but the small number of patients did not allow statistical evaluation. These results demonstrate that low selenium status in alcoholic cirrhosis is correlated to liver function and could be improved by supplementation.

Biochemical markers of hepatic fibrosis

Most liver diseases lead to a pathobiochemical reaction termed liver fibrosis. This is a dynamic process implying different rates of progression or regression. Thus, histological examination of a liver biopsy is essential for a diagnosis but biochemical tests are necessary for assessing the activity of the process and monitoring its evolution. We review the most important constituents of liver connective tissue and the biochemical tests developed for evaluating liver fibrosis. The aminopeptide of type III procollagen is the most widely used parameter: two different radioimmunoassays have been developed with different affinities for the two circulating forms of the molecule. The determination of serum P3P reveals an elevation of blood levels both in acute and chronic liver diseases. In the first, serum P3P is an index of hepatic necrosis and inflammation which correlates with other biochemical parameters. In the second it is an index of active fibrogenesis. Moreover, in primary biliary cirrhosis this parameter is an independent prognostic variable and an important predictor of survival. Other immunoassays exist for different collagen cleavage products, but their clinical value is not established. Laminin and fibronectin are the principal structural glycoproteins in liver. Fibronectin determination does not seem to be of clinical value in liver disease. In contrast, serum laminin correlates with the severity of portal venous pressure in advanced liver disease. Its concentration parallels the severity of varices and may indicate the risk of bleeding. Hyaluronate is a high molecular weight polysaccharide, raised serum concentrations reflect both its increased synthesis by activated fibroblasts and its impaired catabolism by the liver. Thus, it may be useful for evaluating and monitoring the progression of chronic liver disease. The measurement of the activity of prolyl 4-hydroxylase as well as that of lysine oxidase and other enzymes has been proposed, but their clinical value is not sufficiently demonstrated. A panel of tests (e.g., laminin, hyaluronate and the aminopeptide of type III procollagen) seems to be recommended for a biochemical assessment of liver fibrosis in clinical practice.

Determination of selenium in blood components by X-ray emission spectrometry. Procedures, concentration levels, and health implications

Sampling, storing, sample pretreatment, and experimental conditions for selenium (Se) determination in human serum, plasma, and whole blood by X-ray emission spectrometric (XRS) methods are described. Concentration levels in these biological fluids, found by this technique, are discussed and compared to values found by other techniques for the same healthy population group in the same area. XRS analysis of blood from patients with various pathological conditions is reviewed, with special attention to the relation of Se with the concentration level of other essential or nonessential trace elements.