A Meta-analysis on the Effect of Ulinastatin on Serum Levels of C-Reactive Protein,Interleukin 6,and Tumor Necrosis Factor Alpha in Asian Patients with Acute Pancreatitis

Abstract

Objectives: We aimed to investigate the influence of ulinastatin (UTI) on the serum levels of C-reactive protein (CRP), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-α) in Asian patients with acute pancreatitis (AP) by performance of a meta-analysis. Methods: Two investigators independently searched 11 databases, including PUBMED, EBSCO, Ovid, SpringerLink, Wiley, Web of Science, Cochrane Library, Wanfang database, China National Knowledge Infrastructure (CNKI), Chinese Journal Full-text Database, and China Biomedicine Database. The full-text articles were screened and the data were extracted using a standardized data extraction form. All statistical analyses were conducted with Stata software, version 12.0 (Stata Corporation, College Station, TX). Results: A total of 94 studies were initially retrieved, and 10 studies containing 424 Asian patients with AP were ultimately enrolled in this meta-analysis. The results revealed that the serum levels of CRP, IL-6, and TNF-α in Asian AP patients significantly decreased after UTI therapy (CRP: standardized mean difference [SMD] = 3.26, 95% confidence interval [CI] = 1.69-4.83, p < 0.001; IL-6: SMD = 5.92, 95% CI = 2.09-9.75, p = 0.002; TNF-α: SMD = 4.07, 95% CI = 0.79-7.35, p = 0.015). Conclusion: The results of this meta-analysis suggest that UTI can effectively depress the serum levels of CRP, IL-6, and TNF-α in Asian patients with AP, and thereby inhibit inflammation.

Introduction

Acute pancreatitis (AP) is a systemic inflammatory disease that occurs in the pancreas (Avsar et al., 2014). It is a common emergency with a wide spectrum of severity; it is estimated that 70-80% of patients with AP have a mild, self-limiting clinical course, while nearly 20-30% develop a severe form of disease with severe and fatal clinical symptoms (Turkoglu et al., 2014), which can lead to a systemic inflammatory response and multiple organ dysfunction and failure (Fisic et al., 2013). It is a potentially life threatening disease with high mortality and morbidity rates; the estimated mortality rate for all patients with AP is ∼5% (Warndorf et al., 2011). Of note, in the United States, AP has become the leading cause of hospitalization in the benign diseases of the digestive system, resulting in a financial burden of at least 2.5 billion dollars per year (Maleth et al., 2015).

Etiologically, many well-established risk factors have been identified associated with AP, including alcohol consumption, biliary stone, and diabetes mellitus together with hypertriglyceridemia (Lai et al., 2015). The treatment of AP can be absolutely complex, especially when multiple organ systems are involved or when there are several local complications (Stevens et al., 2009). The restoration of normal pancreatic function after the episode is expected.

Ulinastatin (UTI), extracted and purified from the urine of healthy adult men, is extensively applied to treat acute systemic inflammatory disorders, including AP (Lili et al., 2013; Liu et al., 2014). It possesses the function of trypsin inhibitors, which can suppress the proteolytic action of trypsin on a variety of tissues and exert a localized anti-inflammatory effect (Abraham et al., 2013). It has been widely used in patients with acute inflammatory disorders such as AP, systemic inflammatory syndrome, and several organ dysfunction syndromes (Zhao et al., 2015). In patients with AP, both proinflammatory and anti-inflammatory cytokines increase (Ho et al., 2011). The excessive release of the inflammatory mediators during AP is the main cause of the intestinal mucosa injury (Shen et al., 2011).

UTI performed the anti-inflammatory function by inhibiting the inflammatory mediators and cytokines such as C-reactive protein (CRP), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-α) (Park et al., 2010). These three mediators have been mostly studied as markers of severity of AP (Fisic et al., 2013). UTI gained its reputation in the treatment of AP mainly due to its ability to inhibit the pancreatic activity (Maciejewski et al., 2005; Ma et al., 2006; Gao et al., 2009). However, there also have been conflicting results about the effects of UTI in the treatment of AP (Chen et al., 2010). Moreover, there has been no study that investigated the curative effect of UTI in the Asian population.

Therefore, this study focused on the effects of UTI therapy through analyzing the levels of the inflammatory cytokines, including TNF-α, IL-6, and CRP, in Asian patients with AP in a meta-analysis.

Materials and Methods

Search strategy

We searched PUBMED, EBSCO, Ovid, SpringerLink, Wiley, Web of Science, Cochrane Library, Wanfang database, China National Knowledge Infrastructure (CNKI), Chinese Journal Full-text Database, and China Biomedicine Database using a combination of keywords and subject terms. The search had no language restriction, and the publication date was between the inception of each database and November 2014. We also manually searched the bibliographies of the relevant literatures. The following subject terms and key words were used to maximize the search specificity and sensitivity: urinastatin, pancreatitis, CRP, IL-6, and TNF-α.

Eligibility criteria

The following inclusion criteria were applied to the published literatures for our meta-analysis: (1) the study type should be a cohort study; (2) the research topic was the effect of UTI on the serum levels of CRP, IL-6, and TNF-α in patients with AP; (3) the study subjects were clinically and imaging diagnosed Asian AP patients; (4) the detection method was enzyme-linked immunosorbent assay (ELISA) or particle enhanced turbidimetric immunoassay (PETIA); and (5) the serum levels of CRP, IL-6, and TNF-α of AP patients were measured before and after UTI therapy.

The exclusion criteria were as follows: (1) the article was a review, letter, or animal study; (2) the articles were a duplication of a previously published one; (3) there was a lack of data integrity; (4) the article was written neither in Chinese nor in English; and (5) the study was irrelevant to the research theme.

Data abstraction and quality evaluation

Two investigators independently carried out data extraction based on a predefined form. The main information extracted included the following: first author, publication year, country, ethnicity, language, disease, age, gender, and detection method. Any inconsistency during the data extraction process would be resolved through discussion with the other investigators. The quality evaluation of the enrolled studies was performed by more than two investigators, using the critical appraisal skill program (CASP) (www.casp-uk.net/).

Statistical analyses

We conducted all the statistical analyses with Stata software, version 12.0 (Stata Corporation, College Station, TX). For continuous data, the means and standard deviations were pooled to a standardized mean difference (SMD) with 95% confidence interval (CI) using a fixed-effect or random-effect model, with which the influences of UTI on the serum levels of CRP, IL-6, and TNF-α in AP patients were quantified. The Z test was used to determine the significance of pooled SMDs (Chen et al., 2012).

Cochran's Q statistic with a significance level of p < 0.05 and the I² test (0-100%, values of 40% and 75% were considered to indicate moderate and high heterogeneity, respectively) were used to assess heterogeneity across the studies (Peters et al., 2006; Chen et al., 2012). If p < 0.05 or I² > 50%, there was great heterogeneity among the studies, and thereby a random-effect model should be used; otherwise, a fixed-effect model should be applied (Zintzaras and Ioannidis, 2005). Univariate and multivariate analyses were used to identify the source of heterogeneity, and Monte Carlo simulation was performed to correct and verify the results (Ferrenberg and Swendsen, 1988; Huizenga et al., 2011; Jackson et al., 2012).

Sensitivity analysis was performed to evaluate whether the removal of one single study would influence on the overall outcomes. The publication bias, which assesses the reliability of the results, was evaluated by Begger's funnel plot and Egger test (Egger et al., 1997; Sterne and Egger, 2001). All the tests were two sided, and p < 0.05 indicating statistical significance.

Results

Search results and study characteristics

The electronic search initially resulted in 94 studies, among which 10 studies (Zhang et al., 2008a, 2008b; Huang, 2009; Zhang, 2010; Guan, 2011; Yang et al., 2011; Shen, 2012; Abraham et al., 2013; BAO, 2013; Wang et al., 2013) met the inclusion criteria. The 84 removed trials included duplicates (n = 4), non-English and non-Chinese studies (n = 5), animal studies (n = 10), studies irrelevant to the research topic (n = 22), case-control studies (n = 8), studies irrelevant to CRP (n = 12), irrelevant to IL-6 (n = 10), irrelevant to TNF-α (n = 9), and studies with insufficient information (n = 4). The remaining cohort studies were published between 2008 and 2013 (containing 424 patients with AP). The CASP score for each included study is presented in Figure 1.

FIG. 1.

The critical appraisal skill program (CASP) score was applied for the assessment of each included study. +, yes; −, no; ?, unclear.

Serum levels of CRP, IL-6, and TNF-α in AP patients after UTI therapy

Seven studies reported the effects of UTI on the serum CRP level in Asian AP patients, four reported the effect on serum IL-6 level in Asian AP patients, and four reported the effect on serum TNF-α level in Asian AP patients. The heterogeneity test revealed that there was heterogeneity across the included studies (CRP: I² = 96.8%, p < 0.001; IL-6: I² = 99.3%, p < 0.001; TNF-α: I² = 99.2%, p < 0.001), and thus, a random-effect model was used. The results demonstrated that the serum levels of CRP, IL-6, and TNF-α significantly decreased after UTI therapy (CRP: SMD = 3.26, 95% CI = 1.69-4.83, p < 0.001; IL-6: SMD = 5.92, 95% CI = 2.09-9.75, p = 0.002; TNF-α: SMD = 4.07, 95% CI = 0.79-7.35, p = 0.015) (Fig. 2).

FIG. 2.

The forest plots of differences in serum levels of C-reactive protein (CRP), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-α) in Asian patients with acute pancreatitis (AP) before and after ulinastatin (UTI) therapy. A: CRP; B: IL-6; C: TNF-α.

The univariate and multivariate meta-regression analyses suggested that the publication year and sample size were not the main source of heterogeneity or the key factors that influenced the overall effect size (p > 0.05) (Fig. 3).

FIG. 3.

Meta-regression analysis of the differences in serum levels of CRP, IL-6, TNF-α in Asian patients with AP before and after UTI therapy. A, C and E: Year; B, D and F: Sample size.

Sensitivity analysis and publication bias

The sensitivity analysis indicated that none of the studies had a remarkable influence on the pooled SMD (Fig. 4). The funnel plots of the differences in serum IL-6 levels of AP patients before and after UTI therapy were symmetrical, suggesting that no significant publication bias exited (p > 0.05), while funnel plots of the differences in serum levels of CRP and TNF-α were asymmetrical, suggesting there was publication bias (p < 0.05) (Fig. 5).

FIG. 4.

Sensitivity analysis of the differences in the serum levels of CRP, IL-6, and TNF-α in Asian patients with AP before and after UTI therapy. A: CRP; B: IL-6; C: TNF-α.

FIG. 5.

Publication bias of the differences in the serum levels of CRP, IL-6, and TNF-α in Asian patients with AP before and after UTI therapy. A: CRP; B: IL-6; C: TNF-α.

Discussion

This meta-analysis aimed at identifying the influences of UTI on the serum levels of CRP, IL-6, and TNF-α in Asian patients with AP. Our results demonstrated that the serum levels of CRP, IL-6, and TNF-α significantly decreased after UTI therapy, which implied the role of UTI in inhibiting the specific inflammatory cytokines in patients with AP. As an acute inflammatory process of the pancreas, AP may result in the disturbance of normal stimulation-secretion axis inside the pancreatic acinar cells, which consequently induces a subsequent premature enzyme activation involving the metabolism of trypsinogen and the coactivation of pancreatic proenzymes (Digalakis et al., 2009).

The activation of proteolytic enzymes is believed to play an important role in the pathogenesis of pancreatitis; hence, administration of drugs with an antiproteolytic activity is considered to have a therapeutic effect on pancreatic injury (Chen et al., 2010). UTI is a known drug used to effectively alleviate the symptoms and improve the pathophysiology of various types of pancreatitis. UTI possesses multiple functions such as reducing inflammation, improving microcirculation, regulating immune responses, and playing a protective role in the liver, kidney, and some other tissues and organs.

It has been well established that UTI can ameliorate pancreatitis through inhibiting the chain reaction of pancreatic enzyme activation (Tsujino et al., 2005). A previous study showed that UTI was valuable on preventing postendoscopic retrograde cholangiopancreatography pancreatitis and hyperamylasemia for patients with average risk (Chen et al., 2010). Besides, the amelioration in the severity of pancreatic injury was also indicated by the decrease of the serum levels of inflammatory cytokines in the pancreas (Liu et al., 2014). UTI was also found to function as an inhibitor on the activities of trypsin, a-chymotrypsin, IL-6, and TNF-α (Zhang et al., 2010).

CRP is an acute-phase reactant produced by the liver in response to IL-1, IL-6, and TNF-α, and is a nonspecific inflammatory marker that is a most widely available, low-cost, and well-studied marker used in the assessment of severity in AP (Khanna et al., 2013). Meanwhile, TNF-α and IL-6 are also important inflammatory cytokines participating in the pathogenesis of AP, directly injuring cells and resulting in necrosis, inflammation, and edema (Chen et al., 2011). TNF-α, thought to be the first cytokine released, is a principal mediator of immune responses (Ozhan et al., 2010).

IL-6 is a multifunctional cytokine released by macrophages and is one of the most accurate early predictors of AP severity (Pini et al., 2012). The vivo study reported by Hou et al. (2010) showed that UTI could inhibit inflammation through suppressing the expression of TNF-α and IL-6. In AP models, the excessive activation of macrophages/monocytes and neutrophils contributes to the release of humoral mediators, which were involved in the development of remote organ injury (Wang et al., 2014).

Meanwhile, UTI processes anti-inflammatory functions and can directly inhibit neutrophil infiltration and the release of inflammatory mediators and mononuclear macrophage inflammatory cytokines like TNF-α, IL-1, and IL-8 (Yang et al., 2011). Consistent with these properties of UTI, in our meta-analysis, we found that the serum levels of CRP, IL-6, and TNF-α in Asian AP patients significantly decreased after UTI therapy, further confirming the effectiveness of UTI. Despite AP, a report from Cao et al. (2012) also revealed that UTI played a protective role in the septic process by inhibiting TNF-α and IL-6, which further verified the inhibitory role of UTI on the specific inflammatory cytokines.

Nevertheless, the validity of this meta-analysis to some extent is limited. First, no study reported adverse effects, and most of the cohort studies were of poor quality without describing randomization and allocation processes in detail. Therefore, we cannot have a definite conclusion when interpreting the results of these clinical trials, and the meta-analysis based on these studies was not determinate because it was uncertain whether the clinical practitioners considered UTI as a first-line treatment. Although UTI seems to be effective for AP, further studies of high quality investigating the efficacy and safety are to be conducted in the future.

To our knowledge, this is the first meta-analysis to study the efficacy of UTI therapy in Asian patients with AP. In summary, results of the meta-analysis found that UTI can effectively reduce the serum levels of CRP, IL-6, and TNF-α in Asian patients with AP, suggesting that UTI played a protective role in the treatment of AP in Asian patients through inhibiting the inflammation. To enhance the credibility of our results, further studies are required to verify our conclusion.

Footnotes

Acknowledgments

This study was funded by the Tianjin Health Bureau Science Foundation Key Project (2014KR14, Observation of Malignant Biological Behavior in Colorectal Cancer Stem Cells by Molecular Imaging Technique, 2014.6-2016.5). The authors are grateful to the reviewers for critical comments on the article. They also thank those authors who made additional data available from their published articles.

Author Disclosure Statement

No competing financial interests exist.

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