Circulating Leptin Levels as a Potential Biomarker in Inflammatory Bowel Diseases: A Systematic Review and Meta-Analysis

Background: The differential diagnosis of inflammatory bowel diseases (IBDs) between Crohn's disease (CD) and ulcerative colitis (UC) is important for designing an effective therapeutic regimen. However, without any adequate gold standard method for differential diagnosis currently, therapeutic design remains a major challenge in clinical practice. In this context, recent studies have showed that circulating leptin stands out as a potential biomarker for the categorization of IBDs. Thus, we aimed to summarize the current understanding of the prognostic and diagnostic value of serum leptin in patients with IBDs. Methods: A systematic search was performed in PubMed/MEDLINE, Scopus, Cochrane Library, and Web of Science databases. Articles that aimed to study the relationship between circulating levels of leptin and IBDs were included. Finally, the meta-analysis was performed with the mean serum leptin levels in patients with IBDs and healthy controls using RevMan 5.3 software, with I-2 > 50% as a criterion for substantial heterogeneity. Results: Nineteen studies were included. Serum leptin levels among patients with IBDs and healthy controls did not show a significant difference (95% CI, -2.15 to 0.57; I-2, 86%, P <= 0.00001). Similarly, there was no association of leptin levels with the activity of IBDs (95% CI, -0.24 to 0.06; I-2, 50%; P = 0.13). However, serum leptin levels were significantly higher in patients with CD than those in patients with UC (95% CI, -2.09 to -0.37; I-2, 7%; P = 0.36). Conclusion: This review suggested that serum leptin levels might be a promising biomarker to help in the differentiation between CD and UC.