Clinical significance of circulating omentin levels in various malignant tumors: Evidence from a systematic review and meta-analysis.

Aberrant circulating level of omentin has been reported in various solid tumors. However, whether decreased or increased levels of omentin contribute in cancer risk is remained controversial in different epidemiological studies. This comprehensive meta-analysis of observational studies was conducted to investigate the association between circulating omentin level and human cancer risk. An electronic search of health-related databases, was performed to identify all eligible studies in English, up to July 2019. Combined standard mean difference (SMD) with 95%CI was computed to assess the correlation of omentin levels with human cancer risk in a random effect model. The risk of publication bias was also evaluated using Funnel plot and Egger regression tests. A total of 16 studies with 1106 cases and 3078 healthy controls were included. Pooled SMD analysis based on the cancer type, revealed a strong correlation of omentin level and cancer risk in patients with colorectal (SMD = 2.08, 95%CI: 1.67-2.50, P < 0.001), prostate (SMD = 1.38, 95%CI: 1.15-1.62, P < 0.001), and breast (SMD = -0.78, 95%CI: -1.1, -0.45, P < 0.001) cancers. Elevated circulating omentin levels was also found in cancer patients with BMI ≥ 25 (SMD = 1.33, 95%CI: 0.52-2.15, P = 0.001) indicating a potential role for omentin in development of some obesity-linked cancers. The findings of this meta-analysis indicated a significant association of omentin level with greater risk of colorectal, pancreas, and breast tumors. Circulating omentin level may represent a potential novel biomarker for early detection of colorectal, prostate, and breast cancers especially in overweight/obese subjects. Further prospective well-designed studies are warranted to confirm our findings.