Obesity Related Adipokines and Colorectal Cancer: A Review and Meta-Analysis

Obesity has been considered as an important risk factor for the development of colorectal cancer (CRC), butthe association has not been fully elucidated. Obesity is linked significantly to adipose tissue dysfunction andto alteration of adipokines in blood; in particular, obesity-induced inflammation is thought to be an importantlink between obesity and colorectal cancer. Based on epidemiological studies, we undertook a systematic reviewto understand the association of circulating levels of selected adipokines, including adiponectin, leptin, resistin,IL-6 and TNF-α, with the level of CRC risk. Most prospective studies suggested protective effects of adiponectin,but these were attenuated by body mass index (BMI) and waist circumference (WC) data in our meta-analysis.On the other hand, meta-analyses for leptin and CRC did not demonstrate any association, similar to the resultsof systematic review. Although it proved difficult to determine whether other selected adipokines (resistin, IL-6and TNF-α) were related to CRC risk due to small number of reports, the present systematic review suggesteda positive association with elevated resistin levels but null associations with IL-6 and TNF-α.