Case Control Study
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World J Gastroenterol. Jun 28, 2014; 20(24): 7941-7949
Published online Jun 28, 2014. doi: 10.3748/wjg.v20.i24.7941
Association between obesity-related adipokines and colorectal cancer: A case-control study and meta-analysis
Rakhi Kumari Joshi, Woo Jin Kim, Sang-Ah Lee
Rakhi Kumari Joshi, Sang-Ah Lee, Department of Preventive Medicine, Kangwon National University School of Medicine, Chuncheon-si, Gangwon-do 200-701, South Korea
Woo Jin Kim, Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon-si, Gangwon-do 200-701, South Korea
Author contributions: Lee SA designed the research, contributed to writing the manuscript, assisted in revisions to approved the final version of the manuscript; Kim WJ provided the blood samples and contributed to approve the final version of manuscript; Joshi RK performed the statistical analysis and wrote the manuscript.
Supported by Korean Ministry of Health and Welfare through the National R and C Program of Cancer Control (1020420); and 2010 Research Grant from Kangwon National University
Correspondence to: Sang-Ah Lee, PhD, Department of Preventive Medicine, Kangwon National University School of Medicine, 1 Kangwondaehak-gil, Chuncheon-si, Gangwon-do 200-701, South Korea. sangahlee@kangwon.ac.kr
Telephone: +82-33-2558871 Fax: +82-33-2508809
Received: October 25, 2013
Revised: January 24, 2014
Accepted: April 8, 2014
Published online: June 28, 2014
Processing time: 244 Days and 17.8 Hours
Abstract

AIM: To examine the association between obesity-related adipokines (adiponectin, leptin, resistin, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) and colorectal cancer (CRC) risk.

METHODS: Serum levels of adipokines were measured in 100 CRC patients and age- and sex-matched controls for the data analysis. Unconditional logistic regression models were used for estimating ORs and 95%CIs related to each adipokine. For the meta-analysis, studies published before July 2013 available on Medline/PubMed and EMBASE were retrieved. The analysis included a total of 17 relevant studies (including the present case-control study): nine studies on adiponectin and eight on leptin. The effect sizes of ORs and 95%CIs were estimated using RevMan 5.1. Heterogeneity was evaluated using Cochran’s Q-test and I2 statistics.

RESULTS: Among the five adipokines, only resistin levels were significantly higher in cases than in controls (P < 0.001). The case-control study results showed no association between adiponectin and CRC and a negative association between leptin and CRC. However, the results of the meta-analysis showed a significant inverse association between adiponectin and CRC (OR = 0.91, 95%CI: 0.83-1.00, P = 0.04) and no association between CRC and leptin. After stratification by study design, an inverse association between adiponectin and CRC was observed in prospective studies only (OR = 0.90, 95%CI: 0.82-0.99, P = 0.03), whereas the association between leptin and CRC was inconsistent (prospective studies: OR = 1.14, 95%CI: 1.02-1.27, P = 0.02 and retrospective studies: OR = 0.47, 95%CI: 0.29-0.74, P = 0.001). The associations of resistin and TNF-α with CRC risk were positive, but no association was observed for IL-6.

CONCLUSION: Our results suggest a negative association of leptin, positive associations of resistin and TNF-α, and null associations of adiponectin and IL-6 with CRC. However, further studies with larger number of prospective approaches are needed.

Keywords: Obesity; Colorectal cancer; Cancer risk; Adipokines; Obesity-related adipokines

Core tip: Evidence from the previous studies indicates that there is an association of obesity-related adipokines and pro-inflammatory cytokines with colorectal cancer risk, but the results are inconsistent. In this study, a case-control study and meta-analysis were performed to investigate the possible association of adipokines (adiponectin, leptin, and resistin) and pro-inflammatory cytokines (interleukin-6 and tumor necrosis factor-α) with colorectal cancer risk. Although we did not find any significant results, case-control study and meta-analysis results support a previous report and suggest that obesity-related adipokines could be risk factors for colorectal cancer; however, further studies with larger number of prospective approaches are needed.