Variation of a gene for a protein hormone that is secreted by fat cells is associated with a decreased colorectal cancer risk, according to a study in the October 1 issue of JAMA.

Several studies have shown an association between obesity and the risk of colorectal cancer, according to background information in the article. Adiponectin is a hormone secreted by fat tissue, and serum levels of adiponectin are inversely correlated with obesity and high levels of insulin. "While there is evidence of an association between circulating adiponectin levels and colorectal cancer risk, no association between genes of the adiponectin pathway and colorectal cancer have been reported to date," the authors write.

Virginia G. Kaklamani, M.D., D.Sc., of the Feinberg School of Medicine, Northwestern University, Chicago, and colleagues conducted a study to determine the association between variations of the adiponectin (ADIPOQ) and adiponectin receptor 1 (ADIPOR1) genes with colorectal cancer risk. The study consisted of two case-control studies including patients with a diagnosis of colorectal cancer and controls without cancer. Case-control study 1 included a total of 441 patients with colorectal cancer and 658 controls; both groups were of Ashkenazi Jewish ancestry and from New York. Case-control study 2 included 199 patients with colorectal cancer and 199 controls from Chicago, matched 1:1 for sex, age and ethnicity.

"In this clinic-based case-control analysis, we found an association between 1 single-nucleotide polymorphism [SNP; a gene variation] of the ADIPOQ gene (rs266729) and colorectal cancer risk in 2 separate case-control studies, as well as in the combined analysis of both studies after adjustment for age, sex and other SNPs," the researchers write.

They add that the findings suggest that the ADIPOQ gene may harbor SNPs/mutations susceptible to modify colorectal cancer risk. "If these exciting results can be confirmed in other studies, the adiponectin axis may emerge as an important modifier of colorectal cancer risk. Future studies will need to address the potential impact of adiponectin and its SNPs in the prognosis of colorectal cancer and also may be incorporated in genetic risk models for the disease.