Sep 30, 2008 - Health + Traits

Genetic Link Between Obesity and Colorectal Cancer

The connection between obesity and cancer is well established. As many as 25 to 30 percent of several major cancers — colon, breast (postmenopausal), endometrial, kidney, and esophagus — may be accounted for by obesity and physical inactivity. Some studies have also found links between obesity and cancers of the gallbladder, ovaries, and pancreas.

It is not yet clear to scientists, however, how obesity increases the risk for certain cancers. Part of the answer may lie in a hormone released by fat cells — adiponectin. Decreased blood levels of this hormone, which are found in obese people, have been linked with breast, endometrial, prostate and colon cancer.

A new study published today in the Journal of the American Medical Association provides further evidence for adiponectin being the link between obesity and cancer. Researchers have demonstrated that a variant in the gene that encodes the hormone influences the risk of developing colorectal cancer.

Kaklamani et al examined several SNPs in the adiponectin and adiponectin receptor genes in a total of 629 people with colorectal cancer and 855 people without the disease. All subjects except for 37 cases and 37 controls were of European ancestry. The researchers found that people with one or two Gs at rs266729 in the adiponectin gene had 27% lower odds of developing colorectal cancer compared to those with two Cs.

(23andMe customers can look up their data for rs266729 using the Browse Raw Data feature)

According to the report’s senior author, Dr. Boris Pasche, these research findings could help identify people who would benefit from increased colorectal cancer screening.

“Our hope is that we can significantly improve the screening and early detection for this disease, and open new avenues for better understanding the genetic and lifestyle factors that influence colon cancer risk, “ he said in a statement.

Pasche went on to caution that additional studies are needed to confirm whether those without the adiponectin variant that appears to protect people from colorectal cancer will benefit from cancer-prevention lifestyle changes such as diet and exercise.

A different variant in the adiponectin gene was recently identified as a modifier of breast cancer risk in a study co-authored by Pasche. Understanding how variants in this gene influence breast and colorectal cancer risk, and whether the variants affect the risk for other cancers, will require more research.

Colorectal cancer is the second-leading cancer killer of Americans. According to estimates from the American Cancer Society, 149,000 people will be diagnosed with the disease and 50,00 will die this year alone.

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