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, 2008 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.

Reference: JAMA. 2008;300[13]:1523-1531.

About Colorectal Cancer

Colorectal cancer is also called Colon cancer, and Rectal cancer. Colon cancer is cancer of the large intestine (colon), the lower part of your digestive system. Rectal cancer is cancer of the last 6 inches of the colon. Together, they're often referred to as colorectal cancers.

In the United States, colorectal cancer is the fourth most common cancer in men and women. Caught early, it is often curable.  Not counting skin cancers, colorectal cancer is the third most common cancer found in men and women in this country. The American Cancer Society estimates that there will be about 112,000 new cases of colon cancer and 41,000 new cases of rectal cancer in 2008 in the United States. Combined, they will cause about 49,960 deaths.

• Age: The chances of having colorectal cancer go up after age 50. More than 9 out of 10 people found to have colorectal cancer are older than 50.Having had polyps or colorectal cancer before: Some types of polyps increase the risk of colorectal cancer, especially if they are large or if there are many of them. If you have had colorectal cancer (even if it has been completely removed), you are more likely to have new cancers start in other areas of your colon and rectum. The chances of this happening are greater if you had your first colorectal cancer when you were younger than age 60.
• Having a history of bowel disease: Two bowel diseases, called ulcerative colitis and Crohn's disease, increase the risk of colon cancer. In these diseases, the colon is inflamed over a long period of time. If you have either of these diseases your doctor may want you to have colon screening testing more often. (These diseases are different than irritable bowel syndrome (IBS), which does not carry an increased risk for colorectal cancer.).
• Family history of colorectal cancer: If you have close relatives who have had this cancer, your risk might be increased. This is especially true if the family member got the cancer before age 60. People with a family history of colorectal cancer should talk to their doctors about when and how often to have screening tests.
• Certain family syndromes: A syndrome is a group of symptoms. For example, in some families members tend to get a type of syndrome called FAP that involves having hundreds of polyps in their colon or rectum. Cancer often develops in 1 or more of these polyps.If your doctor tells you that you have a condition that makes you or your family members more likely to get colorectal cancer, you will probably need to begin colon cancer testing at a younger age and you might want to talk about genetic counseling.
• Race or ethnic background: Some racial and ethnic groups such as African Americans and Jews of Eastern European descent (Ashkenazi Jews) have a higher colorectal cancer risk. All of the reasons for this are not yet understood.

Several lifestyle-related factors have been linked to colorectal cancer. They include:

• Certain types of diets: A diet that is high in red meats (beef, lamb, or liver) and processed meats such as hot dogs, bologna, and lunch meat can increase your colorectal cancer risk. Cooking meats at very high heat (frying, broiling, or grilling) can create chemicals that might increase cancer risk. Diets high in vegetables and fruits have been linked with a lower risk of colorectal cancer.
• Lack of exercise: Getting more exercise may help reduce your risk.
• Overweight: Being very overweight increases a person's risk of dying from colorectal cancer.
• Smoking: Most people know that smoking causes lung cancer, but long-time smokers are more likely than non-smokers to die of colorectal cancer. Smoking increases the risk of many other cancers, too.
• Alcohol: Heavy use of alcohol has been linked to colorectal cancer.
• Diabetes: People with type 2 diabetes have an increased chance of getting colorectal cancer. They also tend to have a higher death rate from this cancer.

• Other cancers and their treatment: A recent report on testicular cancer survivors found that these men had a higher rate of colorectal cancer. Men who receive radiation therapy for prostate cancer have been reported to have a higher risk of rectal cancer, too.
• Night-shift work: One study suggests that working a night shift at least 3 nights a month for at least 15 years might increase the risk of colorectal cancer in women. More research is needed to check out this finding.

• a change in bowel habits such as diarrhea, constipation, or narrowing of the stool that lasts for more than a few days
• a feeling that you need to have a bowel movement that doesn't go away after doing so
• rectal bleeding, dark stools, or blood in the stool (often, though, the stool will look normal)
• cramping or stomach pain
• weakness and tiredness.

Most people with early colon cancer don't have symptoms, therefore getting tested is very important and can possibly save your life.