UB Epidemiologists Show Link Between Insulin Resistance, Colon And Breast Cancer

EDMONTON -- University at Buffalo epidemiologists are among the first to show that insulin resistance may significantly increase the risk of death from colon cancer, particularly among women.

Their research showed that women with characteristics associated with insulin resistance had 10 times the risk of dying from colon cancer than women without these characteristics. Results showed no significant increased risk of colon cancer deaths among men associated with insulin resistance.

In addition, researchers found that insulin resistance was associated with a five-fold increase in risk of death from breast cancer in women.

Paola Muti, M.D., UB research assistant professor of social and preventive medicine, presented results of the mortality study here today (Thursday, June 12) at the annual meeting of the Society for Epidemiological Research.

Insulin resistance is often a precursor of adult-onset diabetes, although the condition itself does not always have physical symptoms. It is characterized by an inability of cells to absorb insulin readily, and a consequent build-up of insulin and glucose in the blood.

The study involved 22,561 men and 18,495 women ages 45-79 who were participants in the Risk Factors and Life Expectancy Project, a series of multicenter studies being conducted in Italy. After seven years, 15 women and 42 men had died from colon cancer and 21 women had died from breast cancer. Four healthy controls were selected randomly from the study population for each cancer case, after matching for age, smoking and geographic region, to compare with those who had died.

To determine the presence of insulin resistance, researchers looked for evidence of a condition called "Syndrome X," characterized by high blood pressure, high levels of triglycerides, low levels of HDL-cholesterol (the "good" cholesterol), and high levels of uric acid. Participants were deemed to be insulin resistant if these symptoms were present, Muti said. Detailed records were available for those who had died.

Results showed that nearly 27 percent of the women who died from colon cancer had insulin resistance, compared to 3 percent of the controls. For breast cancer, 9.5 percent of those who died were insulin resistant versus 3.5 percent of controls. The prevalence of insulin resistance for men was 4.8 percent among cases versus 2.4 percent among controls.

Muti, who has been researching the role of hormones in the development of cancer, said the association between insulin resistance and colon and breast cancer may be tied to androgen levels, the group of hormones responsible for the development of male characteristics.

"There is strong evidence that women with high levels of androgens are at higher risk of developing breast cancer," Muti said. "Persons with borderline insulin resistance have been shown to have high levels of androgens in some clinical studies. Some scientists say insulin resistance may come first, but there has been no clear indication of a relationship between insulin resistance and breast cancer. This is one of the first studies to show evidence of an association."

If further studies show insulin resistance is a true risk factor for breast and colon cancer, Muti said treatment for insulin resistance may help protect against development of these diseases.

Also participating in the study were Jain Liu, visiting scholar with the UB Department of Social and Preventive Medicine; Maurizio Trevisan, M.D., professor and chair of the department, and Alessandro Menotti of the Risk Factors and Life Expectancy Project.