Insulin and Breast Cancer

While obesity and diabetes have been linked to inflammation which is then contributed to cardiovascular disease, the inflammatory effects of obesity and hyperinsulinemia of diabetes can also contribute to the increased mortality rate of obese woman with breast cancer. It has been suggested that TNF-alpha causes hyperinsulinemia and insulin resistance by inhibiting the serine phosphorylation on IRS-1 which inhibits downstream signaling. In the article, “ORIGINAL REPORTS - Breast Cancer: Associations of Insulin Resistance and Adiponectin With Mortality in Women With Breast Cancer,” the researchers measure glucose, insulin and adiponectin in 527 obese women with Type I-IIIa breast cancer and compared their HOMA score with breast cancer survival. They found that an increase in the HOMA score correlated with a decrease in survival. The HOMA score is a determinant of insulin sensitivity and beta cell function. They also suggested that women with increased levels of adiponectin had an increased survival rate of breast cancer. In people who are obese there is a decrease in adiponectin. The authors also discussed that in another study of non-obese diabetic mice, the mice had severe hyperinsulinemia and insulin resistance, there was accelerated mammary gland development and breast cancer development independent of obesity and inflammation. Their findings supported the tumor promoting effect of increased circulation insulin levels and that insulin could stimulate cell proliferation. In people with diabetes and insulin resistance, they could substantially reduce the impact of insulin resistance through simple lifestyle changes. Thus in obese women with breast cancer they could increase their chance of survival by eating healthier and exercising.

Duggan Catherine, Melinda L. Irwin, Liren Xiao, et al. “ORIGINAL REPORTS - Breast Cancer:

Associations of Insulin Resistance and Adiponectin With Mortality in Women With Breast Cancer.” JCO Jan 1, 2011:32-39; published online on November 29, 2010.