High Insulin, Low Adiponectin Levels Adversely Affect Survival in Breast Cancer Patients

Women with breast cancer who have elevated levels of C-peptide (a marker of insulin secretion) have significantly higher mortality rates than their peers with lower levels, results of the Health, Eating, Activity, and Lifestyle (HEAL) study indicate.

 

Another report by the HEAL investigators shows that two factors associated with obesity—an elevated Homeostatic Model Assessment (HOMA) score (a measure of insulin resistance) and low levels of adiponectin (a peptide hormone with levels inversely correlated to body mass index)— also are associated with increased breast cancer mortality. Both studies are published online in the Journal of Clinical Oncology.

In a study of 604 women with stage I to IIIa breast cancer, Melinda L. Irwin, PhD, MPH, of the Yale School of Health, New Haven, Connecticut, and her associates found that patients who had C-peptide levels greater than 2.5 ng/mL 3 years after diagnosis were at a twofold higher risk of breast cancer death than those with lower levels. Women with type 2 diabetes had an even greater risk of breast cancer death compared with women without type 2 diabetes.
 
The findings suggest that treatment strategies that reduce C-peptide levels in women treated for breast cancer—which could include dietary-induced weight loss, increased physical activity, and insulin-lowering medications—should be explored, according Irwin, the study’s lead author.
 
“There is growing evidence that weight and physical activity affect breast cancer outcomes, and our findings suggest that the mechanism linking lifestyle factors and breast cancer may be the insulin pathway,” she said. “Women treated for breast cancer who are overweight or not currently exercising should definitely seek lifestyle counseling and/or talk with their physician about additional therapeutic options,” she advised.

 

A separate analysis of 527 women participating in the HEAL study showed that increasing HOMA scores were associated with reduced breast cancer survival and all-cause survival. The study also found an association between higher levels of adiponectin and longer breast cancer survival.

 
The finding is believed to be the first association between breast cancer survivorship and levels of adiponectin, a protein hormone that controls processes such as glucose regulation, the breakdown of fatty acids, and energy intake. Levels of this hormone are related to body mass index, with overweight or obese breast cancer patients generally having lower levels of adiponectin and also elevated levels of insulin resistance. Lifestyle interventions that promote weight loss and increase physical activity can raise adiponectin levels and reduce insulin levels.