Oxidative Stress and its Clinical Consequences: Relationship between Diabetes and Cancer

Chronic and acute overproduction of reactive oxygen species (ROS) under pathophysiologic conditions characterises the development of oxidative stress and diseases including cancer and diabetes. These ROS are released principally from mitochondria but also from other sources. Oxidative stress seems to play an important role in mitochondria-mediated disease processes, though the exact molecular mechanisms responsible remain elusive. ROS are generally necessary for the proper functioning of the cell, but excessive ROS production can be harmful, and so antioxidant defenses are required. Diabetes and cancer are heterogeneous, multifactorial, severe and chronic diseases. Epidemiological studies clearly indicate that the risk of several types of cancer (including that of the breast, colorectum, female reproductive organs, liver, pancreas and urinary tract) is higher in diabetic patients. Hyperinsulinemia appears to promote cancer in diabetic patients, as insulin is a growth factor with metabolic and mitogenic effects and its action in malignant cells is favoured by mechanisms that act at both receptor and post-receptor levels. Obesity, hyperglycemia and increased oxidative stress may also contribute to an increased risk of cancer in diabetes patients. In conclusion, diabetes and cancer are conditions related with oxidative stress; a complex relationship that requires clinical attention.