John Seawright, B.S.
The national anthem has been sung, home plate has been cleaned, and the starting lineup announced. The athletes go through the final mental checklist before taking the field. Hat? Check. Glove? Check. Cup? Check. Insulin?
Diabetes is a condition that affects close to 26 million Americans. A diabetic lacks the capability to adequately regulate glucose (sugar) in the blood. Normally, the body relies heavily on the hormone insulin to promote the uptake of glucose from the blood by stimulating glucose transporter proteins to move from inside the cell to the cell membrane, where they are then able to transport glucose from the bloodstream into the tissue. However, in the case of diabetes, either insulin is produced in inconsequential amounts or the body fails to respond to the hormone. Both scenarios result in glucose transporter proteins remaining within the cell, thus resulting in hyperglycemia (a high blood glucose concentration).
Diabetes leads to an increased risk for cardiovascular disease through the process of glycosylation, which links excess glucose with proteins in the blood. Glycosylation can modify protein structure and impair their function. In the bloodstream, glycosylated proteins can induce endothelial dysfunction, arterial distensibility, plaque formation, and atherosclerosis; all of which can lead to a heart attack. Ultimately, up to 70% of diabetics will die from cardiovascular disease.
Physical activity can help mediate blood glucose levels and reduce the risk of cardiovascular disease. One valuable adaptation resulting from exercise is the utilization of an insulin-independent glucose transport protein, allowing glucose transport proteins to be inserted into the cell membrane without using insulin. Thus, glucose can be removed from the bloodstream without insulin. During exercise, muscles use glucose preferentially as its energy source, so glucose levels in the muscle would be expected to fall drastically. However, exercise stimulates the liver to release glucose into the bloodstream and the cardiovascular system increases blood flow which takes the extra glucose to the exercising muscles. These exercise- induced adaptations, along with the insulin-independent glucose transport proteins help maintain appropriate blood glucose levels for the exercising muscles. Thus, exercise is considered a pillar of diabetes treatment. For exercise recommendations, see the Hornsby article under Further Readings.
Professional athletes incapable of producing their own insulin face unique challenges in their blood glucose management than typical exercising diabetics. With their higher levels of activity, these competitive athletes are at a higher risk for exercise-induced hypoglycemia (low blood sugar) that can lead to a diabetic coma. These athletes are unable to properly release glucose from their livers during exercise. Therefore, competitive athletes must be diligent about monitoring their blood glucose, insulin shots, and nutrition. Professional diabetic athletes Mark Lowe, Jerry Stackhouse, and Jay Cutler serve as valuable role models for those diabetics seeking to achieve their athletic and performance goals.
In spite of the challenges of diabetes, many professional athletes and average weekend warriors who suffer from diabetes can improve their disease condition, reduce their risk for heart disease with exercise, and perform at a high level. Play ball!
MayoClinic. Diabetes. 2013; http://www.mayoclinic.com/health/diabetes/DS01121
Selvin E, Marinopoulos S, Berkenblit G, et al. Meta-Analysis: Glycosylated Hemoglobin and Cardiovascular Disease in Diabetes Mellitus. Annals of Internal Medicine. 2004;141(6):421-431. http://www.ncbi.nlm.nih.gov/pubmed/15381515
Sigal RJ, Kenny GP, Wasserman DH, Castaneda-Sceppa C. Physical Activity/Exercise and Type 2 Diabetes. Diabetes Care. October 1, 2004 2004;27(10):2518-2539. http://care.diabetesjournals.org/content/29/6/1433.full.pdf+html
Hornsby WG, Chetlin RD. Management of Competitive Athletes With Diabetes. Diabetes Spectrum. April 1, 2005 2005;18(2):102-107. http://spectrum.diabetesjournals.org/content/18/2/102.full.pdf+html
CBS Local Media P. Famous Athletes with Diabetes. 2013; http://philadelphia.cbslocal.com/photo-galleries/2012/11/01/awareness-month-famous-athletes-with-diabetes/.
Center for Disease Control and Prevention. 2011; Number of Americans with Diabetes Rises to Nearly 26 Million. http://www.cdc.gov/media/releases/2011/p0126_diabetes.html