One of the athletes Rita works with has recently been diagnosed with diabetes. The athlete will be using insulin to control his blood sugar and will be injecting the insulin subcutaneously in the thigh. Rita is concerned about the effects that exercise will have on the activity of the insulin and the patient’s blood sugar.
Question: Based on pharmacokinetic and pharmacodynamic principles, what possible effect could exercise have on insulin?
Considering the pharmacokinetic and pharmacodynamic characteristics of insulin, it is difficult to suppress insulin levels during exercise among diabetic patients who are treated with insulin, as it normally happens in healthy subjects. Among patients with diabetes, hepatic glucose production cannot increase sufficiently to effectively compensate for the increased demand for glucose by the muscles that are being exercised as a result of increasing insulin sensitivity (Way et al., 2016). Among patients with diabetes, there will be increased action and absorption of insulin at the site of injection. The cases of low glucose levels combined with high insulinemia can therefore lead to severe hypoglycemia among patients with diabetes who exercise and take insulin. Prolonged exercising can also expose patients with diabetes to incidences of decreased glucose counter-regulation because of the decrease in cortisol glucagon and epinephrine levels after exercise, which can last up to several hours. Antecedent hypoglycemia can also result in diminished counter-regulation and awareness after a patient with diabetes is involved in the exercise. On the other hand, greatly reducing the dose of insulin in a diabetes patient who exercises while taking large amounts of carbohydrates can result in ketosis or severe hyperglycemia (Shetty et al., 2016). The most effective approach for managing insulin therapy and exercise among athletes would therefore be for the athletes to postpone exercise sessions when their blood glucose level is above 250 mg/dl and only exercise when their metabolic activity is normal (Shetty et al., 2016). Before beginning exercise, it’s also important for diabetes patients to be evaluated for existing macro and microvascular complications. The existence of such complications will therefore determine the exercise regime that might be most suitable for each subject (Shetty et al., 2016).
- Shetty, V. B., Fournier, P. A., Davey, R. J., Retterath, A. J., Paramalingam, N., Roby, H. C., Cooper, M. N., Davis, E. A., & Jones, T. W. (2016). Effect of Exercise Intensity on Glucose Requirements to Maintain Euglycemia During Exercise in Type 1 Diabetes. The Journal of Clinical Endocrinology & Metabolism, 101(3), 972–980. https://doi.org/10.1210/jc.2015-4026
- Way, K. L., Hackett, D. A., Baker, M. K., & Johnson, N. A. (2016). The Effect of Regular Exercise on Insulin Sensitivity in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis. Diabetes & Metabolism Journal, 40(4), 253. https://doi.org/10.4093/dmj.2016.40.4.253