24 Aug Diabetes: Exercise Improves Glycemic Control if Pancreatic Beta-Cell Function Remains
Thomas P. J. Solomon, Ph.D.
Associate Professor of Biomedical Sciences
Department of Biomedical Sciences | Cellular & Metabolic Research Section
Panum Institute 4.5 | University of Copenhagen | Blegdamsvej 3B | 2200 Copenhagen N | Denmark
MedicalResearch.com: What are the main findings of the study?
Dr. Solomon: The main findings were that when impaired glucose tolerant and type 2 diabetic subjects underwent 3-4 months of regular aerobic exercise training, although the majority of subjects (86-90%) increased increased VO2max, lost weight, and increased insulin sensitivity, only around two-thirds of subjects improved glycemic control (HbA1c, fasting glucose, and 2-hour OGTT glucose). The novel finding was that the changes in glycemic control were congruent with changes in oral glucose-stimulated insulin secretion (GSIS). We also found that exercise training-induced changes in glycemic control were related to changes in GSIS (P0.05), but not insulin sensitivity. Furthermore, we found that training-induced improvements in glycemic control were largest in subjects with greater pre-training GSIS, i.e. in subjects with greatest beta-cell function. And, we noted that high pre-training hyperglycemia blunted exercise-induced improvements in beta-cell compensation for insulin resistance.
MedicalResearch.com: Were any of the findings unexpected?
Dr. Solomon: Yes, the finding that exercise-induced changes in glycemic control were not related to changes in insulin sensitivity was intriguing because one may have assumed prior to the study that muscular exercise that improved insulin sensitivity in the majority of our subject cohort (90% of 105 subjects) would extrapolate to improved glycemic control in the same numbers of subjects. However, at best we found glycemic control was improved in only around two-thirds of the 105 subjects.
MedicalResearch.com: What should clinicians and patients take away from your report?
Dr. Solomon: It would important for clinicians and patients to note that despite consistent improvements in fitness, body composition and insulin sensitivity, there will likely be a high intersubject variability in the improvement of glycemic control following aerobic exercise training. It is also important for clinicians to note that greater success following exercise is more likely in subjects with lower pre-training hyperglycemia and better beta-cell function, therefore some consideration of treating the underlying hyperglycemia and/or beta-cell dysfunction may be sensible prior to engaging in an aerobic exercise training regime. However, it is also important to note that there is no evidence base for determining the best approach at present. That said, our findings do indeed highlight the need for individualized treatment so as to maximize the benefit to treating obesity-related hyperglycemia.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Dr. Solomon: Future exercise studies should incorporate a thorough clinical assessment of glycemic control to include HbA1c, fasting glucose, and an OGTT, so that appropriate expectations regarding the clinical effectiveness of exercise training can be drawn. Our findings make it clear that great caution should be taken when assuming that exercise training has a clinically meaningful outcome with regards to glycemic control if only insulin sensitivity has been measured. Also, because baseline and training-induced changes in beta-cell function may be a key determinant of training-induced improvements in glycemic control, it seems sensible that future research must identify the optimal use of exercise in the treatment/prevention of type 2 diabetes. For example it appears that patients may only respond beneficially if there is a reasonable degree of beta-cell function present prior to commencing training. Hence, using aerobic exercise to treat patients with poorly controlled long-term type 2 diabetes may have limited chances of a successfully controling glycemia. In such patients it seems sensible to improve beta-cell function and achieve better glycemic control (possibly by pharmaceutical means) prior to incorporating aerobic exercise as an intervention. Future randomized controlled trials are crucial in order to determine an optimal approach.
Pancreatic beta-cell function is a stronger predictor of changes in glycemic control after an aerobic exercise intervention than insulin sensitivity. Thomas P.J. Solomon, Steven K. Malin, Kristian Karstoft, Sangeeta R. Kashyap,
Jacob M. Haus, and John P. Kirwan
Pancreatic beta-cell function is a stronger predictor of changes in glycemic control after an aerobic exercise intervention than insulin sensitivity. JCEM jc.2013-2232; doi:10.1210/jc.2013-2232