Lower extremity MRI following 10-week supervised exercise intervention in patients with diabetic peripheral neuropathy

Introduction The purpose of this study was to characterize using MRI the effects of a 10-week supervised exercise program on lower extremity skeletal muscle composition, nerve microarchitecture, and metabolic function in individuals with diabetic peripheral neuropathy (DPN). Research design and methods Twenty participants with DPN completed a longitudinal trial consisting of a 30-day control period, during which subjects made no change to their lifestyle, followed by a 10-week intervention program that included three supervised aerobic and resistance exercise sessions per week targeting the upper and lower extremities. The participants' midcalves were scanned with multinuclear MRI two times prior to intervention (baseline 1 and baseline 2) and once following intervention to measure relaxation times (T1, T1ρ, and T2), phosphocreatine recovery, fat fraction, and diffusion parameters. Results There were no changes between baseline 1 and baseline 2 MRI metrics (p>0.2). Significant changes (p<0.05) between baseline 2 and postintervention MRI metrics were: gastrocnemius medialis (GM) T1 -2.3%±3.0% and soleus T2 -3.2%±3.1%. Trends toward significant changes (0.05<p<0.1) between baseline 2 and postintervention MRI metrics were: calf adipose infiltration -2.6%±6.4%, GM T1ρ -4.1%±7.7%, GM T2 -3.5%±6.4%, and gastrocnemius lateral T2 -4.6±7.4%. Insignificant changes were observed in gastrocnemius phosphocreatine recovery rate constant (p>0.3) and tibial nerve fractional anisotropy (p>0.6) and apparent diffusion coefficient (p>0.4). Conclusions The 10-week supervised exercise intervention program successfully reduced adiposity and altered resting tissue properties in the lower leg in DPN. Gastrocnemius mitochondrial oxidative capacity and tibial nerve microarchitecture changes were not observed, either due to lack of response to therapy or to lack of measurement sensitivity.