Insulin resistance in tetraplegia but not in mid-thoracic paraplegia: is the mid-thoracic spinal cord involved in glucose regulation?

Study design: Controlled experimental human study. Objectives: To assess insulin resistance (IR) in tetraplegia and paraplegia, and the role of the spinal cord (SC) in glucose regulation. Setting: Laboratory of Spinal Research, Loewenstein Rehabilitation Hospital. Methods: Glucose and insulin levels and the heart rate variation spectral components LF (low frequency), HF (high frequency) and LF/HF were studied at supine rest, head-up tilt and after a standard meal in three groups: 13 healthy subjects, 7 patients with T(4)-T(6) paraplegia and 11 patients with C(4)-C(7) tetraplegia. Results: Glucose and insulin increased significantly after the meal in all groups (P<0.001). Glucose increased significantly more in the tetraplegia than in the other groups (P<0.01). Increases in insulin level tended to accompany increases in LF/HF after the meal in the tetraplegia and control groups but not in the paraplegia group. Conclusion: Post-prandial IR appears in C(4)-C(7) but not in T(4)-T(6) SC injury. The results of the study, combined with previously published findings, are consistent with the hypotheses that IR is related to activation of the sympathetic nervous system, and that below T(4) the mid-thoracic SC is involved in the regulation of glucose and insulin levels. Spinal Cord (2011) 49, 648-652; doi: 10.1038/sc.2010.152; published online 2 November 2010