Lifestyle intervention for pre-diabetic neuropathy.
The purpose of this study was to evaluate intraepidermal nerve fiber density (IENFD) as a sensitive measure of neuropathy change in patients with neuropathy associated with impaired glucose tolerance (IGT) receiving lifestyle intervention based on that used in the Diabetes Prevention Program. We performed 3-mm skin biopsies with measurement of IENFD at the distal leg and proximal thigh at baseline and after 1 year in 32 subjects with IGT. Each received individualized diet and exercise counseling as a standard of care. Nerve conduction studies, quantitative sensory testing, quantitative sudomotor axon reflex testing, and the Michigan Diabetic Neuropathy score were performed, and a visual analog pain scale was completed. Two-hour oral glucose tolerance tests (OGTTs) following the American Diabetes Association guidelines were performed, and serum lipid levels were measured at baseline and 1 year later. Baseline distal IENFD was 0.9 +/- 1.2 fibers/mm and proximal IENFD was 4.8 +/- 2.3 fibers/mm. Baseline distal IENFD correlated with fasting glucose (P < 0.001) and OGTT (P < 0.01). After 1 year of treatment, there was a 0.3 +/- 1.1-fiber/mm improvement in distal IENFD and a 1.4 +/- 2.3-fiber/mm improvement in proximal IENFD (P < 0.004). The change in proximal IENFD correlated with decreased neuropathic pain (P < 0.05) and a change in sural sensory amplitude (P < 0.03). These findings indicate that diet and exercise counseling for IGT results in cutaneous reinnervation and improved pain. Skin biopsy was the most sensitive measure of neuropathy change over 1 year. IENFD should be included as an end point in future neuropathy trials.