Relationship between electroneurographic changes and serum ubiquitin levels in patients with type 2 diabetes

OBJECTIVE - The aim of the present study was to investigate any relationship between serum ubiquitin levels and electroneurographic changes in peripheral nerves for patients with type 2 diabetes. RESEARCH DESIGN AND METHODS - The study involved 34 patients (19 men, 15 women; mean age 46 +/- 13 years) with type 2 diabetes. Serum ubiquitin values were measured by sandwich enzyme-linked immunosorbent assay. Measurement of nerve conduction velocity (NCV) was performed on three motor (median, tibial, and peroneal) and three sensory (median, ulnar, and sural) nerves. The value of motor compound muscle action potential (CMAP) was obtained from the sum of median, tibial, and peroneal motor nerve amplitudes, and sensory compound nerve action potential (CNAP) was computed as the sum of median and ulnar sensory nerve amplitudes. RESULTS - Patients with diabetes were divided into three groups: group 1 (n = 8) had normal electroneurography results, group 2 (n = 8) had slowed NCV and group 3 (n = 18) had low values of motor CMAP and/or sensory CNAP as well as slowed NCV. Mean ubiquitin level in group 3 (20.4 +/- 2.9 ng/dl) was significantly higher than that in group 1 (11.2 +/- 1.1 ng/dl, t = 11.5, P < 0.0001) and group 2 (13.2 <plus/minus> 2.7 ng/dl, t = 5.9, P < 0.0001). Serum ubiquitin levels were inversely correlated with motor CMAP (r = -0.68) and sensory CNAP (r = -0.61) values. CONCLUSIONS - The results of this study indicate that there could be a relationship between the diminished amplitudes of axons of the peripheral nerve and the increase in serum ubiquitin levels in patients with type 2 diabetes. Further studies are required to confirm this relationship.