The effect of alpha-lipoic acid on the neurovascular reflex arc in patients with diabetic neuropathy assessed by capillary microscopy

Patients with diabetic polyneuropathy are known to have an impaired neurova scular reflex are compared to healthy controls. This is seen in a delayed d ecrease in microcirculation of the ipsilateral hand after cooling of the co ntralateral hand. The aim of this pilot study was to investigate whether in travenous alpha-lipoic acid (ALA) (Thioctacid, Asta Medical therapy might b e able to improve this impaired neurovascular reflex are in patients with d iabetic neuropathy. In addition, clinical effects were evaluated with the a id of the neuropathy symptom score (NSS) and the neuropathy disability scor e (NDS). Ten patients with diabetes mellitus and polyneuropathy (5 females, 5 males, 2 smokers, 5 IDDM, 5 NIDDM, body mass index 26.1 +/- 1.0 kg/m(2), age 58.3 +/- 9.5 years, diabetes duration 15.7 +/- 11.2 years, Hb A(1c) 6. 8 +/- 0.3%) were investigated by nail-fold capillaroscopy after contralater al cooling before and after intravenous therapy with 600 mg alpha-lipoic ac id per day over 3 weeks. Cardiac autonomic neuropathy was excluded by beat- to-beat variation analysis. Symptoms of diabetic neuropathy were evaluated before and after therapy with the aid of the NSS and NDS. Capillary blood c ell velocity (CEV) of the hand was determined before, during, and for the f ollowing 30 min after cooling (3 min at 15 degrees C) of the contralateral hand. Blood pressure, heart rate, and local skin temperature were monitored at 2-min intervals. ALA therapy resulted in a significant improvement of t he microcirculatory response to cooling, as seen by an immediate de crease in CBV of 12.3% (P < 0.02 vs before treatment), which was absent before the rapy. Blood pressure, heart rate, and local skin temperature were not diffe rent between investigations. There was a significant improvement of the NSS after therapy (5.4 +/- 1.1 vs 8.6 +/- 1.1 points, P < 0.01). These results demonstrate that intravenous therapy with ALA has a positive influence on the impaired neurovascular reflex are in patients with diabetic neuropathy. (C) 1999 Academic Press.