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

Microvasc Res. 1999 Jul;58(1):28-34. doi: 10.1006/mvre.1999.2151.


Patients with diabetic polyneuropathy are known to have an impaired neurovascular reflex arc compared to healthy controls. This is seen in a delayed decrease in microcirculation of the ipsilateral hand after cooling of the contralateral hand. The aim of this pilot study was to investigate whether intravenous alpha-lipoic acid (ALA) (Thioctacid, Asta Medica) therapy might be able to improve this impaired neurovascular reflex arc in patients with diabetic neuropathy. In addition, clinical effects were evaluated with the aid of the neuropathy symptom score (NSS) and the neuropathy disability score (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/m2, age 58.3 +/- 9.5 years, diabetes duration 15.7 +/- 11.2 years, Hb A1c 6.8 +/- 0.3%) were investigated by nail-fold capillaroscopy after contralateral cooling before and after intravenous therapy with 600 mg alpha-lipoic acid 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 cell velocity (CBV) of the hand was determined before, during, and for the following 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 the microcirculatory response to cooling, as seen by an immediate decrease in CBV of 12. 3% (P < 0.02 vs before treatment), which was absent before therapy. Blood pressure, heart rate, and local skin temperature were not different 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 arc in patients with diabetic neuropathy.

MeSH terms

  • Adult
  • Aged
  • Antioxidants / pharmacology
  • Antioxidants / therapeutic use*
  • Blood Flow Velocity
  • Body Mass Index
  • Cold Temperature
  • Diabetic Neuropathies / drug therapy*
  • Diabetic Neuropathies / etiology
  • Drug Evaluation
  • Female
  • Free Radical Scavengers / pharmacology
  • Free Radical Scavengers / therapeutic use*
  • Hemodynamics / drug effects
  • Humans
  • Male
  • Microcirculation / drug effects*
  • Middle Aged
  • Nails / blood supply
  • Peripheral Nerves / blood supply*
  • Pilot Projects
  • Reflex, Abnormal / drug effects*
  • Severity of Illness Index
  • Smoking / adverse effects
  • Thioctic Acid / pharmacology
  • Thioctic Acid / therapeutic use*


  • Antioxidants
  • Free Radical Scavengers
  • Thioctic Acid