Preventive effect of acetyl-L-carnitine on the thermal hypoalgesia in streptozotocin-induced diabetic mice.

Hypoalgesia is one of the serious complications in diabetes. Since there are few therapeutic treatments for this diabetic hypoalgesia, the present study was designed to examine the effect of acetyl-L-carnitine (ALC) on the changes of nociceptive threshold in diabetic mice. For prophylactic study, ALC was administered once daily from 1 day after the streptozotocin treatment. Diabetic mice showed shorter tail-flick latency at 1-4 weeks after the streptozotocin treatment and longer tail-flick latency at 6-9 weeks after the streptozotocin treatment. The shortened tail-flick latency in early stage of diabetic mice was not affected by prophylactic treatment with ALC. On the other hand, ALC dose-dependently improved the hypoalgesia in diabetic mice. For therapeutic study, ALC was administered once daily from 7 weeks after the streptozotocin treatment, when tail-flick latency was already prolonged. The therapeutic treatment with ALC also ameliorated the prolonged tail-flick latency in diabetic mice. Both prophylactic and therapeutic treatment with ALC did not affect the tail-flick latency in non-diabetic mice, indicating ALC did not affect the general nociceptive transmission. These results provide evidence of the prophylactic and therapeutic potential of ALC on the progressive diabetic neuropathy.