Vibration induced nerve and arterial injury may be prevented by nicotinamide riboside supplementation
Chaowen Wu, MD-PhD; Plastic Surgery, Medical College of Wisconsin, Milwaukee, WI; Danny Riley, PhD; Medical College of Wisconsin, Milwaukee, WI
Introduction
Hand-arm vibration syndrome (HAVS) manifests in hand numbness and Raynaud’s phenomenon. Despite over a century of characterizing this peculiar phenomenon, little is known about its pathogenesis. Perhaps for this reason, efforts in preventing or treating HAVS have been minimally successful. In this pilot study, we show that mechanical vibration may not be the cause of HAVS, furthermore, supplementation with nicotinamide riboside (NR - a precursor to NAD+ which supports mitochondrial energy metabolism) may prevent the development of vibration induced nerve and vascular injury.
Materials & Methods
Thirty-two 3 month-old Sprague-Dawley rats were divided into 5 groups: non-vibrated control group, tail-vibrated group subjected to 2 hours of tail vibration, tail-vibrated group injected with a bupivacaine tail block, non-vibrated bupivacaine tail block control, and a tail vibrated group treated with twice a day intraperitoneal injections of NR. After 14 days of vibrational trails, sensory testing was performed. Rats were euthanize and ventral tail nerves and arteries were harvested for histological studies.
Results
Although sensory testing were similar in all groups, we found that the tail-vibrated group showed morphological signs of nerve injury whereas non-vibrated nerves and NR treated vibrated nerves did not. Unfortunately bupivacaine tail injections caused direct trauma to the nerves.
Fluorescence imaging of tail arteries showed that NR protected vibration associated damage to the internal elastic lamina of arteries. Intriguingly, arteries from both vibrated and non-vibrated bupivacaine injected tails showed preserved internal elastic lamina morphology and decreased sympathetic staining with tyrosine hydroxylase despite the severity of nerve injury. This may indicate that the sensation of vibration or sympathetic upregulation, rather than the degree of nerve injury, may be responsible for the development of arterial injury.
Conclusions
Our data provide evidence to support that direct mechanical vibration may not be the cause for nerve injury. In addition, NR appears to have a protective effect on arteries from developing signs of vascular disease including preservation of internal elastic lamina integrity and prevention of sympathetic upregulation. Because NR is a health supplement that can be readily purchased, those at risk for developing vibration induced neurovascular injury may be able to take NR to prevent the development of debilitating hand-arm vibration syndrome.
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