Evaluation of Some Phenolic Acids in Diabetic Neuropathy

Background: Streptozotocin (STZ) induced neuropathy is widely used preclinical model for diabetic neuropathy (DN). DN is majorly resulted due to nitrosative and oxidative stress induced by hyperglycemia. Phenolic acids are polyphenols with free radical scavenging anti-inflammatory and neuroprotectiveaction. Methods: In this study STZ (55mg/kg, i.p) was administered in male Wistar rats and animals with hyperglycemia (fasting blood glucose ≥ 200mg/dl) were used for further study. Behavioural changes cold allodynia, mechanical hyperalgesia, heat hyperalgesia, mechanical allodynia were assessed weekly. Motor Nerve Conduction Velocity (MNCV) was also evaluated. Reduced Glutathione and Malondialdehyde were estimated to indicate oxidative stress. C-Reactive Protein (CRP), Insulin assay, serum electrolytes (Na+, K+), TNF-α, IL-6 and INF-γ were also estimated. Isolated sciatic nerve was histopathologically studied to support the results. Results: Treatment with syringic acid (SY) 12.5, 25, 50 mg/kg and of Sinapic acid (SP) 5, 10, 20 mg/kg orally for 5 weeks has shown to reduce blood glucose level. Behavioural changes were found to be improved weekly by SY and SP in dose dependent manner. 5 weeks treatment with SY and SP was able to increase antioxidant GSH and reduce MDA level in cell. Gabapentin, SY and SP treated animals have shown decrease in TNF-α, IL-6 and INF-γ and CRP. Insulin and serum electrolytes were found to be normalised in treated groups. Histopathological study has revealed protective effect of gabapentin, SY and SP by showing reverted neuronal damage. Conclusion: In conclusion, syringic acid and sinapic acid have antihyperglycemic, antioxidant and neuroprotective effect in diabetic neuropathy.