The Protective Effect Of Traditional Chinese Medicine Jingmaitong On Myelin Sheath And Gut Microbiota In Streptozotocin-induced Diabetic Rats

[Objective]Jinmaitong(JMT)is a Chinese herbal formula for treating diabetic peripheral neuropathy(DPN).The present study aims to evaluate the myelin and axon damage caused by hyperglycemia in DPN rats,and explore the potential neuroprotective effect of JMT by modulating gut microbiota associated with DPN phenotypes and neuregulin 1(NRG1)levels.[Methods]Streptozotocin(STZ)-induced diabetic rats were treated with JMT(13.9 g/kg/d)or Neurotropin(NTP,1.6 NU/kg/day)or distilled water(10 mL/kg/day)by oral gavage for 12 weeks.Non-fasting blood glucose level and body weight were monitored every four weeks during the experiment.The mechanical withdraw threshold tests were performed before sacrifice,and morphological changes on sciatic nerves were observed by light and transmission electron microscopes.Intraepidermal nerve fiber densities(IENFD)were measure by inmmunostaining of protein gene product 9.5(PGP 9.5)in plantar skin.Fecal samples were collected for gut microbiota analysis via high-throughput 16S ribosomal RNA gene sequencing,and serum was collected for NRG 1 measurement by enzyme-linked immunosorbent assay.Immumohistocheinistry was used to investigate contactin-associated protein(Caspr)and amyloid precursor protein(APP)expressions.The abundance of identified gut microbiota species and DPN phenotypes were ananlysed by Spearman correlation.[Results]JMT reversed the decreased mechanical withdraw threshold(P<0.001)and intraepidermal nerve fiber density(P<0.05)in diabetic rats,with no significant effect on body weight and non-fasting blood glucose levels(P>0.05).Meanwhile,JMT improved neurological morphology of sciatic nerves by increasing numbers of myelinated axons(P<0.05)and reducing percentages of abnormal fibers(P<0.001),accompanied by up-regulated Caspr positive paranodes numbers and percentages and down-regulated percentages of heminodes and APP colocalization with ??-tublin axons in the sciatic nerves of diabetic rats(P<0.05).Importantly,JMT rescued the gut dysbiosis in DPN rats by enriching the Actinobacteria and Proteobacteria at phylum level and Actinobacteria at class level,which were associated with DPN phenotypes and serum NRG1 levels(P<0.05).[Conclusion]JMT exerts a myelination and neuroprotective effect via the modulation of gut microbiota associated with DPN phenotypes and serum NRG1 levels in STZ-induced diabetic rats,suggesting the therapeutic application of JMT for DPN prevention and treatment.[Innovation]This study identified differences in gut microbiota composition between DPN rats and normal control rats and to report that JMT exerts neuroprotective effects by modulating gut microbiota for the first time.The relationship between the identified bacterial taxa and DPN phenotypes and NRG1 levels provides new scientific evidence for the clinical application of JMT in treating DPN patients.