Study On The Effects And Associated Mechanisms Of Inulin On Peripheral Neuropathy Of Diabetes In Mice

Objective To investigate the protective effects and associated mechanisms of inulin（INU）on alleviation of peripheral neuropathy of type 2 diabetes（T2DM）via anti-inflammation and modulating gut microbiota in db/db mice.Methods 1.Female db/db mice（4 weeks）were adopted to generate a T2 DM model.The experiment was divided into three groups: normal control group（control）,diabetic group（DM group）,and inulin intervention group（INU/DM group）.Fasting blood glucose（FBG）of each mouse from diverse groups was monitored daily from the week 6.Glucose tolerance tests were performed 3 times.Mice with fasting blood glucose ≥11.1mmol/l were defined as the diabetic group（DM group,n=30）.Fifteen mice from the DM group were randomly as allocated into inulin intervention of DM group（INU/DM group）.Fifteen female C57BL/6J mice（4 weeks）were adopted as control group（control）.Inulin was orally administered 5%（wt/wt）to the treated groups（n=15）,and equal volume of normal saline was orally administered to the untreated groups（n=15）.2.Body weight and blood glucose changes in each group were monitored regularly.After inulin treatment 6 weeks,the alteration of glycated hemoglobin（GHb）,serum triglycerides,total cholesterol,plasma LPS levels,plasma IL-6,IL-17 A,TNF-α and IL-10 concentrations in each group were measured.The 16SV3+V4 region amplicon sequencing was used to analyze the composition and diversity of gut microbiota in each group after inulin intervention in 6 weeks.3.To investigate the peripheral nerve function of each group,changes in the pain threshold latency of each group mice were monitored by von Frey filament test and radiant heat test,respectively.The electrophysiological changes of the sciatic nerve in each group were detected by BL-420 S biological function system.Pathological changes of sciatic nerve tissue were observed by transmission electron microscopy and H&E staining in each group.Additionally,the expression of MBP protein and P0 protein in sciatic nerve of each group were observed by western blot.Results 1.Dietary inulin significantly reduced FBG,body weights（BWs）,glycated hemoglobin（GHb）,blood lipid,plasma lipopolysaccharide（LPS）,interleukin（IL）-6,tumor necrosis factor（TNF）-α and IL-17 A in INU/DM group（P<0.05）.However,IL-10 showed no significance in INU/DM group,compared with DM group（P>0.05）.2.Sequencing analysis of the gut microbiota showed that an elevation of Tenericutes（P<0.01）and Mucispirillum（P<0.05）,a reduction of Bacteroides and Alloprevotella in DM group（P<0.05）,compared with control group.Similarly,an increase of Cyanobacteria and Bacteroides,as well as a decrease of Deferribacteres,Tenericutes and Ruminiclostridium₆ in INIU/DM group,compared with DM group（P<0.05）.Correlation analysis revealed that Cyanobacteria and Bacteroides were positively correlated with IL-10;Deferribacteres,Tenericutes and Ruminiclostridium₆ were closely related to IL-6,TNF-α or IL-17 A respectively.Additionally,Ruminiclostridium₆ was positively correlated with LPS.3.Inulin intervention can effectively alleviate the pathological damage,demyelination and axonal degeneration of sciatic nerve in T2 DM mice.Compared with that in control group,the mechanical tingling reflex threshold,thermal radiation contraction reflex latency,sensory nerve conduction velocity and sensory nerve action potential amplitude were significantly decreased in DM group.The ultrastructure and histopathology of the sciatic nerve showed that the medullary fibrous lamellar structure disorder,vacuolar edema and axonal degeneration,compared to DM group.Similary,the expression of myelin basic protein（MBP）and myelin protein（P0）in the sciatic nerve were significantly reduced.The above results suggested that there was severe sciatic nerve injury in T2 DM mice.The above indexes of the INIU/DM group were significantly improved after inulin intervention,compared with that in DM group（P<0.05）.Conclusion Dietary inulin alleviated peripheral neuropathy of T2 DM via suppressing inflammation and modulating gut microbiota.