| Objective To investigate the effects and mechanisms of dietary flaxseed oil(FO)rich in α-linolenic acid(ALA)on type 2 diabetes mellitus(T2DM)in rats.Methods Firstly,SD rats were randomly allocated into four groups(n=10/group): negative control group(PF/CO),model group(DM/CO),positive control group(PF/FO)and intervention group(DM/FO).A diabetic rat model was successfully generated by a single intraperitoneal injection of streptozotocin-nicotinamide(STZ-NA).During the experimental period,body weight(BW)and fasting blood glucose(FBG)were monitored weekly.The feces of rat were collected after 5 weeks of feeding.16 S rRNA hypervariable sequencing was aimed to detect the diversity and abundance of gut microbiota among diverse groups.Quantification analysis of fecal short chain fatty acids(SCFAs)was performed using gas chromatographymass spectrometry(GC-MS).After 5 weeks of intervention,rats were euthanized and plasma/serum and tissue samples were collected to detect associated indications.(1)Plasma glycated hemoglobin(GHb),insulin(INS)and inflammatory cytokines(IL-6,IL-17 A,IL-1β,TNF-α,IL-10)concentrations in each group were measured using the enzyme linked immunosorbent assay(ELISA)kits.(2)Blood lipid levels in each group were respectively assessed using automatic biochemical analyzer.(3)Malondialdehyde(MDA)levels and total superoxide dismutase(SOD)activity in each group were respectively determined with kits.(4)Limulus amebocyte lysate test was used to measure the levels of plasma lipopolysaccharide(LPS)in rats.(5)The levels of MDSCs in peripheral blood and spleen were detected by flow cytometry.(6)Additionally,the expressions of ZO-1,Occludin and Claudin-3 protein in intestine of each group were measured by western blot.(7)Spearman correlated analysis was performed to detect the correlation between plasma inflammatory factors and gut microbiota,and then Pearson correlated analysis was performed to detect the correlation between plasma inflammatory factors and SCFAs in SD rats.Results The BW of DM/CO group were notably decreased compared with that in PF/CO group.In addition,the levels of FBG,GHb and blood lipid in DM/CO group were higher than that in PF/CO group.However,BW,FBG,GHb and blood lipid levels in T2 DM rats were significantly ameliorated after 5 weeks of FO intervention.In our study,the MDA content was dramatically increased and SOD activity was significantly decreased in model group.Feeding of diabetic rats with FO dramatically increased SOD activity compared to model group.However,serum MDA levels were significantly decreased.Our results showed that the levels of plasma pro-inflammatory indicators including IL-1β,IL-6,IL-17 A,TNF-α and LPS in DM/CO group were significantly increased compared to PF/CO group,respectively.However,after the intervention of FO,the above-mentioned pro-inflammatory indicators were significantly decreased.But anti-inflammatory cytokine IL-10 production was not statistically significant in diverse group.Compared with PF/CO group,the proportions of MDSCs in peripheral blood and spleen of DM/CO group were significantly increased.And then the number of MDSCs in peripheral blood and spleen was also significantly increased after FO treatment.In DM/CO group,compared with PF/CO group,the rats intestinal Firmicutes was significantly increased while the relative abundance of Bacteroidetes was dramatically reduced at phylum level.In addition,the proportion of Blautia in DM/CO group was higher than that in PF/CO group.In contrast,the proportion of Alistipes was decreased in DM/CO group compared to PF/CO group by sequencing of gut microbiota.A reduction in the relative abundance of Firmicutes and Blautia,as well as an elevation of Bacteroidetes and Alistipes in DM/FO group compared to DM/CO group.And then the proportion of Tyzzerella was decreased after FO treatment.But it showed no significant difference in diverse group.Spearman correlation analysis revealed that the relative abundance of Firmicutes and Blautia were positively correlated with IL-1β,TNF-α,IL-6 or LPS,respectively.Additionally,Bacteroidetes and Alistipes were negatively correlated with TNF-α or LPS.Similarly,the expression of tight junction protein including ZO-1,Occludin and Claudin-3 in DM/FO group were significantly increased compared to DM/CO group.The fecal concentrations of SCFAs(acetic acid,propionic acid and butyric acid)were analyzed by GC-MS.The results showed that amount of acetic acid,propionic acid and butyric acid of the DM/CO group was decreased compared with that of the PF/CO group,but propionic acid and butyric acid were no significant difference between the two groups.However,the above-mentioned SCFAs in DM/FO group were significantly increased compared with that of the DM/CO group.SCFA concentrations were negatively correlated with inflammatory cytokines(IL-1β,IL-6,IL-17A).Conclusion Dietary FO rich in ALA ameliorates T2 DM via suppressing inflammation and modulating gut microbiota/SCFAs in rats. |
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