| Diabetes is a metabolic disease characterized by high blood glucose levels.The global prevalence of adult diabetes and impaired glucose tolerance has been increasing as people’s lifestyles change,which has become one of the fastest growing challenges to global public health in the 21 st century.According to the International Diabetes Federation,the number of adults with diabetes reached 537 million worldwide in 2021,an increase of 16% compared to 2019.Diabetes is expected to affect 643 million adults by 2030.The existing synthetic anti-diabetic drugs have some limitations.They do not completely reverse the course of its complications and also show significant side effects.In recent years,natural product functional molecules have been developed with great potential due to the advantages of multi-target and multi-signaling pathway network modulation.Oats(Avena sativa L.)are annual herbs that are widely cultivated on a large scale and are one of the oldest crops known to human civilization.As one of the world’s top ten superfoods,oats are rich in various phytochemicals such as proteins,β-glucan,alkaloids,lipids and phenols,which have shown strong biological functions in enhancing body functions,regulating immunity and anti-diabetic.Among them,β-glucan is the main active ingredient with high content in oats.Studies have shown that oat β-glucan may reduce the risk of cardiovascular disease and type Ⅱ diabetes.However,the potential molecular mechanism by which oat β-glucan exerts its anti-diabetic effect is not clear.In this study,the ameliorative effect of oat β-glucan on diabetes and its possible molecular mechanism were firstly investigated,which provided a theoretical basis for the application of oat β-glucan in the prevention and clinical treatment of diabetes.Subsequently,the effect of lnc RNA 495810 on diabetic nephropathy and the intervention effect of oat β-glucan were discussed.The main results obtained are as follows:(1)The effect of oat β-glucan on ameliorating type Ⅱ diabetes.After the intervention of oat β-glucan in type Ⅱ diabetic mice,fasting blood glucose,glucose tolerance and abnormal lipid levels were significantly improved.We also found that oat β-glucan improved abnormal liver function indexes through increasing glycogen content in mice,which in turn delayed the liver damage caused by glycolipotoxicity.In addition,pancreatic pathological analysis showed that oat β-glucan had better protective effects on pancreatic and islet cells in diabetic mice.(2)Serum untargeted metabolomics examined the effects of oat β-glucan on serum metabolites in type Ⅱ diabetic mice.The results showed that the metabolic profile was remarkably changed after oat β-glucan intervention in diabetic mice.88 and 106 differential metabolites were screened in negative ion mode and positive ion mode,respectively.Oat β-glucan significantly affected the serum metabolites of amino acids,organic acids and bile acids.High serum concentration of L-phenylalanine in diabetic mice may disrupt signal transduction via reducing insulin sensitivity,leading to impaired phenylalanine metabolism.Oat β-glucan significantly reduced L-valine levels in BCAAs.In energy metabolism,oat β-glucan ameliorated diabetic impairment by increasing the expression of TCA circulating metabolites hippuric acid and succinic acid to meet energy requirements and promote insulin secretion.In addition,we found that oat β-glucan significantly inhibited deoxycholic acid levels,suggesting that oat β-glucan may improve type Ⅱ diabetes by regulating bile acid metabolism to increase insulin sensitivity.(3)Oat β-glucan improves type Ⅱ diabetes by regulating the TLR4/PI3K/AKT metabolic axis.On one hand,oat β-glucan increased glycogen content,decreased GS phosphorylation,and increased GSK3β phosphorylation through PI3K/AKT/GSK3-mediated GS activation to promote glycogen synthesis.On the other hand,oat β-glucan inhibited gluconeogenesis by decreasing PI3K/AKT/Foxo1-mediated reduction of PEPCK.Moreover,oat β-glucan enhanced gluconeogenesis via increasing the protein levels of COQ9,UQCRC2,COXIV and ATP5 F complexes involved in oxidative phosphorylation and TFAM,a key regulators of mitochondrial gene expression.These results suggest that oat β-glucan maintains glucose homeostasis by promoting glycogen synthesis,glucose catabolism and inhibiting gluconeogenesis.(4)How does oat β-glucan,as a macromolecular complex,enter the cell and perform its function? TLR4 is known to be an important polysaccharide receptor that exerts physiological functions by recognizing different polysaccharides.And PI3K/AKT,as a downstream signaling molecule of TLR4,plays an important role in cellular metabolism.Results showed that TLR4 expression was higher in high glucose-induced Hep G2 cells,p-PI3 K and p-AKT were significantly down-regulated.In contrast,p-PI3 K and p-AKT were up-regulated after oat β-glucan treatment.These data suggest that oat β-glucan may maintain cellular glucose homeostasis through TLR4 receptor and PI3K/AKT intracellular signaling pathways.Immediately after,we further validated the potential function of TLR4 in the regulation of hepatic glucose homeostasis by oat β-glucan through antibody blockade assay.Results showed that blocking TLR4 with anti-TLR4 antibody in high glucose induced Hep G2 cells reduced the increased hepatocyte glucose consumption by oat β-glucan treatment,and also abrogated the expression of p-PI3 K,PI3K,p-AKT and AKT,p-GSK3β,TFAM and oxidative phosphorylation-related proteins induced by oat β-glucan.These data reveal that oat β-glucan maintains hepatic glucose homeostasis through TLR4-mediated intracellular signaling.(5)Oat β-glucan ameliorates diabetic nephropathy via lnc RNA 495810.The results showed that lnc RNA 495810 was widely distributed in the heart,liver,lung,spleen and kidney of diabetic nephropathy mice.LncRNA 495810 expression in the kidney of diabetic nephropathy mice was 11 times higher that of the normal group.In vitro experiments revealed that CD2 AP,target proteins Podocin and Nephrin were decreased,Ccl-2,IL-1β,MCP and TGFβ1 were significantly up-regulated,and the lnc RNA 495810 expression was also significantly increased in high glucose-induced podocytes.These results suggest that lnc RNA 495810 is closely related to the occurrence of diabetic nephropathy.Then,we specifically knocked down lnc RNA495810 in podocytes to assess its effect on the development of diabetic nephropathy.Results showed that lnc RNA 495810 knockdown significantly reversed the inhibitory ability of high glucose on Podocin,Nephrin and CD2 AP in podocytes and down-regulated the expression of IL-1β,Ccl-2 and TGFβ1.CCK8,platelet clone formation and Annexin V-PE/7-AAD double-stained apoptosis assays revealed that lnc RNA 495810 knockout promoted the proliferation of podocytes.Mass spectrometry combined with RNA pull down,RIP and q PCR experiments showed that lnc RNA 495810 justice strand binds to hn RNPA1 and hn RNPA2B1.Enrichment analysis revealed that the genes distributed in biological processes were mainly associated with metabolism.LncRNA 495810 knockdown did not significantly differ on the expression of key enzymes of glycolysis and TCA cycle.Protein levels of UQCRC2,COXIV and ATP5 F complexes involved in oxidative phosphorylation,as well as TFAM,a key regulator of mitochondrial gene expression,were up-regulated after the knockout of lnc RNA 495810.These results suggest that lnc RNA 495810 is involved in glucose metabolism in diabetic nephropathy podocytes.Finally,we found that oat β-glucan significantly inhibited the lnc RNA 495810 expression,up-regulated the expression of target proteins,promoted the podocytes proliferation and restored mitochondrial function in diabetic nephropathy podocyte.In conclusion,oat β-glucan could improve glucose tolerance,dyslipidemia and insulin resistance,and alleviate liver and pancreatic lesions in type Ⅱ diabetic mice.Oat β-glucan maintains hepatic glucose homeostasis through TLR4-mediated intracellular signaling.On one hand,oat β-glucan increased hepatic glycogen content and promoted gluconeogenesis through PI3K/AKT/GSK3-mediated GS activation.and gluconeogenesis was inhibited by down-regulating PI3K/AKT/Foxo1-mediated reduction of PEPCK.On the other hand,oat β-glucan promoted gluconeogenesis through increasing the expression of proteins associated with oxidative phosphorylation.In addition,oat β-glucan promoted the proliferation of diabetic nephropathy podocytes and restored mitochondrial function by upregulating the expression of target proteins through suppressing the lnc RNA 495810 expression.This study provides a theoretical basis for the molecular mechanism of oat β-glucan to improve type Ⅱ diabetes. |
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