| Objective: Diabetes mellitus(DM)is a group of autoimmune,metabolic and genetic diseases characterized by hyperglycemia.About 90% of diabetic patients are T2 DM patients.The main pathological features of T2 DM are insulin resistance(IR)and ? cell dysfunction.Thus,improving IR and ? cell dysfunction is an effective way to prevent and treat T2 DM.Pancreatic duodenal homeobox(PDX1)is a key transcription factor in mature islet ? cells,which plays an important role in maintaining the phenotype of mature ? cells and normal insulin secretion.The expression of PDX1 was decreased when the body was in hyperglycemia for a long time.IR and insulin secretion can be improved by increasing PDX1 expression in T2 DM rats.Evidence has showed that histone acetylation modification is involved in the regulation of PDX1 expression.And Histone deacetylases(HDACs)are the key enzymes that affect histone acetylation modification.Among all the subtypes,HDAC2/3 is most closely related to T2 DM,and histone deacetylases level(Ace-H3K9)in T2 DM patients was decreased.It has been proved that HDAC2 can be combined with PDX1 to inhibit the transcription of insulin gene,and HDAC3 is highly homologous with HDAC2.Whether inhibition of HDAC3 can up regulate the expression of PDX1 in pancreas is unclear.GABA is a natural food ingredient and an important inhibitory neurotransmitter in the central nervous system of mammals.Islet ? cell can produce GABA,and evidence showed that the synthesis of GABA in T2 DM patients was reduced.T2 DM can be imporved by taking GABA orally.GABA can also up-regulate the expression of PDX1 and promote insulin secretion.In addition,we have found that GABA can inhibit HDAC2/3 in nerve cells and fat cells.However,whether GABA can antagonize T2 DM by inhibiting HDAC2/3 remains to be confirmed.In this study,high fat diet(HFD)combined with streptozocin(STZ)was used to establish T2 DM model,in order to explore the anti-T2 DM effect of GABA and its possible mechanism.The results can provide theoretical basis for further explaining the pathogenesis of T2 DM and exploring the effective prevention and treatment of T2 DM.Methods:The male C57/BL6 mice were divided into HFD+STZ group and normal diet group.The mice in the HFD+STZ group were fed a high-fat diet(60% fat energy ratio).After 4 W,STZ(100mg/kg.bw)was injected once.Fasting blood glucose was measuredafter 4 W.when the fasting blood glucose was greater than 7.8 mM,the model was established successfully.The mice in the control group were fed a normal diet,intraperitoneal injection of the same dose of citrate buffer,other conditions were as same as HFD+STZ group.Then HFD+STZ group were divided into T2 DM group and T2DM+GABA group,normal diet group were divided into control group and GABA group.T2DM+GABA group and GABA group were given water containing 2g/L GABA,other two groups were given pure water.The treatment lasted for 4 W,and the fasting blood glucose,body weight,water and food intake were measured every week.The fasting serum insulin level was detected by ELISA and the insulin resistance index was calculated by Home-IR.PDX1 and HDAC2/3 expression were detected by qRT-PCR and Western blot.Western Blot to measure Ace-H3K9 levels.The expression of insulin,PDX1 and the number of ? cells were detected by immunofluorescence.Spss20.0 was used to establish the database and make statistical analysis.The difference was statistically significant at P< 0.05.Results:1.During the establishment of the model,the food intake in HFD + STZ group was higher than that in normal diet group(P< 0.05,P< 0.01);the water intake in HFD+STZ group was lower than that in normal diet group at 1-6 W,and higher than that in normal diet group group at 7-8 W(P< 0.05,P< 0.01);the body weight in HFD + STZ group was higher than that in normal diet group at 2-8 W(P< 0.05,P< 0.01);the fasting blood glucose in the HFD+STZ group was higher than that in the ordinary feed group at5-8 W(P< 0.01).2.During the intervention period,the food intake in T2 DM group was higher than that in the control group(P< 0.01),and the food intake in T2DM+ GABA group was lower than that in T2 DM group(P< 0.01);the water intake in T2 DM group and T2DM+GABA group was higher than that in control group(P< 0.01),while the water intake in T2DM+GABA group was lower than that in T2 DM group(P< 0.01);there was no statistically significant in the weight change of mice in each group(P> 0.05).3.The fasting blood glucose in T2 DM group was higher than that in control group(P< 0.01),and the fasting blood glucose in T2DM+GABA group was higher than that in control group and lower than that in the T2 DM group(P< 0.05,P< 0.01).There was no statistically significant difference between the serum insulin levels of mice in each group(P> 0.05);the insulin resistance index of T2 DM group and T2DM+GABA groupthan control group(P< 0.01),and the insulin resistance index of T2DM+GABA group was lower than T2 DM group(P< 0.01);the insulin expression and islet ? cell number in pancreas tissue in T2 DM group were lower than those in control group(P< 0.01),and the insulin expression and islet ? cell number in pancreas tissue in T2DM+GABA group were higher than those in T2 DM group(P< 0.05,P< 0.01).4.The expression of PDX1 mRNA in the pancreas of GABA group was higher than that of control group,while PDX1 mRNA and protein expression in the pancreas of T2 DM group and T2DM+GABA group was lower than that of control group(P< 0.01),and PDX1 mRNA and protein expression in the pancreas of T2DM+GABA group was higher than that of the T2 DM group(P< 0.05,P< 0.01).The results of immunofluorescence showed that the expression of PDX1 in T2 DM group and T2DM+GABA group was lower than that in the control group(P< 0.01),and the expression of PDX1 in T2DM+GABA group was higher than that in T2 DM group(P< 0.01).5.The expression of HDAC2 mRNA and protein in the pancreatic tissue of GABA group was higher than that of control group(P< 0.01),and the expression of HDAC2/3 mRNA and protein in the pancreatic tissue of T2 DM group was higher than that of control group(P< 0.01),and the expression of HDAC2/3 mRNA and protein in the pancreatic tissue of the T2DM+GABA group was lower than that of T2 DM group(P< 0.01).6.The Ace-H3K9 level in the pancreatic tissue of T2 DM group was lower than that of control group(P< 0.01).The Ace-H3K9 level in the pancreatic tissue of T2DM+GABA group was higher than that of T2 DM group(P< 0.01).Conclusions: GABA possesses effects in alleviating the IR and up-regulating PDX1 expression in pancreas of T2 DM model mice.The inhibition of HDAC2/3 and upregulation of histone acetylation by GABA may be involved in the mechanism of GABA on antagonizing the Type 2 diabetes. |
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