| Background and purpose:Renal gluconeogenesis is substantially stimulated in patients with type 2 diabetes mellitus(T2DM),but the mechanism remains unknown.Renal gluconeogenesis is negatively regulated by insulin.Since T2DM is characterized by chronic subacute inflammation,however,inflammation is well known to induce insulin resistance,this study aimed to investigate whether enhanced renal gluconeogenesis in T2DM was partially resulted from renal inflammation-mediated insulin resistance.If so,whether inflammation inhibitor could partially reverse this change.Methods:1)Type 2 diabetic and normal kidney tissues were acquired for the detection of expression of inflammatory factors and the gluconeogenic enzyme.2)Eight-week old diabetic db/db(C57BLKS/J-LepRdb/LepRdb)mice and their non-diabetic littermates db/m(C57BLKS/J-LepRdb/+)mice were used in this study.Diabetic db/db mice were treated with 1 mg/kg NF-?B inhibitor parthenolide(PTN)or saline as control intraperitoneal every other day.After 12 weeks of treatment,blood,urine and kidney samples were collected for measurement.3)We extracted human proximal tubule primary epithelial cells(PTEC)to detect the regulation of insulin on expression of gluconeogenic gene and to detect whether inflammatory factors could directly induce PTEC insulin resistance.Results:1.Expression of NF-?B and Gluconeogenic Enzymes in T2DM Human Kidney Up-regulated expression of NF-?B and the gluconeogenic rate-limiting enzyme PEPCK could be detected in renal cortex of T2DM patients compared with the non-diabetic controls(p?0.05),but the expression of fructose 1,6-bis phosphatase(FBPase)and glucose 6 phosphatase(G6Pase)was not up-regulated.In addition,biopsies from T2DM patients revealed redistribution of FBPase and PEPCK to the lumen membrane of proximal tubule(PT).2.Results of animal experiments1)The 8-week-old db/db T2DM mice had already developed obesity,hyperglycaemia,insulin resistance(HOMA-IR)and hyperlipidemia in comparison with the control db/m mice(p<0.01).PTN could slightly reduce the blood glucose and HOMA-IR levels in db/db mice at the age of 16 and 20 weeks.However,there was no statistical significance.2)In db/db mice,the renal expression levels of NF-?B and its downstream inflammatory mediators,including intercellular adhesion molecule-1(ICAM-1),tumor necrosis factor alpha(TNF-a),and macrophage inflammatory protein 1 alpha(MIP-1?),were remarkably enhanced relative to those in db/m control mice(p<0.05).Additionally,PTN could down-regulate the renal expression of these inflammatory mediators in db/db mice(p<0.05).3)Consistent with the results in human kidney,db/db mice also displayed enhanced renal expression of PEPCK but not FBPase and G6Pase relative to the db/m mice((PEPCK,1.62±0.47 VS 1 ±0.03,p?0.05)).Moreover,redistribution of PEPCK and FBPase to lumen of PT could also be observed in the kidneys of diabetic mice.In addition,reduced insulin signaling as demonstrated by p-AKT and increased expression of downstream gene FOXO1 and PGC-1a were detected in the kidney of db/db mice compared with db/m mice((FOXO1,1.67±0.18VS1 ±0.31,p<0.05;PGC-1a,1.47±0,36VS1 ±0.09?p?0.05).Consistant with our hypothesis,treatment with NF-?B inhibitor PTN alleviated renal inflammation and insulin resistance in db/db mice.Moreover,it reduced the expression of PEPCK(1.62±0.47 VS 0.89 ±0.14,p?0.05),indicating that inflammation could be one of the triggers for insulin resistance and enhanced renal gluconeogenesis in db/db mice.3.Results of cell experimentsThe expression of gluconeogenic gene in PTEC is negatively regulated by insulin.TNF-a could directly induce PTEC insulin resistance.Conclusion:In summary,our studies demonstrated for the first time that renal inflammation-mediated insulin resistance contributed to enhanced renal gluconeogenesis in db/db mice.This work helps to elucidate the pathophysiological association among inflammation,insulin resistance and enhanced renal gluconeogenesis in type 2 diabetes,and may yield a novel target for hyperglycemia. |
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