Energy metabolism changes of renal cortex in a rat model of progressive kidney disease and its mechanisms / 中华肾脏病杂志

ABSTRACT

Objective To explore the changes of renal cortical energy metabolism and its related molecular mechanisms in rats with progressive kidney disease.Methods A rat model of 5/6 nephrectomy was established as the model of progressive nephropathy.Rats were divided into surgical group (5/6Nx group) and sham-operated group (Sham group).Respectively,the rats were sacrificed at 1 week and 12 weeks after completing the model,and their blood,urine sample and kidney specimens were collected.Blood urea nitrogen,serum creatinine and 24 h urine protein were used to evaluate the renal function.Pathological changes in renal tissue were detected by PAS staining and Sirius red staining.The renal cortical energy metabolites were made quantitative analysis by liquid chromatography-mass spectrometry-based targeted metabolomics.The mRNA expressions of inflammatory cytokines (IL-6,IL-1β),fibrosis factors (fibronectin,collagen-1),glycolytic and tricarboxylic acid (TCA) cycle related enzymes were confirmed by real-time PCR.The protein expressions of fibrotic proteins (fibronectin,collagen-1),silent information regulator 1 (SIRT-1) and liver kinase B1 (LKB1) were tested by Western blotting.Results Compared with those in Sham group,the renal function indexes increased,the renal tissue pathological damage was obvious,the mRNA expressions of renal cortical inflammatory and fibrosis factors increased,and fibrotic proteins also increased in 5/6Nx group rats at 1 week and 12 weeks (all P ＜ 0.05),meanwhile,kidney damage worsened over time.Compared with those in Sham group,in the renal cortex of 5/6Nx group glycolytic metabolite lactate,the TCA cycle metabolites (citrate,isocitrate,oxaloacetate) and the oxidized phosphorylation metabolite reduced coenzyme Ⅰ were up-regulated (all P ＜ 0.05),but adenosine triphosphate (ATP) was no change at 1 week,then the abnormal metabolites increased further at 12 weeks,such as the down-regulation of pyruvate,oxidized coenzyme Ⅰ and ATP (all P ＜ 0.05).The pentose phosphate pathway metabolites (reduction and oxidized coenzyme Ⅱ) shows no statistical significant difference in the two group (all P ＞ 0.05).Compared with those in Sham group,in the 5/6Nx group the mRNA expressions of glycolytic enzyme hexokinase 2 and lactate dehydrogenase a were upregulated in the renal cortex at 1 week,whereas the mRNA expressions of pyruvate dehydrogenase α,pyruvate dehydrogenase β and succinate dehydrogenase of the TCA cycle related enzymes were downregulated (all P ＜ 0.05).Meanwhile,renal abnormal metabolic enzyme mRNA expressions were further increased in the 5/6Nx group at 12 weeks.The protein levels of SIRT-1 and LKB1 were not significantly different in the renal cortex of two group rats at 1 week,while SIRT-1 and LKB1 levels decreased in 5/6Nx group than those in Sham group at 12 weeks (all P＜ 0.05).Conclusions During the progression of nephropathy,rats accompanied with renal fibrosis and inflammatory have energy metabolism changes in the renal cortex which accompanies.The features of metabolic changes are manifested as enhanced glycolysis and decreased oxidative phosphorylation,which is aggravated gradually.Its mechanism is related to the inhibition of energy-regulating proteins LKB1 and SIRT-1.