Clinical Study And Metabolomic Analysis Of Insulin Resistance In Chronic Kidney Disease

Background and objectives:Insulin resistance(IR)is common in patients with chronic kidney disease(CKD).IR not only accelerates the progress of kidney disease,but also is a risk factor for cardiovascular disease among CKD patients.However,the researches on the relationship between CKD and IR are not thorough enough.The subjects are mainly included the whole CKD population,few studies are conceemed about CKD patients with different pathological types and medications.Furthermore,the specific pathogenesis of insulin resistance in CKD is unclear.Recently,metabolomics developed to provide a more direct method of research from the physiological status to the pathological status.It can be applied to the study of the complex pathophysiological changes in kidney disease and may broaden the ideas about the pathogenesis of IR in CKD.In this work,firstly the analysis of insulin resistance in different pathologic types and medical treatments is done clinically.Then,to look for abnormal metabolic pathways,the law of changes of metabolites in serum,liver and muscle tissue of rats with IR induced by CKD or by high-fat diet are analyzed by metabolic profiling.Methods:(l)The patients with CKD stage 1-3 in Chinese PLA General Hospital from August 2014 to April 2015 were screened.The clinical data and laboratory tests between two groups of patients with IgA nephropathy(IgAN)and membranous nephropathy(MN),which were two of the most common pathologic types in CKD,and those who used glucocorticoids that affect blood glucose and who did not,were analyzed and compared the differences of insulin resistance.(2)Male Sprague-Dawley(SD)rats were randomly divided into operation group and sham operation group.The operation group was subjected to 5/6 two-step subtotal nephrectomy and then randomly divided into four groups after two weeks:sham Operation+standard chow diet group(Sh?SCD),subtotal nephrectomy+standard chow diet group(Nx?SCD),sham operation+60%kcal high fat diet group(Sh+HFD),subtotal nephrectomy+60%kcal high fat diet group(Nx+HFD).During 16 weeks of feeding,the body weight,blood urea,creatinine,urinary protein,blood lipids,fasting blood glucose,insulin,visceral fat weight,and pathological changes of kidney,liver,pancreas,subcutaneous adipose and brown adipose tissue were observed.Additionally,insulin sensitivity was evaluated by calculating HOMA-IR and intraperitoneal glucose tolerance test.(3)The metabolic profiles of serum,liver muscle tissue samples from four groups of rats were acquired by UPLC-MS.Differential expression of metabolites were identified by multivariate statistical analysis and their related metabolic pathways were analyzed.Results:(1)Compared with MN group in CKD stage 1-3,IgAN group had significantly lower eGFR(80.30±24.99ml/min·1.73m2 versus 98.09±23.96ml/min·1.73m2,P<0.001)and higher HOMA-IR(1.86±0.99 versus 1.33±0.72,P<0.001).Multivariate logistic regression analysis indicated that BMI was an independent risk factor for IR in patients with IgAN.In CKD stage 1-3,the levels of HOMA-IR(2.14 vs 1.76,P<0.01),TC(5.78±2.06 versus 5.27±2.02,P<0.05)and HDL(1.61±0.57 versus 1.16±0.39,P<0.001)were significantly higher in patients with oral glucocorticoids than in those untreated.(2)Compared with Sh+SCD group,blood urea and creatinine were increased by 2-3 times(P<0.05),fasting blood insulin,HOMA-IR,blood lipids were also increased and area under the curve of IPGTT was elevated significantly in Nx two groups at 1sth week after nephrectomy.In addition,renal pathology showed focal glomerulosclerosis,renal tubular atrophy,tubulointerstitial inflammatory cell infiltration and fibrosis in Nx groups.Compared with Sh?SCD group,the visceral fat weight,fasting blood glucose(7.14±0.51 versus 5.33±0.60,P<0.01),insulin concentration(2.08±0.67 versus 0.68±0.27,P<0.05),HOMA-IR(16.39±5.73 versus 4.09±1.77,P<0.01),and area under the curve of IPGTT were all significantly increased in Sh?HFD group.The changes of Nx+HFD group were similar to those of Sh+HFD group but more obvious.(3)Compared with control,ninety-five differential expression of metabolites in serum,fifty-nine ones in liver tissue and forty-one ones in muscle tissue from rats of CKD concurrent IR were identified.Fifty-eight differential expression of metabolites in serum,thirty-eight ones in liver tissue,and seventeen ones in muscle tissue from rats of high-fat induced IR were also discovered.These metabolites were involved in amino acid metabolism,lipid metabolism,glucose metabolism,nucleic acid metabolism,vitamin and cofactor metabolism.CKD rats,however,had significantly abnormal metabolic pathways in tryptophan metabolism,arginine metabolism and metabolite of TMAO when compared with HF rats.The changes of differential metabolites between CKD-related IR and HF-induced IR were almost in the opposite direction,suggesting IR in CKD and HF may have different pathogenesis.Conclusion:IgAN patients were more likely to have insulin resistance compared with MN patients in CKD stage 1-3;CKD patients with administration of glucocorticoids were prone to insulin resistance and lipid metabolic disturbance;CKD-related IR rat model were successfully established at 18th week after 5/6 subtotal nephrectomy,and high-fat induced IR rat model were successfully established after high-fat diet for 16 weeks.Compared with HF rats,CKD rats showed significant abnormalities in tryptophan metabolism,arginine metabolism and metabolite of TMAO.