Effect Of Rapamycin On NF-κB And MMP9Expression In Kidney Of STZ Induced Diabetic Juvenile Rats

Background and objective:Type1Diabetes mellitus (T1DM) accounts for about95%of childhood andjuvenile diabetes, is characterized by low or absent levels of endogenously producedinsulin and dependence on exogenous insulin therapy, formerly calledinsulin-dependent diabetes mellitus (IDDM). Diabetic nephropathy (DN) remains themost common cause of end-stage renal disease (ESRD)，is one of the chronicdiabetic microvascular complications. About30%-60%of patients with T1DMdevelop microalbuminuria within the10-20years following the onset of diabetes.Chronic Kidney Failure (CKD) generally appears15-20years after the onset ofmicroalbuminuria, seriously threatened human health. Recent studies have found thatextracellular matrix （ECM）remodeling is the main mechanism of diabetic renalpathological changes. Mammalian target of rapamycin (mTOR) signaling pathway,growth factors, oxidative stress, inflammatory reactions are involved in podocyteinjury and extracellular matrix accumulation. And as the critical ECM-degradingenzymes in vivo, Matrix metalloproteinases (MMPs) are also involved in thedevelopment of diabetic nephropathy. The imbalance of the synthesis and degradationof extracellular matrix eventually caused extracellular matrix remodeling, andcontributes to the progression of glomerular sclerosis in diabetic nephropathy. In thisexperiment, with streptozotocin (STZ)-induced diabetic rats as T1DM model toexplore the relationship between inflammation and the expression of MMP9of thekidney. With rapamycin intervention， investigate whether rapamycin can reducekidney damage by inhibiting inflammation, anti-ECM accumulation in diabetic rats.Method:1．Model and experimental grouping: Streptozotocin (STZ), at a dose of70mg/kg body weight dissolved in citrate buffer, was injected intraperitoneally toinduce diabetes. The animals were fasted for12hrs before the STZ injection.Seventy-tow hours and seven days after STZ injection, blood glucose level was checked using the glucometer. The animals with a blood glucose level of more than16.9mmol/L were considered diabetic and included in the study. The animals weresegregated into three groups with ten animals each. The groups included were controlrats (C), STZ induced diabetic rats (D), diabetic rats treated with rapamycin at a doseof1mg/kg.2day by intraperitoneal injection for4weeks (R). The rats of group C andD were received intraperitoneal injection of The same volume of saline for4weeks.2．Specimen Collection：Rats in each group were dealed with in six week.Collected urine samples with metabolic cages method. Collected blood and preparedRenal biopsy.3．Detection index: Blood glucose level was checked using the glucometer.serum creatinine，urea nitrogen，and Urinary protein concentration were detected byBeckman CX-9Automatic biochemical analyzer.24hUpro=Urinary proteinconcentration×24hour urine volume. Renal pathological changes wereobserved under light microscope by HE staining. MMP9, NF-κB p65was detected byimmunohistochemistry.Result:1．Random blood glucose of group D and R were obviously increased than groupC(P＜0.01）, but there were no significant difference between group D and R(P＞0.05). The KWI of group D and R were higher than group C(P＜0.01). Moreover, theKWI of group R were lower than the D group(P＜0.01).2.Scr, BUN and24-hour urine protein of group D and R were obviouslyincreased than group C(P＜0.01), group R were obviously decreased than group D(P＜0.01).3．Compare with group C, the expression of NF-κB of group D and R wereobviously increased (P＜0.01), group R were obviously decreased than group D (P＜0.01). The expression of MMP9of group D and R were obviously decreased thangroup C (P＜0.01)，group R were obviously increased than group D (P＜0.01).4．HE staining: Diabetic model group rats showed proliferation of mesangialcells, mesangial matrix expansion, basement membrane thickening, swelling renaltubule, luminal stenosis. But the Pathological changes of group R were significantlyreduced compared with group B. 5．KWI and24-hour urine protein are negatively associated with the expressionof MMP9.(r=－0.786,－0.731).6．The expression of MMP9and NF-κ B showed a negative correlation(r＝－0.722).Conclusion:1．Rapamycin has a significant protective effect to the kidney of STZ-induceddiabetic juvenile rats. The therapeutic potential of Rapamycin in the treatment ofdiabetic nephropathy as shown by the significant reduction of Scr, Bun and andproteinuria.2． Rapamycin could reduce NF-κB expression and inhibit inhibition ofinflammation in kidney of STZ-induced diabetic juvenile rats, and thenameliorates inflammation-induced renal injury.3．Rapamycin can up-regulate MMP9expressions, improve matrix degradationsand significantly ameliorated glomerulosclerosis and tubulointerstitial fibrosis.