The Effectiveness Of Duodenal-Jejunal Bypass On Renal Function In A Type2Diabetic Nephropathy Rat Model

PART I THE ESTABLISHMENT OF RAT MODELS OF TYPE2DIABETIC NEPHROPATHYBackgroundDiabetic nephropathy is a leading cause of end-stage renal disease, and its incidence is increasing worldwide. More than ninety percent of them are type2diabets mellitus.Once diabetic nephropathy becomes overt, there is no curative therapy, and most patients eventually progress to end-stage renal disease.Animal models of diabetic nephropathy is wildly used to investigate diabetes and the complications. Although numerous animal models have been established in rodents and these diabetic animals develop kidney disease that resembles human disease, no single animal model develops renal changes identical to those seen in humans. Therefore, to fully investigate the disease pathogenesis, appropriate animal models are essential.MethodsThirty SD rats were randomly divided into three groups:the control group(CON), model group(MOD) and the singal-nephrectomy group(NEP). A high fat diet(HFD) and standard diet (STD) were provide. In the NEP group, all rats were treated with singal-nephrectomy. One week later, all rats were fed on HFD for4weeks,and then rats of CON received STD. Rats of MOD and NEP were treated with STZ to induce hyperglycemia. After three days, random blood glucose was measured in duplicate from tail vein blood. Rats with random blood glucose>16.7mmol/L were considered to have diabetes established. At week12, the MOD and NEP group were treated with surgery, while the control group did not undergo any experimental manipulations. All rats were then observed for4weeks post operatively. Body weight, food intake and random blood glucose were measured every week preoperatively and postoperatively. Blood samples were collected from the tail vein and the serum creatinine, Cys_C levels, fasting TC and TG levels were measured. Individual rats were placed in metabolic cages to obtain urine collections. Then the urine volume (Vu), urine creatinine (Cu), and UAER were measured and the GFR was calculated by equation.ResultsThe total mortality of MOD and NEP group were25%and66.67%and the operative mortality were18.18%and55.56%。The features of DM were observed either in MOD group or in NEP group. The serum creatinine levels in NEP group were significantly higher than in CON group at week8, week12and week16. The TC and TG levels in MOD and NEP groups were significantly higher than in CON group at week8and week12. The urine creatinine levels in MOD and NEP groups were significantly lower than in CON group at week12and16. No significant was found within MOD and NEP groups. The urine albumin excretion rate was ascending at week8in NEP group and week12in MOD group.The UAER level in NEP group was significantly higher than in MOD group at week8,12and16.The GFR was ascending at week8in MOD and NEP groups and was significantly higher in NEP group than in MOD group at week8,12and16.ConclusionThe rat model of DN through high fat diet and low dose of STZ injection was representing high UAER and GFR8weeks after STZ injection. While the NEP model represented at4weeks after injection. The NEP method uses less time to establish a DN model. The two models represented similar tendency in blood glucose, UAER and GFR levels even after surgery was performed. While further and long-term research is still needed for the NEP model of DN before its using on diabetes surgical procedures. PART II THE EFFECTIVENESS OF DUODENAL-JEJUNAL BYPASS ON RENAL FUNCTION IN A TYPE2DIABETIC NEPHROPATHY RAT MODELBackgroundDiabetic nephropathy(DN) is one of the most serious complications of type2diabetes mellitus (T2DM), usually accompanied by a progressive rise in proteinuria followed by decline in renal function. In the past two decades, there has been a continual increase in the incidence of ESRD among patients with diabetes, predominantly those with T2DM. Up to30%of people with newly diagnosed T2DM have abnormally high urine albumin levels, and about75%of these people have microalbuminuria and about25%overt DN.Diabetes surgery is growing in popularity and has been shown to have marked effects on diabetes. The improvement of diabetes through RYGB and several other surgical procedures is always accompanied with obvious weight loss, although such loss occurs several weeks after glucose regulation. While several studies have shown it also induces some renal injury. However, the interaction of diabetes surgery on renal function is less clear. In this study, we examined renal function and histological changes in rats with diabetic nephropathy through a duodeno-jejunal bypass (DJB) operation.MethodsRats had diabetes induced through injection of streptozotocin (STZ) and were randomly assigned to the DJB group (DJB), Sham-DJB group (S-DJB) and diabetes group (DM). Six age-matched normal rats were assigned as the control group. DJB and sham surgery were performed. Body weight, kidney weight, food intake and random blood glucose were measured every week preoperatively and postoperatively. The serum creatinine (creatinine in plasma, Cp), Cys_C levels, fasting TC and TG levels were measured using an automatic biochemistry analyzer at the laboratory of the Fourth Hospital of Jinan. The urine volume, urine creatinine, UAER and GFR were measured. Kidney sections were stained with periodic acid-Schiff (PAS), and then the glomerular mesangial area, glomerular area and the ratio of mesangial area/glomerular area which showed the index of mesangial expansion was determined. The immunohistochemical studies of synaptopodin for podocytes in renal sections were also performed.Results1. After surgical intervention In DJB and S-DJB groups, there was a significant decrease in body weight compared with the DM group within2weeks (P<0.05), while no significant differences were found between DJB and S-DJB groups. At the end of study, no significant differences were found between DJB, S-DJB and DM groups in body weight. No significant difference in food intake between DJB and S-DJB groups were found at any stage of the study.2. The KW and KW/BW ratio was higher in S-DJB and DM groups than in DJB and control groups (P<0.05. No significant differences were found in KW and KW/BW ratio between DJB and control groups or S-DJB and DM groups.3. The blood glucose was significantly dropped in the DJB group within2weeks after DJB surgery.4. DJB surgery demonstrated a significant reduction in TC and TG levels compared with S-DJB, DM, and control groups(P<0.05).5. The increase of24h urinary albumin excretion was blocked in the DJB group after surgery (P<0.05).6. DJB group showed less GFR increase than that of S-DJB and DM groups after surgery.7. DJB surgery significantly ameliorated the increase of the mesangial matrix but not the IME compared with that of DM and S-DJB groups.8. In the DJB group, the positive area of synaptopodin staining was higher than that of DM and S-DJB groups (P<0.05). It showed an amelioration of synaptopodin expression area and a return toward the values of normal rats. Conclusion1.DJB surgery ameliorated renal function by inducing an improvement of UAER, GFR and Cys-C levels4and8weeks after surgery.2. It also improved lipid metabolism by decreasing fasting total serum cholesterol (TC) and triglyceride (TG) levels.3. Immuno-staining of synaptopodin showed podocyte injury was also improved in DJB glomeruli compared with sham and DM groups.4.Histological analysis showed that the mesangial expansion was not significantly prevented8weeks after DJB surgery.5.DJB ameliorated renal function in UAER and GFR but not mesangial expansion in a DN rat model. The improvement of renal function may be attributed to reversing the injury or loss of podocytes after DJB surgery.