RENAL MASS REDUCTION INCREASES THE RESPONSE TO EXOGENOUS INSULIN INDEPENDENT OF ACID-BASE STATUS OR PLASMA INSULIN LEVELS IN RATS.

Impairments in insulin sensitivity can occur in patients with chronic kidney disease (CKD). Correction of metabolic acidosis has been associated with improved insulin sensitivity in CKD, suggesting metabolic acidosis may directly promote insulin resistance. Despite this, the effect of acid or alkali loading on insulin sensitivity in a rodent model of CKD (remnant kidney) has not been directly investigated. Such studies could better define the relationship between blood pH and insulin sensitivity. We hypothesized that in remnant kidney rats, acid or alkali loading would promote loss of pH homeostasis and consequently decrease insulin sensitivity. To test this hypothesis, we determined the impact of alkali (2 weeks) or acid (5-7 days) loading on plasma electrolytes, acid-base balance, and insulin sensitivity in either sham control, 2/3 or 5/6 nephrectomy rats. Rats with 5/6 nephrectomy had the greatest response to insulin followed by animals with 2/3 nephrectomy and sham control rats. We found that treatment with a 0.1M sodium bicarbonate solution in drinking water had no effect on insulin sensitivity. Acid loading with 0.1M ammonium chloride resulted in significant reductions in pH and plasma bicarbonate. However, acidosis did not significantly impair insulin sensitivity. Similar effects were observed in Zucker obese rats with 5/6 nephrectomy. The effect of renal mass reduction on insulin sensitivity could not be explained by reduced insulin clearance or increased plasma insulin levels. We found that renal mass reduction alone increases sensitivity to exogenous insulin in rats, and that this is not acutely reversed by development of acidosis.

D-Serine mediates cellular proliferation for kidney remodeling

Background: D-Serine, a long-term undetected enantiomer of serine, is a biomarker that reflects kidney function and disease activity. The physiological functions of D-serine have been unclear. Methods: Dynamics of D-serine was assessed by measuring D-serine in human samples of living kidney donors using two-dimensional high-performance liquid chromatography, and by auto-radiographic studies in mice. Effects of D-serine on kidney were examined by gene expression profiling and metabolic studies using unilateral nephrectomy mice, and genetically modified cells. Results: Unilateral nephrectomy in human living kidney donors decreases urinary excretion and thus increases the blood level of D-serine. D-Serine is quickly and dominantly distributed to the kidney upon injection in mice, suggesting that the kidney is a main target organ. Treatment of D-serine at low dose promotes the enlargement of remnant kidney in mouse model. Mechanistically, D-serine activates the cell cycle for tissue remodeling through an mTOR-related pathway. Conclusions: D-Serine is a physiological molecule that promotes kidney remodeling. Besides its function as a biomarker, D-serine has a physiological activity that influences kidney function.

Comparison of mesenchymal stromal cells from peritoneal dialysis effluent with those from umbilical cords: characteristics and therapeutic effects on chronic peritoneal dialysis in uremic rats

Background A long-term of peritoneal dialysis (PD) using a hypertonic PD solution (PDS) leads to patient’s peritoneal membrane (PM) injury, resulting in ultrafiltration failure (UFF) and PD drop-out. Our previous study shows that PD effluent-derived mesenchymal stromal cells (pMSCs) prevent the PM injury in normal rats after repeated exposure of the peritoneal cavity to a PDS. This study was designed to compare the cytoprotection between pMSCs and umbilical cord-derived MSCs (UC-MSCs) in the treatment of both PM and kidney injury in uremic rats with chronic PD. Methods 5/6 nephrectomized (5/6Nx) Sprague Dawley rats were intraperitoneally (IP) injected Dianeal (4.25% dextrose, 10 mL/rat/day) and were treated with pMSCs or umbilical cord (UC)-MSCs (approximately 2 × 106/rat/week, IP). Ultrafiltration was determined by IP injection of 30 mL of Dianeal (4.25% dextrose) with 1.5-h dewell time, and kidney failure by serum creatinine (SCr) and blood urea nitrogen (BUN). The structure of the PM and kidneys was assessed using histology. Gene expression was examined using quantitative reverse transcription PCR, and protein levels using flow cytometric and Western blot analyses. Results We showed a slight difference in the morphology between pMSCs and UC-MSCs in plastic dishes, and significantly higher expression levels of stemness-related genes (NANOG, OCT4, SOX2, CCNA2, RAD21, and EXO1) and MSCs surface markers (CD29, CD44, CD90 and CD105) in UC-MSCs than those in pMSCs, but no difference in the differentiation to chondrocytes, osteocytes or adipocytes. pMSC treatment was more effective than UC-MSCs in the protection of the MP and remnant kidneys in 5/6Nx rats from PDS-induced injury, which was associated with higher resistance of pMSCs than UC-MSCs to uremic toxins in culture, and more reduction of peritoneal mesothelial cell death by the secretome from pMSCs than from UC-MSCs in response to PDS exposure. The secretome from both pMSCs and UC-MSCs similarly inactivated NOS2 in activated THP1 cells. Conclusions As compared to UC-MSCs, pMSCs may more potently prevent PDS-induced PM and remnant kidney injury in this uremic rat model of chronic PD, suggesting that autotransplantation of ex vivo-expanded pMSCs may become a promising therapy for UFF and deterioration of remnant kidney function in PD patients.

Triple combination therapy with telmisartan, amlodipine, and hydrochlorothiazide ameliorates albuminuria in a normotensive rat remnant kidney model

Background Some types of antihypertensive drugs may have pleiotropic effects in patients with chronic kidney disease (CKD). However, whether triple combination therapy with angiotensin II receptor blockers (ARBs), calcium channel blockers (CCBs), and thiazide diuretics (TZD) confer renoprotective effects in normotensive CKD remains unknown. Thus, we explored this issue using a normotensive rat remnant kidney model. Methods Sprague-Dawley rats were randomly allocated into four groups: sham (n = 10), 5/6 nephrectomy (NTx) (n = 9), NTx treated with telmisartan and amlodipine (dual) (n = 8), and NTx treated with telmisartan, amlodipine, and hydrochlorothiazide (triple) (n = 7), and followed for 4 weeks. Blood pressure (BP), blood chemistry including renal function, urinary albumin excretion (UAE), and renal pathology were evaluated in all groups. Results There was no significant change in systolic BP among the four groups during the study period. Serum blood urea nitrogen (BUN) was significantly higher, and 24-h creatinine clearance (Ccr) was lower in all NTx groups (p < 0.001). Dual therapy further increased the glomerular diameter in NTx rats (p < 0.001), which was significantly ameliorated by triple therapy (p < 0.001). Triple therapy, but not dual therapy, significantly reduced NTx-induced UAE levels (p < 0.05), whereas BUN, 24-h Ccr, and tubulointerstitial injury scores were comparable among all the NTx groups. Conclusions Our results suggest that triple combination therapy with telmisartan, amlodipine, and hydrochlorothiazide could ameliorate glomerular hypertrophy and albuminuria in normotensive CKD rats in a BP-lowering independent manner.

Comparison of mesenchymal stromal cells from peritoneal dialysis effluent with those from umbilical cords: Characteristics and therapeutic effects on chronic peritoneal dialysis in uremic rats

Background: A long-term of peritoneal dialysis (PD) using a hypertonic PD solution (PDS) leads to patient’s peritoneal membrane (PM) injury, resulting in ultrafiltration failure (UFF) and PD drop-out. Our previous study shows that PD effluent-derived mesenchymal stromal cells (pMSCs) prevent the PM injury in normal rats after repeated exposure of the peritoneal cavity to a PDS. This study was designed to compare the cytoprotection between pMSCs and umbilical cord-derived MSCs (UC-MSCs) in the treatment of both PM and kidney injury in uremic rats with chronic PD.Methods: 5/6 nephrectomized (5/6Nx) Sprague Dawley rats were intraperitoneally (IP) injected Dianeal (4.25% dextrose, 10 mL/rat/d), and were treated with pMSCs or umbilical cord (UC)-MSCs (approximately 2×106/rat/wk, IP). Ultrafiltration was determined by IP injection of 30 mL of Dianeal (4.25% dextrose) with 1.5-h dewell time, and kidney failure by serum creatinine (SCr) and blood urea nitrogen (BUN). The structure of the PM and kidneys was assessed using histology. Gene expression was examined using quantitative reverse transcription PCR, and protein levels using flow cytometric and Western blot analyses.Results: We showed a slight difference in the morphology between pMSCs and UC-MSCs in plastic dishes, and significantly higher expression levels of stemness-related genes (NANOG, OCT4, SOX2, CCNA2, RAD21 and EXO1) and MSCs surface markers (CD29, CD44, CD90 and CD105) in UC-MSCs than those in pMSCs, but no difference in the differentiation to chondrocytes, osteocytes or adipocytes. pMSCs treatment was more effective than UC-MSCs in the protection of the MP and remnant kidneys in 5/6Nx rats from PDS-induced injury, which was associated with higher resistance of pMSCs than UC-MSCs to uremic toxins in culture, and more reduction of peritoneal mesothelial cell death by the secretome from pMSCs than from UC-MSCs in response to PDS exposure. The secretome from both pMSCs and UC-MSCs similarly inactivated NOS2 in activated THP1 cells.Conclusions: As compared to UC-MSCs, pMSCs may be more potently prevents PDS-induced PM and remnant kidney injury in this uremic rat model of chronic PD, suggesting that autotransplantation of ex vivo-expanded pMSCs may become a promising therapy for UFF and deterioration of remnant kidney function in PD patients.

Resistance to Tubulointerstitial Injury in a Mouse Remnant Kidney Model

Numerous animal models of CKD have been developed, but mice are relatively resistant to kidney injury. The remnant kidney model mimics progressive renal failure, and widely used in CKD research. The present study was performed to evaluate the effects of combined high-protein diet (HPD) loading and 5/6 nephrectomy (Nx) in a susceptible strain of mice (129/Sv). Mice underwent 5/6 Nx or sham surgery, then 2 weeks later were switched to an HPD, and cardiovascular parameters, kidney function, and renal histology were assessed after 4, 8, or 12 weeks. The 5/6 Nx group showed blood pressure elevation, cardiac hypertrophy, renal function decline, severe albuminuria, and glomerular hypertrophy. However, the glomerulosclerosis by 5/6 Nx was very mild and there was only modest tubulointerstitial inflammation and fibrosis in the 5/6 Nx group, even after 12 weeks of HPD loading. Furthermore, the sham group showed no histological changes. Thus, an HPD alone is insufficient to cause renal pathology, and a combination of 5/6 Nx and HPD loading induces mild renal pathology. Therefore, future studies of CKD using 5/6 Nx should be performed over a relatively long period of time in mice, or should be performed in other animals that are susceptible to kidney injury.

Anticoagulant Related Nephropathy Only Partially Develops in C57BL/6 Mice: Hematuria Is Not Accompanied by Red Blood Cell Casts in the Kidney

Anticoagulant-related nephropathy (ARN) may develop in patients that are on anticoagulation therapy. Rats with 5/6 nephrectomy treated with different anticoagulants showed acute kidney injury (AKI) and red blood cell (RBC) casts in the tubules similar to ARN in humans. The aim of the current study was to investigate the feasibility of inducing ARN in mice. C57BL/6 5/6 nephrectomy mice were treated with warfarin and dabigatran 3 weeks after ablative surgery for 7 days. Two doses of each anticoagulant were used. All anticoagulants resulted in serum creatinine and hematuria increase. Mortality was 63% in 5.0 mg/kg/day of warfarin but only 13% in 2.5 mg/kg/day of warfarin or in 400 mg/kg/day of dabigatran and 0% in 200 mg/kg/day of dabigatran. In spite of increasing hematuria, RBC tubular casts were not seen in mice treated with any anticoagulant. The 5/6 nephrectomy murine model in C57BL/6 mice only partially reproduced ARN in terms of increasing serum creatinine and hematuria, but there were no RBC tubular casts in the remnant kidney.

Compensation Capacity of the Living-Related Donor’s Remnant Kidney and Recipient’s Transplanted Kidney

Introduction: We try to explore the compensatory capacity of living-related donor’s remnant kidney and recipient’s transplanted kidney in terms of the glomerular filtration rate (GFR).

Compensation Capacity of The Living-Related Donor’s Remnant Kidney and Recipient’s Transplanted Kidney

Background: Compensatory renal growth following nephrectomy is common. We try to explore the compensatory capacity of the living-related donor’s remnant kidney and recipient’s transplanted kidney in terms of the glomerular filtration rate (GFR) one month after transplantation. Methods: Clinical data of 94 patients who received living-related kidney transplantation in our hospital between June 2007 and December 2017 were reviewed retrospectively. GFR was calculated by 99mTc-DTPA detection. The GFR compensatory capacity of donor’s remnant and donated kidneys in their new milieus after transplantation was compared. The differential value (D-value) of split renal function was defined as postoperative GFR - preoperative ipsilateral GFR. The compensatory percentage (C-percentage) of split renal function was defined as (postoperative GFR - preoperative ipsilateral GFR)/preoperative ipsilateral GFR. Results: The median D-value of the donor’s remnant kidney increased by 20.8 ml/(min·1.73m2)[IQR=8.9-29.6 ml/(min·1.73m2)] with a C-percentage of 46.6% (IQR=17.0%-73.0%). The median D-value of the donated kidney increased by 30.6 ml/(min·1.73m2)[IQR=19.8-42.3 ml/(min·1.73m2)] with a C-percentage of 67.8% (IQR=39.6%-94.7%). Multivariable analysis showed that only split preoperative GFR in the donor was the independent predictor for C-percentage of the split kidney. Conclusions: Renal function could be well preserved and compensated after kidney donation in most donors and recipients in Chinese population. Healthy donors with a good GFR before operation possessed a mighty functional compensation capacity.