A neutralizing VEGF antibody prevents glomerular hypertrophy in a model of obese type 2 diabetes, the Zucker diabetic fatty rat.

BACKGROUND: Antagonism of vascular endothelial growth factor (VEGF) has improved the outcome in experimental nephropathies of various origins, including diabetic nephropathy in a type 1 diabetic rat model and a type 2 diabetic mouse model. Neutralizing VEGF antibodies prevented glomerular hypertrophy in these models. We examined the renal effects of VEGF blockade in an obese rat model of type 2 diabetic nephropathy and investigated the mechanism underlying the inhibition of glomerular hypertrophy. METHODS: Twenty female Zucker diabetic fatty (ZDF) rats, fed a high-fat diet and aged 10 weeks, were treated with VEGF antibodies or an irrelevant isotype-matched IgG. Ten heterozygous (fa/+) littermates served as additional non-diabetic, lean controls. Urinary albumin excretion (UAE) and creatinine clearance (CrCl) were assessed at baseline, and at 3 and 5 weeks. Kidney weight and glomerular volume were determined at the end of the study. Glomerular apoptosis was examined with anti-active caspase-3 immunohistochemistry. RESULTS: All obese animals had established diabetes, hyperlipidaemia and normal blood pressure, which were not influenced by VEGF antibody treatment. ZDF control rats had increased UAE, CrCl, kidney weights and glomerular volumes compared with non-diabetic, lean control rats. VEGF antibody treatment prevented the glomerular hypertrophy, but did not affect UAE, CrCl and kidney weight. Glomerular anti-active caspase-3 immunostaining was not different between the groups. CONCLUSIONS: Inhibition of VEGF prevented early glomerular hypertrophy in ZDF rats with established diabetes. Increased apoptosis of glomerular endothelial cells does not appear to underly the inhibition of glomerular growth.     

C-peptide prevents glomerular hypertrophy and mesangial matrix expansion in diabetic rats.

BACKGROUND: There is accumulating evidence that C-peptide exerts beneficial renal effects in type-1 diabetes by reducing glomerular hyperfiltration, albuminuria and glomerular hypertrophy in the early stage of nephropathy. The aim of this study was to clarify further the effects of C-peptide on renal structural changes in type-1 diabetic rats. METHODS: The effects of C-peptide or placebo on glomerular volume, mesangial expansion, glomerular basement membrane thickness, albuminuria and glomerular filtration rate (GFR) were studied in three groups of rats: a non-diabetic group (N, n=9) and two groups that, during 8 weeks of diabetes, were left untreated for 4 weeks and then given a subcutaneous infusion of either placebo (D, n=11) or C-peptide (DCp, n=11) during the next 4 weeks. Furthermore, GFR was studied after 4 weeks of diabetes in an additional diabetic group (D-early, n=9) and in an age-matched non-diabetic group (N-early, n=9). RESULTS: After 4 weeks, GFR in the D-early group was 102% higher than in the N-early group. GFR after 8 weeks did not differ between the study groups. The D group presented with a 33% larger glomerular volume than the N group (P<0.001), while glomerular volume in the DCp group was similar to that in the N-group. Total mesangial and mesangial matrix fractions were increased by 46% (P<0.001) and 133% (P<0.001), respectively, in the D group. The corresponding values in the DCp group did not differ from those for the non-diabetic animals. Neither the thickness of the glomerular basement membrane nor the level of albuminuria differed significantly between the study groups. CONCLUSIONS: C-peptide administration in replacement dose to streptozotocin-diabetic rats serves to limit or prevent the glomerular hypertrophy and the mesangial matrix expansion seen in the post-hyperfiltration phase of early diabetic nephropathy.     

Inhibitory effect of a growth hormone receptor antagonist (G120K-PEG) on renal enlargement, glomerular hypertrophy, and urinary albumin excretion in experimental diabetes in mice.

Growth hormone (GH) and IGFs have a long and distinguished history in diabetes, with possible participation in the development of renal complications. To investigate the effect of a newly developed GH receptor (GHR) antagonist (G120K-PEG) on renal/glomerular hypertrophy and urinary albumin excretion (UAE), streptozotocin-induced diabetic and nondiabetic mice were injected with G120K-PEG every 2nd day for 28 days. Placebo-treated diabetic and nondiabetic animals were used as reference groups. Placebo-treated diabetic animals were characterized by growth retardation, hyperphagia, hyperglycemia, increased serum GH levels, reduced serum IGF-I, IGF-binding protein (IGFBP)-3, and liver IGF-I levels, increased kidney IGF-I, renal/glomerular hypertrophy, and increased UAE when compared with nondiabetic animals. No differences were seen between the two diabetic groups with respect to body weight, food intake, blood glucose, serum GH, IGF-I, and IGFBP-3 levels or hepatic IGF-I levels. Kidney IGF-I, kidney weight, and glomerular volume were normalized, while the rise in UAE was partially attenuated in the G120K-PEG-treated diabetic animals. No effect of G120K-PEG treatment on any of the parameters mentioned above was seen in nondiabetic animals. In conclusion, administration of a GHR antagonist in diabetic mice has renal effects without affecting metabolic control and circulating levels of GH, IGF-I, or IGFBP-3, thus indicating that the effect of G120K-PEG may be mediated through a direct inhibitory effect on renal IGF-I through the renal GHR. The present study suggests that specific GHR blockade may present a new concept in the treatment of diabetic kidney disease.     

维生素E和氨基胍在糖尿病肾病治疗中的协同作用

目的探讨维生素E和氨基胍在糖尿病肾病（DN）治疗中的协同作用。方法①以一次性腹腔注射链脲佐菌素（STZ,55mg／kg）诱导糖尿病大鼠模型,将大鼠分为正常对照组、糖尿病对照组、糖尿病加维生素E治疗组、糖尿病加氨基胍治疗组、糖尿病加维生素E加氨基胍治疗组;②观察1、2、4、8、12、16周时各组大鼠24h尿白蛋白排泄率（UAER）,16周时各组大鼠尿素氮（BUN）、血肌酐（SCr）及肾组织病理改变情况;③观察各组大鼠16周时肾小球活性氧（ROS）聚集情况以及肾间质8-羟基脱氧鸟苷（8-OHDG）表达情况。结果与糖尿病组比较,维生素E治疗组在2周时UAER明显下降,但在4、8、12、16周时两组比较无统计学意义;氨基胍治疗组和两药合用组则在包括2周以后的各时间点UAER均较糖尿病组明显下降,且两药合用组UAER下降更明显。16周时各组间BUN、SCr差异无统计学意义。16周时糖尿病组大鼠肾小球系膜区增宽,系膜基质聚集;维生素E治疗组肾组织病理无改善,氨基胍治疗组略有改善,而两药合用组则有明显改善。16周时糖尿病组大鼠肾小球ROS聚集,肾间质8-OHDG表达增强,维生素E组肾组织ROS聚集和8-OHDG表达未减轻,氨基胍治疗有一定程度减轻,两药合用组肾组织ROS聚集和8-OHDG表达则明显减轻。结论维生素E和氨基胍在DN的治疗中具有协同作用,而这一协同作用可能通过协同抗氧化来实现。     

Short-term effects of calcium antagonists on renal haemodynamics in patients with chronic renal failure

Experimental evidence suggests that pharmacological manipulations of glomerular haemodynamics may affect the progression of chronic renal insufficiency and scarring. In this study, we have investigated the short-term (4 weeks) renal haemodynamic effects of nifedipine and nitrendipine (10 mg/thrice daily) in two separate groups of 6 patients with stable chronic renal failure (CRF) (glomerular filtration rate, GFR: 9.7-47.8 ml/min/1.73 m2). Patients were studied on three occasions: (1) before the administration of the calcium antagonist, (2) after 4 weeks of treatment and (3) 4 weeks after the discontinuation of the drug. Mean arterial pressure fell significantly on nifedipine: from 116.33 +/- 12.25 to 107.22 +/- 18.67 mm Hg, p less than 0.05, and on nitrendipine: from 112.22 +/- 10.04 to 102.22 +/- 13.77 mm Hg, p less than 0.05. There was no significant effect of either calcium antagonist on GFR, effective renal plasma flow (ERPF), proteinuria or natriuresis. Consequently, renal vascular resistance (RVR) fell in both experimental groups, nifedipine: from 51.40 +/- 28.77 to 44.97 +/- 30 dyn s cm-5 x 10(3) (mean +/- SD), and nitrendipine: from 37.04 +/- 18.46 to 30.47 +/- 15.56 dyns s cm-5 x 10(3), p less than 0.05. These results show that calcium antagonists reduce systemic blood pressure whilst GFR and ERPF are maintained. The fall in the RVR of patients with CRF treated with calcium antagonists may confer on these agents a therapeutic advantage in the management of progressive renal insufficiency.     

Effects of dietary protein content in streptozotocin-diabetic rats

We evaluated the influence of increased dietary protein intake on glomerular structure and function in Lewis rats made diabetic with streptozotocin. We found that diabetic animals on a 20% or 50% protein diet ate approximately 50% more protein and excreted about 50% more urinary urea nitrogen than did their respective similarly-fed nondiabetic controls. The 50% protein diet was associated with higher glomerular filtration rates (GFR) and renal blood flows (RBF) at two months in both diabetic and control animals compared to their respective controls on the lower protein diet. However, GFR and RBF were not significantly higher in the diabetic animals on the 50% protein diet in the controls on the 20% diet and were slightly, albeit not significantly lower than controls on the 50% diet. Glomerular capillary pressure (PGC) tended to be lower in the diabetic compared to their respective controls, while the high protein diet was associated with higher PGC in diabetic and nondiabetic animals. The PGC in the 50% diabetic rats was not different from the PGC in the nondiabetic rats. Urinary albumin excretion (UAE) rate was greater in the diabetic than in the nondiabetic animals. UAE was greatest in the high protein diabetic animals at six months. Glomerular basement membrane thickness after six months of diabetes was increased essentially equally in both normal and high-protein fed diabetic groups and was largely uninfluenced by diet in the controls. Fractional mesangial volume was increased and relative filtration surface was decreased only in the 50%-protein diet diabetic rats at six months. Thus, high protein diet was associated with increased fractional mesangial volume in diabetic rats, but this could not be explained by increased glomerular capillary flows or pressures. The mechanism of acceleration of mesangial expansion by high protein diet in diabetic animals was not elucidated by these studies.     

Diabetes-induced microvascular dysfunction in the hydronephrotic kidney: role of nitric oxide.

BACKGROUND: Renal hemodynamics in early diabetes are characterized by preglomerular and postglomerular vasodilation and increased glomerular capillary pressure, leading to hyperfiltration. Despite intensive research, the etiology of the renal vasodilation in diabetes remains a matter of debate. The present study investigated the controversial role of nitric oxide (NO) in the renal vasodilation in streptozotocin-induced diabetic rats. METHODS: In the renal microcirculation, basal tone and response to NO synthase blockade were studied using the in vivo hydronephrotic kidney technique. L-arginine analog N-nitro-L-arginine methyl ester (L-NAME) was administered locally to avoid confounding by systemic blood pressure effects. The expression of endothelial NO synthase (eNOS) was investigated in total kidney by immunocytochemistry and in isolated renal vascular trees by Western blotting. Urinary excretion of nitrites/nitrates was measured. RESULTS: Diabetic rats demonstrated a significant basal vasodilation of all preglomerular and postglomerular vessels versus control rats. Vasoconstriction to L-NAME was significantly increased in diabetic vessels. After high-dose L-NAME, there was no difference in diameter between diabetic and control vessels, suggesting that the basal vasodilation is mediated by NO. Immunocytochemically, the expression of eNOS was mainly localized in the endothelium of preglomerular and postglomerular vessels and glomerular capillaries, and was increased in the diabetic kidneys. Immunoblots on isolated renal vascular trees revealed an up-regulation of eNOS protein expression in diabetic animals. The urinary excretion of nitrites/nitrates was elevated in diabetic rats. CONCLUSION: The present study suggests that an up-regulation of eNOS in the renal microvasculature, resulting in an increased basal generation of NO, is responsible for the intrarenal vasodilation characteristic of early diabetes.     

Glomerular abnormalities in long-term experimental diabetes. Role of hemodynamic and nonhemodynamic factors and effects of antihypertensive therapy.

To evaluate the role of glomerular hypertension, glomerular hypertrophy, glomerular lipid deposition, and plasma cholesterol levels in diabetic glomerulopathy, Munich-Wistar rats received streptozocin and daily insulin injections and were assigned to one of three groups: untreated diabetic (DMC), hydralazine-treated diabetic (DMH), and enalapril-treated diabetic (DME). Age-matched control rats were also studied. At 6-10 wk of diabetes, DMC rats showed marked elevations of glomerular pressure and glomerular filtration rate as well as slight glomerular enlargement and cholesterol elevation. DMH and DME rats exhibited arterial hypotension but no change in cholesterol or glomerular volume. Glomerular pressure was normalized by enalapril but not by hydralazine treatment. Additional rats were followed up to 12 mo of diabetes. Slight hypertension was seen in DMC rats, whereas sustained hypotension occurred in DMH and DME rats. Progressive albuminuria occurred in DMC and DMH but not in DME rats. At 12 mo, glomerular hypertension persisted in DMC and DMH rats but was still absent in DME rats. Cholesterol was elevated in DMC and slightly lower in DMH and DME rats. Glomeruli were equally enlarged in the diabetic groups. Glomerular sclerotic lesions and lipid deposits appeared in DMC and DMH but not in DME rats. These findings are consistent with the notion that glomerular hypertension may promote glomerular injury in experimental diabetes. Glomerular lipid deposition may also participate in this process, although a causal relationship was not demonstrated. Glomerular hypertrophy and cholesterol were unrelated to glomerular injury, although they may have exacerbated hemodynamically mediated damage.     

Puberty permits increased expression of renal transforming growth factor-β1 in experimental diabetes

Prepubertal years of diabetes mellitus are relatively protected from clinical manifestations of nephropathy. Transforming growth factor-β1 (TGF-β1) is a major mediator of diabetic kidney disease. Its renal expression, translation, and activation change with sexual maturation in the normal rat. The role of TGF-β1 in postpubertal susceptibility to diabetic renal hypertrophy was addressed in the present study. Male Sprague- Dawley rats were given streptozocin at 4 weeks of age (weanling) or 14 weeks of age (mature) and treated with insulin to maintain blood glucose levels between 300 and 500 mg/dl. Nondiabetic controls received saline. After 6 weeks with ad libitum food and water, kidneys were snap-frozen for measurement of TGF-β1 protein and mRNA. As in previous studies, diabetic renal hypertrophy was blunted in weanling animals compared with mature rats. Message for TGF-β1 was not significantly increased in weanling animals {102 (9)% [mean (SEM)] in nondiabetic controls versus 117 (10)% in diabetic rats; P=0.91}, while it was significantly increased in mature diabetic animals [100 (7)% vs. 146 (11)%; P=0.01]. Immunohistochemistry revealed focal increases in glomerular staining in mature but not weanling diabetic rats. Differences in the control of the renal TGF-β system may explain the permissive role of puberty in the manifestations of diabetic kidney disease. Received: 18 December 2000 / Revised: 25 June 2001 / Accepted: 26 June 2001     

The effect of growth hormone on the development of diabetic kidney disease in rats.

BACKGROUND: Nephropathy is the most severe complication of diabetes mellitus. We investigated the effect of exogenous growth hormone (GH) administration on renal function and matrix deposition in the streptozotocin (STZ) model of type I-diabetic rat. METHODS: Adult female STZ-diabetic rats (D), non-diabetic control rats injected with saline (C) and control and diabetic rats injected with bovine GH for 3 months (CGH and DGH, respectively) were used. RESULTS: The usual renal hypertrophy seen in D animals was more pronounced in the DGH group. Creatinine clearance increased only in the D rats, but not in the other groups, including DGH. Albuminuria was observed in the D animals but was significantly elevated in the DGH group. Glomeruli from DGH animals showed more extensive matrix accumulation (manifested as an increase in mesangial/glomerular area ratio). Renal extractable insulin-like growth factor (IGF-I) mRNA was decreased in the D and DGH groups, but renal IGF-I protein was not significantly increased. Renal IGF binding protein-1 was increased in the D groups and further increased in the DGH group, at both the mRNA and protein levels. CONCLUSIONS: GH-treated diabetic rats had less hyperfiltration and more albuminuria, concomitant with more glomerular matrix deposition, when compared with regular diabetic animals. This was associated with a significant increase in renal IGFBP-1, and dissociated from IGF-I changes. Thus, in this model, GH exacerbates the course of diabetic kidney disease.     

Glomerular structure in IDDM women with low glomerular filtration rate and normal urinary albumin excretion.

Eight women with insulin-dependent diabetes mellitus (IDDM) with low creatinine clearance rate (CCR) and normal urinary albumin excretion (UAE) were compared with three other groups of diabetic women: 19 with normal creatinine clearance rate (CCR) and UAE, 7 with normal CCR and microalbuminuria, and 7 with low CCR and microalbuminuria. The four groups were similar in age, duration of diabetes, HbA1, incidence of urinary tract infection, prevalence of bladder neuropathy, and urinary urea nitrogen excretion rate. The prevalence of hypertension was similar among the groups, although mean arterial pressure was higher in the low CCR and microalbuminuria group. Renal area index was lower in the low CCR and normal UAE groups than in the other groups of diabetic patients, but was not different from normal. Morphometric measures of mesangial expansion and estimates of arteriolar hyalinosis and global glomerulosclerosis were increased to a similar degree in the low CCR and normal UAE, normal CCR and microalbuminuria, and low CCR and microalbuminuria groups compared with the group without abnormalities of renal function. Therefore, it is likely that diabetic glomerulopathy is, at least in part, responsible for the loss of glomerular filtration rate seen in the low CCR and normal UAE patients. Thus, the definition of incipient nephropathy may have to be expanded beyond the concept of microalbuminuria if longitudinal study of such patients reveals an increased risk of the subsequent development of overt nephropathy. Finally, screening for diabetic kidney disease among IDDM patients should include determination of glomerular filtration rate and measurement of UAE and blood pressure, especially among women.     

Hypertension induces oxidative stress but not macrophage infiltration in the kidney in the early stage of experimental diabetes mellitus

BACKGROUND: The combination of diabetes and hypertension increases the incidence and severity of kidney disease in an additive manner. Inflammatory and oxidative stress mechanisms contribute to renal damage in both diabetes and hypertension. Therefore, we investigated whether renal macrophage infiltration and oxidative stress events are additive from the beginning in diabetic animals with coexisting hypertension. METHODS: Diabetes was induced in spontaneously hypertensive rats (SHRs) and their genetically normotensive control Wistar Kyoto (WKY) rats by streptozotocin injection at 12 weeks of age for 10 days, and the effects of hyperglycemia on renal macrophage infiltration and oxidative stress were evaluated. RESULTS: Blood pressure was higher in SHR than in WKY groups. Markers of oxidative stress-induced DNA and protein modification, 8-hydroxy- 2'-deoxyguanosine (8-OHdG) and nitrotyrosine, respectively, and the antioxidant glutathione levels were found to be similar in WKY-control and WKY-diabetic groups. However, 8-OHdG was significantly elevated (p = 0.014), the nitrotyrosine level tended to be elevated (p = 0.068) and the glutathione level was significantly reduced (p = 0.034) in the SHR-diabetic group compared to the SHR-control group. On the other hand, glomerular and tubulointerstitial macrophage infiltration was significantly higher in both WKY-diabetic and SHR-diabetic groups than the respective control groups. CONCLUSIONS: A short duration of diabetes mellitus induces renal oxidative stress in the presence of hypertension; however, renal macrophage infiltration becomes evident in early diabetes regardless of the presence or absence of hypertension. We conclude that the combination of diabetes and hypertension adversely affects oxidative stress in the kidney, but the combination has no additive effect on renal macrophage infiltration, at least in early diabetes.     

The parathyroid hormone-related protein system and diabetic nephropathy outcome in streptozotocin-induced diabetes

The pathophysiology of the diabetic kidney (e.g., hypertrophy, increase urinary albumin excretion (UAE) is still ill-defined. Parathyroid hormone-related protein (PTHrP) is overexpressed in several nephropathies, but its role remains unclear. We evaluated the effect of high glucose on PTHrP and the PTH1 receptor (PTH1R) protein (by Western blot and immunohistochemistry) in the kidney of mice ith streptozotocin-induced diabetes, and in several mouse renal cells in vitro. Diabetic mice showed a significantly increased renal expression of PTHrP and PTH1R proteins with 2-8 weeks from the onset of diabetes. These animals exhibited an intense immunostaining for both proteins in the renal tubules and glomeruli. Using transgenic mice overexpressing PTHrP targeted to the renal proximal tubule, we found a significant increase in the renal hypertrophy index and in UAE in these diabetic mice relative to their control littermates. Moreover, logistic regression analysis showed a significant association between both PTHrP and PTH1R protein levels and UAE in all diabetic mice throughout the study. High-glucose (25 mm) medium was found to increase PTHrP and PTH1R in tubuloepithelial cells, mesangial cells and podocytes in vitro. Moreover, this increase in PTHrP (but not that of PTH1R) was inhibited by the AT1 receptor antagonist losartan. Collectively, these results indicate that the renal PTHrP/PTH1R system is upregulated in streptozotozin-induced diabetes in mice, and appears to adversely affect the outcome of diabetic renal disease. Our findings also suggest that angiotensin II might have a role in the PTHrP upregulation in this condition.     

NADPH氧化酶抑制剂apocynin对大鼠糖尿病肾小球细胞外基质代谢的影响

目的探讨NADPH氧化酶亚基p22phoxmRNA在糖尿病大鼠肾脏表达时间模式及抑制NADPH氧化酶活性对肾小球细胞外基质(ECM)代谢的影响。方法链脲佐菌素诱导的大鼠糖尿病模型随机地分为糖尿病非治疗组(DM),观察12周;NADPH氧化酶抑制剂apocynin治疗组(DM+Apo,0.2g·kg-1·d-1),疗程8周。用RT-PCR检测肾脏NADPH氧化酶亚基p22phoxmRNA的表达。免疫组织化学检测肾脏纤连蛋白(FN)表达。白明胶酶谱法(zymography)检测肾脏基质金属蛋白酶-9(MMP-9)的活性。并测定Scr、尿蛋白量和肾重指数。结果DM组肾脏p22phoxmRNA的表达在4、6和8周时较正常对照组(C)明显升高(P<0.05);12周时降低至正常水平。DM+Apo组肾脏p22phoxmRNA的表达与DM组差异无统计学意义(P>0.05),但可显著逆转由糖尿病导致的肾小球体积、肾小球FN表达、肾小球ECM含量、Scr、尿蛋白量和肾重指数的升高(P<0.05),并显著提高肾脏MMP-9活性(P<0.05)。结论NADPH氧化酶的过度表达在糖尿病肾病(DN)发病的早期阶段起重要作用。抑制NADPH氧化酶活性的治疗措施可减少DN肾小球ECM积聚、延缓DN的发生和发展。     

Tumor necrosis factor-alpha gene expression in diabetic nephropathy: relationship with urinary albumin excretion and effect of angiotensin-converting enzyme inhibition

BACKGROUND: The pathogenic mechanisms and molecular events involved in the development and progression of diabetic nephropathy (DN) are not completely known. Recent data indicate that diabetes includes an inflammatory component that is related to diabetic complications. Tumor necrosis factor (TNF)-alpha, a cytokine with mainly proinflammatory activity, may be synthesized by renal cells. Our objective was to analyze intrarenal TNF-alpha gene expression and its relationship with urinary albumin excretion (UAE). We also investigated the effect of inhibition of angiotensin-converting enzyme on TNF-alpha expression and UAE. METHODS: Streptozotocin-induced diabetic rats received either no treatment or an angiotensin-converting enzyme inhibitor (enalapril). After eight weeks, renal expression of TNF-alpha was evaluated by real-time polymerase chain reaction. RESULTS: Renal cortical messenger RNA levels of TNF-alpha increased significantly and were twice as high in diabetic rats than in nondiabetic control rats. Enalapril administration nearly completely abolished the increase in TNF-alpha messenger RNA expression to the level observed in control rats. UAE was significantly correlated with urinary levels of TNF-alpha (r=0.68, P<0.05) and with renal TNF-alpha expression (r=0.51, P<0.05). CONCLUSION: DN was associated with increased renal expression of TNF-alpha and UAE. Enalapril administration prevented this enhanced expression of TNF-alpha and decreased urinary cytokine excretion and albuminuria. These data provide a novel insight into the pathogenic mechanisms of DN, and support the hypothesis that inflammatory mechanisms may play a significant role in the development and progression of renal injury secondary to diabetes mellitus.     

Attenuating effect of soy protein as compared with casein on glomerular injury in spontaneous hypercholesterolemic male Imai rats

SUMMARY: Soy protein has hypocholesterolemic and oestrogenic properties. Because the reno-protective effect of both lipid-lowering agents and oestrogen has been reported, we investigated whether soy protein has an ability to attenuate glomerular injury in male Imai rats in which hyperc-holesterolemia, focal and segmental glomerulosclerosis (FSGS) and renal insufficiency occur spontaneously. Twenty male Imai rats were randomly divided into two groups and fed diets containing 20.0 g/100 g of either casein or soy protein. Each group was fed freely one of the respective test diets from when they were 8–26 weeks of age. Bodyweight, urinary protein, serum constituents and systolic blood pressure was investigated every 4 or 8 weeks from when rats were 10 weeks through to 26 weeks of age. At 26 weeks of age, rats were studied morphologically. Soy protein-fed animals consumed larger amounts of diet and showed higher urinary urea excretion and a more rapid weight gain than the control casein diet-fed animals. No significant differences were seen in blood pressure between the two groups. the soy protein diet did not influence absolute kidney or heart weight, but significantly reduced those organs to bodyweight ratios. Soy protein diet resulted in less proteinuria, less hyperlipidemia, less hypoalbuminemia, less renal functional impairment, less glomerular hypertrophy, and less renal histological damage as compared with the control casein diet. the soy protein diet tended to affect serum sex-hormone levels with a trend toward lower levels of both testosterone and estradiol. the present study showed a beneficial effect of soy protein diet on glomerular disease in a spontaneous FSGS model, although the mechanisms remain to be determined.     

Mycophenolate mofetil prevents the development of glomerular injury in experimental diabetes

BACKGROUND: Experimental and clinical evidence suggests that inflammation plays a role in the pathogenesis of diabetic nephropathy, in addition to, or in concert with, the associated hemodynamic and metabolic changes. The present study assessed the effects of chronic anti-inflammatory therapy in experimental diabetic nephropathy. METHODS: Adult male Munich-Wistar rats were made diabetic with streptozotocin after uninephrectomy, kept moderately hyperglycemic by daily injections of NPH insulin and distributed among three groups: C, non-diabetic rats; DM, rats made diabetic and treated with insulin as described earlier; and DM+MMF, diabetic rats receiving insulin and treated with mycophenolate mofetil (MMF), 10 mg/kg once daily by gavage. Renal hemodynamic studies were performed 6 to 8 weeks after induction of diabetes. Additional rats were followed during 8 months, at the end of which renal morphological studies were performed. RESULTS: After 6 to 8 weeks, diabetic rats exhibited marked glomerular hyperfiltration and hypertension. Diabetic rats developed progressive albuminuria and exhibited widespread glomerulosclerotic lesions associated with macrophage infiltration at 8 months. Treatment with MMF had no effect on blood pressure, glomerular dynamics or blood glucose levels, but did prevent albuminuria, glomerular macrophage infiltration and glomerulosclerosis. Thus, the renoprotective effect of MMF was not associated with a metabolic or renal hemodynamic effect, and must have derived from its well-known anti-inflammatory properties, which include restriction of lymphocyte and macrophage proliferation and limitation of the expression of adhesion molecules. CONCLUSIONS: These findings are consistent with the notion that inflammatory events are central to the pathogenesis of diabetic nephropathy and suggest that MMF may help prevent the progression of diabetic nephropathy.     

Inhibition of the epidermal growth factor receptor preserves podocytes and attenuates albuminuria in experimental diabetic nephropathy

Aim: Early renal enlargement may predict the future development of nephropathy in patients with diabetes. The epidermal growth factor (EGF)‐EGF receptor (EGFR) system plays a pivotal role in mediating renal hypertrophy, where it may act to regulate cell growth and proliferation and also to mediate the actions of angiotensin II through transactivation of the EGFR. In the present study we sought to investigate the effects of long‐term inhibition of the EGFR tyrosine kinase in an experimental model of diabetes that is characterized by angiotensin II dependent hypertension. Methods: Female heterozygous streptozotocin‐diabetic TGR(mRen‐2)27 rats were treated with the EGFR inhibitor PKI 166 by daily oral dosing for 16 weeks. Results: Treatment of TGR(mRen‐2)27 rats with PKI 166 attenuated the increase in kidney size, glomerular hypertrophy and albuminuria that occurred with diabetes. The reduction in albuminuria, with EGFR inhibition in diabetic TGR(mRen‐2)27 rats, was associated with preservation of the number of glomerular cells staining positively for the podocyte nuclear marker, WT1. Immunostaining for WT1 inversely correlated with glomerular volume in diabetic rats. In contrast to agents that block the renin‐angiotensin system (RAS), EGFR inhibition had no effect on either the quantity of mesangial matrix or the magnitude of tubular injury in diabetic animals. Conclusion: These observations indicate that inhibition of the tyrosine kinase activity of the EGFR attenuates kidney and glomerular enlargement in association with podocyte preservation and reduction in albuminuria in diabetes. Accordingly, targeting the EGF‐EGFR pathway may represent a therapeutic strategy for patients who continue to progress despite RAS‐blockade.     

Effects of nephron loss on glomerular hemodynamics and morphology in diabetic rats

Loss of renal mass in rats with experimental diabetes mellitus leads to exaggerated hypertrophy of remaining nephrons and accelerated diabetic glomerulopathy. To examine factors responsible for glomerular injury in this setting, rats with preexisting diabetes were subjected to unilateral nephrectomy. Micropuncture studies and evaluation of glomerular morphology were performed 2-3 mo later. Nephrectomized diabetic rats demonstrated significant increases in kidney weight, superficial nephron glomerular filtration rate, and superficial nephron plasma flow compared with two-kidney diabetic rats and nephrectomized nondiabetic controls. Glomerular capillary hydraulic pressure was comparable in two-kidney and nephrectomized diabetic rats and was significantly reduced compared with nephrectomized nondiabetic controls. Nephrectomized diabetic rats demonstrated significant albuminuria, mesangial matrix expansion, and focal glomerulosclerosis, whereas two-kidney diabetic rats and nephrectomized nondiabetic controls showed only minimal alterations in glomerular morphology. It is concluded that diabetic rats can undergo glomerular functional compensation in response to nephron loss. Moreover, accelerated glomerular injury caused by nephron loss in diabetic rats could not be attributed to increased glomerular capillary pressure.