Aspartic acid supplementation ameliorates symptoms of diabetic kidney disease in mice.

Diabetic kidney disease (DKD) is among the most common and serious complications of both type 1 and type 2 diabetes. In this study, we used KK/Ta-Ins2Akita (KK-Akita) mice as a model of DKD and KK/Ta (KK) mice as controls to identify novel factors related to the development/progression of DKD. Capillary electrophoresis coupled with mass spectrometry analysis revealed that circulating Asp (l-aspartic acid) levels in diabetic KK-Akita mice tend to be lower than those in control KK mice. Therefore, we evaluated the effect of Asp supplementation to prevent the progression of DKD in KK-Akita mice. Mice were divided into three groups: (a) untreated KK mice (Control group), (b) untreated KK-Akita mice (DKD group), and (c) treated (double-volume Asp diet) KK-Akita mice (Tx group). Kidney sections were stained with fluorescein isothiocyanate-labeled lectins, wheat germ agglutinin (WGA), and anti-endothelial nitric oxide synthase (eNOS) antibody for evaluation of endothelial surface layer (ESL) and NO synthesis. The mesangial area and glomerular size in the DKD group were significantly larger than those in the Control group; however, there was no significant difference in those between the DKD and Tx groups. Albuminuria, the ratio of foot process effacement, and thickness of glomerular basement membrane in the Tx group were significantly lower than those in the DKD group. Furthermore, the expression levels of glomerular WGA and microvascular eNOS in the Tx group improved significantly and approached the level in the Control group. In conclusion, the improvement of albuminuria in the Tx group may be caused by the reduction of oxidative stress in the kidneys, which may lead to the subsequent improvement of glomerular ESL.

Injury to the endothelial surface layer induces glomerular hyperfiltration rats with early-stage diabetes.

Glomerular endothelial surface layer (ESL) may play a role in the mechanisms of albuminuria in diabetic nephropathy, which lack evidence in vivo. The effects of high glucose on the passage of albumin across the glomerular ESL were analysed in streptozotocin-induced diabetic Sprague-Dawley rats for 4 weeks. Albuminuria and glomerular mesangial matrix were significantly increased in diabetic rats. The passage of albumin across the ESL, as measured by albumin-colloid gold particle density in the glomerular basement membrane (GBM), was increased significantly in diabetic rats. The thickness of the glomerular ESL, examined indirectly by infusing Intralipid into vessels using an electron microscope, was significantly decreased and the GBM exhibited little change in diabetic rats. In summary, the glomerular ESL may play a role in the pathogenesis of albuminuria in rats with early-stage diabetes.

Clinical and pathological features of dense deposit disease in Chinese patients.

AIMS: Dense deposit disease (DDD) is a rare disease that has no universally effective treatment. Herein we explore the clinical and pathological features of DDD in Chinese patients and the therapeutic effect of Tripterygium wilfordii (TW). MATERIALS AND METHODS: Clinical and pathological data of 10 Chinese patients with biopsy-proved DDD were collected and analyzed retrospectively. RESULTS: The patients consisted of 6 males and 4 females. All of them had heavy proteinuria and microscopic hematuria. Gross hematuria, renal insufficiency, anemia, hypertension and low serum complement 3 (C3) occurred in 3, 3, 5, 6 and 8 cases, respectively. Under light microscopy (LM), 8 cases exhibited membranoproliferative glomerulonephritis (MPGN). Periodic acid-Schiff (PAS) stain disclosed intense PAS-positive bright ribbon-like thickening of glomerular basement membranes (GBM). Immunofluorescence mainly showed diffuse fine granular and short linear deposition of C3 along the glomerular capillary wall. Under electron microscopy, ribbon-like electrondense intramembranous deposits were identified in the lamina densa of the GBM, along the tubule basement membranes (TBM) and wall of Bowman's capsule. Before admission, 6 cases were treated with prednisone, cyclophosphamide and/or cyclosporin A with no response. Proteinuria in 8 cases who received TW during the course decreased at different degrees. CONCLUSIONS: The clinical and pathological features in DDD patients were various. The effect of TW in patients with DDD merits further investigation.

Dominant mutations of Col4a1 result in basement membrane defects which lead to anterior segment dysgenesis and glomerulopathy.

Members of the type IV collagen family are essential components of all basement membranes (BMs) and define structural stability as well as tissue-specific functions. The major isoform, alpha1.alpha1.alpha2(IV), contributes to the formation of many BMs and its deficiency causes embryonic lethality in mouse. We have identified an allelic series of three ENU induced dominant mouse mutants with missense mutations in the gene Col4a1 encoding the alpha1(IV) subunit chain. Two severe alleles (Bru and Svc) have mutations affecting the conserved glycine residues in the Gly-Xaa-Yaa collagen repeat. Bru heterozygous mice display defects similar to Axenfeld-Rieger anomaly, including iris defects, corneal opacity, vacuolar cataracts, significant iris/corneal adhesions, buphthalmos and optic nerve cupping, a sign indicative of glaucoma. Kidneys of Bru mice have peripheral glomerulopathy characterized by hypertrophy and hyperplasia of the parietal epithelium of Bowman's capsule. A milder allele (Raw) contains a mutation in the Yaa residue of the collagen repeat and was identified by a silvery appearance of the retinal arterioles. All phenotypes are associated with BM defects that affect the eye, kidney and other tissues. This allelic series shows that mutations affecting the collagen domain cause dominant negative effects on the expression and function of the major collagen IV isoform alpha1(IV), and pathological effects vary with the individual mutations.