Changes In Diabetic Kidney Research Articles

Spectral computed tomography parameters could be surrogate imaging markers to detect early perfusion changes in diabetic kidneys.

Kidney microvasculopathy is the baseline pathophysiological feature of diabetic kidney disease (DKD). We aimed to evaluate the spectral computed tomography (CT) parameters for detecting renal perfusion changes among diabetic patients. From August 2020 to June 2022, 34 patients (age, 57.7±10.7 years; male, 20) clinically diagnosed with type 2 diabetes mellitus (DM) and 19 DM-free individuals (age, 48.1±16.9 years; male, 12) were selected for analysis. The series participants formed the DM group and control group, respectively. Spectral parameters, including effective atomic number (Zeff), iodine density (ID), normalized iodine density (NID) and the slope of the energy spectrum curves (λ), between the 2 groups were analyzed using independent samples t-test. Receiver operator characteristic (ROC) curves were used to evaluate the diagnostic performance of spectral parameters for detecting renal perfusion changes. The results indicate that in both cortical and medullary phases, the values of Zeff, ID, NID, and λ40-70 for the renal cortex of the DM group were significantly higher than those in the control group (P<0.05). In the cortex phase, the diagnostic efficacy of cortical spectral CT parameters discriminating DM patients from controls was as follows: the area under ROC curve (AUC) of ID value was 0.816 [95% confidence interval (CI): 0.679-0.921] at the optimal cutoff value 4.14, the AUC of Zeff value was 0.800 (95% CI: 0.668-0.901) at the optimal cutoff value 9.26, the AUC of λ40-70 value was 0.822 (95% CI: 0.675-0.918) at the optimal cutoff value 8.26, and the AUC of NID value was 0.851 (95% CI: 0.684-0.926) at the optimal cutoff value 0.37. In medullary phase: the AUC of ID value was 0.769 (95% CI: 0.617-0.846) at the optimal cutoff value 5.08, the AUC of Zeff value was 0.763 (95% CI: 0.614-0.837) at the optimal cutoff value 9.58, the AUC of λ40-70 value was 0.766 (95% CI: 0.617-0.839) at the optimal cutoff value 10.07, and the AUC of NID value was 0.79 (95% CI: 0.623-0.855) at the optimal cutoff value 1.37. Spectral CT could serve as an alternative protocol for the early identification of kidney injury in diabetic patients.

Changes in Expression of the Connective Tissue Growth Factor in the Kidneys of Diabetic Rats During Aging

Background: Diabetic nephropathy (DN) is the most common cause of chronic renal failure in the world. There appears to be different pathogenetic, hemodynamic and metabolic processes leading to the pathologic mechanisms in DN. We studied the expression of connective tissue growth factor (CTGF) in the kidneys of diabetic rats over time.Methods: Male Sprague-Dawley rats were injected with 55mg/kg streptozotocin (STZ) (diabetes mellitus (DM) group) or with citrate buffer (control group). The rat kidneys were harvested 2 weeks, 2 months, 6 months and 12 months following the STZ challenge, and sectioned into three different kidney structures: glomeruli, proximal convoluted tubule (PCT) and distal convoluted tubule (DCT). Sections were immunohistochemically stained to monitor the expression of CTGF. Results:Significant differences in CTGF expression were observed 2 weeks and 2 months after the STZ challenge, with higher CTGF expression in diabetic rats. Two weeks post DM onset, high CTGF expression was demonstrated in the distal tubules of the diabetic rats. The expression of CTGF in the glomeruli of diabetic rats washighest 12 months after diabetes induction, with a complete absence of CTGF expression in the control groups throughout the study.Conclusions:The major change in expression of CTGF occurs within the first 2 months of DM, particularly in the DTC, implying an early onset of pathophysiological changes in diabetic kidneys, which would normally occur with aging. These findings help to contribute to our understanding of changes associated with DN and guide towards potentially appropriate treatment modalities.Key words: diabetes mellitus (DM), nephropathy, chronic renal failure, connective tissue growth factor (CTGF)

Changes in Expression of the Vascular Endothelial Growth Factor in the Kidneys of Diabetic Rats During Aging

Background. Diabetic nephropathy is the leading cause of end-stage renal disease (ESRD) in most developed countries. A number of specific factors may contribute to the onset and progression of diabetic nephropathy. One of those specific factors is vascular endothelial growth factor (VEGF). We studied the expression of VEGF in the kidneys of diabetic rats during aging. Methods. Male Sprague-Dawley rats were injected with 55mg/kg streptozotocin (STZ) (DM group) or with citrate buffer (control group). Kidneys were collected after 2 weeks, 2 months, 6 months and 12 months, and were analyzed in three different kidney structures: glomeruli, proximal (PCT) and distal convoluted tubules (DCT). Sections were stained immunohistochemically, using VEGF.Results. Significant differences in marker expression were observed after 2 months, with higher VEGF expression in diabetic rats. Positive VEGF cells were detected exclusively in the glomeruli of diabetic rats after 2 months. After 2 weeks of DM onset, high VEGF expression was demonstrated in the distal tubules of diabetic rats, as well as a complete absence of VEGF expression in the distal tubules of the control group. Conclusions. The major change in expression of VEGF occurs after 2 months of DM onset, particularly in the DTC, implying an early onset of pathophysiological changes in diabetic kidneys, which would usually occur with aging. These findings help to contribute to our understanding of changes associated with DN and guide towards potentially appropriate treatment modalities.Key words: diabetes mellitus, kidneys, nephropathy, VEGF

DTI-based radiomics signature for the detection of early diabetic kidney damage

To explore whether a radiomics signature based on diffusion tensor imaging (DTI) can detect early kidney damage in diabetic patients. Twenty-eight healthy volunteers (group A) and thirty type 2 diabetic patients (group B) with micro-normoalbuminuria, a urinary albumin-to-creatinine ratio (ACR) < 30mg/g and an estimated glomerular filtration rate (eGFR) of 60-120mL/(min 1.73 m2) were recruited. Kidney DTI was performed using 1.5T magnetic resonance imaging (MRI).The radiologist manually drew regions of interest (ROI) on the fractional anisotropy (FA) map of the right kidney ROI including the cortex and medulla. The texture features of the ROIs were extracted using MaZda software. The Fisher coefficient, mutual information (MI), and probability of classification error and average correlation coefficient (POE + ACC) methods were used to select the texture features. The most valuable texture features were further selected by the least absolute shrinkage and selection operator (LASSO) algorithm. A LASSO regression model based on the radiomics signature was established. The diagnostic performance of the model for detecting early diabetic kidney changes was evaluated by the area under the receiver operating characteristic (ROC) curve (AUC). Empower (R), R, and MedCalc15.8 software were used for statistical analysis RESULTS: A total of 279 texture features were extracted from ROI of the kidney, and 30 most valuable texture features were selected from groups A and B using MaZda software. After LASSO-logistic regression, a diagnostic model of diabetic kidney damage based on texture features was established. Model discrimination evaluation: AUC = 0.882 (0.770 ± 0.952). Model calibration evaluation: Hosmer-Lemeshow X2 = 5.3611, P = 0.7184, P > 0.05, the model has good calibration. The texture features based on DTI could play a promising role in detecting early diabetic kidney damage.

Dietary zinc reduces endoplasmic reticulum stress and autophagy to protect against diabetic renal damage in streptozotocin-induced diabetic rats

Most of the patients with type 2 diabetes mellitus suffer from renal injury. The current study explored the protective effects of dietary zinc against diabetic renal injury and the underlying molecular mechanisms. In experiments, ZnSO4 at 15 mg/kg was intragastrically administrated into type 2 diabetes mellitus-like Wistar rat models daily for continuously 53 days. Biochemical assay was performed to detect serum fasting blood glucose, blood urea nitrogen (BUN), creatinine, and insulin. The H&E staining, immunohistochemical assay, and Western blotting were performed to detect the changes in kidney tissues. In results, dietary zinc reduced the lipid peroxidation malondialdehyde levels and enhanced the total anti-oxidation capacity levels. The pathological changes in diabetic kidney were improved. The percentage of autophagy-associated LC3-II positive cells was lowered. Western blot levels of LC3-II proteins and endoplasmic reticulum (ER) stress-associated GRP78 proteins were lowered. In conclusion, dietary zinc can relieve ER stress and autophagy in diabetic kidney to improve kidney conditions of type 2 diabetes mellitus-like rat models. These findings may be useful to treat patients with diabetic renal injury.

Changes in expression of special AT-rich sequence binding protein 1 and phosphatase and tensin homologue in kidneys of diabetic rats during ageing.

Background Diabetic nephropathy (DN) is a common complication of diabetes mellitus (DM). We studied the expression of special AT-rich sequence binding protein 1 (SATB1) and phosphatase and tensin homologue (PTEN) in the kidneys of diabetic rats during ageing. Methods Male Sprague Dawley rats were injected with 55 mg/kg streptozotocin (STZ) (DM group) or with citrate buffer (control group). Kidneys were collected after 2 weeks, 6 months and 12 months, and were analysed in three different kidney structures: glomeruli, proximal (PCT) and distal convoluted tubules (DCT). Sections were stained immunohistochemically, using SATB1 and PTEN. Results Significant differences in marker expression were observed after 2 weeks, with higher SATB1 expression and lower PTEN expression in diabetic rats. PTEN was more highly expressed in controls after 6 and 12 months. After 12 months, there was higher SATB1 expression in diabetic rats. In the glomeruli, control rats had higher PTEN expression, whereas diabetic rats had higher SATB1 expression, after 12 months. PTEN expression increased from 2 weeks to 12 months in both the PCT and DCT of control rats. SATB1 was expressed exclusively in the PCT of diabetic rats after 2 weeks, and its expression in the DCT was higher in controls. After 6 months, both the PCT and DCT showed higher SATB1 expression in diabetic rats. Conclusions The major changes in expression of SATB1 and PTEN occur after 2 weeks of DM onset, particularly in the PCT, implying an early onset of pathophysiological changes in diabetic kidneys, which would normally occur with ageing. These findings help to contribute to our understanding of changes associated with DN and guide towards possible appropriate treatment modalities.

Use of intravoxel incoherent motion diffusion-weighted imaging to detect early changes in diabetic kidneys

The purpose of the study was to examine differences in kidney intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) parameters in early-stage diabetic patients versus healthy controls. Nineteen type 2 diabetic patients (group A) with a urinary albumin-to-creatinine ratio (ACR)<30mg/g and an estimated glomerular filtration rate (eGFR) of 80-120mL/(min1.73m2) and twelve healthy volunteers (group B) were recruited. Kidneys were scanned with 1.5-Tesla IVIM-DWI. Nine b values (0, 50, 100, 150, 200, 300, 400, 600, and 800s/mm2) were used. The parameters derived from IVIM-DWI were calculated for each kidney by two radiologists and included the perfusion fraction (f), diffusion coefficient (D), and pseudo-diffusion coefficient (D*). The mean values of f, D, and D* were calculated by selecting multiple regions of interest in the kidney. The diagnostic performance of the f, D, and D* values for the diagnosis of early diabetic kidney changes was determined by receiver operating characteristic analysis. Three radiologists independently measured the parameters derived from IVIM-DWI in the two groups by free-hand placing regions of interest, and the interclass coefficients (ICCs) were analyzed by SPSS.16.0 software. The f values of the kidneys were significantly higher in diabetic patients than in healthy volunteers. The D value of the kidneys was significantly lower in diabetic patients than in healthy volunteers. No significant differences in the D* values of the kidneys were observed between diabetic patients and healthy volunteers. The D values of the right kidneys were significantly higher than those of the left kidneys in both groups. The results of the receiver operating characteristic analysis were as follows: left kidney-f value AUC=0.650 (cutoff point≥27.49%) and D value AUC=0.752 (cutoff point≤1.68×10-3mm2/s); and right kidney-f value AUC=0.650 (cutoff point≥28.24%) and D value AUC=0.752 (cutoff point≤1.81×10-3 mm2/s). The diagnostic performance of the D* value was very low (AUC<0.6). No significant differences were present between the areas under the curves of the f and D values (P>0.05). The ICCs of the f value and D value were between 0.637 and 0.827. The ICC of the D* value was less than 0.3. The results of our study suggest that changes in kidneys detected by IVIM-DWI may serve as indicators of early diabetic kidney disease.

Changes in expression of special AT-rich sequence binding protein 1 and phosphatase and tensin homologue in kidneys of diabetic rats during ageing.

Diabetic nephropathy (DN) is a common complication of diabetes mellitus (DM). We studied the expression of special AT-rich sequence binding protein 1 (SATB1) and phosphatase and tensin homologue (PTEN) in the kidneys of diabetic rats during ageing. Male Sprague Dawley rats were injected with 55 mg/kg streptozotocin (STZ) (DM group) or with citrate buffer (control group). Kidneys were collected after 2 weeks, 6 months and 12 months, and were analysed in three different kidney structures: glomeruli, proximal (PCT) and distal convoluted tubules (DCT). Sections were stained immunohistochemically, using SATB1 and PTEN. Significant differences in marker expression were observed after 2 weeks, with higher SATB1 expression and lower PTEN expression in diabetic rats. PTEN was more highly expressed in controls after 6 and 12 months. After 12 months, there was higher SATB1 expression in diabetic rats. In the glomeruli, control rats had higher PTEN expression, whereas diabetic rats had higher SATB1 expression, after 12 months. PTEN expression increased from 2 weeks to 12 months in both the PCT and DCT of control rats. SATB1 was expressed exclusively in the PCT of diabetic rats after 2 weeks, and its expression in the DCT was higher in controls. After 6 months, both the PCT and DCT showed higher SATB1 expression in diabetic rats. The major changes in expression of SATB1 and PTEN occur after 2 weeks of DM onset, particularly in the PCT, implying an early onset of pathophysiological changes in diabetic kidneys, which would normally occur with ageing. These findings help to contribute to our understanding of changes associated with DN and guide towards possible appropriate treatment modalities.

Bergenin ameliorates diabetic nephropathy in rats via suppressing renal inflammation and TGF-β1-Smads pathway

Context: Diabetic nephropathy (DN) is a serious complication of diabetes. Bergenin (BEG) was previously confirmed to be effective in treating type 2 diabetes in rats.Objective: The objective of this study was to investigate the effects of BEG on renal function in diabetic rats, and meanwhile explore the molecular mechanism.Methods: DN was induced in rats by a single intraperitoneal injection of streptozotocin. The renal function was evaluated by serum creatinine (SCr), blood urea nitrogen (BUN), urinary albumin and renal histopathology. The proliferation of mesangial cells (MCs) was assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H tetrazolium bromide. The production of inflammatory cytokines was detected by ELISA kits, and the levels of Smads were measured by western blotting.Results and conclusion: In DN rats, there were significantly increased levels of SCr, BUN, urinary albumin, plasma glucose and renal index. The histological changes in diabetic kidney revealed noteworthy focal mesangial matrix expansion. In vitro experiment, high glucose markedly promoted MCs proliferation. However, treatment with BEG obviously normalized these functional parameters, improved diabetic histological changes in vivo and inhibited MCs’ proliferation in vitro. Moreover, the levels of tumor necrosis factor-alpha, interleukin-1 (IL-1) and IL-6 in BEG-treated renal tissue and MCs were both reduced. Finally, it showed that BEG markedly reduced transforming growth factor-β1 (TGF-β1) production, down-regulated p-Smad2/3 expression and promoted Smad7 expression both in vivo and in vitro. In conclusion, BEG exerts the effective protective role against kidney injuries of diabetic rat, in which the underlying mechanisms are associated with reducing renal inflammation and blocking TGF-β1-Smads pathway.

Incretin-based therapy: renal effects

Glucagon like peptide-1 (GLP-1) analogues and dipeptidyl peptidase-4 (DPP-4) inhibitors are new classes of hypoglycemic agents with numerous pleiotropic effects. The review summarises data about the influence of GLP-1 analogues and DPP-4 inhibitors on structural and functional changes in diabetic kidneys. Growing evidence indicates that the kidney is one of the loci of the effects and degradation of GLP-1. The potency of the effects of GLP-1 in diabetic kidneys can be reduced by decrease in GLP-1 receptor expression or enhancement of GLP-1 degradation. In experimental models of diabetic nephropathy and non-diabetic renal injury, GLP-1 analogues and DPP-4 inhibitors slow the development of kidney fibrosis and prevent the decline of kidney function. The mechanisms of protective effect include hyperglycaemia reduction, enhancement of sodium excretion, suppression of inflammatory and fibrogenic signalling pathways, reduction of oxidative stress and apoptosis in the kidneys. In clinical studies, the urinary albumin excretion reduction rate while using the GLP-1 analogue and DPP-4 inhibitor treatment was demonstrated in patients with type 2 diabetes. Long-term impact of these agents on renal function in diabetes needs further investigations.

Ultrastructural changes of kidney in diabetic rats.

To demonstrate histopathological changes in diabetic kidneys of the rat on ultrastructural level with focusing on glomerular cellular environment. Male Wistar rats were administered streptozotocin and after 8 weeks, their kidneys were studied using qualitative transmission electron microscope analysis. In diabetic kidneys, the presence of irregularly thickened glomerular membrana basalis (GBM), often up to six times as compared to healthy kidney GBM, mainly around peripheral capillary loops, was striking. We also demonstrated lamination and split appearance of GBM, with presence of delicate fibrillar structure, which was absent within normal GBM. Accumulation of mesangial matrix was found only occasionally. Model may be useful to better understand the mechanisms that play role in the progression of DM-induced renal disease and to comprehend the morphological changes, which this process leaves within the tissue. The clear association between ultra-structure and functional markers may not be necessary (Fig. 4, Ref. 27).

Xuezhikang () reduced renal cell apoptosis in streptozocin-induced diabetic rats through regulation of Bcl-2 family.

To investigate the effect of Xuezhikang (, XZK) on renal cell apoptosis in diabetic rats and the possible mechanism. Sixty-six rats were randomly divided into 3 groups: the normal, model and XZK groups. In each group, the rats were further randomly divided into 3-month and 6-month subgroups, respectively. Diabetes of rats was induced by a single intraperitoneal injection of 1% streptozocin at 60 mg/kg body weight. Rats in the XZK group received gastric perfusion of XZK (1200 mg/kg body weight) everyday for 3 or 6 months, while rats in the normal and model groups received equal volume of saline. Twenty-four hours' urine was collected for urinary albumin excretion (UAE) measurement. Periodic acid-Schiff (PAS) and Masson's trichrome staining were used for saccharides and collagen detection. Cell apoptosis of renal cortex was investigated by TdT-mediated dUTP nick end labeling (TUNEL) staining. Bax and Bcl-2 expressions were detected by immunohistochemistry and Western blot, respectively. Cytochrome C (Cyt C) and caspase-9 concentration were detected by Western blot. Compared with the model group, XZK treatment could significantly decrease the kidney hypertrophy index, 24 h UAE, renal cell apoptosis, cytoplasmic Cyt C level and active caspase-9 level, as well as suppress the increment of Bax and up-regulate the expression of Bcl-2, leading to the suppression of Bax/Bcl-2 ratio at 3 and 6 months (P<0.05 or P<0.01). Moreover, XZK treatment could alleviate the deposition of PAS-stained saccharides and Masson's trichromestained collagen to different extent. Renal cell apoptosis was observed in diabetic kidney, in which mitochondrial apoptotic pathway might be involved. XZK treatment could attenuate pathological changes in diabetic kidney and reduce renal cell apoptosis, probably via the suppression of Bax/Bcl-2 ratio, which lead to inhibition of Cyt C release and following caspase-9 activation.

Ficolin B in Diabetic Kidney Disease in a Mouse Model of Type 1 Diabetes.

Background. The innate immune system may have adverse effects in diabetes and cardiovascular disease. The complement system seems to play a key role through erroneous complement activation via hyperglycaemia-induced neoepitopes. Recently mannan-binding lectin (MBL) was shown to worsen diabetic kidney changes. We hypothesize that mouse ficolin B exerts detrimental effects in the diabetic kidney as seen for MBL. Methods. We induced diabetes with streptozotocin in female wild-type mice and ficolin B knockout mice and included two similar nondiabetic groups. Renal hypertrophy and excretion of urinary albumin and creatinine were quantified to assess diabetic kidney damage. Results. In the wild-type groups, the kidney weighed 24% more in the diabetic mice compared to the controls. The diabetes-induced increase in kidney weight was 29% in the ficolin B knockout mice, that is, equal to wild-type animals (two-way ANOVA, P = 0.60). In the wild-type mice the albumin-to-creatinine ratio (ACR) was 32.5 mg/g higher in the diabetic mice compared to the controls. The difference was 62.5 mg/g in the ficolin B knockout mice, but this was not significantly different from the wild-type animals (two-way ANOVA, P = 0.21). Conclusions. In conclusion, the diabetes-induced effects on kidney weight and ACR were not modified by the presence or absence of ficolin B.

Elevated MBL Levels in Type 1 Diabetic Patients Are Reversed After Simultaneous Pancreas-Kidney Transplantation.

Aim: High levels of circulating Mannan-binding lectin (MBL) are associated with the development of diabetic nephropathy (DN). MBL is an essential component of the acute-phase immune response and initiates the lectin pathway of complement upon binding sugar moieties. In animals, an injurious effect of MBL on diabetic kidney changes has been observed and vasculopathy resulting from hyperglycemia has been shown to be dependent on MBL and lectin complement pathway activation. In humans, the effect of diabetic control on circulating levels of MBL has not been studied so far. Simultaneous pancreas-kidney transplantation (SPK) is an advanced treatment option for type I diabetes (T1D) patients with diabetic nephropathy. By assessing MBL in healthy control subjects and T1D patients before and following SPK, we studied the effect of T1D and SPK on the circulating levels of MBL. Methods: Circulating MBL levels were assessed using sandwich ELISA in plasma of DN (n=21) and SPK patients (n=37), healthy controls (n=19) and DM1 patients (n=15, DM ≥ 40 mL/min). To differentiate between diabetic control and renal failure as possible causes for change in the MBL levels, a subgroup of DN patients receiving a kidney but no pancreas transplant (n=15) were included. In addition, MBL levels were correlated with Hba1c and glucose levels. Results: We found significant elevated levels of MBL in plasma of DN patients compared to healthy controls. MBL levels in DN patients with a normal kidney function were also elevated, although not significant. MBL levels in patients receiving a SPK completely normalized compared to healthy controls. In contrast, MBL levels in DN patient receiving only a kidney transplant remained elevated, suggesting that diabetic control but not reversal of renal failure is associated with a decrease in circulating MBL. In line, glucose levels and Hba1C, but not creatinine levels in DN patients were significantly correlated with levels of MBL. Of interest, we also found a significant correlation between the plasma level of MBL and the duration of T1D before a SPK was needed, suggesting that elevated levels of MBL accelerate the disease progress. Conclusion: In short, we demonstrated that circulating levels of MBL are elevated in DN patients and normalized after SPK. The normalization of MBL levels was independent of renal function, but dependent on diabetic control.

Diabetes‐induced Changes in Mannan‐binding Lectin Levels and Complement Activation in a Mouse Model of Type 1 Diabetes

Circulating mannan-binding lectin (MBL) levels are elevated in type 1 diabetes. Further, high MBL levels are associated with the development of diabetic nephropathy. In animals, a direct effect of MBL on diabetic kidney changes is observed. We hypothesized that MBL levels and detrimental complement activation increase as a consequence of diabetes. We measured plasma MBL before and 7 weeks after inducing diabetes by streptozotocin. Mice have two MBLs, MBL-A and MBL-C. Diabetes induction led to an increase in MBL-C concentration, whereas no change during the study was found in the control group. The increase in MBL-C was associated with the increasing plasma glucose levels. In accordance with the observed changes in circulating MBL levels, liver expression of Mbl2mRNA (encoding MBL-C) was increased in diabetes. Mbl1expression (encoding MBL-A) did not differ between diabetic and control animals. The estimated half-life of recombinant human MBL was significantly prolonged in mice with diabetes compared with control mice. Complement activation in plasma and glomeruli did not differ between groups. We demonstrate for the first time that MBL levels increase after induction of diabetes and in parallel with increasing plasma glucose. Our findings support the previous clinical observations of increased MBL in type 1 diabetes. This change may be explained by alternations in both MBL production and turnover.

Mannan-Binding Lectin in Diabetic Kidney Disease: The Impact of Mouse Genetics in a Type 1 Diabetes Model

Background. Mannan-binding lectin (MBL) is involved in the development of diabetic nephropathy. MBL is a part of the innate immune system where it can activate the complement system. Serum MBL level predicts later renal impairment in diabetes patients. Direct involvement of MBL in the development of diabetic kidney disease is observed in one animal strain. However, this involvement may differ among the animal strains. We thus examined the impact of the genetic background on the role of MBL in diabetic nephropathy. Materials/Methods. C57BL/6JBomTac and 129S6/SvEvTac mice were compared. In both strains, experimental type 1 diabetes was induced in wild-type (WT) and MBL-knockout (MBL-KO) mice by streptozotocin. Nondiabetic WT and MBL-KO mice were used as controls. We tested if MBL modified the diabetes-induced kidney changes by two-way ANOVA allowing for interaction. Results. MBL aggravated diabetes-induced kidney growth and glomerulus enlargement in C57BL/6JBomTac mice. MBL did not modify diabetes effects on glomerular basement membrane thickness or mesangial volume in any strain. Diabetes-induced changes in renal gene transcription of growth factors and matrix components were unaffected by MBL. Conclusions. Strain-specific MBL effects were found on downstream diabetic kidney changes. This emphasizes the importance of genetic background in this model of diabetic complications.

Morphological changes in diabetic kidney are associated with increased O-GlcNAcylation of cytoskeletal proteins including α-actinin 4

PurposeThe objective of the present study is to identify proteins that change in the extent of the modification with O-linked N-acetylglucosamine (O-GlcNAcylation) in the kidney from diabetic model Goto-Kakizaki (GK) rats, and to discuss the relation between O-GlcNAcylation and the pathological condition in diabetes.MethodsO-GlcNAcylated proteins were identified by two-dimensional gel electrophoresis, immunoblotting and peptide mass fingerprinting. The level of O-GlcNAcylation of these proteins was examined by immunoprecipitation, immunoblotting and in situ Proximity Ligation Assay (PLA).ResultsO-GlcNAcylated proteins that changed significantly in the degree of O-GlcNAcylation were identified as cytoskeletal proteins (α-actin, α-tubulin, α-actinin 4, myosin) and mitochondrial proteins (ATP synthase β, pyruvate carboxylase). The extent of O-GlcNAcylation of the above proteins increased in the diabetic kidney. Immunofluorescence and in situ PLA studies revealed that the levels of O-GlcNAcylation of actin, α-actinin 4 and myosin were significantly increased in the glomerulus and the proximal tubule of the diabetic kidney. Immunoelectron microscopy revealed that immunolabeling of α-actinin 4 is disturbed and increased in the foot process of podocytes of glomerulus and in the microvilli of proximal tubules.ConclusionThese results suggest that changes in the O-GlcNAcylation of cytoskeletal proteins are closely associated with the morphological changes in the podocyte foot processes in the glomerulus and in microvilli of proximal tubules in the diabetic kidney. This is the first report to show that α-actinin 4 is O-GlcNAcylated. α-Actinin 4 will be a good marker protein to examine the relation between O-GlcNAcylation and diabetic nephropathy.

Water extract of 1:1 mixture of Phellodendron cortex and Aralia cortex has inhibitory effects on oxidative stress in kidney of diabetic rats

Enhanced activity of the lipid peroxidation and oxidative damages have been implicated in the pathogenesis of diabetic kidney complications. We explored to determine whether these changes in diabetic kidney could be prevented by water extract of mixture of Phellodendron cortex and Aralia cortex (P55A). Greatly elevated content of thiobarbituric acid reactive substances (TBARS) and carbonylated protein in kidneys of diabetic rats were significantly reduced by P55A treatment. In addition, abnormally low ratio of GSH/GSSG in diabetic kidneys was elevated to almost normal levels by the treatment with P55A. These results suggest that P55A extracts exert antioxidant effect by reducing lipid peroxidation and protein carbonylation as well as by elevating the ratio of GSF/GSSG in diabetic kidney.

Melatonin and taurine reduce early glomerulopathy in diabetic rats

Oxidative stress occurs in diabetic patients and experimental models of diabetes. We examined whether two antioxidants, melatonin and taurine, can ameliorate diabetic nephropathy. Enhanced expression of glomerular TGF-β1 and fibronectin mRNAs and proteinuria were employed as indices of diabetic nephropathy. Experimental diabetes was induced by intravenous injection of streptozotocin 50 mg/kg. Two days after streptozotocin, diabetic rats were assigned to one of the following groups: i) untreated; ii) melatonin supplement by 0.02% in drinking water; or iii) taurine supplement by 1% in drinking water. Four weeks after streptozotocin, diabetic rats ( n = 6: plasma glucose 516 ± 12 mg/dl) exhibited 6.1 fold increase in urinary protein excretion, 1.4 fold increase in glomerular TGF-β1 mRNA, 1.7 fold increase in glomerular fibronectin mRNA, 2.2 fold increase in plasma lipid peroxides (LPO), and 44 fold increase in urinary LPO excretion above the values in control rats ( n = 6: plasma glucose 188 ± 14 mg/dl). Chronic administration of melatonin ( n = 6) and taurine ( n = 6) prevented increases in glomerular TGF-β1 and fibronectin mRNAs and proteinuria without having effect on blood glucose. Both treatments reduced lipid peroxidation by nearly 50%. The present data demonstrate beneficial effects of melatonin and taurine on early changes in diabetic kidney and suggest that diabetic nephropathy associated with hyperglycemia is largely mediated by oxidative stress. Science

The role of growth hormone, insulin-like growth factors (IGFs), and IGF-binding proteins in experimental diabetic kidney disease

Early renal changes in type I diabetes are characterized by an increase in renal size, glomerular volume, and kidney function, and later by development of mesangial proliferation, accumulation of glomerular extracellular matrix, and increased urinary albumin excretion (UAE). Growth hormone (GH) and insulin-like growth factors (IGFs) have a long and distinguished history in diabetes mellitus, with possible participation in the development of long-term complications. In experimental diabetes in dwarf rats with isolated GH and IGF-I deficiency, a slower and lesser renal and glomerular hypertrophy is observed as compared with diabetic control animals with intact pituitary. Furthermore, diabetic dwarf rats with a diabetes duration of 6 months display a smaller increase in UAE, indicating that GH and IGF-I may be involved in the development of diabetic kidney changes. In line with this, administration of octreotide to streptozotocin (STZ)-diabetic animals with normal pituitary inhibits initial renal growth without affecting blood glucose levels, and 6 months' administration of octreotide to diabetic rats reduces long-term renal/glomerular hypertrophy and UAE. In addition, the initial increase in renal size and function in experimental diabetes is preceded by an increase in renal IGF-I, IGF-binding proteins (IGFBPs), and IGF-II/mannose-6-phosphate receptor (IGF-II/Man6-P receptor) concentration. Finally, specific changes occur in renal GH-binding protein (GHBP) mRNA, IGF-I receptor mRNA, and IGFBP mRNA expression in long-term diabetes. In conclusion, the knowledge we have today indicates that GH and IGFs, through a complex system consisting of GHBP, IGFs, IGF receptors, and IGFBPs, may be responsible for both early and late renal changes in experimental diabetes.