Glomerulopathy in the KK.Cg-A(y) /J mouse reflects the pathology of diabetic nephropathy

Evaluation of urinary podocin and nephrin as markers of podocyturia in dogs with leishmaniosis

BACKGROUND

Renal disease is the main cause of death in canine leishmaniosis. Detection of an active glomerular injury is important to identify early renal damage and to prevent the development of chronic kidney disease. Podocyturia can indicate renal injury, and podocyte-associated molecules such as podocin and nephrin can be used to identify podocyturia. The purpose of the study was to evaluate urinary podocin and nephrin concentrations in dogs with leishmaniosis as markers of podocyturia.

METHODS

A total of 35 healthy dogs and 37 dogs with leishmaniosis were enrolled in the study. Dogs with leishmaniosis were classified according to the staging of the International Renal Interest Society (IRIS). Urinary podocin and nephrin concentrations were measured in all dogs with a validated enzyme-linked immunosorbent assay test and normalized to creatinine (uPoC and uNeC, respectively). The demographic, clinical, and laboratory data from both groups were analyzed and compared. Subsequently, the laboratory results were analyzed and compared according to IRIS staging in dogs in IRIS stage I and dogs in IRIS stage II + III + IV. The Pearson's correlation test evaluated the relationship between urinary markers of podocyturia.

RESULTS

Compared with healthy dogs, lower urinary podocin [median values (IQR): 15.10 (11.75-17.87) ng/ml versus 8.63 (7.08-13.56) ng/ml; P < 0.01] and nephrin [median values (IQR): 3.2 (3.62-5.43) ng/ml versus 2.67 (2.06-3.44) ng/ml; P < 0.01] were found in infected sick dogs. No significant differences were observed in the uPoC and uNeC between the two groups. Urinary nephrin and podocin concentrations were higher in healthy dogs and in dogs in IRIS stage I (both P < 0.05) compared with dogs in IRIS stages II + III + IV. No significant differences were found for uPoC and uNeC between healthy dogs and dogs with leishmaniosis in different IRIS clinical stages.

CONCLUSIONS

Dogs with leishmaniosis had a low concentration of podocin and nephrin in more advanced IRIS clinical stages, when kidney disease was more severe compared with healthy dogs and dogs in IRIS stage I with mild disease. Urinary nephrin was detectable for the first time in healthy non-infected dogs.

Characterization of selected dietary fibers microparticles and application of the optimized formulation as a fat replacer in hazelnut spreads

The present work demonstrates the application of the spray drying technique to produce microparticulates of different dietary fibers with particle sizes<10 µm. It examines their role as potential fat replacers for hazelnut spread creams. Optimization of a dietary fiber formulation containing inulin, glucomannan, psyllium husk, and chia mucilage to obtain high viscosity, water holding capacity, and oil holding capacity was conducted. Microparticles containing 46.1, 46.2, and 7.6 weight percentages of chia seed mucilage, konjac glucomannan, and psyllium husk showed a spraying yield of 83.45 %, a solubility of 84.63 %, and viscosity of 40.49 Pas. When applied to hazelnut spread creams, microparticles substituted palm oil by 100 %; they produced a product with a total unsaturated and saturated fat reduction of 41 and 77 %, respectively. An increase in dietary fibers of 4 % and a decrease in total calories of 80 % were also induced when compared with the original formulation. Hazelnut spread with dietary fiber microparticles were preferred by 73.13 % of the panelist in the sensory study due to an enhancement in brightness. The demonstrated technique could be used to increase the fiber content while decreasing the fat content in some commercial products, such as peanut butter or chocolate cream.

Adenosine/A1R signaling pathway did not play dominant roles on the influence of SGLT2 inhibitor in the kidney of BSA‐overloaded STZ‐induced diabetic mice

Aims/Introduction

Sodium–glucose cotransporter 2 inhibitors (SGLT2i) have been shown to display excellent renoprotective effects in diabetic kidney disease with macroalbuminuria/proteinuria. Regarding the renoprotective mechanism of SGLT2i, a sophisticated hypothesis was made by explaining the suppression of glomerular hypertension/hyperfiltration through the adenosine/adenosine type 1 receptor (A1R) signaling‐mediated restoration of the tubuloglomerular feedback mechanism; however, how such A1R signaling is relevant for renoprotection by SGLT2i in diabetic kidney disease with proteinuria has not been elucidated.

Materials and Methods

Streptozotocin‐induced diabetic CD‐1 mice were injected with bovine serum albumin (BSA) and treated with SGLT2i in the presence/absence of A1R inhibitor administration.

Results

We found that the influences of SGLT2i are essentially independent of the activation of A1R signaling in the kidney of BSA‐overloaded streptozotocin‐induced diabetic mice. BSA‐overloaded diabetic mice showed the trend of kidney damage with higher glomerular filtration rate (GFR) and the significant induction of fibrogenic genes, such as transforming growth factor‐β2 and collagen type III. SGLT2i TA‐1887 suppressed diabetes‐induced GFR in BSA‐overloaded diabetic mice was associated with the significant suppression of transforming growth factor‐β2 and collagen type III; A1R‐specific inhibitor 8‐cyclopentyl‐1,3‐dipropylxanthine did not cancel the effects of TA‐1887 on either GFR or associated gene levels. Both TA‐1887 and 8‐cyclopentyl‐1,3‐dipropylxanthine‐treated BSA‐overloaded diabetic mice showed suppressed glycated hemoglobin levels associated with the increased food intake. When analyzing the association among histological evaluation, GFR and potential fibrogenic gene levels, each group of mice showed distinct correlation patterns.

Conclusions

A1R signaling activation was not the dominant mechanism on the influence of SGLT2i in the kidney of BSA‐overloaded diabetic mice.

Loganin alleviates testicular damage and germ cell apoptosis induced by AGEs upon diabetes mellitus by suppressing the RAGE/p38MAPK/NF-κB pathway

Diabetes mellitus (DM) damages male reproduction at multiple levels, such as endocrine secretion, spermatogenesis and penile erection. We herein investigated the protective effects and mechanism of loganin targeting the advanced glycation end products (AGEs)/receptor for AGEs (RAGE)/p38 mitogen-activated protein kinase (p38MAPK)/NF-κB signalling pathway. Loganin relieved the general DM symptoms and decreased the blood glucose level of KK-Ay DM mice. Haematoxylin-eosin staining demonstrated that loganin ameliorated testicular histology and function and enhanced the activities of testis-specific markers lactate dehydrogenase (LDH), acid phosphatase (ACP) and gamma-glutamyl transferase (γ-GT). Loganin also showed evident anti-oxidative stress, anti-apoptotic and anti-inflammatory effects on DM-induced reproductive damage by restoring glutathione (GSH) level and superoxide dismutase (SOD) activity, as well as reducing reactive oxygen species (ROS) level and Bax/Bcl-2 ratio in vivo and in vitro. Western blotting exhibited that loganin significantly inhibited the AGEs/RAGE/p38MAPK/NF-κB signalling pathway. Acridine orange and ethidium bromide staining (AOEB) and Western blotting showed that loganin in combination with inhibitors of RAGE, p38MAPK and NF-κB exerted stronger anti-apoptotic effects on AGE-induced GC-2 cell damage compared with loganin alone. In conclusion, loganin can protect against DM-induced reproductive damage, probably by suppressing the AGEs/RAGE/p38MAPK/NF-κB pathway.

The diabetes pandemic suggests unmet needs for 'CKD with diabetes' in addition to 'diabetic nephropathy'-implications for pre-clinical research and drug testing

Curing 'diabetic nephropathy' is considered an unmet medical need of high priority. We propose to question the concept of 'diabetic nephropathy' that implies diabetes as the predominant cause of kidney disease, which may not apply to the majority of type 2 diabetics approaching end-stage kidney disease. With the onset of diabetes, hyperglycaemia/sodium-glucose co-transporter-2-driven glomerular hyperfiltration promotes nephron hypertrophy, which, however, on its own, causes proteinuria not before a decade later, probably because podocyte hypertrophy can usually accommodate an increase in the filtration surface. In contrast, precedent chronic kidney disease (CKD), that is, few nephrons per body mass, e.g. due to poor nephron endowment from birth, obesity, pregnancy, or renal ageing or injury-related nephron loss, usually precedes the onset of type 2 diabetes. This applies in particular in older adults, and each on its own, but especially in combination, further aggravates single nephron hyperfiltration and glomerular hypertrophy. Whenever this additional hyperglycaemia-driven enlargement of the glomerular filtration surface exceeds the capacity of podocytes for hypertrophy, podocytes detachment leads to glomerulosclerosis and nephron loss, i.e. CKD progression. Animal models of 'diabetic nephropathy' based only on hyperglycaemia do not mimic this aspect and therefore poorly predict outcomes of clinical trials usually performed on elderly CKD patients with type 2 diabetes. Thus, we advocate the use of renal mass (nephron) ablation in type 2 diabetic animals to better mimic the pathophysiology of 'CKD with diabetes' in the target patient population and the use of the glomerular filtration rate as a primary endpoint to more reliably predict trial outcomes.

Pharmacological inhibition of TRPV4 channels protects against ischemia-reperfusion-induced renal insufficiency in neonatal pigs

Renal vasoconstriction, an early manifestation of ischemic acute kidney injury (AKI), results in renal hypoperfusion and a rapid decline in kidney function. The pathophysiological mechanisms that underlie ischemia-reperfusion (IR)-induced renal insufficiency are poorly understood, but possibilities include alterations in ion channel-dependent renal vasoregulation. In the present study, we show that pharmacological activation of TRPV4 channels constricted preglomerular microvessels and elicited renal hypoperfusion in neonatal pigs. Bilateral renal ischemia followed by short-term reperfusion increased TRPV4 protein expression in resistance size renal vessels and TRPV4-dependent cation currents in renal vascular smooth muscle cells (SMCs). Selective TRPV4 channel blockers attenuated IR-induced reduction in total renal blood flow (RBF), cortical perfusion, and glomerular filtration rate (GFR). TRPV4 inhibition also diminished renal IR-induced increase in AKI biomarkers. Furthermore, the level of angiotensin II (Ang II) was higher in the urine of IR- compared with sham-operated neonatal pigs. IR did not alter renal vascular expression of Ang II type 1 (AT1) receptors. However, losartan, a selective AT1 receptor antagonist, ameliorated IR-induced renal insufficiency in the pigs. Blockade of TRPV4 channels attenuated Ang II-evoked receptor-operated Ca2+ entry and constriction in preglomerular microvessels. TRPV4 inhibition also blunted Ang II-induced increase in renal vascular resistance (RVR) and hypoperfusion in the pigs. Together, our data suggest that SMC TRPV4-mediated renal vasoconstriction and the ensuing increase in RVR contribute to early hypoperfusion and renal insufficiency elicited by renal IR in neonatal pigs. We propose that multimodal signaling by renal vascular SMC TRPV4 channels controls neonatal renal microcirculation in health and disease.

γ-secretase inhibitor DAPT mitigates cisplatin-induced acute kidney injury by suppressing Notch1 signaling

Organ toxicity, including kidney injury, limits the use of cisplatin for the treatment of multiple human cancers. Hence, interventions to alleviate cisplatin-induced nephropathy are of benefit to cancer patients. Recent studies have demonstrated that pharmacological inhibition of the Notch signaling pathway enhances cisplatin efficacy against several cancer cells. However, whether augmentation of the anti-cancer effect of cisplatin by Notch inhibition comes at the cost of increased kidney injury is unclear. We show here that treatment of mice with cisplatin resulted in a significant increase in Notch ligand Delta-like 1 (Dll1) and Notch1 intracellular domain (N1ICD) protein expression levels in the kidneys. N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), a γ-secretase inhibitor reversed cisplatin-induced increase in renal N1ICD expression and plasma or urinary levels of predictive biomarkers of acute kidney injury (AKI). DAPT also mitigated cisplatin-induced tubular injury and reduction in glomerular filtration rate. Real-time multiphoton microscopy revealed marked necrosis and peritubular vascular dysfunction in the kidneys of cisplatin-treated mice which were abrogated by DAPT. Cisplatin-induced Dll1/Notch1 signaling was recapitulated in a human proximal tubule epithelial cell line (HK-2). siRNA-mediated Dll1 knockdown and DAPT attenuated cisplatin-induced Notch1 cleavage and cytotoxicity in HK-2 cells. These data suggest that Dll1-mediated Notch1 signaling contributes to cisplatin-induced AKI. Hence, the Notch signaling pathway could be a potential therapeutic target to alleviate renal complications associated with cisplatin chemotherapy.

Thrombospondin-1 regulation of latent TGF-β activation: A therapeutic target for fibrotic disease

Transforming growth factor-β (TGF-β) is a central player in fibrotic disease. Clinical trials with global inhibitors of TGF-β have been disappointing, suggesting that a more targeted approach is warranted. Conversion of the latent precursor to the biologically active form of TGF-β represents a novel approach to selectively modulating TGF-β in disease, as mechanisms employed to activate latent TGF-β are typically cell, tissue, and/or disease specific. In this review, we will discuss the role of the matricellular protein, thrombospondin 1 (TSP-1), in regulation of latent TGF-β activation and the use of an antagonist of TSP-1 mediated TGF-β activation in a number of diverse fibrotic diseases. In particular, we will discuss the TSP-1/TGF-β pathway in fibrotic complications of diabetes, liver fibrosis, and in multiple myeloma. We will also discuss emerging evidence for a role for TSP-1 in arterial remodeling, biomechanical modulation of TGF-β activity, and in immune dysfunction. As TSP-1 expression is upregulated by factors induced in fibrotic disease, targeting the TSP-1/TGF-β pathway potentially represents a more selective approach to controlling TGF-β activity in disease.

Hematopoietically expressed homeobox gene is associated with type 2 diabetes in KK Cg-Ay/J mice and a Taiwanese Han Chinese population

Diabetes mellitus (DM) is a chronic disease. The KK Cg-A^y/J (KK-A^y) mouse is an animal model to study type 2 diabetes mellitus (T2D) disease. The present study assessed the expression of hematopoietically expressed homeobox (HHEX) protein in liver tissues of different age groups of mice (6, 16 and 42 weeks) by immunohistochemistry (IHC). The results demonstrated a significant decrease in the percentage of HHEX-positive cells in KK-A^y mice as compared with that in KK-α/α control mice. Furthermore, in Taiwan's Han Chinese population, genotypic and allelic frequency distributions of the rs61862780 single-nucleotide polymorphism (SNP) in the HHEX gene were investigated. The results demonstrated that in the rs61862780 SNP of the 3′-untranslated region (UTR) of HHEX, the frequency of the CC genotype was higher in patients (6.0%) than in controls (2.7%), while the TT genotype frequency was about equal. In the same SNP, the frequency of the C allele was higher in patients (21.0%) than in controls (17.3%), while the T allele frequency was about equal. These results may pave the road for exploring the KK-A^y mouse model and the HHEX SNP rs61862780, which was correlated with the susceptibility to T2D in a Chinese population. Based on these findings, an association of HHEX gene expression with pathological features of T2D was indicated.

Prevention of progression of diabetic nephropathy by the SGLT2 inhibitor ipragliflozin in uninephrectomized type 2 diabetic mice

Diabetic nephropathy is the leading cause of end-stage renal disease in the world. Although recent development of sodium-glucose cotransporter (SGLT) 2 inhibitors offers a new antidiabetic therapeutic strategy, it remains unclear whether such treatments are beneficial for limiting the progression of type 2 diabetic overt nephropathy. This study examined the effect of the SGLT2 inhibitor ipragliflozin on the progression of nephropathy in uninephrectomized KK/A^y type 2 diabetic mice, which exhibit not only typical diabetic symptoms such as hyperglycemia, hyperinsuemia, glucose intolerance, insulin resistance, hyperlipidemia, inflammation, and obesity, but also moderate hypertension and overt nephropathy with decline in renal function. Four-week repeated administration of ipragliflozin improved various diabetic symptoms, including hyperglycemia, insulin resistance, and inflammation by increasing urinary glucose excretion. In addition, ipragliflozin ameliorated albuminuria/proteinuria; decline in renal function, as measured by creatinine clearance; hypertension; and renal injury, including glomerulosclerosis and interstitial fibrosis. These effects were significant at doses of 1 mg/kg or higher and were similar to those observed following administration of losartan (30 mg/kg). These results suggest that the SGLT2 inhibitor ipragliflozin prevents progression to diabetic overt nephropathy in uninephrectomized type 2 diabetic mice. SGLT2 inhibitors may therefore represent a promising therapeutic option for the management of type 2 diabetes to slow the progression of diabetic nephropathy.

Apelin impairs myogenic response to induce diabetic nephropathy in mice

The cause of the invalid reaction of smooth muscle cells to mechanical stimulation that results in a dysfunctional myogenic response that mediates the disruption of renal blood flow (RBF) in patients with diabetes is debatable. The present study revealed that increased apelin concentration in serum of diabetic mice neutralized the myogenic response mediated by apelin receptor (APJ) and resulted in increased RBF, which promoted the progression of diabetic nephropathy. The results showed that apelin concentration, RBF, and albuminuria:creatinine ratio were all increased in kkAy mice, and increased RBF correlated positively with serum apelin both in C57 and diabetic mice. The increased RBF was accompanied by decreased phosphorylation of myosin light chain (MLC), β-arrestin, and increased endothelial NOS in glomeruli. Meanwhile, calcium, phosphorylation of MLC, and β-arrestin were decreased by high glucose and apelin treatment in cultured smooth muscle cells, as well. eNOS was increased by high glucose and increased by apelin in cultured endothelial cells (ECs). Knockdown of β-arrestin expression in smooth muscle cells cancelled phosphorylation of MLC induced by apelin. Therefore, apelin may induce the progression of diabetic nephropathy by counteracting the myogenic response in smooth muscle cells.-Zhang, J., Yin, J., Wang, Y., Li, B., Zeng, X. Apelin impairs myogenic response to induce diabetic nephropathy in mice.

High glucose induces apoptosis via upregulation of Bim expression in proximal tubule epithelial cells

Diabetic nephropathy is the primary cause of end-stage renal disease. Apoptosis of tubule epithelial cells is a major feature of diabetic nephropathy. The mechanisms of high glucose (HG) induced apoptosis are not fully understood. Here we demonstrated that, HG induced apoptosis via upregulating the expression of proapoptotic Bcl-2 homology domain 3 (BH3)-only protein Bim protein, but not bring a significant change in the baseline level of autophagy in HK2 cells. The increase of Bim expression was caused by the ugregulation of transcription factors, FOXO1 and FOXO3a. Bim expression initiates BAX/BAK-mediated mitochondria-dependent apoptosis. Silence of Bim by siRNA in HK2 cells prevented HG-induced apoptosis and also sensitized HK2 cells to autophagy during HG treatment. The autophagy inhibitor 3-MA increased the injury in Bim knockdown HK2 cells by retriggering apoptosis. The above results suggest a Bim-independent apoptosis pathway in HK2 cells, which normally could be inhibited by autophagy. Overall, our results indicate that HG induces apoptosis via up-regulation of Bim expression in proximal tubule epithelial cells.

Human mannose-binding lectin inhibitor prevents Shiga toxin-induced renal injury

Hemolytic uremic syndrome caused by Shiga toxin-producing Escherichia coli (STEC HUS) is a worldwide endemic problem, and its pathophysiology is not fully elucidated. Here we tested whether the mannose-binding lectin (MBL2), an initiating factor of lectin complement pathway activation, plays a crucial role in STEC HUS. Using novel human MBL2-expressing mice (MBL2 KI) that lack murine Mbls (MBL2(+/+)Mbl1(-/-)Mbl2(-/-)), a novel STEC HUS model consisted of an intraperitoneal injection with Shiga toxin-2 (Stx-2) with or without anti-MBL2 antibody (3F8, intraperitoneal). Stx-2 induced weight loss, anemia, and thrombocytopenia and increased serum creatinine, free serum hemoglobin, and cystatin C levels, but a significantly decreased glomerular filtration rate compared with control/sham mice. Immunohistochemical staining revealed renal C3d deposition and fibrin deposition in glomeruli in Stx-2-injected mice. Treatment with 3F8 completely inhibited serum MBL2 levels and significantly attenuated Stx-2 induced-renal injury, free serum hemoglobin levels, renal C3d, and fibrin deposition and preserved the glomerular filtration rate. Thus, MBL2 inhibition significantly protected against complement activation and renal injury induced by Stx-2. This novel mouse model can be used to study the role of complement, particularly lectin pathway-mediated complement activation, in Stx-2-induced renal injury.

Reprogrammed Functional Brown Adipocytes Ameliorate Insulin Resistance and Dyslipidemia in Diet-Induced Obesity and Type 2 Diabetes

Brown adipocytes (BAs) play important roles in body temperature regulation, energy balance, and carbohydrate and lipid metabolism. Activities of BAs are remarkably diminished in obese and diabetic patients, providing possibilities of transplanting functional BAs resulting in therapeutic benefit. Here, we show generation of functional BAs by cellular reprogramming procedures. Transduction of the PRDM16 gene into iPSC-derived embryoid bodies induced BA phenotypes (iBAs). Moreover, normal human fibroblasts were directly converted into BAs (dBAs) by C/EBP-β and C-MYC gene transduction. Approximately 90% of the fibroblasts were successfully converted within 12 days. The dBAs were highly active in mitochondrial biogenesis and oxidative metabolism. Mouse dBAs were induced by Prdm16, C/ebp-β, and L-myc genes, and after transplantation, they significantly reduced diet-induced obesity and insulin resistance in an UCP1-dependent manner. Thus, highly functional BAs can be generated by cellular reprogramming, suggesting a promising tailor-made cell therapy against metabolic disorders including type 2 diabetes mellitus.

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Transduction of PRDM16 into iPSC-derived embryoid body cells induces BA phenotypes

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Human fibroblasts are directly converted into BAs by C/EBP-β and c-Myc transduction

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The efficiency of direct conversion is approximately 90%

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Reprogrammed BAs are metabolically active and reduce obesity and type 2 diabetes

Apelin promotes diabetic nephropathy by inducing podocyte dysfunction via inhibiting proteasome activities

Podocyte injuries are associated with progression of diabetic nephropathy (DN). Apelin, an adipocyte-derived peptide, has been reported to be a promoting factor for DN. In this study, we aim to determine whether apelin promotes progression of DN by inducing podocyte dysfunction. kk-Ay mice were used as models for DN. Apelin and its antagonist, F13A were intraperitoneally administered for 4 weeks, respectively. Renal function and foot process proteins were analysed to evaluate the effects of apelin on kk-Ay mice and podocytes. Apelin increased albuminuria and decreased podocyte foot process proteins expression in kk-Ay mice, which is consistent with the results that apelin receptor (APLNR) levels increased in glomeruli of patients or mice with DN. In cultured podocytes, high glucose increased APLNR expression and apelin administration was associated with increased permeability and decreased foot process proteins levels. All these dysfunctions were associated with decreased 26S proteasome activities and increased polyubiquitinated proteins in both kk-Ay mice and cultured podocytes, as demonstrated by 26S proteasome activation with cyclic adenosine monophosphate (cAMP) or oleuropein. These effects seemed to be related to endoplasmic reticulum (ER) stress, as apelin increased C/EBP homologous protein (CHOP) and peiFα levels while cAMP or oleuropein reduced it in high glucose and apelin treated podocytes. These results suggest that apelin induces podocyte dysfunction in DN through ER stress which was induced by decreased proteasome activities in podocytes.

Nephrin - a biomarker of early glomerular injury

Nephrin is a 180 KD trans-membrane protein expressed in glomerular podocytes. It was first identified in children with congenital nephrotic syndrome of the Finnish type (NPHS1). Nephrin forms an integral part of podocytes, which-together with endothelial cells and the basement-form the glomerular filtration barrier. Podocytopathies result in the detection of nephrin in the urine. We reviewed the literature to determine if urine nephrin measurements could become useful as a biomarker to detect early podocyte injury. Our search identified a total of 19 studies that have been published to date. The most common clinical conditions for which urine nephrin analyses were carried out included diabetic nephropathy, glomerulonephritis and pre-eclampsia. Nephrin measurement was carried out using commercially available ELISA kits, the messenger ribonucleic acid real-time polymerase chain Reaction, or electrophoresis. Nephrinuria showed positive correlation with proteinuria and severity of podocyte injury. In two studies, the level of nephrinuria declined in conjunction with clinical improvement in the patient following immunosuppressive treatment. Currently, there is no published data on the value of measuring urinary nephrin in pediatric patients.