Glomerular Mesangial Expansion Research Articles

Finerenone attenuates downregulation of the kidney GLP-1 receptor and glucagon receptor and cardiac GIP receptor in mice with comorbid diabetes

BackgroundSeveral new treatments have recently been shown to have heart and kidney protective benefits in people with diabetes. Because these treatments were developed in parallel, it is unclear how the different molecular pathways affected by the therapies may overlap. Here, we examined the effects of the mineralocorticoid receptor antagonist finerenone in mice with comorbid diabetes, focusing on the regulation of expression of the glucagon-like peptide-1 receptor (GLP-1R), gastric inhibitory polypeptide receptor (GIPR) and glucagon receptor (GCGR), which are targets of approved or investigational therapies in diabetes.MethodsMale C57BL/6J mice were fed a high fat diet for 26 weeks. Twelve weeks into the high fat diet feeding period, mice received an intraperitoneal injection of streptozotocin before being followed for the remaining 14 weeks (DMHFD mice). After 26 weeks, mice were fed a high fat diet containing finerenone (100 mg/kg diet) or high fat diet alone for a further 2 weeks. Cell culture experiments were performed in primary vascular smooth muscle cells (VSMCs), NRK-49 F fibroblasts, HK-2 cells, and MDCK cells.ResultsDMHFD mice developed albuminuria, glomerular mesangial expansion, and diastolic dysfunction (decreased E/A ratio). Glp1r and Gcgr were predominantly expressed in arteriolar VSMCs and distal nephron structures of mouse kidneys respectively, whereas Gipr was the predominant of the three transcripts in mouse hearts. Kidney Glp1r and Gcgr and cardiac Gipr mRNA levels were reduced in DMHFD mice and this reduction was negated or attenuated with finerenone. Mechanistically, finerenone attenuated upregulation of the profibrotic growth factor Ccn2 in DMHFD kidneys, whereas recombinant CCN2 downregulated Glp1r and Gcgr in VSMCs and MDCK cells respectively.ConclusionsThrough its anti-fibrotic actions, finerenone reverses Glp1r and Gcgr downregulation in the diabetic kidney. Both finerenone and GLP-1R agonists have proven cardiorenal benefits, whereas receptor co-agonists are approved or under development. The current findings provide preclinical rationale for the combined use of finerenone with the GLP-1R agonist family. They also provide mechanism of action insights into the potential benefit of finerenone in people with diabetes for whom GLP-1R agonists or co-agonists may not be indicated.

β-cryptoxanthin suppresses oxidative stress via activation of the Nrf2/HO-1 signaling pathway in diabetic kidney disease.

This study aims to explore the role and investigate mechanisms of β-Cryptoxanthin (BCX) in high glucose (HG)-induced podocyte injury and renal dysfunction. In this study, db/db mice were orally treated with BCX. Blood glucose, body weight, urinary albumin creatinine ratio (ACR) were recorded to evaluate the mice renal function. The H&E, PAS staining, and transmission electron microscopy (TEM) were utilized to examine the effect of BCX on the morphological changes of glomeruli in db/db mice. In addition, reactive oxygen species (ROS) content, mitochondrial membrane potential (MMP) level, ATP level, and SA-β-gal staining were used to assess the podocyte oxidative damage, mitochondrial dysfunction and senescence. Furthermore, the effects of BCX on Nrf2/HO-1 signaling pathway were evaluated in vivo and in vitro through Western blotting, immunohistochemistry and immunofluorescence analysis. In vivo, BCX reversed glomerular mesangial matrix expansion and reduced proteinuria in db/db mice, as well as decreased glomerular oxidative stress and kidney aging. Similarly, in vitro study showed that BCX effectively alleviated the oxidative stress, mitochondrial dysfunction, and senescence induced by HG in podocytes. Furthermore, we identified that the antioxidative effects of BCX are associated with the activation of Nrf2/HO-1 signaling pathway, and that Nrf2 knockdown partially abrogated the protective effects of BCX in vitro. Our study demonstrated for the first time that BCX alleviates podocyte injury in DKD by promoting Nrf2/HO-1 signaling pathways. BCX may be a potential candidate compound for preventing Diabetic kidney disease (DKD).

Glucagon receptor activation contributes to the development of kidney injury.

The underlying causes of diabetic kidney disease are still largely unknown. New insights into the contributing causes of diabetic nephropathy are important to prevent this complication. Hyperglycemia and hypertension are some of the risk factors for diabetic nephropathy. However, the incidence of diabetic nephropathy is increasing despite efforts to normalize blood glucose levels and blood pressure. Therefore, other factors should be investigated as causes of diabetic nephropathy. We investigated whether long-term increased plasma levels of glucagon contribute to the development of pathophysiological changes in kidney function as seen in patients with diabetic nephropathy. Using mouse models of chronic activation and inactivation of glucagon receptor signaling, we investigated whether glucagon is involved in changes in renal function, renal structure, and transcriptional changes. We found several histopathological changes in the kidney, such as thickening of the parietal layer of Bowman's capsule, glomerular mesangial cell expansion, and significant albuminuria in the mice with activated glucagon receptor signaling. Opposite effects on mesangial area expansion and the development of albuminuria were demonstrated in mice with glucagon receptor inactivation. RNA sequencing data revealed that transcription of genes related to fatty acid metabolism, podocytes, Na+-K+-ATPase, and sodium/glucose transport was significantly changed in mice with activated glucagon receptor signaling. These data implicate that glucagon receptor signaling is involved in the development of kidney injury, as seen in type 2 diabetes, and that glucagon receptor is a potential therapeutic target in the treatment of diabetes. NEW & NOTEWORTHY This study suggests that the glucagon receptor is a potential therapeutic target in the treatment of diabetic kidney disease. We show, in mice, that long-term treatment with a glucagon analog showed not only pathophysiological changes and changes in renal function but also transcriptional changes in the kidneys, whereas opposite effects were demonstrated in mice with glucagon receptor inactivation. Therefore, the use of glucagon in a treatment regimen requires investigation of possible metabolic and renal abnormalities.

A case of de novo glomerulonephritis following COVID-19 in a patient with preexistent IgA vasculitis.

During the unprecedented COVID-19 outbreak, new-onset or relapsing glomerulonephritis, such as ANCA-associated glomerulonephritis and Immunoglobulin A (IgA) nephropathy, following COVID-19 has been reported. However, to date, the association of COVID-19 with preexistent IgA vasculitis (IgAV) remains unclear. Here, we present the case of a 20-something old Japanese woman with preexistent IgAV who newly developed glomerulonephritis following COVID-19. At the diagnosis of IgAV, she had cutaneous purpura, joint pains, and gastrointestinal symptoms, but no signs of kidney involvement. Three months ago, she was tested positive for COVID-19 and subsequently developed hematuria and proteinuria. She was then admitted to our hospital and renal biopsy showed glomerular mesangial expansion and hypercellularity and cellular and fibrocellular crescents, accompanied by diffuse IgA and C3 deposits. With the diagnosis of de novo IgAV nephritis, the patient was treated with intravenous methylprednisolone followed by oral prednisolone. She had favorable responses to this treatment and has achieved and maintained the remission of hematuria and proteinuria after initiation of glucocorticoid therapy. Our case highlights that immune response to SARS-CoV-2 infection could trigger the onset of glomerulonephritis in the IgAV patients who have no renal involvement.

SGLT2i and GLP1-RA exert additive cardiorenal protection with a RAS blocker in uninephrectomized db/db mice.

Diabetic Kidney Disease (DKD) is the main cause of end-stage renal disease in the developed world. The current treatment of the DKD with renin-angiotensin system (RAS) blockade does not totally halt the progression to end stage kidney disease. Currently, several drugs have shown to delay DKD progression such as sodium-glucose co-transporter-2 inhibitors (SGLT2i) and glucagon-like-1 receptor agonists (GLP-1RA). We hypothesized that by combining several drugs that prevent DKD progression on top of RAS blockade a synergistic effect would be achieved in terms of cardiorenal protection. In the present study, we analysed if the combination of a RAS blocker (ramipril) with a SGLT2i (empagliflozin) and/or GLP-1RA (semaglutide) in a type 2 diabetic mouse model could have add-on effects in kidney and heart protection. Male and female uninephrectomized type 2 diabetic db/db mice were treated with empagliflozin and/or semaglutide on top of ramipril during 8weeks. During the study body weight, water and food intake were weekly monitored, glycaemia biweekly and albuminuria and glomerular filtration rate (GFR) before and after the treatment. At the end of the experiment, kidney and heart were isolated for histological and gene expression studies as well as for intrarenal RAS state assessment. Semaglutide combined with ramipril and/or empagliflozin significantly decreased albuminuria but only when combined with both compounds, semaglutide further decreased blood glucose, glomerular hyperfiltration in male mice and glomerular mesangial matrix expansion. In kidney, only the triple treatment with empagliflozin, semaglutide and ramipril reduced the expression of the proinflammatory and profibrotic genes ccl2 and TGFß1. In addition, the combination of empagliflozin and semaglutide on top of RAS blockade was superior in decreasing cardiomyocyte hypertrophy and heart fibrosis in db/db mice. Our results suggest that the combination of SGLT2i with GLP-1RA is superior in cardiorenal protection in DKD than the drugs administered alone on top of RAS blockade.

Repurposing Niclosamide to Modulate Renal RNA-Binding Protein HuR for the Treatment of Diabetic Nephropathy in db/db Mice.

Hu antigen R (HuR) plays a key role in regulating genes critical to the pathogenesis of diabetic nephropathy (DN). This study investigates the therapeutic potential of niclosamide (NCS) as an HuR inhibitor in DN. Uninephrectomized mice were assigned to four groups: normal control; untreated db/db mice terminated at 14 and 22 weeks, respectively; and db/db mice treated with NCS (20 mg/kg daily via i.p.) from weeks 18 to 22. Increased HuR expression was observed in diabetic kidneys from db/db mice, which was mitigated by NCS treatment. Untreated db/db mice exhibited obesity, progressive hyperglycemia, albuminuria, kidney hypertrophy and glomerular mesangial matrix expansion, increased renal production of fibronectin and a-smooth muscle actin, and decreased glomerular WT-1+-podocytes and nephrin expression. NCS treatment did not affect mouse body weight, but reduced blood glucose and HbA1c levels and halted the DN progression observed in untreated db/db mice. Renal production of inflammatory and oxidative stress markers (NF-κBp65, TNF-a, MCP-1) and urine MDA levels increased during disease progression in db/db mice but were halted by NCS treatment. Additionally, the Wnt1-signaling-pathway downstream factor, Wisp1, was identified as a key downstream mediator of HuR-dependent action and found to be markedly increased in db/db mouse kidneys, which was normalized by NCS treatment. These findings suggest that inhibition of HuR with NCS is therapeutic for DN by improving hyperglycemia, renal inflammation, and oxidative stress. The reduction in renal Wisp1 expression also contributes to its renoprotective effects. This study supports the potential of repurposing HuR inhibitors as a novel therapy for DN.

Astaxanthin attenuates diabetic kidney injury through upregulation of autophagy in podocytes and pathological crosstalk with mesangial cells

Objectives: Astaxanthin (ATX) is a strong antioxidant drug. This study aimed to investigate the effects of ATX on podocytes in diabetic nephropathy and the underlying renal protective mechanism of ATX, which leads to pathological crosstalk with mesangial cells.Methods: In this study, diabetic rats treated with ATX exhibited reduced 24-h urinary protein excretion and decreased blood glucose and lipid levels compared to vehicle-treated rats. Glomerular mesangial matrix expansion and renal tubular epithelial cell injury were also attenuated in ATX-treated diabetic rats compared to control rats.Results: ATX treatment markedly reduced the α-SMA and collagen IV levels in the kidneys of diabetic rats. Additionally, ATX downregulated autophagy levels. In vitro, compared with normal glucose, high glucose inhibited LC3-II expression and increased p62 expression, whereas ATX treatment reversed these changes. ATX treatment also inhibited α-SMA and collagen IV expression in cultured podocytes. Secreted factors (vascular endothelial growth factor B and transforming growth factor-β) generated by high glucose-induced podocytes downregulated autophagy in human mesangial cells (HMCs); however, this downregulation was upregulated when podocytes were treated with ATX.Conclusions: The current study revealed that ATX attenuates diabetes-induced kidney injury likely through the upregulation of autophagic activity in podocytes and its antifibrotic effects. Crosstalk between podocytes and HMCs can cause renal injury in diabetes, but ATX treatment reversed this phenomenon.

Emerging Therapeutics Targeting Cellular Stress Pathways to Mitigate End-Organ Damage in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease characterized by insulin deficiency and impaired glucose regulation. While daily insulin therapy is life-saving, many patients struggle to achieve optimal glycemic control, leading to microvascular complications affecting various organs, including the kidneys and the liver. This review aims to summarize the current state of knowledge regarding the pathogenesis of hepatic and renal complications in T1D, highlight recent advances in potential therapeutic targets, and provide evidence-based recommendations for mitigating end-organ damage. Chronic hyperglycemia drives diabetic complications through several interrelated mechanisms, including increased polyol pathway flux, advanced glycation end-product (AGE) formation, protein kinase C activation, and mitochondrial reactive oxygen species overproduction. In the liver, these processes contribute to non-alcoholic fatty liver disease, with up to 50% of T1D patients developing hepatic steatosis. Diabetic nephropathy, affecting 25%–40% of long-term T1D patients, is characterized by glomerular basement membrane thickening, mesangial expansion, and tubulointerstitial fibrosis. Recent innovations in T1D management include genomics and precision medicine approaches, gut microbiome modulation, nanomedicine, and artificial intelligence-driven glucose monitoring systems. Emerging immunotherapies aim to fundamentally modify the autoimmune response in T1D. Mitigating T1D complications requires intensive glycemic control, targeted pharmacotherapy, and lifestyle modifications. Emerging therapies and precision medicine approaches offer promising avenues. Ongoing research into molecular mechanisms remains crucial for developing novel interventions and improving long-term outcomes in T1D patients.

Associations of urinary fetuin-A with histopathology and kidney events in biopsy-proven kidney disease.

Fetuin-A is implicated in the pathogenesis of vascular calcification in chronic kidney disease (CKD); however, the relationship between fetuin-A, histopathologic lesions and long-term kidney outcomes in patients with various types of kidney disease remains unclear. We measured urinary fetuin-A levels in 335 individuals undergoing clinically indicated native kidney biopsy. The expressions of fetuin-A mRNA and protein in the kidney were assessed using RNA sequencing and immunohistochemistry. The association of urinary fetuin-A with histopathologic lesions and major adverse kidney events (MAKE), defined as a decline in estimated glomerular filtration rate (eGFR) of at least 40%, kidney failure or death, was analyzed. Urinary fetuin-A levels showed a positive correlation with albuminuria (rs=0.67, P<.001) and a negative correlation with eGFR (rs=-0.46, P<.001). After multivariate adjustment, higher urinary fetuin-A levels were associated with glomerular inflammation, mesangial expansion, interstitial fibrosis and tubular atrophy, and arteriolar sclerosis. Using a 1 transcript per million gene expression cutoff, we found kidney fetuin-A mRNA levels below the threshold in both individuals with normal kidney function and those with CKD. Additionally, immunohistochemistry revealed reduced fetuin-A staining in tubular cells of CKD patients compared with normal controls. During a median 21-month follow-up, 115 patients experienced MAKE, and Cox regression analysis confirmed a significant association between elevated urinary fetuin-A and MAKE. This association remained significant after adjusting for potential confounding factors. Urinary fetuin-A is associated with chronic histological damage and adverse clinical outcomes across a spectrum of biopsy-proven kidney diseases.

Potential Renal Effects of Cigarette Smoking in the Diabetic State-A review

Diabetes is an alarming global systemic metabolic disorder that can pose a major threat to patients. The serious consequences of cigarette smoking on the diabetic kidney are not well known among people in different countries. According to different studies, smoking enhances albuminuria in diabetic patients. On the other hand, urinary albumin is a sensitive indicator of glomerular injury. The abnormal trans-glomerular passage of albumin may be seen due to increased permeability of the glomerular capillary wall and their subsequent impaired reabsorption by the epithelial cells of the proximal tubule. Smoking with hyperglycemia increases lipid accumulation and oxidative stress, which mainly up-regulates TGF-β, accumulates AGEs, reduces nitric oxide production, and eventually causes glomerular basement membrane thickening and mesangial expansion that results in the development of glomerulosclerosis and nephropathy. The complex interaction between cigarette smoking and diabetic mellitus poses multiple challenges for researchers, physicians, and patients. Therefore, the present review article aims to find out the feasible consequences for the kidney of a diabetic patient due to the habit of cigarette smoking which may be useful for academicians and researchers in the future.

ERK1/2-dependent activity of SOX9 is required for sublytic C5b-9-induced expression of FGF1, PDGFα, and TGF-β1 in rat Thy-1 nephritis

Mesangial proliferative glomerulonephritis (MsPGN) and its related rat model Thy-1 nephritis (Thy-1N) are associated with C5b-9 deposition and are characterized by proliferation of glomerular mesangial cell (GMC) and expansion of extracellular matrix (ECM) expansion, alongside overexpression of multiple growth factors. Although fibroblast growth factor 1 (FGF1), platelet-derived growth factor alpha (PDGFα), and transforming growth factor beta 1 (TGF-β1) are well known for their proproliferative and profibrotic roles, the molecular mechanisms responsible for regulating the expression of these growth factors have not been thoroughly elucidated. In this study, we found that sublytic C5b-9 induction of sex-determining region Y-box 9 (SOX9) transactivated FGF1, PDGFα, and TGF-β1 genes in GMCs, resulting in a significant increase in their mRNA and protein levels. Besides, sublytic C5b-9 induction of activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) phosphorylated SOX9 at serine 181 and serine 64, which enhanced SOX9′s ability to transactivate FGF1, PDGFα, and TGF-β1 genes in GMCs. Furthermore, we demonstrated that inhibiting ERK1/2 activation or silencing either ERK1/2 or SOX9 gene led to reduced SOX9 phosphorylation, decreased generation of FGF1, PDGFα, and TGF-β1, and ameliorated glomerular injury in rat Thy-1N. Overall, these findings suggest that expression of FGF1, PDGFα, and TGF-β1 is promoted by ERK1/2-mediated phosphorylation of SOX9, which may provide a valuable insight into the pathogenesis of MsPGN and offer a potential target for the development of novel treatment strategies for MsPGN.

Ultra-High Temperature Treatment of Liquid Infant Formula, Systemic Immunity, and Kidney Development in Preterm Neonates.

Ready-to-feed liquid infant formulas (IFs) are increasingly being used for newborn preterm infants when human milk is unavailable. However, sterilization of liquid IFs by ultra-high temperature (UHT) introduces Maillard reaction products (MRPs) that may negatively affect systemic immune and kidney development. UHT-treated IF without and with prolonged storage (SUHT) are tested against pasteurized IF (PAST) in newborn preterm pigs as a model for preterm infants. After 5 days, blood leukocytes, markers of systemic immunity and inflammation, kidney structure and function are evaluated. No consistent differences between UHT and PAST pigs are observed. However, SUHT increases plasma TNFα and IL-6 and reduces neutrophils and in vitro response to LPS. In SUHT pigs, the immature kidneys show minor upregulation of gene expressions related to inflammation (RAGE, MPO, MMP9) and oxidative stress (CAT, GLO1), together with glomerular mesangial expansion and cell injury. The increased inflammatory status in SUHT pigs appears unrelated to systemic levels of MRPs. SUHT feeding may impair systemic immunity and affect kidney development in preterm newborns. The systemic effects may be induced by local gut inflammatory effects of MRPs. Optimal processing and length of storage are critical for UHT-treated liquid IFs for preterm infants.

An Overview of Major Clinical Predictive Factors and Prognostic Biomarkers of Diabetic Kidney Disease in Children and Adolescents

The onset and progression of diabetic nephropathy represent a significant issue in diabetic management as it is the primary microvascular consequence of both type 1 and type 2 diabetes mellitus and a significant contributor to end stage renal disease-related mortality. Major risk factors for nephropathy in children and adolescents include hyperglycemia, HbA1c, diabetes duration, gender, blood pressure, dyslipidemia, uric acid, family history and genetic factors, smoking, puberty, and obesity. Metabolism and hemodynamic variables interact on a complex basis during disease development. A series of intricate molecular events take place in response to hyperglycemia, which disturbs the body's metabolic environment and causes glomerular enlargement, tubular inflammation, mesangial expansion, oxidative stress, and renal fibrosis. Fortunately, the main approaches for preventing the beginning and reducing the progression of diabetic kidney damage are rigorous glucose control and antihypertensive medications. As children and adolescents with T1D are at risk for developing early diabetic nephropathy, patients with T1D must have the best metabolic control, an early diagnosis, and timely treatment of dyslipidemia and hypertension. Prospects for better diabetic nephropathy outcomes are improving as novel approaches are developed. Novel biomarkers are increasingly proven to be more reliable instruments than the traditional microalbuminuria, which can forecast the development of disease. In addition to glomerular and tubular indicators, inflammation and oxidative stress markers have proven to be reliable diagnostic aids. In order to emphasize the methods being employed lately to enhance therapeutic approaches in diabetic nephropathy, certain emerging critical biomarkers are illustrated in this review.

T-Fiber, A Highland Barley Fiber-Rich Powder, Alleviates Hyperglycemia and Improves Kidney Pathology in Db/db Mice

The role of dietary fiber in highland barley in lowering blood lipids has been continuously studied in recent years. However, its effects on diabetes and diabetic nephropathy are rarely studied. Considering that highland barley bran is rich in dietary fiber, the effective use of dietary fiber in highland barley bran can not only alleviate the symptoms of diabetes but also improve the local economy. This article aimed to study the effects of highland barley fiber-rich powder (T-fiber) with a high-quality natural dietary fiber ratio (insoluble fiber/soluble fiber = 3 : 1) on the symptoms of hyperglycemia in a diabetic mouse model. Compared with the model group’s blood glucose level (30.80 mmol/L), glucose tolerance (28.57 mmol/L), and glycosylated serum protein (2.43 mmol/L), T-fiber presented significant reductions in blood glucose (23.69 mmol/L), better glucose tolerance (21.32 mmol/L), and glycosylated serum protein (1.78 mmol/L) in the diabetic mouse model. Meanwhile, T-fiber effectively alleviated hepatocellular lesions. In addition, T-fiber not only improved kidney function by reducing the 24-hour urine output (8.25 ml), urine protein levels (11.51 mg), and serum creatinine (13.80 μmol/L) but also alleviated renal pathology, including glomerular hypertrophy, mesangial expansion, and fibrosis. The above results proved the ability of T-fiber to reduce blood glucose and alleviate liver and renal function in diabetic mice. Altogether, T-fiber is a capable formula for utilizing highland barley bran dietary fiber, which alleviates diabetes symptoms and endows highland barley with promising value.

The Qi-Bang-Yi-Shen formula ameliorates renal dysfunction and fibrosis in rats with diabetic kidney disease via regulating PI3K/AKT, ERK and PPARγ signaling pathways.

Diabetic kidney disease (DKD) is the leading cause of chronic kidney disease (CKD) and a growing public health problem worldwide. Losartan potassium (Los), an angiotensin II receptor blocker, has been used to treat DKD clinically. Recently, multi-herbal formula has been shown to exhibit therapeutic activities in DKD in China. Thus, we aimed to explore the protective effects of combination of Los and Qi-Bang-Yi-Shen formula (QBF) on DKD rats. Streptozotocin (STZ) injection was used to establish a rat model of DKD. Next, the bloodurea nitrogen (BUN), creatinine (CRE) and uric acid (UA) levels were detected in serum samples from DKD rats. Hematoxylin and eosin (H&E), periodic Acid Schiff (PAS) and Masson staining were performed to observe glomerular injury and glomerular fibrosis in DKD rats. In this study, we found that QBF or Los treatment could decrease serum BUN, CRE, UA levels and reduce urine albumin-to-creatinine ratio (ACR) in DKD rats. Additionally, QBF or Los treatment obviously inhibited glomerular mesangial expansion and glomerular fibrosis, attenuated glomerular injury in kidney tissues of DKD rats. Moreover, QBF or Los treatment significantly reduced PI3K, AKT and ERK1/2 protein expressions, but increased PPARγ level in kidney tissues of DKD rats. As expected, combined treatment of QBF and Los could exert enhanced reno-protective effects compared with the single treatment. Collectively, combination of QBF and Los could ameliorate renal injury and fibrosis in DKD rats via regulating PI3K/AKT, ERK and PPARγ signaling pathways. These findings highlight the therapeutic potential of QBF to prevent DKD progression.

GTS-21, a selective alpha7 nicotinic acetylcholine receptor agonist, ameliorates diabetic nephropathy in Leprdb/db mice

Diabetic nephropathy (DN) is a serious complicating factor in human type 2 diabetes mellitus (T2DM), and it commonly results in end-stage renal disease (ESRD) that requires kidney dialysis. Here, we report that the α7 nicotinic acetylcholine receptor (α7nAChR) agonist GTS-21 exerts a novel anti-inflammatory action to ameliorate DN, as studied using an inbred strain of Leprdb/db mice in which hyperglycemia and obesity co-exist owing to defective leptin receptor (Lepr) signaling. For this analysis, GTS-21 was administered to 10–12 week-old male and female mice as a 4 mg/kg intraperitoneal injection, twice-a-day, for 8 weeks. Kidney function and injury owing to DN were monitored by determination of plasma levels of BUN, creatinine, KIM-1 and NGAL. Histologic analysis of glomerular hypertrophy and mesangial matrix expansion were also used to assess DN in these mice. Concurrently, renal inflammation was assessed by measuring IL-6 and HMGB1, while also quantifying renal cell apoptosis, and apoptotic signaling pathways. We found that Leprdb/db mice exhibited increased markers of BUN, creatinine, NGAL, KIM-1, IL-6, cytochrome C, and HMGB-1. These abnormalities were also accompanied by histologic kidney injury (mesangial matrix expansion and apoptosis). Remarkably, all such pathologies were significantly reduced by GTS-21. Collectively, our results provide new evidence that the α7nAChR agonist GTS-21 has the ability to attenuate diabetes-induced kidney injury. Additional studies are warranted to further investigate the involvement of the vagal cholinergic anti-inflammatory reflex pathway (CAP) in ameliorating diabetic nephropathy.

Advanced glycation endproducts mediate chronic kidney injury with characteristic patterns in different stages.

Advanced glycation endproducts (AGEs) have been confirmed to play a causative role in the development of diabetic nephropathy (DN). In this study, we revealed that AGE-induced kidney injury with characteristic patterns in different stages and moesin phosphorylation plays a role in these processes. In WT mice treated with AGE-modified bovine serum albumin (AGE-BSA), distinct abnormal angiogenesis in Bowman’s capsule of the kidney emerged early after 1 m under AGE-BSA stimulation, while these neovessels became rare after 6 m. AGE-BSA also induced glomerular hypertrophy and mesangial expansion at 1 m but glomerular atrophy and fibrosis at 6 m. Electron microscopy imaging demonstrated the damage of foot process integrity in podocytes and the uneven thickening of the glomerular basement membrane in the AGE-BSA-treated group, which was more significant after 6 m of AGE-BSA treatment than 1 m. The kidney dysfunction appeared along with these AGE-induced morphological changes. However, these AGE-BSA-induced pathological changes were significantly attenuated in RAGE-knockout mice. Moreover, moesin phosphorylation was accompanied by AGE-BSA-induced alterations and moesin deficiency in mice attenuated by AGE-BSA-induced fibrosis. The investigation on glomerular endothelial cells (GECs) also confirmed that the phosphorylation of moesin T558 is critical in AGE-induced tube formation. Overall, this study suggests that AGEs mediate kidney injury with characteristic patterns by binding with RAGE and inducing moesin phosphorylation.

Abstract 044: Stimulation Of Intrarenal Angiotensinogen Expression And The Development Of Hypertension And Kidney Injury In Angiotensin II-infused Hepatic Angiotensinogen Knockout Mice

Regulation of systemic and local angiotensinogen (AGT) levels is a key determinant of tissue angiotensin II (Ang II) levels and inappropriate AGT augmentation promotes the development of hypertension and tissue injury. Kidney and urinary AGT levels are increased in Ang II-mediated hypertension. Recent studies have demonstrated that circulating hepatocyte-derived AGT (hAGT) enters kidneys sustaining kidney and urinary AGT levels. However, roles of hAGT in blood pressure elevation and kidney injury in Ang II-mediated hypertension have not been delineated. This study tested if hAGT contributes to the development of the pathophysiological events in Ang II-infused mice. A low dose of Ang II (400 ng/kg/min) was infused to male wild type (WT) and hAGT gene knockout (KO) mice (N=9 and 13) for 4 weeks. The control group in each genotype received vehicle (Veh) infusion (N=5 and 6). Western blot confirmed non-detectable levels of hAGT in KO mice. hAGT KO markedly decreased plasma AGT levels (WT+Veh:12.2±0.6 vs. hAGT KO+Veh: 0.8±0.1 μg/ml). Ang II infusion did not elevate plasma AGT levels in either WT and hAGT KO mice. Although hAGT KO mice exhibited a lower baseline of systolic blood pressure (SBP) than WT mice, Ang II-mediated increases in SBP was not attenuated in hAGT KO mice (ΔSBP in WT+Ang II: 30.1±4.4 vs. hAGT KO+Ang II: 26.0±4.2 mmHg). Kidney AGT mRNA levels were increased by Ang II infusion to the same extent in both WT and hAGT mice (WT+Ang II: 1.30±0.04 vs. hAGT KO+Ang II: 1.34±0.06, ratio to control). Likewise, Ang II infusion increased IL-6 mRNA to the same magnitude in both WT and hAGT KO mice. Urinary AGT was sustained in hAGT KO+Veh mice (66±9%) compared to WT+Veh mice. Ang II infusion did not alter urinary AGT levels in both groups. Glomerular mesangial expansion and fibrosis by Ang II infusion were not observed. Ang II infusion developed tubulointerstitial fibrosis in renal cortex and medulla. hAGT KO prevented the fibrosis only in the medulla. These outcomes demonstrate that elevation of SBP, augmentation of intrarenal AGT and IL-6 expression, and the development of renal cortical fibrosis in Ang II-mediated hypertension do not require hAGT. In contrast, hAGT contributes to renal medullary fibrosis which may be due to the lower absolute levels of blood pressure.

Podocyte-specific Nlrp3 inflammasome activation promotes diabetic kidney disease

Efficient therapies for diabetic kidney disease (DKD), now the leading cause of kidney failure, are lacking. One hallmark of DKD is sterile inflammation (inflammation in absence of microorganisms), but the underlying molecular mechanisms remain poorly understood. The NLRP3 inflammasome (innate immune system receptors and sensors regulating activation of caspase-1) is a mechanism of sterile inflammation known to be activated by metabolic stimuli and reactive metabolites associated with DKD, including inflammasome activation in podocytes. However, whether NLRP3 inflammasome activation in podocytes contributes to sterile inflammation and glomerular damage in DKD remains unknown. Here, we found that kidney damage, as reflected by increased albuminuria, glomerular mesangial expansion and glomerular basement membrane thickness was aggravated in hyperglycemic mice with podocyte-specific expression of an Nlrp3 gain-of-function mutant (Nlrp3A350V). In contrast, hyperglycemic mice with podocyte-specific Nlrp3 or Caspase-1 deficiency showed protection against DKD. Intriguingly, podocyte-specific Nlrp3 deficiency was fully protective, while podocyte-specific caspase-1 deficiency was only partially protective. Podocyte-specific Nlrp3, but not caspase-1 deficiency, maintained glomerular autophagy in hyperglycemic mice, suggesting that podocyte Nlrp3 exerts both canonical and non-canonical effects. Thus, podocyte NLRP3 inflammasome activation is both sufficient and required for DKD and supports the concept that podocytes exert some immune cell-like functions. Hence, as podocyte NLRP3 exerts non-canonical and canonical effects, targeting NLRP3 may be a promising therapeutic approach in DKD.

MO067: Role of ANT2 in the Development of Obesity-Induced Chronic Kidney Disease

Abstract BACKGROUND AND AIMS Obesity, a widespread condition with an ever-increasing prevalence, imposes a great medical concern since it serves as a risk factor for a wide range of conditions, including the development of chronic kidney disease (CKD). Lipid accumulation and impaired fatty acid β-oxidation in the renal proximal tubular cells (RPTCs) as well as an overall mitochondrial dysfunction have been shown to induce kidney injury, inflammation and fibrosis, leading to the development of CKD. However, the molecular mechanisms linking mitochondrial dysfunction in RPTCs to obesity-induced CKD are not fully understood and require further examination. Adenine nucleotide translocases (ANTs), which transport ADP and ATP through the mitochondrial inner membrane, play an essential role in energy metabolism of eukaryotic cells. ANT2 (Slc25a5) mediates fatty acid-induced uncoupled respiration, and its complete deletion is embryonic lethal. Here we explore its specific role in RPTCs in the development of obesity-induced CKD. METHOD ANT2 protein levels were measured using western blot and immunohistochemistry analyses. RPTC-ANT2-/- animals were generated using the Cre/loxP system. The null mice and their wild-type littermate controls were fed with either a high-fat diet (HFD) or a standard diet (STD) for 24 weeks. Kidney function and lipid content were assessed by biochemical analysis. Histological techniques were used to visualize the morphological changes in the kidney as well as fibrogenesis. Kidney injury and inflammatory markers were measured via qPCR and ELISAs. Mitochondrial function was tested in primary mouse RPTCs extracted from the null and WT animals by measuring oxygen consumption rate via Seahorse as well as reactive oxygen species (ROS) production by DCFDA staining. RESULTS As evident from the double-stained immunofluorescence staining of mouse kidney, high levels of ANT2 were found in RPTCs. Interestingly, its protein expression was downregulated in HFD-fed WT mice. Nullification of ANT2 specifically in RPTCs prevented the obesity-induced kidney dysfunction as reflected by lowered albumin-to-creatinine ratio. This was associated with the improved renal morphology in HFD-fed RPTC-ANT2-/- mice, evident by the reduction in obesity-related increased glomerular and Bowman's space areas and mesangial expansion. Compared with their littermate controls, obese RPTC-ANT2-/- mice showed reduced renal KIM-1 and NGAL protein levels and downregulation in the expression levels of Mcp1 and Lcn2, markers of renal injury and inflammation, respectively. The null mice were also protected from obesity-induced fibrosis, measured by trichrome staining, as well as accumulation of triglycerides and cholesterol in the kidney. In addition, preserved mitochondrial function was found in primary mouse RPTCs lacking ANT2, measured by increased spare respiratory capacity and decreased ROS production. Lastly, downregulated Hif1α gene and protein expression levels were found in RPTCs and kidney tissue lacking ANT2. CONCLUSION Our findings introduce ANT2 in the RPTCs as a key player in the development of obesity-induced CKD. Deletion of RPTC-ANT2 protects the kidney from the deleterious effects of lipotoxicity. Therefore, targeted manipulation of renal mitochondrial metabolism, particularly via inhibiting ANT2, may represent a novel approach for the treatment of obesity-induced CKD.