MO640: Treatment with Sodium–Glucose Cotransporter 2 Inhibitors Increases Klotho in Type 2 Diabetic Patients

BACKGROUND AND AIMS

Klotho (KL) is a transmembrane protein mainly expressed by the tubular cells of the kidneys, with an additional soluble form that is present in blood and urine. Preserved KL has been related to physiological protection of the kidneys. Sodium–glucose cotransporter type-2 inhibitors (SGLT2i) are a new class of anti-diabetic drugs with important renal benefits. The aim of the present study was to analyze the effect of treatment with SGLT2i on soluble KL concentrations as well as on mRNA expression levels of the KL gene in renal tubular cells.

METHOD

Fifty-seven patients (30 males and 27 females; mean age 61 ± 5 years) with type 2 diabetes and chronic kidney disease stage G2-A2, all treated with metformin and blockers of the renin–angiotensin system, were included in the study. All patients were in need of intensified anti-diabetic therapy at the discretion of their physicians in accordance with the routine clinical practice. Forty-five received SGLT2i during 3 months (15 empagliflozin, 15 canagliflozin and 15 dapagliflozin), and the evolution was compared with a group of 12 patients matched by age, sex and stage of CKD who received DPP4 inhibitors (control group). Serum and urine levels of soluble KL and tumor necrosis factor-alpha (TNFa) were determined by ELISA. In addition, the effect on mRNA expression levels of KL was assessed in vitro in renal tubular cells cultures.

RESULTS

Baseline values of serum and urinary KL and TNFa were similar in both groups. Urinary KL was inversely correlated with albuminuria (r = −0.45, P < 0.001) and urine TNFa excretion (r = −0.40, P < 0.01). At the end of the study, there was a similar improvement in metabolic control in both groups; however, only patients treated with SGLT2i showed a significant reduction in albuminuria and urinary TNFa (P < 0.01). Serum and urinary KL increased by 5.2% and 38.9%, respectively, only in patients receiving SGLT2i (P < 0.001 versus baseline), without changes in controls (P < 0.01 between groups). There were no differences among the three drugs in the SGLT2i group. The reduction in albuminuria (β = −0.35, P < 0.01) and urinary TNFa (β = −0.57, P < 0.001) were independently associated with the increase in urine KL, while the change in albuminuria was related to the increase in serum KL (β = −0.39, P < 0.05). Cultured renal tubular cells under high glucose, inflammatory stimulus with TWEAK or serum bovine albumin decreased Klotho mRNA and protein expression within 24 h, an effect that was prevented by all the SGLT2i when added to the cultures.

CONCLUSION

In type 2 diabetic patients, treatment with SGLT2i induces a reduction in albuminuria and modulates inflammation (as reflected by a decrease in the urinary excretion of TNFa), which is associated with a significant increase in soluble KL concentrations. In addition, SGLT2i prevent the reduction in protein and mRNA expression levels of the KL gene in renal tubular cells. The preservation of KL by SGLT2i may be an important mechanism of renal protection.

MO1012: Variability of Klotho and FGF-23 Levels After Kidney Transplantation Depending on the Glomerular Filtration Rate

BACKGROUND AND AIMS

Klotho is a transmembrane protein expressed mainly in distal tubular epithelial cells of the kidneys. Its gene expression and soluble form levels play a crucial role in the interaction of the aging-inflammation binomial and act as a co-receptor for the phosphaturic fibroblast growth factor 23 (FGF-23). Klotho deficiency, which is the norm in chronic kidney disease (CKD), has been reported as an independent risk factor for cardiovascular disease and subclinical atherosclerosis [1, 2]. This study investigates the evolution of Klotho and FGF-23 levels during the first 2 years after kidney transplantation and their variability depending on the glomerular filtration rate (GFR).

METHOD

Serum levels of Klotho and FGF-23 were determined in 42 patients right before kidney transplantation (KT) and at 3rd, 12th and 24th month after KT. The measurements were made by ELISA. The GFR of the kidney graft was performed by indirect methods (formula: MDRa and CKD-EPI) at each study visit. Variables were reported as mean ± SD, and a value of P < .05 was considered to be statistically significant for each test.

RESULTS

KT recipients were divided into two groups arbitrary: the first group with a GFR > 40 mL/min (n = 26) and the other one with a GFR ≤ 40 mL/min (n = 16). At the starting point, there was not found any statistical difference in Klotho and FGF-23 levels between groups (GFR > 40 mL/min: 462.65 ± 264.99 pg/mL and 786.84 ± 521.67 pg/mL, respectively; versus GFR ≤ 40 mL/min: 436.5 ± 189.33 and 779.02 ± 589.86).

Those with better kidney function after KT significantly increased Klotho levels on 12th and 24th month of follow-up (baseline 462.65 ± 264.99 versus 12th month 561.96 ± 314.68 and 24th month 581.15 ± 350.10; P = .001), whereas KT recipients with a GFR ≤ 40 mL/min only proved an increase in Klotho levels at 12th month after a non-significant initial decrease at 3rd month (462 ± 204.91 versus 356.96 ± 177.07, respectively; P = .028). This trend was not confirmed at the 24th month (397.12 ± 182.05). Klotho levels were found significantly different at the 24th month between groups (P = .031). See Fig. 1.

Figure 2 shows the changes in FGF-23 levels. There are significant differences in both groups from baseline to month 24. (P < .001 group GFR > 40 mL/min and P < .001 group GFR ≤ 40 mL/min). FGF-23 dropped significantly in both groups at the 3rd month (P = .018) and 12th months (P = .003).

CONCLUSION

Vascular disease and mineral metabolism malfunction are relevant abnormalities in patients with CKD as well as in KT recipients. This study shows that Klotho is increasingly produced after KT in those patients whose allografts achieve a better function. We failed to prove the same effect on those with a GFR < 40 mL/min. Nonetheless, FGF-23 production declines satisfactorily independently of GRF. These results suggest the promotion of cardiovascular health after KT, particularly in those with higher GFR. The clinical and prognostic value of these changes are yet to be determined.

MO285: FOSL1 Preserves Klotho Expression and Limits Acute Kidney Injury

BACKGROUND AND AIMS

Fosl1 (FRA1, Fos-related-antigen 1) is a transcription factor of the AP-1 complex (activator protein 1) that regulates the expression of genes that regulates processes involved in acute kidney injury (AKI) such differentiation, inflammation, proliferation and cell death. We have now explored the role of Fosl1 in AKI and repair.

METHOD

The function of Fosl1 was explored in murine nephrotoxic AKI induced by folic acid or cisplatin in wild type and genetically modified mice tubular cell Fosl1 deficient mice (Fosl1Δtub). RT-qPCR, western blot, and immunohistochemistry were used to assess gene and protein expression. Direct regulation of Klotho by Fosl1 was explored by chromatin immunoprecipitation (ChIP). Murine tubular cells were cultured in an inflammatory milieu promoted by TWEAK and Fosl1 was targeted by siRNA.

RESULTS

Fosl1 was one of the most upregulated transcription factors in experimental nephrotoxic AKI transcriptomics and also one the transcription factors binding to the Klotho promoter (Panel A). Fosl1 upregulation was confirmed in experimental nephrotoxic AKI and in human AKI and localized to tubular cell nuclei at early times points (panel B). Fosl1 deficient (Fosl1Δtub) mice developed more severe folic acid- or cisplatin-induced AKI and higher proinflammatory cytokine expression and kidney macrophage infiltration (Panel C). Additionally, kidney expression of the nephroprotective and antiaging factor Klotho was more severely depressed in Fosl1Δtub mice (Panel D). Enrichment of AP1 binding sites was found in the Klotho promoter and we confirmed direct Fosl1 binding to the Klotho promoter in a ChIP assay. Moreover, Fosl1Δtub mice had disturbed expression of cell cycle regulators and PCNA expression, suggesting a dysregulation in kidney repair. In tubular cells cultured in an inflammatory milieu, Fosl1 expression was also upregulated. Fosl1 siRNA targeting in cultured tubular cells increased inflammatory gene expression and cell death and decreased Klotho expression.

CONCLUSION

Fosl1 contributes to an adaptive kidney response during AKI that limits kidney injury and includes Klotho expression and Fosl1 deficiency promotes an accelerated loss of klotho and more severe AKI.

MO038SCARF EXPRESSION IN KIDNEY DISEASE

Background and Aims

Chronic kidney disease (CKD) is the most common risk factor for lethal COVID19 and the risk factor that most increases the risk of death of COVID19 patients. Additionally, acute kidney injury (AKI) is frequent in COVID19 and AKI increases the risk of death. However, the underlying cellular and molecular mechanisms of such increased risk are unclear. SARS-CoV-2 and coronavirus-associated receptors and factors (SCARFs) are required for and/or regulate (in a positive or negative manner) coronary cell entry and/or viral replication. We have now studied changes in the expression of genes encoding for SCARF in the context of acute and chronic kidney disease.

Method

Data mining of in-house (experimental models of AKI -folic acid nephropathy- and CKD -Unilateral ureteral obstruction- in mice) and publicly available databases (Nephroseq, published single cell transcriptomics studies) of kidney tissue transcriptomics as well as the Protein Atlas database.

Results

Out of 28 SCARF genes identified by Singh et al (Cell Reports 2020), 26 were represented in the experimental AKI database. Of them 7 (27%) were differentially expressed during AKI (FDR <0.05), 4 of them upregulated and 3 downregulated (Figure 1.A). Additionally, 27 were represented in the experimental CKD database. Of them 17 (63%) were differentially expressed during experimental CKD, 6 of them upregulated and 11 downregulated (Figure 1.B). Two genes were consistently upregulated (Ctsl and Ifitm3) and two consistently downregulated (Tmprss2 and Top3b) in both experimental AKI and CKD (Figure 1.A and B). They encode cathepsin L, interferon induced transmembrane protein 3, transmembrane serine protease 2, DNA topoisomerase III beta, respectively. Single cell transcriptomics databases localized Ctsl expression mainly to podocytes and tubular cells while protein atlas showed clear tubular staining. The main site of Ifitm3 was endothelium in both datasets and it was also localized to leukocytes by single cell transcriptomics. Tmprss2 was mainly localized to tubular cells in both datasets while Top3b was widely expressed in parenchymal renal cells, endothelium and leucocytes in single cell transcriptomics. Increased kidney expression of Ifitm3 and decreased expression of Tmprss2 and Top3b were confirmed in diverse CKD datasets in Nephroseq.

Conclusion

Both AKI and CKD are associated with differential expression of SCARF genes in kidney tissue, the impact of CKD appearing to be larger. Characterization of these changes and their functional impact in kidney tissue and beyond the kidneys may provide clues to the increased risk of severe or lethal COVID19 in kidney disease patients.

Kidney SCARF gene expression

MO458URINARY GROWTH DIFFERENTIATION FACTOR-15 (GDF15) LEVELS AS BIOMARKER OF ADVERSE OUTCOMES AND BIOPSY FINDINGS IN CHRONIC KIDNEY DISEASE

Background and Aims

Growth differentiation factor-15 (GDF15) is a member of the TGF-β superfamily. Increased serum GDF15 has been associated with increased risk of CKD progression. However, no prior study had addressed the significance of urinary GDF15 in adult CKD.

Method

We have now assessed serum and urinary GDF15 in a prospective cohort of 84 patients who underwent kidney biopsy and then were followed for 29±17 months.

Results

There was a statistically significant correlation between serum and urine GDF15 values. However, while serum GDF15 values increased with decreasing glomerular filtration rate, urinary GDF15 did not. Immunohistochemistry located kidney GDF15 expression mainly to tubular cells and kidney GDF15 staining correlated with urinary GDF15 values. Urine GDF15 was significantly higher in patients with a histological diagnosis of diabetic nephropathy than in diabetic patients without diabetic nephropathy. This was not the case for serum GDF15. Both serum and urine GDF15 were associated with patient survival in multivariate models. However, when both urine and serum GDF15 were present in the model, lower urine GDF15 predicted patient survival [B coefficient (SEM) -0.395 (0.182) p 0.03], and higher urine GDF15 predicted a composite of mortality or renal replacement therapy [0.191 (0.06) p 0.002] while serum GDF15 was not predictive. Decision tree analysis yielded similar results. The AUC of the ROC for urine GDF15 as a predictor of mortality was 0.95 (95% CI 0.89-1.00, p &lt;0.001).

Conclusion

In conclusion, urine GDF15 is associated with kidney histology patterns, mortality and need for renal replacement therapy in biopsied CKD patients.

MO017THERAPEUTICAL POTENTIAL OF ENZYME REPLACEMENT: NEW INSIGHTS AND PERSPECTIVES IN HUMAN ENDOTHELIAL CELLS TREATED WITH CHLOROQUINE

Background and Aims

COVID-19 is a pandemic with no end in sight. There is only one approved antiviral agent but global stocks are deemed insufficient. Despite in vitro antiviral activity, clinical trials of chloroquine and hydroxychloroquine were disappointing, and they may even impair outcomes. Chloroquine causes zebroid deposits reminiscent of Fabry disease (α-galactosidase A deficiency) and endothelial cells are key targets of COVID-19. The study aims to investigate in vitro the effect of enzyme replacement therapy (ERT) in chloroquine-induced endothelial dysfunction.

Method

We have explored the effect of chloroquine on cultured endothelial cells and its modulation by recombinant α-galactosidase A (agalsidase-β). Following dose-response studies, 0.5 μg/mL chloroquine was added to cultured human endothelial cells. Neutral red and Lysotracker were used to assess lysosomes. Cytotoxicity was evaluated by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) - MTT assay and cell stress by assessing reactive oxygen species (ROS) and nitric oxide (NO). In endothelial cells, chloroquine induced dose-dependent cytotoxicity at in vitro test concentrations for COVID-19 therapy.

Results

Chloroquine significantly induced the accumulation of acid organelles (P<0.05), increased ROS levels, and decreased NO production (P<0.05), in vitro. These adverse effects of chloroquine on endothelial cell biology were decreased by agalsidase-β (P<0.05).

Conclusion

Chloroquine-induced endothelial cell cytotoxicity and stress is attenuated by agalsidase-β treatment. This suggests that endothelial cell injury may contribute to the failure of chloroquine as therapy for COVID-19 and may be at least in part related to causing dysfunction of the lysosomal enzyme α-galactosidase A.

P0054ACQUIRED DIFFERENTIAL EXPRESSION IN ACUTE KIDNEY INJURY OF GENES RESPONSIBLE FOR HEREDITARY NEPHROPATHIES

Background and Aims

Gene sequencing is becoming an important diagnostic tool in a great number of medical specialties. Despite its interpretation is still a challenge, allows the identification of genes related to hereditary diseases and bild a base for the study of acquired nephropathies. We hypothesize that those genes responsible for hereditary nehpropathies could contribute to the pathogenesis of acquired nephropathies.

Method

In a murine model of acute kidney disease induced by folic acid, we analyzed the kidney transcriptomic after 24 hours of damage. In this database we evaluated if 625 genes described as responsible for hereditary nephropathies were expressed significantly. Later, we evaluated the correlation between diferentially expressed genes and glomerular filtration, using transcriptomic databases of human nephropathies (Nephroseq), so that, we could identify those relevant in acquired human nephropathies and in experimental settings. A functional enrichment analysis was done using the software Gorilla, and some of the genes were validated in our laboratory using RT-PCR.

Results

In acute kidney disease, the renal expression of 3906/25051 (15.59%) genes increased and the expression of 3537 (14.11%) decreased significantly (p&lt;0.05). The percentage of genes expressed diferentially was higher when analysing the 625 genes responsible of familiar nephropathies. We identified 615 of those in the murine model and 105/615 (17.07%) increased it expression, and 155 (25.20%), decreased it (p&lt;0.05 when compared with the database with 25051 genes). 241 of those 260 diferentially expressed genes (92.69%) where associated significantly with glomerular filtration rate in human nephropathies. The most enriched GO process were “complement activation", "protein activation cascade", "activation of immune response" and "RNA processing”. We have validated the expression of 7 of the genes in acute kidney injury (SLC34A1, SLC34A3, Klotho, MAGED2, NLRP3, FN1, COL4A1), which supports the relevance of the transcriptomic results.

Conclusion

Genes involved in familiar nephropathies are overexpressed between genes diferentially expressed in acquired nephropathies, suggesting that they could play a role in the pathogenesis of the last, throught the regulation of the RNA processing, protein activation or immune response and complement regulation. The analysis of the functioning of genes responsible for familiar nephropathies in acquired nephropaties could identify new therapeutic targets in kidney damage.

Targeting local vascular and systemic consequences of inflammation on vascular and cardiac valve calcification

INTRODUCTION

Cardiac valve calcification and vascular calcification (VC) are associated with cardiovascular mortality in the general population and in patients with chronic kidney disease (CKD). CKD, diabetes mellitus, and atherosclerosis are among the causes of systemic inflammation that are associated with VC.

AREAS COVERED

This review collates clinical and experimental evidence that inflammation accelerates VC progression. Specifically, we review the actions of key pro-inflammatory cytokines and inflammation-related transcription factors on VC, and the role played by senescence. Inflammatory cytokines, such as the TNF superfamily and IL-6 superfamily, and inflammation-related transcription factor NF-κB promote calcification in cultured vascular smooth muscle cells, valvular interstitial cells, or experimental animal models through direct effects, but also indirectly by decreasing circulating Fetuin A or Klotho levels.

EXPERT OPINION

Experimental evidence suggests a causal link between inflammation and VC that would change the clinical approach to prevention and treatment of VC. However, the molecular basis remains unclear and little is known about VC in humans treated with drugs targeting inflammatory cytokines. The effect of biologicals targeting TNF-α, RANKL, IL-6, and other inflammatory mediators on VC, in addition to the impact of dietary phosphate in patients with chronic systemic inflammation, requires study.

Osteoprotegerin in exosome-like vesicles from human cultured tubular cells and urine

Urinary exosomes have been proposed as potential diagnostic tools. TNF superfamily cytokines and receptors may be present in exosomes and are expressed by proximal tubular cells. We have now studied the expression of selected TNF superfamily proteins in exosome-like vesicles from cultured human proximal tubular cells and human urine and have identified additional proteins in these vesicles by LC-MS/MS proteomics. Human proximal tubular cells constitutively released exosome-like vesicles that did not contain the TNF superfamily cytokines TRAIL or TWEAK. However, exosome-like vesicles contained osteoprotegerin (OPG), a TNF receptor superfamily protein, as assessed by Western blot, ELISA or selected reaction monitoring by nLC-(QQQ)MS/MS. Twenty-one additional proteins were identified in tubular cell exosome-like vesicles, including one (vitamin D binding protein) that had not been previously reported in exosome-like vesicles. Twelve were extracellular matrix proteins, including the basement membrane proteins type IV collagen, nidogen-1, agrin and fibulin-1. Urine from chronic kidney disease patients contained a higher amount of exosomal protein and exosomal OPG than urine from healthy volunteers. Specifically OPG was increased in autosomal dominant polycystic kidney disease urinary exosome-like vesicles and expressed by cystic epithelium in vivo. In conclusion, OPG is present in exosome-like vesicles secreted by proximal tubular epithelial cells and isolated from Chronic Kidney Disease urine.

TWEAKing renal injury

TWEAK is a recently identified cytokine of the TNF superfamiliy. Through activation of the Fn14 receptor, TWEAK regulates cell proliferation, cell death and inflammation. Recent studies show increased TWEAK and Fn14 expression in tubular cells during acute kidney injury as well as elevated urinary TWEAK levels in patients with active lupus nephritis. Furthermore, glomerular mesangial cells and renal tubular epithelial cells express the Fn14 receptor under the regulation of proinflammatory cytokines. TWEAK weakly increases cell death and promotes secretion of inflammatory mediators in non-stimulated mesangial cells. In addition, in a proinflammatory milieu, TWEAK induces apoptosis of mesangial and tubular cells. The available data suggest that TWEAK is a new player in kidney injury both at the glomerular and tubulointerstitial levels and might be a target for therapeutic intervention.