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Patients with chronic kidney disease (CKD) are at risk of progressive loss of kidney function, heart failure, and cardiovascular death despite current proven therapies, including renin-angiotensin system inhibitors (RASi), sodium glucose co-transporter-2 inhibitors (SGLT2i), and statin-based regimens. RASi and SGLT2i reduce risk of CKD progression irrespective of primary cause of kidney disease, suggesting they target final common pathways. Targeting aldosterone overactivity with a nonsteroidal mineralocorticoid receptor antagonist (MRA) also reduces cardiorenal risk in patients with albuminuric diabetic kidney disease already treated with RASi. Together, these observations provide the rationale for trials to assess effects of inhibiting the aldosterone pathway in a broader range of patients with CKD, including those with non-diabetic causes of CKD or low albuminuria. Aldosterone synthase inhibitors (ASi) have emerged as an alternative to MRAs for aldosterone pathway inhibition. Phase II data from 586 patients with albuminuric CKD have shown that 10 mg of an ASi, vicadrostat (BI 690517), reduced urine albumin-to-creatinine ratio by ∼40% compared to placebo with or without concurrent empagliflozin treatment. MRA and ASi increase risk of hyperkalaemia. Combining their use with an SGLT2i may mitigate some of this risk, improving tolerability, and allowing a wider range of patients to be treated (including those with higher levels of blood potassium than in previous trials). The EASi-KIDNEY (NCT06531824) double-blind placebo-controlled trial will test this approach by assessing the safety and cardiorenal efficacy of vicadrostat in combination with empagliflozin in ∼11,000 patients with CKD. It will be sufficiently large to assess effects in patients with and without diabetes separately., (© The Author(s) 2024. Published by Oxford University Press on behalf of the ERA.)

Background: In the EMPA-KIDNEY trial, empagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, had positive cardiorenal effects in patients with chronic kidney disease who were at risk for disease progression. Post-trial follow-up was designed to assess how the effects of empagliflozin would evolve after the discontinuation of the trial drug., Methods: In the active trial, patients with chronic kidney disease were randomly assigned to receive either empagliflozin (10 mg once daily) or matching placebo and were followed for a median of 2 years. All the patients had an estimated glomerular filtration rate (eGFR) of at least 20 but less than 45 ml per minute per 1.73 m 2 of body-surface area or an eGFR of at least 45 but less than 90 ml per minute per 1.73 m 2 with a urinary albumin-to-creatinine ratio (with albumin measured in milligrams and creatinine measured in grams) of at least 200. Subsequently, surviving patients who consented were observed for 2 additional years. No trial empagliflozin or placebo was administered during the post-trial period, but local practitioners could prescribe open-label SGLT2 inhibitors, including open-label empagliflozin. The primary composite outcome was kidney disease progression or cardiovascular death as assessed from the start of the active-trial period to the end of the post-trial period., Results: Of the 6609 patients who had undergone randomization in the active trial, 4891 (74%) were enrolled in the post-trial period. During this period, the use of open-label SGLT2 inhibitors was similar in the two groups (43% in the empagliflozin group and 40% in the placebo group). During the combined active- and post-trial periods, a primary-outcome event occurred in 865 of 3304 patients (26.2%) in the empagliflozin group and in 1001 of 3305 patients (30.3%) in the placebo group (hazard ratio, 0.79; 95% confidence interval [CI], 0.72 to 0.87). During the post-trial period only, the hazard ratio for a primary-outcome event was 0.87 (95% CI, 0.76 to 0.99). During the combined periods, the risk of kidney disease progression was 23.5% in the empagliflozin group and 27.1% in the placebo group; the risk of the composite of death or end-stage kidney disease was 16.9% and 19.6%, respectively; and the risk of cardiovascular death was 3.8% and 4.9%, respectively. There was no effect of empagliflozin on death from noncardiovascular causes (5.3% in both groups)., Conclusions: In a broad range of patients with chronic kidney disease at risk for progression, empagliflozin continued to have additional cardiorenal benefits for up to 12 months after it was discontinued. (Funded by Boehringer Ingelheim and others; EMPA-KIDNEY ClinicalTrials.gov number, NCT03594110; EuDRACT number, 2017-002971-24.)., (Copyright © 2024 Massachusetts Medical Society.)

Background and Hypothesis: Hyperuricaemia and gout are common in chronic kidney disease (CKD). We aimed to assess the effects of sodium-glucose co-transporter-2 (SGLT2) inhibition on uric acid (urate) and gout in patients with CKD., Methods: The EMPA-KIDNEY trial randomised 6609 patients with CKD (estimated glomerular filtration rate [eGFR] ≥20 and <90 mL/min/1.73m2) to receive either empagliflozin 10 mg daily or matching placebo over a median of two years follow-up. Serum uric acid was measured at randomisation then 2 and 18 months of follow-up and the effects of empagliflozin were analysed using a pre-specified mixed model repeated measures approach. Participant-reported gout events were analysed in Cox regression models (first events) with the Andersen-Gill extension (total events). A post-hoc composite outcome included new initiation of uric acid lowering therapy or colchicine. EMPA-KIDNEY primary and kidney disease progression outcomes were also assessed in subgroups of baseline serum uric acid., Results: Baseline mean ± SD serum uric acid concentration was 431±114 µmol/L. Allocation to empagliflozin resulted in a study-average between-group difference in serum uric acid of -25.6 (95%CI -30.3,-21.0) µmol/L with larger effects in those with higher eGFR (trend P < 0.001) and without diabetes (heterogeneity P < 0.001). Compared to placebo, empagliflozin did not significantly reduce first or total gout events (HR 0.87, 95%CI 0.74-1.02 for the 595 first events, and 0.86, 0.72-1.03 for the 869 total events) with similar hazard ratios for the post-hoc composite and across subgroups, including by diabetes and eGFR. The effect of empagliflozin on the primary outcome and kidney disease progression outcomes were similar irrespective of baseline level of uric acid., Conclusion: SGLT2 inhibition reduces serum uric acid in patients with CKD with larger effects at higher eGFR and in the absence of diabetes. However, the effect on uric acid is modest and did not translate into reduced risk of gout in EMPA-KIDNEY., (© The Author(s) 2024. Published by Oxford University Press on behalf of the ERA.)

Background: EMPA-KIDNEY assessed the effects of empagliflozin 10 mg once daily vs. placebo in 6609 patients with chronic kidney disease (CKD) at risk of progression, including 612 participants from Japan., Methods: Eligibility required an estimated glomerular filtration rate (eGFR) of ≥ 20 < 45; or ≥ 45 < 90 ml/min/1.73m 2 with a urinary albumin-to-creatinine ratio (uACR) of ≥ 200 mg/g. The primary outcome was a composite of kidney disease progression (end-stage kidney disease, a sustained eGFR decline to < 10 ml/min/1.73m 2 or ≥ 40% from randomization, or renal death) or cardiovascular death. In post-hoc analyses, we explored the effects of empagliflozin in participants from Japan vs. non-Japan regions, including additional models assessing whether differences in treatment effects between these regions could result from differences in baseline characteristics., Results: Japanese participants had higher levels of albuminuria and eGFR than those from non-Japan regions. During a median of 2.0 year follow-up, a primary outcome occurred in 432 patients (13.1%) in the empagliflozin group and in 558 patients (16.9%) in the placebo group (hazard ratio [HR], 0.72, 95% confidence interval [95%CI] 0.64-0.82; P < 0.0001). Among the participants from non-Japan regions, there were 399 vs. 494 primary outcomes (0.75, 0.66-0.86), and 33 vs. 64 (0.49, 0.32-0.75; heterogeneity p = 0.06) in Japan. Results were similar when models explicitly considered treatment interactions with diabetes status, categories of eGFR/uACR, and recruitment in Japan (heterogeneity p = 0.08). Safety outcomes were broadly comparable between the two groups, and by Japanese status., Conclusions: Empagliflozin safely reduced the risk of "kidney disease progression or cardiovascular death" in patients with CKD, with consistent effects in participants from Japan., (© 2024. The Author(s).)

Significance Statement: SGLT2 inhibitors reduce risk of kidney progression, AKI, and cardiovascular disease, but the mechanisms of benefit are incompletely understood. Bioimpedance spectroscopy can estimate body water and fat mass. One quarter of the EMPA-KIDNEY bioimpedance substudy CKD population had clinically significant levels of bioimpedance-derived "Fluid Overload" at recruitment. Empagliflozin induced a prompt and sustained reduction in "Fluid Overload," irrespective of sex, diabetes, and baseline N-terminal pro B-type natriuretic peptide or eGFR. No significant effect on bioimpedance-derived fat mass was observed. The effects of SGLT2 inhibitors on body water may be one of the contributing mechanisms by which they mediate effects on cardiovascular risk., Background: CKD is associated with fluid excess that can be estimated by bioimpedance spectroscopy. We aimed to assess effects of sodium glucose co-transporter 2 inhibition on bioimpedance-derived "Fluid Overload" and adiposity in a CKD population., Methods: EMPA-KIDNEY was a double-blind placebo-controlled trial of empagliflozin 10 mg once daily in patients with CKD at risk of progression. In a substudy, bioimpedance measurements were added to the main trial procedures at randomization and at 2- and 18-month follow-up visits. The substudy's primary outcome was the study-average difference in absolute "Fluid Overload" (an estimate of excess extracellular water) analyzed using a mixed model repeated measures approach., Results: The 660 substudy participants were broadly representative of the 6609-participant trial population. Substudy mean baseline absolute "Fluid Overload" was 0.4±1.7 L. Compared with placebo, the overall mean absolute "Fluid Overload" difference among those allocated empagliflozin was -0.24 L (95% confidence interval [CI], -0.38 to -0.11), with similar sized differences at 2 and 18 months, and in prespecified subgroups. Total body water differences comprised between-group differences in extracellular water of -0.49 L (95% CI, -0.69 to -0.30, including the -0.24 L "Fluid Overload" difference) and a -0.30 L (95% CI, -0.57 to -0.03) difference in intracellular water. There was no significant effect of empagliflozin on bioimpedance-derived adipose tissue mass (-0.28 kg [95% CI, -1.41 to 0.85]). The between-group difference in weight was -0.7 kg (95% CI, -1.3 to -0.1)., Conclusions: In a broad range of patients with CKD, empagliflozin resulted in a sustained reduction in a bioimpedance-derived estimate of fluid overload, with no statistically significant effect on fat mass., Trial Registration: Clinicaltrials.gov: NCT03594110 ; EuDRACT: 2017-002971-24 ( https://eudract.ema.europa.eu/ )., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Society of Nephrology.)

Background: Excess aldosterone accelerates chronic kidney disease progression. This phase 2 clinical trial assessed BI 690517, an aldosterone synthase inhibitor, for efficacy, safety, and dose selection., Methods: This was a multinational, randomised, controlled, phase 2 trial. People aged 18 years or older with an estimated glomerular filtration rate (eGFR) of 30 to less than 90 mL/min/1·73 m 2 , a urine albumin to creatinine ratio (UACR) of 200 to less than 5000 mg/g, and serum potassium of 4·8 mmol/L or less, taking an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker, were enrolled. Participants were randomly assigned (1:1) to 8 weeks of empagliflozin or placebo run-in, followed by a second randomisation (1:1:1:1) to 14 weeks of treatment with once per day BI 690517 at doses of 3 mg, 10 mg, or 20 mg, or placebo. Study participants, research coordinators, investigators, and the data coordinating centre were masked to treatment assignment. The primary endpoint was the change in UACR measured in first morning void urine from baseline (second randomisation) to the end of treatment. This study is registered with ClinicalTrials.gov (NCT05182840) and is completed., Findings: Between Feb 18 and Dec 30, 2022, of the 714 run-in participants, 586 were randomly assigned to receive BI 690517 or placebo. At baseline, 33% (n=196) were women, 67% (n=390) were men, 42% (n=244) had a racial identity other than White, and mean participant age was 63·8 years (SD 11·3). Mean baseline eGFR was 51·9 mL/min/1·73 m 2 (17·7) and median UACR was 426 mg/g (IQR 205 to 889). Percentage change in first morning void UACR from baseline to the end of treatment at week 14 was -3% (95% CI -19 to 17) with placebo, -22% (-36 to -7) with BI 690517 3 mg, -39% (-50 to -26) with BI 690517 10 mg, and -37% (-49 to -22) with BI 690517 20 mg monotherapy. BI 690517 produced similar UACR reductions when added to empagliflozin. Investigator-reported hyperkalaemia occurred in 10% (14/146) of those in the BI 690517 3 mg group, 15% (22/144) in the BI 690517 10 mg group, and 18% (26/146) in the BI 690517 20 mg group, and in 6% (nine of 147) of those receiving placebo, with or without empagliflozin. Most participants with hyperkalaemia did not require intervention (86% [72/84]). Adrenal insufficiency was an adverse event of special interest reported in seven of 436 study participants (2%) receiving BI 690517 and one of 147 participants (1%) receiving matched placebo. No treatment-related deaths occurred during the study., Interpretation: BI 690517 dose-dependently reduced albuminuria with concurrent renin-angiotensin system inhibition and empagliflozin, suggesting an additive efficacy for chronic kidney disease treatment without unexpected safety signals., Funding: Boehringer Ingelheim., Competing Interests: Declaration of interests KRT reports grants for investigator-initiated research from NIDDK, NHLBI, NCATS, NIMHD, NIH Data Science office, Travere, Bayer, and Goldfinch Bio; contracts from CDC; consulting fees from Boehringer Ingelheim, Janssen, Novo Nordisk, AstraZeneca, Bayer, Eli Lilly, Gilead, and Merck Sharp & Dohme; payment for manuscript writing for Boehringer Ingelheim, Novo Nordisk, Bayer, Eli Lilly, and Gilead; payment of honoraria for Novo Nordisk, AstraZeneca, Bayer, Eli Lilly, and Gilead; payment for travel for Novo Nordisk; travel to meetings from Novo Nordisk; chair and member of a data safety monitoring committee for NIDDK and George Clinical; and leadership role for the American Society of Nephrology. MEC reports grants for investigator-initiated research and research funding from Baxter and Fresenius; and payment of honoraria for lectures, presentations, and education events from AstraZeneca, Fresenius, Bayer, Pfizer, and Bracepharma. MLC reports research grant support from NIH and NIDDK (all to the University of Minnesota and Cleveland Clinic) and research grant support sponsored by Bayer Pharmaceuticals (all to the University of Minnesota); consulting fees from Bayer Pharmaceuticals, Novo Nordisk, and AstraZeneca; payment for speaker bureaus and educational events from Bayer Pharmaceuticals; payment of honoraria for lectures and educational events from Cardiorenal Connections, Heart in Diabetes, Translational Medicine Academy, and the American College of Cardiology; support to attend investigator meetings for Kidney Precision Medicine Project from the NIH and NIDDK, American Diabetes Association meetings from NIH and NIDDK, and University of Minnesota and American Society of Nephrology meetings from NIH and NIDDK and Cleveland Clinic Foundation (all to the University of Minnesota); participation on and site principle investigator for the Data Safety Monitoring Board for Preventing Early Renal Loss in Diabetes Study for NIH and NIDDK (all to the University of Minnesota); and attendee of Kidney Disease Improving Global Outcomes writing group meetings. DC reports research grants from Boehringer Ingelheim-Lilly, Merck, Janssen, Sanofi, AstraZeneca, CSL Behring, and Novo Nordisk; consulting fees from Boehringer Ingelheim-Lilly, Merck, AstraZeneca, Sanofi, Mitsubishi Tanabe, AbbVie, Janssen, Bayer, Prometic, Bristol Myers Squibb, Maze, Gilead, CSL Behring, Otsuka, Novartis, Youngene, Lexicon, Inversago, GSK, and Novo Nordisk; payment of honoraria for lectures and advisory boards from Boehringer Ingelheim-Lilly, Merck, AstraZeneca, Sanofi, Mitsubishi Tanabe, Janssen, Bayer, and Novo Nordisk; support for traveling to and attending meetings from Boehringer Ingelheim-Lilly, Merck, AstraZeneca, Sanofi, Janssen, Bayer, and Novo Nordisk; and receipt of a drug for research from AstraZeneca. HJLH reports funding to conduct clinical trials from AstraZeneca, Bayer, Boehringer Ingelheim, Janssen, and Novo Nordisk (all to the University of Groningen); consulting fees from AstraZeneca, Bayer, Boehringer Ingelheim, Chinook, CSL Behring, DImerix, Eli Lilly, Fresenius, Gilead, Janssen, Novo Nordisk, Novartis, and Travere Therapeutics; payment of honoraria for lectures from AstraZeneca, Novo Nordisk, and Bayer; support for traveling to and attending the American Diabetes Association meeting and American Society of Nephrology meeting from AstraZeneca and Eli Lilly (to HJLH and the University of Groningen); and receipt of the study drug from AstraZeneca, Bayer, Boehringer Ingelheim, Janssen, and Novo Nordisk. MN reports donations for research through Shogaku Kifu practice from KyowaKiirin, Mitsubishi Tanabe, Chugai, Boehringer Ingelheim, Torii, Takeda, Daiichi Sankyo, and JT; consulting fees from KyowaKiirin and Mitsubishi Tanabe; and payment of honoraria for lectures from KyowaKiirin, Mitsubishi Tanabe, Bayer, Astellas, JT, and AstraZeneca. RCR reports participation as a trial investigator for Novo Nordisk and AstraZeneca; consulting fees from Boehringer Ingelheim, Bayer, AstraZeneca, Chinook, and Novo Nordisk; payment of honoraria for lectures from AstraZeneca, Boehringer Ingelheim, Novo Nordisk, Amgen, and Bayer; and voluntary membership of the steering committee for World Kidney Day and of the Diabetes Committee. AS reports research contracts from Boehringer Ingelheim, Mineralysis, ProKidney, Reata, and Novartis; consulting fees from Boehringer Ingelheim, Ardelyx, and Pro Kidney; payment of honoraria for presentations from ProKidney, Boehringer Ingelheim, AstraZeneca, and Bayer; and participation on an Advisory Board for Travere, Boehringer Ingelheim, and Reata. DdZ reports consulting fees from Bayer, Fresenius, and Travere. PR reports grants and payment of honoraria for lectures, educational events, and steering group participation from AstraZeneca, Bayer, and Novo Nordisk (all to the Steno Diabetes Center Copenhagen); payment of honoraria for lectures and participation in advisory boards from Boehringer Ingelheim, Sanofi, Abbott, and Astellas (all to the Steno Diabetes Center Copenhagen). SJH, LC, SVS, and ZS are employees of Boehringer Ingelheim. All other authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Introduction: Aldosterone synthase (AS) inhibition may overcome increased aldosterone production in response to renin-angiotensin system inhibition. BI 690517 is an AS inhibitor under investigation for chronic kidney disease (CKD)., Methods: This multinational, phase II, double-blind study (NCT05182840) investigated the efficacy and safety of daily oral BI 690517, with or without empagliflozin 10 mg, in participants with CKD. The primary endpoint was change from baseline in urine albumin:creatinine ratio (UACR) at week 14. Between February 18, 2022, and December 30, 2022, 714 adults already treated by angiotensin-converting enzyme inhibitor (30.5%) or angiotensin receptor blocker (69.8%) were randomized (1:1) to an 8-week run-in to assign background empagliflozin (n = 356) or placebo (n = 358). Participants in each group were then randomized (1:1:1:1) to a 14-week treatment period with BI 690517 (3 mg, 10 mg, or 20 mg) or placebo. Of the 714 participants who entered run-in, 586 were randomized to the treatment period. They were predominantly men (66.6%) of white race (58.4%) with a mean (standard deviation [SD]) age of 63.8 (11.3) years. Type 2 diabetes was present in 414 participants (70.6%). The baseline mean (SD) estimated glomerular filtration rate was 51.9 (17.7) mL/min/1.73 m2, and median (interquartile range) UACR was 426.3 mg/g (205.3-888.5)., Conclusion: This study will inform dose selection for further clinical development and determine whether BI 690517, with or without background empagliflozin, has a favorable safety profile and potential for additive kidney protection in participants with CKD already treated with a renin-angiotensin system inhibitor., (© 2023 The Author(s). Published by S. Karger AG, Basel.)

Aims: Evaluate changes in haemodynamic markers as mediators of cardiovascular (CV) and kidney benefits with empagliflozin., Methods: Post-hoc analysis of EMPA-REG OUTCOME in patients with type 2 diabetes (T2D) and established CV disease receiving empagliflozin (10 and 25 mg) or placebo. Outcomes were CV death, hospitalisation for heart failure [HF], HF death, incident/worsening nephropathy, new onset macroalbuminuria, and the composite of sustained estimated glomerular filtration rate decline ≥40 % from baseline, renal replacement therapy or renal death. To be considered a mediator, changes in variable (pulse pressure, mean arterial pressure and cardiac workload) over time had to be (1) affected by active treatment, (2) associated with the outcome, and (3) adjustment for changes over time must reduce treatment effect versus an unadjusted analysis. Variables were evaluated in Cox regression analyses., Results: Pulse pressure, mean arterial pressure and cardiac workload were significantly reduced by empagliflozin vs placebo. Using change from baseline to Week 12 or sensitivity analyses (time-dependent updated mean and current change from baseline) of these CV parameters, only small impacts on empagliflozin effect on CV and kidney outcomes were shown., Conclusions: Improvements in haemodynamic parameters did not substantially mediate empagliflozin benefits on CV and kidney outcomes in patients with T2DM and established CV disease., Competing Interests: Declaration of competing interest B.K.K. reports lecture fees and/or advisory board memberships and/or study participation from Astellas, Bayer, Boehringer Ingelheim, Chiesi, Riepharm, Pfizer, Sanofi, Servier, and Vifor Pharma. He is the past president of the German Hypertension Society DHL. J.F.E.M. reports honoraria from AbbVie, AstraZeneca, Bayer, Boehringer Ingelheim, Novo Nordisk, Sanofi, and Vifor. S.J.H., and M.M. are employees of Boehringer Ingelheim, the manufacturer of empagliflozin. R.C. has received consulting fees from Boehringer Ingelheim and Eli Lilly. L.G. has participated in advisory boards for RES MED, Boehringer Ingelheim, and Sanofi Aventis, S.P. has received research grant from Daiichi Sankyo, honoraria from Daiichi Sankyo, Pfizer, Hanmi, Daewoong, Takeda, Donga and Boryung and Servier. D.F. has received honoraria from Amgen, AstraZeneca, Boehringer Ingelheim, Eli Lilly and Company, Merck & Co., and Sanofi., C.W. reports honoraria from Boehringer Ingelheim, Eli Lilly and Company, Mitsubishi, and Merck Sharp & Dohme., (Copyright © 2023. Published by Elsevier Inc.)

Background: The effects of empagliflozin in patients with chronic kidney disease who are at risk for disease progression are not well understood. The EMPA-KIDNEY trial was designed to assess the effects of treatment with empagliflozin in a broad range of such patients., Methods: We enrolled patients with chronic kidney disease who had an estimated glomerular filtration rate (eGFR) of at least 20 but less than 45 ml per minute per 1.73 m 2 of body-surface area, or who had an eGFR of at least 45 but less than 90 ml per minute per 1.73 m 2 with a urinary albumin-to-creatinine ratio (with albumin measured in milligrams and creatinine measured in grams) of at least 200. Patients were randomly assigned to receive empagliflozin (10 mg once daily) or matching placebo. The primary outcome was a composite of progression of kidney disease (defined as end-stage kidney disease, a sustained decrease in eGFR to <10 ml per minute per 1.73 m 2 , a sustained decrease in eGFR of ≥40% from baseline, or death from renal causes) or death from cardiovascular causes., Results: A total of 6609 patients underwent randomization. During a median of 2.0 years of follow-up, progression of kidney disease or death from cardiovascular causes occurred in 432 of 3304 patients (13.1%) in the empagliflozin group and in 558 of 3305 patients (16.9%) in the placebo group (hazard ratio, 0.72; 95% confidence interval [CI], 0.64 to 0.82; P<0.001). Results were consistent among patients with or without diabetes and across subgroups defined according to eGFR ranges. The rate of hospitalization from any cause was lower in the empagliflozin group than in the placebo group (hazard ratio, 0.86; 95% CI, 0.78 to 0.95; P = 0.003), but there were no significant between-group differences with respect to the composite outcome of hospitalization for heart failure or death from cardiovascular causes (which occurred in 4.0% in the empagliflozin group and 4.6% in the placebo group) or death from any cause (in 4.5% and 5.1%, respectively). The rates of serious adverse events were similar in the two groups., Conclusions: Among a wide range of patients with chronic kidney disease who were at risk for disease progression, empagliflozin therapy led to a lower risk of progression of kidney disease or death from cardiovascular causes than placebo. (Funded by Boehringer Ingelheim and others; EMPA-KIDNEY ClinicalTrials.gov number, NCT03594110; EudraCT number, 2017-002971-24.)., (Copyright © 2022 Massachusetts Medical Society.)

Aims: Sodium-glucose cotransporter 2 inhibitors (SGLT2i) may induce an early post-initiation decrease of estimated glomerular filtration rate (eGFR), which does not impact the SGLT2i benefits. The occurrence, characteristics, determinants, and clinical significance of an initial eGFR change among patients with heart failure with reduced ejection fraction require further study. In this study we aimed to describe eGFR change from randomization to week 4 (as percent of change relative to randomization) and assess its impact in EMPEROR-Reduced., Methods and Results: Landmark analyses (week 4) were performed. eGFR change was available in 3547 patients out of 3730 (95%). The tertiles of post-initiation % eGFR change for empagliflozin were: tertile 1 (T1) ≤-11.4%; T2 ≥-11.4% to ≤-1.0% and T3 ≥0.0%. The placebo group tertiles were: T1 ≤-6.5%; T2 ≥-6.4% to ≤+3.6%; and T3 ≥+3.6%. On average, empagliflozin induced a leftward distributional shift of initial eGFR changes of -2.5 ml/min/1.73 m 2 versus placebo. In the empagliflozin group, after covariate adjustment, the risk of cardiovascular and renal outcomes did not differ between patients in whom early post-treatment initiation eGFR decreased (T1) and patients in whom it increased (T3). However, in the placebo group, patients in whom early post-treatment initiation eGFR decreased (T1) had a higher risk of sustained worsening kidney function and all-cause mortality compared to patients in whom eGFR increased (T3) (hazard ratio [HR] 2.38, 95% confidence interval [CI] 1.25-4.55 and HR 1.37, 95% CI 1.01-1.85, respectively)., Conclusion: A mild eGFR decrease may be expected after the initiation of empagliflozin, and it is not associated with untoward heart failure, mortality, or kidney safety events. Clinicians should not be concerned with early eGFR changes post-initiation of empagliflozin., (© 2022 European Society of Cardiology.)

Objective: To assess the safety of empagliflozin in patients with type 2 diabetes and moderate to severe chronic kidney disease (CKD) (category G3-4) enrolled in clinical trials., Research Design and Methods: This analysis pooled data from 19 randomized, placebo-controlled, phase 1-4 clinical trials and 1 randomized, placebo-controlled extension study in which patients received empagliflozin 10 mg or 25 mg daily. Time to first occurrence of adverse events (AEs) was evaluated using Kaplan-Meier analysis and multivariable Cox regression models., Results: Among a total of 15,081 patients who received at least one study drug dose, 1,522, 722, and 123 were classified as having G3A, G3B, and G4 CKD, respectively, at baseline. Demographic and clinical characteristics were similar between treatment groups across CKD categories. Rates of serious AEs, AEs leading to discontinuation, and events of special interest (including lower limb amputations and acute renal failure [ARF]) were also similar between empagliflozin and placebo across CKD subgroups. In adjusted Cox regression analyses, risks for volume depletion and ARF were similar for empagliflozin and placebo in the combined group with CKD categories G3B and G4 and the G3A group. Notably lower risks were observed in both groups for hyperkalemia (hazard ratio 0.59 [95% CI 0.37-0.96, P = 0.0323] and 0.48 [0.26-0.91, P = 0.0243], respectively) and edema (0.47 [0.33-0.68, P < 0.0001] and 0.44 [0.28-0.68, P = 0.0002], respectively)., Conclusions: Use of empagliflozin in patients with type 2 diabetes and advanced CKD raised no new safety concerns and may have beneficial effects on the development of hyperkalemia and edema., (© 2022 by the American Diabetes Association.)

Background: In EMPEROR-Reduced (Empagliflozin Outcome Trial in Patients With Chronic Heart Failure With Reduced Ejection Fraction), empagliflozin reduced cardiovascular death or heart failure (HF) hospitalization and total HF hospitalizations, and slowed the progressive decline in kidney function in patients with HF and a reduced ejection fraction, with and without diabetes. We aim to study the effect of empagliflozin on cardiovascular and kidney outcomes across the spectrum of kidney function., Methods: In this prespecified analysis, patients were categorized by the presence or absence of chronic kidney disease (CKD) at baseline (estimated glomerular filtration rate [eGFR] <60 ml/min/1.73 m 2 or albumin-to-creatine ratio >300 mg/g). The primary and key secondary outcomes were: (1) a composite of cardiovascular death or HF hospitalization (primary outcome); (2) total HF hospitalizations; and (3) eGFR slope. The direct impact on kidney events was investigated by a prespecified composite kidney outcome (defined as a sustained profound decline in eGFR, chronic dialysis, or transplant). The median follow-up was 16 months., Results: Of 3730 patients who were randomized to empagliflozin or placebo, 1978 (53%) had CKD. Empagliflozin reduced the primary outcome and total HF hospitalizations in patients with and without CKD: hazard ratio (HR)=0.78 (95% CI, 0.65-0.93) and HR=0.72 (95% CI, 0.58-0.90), respectively (interaction P =0.63). Empagliflozin slowed the slope of eGFR decline by 1.11 (0.23-1.98) ml/min/1.73 m 2 /yr in patients with CKD and by 2.41 (1.49-3.32) ml/min/1.73 m 2 /yr in patients without CKD. The risk of the composite kidney outcome was reduced similarly in patients with and without CKD: HR=0.53 (95% CI, 0.31-0.91) and HR=0.46 (95% CI, 0.22-0.99), respectively. The effect of empagliflozin on the primary composite outcome and key secondary outcomes was consistent across a broad range of baseline kidney function, measured by clinically relevant eGFR subgroups or by albuminuria, including patients with eGFR as low as 20 ml/min/1.73 m 2 . Empagliflozin was well tolerated in CKD patients., Conclusions: In EMPEROR-Reduced, empagliflozin had a beneficial effect on the key efficacy outcomes and slowed the rate of kidney function decline in patients with and without CKD, and regardless of the severity of kidney impairment at baseline. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03057977.

Aim: To explore the cardiovascular (CV) and kidney effects of empagliflozin in patients with different clinical phenotypes of diabetic kidney disease (DKD) (i.e. with the presence or absence of overt albuminuria) participating in the EMPA-REG OUTCOME trial., Materials and Methods: EMPA-REG OUTCOME randomized participants (1:1:1) to empagliflozin 10 mg, 25 mg or placebo, added to standard of care. Post hoc, patients with different clinical phenotypes of DKD at baseline were categorized in three subgroups: (a) overt DKD (overt albuminuria [urinary albumin-to-creatinine ratio of >300 mg/g] with any estimated glomerular filtration rate [eGFR]; n = 769); (b) non-overt DKD (kidney impairment [eGFR < 60 mL/min/1.73 m 2 ] without overt albuminuria [urinary albumin-to-creatinine ratio of ≤300 mg/g]; n = 1290); and (c) 'all others' (eGFR ≥ 60 mL/min/1.73 m 2 without overt albuminuria; n = 4893). Analyses included CV (death, hospitalization for heart failure, all-cause hospitalization) and selected kidney outcomes, change in eGFR and kidney safety. Cox proportional hazards models assessed the consistency of treatment effect across subgroups., Results: Empagliflozin significantly reduced the risk of CV and kidney outcomes across all subgroups (P-values for interaction >.05), consistent with the overall trial population findings. Empagliflozin also significantly reduced the yearly loss of eGFR, assessed by chronic slopes, in all subgroups. The adverse event profile of empagliflozin was similar across all subgroups., Conclusions: Empagliflozin may improve CV and kidney outcomes and slow the progression of kidney disease in type 2 diabetes patients with DKD, irrespective of its clinical form, both with or without the presence of overt albuminuria., (© 2020 The Authors. Diabetes, Obesity and Metabolism published by John Wiley & Sons Ltd.)

Objective: To assess the influence of serum carnosinase (CN1) on the course of diabetic kidney disease (DKD)., Methods: hCN1 transgenic (TG) mice were generated in a BTBR Ob/Ob genetic background to allow the spontaneous development of DKD in the presence of serum carnosinase. The influence of serum CN1 expression on obesity, hyperglycemia, and renal impairment was assessed. We also studied if aggravation of renal impairment in hCN1 TG BTBR Ob/Ob mice leads to changes in the renal transcriptome as compared with wild-type BTBR Ob/Ob mice., Results: hCN1 was detected in the serum and urine of mice from two different hCN1 TG lines. The transgene was expressed in the liver but not in the kidney. High CN1 expression was associated with low plasma and renal carnosine concentrations, even after oral carnosine supplementation. Obese hCN1 transgenic BTBR Ob/Ob mice displayed significantly higher levels of glycated hemoglobin, glycosuria, proteinuria, and increased albumin-creatinine ratios (1104 ± 696 vs 492.1 ± 282.2 μg/mg) accompanied by an increased glomerular tuft area and renal corpuscle size. Gene-expression profiling of renal tissue disclosed hierarchical clustering between BTBR Ob/Wt , BTBR Ob/Ob, and hCN1 BTBR Ob/Ob mice. Along with aggravation of the DKD phenotype, 26 altered genes have been found in obese hCN1 transgenic mice; among them claudin-1, thrombospondin-1, nephronectin, and peroxisome proliferator-activated receptor-alpha have been reported to play essential roles in DKD., Conclusions: Our data support a role for serum carnosinase 1 in the progression of DKD. Whether this is mainly attributed to the changes in renal carnosine concentrations warrants further studies., Key Messages: Increased carnosinase 1 (CN1) is associated with diabetic kidney disease (DKD). BTBR Ob/Ob mice with human CN1 develop a more aggravated DKD phenotype. Microarray revealed alterations by CN1 which are not altered by hyperglycemia. These genes have been described to play essential roles in DKD. Inhibiting CN1 could be beneficial in DKD.

Background: Studies of progression of kidney dysfunction typically focus on renal replacement therapy or percentage decline in estimated glomerular filtration rate (eGFR) as outcomes. Our aim was to compare real-world patients with and without T2D to estimate progression from and to clinically defined categories of kidney disease and all-cause mortality., Methods: This was an observational cohort study of 31,931 patients with and 33,201 age/sex matched patients without type 2 diabetes (T2D) who had a serum creatinine and urine albumin-to-creatinine ratio (UACR) or dipstick proteinuria (DP) values. We used the first available serum creatinine value between 2006 and 2012 to calculate baseline eGFR and categorized them and the corresponding UACR/DP values using the Kidney Disease Improving Global Outcomes (KDIGO) categories. To assess our primary outcomes, we extracted probabilities of eGFR progression or mortality from life-table analyses and conducted multivariable Cox regression analyses of relative risk adjusted for age, sex, race/ethnicity, smoking, ischemic heart disease, heart failure, and use of renal-angiotensin-aldosterone system inhibitors., Results: Patterns of eGFR decline were comparable among patients with vs. without T2D with larger percentage declines at higher albuminuria levels across all eGFR categories. eGFR decline was generally larger among T2D patients, particularly in those with severely increased albuminuria. Across all CKD categories, risk of progression to the next higher category of eGFR was substantially increased with increasing albuminuria. For example, the risk was 23.5, 36.2, and 65.1% among T2D patients with eGFR 30-59 ml/min/1.73m 2 and UACR < 30, 30-299, and > 300 mg/dL, respectively (p < 0.001). Other comparisons were similarly significant. Among patients with low eGFR and normal to mildly increased albuminuria, the relative risk was up to 8-fold greater for all-cause mortality compared with the non-CKD subgroup (eGFR> 60 ml/min/1.73m 2 with normal to mildly increased albuminuria)., Conclusions: Presence of albuminuria was associated with accelerated eGFR decline independent of T2D. Risk for adverse outcomes was remarkably high among patients with CKD and normal to mildly increased albuminuria levels. Independent of T2D or albuminuria, a substantial risk for adverse outcomes exists for CKD patients in a routine care setting.

Background: Carnosinase-1 (CN-1) can be detected in 24 h urine of healthy individuals and patients with type 2 diabetes (T2DM). We aimed to assess whether urinary CN-1 is also reliably measured in spot urine and investigated its association with renal function and the albumin/creatinine ratio (ACR). We also assessed associations between the CNDP1 (CTG) n genotype and CN-1 concentrations in serum and urine., Methods: Patients with T2DM ( n = 85) and nondiabetic patients with chronic kidney disease (CKD) ( n = 26) stratified by albuminuria (ACR ≤ 300 mg/g or ACR > 300 mg/g) recruited from the nephrology clinic and healthy subjects ( n = 24) were studied., Results: Urinary CN-1 was more frequently detected and displayed higher concentrations in patients with ACR > 300 mg/g as compared to those with ACR ≤ 300 mg/g irrespective of the baseline disease (T2DM: 554 ng/ml [IQR 212-934 ng/ml] vs. 31 ng/ml [IQR 31-63 ng/ml] ( p < 0.0001) and nondiabetic CKD: 197 ng/ml [IQR 112-739] vs. 31 ng/ml [IQR 31-226 ng/ml] ( p = 0.015)). A positive correlation between urinary CN-1 and ACR was found ( r = 0.68, p < 0.0001). Multivariate linear regression analysis revealed that ACR and serum CN-1 concentrations but not eGFR or the CNDP1 genotype are independent predictors of urinary CN-1, explaining 47% of variation of urinary CN-1 concentrations ( R 2 = 0.47, p < 0.0001)., Conclusion: These results confirm and extend previous findings on urinary CN-1 concentrations, suggesting that assessment of CN-1 in spot urine is as reliable as in 24 h urine and may indicate that urinary CN-1 in macroalbuminuric patients is primarily serum-derived and not locally produced., Competing Interests: The authors have no conflicts of interest to declare., (Copyright © 2019 Angelica Rodriguez-Niño et al.)

This study assessed if serum carnosinase (CNDP1) activity and concentration in patients with type 2 diabetes mellitus (T2D) with diabetic nephropathy (DN) differs from those without nephropathy. In a cross-sectional design 127 patients with T2D with DN ((CTG) 5 homozygous patients n = 45) and 145 patients with T2D without nephropathy ((CTG) 5 homozygous patients n = 47) were recruited. Univariate and multivariate regression analyses were performed to predict factors relevant for serum CNDP1 concentration. CNDP1 (CTG) 5 homozygous patients with T2D with DN had significantly lower CNDP1 concentrations (30.4 ± 18.3 vs 51.2 ± 17.6 µg/ml, p < 0.05) and activity (1.25 ± 0.5 vs 2.53 ± 1.1 µmol/ml/h, p < 0.05) than those without nephropathy. This applied for patients with DN on the whole, irrespective of (CTG) 5 homozygosity. In the multivariate regression analyses, lower serum CNDP1 concentrations correlated with impaired renal function and to a lesser extend with the CNDP1 genotype (95% CI of regression coefficients: eGFR: 0.10-1.94 (p = 0.001); genotype: - 0.05 to 5.79 (p = 0.055)). Our study demonstrates that serum CNDP1 concentrations associate with CNDP1 genotype and renal function in patients with T2D. Our data warrant further studies using large cohorts to confirm these findings and to delineate the correlation between low serum CNDP1 concentrations and renal function deterioration in patients with T2D.

Although methylglyoxal (MGO) has emerged as key mediator of diabetic microvascular complications, the influence of MGO on the vascular transcriptome has not thoroughly been assessed. Since diabetes is associated with low grade inflammation causing sustained nuclear factor-kappa B (NF-κB) activation, the current study addressed 1) to what extent MGO changes the transcriptome of human umbilical vein endothelial cells (HUVECs) exposed to an inflammatory milieu, 2) what are the dominant pathways by which these changes occur and 3) to what extent is this affected by carnosine, a putative scavenger of MGO. Microarray analysis revealed that exposure of HUVECs to high MGO concentrations significantly changes gene expression, characterized by prominent down-regulation of cell cycle associated genes and up-regulation of heme oxygenase-1 (HO-1). KEGG-based pathway analysis identified six significantly enriched pathways of which the p53 pathway was the most affected. No significant enrichment of inflammatory pathways was found, yet, MGO did inhibit VCAM-1 expression in Western blot analysis. Carnosine significantly counteracted MGO-mediated changes in a subset of differentially expressed genes. Collectively, our results suggest that MGO initiates distinct transcriptional changes in cell cycle/apoptosis genes, which may explain MGO toxicity at high concentrations. MGO did not augment TNF-α induced inflammation.

Low serum carnosinase (CN-1) concentrations are associated with low risk for development of diabetic nephropathy (DN) in patients with type 2 diabetes (T2D). Although CN-1 is expressed in the kidney, urinary CN-1 (CNU) excretion and its pathological relevance in patients with T2D have not been investigated to date. The present study therefore assessed the extent of CNU excretion in healthy subjects (n = 243) and in patients with T2D (n = 361) enrolled in the DIAbetes and LifEstyle Cohort Twente-1 (DIALECT-1) in relation to functional renal parameters. CNU was detected in a high proportion of healthy individuals, 180 (74%); median CNU excretion was 0.25 mg/24 h [(IQR 0-0.65 mg/24 h]. In patients with T2D the prevalence and extent of CNU increased in parallel with albuminuria (r = 0.59, p < 0.0001; median CNU 0.1 vs 0.2 vs 1.5 mg/24 h, p < 0.0001; prevalence of CNU 61 vs. 81 vs. 97% p < 0.05 in normo- (n = 241), micro- (n = 80) and macroalbuminuria (n = 40), respectively). Patients with estimated glomerular filtration rate (eGFR) < 30 ml/min/1.73 m 2 displayed higher median CNU excretion rates in comparison to patients with preserved eGFR (> 90 ml/min/1.73 m 2 ) (1.36 vs 0.13 mg/24 h, p < 0.05). Backward stepwise multivariate linear regression analysis revealed albuminuria, eGFR and glycosuria to be independent factors of CNU excretion rates, all together explaining 37% of variation of CNU excretion rates (R 2  = 0.37, p < 0.0001). These results show for the first time that CN-1 can be detected in urine and warrants prospective studies to assess the relevance of CNU for renal function deterioration in diabetes patients.

Carnosinase 1 (CN1) has been postulated to be a susceptibility factor for developing diabetic nephropathy (DN). Although its major substrate, carnosine, is beneficial in rodent models of DN, translation of these findings to humans has been hampered by high CN1 activity in human serum resulting in rapid degradation of carnosine. To overcome this hurdle, we screened a protease-directed small-molecule library for inhibitors of human recombinant CN1. We identified SAN9812 as a potent and highly selective inhibitor of CN1 activity with a K i of 11 nM. It also inhibited CN1 activity in human serum and serum of transgenic mice-overexpressing human CN1. Subcutaneous administration of 30 mg/kg SAN9812 led to a sustained reduction in circulating CN1 activity in human CN1 transgenic (TG) mice. Simultaneous administration of carnosine and SAN9812 increased carnosine levels in plasma and kidney by up to 100-fold compared to treatment-naïve CN1-overexpressing mice. To our knowledge, this is the first study reporting on a potent and selective CN1 inhibitor with in vivo activity. SAN9812, also called carnostatine, may be used to increase renal carnosine concentration as a potential therapeutic modality for renal diseases linked to glycoxidative conditions.

Diabetes is a common cause of chronic kidney disease (CKD), but in aggregate, non-diabetic diseases account for a higher proportion of cases of CKD than diabetes in many parts of the world. Inhibition of the renin-angiotensin system reduces the risk of kidney disease progression and treatments that lower blood pressure (BP) or low-density lipoprotein cholesterol reduce cardiovascular (CV) risk in this population. Nevertheless, despite such interventions, considerable risks for kidney and CV complications remain. Recently, large placebo-controlled outcome trials have shown that sodium-glucose co-transporter-2 (SGLT-2) inhibitors reduce the risk of CV disease (including CV death and hospitalization for heart failure) in people with type 2 diabetes who are at high risk of atherosclerotic disease, and these effects were largely independent of improvements in hyperglycaemia, BP and body weight. In the kidney, increased sodium delivery to the macula densa mediated by SGLT-2 inhibition has the potential to reduce intraglomerular pressure, which may explain why SGLT-2 inhibitors reduce albuminuria and appear to slow kidney function decline in people with diabetes. Importantly, in the trials completed to date, these benefits appeared to be maintained at lower levels of kidney function, despite attenuation of glycosuric effects, and did not appear to be dependent on ambient hyperglycaemia. There is therefore a rationale for studying the cardio-renal effects of SGLT-2 inhibition in people at risk of CV disease and hyperfiltration (i.e. those with substantially reduced nephron mass and/or albuminuria), irrespective of whether they have diabetes.

Aims: We evaluated the simultaneous effects of all clinically recognized categories of albuminuria and estimated glomerular filtration rate (eGFR) on cardiovascular disease (CVD) and mortality METHODS: We conducted a longitudinal observational study of 16,678 type 2 diabetes (T2D) patients. From the first serum creatinine value from 2006 to 2012 and a urine-albumin creatinine ratio (UACR) recorded within 6months, we applied baseline Kidney Disease: Improving Global Outcomes (KDIGO) categories of eGFR and albuminuria. We followed patients for up to 11years to calculate adjusted incidence per 1000person-years (p-y) of first CVD hospitalization and all-cause mortality., Results: Over 98,069p-y of follow-up, CVD hospitalization risk was greater for each higher eGFR and albuminuria category. In eGFR category G2 (60-89mL/min/1.73m2), adjusted incidence per 1000p-y was 14.1 (95% CI 12.9-15.5), 19.8 (17.2-22.8), and 22.8 (17.4-30.0) for normoalbuminuria, microalbuminuria and macroalbuminuria, respectively. For eGFR category G3a (45-59), rates were 26.7 (22.3-32.0), 40.3 (32.2-50.5), and 44.1 (28.8-67.4), respectively. Adjusted risk of all-cause mortality followed a similar pattern., Conclusions: Our data underscore the importance of including detailed eGFR and UACR values in assessing CVD risk. High albuminuria and low eGFR is a potent predictor of CVD and death., (Copyright © 2017. Published by Elsevier Inc.)

We previously demonstrated that polymorphisms in the carnosinase-1 gene (CNDP1) determine the risk of nephropathy in type 2 diabetic patients. Carnosine, the substrate of the enzyme encoded by this gene, is considered renoprotective and could possibly be used to treat diabetic nephropathy (DN). In this study, we examined the effect of carnosine treatment in vivo in BTBR (Black and Tan, BRachyuric) ob/ob mice, a type 2 diabetes model which develops a phenotype that closely resembles advanced human DN. Treatment of BTBR ob/ob mice with 4 mM carnosine for 18 weeks reduced plasma glucose and HbA1c, concomitant with elevated insulin and C-peptide levels. Also, albuminuria and kidney weights were reduced in carnosine-treated mice, which showed less glomerular hypertrophy due to a decrease in the surface area of Bowman's capsule and space. Carnosine treatment restored the glomerular ultrastructure without affecting podocyte number, resulted in a modified molecular composition of the expanded mesangial matrix and led to the formation of carnosine-acrolein adducts. Our results demonstrate that treatment with carnosine improves glucose metabolism, albuminuria and pathology in BTBR ob/ob mice. Hence, carnosine could be a novel therapeutic strategy to treat patients with DN and/or be used to prevent DN in patients with diabetes.

Considering that the homozygous CNDP1 (CTG) 5 genotype affords protection against diabetic nephropathy (DN) in female patients with type 2 diabetes, this study assessed if this association remains gender-specific when applying clinical inclusion criteria (CIC-DN) or biopsy proof (BP-DN). Additionally, it assessed if the prevalence of the protective genotype changes with diabetes duration and time on hemodialysis and if this occurs in association with serum carnosinase (CN-1) activity. Whereas the distribution of the (CTG) 5 homozygous genotype in the no-DN and CIC-DN patients was comparable, a lower frequency was found in the BP-DN patients, particularly in females. We observed a significant trend towards high frequencies of the (CTG) 5 homozygous genotype with increased time on dialysis. This was also observed for diabetes duration but only reached significance when both (CTG) 5 homo- and heterozygous patients were included. CN-1 activity negatively correlated with time on hemodialysis and was lower in (CTG) 5 homozygous patients. The latter remained significant in female subjects after gender stratification. We confirm the association between the CNDP1 genotype and DN to be likely gender-specific. Although our data also suggest that (CTG) 5 homozygous patients may have a survival advantage on dialysis and in diabetes, this hypothesis needs to be confirmed in a prospective cohort study.

Iron has been suggested to affect the clinical course of type 2 diabetes (T2DM) as accompanying increased intracellular iron accumulation may provide an alternative source for reactive oxygen species (ROS). Although carnosine has proven its therapeutic efficacy in rodent models of T2DM, little is known about its efficacy to protect cells from iron toxicity. We sought to assess if high glucose (HG) exposure makes cultured human umbilical vein endothelial cells (HUVECs) and renal proximal tubular epithelial cells (PTECs) more susceptible to metal induced toxicity and if this is ameliorated by L-carnosine. HUVECs and PTECs, cultured under normal glucose (5 mM, NG) or HG (30 mM), were challenged for 24 h with FeCl3. Cell viability was not impaired under HG conditions nor did HG increase susceptibility to FeCl3. HG did not change the expression of divalent metal transporter 1 (DMT1), ferroportin (IREG), and transferrin receptor protein 1 (TFRC). Irrespective of glucose concentrations L-carnosine prevented toxicity in a dose-dependent manner, only if it was present during the FeCl3 challenge. Hence our study indicates that iron induced cytotoxicity is not enhanced under HG conditions. L-Carnosine displayed a strong protective effect, most likely by chelation of iron mediated toxicity.

Serum carnosinase (CN-1) measurements are at present mainly performed by assessing enzyme activity. This method is time-consuming, not well suited for large series of samples and can be discordant to measurements of CN-1 protein concentrations. To overcome these limitations, we developed sandwich ELISA assays using different anti-CN-1 antibodies, i.e., ATLAS (polyclonal IgG) and RYSK173 (monoclonal IgG1). With the ATLAS-based assay, similar amounts of CN-1 were detected in serum and both EDTA and heparin plasma. The RYSKS173-based assay detected CN-1 in serum in all individuals at significantly lower concentrations compared to the ATLAS-based assay (range: 0.1-1.8 vs. 1-50 μg/ml, RYSK- vs. ATLAS-based, P<0.01). CN-1 detection with the RYSK-based assay was increased in EDTA plasma, albeit at significantly lower concentrations compared to ATLAS. In heparin plasma, CN-1 was also poorly detected with the RYSK-based assay. Addition of DTT to serum increased the detection of CN-1 in the RYSK-based assay almost to the levels found in the ATLAS-based assay. Both ELISA assays were highly reproducible (R: 0.99, P<0.01 and R: 0.93, P<0.01, for the RYSK- and ATLAS-based assays, respectively). Results of the ATLAS-based assay showed a positive correlation with CN-1 activity (R: 0.62, P<0.01), while this was not the case for the RYSK-based assay. However, there was a negative correlation between CN-1 activity and the proportion of CN-1 detected in the RYSK-based assay, i.e., CN-1 detected with the RYSK-based assay/CN-1 detected with the ATLAS-based assay × 100% (Spearman-Rang correlation coefficient: -0.6, P<0.01), suggesting that the RYSK-based assay most likely detects a CN-1 conformation with low CN-1 activity. RYSK173 and ATLAS antibodies reacted similarly in Western blot, irrespective of PNGase treatment. Binding of RYSK173 in serum was not due to differential N-glycosylation as demonstrated by mutant CN-1 cDNA constructs. In conclusion, our study demonstrates a good correlation between enzyme activity and CN-1 protein concentration in ELISA and suggests the presence of different CN-1 conformations in serum. The relevance of these different conformations is still elusive and needs to be addressed in further studies.