A role for tubular Na+/H+ exchanger NHE3 in the natriuretic effect of the SGLT2 inhibitor empagliflozin

ASK1 limits kidney glucose reabsorption, growth, and mid-late proximal tubule KIM-1 induction when diabetes and Western diet are combined with SGLT2 inhibition

Selonsertib is an apoptosis signal-regulating kinase 1 inhibitor (ASK1i) that attenuated the decline in creatinine-based estimated GFR in humans with type 2 diabetes and kidney disease but increased the rate of acute kidney injury. This study explored the individual and combined kidney effects of selonsertib and the antihyperglycemic sodium-glucose cotransporter 2 inhibitor (SGLT2i) dapagliflozin in Western diet-fed male Akita mice, a murine model of early type 1 diabetes mellitus showing signs of systemic but no kidney inflammation. ASK1i reduced elevated plasma levels of proinflammatory cytokines/chemokines (IL-6, MCP1/CCL2, KC/CXCL1, and IP-10/CXCL10) without significantly changing hyperglycemia, glomerular hyperfiltration, and albuminuria or affecting the blood glucose and glomerular hyperfiltration-lowering effect of SGLT2i. A potential sign of tubular stress, SGLT2i modestly upregulated kidney cortex transcription of proinflammatory and profibrotic genes and distal tubule injury marker Ngal. Adding ASK1i to SGLT2i lowered the transcription of many of these genes, including Ngal. However, ASK1i enhanced kidney glucose reabsorption independent of SGLT2i, and combined ASK1i + SGLT2i increased kidney weight by 30%. This was associated with and positively correlated with the upregulation of the tubular stress/injury marker KIM-1, primarily in the mid-to-late proximal tubule. Combined ASK1i + SGLT2i increased the tubular injury score but not signs of kidney inflammation or fibrosis beyond a robust increase in kidney mRNA expression of Il6, Ccl2 (Mcp1), and Timp1, associated with increased plasma IL-6 levels. The data support the hypothesis that housekeeping functions of ASK1 limit glucose reabsorption and the associated growth and cellular stress induced in the mid-to-late proximal tubule by combining hyperglycemia and Western diet with SGLT2 inhibition.NEW & NOTEWORTHY Selonsertib is an apoptosis signal-regulating kinase 1 (ASK1) inhibitor that attenuated creatinine-based eGFR decline in humans with type 2 diabetes and kidney disease but increased acute kidney injury rates. Here, we report evidence in a murine model of early type 1 diabetes mellitus that housekeeping functions of ASK1 limit glucose reabsorption and the associated growth and cellular stress induced in the mid-to-late proximal tubule by combining hyperglycemia and Western diet with SGLT2 inhibition.

Renal macro- and microcirculatory perturbations in acute kidney injury and chronic kidney disease associated with heart failure and cardiac surgery

Chronic kidney disease (CKD) affects 50% of patients with heart failure. The pathophysiology of CKD in heart failure is proposed to be driven by macrocirculatory hemodynamic changes, including reduced cardiac output and elevated central venous pressure. However, our understanding of renal microcirculation in heart failure and CKD remains limited. This is largely due to the lack of noninvasive techniques to assess renal microcirculation in patients. Moreover, there is a lack of clinically relevant animal models of heart failure and CKD to advance our understanding of the timing and magnitude of renal microcirculatory dysfunction. Patients with heart failure and CKD commonly require cardiac surgery with cardiopulmonary bypass (CPB) to improve their prognosis. However, acute kidney injury (AKI) is a frequent unresolved clinical complication in these patients. There is emerging evidence that renal microcirculatory dysfunction, characterized by renal medullary hypoperfusion and hypoxia, plays a critical role in the pathogenesis of cardiac surgery-associated AKI. In this review, we consolidate the preclinical and clinical evidence of renal macro- and microcirculatory perturbations in heart failure and cardiac surgery requiring CPB. We also examine emerging biomarkers and therapies that may improve health outcomes for this vulnerable patient population by targeting the renal microcirculation.

Sodium glucose co-transporter 2 inhibitor prevents nephrolithiasis in non-diabetes by restoring impaired autophagic flux

BACKGROUND

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) offer significant cardiovascular and kidney protection, independent of diabetes mellitus (DM). Recent cohort studies also suggest that SGLT2i can decrease the risk of nephrolithiasis in patients with DM. We aimed to use both animal models and human data to investigate whether SGLT2i can prevent nephrolithiasis and explored autophagy as a possible mechanism.

METHODS

We utilised SGLT2i, dapagliflozin (DAPA), on a glyoxylate (GOX)-induced calcium oxalate (CaOx) nephrolithiasis non-DM mouse model to test whether SGLT2i inhibited CaOx stone formation through modulating autophagy. Moreover, the clinical data retrieved from the National Health Insurance Research Database was analysed to confirm the findings from animal models.

FINDINGS

DAPA increased urine citrate, magnesium, pH, and decreased oxalate, effectively inhibiting CaOx stones in GOX mice. While autophagy was increased in the kidneys of GOX mice, as demonstrated by upregulated AMP-activated protein kinase (AMPK) and increased LC3B conversion; impaired autophagic flux was indicated by p62 accumulation. DAPA improved autophagy by downregulating mammalian target of rapamycin (mTOR), AMPK, and restoring autophagic flux. Rapamycin co-treatment preserved DAPA's nephrolithiasis inhibition, while hydroxychloroquine (HCQ) co-treatment abolished it. Finally, cohort data confirmed that SGLT2i reduced nephrolithiasis risk, but this protective effect disappeared if HCQ had been used within the prior year, suggesting that HCQ may compromise SGLT2i's protection against nephrolithiasis.

INTERPRETATION

SGLT2i, DAPA, inhibits nephrolithiasis by restoring impaired autophagic flux, and co-administration with autophagy inhibitor, HCQ, compromises SGLT2i's protection.

FUNDING

This research was funded by grants from the National Science and Technology Council, Taiwan (110-2314-B-006-023, 110-2320-B-006-017MY3, and 112-2314-B-006-058) and the research grants (NCKUH-11202005, -11210020) from the National Cheng Kung University Hospital, Tainan, Taiwan.

Effects of sotagliflozin on kidney and cardiac outcome in a hypertensive model of subtotal nephrectomy in male mice

Dual inhibition of sodium glucose cotransporters 1 and 2 (SGLT1/SGLT2) by sotagliflozin protects the kidney and heart in patients with type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD). To gain mechanistic insights, the current study aimed to establish a murine model of hypertensive CKD that shows cardio-renal protection by sotagliflozin. Since protection by SGLT2 inhibitors can be diabetes-independent, a nondiabetic murine model of subtotal nephrectomy with angiotensin II infusion-facilitated hypertension was followed for 7 weeks. The model showed 40% lower GFR, doubling in plasma FGF23, 50 mmHg higher systolic blood pressure (SBP), 100-fold increased albuminuria, and robust signs of kidney injury, inflammation, and fibrosis versus sham controls, associated with a 30% larger left cardiac ventricle and wall thickness and upregulation of markers of cardiac overload and fibrosis. Sotagliflozin, initiated 1 week after the last surgery, showed target-engagement evidenced by glucosuria, 9 mmHg lower SBP, temporal reduction in body weight and GFR, and 30% higher plasma GLP1. Sotagliflozin, however, did not improve markers of kidney injury, inflammation, fibrosis, albuminuria, and plasma FGF23, or signs of cardiac overload, fibrosis, or impaired function. Limited sotagliflozin responsiveness may relate to short treatment time, limited metabolic benefits in nondiabetic setting and/or the model's dominant angiotensin II-driven effects/hypertension.

Canagliflozin-induced renal glutathione distribution mapping in non-diabetic male rat kidneys

Canagliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, has direct renoprotective effects beyond lowering blood glucose levels. The inhibition of sodium reabsorption via SGLT2 reduces the overload on proximal tubules, thereby suppressing the generation of reactive oxygen species (ROS) and preventing a decline in renal function. To clarify the pharmacological mechanism of SGLT2 inhibitor, we investigated the effects of canagliflozin on oxidative stress in the kidneys of normal, non-diabetic Sprague-Dawley rats. Screening using mass spectrometry images revealed a significant elevation map of the reduced form of glutathione in the renal cortex of canagliflozin-treated non-diabetic rats. These results suggest that canagliflozin reduces oxidative stress through ROS scavenging mechanisms. Considering that ROS play major roles in renal dysfunction regardless of diabetes mellitus, these findings suggest that canagliflozin is applicable to a broader range of renal diseases beyond diabetes.

SGLT2 inhibitors and nephrolithiasis risk in patients with type 2 diabetes: A cohort study and meta-analysis

AIMS

This study aimed to evaluate the relationship between sodium-glucose cotransporter 2 inhibitor (SGLT2i) use and nephrolithiasis risk.

METHODS

In this real-world cohort study, we analyzed electronic health records from the TriNetX Analytics Network, which includes patients from 64 U.S. healthcare organizations. Adult patients with type 2 diabetes (T2D) who initiated SGLT2is, dipeptidyl peptidase-4 inhibitors (DPP4is), or glucagon-like peptide-1 receptor agonists (GLP-1RAs) between January 2015 and December 2023 were included. Comparisons were made between SGLT2is and DPP4is and between SGLT2is and GLP-1RAs. Patients were followed-up for up to 5 years. A meta-analysis was further conducted to synthesize available evidence.

RESULTS

The cohort study included 500,000 patients (250,000 pairs) for SGLT2is vs. DPP4is comparisons and 482,284 patients (241,142 pairs) for SGLT2is vs. GLP-1Ras comparisons. The risk of nephrolithiasis was significantly lower in SGLT2i users compared with DPP4i (HR: 0.86; 95% CI: 0.83-0.90) and GLP-1RA users (HR: 0.90; 95% CI: 0.86-0.94). A meta-analysis combining our study with four additional real-world studies further supported these findings.

CONCLUSIONS

This study suggests that SGLT2is may provide benefits beyond glycemic control by reducing nephrolithiasis risk, offering an advantage when selecting glucose-lowering therapies for patients with T2D.

SGLT2 inhibitors and nephrolithiasis risk: a meta-analysis

BACKGROUND

Sodium-glucose co-transporter 2 (SGLT2) inhibitors are novel anti-diabetic medications with potential beneficial effects on cardiovascular and renal outcomes, metabolic parameters and body weight. In addition to the beneficial effects on renal function, including estimated glomerular filtration rate and reduction in proteinuria, recent studies have investigated the potential role of SGLT2 inhibitor (SGLT2i) therapy on nephrolithiasis development. Nephrolithiasis, a condition affecting almost 10% of the general population at least once during a lifetime, is a common disorder with considerable risk for acute and chronic kidney injury and relatively few effective therapeutic options.

METHODS

We performed a literature search through multiple databases, including PubMed, Ovid MEDLINE, Web of Science, Scopus and Cochrane Library. We followed the systematic review and meta-analysis guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. We included a total of 11 635 698 patients who experienced nephrolithiasis from six clinical trials in this meta-analysis study.

RESULTS

In the pooled analysis, nephrolithiasis occurred in 1.27% of patients in the SGLT2i group (n = 739 197), compared with 1.56% of patients (n = 10 896 501) in the control arm (active control, placebo or no therapy). SGLT-2 inhibitor therapy has been associated with a lower risk for nephrolithiasis compared with placebo {odds ratio [OR] 0.61 [95% confidence interval (CI) 0.53-0.70], P < .00001} or active therapy such as glucagon-like peptide 1 and dipeptidyl peptidase 4 inhibitors [OR 0.66 (95% CI 0.47-0.93), P = .02].

CONCLUSION

We demonstrated a lower risk of nephrolithiasis with SGLT2i therapy compared with placebo or active control. Potential underlying mechanisms include osmotic diuresis leading to a reduction in the concentration of lithogenic substances, anti-inflammatory and anti-fibrotic effects and an increase in urine pH. There is a clear need for future large-scale randomized clinical trials evaluating such associations for better understanding.

Emerging horizons: clinical applications and multifaceted benefits of SGLT-2 inhibitors beyond diabetes

SGLT-2 inhibitors, initially developed for type 2 diabetes, demonstrate profound cardiorenal and metabolic benefits. This review synthesizes evidence from clinical trials and mechanistic studies to elucidate their roles in cardiovascular diseases, chronic kidney disease, and non-alcoholic fatty liver disease. Key findings include a notable reduction in cardiovascular death/heart failure hospitalization, a marked decrease in heart failure hospitalization risk, and significant improvements in renal and hepatic outcomes. Emerging mechanisms, such as autophagy induction, ketone utilization, and anti-inflammatory effects, underpin these benefits. Ongoing trials explore their potential in non-diabetic populations, positioning SGLT-2 inhibitors as transformative agents in multisystem disease management.

Acetazolamide Therapy and Kidney Function in Persons with Nonalbuminuric Diabetes Mellitus Type 1

Key Points

Low-dose acetazolamide reversibly lowered GFR in persons with type 1 diabetes mellitus, suggesting a possible role in relieving glomerular hyperfiltration. Low doses of acetazolamide were well tolerated in persons with type 1 diabetes.

Background

Sodium-glucose cotransporter-2 inhibitors (SGLT2is) lower the risk of kidney failure in persons with type 2 diabetes. The presumed mechanism of action is through greater delivery of sodium to the distal tubule and activation of tubuloglomerular feedback, which lowers GFR and intraglomerular pressure. SGLT2is are not approved for use in persons with type 1 diabetes because of the risk of diabetic ketoacidosis. Acetazolamide, a proximal tubule diuretic, delivers more sodium to the distal nephron and may activate tubuloglomerular feedback in a similar way to SGLT2is without a higher risk of diabetic ketoacidosis. The kidney effects and safety of acetazolamide in persons with type 1 diabetes have not been well studied.

Methods

We conducted a dose-escalation trial to determine the effects of three dosages of oral acetazolamide (62.5, 125, and 250 mg, all twice daily) in 12 persons with type 1 diabetes. Participants were treated for 2 weeks, followed by a 2-week washout period before exposure to the next dosage level. Blood and urine chemistries, as well as iohexol-measured GFR, were assessed before and after each treatment interval. We aimed to identify a dose that maximized measured GFR reductions while minimizing adverse effects.

Results

The mean age was 46±17 years, 100% were White, and 75% were female. The mean measured GFR was 89±18 ml/min per 1.73 m2 at baseline. Acetazolamide reduced measured GFR by 15% (95% confidence interval [CI], 9 to 21), 14% (95% CI, 7 to 21), and 15% (95% CI, 10 to 21) after 2 weeks at the 62.5, 125, and 250 mg twice-daily dosage levels, respectively. The measured GFR reduction was fully reversed after each 2-week washout. Serum bicarbonate was reduced by 2.3, 4.2, and 4.4 mEq/L with escalating doses, and no episodes of hypokalemia (<3.5 mEq/L) were observed.

Conclusions

Among persons with type 1 diabetes and preserved kidney function, acetazolamide caused an acute, reversible reduction in measured GFR without effects on glucose metabolism.

Clinical Trial registry name and registration number:

Acetazolamide in Persons with Type 1 Diabetes, NCT05473364 .

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Water and electrolyte abnormalities in novel pharmacological agents for kidney disease and cancer

This review article series on water and electrolyte disorders is based on the 'Electrolyte Winter Seminar' held annually for young nephrologists in Japan. This is the third article in this series that focuses on water and electrolyte disturbances caused by novel pharmacological agents for kidney disease and cancer. The advent of novel pharmacological agents in cardiorenal medicine and oncology has introduced both therapeutic benefits and challenges in managing medication-induced water and electrolyte disturbances. These medications, including sodium-glucose cotransporter-2 (SGLT2) inhibitors, non-steroidal mineralocorticoid receptor antagonists (ns-MRAs), and immune checkpoint inhibitors (ICIs), significantly impact water and electrolyte homeostasis. SGLT2 inhibitors used widely in diabetes mellitus, heart failure, and chronic kidney disease mitigate hyperkalemia and hypomagnesemia but increase the risk of hypernatremia in patients on fluid restriction. Conversely, they are beneficial for managing hyponatremia in the syndrome of inappropriate antidiuresis (SIAD). ns-MRAs, prescribed for diabetic kidney disease, exhibit a high risk of hyperkalemia, particularly when combined with renin-angiotensin system inhibitors. ICIs, a breakthrough in oncology, frequently induce hyponatremia through immune-related adverse events, such as hypophysitis and non-immune-related adverse events like SIAD. Understanding the pathophysiology of these disturbances and implementing timely interventions, including hormone replacement and water and electrolyte management, is critical for optimizing treatment outcomes.

Genetic deletion of the kidney sodium/proton exchanger-3 (NHE3) does not alter calcium and phosphate balance due to compensatory responses

The sodium/proton exchanger-3 (NHE3) plays a major role in acid-base and extracellular volume regulation and is also implicated in calcium homeostasis. As calcium and phosphate balances are closely linked, we hypothesized that there was a functional link between kidney NHE3 activity, calcium, and phosphate balance. Therefore, we examined calcium and phosphate homeostasis in kidney tubule-specific NHE3 knockout mice (NHE3loxloxPax8 mice). Compared to controls, these knockout mice were normocalcemic with no significant difference in urinary calcium excretion or parathyroid hormone levels. Thiazide-induced hypocalciuria was less pronounced in the knockout mice, in line with impaired proximal tubule calcium transport. Knockout mice had greater furosemide-induced calciuresis and distal tubule calcium transport pathways were enhanced. Despite lower levels of the sodium/phosphate cotransporters (NaPi)-2a and -2c, knockout mice had normal plasma phosphate, sodium-dependent 32Phosphate uptake in proximal tubule membrane vesicles and urinary phosphate excretion. Intestinal phosphate uptake was unchanged. Low dietary phosphate reduced parathyroid hormone levels and increased NaPi-2a and -2c abundances in both genotypes, but NaPi-2c levels remained lower in the knockout mice. Gene expression profiling suggested proximal tubule remodeling in the knockout mice. Acutely, indirect NHE3 inhibition using the SGLT2 inhibitor empagliflozin did not affect urinary calcium and phosphate excretion. No differences in femoral bone density or architecture were detectable in the knockout mice. Thus, a role for kidney NHE3 in calcium homeostasis can be unraveled by diuretics, but NHE3 deletion in the kidneys has no major effects on overall calcium and phosphate homeostasis due, at least in part, to compensating mechanisms.

Gliflozines use in heart failure patients. Focus on renal actions and overview of clinical experience

Use of type 2 sodium-glucose cotransporter inhibitors (SGLT2i) gliflozines have first been applied to treatment of diabetic patients. In this setting, unexpected benefits on concomitant heart failure (HF) were seen in large trials. This clinical benefit was initially traced back to their natriuretic properties and as such they were also included in the therapeutic armamentarium of HF treatment. However, further insight into their mechanism of action has clarified their complex interaction with kidney function which better explains their prompt effectiveness in ameliorating HF outcome in the long-term, independent of left ventricular ejection fraction (LVEF) phenotype and concomitant presence of diabetes and/or chronic renal disease. This mainly results from the ability of SGLT2i to counteract the HF-associated hyperactivity of the sympathetic system and neurohormonal activation by modifying the pattern of renal tubular sodium and glucose reabsorption which results in curbing the overall sodium reabsorption. Their action results in decreased kidney workload and related oxygen consumption thus indirectly reducing sympathetic activity. The complex renal functional changes associated with HF and their modifications during SGLT2i administration will be reviewed.

Salvianolic acid C promotes renal gluconeogenesis in fibrotic kidneys through PGC1α

Impaired renal gluconeogenesis is recently identified as a hallmark of chronic kidney disease. However, the therapeutic approach to promote renal gluconeogenesis in CKD is still lacking. We aimed to study whether Salvianolic acid C (SAC), a nature compound extracted from the traditional Chinese medicine Danshen, inhibits renal fibrosis through promotion of gluconeogenesis. TGF-β stimulated HK2 human renal epithelial cells and mice with unilateral ureteral obstruction (UUO) were used as in vitro and in vivo models to study renal fibrosis. Fibrotic and gluconeogenic changes were determined by Western blotting analysis, quantitative PCR and Masson staining. Glucose and lactate concentrations were measured in cell culture and renal tissues. We found that SAC treatment inhibits the deposition of extracellular matrix proteins and the expression of fibrotic markers such as fibronectin, N-cadherin, Vimentin, aSMA, pSmad3, and Snail in UUO kidneys or renal cells. Inhibition of these fibrotic markers by SAC treatment was associated with enhanced expression of three gluconeogenic enzymes such as PCK1, G6PC and FBP1 in renal tissues or cells. SAC increase the concentration of glucose in the supernatant of renal cells. Lactate concentration was reduced by SAC in renal tissues or cells. Pyruvate and glucose tolerance tests showed that SAC improve the impaired glucose metabolism systemically in UUO mice. Peroxisome proliferator activated receptor gamma coactivator 1 alpha (PGC1ɑ) was downregulated in mouse kidneys after UUO operation, which was increased by SAC treatment. Moreover, PGC1α inhibitor SR-18292 reversed the anti-fibrotic effect and pro-gluconeogenic effect caused by SAC in renal cells. In conclusion, SAC inhibits renal fibrosis through promotion of PGC1α-mediated renal gluconeogenesis.

Empagliflozin in nondiabetic individuals with calcium and uric acid kidney stones: a randomized phase 2 trial

Efficacy of sodium-glucose cotransporter 2 inhibitors for kidney stone prevention in nondiabetic patients is unknown. In a double-blind, placebo-controlled, single-center, crossover phase 2 trial, 53 adults (≥18 and <75 years) with calcium (n = 28) or uric acid (UA; n = 25) kidney stones (at least one previous kidney stone event) without diabetes (HbA1c < 6.5%, no diabetes treatment) were randomized to once daily empagliflozin 25 mg followed by placebo or reverse (2 weeks per treatment). Randomization and analysis were performed separately for both stone types. Primary analyses were conducted in the per protocol set. Primary outcomes were urine relative supersaturation ratios (RSRs) for calcium oxalate (CaOx), calcium phosphate (CaP) and UA-validated surrogates for stone recurrence. Prespecified RSR reductions (≥15%) were met in both groups of stone formers. In patients with calcium stones, empagliflozin reduced RSR CaP (relative difference to placebo, -36%; 95% confidence interval, -48% to -21%; P < 0.001), but not RSRs CaOx and UA. In patients with UA stones, empagliflozin reduced RSR UA (-30%; 95% confidence interval, -44% to -12%; P = 0.002) but not RSRs CaOx and CaP. No serious or prespecified adverse events occurred. Thus, empagliflozin substantially reduced RSRs in nondiabetic adults with calcium and UA kidney stones. ClinicalTrials.gov registration: NCT04911660 .

Sodium-Glucose Cotransporter 2 Inhibitors in Diabetic Kidney Disease and beyond

Background

Sodium-glucose cotransporter 2 inhibitors (SGLT2is) have significantly impacted the management of diabetic kidney disease (DKD) and heart failure (HF), providing benefits beyond glycemic control. This review examines the mechanisms through which SGLT2is provide renal and cardiovascular protection and assesses their clinical efficacy.

Summary

By inducing glucosuria and natriuresis, SGLT2is alleviate multiple complications induced by chronic hyperglycemia. Moreover, SGLT2is reduce albuminuria, improve tubular function, and modulate erythropoiesis. Additionally, they mitigate inflammation and fibrosis by decreasing oxidative stress and downregulating proinflammatory pathways. Clinical trials have demonstrated significant reductions in renal and cardiovascular events among patients with type 2 diabetes mellitus. A comprehensive review of the literature was conducted through PubMed, highlighting the effects of SGLT2is and the results of major clinical trials involving SGLT2is.

Key Messages

SGLT2is play a crucial role in the management of DKD and HF by addressing multiple pathogenic pathways. Currently, SGLT2is are included in clinical guidelines for DKD and HF management, and their benefits extend to nondiabetic populations. Further research is needed to explore SGLT2is' multifaceted mechanisms and potential applications across diverse patient populations and different disease etiologies.

Sodium glucose transporter 2 inhibitors: Will these drugs benefit non-diabetic veterinary patients with cardiac and kidney diseases?

Sodium glucose transporter type 2 (SGLT2) inhibitors have been introduced into human medicine where their beneficial effects go beyond the expected improvement in blood glucose control. These drugs appear to prevent progression of both cardiovascular and kidney diseases, not only in diabetic but also in non-diabetic human patients. As these drugs have received conditional approval for use in diabetic cats and are being used in other veterinary species, the intriguing question as to whether they will have similar cardioprotective and nephroprotective effects in dogs and cats is being asked. The primary mechanism(s) by which SGLT2 inhibitors are cardio- and nephroprotective remain to be fully characterized. This paper reviews these suggested mechanisms in the context of the pathophysiology of progressive cardiovascular and kidney diseases in dogs and cats with the goal of predicting which categories of non-diabetic veterinary patients these drugs might be of most benefit.

Glomerular pressure and tubular oxygen supply: a critical dual target for renal protection

The primary treatment goal of chronic kidney disease (CKD) is preserving renal function and preventing its progression to end-stage renal disease. Glomerular hypertension and tubular hypoxia are critical risk factors in CKD progression. However, the renal hemodynamics make it difficult to avoid both factors due to the existence of peritubular capillaries that supply oxygen to the renal tubules downstream from the glomerulus through the efferent arteriole. In the treatment strategies for balancing glomerular pressure and tubular oxygen supply, afferent and efferent arterioles of the glomerulus determine glomerular filtration rate and blood flow to the peritubular capillaries. Therefore, sodium-glucose cotransporter 2 inhibitors and angiotensin receptor-neprilysin inhibitors as well as classical renin-angiotensin system inhibitors, which can change the diameter of afferent and/or efferent arterioles, are promising options for balancing this dual target and achieving renal protection. This review focuses on the clinical importance of glomerular pressure and tubular oxygen supply and proposes an effective treatment modality for this dual target.

The Effects of SGLT2 Inhibitors on Blood Pressure and Other Cardiometabolic Risk Factors

Beyond their established hypoglycemic, cardioprotective, and nephroprotective properties, sodium-glucose cotransporters 2 (SGLT2) inhibitors exert other pleiotropic actions on blood pressure levels, body weight, and lipid metabolism. Blood pressure (BP) reduction varies based on the background history, including an effect on systolic, diastolic BP, and 24 h BP measurements. The reduction in body weight between 1 and 2 kg for the first months is caused by a reduction in visceral and subcutaneous fat due to glycosuria and loss of calories. Regarding lipid metabolism, a reduction in triglycerides and an increase in total cholesterol, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) have been reported, although these alterations are small and could provide additional cardiovascular protection. Various pathophysiologic mechanisms have been proposed to explain the above-mentioned pleiotropic actions of SGLT2 inhibitors. Natriuresis, osmotic diuresis, body weight reduction, amelioration of endothelial dysfunction and arterial stiffness, sympathetic tone decrease, and uric acid reduction are among those that have been suggested for BP reduction. Apart from glycosuria and calorie loss, other mechanisms seem to contribute to body weight reduction, such as the beiging of white adipose tissue, while the mechanisms involved in lipid metabolism alterations have not been clearly determined.

Sodium Chloride Cotransporter in Hypertension

The sodium chloride cotransporter (NCC) is essential for electrolyte balance, blood pressure regulation, and pathophysiology of hypertension as it mediates the reabsorption of ultrafiltered sodium in the renal distal convoluted tubule. Given its pivotal role in the maintenance of extracellular fluid volume, the NCC is regulated by a complex network of cellular pathways, which eventually results in either its phosphorylation, enhancing sodium and chloride ion absorption from urines, or dephosphorylation and ubiquitination, which conversely decrease NCC activity. Several factors could influence NCC function, including genetic alterations, hormonal stimuli, and pharmacological treatments. The NCC's central role is also highlighted by several abnormalities resulting from genetic mutations in its gene and consequently in its structure, leading to dysregulation of blood pressure control. In the last decade, among other improvements, the acquisition of knowledge on the NCC and other renal ion channels has been favored by studies on extracellular vesicles (EVs). Dietary sodium and potassium intake are also implicated in the tuning of NCC activity. In this narrative review, we present the main cornerstones and recent evidence related to NCC control, focusing on the context of blood pressure pathophysiology, and promising new therapeutical approaches.

Water and sodium conservation response induced by SGLT2 inhibitor ipragliflozin in Dahl salt-sensitive hypertensive rats

Sodium-glucose cotransporter 2 (SGLT2) inhibitors increase urine volume with glucosuria and natriuresis. We recently reported that osmotic diuresis by the SGLT2 inhibitor ipragliflozin induces fluid homeostatic action via the stimulation of fluid intake and vasopressin-induced water reabsorption in euvolemic rats. However, the effects of SGLT2 inhibitors on these parameters in hypervolemic animals remain unclear. In this study, Dahl salt-sensitive hypertensive rats, a hypervolemic rat model, were fed a low-salt (0.3%) or high-salt (8%) diet for 14 days, then divided into vehicle or ipragliflozin (0.01%) groups. During 7 days of treatment, the high-salt diet groups significantly increased fluid intake and urine volume. In the ipragliflozin groups, fluid intake and urine volume increased by 63% and 235%, respectively, in rats fed a normal-salt diet and by 46% and 72%, respectively, in rats fed a high-salt diet. Ipragliflozin increased urinary vasopressin by 200% and solute-free water reabsorption by 196% in the normal-salt group but by only 44% and 38%, respectively, in the high-salt group. A high-salt diet significantly increased fluid balance (fluid intake - urine volume) and Na+ balance (Na+ intake - urinary Na+), but ipragliflozin did not change fluid and Na+ balance in normal- or high-salt groups. A high-salt diet significantly increased systolic blood pressure, but ipragliflozin did not significantly change systolic blood pressure in normal- or high-salt groups. In conclusion, SGLT2 inhibitor ipragliflozin did not change fluid and Na+ balance regardless of basal fluid retention, suggesting the potential of SGLT2 inhibitors to maintain body water and Na+.

Comparative effectiveness of sodium-glucose cotransporter-2 inhibitors for recurrent nephrolithiasis among patients with pre-existing nephrolithiasis or gout: target trial emulation studies

OBJECTIVE

To emulate target trials comparing recurrence of nephrolithiasis among patients with pre-existing nephrolithiasis (overall and stratified by concomitant gout) initiating sodium-glucose cotransporter-2 (SGLT-2) inhibitors versus an active comparator.

DESIGN

Target trial emulation studies.

SETTING

Canadian population database, January 2014 to June 2022.

PARTICIPANTS

20 146 patients with nephrolithiasis and type 2 diabetes, including those with concomitant gout at baseline, a high risk group.

INTERVENTIONS

Initiation of an SGLT-2 inhibitor or glucagon-like peptide-1 (GLP-1) receptor agonist, with a dipeptidyl peptidase-4 (DPP-4) inhibitor as alternative comparator.

MAIN OUTCOME MEASURES

The primary outcome was recurrent nephrolithiasis events ascertained from diagnoses during emergency department visits, hospital admissions, or outpatient visits. Secondary outcomes included nephrolithiasis resulting in hospital admission or emergency department visits and flare-up of gout, as well as a positive control outcome (genital infection) and negative control outcomes (osteoarthritis encounter and appendicitis). Poisson and Cox proportional hazards regression models were used (primary analyses), as well as overlap weighting.

RESULTS

After inverse probability of treatment weighting, 1924 recurrent nephrolithiasis events occurred among the 14 456 weighted patients who used an SGLT-2 inhibitor (105.3 per 1000 person years), compared with 853 events among the 5877 weighted patients who used a GLP-1 receptor agonist (156.4 per 1000 person years). The adjusted rate ratio was 0.67 (95% confidence interval (CI) 0.57 to 0.79) and rate difference was -51 (95% CI -63 to -40) per 1000 person years, with a number needed to treat (NNT) of 20. Among those with recently active nephrolithiasis, the absolute rate difference was 219 per 1000 person years (NNT of 5). Protective associations persisted for nephrolithiasis events that required emergency department visits, hospital admissions, or procedures, and when an SGLT-2 inhibitor was compared with a DPP-4 inhibitor (rate ratio 0.73 (0.68 to 0.78), rate difference -38 (-46 to -29) per 1000 person years (NNT of 26)). Protective associations also persisted among patients with nephrolithiasis and concomitant gout, with a rate ratio of 0.67 (0.57 to 0.79) and rate difference of -53 (95% CI -78 to -27) per 1000 person years versus a GLP-1 receptor agonist (NNT of 19), and 0.63 (0.55 to 0.72) and-62 (-81 to -42) per 1000 person years, respectively, versus a DPP-4 inhibitor (NNT of 16). Furthermore, SGLT-2 inhibitor use was associated with a lower rate of gout flare-ups (rate ratio 0.72, 0.54 to 0.95, rate difference -16, -31 to -1 per 1000 person years) compared with GLP-1 receptor agonists (0.65, 0.52 to 0.82, and -21, -33 to -9 per 1000 person years) compared with DPP-4 inhibitors. SGLT-2 inhibitor initiators showed higher risk of genital infection (eg, hazard ratio 2.21, 95% CI 1.68 to 2.90, and rate difference 13 per 1000 person years), but no altered risk of osteoarthritis encounter (0.87, 0.68 to 1.1, and -2 per 1000 person years) or appendicitis (1.07, 0.69 to 1.67, and 1 per 1000 person years). Results were similar when propensity score overlap weighting was applied.

CONCLUSIONS

The benefits associated with SGLT-2 inhibitor for patients with nephrolithiasis in these target trial emulations suggest they may be a useful addition to current treatments to simultaneously manage nephrolithiasis recurrence and comorbidities, including gout.

State-of-the-Art-Review: Mechanisms of Action of SGLT2 Inhibitors and Clinical Implications

BACKGROUND

Inhibitors of the Na+-coupled glucose transporter SGLT2 (SGLT2i) primarily shift the reabsorption of large amounts of glucose from the kidney's early proximal tubule to downstream tubular segments expressing SGLT1, and the non-reabsorbed glucose is spilled into the urine together with some osmotic diuresis. How can this protect the kidneys and heart from failing as observed in individuals with and without type 2 diabetes?

GOAL

Mediation analyses identified clinical phenotypes of SGLT2i associated with improved kidney and heart outcome, including a reduction of plasma volume or increase in hematocrit, and lowering of serum urate levels and albuminuria. This review outlines how primary effects of SGLT2i on the early proximal tubule can explain these phenotypes.

RESULTS

The physiology of tubule-glomerular communication provides the basis for acute lowering of GFR and glomerular capillary pressure, which contributes to lowering of albuminuria but also to long term preservation of GFR, at least in part by reducing kidney cortex oxygen demand. Functional co-regulation of SGLT2 with other sodium and metabolite transporters in the early proximal tubule explains why SGLT2i initially excrete more sodium than expected and are uricosuric, thereby reducing plasma volume and serum urate. Inhibition of SGLT2 reduces early proximal tubule gluco-toxicity and by shifting transport downstream may simulate "systemic hypoxia", and the resulting increase in erythropoiesis, together with the osmotic diuresis, enhances hematocrit and improves blood oxygen delivery. Cardio-renal protection by SGLT2i is also provided by a fasting-like and insulin-sparing metabolic phenotype and, potentially, by off-target effects on the heart and microbiotic formation of uremic toxins.

Arterial Hypertension: Novel Pharmacological Targets and Future Perspectives

Arterial hypertension (HTN) is one of the major global contributors to cardiovascular diseases and premature mortality, particularly due to its impact on vital organs and the coexistence of various comorbidities such as chronic renal disease, diabetes, cerebrovascular diseases, and obesity. Regardless of the accessibility of several well-established pharmacological treatments, the percentage of patients achieving adequate blood pressure (BP) control is still significantly lower than recommended levels. Therefore, the pharmacological and non-pharmacological management of HTN is currently the major focus of healthcare systems. Various strategies are being applied, such as the development of new pharmacological agents that target different underlying physiopathological mechanisms or associated comorbidities. Additionally, a novel group of interventional techniques has emerged in recent years, specifically for situations when blood pressure is not properly controlled despite the use of multiple antihypertensives in maximum doses or when patients are unable to tolerate or desire not to receive antihypertensive medications. Nonetheless, reducing the focus on antihypertensive medication development by the pharmaceutical industry and increasing recognition of ineffective HTN control due to poor drug adherence demands ongoing research into alternative approaches to treatment. The aim of this review is to summarize the potential novel pharmacological targets for the treatment of arterial hypertension as well as the future perspectives of the treatment strategy.

How can inhibition of glucose and sodium transport in the early proximal tubule protect the cardiorenal system?

What mechanisms can link the inhibition of sodium-glucose cotransporter 2 (SGLT2) in the early proximal tubule to kidney and heart protection in patients with and without type 2 diabetes? Due to physical and functional coupling of SGLT2 to other sodium and metabolite transporters in the early proximal tubule (including NHE3, URAT1), inhibitors of SGLT2 (SGLT2i) reduce reabsorption not only of glucose, inducing osmotic diuresis, but of other metabolites plus of a larger amount of sodium than expected based on SGLT2 inhibition alone, thereby reducing volume retention, hypertension and hyperuricemia. Metabolic adaptations to SGLT2i include a fasting-like response, with enhanced lipolysis and formation of ketone bodies that serve as additional fuel for kidneys and heart. Making use of the physiology of tubulo-glomerular communication, SGLT2i functionally lower glomerular capillary pressure and filtration rate, thereby reducing physical stress on the glomerular filtration barrier, tubular exposure to albumin and nephrotoxic compounds, and the oxygen demand for reabsorbing the filtered load. Together with reduced gluco-toxicity in the early proximal tubule and better distribution of transport work along the nephron, SGLT2i can preserve tubular integrity and transport function and, thereby, glomerular filtration rate in the long-term. By shifting transport downstream, SGLT2i may simulate systemic hypoxia at the oxygen sensors in the deep cortex/outer medulla, which stimulates erythropoiesis and, together with osmotic diuresis, enhances hematocrit and thereby improves oxygen delivery to all organs. The described SGLT2-dependent effects may be complemented by off-target effects of SGLT2i on the heart itself and on the microbiome formation of cardiovascular-effective uremic toxins.

Mechanisms of heart failure and chronic kidney disease protection by SGLT2 inhibitors in nondiabetic conditions

Sodium-glucose cotransporter 2 inhibitors (SGLT2is), initially developed for type 2 diabetes (T2D) treatment, have demonstrated significant cardiovascular and renal benefits in heart failure (HF) and chronic kidney disease (CKD), irrespective of T2D. This review provides an analysis of the multifaceted mechanisms underlying the cardiorenal benefits of SGLT2i in HF and CKD outside of the T2D context. Eight major aspects of the protective effects of SGLT2i beyond glycemic control are explored: 1) the impact on renal hemodynamics and tubuloglomerular feedback; 2) the natriuretic effects via proximal tubule Na+/H+ exchanger NHE3 inhibition; 3) the modulation of neurohumoral pathways with evidence of attenuated sympathetic activity; 4) the impact on erythropoiesis, not only in the context of local hypoxia but also systemic inflammation and iron regulation; 5) the uricosuria and mitigation of the hyperuricemic environment in cardiorenal syndromes; 6) the multiorgan metabolic reprogramming including the potential induction of a fasting-like state, improvement in glucose and insulin tolerance, and stimulation of lipolysis and ketogenesis; 7) the vascular endothelial growth factor A (VEGF-A) upregulation and angiogenesis, and 8) the direct cardiac effects. The intricate interplay between renal, neurohumoral, metabolic, and cardiac effects underscores the complexity of SGLT2i actions and provides valuable insights into their therapeutic implications for HF and CKD. Furthermore, this review sets the stage for future research to evaluate the individual contributions of these mechanisms in diverse clinical settings.

Proximal versus distal diuretics in congestive heart failure

Volume overload represents a hallmark clinical feature linked to the development and progression of heart failure (HF). Alleviating signs and symptoms of volume overload represents a foundational HF treatment target that is achieved using loop diuretics in the acute and chronic setting. Recent work has provided evidence to support guideline-directed medical therapies, such as sodium glucose cotransporter 2 (SGLT2) inhibitors and mineralocorticoid receptor (MR) antagonists, as important adjunct diuretics that may act synergistically when used with background loop diuretics in people with chronic HF. Furthermore, there is growing interest in understanding the role of SGLT2 inhibitors, carbonic anhydrase inhibitors, thiazide diuretics, and MR antagonists in treating volume overload in patients hospitalized for acute HF, particularly in the setting of loop diuretic resistance. Thus, the current review demonstrates that: (i) SGLT2 inhibitors and MR antagonists confer long-term cardioprotection in chronic HF patients but it is unclear whether natriuresis or diuresis represents the primary mechanisms for this benefit, (ii) SGLT2 inhibitors, carbonic anhydrase inhibitors, and thiazide diuretics increase natriuresis in the acute HF setting, but implications on long-term outcomes remain unclear and warrants further investigation, and (iii) a multi-nephron segment approach, using agents that act on distinct segments of the nephron, potentiate diuresis to alleviate signs and symptoms of volume overload in acute HF.

Metabolic Pathways Affected in Patients Undergoing Hemodialysis and Their Relationship with Inflammation

Worldwide, 3.9 million individuals rely on kidney replacement therapy. They experience heightened susceptibility to cardiovascular diseases and mortality, alongside an increased risk of infections and malignancies, with inflammation being key to explaining this intensified risk. This study utilized semi-targeted metabolomics to explore novel metabolic pathways related to inflammation in this population. We collected pre- and post-session blood samples of patients who had already undergone one year of chronic hemodialysis and used liquid chromatography and high-resolution mass spectrometry to perform a metabolomic analysis. Afterwards, we employed both univariate (Mann-Whitney test) and multivariate (logistic regression with LASSO regularization) to identify metabolites associated with inflammation. In the univariate analysis, indole-3-acetaldehyde, 2-ketobutyric acid, and urocanic acid showed statistically significant decreases in median concentrations in the presence of inflammation. In the multivariate analysis, metabolites positively associated with inflammation included allantoin, taurodeoxycholic acid, norepinephrine, pyroglutamic acid, and L-hydroorotic acid. Conversely, metabolites showing negative associations with inflammation included benzoic acid, indole-3-acetaldehyde, methionine, citrulline, alphaketoglutarate, n-acetyl-ornithine, and 3-4-dihydroxibenzeneacetic acid. Non-inflamed patients exhibit preserved autophagy and reduced mitochondrial dysfunction. Understanding inflammation in this group hinges on the metabolism of arginine and the urea cycle. Additionally, the microbiota, particularly uricase-producing bacteria and those metabolizing tryptophan, play critical roles.

Euglycemic Diabetic Ketoacidosis, Recurrent Genital Abscess, and Proximal Renal Tubular Acidosis With Concurrent SGLT-2 Inhibitor: More Than an Association

Sodium-glucose transport protein 2 (SGLT2) inhibitors are a class of antidiabetic medications that have tremendous benefits in diabetic patients through reducing renal tubular glucose reabsorption, therefore inducing a rapid increase in urinary glucose excretion, thus reducing the overall serum blood glucose. However, the medication's use has commonly been associated with emerging complications such as euglycemic diabetic ketoacidosis (eDKA), a rare and life-threatening metabolic disturbance. Other complications that have been associated with this class of medications are recurrent genital abscesses and renal tubular acidosis, which have both been less reported and explored. Below, we detail the case of a woman who was on empagliflozin, an SGLT2 inhibitor, for only two months and developed life-threatening eDKA, recurrent genital abscesses, and proximal renal tubular acidosis all within the two months of initiation of the medication.

Renal handling of albumin in rats with early stage diabetes: A theoretical analysis

In early diabetic nephropathy (DN), recent studies have shown that albuminuria stems mostly from alterations in tubular function rather than from glomerular damage. Several factors in DN, including hyperfiltration, hypertrophy and reduced abundance of the albumin receptors megalin and cubilin, affect albumin endocytosis in the proximal tubule (PT). To assess their respective contribution, we developed a model of albumin handling in the rat PT that couples the transport of albumin to that of water and solutes. Our simulations suggest that, under basal conditions, ∼75% of albumin is retrieved in the S1 segment. The model predicts negligible uptake in S3, as observed experimentally. It also accurately predicts the impact of acute hyperglycaemia on urinary albumin excretion. Simulations reproduce observed increases in albumin excretion in early DN by considering the combined effects of increased glomerular filtration rate (GFR), osmotic diuresis, hypertrophy, and megalin and cubilin downregulation, without stipulating changes in glomerular permselectivity. The results indicate that in isolation, glucose-elicited osmotic diuresis and glucose transporter upregulation raise albumin excretion only slightly. Enlargement of PT diameter not only augments uptake via surface area expansion, but also reduces fluid velocity and thus shear stress-induced stimulation of endocytosis. Overall, our model predicts that downregulation of megalin and cubilin and hyperfiltration both contribute significantly to increasing albumin excretion in rats with early-stage diabetes. The results also suggest that acute sodium-glucose cotransporter 2 inhibition lowers albumin excretion only if GFR decreases sufficiently, and that angiotensin II receptor blockers mitigate urinary albumin loss in early DN in large part by upregulating albumin receptor abundance. KEY POINTS: The urinary excretion of albumin is increased in early diabetic nephropathy (DN). It is difficult to experimentally disentangle the multiple factors that affect the renal handling of albumin in DN. We developed a mathematical model of albumin transport in the rat proximal tubule (PT) to examine the impact of elevated plasma glucose, hyperfiltration, PT hypertrophy and reduced abundance of albumin receptors on albumin uptake and excretion in DN. Our model predicts that glucose-elicited osmotic diuresis per se raises albumin excretion only slightly. Conversely, increases in PT diameter and length favour reduced albumin excretion. Our results suggest that downregulation of the receptors megalin and cubilin in PT cells and hyperfiltration both contribute significantly to increasing albumin excretion in DN. The model helps to better understand the mechanisms underlying urinary loss of albumin in early-stage diabetes, and the impact of specific treatments thereupon.

The Renoprotective Mechanisms of Sodium-Glucose Cotransporter-2 Inhibitors (SGLT2i)-A Narrative Review

Chronic kidney disease (CKD) is a noncommunicable condition that has become a major healthcare burden across the globe, often underdiagnosed and associated with low awareness. The main cause that leads to the development of renal impairment is diabetes mellitus and, in contrast to other chronic complications such as retinopathy or neuropathy, it has been suggested that intensive glycemic control is not sufficient in preventing the development of diabetic kidney disease. Nevertheless, a novel class of antidiabetic agents, the sodium-glucose cotransporter-2 inhibitors (SGLT2i), have shown multiple renoprotective properties that range from metabolic and hemodynamic to direct renal effects, with a major impact on reducing the risk of occurrence and progression of CKD. Thus, this review aims to summarize current knowledge regarding the renoprotective mechanisms of SGLT2i and to offer a new perspective on this innovative class of antihyperglycemic drugs with proven pleiotropic beneficial effects that, after decades of no significant progress in the prevention and in delaying the decline of renal function, start a new era in the management of patients with CKD.

Sodium-Glucose Cotransporter 2 Inhibitor Combined with Conventional Diuretics Ameliorate Body Fluid Retention without Excessive Plasma Volume Reduction

We previously reported that sodium-glucose cotransporter 2 (SGLT2) inhibitors exert sustained fluid homeostatic actions through compensatory increases in osmotic diuresis-induced vasopressin secretion and fluid intake. However, SGLT2 inhibitors alone do not produce durable amelioration of fluid retention. In this study, we examined the comparative effects of the SGLT2 inhibitor dapagliflozin (SGLT2i group, n = 53) and the combined use of dapagliflozin and conventional diuretics, including loop diuretics and/or thiazides (SGLT2i + diuretic group, n = 23), on serum copeptin, a stable, sensitive, and simple surrogate marker of vasopressin release and body fluid status. After six months of treatment, the change in copeptin was significantly lower in the SGLT2i + diuretic group than in the SGLT2i group (-1.4 ± 31.5% vs. 31.5 ± 56.3%, p = 0.0153). The change in the estimated plasma volume calculated using the Strauss formula was not significantly different between the two groups. Contrastingly, changes in interstitial fluid, extracellular water, intracellular water, and total body water were significantly lower in the SGLT2i + diuretic group than in the SGLT2i group. Changes in renin, aldosterone, and absolute epinephrine levels were not significantly different between the two groups. In conclusion, the combined use of the SGLT2 inhibitor dapagliflozin and conventional diuretics inhibited the increase in copeptin levels and remarkably ameliorated fluid retention without excessively reducing plasma volume and activating the renin-angiotensin-aldosterone and sympathetic nervous systems.

SGLT2-independent effects of canagliflozin on NHE3 and mitochondrial complex I activity inhibit proximal tubule fluid transport and albumin uptake

Beyond glycemic control, SGLT2 inhibitors (SGLT2is) have protective effects on cardiorenal function. Renoprotection has been suggested to involve inhibition of NHE3 leading to reduced ATP-dependent tubular workload and mitochondrial oxygen consumption. NHE3 activity is also important for regulation of endosomal pH, but the effects of SGLT2i on endocytosis are unknown. We used a highly differentiated cell culture model of proximal tubule (PT) cells to determine the direct effects of SGLT2i on Na+-dependent fluid transport and endocytic uptake in this nephron segment. Strikingly, canagliflozin but not empagliflozin reduced fluid transport across cell monolayers and dramatically inhibited endocytic uptake of albumin. These effects were independent of glucose and occurred at clinically relevant concentrations of drug. Canagliflozin acutely inhibited surface NHE3 activity, consistent with a direct effect, but did not affect endosomal pH or NHE3 phosphorylation. In addition, canagliflozin rapidly and selectively inhibited mitochondrial complex I activity. Inhibition of mitochondrial complex I by metformin recapitulated the effects of canagliflozin on endocytosis and fluid transport, whereas modulation of downstream effectors AMPK and mTOR did not. Mice given a single dose of canagliflozin excreted twice as much urine over 24 h compared with empagliflozin-treated mice despite similar water intake. We conclude that canagliflozin selectively suppresses Na+-dependent fluid transport and albumin uptake in PT cells via direct inhibition of NHE3 and of mitochondrial function upstream of the AMPK/mTOR axis. These additional targets of canagliflozin contribute significantly to reduced PT Na+-dependent fluid transport in vivo.NEW & NOTEWORTHY Reduced NHE3-mediated Na+ transport has been suggested to underlie the cardiorenal protection provided by SGLT2 inhibitors. We found that canagliflozin, but not empagliflozin, reduced NHE3-dependent fluid transport and endocytic uptake in cultured proximal tubule cells. These effects were independent of SGLT2 activity and resulted from inhibition of mitochondrial complex I and NHE3. Studies in mice are consistent with greater effects of canagliflozin versus empagliflozin on fluid transport. Our data suggest that these selective effects of canagliflozin contribute to reduced Na+-dependent transport in proximal tubule cells.

Renal upregulation of NCC counteracts empagliflozin-mediated NHE3 inhibition in normotensive but not in hypertensive male rat

Sodium-glucose cotransporter-2 inhibitors (SGLT2i) reduce blood pressure (BP) in patients with hypertension, yet the precise molecular mechanisms remain elusive. SGLT2i inhibits proximal tubule (PT) NHE3-mediated sodium reabsorption in normotensive rodents, yet no hypotensive effect is observed under this scenario. This study examined the effect of empagliflozin (EMPA) on renal tubular sodium transport in normotensive and spontaneously hypertensive rats (SHRs). It also tested the hypothesis that EMPA-mediated PT NHE3 inhibition in normotensive rats is associated with upregulation of distal nephron apical sodium transporters. EMPA administration for 14 days reduced BP in 12-wk-old SHRs but not in age-matched Wistar rats. PT NHE3 activity was inhibited by EMPA treatment in both Wistar and SHRs. In Wistar rats, EMPA increased NCC activity, mRNA expression, protein abundance, and phosphorylation levels, but not in SHRs. SHRs showed higher NKCC2 activity and an abundance of cleaved ENaC α and γ subunits compared with Wistar rats, none of which were affected by EMPA. Another set of male Wistar rats was treated with EMPA, the NCC inhibitor hydrochlorothiazide (HCTZ), and EMPA combined with HCTZ or vehicle for 14 days. In these rats, BP reduction was observed only with combined EMPA and HCTZ treatment, not with either drug alone. These findings suggest that NCC upregulation counteracts EMPA-mediated inhibition of PT NHE3 in male normotensive rats, maintaining their baseline BP. Moreover, the reduction of NHE3 activity without further upregulation of major apical sodium transporters beyond the PT may contribute to the BP-lowering effect of SGLT2i in experimental models and patients with hypertension.NEW & NOTEWORTHY This study suggests that reduced NHE3-mediated sodium reabsorption in the renal proximal tubule may account, at least in part, for the BP-lowering effect of SGLT2 inhibitors in the setting of hypertension. It also demonstrates that chronic treatment with SGLT2 inhibitors upregulates NCC activity, phosphorylation, and expression in the distal tubule of normotensive but not hypertensive rats. SGLT2 inhibitor-mediated upregulation of NCC seems crucial to counteract proximal tubule natriuresis in subjects with normal BP.

Metabolic Acidosis in CKD: Pathogenesis, Adverse Effects, and Treatment Effects

Metabolic acidosis is a frequent complication of chronic kidney disease and is associated with a number of adverse outcomes, including worsening kidney function, poor musculoskeletal health, cardiovascular events, and death. Mechanisms that prevent metabolic acidosis detrimentally promote further kidney damage, creating a cycle between acid accumulation and acid-mediated kidney injury. Disrupting this cycle through the provision of alkali, most commonly using sodium bicarbonate, is hypothesized to preserve kidney function while also mitigating adverse effects of excess acid on bone and muscle. However, results from clinical trials have been conflicting. There is also significant interest to determine whether sodium bicarbonate might improve patient outcomes for those who do not have overt metabolic acidosis. Such individuals are hypothesized to be experiencing acid-mediated organ damage despite having a normal serum bicarbonate concentration, a state often referred to as subclinical metabolic acidosis. Results from small- to medium-sized trials in individuals with subclinical metabolic acidosis have also been inconclusive. Well-powered clinical trials to determine the efficacy and safety of sodium bicarbonate are necessary to determine if this intervention improves patient outcomes.

Initial eGFR Changes with SGLT2 Inhibitor in Patients With Type 2 Diabetes and Associations With the Risk of Abnormal Serum Potassium Level

BACKGROUND

Both high and low levels of serum potassium measurements are linked with a higher risk of adverse clinical events among patients with type 2 diabetes. The study was aimed at evaluating the implications of the various degrees of initial estimated glomerular filtration rate (eGFR) change on subsequent serum potassium homeostasis following sodium-glucose cotransporter-2 inhibitor (SGLT2i) initiation among patients with type 2 diabetes.

METHODS AND RESULTS

We used medical data from a multicenter health care provider in Taiwan and recruited 5529 patients with type 2 diabetes with baseline/follow-up eGFR data available after 4 to 12 weeks of SGLT2i treatment from June 1, 2016, to December 31, 2018. SGLT2i treatment was associated with an initial mean (SEM) eGFR decline of -3.5 (0.2) mL/min per 1.73 m2 in overall study participants. A total of 36.7% (n=2028) of patients experienced no eGFR decline, and 57.9% (n=3201) and 5.4% (n=300) of patients experienced an eGFR decline of 0% to 30% and >30%, respectively. Patients with an initial eGFR decline of >30% were associated with higher variability in consequent serum potassium measurement when compared with those without an initial eGFR decline. Participants with a pronounced eGFR decline of >30% were associated with a higher risk of hyperkalemia ≥5.5 (adjusted hazard ratio,4.59 [95% CI, 2.28-9.26]) or use of potassium binder (adjusted hazard ratio, 2.65 [95% CI, 1.78-3.95]) as well as hypokalemia events <3.0 mmol/L (adjusted hazard ratio, 3.21 [95% CI, 1.90-5.42]) or use of potassium supplement (adjusted hazard ratio, 1.87 [95% CI, 1.37-2.56]) following SGLT2i treatment after multivariate adjustment.

CONCLUSIONS

Physicians should be aware that the eGFR trough occurs shortly, and consequent serum potassium changes following SGLT2i initiation.

SGLT2 Inhibitors and Kidney Protection: Mechanisms Beyond Tubuloglomerular Feedback

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce the risk for kidney failure and are a key component of guideline-directed therapy for CKD. While SGLT2 inhibitors' ability to activate tubuloglomerular feedback and reduce hyperfiltration-mediated kidney injury is considered to be the central mechanism for kidney protection, recent data from experimental studies raise questions on the primacy of this mechanism. This review examines SGLT2 inhibitors' role in tubuloglomerular feedback and summarizes emerging evidence on following of SGLT2 inhibitors' other putative mechanisms for kidney protection: optimization of kidney's energy substrate utilization and delivery, regulation of autophagy and maintenance of cellular homeostasis, attenuation of sympathetic hyperactivity, and improvement in vascular health and microvascular function. It is imperative to examine the effect of SGLT2 inhibition on these different physiologic processes to help our understanding of mechanisms underpinning kidney protection with this important class of drugs.

Predicting sex differences in the effects of diuretics in renal epithelial transport during angiotensin II-induced hypertension

Chronic angiotensin II (ANG II) infusion is an experimental model that induces hypertension in rodents. The natriuresis, diuresis, and blood pressure responses differ between males and females. This is perhaps not unexpected, given the rodent kidney, which plays a key role in blood pressure regulation, exhibits marked sex differences. Under normotensive conditions, compared with males, the female rat nephron exhibits lower Na+/H+ exchanger 3 (NHE3) activity along the proximal tubule but higher Na+ transporter activities along the distal segments. ANG II infusion-induced hypertension induces a pressure natriuretic response that reduces NHE3 activity and shifts Na+ transport capacity downstream. The goals of this study were to apply a computational model of epithelial transport along a rat nephron 1) to understand how a 14-day ANG II infusion impacts segmental electrolyte transport in male and female rat nephrons and 2) to identify and explain any sex differences in the effects of loop diuretics, thiazide diuretics, and K+-sparing diuretics. Model simulations suggest that the NHE3 downregulation in the proximal tubule is a major contributor to natriuresis and diuresis in hypertension, with the effects stronger in males. All three diuretics are predicted to induce stronger natriuretic and diuretic effects under hypertension compared with normotension, with relative increases in sodium excretion higher in hypertensive females than in males. The stronger natriuretic responses can be explained by the downstream shift of Na+ transport load in hypertension and by the larger distal transport load in females, both of which limit the ability of the distal segments to further elevate their Na+ transport.NEW & NOTEWORTHY Sex differences in the prevalence of hypertension are found in human and animal models. The kidney, which regulates blood pressure, exhibits sex differences in morphology, hemodynamics, and membrane transporter distributions. This computational modeling study provides insights into how the sexually dimorphic responses to a 14-day angiotensin II infusion differentially impact segmental electrolyte transport in rats. Simulations of diuretic administration explain how the natriuretic and diuretic effects differ between normotension and hypertension and between the sexes.

SGLT2 inhibitors: from glucose-lowering to cardiovascular benefits

An increasing number of individuals are at high risk of type 2 diabetes (T2D) and its cardiovascular complications, including heart failure (HF), chronic kidney disease (CKD), and eventually premature death. The sodium-glucose co-transporter-2 (SGLT2) protein sits in the proximal tubule of human nephrons to regulate glucose reabsorption and its inhibition by gliflozins represents the cornerstone of contemporary T2D and HF management. Herein, we aim to provide an updated overview of the pleiotropy of gliflozins, provide mechanistic insights and delineate related cardiovascular (CV) benefits. By discussing contemporary evidence obtained in preclinical models and landmark randomized controlled trials, we move from bench to bedside across the broad spectrum of cardio- and cerebrovascular diseases. With landmark randomized controlled trials confirming a reduction in major adverse CV events (MACE; composite endpoint of CV death, non-fatal myocardial infarction, and non-fatal stroke), SGLT2 inhibitors strongly mitigate the risk for heart failure hospitalization in diabetics and non-diabetics alike while conferring renoprotection in specific patient populations. Along four major pathophysiological axes (i.e. at systemic, vascular, cardiac, and renal levels), we provide insights into the key mechanisms that may underlie their beneficial effects, including gliflozins' role in the modulation of inflammation, oxidative stress, cellular energy metabolism, and housekeeping mechanisms. We also discuss how this drug class controls hyperglycaemia, ketogenesis, natriuresis, and hyperuricaemia, collectively contributing to their pleiotropic effects. Finally, evolving data in the setting of cerebrovascular diseases and arrhythmias are presented and potential implications for future research and clinical practice are comprehensively reviewed.

Efficacy and Safety of Dapagliflozin in Patients With Acute Heart Failure

BACKGROUND

The primary goals during acute heart failure (AHF) hospitalization are decongestion and guideline-directed medical therapy (GDMT) optimization. Unlike diuretics or other GDMT, early dapagliflozin initiation could achieve both AHF goals.

OBJECTIVES

The authors aimed to assess the diuretic efficacy and safety of early dapagliflozin initiation in AHF.

METHODS

In a multicenter, open-label study, 240 patients were randomized within 24 hours of hospital presentation for hypervolemic AHF to dapagliflozin 10 mg once daily or structured usual care with protocolized diuretic titration until day 5 or hospital discharge. The primary outcome, diuretic efficiency expressed as cumulative weight change per cumulative loop diuretic dose, was compared across treatment assignment using a proportional odds model adjusted for baseline weight. Secondary and safety outcomes were adjudicated by a blinded committee.

RESULTS

For diuretic efficiency, there was no difference between dapagliflozin and usual care (OR: 0.65; 95% CI: 0.41-1.02; P = 0.06). Dapagliflozin was associated with reduced loop diuretic doses (560 mg [Q1-Q3: 260-1,150 mg] vs 800 mg [Q1-Q3: 380-1,715 mg]; P = 0.006) and fewer intravenous diuretic up-titrations (P ≤ 0.05) to achieve equivalent weight loss as usual care. Early dapagliflozin initiation did not increase diabetic, renal, or cardiovascular safety events. Dapagliflozin was associated with improved median 24-hour natriuresis (P = 0.03) and urine output (P = 0.005), expediting hospital discharge over the study period.

CONCLUSIONS

Early dapagliflozin during AHF hospitalization is safe and fulfills a component of GDMT optimization. Dapagliflozin was not associated with a statistically significant reduction in weight-based diuretic efficiency but was associated with evidence for enhanced diuresis among patients with AHF. (Efficacy and Safety of Dapagliflozin in Acute Heart Failure [DICTATE-AHF]; NCT04298229).

Adipocentric origin of the common cardiometabolic complications of obesity in the young up to the very old: pathophysiology and new therapeutic opportunities

Obesity is a multifactorial chronic disease characterized by an excess of adipose tissue, affecting people of all ages. In the last 40 years, the incidence of overweight and obesity almost tripled worldwide. The accumulation of "visceral" adipose tissue increases with aging, leading to several cardio-metabolic consequences: from increased blood pressure to overt arterial hypertension, from insulin-resistance to overt type 2 diabetes mellitus (T2DM), dyslipidemia, chronic kidney disease (CKD), and obstructive sleep apnea. The increasing use of innovative drugs, namely glucagon-like peptide-1 receptor agonists (GLP1-RA) and sodium-glucose cotransporter-2 inhibitors (SGLT2-i), is changing the management of obesity and its related cardiovascular complications significantly. These drugs, first considered only for T2DM treatment, are now used in overweight patients with visceral adiposity or obese patients, as obesity is no longer just a risk factor but a critical condition at the basis of common metabolic, cardiovascular, and renal diseases. An adipocentric vision and approach should become the cornerstone of visceral overweight and obesity integrated management and treatment, reducing and avoiding the onset of obesity-related multiple risk factors and their clinical complications. According to recent progress in basic and clinical research on adiposity, this narrative review aims to contribute to a novel clinical approach focusing on pathophysiological and therapeutic insights.

New functions and roles of the Na+-H+-exchanger NHE3

The sodium/proton exchanger isoform 3 (NHE3) is expressed in the intestine and the kidney, where it contributes to hydrogen secretion and sodium (re)absorption. The roles of this transporter have been studied by the use of the respective knockout mice and by using pharmacological inhibitors. Whole-body NHE3 knockout mice suffer from a high mortality rate (with only ∼30% of mice surviving into adulthood), and based on the expression of NHE3 in both intestine and kidney, some conclusions that were originally derived were based on this rather complex phenotype. In the last decade, more refined models have been developed that added temporal and spatial control of NHE3 expression. For example, novel mouse models have been developed with a knockout of NHE3 in intestinal epithelial cells, tubule/collecting duct of the kidney, proximal tubule of the kidney, and thick ascending limb of the kidney. These refined models have significantly contributed to our understanding of the role of NHE3 in a tissue/cell type-specific manner. In addition, tenapanor was developed, which is a non-absorbable, intestine-specific NHE3 inhibitor. In rat and human studies, tenapanor lowered intestinal Pi uptake and was effective in lowering plasma Pi levels in patients on hemodialysis. Of note, diarrhea is seen as a side effect of tenapanor (with its indication for the treatment of constipation) and in intestine-specific NHE3 knockout mice; however, effects on plasma Pi were not supported by this mouse model which showed enhanced and not reduced intestinal Pi uptake. Further studies indicated that the gut microbiome in mice lacking intestinal NHE3 resembles an intestinal environment favoring the competitive advantage of inflammophilic over anti-inflammatory species, something similar seen in patients with inflammatory bowel disease. This review will highlight recent developments and summarize newly gained insight from these refined models.

Nascent shifts in renal cellular metabolism, structure, and function due to chronic empagliflozin in prediabetic mice

Sodium-glucose cotransporter, type 2 inhibitors (SGLT2i) are emerging as the gold standard for treatment of type 2 diabetes (T2D) with renal protective benefits independent of glucose lowering. We took a high-level approach to evaluate the effects of the SGLT2i, empagliflozin (EMPA) on renal metabolism and function in a prediabetic model of metabolic syndrome. Male and female 12-wk-old TallyHo (TH) mice, and their closest genetic lean strain (Swiss-Webster, SW) were treated with a high-milk-fat diet (HMFD) plus/minus EMPA (@0.01%) for 12-wk. Kidney weights and glomerular filtration rate were slightly increased by EMPA in the TH mice. Glomerular feature analysis by unsupervised clustering revealed sexually dimorphic clustering, and one unique cluster relating to EMPA. Periodic acid Schiff (PAS) positive areas, reflecting basement membranes and mesangium were slightly reduced by EMPA. Phasor-fluorescent life-time imaging (FLIM) of free-to-protein bound NADH in cortex showed a marginally greater reliance on oxidative phosphorylation with EMPA. Overall, net urine sodium, glucose, and albumin were slightly increased by EMPA. In TH, EMPA reduced the sodium phosphate cotransporter, type 2 (NaPi-2), but increased sodium hydrogen exchanger, type 3 (NHE3). These changes were absent or blunted in SW. EMPA led to changes in urine exosomal microRNA profile including, in females, enhanced levels of miRs 27a-3p, 190a-5p, and 196b-5p. Network analysis revealed "cancer pathways" and "FOXO signaling" as the major regulated pathways. Overall, EMPA treatment to prediabetic mice with limited renal disease resulted in modifications in renal metabolism, structure, and transport, which may preclude and underlie protection against kidney disease with developing T2D.NEW & NOTEWORTHY Renal protection afforded by sodium glucose transporter, type 2 inhibitors (SGLT2i), e.g., empagliflozin (EMPA) involves complex intertwined mechanisms. Using a novel mouse model of obesity with insulin resistance, the TallyHo/Jng (TH) mouse on a high-milk-fat diet (HMFD), we found subtle changes in metabolism including altered regulation of sodium transporters that line the renal tubule. New potential epigenetic determinants of metabolic changes relating to FOXO and cancer signaling pathways were elucidated from an altered urine exosomal microRNA signature.

Metabolic Communication by SGLT2 Inhibition

BACKGROUND

SGLT2 (sodium-glucose cotransporter 2) inhibitors (SGLT2i) can protect the kidneys and heart, but the underlying mechanism remains poorly understood.

METHODS

To gain insights on primary effects of SGLT2i that are not confounded by pathophysiologic processes or are secondary to improvement by SGLT2i, we performed an in-depth proteomics, phosphoproteomics, and metabolomics analysis by integrating signatures from multiple metabolic organs and body fluids after 1 week of SGLT2i treatment of nondiabetic as well as diabetic mice with early and uncomplicated hyperglycemia.

RESULTS

Kidneys of nondiabetic mice reacted most strongly to SGLT2i in terms of proteomic reconfiguration, including evidence for less early proximal tubule glucotoxicity and a broad downregulation of the apical uptake transport machinery (including sodium, glucose, urate, purine bases, and amino acids), supported by mouse and human SGLT2 interactome studies. SGLT2i affected heart and liver signaling, but more reactive organs included the white adipose tissue, showing more lipolysis, and, particularly, the gut microbiome, with a lower relative abundance of bacteria taxa capable of fermenting phenylalanine and tryptophan to cardiovascular uremic toxins, resulting in lower plasma levels of these compounds (including p-cresol sulfate). SGLT2i was detectable in murine stool samples and its addition to human stool microbiota fermentation recapitulated some murine microbiome findings, suggesting direct inhibition of fermentation of aromatic amino acids and tryptophan. In mice lacking SGLT2 and in patients with decompensated heart failure or diabetes, the SGLT2i likewise reduced circulating p-cresol sulfate, and p-cresol impaired contractility and rhythm in human induced pluripotent stem cell-derived engineered heart tissue.

CONCLUSIONS

SGLT2i reduced microbiome formation of uremic toxins such as p-cresol sulfate and thereby their body exposure and need for renal detoxification, which, combined with direct kidney effects of SGLT2i, including less proximal tubule glucotoxicity and a broad downregulation of apical transporters (including sodium, amino acid, and urate uptake), provides a metabolic foundation for kidney and cardiovascular protection.

Sodium-Glucose Cotransporter 2 Inhibitors and Nephrolithiasis Risk in Patients With Type 2 Diabetes

Importance

Type 2 diabetes (T2D) is associated with an increased risk of kidney stones. Sodium-glucose cotransporter 2 inhibitors (SGLT2is) might lower the risk of nephrolithiasis by altering urine composition. However, no studies have investigated the association between SGLT2i use and nephrolithiasis risk in patients receiving routine care in the US.

Objective

To investigate the association between SGLT2i use and nephrolithiasis risk in clinical practice.

Design, Setting, and Participants

This new-user, active comparator cohort study used data from commercially insured adults (aged ≥18 years) with T2D who initiated treatment with SGLT2is, glucagon-like peptide 1 receptor agonists (GLP-1RAs), or dipeptidyl peptidase 4 inhibitors (DPP4is) between April 1, 2013, and December 31, 2020. The data were analyzed from July 2021 through June 2023.

Exposure

New initiation of an SGLT2i, GLP-1RA, or DPP4i.

Main Outcomes and Measures

The primary outcome was nephrolithiasis diagnosed by International Classification of Diseases codes in the inpatient or outpatient setting. New SGLT2i users were 1:1 propensity score matched to new users of a GLP-1RA or DPP4i in pairwise comparisons. Incidence rates, rate differences (RDs), and estimated hazard ratios (HRs) with 95% CIs were calculated.

Results

After 1:1 propensity score matching, a total of 716 406 adults with T2D (358 203 pairs) initiating an SGLT2i or a GLP-1RA (mean [SD] age, 61.4 [9.7] years for both groups; 51.4% vs 51.2% female; 48.6% vs 48.5% male) and 662 056 adults (331 028 pairs) initiating an SGLT2i or a DPP4i (mean [SD] age, 61.8 [9.3] vs 61.7 [10.1] years; 47.4% vs 47.3% female; 52.6% vs 52.7% male) were included. Over a median follow-up of 192 (IQR, 88-409) days, the risk of nephrolithiasis was lower in patients initiating an SGLT2i than among those initiating a GLP-1RA (14.9 vs 21.3 events per 1000 person-years; HR, 0.69 [95% CI, 0.67-0.72]; RD, -6.4 [95% CI, -7.1 to -5.7]) or a DPP4i (14.6 vs 19.9 events per 1000 person-years; HR, 0.74 [95% CI, 0.71-0.77]; RD, -5.3 [95% CI, -6.0 to -4.6]). The association between SGLT2i use and nephrolithiasis risk was similar by sex, race and ethnicity, history of chronic kidney disease, and obesity. The magnitude of the risk reduction with SGLT2i use was larger among adults aged younger than 70 years vs aged 70 years or older (HR, 0.85 [95% CI, 0.79-0.91]; RD, -3.46 [95% CI, -4.87 to -2.05] per 1000 person-years; P for interaction <.001).

Conclusions and Relevance

These findings suggest that in adults with T2D, SGLT2i use may lower the risk of nephrolithiasis compared with GLP-1RAs or DPP4is and could help to inform decision-making when prescribing glucose-lowering agents for patients who may be at risk for developing nephrolithiasis.

SGLT2 Inhibition and Kidney Potassium Homeostasis

Pharmacologic inhibition of the sodium-glucose transporter 2 (SGLT2) in the proximal tubule brings about physiologic changes predicted to both increase and decrease kidney K + excretion. Despite these effects, disorders of plasma K + concentration are an uncommon occurrence. If anything, these drugs either cause no effect or a slight reduction in plasma K + concentration in patients with normal kidney function but seem to exert a protective effect against hyperkalemia in the setting of reduced kidney function or when given with drugs that block the renin-angiotensin-aldosterone axis. In this review, we discuss the changes in kidney physiology after the administration of SGLT2 inhibitors predicted to cause both hypokalemia and hyperkalemia. We conclude that these factors offset one another, explaining the uncommon occurrence of dyskalemias with these drugs. Careful human studies focusing on the determinants of kidney K + handling are needed to fully understand how these drugs attenuate the risk of hyperkalemia and yet rarely cause hypokalemia.

Deletion, but Not Heterozygosity, of eNOS Raises Blood Pressure and Aggravates Nephropathy in BTBR ob/ob Mice

INTRODUCTION

ob/ob mice are a leptin-deficient type 2 diabetes mellitus model, which, on a BTBR background, mimics the glomerular pathophysiology of diabetic nephropathy (DN). Since leptin deficiency reduces blood pressure (BP) and endothelial nitric oxide synthase (eNOS) lowers BP and is kidney protective, we attempted to develop a more robust DN model by introducing eNOS deficiency in BTBR ob/ob mice.

METHODS

Six experimental groups included littermate male and female BTBR ob/ob or wild-type for ob (control) as well as wild-type (WT), heterozygote (HET), or knockout (KO) for eNOS. Systolic BP (by automated tail-cuff) and GFR (by FITC-sinistrin plasma kinetics) were determined in awake mice at 27-30 weeks of age, followed by molecular and histological kidney analyses.

RESULTS

Male and female ob/ob WT presented hyperglycemia and larger body and kidney weight, GFR, glomerular injury, and urine albumin to creatinine ratio (UACR) despite modestly lower BP versus control WT. These effects were associated with a higher tubular injury score and renal mRNA expression of NGAL only in males, whereas female ob/ob WT unexpectedly had lower KIM-1 and COL1A1 expression versus control WT, indicating sex differences. HET for eNOS did not consistently alter BP or renal outcome in control or ob/ob. In comparison, eNOS KO increased BP (15-25 mm Hg) and worsened renal markers of injury, inflammation and fibrosis, GFR, UACR, and survival rates, as observed in control and, more pronouncedly, in ob/ob mice and independent of sex.

CONCLUSIONS

Deletion, but not heterozygosity, of eNOS raises blood pressure and aggravates nephropathy in BTBR ob/ob mice.

SGLT2 inhibitor dapagliflozin protects the kidney in a murine model of Balkan nephropathy

Proximal tubular uptake of aristolochic acid (AA) forms aristolactam (AL)-DNA adducts, which cause a p53/p21-mediated DNA damage response and acute tubular injury. Recurrent AA exposure causes kidney function loss and fibrosis in humans (Balkan endemic nephropathy) and mice and is a model of (acute kidney injury) AKI to chronic kidney disease (CKD) transition. Inhibitors of the proximal tubule sodium-glucose transporter SGLT2 can protect against CKD progression, but their effect on AA-induced kidney injury remains unknown. C57BL/6J mice (15-wk-old) were administered vehicle or AA every 3 days for 3 wk (10 and 3 mg/kg ip in females and males, respectively). Dapagliflozin (dapa, 0.01 g/kg diet) or vehicle was initiated 7 days prior to AA injections. All dapa effects were sex independent, including a robust glycosuria. Dapa lowered urinary kidney-injury molecule 1 (KIM-1) and albumin (both normalized to creatinine) after the last AA injection and kidney mRNA expression of early DNA damage response markers (p53 and p21) 3 wk later at the study end. Dapa also attenuated AA-induced increases in plasma creatinine as well as AA-induced up-regulation of renal pro-senescence, pro-inflammatory and pro-fibrotic genes, and kidney collagen staining. When assessed 1 day after a single AA injection, dapa pretreatment attenuated AL-DNA adduct formation by 10 and 20% in kidney and liver, respectively, associated with reduced p21 expression. Initiating dapa application after the last AA injection also improved kidney outcome but in a less robust manner. In conclusion, the first evidence is presented that pretreatment with an SGLT2 inhibitor can attenuate the AA-induced DNA damage response and subsequent nephropathy.NEW & NOTEWORTHY Recurrent exposure to aristolochic acid (AA) causes kidney function loss and fibrosis in mice and in humans, e.g., in the form of the endemic Balkan nephropathy. Inhibitors of the proximal tubule sodium-glucose transporter SGLT2 can protect against CKD progression, but their effect on AA-induced kidney injury remains unknown. Here we provide the first evidence in a murine model that pretreatment with an SGLT2 inhibitor can attenuate the AA-induced DNA damage response and subsequent nephropathy.

The effects of semaglutide, empagliflozin and their combination on the kidney sodium signal from magnetic resonance imaging: A prespecified, secondary analysis from a randomized, clinical trial

AIMS

To evaluate the effect of treatment with semaglutide and empagliflozin on the cortico-medullary sodium gradient (MCR; medulla/cortex ratio), urine sodium/creatinine ratio (UNACR), and estimated plasma volume (ePV) and to compare the MCR between persons with and without type 2 diabetes.

METHODS

Using the 23Na magnetic resonance imaging (23Na-MRI) technique, we investigated the effects of 32 weeks of treatment with semaglutide, empagliflozin or their combination on MCR in 65 participants with type 2 diabetes and high risk of cardiovascular disease. The participants were recruited from a randomized, controlled interventional trial and further characterized by UNACR and ePV. In addition, in a cross-sectional design, we compared MCR by 23Na-MRI in 12 persons with type 2 diabetes and 17 matched controls. Data from the interventional trial were analyzed using a single, multivariate linear mixed model strategy for repeated measurements. Data from the cross-sectional study were analyzed by fitting a linear regression model adjusted for age and sex.

RESULTS

Compared to placebo, semaglutide, but not empagliflozin, significantly decreased the MCR (-9 %, 95%CI (-18, -0.06)%, p = 0.035 and -0.05 %, 95%CI(-0.15, 0.05)%, p = 0.319, respectively). The UNACR decreased in the semaglutide group(-35 %, 95 % CI(-52, -14) %, p = 0.003) but not in the empagliflozin group (7 %, 95 % CI(-21, 44)%, p = 0.657), whereas the ePV decreased in the combination group. The MCR was not different between persons with and without type 2 diabetes.

CONCLUSION

23Na magnetic resonance imaging can identify drug induced changes in the MCR in persons with type 2 diabetes, and 32 weeks of semaglutide decreases the MCR in such persons. There is no difference in the MCR between persons with and without type 2 diabetes.

TRIAL NUMBER AND REGISTRY

EUDRACT 2019-000781-38, clinicaltrialsregister.eu.