Metabolic Communication by SGLT2 Inhibition

Dapagliflozin improves diabetic kidney disease by inhibiting ferroptosis through β-hydroxybutyrate production

BACKGROUND

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease. Sodium-glucose cotransporter protein 2 inhibitors (SGLT2i) are antihyperglycemic agents that provide additional renal-protective effects in patients with DKD, independent of their glucose-lowering effects. However, the underlying mechanism remains unclear. This study hypothesized that SGLT2i could alleviate diabetic kidney injury by inhibiting ferroptosis and explored its potential mechanisms.

METHODS

C57BL/6J mice were randomly divided into the control, DKD, DKD+dapagliflozin, and DKD+insulin treatment groups. Blood glucose levels and body weight were monitored. Renal function, tissue pathology, mitochondrial morphology and function, and lipid peroxidation biomarkers (lipid peroxidation [LPO], malondialdehyde [MDA], glutathione peroxidase 4 [GPX4], glutathione [GSH], and cystine transporter solute carrier family 7 member 11 [SLC7A11]) were evaluated. Human proximal tubule cells (HK2 cells) were exposed to high glucose alone or in combination with dapagliflozin. The mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) level, NAD+/NADH ratio (oxidized/reduced ratio of nicotinamide adenine dinucleotide), and lipid peroxidation were measured. In addition, the role of the β-hydroxybutyrate- Calcium/Calmodulin Dependent Protein Kinase Kinase 2 (BHB-CaMKK2) axis in mediating dapagliflozin regulating ferroptosis was examined.

RESULTS

Dapagliflozin significantly ameliorated kidney injury in mice with DKD. Typical changes in ferroptosis, including lipid peroxidation and impaired antioxidant capacity, increased in mice with DKD and HG-treated HK-2 cells. Dapagliflozin significantly improves ferroptosis-related lipid peroxidation and mitochondrial dysfunction. Furthermore, dapagliflozin suppressed the expression of CaMKK2, a key ferroptosis regulator. Specific CaMKK2 inhibitors alleviated mitochondrial damage and ferroptosis, whereas a CaMKK2 agonist counteracted the protective effects of dapagliflozin against mitochondrial, antioxidant, and anti-ferroptosis effects. In addition, dapagliflozin increased BHB production, which mediates its nephroprotective effects.

CONCLUSION

Dapagliflozin improves DKD by inhibiting ferroptosis, promoting BHB production, and regulating CaMKK2.

A Human Engineered Heart Tissue-Derived Lipotoxic Diabetic Cardiomyopathy Model Revealed Early Benefits of Empagliflozin

Diabetic cardiomyopathy (DbCM) is increasingly prevalent, but intervention targets remain unclear due to the lack of appropriate models and the complexity of risk factors. Here, this work establishes an in vitro assessment system for DbCM function using cardiomyocytes derived from human pluripotent stem cells and engineered heart tissue. This work finds high-fat status in complex diabetes risk factors majorly contributes most to cardiomyocyte death and contractile dysfunction. Notably, PA induced early electrophysiological abnormalities, and lately is associated with cardiac fibrosis, mitochondrial fission, and systolic and diastolic dysfunction at tissue level. Using this in vitro assessment system, this work finds that empagliflozin (EMPA), a first-line glucose-lowering drug, effectively alleviated early PA-induced cardiomyocyte injury. Treatment with EMPA enhanced abnormal diastolic and electrophysiological functions in the PA-hEHT model and significantly reduced endoplasmic reticulum stress, and apoptosis. Furthermore, these promising results are confirmed in a type 2 diabetes mellitus mouse model, reinforcing the potential of EMPA as a therapeutic option to alleviate cardiomyocyte injury under diabetic conditions. These findings suggest that this work has developed an engineered model of diabetic cardiomyopathy that mimics the various stages of lipotoxic myocardial injury and support the use of EMPA as a potential therapeutic option for diabetic or lipotoxic cardiomyopathy.

Modulating the Secretome of Fat to Treat Heart Failure

Heart failure afflicts >6 million individuals in the United States alone and is associated with significant mortality (≈40% within 5 years of diagnosis) and cost (estimated to exceed $70 billion in the United States by 2030). Obesity is a major risk factor for the development of heart failure. The contribution of excess adipose tissue to heart failure pathogenesis is multifactorial. For example, adipose tissue-driven inflammation contributes to the development of other cardiometabolic comorbidities, such as hypertension, leading to left ventricular pressure overload and adverse remodeling of the heart. Adipose tissue also functions as an endocrine organ, and altered secretion of proteins, lipid mediators, metabolites, and small extracellular vesicles (collectively referred to as the secretome) from dysfunctional fat can lead to cardiac inflammation and oxidative stress, which drive changes in structure and function of the heart. In this review, we begin with an overview of current therapies for obesity and what is known about how they influence the heart. Then we focus on mechanisms by which fat communicates with the heart via secreted factors and highlight druggable nodes in this circuit that could be exploited to develop next-generation therapies for heart failure.

Gut-Heart Axis: The Role of Gut Microbiota and Metabolites in Heart Failure

Heart failure is a global health issue with significant mortality and morbidity. There is increasing evidence that alterations in the gastrointestinal microbiome, gut epithelial permeability, and gastrointestinal disorders contribute to heart failure progression through various pathways, including systemic inflammation, metabolic dysregulation, and modulation of cardiac function. Moreover, several medications used to treat heart failure directly impact the microbiome. The relationship between the gastrointestinal tract and the heart is bidirectional, termed the gut-heart axis. It is increasingly understood that diet-derived microbial metabolites are key mechanistic drivers of the gut-heart axis. This includes, for example, trimethylamine N-oxide and short-chain fatty acids. This review discusses current insights into the interplay between heart failure, its associated risk factors, and the gut microbiome, focusing on key metabolic pathways, the role of dietary interventions, and the potential for gut-targeted therapies. Understanding these complex interactions could pave the way for novel strategies to mitigate heart failure progression and improve patient outcomes.

METTL3 mediates atheroprone flow-induced glycolysis in endothelial cells

Atheroprone flow-increased glycolysis in vascular endothelial cells (ECs) is pivotal in EC dysfunction and the initiation of atherosclerosis. Methyltransferase 3 (METTL3) is a major m6A methyltransferase for RNA N6-mehtyladenosine (m6A) modifications to regulate epitranscriptome and cellular functions. With the atheroprone flow upregulating METTL3 and m6A RNA hypermethylation, we investigate the role of METTL3 in atheroprone flow-induced glycolysis in ECs in vitro and in vivo. Compared to pulsatile shear stress (PS, atheroprotective flow), oscillatory shear stress (OS, atheroprone flow) increases METTL3 expression to enhance the m6A modifications of mRNAs encoding HK1, PFKFB3, and GCKR, which are rate-limiting enzymes of glycolysis. These augmented m6A modifications increase the expressions of HK1 and PFKFB3 while decreasing GCKR, resulting in elevated EC glycolysis, as revealed by seahorse analysis. Moreover, a stimulated Raman scattering (SRS) imaging study demonstrates the elevation of glucose incorporation into de novo synthesized lipids in ECs under atheroprone flow in vitro and in vivo. Empagliflozin, a sodium-glucose cotransporter-2 inhibitor (SGLT2i) drug, represses METTL3 expression, thereby mitigating OS-induced glycolysis in ECs. These data suggest mechanisms by which METTL3 links EC mechanotransduction with metabolic reprogramming under atherogenic conditions.

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.

Advances and challenges in kidney fibrosis therapeutics

Chronic kidney disease (CKD) is a major global health burden that affects more than 10% of the adult population. Current treatments, including dialysis and transplantation, are costly and not curative. Kidney fibrosis, defined as an abnormal accumulation of extracellular matrix in the kidney parenchyma, is a common outcome in CKD, regardless of disease aetiology, and is a major cause of loss of kidney function and kidney failure. For this reason, research efforts have focused on identifying mediators of kidney fibrosis to inform the development of effective anti-fibrotic treatments. Given the prominent role of the transforming growth factor-β (TGFβ) family in fibrosis, efforts have focused on inhibiting TGFβ signalling. Despite hopes raised by the efficacy of this approach in preclinical models, translation into clinical practice has not met expectations. Antihypertensive and antidiabetic drugs slow the decline in kidney function and could slow fibrosis but, owing to the lack of technologies for in vivo renal imaging, their anti-fibrotic effect cannot be truly assessed at present. The emergence of new drugs targeting pro-fibrotic signalling, or enabling cell repair and cell metabolic reprogramming, combined with better stratification of people with CKD and the arrival of nanotechnologies for kidney-specific drug delivery, open up new perspectives for the treatment of this major public health challenge.

Sodium-glucose cotransporter 2 inhibitors: a novel approach to prevent the transition from acute kidney injury to chronic kidney disease

PURPOSE OF REVIEW

Acute kidney injury (AKI) often progresses to chronic kidney disease (CKD), yet standardized clinical guidelines for managing this transition remain lacking. Recent studies suggest that sodium-glucose cotransporter 2 inhibitors (SGLT2i) or flozins improve AKI outcomes. Studies on patients living with diabetes post-AKI show flozins reduce mortality, CKD progression, and recurrent AKI, highlighting their potential in mitigating maladaptive kidney repair. We discuss recent preclinical evidence supporting a role of SGLT2i during AKI repair and subsequent CKD.

RECENT FINDINGS

AKI is characterized by endothelial and tubular injury, hypoperfusion, metabolic dysfunction, inflammation, and cell death. SGLT2i restore renal hemodynamics, mitochondrial dysfunction, and reduce oxidative stress, improving recovery following AKI. Additionally, SGLT2i mitigate cell death by counteracting apoptosis and ferroptosis while reducing inflammation through suppression of pro-inflammatory cytokines and inflammasome activation. Beyond AKI, flozins exhibit long-term antifibrotic effects, reducing extracellular matrix deposition even after treatment discontinuation. Preclinical studies demonstrate a sustained protective effect on kidney integrity months after short-term treatment.

SUMMARY

These inhibitors hold promise for broad nephroprotection, with robust biological rationale in maladaptive repair. Further research is needed to optimize their use and establish clinical guidelines for AKI management in both diabetic and nondiabetic populations.

The Role of the Gut Microbiota in Heart Failure: Pathophysiological Insights and Future Perspectives

The gut microbiota has emerged as a crucial player in cardiovascular diseases, including heart failure (HF). Recent studies have highlighted the bidirectional interaction between the gut and the heart, often referred to as the gut-heart axis. Dysbiosis, characterized by alterations in microbial composition and function, has been linked to systemic inflammation, metabolic disturbances, and impaired cardiovascular homeostasis. This review explores the mechanisms through which gut microbiota influences HF, including microbial metabolite production, inflammatory pathways, endothelial dysfunction, hormonal modulation, fluid retention, and sodium absorption. The potential therapeutic implications of microbiota modulation through diet, probiotics, and pharmacological interventions are also discussed. Understanding these mechanisms could pave the way for novel diagnostic and therapeutic strategies in the management of HF. Future research should focus on longitudinal studies to establish causality and the development of personalized microbiota-based interventions.

Translational research on cognitive impairment in chronic kidney disease

Cognitive decline is common in patients with acute or chronic kidney disease. Several areas of brain function can be affected, including short- and long-term memory, attention and inhibitory control, sleep, mood, eating control and motor function. Cognitive decline in kidney disease shares risk factors with cognitive dysfunction in people without kidney disease, such as diabetes, high blood pressure, sedentary lifestyle and unhealthy diet. However, additional kidney-specific risk factors may contribute, such as uremic toxins, electrolyte imbalances, chronic inflammation, acid-base disorders or endocrine dysregulation. Traditional and kidney-specific risk factors may interact to cause damage to the blood-brain barrier, induce vascular damage in the brain and cause neurotoxicity or neuroinflammation. Here, we discuss recent insights into the pathomechanisms of cognitive decline from animal models and novel avenues for prevention and therapy. We focus on a several areas that influence cognition: blood-brain barrier disruption, the role of skeletal muscle, physical activity and the endocrine factor irisin, and the emerging therapeutic role of sodium-glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 (GLP-1) receptor agonists. Taken together, these studies demonstrate the importance of animal models in providing a mechanistic understanding of this complex condition and their potential to explain the mechanisms of novel therapies.

Dietary protein intake and the tubular handling of indoxyl sulfate

BACKGROUND

Chronic kidney disease (CKD) patients are advised to limit their protein intake. A high protein diet is known to induce glomerular hyperfiltration, as well as hypertrophy of the remnant kidney, and glomerulosclerosis. Whether the diet causes changes in kidney tubule transport via gut microbiome metabolites is still unknown. We hypothesized that protein intake affects not only the intestinal generation and absorption, but also the kidney disposal of microbial amino acid metabolites.

METHODS

We combined data from animal models and human studies. 5/6th nephrectomy rats were administered a high (HP) or low-protein (LP) diet for 7 weeks. Plasma and urine concentration of the uremic toxins (UTs) indoxyl sulfate (IS), p-cresyl sulfate (PCS) and p-cresyl glucuronide (PCG) were measured. Their fractional excretion (FE) was calculated. The expression of kidney membrane transporters organic anion transporter 1 (OAT1), OAT3, BCRP, OCT2 and MRP4 was analyzed. Differences in FE of UTs between individuals with higher and lower protein intake in two CKD cohorts were sought.

RESULTS

CKD rats on an HP diet showed increased plasma levels of PCS and PCG but not IS compared with rats on an LP diet. Conversely, urinary excretion and FE of IS were higher in the HP CKD group. BCRP, MRP4 and OCT2 were not influenced by the diet. OAT1 and OAT3 were upregulated in the HP CKD group. In two independent cohorts of CKD patients, individuals with a high dietary protein intake showed a significantly higher FE of IS.

CONCLUSIONS

A HP diet leads to a higher generation and/or absorption of amino acid-derived UT precursors in CKD rodent models and humans, most likely via gut microbiome modulation. We demonstrate that dietary protein intake modulates transcription and expression of OAT1 and OAT3, corroborating the existence of the remote sensing and signaling hypothesis. Dietary protein intake influences kidney physiology beyond glomerular filtration.

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.

Transcriptomics and proteomics characterizing the antioxidant mechanisms of semaglutide in diabetic mice with cognitive impairment

The aim of the present study was to investigate the neuroprotective effects of semaglutide in diabetes‑associated cognitive decline (DACD), while also exploring the underlying mechanisms targeting anti‑oxidative effects. The present study evaluated the antioxidant properties of semaglutide using a DACD model of inflammation. To investigate the underlying mechanisms, omics technologies were employed. Comprehensive transcriptomic and proteomic analysis of the cells was conducted to identify the pathways responsible for the observed antioxidant effects. Semaglutide demonstrated the potential to enhance learning and memory functions while mitigating hippocampal pathological damage. RNA‑sequencing and data‑independent acquisition proteomics analyses identified 13,511 differentially expressed genes and 588 differentially expressed proteins between the control and type 2 diabetes mellitus (T2DM) groups. In addition, 1,378 genes and 2,394 proteins exhibited a differential expression between the T2DM and semaglutide (10 µg/kg) treatment groups. A combined transcriptomic and proteomic analysis unveiled 40 common pathways. Acyl‑CoA oxidase 1 (ACOX1) was observed to be activated during oxidative stress and subsequently suppressed by semaglutide. Of note, the antioxidant and anti‑apoptotic properties of semaglutide in high glucose (HG) conditions were partially reversed upon ACOX1 overexpression. Overall, the present data provided molecular evidence to elucidate the physiological connections between semaglutide and neuronal function, and contribute to clarifying the role of semaglutide in combating oxidative stress and HG‑induced cognitive impairment.

Applications and prospects of phosphoproteomics in renal disease research

Introduction

Phosphoproteomics, an advanced branch of molecular biology, utilizes specific techniques such as mass spectrometry, affinity chromatography, and bioinformatics analysis to explore protein phosphorylation, shedding light on the cellular mechanisms that drive various biological processes. This field has become instrumental in advancing our understanding of renal diseases, from identifying underlying mechanisms to pinpointing new therapeutic targets.

Areas covered

This review will discuss the evolution of phosphoproteomics from its early experimental observations to its current application in renal disease research using liquid chromatography-tandem mass spectrometry (LC-MS/MS). We will explore its role in the identification of disease biomarkers, the elucidation of pathogenic mechanisms, and the development of novel therapeutic strategies. Additionally, the potential of phosphoproteomics in enhancing drug discovery and improving treatment outcomes for renal diseases will be highlighted.

Expert opinion

Phosphoproteomics is rapidly transforming renal disease research by offering unprecedented insights into cellular processes. Utilizing techniques such as LC-MS/MS, it enables the identification of novel biomarkers and therapeutic targets, enhancing our understanding of drug mechanisms. This field promises significant advancements in the diagnosis and treatment of renal diseases, shifting towards more personalized and effective therapeutic strategies. As the technology evolves, its integration into clinical practice is pivotal for revolutionizing renal healthcare.

Targeting Diabetic Atherosclerosis: The Role of GLP-1 Receptor Agonists, SGLT2 Inhibitors, and Nonsteroidal Mineralocorticoid Receptor Antagonists in Vascular Protection and Disease Modulation

Atherosclerosis is a closely related complication of diabetes mellitus (DM), driven by endothelial dysfunction, inflammation, and oxidative stress. The progression of atherosclerosis is accelerated by hyperglycemia, insulin resistance, and hyperlipidemia. Novel antidiabetic agents, SGLT2 inhibitors, and GLP-1 agonists improve glycemic control and offer cardiovascular protection, reducing the risk of major adverse cardiovascular events (MACEs) and heart failure hospitalization. These agents, along with nonsteroidal mineralocorticoid receptor antagonists (nsMRAs), promise to mitigate metabolic disorders and their impact on endothelial function, oxidative stress, and inflammation. This review explores the potential molecular mechanisms through which these drugs may prevent the development of atherosclerosis and cardiovascular disease (CVD), supported by a summary of preclinical and clinical evidence.

The role of the intestinal microbiome in cognitive decline in patients with kidney disease

Cognitive decline is frequently seen in patients with chronic kidney disease (CKD). The causes of cognitive decline in these patients are likely to be multifactorial, including vascular disease, uraemic toxins, blood-brain barrier leakage, and metabolic and endocrine changes. Gut dysbiosis is common in patients with CKD and contributes to the increase in uraemic toxins. However, the gut microbiome modulates local and systemic levels of several metabolites such as short-chain fatty acids or derivatives of tryptophan metabolism, neurotransmitters, endocannabinoid-like mediators, bile acids, hormones such as glucagon-like peptide 1 (GLP1) or cholecystokinin (CCK). These factors can affect gut function, immunity, autonomic nervous system activity and various aspects of brain function. Key areas include blood-brain barrier integrity, nerve myelination and survival/proliferation, appetite, metabolism and thermoregulation, mood, anxiety and depression, stress and local inflammation. Alterations in the composition of the gut microbiota and the production of biologically active metabolites in patients with CKD are well documented and are favoured by low-fiber diets, elevated urea levels, sedentary lifestyles, slow stool transit times and polypharmacy. In turn, dysbiosis can modulate brain function and cognitive processes, as discussed in this review. Thus, the gut microbiome may contribute to alterations in cognition in patients with CKD and may be a target for therapeutic interventions using diet, prebiotics and probiotics.

Albuminuria in Cardiovascular, Kidney, and Metabolic Disorders: A State-of-the-Art Review

Albuminuria-increased urine albumin excretion-is associated with cardiovascular mortality among patients with diabetes, hypertension, chronic kidney disease, or heart failure, as well as among adults with few cardiovascular risk factors. Many authors have hypothesized that albuminuria reflects widespread endothelial dysfunction, but additional work is needed to uncover whether albuminuria is directly pathologic or causative of cardiovascular disease. Urinary albumin-to-creatinine ratio is an attractive, unifying biomarker of cardiovascular, kidney, and metabolic conditions that may be useful for identifying and monitoring disease trajectory. However, albuminuria may develop through unique mechanisms across these distinct clinical phenotypes. This state-of-the-art review discusses the role of albuminuria in cardiovascular, kidney, and metabolic conditions; identifies potential pathways linking albuminuria to adverse outcomes; and provides practical approaches to screening and managing albuminuria for clinical cardiologists. Future research is needed to determine how broadly and how frequently to screen patients for albuminuria, whether it is cost-effective to treat low-grade albuminuria (10-30 mg/g), and how to equitably offer newer antiproteinuric therapies across the spectrum of cardiovascular-kidney-metabolic diseases.

Empagliflozin protects the kidney by reducing toxic ALB (albumin) exposure and preventing autophagic stagnation in proximal tubules

The renoprotective effects of SLC5A2/SGLT2 (solute carrier 5 (sodium/glucose cotransporter), member 2) inhibitors have recently been demonstrated in non-diabetic chronic kidney disease (CKD), even without overt albuminuria. However, the mechanism underlying this renoprotection is largely unclear. We investigated the renoprotective mechanisms of the SLC5A2 inhibitor empagliflozin with a focus on ALB (albumin) reabsorption and macroautophagy/autophagy in proximal tubules using wild-type or drug-inducible lrp2/Megalin or atg5 knockout mice with high-fat diet (HFD)-induced obesity or 5/6 nephrectomy that elevated intraglomerular pressure without overt albuminuria. Empagliflozin treatment of HFD-fed mice reduced several hallmarks of lipotoxicity in the proximal tubules, such as phospholipid accumulation in the lysosome, inflammation and fibrosis. Empagliflozin, which decreases intraglomerular pressure, not only reduced the HFD-induced increase in ALB reabsorption via LRP2 in the proximal tubules (i.e. total nephron ALB filtration), as assessed by urinary ALB excretion caused by genetic ablation of Lrp2, but also ameliorated the HFD-induced imbalance in circulating ALB-bound fatty acids. Empagliflozin alleviated the HFD-induced increase in autophagic demand and successfully prevented autophagic stagnation in the proximal tubules. Similarly, empagliflozin decreased ALB exposure and autophagic demand in 5/6 nephrectomized mice. Finally, empagliflozin reduced HFD-induced vulnerability to ischemia-reperfusion injury, whereas LRP2 blockade and atg5 ablation separately diminished this effect. Our findings indicate that empagliflozin reduces ALB exposure and prevents autophagic stagnation in the proximal tubules even without overt albuminuria. Autophagy improvement may be critical for the renoprotection mediated by SLC5A2 inhibition.

Crosstalk between glomeruli and tubules

Models of kidney injury have classically concentrated on glomeruli as the primary site of injury leading to glomerulosclerosis or on tubules as the primary site of injury leading to tubulointerstitial fibrosis. However, current evidence on the mechanisms of progression of chronic kidney disease indicates that a complex interplay between glomeruli and tubules underlies progressive kidney injury. Primary glomerular injury can clearly lead to subsequent tubule injury. For example, damage to the glomerular filtration barrier can expose tubular cells to serum proteins, including complement and cytokines, that would not be present in physiological conditions and can promote the development of tubulointerstitial fibrosis and progressive decline in kidney function. In addition, although less well-studied, increasing evidence suggests that tubule injury, whether primary or secondary, can also promote glomerular damage. This feedback from the tubule to the glomerulus might be mediated by changes in the reabsorptive capacity of the tubule, which can affect the glomerular filtration rate, or by mediators released by injured proximal tubular cells that can induce damage in both podocytes and parietal epithelial cells. Examining the crosstalk between the various compartments of the kidney is important for understanding the mechanisms underlying kidney pathology and identifying potential therapeutic interventions.

Cellular crosstalk in organotypic vasculature: mechanisms of diabetic cardiorenal complications and SGLT2i responses

BACKGROUND

Diabetic panvascular disease (DPD) is the leading clinical complication of diabetes mellitus (DM), characterized by atherosclerosis across multiple organ vessels. It is a major cause of high disability and mortality rates in DM. However, the pathological mechanisms and key mediators of DPD remain unclear.

METHODS

This study constructed a single-cell organotypic atlas of the vasculature containing 321,358 cells by integrating 14 single-cell datasets from 8 major mouse organs and tissues. A total of 63 cell types were identified, including 9 vascular cell subtypes, whereas the cell-to-cell interaction (CCI) patterns of the organotypic vasculature were systematically analyzed.

RESULTS

Endothelial cells (ECs) were identified as the major cell type involved in CCI within the vasculature, with their ligands interacting with receptors of various cell types, which contribute to multiple biological processes such as stem cell differentiation and immune regulation. Notably, the study examined the cellular communication characteristics of different EC subtypes. Additionally, the inter-organ communication between the heart and kidney-key tissues in DPD-was analyzed. The BMP signaling pathway emerged as a critical communication pathway leading to cardiorenal complications in DM, with SGLT2i having a regulatory role in BMP6 modulation.

CONCLUSIONS

The study provides, for the first time, a single-cell analysis of the CCI patterns of the organotypic vasculature and highlights the central role of ECs. Moreover, the key role of BMP6 in diabetic cardiorenal complications is elucidated. These findings offer new insights into the mechanisms underlying DPD co-morbidities and provide a novel scientific basis for clinical prevention, treatment strategies for DPD, and the understanding of the action mechanism of SGLT2i.

Integrated Omics Insights into Dapagliflozin Effects in Sepsis-Induced Cardiomyopathy

BACKGROUND

Sepsis-induced cardiomyopathy (SIC) is a life-threatening cardiac complication of sepsis with limited therapeutic options. Dapagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, has demonstrated cardioprotective effects in heart failure, but its role in mitigating sepsis-related cardiac dysfunction remains unclear.

METHODS

A retrospective cohort analysis was conducted to assess the impact of pre-hospital dapagliflozin use on major adverse cardiovascular events (MACEs) and survival in patients with SIC. Additionally, a murine SIC model was established using cecal ligation and puncture (CLP) to evaluate the effects of dapagliflozin on cardiac function, histopathology, and biomarkers of myocardial injury. Transcriptomic and metabolomic profiling, combined with multi-omics integration, was employed to elucidate the molecular mechanisms underlying dapagliflozin's cardioprotective effects.

RESULTS

In the clinical cohort, pre-hospital dapagliflozin use was associated with a significant reduction in the risk of MACE and improved survival outcomes. In the murine SIC model, dapagliflozin restored cardiac function, reduced biomarkers of myocardial injury, and alleviated histological damage. Multi-omics analysis revealed that dapagliflozin modulates inflammatory responses, enhances autophagy, and regulates metabolic pathways such as AMPK signaling and lipid metabolism. Key regulatory genes and metabolites were identified, providing mechanistic insights into the underlying actions of dapagliflozin.

CONCLUSIONS

Dapagliflozin significantly improves cardiac outcomes in sepsis-induced cardiomyopathy through the multi-level regulation of inflammation, energy metabolism, and cellular survival pathways. These findings establish dapagliflozin as a promising therapeutic strategy for SIC, offering translational insights into the treatment of sepsis-induced cardiac dysfunction.

Beyond SGLT2: proximal tubule transporters as potential drug targets for chronic kidney disease

The kidneys produce daily about 180 liters of urine but only about 2 liters are excreted. The proximal tubule plays an important role in reabsorbing the majority of filtered urine and many metabolites such as sugars, amino acids, salts or phosphate that are contained in this large volume. Reabsorption of these important metabolites is mediated by a diverse group of highly specialized transport proteins. Another group of transport proteins in the proximal tubule is responsible for the active secretion of metabolic waste products or toxins and drugs into urine. All these transporters have in common that they are directly linked to kidney metabolism and indirectly to whole-body metabolism and functions. In recent years, it has become evident that modulation of these transporters may influence the onset, progression and consequences of kidney disease. This review summarizes recent developments in this field and discusses some examples of drugs already in clinical use or in development. The examples include inhibitors of sugar transporters (SGLT2 inhibitors) that are successfully used in patients with kidney disease, diabetes or heart failure. Likewise, indirect inhibitors (acetazolamide) of an transporter absorbing sodium in exchange for protons (NHE3) are used mostly in patients with heart failure or for prevention of high altitude disease, while direct inhibitors show promise in preclinical studies to reduce damage in episodes of acute kidney disease or high blood pressure. Modulators of transporters mediating the excretion of urate have been used in patients with gout and are also discussed to prevent kidney disease. Novel drugs in development target transporters for phosphate, amino acids, or toxin and drug excretion and may be helpful for specific conditions associated with kidney disease. The advantages and challenges associated with these (novel) drugs targeting proximal tubule transport are discussed.

ABSTRACT

The proximal tubule is responsible for reabsorbing about 60% of filtered solutes and water and is critical for the secretion of metabolic waste products, drugs and toxins. A large number of highly specialized ion channels and transport proteins belonging to the SLC and ABC transporter families are involved. Their activity is directly or indirectly linked to ATP consumption and requires large quantities of energy and oxygen supply. Moreover, the activity of these transporters is often coupled to the movement of Na+ ions thus influencing also salt and water balance, as well as transport and regulatory processes in downstream segments. Because of their relevance for systemic ion balance, for renal metabolism or for affecting regulatory processes, proximal tubule transporters are attractive targets for existing drug and for novel strategies to reduce kidney disease progression or to alleviate the consequences of decreased kidney function. In this review, the relevance of some major proximal tubule transport systems as drug targets in individuals with chronic kidney disease (CKD) is discussed. Inhibitors of the sodium-glucose cotransporter 2, SGLT2, are now part of standard therapy in patients with CKD and/or heart failure. Also, indirect inhibition of Na+/H+-exchangers by carbonic anhydrase inhibitors and uricosuric drugs have been used for decades. Inhibition of phosphate and amino acid transporters have recently been proposed as novel principles to remove excess phosphate or to protect the proximal tubule metabolically, respectively. In addition, organic cation and anion transporters involved in drug and toxin excretion may serve as targets of new drugs. The advantages and challenges associated with (novel) drugs targeting proximal tubule transport are discussed.

Biology of the proximal tubule in body homeostasis and kidney disease

The proximal tubule (PT) is known as the workhorse of the kidney, for both the range and magnitude of the functions that it performs. It is not only responsible for reabsorbing most solutes and proteins filtered by glomeruli, but also for secreting non-filtered substances including drugs and uremic toxins. The PT therefore plays a pivotal role in kidney physiology and body homeostasis. Moreover, it is the major site of damage in acute kidney injury and nephrotoxicity. In this review, we will provide an introduction to the cell biology of the PT and explore how it is adapted to the execution of a myriad of different functions and how these can differ between males and females. We will then discuss how the PT regulates phosphate, glucose and acid-base balance, and the consequences of alterations in PT function for bone and cardiovascular health. Finally, we explore why the PT is vulnerable to ischemic and toxic insults, and how acute injury in the PT can lead to maladaptive repair, chronic damage and kidney fibrosis. In summary, we will demonstrate that knowledge of the basic cell biology of the PT is critical for understanding kidney disease phenotypes and their associated systemic complications, and for developing new therapeutic strategies to prevent these.

Multiomics Analyses Demonstrate the Attenuation of Metabolic Cardiac Disorders Associated With Type 2 Diabetes by Stachydrine in Relation With the Transition of Gastrointestinal Microbiota

Stachydrine (STA) has therapeutic effects on heart disorders. The current study assessed its effects on Type 2 diabetes (T2D) induced cardiac disorders by focusing on the heart-gut axis. Mice were subjected to high-fat diet (HFD) and streptozocin (STZ) to induce cardiac disorders such as inflammation and structural deteriorations, which were handled with STA. Changes regarding the composition and metabolism of gastrointestinal (GI) microbiota were then determined using a multiomics strategy, including amplicon sequencing and metabolomics. The data showed that STA improved heart function, reduced intestinal permeability, and suppressed inflammation in mice in a dose-dependent manner. However, the compound had little influence on the overall alpha diversity of gut microbiota, while it did influence the beta diversity. The analyses based on the multiomics strategy demonstrated that certain GI microbial groups, including Paramuribaculum, Allobaculum, Bifidobacterium, and Adlercreutzia, responded to the STA administration, which contributed to the alternatives of metabolites in the gut. Correlation analyses showed that Duncaniella and Ruminococcus negatively impacted health, while Muribaculum, Paramuribaculum, and Prevotella positively influenced intestinal permeability and heart health. Collectively, STA attenuated T2D-induced cardiac disorders by improving heart structure and function and suppressing inflammation, during which the GI homeostasis of the T2D mice changed to an alternative state that was different from that of healthy mice.

Gut-X axis

Recent advances in understanding the modulatory functions of gut and gut microbiota on human diseases facilitated our focused attention on the contribution of the gut to the pathophysiological alterations of many extraintestinal organs, including the liver, heart, brain, lungs, kidneys, bone, skin, reproductive, and endocrine systems. In this review, we applied the "gut-X axis" concept to describe the linkages between the gut and other organs and discussed the latest findings related to the "gut-X axis," including the underlying modulatory mechanisms and potential clinical intervention strategies.

Spatiotemporal landscape of kidney in a mouse model of hyperuricemia at single-cell level

Serum uric acid is an end-product of purine metabolism. Uric acid concentrations in excess of the physiological range may lead to diseases such as gout, cardiovascular disease, and kidney injury. The kidney includes a variety of cell types with specialized functions such as fluid and electrolyte homeostasis, detoxification, and endocrine functions. Two-thirds of uric acid is excreted through kidney, however, the exploration of markers and new therapeutic targets in renal tissue of hyperuricemia is still lacking. Single-cell and spatial omics techniques represent major milestones in life sciences. The combined measurement of the physical structure and molecular characteristics of tissues facilitates the exploration of the pathophysiological processes underlying disease development and the discovery of possible therapeutic targets. Here, the spatiotemporal atlas of hyperuricemic nephropathy was investigated using single-cell RNA sequencing, spatial transcriptomics, spatial proteomics, and spatial metabolomics in a urate oxidase knockout mouse model. Several emerging targets and pathways especially ribosome and metabolism related to uric acid excretion were discovered and will be investigated further in studies on lowering uric acid.

Chronic kidney disease

Chronic kidney disease (CKD) is defined by persistent abnormalities of kidney function or structure that have consequences for the health. A progressive decline of excretory kidney function has effects on body homeostasis. CKD is tightly associated with accelerated cardiovascular disease and severe infections, and with premature death. Kidney failure without access to kidney replacement therapy is fatal - a reality in many regions of the world. CKD can be the consequence of a single cause, but CKD in adults frequently relates rather to sequential injuries accumulating over the life course or to the presence of concomitant risk factors. The shared pathomechanism of CKD progression is the irreversible loss of kidney cells or nephrons together with haemodynamic and metabolic overload of the remaining nephrons, leading to further loss of kidney cells or nephrons. The management of patients with CKD focuses on early detection and on controlling all modifiable risk factors. This approach includes reducing the overload of the remaining nephrons with inhibitors of the renin-angiotensin system and the sodium-glucose transporter 2, as well as disease-specific drug interventions, if available. Hypertension, anaemia, metabolic acidosis and secondary hyperparathyroidism contribute to cardiovascular morbidity and reduced quality of life, and require diagnosis and treatment.

Exploring the Role of SGLT2 Inhibitors in Cancer: Mechanisms of Action and Therapeutic Opportunities

Cancer cells utilize larger amounts of glucose than their normal counterparts, and the expression of GLUT transporters is a known diagnostic target and a prognostic factor for many cancers. Recent evidence has shown that sodium-glucose transporters are also expressed in different types of cancer, and SGLT2 has raised particular interest because of the current availability of anti-diabetic drugs that block SGLT2 in the kidney, which could be readily re-purposed for the treatment of cancer. The aim of this article is to perform a narrative review of the existing literature and a critical appraisal of the evidence for a role of SGLT2 inhibitors for the treatment and prevention of cancer. SGLT2 inhibitors block Na-dependent glucose uptake in the proximal kidney tubules, leading to glycosuria and the improvement of blood glucose levels and insulin sensitivity in diabetic patients. They also have a series of systemic effects, including reduced blood pressure, weight loss, and reduced inflammation, which also make them effective for heart failure and kidney disease. Epidemiological evidence in diabetic patients suggests that individuals treated with SGLT2 inhibitors may have a lower incidence and better outcomes of cancer. These studies are confirmed by pre-clinical evidence of an effect of SGLT2 inhibitors against cancer in xenograft and genetically engineered models, as well as by in vitro mechanistic studies. The action of SGLT2 inhibitors in cancer can be mediated by the direct inhibition of glucose uptake in cancer cells, as well as by systemic effects. In conclusion, there is evidence suggesting a potential role of SGLT2 inhibitors against different types of cancer. The most convincing evidence exists for lung and breast adenocarcinomas, hepatocellular carcinoma, and pancreatic cancer. Several ongoing clinical trials will provide more information on the efficacy of SGLT2 inhibitors against cancer.

Protein-bound uremic toxins as therapeutic targets for cardiovascular, kidney, and metabolic disorders

Cardiovascular-kidney-metabolic (CKM) syndrome is a systemic clinical condition characterized by pathological and physiological interactions among metabolic abnormalities, chronic kidney disease, and cardiovascular diseases, leading to multi-organ dysfunction and a higher incidence of cardiovascular endpoints. Traditional approaches to managing CKM syndrome risk are inadequate in these patients, necessitating strategies targeting specific CKM syndrome risk factors. Increasing evidence suggests that addressing uremic toxins and/or pathways induced by uremic toxins may reduce CKM syndrome risk and treat the disease. This review explores the interactions among heart, kidney, and metabolic pathways in the context of uremic toxins and underscores the significant role of uremic toxins as potential therapeutic targets in the pathophysiology of these diseases. Strategies aimed at regulating these uremic toxins offer potential avenues for reversing and managing CKM syndrome, providing new insights for its clinical diagnosis and treatment.

Impact of dapagliflozin on metabolic phenotype, hormone levels, and fertility in female mice after prolonged high-fat diet

Introduction

A long-term high-fat diet (HFD) cause obesity and infertility through hypothalamic inflammation and insulin resistance, leading to metabolic abnormalities and ovulation dysfunction. The sodium-glucose cotransporter 2 inhibitors (SGLT2i) have emerged as a treatment for type 2 diabetic patients, regulating adipose tissue metabolism, hypothalamic inflammation, and ovulation in women with polycystic ovary syndrome (PCOS). The study aimed to investigate the pharmacological effects of dapagliflozin on improving insulin resistance, energy metabolism, sex hormones, and fertility in female mice following prolonged consumption of HFD.

Methods

At 6 weeks of age, female mice were fed a HFD and treated with dapagliflozin. Serum hormone concentrations and inflammatory factors in mice aged 28 weeks or 38 weeks were quantified using ultrasensitive enzyme-linked immunosorbent assays (ELISAs). Metabolic parameters were also assessed and documented at different stages of the experiment. At 34 weeks of age, half of the experimental mice in each of the four groups fed with standard chow were mated with male mice. Pregnancy rate, abortion rate, pregnancy-related deaths, and perinatal outcomes were systematically recorded.

Results

After 16 weeks of HFD feeding, dapagliflozin significantly attenuated visceral fat deposition, weight gain, glucose intolerance, and insulin resistance induced by the diet. However, these effects diminished after 32 weeks. Unexpectedly, neither HFD nor dapagliflozin treatment elicited any significant changes in serum IL-6 and TNFα levels. Throughout the experiment period, dapagliflozin exhibited favorable effects on reproductive function along with insulin sensitivity and luteinizing hormone (LH) release from the pituitary gland.

Discussion

In conclusion, this study demonstrates that dapagliflozin alleviated HFD-induced reproductive dysfunction independently of obesity, peripheral tissue insulin resistance, and systemic inflammation, suggesting its potential as a promising treatment for diet-related ovulation disorders.

The evolving understanding of systemic mechanisms in organ-specific IgA nephropathy: a focus on gut-kidney crosstalk

The interplay between multiple organs, known as inter-organ crosstalk, represents a complex and essential research domain in understanding the mechanisms and therapies for kidney diseases. The kidneys not only interact pathologically with many other organs but also communicate with other systems through various signaling pathways. It is of paramount importance to comprehend these mechanisms for the development of more efficient therapeutic strategies. Despite extensive research in IgA nephropathy (IgAN), the most common kidney disease, the elaboration mechanism of IgAN remains challenging. Numerous studies suggest that alterations in the intestinal microbiome and its metabolites are pivotal in the progression of IgAN, opening new avenues for understanding its mechanisms. Interestingly, certain presumed probiotics, such as Akkermansia muciniphila, have been implicated in the onset of IgAN, making the exploration of gut microbiota in the context of IgAN pathogenesis even more intriguing. In this review, we summarize the status of gut microbiology studies of IgAN and explore the possible mechanisms and intervention prospects. Future research and treatment directions may increasingly emphasize systemic, multi-organ combined interventions to decelerate the advancement of kidney disease and enhance the overall prognosis of patients.

Bioactive metabolites: A clue to the link between MASLD and CKD?

Metabolites produced as intermediaries or end-products of microbial metabolism provide crucial signals for health and diseases, such as metabolic dysfunction-associated steatotic liver disease (MASLD). These metabolites include products of the bacterial metabolism of dietary substrates, modification of host molecules (such as bile acids [BAs], trimethylamine-N-oxide, and short-chain fatty acids), or products directly derived from bacteria. Recent studies have provided new insights into the association between MASLD and the risk of developing chronic kidney disease (CKD). Furthermore, alterations in microbiota composition and metabolite profiles, notably altered BAs, have been described in studies investigating the association between MASLD and the risk of CKD. This narrative review discusses alterations of specific classes of metabolites, BAs, fructose, vitamin D, and microbiota composition that may be implicated in the link between MASLD and CKD.

Transcriptomics of SGLT2-positive early proximal tubule segments in mice: response to type 1 diabetes, SGLT1/2 inhibition, or GLP1 receptor agonism

SGLT2 inhibitors (SGLT2i) and GLP1 receptor (GLP1R) agonists have kidney protective effects. To better understand their molecular effects, RNA sequencing was performed in SGLT2-positive proximal tubule segments isolated by immunostaining-guided laser capture microdissection. Male adult DBA wild-type (WT) and littermate diabetic Akita mice ± Sglt1 knockout (Sglt1-KO) were given vehicle or SGLT2i dapagliflozin (dapa; 10 mg/kg diet) for 2 wk, and other Akita mice received GLP1R agonist semaglutide [sema; 3 nmol/(kg body wt·day), sc]. Dapa (254 ± 11 mg/dL) and Sglt1-KO (367 ± 11 mg/dL) but not sema (407 ± 44 mg/dL) significantly reduced hyperglycemia in Akita mice (480 ± 33 mg/dL). The 20,748 detected annotated protein-coding genes included robust enrichment of S1-segment marker genes. Akita showed 198 (∼1%) differentially expressed genes versus WT (DEGs; adjusted P ≤ 0.1), including downregulation of anionic transport, unsaturated fatty acid, and carboxylic acid metabolism. Dapa changed only two genes in WT but restored 43% of DEGs in Akita, including upregulation of the lipid metabolic pathway, carboxylic acid metabolism, and organic anion transport. In Akita, sema restored ∼10% of DEGs, and Sglt1-KO and dapa were synergistic (restored ∼61%), possibly involving additive blood glucose effects (193 ± 15 mg/dL). Targeted analysis of transporters and channels (t test, P < 0.05) revealed that ∼10% of 526 detectable transporters and channels were downregulated by Akita, with ∼60% restored by dapa. Dapa, dapa + Sglt1-KO, and sema also altered Akita-insensitive genes. Among DEGs in Akita, ∼30% were unresponsive to any treatment, indicating potential new targets. In conclusion, SGLT2i restored transcription for multiple metabolic pathways and transporters in SGLT2-positive proximal tubule segments in diabetic mice, with a smaller effect also observed for GLP1R agonism.NEW & NOTEWORTHY SGLT2 inhibitors and GLP1 receptor agonists have kidney protective effects. By combining immunostaining-guided laser capture microdissection and RNA sequencing, the study established how the gene expression profile changes in SGLT2-positive proximal tubule cells in response to type 1 Akita diabetes and to pharmacological intervention by SGLT2 inhibition or GLP1R agonism and genetic deletion of SGLT1. The data also indicate genes unresponsive to those treatments that may include new therapeutical candidates.

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 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.

Biomarker-based prediction of sinus rhythm in atrial fibrillation patients: the EAST-AFNET 4 biomolecule study

BACKGROUND AND AIMS

In patients with atrial fibrillation (AF), recurrent AF and sinus rhythm during follow-up are determined by interactions between cardiovascular disease processes and rhythm control therapy. Predictors of attaining sinus rhythm at follow-up are not well known.

METHODS

To quantify the interaction between cardiovascular disease processes and rhythm outcomes, 14 biomarkers reflecting AF-related cardiovascular disease processes in 1586 patients in the EAST-AFNET 4 biomolecule study (71 years old, 45% women) were quantified at baseline. Mixed logistic regression models including clinical features were constructed for each biomarker. Biomarkers were interrogated for interaction with early rhythm control. Outcome was sinus rhythm at 12 months. Results were validated at 24 months and in external datasets.

RESULTS

Higher baseline concentrations of three biomarkers were independently associated with a lower chance of sinus rhythm at 12 months: angiopoietin 2 (ANGPT2) (odds ratio [OR] .76 [95% confidence interval .65-.89], P < .001), bone morphogenetic protein 10 (BMP10) (OR .83 [.71-.97], P = .017), and N-terminal pro-B-type natriuretic peptide (NT-proBNP) (OR .73 [.60-.88], P < .001). Analysis of rhythm at 24 months confirmed the results. Early rhythm control interacted with the predictive potential of NT-proBNP (Pinteraction = .033). The predictive effect of NT-proBNP was reduced in patients randomized to early rhythm control (usual care: OR .64 [.51-.80], P < .001; early rhythm control: OR .90 [.69-1.18], P = .453). External validation confirmed that low concentrations of ANGPT2, BMP10, and NT-proBNP predict sinus rhythm during follow-up.

CONCLUSIONS

Low concentrations of ANGPT2, BMP10, and NT-proBNP identify patients with AF who are likely to attain sinus rhythm during follow-up. The predictive ability of NT-proBNP is attenuated in patients receiving rhythm control.

Beyond ketosis: the search for the mechanism underlying SGLT2-inhibitor benefit continues

Despite the impressive clinical benefits and widespread adoption of sodium glucose cotransporter 2 inhibitors (SGLT2i) to treat all classes of heart failure, their cardiovascular mechanisms of action are poorly understood. Proposed mechanisms range broadly and include enhanced ketogenesis, where the mild ketosis associated with SGLT2i use is presumed to be beneficial. However, in this issue of the JCI, carefully conducted metabolic flux studies by Goedeke et al. comparing the effects of SGLT2i and exogenous ketones suggest differential effects. Thus, the mechanisms of action for SGLT2i are likely pleiotropic, and further work is needed to fully understand their beneficial effects.

Amino acid metabolism in kidney health and disease

Amino acids form peptides and proteins and are therefore considered the main building blocks of life. The kidney has an important but under-appreciated role in the synthesis, degradation, filtration, reabsorption and excretion of amino acids, acting to retain useful metabolites while excreting potentially harmful and waste products from amino acid metabolism. A complex network of kidney transporters and enzymes guides these processes and moderates the competing concentrations of various metabolites and amino acid products. Kidney amino acid metabolism contributes to gluconeogenesis, nitrogen clearance, acid-base metabolism and provision of fuel for tricarboxylic acid cycle and urea cycle intermediates, and is thus a central hub for homeostasis. Conversely, kidney disease affects the levels and metabolism of a variety of amino acids. Here, we review the metabolic role of the kidney in amino acid metabolism and describe how different diseases of the kidney lead to aberrations in amino acid metabolism. Improved understanding of the metabolic and communication routes that are affected by disease could provide new mechanistic insights into the pathogenesis of kidney diseases and potentially enable targeted dietary or pharmacological interventions.

Handling the sugar rush: the role of the renal proximal tubule

Blood glucose homeostasis is critical to ensure the proper functioning of the human body. Through the processes of filtration, reabsorption, secretion, and metabolism, much of this task falls to the kidneys. With a rise in glucose and other added sugars, there is an increased burden on this organ, mainly the proximal tubule, which is responsible for all glucose reabsorption. In this review, we focus on the current physiological and cell biological functions of the renal proximal tubule as it works to reabsorb and metabolize glucose and fructose. We also highlight the physiological adaptations that occur within the proximal tubule as sugar levels rise under pathophysiological conditions including diabetes. This includes the detrimental impacts of an excess glucose load that leads to glucotoxicity. Finally, we explore some of the emerging therapeutics that modulate renal glucose handling and the systemic protection that can be realized by targeting the reabsorptive properties of the kidney.

Gut Dysbiosis and Its Role in the Anemia of Chronic Kidney Disease

The gut dysbiosis present in chronic kidney disease (CKD) has been associated with anemia. Factors such as the accumulation of gut-derived uremic toxins, increased gut barrier permeability-induced inflammation, and a reduced intestinal production of short-chain fatty acids (SCFAs), all associated with changes in the intestinal microbiota composition in CKD, may lead to the development or worsening of anemia in renal patients. Understanding and addressing these mechanisms related to gut dysbiosis in CKD patients can help to delay the development of anemia and improve its control in this population. One approach is to avoid or reduce the use of drugs linked to gut dysbiosis in CKD, such as phosphate binders, oral iron supplementation, antibiotics, and others, unless they are indispensable. Another approach involves introducing dietary changes that promote a healthier microbiota and/or using prebiotics, probiotics, or symbiotics to improve gut dysbiosis in this setting. These measures can increase the presence of SCFA-producing saccharolytic bacteria and reduce proteolytic bacteria, thereby lowering the production of gut-derived uremic toxins and inflammation. By ameliorating CKD-related gut dysbiosis, these strategies can also improve the control of renal anemia and enhance the response to erythropoiesis-stimulating agents (ESAs) in ESA-resistant patients. In this review, we have explored the relationship between gut dysbiosis in CKD and renal anemia and propose feasible solutions, both those already known and potential future treatments.

Extrarenal Benefits of SGLT2 Inhibitors in the Treatment of Cardiomyopathies

Sodium-glucose cotransporter 2 (SGLT2) inhibitors have emerged as pivotal medications for heart failure, demonstrating remarkable cardiovascular benefits extending beyond their glucose-lowering effects. The unexpected cardiovascular advantages have intrigued and prompted the scientific community to delve into the mechanistic underpinnings of these novel actions. Preclinical studies have generated many mechanistic theories, ranging from their renal and extrarenal effects to potential direct actions on cardiac muscle cells, to elucidate the mechanisms linking these drugs to clinical cardiovascular outcomes. Despite the strengths and limitations of each theory, many await validation in human studies. Furthermore, whether SGLT2 inhibitors confer therapeutic benefits in specific subsets of cardiomyopathies akin to their efficacy in other heart failure populations remains unclear. By examining the shared pathological features between heart failure resulting from vascular diseases and other causes of cardiomyopathy, certain specific molecular actions of SGLT2 inhibitors (particularly those targeting cardiomyocytes) would support the concept that these medications will yield therapeutic benefits across a broad range of cardiomyopathies. This article aims to discuss the important mechanisms of SGLT2 inhibitors and their implications in hypertrophic and dilated cardiomyopathies. Furthermore, we offer insights into future research directions for SGLT2 inhibitor studies, which hold the potential to further elucidate the proposed biological mechanisms in greater detail.

Future of Uremic Toxin Management

During the progression of chronic kidney disease (CKD), the retention of uremic toxins plays a key role in the development of uremic syndrome. Knowledge about the nature and biological impact of uremic toxins has grown exponentially over the past decades. However, the science on reducing the concentration and effects of uremic toxins has not advanced in parallel. Additionally, the focus has remained for too long on dialysis strategies, which only benefit the small fraction of people with CKD who suffer from advanced kidney disease, whereas uremic toxicity effects are only partially prevented. This article reviews recent research on alternative methods to counteract uremic toxicity, emphasizing options that are also beneficial in the earlier stages of CKD, with a focus on both established methods and approaches which are still under investigation or at the experimental stage. We will consequently discuss the preservation of kidney function, the prevention of cardiovascular damage, gastro-intestinal interventions, including diet and biotics, and pharmacologic interventions. In the final part, we also review alternative options for extracorporeal uremic toxin removal. The future will reveal which of these options are valid for further development and evidence-based assessment, hopefully leading to a more sustainable treatment model for CKD than the current one.

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.

Type 2 diabetes mellitus in adults: pathogenesis, prevention and therapy

Type 2 diabetes (T2D) is a disease characterized by heterogeneously progressive loss of islet β cell insulin secretion usually occurring after the presence of insulin resistance (IR) and it is one component of metabolic syndrome (MS), and we named it metabolic dysfunction syndrome (MDS). The pathogenesis of T2D is not fully understood, with IR and β cell dysfunction playing central roles in its pathophysiology. Dyslipidemia, hyperglycemia, along with other metabolic disorders, results in IR and/or islet β cell dysfunction via some shared pathways, such as inflammation, endoplasmic reticulum stress (ERS), oxidative stress, and ectopic lipid deposition. There is currently no cure for T2D, but it can be prevented or in remission by lifestyle intervention and/or some medication. If prevention fails, holistic and personalized management should be taken as soon as possible through timely detection and diagnosis, considering target organ protection, comorbidities, treatment goals, and other factors in reality. T2D is often accompanied by other components of MDS, such as preobesity/obesity, metabolic dysfunction associated steatotic liver disease, dyslipidemia, which usually occurs before it, and they are considered as the upstream diseases of T2D. It is more appropriate to call "diabetic complications" as "MDS-related target organ damage (TOD)", since their development involves not only hyperglycemia but also other metabolic disorders of MDS, promoting an up-to-date management philosophy. In this review, we aim to summarize the underlying mechanism, screening, diagnosis, prevention, and treatment of T2D, especially regarding the personalized selection of hypoglycemic agents and holistic management based on the concept of "MDS-related TOD".

Key results from observational studies and real-world evidence of sodium-glucose cotransporter-2 inhibitor effectiveness and safety in reducing cardio-renal risk

Sodium-glucose cotransporter 2 (SGLT2) inhibitors, originally designed to manage blood sugar levels in individuals with type 2 diabetes (T2D), have emerged as a crucial class of drugs for managing cardio-renal diseases. These drugs work by targeting the SGLT2 protein in the kidneys, promoting the excretion of glucose and influencing metabolic pathways beyond glucose control. The relationship between cardio-renal diseases and SGLT2 inhibitors has been explored through landmark trials and real-world evidence (RWE) studies, demonstrating significant reductions in cardio-renal complications. This review discusses the importance of RWE studies alongside randomized controlled trials in understanding the real-world effectiveness and safety of SGLT2 inhibitors. It outlines the advantages and disadvantages of RWE compared to RCTs, highlighting their complementary roles in providing comprehensive insights into treatment outcomes. By examining a range of RWE studies, the review underscores the cardio-renal benefits of SGLT2 inhibitors across various patient populations. Safety assessments indicate that SGLT2 inhibitors are generally well tolerated, with severe adverse events being rare. Common issues, such as genital mycotic infections and urinary tract infections, are acknowledged, alongside less frequent but significant adverse events including diabetic ketoacidosis, lower-limb amputations, and bone fractures. In summary, SGLT2 inhibitors show promising cardio-renal protective effects in real-world scenarios across diverse populations in T2D, indicating their potential as early intervention measures. Continued research is essential for gaining a thorough understanding of their long-term effects and safety profiles.

Empagliflozin prevents heart failure through inhibition of the NHE1-NO pathway, independent of SGLT2

Sodium glucose cotransporter 2 inhibitors (SGLT2i) constitute the only medication class that consistently prevents or attenuates human heart failure (HF) independent of ejection fraction. We have suggested earlier that the protective mechanisms of the SGLT2i Empagliflozin (EMPA) are mediated through reductions in the sodium hydrogen exchanger 1 (NHE1)-nitric oxide (NO) pathway, independent of SGLT2. Here, we examined the role of SGLT2, NHE1 and NO in a murine TAC/DOCA model of HF. SGLT2 knockout mice only showed attenuated systolic dysfunction without having an effect on other signs of HF. EMPA protected against systolic and diastolic dysfunction, hypertrophy, fibrosis, increased Nppa/Nppb mRNA expression and lung/liver edema. In addition, EMPA prevented increases in oxidative stress, sodium calcium exchanger expression and calcium/calmodulin-dependent protein kinase II activation to an equal degree in WT and SGLT2 KO animals. In particular, while NHE1 activity was increased in isolated cardiomyocytes from untreated HF, EMPA treatment prevented this. Since SGLT2 is not required for the protective effects of EMPA, the pathway between NHE1 and NO was further explored in SGLT2 KO animals. In vivo treatment with the specific NHE1-inhibitor Cariporide mimicked the protection by EMPA, without additional protection by EMPA. On the other hand, in vivo inhibition of NOS with L-NAME deteriorated HF and prevented protection by EMPA. In conclusion, the data support that the beneficial effects of EMPA are mediated through the NHE1-NO pathway in TAC/DOCA-induced heart failure and not through SGLT2 inhibition.

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.

SGLT2 inhibition leads to a restoration of hepatic and circulating metabolites involved in the folate cycle and pyrimidine biosynthesis

Inhibition of sodium-glucose cotransporter 2 (SGLT2) by empagliflozin (EMPA) and other "flozins" can improve glycemic control under conditions of diabetes and kidney disease. Though they act on the kidney, they also offer cardiovascular and liver protection. Previously, we found that EMPA decreased circulating triglycerides and hepatic lipid and cholesterol esters in male TallyHo mice fed a high-milk-fat diet (HMFD). The goal of this study was to determine whether the liver protection is associated with a change in metabolic function by characterizing the hepatic and circulating metabolic and lipidomic profiles using targeted LC-MS. In both male and female mice, HMFD feeding significantly altered the circulating and hepatic metabolome compared with low-fat diet (LFD). Addition of EMPA resulted in the restoration of circulating orotate (intermediate in pyrimidine biosynthesis) and hepatic dihydrofolate (intermediate in the folate and methionine cycles) levels in males and acylcarnitines in females. These changes were partially explained by altered expression of rate-limiting enzymes in these pathways. This metabolic signature was not detected when EMPA was incorporated into an LFD, suggesting that the restoration requires the metabolic shift that accompanies the HMFD. Notably, the HMFD increased expression of 18 of 20 circulating amino acids in males and 11 of 20 in females, and this pattern was reversed by EMPA. Finally, we confirmed that SGLT2 inhibition upregulates ketone bodies including β-hydroxybutyrate. Collectively, this study highlights the metabolic changes that occur with EMPA treatment, and sheds light on the possible mechanisms by which this drug offers liver and systemic protection.NEW & NOTEWORTHY Sodium-glucose cotransporter 2 (SGLT2) inhibitors, including empagliflozin, have emerged as a new treatment option for individuals with type 2 diabetes that have positive impacts on kidney and cardiovascular disease. However, less is known about their impact on other tissues, including the liver. Here, we report that empagliflozin reduces hepatic steatosis that is associated with restoring metabolic intermediates in the folate and pyrimidine biosynthesis pathways. These changes may lead to new approaches to treat nonalcoholic fatty liver disease.