SGLT2 inhibition and renal urate excretion: role of luminal glucose, GLUT9, and URAT1

Medium- and Long-Term Effects of Dapagliflozin on Serum Uric Acid Level in Patients with Type 2 Diabetes: A Real-World Study

We aimed to explore the medium- and long-term (≥12 weeks) effects of dapagliflozin on serum uric acid (SUA) level in patients with type 2 diabetes mellitus (T2DM) in the real world study and to explore the influencing factors of dapagliflozin on reducing SUA level. This observational, prospective cohort study was based on the real world. There were 77 patients included in this study. They were divided into two groups. Patients in treatment group (n = 38) were treated as dapagliflozin 10 mg/d combined with therapy of routine glucose-lowering drugs (GLDs), and patients in the control group (n = 39) were treated with their routine GLDs. All measurements of physical examinations, blood, and urine samples, including age, sex, weight, height, systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting blood glucose (FBG), glycosylated hemoglobin (HbA1c), and SUA, were collected at baseline for all patients in these two groups and repeated after 12, 24, and 48 weeks of therapy. We compared the changes of metabolic indicators including SUA in these two groups to evaluate the effects of dapagliflozin and analyzed its influencing factors. In the dapagliflozin group, mean SUA levels significantly decreased from 334.2 ± 99.1 μmol/L at baseline to 301.9 ± 73.2 μmol/L after 12 weeks therapy (t = 2.378, p = 0.023). There was no significant statistical difference of SUA levels after 24 weeks treatment of dapagliflozin compared with 12-week and 48-week treatment with dapagliflozin (p > 0.05). We found that baseline SUA had a significant impact on the effect of dapagliflozin on reducing SUA (OR 1.014, 95%CI 1.003−1.025, p = 0.014) by logistic regression analysis. Receiver operating characteristic (ROC) curve showed that T2DM patients with SUA level ≥ 314.5 μmol/L had relative accuracy in recognizing the good effects of dapagliflozin on reducing SUA (sensitivity 76.9%, specificity 76.2%). Combination therapy of dapagliflozin with routine blood-glucose-lowering drugs in T2DM patients showed the significant and sustained stable effect of lowering SUA level in this real-world study.

Expectations in children with glomerular diseases from SGLT2 inhibitors

Chronic kidney disease (CKD) is a global public healthcare concern in the pediatric population, where glomerulopathies represent the second most common cause. Although classification and diagnosis of glomerulopathies still rely mostly on histopathological patterns, patient stratification should complement information supplied by kidney biopsy with clinical data and etiological criteria. Genetic determinants of glomerular injury are particularly relevant in children, with important implications for prognosis and treatment. Targeted therapies addressing the primary cause of the disease are available for a limited number of glomerular diseases. Consequently, in the majority of cases, the treatment of glomerulopathies is actually the treatment of CKD. The efficacy of the currently available strategies is limited, but new prospects evolve. Although the exact mechanisms of action are still under investigation, accumulating data in adults demonstrate the efficacy of sodium-glucose transporter 2 inhibitors (SGLT2i) in slowing the progression of CKD due to diabetic and non-diabetic kidney disease. SGLT2i has proved effective on other comorbidities, such as obesity, glycemic control, and cardiovascular risk that frequently accompany CKD. The use of SGLT2i is not yet approved in children. However, no pathophysiological clues theoretically exclude their application. The hallmark of pediatric CKD is the inevitable imbalance between the metabolic needs of a growing child and the functional capacity of a failing kidney to handle those needs. In this view, developing better strategies to address any modifiable progressor in kidney disease is mandatory, especially considering the long lifespan typical of the pediatric population. By improving the hemodynamic adaptation of the kidney and providing additional beneficial effects on the overall complications of CKD, SGLT2i is a candidate as a potentially innovative drug for the treatment of CKD and glomerular diseases in children.

Altered Serum Uric Acid Levels in Kidney Disorders

Serum uric acid levels are altered by kidney disorders because the kidneys play a dominant role in uric acid excretion. Here, major kidney disorders which accompany hyperuricemia or hypouricemia, including their pathophysiology, are discussed. Chronic kidney disease (CKD) and hyperuricemia are frequently associated, but recent clinical trials have not supported the pathogenic roles of hyperuricemia in CKD incidence and progression. Diabetes mellitus (DM) is often associated with hyperuricemia, and hyperuricemia may be associated with an increased risk of diabetic kidney disease in patients with type 2 DM. Sodium-glucose cotransporter 2 inhibitors have a uricosuric effect and can relieve hyperuricemia in DM. Autosomal dominant tubulointerstitial kidney disease (ADTKD) is an important hereditary kidney disease, mainly caused by mutations of uromodulin (UMOD) or mucin-1 (MUC-1). Hyperuricemia and gout are the major clinical manifestations of ADTKD-UMOD and ADTKD-MUC1. Renal hypouricemia is caused by URAT1 or GLUT9 loss-of-function mutations and renders patients susceptible to exercise-induced acute kidney injury, probably because of excessive urinary uric acid excretion. Hypouricemia derived from renal uric acid wasting is a component of Fanconi syndrome, which can be hereditary or acquired. During treatment for human immunodeficiency virus, hepatitis B or cytomegalovirus, tenofovir, adefovir, and cidofovir may cause drug-induced renal Fanconi syndrome. In coronavirus disease 2019, hypouricemia due to proximal tubular injury is related to disease severity, including respiratory failure. Finally, serum uric acid and the fractional excretion of uric acid are indicative of plasma volume status; hyperuricemia caused by the enhanced uric acid reabsorption can be induced by volume depletion, and hypouricemia caused by an increased fractional excretion of uric acid is the characteristic finding in syndromes of inappropriate anti-diuresis, cerebral/renal salt wasting, and thiazide-induced hyponatremia. Molecular mechanisms by which uric acid transport is dysregulated in volume or water balance disorders need to be investigated.

Responses in Blood Pressure and Kidney Function to Soluble Guanylyl Cyclase Stimulation or Activation in Normal and Diabetic Rats

Introduction:

Agonists of soluble guanylate cyclase (sGC) are being developed as treatment for cardiovascular disease. Most effects of nitric oxide (NO) on glomerular and tubular function are mediated through sGC but whether sGC agonists mimic these effects is unknown.

Methods:

Renal clearance and micropuncture studies were performed in Wistar-Froemter rats (WF), with or without streptozotocin diabetes (STZ-WF), and in Goto-Kakizaki rats (GK) with mild type-2 diabetes to test for acute effects of the sGC “stimulator” BAY 41-2272, which synergizes with endogenous NO, and the “activator” runcaciguat, which generates cGMP independent of NO.

Results:

Both sGC agonists reduced arterial blood pressure (MAP). For MAP reductions <10% the drugs increased GFR in WF and STZ-WF but not in GK. Larger MAP reductions outweighed this effect and GFR declined, with better preserved GFR in STZ-WF. Changes in GFR could not be accounted for by changes in RBF, suggesting parallel changes in ultrafiltration pressure and/or ultrafiltration coefficient. The doses chosen for micropuncture in WF and GK reduced MAP by 2–10% and the net effect on single nephron GFR and ultrafiltration pressure was neutral. Effects of the drugs on tubular reabsorption were dominated by declining MAP and no natriuretic effect observed at any dose.

Discussion/Conclusion:

sGC agonists impact kidney function directly and because they reduce MAP. The direct tendency to increase GFR is most apparent for MAP reductions <10%. The direct effect is otherwise subtle and overridden when MAP declines more. Effects of sGC agonists on tubular reabsorption are dominated by effects on MAP.

Renoprotective Effects of SGLT2 Inhibitors

SGLT2 inhibitors can protect the kidneys of patients with and without type 2 diabetes from failing. This includes blood glucose dependent and independent mechanisms. SGLT2 inhibitors lower glomerular pressure and filtration, thereby reducing the physical stress on the filtration barrier and the oxygen demand for tubular reabsorption. This improves cortical oxygenation, which, together with lesser tubular glucotoxicity and improved mitochondrial function and autophagy, can reduce proinflammatory and profibrotic signaling and preserve tubular function and GFR in long term. By shifting transport downstream, SGLT2 inhibitors may mimic systemic hypoxia and stimulate erythropoiesis, which improves oxygen delivery to the kidney and other organs.

Sodium-glucose cotransporter 1 inhibition and gout: Mendelian randomisation study

OBJECTIVE

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) reduce serum urate, but their efficacy depends on renal function which is often impaired in people with gout. SGLT1 is primarily expressed in the small intestine and its inhibition may be a more suitable therapeutic target. We aimed to investigate the association of genetically proxied SGLT1i with gout risk, serum urate levels and cardiovascular safety using Mendelian randomisation (MR).

METHODS

Leveraging data from a genome-wide association study of 344,182 individuals in the UK Biobank, we identified a missense variant in the SLC5A1 gene that associated with glycated haemoglobin (HbA1c) to proxy SGLT1i. Outcome genetic data comprised 13,179 gout cases and 750,634 controls, 457,690 individuals for serum urate levels, and up to 977,323 individuals for cardiovascular safety outcomes. We applied the Wald ratio method and investigated potential genetic confounding using colocalization.

RESULTS

The rs17683430 missense variant was selected to instrument SGLT1i. Genetically proxied SGLT1i was associated with 75% reduction in gout risk (OR 0.25; 95%CI 0.06, 0.99; p = 0.048) and 32.0 μmol/L reduction in serum urate (95%CI -56.7, -7.3; p = 0.01), per 6.7 mmol/mol reduction in HbA1c. SGLT1i was associated with increased levels of low-density lipoprotein cholesterol (0.37 mmol/L; 95%CI 0.17, 0.56; p = 0.0002) but not risk of coronary heart disease, stroke, or chronic kidney disease. Colocalization did not suggest that results are attributable to genetic confounding.

CONCLUSION

SGLT1 inhibition may represent a novel therapeutic option for preventing gout in people with or without comorbid diabetes. Randomised trials are needed to formally investigate efficacy and safety.

SGLT2 inhibitors improve kidney function and morphology by regulating renal metabolic reprogramming in mice with diabetic kidney disease

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease (ESRD) worldwide. SGLT2 inhibitors are clinically effective in halting DKD progression. However, the underlying mechanisms remain unclear. The serum and kidneys of mice with DKD were analyzed using liquid chromatography with tandem mass spectrometry (LC–MS/MS)-based metabolomic and proteomic analyses. Three groups were established: placebo-treated littermate db/m mice, placebo-treated db/db mice and EMPA-treated db/db mice. Empagliflozin (EMPA) and placebo (10 mg/kg/d) were administered for 12 weeks. EMPA treatment decreased Cys-C and urinary albumin excretion compared with placebo by 78.60% and 57.12%, respectively (p < 0.001 in all cases). Renal glomerular area, interstitial fibrosis and glomerulosclerosis were decreased by 16.47%, 68.50% and 62.82%, respectively (p < 0.05 in all cases). Multi-omic analysis revealed that EMPA treatment altered the protein and metabolic profiles in the db/db group, including 32 renal proteins, 51 serum proteins, 94 renal metabolites and 37 serum metabolites. Five EMPA-related metabolic pathways were identified by integrating proteomic and metabolomic analyses, which are involved in renal purine metabolism; pyrimidine metabolism; tryptophan metabolism; nicotinate and nicotinamide metabolism, and glycine, serine and threonine metabolism in serum. In conclusion, this study demonstrated metabolic reprogramming in mice with DKD. EMPA treatment improved kidney function and morphology by regulating metabolic reprogramming, including regulation of renal reductive stress, alleviation of mitochondrial dysfunction and reduction in renal oxidative stress reaction.

Sodium-Glucose Cotransporter-2 Inhibitors Could Help Delay Renal Impairment in Patients with Type 2 Diabetes: A Real-World Clinical Setting

This study compared the renoprotective effects of sodium−glucose cotransporter-2 (SGLT2) inhibitors and dipeptidyl peptidase-4 (DPP-4) inhibitors in patients with type 2 diabetes mellitus (T2DM). We performed a retrospective cohort study using electronic medical records of patients with T2DM. The primary outcome was the first occurrence of an estimated glomerular filtration rate (eGFR) <45 mL/min/1.73 m2 after the index date. We analyzed changes in repeatedly measured laboratory data, such as eGFR and serum uric acid (SUA). We included 2396 patients (1198 patients in each group) in the present study. The rate of renal events was significantly lower in the SGLT2 inhibitors group than that in the DPP-4 inhibitors group (hazard ratio, 0.46; 95% CI, 0.29 to 0.72; p = 0.0007). The annual mean change in the eGFR was significantly smaller in the SGLT2 inhibitors group than that in the DPP-4 inhibitors group, with a between-group difference of 0.86 ± 0.18 mL/min/1.73 m2 per year (95% CI, 0.49 to 1.23; p < 0.0001). Moreover, the mean change in SUA was lower in the SGLT2 inhibitors group. Considering the lower incidence of renal impairment, the slower decline in eGFR, and reduced SUA, SGLT2 inhibitors could help delay renal impairment in patients with T2DM.

A Description of Acute Renal Failure and Nephrolithiasis Associated With Sodium–Glucose Co-Transporter 2 Inhibitor Use: A VigiBase Study

Background: The Food and Drug Administration issued a warning on the risk of acute kidney injury and a signal of nephrolithiasis for patients using sodium–glucose co-transporter 2 inhibitors (SGLT2i). We performed a descriptive analysis on acute renal failure (ARF) and nephrolithiasis cases reported to SGLT2i in the VigiBase^®, in the scope of characterizing the patients and reactions and to report on the disproportionality analysis.

Methods: We analyzed all ARF and nephrolithiasis reports for SGLT2i in VigiBase from inception to September 2021. ARF cases were defined as reports containing at least one of the preferred terms (PTs) included in the ARF narrow Medical Dictionary for Regulatory Activities Standardised Queries (MedDRA SMQ). SGLT2i exposure was considered for reports with at least one gliflozin as a suspected/interacting drug. We characterized the patients, reporters, and reactions, and we present the proportional reporting ratio (PRR).

Results: Of 27,370,413 total reports in VigiBase, we found 3,972 ARF reactions to gliflozins as suspected/interacting drugs in 3,751 patients and 231 nephrolithiasis reactions in 227 patients. Most cases were reported from American regions (3057; 81.49%), for patients of age group 45–64 years (1590; 59%). About 30% (1156) of the ARF reports were registered in 2018, most from spontaneous reporting, and from consumers followed by healthcare professionals (2,235; 61% and 1440; 38%, respectively). Canagliflozin was the most involved gliflozin in the ARF and nephrolithiasis cases (2,640; 67% and 109; 47%, respectively). The great majority of ARF and nephrolithiasis reports were serious (3,761; 95% and 182; 79%, respectively). Of the total ARF cases reported, 51 had fatal outcome, while 152 had not recovered/not resolved outcome. No fatal outcome was reported for nephrolithiasis. Disproportionality analysis in full database showed a PRR of 4.68 (95% CI 4.53–4.83) for all gliflozins–ARF and a PRR of 3.44 (95% CI 3.00–3.95) for all gliflozins–nephrolithiasis.

Conclusion: Most of ARF reports associated with gliflozins were serious, with an important number of cases with fatal outcome. A drug safety signal was found between ARF narrow SMQ and gliflozins. Also, gliflozins were associated with an increase in the proportion of nephrolithiasis reports compared to other medications.

Empagliflozin and Decreased Risk of Nephrolithiasis: A Potential New Role for SGLT2 Inhibition?

CONTEXT

Diabetes mellitus is a risk factor for nephrolithiasis. A recent observational study found that in patients with type 2 diabetes (T2D), SGLT2 inhibitor use was associated with a 49% lower risk of nephrolithiasis compared with GLP-1 receptor agonists.

OBJECTIVE

We examined the association between nephrolithiasis and the SGLT2 inhibitor empagliflozin, using existing data from randomized clinical trials.

METHODS

We pooled data from 15 081 T2D patients randomized to empagliflozin (n = 10 177) or placebo (n = 4904) from 20 phase I-IV trials, including the large cardiovascular outcome trial, EMPA-REG OUTCOME. Incident urinary tract stone events were captured using a predefined collection of MedRA terms. A sensitivity analysis using a narrower definition was also performed. Incidence rate ratios (IRR) and 95% CIs were calculated using the relative risk estimate, stratified by study.

RESULTS

The median exposures to study drug were 543 days (placebo) and 549 days (empagliflozin); 183 patients experienced an incident urolithiasis during follow-up (placebo, 79; empagliflozin, 104), yielding annual incidence rates of 1.01 vs 0.63 events/100 patient-years in the 2 respective groups. The IRR was 0.64 (95% CI, 0.48-0.86), in favor of empagliflozin. In the sensitivity analysis, the results were similar (IRR, 0.62 [95% CI, 0.45-0.85]).

CONCLUSION

Compared with placebo, empagliflozin therapy was associated with an approximate 40% reduced risk of urinary tract stone events in T2D patients. The underlying mechanisms are unknown but may involve altered lithogenic profile of the urine. Dedicated randomized prospective clinical trials are warranted to confirm these initial observations in patients with and without T2D.

Dapagliflozin reduces uric acid concentration, an independent predictor of adverse outcomes in DAPA-HF

AIMS

Blood uric acid (UA) levels are frequently elevated in patients with heart failure and reduced ejection fraction (HFrEF), may lead to gout and are associated with worse outcomes. Reduction in UA is desirable in HFrEF and sodium-glucose cotransporter 2 inhibitors may have this effect. We aimed to examine the association between UA and outcomes, the effect of dapagliflozin according to baseline UA level, and the effect of dapagliflozin on UA in patients with HFrEF in the DAPA-HF trial.

METHODS AND RESULTS

The association between UA and the primary composite outcome of cardiovascular death or worsening heart failure, its components, and all-cause mortality was examined using Cox regression analyses among 3119 patients using tertiles of UA, after adjustment for other prognostic variables. Change in UA from baseline over 12 months was also evaluated. Patients in tertile 3 (UA ≥6.8 mg/dl) versus tertile 1 (<5.4 mg/dl) were younger (66.3 ± 10.8 vs. 68 ± 10.2 years), more often male (83.1% vs. 71.5%), had lower estimated glomerular filtration rate (58.2 ± 17.4 vs. 70.6 ± 18.7 ml/min/1.73 m2 ), and more often treated with diuretics. Higher UA was associated with a greater risk of the primary outcome (adjusted hazard ratio tertile 3 vs. tertile 1: 1.32, 95% confidence interval [CI] 1.06-1.66; p = 0.01). The risk of heart failure hospitalization and cardiovascular death increased by 7% and 6%, respectively per 1 mg/dl unit increase of UA (p = 0.04 and p = 0.07). Spline analysis revealed a linear increase in risk above a cut-off UA value of 7.09 mg/dl. Compared with placebo, dapagliflozin reduced UA by 0.84 mg/dl (95% CI -0.93 to -0.74) over 12 months (p < 0.001). Dapagliflozin improved outcomes, irrespective of baseline UA concentration.

CONCLUSION

Uric acid remains an independent predictor of worse outcomes in a well-treated contemporary HFrEF population. Compared with placebo, dapagliflozin reduced UA and improved outcomes irrespective of UA concentration.

The differential effects of ertugliflozin on glucosuria and natriuresis biomarkers: Prespecified analyses from VERTIS CV

AIMS

This prespecified exploratory analyses from VERTIS CV (NCT01986881) aimed to assess the effects of the sodium-glucose cotransporter-2 (SGLT2) inhibitor ertugliflozin on glucosuria-related (glycated haemoglobin [HbA1c], uric acid, body weight) and natriuresis-related (blood pressure, haemoglobin, haematocrit, serum albumin) biomarkers according to kidney function risk category.

MATERIALS AND METHODS

Patients with type 2 diabetes and atherosclerotic cardiovascular disease were randomized to placebo, ertugliflozin 5 mg, or ertugliflozin 15 mg (1:1:1). Analyses compared placebo (n = 2747) versus ertugliflozin (pooled; n = 5499) on glucosuria- and natriuresis-related biomarkers according to baseline estimated glomerular filtration rate (eGFR) subgroup and Kidney Disease: Improving Global Outcomes in Chronic Kidney Disease (KDIGO CKD) risk category.

RESULTS

Patients were classified according to KDIGO CKD low- (49%), moderate- (32%) and high-/very-high-risk categories (19%), and eGFR groups 1 (25%), 2 (53%) and 3 (19%). At Week 18, the high-/very-high-risk category had a smaller placebo-subtracted least squares mean (LSM) change from baseline (95% confidence interval) in HbA1c (-0.34 [-0.43, -0.25]) compared with the low- and moderate-risk categories (-0.54 [-0.60, -0.49] and - 0.47 [-0.54, -0.40], respectively). This pattern was maintained throughout the study (P_interaction  = 0.0001). Similar patterns based on baseline eGFR G stage were observed. Placebo-subtracted LSM changes from baseline in uric acid were lowest in the high-/very-high-risk category at Weeks 6 and 18, but the pattern was not maintained after Week 156 (P_interaction  = 0.15). Effects of ertugliflozin on body weight and natriuresis-related biomarkers did not differ across KDIGO CKD categories.

CONCLUSIONS

In VERTIS CV, ertugliflozin was associated with physiologically favourable changes in glucosuria- and natriuresis-related biomarkers. Glycaemic efficacy of ertugliflozin was attenuated in patients with higher chronic kidney disease (CKD) risk. Effects on other biomarkers were consistent, regardless of CKD risk stage.

Pharmacokinetics, Mass Balance, and Metabolism of the Novel Urate Transporter 1 Inhibitor [14C]HR011303 in Humans: Metabolism Is Mediated Predominantly by UDP-Glucuronosyltransferase

HR011303, a promising selective urate transporter 1 inhibitor, is currently being studied in a phase III clinical trial in China for the treatment of hyperuricemia and gout. In the current study, the pharmacokinetics, mass balance, and metabolism of HR011303 were examined in six healthy Chinese male subjects who received a single oral dose of 10 mg of [14C]HR011303 (80 µCi). The results showed that HR011303 was rapidly absorbed with a median time to reach C max of 1.50 hours postdose, and the arithmetic mean half-life of total radioactivity was approximately 24.2 hours in plasma. The mean blood-to-plasma radioactivity concentration ratio was 0.66, suggesting the preferential distribution of drug-related components in plasma. At 216 hours postdose, the mean cumulative excreted radioactivity was 91.75% of the dose, including 81.50% in urine and 10.26% in feces. Six metabolites were identified, and the parent drug HR011303 was the most abundant component in plasma and feces, but a minor component in urine. Glucuronidation of the carboxylic acid moiety of HR011303 was the primary metabolic pathway in humans, amounting to 69.63% of the dose (M5, 51.57% of the dose; M5/2, 18.06% of the dose) in the urine; however, it was not detected in plasma. UDP-glucuronosyltransferase (UGT) 2B7 was responsible for the formation of M5. Overall, after a single oral dose of 10 mg of [14C]HR011303 (80 µCi), HR011303 and its main metabolites were eliminated via renal excretion. The major metabolic pathway was carboxylic acid glucuronidation, which was catalyzed predominantly by UGT2B7. SIGNIFICANCE STATEMENT: This study determined the absorption and disposition of HR011303, a selective urate transporter (URAT) 1 inhibitor currently in development for the treatment of hyperuricemia and gout. This work helps to characterize the major metabolic pathways of new URAT inhibitors and identify the absorption and clearance mechanism.

The Pathophysiological Basis of Diabetic Kidney Protection by Inhibition of SGLT2 and SGLT1

SGLT2 inhibitors can protect the kidneys of patients with and without type 2 diabetes mellitus and slow the progression towards end-stage kidney disease. Blocking tubular SGLT2 and spilling glucose into the urine, which triggers a metabolic counter-regulation similar to fasting, provides unique benefits, not only as an anti-hyperglycemic strategy. These include a low hypoglycemia risk and a shift from carbohydrate to lipid utilization and mild ketogenesis, thereby reducing body weight and providing an additional energy source. SGLT2 inhibitors counteract hyperreabsorption in the early proximal tubule, which acutely lowers glomerular pressure and filtration and thereby reduces the physical stress on the filtration barrier, the filtration of tubule-toxic compounds, and the oxygen demand for tubular reabsorption. This improves cortical oxygenation, which, together with lesser tubular gluco-toxicity and improved mitochondrial function and autophagy, can reduce pro-inflammatory, pro-senescence, and pro-fibrotic signaling and preserve tubular function and GFR in the long-term. By shifting transport downstream, SGLT2 inhibitors more equally distribute the transport burden along the nephron and may mimic systemic hypoxia to stimulate erythropoiesis, which improves oxygen delivery to the kidney and other organs. SGLT1 inhibition improves glucose homeostasis by delaying intestinal glucose absorption and by increasing the release of gastrointestinal incretins. Combined SGLT1 and SGLT2 inhibition has additive effects on renal glucose excretion and blood glucose control. SGLT1 in the macula densa senses luminal glucose, which affects glomerular hemodynamics and has implications for blood pressure control. More studies are needed to better define the therapeutic potential of SGLT1 inhibition to protect the kidney, alone or in combination with SGLT2 inhibition.

An Overview of the Cardiorenal Protective Mechanisms of SGLT2 Inhibitors

Sodium-glucose co-transporter 2 (SGLT2) inhibitors block glucose reabsorption in the renal proximal tubule, an insulin-independent mechanism that plays a critical role in glycemic regulation in diabetes. In addition to their glucose-lowering effects, SGLT2 inhibitors prevent both renal damage and the onset of chronic kidney disease and cardiovascular events, in particular heart failure with both reduced and preserved ejection fraction. These unexpected benefits prompted changes in treatment guidelines and scientific interest in the underlying mechanisms. Aside from the target effects of SGLT2 inhibition, a wide spectrum of beneficial actions is described for the kidney and the heart, even though the cardiac tissue does not express SGLT2 channels. Correction of cardiorenal risk factors, metabolic adjustments ameliorating myocardial substrate utilization, and optimization of ventricular loading conditions through effects on diuresis, natriuresis, and vascular function appear to be the main underlying mechanisms for the observed cardiorenal protection. Additional clinical advantages associated with using SGLT2 inhibitors are antifibrotic effects due to correction of inflammation and oxidative stress, modulation of mitochondrial function, and autophagy. Much research is required to understand the numerous and complex pathways involved in SGLT2 inhibition. This review summarizes the current known mechanisms of SGLT2-mediated cardiorenal protection.

SGLT2 Inhibition and Uric Acid Excretion in Patients with Type 2 Diabetes and Normal Kidney Function

Background and objectives: Sodium glucose transporter 2 (SGLT2)-inhibitor-induced uric acid lowering may contribute to kidney protective effects of the drug-class in people with type 2 diabetes. This study investigates mechanisms of plasma uric acid lowering by SGLT2-inhibitors in people with type 2 diabetes with a focus on urate transporter (URAT)1. Methods: We conducted an analysis of two randomized, clinical trials. First, in the Renoprotective Effects of Dapagliflozin in Type 2 Diabetes (RED) study, 44 people with type 2 diabetes were randomized to dapagliflozin or gliclazide for 12 weeks. Plasma uric acid, fractional uric acid excretion and hemodynamic kidney function were measured in the fasted state and during clamped eu- or hyperglycemia. Second, in the Uric Acid Excretion study (UREX) study, 10 people with type 2 diabetes received 1-week empagliflozin, benzbromarone and their combination in a cross-over design and effects on plasma uric acid, fractional uric acid excretion and 24-hr uric acid excretion were measured. Results: In the RED study, compared to the fasted state (5.3±1.1mg/dL), acute hyperinsulinemia and hyperglycemia significantly reduced plasma uric acid by 0.2±0.3 and 0.4±0.3 mg/dL (both p<0.001), while increasing fractional uric acid excretion (by 3.2±3.1% and 8.9±4.5% respectively (both p<0.001). Dapagliflozin reduced plasma uric acid by 0.8±0.8mg/dL, 1.0±1.0mg/dL and by 0.8±0.7mg/dL during fasting, hyperinsulinemic-euglycemic and hyperglycemic conditions (p<0.001), whereas fractional uric acid excretion in 24-hr urine increased by 3.0±2.1% (p<0.001) and 2.6±4.5% during hyperinsulinemic-euglycemic conditions (p=0.003). Fractional uric acid excretion strongly correlated to fractional glucose excretion (r= 0.35, p=0.02). In the UREX study, empagliflozin and benzbromarone both significantly reduced plasma uric acid and increased fractional uric acid excretion. Effects of combination therapy did not differ from benzbromarone monotherapy. Conclusion: In conclusion, SGLT2-inhibitors induce uric acid excretion, which is strongly linked to urinary glucose excretion and which is attenuated during concomitant pharmacological blockade of URAT1.

Sodium Glucose Cotransporter-2 Inhibitors: Spotlight on Favorable Effects on Clinical Outcomes beyond Diabetes

Sodium glucose transporter type 2 (SGLT2) molecules are found in proximal tubules of the kidney, and perhaps in the brain or intestine, but rarely in any other tissue. However, their inhibitors, intended to improve diabetes compensation, have many more beneficial effects. They improve kidney and cardiovascular outcomes and decrease mortality. These benefits are not limited to diabetics but were also found in non-diabetic individuals. The pathophysiological pathways underlying the treatment success have been investigated in both clinical and experimental studies. There have been numerous excellent reviews, but these were mostly restricted to limited aspects of the knowledge. The aim of this review is to summarize the known experimental and clinical evidence of SGLT2 inhibitors' effects on individual organs (kidney, heart, liver, etc.), as well as the systemic changes that lead to an improvement in clinical outcomes.

Extending the ambit of SGLT2 inhibitors beyond diabetes: a review of clinical and preclinical studies on non-diabetic kidney disease

BACKGROUND

Sodium-glucose cotransporter-2 inhibitors (SGLT2i) are novel antidiabetic agents with overwhelming cardiorenal protection. Recent trials focusing on the nephroprotective role of SGLT2i have underscored its success as a phenomenal agent in halting the progression of kidney disease in patients with and without Type 2 diabetes mellitus. Multitudes of pleiotropic effects on tubules have raised hopes for reasonable nephroprotection beyond the purview of the hyperglycemic milieu.

AREA COVERED

This review summarizes various animal and human data as evidence for the utility of SGLT2i in non-diabetic chronic kidney disease (CKD). Web-based medical database entries were searched. On the premise of existing evidence, we have discussed mechanisms likely contributing to nephroprotection by SGLT2i in patients with non-diabetic CKD.

EXPERT OPINION

Further elucidation of mechanisms of nephroprotection offered by SGLT2i is required to extend its use as a nephroprotective agent. The use of non-traditional markers of kidney damage in future studies would improve the evaluation of their role in attenuating CKD progression. Emerging animal data support the early use of SGLT2i in states of modest proteinuria for superior outcomes. Future long-term trials in patients should aim to address the time of intervention with SGLT2i during the natural disease course of CKD for best outcomes.

Renal Tubular Handling of Glucose and Fructose in Health and Disease

The proximal tubule of the kidney is programmed to reabsorb all filtered glucose and fructose. Glucose is taken up by apical sodium-glucose cotransporters SGLT2 and SGLT1 whereas SGLT5 and potentially SGLT4 and GLUT5 have been implicated in apical fructose uptake. The glucose taken up by the proximal tubule is typically not metabolized but leaves via the basolateral facilitative glucose transporter GLUT2 and is returned to the systemic circulation or used as an energy source by distal tubular segments after basolateral uptake via GLUT1. The proximal tubule generates new glucose in metabolic acidosis and the postabsorptive phase, and fructose serves as an important substrate. In fact, under physiological conditions and intake, fructose taken up by proximal tubules is primarily utilized for gluconeogenesis. In the diabetic kidney, glucose is retained and gluconeogenesis enhanced, the latter in part driven by fructose. This is maladaptive as it sustains hyperglycemia. Moreover, renal glucose retention is coupled to sodium retention through SGLT2 and SGLT1, which induces secondary deleterious effects. SGLT2 inhibitors are new anti-hyperglycemic drugs that can protect the kidneys and heart from failing independent of kidney function and diabetes. Dietary excess of fructose also induces tubular injury. This can be magnified by kidney formation of fructose under pathological conditions. Fructose metabolism is linked to urate formation, which partially accounts for fructose-induced tubular injury, inflammation, and hemodynamic alterations. Fructose metabolism favors glycolysis over mitochondrial respiration as urate suppresses aconitase in the tricarboxylic acid cycle, and has been linked to potentially detrimental aerobic glycolysis (Warburg effect). © 2022 American Physiological Society. Compr Physiol 12:2995-3044, 2022.

Dapagliflozin and xanthine oxidase inhibitors improve insulin resistance and modulate renal glucose and urate transport in metabolic syndrome

Disturbance in glucose and uric acid metabolism is the major disorder of metabolic syndrome (MetS). The kidneys play an important role in the management of glucose and uric acid. The aim of our study was to investigate alterations in renal glucose and uric acid transporters in animals with MetS after treatment with dapagliflozin and xanthine oxidase inhibitors (allopurinol and febuxostat). Sprague-Dawley rats were fed normal chow or a high fructose diet for the first 3 months. The fructose-fed animals were then treated with dapagliflozin, allopurinol, febuxostat, or no treatment for the next 3 months. Fasting glucose, insulin resistance, and hyperuricaemia were improved in all treatment groups except that in the fructose group (all p < 0.05). Both allopurinol and febuxostat reversed the increase in levels of sodium glucose cotransporter (SGLT) 1, SGLT2, and glucose transporter (GLUT) 2 (all p < 0.05). Dapagliflozin alleviated hyperuricaemia and induced uricosuria without affecting serum xanthine oxidase activity. Dapagliflozin suppressed the expression of GLUT9, urate transporter, and urate anion exchanger 1 (all p < 0.05), which was similar to the effects of allopurinol and febuxostat. The results suggest that treatment with dapagliflozin and xanthine oxidase inhibitors improved insulin resistance and reversed the increased expression of glucose and urate transporters in the kidney.

URAT1-selective inhibition ameliorates insulin resistance by attenuating diet-induced hepatic steatosis and brown adipose tissue whitening in mice

Objective

Accumulating evidence indicates that high uric acid (UA) is strongly associated with obesity and metabolic syndrome and drives the development of nonalcoholic fatty liver disease (NAFLD) and insulin resistance. Although urate transporter-1 (URAT1), which is primarily expressed in the kidneys, plays a critical role in the development of hyperuricemia, its pathophysiological implication in NAFLD and insulin resistance remains unclear. We herein investigated the role and functional significance of URAT1 in diet-induced obese mice.

Methods

Mice fed a high-fat diet (HFD) for 16–18 weeks or a normal-fat diet (NFD) were treated with or without a novel oral URAT1-selective inhibitor (dotinurad [50 mg/kg/day]) for another 4 weeks.

Results

We found that URAT1 was also expressed in the liver and brown adipose tissue (BAT) other than the kidneys. Dotinurad administration significantly ameliorated HFD-induced obesity and insulin resistance. HFD markedly induced NAFLD, which was characterized by severe hepatic steatosis as well as the elevation of serum ALT activity and tissue inflammatory cytokine genes (chemokine ligand 2 (Ccl2) and tissue necrosis factor α (TNFα)), all of which were attenuated by dotinurad. Similarly, HFD significantly increased URAT1 expression in BAT, resulting in lipid accumulation (whitening of BAT), and increased the production of tissue reactive oxygen species (ROS), which were reduced by dotinurad via UCP1 activation.

Conclusions

In conclusion, a novel URAT1-selective inhibitor, dotinurad, ameliorates insulin resistance by attenuating hepatic steatosis and promoting rebrowning of lipid-rich BAT in HFD-induced obese mice. URAT1 serves as a key regulator of the pathophysiology of metabolic syndrome and may be a new therapeutic target for insulin-resistant individuals, particularly those with concomitant NAFLD.

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URAT1 is expressed in the liver and brown adipose tissue other than in the kidneys.

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URAT1-selective inhibitor ameliorates HFD-induced insulin resistance.

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URAT1-selective inhibitor improves NAFLD through the inhibition of Ccl2 and TNFα.

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URAT1-selective inhibitor promotes rebrowning of HFD-induced lipid-rich BAT.

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URAT1 serves as a key regulator of the pathophysiology of metabolic syndrome.

Urate transport in health and disease

Circulation of urate levels is determined by the balance between urate production and excretion, homeostasis regulated by the function of urate transporters in key epithelial tissues and cell types. Our understanding of these physiological processes and identification of the genes encoding the urate transporters has advanced significantly, leading to a greater ability to predict risk for urate-associated diseases and identify new therapeutics that directly target urate transport. Here, we review the identified urate transporters and their organization and function in the renal tubule, the intestinal enterocytes, and other important cell types to provide a fuller understanding of the complicated process of urate homeostasis and its role in human diseases. Furthermore, we review the genetic tools that provide an unbiased catalyst for transporter identification as well as discuss the role of transporters in determining the observed significant gender differences in urate-associated disease risk.

Association of Sodium-Glucose Transport Protein 2 Inhibitor Use for Type 2 Diabetes and Incidence of Gout in Taiwan

IMPORTANCE

The use of sodium-glucose transport protein 2 (SGLT2) inhibitors is currently a standard intervention in patients with type 2 diabetes (T2DM) and exerts favorable pleiotropic effects to consistently lower blood urate levels. However, to date, no association between SGLT2 inhibitor use and the incidence of gout have been established.

OBJECTIVE

To investigate whether prescribed SGLT2 inhibitors are associated with lower gout incidence in patients with T2DM.

DESIGN, SETTING, AND PARTICIPANTS

In a cohort study, all patients with incident T2DM in Taiwan National Health Institution databases between May 1, 2016, and December 31, 2018, were retrospectively analyzed. As a comparator, patients using dipeptidyl peptidase 4 (DPP4) inhibitors were included. A total of 47 905 individuals receiving an SGLT2 inhibitor and 183 303 receiving a DPP4 inhibitor were evaluated, along with 47 405 pairs of patients using an SGLT2 inhibitor or DPP4 inhibitor in 1:1 propensity score-matched analyses. Data analysis was conducted from April 1 to June 30, 2021.

MAIN OUTCOMES AND MEASURES

A gout diagnosis was based on the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) and the International Statistical Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM). Multiple Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and 95% CIs.

RESULTS

In total, 231 208 patients with T2DM were included in the population; 113 812 individuals (49.22%) were women, and the mean (SD) age was 61.53 (12.86) years. The overall gout incidence was 20.26 per 1000 patient-years for SGLT2 inhibitor users and 24.30 per 1000 patient-years for DPP4 inhibitor users. When potential risk factors were adjusted in the propensity score-matched population, use of SGLT2 inhibitors was associated with a lower risk of gout (HR, 0.89; 95% CI, 0.82-0.96) compared with DPP4 inhibitors, particularly for patients receiving dapagliflozin (HR, 0.86; 95% CI, 0.78-0.95). A sensitivity analysis, performed when a gout diagnosis was ascertained using the ICD-9-CM or ICD-10-CM code with gout-related medication, also showed a significantly lower risk for gout incidence of 15% with SGLT2 inhibitors (HR, 0.85; 95% CI, 0.74-0.97). Subgroup analysis indicated that SGLT2 inhibitor benefits in patients with T2DM to achieve a lower gout risk were not different across subgroups.

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that patients with T2DM who are receiving SGLT2 inhibitors may have a lower risk for gout compared with those receiving DPP4 inhibitors.

Hypouricemic Effects of Chrysanthemum indicum L. and Cornus officinalis on Hyperuricemia-Induced HepG2 Cells, Renal Cells, and Mice

Hyperuricemia, abnormally excess accumulation of uric acid, is caused by an imbalance between the production and excretion of uric acid and is a major cause of gout. We compared the effects of extracts from Chrysanthemum indicum L. (Ci) and Cornus officinalis Siebold and Zucc. (Co) on hyperuricemia, both individually and in combination (FSU-CC), using hypoxanthine-treated human liver cancer (HepG2) cells, primary mouse renal proximal tubule cells, and potassium oxonate induced hyperuricemic mice. The Ci contained 7.62 mg/g luteolin and 0 mg/g loganin, Co contained 0 mg/g luteolin and 4.90 mg/g loganin, and FSH-CC contained 3.95 mg/g luteolin and 2.48 mg/g loganin. We found that treatment with Ci, Co, and FSU-CC suppressed the activity of xanthine oxidase and mRNA expression of xanthine dehydrogenase while inducing an increase in the expression levels of the organic anion transporter 1 (OAT1) and organic anion transporter 3 (OAT3) proteins and a decrease in the expression levels of glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1) proteins. Particularly, treatment and supplementation with FSU-CC showed stronger effects than those of supplementation with either Ci or Co alone. We observed that the excretion of creatinine and uric acid in the combination of Ci and Co was higher than that observed in their individual supplementations and was similar to that of the normal group. Therefore, our data suggest that a combination of Ci and Co may potentially be used for the development of effective natural anti-hyperuricemic functional foods.

A Role for SGLT-2 Inhibitors in Treating Non-diabetic Chronic Kidney Disease

In recent years, inhibitors of the sodium-glucose co-transporter 2 (SGLT2 inhibitors) have been shown to have significant protective effects on the kidney and the cardiovascular system in patients with diabetes. This effect is also manifested in chronic kidney disease (CKD) patients and is minimally due to improved glycaemic control. Starting from these positive findings, SGLT2 inhibitors have also been tested in patients with non-diabetic CKD or heart failure with reduced ejection fraction. Recently, the DAPA-CKD trial showed a significantly lower risk of CKD progression or death from renal or cardiovascular causes in a mixed population of patients with diabetic and non-diabetic CKD receiving dapagliflozin in comparison with placebo. In patients with heart failure and reduced ejection fraction, two trials (EMPEROR-Reduced and DAPA-HF) also found a significantly lower risk of reaching the secondary renal endpoint in those treated with an SGLT2 inhibitor in comparison with placebo. This also applied to patients with CKD. Apart from their direct mechanism of action, SGLT2 inhibitors have additional effects that could be of particular interest for patients with non-diabetic CKD. Among these, SGLT2 inhibitors reduce blood pressure and serum acid uric levels and can increase hemoglobin levels. Some safety issues should be further explored in the CKD population. SGLT2 inhibitors can minimally increase potassium levels, but this has not been shown by the CREDENCE trial. They also increase magnesium and phosphate reabsorption. These effects could become more significant in patients with advanced CKD and will need monitoring when these agents are used more extensively in the CKD population. Conversely, they do not seem to increase the risk of acute kidney injury.

The Role of SGLT2 Inhibitors in Vascular Aging

Vascular aging is defined as organic and functional changes in blood vessels, in which decline in autophagy levels, DNA damage, MicroRNA (miRNA), oxidative stress, sirtuin, and apoptosis signal-regulated kinase 1 (ASK1) are integral thereto. With regard to vascular morphology, the increase in arterial stiffness, atherosclerosis, vascular calcification and high amyloid beta levels are closely related to vascular aging. Further closely related thereto, at the cellular level, is the aging of vascular endothelial cells (ECs) and vascular smooth muscle cells (VSMCs). Vascular aging seriously affects the health, economy and life of patients, but can be delayed by SGLT2 inhibitors through the improvement of vascular function. In the present article, a review is conducted of recent domestic and international progress in research on SGLT2 inhibitors,vascular aging and diseases related thereto, thereby providing theoretical support and guidance for further revealing the relationship between SGLT2 inhibitors and diseases related to vascular aging.

Factors Influencing Early Serum Uric Acid Fluctuation After Bariatric Surgery in Patients with Hyperuricemia

PURPOSE

In the short-term after bariatric surgery, the incidence of gout flare was increased. Patients with hyperuricemia are among the high-risk group of postoperative gout attacks. The drastic fluctuation of uric acid is a risk factor for gout flare. This study aimed to explore factors that influenced the magnitudes of serum uric acid (sUA) fluctuation post-surgery in patients with hyperuricemia.

MATERIALS AND METHODS

One hundred and sixty-five patients with preoperative hyperuricemia undergoing bariatric surgery were reviewed. Pre- and postoperative parameters were collected at baseline and each follow-up point. Univariable and multiple linear regression analyses were performed to explore independent factors that influenced the magnitudes of sUA change.

RESULTS

The sUA significantly declined from 489.4 ± 93.7 to 372.6 ± 101.4 μmmol/L in 1 day after surgery, then increased to 531.6 ± 175.5 μmmol/L at 1-month follow-up, and then dropped to 415.2 ± 105.6 and 396.5 ± 114.2 μmmol/L at 3-month and 6-month follow-up, respectively. Preoperative estimated glomerular filtration rate (eGFR), glycated hemoglobin (HbA1c), magnesium (Mg), sex, and the change of zinc concentration during the first month are significantly related to magnitudes of sUA fluctuation in the short-term post-surgery period. Multiple linear regression analyses showed preoperative eGFR and HbA1c independently influenced the magnitudes of sUA change at 1 day after surgery; sex, the change of zinc concentration, and HbA1c at 1-month follow-up independently influenced the magnitudes of sUA change at 1-month follow-up.

CONCLUSION

Preoperative eGFR, HbA1c, sex, and the change of zinc concentration postoperative are independent factors affecting the magnitude of the fluctuation. Large-scale studies are warranted to support these findings.

Function of Uric Acid Transporters and Their Inhibitors in Hyperuricaemia

Disorders of uric acid metabolism may be associated with pathological processes in many diseases, including diabetes mellitus, cardiovascular disease, and kidney disease. These diseases can further promote uric acid accumulation in the body, leading to a vicious cycle. Preliminary studies have proven many mechanisms such as oxidative stress, lipid metabolism disorders, and rennin angiotensin axis involving in the progression of hyperuricaemia-related diseases. However, there is still lack of effective clinical treatment for hyperuricaemia. According to previous research results, NPT1, NPT4, OAT1, OAT2, OAT3, OAT4, URAT1, GLUT9, ABCG2, PDZK1, these urate transports are closely related to serum uric acid level. Targeting at urate transporters and urate-lowering drugs can enhance our understanding of hyperuricaemia and hyperuricaemia-related diseases. This review may put forward essential references or cross references to be contributed to further elucidate traditional and novel urate-lowering drugs benefits as well as provides theoretical support for the scientific research on hyperuricemia and related diseases.

Serum Uric Acid Concentrations and Risk of Adverse Outcomes in Patients With COVID-19

BACKGROUND

Although hyperuricemia frequently associates with respiratory diseases, patients with severe coronavirus disease 2019 (COVID-19) and severe acute respiratory syndrome (SARS) can show marked hypouricemia. Previous studies on the association of serum uric acid with risk of adverse outcomes related to COVID-19 have produced contradictory results. The precise relationship between admission serum uric acid and adverse outcomes in hospitalized patients is unknown.

METHODS

Data of patients affected by laboratory-confirmed COVID-19 and admitted to Leishenshan Hospital were retrospectively analyzed. The primary outcome was composite and comprised events, such as intensive care unit (ICU) admission, mechanical ventilation, or mortality. Logistic regression analysis was performed to explore the association between serum concentrations of uric acid and the composite outcome, as well as each of its components. To determine the association between serum uric acid and in-hospital adverse outcomes, serum uric acid was also categorized by restricted cubic spline, and the 95% confidence interval (CI) was used to estimate odds ratios (OR).

RESULTS

The study cohort included 1854 patients (mean age, 58 years; 52% women). The overall mean ± SD of serum levels of uric acid was 308 ± 96 µmol/L. Among them, 95 patients were admitted to ICU, 75 patients received mechanical ventilation, and 38 died. In total, 114 patients reached composite end-points (have either ICU admission, mechanical ventilation or death) during hospitalization. Compared with a reference group with estimated baseline serum uric acid of 279-422 µmol/L, serum uric acid values ≥ 423 µmol/L were associated with an increased risk of composite outcome (OR, 2.60; 95% CI, 1.07- 6.29) and mechanical ventilation (OR, 3.01; 95% CI, 1.06- 8.51). Serum uric acid ≤ 278 µmol/L was associated with an increased risk of the composite outcome (OR, 2.07; 95% CI, 1.18- 3.65), ICU admission (OR, 2.18; 95% CI, 1.17- 4.05]), and mechanical ventilation (OR, 2.13; 95% CI, 1.06- 4.28), as assessed by multivariate analysis.

CONCLUSIONS

This study shows that the association between admission serum uric acid and composite outcome of COVID-19 patients was U-shaped. In particular, we found that compared with baseline serum uric acid levels of 279-422 µmol/L, values ≥ 423 µmol/L were associated with an increased risk of composite outcome and mechanical ventilation, whereas levels ≤ 278 µmol/L associated with increased risk of composite outcome, ICU admission and mechanical ventilation.

Dapagliflozin Added to Verinurad Plus Febuxostat Further Reduces Serum Uric Acid in Hyperuricemia: The QUARTZ Study

CONTEXT

Combining a sodium-glucose cotransporter 2 inhibitor with a xanthine oxidase inhibitor (XOI) and a urate transporter 1 (URAT1) inhibitor may enhance serum uric acid (sUA) lowering. However, concerns exist regarding high urinary UA (uUA) excretion rates and subsequent crystallization in renal tubules.

OBJECTIVE

To assess whether dapagliflozin added to verinurad, a selective URAT1 inhibitor, and febuxostat, an XOI, increases uUA excretion.

DESIGN

Randomized, placebo-controlled, 2-way crossover study (NCT03316131).

PATIENTS

Adults with asymptomatic hyperuricemia.

INTERVENTIONS

Subjects (N = 36) were randomized to oral once-daily 9 mg verinurad plus 80 mg febuxostat plus 10 mg dapagliflozin for 7 days and 7 days of oral once-daily 9 mg verinurad plus 80 mg febuxostat plus placebo with an intervening 7- to 21-day washout period.

MAIN OUTCOME MEASURE

Difference in peak uUA excretion between groups from baseline to day 7. Secondary outcomes included changes in sUA levels and 24-h uUA excretion.

RESULTS

Both regimens lowered mean peak uUA excretion (least squares mean changes from baseline: -12.9 mg/h [95% confidence interval (CI): -21.0 to -4.7], dapagliflozin; -13.2 mg/h [95% CI -21.3 to -5.0], placebo). sUA concentrations were lower with dapagliflozin (mean treatment difference -62.3 µmol/L [95% CI -82.8 to -41.8]). Dapagliflozin did not impact verinurad pharmacokinetics, its main metabolites, or febuxostat or fasting plasma glucose levels vs verinurad plus febuxostat. There were no clinically relevant changes in safety parameters.

CONCLUSIONS

Dapagliflozin further reduced sUA without influencing uUA excretion, suggesting that its combination with verinurad and febuxostat at the doses tested does not adversely affect kidney function.

CLINICAL TRIAL REGISTRATION NUMBER

NCT03316131.

Empagliflozin therapy and insulin resistance-associated disorders: effects and promises beyond a diabetic state

Empagliflozin is a SGLT2 inhibitor that has shown remarkable cardiovascular and renal activities in patients with type 2 diabetes (T2D). Preclinical and clinical studies of empagliflozin in T2D population have demonstrated significant improvements in body weight, waist circumference, insulin sensitivity, and blood pressure – effects beyond its antihyperglycaemic control. Moreover, several studies suggested that this drug possesses significant anti-inflammatory and antioxidative stress properties. This paper explores extensively the main preclinical and clinical evidence of empagliflozin administration in insulin resistance-related disorders beyond a diabetic state. It also discusses its future perspectives, as a therapeutic approach, in this high cardiovascular-risk population.

A kidney perspective on the mechanism of action of sodium glucose co-transporter 2 inhibitors

Sodium glucose co-transporter (SGLT) 2 inhibitors reduce the risk of kidney failure in patients with and without type 2 diabetes (T2D). Although the precise underlying mechanisms for these nephroprotective effects are incompletely understood, various hypotheses have been proposed including reductions in intraglomerular pressure through restoration of tubuloglomerular feedback, blood pressure reduction and favorable effects on vascular function, reduction in tubular workload and hypoxia, and metabolic effects resulting in increased autophagy. Here, we review these mechanisms, which may also explain the beneficial effects of SGLT2 inhibitors on kidney function in patients without T2D.

Association of uric acid with kidney function and albuminuria: the Uric Acid Right for heArt Health (URRAH) Project

BACKGROUND

Hyperuricemia is commonly observed in patients with chronic kidney disease (CKD). However, a better understanding of the relationship among uric acid (UA) values, glomerular filtration rate (GFR) and albuminuria may shed light on the mechanisms underlying the excess of cardiovascular mortality associated with both chronic kidney disease and hyperuricemia and lead to better risk stratification. Our main goal was to study the relationships between serum uric acid and kidney disease measures (namely estimated GFR [eGFR] and albuminuria) in a large cohort of individuals at cardiovascular risk from the URic acid Right for heArt Health (URRAH) Project database.

METHODS

Clinical data of 26,971 individuals were analyzed. Factors associated with the presence of hyperuricemia defined on the basis of previously determined URRAH cutoffs for cardiovascular and all-cause mortality were evaluated through multivariate analysis. Chronic kidney disease was defined as eGFR < 60 ml/min per 1.73 m² and/or abnormal urinary albumin excretion diagnosed as: (i) microalbuminuria if urinary albumin concentration was > 30 and ≤ 300 mg/L, or if urinary albumin-to-creatinine ratio (ACR) was > 3.4 mg/mmol and ≤ 34 mg/mmol; (ii) macroalbuminuria if urinary albumin concentration was > 300 mg/L, or if ACR was > 34 mg/mmol.

RESULTS

Mean age was 58 ± 15 years (51% males, 62% with hypertension and 12% with diabetes), mean eGFR was 81 ml/min per 1.73m2²with a prevalence of eGFR < 60 and micro- or macroalbuminuria of 16, 15 and 4%, respectively. Serum uric acid showed a trend towards higher values along with decreasing renal function. Both the prevalence of gout and the frequency of allopurinol use increased significantly with the reduction of eGFR and the increase in albuminuria. Hyperuricemia was independently related to male gender, eGFR strata, and signs of insulin resistance such as body mass index (BMI) and triglycerides.

CONCLUSIONS

The lower the eGFR the higher the prevalence of hyperuricemia and gout. In subjects with eGFR < 60 ml/min the occurrence of hyperuricemia is about 10 times higher than in those with eGFR > 90 ml/min. The percentage of individuals treated with allopurinol was below 2% when GFR was above 60 ml/min, it increased to 20% in the presence of CKD 3b and rose further to 35% in individuals with macroalbuminuria.

The Rationale and Evidence for SGLT2 Inhibitors as a Treatment for Nondiabetic Glomerular Disease

Background

Recent studies show that sodium-glucose cotransporter 2 inhibitors (SGLT2i), originally approved for glycemic control in patients with type 2 diabetes, also exert renoprotective effects independently from effects on dysglycemia. Moreover, recent work indicates that SGLT2i treatment may be effective in patients with nondiabetic chronic kidney disease, including primary and secondary glomerular diseases.

Summary

SGLT2i lower blood glucose by blocking glucose resorption in the early renal proximal tubule through the glucose transporter, SGLT2, leading to enhanced urinary glucose excretion. Recent studies indicate that SGLT2i may have pleiotropic effects on cells other than proximal tubular cells. SGLT2i reduce the glomerular workload by decreasing the intraglomerular pressure, thus ameliorating hyperfiltration, if present, and may also decrease systemic blood pressure. SGLT2i may also act directly on endothelial cells, possibly via modulating the effects of adhesion molecules and reducing inflammatory cytokines and reactive oxygen species. SGLT2i may have direct anti-inflammatory and antifibrotic effects on renal tubules. Some reports suggest direct protective effects on podocytes and mesangial cells as well. Here, we provide a review of the potential mechanisms of renoprotection, therapeutic utility, and potential side effects of SGLT2i in patients with nondiabetic glomerular diseases, based on data from studies carried out in cells, experimental animals, and humans.

Key Messages

SGLT2i may be a promising addition to the glomerular disease treatment armamentarium. However, it is unclear at what point of the natural history of specific glomerular diseases (whether this is immune or nonimmune mediated) SGLT2i can be beneficial. Additionally, further studies are needed to assess the long-term efficacy and safety of SGLT2i in patients with nondiabetic glomerular diseases.

Effects of SGLT2 Inhibitors on Kidney and Cardiovascular Function

SGLT2 inhibitors are antihyperglycemic drugs that protect kidneys and the heart of patients with or without type 2 diabetes and preserved or reduced kidney function from failing. The involved protective mechanisms include blood glucose-dependent and -independent mechanisms: SGLT2 inhibitors prevent both hyper- and hypoglycemia, with expectedly little net effect on HbA1C. Metabolic adaptations to induced urinary glucose loss include reduced fat mass and more ketone bodies as additional fuel. SGLT2 inhibitors lower glomerular capillary hypertension and hyperfiltration, thereby reducing the physical stress on the filtration barrier, albuminuria, and the oxygen demand for tubular reabsorption. This improves cortical oxygenation, which, together with lesser tubular gluco-toxicity, may preserve tubular function and glomerular filtration rate in the long term. SGLT2 inhibitors may mimic systemic hypoxia and stimulate erythropoiesis, which improves organ oxygen delivery. SGLT2 inhibitors are proximal tubule and osmotic diuretics that reduce volume retention and blood pressure and preserve heart function, potentially in part by overcoming the resistance to diuretics and atrial-natriuretic-peptide and inhibiting Na-H exchangers and sympathetic tone.

The Association between Urinary Glucose and Renal Uric Acid Excretion in Non-diabetic Patients with Stage 1-2 Chronic Kidney Disease

Aims: To test the hypothesis that in non-diabetic patients with early-stage chronic kidney disease (CKD), the renal excretion of urate and glucose transportation are coupled and interconnected. Methods: A cross-sectional study of 255 non-diabetic participants with stage 1-2 CKD recruited from our department was conducted. Spearman's correlation and multiple linear regression analyses were used to study the correlation between urinary glucose and renal uric acid excretion. ANOVA was used to compare urinary uric acid excretion among three tertiles of urinary glucose (UG; UG1: UG<0.24 mmol/24 h/1.73 m², UG2: 0.24 mmol/24 h/1.73 m²≤ UG≤0.55 mmol/24 h/1.73 m², and UG3: UG>0.55 mmol/24 h/1.73 m²), the fractional excretion of glucose (FEG; FEG1: FEG<0.04%, FEG2: 0.04%≤FEG≤0.09%, and FEG3: FEG>0.09%) and the excretion of glucose per volume of glomerular filtration (EgGF; EgGF1: EgGF<1.95 μmol/L, EgGF2: 1.95 μmol/L≤ EgGF≤3.99 μmol/L, and EgGF3: EgGF>3.99 μmol/L). Results: According to the multiple linear regression analysis, FEG and EgGF were positively correlated with the excretion of uric acid per volume of glomerular filtration (EurGF) after adjusting for confounding factors. The EurGF levels in the highest tertiles of UG, FEG and EgGF were higher than those in the lowest tertiles of UG, FEG and EgGF. Conclusion: Urinary glucose excretion is closely related to renal excretion of uric acid in non-diabetic patients with stage 1-2 CKD.

Sodium-Glucose Cotransporter-2 (SGLT-2) Attenuates Serum Uric Acid (SUA) Level in Patients with Type 2 Diabetes

BACKGROUND

Hyperuricemia has a strong association with diabetes mellitus. Hyperuricemia can lead to cardiovascular and renal complications in patients with diabetes. The goal of this study was to compare the effect of sodium-glucose cotransporter-2 (SGLT-2) inhibitors dapagliflozin and empagliflozin on serum uric acid (SUA) levels in patients with type 2 diabetes against traditional oral antihyperglycemic drugs (OADs).

METHODS

In this double-blind randomized controlled trial, 70 patients with type 2 diabetes and elevated SUA levels were assigned to two treatment groups. Patients in group A received SGLT-2 inhibitors tablet dapagliflozin 5 mg to 10 mg and empagliflozin 10 mg to 25 mg. Group B patients received OADs such as glimepiride, metformin, sitagliptin, gliclazide, and glibenclamide as monotherapy or combination therapy. The changes in SUA level were primary end points while changes in body weight and body mass index (BMI) from baseline to end point were secondary end points.

RESULTS

After four weeks of treatment, we noted a significant reduction of mean SUA levels in the SGLT-2 inhibitor group from 7.5 ± 2.5 to 6.3 ± 0.8 mg/dl versus comparator group from 7.1 ± 1.8 to 6.8 ± 2.2 mg/dl (p = 0.001). Mean body weight was significantly reduced in the SGLT-2 group from 82 ± 10.4 to 78 ± 12.5 kg versus comparator group from 78 ± 13.2 to 79.2 ± 9.7 kg (p = 0.001). Similarly, the mean BMI of patients in the SGLT-2 group was significantly reduced from 25.7 ± 3.2 to 24.2 ± 3.2 kg/m² versus comparator group from 27.5 ± 4.2 to 28 ± 3.6 kg/m² (p = 0.002).

CONCLUSION

SGLT-2 inhibitors have a strong potential to decrease SUA levels in patients with type 2 diabetes.

Dendrobium officinalis six nostrum ameliorates urate under-excretion and protects renal dysfunction in lipid emulsion-induced hyperuricemic rats

AIM

Hyperuricemia (HUA) is a metabolic disease caused by the overproduction or underexcretion of uric acid (UA). Our previous study found that treatment with Dendrobium officinalis six nostrum (DOS) led to a significant reduction in serum UA (SUA) by inhibiting UA production and promoting UA excretion in a rat model of HUA induced by potassium oxonate (PO) and high-fat sorghum feed. In this study, we aimed to further investigate the effects of DOS on UA excretion by the kidney and intestine to explore whether DOS protects against histopathological changes, and to elucidate its possible mechanisms of action in a lipid emulsion (LE)-induced rat model of HUA.

METHODS

The main chemical constituents of DOS were determined to be acteoside and astilbin by high-performance liquid chromatography (HPLC). Three different doses of DOS (3.3, 6.6, and 13.2 g/kg/day) were given to rats daily after induction of HUA by oral administration of LE for 8 weeks. The levels of creatinine (Cr) in serum and urine and UA in serum, urine, and feces were measured by an automatic biochemical analyzer. The expression of TLR4, NF-κB and urate transport-related transporters (URAT1, ABCG2, and PDZK1) in kidney was measured by Western blot (WB). Intestinal urate transporters (ABCG2 and GLUT9) expression was assayed by IHC and WB. Serum LPS and renal inflammatory factors (IL-6, IL-8 and TNF-α) levels were measured using enzyme-linked immunosorbent assay (ELISA) kits. Hematoxylin and eosin (H&E) staining was used to assess renal histological changes.

RESULTS

DOS treatment significantly reduced the SUA and SCr levels by increasing urine volume, 24 h urine uric acid (UUA), fecal UA (FUA), urine creatinine (UCr), and fractional excretion of UA (FEUA) levels in hyperuricemic rats. Moreover, DOS effectively regulated URAT1, PDZK1, and ABCG2 protein levels in the kidney, as well as restored protein levels of GLUT9 and ABCG2 in the intestine. DOS markedly reduced serum LPS anddown-regulated renal TLR4 and NF-κB protein levels to suppress IL-6, IL-8, and TNF-α secretion. It also improved renal inflammation in hyperuricemic rats. In addition, DOS attenuated histopathological changes in the kidneys of LE-induced rats. HPLC analysis showed levels of acteoside and astilbin of 1.39 mg/g and 0.72 mg/g in DOS, respectively.

CONCLUSION

DOS has anti-hyperuricemic and anti-inflammatory effects in a rat model of HUA. The molecular mechanism appears to involve the regulation of urate transport-related transporters including renal ABCG2, URAT1, and PDZK1, and intestinal GLUT9 and ABCG2, as well as the inhibition of the LPS/TLR4/NF-κB signaling to reduce IL-6, IL-8, and TNF-α secretion in hyperuricemic rats.

Effects of dapagliflozin on serum and urinary uric acid levels in patients with type 2 diabetes: a prospective pilot trial

BACKGROUND

We aimed to evaluate the effects of short-term therapy with dapagliflozin on serum uric acid (SUA) and urinary uric acid (UUA) levels in patients with type 2 diabetes.

METHODS

In this prospective pilot trial, 8 patients with type 2 diabetes mellitus were assigned to the treatment group with dapagliflozin 10 mg once daily for one week, and 7 subjects with normal glucose tolerance were recruited into the control group. Data of anthropometric measurements, SUA, 24-h UUA, fractional excretion of UA (FEUA), serum lipid parameters and 3-h oral glucose tolerance test (OGTT) were collected in both treatment and control groups; all examinations were repeated after treatment. The area under the curve of glucose (AUCGlu) was calculated to reflect the general glucose levels, while insulin resistance and islet β-cell function were reflected by indexes calculated according to the data obtained from the OGTT.

RESULTS

The weight and serum lipid parameters showed no differences before and after treatment with dapagliflozin for one week. We found SUA levels decreased from 347.75 ± 7.75 μmol/L before treatment to 273.25 ± 43.18 μmol/L after treatment, with a statistically significant difference (P = 0.001) and was accompanied by a significant increase in FEUA from 0.009 to 0.029 (P = 0.035); there was a linear correlation between SUA and FEUA levels. Glucose control, insulin sensitivity and islet β-cell function were improved to a certain extent. We also found a positive correlation between the decrease in glucose levels and the improvement in islet β-cell function.

CONCLUSIONS

The SUA-lowering effect of dapagliflozin could be driven by increasing UA excretion within one week of treatment, and a certain degree of improvement in glucose levels and islet β-cell function were observed.Trial registration ClinicalTrials.gov identifier, NCT04014192. Registered 12 July 2019, https://www.clinicaltrials.gov/ct2/show/NCT04014192:term=NCT04014192&draw=2&rank=1. Yes.

Sodium-Glucose Cotransporter-2 Inhibitor Immediately Decreases Serum Uric Acid Levels in Type 2 Diabetic Patients

BACKGROUND Sodium-glucose cotransporter-2 (SGLT2) inhibitors are new antihyperglycemic drugs for type 2 diabetes. SGLT2 inhibitors ameliorate cardiovascular morbidity and mortality as well as kidney disease progression by reducing body weight (BW), blood pressure (BP), visceral adiposity, albuminuria, and serum uric acid and blood glucose levels. However, it is not clear which effects are pronounced, and what mechanisms are associated with these effects. MATERIAL AND METHODS This study recruited patients with type 2 diabetes who were prescribed an SGLT2 inhibitor for the first time in our outpatient department. Clinical parameters were measured before and 6 months after the administration of the SGLT2 inhibitor, without the addition of new drugs and dose changes for all prescribed drugs. RESULTS This study recruited 24 patients with type 2 diabetes. No significant differences in BP, glycated hemoglobin (HbA1c) levels, and low-density lipoprotein cholesterol levels were observed after SGLT2 inhibitor administration. In contrast, BW and serum uric acid levels decreased significantly, and the fractional excretion of uric acid (FEUA) increased significantly after administration. While no significant relationships were observed between serum uric acid and FEUA with respect to the percentage changes from baseline values, the percentage changes in serum uric acid levels from baseline were significantly and positively associated with those in serum creatinine levels. CONCLUSIONS Serum uric acid levels were immediately decreased owing to the administration of SGLT2 inhibitor, but BP, blood glucose, and serum lipid levels were unchanged. These changes in serum uric acid levels may be associated with changes in renal function.

Investigation of the Effects and Mechanisms of Dendrobium loddigesii Rolfe Extract on the Treatment of Gout

Objective

Gout is a chronic disease that causes inflammatory arthritis, which is closely related to urate accumulation induced by a disorder of uric acid metabolism and the consequent deposition of monosodium urate crystals. Dendrobium loddigesii Rolfe is an herbal medicine that has been used in some traditional Chinese medicine formulae in the treatment of gout. This study aimed to explore and verify the antigout activity of Dendrobium loddigesii extract (DLE) on alleviating the hyperuricaemia of mice and the acute gouty arthritis of rats.

Methods

An animal model of hyperuricaemia was established using potassium oxonate (PO). We analysed the expression of uric acid transporter mRNA in the kidney in the hyperuricaemic mice after treatment with DLE. Simultaneously, a monosodium urate crystal-induced acute gouty arthritis rat model was used to evaluate the effects of DLE, according to the level of ankle swelling, as well as the protein levels of inflammatory receptors and cytokines, as assayed by WB and ELISA.

Results

DLE alleviated hyperuricaemia in mice and inhibited acute gouty arthritis in rats (P < 0.05). Meanwhile, DLE regulated the levels of uric acid transporters mRNA transcripts, including mouse organic anion transporter 1 (mOAT1), organic anion transporter 3 (mOAT3), urate transporter 1 (mURAT1), and glucose transporter 9 (mGLUT9) in the kidney (P < 0.05), suggesting that DLE promoted uric acid metabolism. Furthermore, DLE significantly suppressed the protein levels of TLRs, MyD88, and NF-κB in the ankle joint's synovium (P < 0.05), and the serum levels of IL-1β, IL-6, and TNF-α were also reduced, which demonstrated the anti-inflammatory effects of DLE.

Conclusion

DLE alleviates hyperuricaemia by regulating the transcription level of uric acid transporters in the kidney. It also inhibits acute gouty arthritis by inhibiting the pathway of TLRs/MyD88/NF-κB in the ankle joint's synovium. The findings of the present study imply that DLE alleviates gout by promoting uric acid metabolism and inhibiting inflammation related to the TLRs/MyD88/NF-κB pathway.

Sodium-glucose co-transporter-2 inhibitors: peculiar "hybrid" diuretics that protect from target organ damage and cardiovascular events

AIMS

Sodium-glucose co-transporter-2 inhibitors (SGLT2i) have been proven to lead to relevant cardiovascular benefits, regardless of glycemic control function. SGLT2i have on the one hand led to reduction in cardiovascular events such as heart failure and on the other hand to renal protection. Blood pressure reduction and kidney function play a central role in these outcomes. This focused review describes the main mechanisms and clinical aspects of SGLT2i.

DATA SYNTHESIS

These drugs act on the proximal renal tubule and behave as diuretics with a "hybrid" mechanism, as they can favour both natriuresis and enhanced diuresis due to an osmotic effect dependent on glycosuria, resulting in blood pressure decrease. The exclusive peculiarity of these "diuretics", which distinguishes them from loop and thiazide diuretics, lies also in the activation of the tubule-glomerular feedback.

CONCLUSIONS

This mechanism, resulting in modulation of arterioles' tone and renin secretion, contributes to the favorable outcomes, suggesting a wider use of SGLT2i in internal medicine, nephrology and cardiology.

Uric Acid Is a Biomarker of Oxidative Stress in the Failing Heart: Lessons Learned from Trials With Allopurinol and SGLT2 Inhibitors

Hyperuricemia increases the risk of heart failure, and higher levels of serum uric acid are seen in patients who have worse ventricular function, functional capacity, and prognosis. Heart failure is also accompanied by an upregulation of xanthine oxidase, the enzyme that catalyzes the formation of uric acid and a purported source of reactive oxygen species. However, the available evidence does not support the premise that either uric acid or the activation of xanthine oxidase has direct injurious effects on the heart in the clinical setting. Xanthine oxidase inhibitors (allopurinol and oxypurinol) have had little benefit and may exert detrimental effects in patients with chronic heart failure in randomized controlled trials, and the more selective and potent inhibitor febuxostat increases the risk of cardiovascular death more than allopurinol. Instead, the available evidence indicates that changes in xanthine oxidase and uric acid are biomarkers of oxidative stress (particularly in heart failure) and that xanthine oxidase may provide an important source of nitric oxide that quenches the injurious effects of reactive oxygen species. A primary determinant of the cellular redox state is nicotinamide adenine dinucleotide, whose levels drive an inverse relationship between xanthine oxidase and sirtuin-1, a nutrient deprivation sensor that exerts important antioxidant and cardioprotective effects. Interestingly, sodium-glucose cotransporter 2 inhibitors induce a state of nutrient deprivation that includes activation of sirtuin-1, suppression of xanthine oxidase, and lowering of serum uric acid. The intermediary role of sirtuin-1 in both uric acid-lowering and cardioprotection may explain why, in mediation analyses of large-scale cardiovascular trials, the effect of sodium-glucose cotransporter 2 inhibitors to decrease serum uric acid is a major predictor of the ability of these drugs to decrease serious heart failure events.

Glucose transporters in the kidney in health and disease

The kidneys filter large amounts of glucose. To prevent the loss of this valuable fuel, the tubular system of the kidney, particularly the proximal tubule, has been programmed to reabsorb all filtered glucose. The machinery involves the sodium-glucose cotransporters SGLT2 and SGLT1 on the apical membrane and the facilitative glucose transporter GLUT2 on the basolateral membrane. The proximal tubule also generates new glucose, particularly in the post-absorptive phase but also to enhance bicarbonate formation and maintain acid-base balance. The glucose reabsorbed or formed by the proximal tubule is primarily taken up into peritubular capillaries and returned to the systemic circulation or provided as an energy source to further distal tubular segments that take up glucose by basolateral GLUT1. Recent studies provided insights on the coordination of renal glucose reabsorption, formation, and usage. Moreover, a better understanding of renal glucose transport in disease states is emerging. This includes the kidney in diabetes mellitus, when renal glucose retention becomes maladaptive and contributes to hyperglycemia. Furthermore, enhanced glucose reabsorption is coupled to sodium retention through the sodium-glucose cotransporter SGLT2, which induces secondary deleterious effects. As a consequence, SGLT2 inhibitors are new anti-hyperglycemic drugs that can protect the kidneys and heart from failing. Recent studies discovered unique roles for SGLT1 with implications in acute kidney injury and glucose sensing at the macula densa. This review discusses established and emerging concepts of renal glucose transport, and outlines the need for a better understanding of renal glucose handling in health and disease.

Mechanisms of Cardiorenal Effects of Sodium-Glucose Cotransporter 2 Inhibitors: JACC State-of-the-Art Review

Sodium-glucose cotransporter 2 inhibitors (SGLT2i), a new drug class approved for treatment of diabetes, have been shown to possess a favorable metabolic profile and to significantly reduce atherosclerotic events, hospitalization for heart failure, cardiovascular and total mortality, and progression of chronic kidney disease. Although initially considered to be only glucose-lowering agents, the effects of SGLT2i have expanded far beyond that, and their use is now being studied in the treatment of heart failure and chronic kidney disease, even in patients without diabetes. It is therefore critical for cardiologists, diabetologists, nephrologists, and primary care physicians to be familiar with this drug class. This first part of this 2-part review provides an overview of the current understanding of the mechanisms of the cardio-metabolic-renal benefits of SGLT2i. The second part summarizes the recent clinical trials of SGLT2i.

Tubular effects of sodium-glucose cotransporter 2 inhibitors: intended and unintended consequences

PURPOSE OF REVIEW

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are antihyperglycemic drugs that act by inhibiting renal sodium-glucose cotransport. Here we present new insights into 'off target', or indirect, effects of SGLT2 inhibitors.

RECENT FINDINGS

SGLT2 inhibition causes an acute increase in urinary glucose excretion. In addition to lowering blood glucose, there are several other effects that contribute to the overall beneficial renal and cardiovascular effects. Reabsorption of about 66% of sodium is accomplished in the proximal tubule and dependent on the sodium-hydrogen exchanger isoform 3 (NHE3). SGLT2 colocalizes with NHE3, and high glucose levels reduce NHE3 activity. The proximal tubule is also responsible for the majority of phosphate (Pi) reabsorption. SGLT2 inhibition is associated with increases in plasma Pi, fibroblast growth factor 23 and parathyroid hormone levels in nondiabetics and type 2 diabetes mellitus. Studies in humans identified a urate-lowering effect by SGLT2 inhibition which is possibly mediated by urate transporter 1 (URAT1) and/or glucose transporter member 9 in the proximal tubule. Of note, magnesium levels were also found to increase under SGLT2 inhibition, an effect that was preserved in nondiabetic patients with hypomagnesemia.

SUMMARY

Cardiorenal effects of SGLT2 inhibition might involve, in addition to direct effects on glucose homeostasis, effects on NHE3, phosphate, urate, and magnesium homeostasis.

Renal effects of SGLT2 inhibitors: an update

PURPOSE OF REVIEW

SGLT2 inhibitors are a new class of antihyperglycemic drugs that protect kidneys and hearts of type 2 diabetic (T2DM) patients with preserved kidney function from failing. Here we discuss new insights on renal protection.

RECENT FINDINGS

Also in T2DM patients with CKD, SGLT2 inhibition causes an immediate functional reduction in glomerular filtration rate (GFR) and reduces blood pressure and preserves kidney and heart function in the long-term, despite a lesser antihyperglycemic effect. According to modeling studies, the GFR reduction reduces the tubular transport work and metabolic demand, thereby improving renal cortical oxygenation. In humans, the latter is linked to protection from CKD. Urine metabolomics in T2DM patients suggested improved renal mitochondrial function in response to SGLT2 inhibition, and experimental studies indicated improved tubular autophagy. Modeling studies predicted that also in diabetic CKD, SGLT2 inhibition is natriuretic and potentially stimulates erythropoiesis by mimicking systemic hypoxia in the kidney. Meta-analyses indicated that SGLT2 inhibition also reduces risk and severity of acute kidney injury in T2DM patients. Studies in nondiabetic mice implied inhibition of the renal urate transporter URAT1 in the uricosuric effect of SGLT2 inhibition.

SUMMARY

Renoprotection of SGLT2 inhibition involves blood glucose-dependent and independent effects and extends to CKD.

Glucose transporters in adipose tissue, liver, and skeletal muscle in metabolic health and disease

A family of facilitative glucose transporters (GLUTs) is involved in regulating tissue-specific glucose uptake and metabolism in the liver, skeletal muscle, and adipose tissue to ensure homeostatic control of blood glucose levels. Reduced glucose transport activity results in aberrant use of energy substrates and is associated with insulin resistance and type 2 diabetes. It is well established that GLUT2, the main regulator of hepatic hexose flux, and GLUT4, the workhorse in insulin- and contraction-stimulated glucose uptake in skeletal muscle, are critical contributors in the control of whole-body glycemia. However, the molecular mechanism how insulin controls glucose transport across membranes and its relation to impaired glycemic control in type 2 diabetes remains not sufficiently understood. An array of circulating metabolites and hormone-like molecules and potential supplementary glucose transporters play roles in fine-tuning glucose flux between the different organs in response to an altered energy demand.

The ABCG2 Q141K hyperuricemia and gout associated variant illuminates the physiology of human urate excretion

The pathophysiological nature of the common ABCG2 gout and hyperuricemia associated variant Q141K (rs2231142) remains undefined. Here, we use a human interventional cohort study (ACTRN12615001302549) to understand the physiological role of ABCG2 and find that participants with the Q141K ABCG2 variant display elevated serum urate, unaltered FEUA, and significant evidence of reduced extra-renal urate excretion. We explore mechanisms by generating a mouse model of the orthologous Q140K Abcg2 variant and find male mice have significant hyperuricemia and metabolic alterations, but only subtle alterations of renal urate excretion and ABCG2 abundance. By contrast, these mice display a severe defect in ABCG2 abundance and function in the intestinal tract. These results suggest a tissue specific pathobiology of the Q141K variant, support an important role for ABCG2 in urate excretion in both the human kidney and intestinal tract, and provide insight into the importance of intestinal urate excretion for serum urate homeostasis.

The common ABCG2 variant Q141K contributes to hyperuricemia and gout risk. Here, using a human interventional study and a new orthologous mouse model, the authors report a tissue specific pathobiology of the Q141K variant, and support a significant role for ABCG2 in urate excretion in both the kidney and intestine.

Autophagy-dependent and -independent modulation of oxidative and organellar stress in the diabetic heart by glucose-lowering drugs

Autophagy is a lysosome-dependent intracellular degradative pathway, which mediates the cellular adaptation to nutrient and oxygen depletion as well as to oxidative and endoplasmic reticulum stress. The molecular mechanisms that stimulate autophagy include the activation of energy deprivation sensors, sirtuin-1 (SIRT1) and adenosine monophosphate-activated protein kinase (AMPK). These enzymes not only promote organellar integrity directly, but they also enhance autophagic flux, which leads to the removal of dysfunctional mitochondria and peroxisomes. Type 2 diabetes is characterized by suppression of SIRT1 and AMPK signaling as well as an impairment of autophagy; these derangements contribute to an increase in oxidative stress and the development of cardiomyopathy. Antihyperglycemic drugs that signal through insulin may further suppress autophagy and worsen heart failure. In contrast, metformin and SGLT2 inhibitors activate SIRT1 and/or AMPK and promote autophagic flux to varying degrees in cardiomyocytes, which may explain their benefits in experimental cardiomyopathy. However, metformin and SGLT2 inhibitors differ meaningfully in the molecular mechanisms that underlie their effects on the heart. Whereas metformin primarily acts as an agonist of AMPK, SGLT2 inhibitors induce a fasting-like state that is accompanied by ketogenesis, a biomarker of enhanced SIRT1 signaling. Preferential SIRT1 activation may also explain the ability of SGLT2 inhibitors to stimulate erythropoiesis and reduce uric acid (a biomarker of oxidative stress)—effects that are not seen with metformin. Changes in both hematocrit and serum urate are the most important predictors of the ability of SGLT2 inhibitors to reduce the risk of cardiovascular death and hospitalization for heart failure in large-scale trials. Metformin and SGLT2 inhibitors may also differ in their ability to mitigate diabetes-related increases in intracellular sodium concentration and its adverse effects on mitochondrial functional integrity. Differences in the actions of SGLT2 inhibitors and metformin may reflect the distinctive molecular pathways that explain differences in the cardioprotective effects of these drugs.