Characterisation of glomerular haemodynamic responses to SGLT2 inhibition in patients with type 1 diabetes and renal hyperfiltration

SGLT2 inhibition to address the unmet needs in diabetic nephropathy

Current treatment of diabetic nephropathy is effective; however, substantial gaps in care still remain and new therapies are urgently needed to reduce the global burden of the complication. Desirable properties of an "ideal" new drug should include primary prevention of microalbuminuria, additive/synergistic anti-proteinuric effect in combination therapy with renin angiotensin system blockers, reduction of chronic kidney disease progression to lower the risk of end-stage renal disease, and cardiovascular protection. Growing evidence suggests that sodium-glucose cotransporter 2 inhibitors (SGLT2i) may fulfil many of these criteria and represent novel tools to cover the unmet needs in diabetic nephropathy care. However, the underlying mechanisms of SGLT2i renal benefits are still poorly understood and promising results from cardiovascular outcome trials with SGLT2i need confirmation in dedicated renal outcome trials.

The Impact of Sotagliflozin on Renal Function, Albuminuria, Blood Pressure, and Hematocrit in Adults With Type 1 Diabetes

OBJECTIVE

In people with type 2 diabetes, sodium-glucose cotransporter 2 inhibitors (SGLT2i) reduce cardiovascular risk and progression of diabetic kidney disease. Our aim was to determine whether sotagliflozin (SOTA), a dual SGLT1i and SGLT2i, had favorable effects on clinical biomarkers suggestive of kidney protection in adults with type 1 diabetes.

RESEARCH DESIGN AND METHODS

In this 52-week pooled analysis, 1,575 adults enrolled in the inTandem1 and inTandem2 trials were randomized to SOTA 200 mg, 400 mg, or placebo in addition to optimized insulin therapy. Changes in cardiorenal biomarkers were assessed.

RESULTS

At 52 weeks, in response to SOTA 200 and 400 mg, the placebo-corrected least squares mean change from baseline in estimated glomerular filtration rate was -2.0 mL/min/1.73 m² (P = 0.010) and -0.5 mL/min/1.73 m² (P = 0.52), respectively. Systolic blood pressure difference was -2.9 and -3.6 mmHg (P < 0.0001 for both); diastolic blood pressure changed by -1.4 (P = 0.0033) and -1.6 mmHg (P = 0.0008). In participants with baseline urinary albumin-to-creatinine ratio (UACR) ≥30 mg/g, UACR decreased by 23.7% (P = 0.054) and 18.3% (P = 0.18) for SOTA 200 and SOTA 400 mg, respectively, versus placebo. Increases in serum albumin and hematocrit and reductions in uric acid were observed throughout 52 weeks with both SOTA doses.

CONCLUSIONS

SOTA was associated with short- and long-term renal hemodynamic changes, which were similar to those seen with SGLT2i in type 2 diabetes. Further investigation around cardiorenal effects of SOTA in people with type 1 diabetes is justified.

Sodium-Glucose Cotransporter 2 (SGLT2) Inhibition in Kidney Transplant Recipients with Diabetes Mellitus

BACKGROUND

Sodium-glucose cotransporter 2 (SGLT2) inhibition has been shown to reduce cardiovascular mortality and preserve kidney function in patients with type 2 diabetes. Kidney transplant recipients with diabetes demonstrate increased risk and accelerated progression of micro- and macrovascular complications and may specifically benefit from SGLT2 inhibition. However, potential concerns of SGLT2 inhibition include volume depletion and urinary tract infections.

OBJECTIVES

We report data on the use of SGLT2 inhibitors in a case series of ten patients with diabetes after kidney transplantation in order to analyze efficacy, safety, and the effect on renal function.

METHODS

Patients with a stable allograft function and no history of recurrent urinary tract infections were eligible. The SGLT2 inhibitor empagliflozin was given as add-on to preexisting antidiabetic treatment with initial dose reduction of the latter.

RESULTS

Median estimated glomerular filtration rate at baseline was 57 mL/min/1.73 m2 and remained stable throughout the follow-up of 12.0 (5.3-12.0) months. Median HbA1c decreased from 7.3 to 7.1%. The rate of urinary tract infections and other side effects was low.

CONCLUSIONS

SGLT2 inhibition is feasible and well tolerated in selected kidney transplant recipients with diabetes. Whether SGLT2 inhibition is able to reduce cardiovascular mortality and improve allograft survival in these patients has to be addressed in further studies.

Renal effects of a sodium-glucose cotransporter 2 inhibitor, tofogliflozin, in relation to sodium intake and glycaemic status

AIMS

Little is known about whether sodium intake is associated with the clinical effects of SGLT2 inhibitors (SGLT2is); however, SGLT2is may increase urinary sodium excretion. Thus, we investigated the impact of daily sodium intake on the estimated glomerular filtration rate (eGFR) via an SGLT2i, tofogliflozin (TOFO), in patients with type 2 diabetes (T2D).

METHODS

Individual-level data on 775 T2D patients in TOFO Phase 3 trials were analysed. Adjusted changes in variables during 52 weeks of TOFO therapy were compared according to basal daily salt intake (DSI), which was measured based on estimated daily urinary sodium excretion using the Tanaka formula. Multivariable analysis was used to investigate the impact of basal DSI on changes in eGFR at Weeks 4 and 52.

RESULTS

Sixty-six percent of participants were men; mean age, HbA1c, body mass index, eGFR_MDRD and median DSI were 58.5 years, 8.0%, 25.6 kg/m² , 83.9 mL/min/1.73 m² and 9.3 g/d, respectively. In all participants, eGFR_MDRD sharply dipped during Week 4, and gradually increased by Week 52, showing a significant increase overall from baseline to Week 52. Multivariable analysis showed that basal DSI and HbA1c levels were independently correlated with eGFR_MDRD changes at Weeks 4 and 52. Additionally, lower baseline HbA1c and DSI levels were significantly correlated with a greater increase in eGFR_MDRD at Week 52.

CONCLUSIONS

Dietary salt intake, in addition to glycaemic control, correlates with changed eGFR_MDRD via TOFO. Thus, an appropriate dietary approach to therapy should be considered before treatment of T2D patients with an SGLT2i.

Empagliflozin Improves Kidney Outcomes in Patients With or Without Heart Failure

Background In EMPA-REG OUTCOME (Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients) empagliflozin significantly reduced the risk of cardiovascular and kidney outcomes in patients with type 2 diabetes mellitus and established cardiovascular disease. Post hoc, we evaluated empagliflozin on kidney outcomes in patients with or without heart failure (HF). Methods and Results Individuals were randomized to empagliflozin 10 mg, 25 mg, or placebo. Prespecified analyses by baseline HF status included risk of incident or worsening nephropathy and estimated glomerular filtration rate slope analyses. Cox proportional hazards models assessed consistency of treatment effect across subgroups. Safety evaluations included kidney-related adverse events. At baseline, 244 (10.5%) and 462 (9.9%) patients had HF in the placebo and empagliflozin groups, respectively. Overall, the incidence of kidney outcome events was numerically higher in patients with than without HF. In the HF group, empagliflozin reduced risk of incident or worsening nephropathy or cardiovascular death by 43% (hazard ratio, 0.57 [95% CI, 0.42-0.77]) and progression to macroalbuminuria by 50% (hazard ratio, 0.50 [0.33-0.75]). After an initial transient decrease, estimated glomerular filtration rate stabilized over time with empagliflozin but gradually declined with placebo. Kidney effects in patients with HF were consistent with those in the overall study population (all P values for interaction >0.05). Across groups, the incidence rate of kidney-related adverse events/100 patient-years was higher in patients with than without HF; however, overall rates were comparable between groups. Conclusions These findings from EMPA-REG OUTCOME support the hypothesis that empagliflozin could reduce the risk of clinically relevant kidney events and may slow progression of chronic kidney disease in individuals with type 2 diabetes mellitus regardless of HF status. Clinical Trial Registration URL: https://www.clinicaltrials.gov . Unique identifier: NCT01131676.

The effect of SGLT-2 inhibitors on blood pressure: a pleiotropic action favoring cardio- and nephroprotection

Strict blood pressure (BP) control in patients with diabetes is associated with reductions in cardiovascular and renal risk. SGLT-2 inhibitors act in the proximal tubule to reduce glucose reabsorption. They also have mild natriuretic and diuretic effects, combining properties of proximal tubule diuretics and osmotic diuretics, which are expected to reduce BP. Several lines of evidence suggests that SGLT-2 inhibitors produce mild but meaningful reductions in BP and also decrease the incidence of renal outcomes, cardiovascular events and mortality. Thus, recent guidelines for type 2 diabetes suggest that among oral agents to use together with metformin, SGLT-2 inhibitors should be preferred in patients at increased cardiovascular risk, kidney disease or heart failure. This review summarizes current literature on the effect of SGLT-2 inhibitors on BP, and its potential relationships with cardio- and nephroprotection.

Empagliflozin and kidney outcomes in Asian patients with type 2 diabetes and established cardiovascular disease: Results from the EMPA-REG OUTCOME® trial

AIMS/INTRODUCTION

In the EMPA-REG OUTCOME® trial, empagliflozin added to standard of care improved clinically relevant kidney outcomes by 39%, slowed progression of chronic kidney disease, and reduced albuminuria in patients with type 2 diabetes and established cardiovascular disease. This exploratory analysis investigated the effects of empagliflozin on the kidneys in Asian patients.

MATERIALS AND METHODS

Participants in the EMPA-REG OUTCOME® trial were randomized (1:1:1) to empagliflozin 10 mg, 25 mg or a placebo. In patients of Asian race, we analyzed incident or worsening nephropathy (progression to macroalbuminuria, doubling of serum creatinine, initiation of renal-replacement therapy or renal death) and its components, estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio changes, and renal safety.

RESULTS

Of 7,020 treated patients, 1,517 (26.1%) were Asian. In this subgroup, consistent with the overall trial population, empagliflozin reduced the risk of incident or worsening nephropathy (hazard ratio 0.64, 95% confidence interval 0.49-0.83), progression to macroalbuminuria (hazard ratio 0.64, 95% confidence interval 0.49-0.85) and the composite of doubling of serum creatinine, initiation of renal-replacement therapy or renal death (hazard ratio 0.48, 95% confidence interval 0.25-0.92). Furthermore, empagliflozin-treated participants showed slower eGFR decline versus placebo, and showed rapid urine albumin-to-creatinine ratio reduction at week 12, maintained through week 164, with effects most pronounced in those with baseline microalbuminuria or macroalbuminuria. The kidney safety profile of empagliflozin in the Asian subgroup was similar to the overall trial population.

CONCLUSIONS

In Asian patients from the EMPA-REG OUTCOME® trial, empagliflozin improved kidney outcomes, slowed eGFR decline and lowered albuminuria versus placebo, consistent with the overall trial population findings.

Renal Hemodynamic Function and RAAS Activation Over the Natural History of Type 1 Diabetes

RATIONALE & OBJECTIVE

The renin-angiotensin-aldosterone system (RAAS) is associated with renal and cardiovascular disease in diabetes. Unfortunately, early RAAS blockade in patients with type 1 diabetes mellitus (T1DM) does not prevent the development of complications. We sought to examine the role of hyperfiltration and RAAS activation across a wide range of T1DM duration to better understand renal hemodynamic status in patients with T1DM.

STUDY DESIGN

Post hoc analysis of blood samples.

SETTING & PARTICIPANTS

148 Canadian patients with T1DM: 28 adolescents (aged 16.2±2.0 years), 54 young adults (25.4±5.6 years), and 66 older adults (65.7±7.5 years) studied in a clinical investigation unit.

EXPOSURE

Angiotensin II infusion (1ng/kg/min; a measure of RAAS activation) during a euglycemic clamp.

OUTCOMES

Glomerular filtration rate measured using inulin clearance, effective renal plasma flow measured using para-aminohippurate, afferent (R_A) and efferent (R_E) arteriolar resistances, and glomerular hydrostatic pressure estimated using the Gomez equations.

RESULTS

In a stepwise fashion, glomerular filtration rate, effective renal plasma flow, and glomerular hydrostatic pressure were higher, while renal vascular resistance and R_A were lower in adolescents versus young adults versus older adults. R_E was similar in adolescents versus young adults but was higher in older adults. Angiotensin II resulted in blunted renal hemodynamic responses in older adults (renal vascular resistance increase of 3.3% ± 1.6% vs 4.9% ± 1.9% in adolescents; P<0.001), suggesting a state of enhanced RAAS activation.

LIMITATIONS

Homogeneous study participants limit the generalizability of findings to other populations. Studying older adult participants with T1DM may be associated with a survivorship bias.

CONCLUSIONS

A state of relatively low RAAS activity and predominant afferent dilation rather than efferent constriction characterize early adolescents and young adults with T1DM. This state of endogenous RAAS inactivity in early T1DM may explain why pharmacologic blockade of this neurohormonal system is often ineffective in reducing kidney disease progression in this setting. Older adults with long-standing T1DM who have predominant afferent constriction and RAAS activation may experience renoprotection from therapies that target the afferent arteriole. Further work is required to understand the potential role of non-RAAS pharmacologic agents that target R_A in patients with early and long-standing T1DM.

Relation between Blood Pressure Management and Renal Effects of Sodium-Glucose Cotransporter 2 Inhibitors in Diabetic Patients with Chronic Kidney Disease

AIM

The renoprotective effect of sodium-glucose cotransporter 2 inhibitors is thought to be due, at least in part, to a decrease in blood pressure. The aim of this study was to determine the renal effects of these inhibitors in low blood pressure patients and the dependence of such effect on blood pressure management status.

METHODS

The subjects of this retrospective study were 740 patients with type 2 diabetes mellitus and chronic kidney disease who had been managed at the clinical facilities of the Kanagawa Physicians Association. Data on blood pressure management status and urinary albumin-creatinine ratio were analyzed before and after treatment.

RESULTS

Changes in the logarithmic value of urinary albumin-creatinine ratio in 327 patients with blood pressure < 130/80 mmHg at the initiation of treatment and in 413 patients with BP above 130/80 mmHg were -0.13 ± 1.05 and -0.24 ± 0.97, respectively. However, there was no significant difference between the two groups by analysis of covariance models after adjustment of the logarithmic value of urinary albumin-creatinine ratio at initiation of treatment. Changes in the logarithmic value of urinary albumin-creatinine ratio in patients with mean blood pressure of <102 mmHg (n = 537) and those with ≥102 mmHg (n = 203) at the time of the survey were -0.25 ± 1.02 and -0.03 ± 0.97, respectively, and the difference was significant in analysis of covariance models even after adjustment for the logarithmic value of urinary albumin-creatinine ratio at initiation of treatment (p < 0.001).

CONCLUSION

Our results confirmed that blood pressure management status after treatment with SGLT2 inhibitors influences the extent of change in urinary albumin-creatinine ratio. Stricter blood pressure management is needed to allow the renoprotective effects of sodium-glucose cotransporter 2 inhibitors.

Unraveling reno-protective effects of SGLT2 inhibition in human proximal tubular cells

Large clinical trials demonstrated that SGLT2 inhibitors (SGLT2i) slow the progression of kidney function decline in type 2 diabetes. Because the underlying molecular mechanisms are largely unknown, we studied the effects of SGLT2i on gene expression in two human proximal tubular (PT) cell lines under normoglycemic conditions, utilizing two SGLT2i, namely empagliflocin and canagliflocin. Genome-wide expression analysis did not reveal substantial differences between these two SGLT2i. Microarray hybridization analysis identified 94 genes that were both upregulated by TGF-β1 and downregulated by either of the two SGLT2i in HK-2 and RPTEC/TERT1 (renal proximal tubular epithelial cells/telomerase reverse transcriptase 1) cells. Extracellular matrix organization showed the highest significance in pathway enrichment analysis. Differential gene expression of three annotated genes of interest within this pathway was verified on mRNA level in both cell lines. Whereas TGF-β1 induced mRNA expression of thrombospondin 1 (THBS1; 4.3-fold), tenascin C (TNC; 8-fold), and platelet-derived growth factor subunit B (PDGF-B; 4.2-fold), SGLT2i downregulated basal mRNA expression of THBS1 (0.2-fold), TNC (0.5 fold), and PDGF-B (0.6-fold). Administration of SGLT2i in the presence of TGF-β1 resulted in a significant inhibition of TGF-β1-induced THBS1 and TNC mRNA expression and TGF-β1-induced THBS1, TNC, and PDGF-BB protein expression. We conclude that SGLT2i block basal and TGF-β1-induced expression of key mediators of renal fibrosis and kidney disease progression in two independent human PT cell lines.

SGLT2 inhibitors and the kidney: Effects and mechanisms

AIMS

Numerous clinical trials have shown that sodium glucose cotransporter 2 (SGLT2) inhibitors exert a favorable effect on the indices of renal function (albuminuria, glomerular filtration rate decline over time) and the incidence of hard renal endpoints such as renal death or time to initiation of renal replacement therapy.

MATERIALS AND METHODS

In this review, we describe in detail the evidence regarding the nephroprotective mechanisms of SGLT2 inhibitors and describe the risk factors that may predispose to the development of acute kidney injury in patients receiving these drugs.

RESULTS

Although the impact of these drugs on renal hemodynamics seems to represent the most important renoprotective mechanism of action, many other effects of these compounds, including beneficial effects on metabolism and blood pressure, have been proposed to contribute to the observed clinical benefit.

CONCLUSIONS

SGLT2 inhibitors clearly act beneficially in terms of kidney function with many proposed mechanisms.

Empagliflozin and Kidney Function Decline in Patients with Type 2 Diabetes: A Slope Analysis from the EMPA-REG OUTCOME Trial

BACKGROUND

Empagliflozin slowed the progression of CKD in patients with type 2 diabetes and cardiovascular disease in the EMPA-REG OUTCOME Trial. In a prespecified statistical approach, we assessed treatment differences in kidney function by analyzing slopes of eGFR changes.

METHODS

Participants (n=7020) were randomized (1:1:1) to empagliflozin 10 mg/d, empagliflozin 25 mg/d, or placebo added to standard of care. We calculated eGFR slopes using random-intercept/random-coefficient models for prespecified study periods: treatment initiation (baseline to week 4), chronic maintenance treatment (week 4 to last value on treatment), and post-treatment (last value on treatment to follow-up).

RESULTS

Compared with placebo, empagliflozin was associated with uniform shifts in individual eGFR slopes across all periods. On treatment initiation, adjusted mean slope (eGFR change per week, ml/min per 1.73 m²) decreased with empagliflozin (-0.77; 95% confidence interval, -0.83 to -0.71; placebo: 0.01; 95% confidence interval, -0.08 to 0.10; P<0.001). However, annual mean slope (ml/min per 1.73 m² per year) did not decline with empagliflozin during chronic treatment (empagliflozin: 0.23; 95% confidence interval, 0.05 to 0.40; placebo: -1.46; 95% confidence interval, -1.74 to -1.17; P<0.001). After drug cessation, the adjusted mean eGFR slope (ml/min per 1.73 m² per week) increased and mean eGFR returned toward baseline level only in the empagliflozin group (0.56; 95% confidence interval, 0.49 to 0.62; placebo -0.02; 95% confidence interval, -0.12 to 0.08; P<0.001). Results were consistent across patient subgroups at higher CKD risk.

CONCLUSIONS

The hemodynamic effects of empagliflozin, associated with reduction in intraglomerular pressure, may contribute to long-term preservation of kidney function.

The actions of SGLT2 inhibitors on metabolism, renal function and blood pressure

Inhibition of the sodium-glucose cotransporter (SGLT) 2 in the proximal tubule of the kidney has a broad range of effects on renal function and plasma volume homeostasis, as well as on adiposity and energy metabolism across the entire body. SGLT2 inhibitors are chiefly used in type 2 diabetes for glucose control, achieving reductions in HbA_1c of 7-10 mmol/mol (0.6-0.9%) when compared with placebo. This glucose-lowering activity is proportional to the ambient glucose concentration and glomerular filtration of this glucose, so may be greater in those with poor glycaemic control and/or hyperfiltration at baseline. Equally, the glucose-lowering effects of SGLT2 inhibitors are attenuated in individuals without diabetes and those with a reduced eGFR. However, unlike the glucose-lowering effects of SGLT2 inhibitors, the spill-over of sodium and glucose beyond the proximal nephron following SGLT2 inhibition triggers dynamic and reversible realignment of energy metabolism, renal filtration and plasma volume without relying on losses into the urine. In addition, these processes are observed in the absence of significant glucosuria or ongoing natriuresis. In the long term, the resetting of energy/salt/water physiology following SGLT2 inhibition has an impact, not only on adiposity, renal function and blood pressure control, but also on the health and survival of patients with type 2 diabetes. A better understanding of the precise biology underlying the acute actions of SGLT2 inhibitors in the kidney and how they are communicated to the rest of the body will likely lead to improved therapeutics that augment similar pathways in individuals with, or even without, diabetes to achieve additional benefits.

Empagliflozin and Cardio-renal Outcomes in Patients with Type 2 Diabetes and Cardiovascular Disease - Implications for Clinical Practice

In patients with type 2 diabetes (T2D), the excretion of glucose by the kidney with sodium-glucose cotransporter 2 (SGLT2) inhibitors lowers glycosylated haemoglobin (HbA1c) levels, decreases body weight and visceral adiposity, as well as improving cardio-renal haemodynamics. Currently, four SGLT2 inhibitors are approved in the US and Europe to improve glycaemic control - empagliflozin, dapagliflozin, canagliflozin, and ertuglifozin. Recently, the SGLT2 inhibitor empagliflozin was approved by the FDA for the reduction of cardiovascular (CV) death in adults with T2D and CV disease (CVD). This approval was based on the findings of the Empagliflozin, Cardiovascular Outcomes, and Mortality in Type 2 Diabetes (EMPA-REG OUTCOME) study, which was the first study to show a significant reduction of a primary CV endpoint with a glucose-lowering agent. In this study, the primary outcome (CV mortality, non-fatal myocardial infarction [MI] and non-fatal stroke) was reduced by empagliflozin (10.5%; 490/4,687) compared with placebo (12.1%; 282/2,333); hazard ratio (HR), 0.86 (95% confidence interval [CI]: 0.74, 0.99). The primary outcome was driven by a large reduction of CV mortality (relative risk reduction [RRR], 38%). Empagliflozin also reduced all-cause mortality (RRR, 32%). Furthermore, empagliflozin reduced the adjudicated outcome of heart failure (HF) hospitalisation by 35% (HR, 0.65; 95% CI: 0.50, 0.85). Other non-adjudicated measures of HF outcomes were similarly reduced including investigator reported HF, the introduction of loop diuretics and death from HF. In the analysis of renal outcomes, incident or worsening nephropathy was reduced for empagliflozin (12.7%) compared with placebo (18.8%); HR, 0.61 (95% CI: 0.53, 0.70). Empagliflozin significantly reduced the risk of progression to macroalbuminuria (38%) and doubling of creatinine (44%), as well as the need of starting renal-replacement therapy (55%). The benefits of empagliflozin for the reduction of CV death, all-cause death and hospitalisation for HF were observed across a range of baseline subgroups such as HbA1c level and renal function (down to estimated glomerular filtration rate [eGFR] 30 ml/min/1.73 m2). The rapid reduction of HF outcomes with empagliflozin is observed across the spectrum of CVD and HF risk and represents a therapeutic advance in the prevention and perhaps also in the treatment of HF, an often poorly recognised complication of T2D. This review discusses the EMPA-REG OUTCOME study and the implications for treating patients with T2D and CVD.

Renal protection by sodium-glucose cotransporter 2 inhibitors and its underlying mechanisms in diabetic kidney disease

AIM

Diabetic kidney disease (DKD) is the most frequent cause of mortality and morbidity, leading a global health burden. This review will focus on the potential therapeutic interventions using Sodium-glucose cotransporter-2 (SGLT2) inhibitors that could prevent the development and progression of DKD.

RESULTS

SGLT2 inhibitors have been widely used as anti-diabetic drugs. Recent clinical studies have demonstrated that these drugs, which improve glycemic control and hypertension and decrease body weight, decrease the risk of renal function impairment and heart failure in patients with type 2 diabetes. With regard to long-term clinical outcomes, the Empagliflozin, Cardiovascular Outcomes, and Mortality in Type 2 Diabetes (EMPA-REG OUTCOME), the EMPA-REG Renal OUTCOME, and the CANagliflozin cardioVascular Assessment Study (CANVAS) program which have been integrated from CANVAS and CANVAS-Renal (CANVAS-R) trials reported significant risk reductions in primary combined major adverse cardiovascular events. Furthermore, regarding renal outcomes, the EMPA-REG Renal OUTCOME and CANVAS program clearly showed improvements in renal outcomes, including decreases in albuminuria and progression of nephropathy, doubling of serum creatinine levels, and initiation of renal replacement therapy.

CONCLUSIONS

Potential mechanisms of SGLT2 inhibitors related to renoprotection can be divided into two categories: hemodynamic actions and metabolic actions.

SGLT-2 inhibitors in Diabetic Kidney Disease: What Lies Behind their Renoprotective Properties?

BACKGROUND

Despite optimal management of diabetic kidney disease (DKD) with intensive glycemic control and administration of agents blocking the renin-angiotensinaldosterone- system, the residual risk for nephropathy progression to end-stage-renal-disease (ESRD) remains high. Sodium-glucose co-transporter type 2 (SGLT-2)-inhibitors represent a newly-introduced anti-diabetic drug class with pleiotropic actions extending above their glucose-lowering efficacy. Herein, we provide an overview of preclinical and clinical-trial evidence supporting a protective effect of SGLT-2 inhibitors on DKD.

METHODS

A systematic literature search of bibliographic databases was conducted to identify preclinical studies and randomized trials evaluating the effects SGLT-2 inhibitors on DKD.

RESULTS

Preclinical studies performed in animal models of DKD support the renoprotective action of SGLT-2 inhibitors showing that these agents exert albuminuria-lowering effects and reverse glomerulosclerosis. The renoprotective action of SGLT-2 inhibitors is strongly supported by human studies showing that these agents prevent the progression of albuminuria and retard nephropathy progression to ESRD. This beneficial effect of SGLT-2 inhibitors is not fully explained by their glucose-lowering properties. Attenuation of glomerular hyperfiltration and improvement in a number of surrogate risk factors, including associated reduction in systemic blood pressure, body weight, and serum uric acid levels may represent plausible mechanistic explanations for the cardio-renal protection offered by SGLT-2 inhibitors. Furthermore, the tubular cell metabolism seems to be altered towards a ketone-prone pathway with protective activities.

CONCLUSION

SGLT-2 inhibition emerges as a novel therapeutic approach of diabetic with anticipated benefits towards cardio-renal risk reduction. Additional research efforts are clearly warranted to elucidate this favorable effect in patients with overt DKD.

Effects of sodium-glucose cotransporter 2 inhibitor, tofogliflozin, on the indices of renal tubular function in patients with type 2 diabetes

AIMS

Little is known of the effect of sodium-glucose cotransporter 2 (SGLT2) inhibitors on the renal tubules. We investigated the effect of the SGLT2 inhibitor, tofogliflozin (TOFO) on renal tubular indices, according to the degree of albuminuria, in type 2 diabetes mellitus (T2DM) patients with preserved renal function.

MATERIALS AND METHODS

A total of 988 patients, receiving TOFO, were enroled and divided into 3 groups, based on the urine albumin-to-creatinine ratio (UACR). The tubular indices (urinary N-acetyl-beta-d-glucosaminidase [NAG]-to-creatinine and urinary beta-2 microglobulin [beta2MG]-to-creatinine ratios) and UACR were log-transformed in the correlation analysis.

RESULTS

Treatment with TOFO led to similar reductions in glycated haemoglobin (HbA1c) levels, from baseline to week 24, across all groups. The NAG level increased in the normoalbuminuria group and decreased in the macroalbuminuria group significantly (P < .001, both), but did not change in the microalbuminuria group. Significant reductions in the UACR were observed in both microalbuminuria and macroalbuminuria groups (P < .001, both). Significant negative correlations between changes in the NAG and beta2MG levels and their corresponding baseline values were observed in all participants. The reduction in the UACR was negatively correlated with baseline levels. The changes in the tubular indices were positively correlated with reductions in the UACR across groups.

CONCLUSIONS

Logarithmic reductions in the renal tubular indices, via SGLT2 inhibition, were observed in patients with T2DM. TOFO may not only improve the degree of albuminuria but may also have protective effects on the tubules.

Clinical implications of current cardiovascular outcome trials with sodium glucose cotransporter-2 (SGLT2) inhibitors

The final goal in the management of patients with type 2 diabetes (T2D) is reduction in cardiovascular (CV) complications and total mortality. Various factors including hyperglycemia contribute to these complications and mortality directly and indirectly. In recent years, large-scale CV outcome trials with new antidiabetic medications, such as dipeptidyl peptidase-4 (DPP4) inhibitors, glucagon-like peptide-1 (GLP1) receptor agonists, and sodium glucose cotransporter-2 (SGLT2) inhibitors, have been completed. Most clinical trials with DPP4 inhibitors have shown no inferiority compared with placebo treatments in terms of CV safety. However, they did not show benefits in terms of adverse CV events or mortality. CV outcome trials with GLP1 receptor agonists showed inconsistent results: lixisenatide did not show benefits in preventing major adverse CV events. In contrast, liraglutide and semaglutide (longer acting GLP1 receptor agonists) proved to be superior in terms of alleviating CV morbidity and mortality. Two large-scale CV outcome trials with SGLT2 inhibitors showed significant results: empagliflozin proved to be superior in preventing CV and all-cause mortality, and canagliflozin proved to be superior in preventing CV mortality but not all-cause mortality. So far, controlling cardiometabolic risk factors such as hemodynamic changes and weight loss by SGLT2 inhibitors are suggested to be the main mechanisms for these results. However, the risk-benefit profile for these new drugs will need further elucidation, and more studies are warranted to reveal the possible mechanisms. It will also be important to confirm these results from other ongoing trials with SGLT2 inhibitors.

Renin-angiotensin-aldosterone system activation in long-standing type 1 diabetes

BACKGROUND

In type 1 diabetes (T1D), adjuvant treatment with inhibitors of the renin-angiotensin-aldosterone system (RAAS), which dilate the efferent arteriole, is associated with prevention of progressive albuminuria and renal dysfunction. Uncertainty still exists as to why some individuals with long-standing T1D develop diabetic kidney disease (DKD) while others do not (DKD resistors). We hypothesized that those with DKD would be distinguished from DKD resistors by the presence of RAAS activation.

METHODS

Renal and systemic hemodynamic function was measured before and after exogenous RAAS stimulation by intravenous infusion of angiotensin II (ANGII) in 75 patients with prolonged T1D durations and in equal numbers of nondiabetic controls. The primary outcome was change in renal vascular resistance (RVR) in response to RAAS stimulation, a measure of endogenous RAAS activation.

RESULTS

Those with DKD had less change in RVR following exogenous RAAS stimulation compared with DKD resistors or controls (19%, 29%, 31%, P = 0.008, DKD vs. DKD resistors), reflecting exaggerated endogenous renal RAAS activation. All T1D participants had similar changes in renal efferent arteroilar resistance (9% vs. 13%, P = 0.37) irrespective of DKD status, which reflected less change versus controls (20%, P = 0.03). In contrast, those with DKD exhibited comparatively less change in afferent arteriolar vascular resistance compared with DKD resistors or controls (33%, 48%, 48%, P = 0.031, DKD vs. DKD resistors), indicating higher endogenous RAAS activity.

CONCLUSION

In long-standing T1D, the intrarenal RAAS is exaggerated in DKD, which unexpectedly predominates at the afferent rather than the efferent arteriole, stimulating vasoconstriction.

FUNDING

JDRF operating grant 17-2013-312.

Sodium-glucose Cotransporter-2 Inhibitors: Moving Beyond the Glycemic Treatment Goal

Revelations of the multifactorial pathogenesis of type 2 diabetes mellitus (T2DM) that extend beyond the role of insulin and glucose utilization have been crucial in redefining the treatment paradigm. The focus of treatment is currently directed towards achieving wide-ranging targets encompassing the management of cardiovascular comorbidities that have been evidenced as indispensable aspects of T2DM. While most currently prescribed antihyperglycemic agents have little or no effect on reducing cardiovascular risks, some have been associated with undesirable effects on common risk factors such as weight gain and cardiovascular sequelae. Sodium-glucose cotransporter-2 inhibitors (SGLT2i) are newer additions to the array of therapeutic agents for T2DM that have demonstrated robust glycemic control as mono and add-on therapies. Their unique renal mode of action, independent of insulin modulation, confers complementary metabolic benefits. By virtue of these effects, SGLT2i may have a distinct role in the revised treatment recommendations by established working groups such as the American Diabetes Association and the American Association of Clinical Endocrinologists that advocate a more comprehensive management of T2DM, not restricting to glycemic targets. The current review gives an overview of the changing treatment needs for T2DM and discusses the nonglycemic effects of SGLT2i. It provides an updated summary on the efficacy of canagliflozin, dapagliflozin, and empagliflozin in promoting weight loss, stabilizing blood pressure, and other favorable metabolic effects.

Dapagliflozin acutely improves endothelial dysfunction, reduces aortic stiffness and renal resistive index in type 2 diabetic patients: a pilot study

Background

Sodium-glucose cotransporter-2 inhibitors reduce blood pressure (BP) and renal and cardiovascular events in patients with type 2 diabetes through not fully elucidated mechanisms. Aim of this study was to investigate whether dapagliflozin is able to acutely modify systemic and renal vascular function, as well as putative mechanisms.

Methods

Neuro-hormonal and vascular variables, together with 24 h diuresis, urinary sodium, glucose, isoprostanes and free-water clearance were assessed before and after a 2-day treatment with dapagliflozin 10 mg QD in sixteen type 2 diabetic patients; data were compared with those obtained in ten patients treated with hydrochlorothiazide 12.5 mg QD. Brachial artery endothelium-dependent and independent vasodilation (by flow-mediated dilation) and pulse wave velocity were assessed. Renal resistive index was obtained at rest and after glyceryl trinitrate administration. Differences were analysed by repeated measures ANOVA, considering treatment as between factor and time as within factor; Bonferroni post hoc comparison test was also used.

Results

Dapagliflozin decreased systolic BP and induced an increase in 24 h diuresis to a similar extent of hydrochlorothiazide; 24 h urinary glucose and serum magnesium were also increased. 24 h urinary sodium and fasting blood glucose were unchanged. Oxidative stress was reduced, as by a decline in urinary isoprostanes. Flow-mediated dilation was significantly increased (2.8 ± 2.2 to 4.0 ± 2.1%, p < 0.05), and pulse-wave-velocity was reduced (10.1 ± 1.6 to 8.9 ± 1.6 m/s, p < 0.05), even after correction for mean BP. Renal resistive index was reduced (0.62 ± 0.04 to 0.59 ± 0.05, p < 0.05). These vascular modifications were not observed in hydrochlorothiazide-treated individuals.

Conclusions

An acute treatment with dapagliflozin significantly improves systemic endothelial function, arterial stiffness and renal resistive index; this effect is independent of changes in BP and occurs in the presence of stable natriuresis, suggesting a fast, direct beneficial effect on the vasculature, possibly mediated by oxidative stress reduction.

Bolstering your armamentarium with SGLT2 inhibitors

Sodium-glucose cotransporter-2 inhibitors have a unique mechanism of action in the kidneys that causes glucosuria, which lowers plasma glucose. They are also associated with reduced body weight and BP, and a low incidence of hypoglycemia. This article reviews the pharmacologic profiles and clinical implications of canagliflozin, dapagliflozin, and empagliflozin.

The albuminuria-lowering response to dapagliflozin is variable and reproducible among individual patients

AIMS

Albuminuria reduction is essential for renal and cardiovascular protection. We characterized the efficacy of dapagliflozin, a sodium-glucose co-transporter 2 inhibitor, on albuminuria. Secondly, we assessed whether the albuminuria-lowering effect varies among patients, and whether this variability in response is reproducible.

MATERIAL AND METHODS

A double-blind, randomized, placebo controlled crossover trial was conducted. Patients with type 2 diabetes and albumin:creatinine ratio > 100 mg/g on a stable dose of an angiotensin-converting enzyme inhibitor (ACEi) or angiotensin receptor blocker (ARB) were enrolled. Patients were assigned to 6-week treatment periods with dapagliflozin 10 mg/d or placebo in random order, separated by 6-weeks wash-out periods. After the 2 treatment periods, half of the patients were re-exposed for 6 weeks to dapagliflozin 10 mg/d. Primary outcome was change in 24-hour urinary albumin excretion rate (24 h UAE). To assess reproducibility in individual albuminuria response, responses from the first and second exposure to dapagliflozin were correlated.

RESULTS

A total of 33 patients (age, 61 years; female gender, 24.2%; median 24 h UAE, 470 mg/24 h) completed the study. Dapagliflozin, as compared to placebo, reduced 24 h UAE by 36.2% (95% CI, 22.9-47.2; P  < .001). Systolic blood pressure fell by 5.2 mm Hg (95% CI, 0.5-10.0) and eGFR by 5.3 (95% CI, 2.7-8.0). All effects were reversible directly after treatment discontinuation. In a subgroup of 15 patients who were exposed twice to dapagliflozin, 24 h UAE responses showed a large variation among individuals: first exposure (range, -76% to +52%) and second exposure (-90% to +95%) and first and second individual response were significantly correlated (r = 0.69 [95% CI, 0.27-0.89]; P  < .004).

CONCLUSION

Dapagliflozin significantly reduces albuminuria when given as adjunct to ACEi or ARB. The albuminuria response to dapagliflozin markedly varies among patients. This variation is not a random phenomenon, but is reproducible upon re-exposure. These data support personalized therapy approaches to optimize diabetic kidney disease.

EMPA-REG OUTCOME: The Nephrologist's Point of View

There is increasing evidence that sodium glucose cotransporter 2 (SGLT2) inhibitors have renoprotective effects, as demonstrated by the renal analyses from clinical trials including Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients-Removing Excess Glucose (EMPA-REG OUTCOME), CANagliflozin Treatment And Trial Analysis versus SUlphonylurea (CANTATA-SU), and the dapagliflozin renal study. The potential mechanisms responsible are likely multifactorial, and direct renovascular and hemodynamic effects are postulated to play a central role. This report reviews the renal outcomes data from key SGLT2 inhibitor clinical trials, discusses the hypotheses for SGLT2 inhibitor-associated renoprotection, and considers the main renal safety issues associated with SGLT2 inhibitor treatment.

Renal and Vascular Effects of Uric Acid Lowering in Normouricemic Patients With Uncomplicated Type 1 Diabetes

Higher plasma uric acid (PUA) levels are associated with lower glomerular filtration rate (GFR) and higher blood pressure (BP) in patients with type 1 diabetes (T1D). Our aim was to determine the impact of PUA lowering on renal and vascular function in patients with uncomplicated T1D. T1D patients (n = 49) were studied under euglycemic and hyperglycemic conditions at baseline and after PUA lowering with febuxostat (FBX) for 8 weeks. Healthy control subjects were studied under normoglycemic conditions (n = 24). PUA, GFR (inulin), effective renal plasma flow (para-aminohippurate), BP, and hemodynamic responses to an infusion of angiotensin II (assessment of intrarenal renin-angiotensin-aldosterone system [RAAS]) were measured before and after FBX treatment. Arterial stiffness, flow-mediated dilation (FMD), nitroglycerin-mediated dilation (GMD), urinary nitric oxide (NO), and inflammatory markers were measured before and after FBX treatment. Gomez equations were used to estimate arteriolar afferent resistance, efferent resistance (R_E), and glomerular hydrostatic pressure (P_GLO). FBX had a modest systolic BP-lowering effect in T1D patients (112 ± 10 to 109 ± 9 mmHg, P = 0.049) without impacting arterial stiffness, FMD, GMD, or NO. FBX enhanced the filtration fraction response to hyperglycemia in T1D patients through larger increases in R_E, P_GLO, and interleukin-18 but without impacting the RAAS. FBX lowered systolic BP and modulated the renal R_E responses to hyperglycemia but without impacting the RAAS or NO levels, suggesting that PUA may augment other hemodynamic or inflammatory mechanisms that control the renal response to hyperglycemia at the efferent arteriole. Ongoing outcome trials will determine cardiorenal outcomes of PUA lowering in patients with T1D.

Metabolic and hemodynamic effects of sodium-dependent glucose cotransporter 2 inhibitors on cardio-renal protection in the treatment of patients with type 2 diabetes mellitus

The specific sodium-glucose cotransporter 2 inhibitors (SGLT2 inhibitors) inhibit glucose reabsorption in proximal renal tubular cells, and both fasting and postprandial glucose significantly decrease because of urinary glucose loss. As a result, pancreatic β-cell function and peripheral insulin action significantly improve with relief from glucose toxicity. Furthermore, whole-body energy metabolism changes to relative glucose deficiency and triggers increased lipolysis in fat cells, and fatty acid oxidation and then ketone body production in the liver during treatment with SGLT2 inhibitors. In addition, SGLT2 inhibitors have profound hemodynamic effects including diuresis, dehydration, weight loss and lowering blood pressure. The most recent findings on SGLT2 inhibitors come from results of the Empagliflozin, Cardiovascular Outcomes and Mortality in Type 2 Diabetes trial. SGLT2 inhibitors exert extremely unique and cardio-renal protection through metabolic and hemodynamic effects, with long-term durability on the reduction of blood glucose, bodyweight and blood pressure. Although a site of action of SGLT2 inhibitors is highly specific to inhibit renal glucose reabsorption, whole-body energy metabolism, and hemodynamic and renal functions are profoundly modulated during the treatment of SGLT2 inhibitors. Previous studies suggest multifactorial clinical benefits and safety concerns of SGLT2 inhibitors. Although ambivalent clinical results of this drug are still under active discussion, the present review summarizes promising recent evidence on the cardio-renal and metabolic benefits of SGLT2 inhibitors in the treatment of type 2 diabetes.

Sodium glucose cotransporter 2 in mesangial cells and retinal pericytes and its implications for diabetic nephropathy and retinopathy

Retinopathy and nephropathy are life-threatening diabetic complications that decrease patient quality of life. Although the mechanisms underlying these conditions have been extensively studied, they remain unknown. Recent reports have demonstrated the presence of sodium glucose cotransporter 2 (SGLT2) in retinal pericytes and mesangial cells. Hyperglycemia results in functional and morphological changes in these cells, but these effects are attenuated by phlorizin, a nonselective SGLT inhibitor. Based on these findings, we hypothesized that SGLT2 plays a pivotal role in the development of diabetic nephropathy and retinopathy and that SGLT2 inhibitors may directly protect against these complications.

EMPA-REG OUTCOME: The Nephrologist's Point of View

There is increasing evidence that sodium glucose cotransporter 2 (SGLT2) inhibitors have renoprotective effects, as demonstrated by the renal analyses from clinical trials including Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients-Removing Excess Glucose (EMPA-REG OUTCOME), CANagliflozin Treatment And Trial Analysis versus SUlphonylurea (CANTATA-SU), and the dapagliflozin renal study. The potential mechanisms responsible are likely multifactorial, and direct renovascular and hemodynamic effects are postulated to play a central role. This report reviews the renal outcomes data from key SGLT2 inhibitor clinical trials, discusses the hypotheses for SGLT2 inhibitor-associated renoprotection, and considers the main renal safety issues associated with SGLT2 inhibitor treatment.

SGLT2 Inhibitors as a Therapeutic Option for Diabetic Nephropathy

Diabetic nephropathy (DN) is a major cause of end-stage renal disease (ESRD) worldwide. Glycemic and blood pressure (BP) control are important but not sufficient to attenuate the incidence and progression of DN. Sodium–glucose cotransporter (SGLT) 2 inhibitors are a new class of glucose-lowering agent suggested to exert renoprotective effects in glucose lowering-dependent and independent fashions. Experimental studies have shown that SGLT2 inhibitors attenuate DN in animal models of both type 1 diabetes (T1D) and type 2 diabetes (T2D), indicating a potential renoprotective effect beyond glucose reduction. Renoprotection by SGLT2 inhibitors has been demonstrated in T2D patients with a high cardiovascular risk in randomized controlled trials (RCTs). These favorable effects of SGLT2 inhibitors are explained by several potential mechanisms, including the attenuation of glomerular hyperfiltration, inflammation and oxidative stress. In this review article, we discuss the renoprotective effects of SGLT2 inhibitors by integrating experimental findings with the available clinical data.

SGLT2 Inhibition in the Diabetic Kidney-From Mechanisms to Clinical Outcome

Diabetic kidney disease not only has become the leading cause for ESRD worldwide but also, highly contributes to increased cardiovascular morbidity and mortality in type 2 diabetes. Despite increased efforts to optimize renal and cardiovascular risk factors, like hyperglycemia, hypertension, obesity, and dyslipidemia, they are often insufficiently controlled in clinical practice. Although current drug interventions mostly target a single risk factor, more substantial improvements of renal and cardiovascular outcomes can be expected when multiple factors are improved simultaneously. Sodium-glucose cotransporter type 2 in the renal proximal tubule reabsorbs approximately 90% of filtered glucose. In type 2 diabetes, the maladaptive upregulation of sodium-glucose cotransporter type 2 contributes to the maintenance of hyperglycemia. Inhibiting these transporters has been shown to effectively improve glycemic control through inducing glycosuria and is generally well tolerated, although patients experience more genital infections. In addition, sodium-glucose cotransporter type 2 inhibitors favorably affect body weight, BP, serum uric acid, and glomerular hyperfiltration. Interestingly, in the recently reported first cardiovascular safety trial with a sodium-glucose cotransporter type 2 inhibitor, empagliflozin improved both renal and cardiovascular outcomes in patients with type 2 diabetes and established cardiovascular disease. Because the benefits were seen rapidly after initiation of therapy and other glucose-lowering agents, with the exception of liraglutide and semaglutide, have not been able to improve cardiovascular outcome, these observations are most likely explained by effects beyond glucose lowering. In this mini review, we present the drug class of sodium-glucose cotransporter type 2 inhibitors, elaborate on currently available renal and cardiovascular outcome data, and discuss how the effects of these agents on renal physiology may explain the data.

Glomerular Hyperfiltration in Diabetes: Mechanisms, Clinical Significance, and Treatment

An absolute, supraphysiologic elevation in GFR is observed early in the natural history in 10%-67% and 6%-73% of patients with type 1 and type 2 diabetes, respectively. Moreover, at the single-nephron level, diabetes-related renal hemodynamic alterations-as an adaptation to reduction in functional nephron mass and/or in response to prevailing metabolic and (neuro)hormonal stimuli-increase glomerular hydraulic pressure and transcapillary convective flux of ultrafiltrate and macromolecules. This phenomenon, known as glomerular hyperfiltration, classically has been hypothesized to predispose to irreversible nephron damage, thereby contributing to initiation and progression of kidney disease in diabetes. However, dedicated studies with appropriate diagnostic measures and clinically relevant end points are warranted to confirm this assumption. In this review, we summarize the hitherto proposed mechanisms involved in diabetic hyperfiltration, focusing on ultrastructural, vascular, and tubular factors. Furthermore, we review available evidence on the clinical significance of hyperfiltration in diabetes and discuss currently available and emerging interventions that may attenuate this renal hemodynamic abnormality. The revived interest in glomerular hyperfiltration as a prognostic and pathophysiologic factor in diabetes may lead to improved and timely detection of (progressive) kidney disease, and could provide new therapeutic opportunities in alleviating the renal burden in this population.

Influence of sex on hyperfiltration in patients with uncomplicated type 1 diabetes

The aim of this analysis was to examine sex-based differences in renal segmental resistances in healthy controls (HCs) and patients with type 1 diabetes (T1D). We hypothesized that hyperfiltration-an early hemodynamic abnormality associated with diabetic nephropathy-would disproportionately affect women with T1D, thereby attenuating protection against the development of renal complications. Glomerular hemodynamic parameters were evaluated in HC (n = 30) and in normotensive, normoalbuminuric patients with T1D and either baseline normofiltration [n = 36, T1D-N, glomerular filtration rate (GFR) 90-134 ml·min^-1·1.73 m²] or hyperfiltration (n = 32, T1D-H, GFR ≥ 135 ml·min^-1·1.73 m²) during euglycemic conditions (4-6 mmol/l). Gomez's equations were used to derive efferent (R_E) and afferent (R_A) arteriolar resistances, glomerular hydrostatic pressure (P_GLO) from inulin (GFR) and paraaminohippurate [effective renal plasma flow (ERPF)] clearances, plasma protein and estimated ultrafiltration coefficients (K_FG). Female patients with T1D with hyperfiltration (T1D-H) had higher R_E (1,985 ± 487 vs. 1,381 ± 296 dyne·sec^-1·cm^-5, P < 0.001) and filtration fraction (FF, 0.20 ± 0.047 vs. 0.16 ± 0.03 P < 0.05) and lower ERPF (876 ± 245 vs. 1,111 ± 298 134 ml·min^-1·1.73 m²P < 0.05) compared with male T1D-H patients. Overall, T1D-H patients had higher P_GLO and lower R_A vs. HC subjects, although there were no sex-based differences. In conclusion, female T1D-H patients had higher R_E and FF and lower ERPF than their male counterparts with no associated sex differences in R_A Prospective intervention studies should consider sex as a modifier of renal hemodynamic responses to renal protective therapies.

The renal effects of SGLT2 inhibitors and a mini-review of the literature

Sodium-glucose linked transporter 2 (SGLT2) inhibitors are a new and promising class of antidiabetic agents which target renal tubular glucose reabsorption. Their action is based on the blockage of SGLT2 sodium-glucose cotransporters that are located at the luminal membrane of tubular cells of the proximal convoluted tubule, inducing glucosuria. It has been proven that they significantly reduce glycated hemoglobin (HbA1c), along with fasting and postprandial plasma glucose in patients with type 2 diabetes mellitus (T2DM). The glucosuria-induced caloric loss as well as the osmotic diuresis significantly decrease body weight and blood pressure, respectively. Given that SGLT2 inhibitors do not interfere with insulin action and secretion, their efficacy is sustained despite the progressive β-cell failure in T2DM. They are well tolerated, with a low risk of hypoglycemia. Their most frequent adverse events are minor: genital and urinal tract infections. Recently, it was demonstrated that empagliflozin presents a significant cardioprotective effect. Although the SGLT2 inhibitors' efficacy is affected by renal function, new data have been presented that some SGLT2 inhibitors, even in mild and moderate renal impairment, induce significant HbA1c reduction. Moreover, recent data indicate that SGLT2 inhibition has a beneficial renoprotective effect. The role of this review paper is to explore the current evidence on the renal effects of SGLT2 inhibitors.

The Gomez' equations and renal hemodynamic function in kidney disease research

Diabetic kidney disease (DKD) remains the leading cause of end-stage renal disease. A major challenge in preventing DKD is the difficulty in identifying high-risk patients at an early, pre-clinical stage. Albuminuria and eGFR as measures of renal function in DKD research and clinical practice are limited by regression of one-third of patients with microalbuminuria to normoalbuminuria and eGFR is biased and imprecise in the normal-elevated range. Moreover, existing methods that are used to assess renal function do not give detailed insight into the location of the renal hemodynamic effects of pharmacological agents at the segmental level. To gain additional information about the intrarenal circulation in-vivo in humans, mathematical equations were developed by Gomez et al in the 1950s. These equations used measurements of GFR, renal blood flow (RBF), effective renal plasma flow (ERPF), renal vascular resistance (RVR), hematocrit and serum protein to calculate afferent and efferent arteriolar resistances, glomerular hydrostatic pressure and filtration pressure. Although indirect and based on physiological assumptions, these techniques have the potential to improve researchers' ability to identify early pre-clinical changes in renal hemodynamic function in patients with a variety of conditions including DKD, thereby offering tremendous potential in mechanistic human research studies. In this review, we focus on the application of Gomez' equations and summarize the potential and limitations of this technique in DKD research. We also summarize illustrative data derived from Gomez' equations in patients with type 1 (T1D) and type 2 diabetes (T2D) and hypertension.

Fatty Liver and Chronic Kidney Disease: Novel Mechanistic Insights and Therapeutic Opportunities

Chronic kidney disease (CKD) is a risk factor for end-stage renal disease (ESRD) and cardiovascular disease (CVD). ESRD or CVD develop in a substantial proportion of patients with CKD receiving standard-of-care therapy, and mortality in CKD remains unchanged. These data suggest that key pathogenetic mechanisms underlying CKD progression go unaffected by current treatments. Growing evidence suggests that nonalcoholic fatty liver disease (NAFLD) and CKD share common pathogenetic mechanisms and potential therapeutic targets. Common nutritional conditions predisposing to both NAFLD and CKD include excessive fructose intake and vitamin D deficiency. Modulation of nuclear transcription factors regulating key pathways of lipid metabolism, inflammation, and fibrosis, including peroxisome proliferator-activated receptors and farnesoid X receptor, is advancing to stage III clinical development. The relevance of epigenetic regulation in the pathogenesis of NAFLD and CKD is also emerging, and modulation of microRNA21 is a promising therapeutic target. Although single antioxidant supplementation has yielded variable results, modulation of key effectors of redox regulation and molecular sensors of intracellular energy, nutrient, or oxygen status show promising preclinical results. Other emerging therapeutic approaches target key mediators of inflammation, such as chemokines; fibrogenesis, such as galectin-3; or gut dysfunction through gut microbiota manipulation and incretin-based therapies. Furthermore, NAFLD per se affects CKD through lipoprotein metabolism and hepatokine secretion, and conversely, targeting the renal tubule by sodium-glucose cotransporter 2 inhibitors can improve both CKD and NAFLD. Implications for the treatment of NAFLD and CKD are discussed in light of this new therapeutic armamentarium.

The effect of sodium glucose cotransporter 2 inhibition with empagliflozin on microalbuminuria and macroalbuminuria in patients with type 2 diabetes

AIMS/HYPOTHESIS

Sodium glucose cotransporter 2 (SGLT2) inhibition lowers HbA1c, systolic BP (SBP) and weight in patients with type 2 diabetes and reduces renal hyperfiltration associated with type 1 diabetes, suggesting decreased intraglomerular hypertension. As lowering HbA1c, SBP, weight and intraglomerular pressure is associated with anti-albuminuric effects in diabetes, we hypothesised that SGLT2 inhibition would reduce the urine albumin-to-creatinine ratio (UACR) to a clinically meaningful extent.

METHODS

We examined the effect of the SGLT2 inhibitor empagliflozin on UACR by pooling data from patients with type 2 diabetes and prevalent microalbuminuria (UACR = 30-300 mg/g; n = 636) or macroalbuminuria (UACR > 300 mg/g; n = 215) who participated in one of five phase III randomised clinical trials. Primary assessment was defined as percentage change in geometric mean UACR from baseline to week 24.

RESULTS

After controlling for clinical confounders including baseline log-transformed UACR, HbA1c, SBP and estimated GFR (according to the Modification of Diet in Renal Disease [MDRD] formula), treatment with empagliflozin significantly reduced UACR in patients with microalbuminuria (-32% vs placebo; p < 0.001) or macroalbuminuria (-41% vs placebo; p < 0.001). Intriguingly, in regression models, most of the UACR-lowering effect with empagliflozin was not explained by SGLT2 inhibition-related improvements in HbA1c, SBP or weight.

CONCLUSIONS/INTERPRETATION

In patients with type 2 diabetes and either micro- or macroalbuminuria, empagliflozin reduced UACR by a clinically meaningful amount. This effect was largely independent of the known metabolic or systemic haemodynamic effects of this drug class. Our results further support a direct renal effect of SGLT2 inhibitors. Prospective studies are needed to explore the potential of this intervention to alter the course of kidney disease in high-risk patients with diabetes.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01177813 (study 1); NCT01159600 (study 2); NCT01159600 (study 3); NCT01210001 (study 4); and NCT01164501 (study 5).

SGLT2 Inhibitors and the Diabetic Kidney

Diabetic nephropathy (DN) is the most common cause of end-stage renal disease worldwide. Blood glucose and blood pressure control reduce the risk of developing this complication; however, once DN is established, it is only possible to slow progression. Sodium-glucose cotransporter 2 (SGLT2) inhibitors, the most recent glucose-lowering oral agents, may have the potential to exert nephroprotection not only through improving glycemic control but also through glucose-independent effects, such as blood pressure-lowering and direct renal effects. It is important to consider, however, that in patients with impaired renal function, given their mode of action, SGLT2 inhibitors are less effective in lowering blood glucose. In patients with high cardiovascular risk, the SGLT2 inhibitor empagliflozin lowered the rate of cardiovascular events, especially cardiovascular death, and substantially reduced important renal outcomes. Such benefits on DN could derive from effects beyond glycemia. Glomerular hyperfiltration is a potential risk factor for DN. In addition to the activation of the renin-angiotensin-aldosterone system, renal tubular factors, including SGLT2, contribute to glomerular hyperfiltration in diabetes. SGLT2 inhibitors reduce sodium reabsorption in the proximal tubule, causing, through tubuloglomerular feedback, afferent arteriole vasoconstriction and reduction in hyperfiltration. Experimental studies showed that SGLT2 inhibitors reduced hyperfiltration and decreased inflammatory and fibrotic responses of proximal tubular cells. SGLT2 inhibitors reduced glomerular hyperfiltration in patients with type 1 diabetes, and in patients with type 2 diabetes, they caused transient acute reductions in glomerular filtration rate, followed by a progressive recovery and stabilization of renal function. Interestingly, recent studies consistently demonstrated a reduction in albuminuria. Although these data are promising, only dedicated renal outcome trials will clarify whether SGLT2 inhibitors, in addition to their glycemic and blood pressure benefits, may provide nephroprotective effects.