The effect of aliskiren on urinary cytokine/chemokine responses to clamped hyperglycaemia in type 1 diabetes

Markers of Kidney Injury, Inflammation, and Fibrosis Associated With Ertugliflozin in Patients With CKD and Diabetes

Introduction

Sodium-glucose cotransporter-2 (SGLT2) inhibitors improve cardiovascular and kidney outcomes through mechanisms that are incompletely understood. In this exploratory post-hoc analysis of the VERTIS RENAL trial, we report the association between the SGLT2 inhibitor, ertugliflozin, and markers of kidney injury, inflammation, and fibrosis in participants with type 2 diabetes (T2D) and stage 3 chronic kidney disease (CKD).

Methods

Participants were randomized to ertugliflozin (5 or 15 mg/d) or placebo, and plasma samples for biomarker analysis were collected at baseline, 26 weeks, and 52 weeks.

Results

Ertugliflozin-treated participants had lower plasma levels of kidney injury molecule-1 (KIM-1) at 26 weeks (P = 0.044) and 52 weeks (P = 0.007) and higher eotaxin-1 at 52 weeks (P = 0.007) postrandomization compared with placebo. The change in KIM-1 was not associated with the baseline urine albumin to creatinine ratio (UACR) or the estimated glomerular filtration rate (eGFR, P interaction > 0.05). Additionally, the change in KIM-1 was positively correlated with the change in UACR in participants treated with ertugliflozin (P = 0.0071). No other significant associations between ertugliflozin and changes in the markers of tubular injury, inflammation, fibrosis, oxidative stress, and endothelial dysfunction were observed.

Conclusion

In conclusion, in participants with T2D and stage 3 CKD, ertugliflozin was associated with a sustained lowering of the tubular injury marker KIM-1 regardless of baseline kidney function.

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.

Canadians Seeking Solutions and Innovations to Overcome Chronic Kidney Disease (Can-SOLVE CKD): Form and Function

PURPOSE OF REVIEW

This article serves to describe the Can-SOLVE CKD network, a program of research projects and infrastructure that has excited patients and given them hope that we can truly transform the care they receive.

ISSUE

Chronic kidney disease (CKD) is a complex disorder that affects more than 4 million Canadians and costs the Canadian health care system more than $40 billion per year. The evidence base for guiding care in CKD is small, and even in areas where evidence exists, uptake of evidence into clinical practice has been slow. Compounding these complexities are the variations in outcomes for patients with CKD and difficulties predicting who is most likely to develop complications over time. Clearly these gaps in our knowledge and understanding of CKD need to be filled, but the current state of CKD research is not where it needs to be. A culture of clinical trials and inquiry into the disease is lacking, and much of the existing evidence base addresses the concerns of the researchers but not necessarily those of the patients.

PROGRAM OVERVIEW

The Canadian Institutes of Health Research (CIHR) has launched the national Strategy for Patient-Oriented Research (SPOR), a coalition of federal, provincial, and territorial partners dedicated to integrating research into care. Canadians Seeking Solutions and Innovations to Overcome Chronic Kidney Disease (Can-SOLVE CKD) is one of five pan-Canadian chronic kidney disease networks supported through the SPOR. The vision of Can-SOLVE CKD is that by 2020 every Canadian with or at high risk for CKD will receive the best recommended care, experience optimal outcomes, and have the opportunity to participate in studies with novel therapies, regardless of age, sex, gender, location, or ethnicity.

PROGRAM OBJECTIVE

The overarching objective of Can-SOLVE CKD is to accelerate the translation of knowledge about CKD into clinical research and practice. By focusing on the patient's voice and implementing relevant findings in real time, Can-SOLVE CKD will transform the care that CKD patients receive, and will improve kidney health for future generations.

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.

Dipeptidyl Peptidase 4 Inhibition Stimulates Distal Tubular Natriuresis and Increases in Circulating SDF-1α1-67 in Patients With Type 2 Diabetes

OBJECTIVE

Antihyperglycemic agents, such as empagliflozin, stimulate proximal tubular natriuresis and improve cardiovascular and renal outcomes in patients with type 2 diabetes. Because dipeptidyl peptidase 4 (DPP-4) inhibitors are used in combination with sodium-glucose cotransporter 2 (SGLT2) inhibitors, we examined whether and how sitagliptin modulates fractional sodium excretion and renal and systemic hemodynamic function.

RESEARCH DESIGN AND METHODS

We studied 32 patients with type 2 diabetes in a prospective, double-blind, randomized, placebo-controlled trial. Measurements of renal tubular function and renal and systemic hemodynamics were obtained at baseline, then hourly after one dose of sitagliptin or placebo, and repeated at 1 month. Fractional excretion of sodium and lithium and renal hemodynamic function were measured during clamped euglycemia. Systemic hemodynamics were measured using noninvasive cardiac output monitoring, and plasma levels of intact versus cleaved stromal cell-derived factor (SDF)-1α were quantified using immunoaffinity and tandem mass spectrometry.

RESULTS

Sitagliptin did not change fractional lithium excretion but significantly increased total fractional sodium excretion (1.32 ± 0.5 to 1.80 ± 0.01% vs. 2.15 ± 0.6 vs. 2.02 ± 1.0%, P = 0.012) compared with placebo after 1 month of treatment. Moreover, sitagliptin robustly increased intact plasma SDF-1α^1-67 and decreased truncated plasma SDF-1α^3-67. Renal hemodynamic function, systemic blood pressure, cardiac output, stroke volume, and total peripheral resistance were not adversely affected by sitagliptin.

CONCLUSIONS

DPP-4 inhibition promotes a distal tubular natriuresis in conjunction with increased levels of intact SDF-1α^1-67. Because of the distal location of the natriuretic effect, DPP-4 inhibition does not affect tubuloglomerular feedback or impair renal hemodynamic function, findings relevant to using DPP-4 inhibitors for treating type 2 diabetes.

Immunologic Effects of the Renin-Angiotensin System

Inappropriate activation of the renin-angiotensin system (RAS) exacerbates renal and vascular injury. Accordingly, treatment with global RAS antagonists attenuates cardiovascular risk and slows the progression of proteinuric kidney disease. By reducing BP, RAS inhibitors limit secondary immune activation responding to hemodynamic injury in the target organ. However, RAS activation in hematopoietic cells has immunologic effects that diverge from those of RAS stimulation in the kidney and vasculature. In preclinical studies, activating type 1 angiotensin (AT1) receptors in T lymphocytes and myeloid cells blunts the polarization of these cells toward proinflammatory phenotypes, protecting the kidney from hypertensive injury and fibrosis. These endogenous functions of immune AT1 receptors temper the pathogenic actions of renal and vascular AT1 receptors during hypertension. By counteracting the effects of AT1 receptor stimulation in the target organ, exogenous administration of AT2 receptor agonists or angiotensin 1-7 analogs may similarly limit inflammatory injury to the heart and kidney. Moreover, although angiotensin II is the classic effector molecule of the RAS, several RAS enzymes affect immune homeostasis independently of canonic angiotensin II generation. Thus, as reviewed here, multiple components of the RAS signaling cascade influence inflammatory cell phenotype and function with unpredictable and context-specific effects on innate and adaptive immunity.

Update on Estimation of Kidney Function in Diabetic Kidney Disease

The American Diabetes Association recommends annual assessment of glomerular filtration rate (GFR) to screen for diabetic nephropathy. GFR is measured indirectly using markers that, ideally, are eliminated only by glomerular filtration. Measured GFR, although the gold standard, remains cumbersome and expensive. GFR is therefore routinely estimated using creatinine and/or cystatin C and clinical variables. In pediatrics, the Schwartz creatinine-based equation is most frequently used even though combined creatinine and cystatin C-based equations demonstrate stronger agreement with measured GFR. In adults, the CKD Epidemiology Collaboration (CKD-EPI) equations with creatinine and/or cystatin C are the most accurate and precise estimating equations. Despite recent advances, current estimates of GFR lack precision and accuracy before chronic kidney disease stage 3 (GFR < 60 mL/min/1.73 m(2)). There is therefore an urgent need to improve the methods for estimating and measuring GFR. In this review, we examine the current literature and data addressing measurement and estimation of GFR in diabetes.

Early diabetic nephropathy in type 1 diabetes: new insights

PURPOSE OF REVIEW

Despite improvements in glycemic and blood pressure control in patients with type 1 diabetes, diabetic nephropathy remains the most common cause of chronic kidney disease worldwide. A major challenge in preventing diabetic nephropathy is the inability to identify high-risk patients at an early stage, emphasizing the importance of discovering new therapeutic targets and implementation of clinical trials to reduce diabetic nephropathy risk.

RECENT FINDINGS

Limitations of managing patients with diabetic nephropathy with renin-angiotensin-aldosterone system blockade have been identified in recent clinical trials, including the failure of primary prevention studies in T1D and the demonstration of harm with dual renin-angiotensin-aldosterone system blockade. Fortunately, several new targets, including serum uric acid, insulin sensitivity, vasopressin, and sodium-glucose cotransporter-2 inhibition, are promising in the prevention and treatment of diabetic nephropathy.

SUMMARY

Diabetic nephropathy is characterized by a long clinically silent period without signs or symptoms of disease. There is an urgent need for improved methods of detecting early mediators of renal injury, to ultimately prevent the initiation and progression of diabetic nephropathy. In this review, we will focus on early diabetic nephropathy and summarize potential new therapeutic targets.

Fasting blood glucose--a missing variable for GFR-estimation in type 1 diabetes?

OBJECTIVE

Estimation of glomerular filtration rate (eGFR) is one of the current clinical methods for identifying risk for diabetic nephropathy in subjects with type 1 diabetes (T1D). Hyperglycemia is known to influence GFR in T1D and variability in blood glucose at the time of eGFR measurement could introduce bias in eGFR. We hypothesized that simultaneously measured blood glucose would influence eGFR in adults with T1D.

METHODS

Longitudinal multivariable mixed-models were employed to investigate the relationships between blood glucose and eGFR by CKD-EPI eGFRCYSTATIN C over 6-years in the Coronary Artery Calcification in Type 1 diabetes (CACTI) study. All subjects with T1D and complete data including blood glucose and cystatin C for at least one of the three visits (n = 616, 554, and 521, respectively) were included in the longitudinal analyses.

RESULTS

In mixed-models adjusting for sex, HbA1c, ACEi/ARB, protein and sodium intake positive associations were observed between simultaneous blood glucose and eGFRCYSTATIN C (β±SE:0.14±0.04 per 10 mg/dL of blood glucose, p<0.0001), and hyperfiltration as a dichotomous outcome (OR: 1.04, 95% CI: 1.01-1.07 per 10 mg/dL of blood glucose, p = 0.02).

CONCLUSIONS

In our longitudinal data in subjects with T1D, simultaneous blood glucose has an independent positive effect on eGFRCYSTATIN C. The associations between blood glucose and eGFRCYSTATIN C may bias the accurate detection of early diabetic nephropathy, especially in people with longitudinal variability in blood glucose.