Renal hyperfiltration and systemic blood pressure in patients with uncomplicated type 1 diabetes mellitus

Renal and Vascular Effects of Combined SGLT2 and Angiotensin-Converting Enzyme Inhibition

BACKGROUND

The cardiorenal effects of sodium-glucose cotransporter 2 inhibition (empagliflozin 25 mg QD) combined with angiotensin-converting enzyme inhibition (ramipril 10 mg QD) were assessed in this mechanistic study in patients with type 1 diabetes with potential renal hyperfiltration.

METHODS

Thirty patients (out of 31 randomized) completed this double-blind, placebo-controlled, crossover trial. Recruitment was stopped early because of an unexpectedly low proportion of patients with hyperfiltration. Measurements were obtained after each of the 6 treatment phases over 19 weeks: (1) baseline without treatment, (2) 4-week run-in with ramipril treatment alone, (3) 4-week combined empagliflozin-ramipril treatment, (4) a 4-week washout, (5) 4-week combined placebo-ramipril treatment, and (6) 1-week follow-up. The primary end point was glomerular filtration rate (GFR) after combination treatment with empagliflozin-ramipril compared with placebo-ramipril. GFR was corrected for ramipril treatment alone before randomization. At the end of study phase, the following outcomes were measured under clamped euglycemia (4 to 6 mmol/L): inulin (GFR) and para-aminohippurate (effective renal plasma flow) clearances, tubular sodium handling, ambulatory blood pressure, arterial stiffness, heart rate variability, noninvasive cardiac output monitoring, plasma and urine biochemistry, markers of the renin-angiotensin-aldosterone system, and oxidative stress.

RESULTS

Combination treatment with empagliflozin-ramipril resulted in an 8 mL/min/1.73 m² lower GFR compared with placebo-ramipril treatment (P=0.0061) without significant changes to effective renal plasma flow. GFR decrease was accompanied by a 21.3 mL/min lower absolute proximal fluid reabsorption rate (P=0.0092), a 3.1 mmol/min lower absolute proximal sodium reabsorption rate (P=0.0056), and a 194 ng/mmol creatinine lower urinary 8-isoprostane level (P=0.0084) relative to placebo-ramipril combination treatment. Sodium-glucose cotransporter 2 inhibitor/angiotensin-converting enzyme inhibitor combination treatment resulted in additive blood pressure-lowering effects (clinic systolic blood pressure lower by 4 mm Hg [P=0.0112]; diastolic blood pressure lower by 3 mm Hg [P=0.0032]) in conjunction with a 94.5 dynes × sex/cm⁵ lower total peripheral resistance (P=0.0368). There were no significant changes observed to ambulatory blood pressure, arterial stiffness, heart rate variability, or cardiac output with the addition of empagliflozin.

CONCLUSIONS

Adding sodium-glucose cotransporter 2 inhibitor treatment to angiotensin-converting enzyme inhibitor resulted in an expected GFR dip, suppression of oxidative stress markers, additive declines in blood pressure and total peripheral resistance. These changes are consistent with a protective physiologic profile characterized by the lowering of intraglomerular pressure and related cardiorenal risk when adding a sodium-glucose cotransporter 2 inhibitor to conservative therapy.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT02632747.

Glomerular Biomechanical Stress and Lipid Mediators during Cellular Changes Leading to Chronic Kidney Disease

Hyperfiltration is an important underlying cause of glomerular dysfunction associated with several systemic and intrinsic glomerular conditions leading to chronic kidney disease (CKD). These include obesity, diabetes, hypertension, focal segmental glomerulosclerosis (FSGS), congenital abnormalities and reduced renal mass (low nephron number). Hyperfiltration-associated biomechanical forces directly impact the cell membrane, generating tensile and fluid flow shear stresses in multiple segments of the nephron. Ongoing research suggests these biomechanical forces as the initial mediators of hyperfiltration-induced deterioration of podocyte structure and function leading to their detachment and irreplaceable loss from the glomerular filtration barrier. Membrane lipid-derived polyunsaturated fatty acids (PUFA) and their metabolites are potent transducers of biomechanical stress from the cell surface to intracellular compartments. Omega-6 and ω-3 long-chain PUFA from membrane phospholipids generate many versatile and autacoid oxylipins that modulate pro-inflammatory as well as anti-inflammatory autocrine and paracrine signaling. We advance the idea that lipid signaling molecules, related enzymes, metabolites and receptors are not just mediators of cellular stress but also potential targets for developing novel interventions. With the growing emphasis on lifestyle changes for wellness, dietary fatty acids are potential adjunct-therapeutics to minimize/treat hyperfiltration-induced progressive glomerular damage and CKD.

Renal hyperfiltration defined by high estimated glomerular filtration rate: A risk factor for cardiovascular disease and mortality

Renal hyperfiltration, defined as an increased glomerular filtration rate above normal values, is associated with early phases of kidney disease in the setting of various conditions such as obesity and diabetes. Although it is recognized that glomerular hyperfiltration, that is, increased filtration per nephron unit (usually studied at low glomerular filtration levels and often referred to as single nephron hyperfiltration), is a risk factor for the progression of chronic kidney disease, the implications of having renal hyperfiltration for cardiovascular disease and mortality risk are incompletely understood. Recent evidence from diverse populations, including healthy individuals and patients with diabetes or established cardiovascular disease, suggests that renal hyperfiltration is associated with a higher risk of cardiovascular disease and all-cause mortality. In this review, we critically summarize the existing studies, discuss possible mechanisms, and describe the remaining gaps in our knowledge regarding the association of renal hyperfiltration with cardiovascular disease and mortality risk.

High-normal albuminuria is associated with subclinical atherosclerosis in male population with estimated glomerular filtration rate ≥60 mL/min/1.73 m2: A cross-sectional study

Background

Low-grade albuminuria has been considered a predictor of cardiovascular mortality. We investigated the relationship between high-normal albuminuria and subclinical atherosclerosis in non-diabetic men with estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m².

Methods

In this cross-sectional study, 1,756 men with eGFR ≥60 mL/min/1.73 m² and urine albumin-to-creatinine ratio (UACR) <30 mg/g, who attended general health checkups between April 2012 and March 2015, underwent blood sampling, urinalysis, and carotid ultrasonography. We excluded the subjects who were diabetic and/or received an anti-hypertensive drug. Carotid intima-media thickness (IMT) and the number of focal atheromatous plaques were used as indicators of subclinical atherosclerosis. Multiple linear regression analysis was performed to identify clinical factors associated with carotid IMT. Poisson regression analysis was used to assess the determinants of the carotid plaque number.

Results

Median UACR was 4.8 mg/g (interquartile range, 3.6–6.9 mg/g). Compared with subjects with low-normal UACR (<10.0 mg/g), subjects with high-normal UACR (10.0–29.8 mg/g) had greater IMT and higher carotid plaque number. High-normal UACR was independently associated with thickened IMT in the model adjusted for conventional cardiovascular disease risk factors. Moreover, participants with high-normal UACR were also more likely to be associated with increased plaque count (prevalence ratio: 1.06; 95% confidence interval: 1.01–1.14) after adjustment for conventional cardiovascular disease risk factors.

Conclusions

Our results indicate that high-normal albuminuria is associated with both carotid IMT and plaque formation in the non-diabetic male population with eGFR ≥60 mL/min/1.73 m².

Beyond type 2 diabetes: sodium glucose co-transporter-inhibition in type 1 diabetes

Use of sodium glucose cotransporter (SGLT) inhibitors are a well-established therapeutic option in type 2 diabetes (T2D) with a variety of proven therapeutic benefits. They have become a pillar of current treatment guidelines. In type 1 diabetes (T1D), initial exploratory studies have shown benefits in glycemic control, weight control, and cardiovascular risk parameters, leading to trials aiming for regulatory submission with several agents. Results from four 1-year trials, which included a total of 3052 patients, are now available, demonstrating promising findings that target the unmet needs of patients with T1D with a novel insulin-independent adjunct therapy. However, these positive effects must be balanced against the risks associated with this class of drugs. Specifically, current T1D studies have shown an increased risk of diabetic ketoacidosis (DKA), which, in some cases, presented with only slightly elevated glucose levels. While this complication may be clinically manageable once detected, the metabolic shift towards ketogenesis associated with this class of agents mandates appropriate patient selection. Currently, there are no validated tools for DKA risk assessment. Although the experience gained in studies and off-label use provides some indication for appropriate patient selection, this would have to be evaluated closely in the event that these drugs would receive regulatory approval. Risk mitigation includes training in ketone measurement (preferably as blood β-hydroxybutyrate testing), teaching the concept of euglycemic DKA, and providing a clear treatment algorithm to avoid progression of ketosis to full-blown DKA. Because similar unmet needs also exist in pediatric population studies, risk mitigation in youth should be initiated as well to allow an evidence-based, risk-benefit assessment in this vulnerable population.

Inactivation of p66Shc Decreases Afferent Arteriolar KATP Channel Activity and Decreases Renal Damage in Diabetic Dahl SS Rats

Increased expression of adaptor protein p66Shc has been associated with progression of diabetic nephropathy. Afferent arteriolar dilation and glomerular hyperfiltration in diabetes are due to increased K_ATP channel availability and activity. Hyperglycemia was induced in Dahl salt-sensitive (SS) rats in a model of diabetes induced by streptozotocin (STZ). Renal injury was evaluated in SS rats and genetically modified SS rats either lacking p66Shc (p66Shc knockout [p66ShcKO]) or expressing p66Shc mutant (p66Shc-S36A). Afferent arteriolar diameter responses during STZ-induced hyperfiltration were determined by using the juxtamedullary nephron technique. Albuminuria and glomerular injury were mitigated in p66ShcKO and p66Shc-S36A rats with STZ-induced diabetes. SS rats with STZ-induced diabetes had significantly increased afferent arteriolar diameter, whereas p66ShcKO and p66Shc-S36A rats did not. SS rats with STZ-induced diabetes, but not p66ShcKO or p66Shc-S36A rats with STZ-induced diabetes, had an increased vasodilator response to the K_ATP channel activator pinacidil. Likewise, the K_ATP inhibitor glibenclamide resulted in a greater decrease in afferent arteriolar diameter in SS rats with STZ-induced diabetes than in STZ-treated SS p66ShcKO and p66Shc-S36A rats. Using patch-clamp electrophysiology, we demonstrated that p66ShcKO decreases K_ATP channel activity. These results indicate that inactivation of the adaptor protein p66Shc decreases afferent arteriolar K_ATP channel activity and decreases renal damage in diabetic SS rats.

Hyperfiltration, urinary albumin excretion, and ambulatory blood pressure in adolescents with Type 1 diabetes mellitus

Adolescents with Type 1 diabetes mellitus (T1DM) are at risk for hyperfiltration and elevated urinary albumin-to-creatinine ratio (ACR), which are early indicators of diabetic nephropathy. Adolescents with T1DM also develop early changes in blood pressure, cardiovascular structure, and function. Our aims were to define the relationships between hyperfiltration, ACR, and 24-h ambulatory blood pressure over time in adolescents with T1DM. Normotensive, normoalbuminuric adolescents ( n = 98) with T1DM underwent baseline and 2-yr 24-h ambulatory blood pressure monitoring, glomerular filtration rate (eGFR) estimated by cystatin C (Larsson equation), and ACR measurements. Linear regression models adjusted for diabetes duration, sex, and HbA1c were used to determine associations. Hyperfiltration (eGFR ≥ 133 ml/min) was present in 31% at baseline and 21% at 2-yr follow-up. Hyperfiltration was associated with greater odds of rapid GFR decline (>3 ml·min-1·yr-1) [OR: 5.33, 95%; CI: 1.87-15.17; P = 0.002] over 2 yr. Natural log of ACR at baseline was associated with greater odds of hyperfiltration (OR: 1.71, 95% CI: 1.00-2.92; P = 0.049) and 2-yr follow-up (OR: 2.14, 95%; CI: 1.09-4.19; P = 0.03). One SD increase in eGFR, but not ln ACR, at 2-yr follow-up conferred greater odds of nighttime nondipping pattern (OR: 1.96, 95% CI: 1.06-3.63; P = 0.03). Hyperfiltration was prevalent at baseline and at 2-yr follow-up, predicted rapid decline in GFR, and was related to ACR. Elevated GFR at 2-yr follow-up was associated with nighttime nondipping pattern. More work is needed to better understand early relationships between renal hemodynamic and systemic hemodynamic changes in adolescents with T1DM to reduce future cardiorenal complications.

Primary proximal tubule hyperreabsorption and impaired tubular transport counterregulation determine glomerular hyperfiltration in diabetes: a modeling analysis

Glomerular hypertension and hyperfiltration in early diabetes are associated with development and progression of diabetic kidney disease. The tubular hypothesis of diabetic hyperfiltration proposes that it is initiated by a primary increase in sodium (Na) reabsorption in the proximal tubule (PT) and the resulting tubuloglomerular feedback (TGF) response and lowering of Bowman space pressure (P_Bow). Here we utilized a mathematical model of the human kidney to investigate over acute and chronic timescales the mechanisms responsible for the magnitude of the hyperfiltration response. The model implicates that the primary hyperreabsorption of Na in the PT produces a Na imbalance that is only partially restored by the hyperfiltration induced by TGF and changes in P_Bow Thus secondary adaptations are needed to restore Na balance. This may include neurohumoral transport regulation and/or pressure-natriuresis (i.e., the decrease in Na reabsorption in response to increased renal perfusion pressure). We explored the role of each tubular segment in contributing to this compensation and the consequences of impairment in tubular compensation. The simulations indicate that impaired secondary downregulation of transport potentiated the rise in glomerular hypertension and hyperfiltration needed to restore Na balance at a given level of primary PT hyperreabsorption. Therefore, we propose for the first time that both the extent of primary PT hyperreabsorption and the degree of impairment of the distal tubular responsiveness to regulatory signals determine the level of glomerular hypertension and hyperfiltration in the diabetic kidney, thereby extending the tubule-centric concept of diabetic hyperfiltration and potential therapeutic approaches beyond the proximal tubule.

Early changes in cardiovascular structure and function in adolescents with type 1 diabetes

Background

Children with type 1 diabetes (T1D) are at higher risk of early adult-onset cardiovascular disease. We assessed cardiovascular structure and function in adolescents with T1D compared with healthy controls and the relationships between peripheral vascular function and myocardial parameters.

Methods and results

199 T1D [14.4 ± 1.6 years, diabetes duration 6.2 (2.0–12.8) years] and 178 controls (14.4 ± 2.1 years) completed endothelial function by flow mediated vasodilatation (FMD), arterial stiffness using pulse wave velocity (PWV) along with M-mode, pulse wave and tissue Doppler, and myocardial deformation echocardiographic imaging. Systolic (113 ± 10 vs. 110 ± 9 mmHg; p = 0.0005) and diastolic (62 ± 7 vs. 58 ± 7 mmHg; p < 0.0001) blood pressures, carotid femoral PWV and endothelial dysfunction measurements were increased in T1D compared with controls. Systolic and diastolic left ventricular dimensions and function by M-mode and pulse wave Doppler assessment were not significantly different. Mitral valve lateral e’ (17.6 ± 2.6 vs. 18.6 ± 2.6 cm/s; p < 0.001) and a’ (5.4 ± 1.1 vs. 5.9 ± 1.1 cm/s; p < 0.001) myocardial velocities were decreased and E/e’ (7.3 ± 1.2 vs. 6.7 ± 1.3; p = 0.0003) increased in T1D. Left ventricular mid circumferential strain (−20.4 ± 2.3 vs. −19.5 ± 1.7 %; p < 0.001) was higher, whereas global longitudinal strain was lower (−19.0 ± 1.9 vs. −19.8 ± 1.5 % p < 0.001) in T1D.

Conclusions

Adolescents with T1D exhibit early changes in blood pressure, peripheral vascular function and left ventricular myocardial deformation indices with a shift from longitudinal to circumferential shortening. Longitudinal follow-up of these changes in ongoing prospective trials may allow detection of those most at risk for cardiovascular abnormalities including hypertension that could preferentially benefit from early therapeutic interventions.

Glomerular haemodynamic profile of patients with Type 1 diabetes compared with healthy control subjects

AIMS

To evaluate the glomerular haemodynamic profile of patients with Type 1 diabetes with either renal hyperfiltration (GFR ≥ 135 ml/min/1.73 m2 ) or renal normofiltration (GFR 90-134 ml/min/1.73 m2 ) during euglycaemic and hyperglycaemic conditions, and to compare this profile with that of a similar group of healthy control subjects.

METHODS

Gomez's equations were used to derive afferent and efferent arteriolar resistances, glomerular hydrostatic pressure and filtration pressure.

RESULTS

At baseline, during clamped euglycaemia, patients with Type 1 diabetes and hyperfiltration had lower mean ± sd afferent arteriolar resistance than both those with Type 1 diabetes and normofiltration (914 ± 494 vs. 2065 ± 597 dyne/s/cm5 ; P < 0.001) and healthy control subjects (1676 ± 707 dyne/s/cm(5) ; p < 0.001). By contrast, efferent arteriolar resistance was similar in the three groups. Patients with Type 1 diabetes and hyperfiltration also had higher mean ± sd glomerular hydrostatic pressure than both healthy control subjects and patients with Type 1 diabetes and normofiltration (66 ± 6 vs. 60 ± 3 vs. 55 ± 3 mmHg; P < 0.05). Similar findings for afferent arteriolar resistance, efferent arteriolar resistance, glomerular hydrostatic pressure and filtration pressure were observed during clamped hyperglycaemia.

CONCLUSION

Hyperfiltration in Type 1 diabetes is primarily driven by alterations in afferent arteriolar resistance rather than efferent arteriolar resistance. Renal protective therapies should focus on afferent renal arteriolar mechanisms through the use of pharmacological agents that target tubuloglomerular feedback, including sodium-glucose cotransporter 2 inhibitors and incretins.

A systematic review of glomerular hyperfiltration assessment and definition in the medical literature

BACKGROUND AND OBJECTIVES

Evaluation of glomerular hyperfiltration (GH) is difficult; the variable reported definitions impede comparisons between studies. A clear and universal definition of GH would help in comparing results of trials aimed at reducing GH. This study assessed how GH is measured and defined in the literature.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Three databases (Embase, MEDLINE, CINAHL) were systematically searched using the terms "hyperfiltration" or "glomerular hyperfiltration". All studies reporting a GH threshold or studying the effect of a high GFR in a continuous manner against another outcome of interest were included.

RESULTS

The literature search was performed from November 2012 to February 2013 and updated in August 2014. From 2013 retrieved studies, 405 studies were included. Threshold use to define GH was reported in 55.6% of studies. Of these, 88.4% used a single threshold and 11.6% used numerous thresholds adapted to participant sex or age. In 29.8% of the studies, the choice of a GH threshold was not based on a control group or literature references. After 2004, the use of GH threshold use increased (P<0.001), but the use of a control group to precisely define that GH threshold decreased significantly (P<0.001); the threshold did not differ among pediatric, adult, or mixed-age studies. The GH threshold ranged from 90.7 to 175 ml/min per 1.73 m(2) (median, 135 ml/min per 1.73 m(2)).

CONCLUSION

Thirty percent of studies did not justify the choice of threshold values. The decrease of GFR in the elderly was rarely considered in defining GH. From a methodologic point of view, an age- and sex-matched control group should be used to define a GH threshold.

Achieving International Society for Pediatric and Adolescent Diabetes and American Diabetes Association clinical guidelines offers cardiorenal protection for youth with type 1 diabetes

OBJECTIVE

Most youth with type 1 diabetes do not meet the American Diabetes Association (ADA) and International Society for Pediatric and Adolescent Diabetes (ISPAD) targets for hemoglobin A1c (HbA1c), blood pressure (BP), lipids, and body mass index (BMI). We hypothesized that ISPAD/ADA goal achievement at baseline would be associated with cardiorenal risk factors at baseline and 2 yr follow-up in adolescents with type 1 diabetes.

METHODS

We assessed the cross-sectional and longitudinal relationships between ISPAD/ADA goal achievement at baseline and cardiorenal health at baseline and 2-yr follow-up (n = 297; 15.4 ± 2.1 yr at baseline) in adolescents with type 1 diabetes. Goal achievement was defined as HbA1c < 7.5%, BP < 90th percentile for age, sex, and height, low density lipoprotein-cholesterol (LDL-C) <100 mg/dL, high density lipoprotein-cholesterol (HDL-C) >35 mg/dL, triglycerides (TG) <150 mg/dL and BMI <85th percentile for age and sex. Cardiorenal outcomes included pulse-wave velocity (PWV), brachial distensibility (BrachD), augmentation index (AIx), and epidermal growth factor receptor (eGFR) continuously and categorically as hyperfiltration (eGFR ≥ 135 mL/min/1.73 m(2)).

RESULTS

Adolescents with type 1 diabetes who met 1-3 goals, had significantly greater (P < 0.05) baseline PWV (5.1 ± 0.1 vs. 5.4 ± 0.1 m/s), follow-up PWV (5.5 ± 0.1 vs. 5.7 ± 0.1 m/s), greater follow-up eGFR (104 ± 2 vs. 116 ± 3 mL/min/1.73 m(2)), and greater odds of renal hyperfiltration at follow-up (odds ratio (OR): 20.0, 95% confidence interval (CI): 3.8-105.2) compared to those who met 4-6 goals after adjusting for Tanner stage, sex, age, and diabetes duration. No statistically significant differences in the cardiorenal outcomes were observed between adolescents with type 1 diabetes who met 4-6 goals and non-diabetic controls (n = 96).

CONCLUSIONS

In adolescents with type 1 diabetes, baseline ADA/ISPAD goal achievement was associated with cardiorenal protection at baseline and 2-yr follow-up.

Renal function is associated with peak exercise capacity in adolescents with type 1 diabetes

OBJECTIVE

Diabetic nephropathy and cardiovascular disease are strongly related in adults with type 1 diabetes, yet little is known about this relationship in adolescents prior to the onset of detectable clinical disease. We hypothesized that cardiopulmonary fitness would be directly associated with albumin-to-creatinine ratio (ACR) and inversely related to estimated glomerular filtration rate (eGFR) in adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Sixty-nine adolescents with type 1 diabetes and 13 nondiabetic control subjects of similar pubertal stage and BMI had insulin sensitivity (glucose infusion rate [GIR]), measured by hyperinsulinemic-euglycemic clamp, and lean body mass, measured by DEXA. Cardiopulmonary fitness was measured by cycle ergometry to obtain peak volume of oxygen (VO2peak), and renal function was measured by eGFR using the Bouvet equation (measuring creatinine and cystatin C levels) and ACR.

RESULTS

Adolescents (15.5 ± 2.2 years of age) with type 1 diabetes (6.3 ± 3.8 years diabetes duration) had reduced VO2peak (31.5 ± 6.3 vs. 36.2 ± 7.9 mL/kg ⋅ min, P = 0.046) and VO2peak/lean kg (43.7 ± 7.0 vs. 51.0 ± 8.6 mL/lean kg ⋅ min, P = 0.007) compared with nondiabetic control subjects. eGFR was inversely associated with VO2peak and VO2peak/lean kg after adjusting for sex, Tanner stage, GIR, HbA1c level, systolic blood pressure, and LDL cholesterol level (β ± SE, VO2peak: -0.19 ± 0.07, P = 0.02; VO2peak/lean kg: -0.19 ± 0.09, P = 0.048). Moreover, participants in the highest tertile for eGFR had significantly lower sex- and Tanner-adjusted VO2peak and VO2peak/lean kg compared with participants in the lowest tertile.

CONCLUSIONS

Adolescents with type 1 diabetes had reduced exercise capacity, which was strongly associated with renal health, independent of insulin sensitivity. Future studies should examine the underlying interrelated pathophysiology in order to identify probable targets for treatment to reduce cardiovascular and renal complications.

The effect of sex on humanin levels in healthy adults and patients with uncomplicated type 1 diabetes mellitus

Diabetes mellitus (DM) is associated with a loss of renal and vascular protection in women compared with men, but the responsible mechanisms are unclear. Recent experimental work implicated humanin (HN) as a novel cytoprotective hormone in DM. Our goal was to measure sex-related differences in HN levels in uncomplicated type 1 DM patients (T1D) and healthy controls (HC), as well as the interaction between HN, circulating neurohormones, and vascular function. Plasma HN, cGMP and aldosterone, blood pressure (BP), glomerular filtration rate, and effective renal plasma flow (inulin and para-aminohippurate) were measured in HC (11 men, 10 women) and T1D (23 men and 18 women) during clamped euglycemia (4-6 mmol·L(-1)). Plasma HN levels were generally lower in HC men by comparison with the women, but the differences were not statistically significant. In contrast, levels in the T1D men were higher compared with the T1D women (p = 0.026) and HC men (p < 0.0001). In the HC men, but not the women, HN correlated negatively with BP, but not with renal function, cGMP, or aldosterone. In the T1D men, HN negatively correlated with plasma cGMP. In the T1D women, HN did not correlate with neurohormones or vascular function. Future work should determine the role of HN in the pathogenesis of sex-related vascular function differences in DM.

The impact of hyperfiltration on the diabetic kidney

More than two decades ago, hyperfiltration (HF) in diabetes was postulated to be a maladaptive response observed early in the course of diabetic kidney disease (DKD), which may eventually predispose to irreversible damage to nephrons and development of progressive renal disease. Despite this, the potential mechanisms leading to renal HF in diabetes are not fully understood, although several hypotheses have been proposed, including alterations in glomerular haemodynamic function and tubulo-glomerular feedback. Furthermore, the role of HF as a causative factor in renal disease progression is still unclear and warrants further prospective longer-term studies. Although HF has been entrenched as the first stage in the classic albuminuric pathway to end-stage renal disease in DKD, and HF has been shown to predict the progression of albuminuria in many, but not all studies, the concept that HF predisposes to the development of chronic kidney disease (CKD) stage 3, that is, glomerular filtration rate (GFR) decline to<60mL/min/1.73m(2), remains to be proved. Further long-term studies of GFR gradients therefore are required to establish whether HF ultimately leads to decreased kidney function, after adjustment for glycaemic control and other confounders. Whether reversal of HF with therapeutic agents is protective against reducing the risk of development of albuminuria and renal impairment is also worth investigating in prospective randomized trials.

The urinary cytokine/chemokine signature of renal hyperfiltration in adolescents with type 1 diabetes

OBJECTIVE

Urinary cytokine/chemokine levels are elevated in adults with type 1 diabetes (T1D) exhibiting renal hyperfiltration. Whether this observation extends to adolescents with T1D remains unknown. Our first objective was to determine the relationship between hyperfiltration and urinary cytokines/chemokines in normotensive, normoalbuminuric adolescents with T1D using GFR(cystatin). Our second aim was to determine the relationship between urine and plasma levels of inflammatory biomarkers, to clarify the origin of these factors.

METHODS

Urine and serum cytokines/chemokines (Luminex platform) and GFR(cystatin) were measured in normofiltering (n = 111, T1D-N, GFR<135 ml/min/1.73 m(2)) and hyperfiltering (n = 31, T1D-H, GFR ≥ 135 ml/min/1.73 m(2)) adolescents with T1D (ages 10-16), and in age and sex matched healthy control subjects (HC, n = 59).

RESULTS

We noted significant step-wise increases in urinary cytokine/chemokine excretion according to filtration status with highest levels in T1D-H, with parallel trends in serum analyte concentrations. After adjusting for serum glucose at the time of sampling, differences in urinary cytokine excretion were not statistically significant. Only serum IL-2 significantly differed between HC and T1D (p = 0.0076).

CONCLUSIONS

Hyperfiltration is associated with increased urinary cytokine/chemokine excretion in T1D adolescents, and parallel trends in serum cytokine concentration. The GFR-associated trends in cytokine excretion may be driven by the effects of ambient hyperglycemia. The relationship between hyperfiltration, glycemia, and variations in serum and urine cytokine expression and their impact on future renal and systemic vascular complications requires further study.

Glycosuria-mediated urinary uric acid excretion in patients with uncomplicated type 1 diabetes mellitus

Plasma uric acid (PUA) is associated with metabolic, cardiovascular, and renal abnormalities in patients with type 2 diabetes but is less well understood in type 1 diabetes (T1D). Our aim was to compare PUA levels and fractional uric acid excretion (FEUA) in patients with T1D vs. healthy controls (HC) during euglycemia and hyperglycemia. PUA, FEUA, blood pressure (BP), glomerular filtration rate (GFR-inulin), and effective renal plasma flow (ERPF-paraaminohippurate) were evaluated in patients with T1D (n = 66) during clamped euglycemia (glucose 4-6 mmol/l) and hyperglycemia (9-11 mmol/l), and in HC (n = 41) during euglycemia. To separate the effects of hyperglycemia vs. increased glycosuria, parameters were evaluated during clamped euglycemia in a subset of T1D patients before and after sodium glucose cotransporter 2 (SGLT2) inhibition for 8 wk. PUA was lower in T1D vs. HC (228 ± 62 vs. 305 ± 75 μmol/l, P < 0.0001). In T1D, hyperglycemia further decreased PUA (228 ± 62 to 199 ± 65 μmol/l, P < 0.0001), which was accompanied by an increase in FEUA (7.3 ± 3.8 to 11.6 ± 6.7, P < 0.0001). In T1D, PUA levels correlated positively with SBP (P = 0.029) and negatively with ERPF (P = 0.031) and GFR (P = 0.028). After induction of glycosuria with SGLT2 inhibition while maintaining clamped euglycemia, PUA decreased (P < 0.0001) and FEUA increased (P < 0.0001). PUA is lower in T1D vs. HC and positively correlates with SBP and negatively with GFR and ERPF in T1D. Glycosuria rather than hyperglycemia increases uricosuria in T1D. Future studies examining the effect of uric acid-lowering therapies should account for the impact of ambient glycemia, which causes an important uricosuric effect.

Renal hyperfiltration is associated with glucose-dependent changes in fractional excretion of sodium in patients with uncomplicated type 1 diabetes

OBJECTIVE

Renal hyperfiltration is a common abnormality associated with diabetic nephropathy in patients with type 1 diabetes (T1D). In animal models, increased proximal tubular sodium reabsorption results in decreased distal sodium delivery, tubuloglomerular feedback activation, afferent vasodilatation, and hyperfiltration. The role of tubular factors is less well understood in humans. The aim of the current study was therefore to compare the fractional sodium excretion (FENa) in hyperfiltering (T1D-H) versus normofiltering (T1D-N) patients and healthy control (HC) subjects, as well as the role of ambient hyperglycemia on FENa.

RESEARCH DESIGN AND METHODS

Blood pressure, renal function (inulin for glomerular filtration rate [GFR], and paraaminohippurate for effective renal plasma flow), FENa, and circulating neurohormones were measured in T1D-H (n = 28, GFR ≥135 mL/min/1.73 m(2)), T1D-N (n = 30), and HC (n = 35) subjects during clamped euglycemia. Studies were repeated in a subset of patients during clamped hyperglycemia.

RESULTS

During clamped euglycemia, T1D-H exhibited lower FENa than T1D-N and HC subjects (0.64 ± 0.06% vs. 0.91 ± 0.12% and 0.90 ± 0.10%, P < 0.05). During clamped hyperglycemia, FENa increased (Δ + 0.88 ± 0.22% vs. Δ + 0.02 ± 0.21%; between-group effect, P = 0.01) significantly in T1D-H, whereas FENa did not change in T1D-N. When treated as continuous variables, elevated GFR values were associated with hyperglycemia-induced increases in FENa (R(2) = 0.20, P = 0.007).

CONCLUSIONS

Patients with uncomplicated T1D-H exhibit lower FENa under euglycemic conditions, which may help to identify patients with hyperfiltration outside of a controlled laboratory setting. Increased FENa in T1D-H but not T1D-N under clamped hyperglycemic conditions suggests that the mechanisms responsible for increased sodium reabsorption leading to hyperfiltration can be saturated.

A randomized cross-over comparison of short-term exposure of once-daily extended release tacrolimus and twice-daily tacrolimus on renal function in healthy volunteers

Calcineurin inhibitor nephrotoxicity remains an issue for transplant recipients. The pharmacokinetic profile (PK) of the once-daily tacrolimus extended release (Tac-ER) includes equivalent exposure [AUC(0-24 h) ] but lower Cmax versus twice-daily tacrolimus immediate release (Tac-IR). We hypothesized that the unique PK profiles would result in pharmacodynamic differences in renal function. Nineteen healthy male subjects were allocated to once-daily Tac-ER and twice-daily Tac-IR in a prospective, randomized, two period, cross-over study. Tacrolimus was titrated to achieve trough levels of 8-12 ng/ml. Twenty four hours ERPF and GFR estimated by para-aminohippurate and sinistrin clearance were performed at baseline and at the end of each 10-day dosing period. Mean Tac C0 was 11.0 ± 2.2 and 11.3 ± 1.8 ng/ml for Tac-ER and Tac-IR, respectively. The mean Effective 24 h renal plasma flow (ERPF) was significantly higher with Tac-ER compared with Tac-IR (658 ± 127 vs. 610 ± 93 ml/min/1.73 m(2) , P = 0.046). There was a trend to a greater mean GFR over 24 h for Tac-ER at 114.5 ± 13.6 ml/min/1.73 m(2) compared with 108.9 ± 9.7 ml/min/1.73 m(2) for Tac-IR, P = 0.116. Under controlled physiological conditions, ERPF was significantly improved with Tac-ER compared with Tac-IR, likely owing to the differing PKs of these tacrolimus preparations (ClinicalTrials.gov Identifier: NCT01681134).

Renal hemodynamic effect of sodium-glucose cotransporter 2 inhibition in patients with type 1 diabetes mellitus

BACKGROUND

The primary objective of this mechanistic open-label, stratified clinical trial was to determine the effect of 8 weeks' sodium glucose cotransporter 2 inhibition with empagliflozin 25 mg QD on renal hyperfiltration in subjects with type 1 diabetes mellitus (T1D).

METHODS AND RESULTS

Inulin (glomerular filtration rate; GFR) and paraaminohippurate (effective renal plasma flow) clearances were measured in individuals stratified based on having hyperfiltration (T1D-H, GFR ≥ 135 mL/min/1.73m(2), n=27) or normal GFR (T1D-N, GFR 90-134 mL/min/1.73m(2), n=13) at baseline. Renal function and circulating levels of renin-angiotensin-aldosterone system mediators and NO were measured under clamped euglycemic (4-6 mmol/L) and hyperglycemic (9-11 mmol/L) conditions at baseline and end of treatment. During clamped euglycemia, hyperfiltration was attenuated by -33 mL/min/1.73m(2) with empagliflozin in T1D-H, (GFR 172±23-139±25 mL/min/1.73 m(2), P<0.01). This effect was accompanied by declines in plasma NO and effective renal plasma flow and an increase in renal vascular resistance (all P<0.01). Similar significant effects on GFR and renal function parameters were observed during clamped hyperglycemia. In T1D-N, GFR, other renal function parameters, and plasma NO were not altered by empagliflozin. Empagliflozin reduced hemoglobin A1c significantly in both groups, despite lower insulin doses in each group (P≤0.04).

CONCLUSIONS

In conclusion, short-term treatment with the sodium glucose cotransporter 2 inhibitor empagliflozin attenuated renal hyperfiltration in subjects with T1D, likely by affecting tubular-glomerular feedback mechanisms.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT01392560.