Discrepancies between transcutaneous and estimated glomerular filtration rates in rats with chronic kidney disease.

Accurate assessment of the glomerular filtration rate (GFR) is crucial for researching kidney disease in rats. Although validation of methods that assess GFR is crucial, large-scale comparisons between different methods are lacking. Both transcutaneous GFR (tGFR) and a newly developed estimated GFR (eGFR) equation by our group provide a low-invasive approach enabling repeated measurements. The tGFR is a single bolus method using FITC-labeled sinistrin to measure GFR based on half-life of the transcutaneous signal, whilst the eGFR is based on urinary sinistrin clearance. Here, we retrospectively compared tGFR, using both 1- and 3- compartment models (tGFR_1c and tGFR_3c, respectively) to the eGFR in a historic cohort of 43 healthy male rats and 84 male rats with various models of chronic kidney disease. The eGFR was on average considerably lower than tGFR-1c and tGFR-3c (mean differences 855 and 216 µL/min, respectively) and only 20 and 47% of measurements were within 30% of each other, respectively. The relative difference between eGFR and tGFR was highest in rats with the lowest GFR. Possible explanations for the divergence are problems inherent to tGFR, such as technical issues with signal measurement, description of the signal kinetics, and translation of half-life to tGFR, which depends on distribution volume. The unknown impact of isoflurane anesthesia used in determining mGFR remains a limiting factor. Thus, our study shows that there is a severe disagreement between GFR measured by tGFR and eGFR, stressing the need for more rigorous validation of the tGFR and possible adjustments to the underlying technique.

Renal injury in relation to obesity and the additive effect of hypertension in female and male obese and lean ZSF1 rats.

Heart failure with preserved ejection fraction (HFpEF) is characterized by obesity, hypertension, diabetes mellitus, and chronic kidney disease. Obese ZSF1 rats, a model of HFpEF, exhibit multiple such comorbidities that can disturb cardiac function. Little attention has been paid to how these comorbidities affect renal disease in ZSF1 rats. HFpEF is found predominantly in women in whom obesity and hypertension are particularly prevalent. Therefore, we characterized the renal phenotype in female and male lean and obese ZSF1 rats and investigated additional effects of worsened hypertension on disease severity. Systolic blood pressure and renal function were assessed biweekly from 12 to 26 wk. From 19 wk, rats were implanted with either a deoxycorticosterone acetate pellet and fed a high-salt diet (DS) or a placebo pellet and fed a normal-salt diet. At 26 wk of age, terminal glomerular filtration rate was assessed via inulin clearance under isoflurane. Renal sections were processed for histological analysis. Lean and obese ZSF1 rats, both female and male, were mildly hypertensive (systolic blood pressure: 140-150 mmHg). All obese ZSF1 rats showed HFpEF. In female normoglycemic ZSF1 rats, obesity associated with mild proteinuria, decreased glomerular filtration rate, and glomerular hypertrophy. DS-worsened hypertension enhanced proteinuria and triggered glomerulosclerosis. Male obese ZSF1 rats were hyperglycemic and showed proteinuria, glomerular hypertrophy and sclerosis, and tubulointerstitial damage. DS-worsened hypertension aggravated this phenotype in male ZSF1 rats. In conclusion, female obese ZSF1 rats develop mild renal dysfunction and DS-worsened hypertension compromises renal function and structure in normoglycemic female obese ZSF1 rats as in hyperglycemic male obese ZSF1 rats.NEW & NOTEWORTHY Chronic kidney disease coexists with heart failure with a preserved ejection fraction (HFpEF), which is associated with multiple comorbidities and the female sex. We showed that obese, mildly hypertensive female ZSF1 rats, an animal model for HFpEF, simultaneously develop renal disease with diastolic dysfunction. Exacerbation of their hypertension, a comorbidity highly prevalent in HFpEF, compromised renal function and structure similarly in normoglycemic obese female ZSF1 rats and hyperglycemic obese male ZSF1 rats.

A Uremic Pig Model for Peritoneal Dialysis.

With increasing interest in home dialysis, there is a need for a translational uremic large animal model to evaluate technical innovations in peritoneal dialysis (PD). To this end, we developed a porcine model with kidney failure. Stable chronic kidney injury was induced by bilateral subtotal renal artery embolization. Before applying PD, temporary aggravation of uremia was induced by administration of gentamicin (10 mg/kg i.v. twice daily for 7 days), to obtain uremic solute levels within the range of those of dialysis patients. Peritoneal transport was assessed using a standard peritoneal permeability assessment (SPA). After embolization, urea and creatinine concentrations transiently increased from 1.6 ± 0.3 to 7.5 ± 1.2 mM and from 103 ± 14 to 338 ± 67 µM, respectively, followed by stabilization within 1-2 weeks to 2.5 ± 1.1 mM and 174 ± 28 µM, respectively. Gentamicin induced temporary acute-on-chronic kidney injury with peak urea and creatinine concentrations of 16.7 ± 5.3 mM and 932 ± 470 µM respectively. PD was successfully applied, although frequently complicated by peritonitis. SPA showed a low transport status (D/P creatinine at 4 h of 0.41 (0.36-0.53)) with a mass transfer area coefficient of 9.6 ± 3.1, 4.6 ± 2.6, 3.4 ± 2.3 mL/min for urea, creatinine, and phosphate respectively. In conclusion, this porcine model with on-demand aggravation of uremia is suitable for PD albeit with peritoneal transport characterized by a low transport status.

Albumin is an interface between blood plasma and cell membrane, and not just a sponge.

Albumin is the most abundant protein in blood plasma and acts as a carrier for many circulating molecules. Hypoalbuminaemia, mostly caused by either renal or liver disease or malnutrition, can perturb vascular homeostasis and is involved in the development of multiple diseases. Here we review four functions of albumin and the consequences of hypoalbuminaemia on vascular homeostasis. (i) Albumin is the main determinant of plasma colloid osmotic pressure. Hypoalbuminaemia was therefore thought to be the main mechanism for oedema in nephrotic syndrome (NS), however, experimental studies showed that intrarenal mechanisms rather than hypoalbuminaemia determine formation and, in particular, maintenance of oedema. (ii) Albumin functions as an interface between lysophosphatidylcholine (LPC) and circulating factors (lipoproteins and erythrocytes) and the endothelium. Consequently, hypoalbuminaemia results in higher LPC levels in lipoproteins and erythrocyte membrane, thereby increasing atherosclerotic properties of low-density lipoprotein and blood viscosity, respectively. Furthermore, albumin dose-dependently restores LPC-induced inhibition of vasodilation. (iii) Hypoalbuminaemia impacts on vascular nitric oxide (NO) signalling by directly increasing NO production in endothelial cells, leading to reduced NO sensitivity of vascular smooth muscle cells. (iv) Lastly, albumin binds free fatty acids (FFAs). FFAs can induce vascular smooth muscle cell apoptosis, uncouple endothelial NO synthase and decrease endothelium-dependent vasodilation. Unbound FFAs can increase the formation of reactive oxygen species by mitochondrial uncoupling in multiple cell types and induce hypertriglyceridemia in NS. In conclusion, albumin acts as an interface in the circulation and hypoalbuminaemia impairs multiple aspects of vascular function that may underlie the association of hypoalbuminaemia with adverse outcomes. However, hypoalbuminaemia is not a key to oedema in NS. These insights have therapeutic implications.

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

BACKGROUND AND OBJECTIVES: Sodium-glucose transporter 2 (SGLT2) inhibitor-induced uric acid lowering may contribute to kidney-protective effects of the drug class in people with type 2 diabetes. This study investigates mechanisms of plasma uric acid lowering by SGLT2 inhibitors in people with type 2 diabetes with a focus on urate transporter 1. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We conducted an analysis of two randomized clinical trials. First, in the Renoprotective Effects of Dapagliflozin in Type 2 Diabetes study, 44 people with type 2 diabetes were randomized to dapagliflozin or gliclazide for 12 weeks. Plasma uric acid, fractional uric acid excretion, and hemodynamic kidney function were measured in the fasted state and during clamped euglycemia or hyperglycemia. Second, in the Uric Acid Excretion study, ten people with type 2 diabetes received 1 week of empagliflozin, urate transporter 1 blocker benzbromarone, or their combination in a crossover design, and effects on plasma uric acid, fractional uric acid excretion, and 24-hour uric acid excretion were measured. RESULTS: In the Renoprotective Effects of Dapagliflozin in Type 2 Diabetes study, compared with the fasted state (5.3±1.1 mg/dl), acute hyperinsulinemia and hyperglycemia significantly reduced plasma uric acid by 0.2±0.3 and 0.4±0.3 mg/dl (both P<0.001) while increasing fractional uric acid excretion (by 3.2%±3.1% and 8.9%±4.5%, respectively; both P<0.001). Dapagliflozin reduced plasma uric acid by 0.8±0.8 during fasting, 1.0±1.0 in hyperinsulinemic-euglycemic state, and 0.8±0.7 mg/dl during hyperglycemic conditions (P<0.001), respectively, whereas fractional uric acid excretion in 24-hour urine increased by 3.0%±2.1% (P<0.001) and 2.6%±4.5% during hyperinsulinemic-euglycemic conditions (P=0.003). Fractional uric acid excretion strongly correlated to fractional glucose excretion (r=0.35; P=0.02). In the Uric Acid Excretion study, empagliflozin and benzbromarone both significantly reduced plasma uric acid and increased fractional uric acid excretion. Effects of combination therapy did not differ from benzbromarone monotherapy. CONCLUSIONS: In conclusion, SGLT2 inhibitors induce uric acid excretion, which is strongly linked to urinary glucose excretion and is attenuated during concomitant pharmacologic blockade of urate transporter 1. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: Renoprotective Effects of Dapagliflozin in Type 2 Diabetes (RED), NCT02682563; SGLT2 Inhibition: Uric Acid Excretion Study (UREX), NCT05210517.

Whole-body insulin clearance in people with type 2 diabetes and normal kidney function: Relationship with glomerular filtration rate, renal plasma flow, and insulin sensitivity.

OBJECTIVE: Kidney insulin clearance, proposed to be the main route of extra-hepatic insulin clearance, occurs in tubular cells following glomerular filtration and peritubular uptake, a process that may be impaired in people with type 2 diabetes (T2D) and/or impaired kidney function. Human studies that investigated kidney insulin clearance are limited by the invasive nature of the measurement. Instead, we evaluated relationships between whole-body insulin clearance, and gold-standard measured kidney function and insulin sensitivity in adults with T2D and normal kidney function. RESEARCH DESIGN AND METHODS: We determined insulin, inulin/iohexol and para-aminohippuric acid (PAH) clearances during a hyperinsulinemic-euglycemic clamp to measure whole-body insulin clearance and kidney function. Insulin sensitivity was expressed by glucose infusion rate (M value). Associations between whole-body insulin clearance, kidney function and insulin sensitivity were examined using univariable and multivariable linear regressions models. RESULTS: We investigated 44 predominantly male (77%) T2D adults aged 63 ± 7, with fat mass 34.5 ± 9 kg, lean body mass 63.0 ± 11.8 kg, and HbA1c 7.4 ± 0.6%. Average whole-body insulin clearance was 1188 ± 358 mL/min. Mean GFR was 110 ± 22 mL/min, mean ERPF 565 ± 141 mL/min, and M value averaged 3.9 ± 2.3 mg/min. Whole-body insulin clearance was positively correlated with lean body mass, ERPF and insulin sensitivity, but not with GFR. ERPF explained 6% of the variance when entered in a nested multivariable linear regression model op top of lean body mass (25%) and insulin sensitivity (15%). CONCLUSIONS: In adults with T2D and normal kidney function, whole-body insulin clearance was predicted best by lean body mass and insulin sensitivity, and to a lesser extent by ERPF. GFR was not associated with whole-body insulin clearance. In contrast to prior understanding, this suggests that in this population kidney insulin clearance may not play such a dominant role in whole-body insulin clearance.

Kidney hemodynamic profile and systemic vascular function in adults with type 2 diabetes: Analysis of three clinical trials.

AIMS: Glomerular hyperfiltration plays a key role in the pathophysiology of diabetic kidney disease (DKD). Mechanisms underlying this adverse hemodynamic profile are incompletely understood. We hypothesized that systemic vascular pathology, including endothelial dysfunction and arterial stiffness, relates to glomerular hyperfiltration indicated by filtration fraction (FF). METHODS: Baseline data of three trials of overweight adults with type 2 diabetes (TD2, n = 111) with relatively well preserved kidney function were analyzed. Glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and FF, were assessed with gold-standard clearance techniques. Systemic vascular resistance (SVR), an indicator of endothelial dysfunction, and pulse pressure (PP), a measure of arterial stiffness, were derived from continuous beat-to-beat monitoring. RESULTS: SVR related negatively to GFR (ß: -0.382, p < 0.001) and ERPF (ß: -0.475, p < 0.001), and positively to FF (ß:0.369, p < 0.001). Associations between SVR, ERPF and FF persisted after multivariable adjustments.. PP was negatively related to ERPF (ß: -0.252, p = 0.008), and positively to FF (ß: 0.257, p = 0.006), of which the latter remained significant in multivariable regression. CONCLUSION: Parameters of systemic vascular pathology, including endothelial dysfunction and arterial stiffness, relate to an adverse kidney hemodynamic profile characterized by glomerular hyperfiltration, which predisposes to the development of DKD.

Postprandial renal haemodynamic effects of the dipeptidyl peptidase-4 inhibitor linagliptin versus the sulphonylurea glimepiride in adults with type 2 diabetes (RENALIS): A predefined substudy of a randomized, double-blind trial.

AIM: To determine the effect of the dipeptidyl peptidase-4 inhibitor linagliptin on postprandial glomerular hyperfiltration compared with the sulphonylurea glimepiride in adults with type 2 diabetes (T2D). MATERIALS AND METHODS: In this predefined substudy within a randomized, double-blind, parallel-group, intervention trial, overweight people with T2D without renal impairment were treated with once-daily linagliptin 5 mg (N = 10) or glimepiride 1 mg (N = 13) as an add-on to metformin for 8 weeks. After a standardized liquid protein-rich meal, the glomerular filtration rate (GFR) and effective renal plasma flow were determined by inulin and para-aminohippuric acid clearance, respectively, based on timed urine sampling. Intrarenal haemodynamics were estimated using the Gomez equations. Glucoregulatory/vasoactive hormones, urinary pH and fractional excretions (FE) of sodium, potassium and urea were measured. RESULTS: Compared with glimepiride, linagliptin increased the postprandial filtration fraction (FF; mean difference 2.1%-point; P = .016) and estimated glomerular hydraulic pressure (mean difference 3.0 mmHg; P = .050), and tended to increase GFR (P = .08) and estimated efferent renal arteriolar resistance (RE ; P = .08) from baseline to week 8. No differences in FE were noted. Glimepiride reduced HbA1c more than linagliptin (mean difference -0.40%; P = .004), without between-group differences in time-averaged postprandial glucose levels. In the linagliptin group, change in FF correlated with change in mean arterial pressure (R = 0.807; P = .009) and time-averaged mean glucagon (R = 0.782; P = .008), but not with changes in glucose, insulin, intact glucagon-like peptide-1, renin or FENa . Change in glucagon was associated with change in RE (R = 0.830; P = .003). CONCLUSIONS: In contrast to our hypothesis, compared with glimepiride, linagliptin does not reduce postprandial hyperfiltration, yet appears to increase FF after meal ingestion by increasing blood pressure or RE .

Reduced nitric oxide bioavailability impairs myocardial oxygen balance during exercise in swine with multiple risk factors.

In the present study, we tested the hypothesis that multiple risk factors, including diabetes mellitus (DM), dyslipidaemia and chronic kidney disease (CKD) result in a loss of nitric oxide (NO) signalling, thereby contributing to coronary microvascular dysfunction. Risk factors were induced in 12 female swine by intravenous streptozotocin injections (DM), a high fat diet (HFD) and renal artery embolization (CKD). Female healthy swine (n = 13) on normal diet served as controls (Normal). After 5 months, swine were chronically instrumented and studied at rest and during exercise. DM + HFD + CKD swine demonstrated significant hyperglycaemia, dyslipidaemia and impaired kidney function compared to Normal swine. These risk factors were accompanied by coronary microvascular endothelial dysfunction both in vivo and in isolated small arteries, due to a reduced NO bioavailability, associated with perturbations in myocardial oxygen balance at rest and during exercise. NO synthase inhibition caused coronary microvascular constriction in exercising Normal swine, but had no effect in DM + HFD + CKD animals, while inhibition of phosphodiesterase 5 produced similar vasodilator responses in both groups, indicating that loss of NO bioavailability was principally responsible for the observed coronary microvascular dysfunction. This was associated with an increase in myocardial 8-isoprostane levels and a decrease in antioxidant capacity, while antioxidants restored the vasodilation to bradykinin in isolated coronary small arteries, suggesting that oxidative stress was principally responsible for the reduced NO bioavailability. In conclusion, five months of combined exposure to DM + HFD + CKD produces coronary endothelial dysfunction due to impaired NO bioavailability, resulting in impaired myocardial perfusion at rest and during exercise.

Mildly Increased Renin Expression in the Absence of Kidney Injury in the Murine Transverse Aortic Constriction Model.

Cardiorenal syndrome type 2 is characterized by kidney failure as a consequence of heart failure that affects >50% of heart failure patients. Murine transverse aortic constriction (TAC) is a heart failure model, where pressure overload is induced on the heart without any systemic hypertension or its consequences. Whether renal function is altered in this model is debated, and if so, at which time post-TAC renal dysfunction starts to contribute to worsening of cardiac function. We therefore studied the effects of progressive heart failure development on kidney function in the absence of chronically elevated systemic blood pressure and renal perfusion pressure. C57BL/6J mice (N = 129) were exposed to TAC using a minimally invasive technique and followed from 3 to 70 days post-TAC. Cardiac function was determined with 3D ultrasound and showed a gradual decrease in stroke volume over time. Renal renin expression and plasma renin concentration increased with progressive heart failure, suggesting hypoperfusion of the kidney. In addition, plasma urea concentration, a surrogate marker for renal dysfunction, was increased post-TAC. However, no structural abnormalities in the kidney, nor albuminuria were present at any time-point post-TAC. Progressive heart failure is associated with increased renin expression, but only mildly affected renal function without inducing structural injury. In combination, these data suggest that heart failure alone does not contribute to kidney dysfunction in mice.

A systematic review and meta-analysis of COVID-19 in kidney transplant recipients: Lessons to be learned.

Kidney transplant recipients (KTR) may be at increased risk of adverse COVID-19 outcomes, due to prevalent comorbidities and immunosuppressed status. Given the global differences in COVID-19 policies and treatments, a robust assessment of all evidence is necessary to evaluate the clinical course of COVID-19 in KTR. Studies on mortality and acute kidney injury (AKI) in KTR in the World Health Organization COVID-19 database were systematically reviewed. We selected studies published between March 2020 and January 18th 2021, including at least five KTR with COVID-19. Random-effects meta-analyses were performed to calculate overall proportions, including 95% confidence intervals (95% CI). Subgroup analyses were performed on time of submission, geographical region, sex, age, time after transplantation, comorbidities, and treatments. We included 74 studies with 5559 KTR with COVID-19 (64.0% males, mean age 58.2 years, mean 73 months after transplantation) in total. The risk of mortality, 23% (95% CI: 21%-27%), and AKI, 50% (95% CI: 44%-56%), is high among KTR with COVID-19, regardless of sex, age and comorbidities, underlining the call to accelerate vaccination programs for KTR. Given the suboptimal reporting across the identified studies, we urge researchers to consistently report anthropometrics, kidney function at baseline and discharge, (changes in) immunosuppressive therapy, AKI, and renal outcome among KTR.

Safety of electrooxidation for urea removal in a wearable artificial kidney is compromised by formation of glucose degradation products.

A major challenge for the development of a wearable artificial kidney (WAK) is the removal of urea from the spent dialysate, as urea is the waste solute with the highest daily molar production and is difficult to adsorb. Here we present results on glucose degradation products (GDPs) formed during electrooxidation (EO), a technique that applies a current to the dialysate to convert urea into nitrogen, carbon dioxide, and hydrogen gas. Uremic plasma and peritoneal effluent were dialyzed for 8 hours with a WAK with and without EO-based dialysate regeneration. Samples were taken regularly during treatment. GDPs (glyoxal, methylglyoxal, and 3-deoxyglucosone) were measured in EO- and non-EO-treated fluids. Glyoxal and methylglyoxal concentrations increased 26- and 11-fold, respectively, in uremic plasma (at [glucose] 7 mmol/L) and 209- and 353-fold, respectively, in peritoneal effluent (at [glucose] 100 mmol/L) during treatment with EO, whereas no change was observed in GDP concentrations during dialysate regeneration without EO. EO for dialysate regeneration in a WAK is currently not safe due to the generation of GDPs which are not biocompatible.

Simplified Iohexol-Based Method for Measurement of Glomerular Filtration Rate in Goats and Pigs.

The preclinical evaluation of novel therapies for chronic kidney disease requires a simple method for the assessment of kidney function in a uremic large animal model. An intravenous bolus of iohexol was administered to goats (13 measurements in n = 3 goats) and pigs (23 measurements in n = 5 pigs) before and after induction of kidney failure, followed by frequent blood sampling up to 1440 min. Plasma clearance (CL) was estimated by a nonlinear mixed-effects model (CLNLME) and by a one-compartmental pharmacokinetic disposition model using iohexol plasma concentrations during the terminal elimination phase (CL1CMT). A simple method (CLSM) for the calculation of plasma clearance was developed based on the most appropriate relationship between CLNLME and CL1CMT. CLSM and CLNLME showed good agreement (CLNLME/CLSM ratio: 1.00 ± 0.07; bias: 0.03 ± 1.64 mL/min; precision CLSM and CLNLME: 80.9% and 80.7%, respectively; the percentage of CLSM estimates falling within ±30% (P30) or ±10% (P10) of CLNLME: 53% and 12%, respectively). For mGFRNLME vs. mGFRSM, bias was -0.25 ± 2.24 and precision was 49.2% and 53.6%, respectively, P30 and P10 for mGFR based on CLSM were 71% and 24%, respectively. A simple method for measurement of GFR in healthy and uremic goats and pigs was successfully developed, which eliminates the need for continuous infusion of an exogenous marker, urine collection and frequent blood sampling.

Cardiac Protection by Oral Sodium Thiosulfate in a Rat Model of L-NNA-Induced Heart Disease.

Hypertension contributes to cardiac damage and remodeling. Despite the availability of renin-angiotensin system inhibitors and other antihypertensive therapies, some patients still develop heart failure. Novel therapeutic approaches are required that are effective and without major adverse effects. Sodium Thiosulfate (STS), a reversible oxidation product of hydrogen sulfide (H2S), is a promising pharmacological entity with vasodilator and anti-oxidant potential that is clinically approved for the treatment of calciphylaxis and cyanide poisoning. We hypothesized that Sodium Thiosulfate improves cardiac disease in an experimental hypertension model and sought to investigate its cardioprotective effects by direct comparison to the ACE-inhibitor lisinopril, alone and in combination, using a rat model of chronic nitric oxide (NO) deficiency. Systemic nitric oxide production was inhibited in Sprague Dawley rats by administering N-ω-nitro-l-arginine (L-NNA) with the food for three weeks, leading to progressive hypertension, cardiac dysfunction and remodeling. We observed that STS, orally administered via the drinking water, ameliorated L-NNA-induced heart disease. Treatment with STS for two weeks ameliorated hypertension and improved systolic function, left ventricular hypertrophy, cardiac fibrosis and oxidative stress, without causing metabolic acidosis as is sometimes observed following parenteral administration of this drug. STS and lisinopril had similar protective effects that were not additive when combined. Our findings indicate that oral intervention with a H2S donor such as STS has cardioprotective properties without noticeable side effects.

The effect of liraglutide and sitagliptin on oxidative stress in persons with type 2 diabetes.

Glucagon-like peptide 1 receptor agonists have shown cardioprotective effects which have been suggested to be mediated through inhibition of oxidative stress. We investigated the effect of treatment with a glucagon-like peptide 1 receptor agonist (liraglutide) on oxidative stress measured as urinary nucleic acid oxidation in persons with type 2 diabetes. Post-hoc analysis of two independent, randomised, placebo-controlled and double-blinded clinical trials. In a cross-over study where persons with type 2 diabetes and microalbuminuria (LIRALBU, n = 32) received liraglutide (1.8 mg/day) or placebo for 12 weeks in random order, separated by 4 weeks of wash-out. In a parallel-grouped study where obese persons with type 2 diabetes (SAFEGUARD, n = 56) received liraglutide (1.8 mg/day), sitagliptin (100 mg/day) or placebo for 12 weeks. Endpoints were changes in the urinary markers of DNA oxidation (8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG)) and RNA oxidation [8-oxo-7,8-dihydroguanosine (8-oxoGuo)]. In LIRALBU, we observed no significant differences between treatment periods in urinary excretion of 8-oxodG [0.028 (standard error (SE): 0.17] nmol/mmol creatinine, p = 0.87) or of 8-oxoGuo [0.12 (0.12) nmol/mmol creatinine, p = 0.31]. In SAFEGUARD, excretion of 8-oxodG was not changed in the liraglutide group [2.8 (- 8.51; 15.49) %, p = 0.62] but a significant decline was demonstrated in the placebo group [12.6 (- 21.3; 3.1) %, p = 0.02], resulting in a relative increase in the liraglutide group compared to placebo (0.16 nmol/mmol creatinine, SE 0.07, p = 0.02). Treatment with sitagliptin compared to placebo demonstrated no significant difference (0.07 (0.07) nmol/mmol creatinine, p = 0.34). Nor were any significant differences for urinary excretion of 8-oxoGuo liraglutide vs placebo [0.09 (SE: 0.07) nmol/mmol creatinine, p = 0.19] or sitagliptin vs placebo [0.07 (SE: 0.07) nmol/mmol creatinine, p = 0.35] observed. This post-hoc analysis could not demonstrate a beneficial effect of 12 weeks of treatment with liraglutide or sitagliptin on oxidatively generated modifications of nucleic acid in persons with type 2 diabetes.

Skin microvascular function and renal hemodynamics in overweight patients with type 2 diabetes: A cross-sectional study.

OBJECTIVE: Diabetic kidney disease is a microvascular complication of diabetes. Here, we assessed the association between skin microvascular function and renal hemodynamic function in a cohort of well-phenotyped adults with type 2 diabetes (T2D). METHODS: We included 81 overweight/obese adults (age: 62 ± 8 years; BMI: 32 ± 4 kg/m2 ) with well-controlled T2D and no renal impairment. Skin microvascular function was assessed by nailfold capillary density in rest and after arterial occlusion (ie, peak capillary density). Renal hemodynamic functions (ie, measured glomerular filtration rate [mGFR], effective renal blood flow [ERBF], filtration fraction [FF], and effective renal vascular resistance [ERVR]) were assessed by combined inulin and para-aminohippurate clearances and blood pressure measurements. RESULTS: Skin capillary density was 45 ± 10 capillaries/mm2 at baseline and 57 ± 11 capillaries/mm2 during post-occlusive peak; mGFR averaged 108 ± 20 ml/min. In multivariable regression analyses, positive associations between capillary density during post-occlusive peak and mGFR (ß = 0.224; p = 0.022) and ERBF (ß = 0.203; p = 0.020) and a positive trend for hyperemia and mGFR (ß = 0.391; p = 0.053) were observed, while a negative association for post-occlusive capillary density with ERVR (ß = -0.196; p = 0.027) was found. CONCLUSION: These findings indicate that microvascular dysfunction in overweight adults with T2D is associated with lower mGFR and ERPF and higher ERVR. We hypothesize that increased renal vascular resistance may contribute to glomerular dysfunction due to impaired renal perfusion.