Kidney Energetics and Cyst Burden in Autosomal Dominant Polycystic Kidney Disease: A Pilot Study

RATIONALE & OBJECTIVE

In this pilot study, we hypothesized that autosomal dominant polycystic kidney disease (ADPKD) is characterized by impaired kidney oxidative metabolism that associates with kidney size and cyst burden.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

Twenty adults with ADPKD (31±6 years of age, 65% women, BMI: 26.8 [22.7, 30.4] kg/m2, eGFR (2021 CKD-EPI Creatinine): 103±18 ml/min/1.73m2, height-adjusted total kidney volume [HtTKV]: 731±370 ml/m, Mayo Classifications: 1B [5%], 1C [42%], 1D [21%], 1E [32%]) and 11 controls in normal weight category (NWC; 25±3 years of age, 45% women, BMI: 22.5 [21.7, 24.2] kg/m2, eGFR: 113±15 ml/min/1.73m2, HtTKV: 159±31 ml/m) at the University of Colorado Anschutz Medical Campus.

PREDICTORS

ADPKD status (yes/no) and severity (Mayo Classifications).

OUTCOMES

HtTKV and cyst burden by MRI, kidney oxidative metabolism and perfusion by 11C-acetate PET/CT, insulin sensitivity by hyperinsulinemic-euglycemic clamps (presented as ratio of M-value of steady state insulin concentration [M/I]).

ANALYTICAL APPROACH

Chi-square/Fisher's exact tests used for categorical variables and t-tests/ Mann-Whitney U tests for continuous variables. Pearson correlation used to estimate the relationships between variables.

RESULTS

Compared to NWC, participants with ADPKD exhibited lower mean±SD M/I ratio (0.586±0.205 vs. 0.424±0.171 (mg/kg lean/min) / (μIU/mL), p=0.04), lower median [p25, p75] cortical perfusion (1.93 [1.80, 2.09 vs. 0.68 [0.47, 1.04] mL/min/g, p<0.001) and lower median [p25, p75] total kidney oxidative metabolism (0.17 [0.16,0.19] vs. 0.14 [0.12, 0.15] min-1, p=0.001) in voxel-wise models excluding cysts. HtTKV correlated inversely with cortical perfusion (r:-0.83, p<0.001), total kidney oxidative metabolism (r:-0.61, p<0.001) and M/I (r:-0.41, p=0.03).

LIMITATIONS

Small sample size and cross-sectional design.

CONCLUSION

Adults with ADPKD and preserved kidney function exhibited impaired renal perfusion and kidney oxidative metabolism across a wide range of cysts and kidney enlargements.

Combination therapy for kidney disease in people with diabetes mellitus

Diabetic kidney disease (DKD), defined as co-existing diabetes and chronic kidney disease in the absence of other clear causes of kidney injury, occurs in approximately 20-40% of patients with diabetes mellitus. As the global prevalence of diabetes has increased, DKD has become highly prevalent and a leading cause of kidney failure, accelerated cardiovascular disease, premature mortality and global health care expenditure. Multiple pathophysiological mechanisms contribute to DKD, and single lifestyle or pharmacological interventions have shown limited efficacy at preserving kidney function. For nearly two decades, renin-angiotensin system inhibitors were the only available kidney-protective drugs. However, several new drug classes, including sodium glucose cotransporter-2 inhibitors, a non-steroidal mineralocorticoid antagonist and a selective endothelin receptor antagonist, have now been demonstrated to improve kidney outcomes in people with type 2 diabetes mellitus. In addition, emerging preclinical and clinical evidence of the kidney-protective effects of glucagon-like-peptide-1 receptor agonists has led to the prospective testing of these agents for DKD. Research and clinical efforts are geared towards using therapies with potentially complementary efficacy in combination to safely halt kidney disease progression. As more kidney-protective drugs become available, the outlook for people living with DKD should improve in the next few decades.

Minireview: Understanding and targeting inflammatory, hemodynamic and injury markers for cardiorenal protection in type 1 diabetes

The coexistence of cardiovascular disease (CVD) and diabetic kidney disease (DKD) is common in people with type 1 diabetes (T1D) and is strongly associated with an increased risk of morbidity and mortality. Hence, it is imperative to explore robust tools that can accurately reflect the development and progression of cardiorenal complications. Several cardiovascular and kidney biomarkers have been identified to detect at-risk individuals with T1D. The primary aim of this review is to highlight biomarkers of injury, inflammation, or renal hemodynamic changes that may influence T1D susceptibility to CVD and DKD. We will also examine the impact of approved pharmacotherapies for type 2 diabetes, including renin-angiotensin-aldosterone system (RAAS) inhibitors, sodium-glucose cotransporter-2 (SGLT2) inhibitors and glucagon-like peptide-1 receptor agonists (GLP-1RAs) on candidate biomarkers for cardiorenal complications in people with T1D and discuss how these changes may potentially mediate kidney and cardiovascular protection. Identifying predictive and prognostic biomarkers for DKD and CVD may highlight potential drug targets to attenuate cardiorenal disease progression, implement novel risk stratification measures in clinical trials, and improve the assessment, diagnosis, and treatment of at-risk individuals with T1D.

Insulin Secretion, Sensitivity, and Kidney Function in Young Individuals With Type 2 Diabetes

OBJECTIVE

β-Cell dysfunction and insulin resistance magnify the risk of kidney injury in type 2 diabetes. The relationship between these factors and intraglomerular hemodynamics and kidney oxygen availability in youth with type 2 diabetes remains incompletely explored.

RESEARCH DESIGN AND METHODS

Fifty youth with type 2 diabetes (mean age ± SD 16 ± 2 years; diabetes duration 2.3 ± 1.8 years; 60% female; median HbA1c 6.4% [25th, 75th percentiles 5.9, 7.6%]; BMI 36.4 ± 7.4 kg/m2; urine albumin-to-creatinine ratio [UACR] 10.3 [5.9, 58.0] mg/g) 21 control participants with obesity (OCs; age 16 ± 2 years; 29% female; BMI 37.6 ± 7.4 kg/m2), and 20 control participants in the normal weight category (NWCs; age 17 ± 3 years; 70% female; BMI 22.5 ± 3.6 kg/m2) underwent iohexol and p-aminohippurate clearance to assess glomerular filtration rate (GFR) and renal plasma flow, kidney MRI for oxygenation, hyperglycemic clamp for insulin secretion (acute C-peptide response to glucose [ACPRg]) and disposition index (DI; ×103 mg/kg lean/min), and DXA for body composition.

RESULTS

Youth with type 2 diabetes exhibited lower DI (0.6 [0.0, 1.6] vs. 3.8 [2.4, 4.5] × 103 mg/kg lean/min; P < 0.0001) and ACPRg (0.6 [0.3, 1.4] vs. 5.3 [4.3, 6.9] nmol/L; P < 0.001) and higher UACR (10.3 [5.9, 58.0] vs. 5.3 [3.4, 14.3] mg/g; P = 0.003) and intraglomerular pressure (77.8 ± 11.5 vs. 64.8 ± 5.0 mmHg; P < 0.001) compared with OCs. Youth with type 2 diabetes and OCs had higher GFR and kidney oxygen availability (relative hyperoxia) than NWCs. DI was associated inversely with intraglomerular pressure and kidney hyperoxia.

CONCLUSIONS

Youth with type 2 diabetes demonstrated severe β-cell dysfunction that was associated with intraglomerular hypertension and kidney hyperoxia. Similar but attenuated findings were found in OCs.

Interactive Effects of Empagliflozin and Hyperglycemia on Urinary Amino Acids in Individuals With Type 1 Diabetes

Optimizing energy use in the kidney is critical for normal kidney function. Here, we investigate the effect of hyperglycemia and sodium-glucose cotransporter 2 (SGLT2) inhibition on urinary amino acid excretion in individuals with type 1 diabetes (T1D). The open-label ATIRMA trial assessed the impact of 8 weeks of 25 mg empagliflozin orally once per day in 40 normotensive normoalbuminuric young adults with T1D. A consecutive 2-day assessment of clamped euglycemia and hyperglycemia was evaluated at baseline and posttreatment visits. Principal component analysis was performed on urinary amino acids grouped into representative metabolic pathways using MetaboAnalyst. At baseline, acute hyperglycemia was associated with changes in 25 of the 33 urinary amino acids or their metabolites. The most significant amino acid metabolites affected by acute hyperglycemia were 3-hydroxykynurenine, serotonin, glycyl-histidine, and nicotinic acid. The changes in amino acid metabolites were reflected by the induction of four biosynthetic pathways: aminoacyl-tRNA; valine, leucine, and isoleucine; arginine; and phenylalanine, tyrosine, and tryptophan. In acute hyperglycemia, empagliflozin significantly attenuated the increases in aminoacyl-tRNA biosynthesis and valine, leucine, and isoleucine biosynthesis. Our findings using amino acid metabolomics indicate that hyperglycemia stimulates biosynthetic pathways in T1D. SGLT2 inhibition may attenuate the increase in biosynthetic pathways to optimize kidney energy metabolism.

ARTICLE HIGHLIGHTS

Glycoprotein Acetyls Associate With Intraglomerular Hemodynamic Dysfunction, Albuminuria, Central Adiposity, and Insulin Resistance in Youth With Type 1 Diabetes

OBJECTIVES

Glycoprotein acetyls (GlycA's) are biomarkers of systemic inflammation and cardiovascular disease, yet little is known about their role in type 1 diabetes (T1D). In this study we examined the associations among GlycA's, central adiposity, insulin resistance, and early kidney injury in youth with T1D.

METHODS

Glomerular filtration rate and renal plasma flow by iohexol and p-aminohippurate clearance, urine albumin-to-creatinine ratio (UACR), central adiposity by dual-energy x-ray absorptiometry, and estimated insulin sensitivity were assessed in 50 youth with T1D (16±3.0 years of age, 50% female, glycated hemoglobin 8.7±1.3%, T1D duration 5.7±2.6 years). Concentrations of GlycA were quantified by targeted nuclear magnetic resonance spectroscopy. Correlation and multivariable linear regression analyses were performed.

RESULTS

GlycA's were higher in girls vs boys (1.05±0.26 vs 0.84±0.15 mmol/L, p=0.001) and in participants living with overweight/obesity vs normal weight (1.12±0.23 vs 0.87±0.20 mmol/L, p=0.0004). GlycA's correlated positively with estimated intraglomerular pressure (r=0.52, p=0.001), UACR (r=0.53, p<0.0001), and trunk mass (r=0.45, p=0.001), and inversely with estimated insulin sensitivity (r=-0.36, p=0.01). All relationships remained significant after adjustment for age, sex, and glycated hemoglobin.

CONCLUSIONS

As biomarker of inflammation, GlycA's were higher in girls and those with overweight or obese body habitus in T1D. GlycA's associated with parameters of early kidney dysfunction, central adiposity, and insulin resistance.

β1-Integrin blockade prevents podocyte injury in experimental models of minimal change disease

INTRODUCTION

Activation of the focal adhesion kinase (FAK) in podocytes is involved in the pathogenesis of minimal change disease (MCD), but the pathway leading to its activation in this disease is unknown. Here, we tested whether podocyte β1 integrin is the upstream modulator of FAK activation and podocyte injury in experimental models of MCD-like injury.

METHODS

We used lipopolysaccharide (LPS) and MCD sera to induce MCD-like changes in vivo and in cultured human podocytes, respectively. We performed functional studies using specific β1 integrin inhibitors in vivo and in vitro, and integrated histological analysis, western blotting, and immunofluorescence to assess for morphological and molecular changes in podocytes. By ELISA, we measured serum LPS levels in 35 children with MCD or presumed MCD (idiopathic nephrotic syndrome [INS]) and in 18 healthy controls.

RESULTS

LPS-injected mice showed morphological (foot process effacement, and normal appearing glomeruli on light microscopy) and molecular features (synaptopodin loss, nephrin mislocalization, FAK phosphorylation) characteristic of human MCD. Administration of a β1 integrin inhibitor to mice abrogated FAK phosphorylation, and ameliorated proteinuria and podocyte injury following LPS. Children with MCD/INS in relapse had higher serum LPS levels than controls. In cultured human podocytes, β1 integrin blockade prevented cytoskeletal rearrangements following exposure to MCD sera in relapse.

CONCLUSIONS

Podocyte β1 integrin activation is an upstream mediator of FAK phosphorylation and podocyte injury in models of MCD-like injury.

Trajectories of eGFR and risk of albuminuria in youth with type 2 diabetes: results from the TODAY cohort study

BACKGROUND

We conducted exploratory analyses to identify distinct trajectories of estimated glomerular filtration rate (eGFR) and their relationship with hyperfiltration, subsequent rapid eGFR decline, and albuminuria in participants with youth-onset type 2 diabetes enrolled in the Treatment Options for type 2 Diabetes in Adolescents and Youth (TODAY) study.

METHODS

Annual serum creatinine, cystatin C, urine albumin, and creatinine measurements were obtained from 377 participants followed for ≥ 10 years. Albuminuria and eGFR were calculated. Hyperfiltration peak is the greatest eGFR inflection point during follow-up. Latent class modeling was applied to identify distinct eGFR trajectories.

RESULTS

At baseline, participants' mean age was 14 years, type 2 diabetes duration was 6 months, mean HbA1c was 6%, and mean eGFR was 120 ml/min/1.73 m2. Five eGFR trajectories associated with different rates of albuminuria were identified, including a "progressive increasing eGFR" group (10%), three "stable eGFR" groups with varying starting mean eGFR, and an "eGFR steady decline" group (1%). Participants who exhibited the greatest peak eGFR also had the highest levels of elevated albuminuria at year 10. This group membership was characterized by a greater proportion of female and Hispanic participants.

CONCLUSIONS

Distinct eGFR trajectories that associate with albuminuria risk were identified, with the eGFR trajectory characterized by increasing eGFR over time associating with the highest level of albuminuria. These descriptive data support the current recommendations to estimate GFR annually in young persons with type 2 diabetes and provide insight into eGFR-related factors which may contribute to predictive risk strategies for kidney disease therapies in youth with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00081328, date registered 2002. A higher resolution version of the Graphical abstract is available as Supplementary information.

Cystatin C-Based eGFR Changes during Gender-Affirming Hormone Therapy in Transgender Individuals

BACKGROUND

Men with CKD tend to experience a faster eGFR decline than women, potentially because of sex hormones. Limited research exists regarding the effect of gender-affirming hormone therapy (GAHT) on kidney function. Furthermore, monitoring kidney function during GAHT is challenging because serum creatinine is confounded by body composition. To investigate the relationship between sex hormones and kidney function, we studied the changes of serum creatinine and serum cystatin C, a filtration marker less affected by sex, during 1 year of GAHT.

METHODS

As part of the European Network for the Investigation of Gender Incongruence study, we measured serum creatinine and serum cystatin C in 260 transgender women and 285 transgender men before and 12 months after initiating GAHT. Transgender women received estradiol plus cyproterone acetate, while transgender men received testosterone. Cystatin C-based eGFR was calculated using the full-age-spectrum equation.

RESULTS

In transgender women, cystatin C decreased by 0.069 mg/L (95% confidence interval [CI], 0.049 to 0.089), corresponding with a 7 ml/min per 1.73 m 2 increase in eGFR. In transgender men, cystatin C increased by 0.052 mg/L (95% CI, 0.031 to 0.072), corresponding with a 6 ml/min per 1.73 m 2 decrease in eGFR. Creatinine concentrations decreased (-0.065 mg/dl; 95% CI, -0.076 to -0.054) in transgender women and increased (+0.131 mg/dl; 95% CI, 0.119 to 0.142) in transgender men. Changes in creatinine-based eGFR varied substantially depending on the sex used in the equation.

CONCLUSIONS

In this cohort of transgender individuals, cystatin C-based eGFR increased with estradiol and antiandrogen therapy and decreased with testosterone therapy.

Loss of Glomerular Permselectivity in Type 2 Diabetes Associates With Progression to Kidney Failure

We examined whether defects in glomerular size selectivity in type 2 diabetes are associated with progressive kidney disease. Glomerular filtration rate (GFR) and fractional clearances of dextrans of graded sizes were measured in 185 American Indians. The permselectivity model that best fit the dextran sieving data represented the glomerular capillary as being perforated by small restrictive pores and a parallel population of larger nonrestrictive pores characterized by ω0, the fraction of total filtrate volume passing through this shunt. The hazard ratio (HR) for kidney failure was expressed per 1-SD increase of ω0 by Cox regression after adjusting for age, sex, mean arterial pressure, HbA1c, GFR, and the urine albumin-to-creatinine ratio (ACR). Baseline mean ± SD age was 43 ± 10 years, HbA1c 8.9 ± 2.5%, GFR 147 ± 46 mL/min, and median (interquartile range) ACR 41 (11-230) mg/g. During a median follow-up of 17.7 years, 67 participants developed kidney failure. After adjustment, each 1-SD increment in ω0 was associated with a higher risk of kidney failure (HR 1.55 [95% CI 1.17, 2.05]). Enhanced transglomerular passage of test macromolecules was associated with progression to kidney failure, independent of albuminuria and GFR, suggesting that mechanisms associated with impaired glomerular permselectivity are important determinants of progressive kidney disease.

ARTICLE HIGHLIGHTS

Endogenous adenine mediates kidney injury in diabetic models and predicts diabetic kidney disease in patients

Diabetic kidney disease (DKD) can lead to end-stage kidney disease (ESKD) and mortality; however, few mechanistic biomarkers are available for high-risk patients, especially those without macroalbuminuria. Urine from participants with diabetes from the Chronic Renal Insufficiency Cohort (CRIC) study, the Singapore Study of Macro-angiopathy and Micro-vascular Reactivity in Type 2 Diabetes (SMART2D), and the American Indian Study determined whether urine adenine/creatinine ratio (UAdCR) could be a mechanistic biomarker for ESKD. ESKD and mortality were associated with the highest UAdCR tertile in the CRIC study and SMART2D. ESKD was associated with the highest UAdCR tertile in patients without macroalbuminuria in the CRIC study, SMART2D, and the American Indian study. Empagliflozin lowered UAdCR in nonmacroalbuminuric participants. Spatial metabolomics localized adenine to kidney pathology, and single-cell transcriptomics identified ribonucleoprotein biogenesis as a top pathway in proximal tubules of patients without macroalbuminuria, implicating mTOR. Adenine stimulated matrix in tubular cells via mTOR and stimulated mTOR in mouse kidneys. A specific inhibitor of adenine production was found to reduce kidney hypertrophy and kidney injury in diabetic mice. We propose that endogenous adenine may be a causative factor in DKD.

Sodium glucose co-transporter 2 inhibition increases epidermal growth factor expression and improves outcomes in patients with type 2 diabetes

Underlying molecular mechanisms of the kidney protective effects of sodium glucose co-transporter 2 (SGLT2) inhibitors are not fully elucidated. Therefore, we studied the association between urinary epidermal growth factor (uEGF), a mitogenic factor involved in kidney repair, and kidney outcomes in patients with type 2 diabetes (T2D). The underlying molecular mechanisms of the SGLT2 inhibitor canagliflozin on EGF using single-cell RNA sequencing from kidney tissue were examined. Urinary EGF-to-creatinine ratio (uEGF/Cr) was measured in 3521 CANagliflozin cardioVascular Assessment Study (CANVAS) participants at baseline and week 52. Associations of uEGF/Cr with kidney outcome were assessed using multivariable-adjusted Cox regression models. Single-cell RNA sequencing was performed using protocol kidney biopsy tissue from ten young patients with T2D on SGLT2i, six patients with T2D on standard care only, and six healthy controls (HCs). In CANVAS, each doubling in baseline uEGF/Cr was associated with a 12% (95% confidence interval 1-22) decreased risk of kidney outcome. uEGF/Cr decreased after 52 weeks with placebo and remained stable with canagliflozin (between-group difference +7.3% (2.0-12.8). In young persons with T2D, EGF mRNA was primarily expressed in the thick ascending loop of Henle. Expression in biopsies from T2D without SGLT2i was significantly lower compared to HCs, whereas treatment with SGLT2i increased EGF levels closer to the healthy state. In young persons with T2D without SGLT2i, endothelin-1 emerged as a key regulator of the EGF co-expression network. SGLT2i treatment was associated with a shift towards normal EGF expression. Thus, decreased uEGF represents increased risk of kidney disease progression in patients with T2D. Canagliflozin increased kidney tissue expression of EGF and was associated with a downstream signaling cascade linked to tubular repair and reversal of tubular injury.

Kidney Considerations in Pediatric Obesity

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is a common condition and a major cause of morbidity and mortality in adults, but children and adolescents are also at risk for early kidney injury and development of CKD. Obesity contributes both directly and indirectly to the development of CKD. The purpose of this review is to describe obesity-related kidney disease (ORKD) and diabetic kidney disease (DKD) and their impact in the pediatric population.

RECENT FINDINGS

Although obesity-related CKD in childhood and adolescence is uncommon, nascent kidney damage may magnify the lifetime risk of CKD. Glomerular hyperfiltration is an early phenotype of both ORKD and DKD and typically manifests prior to albuminuria and progressive decline in GFR. Novel treatments for obesity and type 2 diabetes exerting protective effects on the kidneys are being investigated for use in the pediatric population. It is important to understand the impact of obesity on the kidneys more fully in the pediatric population to help detect injury earlier and intervene prior to the onset of irreversible progression of disease and to guide future research in this area.

Estimated glomerular filtration rate calculated by serum creatinine lacks precision and accuracy in adults with type 2 diabetes with preserved renal function

AIMS

We evaluated the performance of creatinine-based equations that are currently used to estimate glomerular filtration rate (GFR) in people with type 2 diabetes compared to measured GFR using gold-standard methods.

METHODS

In this post-hoc analysis, 32 participants underwent repeated measurement of GFR by inulin clearance (mGFR). GFR was estimated by serum creatinine using the MDRD (eGFRMDRD) and CKD-EPI (eGFRCKD-EPI) equations four times over the course of one month. Performance was evaluated using measurements of bias (mean difference), precision (SD), and inaccuracy (proportion of eGFR that differed by >20 % of mGFR). Treatment and time effects on bias were evaluated using linear mixed effects models.

RESULTS

At baseline, participants (38 % female) were age 60 ± 8 years, had diabetes duration of 9 ± 7 years, HbA1c 56 ± 9 mmol/mol (7.2 ± 0.8 %), and BMI 31.0 ± 6.2 kg/m2. Mean mGFR was 113 ± 24, mean eGFRMDRD was 93 ± 12, and mean eGFRCKD-EPI was 94 ± 9 mL/min/1.73 m2. When 128 observations (32 participants measured 4 times) were evaluated, both equations substantially underestimated mGFR. For eGFRMDRD, mean bias was -21.5 mL/min/1.73 m2, precision was 22.7 mL/min/1.73 m2, and 46 % of observations differed by >20 %. Results were similar for eGFRCKD-EPI. No time or treatment effects on bias were observed.

CONCLUSIONS

In adults with type 2 diabetes and preserved renal function, eGFR equations underestimated mGFR, lacked precision and accuracy, and performance was lower at higher ranges of mGFR. Current eGFR equations by serum creatinine are inaccurate in adults with type 2 diabetes with preserved renal function, highlighting the necessity to develop new methods to measure kidney function at earlier stages of diabetic kidney disease.

Estimation of glomerular filtration rate in a pediatric population using non-contrast kidney phase contrast magnetic resonance imaging

BACKGROUND

Glomerular filtration rate (GFR) is a key measure of kidney function but often inaccurately ascertained by serum creatinine and cystatin C in pediatrics. In this pilot trial, we evaluated the relationship between GFR calculated by using phase-contrast MRI (PC-MRI) biomarkers and GFR by 125I-iothalamate clearance in youth undergoing bone marrow transplantation (BMT).

METHODS

A total of twenty-one pediatric BMT candidates (8-21 years of age) were recruited for a research kidney PC-MRI. After completion of 125I-iothalamate clearance, same-day PC-MRI measurements were completed of the kidney circulation without a gadolinium-based contrast agent. MRI included a non-contrast balanced-SSFP-triggered angiography to position ECG-gated breath-held 2D PC-MRI flow measurements (1.2 × 1.2 × 6 mm3). A multivariate model of MRI biomarkers estimating GFR (GFR-MRI) was selected using the elastic net approach.

RESULTS

The GFR-MRI variables selected by elastic net included average heart rate during imaging (bpm), peak aorta flow below the kidney artery take-offs (ml/s), average kidney artery blood flow, average peak kidney vein blood flow, and average kidney vein blood flow (ml/s). The GFR-MRI model demonstrated strong agreement with GFR by 125I-iothalamate (R2 = 0.65), which was stronger than what was observed with eGFR by the full age spectrum and Chronic Kidney Disease in Children under 25 (CKiD U25) approaches.

CONCLUSION

In this pilot study, noninvasive GFR-MRI showed strong agreement with gold standard GFR in youth scheduled for BMT. Further work is needed to evaluate whether non-contrast GFR-MRI holds promise to become a superior alternative to eGFR and GFR by clearance techniques. A higher resolution version of the Graphical abstract is available as Supplementary information.

Fructose: A New Variable to Consider in SIADH and the Hyponatremia Associated With Long-Distance Running?

Fructose has recently been proposed to stimulate vasopressin secretion in humans. Fructose-induced vasopressin secretion is not only postulated to result from ingestion of fructose-containing drinks but may also occur from endogenous fructose production via activation of the polyol pathway. This raises the question of whether fructose might be involved in some cases of vasopressin-induced hyponatremia, especially in situations where the cause is not fully known such as in the syndrome of inappropriate secretion of diuretic hormone (SIADH) and exercise-associated hyponatremia, which has been observed in marathon runners. Here we discuss the new science of fructose and vasopressin, and how it may play a role in some of these conditions, as well as in the complications associated with rapid treatment (such as the osmotic demyelination syndrome). Studies to test the role of fructose could provide new pathophysiologic insights as well as novel potential treatment strategies for these common conditions.

Role of endogenous adenine in kidney failure and mortality with diabetes

Diabetic kidney disease (DKD) can lead to end-stage kidney disease (ESKD) and mortality, however, few mechanistic biomarkers are available for high risk patients, especially those without macroalbuminuria. Urine from participants with diabetes from Chronic Renal Insufficiency Cohort (CRIC), Singapore Study of Macro-Angiopathy and Reactivity in Type 2 Diabetes (SMART2D), and the Pima Indian Study determined if urine adenine/creatinine ratio (UAdCR) could be a mechanistic biomarker for ESKD. ESKD and mortality were associated with the highest UAdCR tertile in CRIC (HR 1.57, 1.18, 2.10) and SMART2D (HR 1.77, 1.00, 3.12). ESKD was associated with the highest UAdCR tertile in patients without macroalbuminuria in CRIC (HR 2.36, 1.26, 4.39), SMART2D (HR 2.39, 1.08, 5.29), and Pima Indian study (HR 4.57, CI 1.37-13.34). Empagliflozin lowered UAdCR in non-macroalbuminuric participants. Spatial metabolomics localized adenine to kidney pathology and transcriptomics identified ribonucleoprotein biogenesis as a top pathway in proximal tubules of patients without macroalbuminuria, implicating mammalian target of rapamycin (mTOR). Adenine stimulated matrix in tubular cells via mTOR and stimulated mTOR in mouse kidneys. A specific inhibitor of adenine production was found to reduce kidney hypertrophy and kidney injury in diabetic mice. We propose that endogenous adenine may be a causative factor in DKD.

Pharmacological management of youth with type 2 diabetes and diabetic kidney disease: a comprehensive review of current treatments and future directions

INTRODUCTION

Diabetic kidney disease (DKD) is a leading cause of mortality in people with type 2 diabetes (T2D), and over 50% of individuals with youth-onset T2D will develop DKD as a young adult. Diagnosis of early-onset DKD remains a challenge in young persons with T2D secondary to a lack of available biomarkers for early DKD, while the injuries may still be reversible. Furthermore, multiple barriers exist to initiate timely prevention and treatment strategies for DKD, including a lack of Food and Drug Administration approval of medications in pediatrics; provider comfort with medication prescription, titration, and monitoring; and medication adherence.

AREAS COVERED

Therapies that have promise for slowing DKD progression in youth with T2D include metformin, renin-angiotensin-aldosterone system inhibitors, glucagon-like peptide-1 receptor agonists, sodium glucose co-transporter 2 inhibitors, thiazolidinediones, sulfonylureas, endothelin receptor agonists, and mineralocorticoid antagonists. Novel agents are also in development to act synergistically on the kidneys with the aforementioned medications. We comprehensively review the available pharmacologic strategies for DKD in youth-onset T2D including mechanisms of action, potential adverse effects, and kidney-specific effects, with an emphasis on published pediatric and adult trials.

EXPERT OPINION

Large clinical trials evaluating pharmacologic interventions targeting the treatment of DKD in youth-onset T2D are strongly needed.

Youth-onset type 2 diabetes mellitus: an urgent challenge

The incidence and prevalence of youth-onset type 2 diabetes mellitus (T2DM) and its complications are increasing worldwide. Youth-onset T2DM has been reported in all racial and ethnic groups, but Indigenous peoples and people of colour are disproportionately affected. People with youth-onset T2DM often have a more aggressive clinical course than those with adult-onset T2DM or those with type 1 diabetes mellitus. Moreover, the available treatment options for children and adolescents with T2DM are more limited than for adult patients. Intermediate complications of youth-onset T2DM, such as increased albuminuria, often develop in late childhood or early adulthood, and end-stage complications, including kidney failure, develop in mid-life. The increasing frequency, earlier onset and greater severity of childhood obesity in the past 50 years together with increasingly sedentary lifestyles and an increasing frequency of intrauterine exposure to diabetes are important drivers of the epidemic of youth-onset T2DM. The particularly high risk of the disease in historically disadvantaged populations suggests an important contribution of social and environmental factors, including limited access to high-quality health care, healthy food choices and opportunities for physical activity as well as exposure to stressors including systemic racism and environmental pollutants. Understanding the mechanisms that underlie the development and aggressive clinical course of youth-onset T2DM is key to identifying successful prevention and management strategies.

Renal hemodynamic changes in patients with type 2 diabetes and their clinical impact

The dysfunction of the internal mechanics within the kidney's filtering units, known as glomeruli, has been linked to the emergence and progression of diabetic kidney disease (DKD). To better understand this crucial aspect of kidney function and the pathology of DKD, a variety of methods are employed in research, from the introduction of external compounds, such as inulin, iohexol, iothalamate and p-aminohippurate, to cutting-edge imaging techniques and computational analysis. Given the significance of intraglomerular hemodynamic dysfunction in the pathogenesis and treatment of DKD, it is essential to thoroughly examine the available data on this topic. Accordingly, the aim of this review is to provide a comprehensive appraisal of the role of intraglomerular hemodynamic dysfunction in the development of DKD and the effects of current therapies used to mitigate DKD. Through this analysis, we can gain a deeper understanding of the complex pathogenesis of DKD and potentially discover new avenues for tailored therapeutic management of patients with DKD.

SGLT2 inhibitors mitigate kidney tubular metabolic and mTORC1 perturbations in youth-onset type 2 diabetes

The molecular mechanisms of sodium-glucose cotransporter-2 (SGLT2) inhibitors (SGLT2i) remain incompletely understood. Single-cell RNA sequencing and morphometric data were collected from research kidney biopsies donated by young persons with type 2 diabetes (T2D), aged 12 to 21 years, and healthy controls (HCs). Participants with T2D were obese and had higher estimated glomerular filtration rates and mesangial and glomerular volumes than HCs. Ten T2D participants had been prescribed SGLT2i (T2Di[+]) and 6 not (T2Di[-]). Transcriptional profiles showed SGLT2 expression exclusively in the proximal tubular (PT) cluster with highest expression in T2Di(-) patients. However, transcriptional alterations with SGLT2i treatment were seen across nephron segments, particularly in the distal nephron. SGLT2i treatment was associated with suppression of transcripts in the glycolysis, gluconeogenesis, and tricarboxylic acid cycle pathways in PT, but had the opposite effect in thick ascending limb. Transcripts in the energy-sensitive mTORC1-signaling pathway returned toward HC levels in all tubular segments in T2Di(+), consistent with a diabetes mouse model treated with SGLT2i. Decreased levels of phosphorylated S6 protein in proximal and distal tubules in T2Di(+) patients confirmed changes in mTORC1 pathway activity. We propose that SGLT2i treatment benefits the kidneys by mitigating diabetes-induced metabolic perturbations via suppression of mTORC1 signaling in kidney tubules.

Triglyceride content of lipoprotein subclasses and kidney hemodynamic function and injury in adolescents with type 1 diabetes

AIMS

Elevated triglycerides (TG) are associated with development and progression of kidney disease, and TG distributions across lipoprotein subclasses predict kidney dysfunction in adults with type 1 diabetes (T1D). Little is known regarding these relationships in youth.

METHODS

In this single center study conducted from October 2018-2019, lipid constituents from lipoprotein subclasses were quantified by targeted nuclear magnetic resonance spectroscopy. Glomerular filtration rate (GFR), renal plasma flow (RPF), afferent arteriolar resistance (RA), efferent arteriolar resistance (RE), intraglomerular pressure (PGLO), urine albumin-to-creatinine ratio (UACR), and chitinase-3-like protein 1 (YKL-40), a marker of kidney tubule injury, were assessed. Cross-sectional relationships were assessed by correlation and multivariable linear regression (adjusted for age, sex, HbA1c) models.

RESULTS

Fifty youth with T1D (age 16 ± 3 years, 50 % female, HbA1c 8.7 ± 1.3 %, T1D duration 5.7 ± 2.6 years) were included. Very-low-density lipoprotein (VLDL)-TG concentrations correlated and associated with intraglomerular hemodynamic function markers including GFR, PGLO, UACR, as did small low-density lipoprotein (LDL)-TG and small high-density lipoprotein (HDL)-TG. YKL-40 correlated with all lipoprotein subclasses.

CONCLUSION

TG within lipoprotein subclasses, particularly VLDL, associated with PGLO, GFR, albuminuria, and YKL-40. Lipid perturbations may serve as novel targets to mitigate early kidney disease.

Bromocriptine Improves Central Aortic Stiffness in Adolescents With Type 1 Diabetes: Arterial Health Results From the BCQR-T1D Study

BACKGROUND

The presence of vascular dysfunction is a well-recognized feature in youth with type 1 diabetes (T1D), accentuating their lifetime risk of cardiovascular events. Therapeutic strategies to mitigate vascular dysfunction are a high clinical priority. In the bromocriptine quick release T1D study (BCQR-T1D), we tested the hypothesis that BCQR would improve vascular health in youth with T1D.

METHODS

BCQR-T1D was a placebo-controlled, random-order, double-blinded, cross-over study investigating the cardiovascular and metabolic impact of BCQR in T1D. Adolescents in the BCQR-T1D study were randomized 1:1 to phase-1: 4 weeks of BCQR or placebo after which blood pressure and central aortic stiffness measurements by pulse wave velocity, relative area change, and distensibility from phase-contrast magnetic resonance imaging were performed. Following a 4-week washout period, phase 2 was performed in identical fashion with the alternate treatment.

RESULTS

Thirty-four adolescents (mean age 15.9±2.6 years, hemoglobin A1c 8.6±1.1%, body mass index percentile 71.4±26.1, median T1D duration 5.8 years) with T1D were enrolled and had magnetic resonance imaging data available. Compared with placebo, BCQR therapy decreased systolic (∆=-5 mmHg [95% CI, -3 to -7]; P<0.001) and diastolic blood pressure (∆=-2 mmHg [95% CI, -4 to 0]; P=0.039). BCQR reduced ascending aortic pulse wave velocity (∆=-0.4 m/s; P=0.018) and increased relative area change (∆=-2.6%, P=0.083) and distensibility (∆=0.08%/mmHg; P=0.017). In the thoraco-abdominal aorta, BCQR decreased pulse wave velocity (∆=-0.2 m/s; P=0.007) and increased distensibility (∆=0.05 %/mmHg; P=0.013).

CONCLUSIONS

BCQR improved blood pressure and central and peripheral aortic stiffness and pressure hemodynamics in adolescents with T1D over 4 weeks versus placebo. BCQR may improve aortic stiffness in youth with T1D, supporting future longer-term studies.

Plasma levels of carboxylic acids are markers of early kidney dysfunction in young people with type 1 diabetes

BACKGROUND

We compared plasma metabolites of amino acid oxidation and the tricarboxylic acid (TCA) cycle in youth with and without type 1 diabetes mellitus (T1DM) and related the metabolites to glomerular filtration rate (GFR), renal plasma flow (RPF), and albuminuria. Metabolites associated with impaired kidney function may warrant future study as potential biomarkers or even future interventions to improve kidney bioenergetics.

METHODS

Metabolomic profiling of fasting plasma samples using a targeted panel of 644 metabolites and an untargeted panel of 19,777 metabolites was performed in 50 youth with T1DM ≤ 10 years and 20 controls. GFR and RPF were ascertained by iohexol and p-aminohippurate clearance, and albuminuria calculated as urine albumin to creatinine ratio. Sparse partial least squares discriminant analysis and moderated t tests were used to identify metabolites associated with GFR and RPF.

RESULTS

Adolescents with and without T1DM were similar in age (16.1 ± 3.0 vs. 16.1 ± 2.9 years) and BMI (23.4 ± 5.1 vs. 22.7 ± 3.7 kg/m2), but those with T1DM had higher GFR (189 ± 40 vs. 136 ± 22 ml/min) and RPF (820 ± 125 vs. 615 ± 65 ml/min). Metabolites of amino acid oxidation and the TCA cycle were significantly lower in adolescents with T1DM vs. controls, and the measured metabolites were able to discriminate diabetes status with an AUC of 0.82 (95% CI: 0.71, 0.93) and error rate of 0.21. Lower glycine (r:-0.33, q = 0.01), histidine (r:-0.45, q < 0.001), methionine (r: -0.29, q = 0.02), phenylalanine (r: -0.29, q = 0.01), serine (r: -0.42, q < 0.001), threonine (r: -0.28, q = 0.02), citrate (r: -0.35, q = 0.003), fumarate (r: -0.24, q = 0.04), and malate (r: -0.29, q = 0.02) correlated with higher GFR. Lower glycine (r: -0.28, q = 0.04), phenylalanine (r:-0.3, q = 0.03), fumarate (r: -0.29, q = 0.04), and malate (r: -0.5, q < 0.001) correlated with higher RPF. Lower histidine (r: -0.28, q = 0.02) was correlated with higher mean ACR.

CONCLUSIONS

In conclusion, adolescents with relatively short T1DM duration exhibited lower plasma levels of carboxylic acids that associated with hyperfiltration and hyperperfusion.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03618420 and NCT03584217 A higher resolution version of the Graphical abstract is available as Supplementary information.

Relationship between biomarkers of tubular injury and intrarenal hemodynamic dysfunction in youth with type 1 diabetes

BACKGROUND

Early identification of youth with type 1 diabetes (T1D) at risk for diabetic kidney disease may improve clinical outcomes. We examined the cross-sectional relationship between kidney biomarkers neutrophil gelatinase-associated lipocalin (NGAL), copeptin, interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), chitinase-3-like protein-1 (YKL-40), and monocyte chemoattractant protein-1 (MCP-1) and intrarenal hemodynamic function in adolescents with T1D.

METHODS

Urine albumin-to-creatinine ratio (UACR), renal vascular resistance (RVR), glomerular filtration rate (GFR), intraglomerular pressure (PGLO), efferent arteriole resistance (RE), afferent arteriolar resistance (RA), and renal plasma flow (RPF), and the above indicated biomarkers were assessed in youth aged 12-21 years with and without T1D of < 10 years duration.

RESULTS

Fifty adolescents with T1D (16.1 ± 3.0 years, HbA1c 8.6 ± 1.2%) and 20 adolescents of comparable BMI without T1D (16.1 ± 2.9 years, HbA1c 5.2 ± 0.2%) were enrolled. Adolescents with T1D demonstrated significantly higher GFR, RPF, RE, and PGLO than controls (39%, 33%, 74%, and 29%, respectively, all p < 0.0001). Adolescents with T1D also exhibited significantly lower RVR and RA than controls (25% and 155%, respectively, both p < 0.0001). YKL-40 and KIM-1 concentrations, respectively, were positively associated with GFR (r: 0.43, p = 0.002; r: 0.41, p = 0.003), RPF (r: 0.29, p = 0.08; r: 0.34, p = 0.04), UACR (r: 0.33, p = 0.02; r: 0.50, p = 0.0002), and PGLO (r: 0.45, p = 0.006; r: 0.52, p = 0.001) in adolescents with T1D.

CONCLUSIONS

Higher concentrations of biomarkers YKL-40 and KIM-1 may help define the risk for intraglomerular hemodynamic dysfunction in youth with T1D. A higher resolution version of the Graphical abstract is available as Supplementary information.

Retinal Thickness and Morphology Changes on OCT in Youth with Type 2 Diabetes: Findings from the TODAY Study

Objective

To evaluate changes in retinal thickness and morphology using OCT in youth with type 2 diabetes (T2D) and to identify systemic biomarkers correlating with these changes.

Design

Retrospective subgroup analysis of a prospective study.

Participants

Participants who underwent OCT imaging in the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) trial and its follow-up study TODAY2.

Methods

In 2010-2011 (TODAY) and 2017-2018 (TODAY2), 6 × 6-mm macular volume OCT scans were acquired, segmented, and analyzed to generate total retinal thickness, inner retinal thickness, and outer retinal thickness. The main retinal morphologies graded were intraretinal cystoid spaces, subretinal fluid, and posterior vitreous detachment (PVD).

Main Outcome Measures

Changes in total and individual retinal layer thickness and development of abnormal vitreomacular morphology between TODAY and TODAY2.

Results

Participants had a mean age of 17.9 ± 2.4 years and glycated hemoglobin (HbA1c) of 8.2 ± 2.8% in TODAY and a mean age of 25.0 ± 2.4 years and mean HbA1c of 9.5 ± 2.8% in TODAY2. Longitudinally between assessments, there were overall decreases in outer retinal thickness from 167.2 ± 11.5 microns to 158.4 ± 12.8 microns (P < 0.001) and in photoreceptor thickness from 30.3 ± 2.9 microns to 29.8 ± 4.1 microns (P = 0.04) in the central subfield, while in the inner subfield, we noted a decrease in outer retinal thickness from 150.5 ± 10.1 microns to 144.9 ± 10.5 microns (P < 0.001) and an increase in inner retinal thickness from 136.9 ± 11.5 microns to 137.4 ± 12.6 microns (P = 0.01). Multivariate analysis showed that in the center subfield, HbA1c increases were associated with increases in total retinal thickness (r: 0.67, P = 0.001), whereas fasting glucose was positively correlated with inner retinal thickness (r: 0.02, P = 0.02). In the inner subfield, both systolic (r: -0.22, P < 0.001) and diastolic (r: -0.22, P = 0.003) blood pressures were negatively correlated with total retinal thickness. There was an increase in PVD (18.9%) and cystoid spaces (4.2%).

Conclusions

Youth with T2D develop retinal thickness changes on OCT, including increases in total retinal and inner retinal thickness in the center subfield that correlate with HbA1c and fasting glucose, respectively. Taken together with the increased prevalence of abnormal vitreomacular morphology in this cohort at risk, these findings emphasize the importance of controlling risk factors to prevent the development of sight-threatening retinal complications.

Molecular programs associated with glomerular hyperfiltration in early diabetic kidney disease

Hyperfiltration is a state of high glomerular filtration rate (GFR) observed in early diabetes that damages glomeruli, resulting in an iterative process of increasing filtration load on fewer and fewer remaining functional glomeruli. To delineate underlying cellular mechanisms of damage associated with hyperfiltration, transcriptional profiles of kidney biopsies from Pima Indians with type 2 diabetes with or without early-stage diabetic kidney disease were grouped into two hyperfiltration categories based on annual iothalamate GFR measurements. Twenty-six participants with a peak GFR measurement within two years of biopsy were categorized as the hyperfiltration group, and 26 in whom biopsy preceded peak GFR by over two years were considered pre-hyperfiltration. The hyperfiltration group had higher hemoglobin A1c, higher urine albumin-to-creatinine ratio, increased glomerular basement membrane width and lower podocyte density compared to the pre-hyperfiltration group. A glomerular 1240-gene transcriptional signature identified in the hyperfiltration group was enriched for endothelial stress response signaling genes, including endothelin-1, tec-kinase and transforming growth factor-β1 pathways, with the majority of the transcripts mapped to endothelial and inflammatory cell clusters in kidney single cell transcriptional data. Thus, our analysis reveals molecular pathomechanisms associated with hyperfiltration in early diabetic kidney disease involving putative ligand-receptor pairs with downstream intracellular targets linked to cellular crosstalk between endothelial and mesangial cells.

Renal hemodynamic dysfunction and neuropathy in longstanding type 1 diabetes: Results from the Canadian study of longevity in type 1 diabetes

AIMS

To determine the relationship between renal hemodynamic function and neuropathy in adults with ≥50-years of type 1 diabetes (T1D) compared to nondiabetic controls.

METHODS

Glomerular filtration rate (GFR, inulin), effective renal plasma flow (ERPF, p-aminohippurate), modified Toronto Clinical Neuropathy Score (mTCNS), corneal confocal microscopy, nerve conduction, and heart rate variability (autonomic function) were measured; afferent (RA) and efferent (RE) arteriolar resistances were estimated using the Gomez equations in 74 participants with T1D and in 75 controls. Diabetic kidney disease (DKD) non-resistors were defined by eGFRMDRD < 60 ml/min/1.73 m2 or 24-h urine albumin excretion >30 mg/day. Linear regression was applied to examine the relationships between renal function (dependent variable) and neuropathy measures (independent variable), adjusted for age, sex, HbA1c, systolic blood pressure, low density lipoprotein cholesterol, and 24-h urine albumin to creatinine ratio.

RESULTS

Higher mTCNS associated with lower renal blood flow (β ± SE:-9.29 ± 4.20, p = 0.03) and greater RE (β ± SE:32.97 ± 15.43, p = 0.04) in participants with T1D, but not in controls. DKD non-resistors had a higher mTCNS and worse measures of corneal nerve morphology compared to those without DKD. Renal hemodynamic parameters did not associate with autonomic nerve function.

CONCLUSIONS

Although neurological dysfunction in the presence of diabetes may contribute to impaired renal blood flow resulting in ischemic injury in patients with T1D, early autonomic dysfunction does not appear to be associated with kidney function changes.

Effects of dapagliflozin on volume status and systemic haemodynamics in patients with chronic kidney disease without diabetes: Results from DAPASALT and DIAMOND

AIMS

To assess the effect of sodium-glucose cotransporter-2 inhibitor dapagliflozin on natriuresis, blood pressure (BP) and volume status in patients with chronic kidney disease (CKD) without diabetes.

MATERIALS AND METHODS

We performed a mechanistic open-label study (DAPASALT) to evaluate the effects of dapagliflozin on 24-hour sodium excretion, 24-hour BP, extracellular volume, and markers of volume status during a standardized sodium diet (150 mmol/d) in six patients with CKD. In parallel, in a placebo-controlled double-blind crossover trial (DIAMOND), we determined the effects of 6 weeks of dapagliflozin on markers of volume status in 53 patients with CKD.

RESULTS

In DAPASALT (mean age 65 years, mean estimated glomerular filtration rate [eGFR] 39.4 mL/min/1.73 m² , median urine albumin:creatinine ratio [UACR] 111 mg/g), dapagliflozin did not change 24-hour sodium and volume excretion during 2 weeks of treatment. Dapagliflozin was associated with a modest increase in 24-hour glucose excretion on Day 4, which persisted at Day 14 and reversed to baseline after discontinuation. Mean 24-hour systolic BP decreased by -9.3 (95% confidence interval [CI] -19.1, 0.4) mmHg after 4 days and was sustained at Day 14 and at wash-out. Renin, angiotensin II, urinary aldosterone and copeptin levels increased from baseline. In DIAMOND (mean age 51 years, mean eGFR 59.0 mL/min/1.73 m² , median UACR 608 mg/g), compared to placebo, dapagliflozin increased plasma renin (38.5 [95% CI 7.4, 78.8]%), aldosterone (19.1 [95% CI -5.9, 50.8]%), and copeptin levels (7.3 [95% CI 0.1, 14.5] pmol/L).

CONCLUSIONS

During a standardized sodium diet, dapagliflozin decreased BP but did not increase 24-hour sodium and volume excretion. The lack of increased natriuresis and diuresis may be attributed to activation of intra-renal compensatory mechanisms to prevent excessive water loss.

Aminoaciduria and metabolic dysregulation during diabetic ketoacidosis: Results from the diabetic kidney alarm (DKA) study

OBJECTIVE

We examined changes in the excretion of various amino acids and in glycolysis and ketogenesis-related metabolites, during and after diabetic ketoacidosis (DKA) diagnosis, in youth with known or new onset type 1 diabetes (T1D).

METHODS

Urine samples were collected from 40 youth with DKA (52% boys, mean age 11 ± 4 years, venous pH 7.2 ± 0.1, blood glucose 451 ± 163 mg/dL) at 3 time points: 0-8 h and 12-24 h after starting an insulin infusion, and 3 months after hospital discharge. Mixed-effects models evaluated the changes in amino acids and other metabolites in the urine.

RESULTS

Concentrations of urine histidine, threonine, tryptophan, and leucine per creatinine were highest at 0-8 h (148.8 ± 23.5, 59.5 ± 12.3, 15.4 ± 1.4, and 24.5 ± 2.4% of urine creatinine, respectively), and significantly decreased over 3 months (p = 0.028, p = 0.027, p = 0.019, and p < 0.0001, respectively). Urine histidine, threonine, tryptophan, and leucine per urine creatinine decreased by 10.6 ± 19.2, 0.7 ± 0.9, 1.3 ± 0.9, and 0.5 ± 0.3-fold, respectively, between 0 and 8 h and 3 months.

CONCLUSIONS

In our study, DKA was associated with profound aminoaciduria, suggestive of proximal tubular dysfunction analogous to Fanconi syndrome.

Kidney oxygenation, perfusion and blood flow in people with and without type 1 diabetes

Background

We used magnetic resonance imaging (MRI) to study kidney energetics in persons with and without type 1 diabetes (T1D).

Methods

In a cross-sectional study, 15 persons with T1D and albuminuria and 15 non-diabetic controls (CONs) underwent multiparametric MRI (3 Tesla Philips Scanner) to quantify renal cortical and medullary oxygenation (R₂*, higher values correspond to higher deoxyhaemoglobin concentration), renal perfusion (arterial spin labelling) and renal artery blood flow (phase contrast). Analyses were adjusted for age, sex, systolic blood pressure, plasma haemoglobin, body mass index and estimated glomerular filtration rate (eGFR).

Results

Participants with T1D had a higher median (Q1; Q3) urine albumin creatinine ratio (UACR) than CONs [46 (21; 58) versus 4 (3; 6) mg/g; P < .0001] and a lower mean ± SD eGFR (73 ± 32 mL/min/1.73 m² versus 88 ± 15 mL/min/1.73 m²;  P = .12), although not significantly. Mean medullary R₂* was lower in T1D (34 ± 6/s versus 38 ± 5/s; P < .01) corresponding to a higher oxygenation. R₂* was not different in the cortex. Cortical perfusion was lower in T1D (163 ± 40 versus 224 ± 49 mL/100 g/min; P < .001). Renal artery blood flow was lower in T1D than in CONs (360 ± 130 versus 430 ± 113 mL/min; P = .05). In T1D, lower cortical oxygenation and renal artery blood flow were both associated with higher UACR and lower eGFR (P < .05).

Conclusions

Participants with T1D and albuminuria exhibited higher medullary oxygenation than CONs, despite lower cortical perfusion and renal artery blood flow. This might reflect perturbed kidney energetics leading to a higher setpoint of medullary oxygenation in T1D. Lower cortical oxygenation and renal artery blood flow were associated with higher UACR and lower eGFR in T1D.

MO399: Remodel: A Mechanistic Trial Evaluating the Effects of Semaglutide on the Kidneys In People With Type 2 Diabetes and Chronic Kidney Disease

BACKGROUND AND AIMS

Approximately 40% of people with type 2 diabetes (T2D) develop chronic kidney disease (CKD) and, despite current treatment, T2D is the most common cause of progression to kidney failure. This situation underscores the need for additional pharmacotherapeutic options. Analyses of cardiovascular outcomes trials suggest that glucagon-like peptide-1 receptor agonists (GLP-1RAs), such as semaglutide, lower albuminuria and attenuate estimated glomerular filtration rate (eGFR) decline in people with T2D. Previous analyses suggest that GLP-1RAs reduce hypoxia and inflammation and, thereby, have a mode of action on the kidneys that is distinct from other treatments, such as sodium-glucose cotransporter-2 (SGCT-2) inhibitors and renin–angiotensin–aldosterone system (RAAS) blockers. Furthermore, the primary benefit of semaglutide appears to be in people with an eGFR &lt; 60 mL/min/1.73 m2, a group in which there is a significant residual risk of progression and a consequent unmet need for effective treatment. To gain further insights on the kidney-protective mechanism of action of semaglutide, the REMODEL trial is integrating investigative functional kidney magnetic resonance imaging (MRI) and kidney biopsies; recent developments in these techniques permit elucidation of the mechanisms underlying kidney protection with current therapies. Mechanistic findings of the REMODEL trial will complement those of the ongoing FLOW clinical trial, which is designed to evaluate clinical outcomes in people with T2D and CKD treated with once-weekly (OW) subcutaneous semaglutide.

METHOD

REMODEL (NCT04865770) is a 52-week, multicentre, international clinical trial (Figure 1). Primary endpoints are MRI-based and include change from baseline to week 52 in kidney oxygenation (measured with BOLD MRI R2*), global kidney perfusion (phase-contrast MRI) and kidney inflammation (T1 Mapping MRI). Secondary endpoints evaluated from kidney biopsies in a nested cohort (n ∼ 45) include change from baseline to week 52 in intrarenal mRNA expression, assessed by single-nucleus transcriptomics and glomerular basement membrane width, assessed by morphometry. Other secondary endpoints include the apparent diffusion coefficient (estimating renal fibrosis; evaluated with diffusion-weighted MRI), natriuresis, albumin excretion rate and creatinine clearance. MRI outcomes will also be evaluated at week 4 to identify potential early effects of semaglutide in the kidney. Examples of MRI and kidney biopsy single-cell gene expression profile data from participants with CKD are shown in Figure 2 (data not from REMODEL). Safety will be assessed throughout the trial.

RESULTS

REMODEL was initiated in April 2021 and is being conducted in Canada, France, Italy, Poland, South Africa, Spain and USA.

CONCLUSION

REMODEL will investigate the effect of the GLP-1RA semaglutide on inflammatory and hypoxia-related pathways in the kidney. The combination of MRI and tissue-level interrogation with biopsies will complement standard laboratory findings, enabling the identification of cells and pathways involved in kidney disease and protection. The trial will provide valuable mechanistic insights on the use of OW semaglutide in people with T2D and CKD and may stimulate the development of a precision medicine approach to the management of such individuals. In addition, REMODEL will complement the findings of the FLOW trial.

Coffee Consumption May Mitigate the Risk for Acute Kidney Injury: Results from the Atherosclerosis Risk in Communities (ARIC) Study

Introduction

Coffee is one of the most frequently consumed beverages worldwide and has been found to have a wide assortment of health benefits. Although habitual coffee consumption is associated with a lower incidence of chronic kidney disease, an association between coffee and acute kidney injury (AKI) has not yet been revealed.

Methods

In the Atherosclerosis Risk in Communities (ARIC) Study, a prospective cohort study of 14,207 adults aged 45 to 64 years, coffee consumption (cups/d) was assessed at a single visit via food frequency questionnaires and compared with incident AKI defined by hospitalization with an AKI-related International Classification of Diseases code.

Results

In ARIC, there were 1694 cases of incident AKI in a median of 24 follow-up years. Higher coffee consumption was associated with lower AKI risk versus no consumption (hazard ratio [HR] <1 cup/d: 0.92 [95% CI: 0.79–1.08]; 1 cup/d: 1.08 [95% CI: 0.94–1.24]; 2 to 3 cups/d: 0.83 [95% CI: 0.72–0.95]; >3 cups/d: 0.83 [95% CI: 0.71–0.96]; reference: never, P = 0.003). Trends for AKI risk across coffee categories remained significant after multivariable adjustment for age, sex, race-center, education, total daily energy intake, physical activity, smoking, alcohol intake, diet quality (Dietary Approaches to Stop Hypertension [DASH] score), systolic blood pressure (BP), diabetes status, use of antihypertensive agents, estimated glomerular filtration rate (eGFR), and body mass index (BMI) (P = 0.02).

Conclusion

Higher coffee intake was associated with a lower risk of incident AKI and could present an opportunity for cardiorenal protection through diet. Further evaluation of the physiological mechanisms underlying the cardiorenal protective effects of coffee consumption is necessary.

Minimal Change Disease Is Associated With Endothelial Glycocalyx Degradation and Endothelial Activation

Introduction

Minimal change disease (MCD) is considered a podocyte disorder triggered by unknown circulating factors. Here, we hypothesized that the endothelial cell (EC) is also involved in MCD.

Methods

We studied 45 children with idiopathic nephrotic syndrome (44 had steroid sensitive nephrotic syndrome [SSNS], and 12 had biopsy-proven MCD), 21 adults with MCD, and 38 healthy controls (30 children, 8 adults). In circulation, we measured products of endothelial glycocalyx (EG) degradation (syndecan-1, heparan sulfate [HS] fragments), HS proteoglycan cleaving enzymes (matrix metalloprotease-2 [MMP-2], heparanase activity), and markers of endothelial activation (von Willebrand factor [vWF], thrombomodulin) by enzyme-linked immunosorbent assay (ELISA) and mass spectrometry. In human kidney tissue, we assessed glomerular EC (GEnC) activation by immunofluorescence of caveolin-1 (n = 11 MCD, n = 5 controls). In vitro, we cultured immortalized human GEnC with sera from control subjects and patients with MCD/SSNS sera in relapse (n = 5 per group) and performed Western blotting of thrombomodulin of cell lysates as surrogate marker of endothelial activation.

Results

In circulation, median concentrations of all endothelial markers were higher in patients with active disease compared with controls and remained high in some patients during remission. In the MCD glomerulus, caveolin-1 expression was higher, in an endothelial-specific pattern, compared with controls. In cultured human GEnC, sera from children with MCD/SSNS in relapse increased thrombomodulin expression compared with control sera.

Conclusion

Our data show that alterations involving the systemic and glomerular endothelium are nearly universal in patients with MCD and SSNS, and that GEnC can be directly activated by circulating factors present in the MCD/SSNS sera during relapse.

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

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

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 (β: -0.382, p < 0.001) and ERPF (β: -0.475, p < 0.001), and positively to FF (β:0.369, p < 0.001). Associations between SVR, ERPF and FF persisted after multivariable adjustments.. PP was negatively related to ERPF (β: -0.252, p = 0.008), and positively to FF (β: 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.

Structural Lesions on Kidney Biopsy in Youth-Onset and Adult-Onset Type 2 Diabetes

OBJECTIVE

Type 2 diabetes (T2D) is a leading cause of end-stage kidney disease worldwide. Recent studies suggest a more aggressive clinical course of diabetic kidney disease in youth-onset compared with adult-onset T2D. We compared kidney structural lesions in youth- and adult-onset T2D to determine if youth onset was associated with greater early tissue injury.

RESEARCH DESIGN AND METHODS

Quantitative microscopy was performed on kidney tissue obtained from research kidney biopsies in 161 Pima Indians (117 women, 44 men) with T2D. Onset of T2D was established by serial oral glucose tolerance testing, and participants were stratified as youth onset (age <25 years) or adult onset (age ≥25 years). Associations between clinical and morphometric parameters and age at onset were tested using linear models.

RESULTS

At biopsy, the 52 participants with youth-onset T2D were younger than the 109 with adult-onset T2D (39.1 ± 9.9 vs. 51.4 ± 10.2 years; P < 0.0001), but their diabetes duration was similar (19.3 ± 8.1 vs. 17.0 ± 7.8 years; P = 0.09). Median urine albumin-to-creatinine ratio was higher in the youth-onset group (58 [25th-75th percentile 17-470] vs. 27 [13-73] mg/g; P = 0.02). Youth-onset participants had greater glomerular basement membrane (GBM) width (552 ± 128 vs. 490 ± 114 nm; P = 0.002) and mesangial fractional volume (0.31 ± 0.10 vs. 0.27 ± 0.08; P = 0.001) than adult-onset participants. Glomerular sclerosis percentage, glomerular volume, mesangial fractional volume, and GBM width were also inversely associated with age at diabetes onset as a continuous variable.

CONCLUSIONS

Younger age at T2D onset strongly associates with more severe kidney structural lesions. Studies are underway to elucidate the pathways underlying these associations.

Early microvascular complications in type 1 and type 2 diabetes: recent developments and updates

The prevalence of youth-onset diabetes is progressing rapidly worldwide, and poor glycemic control, in combination with prolonged diabetes duration and comorbidities including hypertension, has led to the early development of microvascular complications including diabetic kidney disease, retinopathy, and neuropathy. Pediatric populations with type 1 (T1D) and type 2 (T2D) diabetes are classically underdiagnosed with microvascular complications, and this leads to both undertreatment and insufficient attention to the mitigation of risk factors that could help attenuate further progression of complications and decrease the likelihood for long-term morbidity and mortality. This narrative review aims to present a comprehensive summary of the epidemiology, risk factors, symptoms, screening practices, and treatment options, including future opportunities for treatment advancement, for microvascular complications in youth with T1D and T2D. We seek to uniquely focus on the inherent challenges of managing pediatric populations with diabetes and discuss the similarities and differences between microvascular complications in T1D and T2D, while presenting a strong emphasis on the importance of early identification of at-risk youth. Further investigation of possible treatment mechanisms for microvascular complications in youth with T1D and T2D through dedicated pediatric outcome trials is necessary to target the brief window where early pathological vascular changes may be significantly attenuated.

Tubular injury in diabetic ketoacidosis: Results from the diabetic kidney alarm study

OBJECTIVE

Glomerular injury is a recognized complication of diabetic ketoacidosis (DKA), yet the tubular lesions are poorly understood. The aim of this prospective study was to evaluate the presence and reversibility of tubular injury during DKA in children with type 1 diabetes (T1D).

RESEARCH DESIGN AND METHODS

Blood and urine samples were collected from 40 children with DKA (52% boys, mean age 11 ± 4 years, venous pH 7.2 ± 0.1, glucose 451 ± 163 mg/dL) at three timepoints: 0-8 and 12-24 h after starting insulin, and 3 months after discharge. Mixed-effects models evaluated the changes in tubular injury markers over time (neutrophil gelatinase-associated lipocalin [NGAL], kidney injury molecule 1 [KIM-1], and interleukin 18 [IL-18]). We also evaluated the relationships among the tubular injury biomarkers, copeptin, a vasopressin surrogate, and serum uric acid (SUA).

RESULTS

Serum NGAL, KIM-1, and IL-18 were highest at 0-8 h (306.5 ± 45.9 ng/mL, 128.9 ± 10.1 pg/mL, and 564.3 ± 39.2 pg/mL, respectively) and significantly decreased over 3 months (p = 0.03, p = 0.01, and p < 0.001, respectively). There were strong relationships among increases in copeptin and SUA and rises in tubular injury biomarkers. At 0-8 h, participants with acute kidney injury (AKI) [17%] showed significantly higher concentrations of tubular injury markers, copeptin, and SUA.

CONCLUSIONS

DKA was characterized by tubular injury, and the degree of injury associated with elevated copeptin and SUA. Tubular injury biomarkers, copeptin and SUA may be able to predict AKI in DKA.