Insufficient nitric oxide (NO) bioavailability plays an important role in endothelial dysfunction and arterial stiffening with aging. Supplementation with sodium nitrite, a precursor of NO, ameliorates age-related vascular endothelial dysfunction and arterial stiffness in mice, but effects on humans, including the metabolic pathways altered, are unknown. The purpose of this study was to determine the safety, feasibility, and efficacy of oral sodium nitrite supplementation for improving vascular function in middle-aged and older adults and to identify related circulating metabolites. Ten weeks of sodium nitrite (80 or 160 mg/day, capsules, TheraVasc; randomized, placebo control, double blind) increased plasma nitrite acutely (5- to 15-fold, P < 0.001 vs. placebo) and chronically ( P < 0.10) and was well tolerated without symptomatic hypotension or clinically relevant elevations in blood methemoglobin. Endothelial function, measured by brachial artery flow-mediated dilation, increased 45-60% vs. baseline ( P < 0.10) without changes in body mass or blood lipids. Measures of carotid artery elasticity (ultrasound and applanation tonometry) improved (decreased β-stiffness index, increased cross-sectional compliance, P < 0.05) without changes in brachial or carotid artery blood pressure. Aortic pulse wave velocity was unchanged. Nitrite-induced changes in vascular measures were significantly related to 11 plasma metabolites identified by untargeted analysis. Baseline abundance of multiple metabolites, including glycerophospholipids and fatty acyls, predicted vascular changes with nitrite. This study provides evidence that sodium nitrite supplementation is well tolerated, increases plasma nitrite concentrations, improves endothelial function, and lessens carotid artery stiffening in middle-aged and older adults, perhaps by altering multiple metabolic pathways, thereby warranting a larger clinical trial.
On the basis of earlier observations, we evaluated the association between overweight and obesity and rapid progression of autosomal dominant polycystic kidney disease in participants in the Tolvaptan Efficacy and Safety in Management of Autosomal Dominant Polycystic Kidney Disease and Its Outcomes (TEMPO) 3:4 trial. More importantly, we also determined whether efficacy of tolvaptan was attenuated in individuals with baseline overweight or obesity.
ABSTRACT Innate and adaptive immune cells modulate Autosomal Dominant Polycystic Kidney Disease (ADPKD) severity, a common kidney disease with inadequate treatment options. ADPKD shares parallels with cancer where immune checkpoint inhibitors have been shown to reactivate CD8 + T cells and slow tumor growth. We have shown that, in PKD, CD8 + T cell loss worsens disease. This study used orthologous early-onset and adult-onset ADPKD models ( Pkd1 p.R3277C) to evaluate the role of immune checkpoints in PKD. Flow cytometry of kidney cells showed increased levels of PD-1 on CD8 + T cells and PD-L1 on macrophages and epithelial cells in Pkd1 RC/RC mice versus wildtypes, paralleling disease severity. PD-L1 was also upregulated in ADPKD human cells and patient kidney tissue versus controls. Genetic PD-L1 loss or treatment with an anti-PD-1 antibody did not impact PKD severity in early-onset or adult-onset ADPKD models. However, treatment with anti-PD-1 plus anti-CTLA-4, blocking two immune checkpoints, improved PKD outcomes in adult-onset ADPKD mice; neither monotherapy altered PKD. Combination therapy resulted in increased kidney CD8 + T cell numbers/activation and decreased kidney regulatory T cell numbers. Together, our data suggests that immune checkpoint activation is an important feature of and potential novel therapeutic target in ADPKD.
Background: Long-term clinical outcomes in children with very-early onset (VEO; diagnosis in utero or within the first 18 months of life) autosomal dominant polycystic kidney disease (ADPKD) are currently not well understood. We conducted a longitudinal retrospective cohort study to assess the association between VEO status and adverse clinical outcomes. Methods: Seventy patients with VEO-ADPKD matched (by year of birth, sex and race/ethnicity) to 70 patients with non-VEO-ADPKD who participated in research at the University of Colorado were studied. Kaplan-Meier survival analysis was performed. The predictor was VEO status, and outcomes were progression to end-stage renal disease (ESRD), development of hypertension, progression to estimated glomerular filtration rate (eGFR <90 ml/min/1.73 m2), glomerular hyperfiltration (eGFR ≥140 ml/min/1.73 m2) and height-adjusted total kidney volume (htTKV) measured by MRI ≥600 ml/m. Results: Median follow-up was until 16.0 years of age. There were only 4 ESRD events during the follow-up period, all in the VEO group (p < 0.05). VEO patients were more likely to develop hypertension (hazard ratio, HR 3.15, 95% CI 1.86-5.34; p < 0.0001) and to progress to eGFR <90 ml/min/1.73 m2 (HR 1.97, 95% CI 1.01-3.84; p < 0.05) than non-VEO patients. There was no difference between groups in the development of glomerular hyperfiltration (HR 0.89, 95% CI 0.56-1.42; p = 0.62). There were only 7 patients who progressed to htTKV ≥600 ml/m, 4 in the VEO group and 3 in the non-VEO group (p < 0.01). Conclusions: Several clinical outcomes are worse in patients with VEO-ADPKD compared to non-VEO ADPKD. Children with VEO-ADPKD represent a particularly high-risk group of ADPKD patients.
Serum concentrations of fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH) are elevated in patients with CKD, and higher concentrations are well established as risk factors for cardiovascular disease and death (1). In the Systolic Blood Pressure Intervention Trial (SPRINT), intensive systolic BP lowering led to lower rates of cardiovascular events and mortality despite a more rapid decline in eGFR (2). Given that FGF23 and PTH would be expected to increase in the setting of declining eGFR, the effects of intensive systolic BP control on these key potential intermediates are of considerable interest. The SPRINT, described in detail elsewhere (2,3), was a randomized, controlled trial among nondiabetic persons with hypertension evaluating the effects of intensive systolic BP lowering (<120 mm Hg) versus standard systolic BP target (<140 mm Hg). Of the 9361 participants enrolled in the SPRINT, 1000 participants with an eGFR<60 ml/min per 1.73 m2 were randomly chosen to have repeated serum measurements of intact FGF23 (Kainos), intact PTH, calcium, phosphate, and urine creatinine and phosphate (4). Using these data, we calculated fractional excretion of phosphate (FePhos) and fractional excretion of calcium. We evaluated the changes in each parameter from baseline to year 1 stratified by intervention status. We used linear mixed models to evaluate the effect of randomization to the intensive BP lowering arm on longitudinal changes in serum FGF23, PTH, calcium, phosphate, FePhos, and fractional excretion of calcium. Of the 1000 participants with CKD randomly sampled for this study, 987 had specimens available at year 1. Baseline characteristics stratified by intervention arm are reported elsewhere (5). The mean age was 72±9 years old, 42% were women, and the mean eGFR was 46±10 ml/min per 1.73 m2. Baseline intact FGF23 concentrations were 65 and 66 pg/ml in the standard and intensive arms, respectively. The mean eGFR changes were +1.58 and −2.12 ml/min per 1.73 m2 in the standard and intensive arms, respectively. Compared with participants in the standard arm, participants in the intensive arm experienced an 11.5% (95% confidence interval, 6.0 to 17.0) increase in FGF23 over the year (Table 1). This relative difference in FGF23 was unchanged by adjustment for concurrent changes in eGFR and albuminuria. There were no relative differences in serum PTH, calcium, or phosphate across treatment arms. In parallel with the increase in FGF23 in the intensive arm, FePhos rose by 4.2% in the intensive arm relative to the standard arm, although this association was not statistically significant (P=0.15). Table 1. - Effect of intensive BP therapy on markers of mineral metabolism Outcome Intensive Arm, a % Change/yr (95% CI) Standard Arm, % Change/yr (95% CI) Difference between Arms, b % Change/yr (95% CI) P Value ΔIntact FGF23 −0.6 (−4.4 to 3.2) −12.1 (−16.1 to −8.0) 11.5 (6.0 to 17.0) 0.01 ΔIntact PTH −4.6 (−7.7 to −1.4) −3.0 (−6.1 to 0.1) −1.6 (−6.1 to 2.9) 0.33 ΔPhosphate 1.19 (0.08 to 2.31) −0.06 (−1.24 to 1.13) 1.25 (−0.38 to 2.88) 0.13 ΔCalcium 0.26 (−0.23 to 0.74) 0.13 (−0.39 to 0.65) 0.13 (−0.59 to 0.84) 0.73 ΔFractional excretion of phosphate 2.69 (−1.17 to 6.56) −1.49 (−5.56 to 2.60) 4.18 (−1.45 to 9.80) 0.15 ΔFractional excretion of calcium −13.46 (−21.17 to −5.78) −7.83 (−15.89 to 0.32) −5.63 (−16.85 to 5.56) 0.33 95% CI, 95% confidence interval; FGF23, fibroblast growth factor 23; PTH, parathyroid hormone.aValues adjusted for baseline concentrations.bStandard arm serves as reference. In this analysis of randomized, controlled trial participants with hypertension and CKD, we demonstrate that randomization to the intensive BP arm resulted in a relative increase in FGF23 over 1 year and was accompanied with a nonsignificant increase in FePhos. Moreover, the change in FGF23 did not seem to be explained by the observed concurrent decrease in eGFR. The clinical implications of these findings are uncertain. Although longitudinal increases in FGF23 levels have been associated with greater cardiovascular risk in patients with CKD (6), the intensive arm of the SPRINT experienced lower cardiovascular events and mortality risk despite the concurrent rise in FGF23 (2). Thus, mechanisms leading from intensive BP lowering to cardiovascular protection are likely via pathways distinct from FGF23. A priori, we hypothesized that reductions in eGFR due to intensive BP lowering would lead to increases in FGF23 and PTH. However, we found that the increases in FGF23 persisted despite accounting for concurrent changes in eGFR, and PTH did not change. These findings suggest that mechanisms beyond changes in eGFR may be driving increases in FGF23. Responsible mechanisms and the examination of other markers of mineral metabolism (e.g., Klotho) require additional investigation. The observed rise in FePhos in the intensive arm suggests that the changes in FGF23 may be biologically meaningful. This study has important limitations. Implicit in the evaluation of 1-year changes in FGF23, participants had to survive to year 1, and some participants had cardiovascular events prior to the year 1 measurement. It would be optimal to examine the association of changes in FGF23 with subsequent cardiovascular risk. However, this inherent survival bias to year 1, the small sample size with repeated measurement, and the short-term follow-up after year 1 in the SPRINT preclude us from evaluating the clinical consequences of these increases in FGF23. We previously found that baseline FGF23 concentrations in the SPRINT had no independent associations with cardiovascular events or mortality after adjustment for eGFR (4). In addition, among SPRINT participants with CKD, randomization to the intensive arm was associated with a statistically significant reduction in mortality risk (2). Thus, although a longitudinal rise in FGF23 is of high interest and warrants future study, we do not believe that these findings should dissuade clinicians from pursuing aggressive systolic BP lowering in their patients with CKD. In conclusion, among SPRINT participants with CKD, those randomized to the intensive BP arm experienced a 12% relative increase in serum FGF23 over 1 year compared with participants in the standard arm. Further investigation is needed to understand the clinical consequences of changes in FGF23 that occur during intensive BP lowering. Disclosures Dr. Chonchol reports grants from Otsuka, grants from Sanofi, and grants from Kadmon outside the submitted work. Dr. Shlipak is a scientific advisor for TAI Diagnostics. All remaining authors have nothing to disclose. Funding This work was supported by the National Institutes of Health (NIH) and the National Research Service Award through the National Institutes of Diabetes and Digestive and Kidney Diseases (NIDDK) grants RO1DK098234 and K24DK110427 to J.H.I. and T32DK104717, F32DK116476, and K23DK118197 to C.G., the NIH Loan Repayment Program to C.G., and the American Heart Association grant 14EIA18560026 to J.H.I.. SPRINT is funded with federal funds from the NIH, including the National Heart, Lung, and Blood Institute, the NIDDK, the National Institute on Aging, and the National Institute of Neurological Disorders and Stroke contracts HHSN268200900040C, HHSN268200900046C, HHSN268200900047C, HHSN268200900048C, and HHSN268200900049C, and interagency agreement A-HL-13-002- 001. It was also supported in part with resources and use of facilities through the Department of Veterans Affairs. We also acknowledge the support from the following Clinical and Translation Science Awards funded by National Center for Advancing Translational Sciences, Case Western Reserve University, UL1TR000439; Ohio State University, UL1RR025755; University of Pennsylvania, UL1RR024134 and UL1TR000003; Boston University, UL1RR025771; Stanford University, UL1TR000093; Tufts University, UL1RR025752, UL1TR000073, and UL1TR001064; University of Illinois, UL1TR000050; University of Pittsburgh, UL1TR000005; University of Texas, Southwestern, 9U54TR000017-06; University of Utah, UL1TR000105-05; Vanderbilt University, UL1 TR000445; George Washington University, UL1TR000075; University of CA, Davis, UL1 TR000002; University of Florida, UL1 TR000064; University of Michigan, UL1TR000433; Tulane University, P30GM103337 Centers of Biomedical Research Excellence Award National Institute of General Medical Sciences; and Wake Forest University, UL1TR001420.
