Publications by authors named "Samir M Parikh"

86 Publications

Role of endothelial microRNA 155 on capillary leakage in systemic inflammation.

Crit Care 2021 02 22;25(1):76. Epub 2021 Feb 22.

Division of Nephrology and Hypertension, Hannover Medical School, Hannover, Germany.

Background: Capillary leakage is a key contributor to the pathological host response to infections. The underlying mechanisms remain incompletely understood, and the role of microRNAs (MIR) has not been investigated in detail. We hypothesized that specific MIRs might be regulated directly in the endothelium thereby contributing to vascular leakage.

Methods: SmallRNA sequencing of endotoxemic murine pulmonary endothelial cells (ECs) was done to detect regulated vascular MIRs. In vivo models: transgenic zebrafish (flk1:mCherry/l-fabp:eGFP-DPB), knockout/wildtype mouse (B6.Cg-Mir155tm1.1Rsky/J); disease models: LPS 17.5 mg/kgBW and cecal ligation and puncture (CLP); in vitro models: stimulated human umbilical vein EC (HUVECs), transendothelial electrical resistance.

Results: Endothelial MIR155 was identified as a promising candidate in endotoxemic murine pulmonary ECs (25 × upregulation). Experimental overexpression in a transgenic zebrafish line and in HUVECs was sufficient to induce spontaneous vascular leakage. To the contrary, genetic MIR155 reduction protects against permeability both in vitro and in endotoxemia in vivo in MIR155 heterozygote knockout mice thereby improving survival by 40%. A tight junction protein, Claudin-1, was down-regulated both in endotoxemia and by experimental MIR155 overexpression. Translationally, MIR155 was detectable at high levels in bronchoalveolar fluid of patients with ARDS compared to healthy human subjects.

Conclusions: We found that MIR155 is upregulated in the endothelium in mouse and men as part of a systemic inflammatory response and might contribute to the pathophysiology of vascular leakage in a Claudin-1-dependent manner. Future studies have to clarify whether MIR155 could be a potential therapeutic target.
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http://dx.doi.org/10.1186/s13054-021-03500-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7901081PMC
February 2021

Targeting energy pathways in kidney disease: the roles of sirtuins, AMPK, and PGC1α.

Kidney Int 2020 Dec 8. Epub 2020 Dec 8.

Harvard Medical School, Boston, Massachusetts, USA; Division of Nephrology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA. Electronic address:

The kidney has extraordinary metabolic demands to sustain the active transport of solutes that is critical to renal filtration and clearance. Mitochondrial health is vital to meet those demands and maintain renal fitness. Decades of studies have linked poor mitochondrial health to kidney disease. Key regulators of mitochondrial health-adenosine monophosphate kinase, sirtuins, and peroxisome proliferator-activated receptor γ coactivator-1α-have all been shown to play significant roles in renal resilience against disease. This review will summarize the latest research into the activities of those regulators and evaluate the roles and therapeutic potential of targeting those regulators in acute kidney injury, glomerular kidney disease, and renal fibrosis.
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http://dx.doi.org/10.1016/j.kint.2020.09.037DOI Listing
December 2020

Endothelial Biomarkers Are Associated With Indirect Lung Injury in Sepsis-Associated Pediatric Acute Respiratory Distress Syndrome.

Crit Care Explor 2020 Dec 4;2(12):e0295. Epub 2020 Dec 4.

Pediatric Sepsis Program, Children's Hospital of Philadelphia, Philadelphia, PA.

Objectives: Acute respiratory distress syndrome occurring in the setting of direct versus indirect lung injury may reflect different pathobiologies amenable to different treatment strategies. We sought to test whether a panel of plasma biomarkers differed between children with sepsis-associated direct versus indirect acute respiratory distress syndrome. We hypothesized that a biomarker profile indicative of endothelial activation would be associated with indirect acute respiratory distress syndrome.

Design: Observational cohort.

Setting: Academic PICU.

Subjects: Patients less than 18 years old with sepsis-associated direct (pneumonia, = 52) or indirect (extrapulmonary sepsis, = 46) acute respiratory distress syndrome.

Interventions: None.

Measurements And Main Results: Of 58 biomarkers examined, 33 differed by acute respiratory distress syndrome subtype. We used classification and regression tree methodology to examine associations between clinical and biochemical markers and acute respiratory distress syndrome subtype. The classification and regression tree model using only clinical variables (age, sex, race, oncologic comorbidity, and Pediatric Risk of Mortality-III score) performed worse than the classification and regression tree model using five clinical variables and 58 biomarkers. The best classification and regression tree model used only four endothelial biomarkers, including elevated angiopoietin-2/angiopoietin-1 ratio, vascular cell-adhesion molecule, and von Willebrand factor, to identify indirect acute respiratory distress syndrome. Test characteristics were 89% (80-97%) sensitivity, 80% (69-92%) specificity, positive predictive value 84% (74-93%), and negative predictive value 86% (76-96%).

Conclusions: Indirect lung injury in children with acute respiratory distress syndrome is characterized by a biomarker profile indicative of endothelial activation, excess inflammation, and worse outcomes. A model using four biomarkers has the potential to be useful for more precisely identifying patients with acute respiratory distress syndrome whose pathobiology may respond to endothelial-targeted therapies in future trials.
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http://dx.doi.org/10.1097/CCE.0000000000000295DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7721219PMC
December 2020

Author Correction: A natural mouse model reveals genetic determinants of systemic capillary leak syndrome (Clarkson disease).

Commun Biol 2019 Nov 25;2(1):439. Epub 2019 Nov 25.

Lung and Vascular Inflammation Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, 20892, USA.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s42003-019-0691-0DOI Listing
November 2019

Nicotinamide riboside with pterostilbene (NRPT) increases NAD in patients with acute kidney injury (AKI): a randomized, double-blind, placebo-controlled, stepwise safety study of escalating doses of NRPT in patients with AKI.

BMC Nephrol 2020 08 13;21(1):342. Epub 2020 Aug 13.

Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.

Background: Preclinical studies have identified both NAD and sirtuin augmentation as potential strategies for the prevention and treatment of AKI. Nicotinamide riboside (NR) is a NAD precursor vitamin and pterostilbene (PT) is potent sirtuin activator found in blueberries. Here, we tested the effect of combined NR and PT (NRPT) on whole blood NAD levels and safety parameters in patients with AKI.

Methods: We conducted a randomized, double-blind, placebo-controlled study of escalating doses of NRPT in 24 hospitalized patients with AKI. The study was comprised of four Steps during which NRPT (5 subjects) or placebo (1 subject) was given twice a day for 2 days. NRPT dosing was increased in each Step: Step 1250/50 mg, Step 2500/100 mg, Step 3750/150 mg and Step 41,000/200 mg. Blood NAD levels were measured by liquid chromatography-mass spectrometry and safety was assessed by history, physical exam, and clinical laboratory testing.

Results: AKI resulted in a 50% reduction in whole blood NAD levels at 48 h compared to 0 h in patients receiving placebo (p = 0.05). There was a trend for increase in NAD levels in all NRPT Steps individually at 48 h compared to 0 h, but only the change in Step 2 reached statistical significance (47%, p = 0.04), and there was considerable interindividual variability in the NAD response to treatment. Considering all Steps together, NRPT treatment increased NAD levels by 37% at 48 h compared to 0 h (p = 0.002). All safety laboratory tests were unchanged by NRPT treatment, including creatinine, estimated glomerular filtration rate (eGFR), electrolytes, liver function tests, and blood counts. Three of 20 patients receiving NRPT reported minor gastrointestinal side effects.

Conclusion: NRPT increases whole blood NAD levels in hospitalized patients with AKI. In addition, NRPT up to a dose of 1000 mg/200 mg twice a day for 2 days is safe and well tolerated in these patients. Further studies to assess the potential therapeutic benefit of NRPT in AKI are warranted.

Trial Registration: NCT03176628 , date of registration June 5th, 2017.
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http://dx.doi.org/10.1186/s12882-020-02006-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7427083PMC
August 2020

Mitochondrial transplantation by intra-arterial injection for acute kidney injury.

Am J Physiol Renal Physiol 2020 09 20;319(3):F403-F413. Epub 2020 Jul 20.

Department of Cardiac Surgery, Boston Children's Hospital, Department of Surgery, Harvard Medical School, Boston, Massachusetts.

Acute kidney injury is a common clinical disorder and one of the major causes of morbidity and mortality in the postoperative period. In this study, the safety and efficacy of autologous mitochondrial transplantation by intra-arterial injection for renal protection in a swine model of bilateral renal ischemia-reperfusion injury were investigated. Female Yorkshire pigs underwent percutaneous bilateral temporary occlusion of the renal arteries with balloon catheters. Following 60 min of ischemia, the balloon catheters were deflated and animals received either autologous mitochondria suspended in vehicle or vehicle alone, delivered as a single bolus to the renal arteries. The injected mitochondria were rapidly taken up by the kidney and were distributed throughout the tubular epithelium of the cortex and medulla. There were no safety-related issues detected with mitochondrial transplantation. Following 24 h of reperfusion, estimated glomerular filtration rate and urine output were significantly increased while serum creatinine and blood urea nitrogen were significantly decreased in swine that received mitochondria compared with those that received vehicle. Gross anatomy, histopathological analysis, acute tubular necrosis scoring, and transmission electron microscopy showed that the renal cortex of the vehicle-treated group had extensive coagulative necrosis of primarily proximal tubules, while the mitochondrial transplanted kidney showed only patchy mild acute tubular injury. Renal cortex IL-6 expression was significantly increased in vehicle-treated kidneys compared with the kidneys that received mitochondrial transplantation. These results demonstrate that mitochondrial transplantation by intra-arterial injection provides renal protection from ischemia-reperfusion injury, significantly enhancing renal function and reducing renal damage.
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http://dx.doi.org/10.1152/ajprenal.00255.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7509287PMC
September 2020

Mitochondrial Metabolism in Acute Kidney Injury.

Semin Nephrol 2020 03;40(2):101-113

Division of Nephrology, Center for Vascular Biology Research, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA. Electronic address:

The kidney is a highly metabolic organ that requires substantial adenosine triphosphate for the active transport required to maintain water and solute reabsorption. Aberrations in energy availability and energy utilization can lead to cellular dysfunction and death. Mitochondria are essential for efficient energy production. The pathogenesis of acute kidney injury is complex and varies with different types of injury. However, multiple distinct acute kidney injury syndromes share a common dysregulation of energy metabolism. Pathways of energy metabolism and mitochondrial dysfunction are emerging as critical drivers of acute kidney injury and represent new potential targets for treatment. This review shows the basic metabolic pathways that all cells depend on for life; describes how the kidney optimizes those pathways to meet its anatomic, physiologic, and metabolic needs; summarizes the importance of metabolic and mitochondrial dysfunction in acute kidney injury; and analyzes the mitochondrial processes that become dysregulated in acute kidney injury including mitochondrial dynamics, mitophagy, mitochondrial biogenesis, and changes in mitochondrial energy metabolism.
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http://dx.doi.org/10.1016/j.semnephrol.2020.01.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7282287PMC
March 2020

The Angiopoietin-Tie2 Pathway in Critical Illness.

Crit Care Clin 2020 Apr 31;36(2):201-216. Epub 2020 Jan 31.

Department of Medicine, Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, RN330C, Boston, MA 02215, USA. Electronic address:

Lethal features of sepsis and acute respiratory distress syndrome (ARDS) relate to the health of small blood vessels. For example, alveolar infiltration with proteinaceous fluid is often driven by breach of the microvascular barrier. Spontaneous thrombus formation within inflamed microvessels exacerbates organ ischemia, and in its final stages, erupts into overt disseminated intravascular coagulation. Disruption of an endothelial signaling axis, the Angiopoietin-Tie2 pathway, may mediate the abrupt transition from microvascular integrity to pathologic disruption. This review summarizes preclinical and clinical results that implicate the Tie2 pathway as a promising target to restore microvascular health in sepsis and ARDS.
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http://dx.doi.org/10.1016/j.ccc.2019.12.003DOI Listing
April 2020

Acute Kidney Injury and Electrolyte Abnormalities After Chimeric Antigen Receptor T-Cell (CAR-T) Therapy for Diffuse Large B-Cell Lymphoma.

Am J Kidney Dis 2020 07 20;76(1):63-71. Epub 2020 Jan 20.

Renal Division, Department of Internal Medicine, Massachusetts General Hospital, Boston, MA. Electronic address:

Rationale & Objective: Cytokine release syndrome is a well-known complication of chimeric antigen receptor T-cell (CAR-T) therapy and can lead to multiorgan dysfunction. However, the nephrotoxicity of CAR-T therapy is unknown. We aimed to characterize the occurrence, cause, and outcomes of acute kidney injury (AKI), along with the occurrence of electrolyte abnormalities, among adults with diffuse large B-cell lymphoma receiving CAR-T therapy.

Study Design: Case series.

Setting & Participants: We reviewed the course of 78 adults receiving CAR-T therapy with axicabtagene ciloleucel or tisagenlecleucel at 2 major cancer centers between October 2017 and February 2019. Baseline demographics, comorbid conditions, medications, and laboratory values were obtained from electronic health records. AKI was defined using KDIGO (Kidney Disease: Improving Global Outcomes) criteria. The cause, clinical course, and outcome of AKI events and electrolyte abnormalities in the first 30 days after CAR-T infusion were characterized using data contained in electronic health records.

Results: Among 78 patients receiving CAR-T therapy, cytokine release syndrome occurred in 85%, of whom 62% were treated with tocilizumab. AKI occurred in 15 patients (19%): 8 had decreased kidney perfusion, 6 developed acute tubular necrosis, and 1 patient had urinary obstruction related to disease progression. Those with acute tubular necrosis and obstruction had the longest lengths of stay and highest 60-day mortality. Electrolyte abnormalities were common; hypophosphatemia, hypokalemia, and hyponatremia occurred in 75%, 56%, and 51% of patients, respectively.

Limitations: Small sample size; AKI adjudicated by retrospective chart review; lack of biopsy data.

Conclusions: In this case series of patients with diffuse large B-cell lymphoma receiving CAR-T therapy, AKI and electrolyte abnormalities occurred commonly in the context of cytokine release syndrome.
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http://dx.doi.org/10.1053/j.ajkd.2019.10.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7311244PMC
July 2020

Erratum: Author Correction: A natural mouse model reveals genetic determinants of systemic capillary leak syndrome (Clarkson disease).

Commun Biol 2019;2:439. Epub 2019 Nov 25.

2Lung and Vascular Inflammation Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892 USA.

[This corrects the article DOI: 10.1038/s42003-019-0647-4.].
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http://dx.doi.org/10.1038/s42003-019-0691-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6877516PMC
November 2019

A natural mouse model reveals genetic determinants of systemic capillary leak syndrome (Clarkson disease).

Commun Biol 2019 31;2:398. Epub 2019 Oct 31.

Lung and Vascular Inflammation Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892 USA.

The systemic capillary leak syndrome (SCLS, Clarkson disease) is a disorder of unknown etiology characterized by recurrent episodes of vascular leakage of proteins and fluids into peripheral tissues, resulting in whole-body edema and hypotensive shock. The pathologic mechanisms and genetic basis for SCLS remain elusive. Here we identify an inbred mouse strain, SJL, which recapitulates cardinal features of SCLS, including susceptibility to histamine- and infection-triggered vascular leak. We named this trait "Histamine hypersensitivity" (Hhs/) and mapped it to Chromosome 6. is syntenic to the genomic locus most strongly associated with SCLS in humans (3p25.3), revealing that the predisposition to develop vascular hyperpermeability has a strong genetic component conserved between humans and mice and providing a naturally occurring animal model for SCLS. Genetic analysis of may reveal orthologous candidate genes that contribute not only to SCLS, but also to normal and dysregulated mechanisms underlying vascular barrier function more generally.
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http://dx.doi.org/10.1038/s42003-019-0647-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6823437PMC
April 2020

NAD homeostasis in renal health and disease.

Nat Rev Nephrol 2020 02 31;16(2):99-111. Epub 2019 Oct 31.

Division of Nephrology, Center for Vascular Biology Research and Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.

The mammalian kidney relies on abundant mitochondria in the renal tubule to generate sufficient ATP to provide the energy required for constant reclamation of solutes from crude blood filtrate. The highly metabolically active cells of the renal tubule also pair their energetic needs to the regulation of diverse cellular processes, including energy generation, antioxidant responses, autophagy and mitochondrial quality control. Nicotinamide adenine dinucleotide (NAD) is essential not only for the harvesting of energy from substrates but also for an array of regulatory reactions that determine cellular health. In acute kidney injury (AKI), substantial decreases in the levels of NAD impair energy generation and, ultimately, the core kidney function of selective solute transport. Conversely, augmentation of NAD may protect the kidney tubule against diverse acute stressors. For example, NAD augmentation can ameliorate experimental AKI triggered by ischaemia-reperfusion, toxic injury and systemic inflammation. NAD-dependent maintenance of renal tubular metabolic health may also attenuate long-term profibrotic responses that could lead to chronic kidney disease. Further understanding of the genetic, environmental and nutritional factors that influence NAD biosynthesis and renal resilience may lead to novel approaches for the prevention and treatment of kidney disease.
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http://dx.doi.org/10.1038/s41581-019-0216-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7223841PMC
February 2020

Neutrophil activation in systemic capillary leak syndrome (Clarkson disease).

J Cell Mol Med 2019 08 18;23(8):5119-5127. Epub 2019 Jun 18.

Lung and Vascular Inflammation Section, Laboratory of Allergic Diseases, NIAID/NIH, Bethesda, Maryland.

Systemic capillary leak syndrome (SCLS; Clarkson disease) is a rare orphan disorder characterized by transient yet recurrent episodes of hypotension and peripheral oedema due to diffuse vascular leakage of fluids and proteins into soft tissues. Humoral mediators, cellular responses and genetic features accounting for the clinical phenotype of SCLS are virtually unknown. Here, we searched for factors altered in acute SCLS plasma relative to matched convalescent samples using multiplexed aptamer-based proteomic screening. Relative amounts of 612 proteins were changed greater than twofold and 81 proteins were changed at least threefold. Among the most enriched proteins in acute SCLS plasma were neutrophil granule components including bactericidal permeability inducing protein, myeloperoxidase and matrix metalloproteinase 8. Neutrophils isolated from blood of subjects with SCLS or healthy controls responded similarly to routine pro-inflammatory mediators. However, acute SCLS sera activated neutrophils relative to remission sera. Activated neutrophil supernatants increased permeability of endothelial cells from both controls and SCLS subjects equivalently. Our results suggest systemic neutrophil degranulation during SCLS acute flares, which may contribute to the clinical manifestations of acute vascular leak.
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http://dx.doi.org/10.1111/jcmm.14381DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6653644PMC
August 2019

An Evolutionarily Conserved uORF Regulates PGC1α and Oxidative Metabolism in Mice, Flies, and Bluefin Tuna.

Cell Metab 2019 07 16;30(1):190-200.e6. Epub 2019 May 16.

Dana-Farber Cancer Institute, Boston, MA 02115, USA; Department of Cell Biology, Harvard University Medical School, Boston, MA 02115, USA. Electronic address:

Mitochondrial abundance and function are tightly controlled during metabolic adaptation but dysregulated in pathological states such as diabetes, neurodegeneration, cancer, and kidney disease. We show here that translation of PGC1α, a key governor of mitochondrial biogenesis and oxidative metabolism, is negatively regulated by an upstream open reading frame (uORF) in the 5' untranslated region of its gene (PPARGC1A). We find that uORF-mediated translational repression is a feature of PPARGC1A orthologs from human to fly. Strikingly, whereas multiple inhibitory uORFs are broadly present in fish PPARGC1A orthologs, they are completely absent in the Atlantic bluefin tuna, an animal with exceptionally high mitochondrial content. In mice, an engineered mutation disrupting the PPARGC1A uORF increases PGC1α protein levels and oxidative metabolism and confers protection from acute kidney injury. These studies identify a translational regulatory element governing oxidative metabolism and highlight its potential contribution to the evolution of organismal mitochondrial function.
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http://dx.doi.org/10.1016/j.cmet.2019.04.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6620024PMC
July 2019

Author Correction: Metabolic reprogramming by the S-nitroso-CoA reductase system protects against kidney injury.

Nature 2019 Jun;570(7759):E23

Institute for Transformative Molecular Medicine, Department of Medicine, Case Western Reserve University and University Hospitals Cleveland Medical Center, Cleveland, OH, USA.

Change history: In Fig. 1j of this Letter, one data point was inadvertently omitted from the graph for the acute kidney injury (AKI), double knockout (-/-), S-nitrosothiol (SNO) condition at a nitrosylation level of 25.9 pmol mg and the statistical significance given of P = 0.0221 was determined by Fisher's test instead of P = 0.0032 determined by Tukey's test (with normalization for test-day instrument baseline). Figure 1 and its Source Data have been corrected online.
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http://dx.doi.org/10.1038/s41586-019-1225-0DOI Listing
June 2019

Metabolic Stress Resistance in Acute Kidney Injury: Evidence for a PPAR-Gamma-Coactivator-1 Alpha-Nicotinamide Adenine Dinucleotide Pathway.

Authors:
Samir M Parikh

Nephron 2019 3;143(3):184-187. Epub 2019 May 3.

Division of Nephrology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA,

Acute kidney injury (AKI) is estimated to affect 3-10% of all hospitalized adults in the United States, making it one of the most common inpatient diagnoses. Despite this staggering incidence, most individuals exposed to AKI stressors, such as intravenous radiocontrast or cardiopulmonary bypass, do not develop AKI. In fact, whereas animal models of ischemia, sepsis, or nephrotoxicity suggest near-uniform responses to stressors, the natural history of stressed patients is highly heterogeneous. Recent studies of mitochondrial perturbations underlying experimental and human AKI suggest a conserved metabolic contribution to this variance. The renal tubule is only second to the heart in terms of mitochondrial abundance, reflecting the exquisite need for fuel combustion to generate the energy for active solute transport. The homeostasis of nicotinamide adenine dinucleotide (NAD+), a requisite coenzyme in oxidative metabolism, may be an important determinant of the renal response to AKI stressors. This mini-review highlights recent studies implicating NAD+ dysregulation in experimental and human AKI and summarizes findings from a pilot randomized trial to augment NAD+ among at-risk individuals.
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http://dx.doi.org/10.1159/000500168DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6821556PMC
July 2020

TFEB-driven lysosomal biogenesis is pivotal for PGC1α-dependent renal stress resistance.

JCI Insight 2019 03 14;5. Epub 2019 Mar 14.

Division of Nephrology.

Because injured mitochondria can accelerate cell death through the elaboration of oxidative free radicals and other mediators, it is striking that proliferator gamma coactivator 1-alpha (PGC1α), a stimulator of increased mitochondrial abundance, protects stressed renal cells instead of potentiating injury. Here we report that PGC1α's induction of lysosomes via transcription factor EB (TFEB) may be pivotal for kidney protection. CRISPR and stable gene transfer showed that PGC1α knockout tubular cells were sensitized to the genotoxic stressor cisplatin whereas transgenic cells were protected. The biosensor mtKeima unexpectedly revealed that cisplatin blunts mitophagy both in cells and mice. PGC1α not only counteracted this effect but also raised basal mitophagy, as did the downstream mediator nicotinamide adenine dinucleotide (NAD+). PGC1α did not consistently affect known autophagy pathways modulated by cisplatin. Instead RNA sequencing identified coordinated regulation of lysosomal biogenesis via TFEB. This effector pathway was sufficiently important that inhibition of TFEB or lysosomes unveiled a striking harmful effect of excess PGC1α in cells and conditional mice. These results uncover an unexpected effect of cisplatin on mitophagy and PGC1α's exquisite reliance on lysosomes for kidney protection. Finally, the data illuminate TFEB as a novel target for renal tubular stress resistance.
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http://dx.doi.org/10.1172/jci.insight.126749DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6538327PMC
March 2019

Metabolic reprogramming by the S-nitroso-CoA reductase system protects against kidney injury.

Nature 2019 01 28;565(7737):96-100. Epub 2018 Nov 28.

Institute for Transformative Molecular Medicine, Department of Medicine, Case Western Reserve University and University Hospitals Cleveland Medical Center, Cleveland, OH, USA.

Endothelial nitric oxide synthase (eNOS) is protective against kidney injury, but the molecular mechanisms of this protection are poorly understood. Nitric oxide-based cellular signalling is generally mediated by protein S-nitrosylation, the oxidative modification of Cys residues to form S-nitrosothiols (SNOs). S-nitrosylation regulates proteins in all functional classes, and is controlled by enzymatic machinery that includes S-nitrosylases and denitrosylases, which add and remove SNO from proteins, respectively. In Saccharomyces cerevisiae, the classic metabolic intermediate co-enzyme A (CoA) serves as an endogenous source of SNOs through its conjugation with nitric oxide to form S-nitroso-CoA (SNO-CoA), and S-nitrosylation of proteins by SNO-CoA is governed by its cognate denitrosylase, SNO-CoA reductase (SCoR). Mammals possess a functional homologue of yeast SCoR, an aldo-keto reductase family member (AKR1A1) with an unknown physiological role. Here we report that the SNO-CoA-AKR1A1 system is highly expressed in renal proximal tubules, where it transduces the activity of eNOS in reprogramming intermediary metabolism, thereby protecting kidneys against acute kidney injury. Specifically, deletion of Akr1a1 in mice to reduce SCoR activity increased protein S-nitrosylation, protected against acute kidney injury and improved survival, whereas this protection was lost when Enos (also known as Nos3) was also deleted. Metabolic profiling coupled with unbiased mass spectrometry-based SNO-protein identification revealed that protection by the SNO-CoA-SCoR system is mediated by inhibitory S-nitrosylation of pyruvate kinase M2 (PKM2) through a novel locus of regulation, thereby balancing fuel utilization (through glycolysis) with redox protection (through the pentose phosphate shunt). Targeted deletion of PKM2 from mouse proximal tubules recapitulated precisely the protective and mechanistic effects of S-nitrosylation in Akr1a1 mice, whereas Cys-mutant PKM2, which is refractory to S-nitrosylation, negated SNO-CoA bioactivity. Our results identify a physiological function of the SNO-CoA-SCoR system in mammals, describe new regulation of renal metabolism and of PKM2 in differentiated tissues, and offer a novel perspective on kidney injury with therapeutic implications.
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http://dx.doi.org/10.1038/s41586-018-0749-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6318002PMC
January 2019

Multiplexed, high-throughput measurements of cell contraction and endothelial barrier function.

Lab Invest 2019 01 11;99(1):138-145. Epub 2018 Oct 11.

Center for Vascular Biology Research, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.

Vascular leakage, protein exudation, and edema formation are events commonly triggered by inflammation and facilitated by gaps that form between adjacent endothelial cells (ECs) of the vasculature. In such paracellular gap formation, the role of EC contraction is widely implicated, and even therapeutically targeted. However, related measurement approaches remain slow, tedious, and complex to perform. Here, we have developed a multiplexed, high-throughput screen to simultaneously quantify paracellular gaps, EC contractile forces, and to visualize F-actin stress fibers, and VE-cadherin. As proof-of-principle, we examined barrier-protective mechanisms of the Rho-associated kinase inhibitor, Y-27632, and the canonical agonist of the Tie2 receptor, Angiopoietin-1 (Angpt-1). Y-27632 reduced EC contraction and actin stress fiber formation, whereas Angpt-1 did not. Yet both agents reduced thrombin-, LPS-, and TNFα-induced paracellular gap formation. This unexpected result suggests that Angpt-1 can achieve barrier defense without reducing EC contraction, a mechanism that has not been previously described. This insight was enabled by the multiplex nature of the force-based platform. The high-throughput format we describe should accelerate both mechanistic studies and the screening of pharmacological modulators of endothelial barrier function.
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http://dx.doi.org/10.1038/s41374-018-0136-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6309267PMC
January 2019

Decreased PGC-1α Post-Cardiopulmonary Bypass Leads to Impaired Oxidative Stress in Diabetic Patients.

Ann Thorac Surg 2019 02 3;107(2):467-476. Epub 2018 Oct 3.

Department of Anesthesia, Critical Care, and Pain Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts. Electronic address:

Background: The mechanism of mitochondrial dysfunction after cardiopulmonary bypass (CPB) in patients with diabetes mellitus lacks understanding. We hypothesized that impaired beta-oxidation of fatty acids leads to worsened stress response in this patient population after cardiac surgery.

Methods: After Institutional Review Board approval, right atrial tissue samples were collected from 35 diabetic patients and 33 nondiabetic patients before and after CPB. Patients with glycated hemoglobin of 6.0 or greater and a clinical diagnosis of diabetes mellitus were considered to be diabetic. Immunoblotting and microarray analysis were performed to assess protein and gene expression changes. Blots were quantified with ImageJ and analyzed using one-way analysis of variance with multiple Student's t test comparisons after normalization. All p values less than 0.05 were considered significant. Immunohistochemistry was performed for cellular lipid deposition assessment.

Results: Diabetic patients had significantly lower levels of PGC-1α before and after CPB (p < 0.01 for both) compared with nondiabetic patients. Several upstream regulators of PGC-1α (SIRT1 and CREB) were significantly higher in nondiabetic patients before CPB (p = 0.01 and 0.0018, respectively). Antioxidant markers (NOX4 and GPX4), angiogenic factors (TGF-β, NT3, and Ang1), and the antiapoptotic factor BCL-xL were significantly lower in diabetic patients after CPB (p < 0.05). The expression of genes supporting mitochondrial energy production (CREB5 and SLC25A40) and angiogenic genes (p < 0.05) was significantly downregulated in diabetic patients after CPB. Immunohistochemistry results showed significantly increased lipid deposition in diabetic myocardial tissue.

Conclusions: Decreased PGC-1α in diabetic patients may lead to impaired mitochondrial function and attenuated antiapoptotic and angiogenic responses after CPB. Therefore, PGC-1α and upstream regulators could serve as a target for improving beta-oxidation in diabetic patients.
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http://dx.doi.org/10.1016/j.athoracsur.2018.08.009DOI Listing
February 2019

Serum Angiopoietin-2 Predicts Mortality and Kidney Outcomes in Decompensated Cirrhosis.

Hepatology 2019 02 4;69(2):729-741. Epub 2019 Jan 4.

Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Boston, MA.

Acute kidney injury in decompensated cirrhosis has limited therapeutic options, and novel mechanistic targets are urgently needed. Angiopoietin-2 is a context-specific antagonist of Tie2, a receptor that signals vascular quiescence. Considering the prominence of vascular destabilization in decompensated cirrhosis, we evaluated Angiopoietin-2 to predict clinical outcomes. Serum Angiopoietin-2 was measured serially in a prospective cohort of hospitalized patients with decompensated cirrhosis and acute kidney injury. Clinical characteristics and outcomes were examined over a 90-day period and analyzed according to Angiopoietin-2 levels. Primary outcome was 90-day mortality. Our study included 191 inpatients (median Angiopoietin-2 level 18.2 [interquartile range 11.8, 26.5] ng/mL). Median Model for End-Stage Liver Disease (MELD) score was 23 [17, 30] and 90-day mortality was 41%. Increased Angiopoietin-2 levels were associated with increased mortality (died 21.9 [13.9, 30.3] ng/mL vs. alive 15.2 [9.8, 23.0] ng/mL; P < 0.001), higher Acute Kidney Injury Network stage (stage I 13.4 [9.8, 20.1] ng/mL vs. stage II 20.0 [14.1, 26.2] ng/mL vs. stage III 21.9 [13.0, 29.5] ng/mL; P = 0.002), and need for renal replacement therapy (16.5 [11.3, 23.6] ng/mL vs. 25.1 [13.3, 30.3] ng/mL; P = 0.005). The association between Angiopoietin-2 and mortality was significant in unadjusted and adjusted Cox regression models (P ≤ 0.001 for all models), and improved discrimination for mortality when added to MELD score (integrated discrimination increment 0.067; P = 0.001). Conclusion: Angiopoietin-2 was associated with mortality and other clinically relevant outcomes in a cohort of patients with decompensated cirrhosis with acute kidney injury. Further experimental study of Angiopoietin/Tie2 signaling is warranted to explore its potential mechanistic and therapeutic role in this population.
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http://dx.doi.org/10.1002/hep.30230DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6351209PMC
February 2019

De novo NAD biosynthetic impairment in acute kidney injury in humans.

Nat Med 2018 09 20;24(9):1351-1359. Epub 2018 Aug 20.

Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.

Nicotinamide adenine dinucleotide (NAD) extends longevity in experimental organisms, raising interest in its impact on human health. De novo NAD biosynthesis from tryptophan is evolutionarily conserved yet considered supplanted among higher species by biosynthesis from nicotinamide (NAM). Here we show that a bottleneck enzyme in de novo biosynthesis, quinolinate phosphoribosyltransferase (QPRT), defends renal NAD and mediates resistance to acute kidney injury (AKI). Following murine AKI, renal NAD fell, quinolinate rose, and QPRT declined. QPRT mice exhibited higher quinolinate, lower NAD, and higher AKI susceptibility. Metabolomics suggested an elevated urinary quinolinate/tryptophan ratio (uQ/T) as an indicator of reduced QPRT. Elevated uQ/T predicted AKI and other adverse outcomes in critically ill patients. A phase 1 placebo-controlled study of oral NAM demonstrated a dose-related increase in circulating NAD metabolites. NAM was well tolerated and was associated with less AKI. Therefore, impaired NAD biosynthesis may be a feature of high-risk hospitalizations for which NAD augmentation could be beneficial.
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http://dx.doi.org/10.1038/s41591-018-0138-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6129212PMC
September 2018

Esmolol infusion in patients with septic shock and tachycardia: a prospective, single-arm, feasibility study.

Pilot Feasibility Stud 2018 3;4:132. Epub 2018 Aug 3.

6Department of Anesthesia, University of Chicago, Chicago, IL USA.

Background: High adrenergic tone appears to be associated with mortality in septic shock, while adrenergic antagonism may improve survival. In preparation for a randomized trial, we conducted a prospective, single-arm pilot study of esmolol infusion for patients with septic shock and tachycardia that persists after adequate volume expansion.

Methods: From April 2016 to March 2017, we enrolled patients admitted to an intensive care unit with sepsis who were receiving vasopressor infusion and were tachycardic despite adequate volume expansion. All patients received a continuous intravenous infusion of esmolol, targeted to heart rate 80-90/min, while receiving vasopressors. The feasibility outcomes were proportion of eligible patients consented, compliance with pre-infusion safety check, and compliance with the titration protocol. The primary clinical outcome was organ-failure-free days (OFFD) at 28 days.

Results: We enrolled 7 of 10 eligible patients. Mean age was 46 (± 19) years, and mean admission APACHE II was 28 (± 8). Median norepinephrine infusion rate at the initiation of esmolol infusion was 0.20 (0.14-0.23) μg/kg/min. Compliance with the safety check was 100%; compliance with components of the titration protocol was 98-100%. OFFD were 26 (24.5-26); all patients survived to day 90. Median peak esmolol infusion was 50 (25-50) μg/kg/min. Median peak norepinephrine infusion rate during esmolol infusion was 0.46 (0.13-0.50) μg/kg/min. Four patients achieved target heart rate. Protocol-defined stop events, suggesting possible intolerance to a given infusion rate, occurred in three patients, all of whom were receiving at least 50 μg/kg/min of esmolol.

Conclusions: In a pilot, single-arm study, we report the first published experience with esmolol infusion in tachycardic patients with septic shock in the United States. These findings support a phase 2 trial of esmolol infusion for septic shock. Lower infusion rates of esmolol infusion may be better tolerated and more feasible than higher infusion rates for such a trial.

Trial Registration: This study was retrospectively registered at ClinicalTrials.gov (NCT02841241) on 19 July 2016.
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http://dx.doi.org/10.1186/s40814-018-0321-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6091011PMC
August 2018

Molecular Regulation of Acute Tie2 Suppression in Sepsis.

Crit Care Med 2018 09;46(9):e928-e936

Department of Nephrology and Hypertension, Hannover Medical School, Hannover, Germany.

Objectives: Tie2 is a tyrosine kinase receptor expressed by endothelial cells that maintains vascular barrier function. We recently reported that diverse critical illnesses acutely decrease Tie2 expression and that experimental Tie2 reduction suffices to recapitulate cardinal features of the septic vasculature. Here we investigated molecular mechanisms driving Tie2 suppression in settings of critical illness.

Design: Laboratory and animal research, postmortem kidney biopsies from acute kidney injury patients and serum from septic shock patients.

Setting: Research laboratories and ICU of Hannover Medical School, Harvard Medical School, and University of Groningen.

Patients: Deceased septic acute kidney injury patients (n = 16) and controls (n = 12) and septic shock patients (n = 57) and controls (n = 22).

Interventions: Molecular biology assays (Western blot, quantitative polymerase chain reaction) + in vitro models of flow and transendothelial electrical resistance experiments in human umbilical vein endothelial cells; murine cecal ligation and puncture and lipopolysaccharide administration.

Measurements And Main Results: We observed rapid reduction of both Tie2 messenger RNA and protein in mice following cecal ligation and puncture. In cultured endothelial cells exposed to tumor necrosis factor-α, suppression of Tie2 protein was more severe than Tie2 messenger RNA, suggesting distinct regulatory mechanisms. Evidence of protein-level regulation was found in tumor necrosis factor-α-treated endothelial cells, septic mice, and septic humans, all three of which displayed elevation of the soluble N-terminal fragment of Tie2. The matrix metalloprotease 14 was both necessary and sufficient for N-terminal Tie2 shedding. Since clinical settings of Tie2 suppression are often characterized by shock, we next investigated the effects of laminar flow on Tie2 expression. Compared with absence of flow, laminar flow induced both Tie2 messenger RNA and the expression of GATA binding protein 3. Conversely, septic lungs exhibited reduced GATA binding protein 3, and knockdown of GATA binding protein 3 in flow-exposed endothelial cells reduced Tie2 messenger RNA. Postmortem tissue from septic patients showed a trend toward reduced GATA binding protein 3 expression that was associated with Tie2 messenger RNA levels (p < 0.005).

Conclusions: Tie2 suppression is a pivotal event in sepsis that may be regulated both by matrix metalloprotease 14-driven Tie2 protein cleavage and GATA binding protein 3-driven flow regulation of Tie2 transcript.
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http://dx.doi.org/10.1097/CCM.0000000000003269DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6095816PMC
September 2018

Reply.

J Allergy Clin Immunol 2018 04 21;141(4):1540-1541. Epub 2018 Feb 21.

Harvard Medical School, Boston, Mass.

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http://dx.doi.org/10.1016/j.jaci.2017.11.054DOI Listing
April 2018

Tie2 protects the vasculature against thrombus formation in systemic inflammation.

J Clin Invest 2018 04 5;128(4):1471-1484. Epub 2018 Mar 5.

Division of Nephrology and Department of Medicine.

Disordered coagulation contributes to death in sepsis and lacks effective treatments. Existing markers of disseminated intravascular coagulation (DIC) reflect its sequelae rather than its causes, delaying diagnosis and treatment. Here we show that disruption of the endothelial Tie2 axis is a sentinel event in septic DIC. Proteomics in septic DIC patients revealed a network involving inflammation and coagulation with the Tie2 antagonist, angiopoietin-2 (Angpt-2), occupying a central node. Angpt-2 was strongly associated with traditional DIC markers including platelet counts, yet more accurately predicted mortality in 2 large independent cohorts (combined N = 1,077). In endotoxemic mice, reduced Tie2 signaling preceded signs of overt DIC. During this early phase, intravital imaging of microvascular injury revealed excessive fibrin accumulation, a pattern remarkably mimicked by Tie2 deficiency even without inflammation. Conversely, Tie2 activation normalized prothrombotic responses by inhibiting endothelial tissue factor and phosphatidylserine exposure. Critically, Tie2 activation had no adverse effects on bleeding. These results mechanistically implicate Tie2 signaling as a central regulator of microvascular thrombus formation in septic DIC and indicate that circulating markers of the Tie2 axis could facilitate earlier diagnosis. Finally, interventions targeting Tie2 may normalize coagulation in inflammatory states while averting the bleeding risks of current DIC therapies.
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http://dx.doi.org/10.1172/JCI97488DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5873892PMC
April 2018

PAR1 agonists stimulate APC-like endothelial cytoprotection and confer resistance to thromboinflammatory injury.

Proc Natl Acad Sci U S A 2018 01 17;115(5):E982-E991. Epub 2018 Jan 17.

Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115;

Stimulation of protease-activated receptor 1 (PAR1) on endothelium by activated protein C (APC) is protective in several animal models of disease, and APC has been used clinically in severe sepsis and wound healing. Clinical use of APC, however, is limited by its immunogenicity and its anticoagulant activity. We show that a class of small molecules termed "parmodulins" that act at the cytosolic face of PAR1 stimulates APC-like cytoprotective signaling in endothelium. Parmodulins block thrombin generation in response to inflammatory mediators and inhibit platelet accumulation on endothelium cultured under flow. Evaluation of the antithrombotic mechanism showed that parmodulins induce cytoprotective signaling through Gβγ, activating a PI3K/Akt pathway and eliciting a genetic program that includes suppression of NF-κB-mediated transcriptional activation and up-regulation of select cytoprotective transcripts. is among the up-regulated transcripts, and knockdown of stanniocalin-1 blocks the protective effects of both parmodulins and APC. Induction of this signaling pathway in vivo protects against thromboinflammatory injury in blood vessels. Small-molecule activation of endothelial cytoprotection through PAR1 represents an approach for treatment of thromboinflammatory disease and provides proof-of-principle for the strategy of targeting the cytoplasmic surface of GPCRs to achieve pathway selective signaling.
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http://dx.doi.org/10.1073/pnas.1718600115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5798377PMC
January 2018

Renal PGC1α May Be Associated with Recovery after Delayed Graft Function.

Nephron 2018 21;138(4):303-309. Epub 2017 Dec 21.

Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.

Background: Delayed renal graft function (DGF) contributes to the determination of length of hospitalization, risk of acute rejection, and graft loss. Existing tools aid the diagnosis of specific DGF etiologies such as antibody-mediated rejection, but markers of recovery have been elusive. The peroxisome proliferator gamma co-activator-1-alpha (PGC1α) is highly expressed in the renal tubule, regulates mitochondrial biogenesis, and promotes recovery from experimental acute kidney injury.

Objectives: We aimed to determine the association between renal allograft PGC1α expression and recovery from delayed graft function.

Methods: We retrospectively analyzed patients undergoing renal transplantation at a single center from January 1, 2008 to June 30, 2014. PGC1α expression was assessed by immunostaining and ultrastructural characteristics by transmission electron microscopy. Of 34 patients who underwent renal biopsy for DGF within 30 days of transplant, 21 were included for analysis.

Results: Low PGC1α expression was associated with a significantly longer time on dialysis after transplant (median of 35.5 vs. 16 days, p < 0.05) and a significantly higher serum creatinine (sCr) at 4 weeks after transplantation among those who discontinued dialysis (5 vs. 1.65 mg/dL, p < 0.0001). Low PGC1α expression was not associated with higher sCr at 12 weeks after transplantation. Ultrastructural characteristics including apical membrane blebbing and necrotic luminal debris were not informative regarding clinical outcomes.

Conclusions: These data suggest that higher PGC1α expression is associated with faster and more complete recovery from DGF. Mitochondrial biogenesis may be a therapeutic target for DGF. Larger studies are needed to validate these findings.
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http://dx.doi.org/10.1159/000485663DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5858968PMC
September 2019