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      Tenofovir alafenamide nephrotoxicity in an HIV-positive patient : A case report

      case-report

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          Abstract

          Rationale:

          Tenofovir alafenamide (TAF) is novel prodrug of Tenofovir, a nucleotide reverse transcriptase inhibitor. TAF is less nephrotoxic than its predecessor prodrug, tenofovir disoproxil fumarate (TDF). Tenofovir causes mitochondrial dysfunction and tubular injury when there is elevated accumulation in proximal tubule cells. TAF's unique pharmacokinetic profile enables provision of lower required doses for antiviral efficacy. Lower concentrations reach renal tubules minimizing intracellular accumulation and mitochondrial damage. TAF has not been associated with the histologic markers of tenofovir-associated nephrotoxicity that are seen with TDF, such as dysmorphic mitochondria in proximal tubule cells. Here, we report a patient with dysmorphic mitochondria on kidney biopsy after initiating therapy with TAF.

          Lessons:

          This case suggests that at risk individuals may experience tubular mitochondrial injury from lower concentrations of tenofovir with TAF.

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          Most cited references9

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          Tenofovir nephrotoxicity: acute tubular necrosis with distinctive clinical, pathological, and mitochondrial abnormalities.

          Tenofovir, a widely prescribed antiretroviral medication for treatment of HIV-1 infection, is infrequently associated with renal dysfunction and biopsy findings of acute tubular necrosis. We examined the clinical and pathological findings in 13 cases of tenofovir nephrotoxicity (7 men and 6 women, mean age of 51.1±9.6 years). Patients received tenofovir therapy for a mean of 19.6 months (range, 3 weeks to 8 years; median 8 months). Nine patients presented with acute kidney injury, and four had mild renal insufficiency with subnephrotic proteinuria. Mean baseline serum creatinine was 1.3±0.3 mg/dl, reaching 5.7±4.0 mg/dl at the time of biopsy, with mean proteinuria of 1.6±0.3 g/day. Glycosuria was documented in seven patients, five of whom were normoglycemic. Renal biopsy revealed toxic acute tubular necrosis, with distinctive proximal tubular eosinophilic inclusions representing giant mitochondria visible by light microscopy. Electron microscopy showed mitochondrial enlargement, depletion, and dysmorphic changes. Clinical follow-up after tenofovir discontinuation was available for 11 of 13 patients (mean duration 13.6 months). Significant recovery of renal function occurred in all patients, including four who required transient hemodialysis. Our study shows that tenofovir nephrotoxicity is a largely reversible form of toxic acute tubular necrosis targeting proximal tubules and manifesting distinctive light microscopic and ultrastructural features of mitochondrial injury.
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            Tenofovir-associated Fanconi syndrome: review of the FDA adverse event reporting system.

            S. Gupta (2008)
            Tenofovir disoproxil fumarate (TDF) is a commonly used HIV antiretroviral. A relatively uncommon adverse effect of this drug is Fanconi syndrome. What is known about this toxicity, especially in regards to concomitant medication use and outcomes, is limited to isolated case reports and small case series. Therefore, a retrospective review of the FDA Adverse Event Reporting System from 2001 through 2006 was conducted to examine demographics, concomitant medication use, outcomes, and temporal trends in reporting of Fanconi syndrome associated with TDF use. In this large case series of 164 subjects who met the case definition for Fanconi syndrome, the majority (83%) of the subjects received protease inhibitors (PI) with TDF; specifically, 74% of the total received a ritonavir-boosted PI. Didanosine was the most commonly (43%) prescribed nucleoside reverse transcriptase inhibitor (NRTI). The combination of didanosine with boosted PI was frequently observed (34%), and in particular, didanosine plus lopinavir/ritonavir was documented for 22%. Nearly half (46%) of the total were hospitalized. Fracture (2%) and requirement for dialysis (2%) were infrequent while Fanconi syndrome contributed to death in 2% of these subjects. Patients receiving ritonavir-boosted protease inhibitors or didanosine with tenofovir should be closely monitored for development of nephrotoxicity. Although reporting biases and the exclusion of reports with serious confounding conditions likely affected the estimation of outcomes in this case series, severe complications of tenofovir-associated Fanconi syndrome were uncommon.
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              Rap1b GTPase ameliorates glucose-induced mitochondrial dysfunction.

              The role of tubular injury in diabetic nephropathy is relatively unknown, despite that apoptosis of tubular epithelial cells is commonly observed in human renal biopsies. The GTPase Ras-proximate-1 (Rap1b) is upregulated in the hyperglycemic state and is known to increase B-Raf, an antiapoptotic effector protein. In this study, the effects of high glucose on renal tubular apoptosis and the potential ability for Rap1b to ameliorate these effects were investigated. In the kidneys of diabetic mice, apoptotic tubular cells and dysmorphic mitochondria were observed, Bcl-2 expression was decreased, and Bax expression was increased. Total Rap1b expression was slightly increased, but its associated GTPase activity was significantly decreased. In vitro, high extracellular glucose led to decreased Bcl-2 expression, reduced Rap1b GTPase activity, and increased levels of both Bax and GTPase activating protein in a proximal tubular cell line (HK-2). These changes were accompanied by increased DNA fragmentation, decreased high molecular weight mitochondrial DNA, altered mitochondrial morphology and function, disrupted Bcl-2-Bax and Bcl-2-Rap1b interactions, and reduced cell survival. Overexpression of Rap1b partially prevents these abnormalities. Furthermore, the BH4 domain of Bcl-2 was found to be required for successful protein-protein interaction between Bcl-2 and Rap1b. In summary, these data suggest that Rap1b ameliorates glucose-induced mitochondrial dysfunction in renal tubular cells.
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                Author and article information

                Journal
                Medicine (Baltimore)
                Medicine (Baltimore)
                MEDI
                Medicine
                Wolters Kluwer Health
                0025-7974
                1536-5964
                September 2017
                08 September 2017
                : 96
                : 36
                : e8046
                Affiliations
                [a ]Department of Medicine
                [b ]Department of Pathology, Johns Hopkins University, Baltimore, MD.
                Author notes
                []Correspondence: Tessa K. Novick, 1830 E. Monument St, 4th Floor, Suite 416, Baltimore, MD (e-mail: tnovick1@ 123456jhmi.edu ); Mohamed G. Atta, 1830 E. Monument St, 4th Floor, Suite 416, Baltimore, MD (e-mail: matta1@ 123456jhmi.edu ).
                Article
                MD-D-17-04600 08046
                10.1097/MD.0000000000008046
                6393094
                28885375
                85c87074-0b49-4a19-b715-99fe316b33b6
                Copyright © 2017 the Author(s). Published by Wolters Kluwer Health, Inc.

                This is an open access article distributed under the Creative Commons Attribution-NoDerivatives License 4.0, which allows for redistribution, commercial and non-commercial, as long as it is passed along unchanged and in whole, with credit to the author. http://creativecommons.org/licenses/by-nd/4.0

                History
                : 24 July 2017
                : 17 August 2017
                : 21 August 2017
                Categories
                4850
                Research Article
                Clinical Case Report
                Custom metadata
                TRUE

                hiv,proximal tubule injury,tenofovir alafenamide,tenofovir nephrotoxicity

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