Enhanced Uridine Bioavailability Following Administration of a Triacetyluridine-Rich Nutritional Supplement

et al. (2011) Enhanced Uridine Bioavailability Following Administration of a Triacetyluridine-Rich Nutritional Supplement. PLoS ONE 6(2): e14709. doi:10.1371/journal.pone.0014709 Enhanced Uridine Bioavailability Following Administration of a Triacetyluridine-Rich Nutritional Supplement Melissa E. Weinberg 0 Mark C. Roman 0 Peyton Jacob 0 Michael Wen 0 Polly Cheung 0 Ulrich A. Walker 0 Kathleen Mulligan 0 Morris Schambelan 0 Wen-Liang Zhou, Sun Yat-Sen University, China 0 1 University of California San Francisco , San Francisco , California, United States of America, 2 Tampa Bay Analytical Research Inc., Largo, Florida, United States of America, 3 Department of Rheumatology, Basel University , Basel , Switzerland Background: Uridine is a therapy for hereditary orotic aciduria and is being investigated in other disorders caused by mitochondrial dysfunction, including toxicities resulting from treatment with nucleoside reverse transcriptase inhibitors in HIV. Historically, the use of uridine as a therapeutic agent has been limited by poor bioavailability. A food supplement containing nucleosides, NucleomaxXH, has been reported to raise plasma uridine to supraphysiologic levels. Methodology/Principal Findings: Single- and multi-dose PK studies following NucleomaxXH were compared to single-dose PK studies of equimolar doses of pure uridine in healthy human volunteers. Product analysis documented that more than 90% of the nucleoside component of NucleomaxXH is in the form of triacetyluridine (TAU). Single and repeated dosing with NucleomaxXH resulted in peak plasma uridine concentrations 1-2 hours later of 150.9639.3 mM and 161.4631.5 mM, respectively, levels known to ameliorate mitochondrial toxicity in vitro. Cmax and AUC were four-fold higher after a single dose of NucleomaxXH than after uridine. No adverse effects of either treatment were observed. Conclusions/Significance: NucleomaxXH, containing predominantly TAU, has significantly greater bioavailability than pure uridine in human subjects and may be useful in the management of mitochondrial toxicity. - Funding: Funding was provided by National Center for Complementary and Alternative Medicine grant number AT003374, NIH/NCRR UCSF-CTSI grant number UL1 RR024131, NIH training grant T32-DK07418, and NIH grant number P30-DA12393. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: Ulrich Walker serves as a consultant to Pharmanord. Tampa Bay Analytical Research was not a funder of this study. The Product Safety Working Group of the NIHs National Center for Complementary and Alternative Medicine required the authors to perform an independent product analysis of the supplement, NucleomaxX, under investigation. In fact, the NIH suggested the authors contract with Mark Roman at Tampa Bay Analytical Research. The authors were solely responsible for the design, conduct, and interpretation of all studies. This relationship does not alter the authors adherence to all the PLoS ONE policies on sharing data and materials. Uridine, a pyrimidine nucleoside that plays an essential role in the synthesis of RNA and other key physiologic processes [1], has been used as a treatment for patients with hereditary orotic aciduria for more than four decades. The therapeutic potential of uridine has also been assessed in a diverse group of clinical disorders including cystic fibrosis, liver dysfunction, chemotherapy toxicity, pervasive developmental delay, schizophrenia, epilepsy, and diabetes-induced peripheral neuropathy [2]; and, recently, as a treatment for mitochondrial dysfunction associated with treatment with nucleoside reverse transcriptase inhibitors in patients with HIV infection [36]. Circulating levels of uridine are tightly regulated, in the range of 38 mM, both by the liver, which synthesizes and degrades uridine, and by erythrocytes that store UDP-glucose, which may be catabolized to provide glucose and uridine [2]. Uridine is absorbed from the gastrointestinal tract via facilitated diffusion or specific uridine transporters [7]. Historically, the use of uridine as a therapeutic agent has been limited by poor bioavailability. In a pharmacokinetic (PK) study of orally-administered uridine, the maximum tolerated dose was 1012 g/m2 for a single dose and 5 g/m2 for a multiple-dose regimen (every 6 hours for 3 days), resulting in peak serum uridine concentrations of 6080 mM after a single dose and a steady-state serum uridine level of 50 mM after multiple doses [8]. The dose-limiting side effect was diarrhea. Recently, administration of NucleomaxXH, a food supplement that contains approximately 6 g of nucleosides (the equivalent of about 3.5 g/m2 in an average-sized male), achieved higher peak uridine levels (100150 mM) during a single dose PK study [9] than were achieved in prior studies using uridine. NucleomaxXH is apparently well-tolerated. Although these results suggest that the formulation of uridine in NucleomaxXH may have enhanced bioavailability, the differences in plasma uridine levels achieved in studies of uridine and those of NucleomaxxH could also be explained by the fact that different analytic techniques and study designs were employed. We therefore performed an analysis of the nucleoside components of NucleomaxXH and compared the PK profiles achieved following equimolar doses of the pyrimidine nucleosides provided by NucleomaxXH to that of pure uridine in healthy human volunteers. In addition, because the optimal dosing regimen of NucleomaxXH is not known, we also performed multiple-dose PK studies using NucleomaxXH to determine whether repeated dosing had a cumulative effect on plasma uridine levels. Ethics Statement All studies were approved by the Clinical and Translational Sciences Institute Clinical Research Center (CRC) at San Francisco General Hospital Advisory Committee and the University of California San Francisco Institutional Review Board. All subjects provided written informed consent. Product Analysis To determine the total nucleoside content in NucleomaxXH, the contents of 10 sachets, each containing 36 gm of NucleomaxXH, were combined, homogenized and passed through a 60 mesh sieve. Nucleosides were extracted in aqueous solution containing ascorbic acid and quantified by reversed-phase high performance liquid chromatography (HPLC) with ultraviolet (UV) detection. Laboratory validation was performed to determine the repeatability, accuracy, selectivity, ruggedness and linearity of the method. To determine the repeatability precision, four replicate test preparations of the NucleomaxXH product were prepared and analyzed on three separate days, for a total of 12 replicate preparations. The within-day, between-day, and total repeatability precision of the uridine and TAU content were calculated from the results. Accuracy was determined by spiking a placebo (a mixture of casein and sucrose) with ur (...truncated)