BACKGROUND We hypothesized that obesity-associated hepatosteatosis is a pathophysiological chemical depot for fat-soluble vitamins and altered normal physiology. Using α-tocopherol (vitamin E) as a model vitamin, pharmacokinetics and kinetics principles were used to determine whether excess liver fat sequestered α-tocopherol in women with obesity-associated hepatosteatosis versus healthy controls.METHODS Custom-synthesized deuterated α-tocopherols (d3- and d6-α-tocopherols) were administered to hospitalized healthy women and women with hepatosteatosis under investigational new drug guidelines. Fluorescently labeled α-tocopherol was custom-synthesized for cell studies.RESULTS In healthy subjects, 85% of intravenous d6-α-tocopherol disappeared from the circulation within 20 minutes but reappeared within minutes and peaked at 3–4 hours; d3- and d6-α-tocopherols localized to lipoproteins. Lipoprotein redistribution occurred only in vivo within 1 hour, indicating a key role of the liver in uptake and re-release. Compared with healthy subjects who received 2 mg, subjects with hepatosteatosis had similar d6-α-tocopherol entry rates into liver but reduced initial release rates (P < 0.001). Similarly, pharmacokinetics parameters were reduced in hepatosteatosis subjects, indicating reduced hepatic d6-α-tocopherol output. Reductions in kinetics and pharmacokinetics parameters in hepatosteatosis subjects who received 2 mg were echoed by similar reductions in healthy subjects when comparing 5- and 2-mg doses. In vitro, fluorescent-labeled α-tocopherol localized to lipid in fat-loaded hepatocytes, indicating sequestration.CONCLUSIONS The unique role of the liver in vitamin E physiology is dysregulated by excess liver fat. Obesity-associated hepatosteatosis may produce unrecognized hepatic vitamin E sequestration, which might subsequently drive liver disease. Our findings raise the possibility that hepatosteatosis may similarly alter hepatic physiology of other fat-soluble vitamins.TRIAL REGISTRATION ClinicalTrials.gov, NCT00862433.FUNDING National Institute of Diabetes and Digestive and Kidney Diseases and NIH grants DK053213-13, DK067494, and DK081761.
Pierre-Christian Violet, Ifechukwude C. Ebenuwa, Yu Wang, Mahtab Niyyati, Sebastian J. Padayatty, Brian Head, Kenneth Wilkins, Stacey Chung, Varsha Thakur, Lynn Ulatowski, Jeffrey Atkinson, Mikel Ghelfi, Sheila Smith, Hongbin Tu, Gerd Bobe, Chia-Ying Liu, David W. Herion, Robert D. Shamburek, Danny Manor, Maret G. Traber, Mark Levine
Submitter: Francesco Galli | firstname.lastname@example.org
Department of Pharmaceutical Sciences, University of Perugia, Italy
Published March 13, 2020
Dear EIC and readers,
This e-letter is to inform you that Violet P-C et al. in their study “Vitamin E sequestration by liver fat in humans” now in pre-print on JCI Insight (doi: 10.1172/jci.insight.133309) ignores past that, in our opinion, has already demonstrated the sequestration, and thus the accumulation, of vitamin E in fatty liver. This was demonstrated in humans by Nagita and Ando more than 20 years ago (1) and was recapitulated by Bartolini et al. (2) in animal models and human liver cells that develop steatosis as a consequence of the same treatments utilized in the study of Violet et al.
Furthermore, two recent review articles discussed this sequestration/accumulation of vitamin E as a risk factor for changes in the vitamin status, hepatic lipotoxicity, and evolution of NAFLD to NASH (3, 4). Finally, vitamin E accumulation was discussed as a possible cause of increased vitamin E oxidation in fatty liver patients in (5).
In addition, in vitro data about the accumulation in lipid droplets of fluorescent vitamin E during the development of steatosis published by Violet et al. were already demonstrated by Bartolini et al. (2), utilizing a similar cellular approach and reagents (the fluorescent probe utilized in our study was kindly provided by one of the co-authors of this article).
Therefore, although I recognize that this JCI Insight study adds some information on vitamer and metabolite kinetics, as well as on lipoprotein-related aspects of this sequestration, the accumulation of vitamin E in the fatty liver of humans is not an original finding, as it is for the mechanistic and subcellular aspects that characterize this process. This is the main information the reader catches reading Violet et al. In our opinion, this is a duplication of already existing scientific information.
Submitter: Mark Levine | email@example.com
Authors: Mark Levine, Pierre-Christian Violet, and Ifechukwude Ebenuwa
Published March 13, 2020
While we appreciate the feedback from the author, we feel that the assertions made are thoroughly unsupported by any of the articles and references cited [1-5]. How can it be that the concept of sequestration was “already demonstrated”, yet the word sequestration doesn’t even appear in any of the references cited? A major finding of our paper is that excess liver fat sequesters vitamin E and makes it less available locally in people without detectable liver disease . Over time, such sequestration has the potential to cause disease. Additional points in response to this letter: 1) the concept of a-tocopherol sequestration in liver fat in humans could not be addressed without the novel dual isotope technique in which intravenous and oral deuterated a-tocopherols are administered simultaneously, with kinetics measurements of tocopherols released from liver in our specifically screened and selected cohort. Such studies have never been conducted previously in humans . 2) A key inference from our findings is that a-tocopherol sequestration in fat may play a role in the initial disease development. 3) Our study focuses on subjects who do not have advanced liver disease, but rather simply have liver fat, or hepato-steatosis, with no evidence of liver damage . In contrast, the references cited [1-5] concern a-tocopherol in liver disease once it has already occurred. For example, in the first study cited , every subject had current or very recent liver injury, in contrast to our subjects who had fatty liver only. 4) The second reference , as quoted from the paper, describes a model to “characterize the effect that lipid accumulation and lipotoxicity may have on CYP4F2 gene transcription and protein expression”. The use of reagents similar to what were used by us has no relevance if the insights about their use are not articulated. Once again, no mention of tocopherol sequestration in fat, nor that such sequestration could drive disease development, as a consequence of localized deficiency. 5) We have found no evidence to suggest that findings or conclusions similar to ours  were reached in any of the references provided [1-5]. In Dr. Albert Szent-Gyorgi’s words, “Discovery is seeing what everybody else has seen, and thinking what nobody else has thought.”
Mark Levine M.D.
Pierre-Christian Violet Ph.D.
Ifechukwude Ebenuwa M.D.
Molecular and Clinical Nutrition Section
National Institute of Diabetes and Digestive and Kidney Diseases
National Institutes of Health
Bethesda MD USA 20892 -1372