Vitamin B1 (thiamine) is critical in normal cellular metabolism. Thiamine deficiency diseases, notably wet and dry beriberi, and Wernicke's encephalopathy, a severe neurological syndrome associated with thiamine deficiency, are associated with many diseases and conditions that result from under-nutrition and malabsorption of thiamine (e.g. alcoholism, bariatric surgery) or hyper-metabolic states (e.g., cancer). However mechanistic studies following a recent and disastrous clinical drug trial (that was terminated because the drug, fedratinib, led to Wernicke's encephalopathy) highlighted the importance of pharmaceutical agents as contributors to thiamine deficiency. That is, fedratinib was shown to be a potent inhibitor of thiamine absorption via the thiamine transporter, SLC19A3. In this research application, we bring together NIH and USDA nutrition supported researchers, in response to PAR-15-024. In particular, we propose to test the hypotheses that commonly used medications inhibit SLC19A3-mediated intestinal absorption of thiamine resulting in drug-vitamin interactions. Secondly, we propose that these drug-thiamine interactions produce a detectable metabolic signature that relates to reduction in the activity of enzymes that are dependent on thiamine pyrophosphate (TPP), the active metabolite of thiamine. Our hypotheses are based on exciting preliminary studies in our laboratories demonstrating that several prescription drugs, e.g., metformin, pyrimethamine and amiloride, are inhibitors of SLC19A3.
Three aims are proposed: 1. Develop and characterize a humanized transgenic mouse model of SLC19A3 that can serve as an animal model to test drugs for their potential to cause thiamine deficiency. 2. Determine the effects of metformin on the pharmacokinetics and metabolic signatures of thiamine in healthy volunteers using a randomized crossover study; and 3. Use a novel miniaturized assay to screen a 2000-compound library of prescription drugs and bioactives to identify compounds that inhibit SLC19A3 and determine the key structural moieties for SLC19A3 inhibition using quantitative structure activity relationship modeling (QSAR). A multi-tiered approach will be used for the proposed studies including drug-vitamin interaction studies in healthy volunteers; metabolomic methods to identify metabolic signatures of thiamine; small molecule screening to identify inhibitors of SLC19A3; and creation and characterization of humanized mouse models of SLC19A3. Collectively, these novel studies will lead to a new knowledge of drug-vitamin interactions and their metabolic signatures. Specifically, the studies will lead to new tools that can be used in nutrient research and to a recognition that therapeutic drugs may adversely affect thiamine absorption and contribute to thiamine deficiency.
Poor nutrition and many diseases are associated with low levels of vitamin B1 (thiamine), which in turn causes health problems such as delirium and tremors. In this research, we will determine whether therapeutic medications contribute to low levels of thiamine by preventing its absorption in the stomach and intestine. Various research methods, which include human and cellular studies and computer methods will be used.
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