The essentiality of thiamin stems from its roles as a co-factor (mainly in the form of thiamin pyrophosphate, TPP) in critical metabolic reactions including oxidative energy metabolism and reduction of cellular oxidative stress. Like other mammalian cells, pancreatic acinar cells (PAC) obtain thiamin from their surroundings and convert it to TPP; mitochondria then take up TPP by a carrier-mediated process that involves the mitochondrial TPP (MTPP) transporter (MTPPT; product of SLC25A19 gene). Previous studies have characterized different physiological/biological aspects of the MTPP uptake process, but little is known about its possible adaptive-regulation. We addressed this issue using pancreatic acinar 266-6 cells (PAC 266-6) maintained under thiamin-deficient (DEF) and over-supplemented (OS) conditions, as well as thiamin-DEF and -OS transgenic mice carrying the SLC25A19 promoter. We found that maintaining PAC 266-6 under thiamin-DEF condition leads to a significant induction in mitochondrial [³H]-TPP uptake, as well as in level of expression of the MTPPT protein and mRNA compared to -OS cells. Similar findings were observed in mitochondria from thiamin-DEF mice compared to -OS. Subsequently, we demonstrated that adaptive-regulation of MTTP protein was partly mediated via transcriptional mechanism(s) via studies with PAC 266-6 transfected with the SLC25A19 promoter, and transgenic mice carrying the SLC25A19 promoter. This transcriptional regulation appeared to be, at least in part, mediated via epigenetic mechanism(s) involving histone modifications. These studies report, for the first time, that the PAC mitochondrial TPP uptake process is adaptively-regulated by the prevailing thiamin level and that this regulation is transcriptionally mediated and involves epigenetic mechanism(s).