Sensitivity to Thiamine Deficiency in Cultured Human Cells is Dependent on Cell Type and is Enhanced in Cells From Thiamine-Responsive Megaloblastic Anemia Patients

Abstract

To address tissue-specific variation in sensitivity to thiamine deficiency, three human cell types were grown in medium with various thiamine concentrations. The activity of a cytosolic and a mitochondrial thiamine diphosphate-dependent enzyme was examined. Each cell type displayed a unique response to thiamine depletion with respect to α-ketoglutarate dehydrogenase and transketolase activity and to inhibition of cell growth. Loss of α-ketoglutarate dehydrogenase activity was similar in lymphoblasts and fibroblasts, whereas loss of activity in neuroblastoma cells was significantly more resistant to thiamine depletion. Transketolase activity in neuroblastoma cells was only moderately resistant to thiamine depletion, with the activity in fibroblasts being the most and in lymphoblasts the least resistant. Total transketolase activity was 33% higher in fibroblasts than in lymphoblasts and neuroblastoma cells, indicating a differential requirement for production and maintenance of transketolase activity in this cell type. Compared with normal lymphoblasts, those derived from patients with thiamine-responsive megaloblastic anemia were 100 to 1000 times more sensitive to thiamine depletion. Although fibroblasts from these patients also demonstrated a 1000-fold increase in sensitivity with respect to transketolase activity, α-ketoglutarate dehydrogenase activity demonstrated no enhanced sensitivity. The results indicate a complex, cell-type dependent regulation of intracellular pools of thiamine and its phosphorylated derivatives in response to fluctuating extracellular thiamine levels.