Thiamine Deficiency in Cultured Neuroblastoma Cells: Effect on Mitochondrial Function and Peripheral Benzodiazepine Receptors

Abstract

When neuroblastoma cells were transferred to a medium of low (6 nM) thiamine concentration, a 16‐fold decrease in total intracellular thiamine content occurred within 8 days. Respiration and ATP levels were only slightly affected, but addition of a thiamine transport inhibitor (amprolium) decreased ATP content and increased lactate production. Oxygen consumption became low and insensitive to oligomycin and uncouplers. At least 25% of mitochondria were swollen and electron translucent. Cell mortality increased to 75% within 5 days. [3H]PK 11195, a specific ligand of peripheral benzodiazepine receptors (located in the outer mitochondrial membrane) binds to the cells with high affinity (KD = 1.4 ± 0.2 nM). Thiamine deficiency leads to an increase in both Bmax and KD. Changes in binding parameters for peripheral benzodiazepine receptors may be related to structural or permeability changes in mitochondrial outer membranes. In addition to the high‐affinity (nanomolar range) binding site for peripheral benzodiazepine ligands, there is a low‐affinity (micromolar range) saturable binding for PK 11195. At micromolar concentrations, peripheral benzodiazepines inhibit thiamine uptake by the cells. Altogether, our results suggest that impairment of oxidative metabolism, followed by mitochondrial swelling and disorganization of cristae, is the main cause of cell mortality in severely thiamine‐deficient neuroblastoma cells.

OCT1 is a high-capacity thiamine transporter that regulates hepatic steatosis and is a target of metformin

“…6E and SI Appendix, Fig. S6 E and F), consistent with an effect of thiamine depletion on energy production, as has been observed previously (27). Consistently, β-oxidation (of 14 C-palmitic acid) was also elevated in hepatocytes isolated from the mice fed thiaminedeficient diets for 1 wk (3.8 ± 1.0 dpm/μg protein/2 h for Oct1 +/+ mice on a thiamine-deficient diet versus 3.0 ± 0.3 dpm/μg protein/2 h for Oct1 +/+ mice on normal chow).…”

Molecular Characterization of a Specific Thiamine Triphosphatase Widely Expressed in Mammalian Tissues

“…1 and 32). In thiamine deficiency models, all thiamine compounds are decreased (33)(34)(35), and it is thus difficult to estimate the contribution of each of these compounds to the symptoms or neuronal death observed. There is still no clear evidence for a regionspecific decrease of ThDP levels, and it remains uncertain how it can be linked to selective vulnerability (36).…”

Mechanisms involved in the inhibitory effect of chronic alcohol exposure on pancreatic acinar thiamin uptake

“…This is because reducing the intracellular level of an essential micronutrient like thiamin [which is involved in cellular energy metabolism, reduction of oxidative stress, and normal function/integrity of the mitochondria (1-3, 14, 26)] may lead to acute energy failure, oxidative stress, and impairment in mitochondrial function (2,3,5,14,26). This may weaken the pancreas and lower its defense mechanisms against subsequent external/internal insults.…”

“…The vitamin acts as a cofactor for multiple enzymes (transketolase, pyruvate dehydrogenase, ␣-ketoglutarate dehydrogenase, and branched-chain ketoacid dehydrogenase); these enzymes participate in a variety of metabolic reactions related to oxidative energy (sugar) metabolism, ATP production (1, 26), and reduction of cellular oxidative stress (3,14). Thus it is not surprising that cellular thiamin deficiency leads to acute energy failure and to a propensity for oxidative stress (2,3,5,14,26); such a deficiency also leads to functional and structural abnormalities in mitochondria (2).The pancreas is a complex organ with important exocrine and endocrine functions. A variety of disease conditions and factors affect the health of this vital organ, leading to significant morbidity and mortality.…”