Thiamine deficiency contributes to synapse and neural circuit defects

BACKGROUND: The previous studies have demonstrated the reduction of thiamine diphosphate is specific to Alzheimer's disease (AD) and causal factor of brain glucose hypometabolism, which is considered as a neurodegenerative index of AD and closely correlates with the degree of cognitive impairment. The reduction of thiamine diphosphate may contribute to the dysfunction of synapses and neural circuits, finally leading to cognitive decline. RESULTS: To demonstrate this hypothesis, we established abnormalities in the glucose metabolism utilizing thiamine deficiency in vitro and in vivo, and we found dramatically reduced dendrite spine density. We further detected lowered excitatory neurotransmission and impaired hippocampal long-term potentiation, which are induced by TPK RNAi in vitro. Importantly, via treatment with benfotiamine, Aß induced spines density decrease was considerably ameliorated. CONCLUSIONS: These results revealed that thiamine deficiency contributed to synaptic dysfunction which strongly related to AD pathogenesis. Our results provide new insights into pathogenesis of synaptic and neuronal dysfunction in AD.

A Korean Female Patient with Thiamine-responsive Pyruvate Dehydrogenase Complex Deficiency Due to a Novel Point Mutation (Y161C)in the PDHA1 Gene

Pyruvate dehydrogenase complex (PDHC) deficiency is mostly due to mutations in the X-linked E1alpha subunit gene (PDHA1). Some of the patients with PDHC deficiency showed clinical improvements with thiamine treatment. We report the results of biochemical and molecular analysis in a female patient with lactic acidemia. The PDHC activity was assayed at different concentrations of thiamine pyrophosphate (TPP). The PDHC activity showed null activity at low TPP concentration (1 x 10(-3) mM), but significantly increased at a high TPP concentration (1 mM). Sequencing analysis of PDHA1 gene of the patient revealed a substitution of cysteine for tyrosine at position 161 (Y161C). Thiamine treatment resulted in reduction of the patient's serum lactate concentration and dramatic clinical improvement. Biochemical, molecular, and clinical data suggest that this patient has a thiamine-responsive PDHC deficiency due to a novel mutation, Y161C. Therefore, to detect the thiamine responsiveness it is necessary to measure activities of PDHC not only at high but also at low concentration of TPP.

Regulation of mammalian pyruvate dehydrogenase complex by phosphorylation: complexity of multiple phosphorylation sites and kinases

This review summarizes the recent developments on the regulation of human pyruvate dehydrogenase complex (PDC) by site-specific phosphorylation by four kinases. Mutagenic analysis of the three phosphorylation sites of human pyruvate dehydrogenase (E1) showed the site-independent mechanism of phosphorylation as well as site-independent dephosphorylation of the three phosphorylation sites and the importance of each phosphorylation site for the inactivation of E1. Both the negative charge and size of the group introduced at site 1 were involved in human E1 inactivation. Mechanism of inactivation of E1 was suggested to be site-specific. Phosphorylation of site 1 affected E1 interaction with the lipoyl domain of dihydrolipoamide acetyltransferase, whereas phosphorylation site 3 appeared to be closer to the thiamine pyrophosphate (TPP)-binding region affecting coenzyme interaction with human E1. Four isoenzymes of pyruvate dehydrogenase kinase (PDK) showed different specificity for the three phosphorylation sites of E1. All four PDKs phosphorylated sites 1 and 2 in PDC with different rates, and only PDK1 phosphorylated site 3. PDK2 was maximally stimulated by the reduction/acetylation of the lipoyl groups of E2. Presence of the multiple phosphorylation sites and isoenzymes of PDK is important for the tissue-specific regulation of PDC under different physiological conditions.

Utilidad del pirofosfato de tiamina (cocarboxilasa) estable en solución en dos casos posinfarto del miocardio / Usefulnes of solution-stable tiamyne pyrophosphate (cocarboxylase) on two cases of postmyocardial infarction

En este estudio clínico se analizó el papel central que desempeña la cocarboxilasa (pirofosfato de tiamina) en el metabolismo energético celular, en particular en el tejido miocárdico, cuya dependencia de la energía es absolutamente constante. Se estudiaron dos casos de posinfarto agudo del miocardio, en los cuales la zona de necrosis desapareció después del tratamiento con cocarboxilasa con sus enlaces de fosfato estables en solución fisiológica. En uno de estos pacientes se mostró lisis completa de un trombo