Molecular mechanisms of the non-coenzyme action of thiamin in brain. Biochemical, structural and pathway analysis

Thiamin (vitamin B1) is a pharmacological agent boosting central metabolism through the action of the coenzyme thiamin diphosphate (ThDP). However, positive effects, including improved cognition, of high thiamin doses in neurodegeneration may be observed without increased ThDP or ThDPdependent enzymes in brain. Here, we determine protein partners and metabolic pathways where thiamin acts beyond its coenzyme role. Malate dehydrogenase, glutamate dehydrogenase and pyridoxal kinase were identified as abundant proteins binding to thiamin- or thiazolium-modified sorbents. Kinetic studies, supported by structural analysis, revealed allosteric regulation of these proteins by thiamin and/or its derivatives. Thiamin triphosphate and adenylated thiamin triphosphate activate glutamate dehydrogenase. Thiamin and ThDP regulate malate dehydrogenase isoforms and pyridoxal kinase. Thiamin regulation of enzymes related to malate-aspartate shuttle may impact on malate/citrate exchange, responsible for exporting acetyl residues from mitochondria. Indeed, bioinformatic analyses found an association between thiamin- and thiazolium-binding proteins and the term acetylation. Our interdisciplinary study shows that thiamin is not only a coenzyme for acetyl-CoA production, but also an allosteric regulator of acetyl-CoA metabolism including regulatory acetylation of proteins and acetylcholine biosynthesis. Moreover, thiamin action in neurodegeneration may also involve neurodegeneration-related 14-3-3, DJ-1 and β-amyloid precursor proteins identified among the thiamin- and/or thiazolium-binding proteins

ARDD 2020: from aging mechanisms to interventions

Aging is emerging as a druggable target with growing interest from academia, industry and investors. New technologies such as artificial intelligence and advanced screening techniques, as well as a strong influence from the industry sector may lead to novel discoveries to treat age-related diseases. The present review summarizes presentations from the 7th Annual Aging Research and Drug Discovery (ARDD) meeting, held online on the 1st to 4th of September 2020. The meeting covered topics related to new methodologies to study aging, knowledge about basic mechanisms of longevity, latest interventional strategies to target the aging process as well as discussions about the impact of aging research on society and economy. More than 2000 participants and 65 speakers joined the meeting and we already look forward to an even larger meeting next year. Please mark your calendars for the 8th ARDD meeting that is scheduled for the 31st of August to 3rd of September, 2021, at Columbia University, USA

Identification of differentially expressed micro- and mRNA clusters in blood of patients with coronary artery disease: intersection with calcification pathways and implications in cardio-vascular diseases

<p>Coronary artery disease (CAD) is one of the main and common types of cardio-vascular diseases, which occurs as a result of atherosclerotic plaque formation in blood vessels during ageing. Increased levels of calcium deposition were detected in blood vessels of patients with CAD and linked to early CAD formation. Here, we hypothesized that these two processes are linked and possess common molecular basis, which is realized through regulation of target genes involved in calcification and CAD.</p> <p>To validate our hypothesis, we used a bioinformatics approach, in which micro- and mRNA data of blood samples from 12 patients with CAD were analyzed. Several high quality data sets were extracted from GEO database, analyzed by commercially available program TR GeneGo Metacore, statistically verified by J-express algorithms and analyzed using statistical methods implemented in R.</p> <p>Analysis of GEO data revealed patterns of differentially expressed microRNAs in patients with CAD. We have shown the involvement of the differentially expressed microRNAs (hsa-miR-154; hsa-miR-451; hsa-miR-17) in signalling pathways associated with vascular calcification. Additionally, we obtained data of mRNA expression, showing several clusters of genes, which are involved in vascular calcification pathways in patients with CAD and developed an interaction map of differentially expressed genes in the blood of CAD patients and genes associated with vascular calcification.</p> <p>We conclude that patients with CAD have several differentially expressed gene markers, which may have different impact on calcification development. Data provided may have a positive outcome for cardio-vascular diagnosis strategy and personalized medicine.</p

Multiple Forms of Glutamate Dehydrogenase in Animals: Structural Determinants and Physiological Implications

Glutamate dehydrogenase (GDH) of animal cells is usually considered to be a mitochondrial enzyme. However, this enzyme has recently been reported to be also present in nucleus, endoplasmic reticulum and lysosomes. These extramitochondrial localizations are associated with moonlighting functions of GDH, which include acting as a serine protease or an ATP-dependent tubulin-binding protein. Here, we review the published data on kinetics and localization of multiple forms of animal GDH taking into account the splice variants, post-translational modifications and GDH isoenzymes, found in humans and apes. The kinetic properties of human GLUD1 and GLUD2 isoenzymes are shown to be similar to those published for GDH1 and GDH2 from bovine brain. Increased functional diversity and specific regulation of GDH isoforms due to alternative splicing and post-translational modifications are also considered. In particular, these structural differences may affect the well-known regulation of GDH by nucleotides which is related to recent identification of thiamine derivatives as novel GDH modulators. The thiamine-dependent regulation of GDH is in good agreement with the fact that the non-coenzyme forms of thiamine, i.e., thiamine triphosphate and its adenylated form are generated in response to amino acid and carbon starvation

Cellular thiamine status is coupled to function of mitochondrial 2-oxoglutarate dehydrogenase

Decreased thiamine and reduced activity of thiamine diphosphate (ThDP)-dependent 2-oxoglutarate dehydrogenase (OGDH) cause neurodegeneration. We hypothesized on concerted cell-specific regulation of the thiamine metabolism and ThDP-dependent reactions. We identified a smaller thiamine pool, a lower expression of the mitochondrial ThDP transporter, and a higher expression of OGDH in rat astrocytes versus neuroblastoma N2A. According to the data, the astrocytic OGDH may be up-regulated by an increase in intracellular ThDP, while the neuroblastomal OGDH functions at full ThDP saturation. Indeed, in rat astrocytes and brain cortex, OGDH inhibition by succinyl phosphonate (SP) enlarged the pool of thiamine compounds. Increased ThDP level in response to the OGDH inhibition presumably up-regulated the enzyme to compensate for a decrease in reducing power which occurred in SP-treated astrocytes. Under the same SP treatment of N2A cells, their thiamine pool and reducing power were unchanged, although SP action was evident from accumulation of glutamate. The presented data indicate that functional interplay between OGDH, other proteins of the tricarbocylic acid cycle and proteins of thiamine metabolism is an important determinant of physiology-specific networks and their homeostatic mechanisms

Molecular mechanisms of the non-coenzyme action of thiamin in brain: biochemical, structural and pathway analysis.

Thiamin (vitamin B1) is a pharmacological agent boosting central metabolism through the action of the coenzyme thiamin diphosphate (ThDP). However, positive effects, including improved cognition, of high thiamin doses in neurodegeneration may be observed without increased ThDP or ThDP-dependent enzymes in brain. Here, we determine protein partners and metabolic pathways where thiamin acts beyond its coenzyme role. Malate dehydrogenase, glutamate dehydrogenase and pyridoxal kinase were identified as abundant proteins binding to thiamin- or thiazolium-modified sorbents. Kinetic studies, supported by structural analysis, revealed allosteric regulation of these proteins by thiamin and/or its derivatives. Thiamin triphosphate and adenylated thiamin triphosphate activate glutamate dehydrogenase. Thiamin and ThDP regulate malate dehydrogenase isoforms and pyridoxal kinase. Thiamin regulation of enzymes related to malate-aspartate shuttle may impact on malate/citrate exchange, responsible for exporting acetyl residues from mitochondria. Indeed, bioinformatic analyses found an association between thiamin- and thiazolium-binding proteins and the term acetylation. Our interdisciplinary study shows that thiamin is not only a coenzyme for acetyl-CoA production, but also an allosteric regulator of acetyl-CoA metabolism including regulatory acetylation of proteins and acetylcholine biosynthesis. Moreover, thiamin action in neurodegeneration may also involve neurodegeneration-related 14-3-3, DJ-1 and β-amyloid precursor proteins identified among the thiamin- and/or thiazolium-binding proteins