3-Hydroxybutyrate Is Active Compound in Flax that Upregulates Genes Involved in DNA Methylation

Abstract

In mammalian cells, 3-hydroxybutyrate (3-HB) is not only an intermediate metabolite during the oxidation of fatty acids, but also an important signaling molecule. On the other hand, the information about the metabolism or function of this compound in plants is scarce. In our study, we show for the first time that this compound naturally occurs in flax. The expression of bacterial β-ketothiolase in flax affects expression of endogenous genes of the 3-HB biosynthesis pathway and the compound content. The increase in 3-HB content in transgenic plants or after control plants treatment with 3-HB resulted in upregulation of genes involved in chromatin remodeling. The observation that 3-HB is an endogenous activator of methyltransferase 3 (CMT3), decreased DNA methylation I (DDM1), DEMETER DNA glycosylase (DME), and an inhibitor of sirtuin 1 (SRT1) provides an example of integration of different genes in chromatin remodeling. The changes in chromatin remodeling gene expression concomitant with those involved in phenolics and the lignin biosynthesis pathway suggest potential integration of secondary metabolic status with epigenetic changes.Initially, investigated degradation assays carried out with isolated PHB granules revealed, as a first step, the release of 3-hydroxybutyrate (3-HB) in a hydrolytic reaction, then conversion to 3-hydroxybutyryl coenzyme A and further to acetyl-CoA via acetoacetyl-CoA in the reverse direction and by the same enzymes of the synthesis pathway. In a more recent study, the intracellular degradation of PHB by PHB depolymerase PhaZ1 to (n)-3-HB-CoA and its conversion to crotonyl-CoA converted to acetoacetyl-CoA finally cleaved by a 3-ketoacyl-CoA thiolase to two molecules of acetyl-CoA was shown [6,7].In vertebrates, 3-HB is a product of the normal metabolism of fatty acid oxidation. However the possibility that part of 3-HB derives from bacterial PHB metabolism cannot be excluded as gut microbiota can be a source of PHB [8]. The possibility that part of 3-HB derives from bacterial PHB metabolism cannot be excluded. The 3-HB in humans serves as a metabolic fuel in tissues and its synthesis is increased during metabolic stress conditions, such as exercise, fasting, and severe acute illness. Furthermore, 3-HB has been reported to lower reactive oxygen species (ROS) dependent oxidative stress [9], to inhibit histone deacetylase (HDAC) induced by oxidative stress [10] and to promote the expression of brain-derived neurotrophic factor [11]. It has also been reported that specific supplementation with 3-HB increases lifespan in C. elegans roundworms by 20% [12]. A more recent study reported that 3-HB infusion in ischemia in mice reduced infarct size, mediated by histone deacetylase sirtuin 3, and reduced ROS production [13]. In the mitochondria 3-HB is also known to increase the expression of neurotrophic factor that facilitates respiration [14]. Very recently the study of healthy human subjects with and without continuous infusion of 3-HB demonstrated reduced cerebral glucose uptake and neuroprote...

3-Hydroxybutyrate as a Metabolite and a Signal Molecule Regulating Processes of Living Organisms

“…However, there are reports that PHB can also be synthesized naturally in plants [ 15 , 154 ]. The work of Mierziak et al proves that 3-hydroxybutyrate occurs naturally in flax [ 155 ]. It is not yet possible to identify the origin of 3-HB in plants.…”

“…Another possibility is de novo synthesis from acetyl-CoA or another as yet undiscovered metabolic pathway. As mentioned earlier, plants contain enzymes that are involved in the synthesis of 3-HB in bacteria [ 15 , 130 , 155 ]. Flax with the introduced bacterial β-ketothiolase gene (the first enzyme in the 3-HB synthesis pathway) showed an increased content of 3-HB as well as overexpression of the endogenous plant beta-ketothiolase gene.…”

“…Flax with the introduced bacterial β-ketothiolase gene (the first enzyme in the 3-HB synthesis pathway) showed an increased content of 3-HB as well as overexpression of the endogenous plant beta-ketothiolase gene. This may suggest the metabolic control of gene expression in its synthesis pathway by 3-HB [ 155 ].…”

“…Literature data indicate that HDAC inhibition by beta-hydroxybutyrate in animals correlates with global changes in the transcription of many genes in animal cells. In the case of plants, it seems that genes involved in the phenylpropanoid pathway may be one of the recipients of epigenetic changes induced by 3-HB [ 155 ].…”

Biostimulant Effects of Chaetomium globosum and Minimedusa polyspora Culture Filtrates on Cichorium intybus Plant: Growth Performance and Metabolomic Traits

“…Differently from animals, in which 3-OH-butyrate is an intermediate metabolite of fatty acids, the physiological importance and the metabolism of 3-OH-butyrate in plants are not fully understood and characterized. Mierziak et al ( 2020 ) demonstrated that 3-OH-butyrate occurs naturally in flax and could act as a regulatory molecule that most likely influences the expression of genes involved in DNA methylation, thereby altering DNA methylation levels. Recent studies showed that plants contain enzymes such as β-ketothiolase (EC 2.3.1.9) and acetoacetyl-CoA-reductase (EC 1.1.1.36), which are involved in the synthesis of 3-OH-butyrate as in bacteria and animals (Xu et al, 1997 ; Beaudoin et al, 2009 ; Jin et al, 2012 ; Tsuda et al, 2016 ; Mierziak et al, 2021 ).…”