A 2-hydroxybutyrate-mediated feedback loop regulates muscular fatigue 2024 Wadsworth et al

Andy

Andy

Retired committee member
[In mice]

Abstract

Several metabolites have been shown to have independent and at times unexpected biological effects outside of their metabolic pathways. These include succinate, lactate, fumarate, and 2-hydroxyglutarate. 2-Hydroxybutyrate (2HB) is a byproduct of endogenous cysteine synthesis, produced during periods of cellular stress. 2HB rises acutely after exercise; it also rises during infection and is also chronically increased in a number of metabolic disorders. We show here that 2HB inhibits branched-chain aminotransferase enzymes, which in turn triggers a SIRT4-dependent shift in the compartmental abundance of protein ADP-ribosylation. The 2HB-induced decrease in nuclear protein ADP-ribosylation leads to a C/EBPβ-mediated transcriptional response in the branched-chain amino acid degradation pathway. This response to 2HB exposure leads to an improved oxidative capacity in vitro. We found that repeated injection with 2HB can replicate the improvement to oxidative capacity that occurs following exercise training. Together, we show that 2-HB regulates fundamental aspects of skeletal muscle metabolism.

eLife assessment
The work by Johnson and co-workers has identified an important role of 2-Hydroxybutyrate in skeletal muscle oxidative capacity in the early stages of exercise. Mechanistically, they show convincing data to support a role of 2-Hydroxybutyrate in the regulation of BCAA metabolism via SIRT4, ADP-Ribosylation, and CEBP. However, whether this is the sole mechanism and if these translate to longer exercise training regimes requires future experiments.

Open access, https://elifesciences.org/articles/92707#s4
 
Andy said:
2-Hydroxybutyrate (2HB) is a byproduct of endogenous cysteine synthesis, produced during periods of cellular stress. 2HB rises acutely after exercise
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2-hydroxybutyrate and cysteine were both elevated in Jason et al 2022's pre-illness data study in ME/CFS:

chillier said:
Despite the small n=18 sample size and weird issues with categorization of severe ME I really like this paper. I like that by looking at the metabolites prior to illness maybe you are looking at a risk factor for ME, instead of what could be fallout. They use Bonferroni multiple test correction with an adjusted p value cut off of 0.01. I respect the restraint, that might even be a little too strict. I've reanalysed it using Benjamini-Hochberg correction and a FDR cut off of 0.05 to see if there might be anything else interesting in there. Here are scatter plots for the 25 metabolites that meet those criteria ordered from most to least significant (from left to right).

View attachment 21342
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I don't recall seeing it in other metabolomics studies, but on the other hand the design of this one is quite unique.
 
Thanks for posting @Andy. This possibly deserves some discussion as to what goes wrong between what is a normal muscle recovery post exercise and what is metabolic abnormality, particularly seeing it is also identified pre ME/CFS onset.

Elevated 2-Hydroxybutyrate (2HB) is usually a sign of pre-diabetes or insulin resistance or hyperinsulinemia. Within 2 years before my ME/CFS onset, I had to do a blood glucose test following an abnormal Hb1c test. My fasting blood glucose tested fine. Within a couple of months post ME/CFS onset, I experienced hyperglycemic events with sweetened food. I can only assume my 2HB was also elevated pre and post onset of ME/CFS.

In the study above I refer to "We show here that 2HB inhibits branched-chain aminotransferase enzymes...".

From the following study:
The mechanism of branched-chain amino acid transferases in different diseases: Research progress and future prospects
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9478667/

Inflammatory disease (ID) is a defense response of the human body against the invasion of pathogens. It was a common clinical-pathological process. ID can develop into a series of diseases, including cancer. One pathogenesis of chronic ID was the activation of human macrophages stimulated by pro-inflammatory factors, which increases the levels of IRG1 and itaconic acid in vivo. Studies have shown that BCAT was overexpressed in macrophages of ID, and BCAT1 regulates macrophage activation through redox-mediated mitochondrial function (93, 94). This was reflected in that inhibiting the expression of BCAT1 could effectively reduce oxygen consumption and glycolysis, and reduced the content of IRG1, itaconic acid and α-KG, thereby reduced the symptoms of inflammation. In addition, inhibition of BCAT1 expression can effectively alleviate the symptoms of sepsis-induced reduction in muscle protein synthesis in systemic inflammation (95). These studies suggest that BCAT1 may be a potential target for targeted therapy of macrophage-dependent ID by indicating BCAT1.
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Here is the metabolic pathway for the production of 2HB: a byproduct of (excess) 2ketobutyrate (2KB) mediated by lactate dehydrogenase (LDH), the enzymes activity enhanced with high NADH/NAD+ ratio.

[Courtesy of the following link:
Which Role Plays 2-Hydroxybutyric Acid on Insulin Resistance?
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8703345/]

tileshop.fcgi


Under hyperglycemic circumstances caused by IR, more glucose will flow through the glycolytic pathway, producing more pyruvate and acetyl-CoA, leading to more NADH synthesis. This way, NADH accumulates and initiates an electron pressure on the mitochondrial electron transport chain, resulting in oxidative stress since NAD+ is not supplied. Despite the fact that glutathione (GSH) exhibits antioxidant properties and is useful to balance the system when NADPH levels become lower, the GSH is unable to regenerate. As a result, cellular antioxidant activity may be compromised, resulting in increased levels of reactive oxygen species capable of attacking macromolecules and inducing oxidative damage. To overcome the oxidative stress, hepatic cells generate GSH by cysteine anabolism, which produces the by-product α-ketobutyrate that will be then converted to 2-hydroxybutiric acid. Simultaneously, FFA plays a key role and is inextricably linked to IR. Lipid oxidation (triglycerides and phospholipids are hydrolyzed by cellular lipases) in IR-treated adipose tissue in increased FFA concentrations, which are oxidized by the TCA cycle and hence produce NADH [35]. Such a TCA cycle excess results in the accumulation of amino acids such as glutamate and alanine, as well as αKB, the precursor for 2HB [27,36]. It is worth noting the symbiotic effect between the FFA entrance in non-adipose tissues and the development of IR [35]. In the end, 2HB levels and biological activity are highly translated in the human body (Figure 1).
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So, while this might explain (somewhat) why 2HB increases with insulin resistance in response to infection, but why does it increase post exercise, and is there a link between the two involved in PEM? There might be a link here to explain RED-S syndrome too?


I do observe some anomalies with respect to ME/CFS however, in that metabolic studies suggest ME/CFS patients are producing LESS pyruvate and furthermore, there is evidence of reduced lipid oxidation and reduced acetate levels, that more energy is being derived by amino acid catabolism. So how is the NADH/NAD+ ratio impacted by this...high production of NADH via the PPP I assume?
 
chillier said:
@forestglip was 2-hydroxybutyrate significant in that study? Is it possible to get the mann whitney p value for this? I wasn't clear in your post whether it was significant or simply alphabetically at the top of the list of the all metabolites with a positive fold change.
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Oh, sure. Using wilcox.test(data[[column_name]] ~ data$Group, exact=TRUE):

2-hydroxybutyrate/2-hydroxyisobutyrate 0.8391037
2-hydroxybutyrate_2-hydroxyisobutyrate_box.png

I should make that list more clear what it is showing.
 
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