Reinforcing the Evidence of Mitochondrial Dysfunction in [LC] Using a Multiplatform Mass Spectrometry-Based Metabolomics Approach, 2024, Martínez +

[SNT Gatchaman]

Reinforcing the Evidence of Mitochondrial Dysfunction in Long COVID Patients Using a Multiplatform Mass Spectrometry-Based Metabolomics Approach
Sara Martínez; Oihane E. Albóniga; María Rosa López-Huertas; Ana Gradillas; Coral Barbas

Despite the recent and increasing knowledge surrounding COVID-19 infection, the underlying mechanisms of the persistence of symptoms for a long time after the acute infection are still not completely understood.

Here, a multiplatform mass spectrometry-based approach was used for metabolomic and lipidomic profiling of human plasma samples from Long COVID patients (n = 40) to reveal mitochondrial dysfunction when compared with individuals fully recovered from acute mild COVID-19 (n = 40). Untargeted metabolomic analysis using CE-ESI(+/−)-TOF-MS and GC-Q-MS was performed. Additionally, a lipidomic analysis using LC-ESI(+/−)-QTOF-MS based on an in-house library revealed 447 lipid species identified with a high confidence annotation level. The integration of complementary analytical platforms has allowed a comprehensive metabolic and lipidomic characterization of plasma alterations in Long COVID disease that found 46 relevant metabolites which allowed to discriminate between Long COVID and fully recovered patients.

We report specific metabolites altered in Long COVID, mainly related to a decrease in the amino acid metabolism and ceramide plasma levels and an increase in the tricarboxylic acid (TCA) cycle, reinforcing the evidence of an impaired mitochondrial function. The most relevant alterations shown in this study will help to better understand the insights of Long COVID syndrome by providing a deeper knowledge of the metabolomic basis of the pathology.

Link | PDF (Journal of Proteome Research)

 

[John Mac]

Cause or Effect?

 

[poetinsf]

Yet another paper with no stated hypothesis and unwarranted conclusion. Just poke around, find some anomaly, write paper about its grand implication so that you can put it under your belt.

 

[wigglethemouse]

Access to the Supplementary information is available here with no paywall
https://pubs.acs.org/doi/suppl/10.1021/acs.jproteome.3c00706/suppl_file/pr3c00706_si_001.pdf

From the supplementary information it can be seen that just like with ME/CFS metabolomics studies, ceramides (cer) are significantly altered as shown below. It's interesting that in the synthesis pathway this change in ceramides is shown to be related to sphingomyelins (SM) another metabolite that's shown up in ME/CFS studies.

 

[wigglethemouse]

Tess Falor on a Twitter thread about the Lisbon conference presentations reported Jonas Berquist & Chris Armstrong have been doing home and longitudinal sampling and have 3000 samples measuring 630 different metabolites with preliminary data showing low ceramides, which matches this and other studies.

 

[SNT Gatchaman]

Yet another paper with no stated hypothesis and unwarranted conclusion. Just poke around, find some anomaly, write paper about its grand implication so that you can put it under your belt.

Some introductory and concluding quotes from the paper —

Several targeted 6 and untargeted 7 metabolomics approaches have proven that one of the major dysregulations of the metabolic pathways described in Long COVID syndrome is that of the TCA cycle (tricarboxylic acid cycle)

To capture the full complexity of the biochemical networks ensuring the maximum coverage of the metabolome and lipidome, our study has been based on the use of a multiplatform metabolomic approach combining three separation techniques, coupled to mass spectrometry (MS). Specifically, in the present work we have used capillary electrophoresis (CE-MS), gas chromatography (GC-MS), and liquid chromatography (LCMS)

Data determining differences in the level of metabolic and lipidomic profiles when Long COVID is compared to fully recovered COVID-19 are scarce. 8 Thus, in this study we have recruited Long COVID patients, with persistent symptoms for more than 12 weeks after infection, and individuals fully recovered from mild COVID-19 infection

To our knowledge, this study represents the first in the field of Long COVID research that employs a multiplatform metabolomic approach

From all the lipid subclasses analyzed, the main one that resulted to be significantly altered in our comparison was ceramides, which were significantly decreased

significant decrease in Cer was observed in the plasma of Long COVID patients consequently suggesting a possible accumulation in other organelles, the mitochondria being one of the potential candidates. Increased intracellular levels of Cer in the mitochondria have been previously reported to lead to impair mitochondrial function because of the interference with the respiratory chain activity and the production of reactive oxygen species (ROS) and oxidative stress.

In summary, this work, using for the first time a multiplatform analysis (CE-MS, GC-MS, and LC-MS) to study Long COVID patients when compared to those fully recovered from acute COVID-19 infection, reports and confirms the finding of previous studies which suggest that a mitochondrial dysregulation is the main pathological cause of Long COVID syndrome by observing mainly amino acid metabolism alterations (Asp, Gln, Ile, Phe, Pro), TCA cycle impairment (fumaric acid, malic acid, α-ketoglutaric acid), and lipid dysregulation (Cer). In addition, alterations in cytokine plasma levels (IL-6, TNF-α) suggest a reprogramming of the proinflammatory cells contributing to disease pathogenesis.

 

[Hutan]

Thanks for posting this @SNT Gatchaman.

It sounds as though ceramide levels in plasma might be changed by diet and exercise.
Plasma Ceramides Pathophysiology, Measurements, Challenges, and Opportunities
But, high levels of ceramides in the plasma sounds to be problematic, rather than lower levels.

In particular, circulating ceramides are elevated in obese subjects, prediabetes, and type 2 diabetes, and correlated with the risk of developing atherosclerosis and cardiovascular disease [46].

I'm wondering, are the disease group and control group well matched?

 

[Hutan]

From that Plasma ceramide paper - it looks as though things are more complicated than high or low. Drawing conclusions based on total ceramides might not be a good idea.

Interestingly, the effect of 5 days of controlled bed rest on circulating ceramides was evaluated in healthy subjects of both genders (opposite experimental setting respect to the evaluation of acute and chronic exercise), showing that single ceramides decreased (especially C24:0) while ceramide ratios and the CERT1 score, associated with cardiovascular risk, increased especially in the elderly, independently of changes in circulating lipoproteins [76]. Moreover, the C18:0/C24:0 ceramide ratio corresponded to lower physical performance (6-minute walk test), and metabolic biomarkers (e.g., adiponectin, and fibroblast growth factor 2) inversely correlated with ceramides [76].

 

[SNT Gatchaman]

I'll expand one of the quotes —

As previously mentioned, significant decrease in Cer was observed in the plasma of Long COVID patients consequently suggesting a possible accumulation in other organelles, the mitochondria being one of the potential candidates. Increased intracellular levels of Cer in the mitochondria have been previously reported to lead to impair mitochondrial function because of the interference with the respiratory chain activity and the production of reactive oxygen species (ROS) and oxidative stress. In addition, an accumulation of Cer in the mitochondria increases the permeability of the outer mitochondrial membrane and stimulates the release of some proapoptotic proteins. 50 This mitochondrial Cer accumulation has been previously observed in the pathogenesis of other diseases such as type 2 diabetes 51 or Alzheimer’s disease.52 While it is not possible to confirm the accumulation of Cer in the mitochondria, given the changes observed in the pathogenesis of Long COVID, this approach aligns more closely with the observed results

Those refs are —

Ceramide and the mitochondrial respiratory chain (2014, Biochimie)

Sphingolipids as a Culprit of Mitochondrial Dysfunction in Insulin Resistance and Type 2 Diabetes (2021, Frontiers in Endocrinology)

Diverse Roles of Ceramide in the Progression and Pathogenesis of Alzheimer’s Disease (2022, Biomedicines)

 

[Hutan]

It's an interesting finding for sure, but there's that speculative leap from ceramide plasma levels to cellular levels.

In Type 2 diabetes, the reports were that plasma levels were high, and that levels are also high in mitochondria.
But in this study all we know is that plasma levels are low. Is there any reason to assume that that means that levels are high in mitochondria?

 

[SNT Gatchaman]

No, it's conjecture: "While it is not possible to confirm the accumulation of Cer in the mitochondria". I don't know if newer technology can or will be able to interrogate mito membrane lipid constituents. But that would open up a lot of avenues for investigation that could be of high relevance for us. Eg —

Reign in the membrane: How common lipids govern mitochondrial function
Funai; Summers; Rutter

The lipids that make up biological membranes tend to be the forgotten molecules of cell biology. The paucity of data on these important entities likely reflects the difficulties of studying and understanding their biological roles, rather than revealing a lack of importance. Indeed, the lipid composition of biological membranes has a profound impact on a diverse array of cellular processes. The focus of this review is on the effects of different lipid classes on the function of mitochondria, particularly bioenergetics, in health and disease.

Link | PubMed (Current Opinion in Cell Biology)

Studies conducted in cultured cells or isolated mitochondria demonstrate that ceramides inhibit electron transport chain activity and induce formation of reactive oxygen species.

Membrane lipids are abundant and fairly difficult to both analyze and manipulate with precision. As a result, our understanding of the biological impact of these common molecules dramatically lags behind other small and large biological molecules. We have clear evidence that the quantity and quality of membrane lipids have profound effects on mitochondria, particularly on the complex processes that underlie OXPHOS. We are still at the very beginning in our development of a mechanistic understanding of these effects. As that knowledge evolves in concert with an enhanced ability to quantitate mitochondrial lipids in different physiological and pathophysiological states, we will be better able to define (and hopefully someday use) these complex interactions to manipulate mitochondrial efficiency and function.