Tag: anaerobic metabolism

Decreased Fatty Acid Oxidation and Altered Lactate Production during Exercise in Patients with Post-acute COVID-19 Syndrome

To the Editor:

After acute infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), many individuals experience a range of symptoms including dyspnea, exercise intolerance, and chest pain commonly referred to as “post–COVID-19 syndrome” or as post-acute sequelae of SARS-CoV-2 infection (PASC) (). Exertional dyspnea and physical activity intolerance in PASC can be debilitating despite mild acute coronavirus disease (COVID-19) and normal resting pulmonary physiology and cardiac function (). There is an urgent need to understand the pathogenesis of PASC and find effective treatments. The cardiopulmonary exercise test (CPET) is commonly used to investigate unexplained exertional dyspnea; as such, it could provide insight into mechanisms of PASC. CPET data can be used to calculate rates of β-oxidation of fatty acids (FATox) and of lactate clearance, providing insight into mitochondrial function (). Fit individuals have better mitochondrial function and a higher rate of FATox during exercise than less fit individuals (). Our results suggest that patients with PASC have significant impairment in fat β-oxidation and increased blood lactate accumulation during exercise, regardless of previous comorbidities.

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Source: de Boer, E., Petrache, I., Goldstein, N. M., Olin, J. T., Keith, R. C., Modena, B., Mohning, M. P., Yunt, Z. X., San-Millán, I., & Swigris, J. J. (2022). Decreased Fatty Acid Oxidation and Altered Lactate Production during Exercise in Patients with Post-acute COVID-19 Syndrome. American journal of respiratory and critical care medicine, 205(1), 126–129. https://doi.org/10.1164/rccm.202108-1903LE  I https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8865580/ (Full text)

Lessons from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome for Long COVID Part 4: Heart Rate Monitoring to Manage Postexertional Symptom Exacerbation

The physiology underlying postexertional symptom exacerbation (PESE) is abnormal in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and likely long COVID. Activity pacing approaches appear warranted to accommodate the unusual physiological deficits of PESE.

The Rationale for Heart Rate Monitoring

Similar to people living with ME/CFS,7 people living with long COVID have reported finding activity pacing to be helpful. This idea is reflected in current safe rehabilitation guidelines for this condition.8 PESE is challenging to self-manage because of the variability in onset, duration, and nature from person to person.2,6 Social stigma associated with PESE may lead people to overexert to meet the demands of their daily tasks. This stigma may be exacerbated by people telling patients that “it’s all in their head” or they “just need to exercise.” Variability and stigma, in turn, make it difficult to identify important activity triggers in the early stages of learning to manage PESE.

PESE is characterized by aerobic system dysfunction. Pacing based on heart rate can help the patient avoid the dysfunctional aerobic system by keeping their activity intensity at a level anaerobic metabolism will dominate. Heart rate monitoring (HRM) provides an element of predictive potential for the patient to understand when their activities exceed physiological limits and eventually may result in PESE. In this post, we will discuss activity pacing to manage PESE that is based on HRM.

Source: Todd E. Davenport, Staci R. Stevens, Jared Stevens, Christopher R. Snell, J. Mark Van Ness. Lessons from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome for Long COVID Part 4: Heart Rate Monitoring to Manage Postexertional Symptom Exacerbation. Published online on February 23, 2022. https://doi.org/10.2519/jospt.blog.20220223 (Full text)

Dysregulated Provision of Oxidisable Substrates to the Mitochondria in ME/CFS Lymphoblasts

Abstract:

Although understanding of the biomedical basis of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is growing, the underlying pathological mechanisms remain uncertain. We recently reported a reduction in the proportion of basal oxygen consumption due to ATP synthesis by Complex V in ME/CFS patient-derived lymphoblast cell lines, suggesting mitochondrial respiratory inefficiency. This was accompanied by elevated respiratory capacity, elevated mammalian target of rapamycin complex 1 (mTORC1) signaling activity and elevated expression of enzymes involved in the TCA cycle, fatty acid β-oxidation and mitochondrial transport. These and other observations led us to hypothesise the dysregulation of pathways providing the mitochondria with oxidisable substrates.

In our current study, we aimed to revisit this hypothesis by applying a combination of whole-cell transcriptomics, proteomics and energy stress signaling activity measures using subsets of up to 34 ME/CFS and 31 healthy control lymphoblast cell lines from our growing library. While levels of glycolytic enzymes were unchanged in accordance with our previous observations of unaltered glycolytic rates, the whole-cell proteomes of ME/CFS lymphoblasts contained elevated levels of enzymes involved in the TCA cycle (p = 1.03 × 10-4), the pentose phosphate pathway (p = 0.034, G6PD p = 5.5 × 10-4), mitochondrial fatty acid β-oxidation (p = 9.2 × 10-3), and degradation of amino acids including glutamine/glutamate (GLS p = 0.034, GLUD1 p = 0.048, GOT2 p = 0.026), branched-chain amino acids (BCKDHA p = 0.028, BCKDHB p = 0.031) and essential amino acids (FAH p = 0.036, GCDH p = 0.006). The activity of the major cellular energy stress sensor, AMPK, was elevated but the increase did not reach statistical significance. The results suggest that ME/CFS metabolism is dysregulated such that alternatives to glycolysis are more heavily utilised than in controls to provide the mitochondria with oxidisable substrates.

Source: Missailidis D, Sanislav O, Allan CY, Smith PK, Annesley SJ, Fisher PR. Dysregulated Provision of Oxidisable Substrates to the Mitochondria in ME/CFS Lymphoblasts. Int J Mol Sci. 2021 Feb 19;22(4):2046. doi: 10.3390/ijms22042046. PMID: 33669532; PMCID: PMC7921983. https://www.mdpi.com/1422-0067/22/4/2046/htm (Full text)

Elevated Energy Production in Chronic Fatigue Syndrome Patients

Abstract:

Chronic Fatigue Syndrome (CFS) is a debilitating disease characterized by physical and mental exhaustion. The underlying pathogenesis is unknown, but impairments in certain mitochondrial functions have been found in some CFS patients. To thoroughly reveal mitochondrial deficiencies in CFS patients, here we examine the key aspects of mitochondrial function in blood cells from a paired CFS patient-control series. Surprisingly, we discover that in patients the ATP levels are higher and mitochondrial cristae are more condensed compared to their paired controls, while the mitochondrial crista length, mitochondrial size, shape, density, membrane potential, and enzymatic activities of the complexes in the electron transport chain remain intact. We further show that the increased ATP largely comes from non-mitochondrial sources. Our results indicate that the fatigue symptom in this cohort of patients is unlikely caused by lack of ATP and severe mitochondrial malfunction. On the contrary, it might be linked to a pathological mechanism by which more ATP is produced by non-mitochondrial sources.

 

Source: Lawson N, Hsieh CH, March D, Wang X. Elevated Energy Production in Chronic Fatigue Syndrome Patients. J Nat Sci. 2016;2(10). pii: e221. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5065105/ (Full article)