The Link Between Energy-Related Sensations and Metabolism: Implications for Treating Fatigue

Energy-related sensations include sensation of energy and fatigue as well as subjective energizability and fatigability. First, we introduce interdisciplinary useful definitions of all constructs and review findings regarding the question of whether sensations of fatigue and energy are two separate constructs or two ends of a single dimension. Second, we describe different components of the bodily energy metabolism system (e.g., mitochondria; autonomic nervous system). Third, we review the link between sensation of fatigue and different components of energy metabolism. Finally, we present an overview of different treatments shown to affect both energy-related sensations and metabolism before outlining future research perspectives.

Feasibility of Vitamin C in the Treatment of Post Viral Fatigue with Focus on Long COVID, Based on a Systematic Review of IV Vitamin C on Fatigue

Fatigue is common not only in cancer patients but also after viral and other infections. Effective treatment options are still very rare. Therefore, the present knowledge on the pathophysiology of fatigue and the potential positive impact of treatment with vitamin C is illustrated. Additionally, the effectiveness of high-dose IV vitamin C in fatigue resulting from various diseases was assessed by a systematic literature review in order to assess the feasibility of vitamin C in post-viral, especially in long COVID, fatigue. Nine clinical studies with 720 participants were identified. Three of the four controlled trials observed a significant decrease in fatigue scores in the vitamin C group compared to the control group. Four of the five observational or before-and-after studies observed a significant reduction in pre-post levels of fatigue. Attendant symptoms of fatigue such as sleep disturbances, lack of concentration, depression, and pain were also frequently alleviated. Oxidative stress, inflammation, and circulatory disorders, which are important contributors to fatigue, are also discussed in long COVID fatigue. Thus, the antioxidant, anti-inflammatory, endothelial-restoring, and immunomodulatory effects of high-dose IV vitamin C might be a suitable treatment option.

Metabolic and Structural Skeletal Muscle Health in Systemic Lupus Erythematosus-Related Fatigue: A Multimodal Magnetic Resonance Imaging Study

OBJECTIVE

To investigate the potential structural and metabolic role of skeletal muscle in systemic lupus erythematosus (SLE)-related fatigue.

METHODS

A case-control, multimodal magnetic resonance imaging (MRI) study was conducted. Cases were patients with inactive SLE who reported chronic fatigue. Controls were age- and sex-matched healthy members of the general population. Patients were clinically characterized and then underwent a 3T whole-body MRI scan. Resting and dynamic ³¹ P MRI spectroscopy of the calf muscles was applied, from which phosphocreatine (PCr) recovery halftime, a marker of mitochondrial dysfunction, was computed. In addition, microstructural sequences (T1-weighted anatomic images, T2 mapping, and diffusion tensor imaging) were acquired. Descriptive statistics evaluated group differences and within-case physical fatigue correlations were explored.

RESULTS

Of the 37 recruits (mean age 43.8 years, 89.2% female), cases (n = 19) reported higher levels of physical fatigue, pain, depression, and sleep disturbance compared to the control group (P < 0.0001). PCr was greater (P = 0.045) among cases (mean ± SD 33.0 ± 9.0 seconds) compared to controls (mean ± SD 27.1 ± 6.6 seconds). No microstructural group differences were observed. Within cases, physical fatigue did not correlate with PCr (r = -0.28, P = 0.25).

CONCLUSION

We report preliminary data demonstrating greater skeletal muscle mitochondrial dysfunction among fatigued patients with SLE compared to healthy controls.

Biostatistics as a Tool for Medical Research: What are we Doing Wrong?

As the data resulting from modern clinical research are astonishingly complex, statistics constitute an integral component of the research project, from the study conception and design to the reporting of the results. At the same time, the Medical Literature is not immune to statistical pitfalls. In the following lines we identify eleven common statistical mistakes, elucidate their effects on the study credibility, and provide tips and tricks to avoid them.

Malondialdehyde and advanced oxidation protein products are not increased in psoriasis: a controlled study

This study investigated oxidative stress in patients with psoriasis of low and medium disease activity. We measured advanced oxidation protein products (AOPP) and malondialdehyde (MDA) in plasma using UV-spectrophotometry and high performance liquid chromatography connected to a fluorescence detector in 84 patients and 84 matched healthy subjects. AOPP is a marker of protein oxidation due to inflammation, whereas MDA is a hydroxyl radical initiated lipid peroxidation product. Clinico-demographic variables including age, gender, disease severity, and fatigue were assessed in relation to AOPP and MDA. Disease severity was evaluated with the Psoriasis Area and Severity Index and the Dermatology Life Quality Index. Median (interquartile range, IQR) AOPP concentrations were 66 µmol/l (IQR 54-102) in patients and 69 µmol/l (IQR 55-87) in healthy subjects (P = 0.75). Median plasma MDA concentrations were significantly lower in patients than in healthy subjects (0.68 µM, IQR 0.54-0.85 vs. 0.76 µM, IQR 0.60-0.97; P = 0.03). Plasma levels of AOPP and MDA did not indicate oxidative stress in patients with mild psoriasis. Higher AOPP concentrations were associated with male gender, high body mass index, and high hemoglobin values. Elevated MDA concentrations were associated with advanced age and male gender. No associations with disease severity were detected. Although, the two selected biomarkers do not provide a complete measure of oxidative damage, our study demonstrates that a number of physiological and methodological factors influence the levels of MDA and AOPP. Such methodological issues are important to consider when interpreting results using these biomarkers in patients with psoriasis.

Unmet Needs in the Pathogenesis and Treatment of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune rheumatic disease with a prevalence of approximately 1 in 1000. Over the last 30 years, advances in treatment such as use of corticosteroids and immunosuppressants have improved life expectancy and quality of life for patients with lupus and the key unmet needs have therefore changed. With the reduced mortality from disease activity, development of cardiovascular disease (CVD) has become an increasingly important cause of death in patients with SLE. The increased CVD risk in these patients is partly, but not fully explained by standard risk factors, and abnormalities in the immune response to lipids may play a role. Invariant natural killer T cells, which are triggered specifically by lipid antigens, may protect against progression of subclinical atherosclerosis. However, currently our recommendation is that clinicians should focus on optimal management of standard CVD risk factors such as smoking, blood pressure and lipid levels. Fatigue is one of the most common and most limiting symptoms suffered by patients with SLE. The cause of fatigue is multifactorial and disease activity does not explain this symptom. Consequently, therapies directed towards reducing inflammation and disease activity do not reliably reduce fatigue and new approaches are needed. Currently, we recommend asking about sleep pattern, optimising pain relief and excluding other causes of fatigue such as anaemia and metabolic disturbances. For the subgroup of patients whose disease activity is not fully controlled by standard treatment regimes, a range of different biologic agents have been proposed and subjected to clinical trials. Many of these trials have given disappointing results, though belimumab, which targets B lymphocytes, did meet its primary endpoint. New biologics targeting B cells, T cells or cytokines (especially interferon) are still going through trials raising the hope that novel therapies for patients with refractory SLE may be available soon.

Classifying oxidative stress by F2-isoprostane levels across human diseases: A meta-analysis

The notion that oxidative stress plays a role in virtually every human disease and environmental exposure has become ingrained in everyday knowledge. However, mounting evidence regarding the lack of specificity of biomarkers traditionally used as indicators of oxidative stress in human disease and exposures now necessitates re-evaluation. To prioritize these re-evaluations, published literature was comprehensively analyzed in a meta-analysis to quantitatively classify the levels of systemic oxidative damage across human disease and in response to environmental exposures.

In this meta-analysis, the F₂-isoprostane, 8-iso-PGF_2α, was specifically chosen as the representative marker of oxidative damage. To combine published values across measurement methods and specimens, the standardized mean differences (Hedges’ g) in 8-iso-PGF_2α levels between affected and control populations were calculated.

The meta-analysis resulted in a classification of oxidative damage levels as measured by 8-iso-PGF_2α across 50 human health outcomes and exposures from 242 distinct publications. Relatively small increases in 8-iso-PGF_2α levels (g<0.8) were found in the following conditions: hypertension (g=0.4), metabolic syndrome (g=0.5), asthma (g=0.4), and tobacco smoking (g=0.7). In contrast, large increases in 8-iso-PGF_2α levels were observed in pathologies of the kidney, e.g., chronic renal insufficiency (g=1.9), obstructive sleep apnoea (g=1.1), and pre-eclampsia (g=1.1), as well as respiratory tract disorders, e.g., cystic fibrosis (g=2.3).

In conclusion, we have established a quantitative classification for the level of 8-iso-PGF_2α generation in different human pathologies and exposures based on a comprehensive meta-analysis of published data. This analysis provides knowledge on the true involvement of oxidative damage across human health outcomes as well as utilizes past research to prioritize those conditions requiring further scrutiny on the mechanisms of biomarker generation.

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Oxidative damage is highly variable in human conditions as measured by F₂-isoprostanes.

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Respiratory tract and urogenital diseases have the highest F₂-isoprostanes.

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Cancer and cardiovascular diseases have surprisingly low F₂-isoprostanes.

Heat shock proteins and chronic fatigue in primary Sjögren's syndrome

Fatigue occurs frequently in patients with cancer, neurological diseases and chronic inflammatory diseases, but the biological mechanisms that lead to and regulate fatigue are largely unknown. When the innate immune system is activated, heat shock proteins (HSPs) are produced to protect cells. Some extracellular HSPs appear to recognize cellular targets in the brain, and we hypothesize that fatigue may be generated by specific HSPs signalling through neuronal or glial cells in the central nervous system. From a cohort of patients with primary Sjögren’s syndrome, 20 patients with high and 20 patients with low fatigue were selected. Fatigue was evaluated with a fatigue visual analogue scale. Plasma concentrations of HSP32, HSP60, HSP72 and HSP90α were measured and analysed to determine if there were associations with the level of fatigue. Plasma concentrations of HSP90α were significantly higher in patients with high fatigue compared with those with low fatigue, and there was a tendency to higher concentrations of HSP72 in patients with high fatigue compared with patients with low fatigue. There were no differences in concentrations of HSP32 and HSP60 between the high- and low-fatigue groups. Thus, extracellular HSPs, particularly HSP90α, may signal fatigue in chronic inflammation. This supports the hypothesis that fatigue is generated by cellular defence mechanisms.

Fatigue-induced Orosomucoid 1 Acts on C-C Chemokine Receptor Type 5 to Enhance Muscle Endurance

Understanding and managing fatigue is a significant challenge in clinic and society. In attempting to explore how the body responds to and regulates fatigue, we found in rodent fatigue models that orosomucoid 1 (ORM1) was significantly increased in multiple tissues, including blood and muscle. Interestingly, administration of exogenous ORM1 increased muscle glycogen and enhanced muscle endurance, whereas ORM1 deficiency resulted in a significant decrease of muscle endurance both in vivo and in vitro, which could largely be restored by exogenous ORM1. Further studies demonstrated that ORM1 can bind to C-C chemokine receptor type 5 (CCR5) on muscle cells and deletion of the receptor abolished the effect of ORM1. Thus, fatigue upregulates the level of ORM1, which in turn functions as an anti-fatigue protein to enhance muscle endurance via the CCR5 pathway. Modulation of the level of ORM1 and CCR5 signaling could be a novel strategy for the management of fatigue.

Nonenzymatic antioxidants in saliva of patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody-directed self-antigens, immune complex formation and immune deregulation, resulting in damage to essentially all the organs. SLE is associated with the increased production of free radicals. Increase in free radicals or impaired antioxidant defense system in SLE causes oxidative stress. Considering that saliva could be a reflection of the state of health, the purpose of this study was to evaluate some antioxidants in the saliva and serum of patients with SLE and compare these with healthy individuals. This could help us in obtaining a possible marker in saliva in the future. During the course of the practical part of the project, 30 patients with SLE and 30 healthy controls were investigated. After centrifugation of un-stimulated saliva and blood samples, they were examined using spectrophotometric methods and the results were analyzed by statistical software. According to the results, concentrations of malondialdehyde, uric acid and total antioxidants were significantly increased but the level of reduced glutathion was reduced significantly in the saliva and serum of SLE patients as compared to controls. It is therefore suggested that antioxidant power is impaired in saliva and serum of SLE patients. As there was a positive correlation between the antioxidant level of saliva and blood serum, the antioxidant status of saliva could be an indicator of serum antioxidants.

Alternations of salivary antioxidant enzymes in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease with chronic systemic inflammation. Oxidative stress may play a role in the pathogenesis of SLE. An increase in free radicals or an impaired antioxidant defense system in SLE causes oxidative stress. Therefore, oxidative damage plays an important role in the pathogenesis of SLE. Variations in antioxidant activity have been previously studied in serum of patients with this disease. However, salivary factors have not been evaluated. Considering that saliva, the noninvasive biological fluid, could be a reflection of the state of health, the purpose of this study was evaluation of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) activity in the saliva of patients with SLE. During the course of the practical part of the project, 30 patients with SLE and 30 healthy controls were selected to donate their saliva samples. After centrifugation of un-stimulated saliva, biological activity of POD, CAT and SOD were evaluated on their appropriate substrates using spectrophotometric methods and the results were statistically analyzed. The results showed that activities of antioxidant enzymes SOD and CAT were significantly reduced in saliva of SLE patients as compared to controls. The results suggest that antioxidant status was impaired in the saliva of SLE patients, and antioxidant status of saliva could be one of the non-invasive markers for SLE.

The Neuro-Immune Pathophysiology of Central and Peripheral Fatigue in Systemic Immune-Inflammatory and Neuro-Immune Diseases

Many patients with systemic immune-inflammatory and neuro-inflammatory disorders, including depression, rheumatoid arthritis, systemic lupus erythematosus, Sjögren's disease, cancer, cardiovascular disorder, Parkinson's disease, multiple sclerosis, stroke, and chronic fatigue syndrome/myalgic encephalomyelitis, endure pathological levels of fatigue. The aim of this narrative review is to delineate the wide array of pathways that may underpin the incapacitating fatigue occurring in systemic and neuro-inflammatory disorders. A wide array of immune, inflammatory, oxidative and nitrosative stress (O&NS), bioenergetic, and neurophysiological abnormalities are involved in the etiopathology of these disease states and may underpin the incapacitating fatigue that accompanies these disorders. This range of abnormalities comprises: increased levels of pro-inflammatory cytokines, e.g., interleukin-1 (IL-1), IL-6, tumor necrosis factor (TNF) α and interferon (IFN) α; O&NS-induced muscle fatigue; activation of the Toll-Like Receptor Cycle through pathogen-associated (PAMPs) and damage-associated (DAMPs) molecular patterns, including heat shock proteins; altered glutaminergic and dopaminergic neurotransmission; mitochondrial dysfunctions; and O&NS-induced defects in the sodium-potassium pump. Fatigue is also associated with altered activities in specific brain regions and muscle pathology, such as reductions in maximum voluntary muscle force, downregulation of the mitochondrial biogenesis master gene peroxisome proliferator-activated receptor gamma coactivator 1-alpha, a shift to glycolysis and buildup of toxic metabolites within myocytes. As such, both mental and physical fatigue, which frequently accompany immune-inflammatory and neuro-inflammatory disorders, are the consequence of interactions between multiple systemic and central pathways.

Is depression associated with increased oxidative stress? A systematic review and meta-analysis

BACKGROUND

It has been suggested that depressed persons have increased oxidative stress and decreased anti-oxidant defences. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) and F2-isoprostanes, measures of oxidative DNA and lipid damage respectively, are among the most reliable oxidative stress markers, but studies on their association with depression show conflicting results. This meta-analysis quantifies the association between depression and these markers and explores factors that may explain inconsistencies in the results.

METHODS

A systematic literature search was conducted in PubMed, EMBASE and PsycINFO. Studies assessing the association of 8-OHdG or F2-isoprostanes with elevated depressive symptoms, major depressive disorder (MDD) or bipolar disorder (BD) were pooled in two random-effect models.

RESULTS

The pooled effect size (Hedges' g) for the association of depression with oxidative stress was 0.31 (p=0.01, I(2)=75%) for 8-OHdG (10 studies, 1308 subjects) and 0.48 (p=0.001, I(2)=73%) for F2-isoprostanes (8 studies, 2471 subjects), indicating that both markers are increased in depression. There was no indication of publication bias for either marker. The F2-isoprostane results did not differ by type of depression, biological specimen, laboratory method or quality, however subgroup analyses in the 8-OHdG studies showed significantly stronger associations in plasma/serum vs. urine samples (p<0.01), in measurements performed with immuno-assay vs. chromatography-mass spectrometry (p<0.01) and weaker associations in high quality studies vs. low (p=0.02).

CONCLUSION

This meta-analysis finds that oxidative stress, as measured by 8-OHdG and F2-isoprostanes, is increased in depression. Larger-scale studies are needed to extend the evidence on oxidative stress in depression, and examine the potential impact of treatment.

Association of Mitochondrial Dysfunction and Fatigue: A Review of the Literature

Fatigue is often described by patients as a lack of energy, mental or physical tiredness, diminished endurance, and prolonged recovery after physical activity. Etiologic mechanisms underlying fatigue are not well understood; however, fatigue is a hallmark symptom of mitochondrial disease, making mitochondrial dysfunction a putative biological mechanism for fatigue. Therefore, this review examined studies that investigated the association of markers of mitochondrial dysfunction with fatigue and proposes possible research directions to enhance understanding of the role of mitochondrial dysfunction in fatigue. A thorough search using PubMed, Scopus, Web of Science, and Embase databases returned 1,220 articles. After application of inclusion and exclusion criteria, a total of 25 articles meeting eligibility criteria were selected for full review. Dysfunctions in the mitochondrial structure, mitochondrial function (mitochondrial enzymes and oxidative/nitrosative stress), mitochondrial energy metabolism (ATP production and fatty acid metabolism), immune response, and genetics were investigated as potential contributors to fatigue. Carnitine was the most investigated mitochondrial function marker. Dysfunctional levels were reported in all the studies investigating carnitine; however, the specific type of carnitine that was dysfunctional varied. Genetic profiles were the second most studied mitochondrial parameter. Six common pathways were proposed: metabolism, energy production, protein transport, mitochondrial morphology, central nervous system dysfunction and post-viral infection. Coenzyme Q10 was the most commonly investigated mitochondrial enzyme. Low levels of Coenzyme Q10 were consistently associated with fatigue. Potential targets for further investigation were identified as well as gaps in the current literature.

Oxidative stress and its biomarkers in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease whose etiology remains largely unknown. The uncontrolled oxidative stress in SLE contributes to functional oxidative modifications of cellular protein, lipid and DNA and consequences of oxidative modification play a crucial role in immunomodulation and trigger autoimmunity. Measurements of oxidative modified protein, lipid and DNA in biological samples from SLE patients may assist in the elucidation of the pathophysiological mechanisms of the oxidative stress-related damage, the prediction of disease prognosis and the selection of adequate treatment in the early stage of disease. Application of these biomarkers in disease may indicate the early effectiveness of the therapy. This review is intended to provide an overview of various reactive oxygen species (ROS) formed during the state of disease and their biomarkers linking with disease. The first part of the review presents biochemistry and pathophysiology of ROS and antioxidant system in disease. The second part of the review discusses the recent development of oxidative stress biomarkers that relates pathogenesis in SLE patients and animal model. Finally, this review also describes the reported clinical trials of antioxidant in the disease that have evaluated the efficacy of antioxidant in the management of disease with ongoing conventional therapy.