Katrine Brække Norheim

Biological mechanisms of chronic fatigue

Chronic fatigue is a common, poorly understood and disabling phenomenon in many diseases. We aim to provide an overview of fatigue in chronic autoimmune and inflammatory disease. Fatigue measurement, prevalence and confounding factors such as depression, sleep disorders and pain are reviewed in the first half of the article. In the second half of the article, we describe explanatory models of fatigue and fatigue signalling, with an emphasis on cytokines and sickness behaviour, oxidative stress, mitochondrial dysfunction and the impact of certain genes on fatigue.

Improved detection of advanced oxidation protein products in plasma

BACKGROUND Oxidative stress has been associated with many diseases and can among others be assessed as increased levels of advanced oxidation protein products (AOPP). Current AOPP methods suffer from poor reproducibility and accuracy due to precipitation of lipids in plasma samples. We therefore aimed to develop a robust method in which plasma lipids are solubilized. METHODS Plasma was diluted with citric acid, and AOPP measured as absorbance at 340 nm. The method was optimized and validated, and then used to analyze AOPP levels in plasma from healthy control subjects (HC), and in three patients groups; chronic kidney disease (CKD), primary Sjögrens Syndrome (pSS) and systemic lupus erythematosus (SLE). RESULTS AOPP was detected with improved precision compared to established methods where lipids precipitate. Within- and between days variations were less than 1.4% and 2.2%, respectively. A control chart was established and the long-term reproducibility followed over six months. CONCLUSIONS This improved method detects plasma AOPP with significantly better reproducibility and accuracy compared to previously reported methods. Solubilization of plasma lipids before spectrophotometric measure of AOPP levels is novel. It prevents both loss of lipoproteins due to precipitation and overestimation as a result of light scattering.

Interleukin-1 Inhibition and Fatigue in Primary Sjögren's Syndrome – A Double Blind, Randomised Clinical Trial

Objectives Fatigue is a major cause of disability in primary Sjögrens syndrome (pSS). Fatigue has similarities with sickness behaviour in animals; the latter mediated by pro-inflammatory cytokines, in particular interleukin (IL)-1, acting on neuronal brain cells. We hypothesised that IL-1 inhibition might improve fatigue in pSS patients; thus, we examined the effects and safety of an IL-1 receptor antagonist (anakinra) on fatigue. Methods Twenty-six pSS patients participated in a double-blind, placebo-controlled parallel group study. Patients were randomised to receive either anakinra or a placebo for four weeks. Fatigue was evaluated by a fatigue visual analogue scale and the Fatigue Severity Scale. The primary outcome measure was a group-wise comparison of the fatigue scores at week 4, adjusted for baseline values. Secondary outcome measures included evaluation of laboratory results and safety. The proportion of patients in each group who experienced a 50% reduction in fatigue was regarded as a post-hoc outcome. All outcomes were measured at week 4. Results There was no significant difference between the groups in fatigue scores at week 4 compared to baseline after treatment with anakinra. However, six out of 12 patients on anakinra versus one out of 13 patients on the placebo reported a 50% reduction in fatigue VAS (p = 0.03). There were two serious adverse events in each group. Conclusions This randomised, double-blind, placebo-controlled trial of IL-1 blockade did not find a significant reduction in fatigue in pSS in its primary endpoint. A 50% reduction in fatigue was analysed post-hoc, and significantly more patients on the active drug than on placebo reached this endpoint. Although not supported by the primary endpoint, this may indicate that IL-1 inhibition influences fatigue in patients with pSS. Trial registration ClinicalTrials.gov NCT00683345

Genome-wide DNA methylation analysis in multiple tissues in primary Sjögren's syndrome reveals regulatory effects at interferon-induced genes

Objectives Increasing evidence suggests an epigenetic contribution to the pathogenesis of autoimmune diseases, including primary Sjögrens Syndrome (pSS). The aim of this study was to investigate the role of DNA methylation in pSS by analysing multiple tissues from patients and controls. Methods Genome-wide DNA methylation profiles were generated using HumanMethylation450K BeadChips for whole blood, CD19+ B cells and minor salivary gland biopsies. Gene expression was analysed in CD19+ B cells by RNA-sequencing. Analysis of genetic regulatory effects on DNA methylation at known pSS risk loci was performed. Results We identified prominent hypomethylation of interferon (IFN)-regulated genes in whole blood and CD19+ B cells, including at the genes MX1, IFI44L and PARP9, replicating previous reports in pSS, as well as identifying a large number of novel associations. Enrichment for genomic overlap with histone marks for enhancer and promoter regions was observed. We showed for the first time that hypomethylation of IFN-regulated genes in pSS B cells was associated with their increased expression. In minor salivary gland biopsies we observed hypomethylation of the IFN-induced gene OAS2. Pathway and disease analysis resulted in enrichment of antigen presentation, IFN signalling and lymphoproliferative disorders. Evidence for genetic control of methylation levels at known pSS risk loci was observed. Conclusions Our study highlights the role of epigenetic regulation of IFN-induced genes in pSS where replication is needed for novel findings. The association with altered gene expression suggests a functional mechanism for differentially methylated CpG sites in pSS aetiology.

Oxidative stress, as measured by protein oxidation, is increased in primary Sjøgren's syndrome

Objective: Oxidative stress is an imbalance between the production of reactive oxygen species (ROS) and physiological antioxidant defences. It occurs frequently in conditions characterized by immune activation and inflammation. Plasma levels of oxidized end products have never been evaluated in primary Sjøgrens syndrome (pSS). The aim of this study was to investigate the level of oxidative stress in primary Sjøgrens syndrome. As a secondary outcome, the association between oxidative stress and fatigue was explored. Methods: A cross-sectional study of 26 pSS patients was carried out. Oxidative stress was assessed using two markers of protein oxidation, protein carbonyl (PC) and advanced oxidation protein products (AOPP). Reference values for the oxidative stress markers were obtained from 15 healthy subjects. Results: AOPP and PC levels were increased in the pSS patients compared to the healthy subjects. This is a novel finding. There were no associations between oxidative stress measures and fatigue in the patients. Conclusions: Patients with pSS have increased levels of oxidative stress compared to healthy subjects.

Primary Sjögren's Syndrome: Fatigue Is an Ever‐Present, Fluctuating, and Uncontrollable Lack of Energy

To examine how fatigue may differ from ordinary tiredness in patients with primary Sjögrens syndrome (SS).

Fatigue in Newly Diagnosed Inflammatory Bowel Disease

BACKGROUND AND AIMS The present study investigated the prevalence and severity of fatigue in patients with newly diagnosed and untreated ulcerative colitis (UC) and Crohns disease (CD) and examined relevant disease variables that may influence the severity of fatigue. METHODS Eighty-one patients with inflammatory bowel disease (IBD) (60 with UC and 21 with CD) were assessed for fatigue using two fatigue instruments: the Fatigue Severity Scale (FSS) and a fatigue visual analogue scale (fVAS). Cut-off for fatigue was defined as ≥4 for FSS and ≥50 for fVAS. Results were compared with fatigue scores from age-and gender-matched healthy individuals. Disease activity was assessed by symptom scores using the Mayo score in UC patients and the Harvey-Bradshaw index for CD patients, as well as C-reactive protein (CRP) and faecal calprotectin. RESULTS The prevalence of fatigue based on FSS and fVAS was 47 and 42%, respectively, in UC and 62 and 48% in CD. In multivariate regression models, disease activity markers were not associated with fatigue, while a significant relationship was found with age and depression for both fatigue measures. CONCLUSIONS Close to 50% of patients with IBD reported fatigue at the time of diagnosis. In newly diagnosed patients with active disease, the severity of fatigue was not associated with measures of disease activity.

Fatigue in psoriasis: a phenomenon to be explored*

Fatigue is a prevalent and substantial phenomenon in many patients with chronic inflammatory diseases, often rated by patients as the most troublesome symptom and aspect of their disease. It frequently interferes with physical and social functions and may lead to social withdrawal, long‐standing sick leave and disability. Although psychological and somatic factors such as depression, sleep disorders, pain and anaemia influence fatigue, the underlying pathophysiological mechanisms by which fatigue is generated and regulated are largely unknown. Increasing evidence points towards a genetic and molecular basis for fatigue as part of the innate immune system and cellular stress responses. Few studies have focused on fatigue in dermatological diseases. Most of these studies describe fatigue as a phenomenon related to psoriatic arthritis and describe the beneficial effects of biological agents on fatigue observed in clinical studies. It is therefore possible that this problem has been underestimated and deserves more attention in the dermatological community. In this review, we provide a definition and explanation for chronic fatigue, describe some commonly used instruments for measuring fatigue, and present hypothetical biological mechanisms with an emphasis on activation of the innate immune system and oxidative stress. An overview of relevant clinical studies covering the theme ‘psoriasis and fatigue’ is given.

Metabolomics study of fatigue in patients with rheumatoid arthritis naïve to biological treatment.

Fatigue occurs in all chronic inflammatory diseases, in cancer, and in some neurological conditions. Patients often regard fatigue as one of their most debilitating problems, but currently there is no established treatment and the mechanisms that lead to and regulate fatigue are incompletely understood. Our objective was to more completely understand the physiology of this phenomenon. Twenty-four patients with rheumatoid arthritis (RA) naïve to treatment with biological drugs were enrolled for the study. Fatigue was measured with a fatigue visual analogue scale (fVAS). Ethylenediaminetetraacetic acid (EDTA) plasma samples were subjected to gas chromatography–time-of-flight mass spectrometry (GC/MS-TOF)-based metabolite profiling. Obtained metabolite data were evaluated by multivariate data analysis with orthogonal projections to latent structures (OPLS) method to pinpoint metabolic changes related to fatigue severity. A significant multivariate OPLS model was obtained between the fVAS scores and the measured metabolic levels. Increasing fatigue scores were associated with a metabolic pattern characterized by down-regulation of metabolites from the urea cycle, fatty acids, tocopherols, aromatic amino acids, and hypoxanthine. Uric acid levels were increased. Apart from fatigue, we found no other disease-related variables that might be responsible for these changes. Our MS-based metabolomic approach demonstrated strong associations between fatigue and several biochemical patterns related to oxidative stress.

Epigenome-wide DNA methylation patterns associated with fatigue in primary Sjögren’s syndrome

OBJECTIVE Chronic fatigue is a common, disabling and poorly understood phenomenon. Recent studies indicate that epigenetic mechanisms may be involved in the expression of fatigue, a prominent feature of primary SS (pSS). The aim of this study was to investigate whether DNA methylation profiles of whole blood are associated with fatigue in patients with pSS. METHODS Forty-eight pSS patients with high (n = 24) or low (n = 24) fatigue as measured by a visual analogue scale were included. Genome-wide DNA methylation was investigated using the Illumina HumanMethylation450 BeadChip array. After quality control, a total of 383 358 Cytosine-phosphate-Guanine (CpG) sites remained for further analysis. Age, sex and differential cell count estimates were included as covariates in the association model. A false discovery rate-corrected P < 0.05 was considered significant, and a cut-off of 3% average difference in methylation levels between high- and low-fatigue patients was applied. RESULTS A total of 251 differentially methylated CpG sites were associated with fatigue. The CpG site with the most pronounced hypomethylation in pSS high fatigue annotated to the SBF2-antisense RNA1 gene. The most distinct hypermethylation was observed at a CpG site annotated to the lymphotoxin alpha gene. Functional pathway analysis of genes with differently methylated CpG sites in subjects with high vs low fatigue revealed enrichment in several pathways associated with innate and adaptive immunity. CONCLUSION Some genes involved in regulation of the immune system and in inflammation are differently methylated in pSS patients with high vs low fatigue. These findings point to functional networks that may underlie fatigue. Epigenetic changes could constitute a fatigue-regulating mechanism in pSS.