Gene expression profiling in patients with polymyalgia rheumatica before and after symptom-abolishing glucocorticoid treatment

Abstract Background The pathophysiology, including the impact of gene expression, of polymyalgia rheumatica (PMR) remains elusive. We profiled the gene expression in muscle tissue in PMR patients before and after glucocorticoid treatment. Methods Gene expression was measured using Affymetrix Human Genome U133 Plus 2.0 arrays in muscle biopsies from 8 glucocorticoid-naive patients with PMR and 10 controls before and after prednisolone-treatment for 14 days. For 14 genes, quantitative real-time PCR (qRT-PCR, n = 9 in both groups) was used to validate the microarray findings and to further investigate the expression of genes of particular interest. Results Prednisolone normalized erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) in PMR patients. A total of 165 putatively clinically relevant, differentially expressed genes were identified (cut-off: fold difference > ±1.2, difference of mean > 30, and p < 0.05); of these, 78 genes differed between patients and controls before treatment, 131 genes responded to treatment in a given direction only in patients, and 44 fulfilled both these criteria. In 43 of the 44 genes, treatment counteracted the initial difference. Functional clustering identified themes of biological function, including regulation of protein biosynthesis, and regulation of transcription and of extracellular matrix processes. Overall, qRT-PCR confirmed the microarray findings: Microarray-detected group differences were confirmed for 9 genes in 17 of 18 comparisons (same magnitude and direction of change); lack of group differences in microarray testing was confirmed for 5 genes in 8 of 10 comparisons. Before treatment, using qRT-PCR, expression of interleukin 6 (IL-6) was found to be 4-fold higher in patients (p < 0.05). Conclusions This study identifies genes in muscle, the expression of which may impact the pathophysiology of PMR. Moreover, the study adds further evidence of the importance of IL-6 in the disease. Follow-up studies are needed to establish the exact pathophysiological relevance of the identified genes. The study was retrospectively listed on the ISRCTN registry with study ID ISRCTN69503018 and date of registration the 26th of July 2017

Contraction and AICAR Stimulate IL-6 Vesicle Depletion From Skeletal Muscle Fibers In Vivo

Recent studies suggest that interleukin 6 (IL-6) is released from contracting skeletal muscles; however, the cellular origin, secretion kinetics, and signaling mechanisms regulating IL-6 secretion are unknown. To address these questions, we developed imaging methodology to study IL-6 in fixed mouse muscle fibers and in live animals in vivo. Using confocal imaging to visualize endogenous IL-6 protein in fixed muscle fibers, we found IL-6 in small vesicle structures distributed throughout the fibers under basal (resting) conditions. To determine the kinetics of IL-6 secretion, intact quadriceps muscles were transfected with enhanced green fluorescent protein (EGFP)-tagged IL-6 (IL-6-EGFP), and 5 days later anesthetized mice were imaged before and after muscle contractions in situ. Contractions decreased IL-6-EGFP–containing vesicles and protein by 62% (P < 0.05), occurring rapidly and progressively over 25 min of contraction. However, contraction-mediated IL-6-EGFP reduction was normal in muscle-specific AMP-activated protein kinase (AMPK) α2-inactive transgenic mice. In contrast, the AMPK activator AICAR decreased IL-6-EGFP vesicles, an effect that was inhibited in the transgenic mice. In conclusion, resting skeletal muscles contain IL-6–positive vesicles that are expressed throughout myofibers. Contractions stimulate the rapid reduction of IL-6 in myofibers, occurring through an AMPKα2-independent mechanism. This novel imaging methodology clearly establishes IL-6 as a contraction-stimulated myokine and can be used to characterize the secretion kinetics of other putative myokines

Adaptação de longo prazo ao treinamento cíclico induzido eletricamente em indivíduos com severa lesão na medula espinhal

Indivíduos com lesão da medula espinhal (LME) mais freqüentemente adquirem essa condição na juventude e são relegados a uma vida de maior ou menor inatividade física. Em adição às implicações primárias da LME, indivíduos com LME severa são estigmatizados e relegados a uma condição de vida física inativa. É desconhecido se essas condições relatadas são potencialmente reversíveis e o objetivo do presente estudo foi, portanto, examinar os efeitos do exercício em indivíduos com LME. Então, 10 indivíduos (6 com tetraplegia e 4 com paraplegia; idade de 27 a 45 anos; tempo de lesão de 3 a 23 anos) foram treinados por 1 ano em cicloergometria com estimulação elétrica controlada por feedback. Eles treinaram 3 vezes por semana (média 2,3 vezes), 30 minutos em cada sessão. Os músculos glúteos, isquiotibiais e quadríceps foram estimulados por eletrodos colocados na superfície da pele sobre seus pontos motores. Durante o primeiro treino, uma variação substancial na performance foi observada entre os pacientes. A maioria dos indivíduos foi capaz de realizar o exercício por 30 minutos na primeira sessão, mas dois indivíduos foram capazes de realizar o exercício por apenas poucos minutos. Depois do treino de 1 ano, todos os indivíduos foram capazes de realizar 30 minutos contínuos de treino e o trabalho produzido teve aumento de 4 ± 1 (média de “erro-padrão” EP) para 17 ± 2 kJ por sessão de treino (P &lt; 0,05). A taxa de captação máxima de O2 durante o exercício com estimulação elétrica aumentou de 1,20 ± 0,08 l/min, mensurada depois de poucas semanas de exercício, para 1,43 ± 0,09 l/min após 1 ano de treinamento (P &lt; 0,05). Imagens de corte com ressonância magnética foram feitas na coxa para avaliar a massa muscular, que teve um aumento de 12% (média, P &lt; 0,05) em 1 ano de treinamento. Em biópsias feitas antes do exercício, vários estados de atrofia foram observados nas fibras musculares dos indivíduos, um fenômeno que foi parcialmente normalizado em todos os pacientes depois do treinamento. É sabido que a distribuição do tipo de fibra no músculo esquelético é alterada para fibras do tipo II B (contração rápida, rapidamente fatigável, glicolíticas) dentro dos primeiros 2 anos após a lesão medular. Nessa avaliação, os músculos continham 63% de miosina de cadeia pesada (MHC) isoforme II B, 33% de MHC isoforme II A (contração rápida e resistentes à fadiga) e menos de 5% de MHC isoforme I (fibras de contração lenta) antes do treinamento. Uma transformação para obterem-se fibras com proteínas contráteis mais resistentes à fadiga foi encontrada após 1 ano de treinamento. A porcentagem de MHC isoforme II A aumentou para 61% do total de proteínas contráteis e houve uma diminuição de 32% nas fibras rapidamente fatigáveis do tipo MHC isoforme II, enquanto as MHC isoformes I somente compunham 7% da quantidade total de MHC. Essa alteração foi acompanhada de um aumento de 100% na atividade enzimática da citrato sintetase, como um indicador da capacidade oxidativa mitocondrial. Conclui-se que as alterações na performance, nesse exercício e nas características do músculo esquelético, associadas à inatividade que ocorre em indivíduos com LME, são reversíveis, mesmo até 20 anos após a lesão. Sucede que o treino com exercícios induzidos por estimulação elétrica dos músculos paralisados é uma efetiva ferramenta de reabilitação que deveria ser oferecida aos indivíduos com LME no futuro.Spinal cord injured (SCI) individuals most often contract their injury at a young age and are deemed to a life of more or less physical inactivity. In addition to the primary implications of the SCI, severe SCI individuals are stigmatized by conditions related to their physically inactive lifestyle. It is unknown if these inactivity related conditions are potentially reversible and the aim of the present study was, therefore, to examine the effect of exercise on SCI individuals. Ten such individuals (six with tetraplegia and four with paraplegia; age 27-45 years; time since injury 3-23 years) were exercise trained for 1 year using an electrically induced computerized feedback controlled cycle ergometer. They trained for up to three times week (mean 2.3 times), 30 min on each occasion. The gluteal, hamstring and quadriceps muscles were stimulated via lectrodes placed on the skin over their motor points. During lie first training bouts, a substantial variation in performance was seen between the subjects. A majority of them were capable of performing 30 min of exercise in the first bout, however, two individuals were only able to perform a few minutes of exercise. After training for 1 year all of the subjects were able to perform 30 min of continuous training and the work output had increased from 4±1 (mean±SE) to 17±2 kilo Joules per training bout (P&lt;0.05). The maximal oxygen uptake during electrically induced exercise increased from 1.20±0.08 litres per minute measured after a few weeks habituation to the exercise to 1.43±0.09 litres per minute after training for 1 year (P&lt;0.05). Magnetic resonance cross sectional images of the thigh were performed to estimate muscle mass and an increase of 12% (mean, P&lt;0.05) was seen in response to 1 year of training. In biopsies taken before exercise various degrees of atrophy were observed in the individual muscle fibres, a phenomenon that was partially normalized in all subjects after training. The fibre type distribution in skeletal muscles is known to shift towards type IIB fibres (fast twitch, fast fatiguable, glycolytic fibres) within the first 2 years after the spinal cord injury. The muscle in the present investigation contained 63% of myosin heavy chain (MHQ isoform IIB, 33% MHC isoform IIA (fast twitch, fatigue resistant) and less than 5% MHC isoform I (slow twitch) before training. A shift towards more fatigue resistant contractile proteins was found after 1 year of training. The percentage of MHC isoform IIA increased to 61% of all contractile protein and a corresponding decrease to 32% was seen in the fast fatiguable MHC isoform IIB, where as MHC 1 only comprised 7% of the total amount of MHC. This shift was accompanied by a doubling of the enzymatic activity of citrate synthase, as an indicator of mitochondrial oxidative capacity. It is concluded that inactivity-associated changes in exercise perfomance capacity and skeletal muscle occurring in SCI individuals after injury are reversible, even up to over 20 years after the injury. It follows that electrically induced exercise training of the paralysed limbs is an effective rehabilitation tool that should be offered to SCI individuals in the future