This observational study focused on the impact of Interleukin-6 (IL-6)-related factors (notably the IL-6 receptor (IL-6R) gene's rs2228145 polymorphism) on long-COVID risk in individuals who had previously experienced COVID-19 infection(s). The purpose of the study was to better understand such factors' contribution to longCOVID risk, and thus possibly initiate future strategies for using IL-6-related factors as biomarkers predictive of risk (while also obtaining data that may influence long-COVID management and treatment more generally). DNA and blood samples, plus questionnaire responses regarding long-COVID symptoms (including chronic fatigue and cognitive impairment), were collected from 175 participants who had previously experienced COVID-19 infection(s). Potential associations between self-reported long-COVID symptoms and participants' rs2228145 genotypes (determined using TaqMan-based genotyping assays) and/or their circulating IL-6, sIL-6R and sgp130 levels (determined using ELISA) were evaluated. Univariate-regression analyses demonstrated that odds of exhibiting long-COVID symptoms increased with severity/number of previous COVID-19 infection(s) and with hypertension as a co-morbidity, while vaccination decreased the likelihood of developing long-COVID. While long-COVID sufferers exhibited higher IL-6 signalling activity than healthy control individuals, rs2228145 genotype was not associated with long-COVID odds-ratios in- the entire-study cohort. Following identification of significant seasonal variations within our dataset, the entire-study cohort was stratified depending on when samples/questionnaire responses were obtained. In the resulting 'summer' sub-cohort (but not the 'winter' sub-cohort), the rs2228145 AA genotype was significantly over-represented amongst those exhibiting long-COVID symptoms, and long-COVID odds-ratios were significantly reduced for the CC and AC genotypes. While interpretation is complicated by seasonal variations, these findings may be of medical/biomedical value. Importantly, as IL-6 was higher in long-COVID sufferers than healthy controls, and rs2228145 AA genotype-bearing individuals within our 'summer' sub-cohort were at elevated risk of developing long-COVID, these findings point towards possible future use of IL-6 and/or rs2228145 genotype as biomarkers predictive of long-COVID risk, which may bring advantages regarding management and treatment of long-COVID.

Glycan-glycan interactions between viral particles and host cells may lengthen the dwell time of the virus on the cell surface to facilitate cellular receptor engagement. Here, we present a protocol for visualizing glycan-mediated binding between virus or virus-like-particles (VLPs) and human peripheral blood mononuclear cells using transmission electron microscopy (TEM). We describe steps for virus and VLP production, isolation of human peripheral blood mononuclear cells, and sample preparation. We then detail procedures for thin-section TEM.For complete details on the use and execution of this protocol, please refer to Spillings et al.1

The cytokine interleukin-6 (IL-6) is involved in a diverse set of physiological processes. Traditionally, IL-6 has been thought of in terms of its inflammatory actions during the acute phase response and in chronic conditions such as rheumatoid arthritis and obesity. However, IL-6 is also an important signaling molecule during exercise, being acutely released from working muscle fibers with increased exercise duration, intensity, and muscle glycogen depletion. In this context, IL-6 enables muscle-organ crosstalk, facilitating a coordinated response to help maintain muscle energy homeostasis, while also having anti-inflammatory actions. The range of actions of IL-6 can be explained by its dichotomous signaling pathways. Classical signaling involves IL-6 binding to a cell-surface receptor (mbIL-6R; present on only a small number of cell types) and is the predominant signaling mechanism during exercise. Trans-signaling involves IL-6 binding to a soluble version of its receptor (sIL-6R), with the resulting complex having a much greater half-life and the ability to signal in all cell types. Trans-signaling drives the inflammatory actions of IL-6 and is the predominant pathway in disease. A single nucleotide polymorphism (rs2228145) on the IL-6R gene can modify the classical/trans-signaling balance through increasing the levels of sIL-6R. This SNP has clinical significance, having been linked to inflammatory conditions such as rheumatoid arthritis and type 1 diabetes, as well as to the severity of symptoms experienced with COVID-19. This review will describe how acute exercise, chronic training and the rs2228145 SNP can modify the IL-6 signaling pathway and the consequent implications for health and athletic performance.

Given the variability in inflammatory responses to SARS-CoV-2 infection observed within human populations, we aimed to develop an in vitro model system (based on monocyte-macrophages, a key relevant cell type) that could yield insights regarding the impact of rs2228145, a clinically relevant polymorphism within the coding region of a key inflammatory gene in the body’s response to SARS-CoV-2 infection: the interleukin-6 receptor (IL-6R) gene. Three monocyte-macrophage cell-lines (U937, THP-1, MM6) were shown to exhibit AA, AC and CC rs2228145 genotypes, respectively, and to exhibit an MM6 > THP-1 > U937 pattern regarding basal levels of soluble IL-6R (sIL-6R) release. Similar MM6 > THP-1 > U937 patterns were seen regarding the extents to which (i) circulating levels of the IL-6/sIL-6R ‘active complex’ increased and (ii) phosphorylation of the downstream transcription-factor STAT3 occurred, following treatment with SARS-CoV-2 spike protein (SP). Moreover, a blocking antibody for the ACE-2 entry receptor for SARS-CoV-2 suppressed effects (i) and (ii), suggesting that interaction between SP and ACE-2 is the initial event that triggers IL-6/IL-6R signalling in our system. Production of IL-8 occurred to greater extents in A549 lung epithelial cells treated with tissue-culture supernatants from SP-treated MM6 cultures than SP-treated THP-1 or U937 cultures. Our data indicate that the rs2228145 genotype significantly impacts upon SP-associated IL-6/sIL-6R signalling in vitro, suggesting that it may influence in vivo risk of developing severe COVID-19 and/or long-COVID symptoms following infection by SARS-CoV-2. Thus, the rs2228145 genotype may have potential as a biomarker that differentiates between patients at risk of developing severe and/or prolonged symptoms following infection by SARS-CoV-2 and those who are at less risk.

The calcified cartilage zone (CCZ) is a thin interlayer between the hyaline articular cartilage and the subchondral bone and plays an important role in maintaining the joint homeostasis by providing biological and mechanical support from unmineralized cartilage to the underlying mineralized subchondral bone. The hallmark of CCZ characteristics in osteoarthritis (OA) is less well known. The aim of our study is to evaluate the structural, molecular, and biochemical composition of CCZ in tissues affected by primary knee OA and its relationship with disease severity. We collected osteochondral tissue samples stratified according to disease severity, from 16 knee OA patients who underwent knee replacement surgery. We also used meniscectomy-induced rat samples to confirm the pathophysiologic changes of human samples. We defined the characteristics of the calcified cartilage layer using a combination of morphological, biochemical, proteomic analyses on laser micro-dissected tissue. Our results demonstrated that the Calcium/Phosphate ratio is unchanged during the OA progression, but the calcium-binding protein and cadherin binding protein, as well as carbohydrate metabolism-related proteins, undergo significant changes. These changes were further accompanied by thinning of the CCZ, loss of collagen and proteoglycan content, the occurrence of the endochondral ossification, neovasculature, loss of the elastic module, loss of the collagen direction, and increase of the tortuosity indicating an altered structural and mechanical properties of the CCZ in OA. In conclusion, our results suggest that the calcified cartilage changes can reflect the disease progression.

Objectives: Genomic markers linked to exercise-associated health benefits and/or sporting performance are increasingly used to guide decision-making in healthcare and sport/exercise science. This project investigated whether the IL-6R SNP “rs2228145” might be provisionally designated a novel physical activity/exercise marker. rs2228145 results in an Aspartate358/Alanine358 change adjacent to the site where the IL-6R protein is cleaved into two fragments, resulting in ~two-fold increases in blood-borne levels of soluble IL-6R [‘sIL-6R’].Methods: Cohorts of staff/students at Cardiff Metropolitan University donated/completed: [i] finger-prick capillary blood samples (subjected to ELISAs for sIL-6R, the associated signalling protein sgp130, and the IL-6/sIL-6R complex); [ii] cheek-swab samples containing buccal epithelial cell DNA (subjected to PCR-based IL-6R/rs2228145 genotyping assays); [iii] International Physical Activity Questionnaires (to estimate physical activity levels in the week preceding sample donation).Results: As expected, we observed significant genotype-dependent differences in blood-borne sIL-6R levels (CC (44.1±21.7ng/mL) vs. AC (28.6±7.3ng/mL) vs. AA (19.9±6.5ng/mL; P<0.05)); Importantly, AA homozygotes undertook significantly more physical activity than AC heterozygotes (6318±899 v. 3904±2280 MET-mins/week; P<0.01). Genotype was significantly associated with physical activity levels (P<0.05), and sIL-6R (P=0.197) and sgp130 (P=0.160) showed non-significant correlations with physical activity levels.Conclusions: These data suggest that IL-6R/rs2228145 genotype may influence participation in physical activity/exercise, perhaps by impacting on abilities to tolerate activity without experiencing adverse-effects. Although more research is required to confirm these preliminary findings, designation of IL-6R/rs2228145 as a novel marker, and determination of participants’ IL-6R/rs2228145 genotypes, may in future be useful tools to aid exercise-providers in designing personalised exercise programmes matched to clients/patients.

15 Introduction: IL-6 has been ascribed both positive and negative roles in the context of 16 exercise and training. The dichotomous nature of IL-6 signalling appears to be determined by 17 the respective concentration of its receptors (both membrane-bound (IL-6R) and soluble (sIL18 6R) forms). The purpose of the present study was to investigate the response of sIL-6R to 19 long-term training, and to investigate the relationship between sIL-6R, self-reported measures 20 of wellbeing, and upper respiratory illness symptoms (URS) in highly-trained endurance 21 athletes. Methods: Twenty-nine athletes provided resting blood samples, and completed 22 wellbeing and illness monitoring questionnaires, on a weekly basis for a period of 18 weeks 23 during a winter training block. Results: URS were not correlated to concentrations of sIL-6R 24 or cortisol, but there was a non-significant trend (P=0.08) for the most illness-prone athletes 25 (as defined by self-reported illness questionnaire data) to exhibit higher average sIL-6R 26 concentrations compared to the least ill (23.7±4.3 Vs 20.1±3.8 ng/ml). Concentrations of sIL27 6R were positively correlated to subjective measures of stress (r=0.64, P=0.004) and mood 28 (r=0.49, P=0.02), but were negatively correlated to sleep quality (r=-0.43, P=0.05) and 29 cortisol concentration (r=-0.17, P=0.04). In a sub-group of 10 athletes, weekly training 30 distance was quantified by coaching staff, and this negatively correlated with sIL-6R in the 31 following week (r=-0.74, P<0.005). Conclusion: The findings of the current study suggest 32 that sIL-6R is responsive to prolonged periods of exercise training, with sIL-6R levels 33 varying related to the volume of training performed in the preceding week. Importantly, our 34 data indicate that changes in sIL-6R levels could be linked to common symptoms of 35 overreaching such as high levels of stress, and/or depressed mood. 36 37

Niemann-Pick disease type C1 (NPC disease) is a neurodegenerative multi-lipid lysosomal storage disease caused by mutations in the NPC1 gene presenting with reduced lysosomal Ca2+ signalling and inhibited late endosome-lysosome transport. Elevating cytosolic Ca2+ levels in NPC cells has been shown to reduce lysosomal lipid storage. Treating Npc1-/- mice with the Ca2+ modulator curcumin led to reduced lipid storage, improved life expectancy and function. These studies led to reported utilisation of curcumin supplements by NPC disease families despite there being no clinical evidence of benefit and a report indicating no benefit of nanoformulated curcumin in Npc1-/- mice. The aim of this study was to determine whether various commercially available curcumin nanoformulations were capable of reproducing the findings obtained with unformulated pharmaceutical grade curcumin. We compared seven curcumin nanoformulations in Npc1-/- mouse astrocytes. All the nanoformulations elevate cytosolic Ca2+ levels but only two lowered lysosomal lipid storage. Importantly, some caused elevations in NPC lysosomal storage and/or decreased cellular viability. Although this is an in vitro study, our findings suggest that care should be taken when contemplating the use of curcumin supplements for NPC disease.

INTRODUCTION:Interleukin 6 (IL-6) has been ascribed both positive and negative roles in the context of exercise and training. The dichotomous nature of IL-6 signaling seems to be determined by the respective concentration of its receptors (both membrane-bound [IL-6R] and soluble [sIL-6R] forms). The purpose of the present study was to investigate the response of sIL-6R to long-term training and to investigate the relationship between sIL-6R, self-reported measures of well-being, and upper respiratory symptoms in highly trained endurance athletes. METHODS:Twenty-nine athletes provided resting blood samples and completed well-being and illness monitoring questionnaires on a weekly basis for a period of 18 wk during a winter training block. RESULTS:Upper respiratory symptoms were not correlated to concentrations of sIL-6R or cortisol, but there was a nonsignificant trend (P = 0.08) for the most illness-prone athletes (as defined by self-reported illness questionnaire data) to exhibit higher average sIL-6R concentrations compared with the least ill (23.7 ± 4.3 vs 20.1 ± 3.8 ng·mL). Concentrations of sIL-6R were positively correlated to subjective measures of stress (r = 0.64, P = 0.004) and mood (r = 0.49, P = 0.02) but were negatively correlated to sleep quality (r = -0.43, P = 0.05) and cortisol concentration (r = -0.17, P = 0.04). In a subgroup of 10 athletes, weekly training distance was quantified by coaching staff, and this negatively correlated with sIL-6R in the following week (r = -0.74, P < 0.005). CONCLUSION:The findings of the current study suggest that sIL-6R is responsive to prolonged periods of exercise training, with sIL-6R levels varying related to the volume of training performed in the preceding week. Importantly, our data indicate that changes in sIL-6R levels could be linked to common symptoms of overreaching, such as high levels of stress, and/or depressed mood.

In this review, we discuss exercise as an oxidative stressor, and elucidate the mechanisms and downstream consequences of exercise-induced oxidative stress. Reactive oxygen species (ROS) are generated in the mitochondria of contracting skeletal myocytes; also, their diffusion across the myocyte membrane allows their transport to neighbouring muscle tissue and to other regions of the body. Although very intense exercise can induce oxidative damage within myocytes, the magnitudes of moderate-intensity exercise-associated increases in ROS are quite modest (~two-fold increases in intracellular and extracellular ROS concentrations during exercise), and so the effects of such increases are likely to involve redox-sensitive signalling effects rather than oxidative damage. Therefore, the responses of muscle and non-muscle cells to exercise-associated redox-sensitive signalling effects will be reviewed; for example, transcription factors such as Peroxisome Proliferator Activated Receptor-gamma (PPARγ) and Liver X-Receptor-alpha (LXRα) comprise redox-activable signalling systems, and we and others have reported exercise-associated modulation of PPARγ and/or LXRα-regulated genes in skeletal myocyte and in non-muscle cell-types such as monocyte-macrophages. Finally, the consequences of such responses in the context of management of chronic inflammatory conditions, and also their implications for the design of exercise training programmes (particularly the use of dietary antioxidants alongside exercise), will be discussed.

The assessment of the mean annual runoff and its interannual variability in a basin is the first and fundamental task for several activities related to water resources management and water quality analysis. The scarcity of observed runoff data is a common problem worldwide so that the runoff estimation in ungauged basins is still an open question. In this context, the main aim of this work is to propose and test a simple tool able to estimate the probability distribution of the annual surface runoff in ungauged river basins in arid and semi-arid areas using a simplified Fu's parameterization of the Budyko's curve at regional scale. Starting from a method recently developed to derive the distribution of annual runoff, under the assumption of negligible inter-annual change in basin water storage, we here generalize the application to any catchment where the parameter of the Fu's curve is known. Specifically, we provide a closed-form expression of the annual runoff distribution as a function of the mean and standard deviation of annual rainfall and potential evapotranspiration, and the Fu's parameter. The proposed method is based on a first order Taylor expansion of the Fu's equation and allows calculating the probability density function of annual runoff in seasonally dry arid and semi-arid geographic context around the world by taking advantage of simple easy-to-find climatic data and the many studies with estimates of the Fu's parameter worldwide. The computational simplicity of the proposed tool makes it a valuable supporting tool in the field of water resources assessment for practitioners, regional agencies and authorities.

Monocytes may be primed towards differentiation into classically activated M1 macrophages or alternatively activated M2 macrophages. M1 macrophages greatly contribute to the inflammation which promotes insulin resistance, whereas M2 macrophages resolve inflammation. We have previously shown that exercise increases M2 marker expression in mixed mononuclear cells, possibly via activation of the nuclear transcription factor PPARγ. However, these effects have not been demonstrated specifically within monocytes. Thus, we aimed to investigate whether moderate-intensity exercise elicited similar effects on monocytic M1/M2 marker expression and PPARγ activity to those reported previously in mononuclear cells, so as to further elucidate the mechanisms by which exercise may alter inflammatory status and, accordingly, prevent insulin resistance.

Objectives-MMP-9 is involved in degrading the extracellular matrix (ECM); specifically elastin, which provides elasticity to the arterial wall. Elastin degradation and restructuring of the ECM results in increased vascular remodelling and arterial stiffness. Conversely, exercise improves age-related vascular stiffening. Therefore, this study aimed to investigate whether participation in a green-exercise programme affects vascular haemodynamics and mRNA expression of MMP-9. Methods-Thirty-six healthy, sedentary individuals (44±2yrs; not taking any cardiovascular-acting medication) joining a moderate-intensity, aerobic green-exercise programme, were recruited. At baseline and 8-weeks into the programme, physical activity (measured in weekly MET-minutes [IPAQ]), supine mean arterial blood pressure (MAP), augmentation index (AIx) and aortic pulse wave velocity (aPWV) data were collected and blood samples were obtained. Leukocytic MMP9 mRNA expression (RT-PCR) and plasma protein levels (ELISA) were analysed; AIx and aPWV were measured via applanation tonometry (SphygmoCor, Atcor Medical, Australia). Results-The cohort was split into those who adhered (n=17) and did not adhere (n=19) to the programme. MMP-9 expression, MAP and AIx all decreased significantly in the exerciseadherent group (cf. the non-adherent group), while significant correlations were seen between: (i) ΔMMP-9 expression and ΔMET-minutes/wk; (ii) ΔMMP-9 expression and ΔAIx; (iii) ΔAIx and ΔMET-minutes/wk (P<0.05 in all cases). aPWV did not change significantly between the groups. Conclusions-These findings suggest that exercise-induced down-regulation of MMP-9 may contribute to reduced ECM degradation and therefore ameliorate vascular remodelling. Additional studies are needed to explore these findings further; however, these data may provide a biomolecular mechanism for aerobic exercise’s ability to delay age-related increases in arterial stiffening.

Acute increases in interleukin (IL)-6 following prolonged exercise are associated with the induction of a transient anti-inflammatory state (e.g., increases in IL-10) that is partly responsible for the health benefits of regular exercise. The purposes of this study were to investigate the IL-6-related inflammatory response to high-intensity interval exercise (HIIE) and to determine the impact of exercise intensity and volume on this response. Ten participants (5 males and 5 females) completed 3 exercise bouts of contrasting intensity and volume (LOW, MOD, and HIGH). The HIGH protocol was based upon standard HIIE protocols, while the MOD and LOW protocols were designed to enable a comparison of exercise intensity and volume with a fixed duration. Inflammatory cytokine concentrations were measured in plasma (IL-6, IL-10) and also determined the level of gene expression (IL-6, IL-10, and IL-4R) in peripheral blood. The plasma IL-6 response to exercise (reported as fold changes) was significantly greater in HIGH (2.70 ± 1.51) than LOW (1.40 ± 0.32) (P = 0.04) and was also positively correlated to the mean exercise oxygen uptake (r = 0.54, P < 0.01). However, there was no change in anti-inflammatory IL-10 or IL-4R responses in plasma or at the level of gene expression. HIIE caused a significant increase in IL-6 and was greater than that seen in low-intensity exercise of the same duration. The increases in IL-6 were relatively small in magnitude, and appear to have been insufficient to induce the acute systemic anti-inflammatory effects, which are evident following longer duration exercise.

BACKGROUND:To evaluate the ability of community-based exercise programmes to facilitate public participation in exercise and hence improved cardiovascular health, we assessed the respective impacts of: a continuously monitored exercise programme based within our university (study 1); a Valleys Regional Park-facilitated community-based outdoor exercise programme (study 2); a Wales National Exercise Referral Scheme-delivered exercise-referral programme (study 3).METHODS:Biomolecular (monocytic PPARγ target gene expression), vascular haemodynamic (central/peripheral blood pressure, arterial stiffness), clinical (insulin sensitivity, blood lipids) and anthropometric (body mass index, waist circumference, heart rate) parameters were investigated using RT-PCR, applanation tonometry, chemical analysis and standard anthropometric techniques.RESULTS:In studies 1-3, 22/28, 32/65 and 11/14 participants adhered to their respective exercise programmes, and underwent significant increases in physical activity levels. Importantly, beneficial effects similar to those seen in our previous studies (eg, modulations in expression of monocytic PPARγ target genes, decreases in blood pressure/arterial stiffness, improvements in blood lipids/insulin sensitivity) were observed (albeit to slightly differing extents) only in participants who adhered to their respective exercise programmes. While study 1 achieved more intense exercise and more pronounced beneficial effects, significant cardiovascular risk-lowering health benefits related to biomolecular markers, blood pressure, arterial stiffness and blood lipids were achieved via community/referral-based delivery modes in studies 2 and 3.CONCLUSIONS:Because cardiovascular health benefits were observed in all 3 studies, we conclude that the majority of benefits previously reported in laboratory-based studies can also be achieved in community-based/exercise-referral settings. These findings may be of use in guiding policymakers with regard to introduction and/or continued implementation of community/referral-based exercise programmes.

Background: Augmentation Index (AIx) is considered a sensitive marker of arterial stiffness in young individuals. Increased levels of inflammatory markers such as interleukin-6 (IL-6) are associated with increased levels of arterial stiffness in older and diseased populations. However, little is known about these associations in young healthy individuals, as concentrations are prone to fluctuation. Data suggests that increased levels of the soluble IL-6 receptor (sIL-6R) facilitate the detrimental pro-inflammatory signalling of IL-6, which may highlight sIL-6R’s role as a mediator of chronic inflammation and associated disease states. Therefore, the aim of the study was to determine the associations between sIL-6R and IL-6 with AIx in a young healthy cohort. Methods: In 20 healthy male subjects (age 22±3 years), self-reported physical activity levels (PA) were determined via International Physical Activity Questionnaire. Peripheral and central blood pressure and AIx@75 were measured using the Mobil-O-Graph system (IEM). Plasma concentrations of sIL-6R and IL-6 were assessed via enzyme-linked immunosorbent assay (RnD systems). Results: AIx@75 was significantly associated with levels of sIL-6R (r=0.5, P=0.02) but not associated with levels of IL-6 or PA (P>0.05). Conclusion: These novel pilot data suggest that elevated concentrations of sIL-6R at an early age may be indicative of an underlying vulnerability to inflammation-associated vascular stiffening. Furthermore, the absence of any association between IL-6 and AIx in our study implies that sIL-6R may be a more suitable biomarker than IL-6 for use in understanding the mechanisms by which inflammation affects vascular stiffening. However, larger studies are required to confirm our findings.

Peroxisome proliferator-activated receptor gamma (PPARγ) is known to be activated via exercise-associated transient increases in oxidative stress. However, the precise mechanism(s) triggering PPARγ activation in monocytes during/following exercise remain to be confirmed. Here, two cohorts of five healthy male individuals undertook exercise bouts (cycling; 70% VO2max; 45 min) in the presence/absence of dietary antioxidant supplementation (vitamins C (1000 mg/day) and E (400IU/day) for four weeks before exercise); monocytic 5' adenosine monophosphate-activated protein kinase (AMPK)/PPARγ co-activator-1alpha (PGC-1α)/PPARγ signalling was investigated in samples obtained before exercise and up to 24 h after exercise, while THP-1 cells were cultured as an in vitro monocyte model. In THP-1 cells, AMPKα1 was phosphorylated within 1h of menadione (15 μM)-triggered increases in [reactive oxygen species (ROS)]cyto, an effect which was followed by upregulation of PPARγ and several of its target genes (PGC-1α, liver X receptor alpha [LXRα] and ATP-binding cassette subfamily A, member 1 [ABCA1]; 24-72 h), with these effects being blunted by co-administration of vitamin C (62.5 μM). Conversely, treatment with oxidised low-density lipoprotein (oxLDL) (1 μg/mL; 24-72 h), but not non-oxidised LDL, upregulated the above PPARγ-regulated genes without affecting AMPKα1 phosphorylation. In vivo, dietary antioxidant supplementation (which is known to prevent exercise-triggered increases in oxLDL levels) blunted exercise-associated upregulation of the above PPARγ-regulated genes, but had no effect on exercise-associated transient [ROS]cyto increases, or on AMPK phosphorylation. These data suggest that exercise-associated PPARγ signalling effects appear, at least in monocytes, to be mediated by increased generation of PPARγ ligands via oxidation of lipoproteins (following exercise-associated transient increases in oxidative stress), rather than via [ROS]cyto-mediated AMPK activation. These findings may be of clinical relevance, as PPARγ activation in monocytes is associated with beneficial effects related to type-2 diabetes and its cardiovascular complications.

Interluekin-6 (IL-6) plays an important role in immunological, inflammatory and metabolic responses to exercise. The downstream effects of IL-6 signalling are dependent on the binding to its receptors, both soluble (sIL-6R) and membrane bound. There is evidence that sIL-6R concentrations change in response to exercise and are related to exercise load and fatigue. However, considerably less is known about the sIL-6R response to prolonged exercise training. Knowledge of the receptor response to training may provide insight into the mechanisms underlying cytokine regulation of a number of biological processes. This study investigated the effect of a prolonged period of training on sIL-6R and how this related to perceptions of fatigue. Ten (7 females, 3 males) highly trained swimmers participated. sIL-6R was determined from capillary blood samples collected prior to training each week for a period of 18 weeks. Participants also completed a subjective wellbeing-monitoring questionnaire once a week prior to training. sIL-6R was negatively correlated to weekly training volume (r = -0.68, r2 = 0.47, p < 0.005). sIL-6R was 74% higher (25.7 Vs 14.8 ng/ml, p = 0.04) in those reporting lowest Vs highest ratings of fatigue. This study provides a) further evidence for the role of the sIL-6R in sensations of fatigue at rest and b) novel evidence that the sIL-6R is responsive to long-term endurance training and that this response is associated with training volume. sIL-6R appears to be responsive to weekly training mileage, decreasing during periods of increased training mileage and returning to baseline levels when training mileage is reduced. Given that IL-6 in combination with sIL-6R is reported to have a greater sensitising effect with regard to nociception/inflammatory hyperalgesia than IL-6 alone, the observed decline in circulating sIL-6R may provide a mechanism for the impact of exercise on perceptions of fatigue, and hence the ability to adhere to high-mileage training.

IL-6 plays a mechanistic role in conditions such as metabolic syndrome, chronic fatigue syndrome and clinical depression and also plays a major role in inflammatory and immune responses to exercise. The purpose of this study was to investigate the levels of resting and post exercise IL-6 when measured in venous plasma, saliva and capillary plasma. Five male and five females completed 2 separate exercise trials, both of which involved standardized exercise sessions on a cycle ergometer. Venous blood and saliva samples were taken immediately before and after Trial A, venous and capillary blood samples were taken immediately before and after Trial B. IL-6 values were obtained using a high-sensitivity enzyme-linked immunosorbent assay (ELISA). In Trial A venous plasma IL-6 increased significantly from 0.4±0.14pg/ml to 0.99±0.29pg/ml (P<0.01) while there was no increase in salivary IL-6. Venous plasma and salivary IL-6 responses were not correlated at rest, post exercise or when expressed as an exercise induced change. In Trial B venous and capillary plasma IL-6 increased significantly (venous: 0.22±0.18 to 0.74±0.28pg/ml (P⩽0.01); capillary: 0.37±0.22 to 1.08±0.30pg/ml (P<0.01). Venous and capillary plasma responses did not correlate at rest (r=0.59, P=0.07) but did correlate post exercise (r=0.79, P⩾0.001) and when expressed as an exercise induced change (r=0.71, P=0.02). Saliva does not appear to reflect systemic IL-6 responses, either at rest or in response to exercise. Conversely, capillary plasma responses are reflective of systemic IL-6 responses to exercise.