Dose-Response of Myofibrillar Protein Synthesis To Ingested Whey Protein During Energy Restriction in Overweight Postmenopausal Women: A Randomized, Controlled Trial

BACKGROUND

Diet-induced weight loss is associated with a decline in lean body mass, as mediated by an impaired response of muscle protein synthesis (MPS). The dose-response of MPS to ingested protein, with or without resistance exercise, is well characterized during energy balance but limited data exist under conditions of energy restriction in clinical populations.

OBJECTIVE

To determine the dose-response of MPS to ingested whey protein following short-term diet-induced energy restriction in overweight, postmenopausal, women at rest and postexercise.

DESIGN

Forty middle-aged (58.6±0.4 y), overweight (BMI: 28.6±0.4), postmenopausal women were randomly assigned to 1 of 4 groups: Three groups underwent 5 d of energy restriction (∼800 kcal/d). On day 6, participants performed a unilateral leg resistance exercise bout before ingesting either a bolus of 15g (ERW15, n = 10), 35g (ERW35, n = 10) or 60g (ERW60, n = 10) of whey protein. The fourth group (n = 10) ingested a 35g whey protein bolus after 5 d of an energy balanced diet (EBW35, n = 10). Myofibrillar fractional synthetic rate (FSR) was calculated under basal, fed (FED) and postexercise (FED-EX) conditions by combining an L-[ring-13C6] phenylalanine tracer infusion with the collection of bilateral muscle biopsies.

RESULTS

Myofibrillar FSR was greater in ERW35 (0.043±0.003%/h, P = 0.013) and ERW60 (0.042±0.003%/h, P = 0.026) than ERW15 (0.032 ± 0.003%/h), with no differences between ERW35 and ERW60 (P = 1.000). Myofibrillar FSR was greater in FED (0.044 ± 0.003%/h, P < 0.001) and FED-EX (0.048 ± 0.003%/h, P < 0.001) than BASAL (0.027 ± 0.003%/h), but no differences were detected between FED and FED-EX (P = 0.732) conditions. No differences in myofibrillar FSR were observed between EBW35 (0.042 ± 0.003%/h) and ERW35 (0.043 ± 0.003%/h, P = 0.744).

CONCLUSION

A 35 g dose of whey protein, ingested with or without resistance exercise, is sufficient to stimulate a maximal acute response of MPS following short-term energy restriction in overweight, postmenopausal women, and thus may provide a per serving protein recommendation to mitigate muscle loss during a weight loss program.

TRIAL REGISTRY

clinicaltrials.gov (ID: NCT03326284).

Resistance Exercise Counteracts the Impact of Androgen Deprivation Therapy on Muscle Characteristics in Cancer Patients

CONTEXT

Androgen deprivation therapy (ADT) forms the cornerstone in prostate cancer (PCa) treatment. However, ADT also lowers skeletal muscle mass.

OBJECTIVE

To identify the impact of ADT with and without resistance exercise training on muscle fiber characteristics in PCa patients.

METHODS

Twenty-one PCa patients (72 ± 6 years) starting ADT were included. Tissue samples from the vastus lateralis muscle were assessed at baseline and after 20 weeks of usual care (n = 11) or resistance exercise training (n = 10). Type I and II muscle fiber distribution, fiber size, and myonuclear and capillary contents were determined by immunohistochemistry.

RESULTS

Significant decreases in type I (from 7401 ± 1183 to 6489 ± 1293 μm2, P < .05) and type II (from 6225 ± 1503 to 5014 ± 714 μm2, P < .05) muscle fiber size were observed in the usual care group. In addition, type I and type II individual capillary-to-fiber ratio (C/Fi) declined (-12% ± 12% and -20% ± 21%, respectively, P < .05). In contrast, significant increases in type I (from 6700 ± 1464 to 7772 ± 1319 μm2, P < .05) and type II (from 5248 ± 892 to 6302 ± 1385 μm2, P < .05) muscle fiber size were observed in the training group, accompanied by an increase in type I and type II muscle fiber myonuclear contents (+24% ± 33% and +21% ± 23%, respectively, P < .05) and type I C/Fi (+18% ± 14%, P < .05).

CONCLUSION

The onset of ADT is followed by a decline in both type I and type II muscle fiber size and capillarization in PCa patients. Resistance exercise training offsets the negative impact of ADT and increases type I and II muscle fiber size and type I muscle fiber capillarization in these patients.

Anabolic effects of oral leucine-rich protein with and without β-hydroxybutyrate on muscle protein metabolism in a novel clinical model of systemic inflammation-a randomized crossover trial

BACKGROUND

β-lactoglobulin (BLG) stimulates muscle protein synthesis and β-hydroxybutyrate (BHB) inhibits muscle breakdown. Whether combining the 2 can additively attenuate disease-induced muscle loss is unknown.

OBJECTIVE

Based on previous observations of anticatabolic effects of protein and ketone bodies during inflammation, and using a novel model combining ongoing systemic inflammation, fasting, and immobilization, we tested whether the anticatabolic muscle response to oral amino acids is altered compared with control conditions, as well as whether coadministration of oral BHB and BLG further improves the muscle anabolic response. Muscle net balance (NBphe) was the primary outcome and intramyocellular signals were assessed.

METHODS

In a randomized crossover design, 8 young men underwent either preconditioning with LPS (prestudy day: 1 ng/kg, study day: 0.5 ng/kg) combined with a 36-h fast and bed rest to mimic catabolic inflammatory disease (CAT) or an overnight fast (control [CTR]) prior to isocaloric nutritional interventions on 3 occasions separated by ∼6 wk (range 42 to 83 d).

RESULTS

NBphe increased similarly upon all conditions (interaction P = 0.65). From comparable baseline rates, both Rdphe [muscle synthesis, median ratio (95% CI): 0.44 (0.23, 0.86) P = 0.017] and Raphe [muscle breakdown, median ratio (95% CI): 0.46 (0.27, 0.78) P = 0.005] decreased following BHB + BLG compared with BLG. BLG increased Rdphe more under CAT conditions compared with CTR (interaction P = 0.02). CAT increased inflammation, energy expenditure, and lipid oxidation and decreased Rdphe and anabolic signaling [mammalian target of rapamycin (mTOR) and eukaryotic translation initiation factor 4E-binding protein 1 (4EPB1) phosphorylation].

CONCLUSION

In contrast to our initial hypothesis, NBphe increased similarly following BLG during CAT and CTR conditions; CAT however, specifically stimulated the BLG-mediated increase in protein synthesis, whereas BHB coadministration did not affect NBphe, but distinctly dampened the BLG-induced increase in muscle amino acid fluxes thereby liberating circulating amino acids for anabolic actions elsewhere.

The effect of daily protein supplementation, with or without resistance training for 1 year, on muscle size, strength, and function in healthy older adults: A randomized controlled trial

BACKGROUND

Protein supplementation alone or combined with resistance training has been proposed to be effective in counteracting age-related losses of muscle mass and strength.

OBJECTIVES

To investigate the effect of protein supplementation alone or combined with light-intensity or heavy-load resistance exercise on muscle size, strength, and function in older adults.

METHODS

In a 1-y randomized controlled trial, 208 healthy older adults (>65 y) were randomly assigned to 1 of 5 interventions: 1) carbohydrate supplementation (CARB); 2) collagen protein supplementation (COLL); 3) whey protein supplementation (WHEY); 4) light-intensity resistance training 3-5 times/wk with whey protein supplementation (LITW); and 5) heavy resistance training 3 times weekly with whey protein supplementation (HRTW). Protein supplements contained 20 g protein + 10 g carbohydrate, whereas CARB contained 30 g of carbohydrates. All intervention groups received the supplement twice daily. The primary outcome was change in the quadriceps cross-sectional area (qCSA). Secondary outcomes included measures of lower extremity strength and power, functional capabilities, and body composition.

RESULTS

There were 184 participants who completed the study. COLL and WHEY did not affect any measured parameter compared to CARB. Compared to WHEY, HRTW improved the qCSA size (between-group difference, +1.68 cm2; 95% CI, +0.41 to +2.95 cm2; P = 0.03), as well as dynamic (+18.4 Nm; 95% CI, +10.1 to +26.6 Nm; P < 10-4) and isometric knee extensor strength (+23.9 Nm; 95% CI, +14.2 to +33.6 Nm; P < 10-5). LITW did not improve the qCSA size, but increased dynamic knee extensor strength compared to WHEY (+13.7 Nm; 95% CI, +5.3 and +22.1 Nm; P = 0.01).

CONCLUSIONS

Recommending protein supplementation as a stand-alone intervention for healthy older individuals seems ineffective in improving muscle mass and strength. Only HRTW was effective in both preserving muscle mass and increasing strength. Thus, we recommend that future studies investigate strategies to increase long-term compliance to heavy resistance exercise in healthy older adults. This trial was registered at clinicaltrials.gov as NCT02034760.

β-Lactoglobulin Elevates Insulin and Glucagon Concentrations Compared with Whey Protein-A Randomized Double-Blinded Crossover Trial in Patients with Type Two Diabetes Mellitus

Whey protein is an insulinotropic fraction of dairy that reduces postprandial glucose levels in patients with type 2 diabetes mellitus (T2DM). We have recently shown that β-lactoglobulin (BLG), the largest protein fraction of whey, elevates insulin concentrations compared with iso-nitrogenous whey protein isolate (WPI) in healthy individuals. We therefore hypothesized that BLG pre-meals would lower glucose levels compared with WPI in patients with T2DM. We investigated 16 participants with T2DM using a randomized double-blinded cross-over design with two pre-meal interventions, (i) 25 g BLG and (ii) 25 g WPI prior to an oral glucose tolerance test (OGTT), followed by four days of continuous glucose monitoring (CGM) at home. BLG increased concentrations of insulin with 10%, glucagon with 20%, and glucose with 10% compared with WPI after the OGTT (all p < 0.05). Both BLG and WPI reduced the interstitial fluid (ISF) glucose concentrations (using CGM) with 2 mM and lowered glycemic variability with 10-15%, compared with tap-water (p < 0.05), and WPI lowered the ISF glucose with 0.5 mM compared with BLG from 120 min and onwards (p < 0.05). In conclusion, BLG pre-meals resulted in higher insulin, glucagon, and glucose concentrations compared with WPI in participants with T2DM. Pre-meal servings of WPI remains the most potent protein in terms of lowering postprandial glucose excursions.

Effects of protein intake prior to carbohydrate-restricted endurance exercise: a randomized crossover trial

Background

Deliberately training with reduced carbohydrate availability, a paradigm coined training low, has shown to promote adaptations associated with improved aerobic capacity. In this context researchers have proposed that protein may be ingested prior to training as a means to enhance the protein balance during exercise without spoiling the effect of the low carbohydrate availability. Accordingly, this is being practiced by world class athletes. However, the effect of protein intake on muscle protein metabolism during training low has not been studied.

This study aimed to examine if protein intake prior to exercise with reduced carbohydrate stores benefits muscle protein metabolism in exercising and non-exercising muscles.

Methods

Nine well-trained subjects completed two trials in random order both of which included a high-intensity interval ergometer bike ride (day 1), a morning (day 2) steady state ride (90 min at 65% VO₂peak, 90ss), and a 4-h recovery period. An experimental beverage was consumed before 90ss and contained either 0.5 g whey protein hydrolysate [WPH]/ kg lean body mass or flavored water [PLA]. A stable isotope infusion (L-[ring-¹³C₆]-phenylalanine) combined with arterial-venous blood sampling, and plasma flow rate measurements were used to determine forearm protein turnover. Myofibrillar protein synthesis was determined from stable isotope incorporation into the vastus lateralis.

Results

Forearm protein net balance was not different from zero during 90ss exercise (nmol/100 ml/min, PLA: 0.5 ± 2.6; WPH: 1.8, ± 3.3) but negative during the 4 h recovery (nmol/100 ml/min, PLA: − 9.7 ± 4.6; WPH: − 8.7 ± 6.5); no interaction (P = 0.5) or main effect of beverage (P = 0.11) was observed. Vastus lateralis myofibrillar protein synthesis rates were increased during 90ss exercise (+ 0.02 ± 0.02%/h) and recovery (+ 0.02 ± 0.02%/h); no interaction (P = 0.3) or main effect of beverage (P = 0.3) was observed.

Conclusion

We conclude that protein ingestion prior to endurance exercise in the energy- and carbohydrate-restricted state does not increase myofibrillar protein synthesis or improve net protein balance in the exercising and non-exercising muscles, respectively, during and in the hours after exercise compared to ingestion of a non-caloric control.

Trial registration

clinicaltrials.gov, NCT01320449. Registered 10 May 2017 – Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03147001

No effect of anti-inflammatory medication on postprandial and postexercise muscle protein synthesis in elderly men with slightly elevated systemic inflammation

BACKGROUND

Based on circulating C-reactive protein (CRP) levels, some individuals develop slightly increased inflammation as they age. In elderly inflamed rats, the muscle response to protein feeding is impaired, whereas it can be maintained by treatment with non-steroidal anti-inflammatory drugs (NSAIDs). It is unknown whether this applies to elderly humans with increased inflammation. Thus, the muscle response to whey protein bolus ingestion with and without acute resistance exercise was compared between healthy elderly individuals and elderly individuals with slightly increased inflammation±NSAID treatment.

METHODS

Twenty-four elderly men (>60years) were recruited. Of those, 14 displayed a slightly increased systemic inflammation (CRP>2mg/l) and were randomly assigned to NSAID (Ibuprofen 1800mg/day) or placebo treatment for 1week. The remaining 10 elderly individuals served as healthy controls (CRP<1mg/l). The muscle protein synthetic response was measured as the fractional synthetic rate (FSR) and p70S6K phosphorylation-to-total protein ratio.

RESULTS

The basal myofibrillar FSR and the myofibrillar FSR responses to whey protein bolus ingestion with and without acute resistance exercise were maintained in inflamed elderly compared to healthy controls (p>0.05) and so was p70S6K phosphorylation. Moreover, NSAID treatment did not significantly improve the myofibrillar and connective tissue FSR responses or reduce the plasma CRP level in inflamed, elderly individuals (p>0.05).

CONCLUSION

A slight increase in systemic inflammation does not affect the basal myofibrillar FSR or the myofibrillar FSR responses, which suggests that elderly individuals with slightly increased inflammation can benefit from protein ingestion and resistance exercise to stimulate muscle protein anabolism. Moreover, the NSAID treatment did not significantly affect the myofibrillar or connective tissue FSR responses to protein ingestion and acute resistance exercise.

Interactions between muscle stem cells, mesenchymal-derived cells and immune cells in muscle homeostasis, regeneration and disease

Recent evidence has revealed the importance of reciprocal functional interactions between different types of mononuclear cells in coordinating the repair of injured muscles. In particular, signals released from the inflammatory infiltrate and from mesenchymal interstitial cells (also known as fibro-adipogenic progenitors (FAPs)) appear to instruct muscle stem cells (satellite cells) to break quiescence, proliferate and differentiate. Interestingly, conditions that compromise the functional integrity of this network can bias muscle repair toward pathological outcomes that are typically observed in chronic muscular disorders, that is, fibrotic and fatty muscle degeneration as well as myofiber atrophy. In this review, we will summarize the current knowledge on the regulation of this network in physiological and pathological conditions, and anticipate the potential contribution of its cellular components to relatively unexplored conditions, such as aging and physical exercise.

Bosentan Improves Exercise Capacity in Adolescents and Adults After Fontan Operation

Background—

The Fontan procedure has improved survival in children with functionally univentricular hearts. With time, however, complications such as reduced exercise capacity are seen more frequently. Exercise intolerance is multifactorial, but pulmonary vascular resistance probably plays a crucial role. Elevated pulmonary vascular resistance has been associated with raised levels of endothelin-1, which are common both before and after Fontan operations. Treatment with endothelin-1 receptor antagonists could theoretically improve cardiopulmonary hemodynamics and exercise capacity. The aim of this study was therefore to examine the efficacy and safety of bosentan in Fontan patients.

Methods and Results—

Seventy-five adolescents and adults were randomized 1:1 to 14 weeks of treatment with bosentan or placebo. Cardiopulmonary exercise test, functional class, blood samples, and quality-of-life questionnaires were evaluated at baseline and at the end of treatment. Sixty-nine patients (92%) completed the study. Peak oxygen consumption increased 2.0 mL·kg −1 ·min −1 (from 28.7 to 30.7 mL·kg −1 ·min −1 ) in the bosentan group compared with 0.6 mL·kg −1 ·min −1 (from 28.4 to 29.0 mL·kg −1 ·min −1 ) in the placebo group ( P =0.02). Cardiopulmonary exercise test time increased by 0.48 minute (from 6.79 to 7.27 minutes) versus 0.08 minute (from 6.94 to 7.02 minutes; P =0.04). Nine bosentan-treated patients improved 1 functional class, whereas none improved in the placebo group ( P =0.0085). Side effects were mild and occurred equally in both groups. No serious adverse effects were seen, and no patients had liver enzyme levels above the 3-fold upper limit.

Conclusions—

Bosentan improves exercise capacity, exercise time, and functional class in Fontan patients without serious adverse events or hepatotoxicity.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01292551.

Alterations in molecular muscle mass regulators after 8 days immobilizing Special Forces mission

In military operations, declined physical capacity can endanger the life of soldiers. During special support and reconnaissance (SSR) missions, Special Forces soldiers sustain 1-2 weeks full-body horizontal immobilization, which impairs muscle strength and performance. Adequate muscle mass and strength are necessary in combat or evacuation situations, which prompt for improved understanding of muscle mass modulation during SSR missions. To explore the molecular regulation of myofiber size during a simulated SSR operation, nine male Special Forces soldiers were biopsied in m. vastus lateralis pre and post 8 days immobilizing restricted prone position. After immobilization, total mammalian target of rapamycin protein was reduced by 42% (P < 0.05), whereas total and phosphorylated protein levels of Akt, ribosomal protein S6k, 4E-BP1, and glycogen synthase kinase3β were unchanged. Messenger RNA (mRNA) levels of the atrogenes forkhead box O3 (FoxO3), atrogin1, and muscle ring finger protein1 (MuRF1) increased by 36%, 53%, and 71% (P < 0.01), MuRF1 protein by 51% (P = 0.05), whereas FoxO1 and peroxisome proliferator-activated receptor γ coactivator-1 β mRNAs decreased by 29% and 40% (P < 0.01). In conclusion, occupational immobilization in Special Forces soldiers led to modulations in molecular muscle mass regulators during 8 days prone SSR mission, which likely contribute to muscle loss observed in such operations. The present data expand our knowledge of human muscle mass regulation during short-term immobilization.

The heat shock protein response following eccentric exercise in human skeletal muscle is unaffected by local NSAID infusion

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely consumed in relation to pain and injuries in skeletal muscle, but may adversely affect muscle adaptation probably via inhibition of prostaglandin synthesis. Induction of heat shock proteins (HSP) represents an important adaptive response in muscle subjected to stress, and in several cell types including cardiac myocytes prostaglandins are important in induction of the HSP response. This study aimed to determine the influence of NSAIDs on the HSP response to eccentric exercise in human skeletal muscle. Healthy males performed 200 maximal eccentric contractions with each leg with intramuscular infusion of the NSAID indomethacin or placebo. Biopsies were obtained from m. vastus lateralis before and after (5, 28 hrs and 8 days) the exercise bout from both legs (NSAID vs unblocked leg) and analysed for expression of the HSPs HSP70, HSP27 and αB-crystallin (mRNA and protein). NSAID did not affect the mRNA expression of any of the HSPs. Compared to pre values, the mRNA expression of all HSPs was increased; αB-crystallin, 3.6- and 5.4-fold; HSP70, 26- and 3.4-fold; and HSP27: 4.8- and 6.5-fold at 5 and 28 hrs post-exercise, respectively (all p < 0.008). Immunohistochemical stainings for αB-crystallin and HSP70 revealed increased staining in some samples but with no differences between legs. Changes in force-generating capacity correlated with both αB-crystallin and HSP70 mRNA and immunohistochemisty data. Increased expression of HSPs was observed on mRNA and protein level following eccentric exercise; however, this response was unaffected by local intramuscular infusion of NSAIDs.

Activated protein synthesis and suppressed protein breakdown signaling in skeletal muscle of critically ill patients

Background

Skeletal muscle mass is controlled by myostatin and Akt-dependent signaling on mammalian target of rapamycin (mTOR), glycogen synthase kinase 3β (GSK3β) and forkhead box O (FoxO) pathways, but it is unknown how these pathways are regulated in critically ill human muscle. To describe factors involved in muscle mass regulation, we investigated the phosphorylation and expression of key factors in these protein synthesis and breakdown signaling pathways in thigh skeletal muscle of critically ill intensive care unit (ICU) patients compared with healthy controls.

Methodology/Principal Findings

ICU patients were systemically inflamed, moderately hyperglycemic, received insulin therapy, and showed a tendency to lower plasma branched chain amino acids compared with controls. Using Western blotting we measured Akt, GSK3β, mTOR, ribosomal protein S6 kinase (S6k), eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), and muscle ring finger protein 1 (MuRF1); and by RT-PCR we determined mRNA expression of, among others, insulin-like growth factor 1 (IGF-1), FoxO 1, 3 and 4, atrogin1, MuRF1, interleukin-6 (IL-6), tumor necrosis factor α (TNF-α) and myostatin. Unexpectedly, in critically ill ICU patients Akt-mTOR-S6k signaling was substantially higher compared with controls. FoxO1 mRNA was higher in patients, whereas FoxO3, atrogin1 and myostatin mRNAs and MuRF1 protein were lower compared with controls. A moderate correlation (r² = 0.36, p<0.05) between insulin infusion dose and phosphorylated Akt was demonstrated.

Conclusions/Significance

We present for the first time muscle protein turnover signaling in critically ill ICU patients, and we show signaling pathway activity towards a stimulation of muscle protein synthesis and a somewhat inhibited proteolysis.

Early osteoarthritis and microdialysis: a novel in vivo approach for measurements of biochemical markers in the perisynovium and intraarticularly

The microdialysis technique was evaluated as a possible method to obtain local measurements of biochemical markers from knee joints with degenerative changes. Seven patients scheduled for arthroscopy of the knee due to minor to moderate degenerative changes had microdialysis catheters inserted under ultrasonographic guidance, intraarticularly and in the synovium-close tissue. Catheters were perfused at a rate of 2 μl/min for approximately 100 min with a Ringer solution containing radioactively labeled glucose, and the positions of the catheters were later visualized during arthroscopy. All intraarticular catheters and 6/7 subsynovial catheters were positioned correctly. Relative recovery (RR) was intraarticularly 0.64 ± 0.02 (mean ± SEM) and synovium-close 0.54 ± 0.06. Mean values of cartilage oligomeric matrix protein (COMP), aggrecan and glucosyl-galactosyl-pyridinoline in the intraarticular dialysates were 18.1 ± 7.0 U/l, 243.6 ± 108.6 ng/ml and 108.0 ± 29.0 pmol/ml, respectively. COMP and glucosyl-galactosyl-pyridinoline concentrations were significantly higher intraarticularly compared to perisynovial tissue (P < 0.05), whereas for aggrecan, no significant difference was found (P = 0.06). The microdialysis method can be used for intraarticular and subsynovial determination of metabolites in human knees at these sites. The present methodology displays a potential for future studies of simultaneous biochemical changes within and around joints.

Exercise increases interleukin-10 levels both intraarticularly and peri-synovially in patients with knee osteoarthritis: a randomized controlled trial

Introduction

The microdialysis method was applied to the human knee joint with osteoarthritis (OA) in order to reveal changes in biochemical markers of cartilage and inflammation, intraarticularly and in the synovium, in response to a single bout of mechanical joint loading.

Methods

Thirty-one female subjects with OA of the knee were randomized to non-exercise (NEx) or exercise (Ex) groups. Following acute resistance exercise (25 sets of 10 repetitions at 60% of 1 Repetition Maximum) or none (NEx), peripheral nerve blocks just below the inguinal ligament were applied and two microdialysis catheters were positioned in two different compartments, intraarticularly and peri-synovially. The microdialysis catheters were perfused at a slow rate (2 μl/minute) with a solution of Ringer-acetate and radioactively labelled glucose allowing for determination of relative recovery (RR) and calculation of interstitial concentrations of inflammatory and cartilage biomarkers over a three-hour period.

Results

A significant increase of Interleukin (IL) -10 was discovered in both positions of the knee in the Ex group over the three hours post exercise, whereas IL-10 remained stationary over time in the NEx group. IL-6 and IL-8 displayed significant increases over time regardless of group and position of the catheter. Cartilage oligomeric matrix protein (COMP) decreased intraarticularly in the post exercise period in the Ex group compared to the NEx group.

Conclusions

Exercise caused an increase in both intraarticular and peri-synovial concentrations of IL-10 in a group of human females with knee OA. This suggests a positive effect of exercise on a chondroprotective anti-inflammatory cytokine response in patients with knee OA and might contribute to explaining the beneficial effect that exercise has on OA.

Trial registration

NCT01090375.

Local NSAID infusion inhibits satellite cell proliferation in human skeletal muscle after eccentric exercise

Despite the widespread consumption of nonsteroidal anti-inflammatory drugs (NSAIDs), the influence of these drugs on muscle satellite cells is not fully understood. The aim of the present study was to investigate the effect of a local NSAID infusion on satellite cells after unaccustomed eccentric exercise in vivo in human skeletal muscle. Eight young healthy males performed 200 maximal eccentric contractions with each leg. An NSAID was infused via a microdialysis catheter into the vastus lateralis muscle of one leg (NSAID leg) before, during, and for 4.5 h after exercise, with the other leg working as a control (unblocked leg). Muscle biopsies were collected before and 8 days after exercise. Changes in satellite cells and inflammatory cell numbers were investigated by immunohistochemistry. Satellite cells were identified using antibodies against neural cell adhesion molecule and Pax7. The number of Pax7(+) cells per myofiber was increased by 96% on day 8 after exercise in the unblocked leg (0.14 +/- 0.04, mean +/- SE) compared with the prevalue (0.07 +/- 0.02, P < 0.05), whereas the number of Pax7(+) cells was unchanged in the leg muscles exposed to the NSAID (0.07 +/- 0.01). The number of inflammatory cells (CD68(+) or CD16(+) cells) was not significantly increased in either of the legs 8 days after exercise and was unaffected by the NSAID. The main finding in the present study was that the NSAID infusion for 7.5 h during the exercise day suppressed the exercise-induced increase in the number of satellite cells 8 days after exercise. These results suggest that NSAIDs negatively affect satellite cell activity after unaccustomed eccentric exercise.