Carnosine, oxidative and carbonyl stress, antioxidants and muscle fiber characteristics of quadriceps muscle of patients with COPD

Background: Oxidative/carbonyl stress is elevated in lower-limb muscles of patients with Chronic Obstructive Pulmonary Disease (COPD). Carnosine is a skeletal muscle antioxidant particularly present in fast-twitch fibers. Aims: To compare muscle carnosine, oxidative/carbonyl stress, antioxidants and fiber characteristics between patients with COPD and healthy controls (HCs), and between patients after stratification for airflow limitation (mild/moderate vs. severe/very-severe). To investigate correlates of carnosine in patients with COPD. Methods: A vastus lateralis muscle biopsy was obtained from 40 patients with stable COPD and 20 age/sex matched HCs. Carnosine, oxidative/carbonyl stress, antioxidants, fiber characteristics, quadriceps strength and endurance (QE), VO2peak (incremental cycle test) and physical activity (PA) were determined. Results: Patients with COPD had a similar carnosine concentration (4.16 mmol/kg wet weight (WW) (SD 1.93)) to HCs (4.64 mmol/kgWW (SD 1.71)) and significantly higher percentage of fast-twitch fibers and lower QE, VO2peak and PA vs. HCs. Patients with severe/very-severe COPD had a 30% lower carnosine concentration (3.24 mmol/kgWW (SD 1.79); n=15) vs. patients with mild/moderate COPD (4.71 mmol/kgWW (SD 1.83); n=25; P=0.02) and significantly lower VO2peak and PA vs. patients with mild/moderate COPD. Carnosine correlated significantly with QE (rs=0.427), VO2peak (rs=0.334), PA (rs=0.379) and lung function parameters in patients with COPD. Conclusion: Despite having the highest proportion of fast-twitch fibers, patients with severe/very-severe COPD displayed a 30% lower muscle carnosine concentration compared to patients with mild/moderate COPD. As no oxidative/carbonyl stress markers, nor antioxidants were affected, the observed carnosine deficiency is thought to be a possible first sign of muscle redox balance abnormalities.

Cores of Reproducibility in Physiology (CORP): quantification of human skeletal muscle carnosine concentration by proton magnetic resonance spectroscopy

Non-invasive techniques to quantify metabolites in skeletal muscle provide unique insight into human physiology and enable the translation of research into practice. Proton magnetic resonance spectroscopy (1H-MRS) permits the assessment of several abundant muscle metabolites in vivo, including carnosine, a dipeptide composed of the amino acids histidine and beta-alanine. Muscle carnosine loading - accomplished by chronic oral beta-alanine supplementation - improves muscle function, exercise capacity and has pathophysiological relevance in multiple diseases. Moreover, the marked difference in carnosine content between fast-twitch and slow-twitch muscle fibers has rendered carnosine an attractive candidate to estimate human muscle fiber type composition. However, the quantification of carnosine using 1H-MRS requires technical expertise in order to obtain accurate and reproducible data. In this review, we describe the technical and physiological factors that impact the detection, analysis and quantification of carnosine in muscle using 1H-MRS. We discuss potential sources of error during the acquisition and pre-processing of the 1H-MRS spectra, and present best practices to enable the accurate, reliable and reproducible application of this technique.

Individual Participant Data Meta-Analysis Provides No Evidence of Intervention Response Variation in Individuals Supplementing With Beta-Alanine

Currently, little is known about the extent of interindividual variability in response to beta-alanine (BA) supplementation, nor what proportion of said variability can be attributed to external factors or to the intervention itself (intervention response). To investigate this, individual participant data on the effect of BA supplementation on a high-intensity cycling capacity test (CCT110%) were meta-analyzed. Changes in time to exhaustion (TTE) and muscle carnosine were the primary and secondary outcomes. Multilevel distributional Bayesian models were used to estimate the mean and SD of BA and placebo group change scores. The relative sizes of group SDs were used to infer whether observed variation in change scores were due to intervention or non-intervention-related effects. Six eligible studies were identified, and individual data were obtained from four of these. Analyses showed a group effect of BA supplementation on TTE (7.7, 95% credible interval [CrI] [1.3, 14.3] s) and muscle carnosine (18.1, 95% CrI [14.5, 21.9] mmol/kg DM). A large intervention response variation was identified for muscle carnosine (σIR = 5.8, 95% CrI [4.2, 7.4] mmol/kg DM) while equivalent change score SDs were shown for TTE in both the placebo (16.1, 95% CrI [13.0, 21.3] s) and BA (15.9, 95% CrI [13.0, 20.0] s) conditions, with the probability that SD was greater in placebo being 0.64. In conclusion, the similarity in observed change score SDs between groups for TTE indicates the source of variation is common to both groups, and therefore unrelated to the supplement itself, likely originating instead from external factors such as nutritional intake, sleep patterns, or training status.

Low efficiency of β-alanine supplementation to increase muscle carnosine

Supplementation with β-alanine (BA) increases muscle carnosine content, although the amount of BA used for muscle carnosine loading has been suggested to be low. However, methodological issues may have underestimated the amount of BA used. The aim of this study was to determine the estimated amount of BA converted to muscle carnosine, using a retrospective analysis from a 4-week randomized controlled trial investigating the effects of BA supplementation on muscle carnosine content of the m. vastus lateralis. Twenty-five males (age 27±5 years, height 1.74±0.09 m, body mass 77.4±11.5 kg) were supplemented with 6.4 g·day-1 of BA (N=17) or placebo (PL; N=8) for 28 days. Pre- and postsupplementation participants provided a muscle biopsy subsequently analysed for carnosine content using HPLC. Data were analysed using mixed-models and Pearson’s correlations. Muscle carnosine content increased by +11.0±6.7 mmol·kg-1dm (P<0.0001) in BA, with no change in PL (P=0.99). The estimated amount of BA converted to muscle carnosine was 2.1±1.2% (Range: 0.5 to 4.5%) of the total dose ingested. Pearson’s correlations showed that pre-supplementation carnosine was correlated to post-supplementation carnosine in the BA group (r=0.65, r2=0.38, P=0.009), but not the absolute change in carnosine (r=-0.28, r2=0.08, P=0.28) or the amount of BA used (r=-0.31, r2=0.10, P=0.22). The estimated amount of ingested BA used for carnosine synthesis was extremely low following 4 weeks of BA supplementation at 6.4 g·day-1. Data suggest that very little of the BA ingested is used for muscle carnosine synthesis and highlights the potential for further work to optimise BA supplementation in humans.

Low efficiency of β-alanine supplementation to increase muscle carnosine

Supplementation with β-alanine (BA) increases muscle carnosine content, although the amount of BA used for muscle carnosine loading has been suggested to be low. However, methodological issues may have underestimated the amount of BA used. The aim of this study was to determine the estimated amount of BA converted to muscle carnosine, using a retrospective analysis from a 4-week randomized controlled trial investigating the effects of BA supplementation on muscle carnosine content of the m. vastus lateralis. Twenty-five males (age 27±5 years, height 1.74±0.09 m, body mass 77.4±11.5 kg) were supplemented with 6.4 g·day-1 of BA (N=17) or placebo (PL; N=8) for 28 days. Pre- and postsupplementation participants provided a muscle biopsy subsequently analysed for carnosine content using HPLC. Data were analysed using mixed-models and Pearson’s correlations. Muscle carnosine content increased by +11.0±6.7 mmol·kg-1dm (P<0.0001) in BA, with no change in PL (P=0.99). The estimated amount of BA converted to muscle carnosine was 2.1±1.2% (Range: 0.5 to 4.5%) of the total dose ingested. Pearson’s correlations showed that pre-supplementation carnosine was correlated to post-supplementation carnosine in the BA group (r=0.65, r2=0.38, P=0.009), but not the absolute change in carnosine (r=-0.28, r2=0.08, P=0.28) or the amount of BA used (r=-0.31, r2=0.10, P=0.22). The estimated amount of ingested BA used for carnosine synthesis was extremely low following 4 weeks of BA supplementation at 6.4 g·day-1. Data suggest that very little of the BA ingested is used for muscle carnosine synthesis and highlights the potential for further work to optimise BA supplementation in humans.

Beta-alanine supplementation in patients with COPD receiving non-linear periodised exercise training or neuromuscular electrical stimulation: protocol of two randomised, double-blind, placebo-controlled trials

IntroductionExercise intolerance is common in patients with chronic obstructive pulmonary disease (COPD) and, although multifactorial, it is largely caused by lower-limb muscle dysfunction. Research has shown that patients with severe to very severe COPD have significantly lower levels of muscle carnosine, which acts as a pH buffer and antioxidant. Beta-alanine (BA) supplementation has been shown to consistently elevate muscle carnosine in a variety of populations and may therefore improve exercise tolerance and lower-limb muscle function. The primary objective of the current studies is to assess the beneficial effects of BA supplementation in enhancing exercise tolerance on top of two types of exercise training (non-linear periodised exercise (NLPE) training or neuromuscular electrical stimulation (NMES)) in patients with COPD.Methods and analysisTwo randomised, double-blind, placebo-controlled trials have been designed. Patients will routinely receive either NLPE (BASE-TRAIN trial) or NMES (BASE-ELECTRIC trial) as part of standard exercise-based care during their 8-to-10 week pulmonary rehabilitation (PR) programme. A total of 222 patients with COPD (2×77 = 154 patients in the BASE-TRAIN trial and 2×34 = 68 patients in the BASE-ELECTRIC trial) will be recruited from two specialised PR centres in The Netherlands. For study purposes, patients will receive 3.2 g of oral BA supplementation or placebo per day. Exercise tolerance is the primary outcome, which will be assessed using the endurance shuttle walk test (BASE-TRAIN) or the constant work rate cycle test (BASE-ELECTRIC). Furthermore, quadriceps muscle strength and endurance, cognitive function, carnosine levels (in muscle), BA levels (in blood and muscle), markers of oxidative stress and inflammation (in blood, muscles and lungs), physical activity and quality of life will be measured.Ethics and disseminationBoth trials were approved by CMO Regio Arnhem-Nijmegen, The Netherlands (NL70781.091.19. and NL68757.091.19).Trial registration numberNTR8427 (BASE-TRAIN) and NTR8419 (BASE-ELECTRIC).