Increases Muscle Carnosine Content Research Articles

Beta-Alanine for Improving Exercise Capacity, Muscle Strength, and Functional Performance of Older Adults: A Systematic Review.

Beta-alanine supplementation increases muscle carnosine content and also improves exercise capacity and performance in young adults, with mixed findings emerging from the few studies investigating its effects on older participants. Therefore, this study aimed to systematically review the evidence regarding the effects of beta-alanine on exercise capacity, muscle strength, and functional performance of older adults. This systematic review was conducted following the specific methodological guidelines of the Preferred Report Items for Systematic Reviews and Meta-Analyses and the Physiotherapy Evidence Database scale. Furthermore, the Cochrane risk-of-bias assessment tool was used. The search was carried out in five relevant databases (MEDLINE, Embase, Web of Science, Scopus, and Cochrane Library) from inception up to March 2024. Of the 1,749 registers identified, only five met the established criteria and were included in this systematic review. A total of 163 older adults (mean age ± SD: 69.1 ± 2.8years; range: 66.2-72.7years) were included across all five studies. The majority of studies included participants from both genders. The mean intervention duration ± SD was 11.7 ± 1.0weeks. The mean daily dosage was 2.7 ± 0.4g/day (range: 2.4-3.2g/day). Overall, exercise capacity may be improved following supplementation protocols with dosages ranging from 2.4 to 3.2g/day. Muscle strength and functional performance do not seem to be improved by beta-alanine since these tasks are not significantly impacted by acidosis buildup.

Beta-alanine did not improve high-intensity performance throughout simulated road cycling

ABSTRACT This study investigated the effect of beta-alanine supplementation on short-duration sprints and final 4-km simulated uphill cycling time-trial performance during a comprehensive and novel exercise protocol representative of the demands of road-race cycling, and determined if changes were related to increases in muscle carnosine content. Seventeen cyclists (age 38 ± 9 y, height 1.76 ± 0.07 m, body mass 71.4 ± 8.8 kg, V̇O2max 52.4 ± 8.3 ml·kg−1·min−1) participated in this placebo-controlled, double-blind study. Cyclists undertook a prolonged intermittent cycling protocol lasting 125 min, with a 10-s sprint every 20 min, finishing with a 4-km time-trial at 5% simulated incline. Participants completed two familiarization sessions, and two main sessions, one pre-supplementation and one post-supplementation following 28 days of 6.4 g·day−1 of beta-alanine (N=11) or placebo (N=6; maltodextrin). Muscle biopsies obtained pre- and post-supplementation were analysed for muscle carnosine content. There were no main effects on sprint performance throughout the intermittent cycling test (all P>0.05). There was no group (P=0.69), time (P=0.50) or group x time interaction (P=0.26) on time-to-complete the 4-km time-trial. Time-to-completion did not change from pre- to post-supplementation for BA (−19.2 ± 45.6 s, P=0.43) or PL (+2.8 ± 31.6 s, P=0.99). Beta-alanine supplementation increased muscle carnosine content from pre- to post-supplementation (+9.4 ± 4.0 mmol·kg−1dm; P<0.0001) but was not related to performance changes (r=0.320, P=0.37). Chronic beta-alanine supplementation increased muscle carnosine content but did not improve short-duration sprint performance throughout simulated road race cycling, nor 4-km uphill time-trial performance conducted at the end of this cycling test. Highlights Performance during prolonged cycling events often depends on the ability to maintain an increased power output during higher intensity periods. Thus, cyclists are likely heavily dependent on their ability to resist fatigue during these periods of high-intensity activity. Meta-analytical data show beta-alanine to be an effective supplement to improve exercise outcomes, but little work exists on its efficacy during dynamic actions that are common during prolonged cycling. Beta-alanine supplementation increased muscle carnosine content but did not generate improvements in the performance of high-intensity cycling (10-s sprints or 4-km uphill time-trial) during a simulated road race cycling protocol. These data suggest that short duration sprints (≤10 s) and longer duration (>10 min) high-intensity activity throughout endurance cycling may not be improved with beta-alanine supplementation despite increases in muscle carnosine content.

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&lt;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&lt;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.

Can the Skeletal Muscle Carnosine Response to Beta-Alanine Supplementation Be Optimized?

Carnosine is an abundant histidine-containing dipeptide in human skeletal muscle and formed by beta-alanine and L-histidine. It performs various physiological roles during exercise and has attracted strong interest in recent years with numerous investigations focused on increasing its intramuscular content to optimize its potential ergogenic benefits. Oral beta-alanine ingestion increases muscle carnosine content although large variation in response to supplementation exists and the amount of ingested beta-alanine converted into muscle carnosine appears to be low. Understanding of carnosine and beta-alanine metabolism and the factors that influence muscle carnosine synthesis with supplementation may provide insight into how beta-alanine supplementation may be optimized. Herein we discuss modifiable factors that may further enhance the increase of muscle carnosine in response to beta-alanine supplementation including, (i) dose; (ii) duration; (iii) beta-alanine formulation; (iv) dietary influences; (v) exercise; and (vi) co-supplementation with other substances. The aim of this narrative review is to outline the processes involved in muscle carnosine metabolism, discuss theoretical and mechanistic modifiable factors which may optimize the muscle carnosine response to beta-alanine supplementation and to make recommendations to guide future research.

Exercise and β-alanine supplementation on carnosine-acrolein adduct in skeletal muscle

Previous studies have demonstrated that exercise results in reactive aldehyde production and that β-alanine supplementation increases carnosine content in skeletal muscle. However, little is known about the influence exercise and β-alanine supplementation have on the formation of carnosine-aldehydes. The goal of the present study was to monitor the formation of carnosine-aldehyde adducts, following high-intensity intermittent exercise, before and after β-alanine supplementation. Vastus lateralis biopsy samples were taken from 14 cyclists, before and after a 28 day β-alanine supplementation, following 4 bouts of a 30 s all-out cycling test, and carnosine and CAR-aldehyde adducts [carnosine-acrolein, CAR-ACR (m/z 303), carnosine-4-hydroxy-2-hexenal, CAR-HHE (m/z 341) and carnosine-4-hydroxy-2-nonenal, CAR-HNE (m/z 383)] were quantified by HPLC-MS/MS. β-alanine supplementation increased muscle carnosine content by ~50% (p = 0.0001 vs. Pre-Supplementation). Interestingly, there was a significant increase in post-exercise CAR-ACR content following β-alanine supplementation (p < 0.001 vs. post-exercise before supplementation), whereas neither exercise alone nor supplementation alone increased CAR-ACR formation. These results suggest that carnosine functions as an acrolein-scavenger in skeletal muscle. Such a role would be relevant to the detoxification of this aldehyde formed during exercise, and appears to be enhanced by β-alanine supplementation. These novel findings not only have the potential of directly benefiting athletes who engage in intensive training regimens, but will also allow researchers to explore the role of muscle carnosine in detoxifying reactive aldehydes in diseases characterized by abnormal oxidative stress.

Comparison of sustained-release and rapid-release \u03b2-alanine formulations on changes in skeletal muscle carnosine and histidine content and isometric performance following a muscle-damaging protocol

β-alanine supplementation increases muscle carnosine content and improves anaerobic exercise performance by enhancing intracellular buffering capacity. β-alanine ingestion in its traditional rapid-release formulation (RR) is associated with the symptoms of paresthesia. A sustained-release formulation (SR) of β-alanine has been shown to circumvent paresthesia and extend the period of supply to muscle for carnosine synthesis. The purpose of this investigation was to compare 28 days of SR and RR formulations of β-alanine (6 g day−1) on changes in carnosine content of the vastus lateralis and muscle fatigue. Thirty-nine recreationally active men and women were assigned to one of the three groups: SR, RR, or placebo (PLA). Participants supplementing with SR and RR formulations increased muscle carnosine content by 50.1% (3.87 mmol kg−1ww) and 37.9% (2.62 mmol kg−1ww), respectively. The change in muscle carnosine content in participants consuming SR was significantly different (p = 0.010) from those consuming PLA, but no significant difference was noted between RR and PLA (p = 0.077). Although participants ingesting SR experienced a 16.4% greater increase in muscle carnosine than RR, fatigue during maximal voluntary isometric contractions was significantly attenuated in both SR and RR compared to PLA (p = 0.002 and 0.024, respectively). Symptoms of paresthesia were significantly more frequent in RR compared to SR, the latter of which did not differ from PLA. Results of this study demonstrated that only participants consuming the SR formulation experienced a significant increase in muscle carnosine. Differences in the muscle carnosine response between these formulations may have practical significance for athletic populations in which small changes may have important implications on performance.

Identification of single nucleotide polymorphisms in carnosine-related genes and effects of genotypes on pork meat quality attributes

Carnosine has pH-buffering and antioxidant properties that may bring advantages in terms of meat quality attributes. This study aimed at identifying polymorphisms in carnosine-related genes (CARNS1, SLC6A6, SLC15A3, SLC15A4) that might associate with muscle carnosine content and meat quality traits in pigs (Duroc, Landrace, Yorkshire). Twenty seven SNPs were identified and association analyses performed for SLC15A3 c.*35C>T and c.*52C>T (3′ UTR region), and SLC15A4 c.658A>G (Ile220Val) and c.818G>A (Ser273Asn) SNPs. Associations were observed for SNP c.658A>G with carnosine content, color b* and L*, drip and cooking losses, pH24h and glycolytic potential values (P≤0.05). The same associations were observed for SNP c.818G>A, but they were not significant after FDR correction. Results suggest that specific SLC15A4 gene variants might increase muscle carnosine content and improve meat quality. With a minor allele frequency of 0.17 for SNP c.658A>G in Yorkshire pigs, selection in favor of the c.658A allele may be considered as a mean to improve pork quality attributes.

Twenty-four Weeks Of Beta-alanine Supplementation Increases Muscle Carnosine Content Despite Downregulation Of Beta-alanine Transporter Expression

Skeletal muscle carnosine content can be increased via chronic beta-alanine ingestion, but the maximum increase achievable with supplementation is unknown. Additionally, the effects of prolonged supplementation on carnosine-related gene expression in humans are not known. Since athletes are likely to supplement for extended periods of time, determination of the long-term effects of beta-alanine supplementation is warranted. PURPOSE: To investigate the effects of 24-weeks of beta-alanine supplementation on muscle carnosine content and expression of genes related to carnosine metabolism. METHODS: Twenty-four males were supplemented with 6.4 g·day-1 of sustained release beta-alanine (BA; N=15) or placebo (PL; N=9) for 24 weeks. Every 4 weeks participants provided a muscle biopsy from the m. vastus lateralis, which was subsequently analysed for muscle carnosine content and gene expression (CARNS, TauT, ABAT, CNDP2, PHT1, PEPT2, PAT1). RESULTS: Carnosine content was increased from baseline at every time point in BA (all P<0.0001; Week 4: +11.4±7.0 mmol·kg-1dm, Week 8: +13.9±7.8 mmol·kg-1dm, Week 12: +17.0±8.6 mmol·kg-1dm, Week 16: +17.6±8.4 mmol·kg-1dm, Week 20: +21.2±7.9 mmol·kg-1dm, Week 24: +20.2±7.6 mmol·kg-1dm), but not PL (all P>0.05). Maximal changes ranged from +17.1 to +41.3 mmol·kg-1dm, and absolute maximal content ranged from 31.8 to 63.9 mmol·kg-1dm. There was an effect of supplement (P=0.002) on TauT with lower expression in BA (-36%, -39%, -27%, -57%, -46% and -35% at Weeks 4, 8, 12, 16, 20 and 24); no further differences in gene expression were shown. CONCLUSION: Twenty-four weeks of beta-alanine supplementation increased muscle carnosine content in all individuals at all time points, although absolute maximal changes were variable. Downregulation of the beta-alanine transporter TauT suggests it plays an important role in muscle carnosine accumulation with beta-alanine supplementation. These data demonstrate that individuals who supplement with beta-alanine for prolonged periods can maintain elevated muscle content throughout supplementation, despite downregulation of beta-alanine transporter expression.

Twenty-four Weeks of β-Alanine Supplementation on Carnosine Content, Related Genes, and Exercise

Skeletal muscle carnosine content can be increased through β-alanine (BA) supplementation, but the maximum increase achievable with supplementation is unknown. No study has investigated the effects of prolonged supplementation on carnosine-related genes or exercise capacity. This study aimed to investigate the effects of 24 wk of BA supplementation on muscle carnosine content, gene expression, and high-intensity cycling capacity (CCT110%). Twenty-five active males were supplemented with 6.4 g·d of sustained release BA or placebo for a 24 wk period. Every 4 wk participants provided a muscle biopsy and performed the CCT110%. Biopsies were analyzed for muscle carnosine content and gene expression (CARNS, TauT, ABAT, CNDP2, PHT1, PEPT2, and PAT1). Carnosine content was increased from baseline at every time point in BA (all P < 0.0001; week 4 = +11.37 ± 7.03 mmol·kg dm, week 8 = +13.88 ± 7.84 mmol·kg dm, week 12 = +16.95 ± 8.54 mmol·kg dm, week 16 = +17.63 ± 8.42 mmol·kg dm, week 20 = +21.20 ± 7.86 mmol·kg dm, and week 24 = +20.15 ± 7.63 mmol·kg dm) but not placebo (all P > 0.05). Maximal increases were +25.66 ± 7.63 mmol·kg dm (range = +17.13 to +41.32 mmol·kg dm), and absolute maximal content was 48.03 ± 8.97 mmol·kg dm (range = 31.79 to 63.92 mmol·kg dm). There was an effect of supplement (P = 0.002) on TauT; no further differences in gene expression were shown. Exercise capacity was improved in BA (P = 0.05) with possible to almost certain improvements across all weeks. Twenty-four weeks of BA supplementation increased muscle carnosine content and improved high-intensity cycling capacity. The downregulation of TauT suggests it plays an important role in muscle carnosine accumulation with BA supplementation, whereas the variability in changes in muscle carnosine content between individuals suggests that other determinants other than the availability of BA may also bear a major influence on muscle carnosine content.

Muscle Carnosine Concentration with the Co-Ingestion of Carbohydrate with β-alanine in Male Rats

ABSTRACTMuscle carnosine is an intracellular buffer. The intake of β-alanine, combined with carbohydrate and protein, enhanced carnosine loading in human muscle. The aim of the present study was to examine if muscle carnosine loading was enhanced by β-alanine intake and co-ingestion of glucose in male rats. Thirty-six male rats were divided into three groups and supplemented for four weeks: β-alanine (βA group, 1.8% β-alanine in drinking water), β-alanine and glucose (βAGL group, 1.8% β-alanine and 5% glucose in drinking water), and control (C group, drinking water). During the supplementation period, rats were exercised (20 m·min−1, 10 min·day−1, 4 days·week−1 for 4 weeks). Muscle carnosine concentration was quantified in soleus (n = 12) and rectus femoris (n = 6) muscles using high-performance liquid chromatography. In soleus muscle, carnosine concentration was 2.24 ± 1.10, 6.12 ± 1.08, and 6.93 ± 2.56 mmol/kg dw for control, βA, and βAGL, respectively. In rectus femoris, carnosine concentration was 2.26 ± 1.31, 7.90 ± 1.66, and 8.59 ± 2.33 mmol/kg dw for control, βA, and βAGL respectively. In each muscle, βA and βAGL resulted in similar carnosine increases compared to the control. In conclusion, β-alanine intake for four weeks, either alone or with glucose co-ingestion, equally increased muscle carnosine content. It appears that the potential insulin response to fluid glucose intake does not affect muscle carnosine loading in male rats.

Effect of Four Weeks of β-alanine Supplementation on Muscle Carnosine and Blood Serum Lactate during Exercise in Male Rats

ABSTRACTβ-alanine (BA) supplementation may increase muscle buffering capacity and affect physiological responses during exercise. We examined the effects of 4 weeks of BA supplementation on muscle carnosine and serum lactate in male rats. Rats (n = 24, age: 2 months, body weight: 265±22 g) were divided into a BA supplementation or control group. Along with aerobic acclimatization exercise (15 m·min−1, 8–10 min·day−1, 4 days·week−1 for 4 weeks), the BA group had access to BA powder in their drinking water (1.8%) with the control group having access to plain water for 4 weeks. After 4 weeks, rats ran on a treadmill at speeds of 15, 20, 25, 30, and 35 m·min−1, respectively, each for 4 min, in order to measure post-exercise serum lactate. Muscle carnosine and serum lactate levels were measured with high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbant assay (ELISA) procedures, respectively. Following BA supplementation, carnosine content in the m.rectus femoris increased by 117% (p < .01) and serum lactate decreased by 7.4% (p < .01). It was concluded that β-alanine supplementation increases muscle carnosine content and reduces serum lactate; these changes may indicate an adaptation of rat skeletal muscles to postpone peripheral muscle fatigue during high-intensity exercise.

β-Alanine Ingestion Increases Muscle Carnosine Content and Combat Specific Performance in Tactical Athletes

PURPOSE: To examine the effect of β-alanine ingestion on tissue carnosine levels and the impact such changes would have on combat specific activity. METHODS: Eighteen soldiers (19.9±0.8y) from an elite combat unit were randomly assigned to either a β-alanine (BA) or placebo (PL) group. Before and following a 30-day supplementation period carnosine content of the gastrocnemius muscle and brain was determined by proton magnetic resonance spectroscopy. During each testing session participants performed military relevant tasks that included a 2.5km run, a 1-min sprint, 50-m casualty carry, repeated 30-m sprints with target shooting, and a 2-min serial subtraction test (SST) to assess cognitive function under stressful conditions. RESULTS: A significant elevation (p=0.048) in muscle carnosine content was noted in BA compared to PL. Changes in muscle carnosine content was correlated to changes in fatigue rate (r=0.633, p=0.06). No changes (p=0.607) were observed in brain carnosine content. Following supplementation, no differences were noted in 2.5km run, 1-min sprint, repeated sprint, or marksmanship performance, but participants in BA significantly (p=0.044) improved their time for the 50-m casualty carry and increased their performance (p=0.022) in the SST compared to PL. CONCLUSIONS: 30-days of β-alanine ingestion can increase muscle carnosine content and improve aspects of military specific performance. Although cognitive performance was significantly greater in participants consuming β-alanine compared to placebo, current study methods were unable to detect any change in brain carnosine levels, thus the precise mechanism underlying these effects remains elusive.

Muscle histidine-containing dipeptides are elevated by glucose intolerance in both rodents and men.

ObjectiveMuscle carnosine and its methylated form anserine are histidine-containing dipeptides. Both dipeptides have the ability to quench reactive carbonyl species and previous studies have shown that endogenous tissue levels are decreased in chronic diseases, such as diabetes.Design and Methods Rodent study: Skeletal muscles of rats and mice were collected from 4 different diet-intervention studies, aiming to induce various degrees of glucose intolerance: 45% high-fat feeding (male rats), 60% high-fat feeding (male rats), cafeteria feeding (male rats), 70% high-fat feeding (female mice). Body weight, glucose-tolerance and muscle histidine-containing dipeptides were assessed. Human study: Muscle biopsies were taken from m. vastus lateralis in 35 males (9 lean, 8 obese, 9 prediabetic and 9 newly diagnosed type 2 diabetic patients) and muscle carnosine and gene expression of muscle fiber type markers were measured.ResultsDiet interventions in rodents (cafeteria and 70% high-fat feeding) induced increases in body weight, glucose intolerance and levels of histidine-containing dipeptides in muscle. In humans, obese, prediabetic and diabetic men had increased muscle carnosine content compared to the lean (+21% (p>0.1), +30% (p<0.05) and +39% (p<0.05), respectively). The gene expression of fast-oxidative type 2A myosin heavy chain was increased in the prediabetic (1.8-fold, p<0.05) and tended to increase in the diabetic men (1.6-fold, p = 0.07), compared to healthy lean subjects.ConclusionMuscle histidine-containing dipeptides increases with progressive glucose intolerance, in male individuals (cross-sectional). In addition, high-fat diet-induced glucose intolerance was associated with increased muscle histidine-containing dipeptides in female mice (interventional). Increased muscle carnosine content might reflect fiber type composition and/or act as a compensatory mechanism aimed at preventing cell damage in states of impaired glucose tolerance.

β-Alanine ingestion increases muscle carnosine content and combat specific performance in soldiers.

The purpose of this study was to examine the effect of β-alanine (BA) ingestion on tissue carnosine levels and the impact such changes would have on combat specific activity. Eighteen soldiers (19.9 ± 0.8 year) from an elite combat unit were randomly assigned to either a BA or placebo (PL) group. Before and following a 30-day supplementation period carnosine content of the gastrocnemius muscle and brain was determined by proton magnetic resonance spectroscopy. During each testing session, participants performed military relevant tasks that included a 2.5 km run, a 1-min sprint, 50-m casualty carry, repeated 30-m sprints with target shooting, and a 2-min serial subtraction test (SST) to assess cognitive function under stressful conditions. A significant elevation (p = 0.048) in muscle carnosine content was noted in BA compared to PL. Changes in muscle carnosine content was correlated to changes in fatigue rate (r = 0.633, p = 0.06). No changes (p = 0.607) were observed in brain carnosine content. Following supplementation, no differences were noted in 2.5 km run, 1-min sprint, repeated sprint, or marksmanship performance, but participants in BA significantly (p = 0.044) improved their time for the 50-m casualty carry and increased their performance (p = 0.022) in the SST compared to PL. In summary, 30-days of BA ingestion can increase muscle carnosine content and improve aspects of military specific performance. Although cognitive performance was significantly greater in participants consuming BA compared to placebo, current study methods were unable to detect any change in brain carnosine levels, thus, the precise mechanism underlying these effects remains elusive.

Effects of Carnosine and Beta-Alanine Ingestion on Anaerobic Sprint Performance and Peripheral Blood Mononuclear Cell Interleukin-6 and -10 Gene Expression

Chronic administration of β-alanine has been shown to increase muscle carnosine content and improve anaerobic performance. It is not clear whether acute ingestion of carnosine and beta alanine may have the same effects. With a view to investigating acute effects of carnosine and β-alanine ingestion on anaerobic intermittent running performance and on the responses of Interleukin-6 and -10 to exercise, twelve healthy, young, active participants (age: 21 ± 4 years) underwent the running-based anaerobic test (RAST) twice (with 30 min recovery in between) on two separate occasions (randomized, crossover design). The test consisted of 6 × 35-m sprints interspersed with 10 s rests after acute ingestion (4 hours before the test) of either 2 g L-carnosine + 2 g β-alanine or placebo. The overall performance decreased (RAST1 vs RAST2, carnosine + β-alanine: 32.8 ± 1.3 s, 33.4 ± 1.2 s; Placebo: 32.9 ± 1.0 s, 33.6 ± 1.2 s), pain after RASTs increased (RAST1 vs RAST2, carnosine + β-alanine: 3.0 ± 2.1 a.u., 4.2 ± 1.9 a.u.; Placebo: 3.0 ± 1.8 a.u., 3.4 ± 1.2 a.u.) almost in the same way in both groups, and RPE did not show any difference. IL6 and IL10 gene expression increased and decreased respectively in response to exercise in the same fashion in both conditions. During RAST 2 we found a potentially increased performance in the carnosine + β-alanine group (main effect of condition, p < 0.05). In conclusion these findings suggest that acute administration of carnosine + β-alanine does not influence the cytokine response to exercise but might have a very small enhancing effect on anaerobic sprint performance.

Role of β-Alanine Supplementation on Muscle Carnosine and Exercise Performance

In this narrative review, we present and discuss the current knowledge available on carnosine and beta-alanine metabolism as well as the effects of beta-alanine supplementation on exercise performance. Intramuscular acidosis has been attributed to be one of the main causes of fatigue during intense exercise. Carnosine has been shown to play a significant role in muscle pH regulation. Carnosine is synthesized in skeletal muscle from the amino acids l-histidine and beta-alanine. The rate-limiting factor of carnosine synthesis is beta-alanine availability. Supplementation with beta-alanine has been shown to increase muscle carnosine content and therefore total muscle buffer capacity, with the potential to elicit improvements in physical performance during high-intensity exercise. Studies on beta-alanine supplementation and exercise performance have demonstrated improvements in performance during multiple bouts of high-intensity exercise and in single bouts of exercise lasting more than 60 s. Similarly, beta-alanine supplementation has been shown to delay the onset of neuromuscular fatigue. Although beta-alanine does not improve maximal strength or VO2max, some aspects of endurance performance, such as anaerobic threshold and time to exhaustion, can be enhanced. Symptoms of paresthesia may be observed if a single dose higher than 800 mg is ingested. The symptoms, however, are transient and related to the increase in plasma concentration. They can be prevented by using controlled release capsules and smaller dosing strategies. No important side effect was related to the use of this amino acid so far. In conclusion, beta-alanine supplementation seems to be a safe nutritional strategy capable of improving high-intensity anaerobic performance.

β-Alanine supplementation reduces acidosis but not oxygen uptake response during high-intensity cycling exercise

The oral ingestion of beta-alanine, the rate-limiting precursor in carnosine synthesis, has been shown to elevate the muscle carnosine content. Carnosine is thought to act as a physiologically relevant pH buffer during exercise but direct evidence is lacking. Acidosis has been hypothesised to influence oxygen uptake kinetics during high-intensity exercise. The present study aimed to investigate whether oral beta-alanine supplementation could reduce acidosis during high-intensity cycling and thereby affect oxygen uptake kinetics. 14 male physical education students participated in this placebo-controlled, double-blind study. Subjects were supplemented orally for 4 weeks with 4.8 g/day placebo or beta-alanine. Before and after supplementation, subjects performed a 6-min cycling exercise bout at an intensity of 50% of the difference between ventilatory threshold (VT) and VO(2peak). Capillary blood samples were taken for determination of pH, lactate, bicarbonate and base excess, and pulmonary oxygen uptake kinetics were determined with a bi-exponential model fitted to the averaged breath-by-breath data of three repetitions. Exercise-induced acidosis was significantly reduced following beta-alanine supplementation compared to placebo, without affecting blood lactate and bicarbonate concentrations. The time delay of the fast component (Td(1)) of the oxygen uptake kinetics was significantly reduced following beta-alanine supplementation compared to placebo, although this did not reduce oxygen deficit. The parameters of the slow component did not differ between groups. These results indicate that chronic beta-alanine supplementation, which presumably increased muscle carnosine content, can attenuate the fall in blood pH during high-intensity exercise. This may contribute to the ergogenic effect of the supplement found in some exercise modes.

β-Alanine Improves Sprint Performance in Endurance Cycling

Recent research has shown that chronic dietary beta-alanine (betaALA) supplementation increases muscle carnosine content, which is associated with better performance in short (1-2 min) maximal exercise. Success in endurance competitions often depends on a final sprint. However, whether betaALA can be ergogenic in sprint performance at the end of an endurance competition is at present unknown. Therefore, we investigated the effect of 8-wk betaALA administration in moderately to well-trained cyclists on sprint performance at the end of a simulated endurance cycling race. A double-blind study was performed, which consisted of two experimental test sessions interspersed by an 8-wk betaALA (2-4 g.d; n = 9) or matched placebo (PL; n = 8) supplementation period. In the pretesting and the posttesting, subjects performed a 10-min time trial and a 30-s isokinetic sprint (100 rpm) after a 110-min simulated cycling race. Capillary blood samples were collected for determination of blood lactate concentration and pH. Mean power output during the time trial was approximately 300 W and was similar between PL and betaALA during either the pretesting or the posttesting. However, compared with PL, during the final sprint after the time trial, betaALA on average increased peak power output by 11.4% (95% confidence interval = +7.8 to +14.9%, P = 0.0001), whereas mean power output increased by 5.0% (95% confidence interval = +2.0 to +8.1%, P = 0.005). Blood lactate and pH values were similar between groups at any time. Oral betaALA supplementation can significantly enhance sprint performance at the end of an exhaustive endurance exercise bout.

Creatine Supplementation Augments Skeletal Muscle Carnosine Content in Senescence-Accelerated Mice (SAMP8)

The histidine-containing dipeptides (HCD) carnosine and anserine are found in high concentrations in mammalian skeletal muscle. Given its versatile biologic properties, such as antioxidative, antiglycation, and pH buffering capacity, carnosine has been implicated as a protective factor in the aging process. The present study aimed to systematically explore age-related changes in skeletal muscles HCD content in a murine model of accelerated aging. Additionally, we investigated the effect of lifelong creatine supplementation on muscle HCD content and contractile fatiguability. Male senescence-accelerated mice (SAMP8) were fed control or creatine-supplemented (2% of food intake) diet from the age of 10 to 60 weeks. At week 10, 25, and 60, tibialis anterior muscles were dissected and analysed for HCD and taurine content by HPLC. Soleus and EDL muscles were tested for in vitro contractile fatigue and recovery. From 10 to 60 weeks of age, muscular carnosine (-45%), taurine (-24%), and total creatine (-42%) concentrations gradually and significantly decreased. At 25 but not at 60 weeks, oral creatine supplementation significantly increased carnosine (+88%) and anserine (+40%) content compared to age-matched control-fed animals. Taurine and total creatine content were not affected by creatine supplementation at any age. Creatine-treated mice showed attenuated muscle fatigue (soleus) and enhanced force recovery (m. extensor digitorum longus [EDL]) compared to controls at 25 weeks, but not at 60 weeks. From the present study, we can conclude that skeletal muscle tissue exhibits a significant decline in HCD content at old age. Oral creatine supplementation is able to transiently but potently increase muscle carnosine and anserine content, which coincides with improved resistance to contractile fatigue.