Effect of beta-alanine supplementation on muscle carnosine concentrations and exercise performance

High-intensity exercise results in reduced substrate levels and accumulation of metabolites in the skeletal muscle. The accumulation of these metabolites (e.g. ADP, Pi and H⁺) can have deleterious effects on skeletal muscle function and force generation, thus contributing to fatigue. Clearly this is a challenge to sport and exercise performance and, as such, any intervention capable of reducing the negative impact of these metabolites would be of use. Carnosine (β-alanyl-l-histidine) is a cytoplasmic dipeptide found in high concentrations in the skeletal muscle of both vertebrates and non-vertebrates and is formed by bonding histidine and β-alanine in a reaction catalysed by carnosine synthase. Due to the pKa of its imidazole ring (6.83) and its location within skeletal muscle, carnosine has a key role to play in intracellular pH buffering over the physiological pH range, although other physiological roles for carnosine have also been suggested. The concentration of histidine in muscle and plasma is high relative to its K _m with muscle carnosine synthase, whereas β-alanine exists in low concentration in muscle and has a higher K _m with muscle carnosine synthase, which indicates that it is the availability of β-alanine that is limiting to the synthesis of carnosine in skeletal muscle. Thus, the elevation of muscle carnosine concentrations through the dietary intake of carnosine, or chemically related dipeptides that release β-alanine on absorption, or supplementation with β-alanine directly could provide a method of increasing intracellular buffering capacity during exercise, which could provide a means of increasing high-intensity exercise capacity and performance. This paper reviews the available evidence relating to the effects of β-alanine supplementation on muscle carnosine synthesis and the subsequent effects on exercise performance. In addition, the effects of training, with or without β-alanine supplementation, on muscle carnosine concentrations are also reviewed.     

The high intracellular ph buffering of hagfish (Eptatretus cirrhatus) dental plate retractor muscle cannot be attributed to the known histidine-related compounds present in other vertebrates

• 1.1. Intracellular pH buffering capacity of hagfish (Eplatretus cirrhatus) dental plate retractor muscles is among the highest reported for any vertebrate muscle.
• 2.2. Over 80% of the pH buffering capacity of hagfish retractor and myotome muscle is due to components other than proteins and phosphate.
• 3.3. The muscles have less than 0.5 μmol/g wet weight of l-histidine, and lack l-l-methyl histidine, l-3-methyl histidine and the histidine-containing dipeptides anserine, carnosine and ophidine.
• 4.4. Instead, they contain an unidentified low molecular weight acid-soluble compound to which the high pH buffering capacity can be attributed.

     

Muscle dysmorphia in elite-level power lifters and bodybuilders: a test of differences within a conceptual model

The purpose of this study was to determine if associated characteristics of muscle dysmorphia (MD) were different between elite-level competitive bodybuilders and power lifters. Elite-level competitive bodybuilders (n = 100) and power lifters (n = 68) completed the muscle dysmorphia inventory (MDI) at the time of or immediately before competition. A 2 x 6 (group x MDI subscales) multivariate analysis of variance indicated that bodybuilders were significantly more likely to report body size-symmetry concerns (F(1, 167) = 10.31, p < 0.001), physique protection (F(1, 167) = 10.27, p < 0.001), dietary behavior (F(1, 167) = 28.38, p < 0.001), and pharmacological use (F(1, 167) = 19.64, p < 0.001) than were power lifters. These results suggest that elite-level bodybuilders are significantly more likely to engage in characteristics associated with MD than are elite-level power lifters.     

Carnosine and anserine concentrations in the quadriceps femoris muscle of healthy humans

The content of anserine and carnosine in the lateral portion of the quadriceps femoris muscle of 50 healthy, human subjects has been studied. Anserine was undetectable in all muscle samples examined. Muscle carnosine values for the group conformed to a normal distribution with a mean (SD) value of 20.0 (4.7) mmol.kg-1 of dry muscle mass. The concentration of carnosine was significantly higher in the muscle of male subjects (21.3, 4.2 mmol.kg-1 dry mass) than in females of a similar age and training status (17.5, 4.8 mmol.kg-1 dry mass) (P less than 0.005). The test-retest reliability of measures was determined on a subgroup of 17 subjects. No significant difference in mean carnosine concentration was found between the two trials [21.5 (4.0) and 22.0 (5.2) mmol.kg-1 dry muscle mass; P greater than 0.05]. The importance of carnosine as a physicochemical buffer within human muscle was examined by calculating its buffering ability over the physiological pH range. From the range of carnosine concentrations observed (7.2-30.7 mmol.kg-1 dry muscle mass), it was estimated that the dipeptide could buffer between 2.4 and 10.1 mmol H+.kg-1 dry mass over the physiological pH range 7.1-6.5, contributing, on average, approximately 7% to the total muscle buffering. This suggests that in humans, in contrast to many other species, carnosine is of only limited importance in preventing the reduction in pH observed during high intensity exercise.     

Buffering capacity of deproteinized human vastus lateralis muscle

The in vitro deproteinized vastus lateralis muscle buffer capacity, carnosine, and histidine levels were examined in 20 men from 4 distinct populations (5 sprinters, 800-m runners; 5 rowers; 5 marathoners; 5 untrained). Needle biopsies were obtained at rest from the vastus lateralis muscle. The buffer capacity was determined in deproteinized homogenates by repeatedly titrating supernatant extracts over the pH range of 7.0-6.0 with 0.01 N HCl. Carnosine and histidine levels were determined on an amino acid AutoAnalyzer. Fast-twitch fiber percentage was determined by staining intensity of myosin adenosinetriphosphatase. High-intensity running performance was assessed on an inclined treadmill run to fatigue (20% incline; 3.5 m X s-1). Significantly (P less than 0.01) elevated buffer capacities, carnosine levels, and high-intensity running performances were demonstrated by the sprinters and rowers, but no significant differences existed between these variables for the marathoners vs. untrained subjects. Low but significant (P less than 0.05) interrelationships were demonstrated between buffer capacity, carnosine levels, and fast-twitch fiber composition. These findings indicate that the sprinters and rowers possess elevated buffering capabilities and carnosine levels compared with marathon runners and untrained subjects.     

Comparison of the carnosine and taurine contents of vastus lateralis of elderly Korean males, with impaired glucose tolerance, and young elite Korean swimmers

The carnosine and taurine contents of the vastus lateralis of two diverse groups of Korean male subjects (elderly and impaired glucose-tolerant (IGT) subjects and young elite swimmers at a national sport university) having a similar national diet, were examined. Despite marked differences in age, fitness and clinical status the two groups showed almost identical muscle carnosine and taurine contents. In the case of carnosine, the results suggest a similar contribution to intracellular buffering capacity in the two groups of subjects, with no evidence of a reduction of this in elderly IGT subjects. In addition, both groups showed the same inverse relationship between the muscle carnosine and taurine contents; the spread of values between subjects, within-groups, most likely reflect variations in the type I (low carnosine, high taurine) or type II (high carnosine, low taurine) composition of the vastus lateralis. The relationship is consistent with a role of taurine in osmoregulation, compensating for variations between fibre types in the carnosine content.     

Beta-alanine (Carnosyn?) supplementation in elderly subjects (60–80?years): effects on muscle carnosine content and physical capacity

The aim of this study was to investigate the effects of beta-alanine supplementation on exercise capacity and the muscle carnosine content in elderly subjects. Eighteen healthy elderly subjects (60-80 years, 10 female and 4 male) were randomly assigned to receive either beta-alanine (BA, n=12) or placebo (PL, n=6) for 12 weeks. The BA group received 3.2 g of beta-alanine per day (2×800 mg sustained-release Carnosyn? tablets, given 2 times per day). The PL group received 2× (2×800 mg) of a matched placebo. At baseline (PRE) and after 12 weeks (POST-12) of supplementation, assessments were made of the muscle carnosine content, anaerobic exercise capacity, muscle function, quality of life, physical activity and food intake. A significant increase in the muscle carnosine content of the gastrocnemius muscle was shown in the BA group (+85.4%) when compared with the PL group (+7.2%) (p=0.004; ES: 1.21). The time-to-exhaustion in the constant-load submaximal test (i.e., TLIM) was significantly improved (p=0.05; ES: 1.71) in the BA group (+36.5%) versus the PL group (+8.6%). Similarly, time-to-exhaustion in the incremental test was also significantly increased (p=0.04; ES 1.03) following beta-alanine supplementation (+12.2%) when compared with placebo (+0.1%). Significant positive correlations were also shown between the relative change in the muscle carnosine content and the relative change in the time-to-exhaustion in the TLIM test (r=0.62; p=0.01) and in the incremental test (r=0.48; p=0.02). In summary, the current data indicate for the first time, that beta-alanine supplementation is effective in increasing the muscle carnosine content in healthy elderly subjects, with subsequent improvement in their exercise capacity.     

Non-bicarbonate intracellular pH buffering of reptilian muscle

Summary Non-bicarbonate intracellular pH buffering values of skeletal and cardiac muscles were measured for 16 species of Australian reptiles from four orders (snakes, skelctal 19–36 slykes, cardiac 9–17 slykes; lizards, skeletal 25–54 slykes, cardiac 17–19 slykes; turtles, skeletal 25–43 slykes, cardiac 11–24 slykes; crocodile, skeletal 43 slykes). Although a positive correlation between pH buffering capacity and dependence on anaerobic muscle work was found, even the highest reptilian pH buffering values were low relative to equivalent white anaerobic muscles of fish, birds, and mammals. The low non-bicarbonate intracellular pH buffering capacity of reptilian muscle arises through lower contributions from proteins (10–14 slykes), non-protein histidine (7–18 slykes) and phosphate (5–15 slykes). It is concluded that while other vertebrates depend on these intracellular buffers for regulating muscle pH during anaerobic muscle work, reptiles rely less on buffering and instead may tolerate greater pH fluctuations.Abbreviations intracellular pH buffering capacity - EDTA ethylenediaminetetra-acetic acid - HPLC high performance liquid chromatography - I.D. internal diameter - LDH lactate dehydrogenase     

Vegetarianism,female gender and increasing age,but not <Emphasis Type="Italic">CNDP1</Emphasis> genotype,are associated with reduced muscle carnosine levels in humans

Carnosine is found in high concentrations in skeletal muscles, where it is involved in several physiological functions. The muscle carnosine content measured within a population can vary by a factor 4. The aim of this study was to further characterize suggested determinants of the muscle carnosine content (diet, gender and age) and to identify new determinants (plasma carnosinase activity and testosterone). We investigated a group of 149 healthy subjects, which consisted of 94 men (12 vegetarians) and 55 women. Muscle carnosine was quantified in M. soleus, gastrocnemius and tibialis anterior using magnetic resonance proton spectroscopy and blood samples were collected to determine CNDP1 genotype, plasma carnosinase activity and testosterone concentrations. Compared to women, men have 36, 28 and 82% higher carnosine concentrations in M. soleus, gastrocnemius and tibialis anterior muscle, respectively, whereas circulating testosterone concentrations were unrelated to muscle carnosine levels in healthy men. The carnosine content of the M. soleus is negatively related to the subjects’ age. Vegetarians have a lower carnosine content of 26% in gastrocnemius compared to omnivores. In contrast, there is no difference in muscle carnosine content between omnivores with a high or low ingestion of β-alanine. Muscle carnosine levels are not related to the polymorphism of the CNDP1 gene or to the enzymatic activity of the plasma carnosinase. In conclusion, neither CNDP1 genotype nor the normal variation in circulating testosterone levels affects the muscular carnosine content, whereas vegetarianism, female gender and increasing age are the factors associated with reduced muscle carnosine stores.     

Medication in elderly people: its influence on salivary pattern,signs and symptoms of dry mouth

doi:10.1111/j.1741‐2358.2009.00293.x
Medication in elderly people: its influence on salivary pattern, signs and symptoms of dry mouth Objective: To compare stimulated and non‐stimulated salivary flow, pH, buffering capacity and presence of signs and symptoms of hyposialie and xerostomia in elderly patients, with senile dementia using medication and healthy elderly subjects not using medication. Methods: Forty individuals (mean age: 68.5 years) were divided into two groups, according to the use (G1) or non‐use (G2) of medication and the presence (G1) or absence (G2) of senile dementia. Data with reference to the general health condition, use of medication and the patient’s complaints were collected during anamnesis. Clinical examination identified signs associated with hyposialie and xerostomia. Stimulated and non‐stimulated saliva flow, pH and buffering capacity were verified. Results: The stimulated saliva flow in both groups was below normal parameters. The drugs used by individuals in G1 showed xerostomic potential. Individuals with a higher consumption of xerostomic medication presented with dry and cracked lips. A significant negative relationship was found between drugs consumption and the buffering capacity (p < 0.001), and the resting saliva flow rate (p = 0.002). Conclusion: The use of medication increases the chance that an elderly person may present signs related to xerostomia and alterations in stimulated saliva flow and buffering capacity.     

Role of histidine-related compounds as intracellular proton buffering constituents in vertebrate muscle

The intracellular non-bicarbonate buffering capacity of vertebrate muscle is mainly supported by the imidazole groups of histidine residues in proteins, free L-histidine in some fish species, and histidine-containing dipeptides such as carnosine, anserine, and balenine (ophidine). The proton buffering capacity markedly differs between muscle types and animal species depending on the ability for anaerobic exercise. The capacity is typically high in fast-twitch glycolytic muscles of vertebrates adapted for anaerobic performance such as burst swimming in fishes, prolonged anoxic diving in marine mammals, flight in birds, sprint running in mammalian sprinters, and hopping locomotion in some terrestrial mammals. A high correlation between buffering capacity, concentration of histidine-related compounds in muscle, and percentage of fast-twitch fibers in all vertebrates adapted for intense anaerobic performance clearly supports the idea that proton buffering is the main physiological function of histidine-related compounds.     

Reduced muscle carnosine content in type 2, but not in type 1 diabetic patients

Carnosine is present in high concentrations in skeletal muscle where it contributes to acid buffering and functions also as a natural protector against oxidative and carbonyl stress. Animal studies have shown an anti-diabetic effect of carnosine supplementation. High carnosinase activity, the carnosine degrading enzyme in serum, is a risk factor for diabetic complications in humans. The aim of the present study was to compare the muscle carnosine concentration in diabetic subjects to the level in non-diabetics. Type 1 and 2 diabetic patients and matched healthy controls (total n=58) were included in the study. Muscle carnosine content was evaluated by proton magnetic resonance spectroscopy (3 Tesla) in soleus and gastrocnemius. Significantly lower carnosine content (-45%) in gastrocnemius muscle, but not in soleus, was shown in type 2 diabetic patients compared with controls. No differences were observed in type 1 diabetic patients. Type II diabetic patients display a reduced muscular carnosine content. A reduction in muscle carnosine concentration may be partially associated with defective mechanisms against oxidative, glycative and carbonyl stress in muscle.     

Buffering capacity of vertebrate muscle: Correlations with potentials for anaerobic function

Summary Buffering capacities (), measured in slykes (moles of base required to titrate the pH of one gram wet weight of muscle by one pH unit, over the pH range of pH 6 to pH 7) due to non-bicarbonate buffers were measured in locomotory muscles from a variety of terrestrial and marine mammals and teleost fishes (Tables 1 and 2). The highest buffering capacities were found in muscles capable of either intense, burst glycolytic function or prolonged, low-level anaerobic function. Marine mammals had higher muscle buffering capacity on the average than terrestrial mammals. Among the fishes studied, warm-bodied species had the greatest values of all animals examined (Table 2). Deep-sea fishes and shallow-living fishes with sluggish locomotory abilities had low values. Fish white muscle displayed higher buffering capacity than red muscle (Fig. 1; Table 2), in keeping with the more aerobic poise and higher capillary density of the latter type of muscle. Strong correlations were found between (1) and muscle myoglobin concentrations in the mammalian species (Table 1; Fig. 2), and (2) and muscle lactate dehydrogenase (LDH) activities in both the mammals and the fishes (Tables 1 and 2; Fig. 3). No correlation was found between and the activity of a citric acid cycle indicator enzyme, citrate synthase, in the mammalian species. While strongly correlated with buffering capacity, the amounts of myoglobin and LDH in a muscle are not the principal determinants of . The results indicate that muscle intracellular buffering capacity is especially critical in locomotory muscles which must function under conditions (burst locomotion and prolonged, low-level anaerobic function) where circulatory perfusion is inadequate to rapidly remove the acidic end-products such as lactic acid that are produced by anaerobic glycolysis. In this respect, the locomotory muscle of diving mammals and the white skeletal muscles of teleost fishes face a common acid-base regulatory problem and utilize a common biochemical strategy to resolve it.     

Do sperm contribute to the buffering capacity of steelhead trout (Oncorhynchus mykiss) semen?

The motility of salmonid sperm is pH-sensitive and the buffering capacity of the seminal plasma is low. The objective of the present study was to determine the extent to which sperm contribute to the buffering capacity of whole steelhead (Oncorhynchus mykiss) semen. To determine the buffering capacity, semen and seminal plasma samples were titrated with HCl and pH measurements taken at 1-2 min. The buffering capacity of semen was not different from that of seminal plasma over the pH range 7.5 to 8.5 and was approximately 15% to 20% less over the range 6.0 to 7.0. Comparable results were obtained for the semen and seminal plasma of the chinook salmon (Oncorhynchus tshawytscha). To assess whether the intracellular environment could influence the buffering capacity, the effects of cell disruption with n-butanol and Triton X-100 (TX-100) were determined. Over the pH range 7.5 to 8.5, the presence of n-butanol or TX-100 resulted in a doubling of the buffering capacity of the semen; TX-100, but not n-butanol, increased semen buffering capacity over the pH range 6.0 to 7.0. To determine whether the sperm's intracellular compartment might contribute to the buffering capacity over a longer duration, semen and seminal plasma samples were acidified with HCl and the pH measured over several hours. These data suggest that intact sperm contribute no more than about 25% to the buffering capacity of whole semen. The buffering capacity of steelhead semen and seminal plasma were comparably and modestly temperature sensitive. The results suggest that the sperm may contribute to the buffering capacity of the semen over a physiological pH range, however, if so, the effect is relatively small.     

Muscle buffering capacity and dipeptide content in the thoroughbred horse, greyhound dog and man

1. Muscle buffering capacity (beta m) and dipeptide content were measured in locomotory muscles of the Thoroughbred horse, Greyhound dog and Man. 2. Beta m and carnosine contents were highest in the horse. Anserine was only found in dog muscle. 3. The higher beta m in horse and dog muscle, compared with man, appears to be predominantly due to higher muscle contents of histidine containing dipeptides in these species.     

Carnosine: from exercise performance to health

Carnosine was first discovered in skeletal muscle, where its concentration is higher than in any other tissue. This, along with an understanding of its role as an intracellular pH buffer has made it a dipeptide of interest for the athletic population with its potential to increase high-intensity exercise performance and capacity. The ability to increase muscle carnosine levels via β-alanine supplementation has spawned a new area of research into its use as an ergogenic aid. The current evidence base relating to the use of β-alanine as an ergogenic aid is reviewed here, alongside our current thoughts on the potential mechanism(s) to support any effect. There is also some emerging evidence for a potential therapeutic role for carnosine, with this potential being, at least theoretically, shown in ageing, neurological diseases, diabetes and cancer. The currently available evidence to support this potential therapeutic role is also reviewed here, as are the potential limitations of its use for these purposes, which mainly focusses on issues surrounding carnosine bioavailability.     

Optimizing human in vivo dosing and delivery of β-alanine supplements for muscle carnosine synthesis

Interest into the effects of carnosine on cellular metabolism is rapidly expanding. The first study to demonstrate in humans that chronic β-alanine (BA) supplementation (~3-6 g BA/day for ~4 weeks) can result in significantly augmented muscle carnosine concentrations (>50%) was only recently published. BA supplementation is potentially poised for application beyond the niche exercise and performance-enhancement field and into other more clinical populations. When examining all BA supplementation studies that directly measure muscle carnosine (n=8), there is a significant linear correlation between total grams of BA consumed (of daily intake ranges of 1.6-6.4 g BA/day) versus both the relative and absolute increases in muscle carnosine. Supporting this, a recent dose-response study demonstrated a large linear dependency (R2=0.921) based on the total grams of BA consumed over 8 weeks. The pre-supplementation baseline carnosine or individual subjects' body weight (from 65 to 90 kg) does not appear to impact on subsequent carnosine synthesis from BA consumption. Once muscle carnosine is augmented, the washout is very slow (~2%/week). Recently, a slow-release BA tablet supplement has been developed showing a smaller peak plasma BA concentration and delayed time to peak, with no difference in the area under the curve compared to pure BA in solution. Further, this slow-release profile resulted in a reduced urinary BA loss and improved retention, while at the same time, eliciting minimal paraesthesia symptoms. However, our complete understanding of optimizing in vivo delivery and dosing of BA is still in its infancy. Thus, this review will clarify our current knowledge of BA supplementation to augment muscle carnosine as well as highlight future research questions on the regulatory points of control for muscle carnosine synthesis.     

pH changes in the rhizosphere in relation to the pH-buffering of soils

Summary pH values in the rhizosphere of peanut seedlings were measured with Sb micro electrodes in soils with a bulk pH between 3.9 and 7.7. Within 2–2.5 days the roots decreased soil pH to a minimum value which was linearly correlated with short term buffering capacity of the soils as determined by addition of HCl to soil suspensions. The greatest distance from the root surface where pH dropped significantly was found in soils with pH near 6. This maximum distance was also correlated with pH-buffering. The low buffering capacity for soils of pH near 6 seems to be valid for a large number of soils with different properties.     

Determination of buffering capacity of rat myocardium during ischemia

To determine the buffering capacity of ischemic rat myocardium, lactate production was altered by glycogen depletion prior to total global ischemia. Lactate production was monitored by 1H-NMR spectroscopy in perfused rat hearts and determined by enzymatic assay of freeze-clamped tissue extracts. Intracellular pH was measured by 31P-NMR spectroscopy. The relationship between total lactate produced and pH varied considerably, depending on the final pH reached. At pH greater than 6.4 this relationship is linear with a total buffering capacity (delta lactate/delta pH) of 25 mumol H+/g wet weight per pH unit. At lower pH values (pH less than 6.4), the total buffering capacity increases progressively. Since ischemia is invariably accompanied by ATP and phosphocreatine (PCr) hydrolysis, the proton production/consumption during high-energy phosphate hydrolysis must be considered when evaluating the intrinsic buffering capacity of the myocardium against proton loads produced by lactate production from glucose and glycogen. Schemes are presented which allow an estimation of the contribution of ATP and PCr hydrolysis and the buffering by the CO2/HCO3- system during ischemia. At pH greater than 6.4, the majority (about 60%) of buffering is due to hydrolysis of adenosine triphosphate, phosphocreatine in the heart, and neutralization of sodium bicarbonate in the perfusate. At pH less than 6.4 an increasing proportion of cardiac buffering is from intrinsic cardiac buffers, most likely from intracellular proteins. After correction for these contributions to the observed total cardiac buffering capacity, the intrinsic buffering capacity of the myocardium can be accounted for by a high capacity (170 mumol/g wet weight) but low pKa (5.2) buffering system.     

Isokinetic strength in weight-trainers

Isokinetic strength of ankle plantarflexion (APF), knee extension (KE) and elbow extension (EE) was measured in male weight-trainers (6 power-lifters and 7 bodybuilders) and 25 untrained men of similar age and height. The weight-trainers exceeded control subjects by 21%, 25% and 73% in APF, KE and EE strength respectively. A similar pattern was obtained for limb girth, in which the weight-trainers exceeded control subjects by 6%, 13%, and 31% in calf, thigh and arm girth, respectively. Strength was similarly enhanced in the weight-trainers at the lower and higher velocities (APF 0.10, 0.63 rad X s-1, KE and EE 0.52, 3.14 rad X s-1) tested, and accounted for the positive correlation (r = 0.84) observed between low and high velocity strength. The powerlifters differed significantly from the bodybuilders only in their greater low velocity APF strength. The relatively greater enhancement of upper versus lower limb strength and muscle mass in the weight-trainers was considered in respect to training habits, trainability of different muscle groups and the state of training of muscle groups in untrained men.