D. L. Sparkes’s research while affiliated with University of Newcastle Australia and other places

Concentrations of free amino acids and [K⁺] in human sweat can be many times higher than in plasma. Conversely, [Na⁺] and [Cl⁻] in sweat are hypotonic to plasma. It was hypothesised that the amino acids and K⁺ were directly or indirectly associated with the resorption of Na⁺ and Cl⁻ in the sweat duct. The implication would be that, as resources of these components became limiting during prolonged exercise then the capacity to resorb [Na⁺] and [Cl⁻] would diminish, resulting in progressively higher levels in sweat. If this were the case, then [Na⁺] and [Cl⁻] in sweat would have inverse relationships with [K⁺] and the amino acids during exercise. Forearm sweat was collected from 11 recreational athletes at regular intervals during a prolonged period of cycling exercise after 15, 25, 35, 45, 55 and 65 minutes. The subjects also provided passive sweat samples via 15 minutes of thermal stimulation. The sweat samples were analysed for concentrations of amino acids, Na⁺, Cl⁻, K⁺, Mg²⁺ and Ca²⁺. The exercise sweat had a total amino acid concentration of 6.4 ± 1.2mM after 15 minutes which was lower than the passive sweat concentration at 11.6 ± 0.8mM (p<0.05) and showed an altered array of electrolytes, indicating that exercise stimulated a change in sweat composition. During the exercise period, [Na⁺] in sweat increased from 23.3 ± 3.0mM to 34.6 ± 2.4mM (p<0.01) over 65 minutes whilst the total concentrations of amino acids in sweat decreased from 6.4 ± 1.2mM to 3.6 ± 0.5mM. [Na⁺] showed significant negative correlations with the concentrations of total amino acids (r = -0.97, p<0.05), K⁺ (r = -0.93, p<0.05) and Ca²⁺ (r = -0.83, p<0.05) in sweat. The results supported the hypothesis that amino acids and K⁺, as well as Ca²⁺, were associated with resorption of Na⁺ and Cl⁻.

Maintenance of metabolic homeostasis is vital to optimise the supply of nutrients to support exercise and facilitate recovery and repair processes in horses. This study assessed the effects of exercise on resting plasma homeostasis in horses upon initiation of a training program to attain fitness in preparation for competitive harness racing. Four Standardbred horses (three males and one female) that had not been in work for at least 6 months were assessed prior to the commencement of the training program and then progressively on a weekly basis for 8 weeks. Resting plasma samples were collected in the early morning prior to exercise training and feeding. Samples were analysed for amino acid composition, cholesterol, palmitic acid and stearic acid on a weekly basis, and red blood cell counts and haemoglobin were analysed at weeks 0, 4 and 8. The red cell counts and levels of haemoglobin increased progressively over the training period (P≤0.05). Specific amino acids in the plasma displayed temporal variations during the training period. Glycine was the most abundant amino acid in resting horse plasma and together with serine was reduced throughout the first half of the training period, eventually returning to initial levels at weeks 7 and 8 (P≤0.05). A number of amino acids were noted to increase in concentration throughout the 8 week training period including ornithine, histidine and hydroxyproline (P≤0.05). Cholesterol fell to substantially lower levels after 8 weeks of exercise (P≤0.05). Palmitic acid showed three 'peaks' of elevated concentrations in plasma (P≤0.05) following the initiation of exercise and then again at the transitions into harder fast work sessions. Stearic acid was relatively constant throughout the exercise period. Adjustments in the plasma composition of these key metabolites were consistent with supporting the increased metabolic demands associated with the higher levels of exercise training.

Fluid collected during sweating is enriched with amino acids derived from the skin's natural moisturising factors and has been termed "faux" sweat. Little is known about sex differences in sweat amino acid composition or whether faux sweat amino acid losses affect nitrogen balance. Faux sweat collected by healthy adults (n = 47) after exercise, and at rest by chronic fatigue patients, was analysed for amino acid composition. Healthy females had higher total amino acid concentrations in sweat (10.5 ± 1.2 mM) compared with healthy males (6.9 ± 0.9 mM). Females had higher levels of 13 amino acids in sweat including serine, alanine and glycine. Higher hydroxyproline and proline levels suggested greater collagen turnover in females. Modelling indicated that with conservative levels of exercise, amino acid losses in females via faux sweat were triple than those predicted for urine, whereas in males they were double. It was concluded that females were more susceptible to key amino acid loss during exercise and/or hot conditions. Females reporting chronic fatigue had higher levels of methionine in faux sweat than healthy females. Males reporting chronic fatigue had higher levels of numerous amino acids in faux sweat compared to healthy males. Higher amino acid loss in faux sweat associated with chronic fatigue could contribute to a hypometabolic state. Depending on activity levels, climatic conditions and gender, amino acid losses in sweat and skin leachate could influence daily protein turnover where periods of continuously high turnover could lead to a negative net nitrogen balance.

Background The excretion of amino acids in urine represents an important avenue for the loss of key nutrients. Some amino acids such as glycine and histidine are lost in higher abundance than others. These two amino acids perform important physiological functions and are required for the synthesis of key proteins such as haemoglobin and collagen. Methods Stage 1 of this study involved healthy subjects (n?=?151) who provided first of the morning urine samples and completed symptom questionnaires. Urine was analysed for amino acid composition by gas chromatography. Stage 2 involved a subset of the initial cohort (n?=?37) who completed a 30?day trial of an amino acid supplement and subsequent symptom profile evaluation. Results Analyses of urinary amino acid profiles revealed that three groups could be objectively defined from the 151 participants using k-means clustering. The amino acid profiles were significantly different between each of the clusters (Wilks? Lambda?=?0.13, p?<?0.0001). Cluster 1 had the highest loss of amino acids with histidine being the most abundant component. Cluster 2 had glycine present as the most abundant urinary amino acid and cluster 3 had equivalent abundances of glycine and histidine. Strong associations were observed between urinary proline concentrations and fatigue/pain scores (r?=?.56 to .83) for females in cluster 1, with several other differential sets of associations observed for the other clusters. Conclusions Different phenotypic subsets exist in the population based on amino acid excretion characteristics found in urine. Provision of the supplement resulted in significant improvements in reported fatigue and sleep for 81% of the trial cohort with all females reporting improvements in fatigue. Trial registration The study was registered on the 18th April 2011 with the Australian New Zealand Clinical Trials Registry (ACTRN12611000403932).

Sweat contains amino acids and electrolytes derived from plasma and athletes can lose 1-2L of sweat per hour during exercise. Sweat may also contain contributions of amino acids as well as urea, sodium and potassium from the natural moisturizing factors (NMF) produced in the stratum corneum. In preliminary experiments, one participant was tested on three separate occasions to compare sweat composition with surface water washings from the same area of skin to assess contributions from NMF. Two participants performed a 40 minute self-paced cycle session with sweat collected from cleansed skin at regular intervals to assess the contributions to the sweat load from NMF over the period of exercise. The main study investigated sweat amino acid composition collected from nineteen male athletes following standardised endurance exercise regimes at 32–34°C and 20–30% RH. Plasma was also collected from ten of the athletes to compare sweat and plasma composition of amino acids. The amino acid profiles of the skin washings were similar to the sweat, suggesting that the NMF could contribute certain amino acids into sweat. Since the sweat collected from athletes contained some amino acid contributions from the skin, this fluid was subsequently referred to as “faux” sweat. Samples taken over 40 minutes of exercise showed that these contributions diminished over time and were minimal at 35 minutes. In the main study, the faux sweat samples collected from the athletes with minimal NMF contributions, were characterised by relatively high levels of serine, histidine, ornithine, glycine and alanine compared with the corresponding levels measured in the plasma. Aspartic acid was detected in faux sweat but not in the plasma. Glutamine and proline were lower in the faux sweat than plasma in all the athletes. Three phenotypic groups of athletes were defined based on faux sweat volumes and composition profiles of amino acids with varying relative abundances of histidine, serine, glycine and ornithine. It was concluded that for some individuals, faux sweat resulting from exercise at 32–34°C and 20–30% RH posed a potentially significant source of amino acid loss.

Little is known about the amino acid composition of horse sweat, but significant fluid losses can occur during exercise with the potential to facilitate substantial nutrient losses. Sweat and plasma amino acid compositions for Standardbred horses were assessed to determine losses during a standardised training regime. Two cohorts of horses 2013 (n=5) and 2014 (n=6) were assessed to determine baseline levels of plasma and sweat amino acids. An amino acid supplement designed to counter losses in sweat during exercise was provided after morning exercise daily for 5 weeks (2013, n=5; 2014, n=4). After the supplementation period, blood and sweat samples were collected to assess amino acid composition changes. From baseline assessments of sweat in both cohorts, it was found that serine, glutamic acid, histidine and phenylalanine were present at up to 9 times the corresponding plasma concentrations and aspartic acid at 0-2.2 μmol/l in plasma was measured at 154-262 μmol/l in sweat. In contrast, glutamine, asparagine, methionine and cystine were conserved in the plasma by having lower concentrations in the sweat. The predominant plasma amino acids were glycine, glutamine, alanine, valine, serine, lysine and leucine. As the sweat amino acid profile did not simply reflect plasma composition, it was proposed that mechanisms exist to generate high concentrations of certain amino acids in sweat whilst selectively preventing the loss of others. The estimated amino acid load in 16 l of circulating plasma was 3.8-4.3 g and the calculated loss via sweat during high intensity exercise was 1.6-3.0 g. Following supplementation, total plasma amino acid levels from both cohorts increased from initial levels of 2,293 and 2,044 µmol/l to post-supplementation levels of 2,674 and 2,663 µmol/l respectively (P<0.05). It was concluded that the strategy of providing free amino acids immediately after exercise resulted in raising resting plasma amino acid levels.

Fatigue Reviva™ was developed to provide a source of amino acids for rapid uptake by the body while avoiding the need for digestion of proteins. Complex amino acid formulations have significant palatability issues and thus new products require significant development and testing. An initial pilot study with 18 professional male ath-letes and 21 males recruited from the general public was undertaken to evaluate product palatability and toler-ance over a 30 day period. This investigation found that Fatigue Reviva™ was well tolerated in terms of palat-ability and usage across 39 participants with only two of the 39 subjects reporting an issue with taste and five reporting an issue with flatulence. The professional athlete cohort reported a significantly lower level of fatigue compared with the general public group prior to commencement of supplementation. The general public group reported a significant reduction in fatigue following the use of Fatigue Reviva™ over the 30-day period. Com-pliance was extremely poor amongst the professional athlete group and as a result, changes in fatigue could not be statistically assessed for this group over the study period. Preliminary assessment of the product indicated that it has the potential to significantly reduce fatigue. Minor modifications to the product were identified for future development.

A new dietary supplement, Fatigue RevivaTM, has been recently developed to address issues related to amino acid depletion following illness or in conditions of sub-health where altered amino acid homeostasis has been associated with fatigue. Complex formulations of amino acids present significant challenges due to solubility and taste constraints. This initial study sets out to provide an initial appraisal of product palatability and to gather pilot evidence for efficacy. Males reporting symptoms of sub-health were recruited on the basis of being free from any significant medical or psychological condition. Each participant took an amino acid based dietary supplement (Fatigue RevivaTM) daily for 30 days. Comparisons were then made between pre- and post-supplement general health symptoms and urinary amino acid profiles. Seventeen men took part in the study. Following amino acid supplementation the total Chalder fatigue score improved significantly (mean +/- SEM, 12.5 +/- 0.9 versus 10.0 +/- 1.0, P<0.03). When asked whether they thought that the supplement had improved their health, 65% of participants responded positively. A subgroup of participants reported gastrointestinal symptoms which were attributed to the supplement and which were believed to result from the component fructooligosaccharide. Analysis of urinary amino acids revealed significant alterations in the relative abundances of a number of amino acids after supplementation including an increase in valine, isoleucine and glutamic acid and reduced levels of glutamine and ornithine. Discriminant function analysis of the urinary amino acid data revealed significant differences between the pre- and post-supplement urine excretion profiles. The results indicated that Fatigue RevivaTM was palatable and that 65% of the study group reported that they felt the product had improved their health. The product could provide an effective tool for the management of unexplained fatigue and symptoms of sub-health. Further product development may yield additional options for those patients susceptible to fructooligosaccharide.

To examine altered amino acid homeostasis as a predisposing factor of fatigue in female radiotherapy breast cancer patients. Participants underwent breast-conserving surgery and adjuvant breast irradiation and were free from significant fatigue pre-radiotherapy. The Functional Assessment of Cancer Therapy fatigue subscale was used to assess fatigue pre- and post-radiotherapy. Blood biochemistry factors and urinary and plasma amino acid levels were measured. One third of 27 patients developed fatigue and were designated as the fatigued cohort. It was possible to differentiate between fatigued subjects pre- and post-radiotherapy based upon their urinary amino acid profiles. Univariate analysis supported altered amino acid homeostasis within the fatigued cohort. Urinary levels of histidine and alanine were increased pre-radiotherapy whilst threonine, methionine, alanine, serine, asparagine and glutamine levels were higher after 5weeks of radiotherapy for the fatigued cohort. Fatigue was accompanied by altered amino acid homeostasis with increased amino acid excretion suggestive of a catabolic response.