Protein catabolism and high lipid metabolism associated with long-distance exercise are revealed by plasma NMR metabolomics in endurance horses

Nuclear Magnetic Resonance (NMR) Metabolomics: Current Applications in Equine Health Assessment

Metabolomics can allow for the comprehensive identification of metabolites within biological systems, at given time points, in physiological and pathological conditions. In the last few years, metabolomic analysis has gained popularity both in human and in veterinary medicine, showing great potential for novel applications in clinical activity. The aim of applying metabolomics in clinical practice is understanding the mechanisms underlying pathological conditions and the influence of certain stimuli (i.e., drugs, nutrition, exercise) on body systems, in the attempt of identifying biomarkers that can help in the diagnosis of diseases. Proton Nuclear Magnetic Resonance spectroscopy (1H-NMR) is well tailored to be used as an analytical platform for metabolites' detection at the base of metabolomics studies, due to minimal sample preparation and high reproducibility. In this mini-review article, the scientific production of NMR metabolomic applications to equine medicine is examined. The research works are very different in methodology and difficult to compare. Studies are mainly focused on exercise, reproduction, and nutrition, other than respiratory and musculoskeletal diseases. The available information on this topic is still scant, but a greater collection of data could allow researchers to define new reliable markers to be used in clinical practice for diagnostic and therapeutical purposes.

Current Understanding of Equine Gut Dysbiosis and Microbiota Manipulation Techniques: Comparison with Current Knowledge in Other Species

Understanding the importance of intestinal microbiota in horses and the factors influencing its composition have been the focus of many studies over the past few years. Factors such as age, diet, antibiotic administration, and geographic location can affect the gut microbiota. The intra- and inter-individual variability of fecal microbiota in horses complicates its interpretation and has hindered the establishment of a clear definition for dysbiosis. Although a definitive causal relationship between gut dysbiosis in horses and diseases has not been clearly identified, recent research suggests that dysbiosis may play a role in the pathogenesis of various conditions, such as colitis and asthma. Prebiotics, probiotics, and fecal microbiota transplantation to modulate the horse's gastrointestinal tract may eventually be considered a valuable tool for preventing or treating diseases, such as antibiotic-induced colitis. This article aims to summarize the current knowledge on the importance of intestinal microbiota in horses and factors influencing its composition, and also to review the published literature on methods for detecting dysbiosis while discussing the efficacy of gut microbiota manipulation in horses.

Untargeted Metabolomics Profiling Reveals Exercise Intensity-Dependent Alterations in Thoroughbred Racehorses' Plasma after Routine Conditioning Sessions

Thoroughbred (TB) racehorses undergo rigorous conditioning programs to optimize their physical and mental capabilities through varied exercise sessions. While conventional investigations focus on limited hematological and biochemical parameters, this field study employed untargeted metabolomics to comprehensively assess metabolic responses triggered by exercise sessions routinely used in TB conditioning. Blood samples were collected pre- and post-exercise from ten racehorses, divided into two groups based on exercise intensity: high intensity (n = 6, gallop at ± 13.38 m/s, 1400 m) and moderate intensity (n = 4, soft canter at ± 7.63 m/s, 2500 m). Intensity was evaluated through monitoring of the speed, heart rate, and lactatemia. Resting and 30 min post-exercise plasma samples were analyzed using ultraperformance liquid chromatography coupled with high-resolution mass spectrometry. Unsupervised principal component analysis revealed exercise-induced metabolome changes, with high-intensity exercise inducing greater alterations. Following high-intensity exercise, 54 metabolites related to amino acid, fatty acid, nucleic acid, and vitamin metabolism were altered versus 23 metabolites, primarily linked to fatty acid and amino acid metabolism, following moderate-intensity exercise. Metabolomics confirmed energy metabolism changes reported by traditional biochemistry studies and highlighted the involvement of lipid and amino acid metabolism during routine exercise and recovery, aspects that had previously been overlooked in TB racehorses.

Metabolomics-a powerful tool in livestock research

Advancements in the Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS) along with recent developments in omics sciences have resulted in a better understanding of molecular mechanisms and pathways associated with the physio-pathological state of the animal. Metabolomics is a post-genomics tool that deals with small molecular metabolites in a given set of time which provides clear information about the status of an organism. Recently many researchers mainly focus their research on metabolomics studies due to its valuable information in the various fields of livestock management and precision dairying. The main aim of the present review is to provide an insight into the current research output from different sources and application of metabolomics in various areas of livestock including nutri-metabolomics, disease diagnosis advancements, reproductive disorders, pharmaco-metabolomics, genomics studies, and dairy production studies. The present review would be helpful in understanding the metabolomics methodologies and use of livestock metabolomics in various areas in a brief way.

Identification of Differentially Expressed Genes after Endurance Runs in Karbadian Horses to Determine Candidates for Stress Indicators and Performance Capability

RNA sequencing makes it possible to uncover genetic mechanisms that underlie certain performance traits. In order to gain a deeper insight into the genetic background and biological processes involved in endurance performance in horses, the changes in the gene expression profiles induced by endurance runs over long (70 km) and short (15 km) distances in the blood of Kabardian horses (Equus caballus) were analyzed. For the long-distance runs, we identified 1484 up- and 691 downregulated genes, while after short-distance runs, only 13 up- and 8 downregulated genes (FC > |1.5|; p < 0.05) were found. These differentially expressed genes (DEGs) are involved in processes and pathways that are primarily related to stress response (interleukin production, activation of inflammatory system) but also to metabolism (carbohydrate catabolic process, lipid biosynthesis, NADP metabolic process). The most important genes involved in these processes therefore represent good candidates for the monitoring and evaluation of the performance of horses in order to avoid excessive demands when endurance performance is required, like ACOD1, CCL5, CD40LG, FOS, IL1R2, IL20RA, and IL22RA2, on the one hand, and, on the other hand, for assessing the suitability of a horse for endurance races, like GATA2, GYG1, HIF1A, MOGAT1, PFKFB3, PLIN5, SIK1, and STBD1.

Plasma Non-targeted Metabolomics Analysis of Yili Horses Raced on Tracks With Different Surface Hardness

In this study, the plasma non-targeted metabolomics of Yili horses were characterized before and after exercise on tracks that differed in surface hardness to better understand exercise-related biochemical changes. Blood samples were obtained from eight trained Yili horses before and immediately after exercise. Samples were used for metabolomic analysis by ultra-performance liquid chromatography-Q-EXACTIVE mass spectrometry. In total, 938 significantly different metabolites involving sugar, lipid, and amino acid metabolism were detected in the plasma, with significant increases in glucose, glucoheptanoic acid, lactic acid, malic acid, and methylmalonic acid and significant decreases in creatinine, D-tryptophan, carnitine, and citric acid after exercise. Among these metabolites, acetylcarnitine, tuliposide, vitamin C, and methylmalonic acid showed regular changes in concentration after exercise on tracks that differed in surface hardness, providing new insights into equine exercise physiology. The findings indicated the potential of vitamin C and methylmalonic acid as novel biomarkers of equine locomotor injury.

Mining the equine gut metagenome: poorly-characterized taxa associated with cardiovascular fitness in endurance athletes

Emerging evidence indicates that the gut microbiome contributes to endurance exercise performance. Still, the extent of its functional and metabolic potential remains unknown. Using elite endurance horses as a model system for exercise responsiveness, we built an integrated horse gut gene catalog comprising ~25 million unique genes and 372 metagenome-assembled genomes. This catalog represents 4179 genera spanning 95 phyla and functional capacities primed to exploit energy from dietary, microbial, and host resources. The holo-omics approach shows that gut microbiomes enriched in Lachnospiraceae taxa are negatively associated with cardiovascular capacity. Conversely, more complex and functionally diverse microbiomes are associated with higher glucose concentrations and reduced accumulation of long-chain acylcarnitines and non-esterified fatty acids in plasma, suggesting increased ß-oxidation capacity in the mitochondria. In line with this hypothesis, more fit athletes show upregulation of mitochondrial-related genes involved in energy metabolism, biogenesis, and Ca²⁺ cytosolic transport, all of which are necessary to improve aerobic work power, spare glycogen usage, and enhance cardiovascular capacity. The results identify an associative link between endurance performance and gut microbiome composition and gene function, laying the basis for nutritional interventions that could benefit horse athletes.

An integrated gene catalog of the gut microbiome in elite endurance horses is build. The holo-omics analyses identify an associative link between endurance performance and gut microbiome composition and gene function.

Comparative metabolomic analysis in horses and functional analysis of branched chain (alpha) keto acid dehydrogenase complex in equine myoblasts under exercise stress

The integration of metabolomics and transcriptomics may elucidate the correlation between the genotypic and phenotypic patterns in organisms. In equine physiology, various metabolite levels vary during exercise, which may be correlated with a modified gene expression pattern of related genes. Integrated metabolomic and transcriptomic studies in horses have not been conducted to date. The objective of this study was to detect the effect of moderate exercise on the metabolomic and transcriptomic levels in horses. In this study, using nuclear magnetic resonance (NMR) spectroscopy, we analyzed the concentrations of metabolites in muscle and plasma; we also determined the gene expression patterns of branched chain (alpha) keto acid dehydrogenase kinase complex (BCKDK), which encodes the key regulatory enzymes in branched-chain amino acid (BCAA) catabolism, in two breeds of horses, Thoroughbred and Jeju, at different time intervals. The concentrations of metabolites in muscle and plasma were measured by ¹H NMR (nuclear magnetic resonance) spectroscopy, and the relative metabolite levels before and after exercise in the two samples were compared. Subsequently, multivariate data analysis based on the metabolic profiles was performed using orthogonal partial least square discriminant analysis (OPLS-DA), and variable important plots and t-test were used for basic statistical analysis. The stress-induced expression patterns of BCKDK genes in horse muscle-derived cells were examined using quantitative reverse transcription polymerase chain reaction (qPCR) to gain insight into the role of transcript in response to exercise stress. In this study, we found higher concentrations of aspartate, leucine, isoleucine, and lysine in the skeletal muscle of Jeju horses than in Thoroughbred horses. In plasma, compared with Jeju horses, Thoroughbred horses had higher levels of alanine and methionine before exercise; whereas post-exercise, lysine levels were increased. Gene expression analysis revealed a decreased expression level of BCKDK in the post-exercise period in Thoroughbred horses.

Metabolomics in clinical and forensic toxicology, sports anti-doping and veterinary residues

Metabolomics is a multidisciplinary field providing workflows for complementary approaches to conventional analytical determinations. It allows for the study of metabolically related groups of compounds or even the study of novel pathways within the biological system. The procedural stages of metabolomics; experimental design, sample preparation, analytical determinations, data processing and statistical analysis, compound identification and validation strategies are explored in this review. The selected approach will depend on the type of study being conducted. Experimental design influences the whole metabolomics workflow and thus needs to be properly assessed to ensure sufficient sample size, minimal introduced and biological variation and appropriate statistical power. Sample preparation needs to be simple, yet potentially global in order to detect as many compounds as possible. Analytical determinations need to be optimised either for the list of targeted compounds or a universal approach. Data processing and statistical analysis approaches vary widely and need to be better harmonised for review and interpretation. This includes validation strategies that are currently deficient in many presented workflows. Common compound identification approaches have been explored in this review. Metabolomics applications are discussed for clinical and forensic toxicology, human and equine sports anti-doping and veterinary residues.

The plasma metabolome of Atlantic salmon as studied by 1H NMR spectroscopy using standard operating procedures: effect of aquaculture location and growth stage

INTRODUCTION

Metabolomics applications to the aquaculture research are increasing steadily. The use of standardized proton nuclear magnetic resonance (¹H NMR) spectroscopy can provide the aquaculture industry with an unbiased, reproducible, and high-throughput screening tool, which can help to diagnose nutritional and disease-related metabolic disorders in farmed fish.

OBJECTIVE

Standard operating procedures developed for analysing (human) plasma by ¹H NMR were applied to fingerprint the metabolome in plasma samples collected from Atlantic salmon. The aim was to explore the metabolome of salmon plasma in relation to growth stage and sampling site.

METHODS

A total of 72 salmon were collected from three aquaculture sites in Norway (Lat. 65, 67, and 70 °N) and over two sampling events (December 2017 and November 2018). Plasma drawn from each salmon was measured by ¹H NMR and metabolites were quantified using the SigMa software. The NMR data was analysed by principal component analysis (PCA) and ANOVA-simultaneous component analysis (ASCA).

RESULTS

Important metabolic differences were evidenced, with adult salmon having a much higher content of very low-density lipoproteins and cholesterol in their plasma, while smolts displayed significantly higher levels of propylene glycol. Overall, 24% of the metabolite variation was due to the growth stage, whereas 12% of the metabolite variation was related to the aquaculture site and practice (p < 0.001).

CONCLUSION

This study provides a baseline investigation of the plasma metabolome of the Atlantic salmon and demonstrates how ¹H NMR metabolomics can be used in future investigations for comparing aquaculture practices and their influence on the fish metabolome.

Flexibility of equine bioenergetics and muscle plasticity in response to different types of training: An integrative approach, questioning existing paradigms

Equine bioenergetics have predominantly been studied focusing on glycogen and fatty acids. Combining omics with conventional techniques allows for an integrative approach to broadly explore and identify important biomolecules. Friesian horses were aquatrained (n = 5) or dry treadmill trained (n = 7) (8 weeks) and monitored for: evolution of muscle diameter in response to aquatraining and dry treadmill training, fiber type composition and fiber cross-sectional area of the M. pectoralis, M. vastus lateralis and M. semitendinosus and untargeted metabolomics of the M. pectoralis and M. vastus lateralis in response to dry treadmill training. Aquatraining was superior to dry treadmill training to increase muscle diameter in the hindquarters, with maximum effect after 4 weeks. After dry treadmill training, the M. pectoralis showed increased muscle diameter, more type I fibers, decreased fiber mean cross sectional area, and an upregulated oxidative metabolic profile: increased β-oxidation (key metabolites: decreased long chain fatty acids and increased long chain acylcarnitines), TCA activity (intermediates including succinyl-carnitine and 2-methylcitrate), amino acid metabolism (glutamine, aromatic amino acids, serine, urea cycle metabolites such as proline, arginine and ornithine) and xenobiotic metabolism (especially p-cresol glucuronide). The M. vastus lateralis expanded its fast twitch profile, with decreased muscle diameter, type I fibers and an upregulation of glycolytic and pentose phosphate pathway activity, and increased branched-chain and aromatic amino acid metabolism (cis-urocanate, carnosine, homocarnosine, tyrosine, tryptophan, p-cresol-glucuronide, serine, methionine, cysteine, proline and ornithine). Trained Friesians showed increased collagen and elastin turn-over. Results show that branched-chain amino acids, aromatic amino acids and microbiome-derived xenobiotics need further study in horses. They feed the TCA cycle at steps further downstream from acetyl CoA and most likely, they are oxidized in type IIA fibers, the predominant fiber type of the horse. These study results underline the importance of reviewing existing paradigms on equine bioenergetics.

Understanding the Holobiont: Crosstalk Between Gut Microbiota and Mitochondria During Long Exercise in Horse

Endurance exercise has a dramatic impact on the functionality of mitochondria and on the composition of the intestinal microbiome, but the mechanisms regulating the crosstalk between these two components are still largely unknown. Here, we sampled 20 elite horses before and after an endurance race and used blood transcriptome, blood metabolome and fecal microbiome to describe the gut-mitochondria crosstalk. A subset of mitochondria-related differentially expressed genes involved in pathways such as energy metabolism, oxidative stress and inflammation was discovered and then shown to be associated with butyrate-producing bacteria of the Lachnospiraceae family, especially Eubacterium. The mechanisms involved were not fully understood, but through the action of their metabolites likely acted on PPARγ, the FRX-CREB axis and their downstream targets to delay the onset of hypoglycemia, inflammation and extend running time. Our results also suggested that circulating free fatty acids may act not merely as fuel but drive mitochondrial inflammatory responses triggered by the translocation of gut bacterial polysaccharides following endurance. Targeting the gut-mitochondria axis therefore appears to be a potential strategy to enhance athletic performance.

Metabolomics and Lipidomics: Expanding the Molecular Landscape of Exercise Biology

Dynamic changes in circulating and tissue metabolites and lipids occur in response to exercise-induced cellular and whole-body energy demands to maintain metabolic homeostasis. The metabolome and lipidome in a given biological system provides a molecular snapshot of these rapid and complex metabolic perturbations. The application of metabolomics and lipidomics to map the metabolic responses to an acute bout of aerobic/endurance or resistance exercise has dramatically expanded over the past decade thanks to major analytical advancements, with most exercise-related studies to date focused on analyzing human biofluids and tissues. Experimental and analytical considerations, as well as complementary studies using animal model systems, are warranted to help overcome challenges associated with large human interindividual variability and decipher the breadth of molecular mechanisms underlying the metabolic health-promoting effects of exercise. In this review, we provide a guide for exercise researchers regarding analytical techniques and experimental workflows commonly used in metabolomics and lipidomics. Furthermore, we discuss advancements in human and mammalian exercise research utilizing metabolomic and lipidomic approaches in the last decade, as well as highlight key technical considerations and remaining knowledge gaps to continue expanding the molecular landscape of exercise biology.

Metabolic Predictors of Equine Performance in Endurance Racing

Equine performance in endurance racing depends on the interplay between physiological and metabolic processes. However, there is currently no parameter for estimating the readiness of animals for competition. Our objectives were to provide an in-depth characterization of metabolic consequences of endurance racing and to establish a metabolic performance profile for those animals. We monitored metabolite composition, using a broad non-targeted metabolomics approach, in blood plasma samples from 47 Arabian horses participating in endurance races. The samples were collected before and after the competition and a total of 792 metabolites were measured. We found significant alterations between before and after the race in 417 molecules involved in lipids and amino acid metabolism. Further, even before the race starts, we found metabolic differences between animals who completed the race and those who did not. We identified a set of six metabolite predictors (imidazole propionate, pipecolate, ethylmalonate, 2R-3R-dihydroxybutyrate, β-hydroxy-isovalerate and X-25455) of animal performance in endurance competition; the resulting model had an area under a receiver operating characteristic (AUC) of 0.92 (95% CI: 0.85-0.98). This study provides an in-depth characterization of metabolic alterations driven by endurance races in equines. Furthermore, we showed the feasibility of identifying potential metabolic signatures as predictors of animal performance in endurance competition.

Metabolomics in equine sport and exercise

metabolomics is the high-throughput, multiparametric identification and classification of hundreds of low molecular weight metabolites in a biological sample. Ultimately, metabolites are the downstream readouts of cellular signalling, transcriptomic and proteomic changes that can provide a comprehensive view of tissue and organismal phenotype. The popularity of metabolomics in human sport and exercise has been gaining over the past decade and has provided important insights into the energetic demands and mechanistic underpinnings of exercise and training. To the contrary, metabolomics in the field of equine exercise physiology is lagging despite the horse's superior aerobic and muscular capabilities, as well as its prominence in competitive sport. As such, this narrative review aims to describe metabolomics, its routine implementation, the various analytical methods applied and the state of its use in the equine athlete. Sufficient attention will be paid to methodological considerations, as well as gaps in the equine literature, particularly with regard to the skeletal muscle metabolome. Finally, there will be a brief discussion of the future directions and barriers to metabolomics use in the athletic horse. A thorough understanding of the metabolomics changes that occur in the equine athlete with exercise will undoubtedly help to improve horse management and health across the lifespan.

Priming for welfare: gut microbiota is associated with equitation conditions and behavior in horse athletes

We simultaneously measured the fecal microbiota and multiple environmental and host-related variables in a cohort of 185 healthy horses reared in similar conditions during a period of eight months. The pattern of rare bacteria varied from host to host and was largely different between two time points. Among a suite of variables examined, equitation factors were highly associated with the gut microbiota variability, evoking a relationship between gut microbiota and high levels of physical and mental stressors. Behavioral indicators that pointed toward a compromised welfare state (e.g. stereotypies, hypervigilance and aggressiveness) were also associated with the gut microbiota, reinforcing the notion for the existence of the microbiota-gut-brain axis. These observations were consistent with the microbiability of behaviour traits (> 15%), illustrating the importance of gut microbial composition to animal behaviour. As more elite athletes suffer from stress, targeting the microbiota offers a new opportunity to investigate the bidirectional interactions within the brain gut microbiota axis.

The Genetics of Racing Performance in Arabian Horses

Arabian horses are commonly believed to be one of the oldest and most influential horse breeds in the world. The high financial benefits obtained from races tend to search for genetic markers strongly correlated with the results achieved. To date, the modern approaches such as transcriptome, miRNAome, and metabolome analyses have been used to investigate the genetic background of racing performance as well as endurance capacity in Arabians. The analysis of polymorphisms at the genome level has also been applied to the detection of genetic variants associated with exercise phenotype in the Arabian breed. The presented review summarizes these findings, with a focus on the genetics underlying flat racing and endurance performance traits in different Arabian horse populations.

Unraveling the effects of the gut microbiota composition and function on horse endurance physiology

An integrated analysis of gut microbiota, blood biochemical and metabolome in 52 endurance horses was performed. Clustering by gut microbiota revealed the existence of two communities mainly driven by diet as host properties showed little effect. Community 1 presented lower richness and diversity, but higher dominance and rarity of species, including some pathobionts. Moreover, its microbiota composition was tightly linked to host blood metabolites related to lipid metabolism and glycolysis at basal time. Despite the lower fiber intake, community type 1 appeared more specialized to produce acetate as a mean of maintaining the energy supply as glucose concentrations fell during the race. On the other hand, community type 2 showed an enrichment of fibrolytic and cellulolytic bacteria as well as anaerobic fungi, coupled to a higher production of propionate and butyrate. The higher butyrate proportion in community 2 was not associated with protective effects on telomere lengths but could have ameliorated mucosal inflammation and oxidative status. The gut microbiota was neither associated with the blood biochemical markers nor metabolome during the endurance race, and did not provide a biomarker for race ranking or risk of failure to finish the race.

A First Step Toward Unraveling the Energy Metabolism in Endurance Horses: Comparison of Plasma Nuclear Magnetic Resonance Metabolomic Profiles Before and After Different Endurance Race Distances

Endurance racing places high demands on energy metabolism pathways. Metabolomics can be used to investigate biochemical responses to endurance exercise in humans, laboratory animals, and horses. Although endurance horses have previously been assessed in the field (i.e., during races) using broad-window Nuclear Magnetic Resonance metabolomics, these studies included several different race locations, race distances, age classes, and race statuses (finisher or elimination). The present NMR metabolomics study focused on 40 endurance horses racing in three race categories over 90, 120, or 160 km. The three races took place in the same location. Given that energy metabolism is closely related to exercise intensity and duration (and therefore distance covered), the study's objective was to determine whether the metabolic pathways recruited during the race varied as a function of the total ride distance. For each horse, a plasma sample was collected the day before the race, and another was collected at the end of the race. Sixteen, 15, and 9 horses raced over 90, 120, and 160 km, respectively. Proton NMR spectra (500 MHz) were acquired for these 80 plasma samples. After processing, the spectra were divided into bins representing the NMR variables and then classified using orthogonal projection on latent structure models supervised by the sampling time (pre- or post-race) or the distance covered. The models revealed that the post-race metabolomic profiles are associated to the total ride distance groups. By combining biochemical assay results and NMR data in multiblock models, we further showed that enzymatic activities and metabolites are significantly associated to the race category. In the highest race category (160 km), there appears to be a metabolic switch from carbohydrate consumption to lipid consumption in order to maintain glycaemia. Furthermore, signs of protein breakdown were more apparent in the longest race category. The metabolic shift seen in the different racing categories could be related to a mixture of three important factors that are the ride distance, the training status and the inherited endurance capacity of the various horses competing.

The lipidome of Thoroughbred racehorses before and after supramaximal exercise

BACKGROUND

A comprehensive study of the effect of supramaximal exercise in lipid homeostasis of Thoroughbreds provides the basis for future research on the role of lipids on energy metabolism in racehorses.

OBJECTIVE

To compare the plasma lipidome of Thoroughbreds before and after supramaximal exercise using an untargeted lipidomics approach.

STUDY DESIGN

Pilot experimental study.

METHODS

Four Thoroughbred horses were used. The maximal oxygen consumption (VO_{2 max} ) was calculated for each horse. Horses then underwent treadmill exercise at the speed for which the oxygen requirements had been calculated to be 115% VO_{2 max} . Plasma samples were obtained before (T0) and immediately (T1), 15 (T2) and 30 (T3) minutes post-exercise, and evaluated using liquid chromatography/mass spectrometry. Data analysis consisted of principal component analysis and one-way repeated measures analysis of variance.

RESULTS

A total of 933 plasma lipids were detected. Supramaximal exercise-induced significant changes in the signal intensity of 13 lipids; all ubiquitous in the organism as major components of biological membranes or energy substrates.

MAIN LIMITATIONS

A treadmill was used to replicate track conditions. Also, sample size involved only four horses and the statistical analyses failed to achieve the desired power of 80%.

CONCLUSIONS

The findings in this pilot study suggest that supramaximal exercise induces changes in specific plasma lipids in Thoroughbred racehorses. While the biological significance of these findings remains to be determined, these results provide baseline information for future studies in lipidomics applied to equine exercise physiology. Further research is warranted to better understand the role of lipids on energy metabolism in Thoroughbred racehorses.

Serum metabolomics of Alaskan sled dogs during endurance racing

Long distance racing sled dogs are fed diets high in fat since lipid metabolism has long been thought to be the major substrate utilised during endurance racing. However, recent studies suggests that sled dogs are equally, if not more, dependent on carbohydrate metabolism. Considering the metabolic disparity regarding the energetics of endurance exercise, our study aimed to explore the serum metabolomic profiles of sled dogs running a 1,609 km (1000 mile) race. We hypothesised that there would be amino acid depletion due to gluconeogenesis and alteration in the citric acid cycle (CAC) based on the limited carbohydrate diet they consume. Serum was obtained from 6 Alaskan sled dogs approximately 24 h prior to the race (Whitehorse), at the midrace checkpoint (Dawson City), and again at the finish (Fairbanks). Serum was analysed using liquid chromatography-mass spectrometry for over 200 metabolites involved in amino acid, lipid, and carbohydrate metabolism with MetaboAnalyst Software 3.0. Major metabolic changes observed were decreased free fatty acids and enhanced acyl-carnitine derivatives during the race compared to baseline. Serum depletion of nearly all amino acids except for branched chain amino acids and phenylalanine was observed suggesting extensive protein catabolism. Many of the CAC intermediates were variable with increases in abnormal end glycation products. These results highlight that sled dogs display general amino acid depletion for pyruvate, acetyl CoA and CAC pathway intermediates with increased carnitine bound lipid metabolites, suggesting rate limiting beta-oxidation during endurance exercise, particularly at mid race. Further metabolomic studies to assess the influence of exercise and nutritional regimens are warranted to better understand substrate utilisation in working dogs.

Characterization of plasma metabolites at late gestation and lactation in early parity sows on production and post-weaning reproductive performance

Lactation is a very energy demanding period for sows. The current study provides a better understanding of the biochemical response of first- (n = 246) or second-parity (n = 127) sows during late gestation through lactation and assesses relationships with piglet production and dam reproductive performance. Plasma samples were collected from first- or second-parity dams at late gestation (110 d gestation [d110G]), d 1 post-farrowing (d1PF), and weaning (WN) then analyzed for various stress and protein metabolism compounds, including; creatine, creatine phosphokinase (CPK) activity, creatinine, urea nitrogen, albumin, and lactate. Litter performance was measured as number of piglets nursed and piglet ADG. Post-weaning reproductive performance was assessed by measuring weaning-to-estrus interval (WEI) and subsequent ovulation rate collected at time of harvest. Plasma creatine and CPK activity increased (P < 0.05) between d110G and d1PF. Plasma creatinine decreased (P < 0.05) from d110G through WN in first-parity dams, but remained similar between d110G and d1PF before declining (P < 0.05) at WN in second-parity dams. Plasma urea nitrogen increased (P < 0.05) over the course of the study and was negatively (P < 0.05) associated with piglet ADG at d110G and d1PF and with ovulation rate at d110G (P < 0.05). Similarly, plasma albumin increased (P < 0.05) in first-parity dams over the course of the study, whereas it plateaued (P < 0.05) at d1PF and remained similar (P > 0.10) through WN in second-parity dams. First-parity dams had less (P < 0.05) plasma lactate at d110G than at d1PF or WN. However, second-parity dams had increased (P < 0.05) plasma lactate at d110G and d1PF, then decreased (P < 0.05) levels at WN. Plasma lactate at WN was positively (P < 0.05) associated with WEI in first-parity dams, but negatively (P < 0.05) related to WEI at d1PF in second-parity dams. Plasma lactate levels at all time points were positively (P < 0.05) associated with ovulation rate in second-parity dams. The biochemical profile of these dams differed by parity and merits further investigations into these differences to identify methods to improve physiological response to lactation for improved animal welfare, production, and reproductive performance.

Effect of reduced protein intake on endurance performance and water turnover during low intensity long duration exercise in Alaskan sled dogs

Increased nutritional demands for endurance exercise of dogs are typically met through increased amounts of their current food. As a result, protein intake is also increased, and excessive nitrogen may affect the dog’s water balance. Sixteen unconditioned Alaskan sled dogs underwent a 6-week exercise training protocol, wherein 8 dogs were fed increasing amounts of their normal kibble to maintain body weight, while the other 8 were fed the same amount of kibble, with increasing calorie needs met by equal amounts of sugar and oil. The diets resulted in similar calorie intakes (181.3±20.0 and 205.7±36.3 kcal/kg0.75, for the control and low protein dogs respectively) but control dogs had higher protein intakes (32.2±0.0 and 19.4±2.4% of metabolic energy intake). After 6 weeks of training the dogs completed a 5 day exercise test in which they travelled 24 km per day, where total energy expenditure was determined using doubly-labelled water technique. Dogs expended an average of 1,491±264 kcal/day (145±25 kcal/kg0.75/day), with no difference between the dietary treatments and no negative performance indicators. Following the exercise test the dogs underwent a 24 hour dehydration test (water withheld) followed by an 8 hour rehydration test (with ad libitum water intake recorded) where total body water was determined using deuterium oxide. Blood and urinary samples were also collected. Following exercise conditioning, control dogs had higher serum urea nitrogen than low protein dogs, and this as well as albumin decreased further during the 5 day exercise test. Low-protein dogs had lower overall total body water and higher fractional excretion of Na+, suggesting some renal adaptation. These findings suggest that reduced protein intake did not negatively affect athletic performance, though some facets of body chemistry were altered.

Environmental metabolomics with data science for investigating ecosystem homeostasis

A natural ecosystem can be viewed as the interconnections between complex metabolic reactions and environments. Humans, a part of these ecosystems, and their activities strongly affect the environments. To account for human effects within ecosystems, understanding what benefits humans receive by facilitating the maintenance of environmental homeostasis is important. This review describes recent applications of several NMR approaches to the evaluation of environmental homeostasis by metabolic profiling and data science. The basic NMR strategy used to evaluate homeostasis using big data collection is similar to that used in human health studies. Sophisticated metabolomic approaches (metabolic profiling) are widely reported in the literature. Further challenges include the analysis of complex macromolecular structures, and of the compositions and interactions of plant biomass, soil humic substances, and aqueous particulate organic matter. To support the study of these topics, we also discuss sample preparation techniques and solid-state NMR approaches. Because NMR approaches can produce a number of data with high reproducibility and inter-institution compatibility, further analysis of such data using machine learning approaches is often worthwhile. We also describe methods for data pretreatment in solid-state NMR and for environmental feature extraction from heterogeneously-measured spectroscopic data by machine learning approaches.

Understanding the response to endurance exercise using a systems biology approach: combining blood metabolomics, transcriptomics and miRNomics in horses

Background

Endurance exercise in horses requires adaptive processes involving physiological, biochemical, and cognitive-behavioral responses in an attempt to regain homeostasis. We hypothesized that the identification of the relationships between blood metabolome, transcriptome, and miRNome during endurance exercise in horses could provide significant insights into the molecular response to endurance exercise.

For this reason, the serum metabolome and whole-blood transcriptome and miRNome data were obtained from ten horses before and after a 160 km endurance competition.

Results

We obtained a global regulatory network based on 11 unique metabolites, 263 metabolic genes and 5 miRNAs whose expression was significantly altered at T1 (post- endurance competition) relative to T0 (baseline, pre-endurance competition). This network provided new insights into the cross talk between the distinct molecular pathways (e.g. energy and oxygen sensing, oxidative stress, and inflammation) that were not detectable when analyzing single metabolites or transcripts alone. Single metabolites and transcripts were carrying out multiple roles and thus sharing several biochemical pathways.

Using a regulatory impact factor metric analysis, this regulatory network was further confirmed at the transcription factor and miRNA levels.

In an extended cohort of 31 independent animals, multiple factor analysis confirmed the strong associations between lactate, methylene derivatives, miR-21-5p, miR-16-5p, let-7 family and genes that coded proteins involved in metabolic reactions primarily related to energy, ubiquitin proteasome and lipopolysaccharide immune responses after the endurance competition. Multiple factor analysis also identified potential biomarkers at T0 for an increased likelihood for failure to finish an endurance competition.

Conclusions

To the best of our knowledge, the present study is the first to provide a comprehensive and integrated overview of the metabolome, transcriptome, and miRNome co-regulatory networks that may have a key role in regulating the metabolic and immune response to endurance exercise in horses.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3571-3) contains supplementary material, which is available to authorized users.

Integrated mRNA and miRNA expression profiling in blood reveals candidate biomarkers associated with endurance exercise in the horse

The adaptive response to extreme endurance exercise might involve transcriptional and translational regulation by microRNAs (miRNAs). Therefore, the objective of the present study was to perform an integrated analysis of the blood transcriptome and miRNome (using microarrays) in the horse before and after a 160 km endurance competition. A total of 2,453 differentially expressed genes and 167 differentially expressed microRNAs were identified when comparing pre- and post-ride samples. We used a hypergeometric test and its generalization to gain a better understanding of the biological functions regulated by the differentially expressed microRNA. In particular, 44 differentially expressed microRNAs putatively regulated a total of 351 depleted differentially expressed genes involved variously in glucose metabolism, fatty acid oxidation, mitochondrion biogenesis, and immune response pathways. In an independent validation set of animals, graphical Gaussian models confirmed that miR-21-5p, miR-181b-5p and miR-505-5p are candidate regulatory molecules for the adaptation to endurance exercise in the horse. To the best of our knowledge, the present study is the first to provide a comprehensive, integrated overview of the microRNA-mRNA co-regulation networks that may have a key role in controlling post-transcriptomic regulation during endurance exercise.

Energetics of endurance exercise in young horses determined by nuclear magnetic resonance metabolomics

Long-term endurance exercise severely affects metabolism in both human and animal athletes resulting in serious risk of metabolic disorders during or after competition. Young horses (up to 6 years old) can compete in races up to 90 km despite limited scientific knowledge of energetic metabolism responses to long distance exercise in these animals. The hypothesis of this study was that there would be a strong effect of endurance exercise on the metabolomic profiles of young horses and that the energetic metabolism response in young horses would be different from that of more experienced horses. Metabolomic profiling is a powerful method that combines Nuclear Magnetic Resonance (NMR) spectrometry with supervised Orthogonal Projection on Latent Structure (OPLS) statistical analysis. ¹H-NMR spectra were obtained from plasma samples drawn from young horses (before and after competition). The spectra obtained before and after the race from the same horse (92 samples) were compared using OPLS. The statistical parameters showed the robustness of the model (R2Y = 0.947, Q2Y = 0.856 and cros-validated ANOVA p < 0.001). For confirmation of the predictive value of the model, a test set of 104 sample spectra were projected by the model, which provided perfect predictions as the area under the receiving-operator curve was 1. The metabolomic profile determined with the OPLS model showed that glycemia after the race was lower than glycemia before the race, despite the involvement of lipid and protein catabolism. An OPLS model was calculated to compare spectra obtained on plasma taken after the race from 6-year-old horses and from experienced horses (cross-validated ANOVA p < 0.001). The comparison of metabolomic profiles in young horses to those from experienced horses showed that experienced horses maintained their glycemia with higher levels of lactate and a decrease of plasma lipids after the race.