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The microbiome of professional athletes differs from that of more sedentary subjects in composition and particularly at the functional metabolic level.
Barton, W, Penney, NC, Cronin, O, Garcia-Perez, I, Molloy, MG, Holmes, E, Shanahan, F, Cotter, PD, O'Sullivan, O
Gut. 2018;67(4):625-633
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The human gut microbiome is known to actively influence metabolism, immunity and development. It has been shown that increased physical activity and healthy diet is associated with positive changes in faecal microbial diversity and composition compared with sedentary individuals. The aim of this study was to assess the metabolic activity of the microbiota between extremely active and sedentary individuals. Metabolic and genetic factors of the gut microbiome were analysed in 40 professional rugby players and 46 sedentary controls. This study found significant differences in faecal microbiota between athletes and sedentary controls at the functional metabolic level, providing deeper insight into the link between sustained physical activity and metabolic health. Based on these results, the authors conclude exercise may be an effective way to manipulate the gut microbiome and suggest further controlled trials be done to better understand the relationship between diet, exercise and the gut microbiome.
Abstract
OBJECTIVE It is evident that the gut microbiota and factors that influence its composition and activity effect human metabolic, immunological and developmental processes. We previously reported that extreme physical activity with associated dietary adaptations, such as that pursued by professional athletes, is associated with changes in faecal microbial diversity and composition relative to that of individuals with a more sedentary lifestyle. Here we address the impact of these factors on the functionality/metabolic activity of the microbiota which reveals even greater separation between exercise and a more sedentary state. DESIGN Metabolic phenotyping and functional metagenomic analysis of the gut microbiome of professional international rugby union players (n=40) and controls (n=46) was carried out and results were correlated with lifestyle parameters and clinical measurements (eg, dietary habit and serum creatine kinase, respectively). RESULTS Athletes had relative increases in pathways (eg, amino acid and antibiotic biosynthesis and carbohydrate metabolism) and faecal metabolites (eg, microbial produced short-chain fatty acids (SCFAs) acetate, propionate and butyrate) associated with enhanced muscle turnover (fitness) and overall health when compared with control groups. CONCLUSIONS Differences in faecal microbiota between athletes and sedentary controls show even greater separation at the metagenomic and metabolomic than at compositional levels and provide added insight into the diet-exercise-gut microbiota paradigm.
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Effect of a Protein Supplement on the Gut Microbiota of Endurance Athletes: A Randomized, Controlled, Double-Blind Pilot Study.
Moreno-Pérez, D, Bressa, C, Bailén, M, Hamed-Bousdar, S, Naclerio, F, Carmona, M, Pérez, M, González-Soltero, R, Montalvo-Lominchar, MG, Carabaña, C, et al
Nutrients. 2018;10(3)
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Protein supplements are popular among athletes to improve performance and increase muscle mass. However, their effect on other aspects of health is less well known. Dietary changes can affect gut microbiota balance, with beneficial or harmful consequences for the host. This small pilot study was performed on cross-country runners whose diets were complemented with a protein supplement (whey isolate and beef hydrolysate) or maltodextrin (control) for 10 weeks. Microbiota, water content, pH, ammonia, and short-chain fatty acids (SCFAs) were analysed in faecal samples, and oxidative stress markers were measured in blood plasma and urine. Faecal pH, water content, ammonia, and SCFA concentrations did not change, indicating that protein supplementation did not increase the presence of these metabolites of fermentation. Similarly, it had no impact on plasma or urine malondialdehyde levels. Protein supplementation did however increase the abundance of the Bacteroidetes phylum and decrease the presence of health-related taxa including Roseburia, Blautia, and Bifidobacterium longum. The authors concluded that long-term protein supplementation may have a negative impact on gut microbiota. Further research is needed to establish the impact of protein supplements on gut microbiota.
Expert Review
Conflicts of interest:
None
Take Home Message:
- Long-term protein supplementation may have a negative impact on gut microbiota.
- Further research is needed to establish the impact of protein supplements on gut microbiota and whether there is a differential impact between protein from animal and plant sources.
Evidence Category:
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A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
This is a very interesting study that is relevant to athletic populations.
Clinical practice applications:
Potentially there is a role for probiotics / prebiotics when increasing protein intake (particularly of animal origin) to maintain microbiota diversity and prevent ensuing health complications.
Considerations for future research:
Further, larger scale, research is needed to understand whether the same effect of protein supplementation would be seen with plant-based proteins or whether this is unique to animal based protein supplementation. For example, is the hydrolysation of the proteins to account for the largest effect or could a whole food protein, i.e. not hydrolysed, elicit the same effects?
Also, is this effect seen in other sports, e.g. non-endurance. What about the effect under different conditions e.g. energy deficit vs. energy excess?
Abstract
Nutritional supplements are popular among athletes to improve performance and physical recovery. Protein supplements fulfill this function by improving performance and increasing muscle mass; however, their effect on other organs or systems is less well known. Diet alterations can induce gut microbiota imbalance, with beneficial or deleterious consequences for the host. To test this, we performed a randomized pilot study in cross-country runners whose diets were complemented with a protein supplement (whey isolate and beef hydrolysate) (n = 12) or maltodextrin (control) (n = 12) for 10 weeks. Microbiota, water content, pH, ammonia, and short-chain fatty acids (SCFAs) were analyzed in fecal samples, whereas malondialdehyde levels (oxidative stress marker) were determined in plasma and urine. Fecal pH, water content, ammonia, and SCFA concentrations did not change, indicating that protein supplementation did not increase the presence of these fermentation-derived metabolites. Similarly, it had no impact on plasma or urine malondialdehyde levels; however, it increased the abundance of the Bacteroidetes phylum and decreased the presence of health-related taxa including Roseburia, Blautia, and Bifidobacterium longum. Thus, long-term protein supplementation may have a negative impact on gut microbiota. Further research is needed to establish the impact of protein supplements on gut microbiota.
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Enhanced 400-m sprint performance in moderately trained participants by a 4-day alkalizing diet: a counterbalanced, randomized controlled trial.
Limmer, M, Eibl, AD, Platen, P
Journal of the International Society of Sports Nutrition. 2018;15(1):25
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Alkaline diets and supplements have recently gained attention as a means to bring balance to the overly acidic Western diet. While the effects of the acid-base balance of diets on high-intensity athletic performance have not yet been extensively researched, it is hypothesised an acidizing diet can reduce exercise performance during anaerobic activities. The aim of this randomised, single-blind, crossover trial was to investigate the influence of an acidising or alkalising diet on 400-m sprint performance among 14 moderately trained students. Participants completed a baseline 400-m sprint and were then randomised to consume either an acidising or alkalising diet for four days. Each intervention period concluded with a 400-m sprint and a three-day washout period. Blood lactate concentrations, blood gas parameters and urinary pH were measured to determine extracellular buffering capacity. This study found the alkalising diet improved 400-m sprint time and higher blood lactate significantly compared with the acidising diet. Blood pH values remained unchanged between groups. Based in these results, the authors conclude it is possible to improve anaerobic exercise performance through alkalisation through diet rather than supplementation.
Abstract
BACKGROUND Sodium bicarbonate (NaHCO3) is an alkalizing agent and its ingestion is used to improve anaerobic performance. However, the influence of alkalizing nutrients on anaerobic exercise performance remains unclear. Therefore, the present study investigated the influence of an alkalizing versus acidizing diet on 400-m sprint performance, blood lactate, blood gas parameters, and urinary pH in moderately trained adults. METHODS In a randomized crossover design, eleven recreationally active participants (8 men, 3 women) aged 26.0 ± 1.7 years performed one trial under each individual's unmodified diet and subsequently two trials following either 4 days of an alkalizing (BASE) or acidizing (ACID) diet. Trials consisted of 400-m runs at intervals of 1 week on a tartan track in a randomized order. RESULTS We found a significantly lower 400-m performance time for the BASE trial (65.8 ± 7.2 s) compared with the ACID trial (67.3 ± 7.1 s; p = 0.026). In addition, responses were significantly higher following the BASE diet for blood lactate (BASE: 16.3 ± 2.7; ACID 14.4 ± 2.1 mmol/L; p = 0.32) and urinary pH (BASE: 7.0 ± 0.7; ACID 5.5 ± 0.7; p = 0.001). CONCLUSIONS We conclude that a short-term alkalizing diet may improve 400-m performance time in moderately trained participants. Additionally, we found higher blood lactate concentrations under the alkalizing diet, suggesting an enhanced blood or muscle buffer capacity. Thus, an alkalizing diet may be an easy and natural way to enhance 400-m sprint performance for athletes without the necessity of taking artificial dietary supplements.
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Dietary nitrate does not modify blood pressure and cardiac output at rest and during exercise in older adults: a randomised cross-over study.
Oggioni, C, Jakovljevic, DG, Klonizakis, M, Ashor, AW, Ruddock, A, Ranchordas, M, Williams, E, Siervo, M
International journal of food sciences and nutrition. 2018;69(1):74-83
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Nitrates are naturally-occurring compounds that are produced within the body and also found in food. The main sources of nitrates in the diet come from cured meats and vegetables such as spinach, rocket and beetroot. Nitrate supplements have been associated with beneficial effects on heart and metabolic health, and improvements in athletic performance. Many of these benefits have been observed in younger adults. The objective of this randomised controlled trial was to investigate the effects of 7 days’ consumption of beetroot juice compared with placebo on (1) blood pressure (BP) measured in resting conditions and during exercise, (2) cardiac and peripheral vascular function and (3) biomarkers of inflammation, oxidative stress and endothelial integrity, in older adults. Twenty non-smoking healthy participants aged 60-75 years were recruited. Each participant was given 70ml of either beetroot juice rich in nitrates, or beetroot juice low in nitrates (placebo), twice a day for 7 days. All participants took both the 7-day courses, with at least 7 days rest in between. Measurement was conducted before and after each 7-day intervention period. Consumption of nitrates had no effect on resting systolic and diastolic BP. Nitrate consumption did not improve heart function during exercise. Nitrate consumption did not change markers of inflammation, oxidative stress and endothelial integrity. The authors concluded that this study does not support the short-term benefits of dietary nitrate supplementation on physiological and biochemical markers of heart health in older healthy adults.
Abstract
Dietary nitrate (NO3-) supplementation has been associated with improved vascular and metabolic health. We conducted a double-blind, cross-over, placebo-controlled RCT to investigate the effects of 7-d consumption of beetroot juice compared with placebo on (1) blood pressure (BP) measured in resting conditions and during exercise, (2) cardiac and peripheral vascular function and (3) biomarkers of inflammation, oxidative stress and endothelial integrity. Twenty non-smoking healthy participants aged 60-75 years and BMI 20.0-29.9 kg/m2 were recruited. Measurement was conducted before and after each 7-d intervention period. Consumption of NO3- had no effect on resting systolic and diastolic BP. NO3- consumption did not improve indexes of central and peripheral cardiac function responses during cardiopulmonary exercise testing. Dietary NO3- supplementation did not modify biomarkers of inflammation, oxidative stress and endothelial integrity. This study does not support the short-term benefits of dietary NO3- supplementation on physiological and biochemical markers of vascular health in older healthy adults.
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Effects of n-3 fatty acids and exercise on oxidative stress parameters in type 2 diabetic: a randomized clinical trial.
Fayh, APT, Borges, K, Cunha, GS, Krause, M, Rocha, R, de Bittencourt, PIH, Moreira, JCF, Friedman, R, da Silva Rossato, J, Fernandes, JR, et al
Journal of the International Society of Sports Nutrition. 2018;15:18
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An elevated blood glucose level is one of the key metabolic abnormalities associated with complications in type 2 diabetes. Literature shows that individuals with type 2 diabetes have higher inflammatory levels than those with normal blood glucose tolerance. The aim of this study was to examine if omega-3 polyunsaturated fatty acid (PUFA) supplementation can reduce the inflammatory response associated with high-intensity exercise in type 2 diabetic individuals. This was a randomised, double-blind controlled study, which recruited 30 type 2 diabetic men and women aged between 30 and 60 years. Results indicate that after 8 weeks, omega-3 PUFA supplementation diminished the concentration of the total reactive antioxidant potential and triglyceride levels after high intensity exercise, however did not reduce the inflammatory response.
Abstract
BACKGROUND The relationship between diabetes and oxidative stress has been previously reported. Exercise represents a useful non-pharmacological strategy for the treatment in type 2 diabetic (T2DM) patients, but high intensity exercise can induce a transient inflammatory state and increase oxidative stress. Nutritional strategies that may contribute to the reduction of oxidative stress induced by acute exercise are necessary. The aim of this study was to examine if n-3 PUFA supplementation intervention can attenuate the inflammatory response and oxidative stress associated with high intensity exercise in this population. As a primary outcome, lipoperoxidation measurements (TBARS and F2-isoprostanes) were selected. METHODS Thirty T2DM patients, without chronic complications, were randomly allocated into two groups: placebo (gelatin capsules) or n-3 PUFA (capsules containing 180 mg of eicosapentaenoic acid and 120 mg of docosahexaenoic acid). Blood samples were collected fasting before and after 8 weeks supplementation. In the beginning and at the end of protocol, an acute exercise was performed (treadmill), and new blood samples were collected before and immediately after the exercise for measurements of oxidative stress and high-sensitivity C-reactive protein (hs-CRP). RESULTS After the supplementation period, a decrease in triglycerides levels was observed only in n-3 PUFA supplementation group (mean difference and 95% CI of 0.002 (0.000-0.004), p = 0.005). Supplementation also significantly reduced TRAP levels after exercise (mean difference and 95% CI to 9641 (- 20,068-39,351) for - 33,884 (- 56,976 - -10,793), p = 0.004, Cohen's d effect size = 1.12), but no significant difference was observed in n-3 PUFA supplementation group in lipoperoxidation parameters as TBARS (mean difference and 95% CI to - 3.8 (- 10-2.4) for - 2.9 (- 1.6-7.4) or F2-isoprostanes (mean difference and 95% CI -0.05 (- 0.19-0.10) for - 0.02 (- 0.19-0.16), p > 0.05 for both. CONCLUSION PUFA n-3 supplementation reduced triglycerides as well as TRAP levels after exercise, without a significant effect on inflammatory and oxidative stress markers.This study is registered at ClinicalTrials.gov with the registration number of NCT03182712.
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The Association between Breakfast Skipping and Body Weight, Nutrient Intake, and Metabolic Measures among Participants with Metabolic Syndrome.
Zhang, L, Cordeiro, LS, Liu, J, Ma, Y
Nutrients. 2017;9(4)
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There is conflicting evidence on the benefits of either skipping breakfast versus the idea that breakfast is the most important meal of the day. This study examines the effects of skipping breakfast on weight loss in a group of 240 participants diagnosed as having Metabolic syndrome (MetS). The study looked at data from a diet trial looking at the effects of a high fibre diet or the American Heart Association diet on MetS, in which they all also monitored breakfast eating patterns, to see if there was any change to body weight, nutrient intakes, and selected metabolic measures. The study lasted one year, and dietary recalls were collected throughout. The results showed that at the start of the trial 32.9% of the participants self-reported regularly skipped breakfast and generally they had lower levels of vitamins B1, B3 and folate intake. They also had a higher fat intake compared to those who ate breakfast. However, at the end of the year there was no statistical differences between those who ate and those who skipped breakfast when it came to the other metabolic parameters of weight, BMI, weight circumference, blood pressure, cholesterol, and fasting glucose. Interestingly at the end of the trial only 14% reported skipping breakfast suggesting that participants had the intention to change their eating patterns because of having participated in the trial. The study concluded that skipping breakfast alone was not enough to influence MetS.
Abstract
The effect of skipping breakfast on health, especially in adults, remains a controversial topic. A secondary data analysis was conducted to examine associations between breakfast eating patterns and weight loss, nutrient intake, and metabolic parameters among participants with metabolic syndrome (MetS) (n = 240). Three randomly selected 24-h dietary recalls were collected from each participant at baseline and at the one-year visit. Skipped breakfast was seen in 32.9% at baseline and in 17.4% at the one-year visit, respectively. At baseline, after adjustment for demographics and physical activity, participants who ate breakfast had a higher thiamin, niacin, and folate intake than did breakfast skippers (p < 0.05); other selected parameters including body weight, dietary quality scores, nutrient intake, and metabolic parameters showed no significant differences between the two groups (p ≥ 0.05). From baseline to one year, after adjustment for covariates, mean fat intake increased by 2.7% (95% confidence intervals (CI): -1.0, 6.5%) of total energy in breakfast skippers in comparison to the 1.2% decrease observed in breakfast eaters (95% CI: -3.4, 1.1%) (p = 0.02). Mean changes in other selected parameters showed no significant differences between breakfast skippers and eaters (p > 0.05). This study did not support the hypothesis that skipping breakfast has impact on body weight, nutrient intakes, and selected metabolic measures in participants with MetS.
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Effect of protein and carbohydrate solutions on running performance and cognitive function in female recreational runners.
Gui, Z, Sun, F, Si, G, Chen, Y
PloS one. 2017;12(10):e0185982
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Research has shown that consuming a carbohydrate-electrolyte solution (CES) during endurance exercise can improve performance, delay fatigue and ameliorate post-exercise cognitive dysfuction when compared with a noncaloric placebo (PLA). The addition of protein to the CES (CPES) has been suggested to increase these benefits however the current data is limited. The aim of this crossover study was to investigate whether the added protein to a CES would improve exercise performance and cognitive function in 11 female recreational marathon runners. Participants were randomised to consume one of the three solutions (CES, CPES or PLA) every 2.5km during a 21km run, with a 28-day interval, and their VO2max and cognitive function were recorded after the run. This study showed that CES improved endurance performance compared with PLA, however adding protein to the CES did not provide any additional performance benefit. The CPES solution did benefit visual motor speed compared to PLA, but no differences were found in the other cognitive function tests.
Abstract
This study compared the effects of a carbohydrate-electrolyte-protein solution (CEPS, 2% protein plus 4% carbohydrate), carbohydrate-electrolyte solution (CES, 6% carbohydrate), and noncaloric sweetened placebo (PLA) on both 21-km running performance and cognitive function. Eleven female recreational endurance runners performed a 21-km time-trial running on three occasions, separated by at least 28 days. In a randomized cross-over design, they ingested CEPS, CES, or PLA at a rate of 150 mL every 2.5 km with no time feedback. A cognitive function test was performed before and after the run. Participants ingested approximately 24 g/h carbohydrate plus 12 g/h protein in CEPS trial, and 36 g/h carbohydrate in CES trial during each 21-km trial. Time to complete the time-trial was slightly shorter (P < 0.05) during CES (129.6 ± 8.8 min) than PLA (134.6 ± 11.5 min), with no differences between CEPS and the other two trials. The CEPS trial showed higher composite of visual motor speed than the PLA trial (P < 0.05). In conclusion, CES feedings might improve 21-km time-trial performance in female recreational runners compared with a PLA. However, adding protein to the CES provided no additional time-trial performance benefit. CEPS feeding during prolonged exercise could benefit visual motor speed compared to PLA alone, but no differences in the performance of the other cognitive function tests were found.
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Effects of Two Years of Calorie Restriction on Aerobic Capacity and Muscle Strength.
Racette, SB, Rochon, J, Uhrich, ML, Villareal, DT, DAS, SK, Fontana, L, Bhapkar, M, Martin, CK, Redman, LM, Fuss, PJ, et al
Medicine and science in sports and exercise. 2017;49(11):2240-2249
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Caloric restriction (CR) has been shown to increase lifespan and delay age-related disease in many species. As a part of the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) study, this particular study aimed to determine whether long-term CR adversely affects aerobic capacity and muscle strength in 218 healthy, nonobese adults. Participants were randomised to 25% CR or control group, and a VO2max treadmill test, knee flexor and extensor strength were all measured at baseline, one year and two years. This study showed that two years of CR without a structured exercise component did not appear to compromise aerobic capacity in healthy nonobese adults.
Abstract
PURPOSE Calorie restriction (CR) improves health span and delays age-related diseases in many species. The multicenter Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) study was the first randomized controlled trial of CR in nonobese humans. The aim of this investigation was to determine the effects of CR on V˙O2max and muscle strength in the CALERIE trial. METHODS Healthy, normal-weight, and mildly overweight women and men (n = 218, mean ± SE age = 37.9 ± 0.5 yr) were randomized to 25% CR or an ad libitum (AL) control condition in a 2:1 allocation (143 CR, 75 AL). V˙O2max was determined with an incremental treadmill test; the strength of the knee flexors and extensors was assessed by dynamometry at baseline, 1 yr, and 2 yr. RESULTS The CR group achieved an average 11.9% ± 0.7% CR during the 2-yr intervention. Body weight decreased in CR (-7.7 ± 0.4 kg), but not AL (+0.2 ± 0.5 kg). Absolute V˙O2max (L·min) decreased at 1 and 2 yr with CR, whereas V˙O2max expressed relative to body mass increased at both time points (1 yr: +2.2 ± 0.4; 2 yr: +1.9 ± 0.5 mL·kg·min) and relative to AL. The CR group increased their treadmill test time and workload at 1 and 2 yr. Strength results in CR were similar, with decreases in absolute flexor and extensor strength, but increases when expressed relative to body mass. No changes were observed for V˙O2max expressed relative to lean body mass or leg lean mass. CONCLUSIONS Two years of modest CR without a structured exercise component did not appear to compromise aerobic capacity in healthy nonobese adults. The clinical implications of the observed changes in V˙O2max and muscle strength will be important to explore in future studies.
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The Effect of Post-Resistance Exercise Amino Acids on Plasma MCP-1 and CCR2 Expression.
Wells, AJ, Hoffman, JR, Jajtner, AR, Varanoske, AN, Church, DD, Gonzalez, AM, Townsend, JR, Boone, CH, Baker, KM, Beyer, KS, et al
Nutrients. 2016;8(7)
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Background: Innate immune response is generally considered to have an important role in tissue remodeling of the damaged localised skeletal muscle as a result of intense resistance exercise. Monocytes are leukocytes that also influence our adaptive immune system. Aim & Objective: The purpose of this study was to examine the changes in the markers of monocytes recruitment after a bout of high resistance exercise and ingestion of amino acid supplement. Method: Ten resistant trained men between the ages of 18 and 35 were recruited in this randomised crossover design study. Blood sample were taken at various time to measure and assess the plasma concentrations of monocyte chemoattractant protein 1 (MCP-1), myoglobin, cortisol and insulin concentrations; and expressions of C-C chemokine receptor-2 (CCR2), and macrophage-1 antigen (CD11b) on classical monocytes. Result & conclusion: No significant differences were noted for the markers myoglobin, insulin or cortisol in the treatment group in this study. Ingestion of supplement increased the CCR2 expression on CD14+ monocytes at 1H, 2H and 5H(P’s ≤ 0.001) after the exercise, but did not appear to have any influence on CD11b expression on CD14++CD16- ́ monocytes. To conclude it seems that amino acids are important regulator of immune response but more research is needed.
Abstract
The recruitment and infiltration of classical monocytes into damaged muscle is critical for optimal tissue remodeling. This study examined the effects of an amino acid supplement on classical monocyte recruitment following an acute bout of lower body resistance exercise. Ten resistance-trained men (24.7 ± 3.4 years; 90.1 ± 11.3 kg; 176.0 ± 4.9 cm) ingested supplement (SUPP) or placebo (PL) immediately post-exercise in a randomized, cross-over design. Blood samples were obtained at baseline (BL), immediately (IP), 30-min (30P), 1-h (1H), 2-h (2H), and 5-h (5H) post-exercise to assess plasma concentrations of monocyte chemoattractant protein 1 (MCP-1), myoglobin, cortisol and insulin concentrations; and expressions of C-C chemokine receptor-2 (CCR2), and macrophage-1 antigen (CD11b) on classical monocytes. Magnitude-based inferences were used to provide inferences on the true effects of SUPP compared to PL. Changes in myoglobin, cortisol, and insulin concentrations were similar between treatments. Compared to PL, plasma MCP-1 was "very likely greater" (98.1% likelihood effect) in SUPP at 2H. CCR2 expression was "likely greater" at IP (84.9% likelihood effect), "likely greater" at 1H (87.7% likelihood effect), "very likely greater" at 2H (97.0% likelihood effect), and "likely greater" at 5H (90.1% likelihood effect) in SUPP, compared to PL. Ingestion of SUPP did not influence CD11b expression. Ingestion of an amino acid supplement immediately post-exercise appears to help maintain plasma MCP-1 concentrations and augment CCR2 expression in resistance trained men.
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Altered metabolic homeostasis is associated with appetite regulation during and following 48-h of severe energy deprivation in adults.
Karl, JP, Smith, TJ, Wilson, MA, Bukhari, AS, Pasiakos, SM, McClung, HL, McClung, JP, Lieberman, HR
Metabolism: clinical and experimental. 2016;65(4):416-27
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Intermittent periods of substantial energy deficit, common among military personnel, result in multiple endocrine and metabolic signals. To date, the association between metabolic and endocrine markers with appetite regulation remain controversial. Using a novel model, the aim of this crossover study was to determine the effects of severe energy deprivation on cognitive function, and explore the metabolic response and its impact on appetite regulation in 23 young adults. Following prescribed exercise, participants were randomised to consume an energy balanced or energy deficit diet. The findings of this study showed that during energy deprivation, metabolic homeostasis modulates appetite independent of diet volume. Though further studies are required, these results suggest that metabolic and endocrine signals are associated with adipose and lean tissue loss to restore energy balance.
Abstract
BACKGROUND Military personnel frequently endure intermittent periods of severe energy deficit which can compromise health and performance. Physiologic factors contributing to underconsumption, and the subsequent drive to overeat, are not fully characterized. This study aimed to identify associations between appetite, metabolic homeostasis and endocrine responses during and following severe, short-term energy deprivation. METHODS Twenty-three young adults (17M/6F, 21±3years, BMI 25±3kg/m(2)) participated in a randomized, controlled, crossover trial. During separate 48-h periods, participants increased habitual energy expenditure by 1647±345kcal/d (mean±SD) through prescribed exercise at 40-65% VO2peak, and consumed provided isovolumetric diets designed to maintain energy balance at the elevated energy expenditure (EB; 36±93kcal/d energy deficit) or to produce a severe energy deficit (ED; 3681±716kcal/d energy deficit). Appetite, markers of metabolic homeostasis and endocrine mediators of appetite and substrate availability were periodically measured. Ad libitum energy intake was measured over 36h following both experimental periods. RESULTS Appetite increased during ED and was greater than during EB despite maintenance of diet volume (P=0.004). Ad libitum energy intake was 907kcal/36h [95% CI: 321, 1493kcal/36h, P=0.004] higher following ED compared to following EB. Serum beta-hydroxybutyrate, free fatty acids, branched-chain amino acids, dehydroepiandrosterone-sulfate (DHEA-S) and cortisol concentrations were higher (P<0.001 for all), whereas whole-body protein balance was more negative (P<0.001), and serum glucose, insulin, and leptin concentrations were lower (P<0.001 for all) during ED relative to during EB. Cortisol concentrations, but not any other hormone or metabolic substrate, were inversely associated with satiety during EB (R(2)=0.23, P=0.04). In contrast, serum glucose and DHEA-S concentrations were inversely associated with satiety during ED (R(2)=0.68, P<0.001). No associations between physiologic variables measured during EB and ad libitum energy intake following EB were observed. However, serum leptin and net protein balance measured during ED were inversely associated with ad libitum energy intake following ED (R(2)=0.48, P=0.01). CONCLUSION These findings suggest that changes in metabolic homeostasis during energy deprivation modulate appetite independent of reductions in diet volume. Following energy deprivation, physiologic signals of adipose and lean tissue loss may drive restoration of energy balance. CLINICAL TRIALS REGISTRATION www.clinicaltrials.gov #NCT01603550.