Responses In Young Men Research Articles

Muscle Protein Synthesis in Response to Plant-Based Protein Isolates With and Without Added Leucine Versus Whey Protein in Young Men and Women

BackgroundPlant-based protein supplements often contain lower amounts of leucine and other essential amino acids (EAAs), potentially making them less effective in stimulating muscle protein synthesis (MPS) than animal-based proteins. Combining plant proteins could improve the EAA profile and more effectively support MPS. ObjectivesThe aim of this study was to determine the effect of a novel plant-based blend protein (PBP), PBP with added leucine (PBP + Leu) to levels equivalent to whey protein isolate (WHEY) on aminoacidemia and MPS responses in young men and women. We hypothesized that PBP + Leu would stimulate MPS equivalent to WHEY, and both would be greater than PBP. MethodsWe employed a randomized, double-blind, crossover study consisting of 3 separate study visits to compare PBP, PBP + Leu, and WHEY. To measure MPS response to ingestion of the supplements, a primed continuous infusion of L-[ring13C6] phenylalanine was administered for 8 h at each study visit. Skeletal muscle tissue and blood samples were collected to measure aminoacidemia and MPS. ResultsAll protein supplements increased mixed MPS above postabsorptive levels (P < 0.001). However, MPS increase following ingestion of PBP was less than that following ingestion of PBP + Leu (P = 0.002) and WHEY (P = 0.046). There were no differences in MPS between PBP + Leu and WHEY (P = 0.052). ConclusionsConsumption of PBP isolate with added leucine stimulated MPS to a similar extent as whey protein in young men and women. PBPs containing higher leucine content promote anabolism to a similar extent as animal-based proteins.This study was registered at clinicaltrials.gov as NCT05139160.

The effects of separate and simultaneous upper and lower body cycling on cardiorespiratory responses in young men.

The aim of the present study was to examine the relative cardiorespiratory and perceptual responses to upper body ergometry, lower body ergometry, and combined upper and lower body ergometry at increasing exercising intensities. Eight healthy males between 19 and 30 years of age completed three exercise sessions over seven days that included graded leg ergometry, arm ergometry, and combined arm and leg ergometry in counterbalanced fashion. During leg-only and arm-only sessions, participants exercised at workloads of 0, 32, 64, and 95 W. The combined session involved simultaneous arm and leg ergometry at 0, 32, 64, and 95 W, thus eliciting double the total power output of arm-only and leg-only sessions. At all workloads, oxygen consumption and minute ventilation responses were greater during combined arm and leg exercise than during leg-only or arm-only exercise. However, the pattern of changes in heart rate, systolic blood pressure, rate pressure product, and rating of perceived exertion (RPE) were similar in response to arm-only and combined upper and lower body exercise, despite combined exercise involving double the workload. These cardiorespiratory and perceptual responses were significantly lower during leg-only only exercise. The results of the study add to limited research comparing physiological and perceptual responses to upper, lower, and combined upper and lower body exercise. The findings highlight heightened cardiorespiratory and perceptual responses to upper body exercise alone or in combination with lower body exercise. Training that combines upper and lower body may create higher power output and elicit greater caloric expenditure while eliciting similar cardiovascular responses as upper body only exercise at moderate and higher intensities.

The Effect Of Exercise Intensity On Metaboreceptor-mediated Pressor Responses In Young Men

The Effect Of Exercise Intensity On Metaboreceptor-mediated Pressor Responses In Young Men

Walking Initiated 20 Minutes before the Time of Individual Postprandial Glucose Peak Reduces the Glucose Response in Young Men with Overweight or Obesity: A Randomized Crossover Study

Although a single bout of postmeal exercise can lower postprandial glucose (PPG), its optimal timing remains unclear. This study aimed to investigate the effect of exercise timing using an individualized approach on PPG in overweight or obese young men. Twenty men [age: 23.0±4.3y; BMI (kg/m2): 27.4±2.8] each completed three 240-min trials in a randomized order separated by 6-14 d: 1) sitting (SIT), 2) walking initiated at each participant's PPG-peak time (PPGP) (iP), and 3) walking initiated 20min before the PPGP (20iP). For each participant, PPGP was predetermined using continuous glucose monitoring. Walking was performed at 50% maximal oxygen consumption for 30min. Venous blood was collected at 15- and 30-min intervals for 0-120min and 120-240min, respectively. The primary outcome was plasma PPG. Generalized estimating equations were used for comparison between trials. Compared with SIT, the 4-h incremental AUCs (iAUCs) for plasma PPG (-0.6 mmol · L-1 · h; P=0.047) and insulin (-28.7%, P < 0.001) were reduced in 20iP only, and C-peptide concentrations were lower after iP (-14.9%, P=0.001) and 20iP (-28.7%, P < 0.001). Plasma insulin (-11.1%, P=0.006) and C-peptide (-8.3%, P=0.012) were lower due to the 20iP compared with iP treatment. Finally, PPG reductions due to iP and 20iP occurred only in men with a BMI > 27.5 kg/m2 (iP, -11.2%; 20iP, -14.7%; P=0.047) and higher glucose iAUC values during SIT (iP, -25.5%; 20iP, -25.7%; P < 0.001). Walking initiated 20min before PPGP lowered PPG and plasma insulin and C-peptide concentrations in young men with overweight or obesity, in particular in those with high BMI or glucose iAUC values during SIT; it also lowered plasma insulin and C-peptide concentrations more effectively than did exercise initiated at PPGP. This trial was registered at the Chinese Clinical Trial Registry (http://www.chictr.org.cn/index.aspx) as ChiCTR1900023175.

Ventilatory response to hypercapnia is increased after 4\xa0h of head down bed rest

Head-down bed rest (HDBR) has previously been shown to alter cerebrovascular and autonomic control. Previous work found that sustained HDBR (≥ 20 days) attenuates the hypercapnic ventilatory response (HCVR); however, little is known about shorter-term effects of HDBR nor the influence of HDBR on the hypoxic ventilatory response (HVR). We investigated the effect of 4-h HDBR on HCVR and HVR and hypothesized attenuated ventilatory responses due to greater carotid and brain blood flow. Cardiorespiratory responses of young men (n = 11) and women (n = 3) to 5% CO2 or 10% O2 before and after 4-h HDBR were examined. HDBR resulted in lower HR, lower cardiac output index, lower common carotid artery flow, higher SpO2, and higher pulse wave velocity. After HDBR, tidal volume and ventilation responses to 5% CO2 were enhanced (all P < 0.05), yet no other changes in cardiorespiratory variables were evident. There was no influence of HDBR on the cardiorespiratory responses to hypoxia (all P > 0.05). Short-duration HDBR does not alter the HVR, yet enhances the HCVR, which we hypothesize is a consequence of cephalic CO2 accumulation from cerebral congestion.

Cardiac autonomic and blood pressure responses to an acute session of battling ropes exercise

BackgroundBattling rope (BTR) exercise has become incredibly popular among not only fitness enthusiasts and athletes but in the general exercising population. Despite its popularity, research regarding the acute cardiovascular responses to BTR exercise is limited. This investigation evaluated the effects of acute BTR exercise on heart rate variability (HRV) and blood pressure (BP) responses in young men with elevated BP. Materials and methodsEleven young men with elevated BP completed either a BTR or a non-exercise control trial in randomized order. The BTR trial consisted of 10 rounds of BTR exercise. Each round included 30 s of exercise followed by 30 s of rest. HRV and BP were evaluated at baseline and 3, 10, and 30 min following each trial. ResultsThere were significant elevations (p ˂0.01) in heart rate, markers of sympathetic activity (nLF), and sympathovagal balance (LnLF/LnHF, nLF/nHF) for 30 min following the BTR trial, whereas no changes from baseline were detected after control. Additionally, there were significant reductions (p ˂0.01) in markers of vagal tone (RMSSD, LnHF and nHF) and LnLF (both sympathetic and vagal modulations) for 30 min; as well as (p ˂0.01) systolic BP and diastolic BP at 10 and 30 min after the BTR, but not the control trial. ConclusionCurrent findings revealed that BTR exercise elevates sympathovagal balance for 30 min post-intervention, which is concurrent with an impressive hypotensive effect. Further investigations are warranted to assess the potential clinical application of BTR exercise not only in cohorts needing BP control but also in populations with limited locomotion that might benefit from post-exercise hypotension.

Common and differential associations between levels of alcohol drinking, gender-specific neurobehaviors and mental distress in college students.

Binge drinking is associated with poor academic behaviors and performance. Excessive alcohol drinking induces molecular changes and neurobehaviors that support use of other substances and alter cognitive functions.The purpose of this study was to compare neurobehaviors and academic effort among college students with low alcohol use with those of high alcohol consumption and build conceptual models that represent the integration of the different variables. College students from several U.S colleges were assessed through an anonymous online survey for alcohol use, academic performance, lifestyle factors and mental distress. Our results depicted common neurobehaviors and differential responses to high alcohol use. The common responses in young men and women with high alcohol use are reflective of a hyperactive limbic system. The different responses involve cognitive aptitudes, typically controlled by cortical regions and affected by levels of brain connectivity known to be dissimilar between men and women.

Contribution of nitric oxide synthase to cutaneous vasodilatation and sweating in men of black‐African and Caucasian descent during exercise in the heat

What is the central question of this study? Nitric oxide modulates cutaneous vasodilatation and sweating during exercise-induced heat stress in young men. However, it remains uncertain whether these effects are reduced in black-African descendants, who commonly demonstrate reduced nitric oxide bioavailability. Therefore, we assessed whether black-African descendants display reduced nitric oxide-dependent cutaneous vasodilatation and sweating compared with Caucasians in these conditions. What is the main finding and its importance? Nitric oxide-dependent cutaneous vasodilatation and sweating were similar between groups, indicating that reduced nitric oxide bioavailability in black-African descendants does not attenuate these heat-loss responses during an exercise-induced heat stress. Men of black-African descent are at an increased risk of heat-related illness relative to their Caucasian counterparts. This might be attributable, in part, to reduced cutaneous nitric oxide (NO) bioavailability in this population, which might alter local cutaneous vasodilatation and sweating. To evaluate this, we compared these heat-loss responses in young men (18-30years of age) of black-African (n=10) and Caucasian (n=10) descent during rest, exercise and recovery in the heat. Participants were matched for physical characteristics and fitness, and they were all born and raised in the same temperate environment (i.e. Canada; second generation and higher). Both groups rested for 10min and then performed 50min of moderate-intensity exercise at 200Wm-2 , followed by 30min of recovery in hot, dry heat (35°C, 20% relative humidity). Local cutaneous vascular conductance (CVC%max ) and sweat rate (SR) were measured at two forearm skin sites treated with either lactated Ringer solution (control) or 10mm NG -nitro-l-arginine methyl ester (l-NAME, a nitric oxide (NO) synthase inhibitor). l-NAME significantly reduced CVC%max throughout rest, exercise and recovery in both groups (both P<0.001). However, there were no significant main effects for the contribution of NO to CVC%max between groups (all P>0.500). l-NAME significantly reduced local SR in both groups (both P<0.050). The contribution of NO to SR was similar between groups such that l-NAME reduced SR relative to control at 40 and 50min into exercise (both P<0.05). We demonstrate that ethnicity per se does not influence NO-dependent cutaneous vasodilatation and sweating in healthy young men of black-African and Caucasian descent during exercise in dry heat.

The Degree of Aminoacidemia after Dairy Protein Ingestion Does Not Modulate the Postexercise Anabolic Response in Young Men: A Randomized Controlled Trial

BackgroundResistance exercise and dietary protein stimulate muscle protein synthesis (MPS). The rate at which proteins are digested and absorbed into circulation alters peak plasma amino acid concentrations and may modulate postexercise MPS. A novel mineral modified milk protein concentrate (mMPC), with identical amino acid composition to standard milk protein concentrate (MPC), was formulated to induce rapid aminoacidemia. ObjectiveThe aim of this study was to determine whether rapid aminoacidemia and greater peak essential amino acid (EAA) concentrations induced by mMPC would stimulate greater postresistance exercise MPS, anabolic signaling, and ribosome biogenesis compared to standard dairy proteins, which induce a small but sustained plasma essential aminoacidemia. MethodsThirty healthy young men (22.5 ± 3.0 y; BMI 23.8 ± 2.7 kg/m2) received primed constant infusions of l-[ring-13C6]-phenylalanine and completed 3 sets of leg presses and leg extensions at 80% of 1 repetition. Afterwards, participants were randomly assigned in a double-blind fashion to consume 25 g mMPC, MPC, or calcium caseinate (CAS). Vastus lateralis biopsies were collected at rest, and 2 and 4 h post exercise. ResultsPlasma EAA concentrations, including leucine, were 19.2–26.6% greater in the mMPC group 45–90 min post ingestion than in MPC and CAS groups (P < 0.001). Myofibrillar fractional synthetic rate from baseline to 4 h was increased by 82.6 ± 64.8%, 137.8 ± 72.1%, and 140.6 ± 52.4% in the MPC, mMPC, and CAS groups, respectively, with no difference between groups (P = 0.548). Phosphorylation of anabolic signaling targets (P70S6KThr389, P70S6KThr421/Ser424, RPS6Ser235/236, RPS6Ser240/244, P90RSKSer380, 4EBP1) were elevated by <3-fold at both 2 and 4 h post exercise in all groups (P < 0.05). ConclusionsThe amplitude of plasma leucine and EAA concentrations does not modulate the anabolic response to resistance exercise after ingestion of 25 g dairy protein in young men. This trial was registered at http://www.anzctr.org.au/ as ACTRN12617000393358.

Effects of isomaltulose ingestion on postexercise hydration state and heat loss responses in young men.

What is the central question of this study? What are the effects of isomaltulose, an ingredient in carbohydrate-electrolyte beverages to maintain glycaemia and attenuate the risk of dehydration during exercise heat stress, on postexercise rehydration and physiological heat loss responses? What is the main finding and its importance? Consumption of a 6.5% isomaltulose-electrolyte beverage following exercise heat stress restored hydration following a 2h recovery as compared to a 2% solution or water only. While the 6.5% isomaltulose-electrolytes increased plasma volume and plasma osmolality, which are known to modulate postexercise heat loss, sweating and cutaneous vascular responses did not differ between conditions. Consequently, ingestion beverages containing 6.5% isomaltulose-electrolytes enhanced postexercise rehydration without affecting heat loss responses. Isomaltulose is a disaccharide carbohydrate widely used during exercise to maintain glycaemia and hydration. We investigated the effects of ingesting a beverage containing isomaltulose and electrolytes on postexercise hydration state and physiological heat loss responses. In a randomized, single-blind cross-over design, 10 young healthy men were hypohydrated by performing up to three 30min successive moderate-intensity (50% heart rate reserve) bouts of cycling, each separated by 10min, while wearing a water-perfusion suit heated to 45°C. The protocol continued until a 2% reduction in body mass was achieved. Thereafter, participants performed a final 15min moderate-intensity exercise bout followed by a 2h recovery. Following cessation of exercise, participants ingested a beverage consisting of (i) water only (Water), (ii) 2% isomaltulose (CHO-2%), or (iii) 6.5% isomaltulose (CHO-6.5%) equal to the volume of 2% body mass loss within the first 30min of the recovery. Changes in plasma volume (ΔPV) after fluid ingestion were greater for CHO-6.5% compared with CHO-2% (120min postexercise) and Water (90 and 120min) (all P≤0.040). Plasma osmolality remained elevated with CHO-6.5% compared with consumption of the other beverages at 30 and 90min postexercise (all P≤0.050). Urine output tended to be reduced with CHO-6.5% compared to other fluid conditions (main effect, P=0.069). Rectal and mean skin temperatures, chest sweat rate and cutaneous perfusion did not differ between conditions (all P>0.05). In conclusion, compared with CHO-2% and Water, consuming a beverage consisting of CHO-6.5% and electrolytes during recovery under heat stress enhances PV recovery without modulating physiological heat loss responses.

The effects of partial sleep deprivation and the maximal ndks exercise testing protocol on s-klotho, maximal oxygen uptake, and hemodynamic responses in young men

The effects of partial sleep deprivation and the maximal ndks exercise testing protocol on s-klotho, maximal oxygen uptake, and hemodynamic responses in young men

Effect of Prehypertension and Blood Pressure Reactivity on Orthostatic Response in Young Men: Relationship with HF and LF HRV Power

The orthostatic test is commonly used to evaluate sympathetically mediated blood pressure (BP) reactivity in health and disease. Whether orthostatic hyperreactivity is inherent in prehypertensives, if the cardiovascular response is the same between normotensives and prehypertensives of the same reactivity, and what are the explanatory variables for cardiovascular orthostatic responses till now remains unclear.The study was carried out in 81 normotensive and 69 prehypertensive men enrolled from V.N. Karazin Kharkiv National University student population. Informed consent was given by each participant. After 5 min of supine rest subjects moved into the standing position for 5 minutes. ECG was continuously recorded, heart rate (HR), low frequency and high frequency HRV power (LF and HF) were interpreted (CardioLab 2010). Systolic and diastolic BP (SBP and DBP) were measured at the end of each stage (Nissei WS‐1011). All subjects were divided into normoreactors with DBP response (ΔDBP) less than 11 mm Hg and hyperreactors with ΔDBP more than 11 mm Hg. GLM MANOVA was used to test for possible effects of orthostatic reactivity, prehypertension and their interaction on HR, SBP, DBP, LnLF, LnHF and their responses. The stepwise multiple linear regression analysis was carried out to assess the relative importance of orthostatic reactivity, prehypertension, LnLF and LnHF power in cardiovascular responses.An exaggerated ΔDBP was observed in 47.4% of normotensives and 44.6% of prehypertensives. In normotensive and prehypertensive hyperreactors the resting DBP (DBPrest) was less compared with normoreactors (Table 1) possibly due to the higher sensitivity of baroreceptors in hyperreactors.The ΔSBP was less in prehypertensive then in normotensive normoreactors (Figure 1) supposedly due to some degree of autonomic failure and desensitization of arterial baroreceptors by a persistent increase in BP. Apparently, they are at high risk of orthostatic hypotension development.The multiple linear regression analysis revealed that the ΔHR was not associated with orthostatic reactivity (Table 2) but was negatively associated with ΔLnHF in all subjects and with ΔLnLF in prehypertensives, indicating that the increment of HR depends on decrease in the cardiovagal outflow in all subjects and, also, on decrease in inhibitory influence on presympathetic medullary neurons, according to our hypothesis, in prehypertensives.The ΔSBP was positively associated with orthostatic reactivity and negatively with resting LnLF by height interaction (Table 2), indicating that the taller is the subject the more the inhibition of resting sympathetic outflow reduced increment in SBP. The ΔSBP and ΔDBP were positively associated with ΔLnLF by resting LnHF interaction (ΔLnLF*LnHFrest) indicating that the increment of BP led to the increase in inhibition of the sympathetic nervous system activity in the case of high cardiovagal outflow.In conclusion, in hyperreactors the resting DBP was less compared with normoreactors; prehypertensive normoreactors may represent a population developing orthostatic hypotension; the increment in HR was determined by decrease in cardiovagal outflow in all subjects and by decrease in sympathetic inhibition in prehypertensives; the inhibition of resting sympathetic outflow reduced increment in SBP depending on height; the increments of BP caused inhibition of the sympathetic nervous system activity only in the case of high cardiovagal activity.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Personalized mathematical model of endotoxin-induced inflammatory responses in young men and associated changes in heart rate variability

The objective of this study was to develop a personalized inflammatory model and estimate subject-specific parameters that could be related to changes in heart rate variability (HRV), a measure that can be obtained non-invasively in real time. An inflammatory model was developed and calibrated to measurements of interleukin-6 (IL-6), tumor necrosis factor (TNF-alpha), interleukin-8 (IL-8) and interleukin-10 (IL-10) over 8 hours in 20 subjects administered a low dose of lipopolysaccharide. For this model, we estimated 11 subject-specific parameters for all 20 subjects. Estimated parameters were correlated with changes in HRV, computed from ECG measurements using a built-in HRV module available in Labchart. Results revealed that patients could be separated into two groups expressing normal and abnormal responses to endotoxin. Abnormal responders exhibited increased HRV, most likely as a result of increased vagal firing. The observed correlation between the inflammatory response and HRV brings us a step further towards understanding if HRV predictions can be used as a marker for inflammation. Analyzing HRV parameters provides an easy, non-invasively obtained measure that can be used to assess the state of the subject, potentially translating to identifying a non-invasive marker that can be used to detect the onset of sepsis.

The effect of endothelin A and B receptor blockade on cutaneous vascular and sweating responses in young men during and following exercise in the heat.

During exercise, cutaneous vasodilation and sweating responses occur, whereas these responses rapidly decrease during postexercise recovery. We hypothesized that the activation of endothelin A (ETA) receptors, but not endothelin B (ETB) receptors, attenuate cutaneous vasodilation during high-intensity exercise and contribute to the subsequent postexercise suppression of cutaneous vasodilation. We also hypothesized that both receptors increase sweating during and following high-intensity exercise. Eleven men (24 ± 4 yr) performed an intermittent cycling protocol consisting of two 30-min bouts of moderate- (40% V̇o2peak) and high-intensity (75% V̇o2peak) exercise in the heat (35°C), each separated by a 20- and 40-min recovery period, respectively. Cutaneous vascular conductance (CVC) and sweat rate were evaluated at four intradermal microdialysis skin sites: 1) lactated Ringer (control), 2) 500 nM BQ123 (a selective ETA receptor blocker), 3) 300 nM BQ788 (a selective ETB receptor blocker), or 4) a combination of BQ123 + BQ788. There were no between-site differences in CVC during each exercise bout (all P > 0.05); however, CVC following high-intensity exercise was greater at BQ123 (56 ± 9%max) and BQ123 + BQ788 (55 ± 14%max) sites relative to the control site (43 ± 12%max) (all P ≤ 0.05). Sweat rate did not differ between sites throughout the protocol (all P > 0.05). We show that neither ETA nor ETB receptors modulate cutaneous vasodilation and sweating responses during and following moderate- and high-intensity exercise in the heat, with the exception that ETA receptors may partly contribute to the suppression of cutaneous vasodilation following high-intensity exercise.

Effects of Circadian Rhythm on Power, Force, and Hormonal Response in Young Men.

Circadian rhythms (CRs) persist in many physiological systems related to performance. The effects of circadian patterns on dynamic muscular power are minimal and conflicting. Furthermore, no study to date has investigated the effect of CR on bench press throws (BPTs) despite its popularity as a modality to increase muscular power. The purpose of this study was to examine the effects of circadian variations on muscular power output and hormonal changes in men. College aged men (n = 7, age: 23.6 ± 1.3 years, height: 179.9 ± 5.4 cm, and body mass: 81.5 ± 19.7 kg.) were recruited for this repeated measures study. Testing occurred at 4 different times of day (04:00, 10:00, 16:00, and 22:00 hours). Testosterone (T) and cortisol (C) hand dynamometer strength (GS), heart rate (HR), mental readiness (MR), BPT and squat jumps (SJs), power (P), and force (F) were measured at each time point. Statistical significance was set at (p ≤ 0.05). There were no significant differences in HR, MR, and GS among all time points. There were no decrements in P or F in BPT or SJ among any time point (p ≥ 0.05). Testosterone and C decreased significantly throughout the day (p ≤ 0.05). Although P and F output differed at various percentages of 1 repetition maximum, they were not affected by circadian pattern, such that muscular performance was not impaired at any time point. Practical implications of these data indicate that high force and power exercises using BPT or SJ may be performed any time of day without detrimental decreases in acute performance.

Diurnal variation in the diving bradycardia response in young men.

The present study aimed to examine diurnal variation of the diving bradycardia responses on the same day. Eighteen young men (age 26±2years; height 174.2±6.0cm; body mass 70.2±8.1kg; body fat 18.0±3.8%; mean±standard deviation) participated in this study. Oral temperature, heart rate variability (HRV) from 5-min of electrocardiogram data, and diving bradycardia responses were measured at 0900, 1300, and 1700hours daily. All participants performed diving reflex tests twice in the sitting position with the face immersed in cold water (1.9-3.1°C) and apnea at midinspiration for a minimum of 30s and as long as possible, in consecutive order. Oral temperature was found to be less in the morning (0900) than in the afternoon (1300) and evening (1700). In the frequency domain parameters of heart rate variability, the natural logarithms of high-frequency power were higher in the morning than in the evening. All participants showed bradycardia response to the two diving reflex tests. The peak values of R-R interval during the diving reflex test both for as long as possible and 30s were longer in the morning than in the afternoon and evening. Our results indicated that the maximal bradycardia during the diving reflex test exhibits a diurnal variation, with peak levels at morning and gradual decrease towards the evening. The HRV indexes show the same variation.

Differences in postprandial protein handling after beef compared with milk ingestion during postexercise recovery: a randomized controlled trial

Protein consumed after resistance exercise increases postexercise muscle protein synthesis rates. To date, dairy protein has been studied extensively, with little known about the capacity of other protein-dense foods to augment postexercise muscle protein synthesis rates. We aimed to compare protein digestion and absorption kinetics, postprandial amino acid availability, anabolic signaling, and the subsequent myofibrillar protein synthetic response after the ingestion of milk compared with beef during recovery from resistance-type exercise. In crossover trials, 12 healthy young men performed a single bout of resistance exercise. Immediately after cessation of exercise, participants ingested 30 g protein by consuming isonitrogenous amounts of intrinsically l-[1-(13)C]phenylalanine-labeled beef or milk. Blood and muscle biopsy samples were collected at rest and after exercise during primed continuous infusions of l-[ring-(2)H5]phenylalanine and l-[ring-3,5-(2)H2]tyrosine to assess protein digestion and absorption kinetics, plasma amino acid availability, anabolic signaling, and subsequent myofibrillar protein synthesis rates in vivo in young men. Beef protein-derived phenylalanine appeared more rapidly in circulation compared with milk ingestion (P < 0.001). The availability of phenylalanine during the 5-h postexercise period tended to be higher after beef (64% ± 3%) ingestion than after milk ingestion (57% ± 3%; P = 0.08). Both beef and milk ingestion were followed by an increase in the phosphorylation of mammalian target of rapamycin complex 1 and 70-kDa S6 protein kinase 1 during postexercise recovery. Milk ingestion increased myofibrillar protein synthesis rates to a greater extent than did beef ingestion during the 0- to 2-h postexercise phase (P = 0.013). However, the increase in myofibrillar protein synthesis rates did not differ between milk and beef ingestion during the entire 0- to 5-h postexercise phase (P = 0.114). Both milk and beef ingestion augment the postexercise myofibrillar protein synthetic response in young men, with a stronger stimulation of myofibrillar protein synthesis during the early postprandial stage after milk ingestion. This trial was registered at www.clinicaltrials.gov as NCT01578590.

Protein kinetics in human endotoxaemia and their temporal relation to metabolic, endocrine and proinflammatory cytokine responses.

Sepsis is associated with profound alterations in protein metabolism. The unpredictable time course of sepsis and the multiplicity of confounding factors prevent studies of temporal relations between the onset of endocrine and proinflammatory cytokine responses and the onset of protein catabolism. This study aimed to determine the time course of whole-body protein catabolism, and relate it to the endocrine, metabolic and cytokine responses in a human endotoxaemia model of early sepsis. Six healthy male volunteers were studied twice in random order, before and for 600 min after administration of either an intravenous bolus of Escherichia coli lipopolysaccharide (LPS) or sterile saline. Whole-body protein synthesis, breakdown and net protein breakdown were measured by amino acid tracer infusion, and related to changes in plasma levels of growth hormone, glucagon, cortisol, insulin-like growth factor (IGF) 1, tumour necrosis factor (TNF) α and interleukin (IL) 6. Protein synthesis, breakdown and net protein breakdown increased and peaked 120 min after LPS administration (P < 0·001), the alterations persisting for up to 480 min. These peaks coincided with peaks in plasma growth hormone, TNF-α and IL-6 concentrations (P = 0·049, P < 0·001 and P < 0·001 for LPS versus saline), whereas plasma cortisol concentration peaked later. No alterations in plasma insulin or glucagon concentrations, or in the IGF axis were observed during the period of abnormalities of protein metabolism. LPS administration induced an early protein catabolic response in young men and this coincided with changes in plasma growth hormone, TNF-α and IL-6 concentrations, rather than changes in cortisol, glucagon, insulin or the IGF axis. Surgical relevance Sepsis in surgical patients is common and remains associated with substantial mortality. Although sepsis is a heterogeneous condition and its pathophysiology therefore difficult to study, a universal and profound clinical problem is protein catabolism not responsive to nutritional support. Human experimental endotoxaemia is a promising model of clinical sepsis that can be used to elucidate underlying pathophysiology and explore novel therapeutic approaches. This study demonstrates that human experimental endotoxaemia replicates the changes in whole-body protein turnover seen in clinical sepsis. Frequent measurements allowed identification of tumour necrosis factor (TNF) α, interleukin (IL) 6 and growth hormone as putative mediators. Human experimental endotoxaemia is a valid model for further study of mechanisms and putative therapies of catabolism associated with sepsis. In particular, effects of TNF-α and IL-6 blockade should be evaluated.

Ingestion of glucose and Vitamin C affects orthostatic stress-induced cardiovascular responses in young men

Aim: We hypothesized that coadministration of glucose and Vitamin C will reduce the orthostatic tolerance in normal young male volunteers. Materials and Methods: In a randomized controlled crossover fashion, nine nonobese, young men ingested nothing (control), and glucose (75 g) alone and with Vitamin C (1 g) 10 min before standing on 3 separate days of appointment. We measured the supine and standing blood pressure, heart rate, hematocrit, and blood glucose levels. The orthostatic tolerance was evaluated as the time to presyncope during motionless standing or until presyncopal symptoms were observed. Results: During the first 60 min of standing, 89%, 78%, and 0% of patients experienced the presyncopal symptoms when ingested nothing, glucose alone, and glucose + Vitamin C, respectively. Ingesting glucose alone did not affect the orthostatic tolerance (61.4 ± 1.4 vs. 63.0 ± 1.7 min; P > 0.05) while ingesting glucose with Vitamin C significantly improved the orthostatic tolerance (86.6 ± 2.2 vs. 63.0 ± 1.7 min; P < 0.001). Increases in the systolic blood pressure (SBP) and heart rate induced by standing were significantly enhanced when glucose + Vitamin C was ingested, while changes in diastolic blood pressure were not significantly affected. Ingestion of glucose alone or with Vitamin C led to a comparable significant increase in blood glucose levels after standing. However, a significant increase in hematocrit level was observed after standing when glucose + Vitamin C but not when glucose alone was ingested. Conclusion: The present study reveals that the oral glucose loading with Vitamin C ingestion improves the orthostatic tolerance, and the improvement is associated with an enhanced SBP, heart rate, and hematocrit level.

Body height affects the strength of immune response in young men, but not young women.

Body height and other body attributes of humans may be associated with a diverse range of social outcomes such as attractiveness to potential mates. Despite evidence that each parameter plays a role in mate choice, we have little understanding of the relative role of each, and relationships between indices of physical appearance and general health. In this study we tested relationships between immune function and body height of young men and women. In men, we report a non-linear relationship between antibody response to a hepatitis-B vaccine and body height, with a positive relationship up to a height of 185 cm, but an inverse relationship in taller men. We did not find any significant relationship between body height and immune function in women. Our results demonstrate the potential of vaccination research to reveal costly traits that govern evolution of mate choice in humans and the importance of trade-offs among these traits.