Similar performance after intake of carbohydrate plus whey protein and carbohydrate only in the early phase after non-exhaustive cycling.

AIM: The aim of the present study was to compare performance 5 h after a 90-min endurance training session when either carbohydrate only or carbohydrate with added whey hydrolysate or whey isolate was ingested during the first 2 h of the recovery period. METHODS: Thirteen highly trained competitive male cyclists completed three exercise and diet interventions (double-blinded, randomized, crossover design) separated by 1 week. The 90-min morning session (EX1) included a 60 min time-trial (TT60 ). Immediately and 1 h after exercise, participants ingested either (1) 1.2 g carbohydrate∙kg-1 ∙h-1 (CHO), (2) 0.8 g carbohydrate∙kg-1 ∙h-1 + 0.4 g isolate whey protein∙kg-1 ∙h-1 (ISO) or (3) 0.8 g carbohydrate∙kg-1 ∙h-1 + 0.4 g hydrolysate whey protein∙kg-1 ∙h-1 (HYD). Additional intakes were identical between interventions. After 5 h of recovery, participants completed a time-trial performance (TTP ) during which a specific amount of work was performed. Blood and urine were collected throughout the day. RESULTS: TTP did not differ significantly between dietary interventions (CHO: 43:54 ± 1:36, ISO: 46:55 ± 2:32, HYD: 44:31 ± 2:01 min). Nitrogen balance during CHO was lower than ISO (p < 0.0001) and HYD (p < 0.0001), with no difference between ISO and HYD (p = 0.317). In recovery, the area under the curve for blood glucose was higher in CHO compared to ISO and HYD. HR, VO2 , RER, glucose, and lactate during EX2 were similar between interventions. CONCLUSION: Performance did not differ after 5 h of recovery whether carbohydrate only or isocaloric carbohydrate plus protein was ingested during the first 2 h. Correspondingly, participants were not in negative nitrogen balance in any dietary intervention.

L-Alanylglutamine inhibits signaling proteins that activate protein degradation, but does not affect proteins that activate protein synthesis after an acute resistance exercise.

Sustamine™ (SUS) is a dipeptide composed of alanine and glutamine (AlaGln). Glutamine has been suggested to increase muscle protein accretion; however, the underlying molecular mechanisms of glutamine on muscle protein metabolism following resistance exercise have not been fully addressed. In the present study, 2-month-old rats climbed a ladder 10 times with a weight equal to 75 % of their body mass attached at the tail. Rats were then orally administered one of four solutions: placebo (PLA-glycine = 0.52 g/kg), whey protein (WP = 0.4 g/kg), low dose of SUS (LSUS = 0.1 g/kg), or high dose of SUS (HSUS = 0.5 g/kg). An additional group of sedentary (SED) rats was intubated with glycine (0.52 g/kg) at the same time as the ladder-climbing rats. Blood samples were collected immediately after exercise and at either 20 or 40 min after recovery. The flexor hallucis longus (FHL), a muscle used for climbing, was excised at 20 or 40 min post exercise and analyzed for proteins regulating protein synthesis and degradation. All supplements elevated the phosphorylation of FOXO3A above SED at 20 min post exercise, but only the SUS supplements significantly reduced the phosphorylation of AMPK and NF-kB p65. SUS supplements had no effect on mTOR signaling, but WP supplementation yielded a greater phosphorylation of mTOR, p70S6k, and rpS6 compared with PLA at 20 min post exercise. However, by 40 min post exercise, phosphorylation of mTOR and rpS6 in PLA had risen to levels not different than WP. These results suggest that SUS blocks the activation of intracellular signals for MPB, whereas WP accelerates mRNA translation.

The effect of an amino acid beverage on glucose response and glycogen replenishment after strenuous exercise.

PURPOSE: We previously reported that an amino acid mixture (AA) was able to lower the glucose response to an oral glucose challenge in both rats and humans. Increased glucose uptake and glycogen storage in muscle might be associated with the faster blood glucose clearance. We therefore tested the effect of two different doses of AA provided with a carbohydrate supplement on blood glucose homeostasis and muscle glycogen replenishment in human subjects after strenuous aerobic exercise. METHODS: Ten subjects received a carbohydrate (1.2 g/kg body weight, CHO), CHO/HAA (CHO + 13 g AA), or CHO/LAA (CHO + 6.5 g AA) supplement immediately and 2 h after an intense cycling bout. Muscle biopsies were performed immediately and 4 h after exercise. RESULTS: The glucose responses for CHO/HAA and CHO/LAA during recovery were significantly lower than CHO, as was the glucose area under the curve (CHO/HAA 1259.9 ± 27.7, CHO/LAA 1251.5 ± 47.7, CHO 1376.8 ± 52.9 mmol/L 4 h, p < 0.05). Glycogen storage rate was significantly lower in CHO/HAA compared with CHO, while it did not differ significantly between CHO/LAA or CHO (CHO/HAA 15.4 ± 2.0, CHO/LAA 18.1 ± 2.0, CHO 21.5 ± 1.4 µmol/g wet muscle 4 h). CHO/HAA caused a significantly higher insulin response and a greater effect on mTOR and Akt/PKB phosphorylation compared with CHO. Phosphorylation of AS160 and glycogen synthase did not differ across treatments. Likewise, there were no differences in blood lactate across treatments. CONCLUSIONS: The AA lowered the glucose response to a carbohydrate supplement after strenuous exercise. However, it was not effective in facilitating subsequent muscle glycogen storage.

An amino acid mixture improves glucose tolerance and lowers insulin resistance in the obese Zucker rat.

The purpose of this investigation was to test an amino acid mixture on glucose tolerance in obese Zucker rats [experiment (Exp)-1] and determine whether differences in blood glucose were associated with alterations in muscle glucose uptake [experiment (Exp)-2]. Exp-1 rats were gavaged with either carbohydrate (OB-CHO), carbohydrate plus amino acid mixture (OB-AA-1), carbohydrate plus amino acid mixture with increased leucine concentration (OB-AA-2) or water (OB-PLA). The glucose response in OB-AA-1 and OB-AA-2 were similar, and both were lower compared to OB-CHO. This effect of the amino acid mixtures did not appear to be solely attributable to an increase in plasma insulin. Rats in Exp-2 were gavaged with carbohydrate (OB-CHO), carbohydrate plus amino acid mixture (OB-AA-1) or water (OB-PLA). Lean Zuckers were gavaged with carbohydrate (LN-CHO). Fifteen minutes after gavage, a radiolabeled glucose analog was infused through a catheter previously implanted in the right jugular vein. Blood glucose was significantly lower in OB-AA-1 compared to OB-CHO while the insulin responses were similar. Glucose uptake was greater in OB-AA-1 compared with OB-CHO, and similar to that in LN-CHO in red gastrocnemius muscle (5.15 ± 0.29, 3.8 ± 0.27, 5.18 ± 0.34 µmol/100 g/min, respectively). Western blot analysis showed that Akt substrate of 160 kDa (AS160) phosphorylation was enhanced for OB-AA-1 and LN-CHO compared to OB-CHO. These findings suggest that an amino acid mixture improves glucose tolerance in an insulin resistant model and that these improvements are associated with an increase in skeletal muscle glucose uptake possibly due to improved intracellular signaling.

Effect of acute DHEA administration on free testosterone in middle-aged and young men following high-intensity interval training.

With advancing age, plasma testosterone levels decline, with free testosterone levels declining more significantly than total testosterone. This fall is thought to underlie the development of physical and mental weakness that occurs with advancing age. In addition, vigorous exercise can also lower total and free testosterone levels with the decline greatest in physically untrained men. The purpose of the study was to evaluate the effect of oral DHEA supplementation, a testosterone precursor, on free testosterone in sedentary middle-aged men during recovery from a high-intensity interval training (HIIT) bout of exercise. A randomized, double-blind, placebo-controlled crossover study was conducted for 8 middle-aged participants (aged 49.3 ± 2.4 years) and an additional 8 young control participants (aged 21.4 ± 0.3 years). Each participant received DHEA (50 mg) and placebo on separate occasions one night (12 h) before a 5-session, 2-min cycling exercise (100% VO2max). While no significant age difference in total testosterone was found, middle-aged participants exhibited significantly lower free testosterone and greater luteinizing hormone (LH) levels than the young control group. Oral DHEA supplementation increased circulating DHEA-S and free testosterone levels well above baseline in the middle-aged group, with no significant effect on total testosterone levels. Total testosterone and DHEA-S dropped significantly until 24 h after HIIT for both age groups, while free testosterone of DHEA-supplemented middle-aged men remained unaffected. These results demonstrate acute oral DHEA supplementation can elevate free testosterone levels in middle-aged men and prevent it from declining during HIIT. Therefore, DHEA supplementation may have significant benefits related to HIIT adaptation.

Effect of dehydroepiandrosterone administration on recovery from mix-type exercise training-induced muscle damage.

This study aimed to determine the role of DHEA-S in coping against the exercise training mixing aerobic and resistance components. During 5-day successive exercise training, 16 young male participants (19.2 ± 1.2 years) received either a placebo (flour capsule) or DHEA (100 mg/day) in a double-blinded and placebo-controlled design. Oral DHEA supplementation significantly increased circulating DHEA-S by 2.5-fold, but a protracted drop (~35 %) was observed from Day 3 during training. In the Placebo group, only a minimal DHEA-S reduction (~17 %) was observed. Changes in testosterone followed a similar pattern as DHEA-S. Muscle soreness was elevated significantly on Day 2 for both groups to a similar extent. Lower muscle soreness was observed in the DHEA-supplemented group on Day 3 and Day 6. In the Placebo group, training increased circulating creatine kinase (CK) levels by approximately ninefold, while only a threefold increase was observed in the DHEA-supplemented group. This mix-type exercise training improved glucose tolerance in both groups, while lowering the insulin response to the glucose challenge, but no difference between treatments was observed. Our results suggest that DHEA-S may play a role in protecting skeletal muscle from exercise training-induced muscle damage.

Effect of insulin and contraction on glycogen synthase phosphorylation and kinetic properties in epitrochlearis muscles from lean and obese Zucker rats.

In the present study, the effects of insulin and contraction on glycogen synthase (GS) kinetic properties and phosphorylation were investigated in epitrochlearis muscles from lean and obese Zucker rats. Total GS activity and protein expression were ~15% lower in epitrochlearis from obese rats compared with lean rats. Insulin-stimulated GS fractional activity and affinity for UDP-glucose were lower (higher K(m)) in muscles from obese rats. GS Ser(641) and Ser(645,649,653,657) phosphorylation was higher in insulin-stimulated muscles from obese rats, which agreed with lower GS activation. Contraction-mediated GS dephosphorylation of Ser(641), Ser(641+645), Ser(645,649,653,657), and Ser(7+10) was normal in muscles from obese Zucker rats, and GS fractional activity increased to similar levels in epitrochlearis muscles from lean and obese rats. GS affinity for UDP glucose was ~0.8, ~0.4, and ~0.1 mM with assay buffers containing 0, 0.17, and 12 mM glucose 6-phosphate, respectively. Contraction increased affinity for UDP-glucose (reduced K(m)) at a physiological concentration of glucose 6-phosphate (0.17 mM) to ~0.2 mM in muscles from both lean and obese rats. Interestingly, in the absence of glucose 6-phosphate in the assay buffer, contraction (and insulin) did not influence GS affinity for UDP-glucose, indicating that affinity is regulated by sensitivity for glucose 6-phosphate. In conclusion, contraction-mediated activation and dephosphorylation of GS were normal in muscles from obese Zucker rats, whereas insulin-mediated GS activation and dephosphorylation were impaired.

An amino acid mixture improves glucose tolerance and insulin signaling in Sprague-Dawley rats.

The aims of this investigation were to evaluate the effect of an amino acid supplement on the glucose response to an oral glucose challenge (experiment 1) and to evaluate whether differences in blood glucose response were associated with increased skeletal muscle glucose uptake (experimental 2). Experiment 1 rats were gavaged with either glucose (CHO), glucose plus an amino acid mixture (CHO-AA-1), glucose plus an amino acid mixture with increased leucine concentration (CHO-AA-2), or water (PLA). CHO-AA-1 and CHO-AA-2 had reduced blood glucose responses compared with CHO, with no difference in insulin among these treatments. Experiment 2 rats were gavaged with either CHO or CHO-AA-1. Fifteen minutes after gavage, a bolus containing 2-[(3)H]deoxyglucose and [U-(14)C]mannitol was infused via a tail vein. Blood glucose was significantly lower in CHO-AA-1 than in CHO, whereas insulin responses were similar. Muscle glucose uptake was higher in CHO-AA-1 compared with CHO in both fast-twitch red (8.36 ± 1.3 vs. 5.27 ± 0.7 µmol·g(-1)·h(-1)) and white muscle (1.85 ± 0.3 vs. 1.11 ± 0.2 µmol·g(-1)·h(-1)). There was no difference in Akt/PKB phosphorylation between treatment groups; however, the amino acid treatment resulted in increased AS160 phosphorylation in both muscle fiber types. Glycogen synthase phosphorylation was reduced in fast-twitch red muscle of CHO-AA-1 compared with CHO, whereas mTOR phosphorylation was increased. These differences were not noted in fast-twitch white muscle. These findings suggest that amino acid supplementation can improve glucose tolerance by increasing skeletal muscle glucose uptake and intracellular disposal through enhanced intracellular signaling.

A low carbohydrate-protein supplement improves endurance performance in female athletes.

The purpose of this study was to investigate if a low mixed carbohydrate (CHO) plus moderate protein (PRO) supplement, provided during endurance exercise, would improve time to exhaustion (TTE) in comparison to a traditional 6% CHO supplement. Fourteen (n = 14) trained female cyclists and triathletes cycled on 2 separate occasions for 3 hours at intensities varying between 45 and 70% VO2max, followed by a ride to exhaustion at an intensity approximating the individual's ventilatory threshold average 75.06% VO2max. Supplements (275 mL) were provided every 20 minutes during exercise and were composed of a CHO mixture (1% each of dextrose, fructose, and maltodextrin) + 1.2% PRO (CHO + PRO) or 6% dextrose only (CHO). The TTE was significantly greater with CHO + PRO in comparison to with CHO (49.94 ± 7.01 vs. 42.36 ± 6.21 minutes, respectively, p < 0.05). Blood glucose was significantly lower during the CHO + PRO trial (4.07 ± 0.12 mmol · L(-1)) compared to during the CHO trial (4.47 ± 0.12 mmol · L(-1)), with treatment × time interactions occurring from 118 minutes of exercise until exhaustion (p < 0.05). Results from the present study suggest that the addition of a moderate amount of PRO to a low mixed CHO supplement improves endurance performance in women above that of a traditional 6% CHO supplement. Improvement in performance occurred despite CHO + PRO containing a lower CHO and caloric content. It is likely that the greater performance seen with CHO + PRO was a result of the CHO-PRO combination and the use of a mixture of CHO sources.

Postexercise carbohydrate-protein supplementation improves subsequent exercise performance and intracellular signaling for protein synthesis.

Postexercise carbohydrate-protein (CHO + PRO) supplementation has been proposed to improve recovery and subsequent endurance performance compared to CHO supplementation. This study compared the effects of a CHO + PRO supplement in the form of chocolate milk (CM), isocaloric CHO, and placebo (PLA) on recovery and subsequent exercise performance. Ten cyclists performed 3 trials, cycling 1.5 hours at 70% VO2max plus 10 minutes of intervals. They ingested supplements immediately postexercise and 2 hours into a 4-hour recovery. Biopsies were performed at recovery minutes 0, 45, and 240 (R0, R45, REnd). Postrecovery, subjects performed a 40-km time trial (TT). The TT time was faster in CM than in CHO and in PLA (79.43 ± 2.11 vs. 85.74 ± 3.44 and 86.92 ± 3.28 minutes, p ≤ 0.05). Muscle glycogen resynthesis was higher in CM and in CHO than in PLA (23.58 and 30.58 vs. 7.05 µmol·g⁻¹ wet weight, p ≤ 0.05). The mammalian target of rapamycin phosphorylation was greater at R45 in CM than in CHO or in PLA (174.4 ± 36.3 vs. 131.3 ± 28.1 and 73.7 ± 7.8% standard, p ≤ 0.05) and at REnd in CM than in PLA (94.5 ± 9.9 vs. 69.1 ± 3.8%, p ≤ 0.05). rpS6 phosphorylation was greater in CM than in PLA at R45 (41.0 ± 8.3 vs. 15.3 ± 2.9%, p ≤ 0.05) and REnd (16.8 ± 2.8 vs. 8.4 ± 1.9%, p ≤ 0.05). FOXO3A phosphorylation was greater at R45 in CM and in CHO than in PLA (84.7 ± 6.7 and 85.4 ± 4.7 vs. 69.2 ± 5.5%, p ≤ 0.05). These results indicate that postexercise CM supplementation can improve subsequent exercise performance and provide a greater intracellular signaling stimulus for PRO synthesis compared to CHO and placebo.

Nitric oxide enhancement supplement containing beet nitrite and nitrate benefits high intensity cycle interval training.

This study investigated the effects of a beet nitric oxide enhancing (NOE) supplement comprised of nitrite and nitrate on cycling performance indices in trained cyclists. METHODS: Subjects completed a lactate threshold test and a high-intensity interval (HIIT) protocol at 50% above functional threshold power with or without oral NOE supplement. RESULTS: NOE supplementation enhanced lactate threshold by 7.2% (Placebo = 191.6 ± 37.3 W, NOE = 205.3 ± 39.9; p = 0.01; Effect Size (ES) = 0.40). During the HIIT protocol, NOE supplementation improved time to exhaustion 18% (Placebo = 1251 ± 562s, NOE = 1474 ± 504s; p = 0.02; ES = 0.42) and total energy expended 22.3% (Placebo = 251 ± 48.6 kJ, NOE = 306.6 ± 55.2 kJ; p = 0.01; ES = 1.079). NOE supplementation increased the intervals completed (Placebo = 7.00 ± 2.5, NOE = 8.14 ± 2.4; p = 0.03; ES = 0.42) and distance cycled (Placebo = 10.9 ± 4.0 km, NOE = 13.5 ± 3.9 km; p = 0.01; ES = 0.65). Also, target power was achieved at a higher cadence during the HIIT work and rest periods (p = 0.02), which enhanced muscle oxygen saturation (SmO2) recovery. Time-to-fatigue was negatively correlated with the degree of SmO2, desaturation during the HIIT work interval segment (r = -0.67; p 0.008), while both SmO2 desaturation and the SmO2 starting work segment saturation level correlated with a cyclist's kJ expended (SmO2 desaturation: r = -0.51, p = 0.06; SmO2 starting saturation: r = 0.59, p = 0.03). CONCLUSION: NOE supplementation containing beet nitrite and nitrate enhanced submaximal (lactate threshold) and HIIT maximal effort work. The NOE supplementation resulted in a cyclist riding at higher cadence rates with lower absolute torque values at the same power during both the work and rest periods, which in-turn delayed over-all fatigue and improved total work output.

Isolating promoters of multigene family members from the polyploid sugarcane genome by PCR-based walking in BAC DNA.

The availability of a wider range of promoters for regulated expression in valuable transgenic crops would benefit functional genomics studies and current biotechnology programs aimed at improved productivity. Polymerase chain reaction (PCR)-based genome walking techniques are commonly used to isolate promoters or 5' flanking genomic regions adjacent to known cDNA sequences in genomes that are not yet completely sequenced. However, these techniques are problematic when applied directly to DNA isolated from crops with highly complex and large genomes. An adaptor ligation-mediated PCR-based BAC genome walking method is described here for the efficient isolation of promoters of multigene family members, such as the putative defense and fiber biosynthesis DIRIGENT genes that are abundant in the stem of sugarcane, a species with a highly polyploid genome. The advantage of this method is the efficient and specific amplification of the target promoter using BAC genomic DNA as template for the adaptor ligation-mediated PCR walking.

Effect of mild intermittent hypoxia on glucose tolerance, muscle morphology and AMPK-PGC-1alpha signaling.

The main goal of this study was to investigate the long-term effect of daily 8-hour mild intermittent hypoxia (14-15% O2) on glucose tolerance and muscle morphology of Sprague-Dawley rats. The involvement of AMPK-PGC-1alpha-VEGF signaling pathways in the skeletal muscle was also determined during the first 8 hours of hypoxia. We found that mRNA levels of VEGF and PGC-1alpha were significantly increased above control after 8-h mild hypoxia without a change in AMPK phosphorylation. After 8 weeks of mild intermittent hypoxia treatment, plasma glucose and insulin levels in oral glucose tolerance test (OGTT), epididymal fat mass, and body weight were significantly lower compared to the control group. While soleus muscle weight was not changed, capillary and fiber densities in the hypoxia group were 33% and 35% above the control suggesting reorganization of muscle fibers. In conclusion, our data provide strong evidence that long-term mild intermittent hypoxia decreases the diffusion distance of glucose and insulin across muscle fibers, and decreases adiposity in rats. These changes may account for the improved glucose tolerance observed following the 8-week hypoxia treatment, and provides grounds for investigating the development of a mild non-pharmacological intervention in the treatment of obesity and type 2 diabetes.

Added protein maintains efficacy of a low-carbohydrate sports drink.

The purpose of the present study was to investigate the aerobic capacity characteristics of an isocaloric carbohydrate (CHO) plus protein (PRO) drink and a low-calorie CHO plus PRO drink against a traditional 6% CHO sports beverage. Twelve male and female trained cyclists exercised on 4 separate occasions at intensities that varied between 55 and 75% V(O2)max for 2.5 hours and then at 80% V(O2)max until fatigued. Supplements (255.4 +/- 9.1 mL) were provided every 20 minutes and consisted of a 4.5% carbohydrate plus 1.15% protein complex (CHO/PRO H), a 3% carbohydrate plus 0.75% protein complex (CHO/PRO L), a 6% carbohydrate supplement (CHO), or a placebo (PLA). Time to fatigue at 80% V(O2)max was significantly longer (p < 0.05) during the CHO (26.9 +/- 6.1 minutes, mean +/- SE), the CHO/PRO H (30.5 +/- 5.9 minutes), and the CHO/PRO L (28.9 +/- 6.5 minutes) trials compared with the PLA trial (14.7 +/- 3.4 minutes), with no significant differences among the CHO, CHO/PRO H, and CHO/PRO L treatments. In general, blood glucose, plasma insulin, and carbohydrate oxidation were elevated above PLA during the CHO, CHO/PRO H, and CHO/PRO L trials, whereas plasma free fatty acids, rating of perceived exertion, and fat oxidation values were lower during the CHO, CHO/PRO H, and CHO/PRO L trials compared with the PLA trial. Only minor differences in blood parameters occurred among the CHO, CHO/PRO H, and CHO/PRO L treatments. In summary, partially substituting PRO for CHO in a sports drink did not enhance aerobic capacity, but substitution was able to occur without loss of efficacy. Thus, adding PRO to a low-calorie CHO sports drink may be an effective strategy to enhance aerobic capacity while limiting carbohydrate and caloric consumption.

The effect of a low carbohydrate beverage with added protein on cycling endurance performance in trained athletes.

Ingesting carbohydrate plus protein during prolonged variable intensity exercise has demonstrated improved aerobic endurance performance beyond that of a carbohydrate supplement alone. The purpose of the present study was to determine if a supplement containing a mixture of different carbohydrates (glucose, maltodextrin, and fructose) and a moderate amount of protein given during endurance exercise would increase time to exhaustion (TTE), despite containing 50% less total carbohydrate than a carbohydrate-only supplement. We also sought post priori to determine if there was a difference in effect based on percentage of ventilatory threshold (VT) at which the subjects cycled to exhaustion. Fifteen trained male and female cyclists exercised on 2 separate occasions at intensities alternating between 45 and 70% VO2max for 3 hours, after which the workload increased to ∼74-85% VO2max until exhaustion. Supplements (275 mL) were provided every 20 minutes during exercise, and these consisted of a 3% carbohydrate/1.2% protein supplement (MCP) and a 6% carbohydrate supplement (CHO). For the combined group (n = 15), TTE in MCP did not differ from CHO (31.06 ± 5.76 vs. 26.03 ± 4.27 minutes, respectively, p = 0.064). However, for subjects cycling at or below VT (n = 8), TTE in MCP was significantly greater than for CHO (45.64 ± 7.38 vs. 35.47 ± 5.94 minutes, respectively, p = 0.006). There were no significant differences in TTE for the above VT group (n = 7). Our results suggest that, compared to a traditional 6% CHO supplement, a mixture of carbohydrates plus a moderate amount of protein can improve aerobic endurance at exercise intensities near the VT, despite containing lower total carbohydrate and caloric content.

Co-ingestion of carbohydrate and whey protein induces muscle strength and myofibrillar protein accretion without a requirement of satellite cell activation.

Muscle development is controlled by the balance between muscle protein synthesis and protein degradation. Protein supplementation has been widely known to enhance muscle protein synthesis, and carbohydrate supplementation may attenuate protein degradation. The purpose of this study was to compare the effects of whey protein plus carbohydrate (CP), whey protein (WP), and placebo (PLA) supplements on resistance training adaptations. Two-month old rats were trained by ladder climbing every 3 days for 8 weeks. PLA, WP, or CP was given immediately after each exercise session. Non-exercise rats were used as a sedentary control (SED). Total body composition was assessed and blood samples were collected before, middle, and end of training. The flexor hallucis longus (FHL) was excised 24 h after the last exercise session. Following training, maximal carrying capacity was significantly greater in CP than PLA and WP. This improved training performance in CP paralleled an increase in total muscle and myofibrillar protein content. Muscle and fiber cross sectional areas (CSA) were significantly increased by exercise training, with a concomitant increase in myonuclear domain. CP significantly elevated IGF-1 protein expression over SED, but there were no significant differences in myostatin, Pax7, MyoD, or myogenin across treatment groups. There was also no difference in the number of total nuclei in each fiber CSA among groups. Corticosterone levels were significantly elevated in PLA and WP over 8 weeks of training, whereas this change in corticosterone over time was not observed in the CP group. The results suggest that the greater improvement of maximal caring capacity for CP compared with PLA and WP was associated with a greater increase in myofibrillar protein content. Satellite cell activation did not appear to contribute to the observed gains in muscle hypertrophy and strength.

Aerobic exercise induces tumor suppressor p16INK4a expression of endothelial progenitor cells in human skeletal muscle.

Aerobic exercise induces oxidative stress and DNA damage, nevertheless, lowers cancer incidence. It remains unclear how genetic stability is maintained under this condition. Here, we examined the dynamic change of the tumor suppressor p16INK4a in cells of skeletal muscle among young men following 60-min of aerobic cycling at 70% maximal oxygen consumption (V̇O2max). Rg1 (5 mg, an immunostimulant ginsenoside) and placebo (PLA) were supplemented 1 h before exercise. Data from serial muscle biopsies shows unchanged p16INK4a+ cells after exercise followed by a considerable increase (+21-fold) in vastus lateralis muscle 3 h later. This increase was due to the accumulation of endothelial progenitor cells (p16INK4a+/CD34+) surrounding myofibers and other infiltrated nucleated cells (p16INK4a+/CD34-) in necrotic myofibers. During the Rg1 trial, acute increases of p16INK4a+ cells in the muscle occurred immediately after exercise (+3-fold) and reversed near baseline 3 h later. Rg1 also lowered IL-10 mRNA relative to PLA 3 h after exercise. Post-exercise increases in VEGF mRNA and CD163+ macrophages were similar for PLA and Rg1 trials. Conclusion: The marked increases in p16INK4a protein expression of endothelial progenitor cells in skeletal muscle implicates a protective mechanism for maintaining genetic stability against aerobic exercise. Rg1 accelerates resolution of the exercise-induced stress response.

Exhaustive Exercise and Post-exercise Protein Plus Carbohydrate Supplementation Affect Plasma and Urine Concentrations of Sulfur Amino Acids, the Ratio of Methionine to Homocysteine and Glutathione in Elite Male Cyclists.

Plasma and tissue sulfur amino acid (SAA) availability are crucial for intracellular methylation reactions and cellular antioxidant defense, which are important processes during exercise and in recovery. In this randomized, controlled crossover trial among eight elite male cyclists, we explored the effect of exhaustive exercise and post-exercise supplementation with carbohydrates and protein (CHO+PROT) vs. carbohydrates (CHO) on plasma and urine SAAs, a potential new marker of methylation capacity (methionine/total homocysteine ratio [Met/tHcy]) and related metabolites. The purpose of the study was to further explore the role of SAAs in exercise and recovery. Athletes cycled to exhaustion and consumed supplements immediately after and in 30 min intervals for 120 min post-exercise. After ~18 h recovery, performance was tested in a time trial in which the CHO+PROT group cycled 8.5% faster compared to the CHO group (41:53 ± 1:51 vs. 45:26 ± 1:32 min, p < 0.05). Plasma methionine decreased by ~23% during exhaustive exercise. Two h post-exercise, further decline in methionine had occured by ~55% in the CHO group vs. ~33% in the CHO+PROT group (pgroup × time < 0.001). The Met/tHcy ratio decreased by ~33% during exhaustive exercise, and by ~54% in the CHO group vs. ~27% in the CHO+PROT group (pgroup × time < 0.001) post-exercise. Plasma cystathionine increased by ~72% in the CHO group and ~282% in the CHO+PROT group post-exercise (pgroup × time < 0.001). Plasma total cysteine, taurine and total glutathione increased by 12% (p = 0.03), 85% (p < 0.001) and 17% (p = 0.02), respectively during exhaustive exercise. Using publicly available transcriptomic data, we report upregulated transcript levels of skeletal muscle SLC7A5 (log2 fold-change: 0.45, FDR:1.8e-07) and MAT2A (log2 fold-change: 0.38, FDR: 3.4e-0.7) after acute exercise. Our results show that exercise acutely lowers plasma methionine and the Met/tHcy ratio. This response was attenuated in the CHO+PROT compared to the CHO group in the early recovery phase potentially affecting methylation capacity and contributing to improved recovery.

Coingestion of protein and carbohydrate in the early recovery phase, compared with carbohydrate only, improves endurance performance despite similar glycogen degradation and AMPK phosphorylation.

The present study compared the effects of postexercise carbohydrate plus protein (CHO+PROT) and carbohydrate (CHO)-only supplementation on muscle glycogen metabolism, anabolic cell signaling, and subsequent exercise performance. Nine endurance-trained males cycled twice to exhaustion (muscle glycogen decreased from ~495 to ~125 mmol/kg dry wt) and received either CHO only (1.2 g·kg-1·h-1) or CHO+PROT (0.8/0.4 g·kg-1·h-1) during the first 90 min of recovery. Glycogen content was similar before the performance test after 5 h of recovery. Glycogen synthase (GS) fractional activity increased after exhaustive exercise and remained activated 5 h after, despite substantial glycogen synthesis (176.1 ± 19.1 and 204.6 ± 27.0 mmol/kg dry wt in CHO and CHO+PROT, respectively; P = 0.15). Phosphorylation of GS at site 3 and site 2+2a remained low during recovery. After the 5-h recovery, cycling time to exhaustion was improved by CHO+PROT supplementation compared with CHO supplementation (54.6 ± 11.0 vs. 46.1 ± 9.8 min; P = 0.009). After the performance test, muscle glycogen was equally reduced in CHO+PROT and CHO. Akt Ser473 and p70s6k Thr389 phosphorylation was elevated after 5 h of recovery. There were no differences in Akt Ser473, p70s6k Thr389, or TSC2 Thr1462 phosphorylation between treatments. Nitrogen balance was positive in CHO+PROT (19.6 ± 7.6 mg nitrogen/kg; P = 0.04) and higher than CHO (-10.7 ± 6.3 mg nitrogen/kg; P = 0.009). CHO+PROT supplementation during exercise recovery improved subsequent endurance performance relative to consuming CHO only. This improved performance after CHO+PROT supplementation could not be accounted for by differences in glycogen metabolism or anabolic cell signaling, but may have been related to differences in nitrogen balance.NEW & NOTEWORTHY Endurance athletes competing consecutive days need optimal dietary intake during the recovery period. We report that coingestion of protein and carbohydrate soon after exhaustive exercise, compared with carbohydrate only, resulted in better performance the following day. The better performance after coingestion of protein and carbohydrate was not associated with a higher rate of glycogen synthesis or activation of anabolic signaling compared with carbohydrate only. Importantly, nitrogen balance was positive after coingestion of protein and carbohydrate, which was not the case after intake of carbohydrate only, suggesting that protein synthesis contributes to the better performance the following day.

Inorganic Nitrate Supplementation for Cardiovascular Health.

Nitric oxide (NO) is continually produced by the enzyme nitric oxide synthase (NOS) and is essential to the control and effectiveness of the cardiovascular system. However, there is a substantial reduction in NOS activity with aging that can lead to the development of hypertension and other cardiovascular complications. Fortunately, NO can also be produced by the sequential reduction of inorganic nitrate to nitrite and then to NO. Nitric oxide from inorganic nitrate supplementation has been found to have the same cardioprotective benefits of NO produced by NOS. Moreover, it can effectively compensate for declining NOS activity due to aging or NOS inhibition by oxidative stress, hypoxia, or other factors. This review covers some of the major cardiovascular regulatory actions of NO and presents evidence that NO from inorganic nitrate supplementation can provide (1) compensation when NOS activity is inadequate, and (2) cardioprotective benefits beyond that provided by a healthy NOS system. In addition, it discusses how to obtain a safe and efficacious range of inorganic nitrate.