IMPROVED NET PROTEIN BALANCE, LEAN MASS, AND GENE EXPRESSION CHANGES WITH OXANDROLONE TREATMENT IN THE SEVERELY BURNED

To investigate the metabolic basis of skin wound healing, we measured in anesthetized rabbits the responses of protein kinetics in scalded skin to insulin and amino acids.l-[ ring-13C6]Phe was infused on the 7th day after the ear was scalded, and the scalded ear was used as an arteriovenous unit to reflect protein kinetics in skin wound. The ipsilateral carotid artery was clamped to control the wound blood flow within four- to fivefold the normal skin rate to measure the enrichment difference in the scalded ear during hyperaminoacidemia. Neither insulin (2.5 mU · kg−1· min−1) nor amino acid (2.5 mg · kg−1· min−1) infusion alone improved net protein balance in the skin wound. In contrast, combined infusion of insulin and amino acids increased the net protein balance in skin wound from −6.5 ± 4.5 to 1.4 ± 5.2 μmol · 100 g−1· h−1( P < 0.01, control vs. insulin plus amino acids). We conclude that there is an interactive effect of insulin and sufficient amino acid supply on protein metabolism in skin wound, meaning that their combined anabolic effect is greater than the sum of their individual effects.

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Dose-Dependent Increases in Whole-Body Net Protein Balance and Dietary Protein-Derived Amino Acid Incorporation into Myofibrillar Protein During Recovery from Resistance Exercise in Older Men

Journal of Nutrition ◽

10.1093/jn/nxy263 ◽

2019 ◽

Vol 149 (2) ◽

pp. 221-230 ◽

Cited By ~ 23

Author(s):

Andrew M Holwerda ◽

Kevin J M Paulussen ◽

Maarten Overkamp ◽

Joy P B Goessens ◽

Irene Fleur Kramer ◽

...

Keyword(s):

Amino Acid ◽

Resistance Exercise ◽

Dietary Protein ◽

Older Men ◽

Myofibrillar Protein ◽

Whole Body ◽

Protein Balance ◽

Dose Dependent ◽

Net Protein ◽

Myofibrillar Protein Synthesis

ABSTRACT Background Age-related decline in skeletal muscle mass is at least partly attributed to anabolic resistance to food intake. Resistance exercise sensitizes skeletal muscle tissue to the anabolic properties of amino acids. Objective The present study assessed protein digestion and amino acid absorption kinetics, whole-body protein balance, and the myofibrillar protein synthetic response to ingestion of different amounts of protein during recovery from resistance exercise in older men. Methods Forty-eight healthy older men [mean ± SEM age: 66 ± 1 y; body mass index (kg/m2): 25.4 ± 0.3] were randomly assigned to ingest 0, 15, 30, or 45 g milk protein concentrate after a single bout of resistance exercise consisting of 4 sets of 10 repetitions of leg press and leg extension and 2 sets of 10 repetitions of lateral pulldown and chest press performed at 75–80% 1-repetition maximum. Postprandial protein digestion and amino acid absorption kinetics, whole-body protein metabolism, and myofibrillar protein synthesis rates were assessed using primed, continuous infusions of l-[ring-2H5]-phenylalanine, l-[ring-2H2]-tyrosine, and l-[1-13C]-leucine combined with ingestion of intrinsically l-[1-13C]-phenylalanine and l-[1-13C]-leucine labeled protein. Results Whole-body net protein balance showed a dose-dependent increase after ingestion of 0, 15, 30, or 45 g of protein (0.015 ± 0.002, 0.108 ± 0.004, 0.162 ± 0.008, and 0.215 ± 0.009 μmol Phe · kg−1 · min−1, respectively; P < 0.001). Myofibrillar protein synthesis rates were higher after ingesting 30 (0.0951% ± 0.0062%/h, P = 0.07) or 45 g of protein (0.0970% ± 0.0062%/h, P < 0.05) than after 0 g (0.0746% ± 0.0051%/h). Incorporation of dietary protein–derived amino acids (l-[1-13C]-phenylalanine) into de novo myofibrillar protein showed a dose-dependent increase after ingestion of 15, 30, or 45 g protein (0.0171 ± 0.0017, 0.0296 ± 0.0030, and 0.0397 ± 0.0026 mole percentage excess, respectively; P < 0.05). Conclusions Dietary protein ingested during recovery from resistance exercise is rapidly digested and absorbed. Whole-body net protein balance and dietary protein-derived amino acid incorporation into myofibrillar protein show dose-dependent increases. Ingestion of ≥30 g protein increases postexercise myofibrillar protein synthesis rates in older men. This trial was registered at Nederlands Trial Register as NTR4492.

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Net Protein Balance after Load Carriage Exercise is Enhanced by Amino Acid Supplementation

The FASEB Journal ◽

10.1096/fasebj.29.1_supplement.742.4 ◽

2015 ◽

Vol 29 (S1) ◽

Author(s):

Holly McClung ◽

Lee Margolis ◽

Nancy Murphy ◽

Gregory Lin ◽

Jay Hydren ◽

...

Keyword(s):

Amino Acid ◽

Load Carriage ◽

Amino Acid Supplementation ◽

Protein Balance ◽

Acid Supplementation ◽

Net Protein

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Intermittent Fasting Promotes Fat Loss With Lean Mass Retention, Increased Hypothalamic Norepinephrine Content, and Increased Neuropeptide Y Gene Expression in Diet-Induced Obese Male Mice

Endocrinology ◽

10.1210/en.2015-1622 ◽

2015 ◽

Vol 157 (2) ◽

pp. 679-691 ◽

Cited By ~ 50

Author(s):

Juliet D. Gotthardt ◽

Jessica L. Verpeut ◽

Bryn L. Yeomans ◽

Jennifer A. Yang ◽

Ali Yasrebi ◽

...

Keyword(s):

Gene Expression ◽

Weight Loss ◽

Neuropeptide Y ◽

Lean Mass ◽

Area Under The Curve ◽

Intermittent Fasting ◽

Oral Glucose ◽

Tissue Homogenates ◽

Ad Libitum ◽

The Imf

Abstract Clinical studies indicate alternate-day, intermittent fasting (IMF) protocols result in meaningful weight loss in obese individuals. To further understand the mechanisms sustaining weight loss by IMF, we investigated the metabolic and neural alterations of IMF in obese mice. Male C57/BL6 mice were fed a high-fat diet (HFD; 45% fat) ad libitum for 8 weeks to promote an obese phenotype. Mice were divided into four groups and either maintained on ad libitum HFD, received alternate-day access to HFD (IMF-HFD), and switched to ad libitum low-fat diet (LFD; 10% fat) or received IMF of LFD (IMF-LFD). After 4 weeks, IMF-HFD (∼13%) and IMF-LFD (∼18%) had significantly lower body weights than the HFD. Body fat was also lower (∼40%–52%) in all diet interventions. Lean mass was increased in the IMF-LFD (∼12%–13%) compared with the HFD and IMF-HFD groups. Oral glucose tolerance area under the curve was lower in the IMF-HFD (∼50%), whereas the insulin tolerance area under the curve was reduced in all diet interventions (∼22%–42%). HPLC measurements of hypothalamic tissue homogenates indicated higher (∼55%–60%) norepinephrine (NE) content in the anterior regions of the medial hypothalamus of IMF compared with the ad libitum-fed groups, whereas NE content was higher (∼19%–32%) in posterior regions in the IMF-LFD group only. Relative gene expression of Npy in the arcuate nucleus was increased (∼65%–75%) in IMF groups. Our novel findings indicate that intermittent fasting produces alterations in hypothalamic NE and neuropeptide Y, suggesting the counterregulatory processes of short-term weight loss are associated with an IMF dietary strategy.

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Whole-body net protein balance plateaus in response to increasing protein intakes during post-exercise recovery in adults and adolescents

Nutrition & Metabolism ◽

10.1186/s12986-018-0301-z ◽

2018 ◽

Vol 15 (1) ◽

Cited By ~ 10

Author(s):

Michael Mazzulla ◽

Kimberly A. Volterman ◽

Jeff E. Packer ◽

Denise J. Wooding ◽

Jahmal C. Brooks ◽

...

Keyword(s):

Whole Body ◽

Exercise Recovery ◽

Protein Balance ◽

Post Exercise ◽

Post Exercise Recovery ◽

Net Protein

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Combined ingestion of protein and carbohydrate improves protein balance during ultra-endurance exercise

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00543.2003 ◽

2004 ◽

Vol 287 (4) ◽

pp. E712-E720 ◽

Cited By ~ 86

Author(s):

René Koopman ◽

Daphne L. E. Pannemans ◽

Asker E. Jeukendrup ◽

Annemie P. Gijsen ◽

Joan M. G. Senden ◽

...

Keyword(s):

Endurance Exercise ◽

Whole Body ◽

Protein Balance ◽

Entire Study ◽

Carbohydrate Ingestion ◽

Body Protein ◽

Exercise Period ◽

Postexercise Recovery ◽

Ultra Endurance ◽

Net Protein

The aims of this study were to compare different tracer methods to assess whole body protein turnover during 6 h of prolonged endurance exercise when carbohydrate was ingested throughout the exercise period and to investigate whether addition of protein can improve protein balance. Eight endurance-trained athletes were studied on two different occasions at rest (4 h), during 6 h of exercise at 50% of maximal O2 uptake (in sequential order: 2.5 h of cycling, 1 h of running, and 2.5 h of cycling), and during subsequent recovery (4 h). Subjects ingested carbohydrate (CHO trial; 0.7 g CHO·kg−1·h−1) or carbohydrate/protein beverages (CHO + PRO trial; 0.7 g CHO·kg−1·h−1 and 0.25 g PRO·kg−1·h−1) at 30-min intervals during the entire study. Whole body protein metabolism was determined by infusion of l-[1-13C]leucine, l-[2H5]phenylalanine, and [15N2]urea tracers with sampling of blood and expired breath. Leucine oxidation increased from rest to exercise [27 ± 2.5 vs. 74 ± 8.8 (CHO) and 85 ± 9.5 vs. 200 ± 16.3 mg protein·kg−1·h−1 (CHO + PRO), P < 0.05], whereas phenylalanine oxidation and urea production did not increase with exercise. Whole body protein balance during exercise with carbohydrate ingestion was negative (−74 ± 8.8, −17 ± 1.1, and −72 ± 5.7 mg protein·kg−1·h−1) when l-[1-13C]leucine, l-[2H5]phenylalanine, and [15N2]urea, respectively, were used as tracers. Addition of protein to the carbohydrate drinks resulted in a positive or less-negative protein balance (−32 ± 16.3, 165 ± 4.6, and 151 ± 13.4 mg protein·kg−1·h−1) when l-[1-13C]leucine, l-[2H5]phenylalanine, and [15N2]urea, respectively, were used as tracers. We conclude that, even during 6 h of exhaustive exercise in trained athletes using carbohydrate supplements, net protein oxidation does not increase compared with the resting state and/or postexercise recovery. Combined ingestion of protein and carbohydrate improves net protein balance at rest as well as during exercise and postexercise recovery.

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Effect of glycogen availability on human skeletal muscle protein turnover during exercise and recovery

Journal of Applied Physiology ◽

10.1152/japplphysiol.00108.2009 ◽

2010 ◽

Vol 109 (2) ◽

pp. 431-438 ◽

Cited By ~ 63

Author(s):

Krista R. Howarth ◽

Stuart M. Phillips ◽

Maureen J. MacDonald ◽

Douglas Richards ◽

Natalie A. Moreau ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Synthesis ◽

Protein Turnover ◽

Muscle Protein ◽

Whole Body ◽

Skeletal Muscle Protein ◽

Protein Balance ◽

Body Protein ◽

Muscle Protein Turnover ◽

Net Protein

We examined the effect of carbohydrate (CHO) availability on whole body and skeletal muscle protein utilization at rest, during exercise, and during recovery in humans. Six men cycled at ∼75% peak O2 uptake (V̇o2peak) to exhaustion to reduce body CHO stores and then consumed either a high-CHO (H-CHO; 71 ± 3% CHO) or low-CHO (L-CHO; 11 ± 1% CHO) diet for 2 days before the trial in random order. After each dietary intervention, subjects received a primed constant infusion of [1-13C]leucine and l-[ring-2H5]phenylalanine for measurements of the whole body net protein balance and skeletal muscle protein turnover. Muscle, breath, and arterial and venous blood samples were obtained at rest, during 2 h of two-legged kicking exercise at ∼45% of kicking V̇o2peak, and during 1 h of recovery. Biopsy samples confirmed that the muscle glycogen concentration was lower in the L-CHO group versus the H-CHO group at rest, after exercise, and after recovery. The net leg protein balance was decreased in the L-CHO group compared with at rest and compared with the H-CHO condition, which was primarily due to an increase in protein degradation (area under the curve of the phenylalanine rate of appearance: 1,331 ± 162 μmol in the L-CHO group vs. 786 ± 51 μmol in the H-CHO group, P < 0.05) but also due to a decrease in protein synthesis late in exercise. There were no changes during exercise in the rate of appearance compared with rest in the H-CHO group. Whole body leucine oxidation increased above rest in the L-CHO group only and was higher than in the H-CHO group. The whole body net protein balance was reduced in the L-CHO group, largely due to a decrease in whole body protein synthesis. These data extend previous findings by others and demonstrate, using contemporary stable isotope methodology, that CHO availability influences the rates of skeletal muscle and whole body protein synthesis, degradation, and net balance during prolonged exercise in humans.

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Intracellular signaling pathways regulating net protein balance following diaphragm muscle denervation

AJP Cell Physiology ◽

10.1152/ajpcell.00172.2010 ◽

2011 ◽

Vol 300 (2) ◽

pp. C318-C327 ◽

Cited By ~ 25

Author(s):

Heather M. Argadine ◽

Carlos B. Mantilla ◽

Wen-Zhi Zhan ◽

Gary C. Sieck

Keyword(s):

Protein Synthesis ◽

Protein Degradation ◽

Nuclear Translocation ◽

Glycogen Synthase ◽

Diaphragm Muscle ◽

Initiation Factor ◽

Protein Balance ◽

Downstream Effector ◽

Ampk Phosphorylation ◽

Net Protein

Unilateral denervation (DNV) of rat diaphragm muscle increases protein synthesis at 3 days after DNV (DNV-3D) and degradation at DNV-5D, such that net protein breakdown is evident by DNV-5D. On the basis of existing models of protein balance, we examined DNV-induced changes in Akt, AMP-activated protein kinase (AMPK), and ERK½ activation, which can lead to increased protein synthesis via mammalian target of rapamycin (mTOR)/p70S6 kinase (p70S6K), glycogen synthase kinase-3β (GSK3β), or eukaryotic initiation factor 4E (eIF4E), and increased protein degradation via forkhead box protein O (FoxO). Protein phosphorylation was measured using Western analyses through DNV-5D. Akt phosphorylation decreased at 1 h and 6 h after DNV compared with sham despite decreased AMPK phosphorylation. Both Akt and AMPK phosphorylation returned to sham levels by DNV-1D. Phosphorylation of their downstream effector mTOR (Ser2481) did not change at any time point after DNV, and phosphorylated p70S6K and eIF4E-binding protein 1 (4EBP1) increased only by DNV-5D. In contrast, ERK½ phosphorylation and its downstream effector eIF4E increased 1.7-fold at DNV-1D and phosphorylated GSK3β increased 1.5-fold at DNV-3D ( P < 0.05 for both comparisons). Thus, following DNV there are differential effects on protein synthetic pathways with preferential activation of GSK3β and eIF4E over p70S6K. FoxO1 nuclear translocation occurred by DNV-1D, consistent with its role in increasing expression of atrogenes necessary for subsequent ubiquitin-proteasome activation evident by DNV-5D. On the basis of our results, increased protein synthesis following DNV is associated with changes in ERK½-dependent pathways, but protein degradation results from downregulation of Akt and nuclear translocation of FoxO1. No single trigger is responsible for protein balance following DNV. Protein balance in skeletal muscle depends on multiple synthetic/degradation pathways that should be studied in concert.

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