Protein Intake in Early Infancy: Effects on Plasma Amino Acid Concentrations, Insulin Metabolism, and Growth

Dietary protein intake is critical for the maintenance of skeletal muscle mass. Plasma amino acid concentrations increase with protein intake and increases in muscle protein synthesis are dependent on leucine concentrations. We aimed to investigate the effect of a mixed meal and free amino acids intake on plasma leucine concentrations. In this randomized crossover study, 10 healthy young men (age 25 ± 1 years, height 1.73 ± 0.02 m, weight 65.8 ± 1.5 kg) underwent tests under different conditions—intake of 2 g of leucine (LEU), intake of a mixed meal (protein 27.5 g, including 2.15 g of leucine, protein: fat: carbohydrate ratio—22:25:53) only (MEAL), intake of 2 g of leucine immediately after a mixed meal (MEAL-LEU) and intake of 2 g of leucine 180 min after a mixed meal (MEAL-LEU180). Blood samples were collected within 420 min (240 min for LEU only) after intake and changes in amino acid concentrations were evaluated. Although the maximum plasma leucine concentration increased to 442 ± 24 µM for LEU, it was lower at 347 ± 16 µM (p < 0.05 vs. LEU) for MEAL-LEU, 205 ± 8 µM (p < 0.05 vs. LEU) for MEAL. The maximum plasma leucine concentration for MEAL-LEU180 increased to 481 ± 27 µM and compared to LEU there was no significant difference (p > 0.1). The observation that rapid elevations in plasma leucine concentrations are suppressed when leucine is ingested at the same time as a meal suggests that the timing of its intake must be considered to maximize the anabolic response.

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The effect of insulin deficiency, dietary protein intake, and plasma amino acid concentrations on brain amino acid levels in rats

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y85-084 ◽

1985 ◽

Vol 63 (5) ◽

pp. 487-494 ◽

Cited By ~ 23

Author(s):

N. Theresa Glanville ◽

G. Harvey Anderson

Keyword(s):

Amino Acid ◽

Dietary Protein ◽

Protein Intake ◽

Plasma Amino Acid ◽

Dietary Protein Intake ◽

Influx Rate ◽

Amino Acid Levels ◽

The Brain ◽

Amino Acid Concentrations ◽

Brain Amino Acid

The effect of diabetes (streptozotocin, 65 mg/kg ip), dietary protein intake (15–60%), and plasma amino acid concentrations on brain large neutral amino acid levels in rats was examined. After 20 days, the plasma concentrations of methionine and the branched chain amino acids (BCAA), valine, isoleucine, and leucine were increased in diabetic rats. In brain tissue, methionine and valine levels were increased but threonine, tyrosine, and tryptophan concentrations were depressed. Increased protein consumption promoted a diabetic-like plasma amino acid pattern in normal rats while enhancing that of diabetic animals. However, with the exception of threonine, glycine, valine, and tyrosine, there was little effect on brain amino acid levels. A good association was found between the calculated brain influx rate and the actual brain concentration of threonine, methionine, tyrosine, and tryptophan in diabetic animals. There was no correlation, however, between brain influx rate and brain BCAA levels. Thus, the brain amino acid pattern in diabetes represents the combined effects of insulin insufficiency and composition of the diet ingested on plasma amino acid levels as well as metabolic adaptation within the brain itself.

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THE EFFECT OF PROTEIN INTAKE ON PLASMA AMINO ACID CONCENTRATIONS, ENZYMATIC ACTIVITY, AND FOOD INTAKE OF RATS

Nutrition Reviews ◽

10.1111/j.1753-4887.1968.tb00956.x ◽

2009 ◽

Vol 26 (9) ◽

pp. 286-288

Keyword(s):

Amino Acid ◽

Food Intake ◽

Enzymatic Activity ◽

Protein Intake ◽

Plasma Amino Acid ◽

Amino Acid Concentrations

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Impact on Isoleucine and Valine Supplementation When Decreasing Use of Medical Food in the Nutritional Management of Methylmalonic Acidemia

Nutrients ◽

10.3390/nu12020473 ◽

2020 ◽

Vol 12 (2) ◽

pp. 473

Author(s):

Laurie E. Bernstein ◽

Casey Burns ◽

Morgan Drumm ◽

Sommer Gaughan ◽

Melissa Sailer ◽

...

Keyword(s):

Amino Acid ◽

Total Protein ◽

Protein Intake ◽

Chart Review ◽

Methylmalonic Acidemia ◽

Plasma Amino Acid ◽

Medical Food ◽

Natural Protein ◽

Total Protein Intake ◽

Amino Acid Concentrations

Background: Methylmalonic acidemia (MMA) is an autosomal recessive disorder treated with precursor-free medical food while limiting natural protein. This retrospective chart review was to determine if there was a relationship between medical food, valine (VAL) and/or isoleucine (ILE) supplementation, total protein intake, and plasma amino acid profiles. Methods: A chart review, of patients aged 31 days or older with MMA treated with dietary intervention and supplementation of VAL and/or ILE and followed at the Children’s Hospital Colorado Inherited Metabolic Diseases Clinic. Dietary prescriptions and plasma amino acid concentrations were obtained at multiple time points. Results: Baseline mean total protein intake for five patients was 198% of Recommended Dietary Allowance (RDA) with 107% natural protein and 91% medical food. Following intervention, total protein intake (p = 0.0357), protein from medical food (p = 0.0142), and leucine (LEU) from medical food (p = 0.0276) were lower, with no significant change in natural protein intake (p = 0.2036). At baseline, 80% of patients received VAL supplementation and 100% received ILE supplementation. After intervention, only one of the cohort remained on supplementation. There was no statistically significant difference in plasma propiogenic amino acid concentrations. Conclusions: Decreased intake of LEU from medical food allowed for discontinuation of amino acid supplementation, while meeting the RDA for protein.

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