LAT1 and SNAT2 Protein Expression and Membrane Localization of LAT1 Are Not Acutely Altered by Dietary Amino Acids or Resistance Exercise Nor Positively Associated with Leucine or Phenylalanine Incorporation in Human Skeletal Muscle.
Level 3 - non-randomized controlled study
Non-randomized parallel-group trial in humans
PubMed 34836160 · doi:10.3390/nu13113906
What was done
Fourteen healthy young males consumed a carbohydrate (0.75 g·kg⁻¹) and amino acid (0.25 g·kg⁻¹) beverage enriched with L-[1-¹³C]leucine and L-[ring-²H₅]phenylalanine either at rest (FED: n = 7, 23 ± 5 y, 77 ± 4 kg) or after a bout of resistance exercise (EXFED: n = 7, 22 ± 2 y, 78 ± 11 kg). Muscle biopsies were taken at 0, 120, and 300 min postprandial to assess LAT1 and SNAT2 protein expression (immunoblot), LAT1 membrane localization (immunofluorescence), and dietary amino acid incorporation into myofibrillar protein (ΔLEU and ΔPHE).
What was found
Basal LAT1 and SNAT2 protein contents correlated with each other (r = 0.55, p = 0.04), but their expression did not change over time in either group (all p > 0.05). LAT1 membrane localization (outer 1.5 µm intensity or membrane-to-fiber ratio) did not change across time in FED or EXFED (all p > 0.05). Basal SNAT2 expression was not correlated with ΔLEU or ΔPHE (all p ≥ 0.05). Basal LAT1 expression negatively correlated with ΔPHE in FED (r = -0.76, p = 0.04) and EXFED (r = -0.81, p = 0.03), but not with ΔLEU (p > 0.05). Basal LAT1 membrane localization did not correlate with ΔLEU or ΔPHE (all p > 0.05).
Why it matters
The findings suggest that acute postprandial and post-exercise stimulation of myofibrillar protein synthesis in healthy young men occurs without rapid changes in LAT1 or SNAT2 protein expression or LAT1 translocation to the sarcolemma.
Limits
The study had a very small sample size (n = 7 per group) and included only young, healthy males. Randomization was not explicitly stated in the abstract, and functional amino acid transport kinetics were not directly measured.
Cited by
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