Regulation of Amino Acid Transporters and Sensors in Response to a High protein Diet: A Randomized Controlled Trial in Elderly Men.
Study Goal
The researchers aimed to determine whether consuming twice the recommended daily allowance (RDA) of protein affects the expression of amino acid transporters, sensors, and mTORC1 activity in older men.
Results Summary
Consuming twice the RDA of protein reduced LAT1 expression but did not alter mTORC1 activity or plasma leucine levels. Total RPS6 increased, suggesting potential improvements in muscular translational capacity.
Population
Older men aged 70-81 years.
Effective Dosage
0.8 g/kg/d (RDA) and 1.6 g/kg/d (2RDA).
Duration
10 weeks.
Interactions
None mentioned.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
consumption of a diet containing twice the recommended daily allowance (RDA) of protein intake (2RDA) for ten weeks | decrease | protein expression of L-type amino acid transporter 1 (LAT1) | 26 older men (70-81 years) | - | reduced | #1 |
consumption of a diet containing twice the recommended daily allowance (RDA) of protein intake (2RDA) for ten weeks | no change | plasma leucine concentration | 26 older men (70-81 years) | - | unaltered | #2 |
consumption of a diet containing twice the recommended daily allowance (RDA) of protein intake (2RDA) for ten weeks | no change | basal mTORC1 activity | 26 older men (70-81 years) | - | unaltered | #3 |
consumption of a diet containing twice the recommended daily allowance (RDA) of protein intake (2RDA) for ten weeks | no change | expression of AA sensors and mediators, including leucyl tRNA synthetase (LRS), cytosolic arginine sensor for mTORC1 (CASTOR1), Sestrin2 and Rag proteins | 26 older men (70-81 years) | - | did not affect | #4 |
consumption of a diet containing twice the recommended daily allowance (RDA) of protein intake (2RDA) for ten weeks | increase | total ribosomal protein S6 (RPS6) | 26 older men (70-81 years) | - | upregulated | #5 |
Ten weeks of 2RDA diet | no change | fasting mTORC1 signaling | 26 older men (70-81 years) | - | did not affect | #6 |
Ten weeks of 2RDA diet | increase | total RPS6 | 26 older men (70-81 years) | - | increased | #7 |
BACKGROUND: The mammalian target of rapamycin complex 1 (mTORC1) is fundamental for many cellular processes, yet it is often dysregulated with aging. Increased amino acid (AA) availability is correlated with the expression of AA transporters (AAT) and mTORC1 activity. Although many AA sensors and mediators have been proposed to relay the AA signal to mTORC1, it has not yet been determined if chronic dietary intervention affects the expression of AAT, sensors and mediators and their relationships with mTORC1 activity. OBJECTIVE AND DESIGN: This study investigated whether the consumption of a diet containing either the current recommended daily allowance (RDA) of protein intake (0.8 g/kg/d) or twice the RDA (2RDA) for ten weeks affected the expression of targets associated with AA transport, sensing and mTORC1 regulation in 26 older men (70-81 years). METHOD: Muscle biopsies were collected before and after the intervention under fasting conditions. Diets were controlled by providing fully prepared meals and snacks. Western blot and quantitative polymerase chain reaction were used to measure protein and gene expression respectively. RESULTS: Consumption of 2RDA reduced the protein expression of L-type amino acid transporter 1 (LAT1). However, plasma leucine concentration and basal mTORC1 activity were unaltered. The downregulation of LAT1 did not affect the expression of AA sensors and mediators, including leucyl tRNA synthetase (LRS), cytosolic arginine sensor for mTORC1 (CASTOR1), Sestrin2 and Rag proteins. Instead, total ribosomal protein S6 (RPS6) was upregulated with 2RDA. CONCLUSION: Ten weeks of 2RDA diet did not affect the fasting mTORC1 signaling, but increased total RPS6 might suggest improved muscular translational capacity to maintain muscular mass.