Minimal dose of milk protein concentrate to enhance the anabolic signalling response to a single bout of resistance exercise; a randomised controlled trial

J Int Soc Sports Nutr. 2017 Jun 8:14:17. doi: 10.1186/s12970-017-0175-x. eCollection 2017.

Abstract

Background: Resistance training is a potent stimulus to induce muscle hypertrophy. Supplemental protein intake is known to enhance gains in muscle mass through activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway, which initiates protein translation. While the optimal dose of high quality protein to promote post exercise anabolism in young or older men has been investigated, little is known about the minimum doses of protein required to potentiate the resistance exercise activation of anabolic signalling in middle aged men.

Methods: Twenty healthy men (46.3 ± 5.7 years, BMI: 23.9 ± 6.6 kg/m2) completed a single bout of unilateral resistance exercise consisting of 4 sets of leg extension and press at 80% of 1 repetition maximum. Participants were randomised to consume either formulated milk product containing 9 g milk protein (FMP) or an isoenergetic carbohydrate placebo (CHO) immediately post exercise, in a double blind fashion. A single muscle biopsy was collected at pre-exercise baseline and then bilateral biopsies were collected 90 and 240 min after beverage consumption.

Results: P70S6KThr389 phosphorylation was increased with exercise irrespective of group, P70S6KThr421/Ser424 was increased with exercise only in the FMP group at 240 min. Likewise, rpS6 Ser235/236 phosphorylation was increased with exercise irrespective of group, rpS6 Ser240/244 increased to a greater extent following exercise in the FMP group. mRNA expression of the amino acid transporter, LAT1/ SLC7A5 increased with both exercise and beverage consumption irrespective of group. PAT1/ SLC36A1, CAT1/ SLC7A1 and SNAT2/ SLC38A2 mRNA increased only after exercise regardless of group.

Conclusions: Nine grams of milk protein is sufficient to augment some measures of downstream mTORC1 signalling after resistance exercise but does not potentiate exercise induced increases in amino acid transporter expression. Formulated products containing nine grams of milk protein would be expected stimulate muscle anabolism after resistance exercise.

Trial registration: New Zealand Clinical Trials Registry ACTRN12615001375549. Registered: 17 December, 2015.

Keywords: Middle age; P70SK; Protein phosphorylation; Skeletal muscle; Supplement.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Amino Acid Transport System A / metabolism
  • Amino Acid Transport Systems / metabolism
  • Cationic Amino Acid Transporter 1 / metabolism
  • Double-Blind Method
  • Exercise / physiology*
  • Humans
  • Large Neutral Amino Acid-Transporter 1 / metabolism
  • Male
  • Mechanistic Target of Rapamycin Complex 1 / metabolism
  • Middle Aged
  • Milk Proteins / administration & dosage*
  • Phosphorylation
  • Resistance Training*
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism*
  • Symporters / metabolism

Substances

  • Amino Acid Transport System A
  • Amino Acid Transport Systems
  • Cationic Amino Acid Transporter 1
  • Large Neutral Amino Acid-Transporter 1
  • Milk Proteins
  • SLC36A1 protein, human
  • SLC38A2 protein, human
  • SLC7A1 protein, human
  • Symporters
  • Mechanistic Target of Rapamycin Complex 1
  • Ribosomal Protein S6 Kinases, 70-kDa