Effects Of Collagen Peptide Versus Free Amino Acid Ingestion On Muscle Connective Protein Synthesis Rates

Collagen protein ingestion has been suggested to increase connective protein synthesis rates. Such anabolic properties may be attributed to the delivery of amino acid precursors and/or to the anabolic signaling properties of bioactive peptides that have been proposed to be present in (hydrolyzed) collagen. PURPOSE: To assess the impact of ingesting a single bolus of collagen protein or an equivalent amount of free amino acids on myofibrillar and muscle connective protein synthesis rates. METHODS: In a randomized, double blind, parallel design, 45 young male (n = 21) and female (n = 24) adults (age: 23 ± 3y; BMI: 22.3 ± 2.2 kg/m2) received intravenous infusions with L-[ring-13C6]-phenylalanine. Following unilateral resistance exercise, subjects ingested either 30 g collagen protein (COLL, n = 15), 30 g of free amino acids reflecting the amino acid profile of collagen (AA, n = 15), or a non-caloric placebo (PLA, n = 15). Blood and muscle samples were collected over 6 h to assess myofibrillar and muscle connective protein synthesis rates. RESULTS: Both collagen and free amino acid ingestion strongly increased circulating plasma amino acids levels. Myofibrillar protein synthesis rates were higher in the exercised leg (0.049 ± 0.010, 0.048 ± 0.011, and 0.045 ± 0.013%·h−1) when compared to post-absorptive values (0.033 ± 0.011, 0.029 ± 0.012, and 0.032 ± 0.016%·h−1) and rates observed in the rested leg (0.039 ± 0.011, 0.037 ± 0.010, and 0.036 ± 0.015%·h−1 in PLA, COLL and AA, respectively; P < 0.001) with no differences between groups (P > 0.05). Muscle connective protein synthesis rates were higher in the exercised leg (0.098 ± 0.023, 0.092 ± 0.028, and 0.085 ± 0.024%·h−1) when compared to post-absorptive values (0.060 ± 0.022, 0.058 ± 0.022, and 0.061 ± 0.022%·h−1) and rates observed in the rested leg (0.065 ± 0.014, 0.063 ± 0.017, and 0.061 ± 0.025%·h−1 in PLA, COLL and AA, respectively; P < 0.001), with no differences between groups (P > 0.05). CONCLUSIONS: Resistance exercise increases myofibrillar and muscle connective protein synthesis rates. Ingestion of collagen or an equivalent amount of free amino acids during recovery from exercise strongly increases plasma amino acid levels but does not further increase myofibrillar or muscle connective protein synthesis rates in healthy, recreationally active, young men and women.