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Intake of low-dose leucine-rich essential amino acids stimulates muscle anabolism equivalently to bolus whey protein in older women, at rest and after exercise
Syed SI Bukhari , Bethan E. Phillips Atherton, Daniel J. Wilkinson , Marie C Limb , Debbie Rankin , William K Mitchell , Hisamine Koboyashi , Paul L. Greenhaff , Kenneth Smith , Philip J. Atherton
American Journal of Physiology - Endocrinology and Metabolism Published 31 March 2015 Vol. no. , DOI: 10.1152/ajpendo.00481.2014
Abstract
Dysregulated anabolic responses to nutrition/exercise may contribute to sarcopenia; however, these characteristics are poorly defined in female populations. We determined the effects of two-feeding regimes in older women (66±2.5y N=8/group): bolus-whey protein (WP-20 g) or novel low-dose leucine-enriched essential amino acids (EAA) (LEAA-3g [40% leucine]). Using 13C6-Phenylalanine infusions, we quantified muscle (MPS) and albumin (APS) protein synthesis at baseline and both in response to feeding (FED) and feeding-plus-exercise (FED-EX; RE: 6×8 knee-extensions at 75%-1RM). We also quantified plasma insulin/AA concentrations, whole-leg (LBF)/muscle microvascular blood-flow (MBF), and muscle anabolic signaling by phospho-immunoblotting. Plasma insulinemia and EAA-aemia were markedly greater after WP than LEAA (P<0.001). Neither LEAA nor WP modified LBF in response to FED or FED-EX, while MBF increased to a similar extent in both groups, only after FED-EX (P<0.05). In response to FED, both WP and LEAA equally stimulated MPS 0-2h (P<0.05), abating thereafter (0-4h; P>0.05). In contrast, after FED-EX, MPS increased 0-2h and remained elevated 0-4h (P<0.05) with both WP and LEAA. No anabolic signals quantifiably increased after FED, but p70S6K1Thr389 increased after FED-EX (2h; P<0.05). APS increased similarly after WP and LEAA. Older women remain subtly responsive to nutrition±exercise. Intriguingly though, bolus-WP offers no trophic advantage over LEAA.
Syed SI Bukhari , Bethan E. Phillips Atherton, Daniel J. Wilkinson , Marie C Limb , Debbie Rankin , William K Mitchell , Hisamine Koboyashi , Paul L. Greenhaff , Kenneth Smith , Philip J. Atherton
American Journal of Physiology - Endocrinology and Metabolism Published 31 March 2015 Vol. no. , DOI: 10.1152/ajpendo.00481.2014
Abstract
Dysregulated anabolic responses to nutrition/exercise may contribute to sarcopenia; however, these characteristics are poorly defined in female populations. We determined the effects of two-feeding regimes in older women (66±2.5y N=8/group): bolus-whey protein (WP-20 g) or novel low-dose leucine-enriched essential amino acids (EAA) (LEAA-3g [40% leucine]). Using 13C6-Phenylalanine infusions, we quantified muscle (MPS) and albumin (APS) protein synthesis at baseline and both in response to feeding (FED) and feeding-plus-exercise (FED-EX; RE: 6×8 knee-extensions at 75%-1RM). We also quantified plasma insulin/AA concentrations, whole-leg (LBF)/muscle microvascular blood-flow (MBF), and muscle anabolic signaling by phospho-immunoblotting. Plasma insulinemia and EAA-aemia were markedly greater after WP than LEAA (P<0.001). Neither LEAA nor WP modified LBF in response to FED or FED-EX, while MBF increased to a similar extent in both groups, only after FED-EX (P<0.05). In response to FED, both WP and LEAA equally stimulated MPS 0-2h (P<0.05), abating thereafter (0-4h; P>0.05). In contrast, after FED-EX, MPS increased 0-2h and remained elevated 0-4h (P<0.05) with both WP and LEAA. No anabolic signals quantifiably increased after FED, but p70S6K1Thr389 increased after FED-EX (2h; P<0.05). APS increased similarly after WP and LEAA. Older women remain subtly responsive to nutrition±exercise. Intriguingly though, bolus-WP offers no trophic advantage over LEAA.
