TY - JOUR

T1 - Divergent Anabolic Response to Exercise in Young and Older Adult Men-Dependency on Time Frame of Measurement

AU - Reitelseder, Soren

AU - Bulow, Jacob

AU - Holm, Lars

PY - 2021

Y1 - 2021

N2 - Older adults' skeletal muscle has shown to be less responsive to anabolic stimuli as compared to young both in vitro, in short and controlled in vivo settings and in long-term training studies. However, to translate controlled mechanistic findings to long-term adaptations intermediate measures allowing daily life routines with regard to activity and diet would be useful to evaluate physiological interventions. The purpose of this study was to investigate the exercise effect in young and older adults with 2 independent methods to measure muscle protein synthesis rate. Healthy young and old men were recruited to the study protocol where myofibrillar fractional synthesis rate was measured during 2 days allowing normal activities of daily living with D2O-labeled alanine and during 4 hours in the overnight fasted state with [C-13(6)]phenylalanine infusion. During this period 1 leg completed an exercise session every day (exercise leg) while the contralateral leg was kept inactive (normal leg). Both legs were used for activities of daily living. Two-day myofibrillar fractional synthesis rate was significantly higher in the exercise leg in both young and old as compared to normal leg with no age difference. The 4-hour overnight fasted myofibrillar fractional synthesis rate showed that only young exercise leg was significantly higher than normal leg. The present findings support the notion that anabolic resistance exists in the skeletal muscle of healthy older men when evaluated in controlled settings. However, this response is not as clear when measured during daily life where variance is greater, which calls for further investigations in larger cohorts.

AB - Older adults' skeletal muscle has shown to be less responsive to anabolic stimuli as compared to young both in vitro, in short and controlled in vivo settings and in long-term training studies. However, to translate controlled mechanistic findings to long-term adaptations intermediate measures allowing daily life routines with regard to activity and diet would be useful to evaluate physiological interventions. The purpose of this study was to investigate the exercise effect in young and older adults with 2 independent methods to measure muscle protein synthesis rate. Healthy young and old men were recruited to the study protocol where myofibrillar fractional synthesis rate was measured during 2 days allowing normal activities of daily living with D2O-labeled alanine and during 4 hours in the overnight fasted state with [C-13(6)]phenylalanine infusion. During this period 1 leg completed an exercise session every day (exercise leg) while the contralateral leg was kept inactive (normal leg). Both legs were used for activities of daily living. Two-day myofibrillar fractional synthesis rate was significantly higher in the exercise leg in both young and old as compared to normal leg with no age difference. The 4-hour overnight fasted myofibrillar fractional synthesis rate showed that only young exercise leg was significantly higher than normal leg. The present findings support the notion that anabolic resistance exists in the skeletal muscle of healthy older men when evaluated in controlled settings. However, this response is not as clear when measured during daily life where variance is greater, which calls for further investigations in larger cohorts.

KW - Alanine

KW - Daily living

KW - Deuterated water

KW - Muscle protein synthesis

KW - Phenylalanine

KW - MUSCLE PROTEIN-SYNTHESIS

KW - IN-VIVO

KW - RESISTANCE EXERCISE

KW - PHYSICAL-ACTIVITY

KW - AGE

KW - STRENGTH

KW - RATES

KW - VALIDATION

KW - (H2O)-H-2

KW - BREAKDOWN

U2 - 10.1093/gerona/glab040

DO - 10.1093/gerona/glab040

M3 - Journal article

C2 - 33539523

VL - 76

SP - 996

EP - 999

JO - Journals of Gerontology. Series A: Biological Sciences & Medical Sciences

JF - Journals of Gerontology. Series A: Biological Sciences & Medical Sciences

SN - 1079-5006

IS - 6

ER -