Abstract
Objectives
Older adults are at increased risk of being hospitalized or bedridden and experiencing a host of negative health outcomes including loss of lean body mass. We hypothesized that supplementing daily meals with a small quantity (3–4 g/meal) of leucine will partially preserve lean leg mass and function during bed rest.
Methods
Men and women (67.8 ± 1.1 y) were randomized to receive isoenergentic meals supplemented with leucine (LEU, 0.06 g/kg/meal; n = 10) or an alanine control, (CON, 0.06 g/kg/meal; n = 10). Subjects were admitted to the Clinical Research Center for 7 days of bed rest followed by 7 days of rehabilitation. Muscle fiber type and cross-sectional area (CSA) as well as single fiber characteristics were assessed from biopsies of the vastus lateralis obtained prior to (Pre-BR) and after bed rest (Post-BR) and after rehabilitation (Post-RE). Body composition measured using iDEXA was also determined at the same time points.
Results
Leucine-supplementation partially protected leg lean mass during bed rest (−1035 vs. −423 ± 143 g; P = 0.008). Leg lean mass did not differ between the groups Post-RE (P = 0.16). There was no significant effect of time (P = 0.16) or treatment (P = 0.92) on muscle fiber CSA; however, CON subjects, but not LEU subjects, exhibited an increased number of smaller fibers (<2000 um) and fewer larger fibers (>6000 um) Post-BR. Additionally, CON subjects tended to have a greater decrement in fiber width (P = 0.085) that did not return to baseline following rehabilitation.
Conclusions
Supplementing older adults with moderate amounts of leucine has the potential to partially negate some of the deleterious effects on muscle health during short bouts of inactivity.
Funding Sources
National Institutes of Health, The Claude D. Pepper Older Americans Independence Center, Sealy Center on Aging and Institute for Translational Sciences-Clinical Research Center.
Key Recommendations from the 2021 “Inclusion of Older Adults in Clinical Research” Workshop
