Aging and Chronic Disease
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, 0.06g/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.