Twelve Weeks Of Endurance Training Increases Free Fatty Acid Mobilization And Reesterification In Postmenopausal Women

Abstract

Despite far-ranging interest in the metabolic consequences of aging, the effects of menopause on FFA mobilization (FFA Ra), reesterification (Rs) and oxidation have been little studied in humans. PURPOSE: We examined the effects of exercise intensity and training on rates of lipolysis, plasma free fatty acid (FFA) appearance (Ra), disappearance (Rd), Rs, and oxidation (Roxp) in postmenopausal (PM) women. METHODS: Ten sedentary but healthy women (55±0.6 yr) completed 12 wk of supervised endurance exercise training on a cycle ergometer [5 days/wk, 1 h/day, 65% peak oxygen consumption (VO2peak)]. Flux rates were determined by continuous infusion of [1-13C]palmitate and [1,1,2,3,3-2H5]glycerol during 90 min of rest and 60 min of cycle ergometer exercise during one pretraining exercise trial [65% VO2peak (PRE)] and two post-training exercise trials [at power outputs that elicited 65% pretraining VO2peak (ABT) and 65% post-training VO2peak (RLT)]. All flux data were compared using a repeated-measures ANOVA. RESULTS: Initial body weights (68.2±4.5 kg) were maintained over the course of study. Training increased VO2peak by 16.3±3.9% (1.69 ± 0.08 vs. 1.95 ± 0.08 L/min P<0.05) (Zarins ZA, Wallis GA, Faghihnia N, Johnson ML, Fattor JA, Horning MA and Brooks GA. Effects of endurance training on cardiorespiratory fitness and substrate partitioning in postmenopausal women. Metabolism 58: 9: 1338-1346, 2009). Glycerol Ra was elevated in the RLT trial (4.08 ± 0.45 vs. 5.3 ± 0.69 mmol kg-1 min-1 P<0.05), but not the ABT (4.16 ± 0.56 mmol kg−1 min-1) trial after training. Rates of plasma FFA Ra (5.7±0.8 vs 8.2±1.2 mmol kg-1 min-1), Rd (5.35 ± 0.8 vs 8.06 ± 1.3 mmol kg-1 min-1), and RoxP (3.1 ± 0.4 vs 4.9 ± 0.6 mmol kg-1 min-1) were elevated during the ABT compared to PRE trial (P<0.05). FFA Rs accounted for most (50-70%) of Rd during exercise; training reduced FFA Rs during ABT (8.1 ± 0.8 vs. 6.2 ± 1.2 umol kg-1 min-1), but not RLT (11.3 ± 2.0 umol kg-1 min-1 P<0.05) compared to PRE. CONCLUSIONS: We conclude that, in spite of the large age-related decrease in metabolic scope in PM women, endurance training increases the capacities for FFA mobilization and oxidation during exercises of a given power output. However, after menopause total lipid oxidation capacity remains low, with reesterification accounting for most of FFA Rd. Supported by NIH grant R01 AR042906