L-citrulline With Low-intensity Resistance Training Improves Endothelial Function And Lean Mass In Postmenopausal Women

Aging and menopause lead to low L-arginine (ARG) availability, the substrate for nitric oxide (NO) synthesis, causing endothelial dysfunction. Endothelial dysfunction is associated with muscle mass loss in older adults. L-citrulline supplementation (CIT), the precursor of ARG and NO, has improved endothelial function in older women and lean mass (LM) in malnourished older women. Low-intensity resistance training (LIRT) alone enhanced endothelial function and strength, but not LM in older women. PURPOSE: To investigate the effects of CIT alone and combined with LIRT on endothelial function and appendicular LM index (ALMI) in postmenopausal women. METHODS: Twenty-six postmenopausal women (aged 63 ± 1 years) were randomized to either 10 g/day of CIT (n = 14) or placebo (PL, n = 12) alone for 4 weeks and combined with LIRT (CIT + LIRT or PL + LIRT) for another 4 weeks. Serum ARG levels and brachial artery flow-mediated dilation (FMD) were assessed at 0, 4, and 8 weeks. ALMI was determined using a whole-body dual-energy X-ray absorptiometry (DXA) scan and calculated as (arm LM + leg LM)/height2. RESULTS: There were significant group-by-time interactions for ARG, FMD, and ALMI (all P < 0.01). CIT increased ARG levels from 0 to 4 weeks (CIT: Δ14 ± 2 vs. PL: Δ-2 ± 1 μmol/L, P < 0.01) and from 4 to 8 weeks (CIT + LIRT: Δ6 ± 1 vs. PL + LIRT: Δ3 ± 1 μmol/L, P < 0.05) compared to PL. CIT enhanced FMD after 4 weeks (CIT: Δ0.8 ± 0.5 vs. PL: Δ-0.7 ± 0.4, P < 0.05), and further improved after 8 weeks compared to PL (CIT + LIRT: Δ1.9 ± 0.5 vs. PL + LIRT: Δ-0.1 ± 0.3, P < 0.01). ALMI did not increase after CIT alone, but increased after 8 weeks (CIT + LIRT: Δ0.2 ± 0.1 vs. PL + LIRT: Δ0 ± 0, P < 0.01). CONCLUSION: CIT supplementation alone enhanced ARG but not ALMI. When CIT is combined with LIRT has an additive effect on increasing ARG, endothelial function, and ALMI. Our findings suggest that CIT supplementation combined with LIRT leads to greater improvement in endothelial function and LM in postmenopausal women.