Author(s): HANQUET, M., MALLINSON, J., SHETH, A., COOPER, S., GREENHAFF, P.L., PEÇANHA, T., JOANISSE, S., Institution: UNIVERSITY OF NOTTINGHAM, Country: UNITED KINGDOM, Abstract-ID: 1981

INTRODUCTION:
The menopause transition is purported to accelerate age-related declines in skeletal muscle mass and risk of sarcopenia in women [1]. It is unclear whether menopause-associated declines in ovarian hormones are related to changes in skeletal muscle-related physiology, such as mitochondrial and vascular function. This ongoing study aims to compare skeletal muscle mitochondrial respiration and peripheral vascular function in pre- and post-menopausal women.
METHODS:
Healthy, recreationally active, pre-menopause (PreM: n=7; 43.5±1.6yrs; 24.4±2.8kg/m2) and post-menopause (PostM: n=8; 54.7±3.6yrs; 25.2±1.4kg/m2) women were recruited. Women on hormonal contraception or replacement therapy were excluded. Body composition (dual-energy X-ray absorptiometry, DEXA) and maximal voluntary isometric knee extensor strength (Cybex dynamometer, MVC) were assessed. Mitochondrial respiration and ADP sensitivity were measured in permeabilised vastus lateralis muscle fibres via high-resolution respirometry (Oroboros O2k). Peripheral vascular function was assessed via femoral artery blood flow during 60 seconds of passive leg movement (PLM) using Doppler ultrasonography. Blood flow velocity and arterial diameter were used to derive mean resting flow, PLM peak flow, and baseline-corrected incremental area under the curve (AUC). Data are expressed as mean ± SD; differences were assessed using Student’s independent t-test (significance set at p<0.05).
RESULTS:
PreM had greater circulating oestradiol concentration than PostM (214.6±65.9pmol·L⁻¹ vs below detection limit [<88pmol·L⁻¹]; p=0.002). Lean body mass was similar between groups (PreM: 43.9±4.8; PostM: 42.8±3.4kg; p=0.61), while fat body mass tended to be greater in PostM (28.6±9.3 vs 21.1±4.4 kg; p=0.07). MVC (PreM: 156±43; PostM: 139±33Nm) and MVC expressed relative to leg lean mass (PreM: 19.4±5.7; PostM: 18.9±2.9Nm·kg⁻¹) did not differ between groups (p>0.05). Maximal rates of muscle mitochondrial respiration did not differ between groups (p>0.05) for CI LEAK (PreM: 3.3±0.8; PostM: 4.0±1.1pmol·s⁻¹·mg⁻¹), CI-OXPHOS (PreM: 32.2±16.4; PostM: 32.4±17.4pmol·s⁻¹·mg⁻¹), or CI+II OXPHOS (PreM: 42.3±20.6; PostM: 44.3±19.8pmol·s⁻¹·mg⁻¹), nor for ADP sensitivity (apparent Km: PreM: 502.0±286.0; PostM: 271.5±222.2μM; p=0.15). Peripheral vascular function was not different between PreM and PostM, as demonstrated by no differences in resting (PreM: 351.8±144.8; PostM: 286.5±142.4ml·min⁻¹) and PLM peak (PreM: 1050.3±524.1; PostM: 957.6±397.7ml·min⁻¹) blood flow, and AUC during PLM (PreM: 405.3±376.4; PostM: 396.4±208.2ml), even when normalised to leg lean mass (p>0.05).
CONCLUSION:
Menopausal status did not affect knee extensor strength, skeletal muscle mitochondrial respiration, or peripheral vascular function. These findings suggest that reductions in circulating ovarian hormones during menopause is not a determinant of muscle adaptations in healthy, recreationally active women.

[1] Sipila S. et al., 2020 (PMID:32017473)