ECSS Paris 2023: OP-PN24
INTRODUCTION: A single exercise bout can increase circulating levels of exerkines essential for neuroplasticity, such as mature BDNF (mBDNF), proBDNF and lactate (LAC) [1, 2]. Increases in these exerkines may furthermore be influenced by BDNF genotype [3] and muscle fiber type (FT) [2, 4]. This study investigated acute effects of exercise intensity on mBDNF, proBDNF and LAC, and how these effects are influenced by BDNF genotype and FT. METHODS: Healthy, physically fit adults (n=16, 8 females, 31±6 yrs, body mass index 22.4±1.5, VO2max 54.9±4.1 mL/kg/min) cycled for 20 min at 40% (I40), 60% (I60) and 80% (I80) of VO2max, separated by 30-min rest. Forearm venous plasma LAC (mmol/L), serum mBDNF (pg/mL) and plasma proBDNF (pg/mL) were analysed in blood samples taken before and after cycling at each intensity. A muscle biopsy was used to identify participants with dominance of slow-twitch (%Type I>50, n=10) or fast-twitch (%Type I<50, n=6) muscle fibers. The BDNF rs6265 polymorphism was genotyped to identify Val66Met (G/A, n=5) or Val66Val (G/G, n=11) gene carriers. Linear mixed-effects models were used to assess the effects of time, intensity, as well as interactions with BDNF genotype and FT. Associations between exercise-induced changes (delta) in LAC, mBDNF and proBDNF were assessed with Spearman correlation. A significance level was set at p<0.05. All summary statistics are expressed as mean ± SEM. RESULTS: LAC increased by 51% after exercise at I60 (1.3±0.1 vs 1.9±0.2, p<0.05) and by 495% at I80 (1.0±0.1 vs. 5.8±0.5, p<0,001). mBDNF increased by 16% after exercise at I40, by 30% at I60 and by 41% at I80 (10804.4±528.8 vs 12584.1±559.2, p<0.05; 10972.3±472.8 vs 14213.9±555.5, p<0.001 and 11279.3±643.0 vs 15900.0±985.9, p<0.001, respectively). proBDNF increased only after exercise at I80 (211.6±79.4 vs 317.9±109.2, p<0.001). The I80 effect on LAC was 65% larger in G/A versus G/G carriers (p<0.001). The I80 effect on mBDNF was 43% larger in participants with fast-twitch FT dominance (p<0.05). A non-significant trend of higher proBDNF levels in G/G carriers (p=0.06) was shown, irrespective of time and intensity. At I80, delta LAC was positively associated with delta mBDNF (r = 0.58, p=0.025), but not with delta proBDNF. CONCLUSION: Exercise acutely induced intensity-dependent effects on LAC, mBDNF and proBDNF. Results furthermore suggest that these effects can indeed be influenced by BDNF genotype and FT. While an indication of higher proBDNF was shown in G/G carriers, delta LAC at I80 was higher in G/A carriers. However, in contrast to previous reports of G/As negative effect on aerobic training response [3], the acute mBDNF response was independent of BDNF genotype. Finally, higher neurotrophic response to aerobic exercise (higher delta mBDNF) was indicated in individuals with fast-twitch FT dominance. REFERENCES: 1. Dinoff, A. et al., Eur J Neurosci, 2017. 2. Edman, S. et al. Function (Oxf), 2024. 3. Lemos, J.R. et al., Physiol Genomics, 2016. 4. Mazo, C.E. et al., Brain Plast, 2022.
Read CV Olga TarassovaECSS Paris 2023: OP-PN24
INTRODUCTION: The relationship between sex steroid hormones and skeletal muscle mass and function remains ambiguous in males, with much of our knowledge stemming from research relying on exogenous manipulation of testosterone. This study aimed to address the relationship between endogenous sex steroid hormones and muscle outcomes across the male lifespan. METHODS: 82 biological males, aged 18-80 years and stratified by decade, participated in this study. Body composition was assessed via dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed topography (pQCT). Muscle strength was assessed using a leg press 5-repetition maximum (5RM) test. In a fasted state, a muscle biopsy was procured from the vastus lateralis and a venous blood sample taken. Testosterone and dihydrotestosterone were profiled using gas-chromatography mass-spectrometry, and sex-hormone-binding-globulin (SHBG) measured via immunoassay. Free testosterone was estimated using the Vermeulen equation and the free androgen index (FAI). Transcriptomic analysis were performed using RNA-sequencing, and muscle samples were immunohistochemically stained to assess fibre morphology and type. All analyses were performed using RStudio (version 4.3.1). RESULTS: Free testosterone (β = -0.004, p < 0.001) and FAI (β = -0.669, p < 0.001) decreased with age and were associated with measures of body composition and muscle strength. However, these relationships became non-significant following adjustment for age, physical activity and dietary protein (p > 0.05). Age was positively associated with bodyfat percentage (β = 0.129, p = 0.02) but not with intramuscular or subcutaneous fat mass (p > 0.05), and was negatively associated with thigh muscle cross-sectional area (CSA) (β = -0.65, p < 0.001), appendicular lean mass (ALM) (β = -0.09, p < 0.001), ALM index (ALM normalised to height) (β = -0.018, p = 0.028); relationships that remained significant following adjustment for physical activity, dietary protein, total testosterone, free testosterone, and FAI. CONCLUSION: Our results suggest that age, not endogenous testosterone concentrations, is a primary determinant of muscle outcomes. Ongoing transcriptomic analysis aims to map muscle signalling pathways throughout the aging continuum and determine the influence, or lack thereof, of sex steroid hormones on skeletal muscle gene expression across the male lifespan.
Read CV Ross WilliamsECSS Paris 2023: OP-PN24
INTRODUCTION: Antarctic expeditions present extreme physiological challenges due to cold temperatures, high physical exertion, and 24-hour daylight. This observational study evaluated endocrine adaptation in nine participants (six men, three women) during a 47-day, 1,000 km unassisted ski expedition (Ex). METHODS: Saliva was sampled at 5 times of day on 8 occasions: 30 d and 14 d before, 3 times during (1 d, 15 d, 30 d) and 3 times after the Ex (+1 d, +6 d, +30 d). Hair was sampled before, during after the expedition. Blood was sampled before and after. Cortisol, testosterone (T), and androstenedione (A4) were measured via tandem mass spectrometry, and thyroid hormones via immunoassay. Diurnal slope (DS) and Area under the curve (AUC) was calculated for saliva steroids. Body mass and body composition (skinfold thickness) was measured throughout the expedition. Body composition was measured before and after by DXA. The effect of time and sex X time were assessed with Aligned Rank Transform test. RESULTS: Cortisol, A4 and T DS were preserved throughout the Ex. Average cortisol concentration increased during the Ex (p<0.05) and reverted to baseline over the next 15d with no sex differences. Morning T and T:cortisol ratio decreased during the Ex with a greater effect seen among men. Post-ex recovery of T was demonstrated in men. A4:cortisol ratio decreased during the Ex and recovered afterwards with no sex differences. No significant changes were seen in blood or hair steroid hormones. Gonadotropins in women indicated central suppression pre-expedition, normalizing post-expedition. Thyroid-stimulating hormone levels increased post-expedition without significant changes in free T3 or T4, consistent with mild polar T3 syndrome. Weight decreased during the Ex (79.7±20.6 vs 72.6±8.6kg) with near-linear decrease in FM for all participants, but a smaller rate of decrease for women than men (p<0.05). FFM decreased overall but with substantial inter-individual variation, being relatively preserved among women. A sex-dimorphic clustering of body composition occurred after 30d. DEXA showed regional FM loss and FFM gain, especially in the trunk. CONCLUSION: These findings highlight the adaptability of hypothalamic-pituitary function to combined stressors of exercise, energy deficit, and cold. Exercise demands overshadowed the effects of continuous daylight in controlling hypothalamic-pituitary-adrenal and gonadal axis function. This is the first study to capture in situ endocrine responses during an Antarctic traverse, advancing our understanding of human endocrine adaptation to exercise in extreme environments.
Read CV Robert GiffordECSS Paris 2023: OP-PN24