Cerebral blood flow, frontal lobe oxygenation and intra-arterial blood pressure during sprint exercise in normoxia and severe acute hypoxia in humans.

Cerebral blood flow (CBF) is regulated to secure brain O2 delivery while simultaneously avoiding hyperperfusion; however, both requisites may conflict during sprint exercise. To determine whether brain O2 delivery or CBF is prioritized, young men performed sprint exercise in normoxia and hypoxia (PIO2 = 73 mmHg). During the sprints, cardiac output increased to ∼22 L min-1, mean arterial pressure to ∼131 mmHg and peak systolic blood pressure ranged between 200 and 304 mmHg. Middle-cerebral artery velocity (MCAv) increased to peak values (∼16%) after 7.5 s and decreased to pre-exercise values towards the end of the sprint. When the sprints in normoxia were preceded by a reduced PETCO2, CBF and frontal lobe oxygenation decreased in parallel ( r = 0.93, P < 0.01). In hypoxia, MCAv was increased by 25%, due to a 26% greater vascular conductance, despite 4-6 mmHg lower PaCO2 in hypoxia than normoxia. This vasodilation fully accounted for the 22 % lower CaO2 in hypoxia, leading to a similar brain O2 delivery during the sprints regardless of PIO2. In conclusion, when a conflict exists between preserving brain O2 delivery or restraining CBF to avoid potential damage by an elevated perfusion pressure, the priority is given to brain O2 delivery.

Greater basal skeletal muscle AMPKα phosphorylation in men than in women: Associations with anaerobic performance.

OBJECTIVES: This study was designed to investigate the association of gender, fibre type composition, and anaerobic performance with the basal skeletal muscle signalling cascades regulating muscle phenotype. DESIGN: Muscle biopsies were obtained from 25 men and 10 women all young and healthy. METHODS: Protein phosphorylation of Thr(172)AMPKα, Ser(221)ACCß, Thr(286)CaMKII as well as total protein abundance of PGC-1α, SIRT1, and CnA were measured by Western blot and anaerobic performance by the Wingate test. RESULTS: Percent type I myosin heavy chain (MHC I) was lower in men (37.1 ± 10.4 vs. 58.5 ± 12.5, P < .01). Total, free testosterone and free androgen index were higher in men (11.5, 36.6 and 40.6 fold, respectively, P < .01). AMPKα phosphorylation was 2.2-fold higher in men compared to women (P < .01). Total Ser(221)ACCß and Thr(286)CaMKII fractional phosphorylation tended to be higher in men (P = .1). PGC1-α and SIRT1 total protein expression was similar in men and women, whereas CnA tended to be higher in men (P = .1). Basal AMPKα phosphorylation was linearly related to the percentage of MHC I in men (r = 0.56; P < .01), but not in women. No association was observed between anaerobic performance and basal phosphorylations in men and women, analysed separately. CONCLUSION: In summary, skeletal muscle basal AMPKα phosphorylation is higher in men compared to women, with no apparent effect on anaerobic performance.

Androgen receptor CAG and GGN repeat polymorphisms and bone mass in boys and girls / Polimorfismos CAG y GGN del gen del receptor de andrógenos y masa ósea en niños y niñas

Introduction: the human androgen receptor (AR) gene possesses two trinucleotide polymorphic repeats, (CAG and GGN) that affect the amount of AR protein translated. In this study, we genotyped these polymorphic tracts in a representative sample of Caucasian children (Tanner ≤5), 152 boys (11.5±2.6 yrs) and 116 girls (10.1±3.2 yrs) from Spain and investigated their association with bone mass. Methods: the length of CAG and GGN repeats was determined by PCR and fragment analysis. Body composition was assessed by dual energy x-ray absorptiometry (DXA). Individuals were grouped as CAG short (CAGS) if harboring repeat lengths of ≤21 and CAG long (CAGL) if CAG >21. Moreover, subjects were grouped as GGN short (GGNS) if harboring repeat lengths of ≤23 and GGN long (GGNL) if GGN >23. Results: in boys, significant differences in height, body mass, whole body bone mineral density (BMD) and content (BMC), upper extremities BMC, lower extremities BMC, femoral neck BMD, Ward’s triangle BMC and BMD and lumbar spine BMD were observed between CAGS and CAGL groups (P<0.05). Thus, upper extremities BMD differed between GGNS and GGNL groups. After adjusting for confounding variables, only upper extremities BMD between GGNS and GGNL groups remained significant (P<0.05). No differences were observed in girls in any measured site in relation to either CAG or GGN polymorphisms length. Conclusions: our results support the hypothesis that longer alleles of the AR CAG and GGN polymorphisms are associated with increased bone mass in prepubertal boys (AU)

Introducción: el gen humano del receptor de andrógenos (AR) posee dos repeticiones polimórficas de trinucleótidos (CAG y GGN) que afectan a la cantidad de proteína AR traducida. En este estudio, genotipamos esos tractos polimórficos en una muestra representativa de niños caucásicos españoles (Tanner ≤5), compuesta por 152 niños (11.5±2.6 años) y 116 niñas (10.1±3.2 años) e investigamos su asociación con la masa ósea. Métodos: la longitud de las repeticiones CAG y GGN se determinó mediante PCR y análisis de fragmentos. La composición corporal se midió mediante absorciometría dual de rayos X (DXA). Los participantes fueron agrupados como CAG cortos (CAGS) si poseían una longitud de repeticiones ≤21 y CAG largos si esta era >21. Además, los participantes se agruparon como GGN cortos (GGNS) si poseían una longitud de repeticiones ≤23 y GGN largos (GGNL) si esta era >23. Resultados: en los niños se encontraron diferencias en talla, peso corporal, densidad mineral ósea (BMD) y contenido mineral óseo (BMC) del cuerpo entero, BMC de las extremidades superiores e inferiores, BMD del cuello del fémur, BMC y BMD del triángulo de Ward’s y BMD de la espina lumbar entre los grupos CAGS y CAGL (P<0,05). Además, el BMD de las extremidades superiores fue significativamente diferente entre los grupos GGNS y GGNL. Tras ajustar por variables confusoras, la única diferencia que se mantuvo significativa fue la del BMD en las extremidades superiores entre los grupos GGNS y GGNL (P<0,05). No se observaron diferencias entre los grupos CAG y GGN y la masa ósea en las niñas. Conclusiones: nuestros resultados apoyan la hipótesis de que los alelos largos de los polimorfismos CAG y GGN del AR están asociados con una mayor masa ósea en niños prepúberes (AU)