Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, C041

Oral Communications

The influence of myostatin on sexual dimorphism of human skeletal muscle

P. E. Aylwin1, B. T. Elliott1

1. University of Westminster, London, Please Select, United Kingdom.

  • Concentration of total myostatin, free myostatin, FLRG, GDF11 and Activin A (left to right, top to bottom, each pg.mL-1) as a funciton of sex (n = 39 males, 49 females). Individual data points as shown, horizontal lines indicate group means.

Sexual dimorphism in the adult human is partially characterised by larger skeletal muscle mass in the male compared to the female (Gluckmann, 1974), which is in part controlled by post-pubertal differences in circulating testosterone, growth hormone and insulin-like growth factor. Myostatin is a muscle-specific negative regulator of muscle mass (McPherron et al., 1997), acts in an endocrine manner, and can be inhibited by circulating peptides, including follistatin related gene protein (FLRG). Whilst animal studies have suggested differences in myostatin content (McMahon et al., 2003) that may be linked to growth hormone activity (Oldham et al., 2009), the role of myostatin in human sexual dimorphism has yet to be investigated. Thus, we aimed to investigate the existence of sex related differences in myostatin levels in humans, as a potential regulator of sexual dimorphism of skeletal muscle. Following written informed consent, n = 88 (39 males, 49 females; sex self-declared) healthy individuals (age range 18-68 years) took part. Participants attended in a rested fasted state. Body composition was measured by stadiometer and air volume displacement. Venous blood samples were collected and immediately centrifuged and with plasma aliquots frozen at -80oC. Plasma samples were analysed in triplicate by ELISA for total and free myostatin, FLRG and growth and differentiation factor 11 (GDF11). Values are given here as ‘mean±SE', compared by unpaired t-test (total and free myostatin, FLRG and activin A) or Mann-Whitney (GDF11) as appropriate, with statistical significance set at p>0.05 throughout. Males show greater muscle mass than females (57.59±2.03 vs 43.16±1.04 kg, p < 0.001). Total and free myostatin were significantly (p=0.008 and p=0.005 respectively) lower in females. Total myostatin was 578.00±38.60 pg.mL-1 higher in males, Free myostatin was 384.28±31.20 pg.mL-1 higher in males. This difference was no longer present when normalised to fat free mass. No other endocrine factors measured were significantly different between sexes in their absolute concentrations. Similarly, to myostatin, Activin A and GDF11 were not significantly different between males and females, when normalised to FFM. However, FLRG was significantly (p=0.004) lower in males than females, when normalised to FFM. Myostatin is a negative regulator of skeletal muscle growth and has been found in animal models to be differentially regulated between males and females, possibly accounting for mammalian sex-related differences in skeletal muscle growth. Whilst absolute myostatin (total and free) differed between sexes, normalization to FFM removed this difference, suggesting myostatin's effect on muscle mass is not sex dependent. Despite more FLRG per kg of muscle mass in females, female participants show reduced muscle mass, suggesting a sex dependent sensitivity to FLRG in the adult human.

Where applicable, experiments conform with Society ethical requirements