Purpose: Asprosin, an orexigenic hormone that stimulates hepatic glucose release, is elevated in insulin resistance and associated with obesity. Plasma asprosin concentrations may also be related to female sex hormone levels; higher levels are reported in women with polycystic ovary syndrome (PCOS) but this may be related to peripheral insulin resistance also associated with PCOS. Clarification of female-specific factors influence on the plasma asprosin response is crucial for studies investigating asprosin. Therefore, this study determined the association of menstrual phase, oral contraceptive (OC) use (as a pharmacological influence on sex hormone levels) and training status (as a physiological influence on sex hormone levels) on plasma asprosin levels in pre-menopausal women. Methods: Fasting plasma asprosin, 17β-estradiol (E2) and progesterone, were assessed in 32 healthy untrained and trained women with regular menstrual cycles (non-OC; n = 8 untrained, n = 6 trained) or using OC (n = 10 untrained, n = 8 trained) during early follicular, late follicular and mid-luteal menstrual phases (or the time-period equivalent for OC users). Results: Asprosin was lower in OC (0.75 ± 0.38 ng mL−1) than non-OC users (1.00 ± 0.37 ng mL−1; p = 0.022). Across a cycle, asprosin was highest in the early follicular equivalent time-point in OC users (0.87 ± 0.37 ng mL−1) but highest in the mid-luteal phase in non-OC users (1.09 ± 0.40 ng mL−1). Asprosin concentrations varied more across a cycle in untrained than trained women, with higher concentrations in the early follicular phase compared to the late follicular and mid-luteal (training status-by-menstrual phase interaction p = 0.028). Conclusion: These findings highlight the importance of considering OC use, menstrual cycle phase and to a lesser extent training status when investigating circulating asprosin concentrations in females.
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