FOLLISTATIN HAS A BIPHASIC RESPONSE BUT FOLLICLE-STIMULATING-HORMONE IS UNCHANGED DURING AN INFLAMMATORY EPISODE IN GROWING LAMBS

The effects on plasma follistatin concentrations of an inflammatory ep isode, induced by the intrathoracic injection of yeast, were examined in growing lambs; this model results in acute loss of appetite, food i ntake and liveweight and the activation of the acute-phase pathway for several weeks as adjudged by the production of haptoglobin and other acute-phase proteins. In these animals (n = 8) there was a biphasic re sponse in follistatin concentrations, with an initial 200% increase (P < 0.001) in follistatin within 24 h of injection of yeast. Thereafter , follistatin concentrations were depressed to 70% of pretreatment lev els 48 h after injection (P < 0.01), followed by a gradual recovery of concentrations to pretreatment values. In another group of lambs (n = 16) that were feed-restricted to mimic the reduced food intakes and l iveweight changes in the yeast-injected group, plasma follistatin was also reduced to around 70% of pretreatment levels (P < 0.01) within 1 day of the dietary regimen being implemented, followed by a gradual re turn to pretreatment values as food intakes were increased. Plasma fol listatin correlated significantly (r = 0.57, P < 0.0001) with food int ake, but not with liveweight changes. Plasma follistatin concentration s were unchanged in a third group fed ad libitum (n = 8), except durin g two periods when food intakes were significantly (P < 0.05) reduced, when follistatin concentrations also decreased (P < 0.01). Plasma fol licle-stimulating hormone (FSH) concentrations in the three groups of lambs were not significantly affected by the treatment regimes or chan ges in follistatin concentrations. These findings indicate that periph eral follistatin concentrations are modulated by both inflammatory and nutritional mechanisms, and that significant fluctuations in follista tin levels can occur without detectable perturbations in FSH secretion .