POSTPRANDIAL FREE FATTY-ACIDS STIMULATE ACTIVITY OF HUMAN CORTICOSTEROID-BINDING GLOBULIN

The effect of postprandial variation of free fatty acids (FFA) on seru m corticosteroid binding globulin (CBG) properties and cortisol (hydro cortisone) concentrations were explored in 11 women (20-30 yr) during 8 h after an oral load of tallow (26% C-16:0, 18% C-18:0, and 43% Cl-1 8.1), oleic-sunflower (oleic-SF; 73% C-18:1), sunflower (SF; 67% Cl-18 :2), and mixed oil (MO; 39% C-18:1 and 48% C-18:2) Serum FFA increased little after SF and MO but more than doubled in the late postprandial period (6 and 8 h) after oleic-SF (due to monounsaturated FFA) or tal low (due to saturated and monounsaturated FFA). CBG concentrations rem ained unchanged, but in relation with the postprandial elevation of se rum FFA, CBG binding activity was increased after tallow or oleic-SF a s a result of a combined two- to threefold increase in affinity consta nt and a 50% reduction in binding sites. Immunological and in vitro bi nding studies showed the changes in CBG behavior to be conformational and to be mediated mainly by monounsaturated FFA, especially C-18:1 Th e modifications of CBG properties were associated with sustained high concentrations of cortisol (suppression of midday decrease) 6 and 8 h after tallow or oleic-SF. Thus dietary FFA may have an impact on bioav ailability of glucocorticoids.