Dietary lipids modify brush border membrane composition and nutrient transport in chicken small intestine

The influence of dietary fatty acids (FA) on intestinal brush border FA composition and nutrient transport functions was studied in broiler chickens. Ross chicks (2 wk old) were fed for 14 d a standard diet (CTL) or diets enriched with saturated fatty acids (SFA; 60 g/kg lard, LAR diet), (n-3) PUFA (60 g/kg linseed oil, LSO diet) and (n-6) PUFA (60 g/kg sunflower oil, SFO diet). The SFA of the brush border membrane were within 40-44% of total FA in spite of wide variability in dietary SFA concentration (13-32%); membrane (n-6) and (n-3) PUFA strongly reflected their dietary intake and thus the (n-6)/(n-3) ratio. However, the membrane polyunsaturated/saturated ratio (P/S) was close to unity, whereas in the diets, it was between 0.9 and 5. The transport kinetic constants (V(max), K(m), K(d)) of D-glucose (substrate of the sodium glucose cotransporter 1), L-lysine (through systems b(0,+) and y(+)(m)) and L-methionine (through systems B and L) were studied in jejunal brush border membrane vesicles. The changes in dietary FA intake did not affect the K(m) of the substrates for their transporters. Both LAR and SFO diets reduced the D-glucose V(max), which was compensated for by an increase in the K(d). The LAR diet reduced lysine transport across y(+)(m), whereas the LSO diet increased the V(max) for both lysine and methionine.