MEAL FREQUENCY AND DIURNAL LEUCINE OXIDATION IN MATURE RATS

The hypothesis that meal frequency influences diurnal leucine oxidation, and thus leucine utilization for protein metabolism, in mature rats was studied. Therefore rats were conditioned on a liquid feed (40 mi Nutrison/day) for 6 days. In a cross-over design, either two meals of 20 mi (2 x 20; 0 and 5 h) or five meals of 8 mi (5 x 8; 0, 2, 4, 6, and 8 h) were offered within a 10-h feeding period. On day 7, rats were subjected to a constant infusion of L-[1-C-14]leucine combined with a (CO2)-C-14 breath test, covering both the postabsorptive and feeding periods. The 5 x 8 regimen resulted in a higher (CO2)-C-14 output during the postabsorptive period (p < 0.05). Ingestion of either meal profoundly increased (CO2)-C-14 output. The subsequent pattern of (CO2)-C-14 output was clearly reflecting meal frequency and size. Possible consequences of an increase in the number of meals during the feeding period for amino-acid utilization are discussed.