Meeting Abstract
Researchers have shown that organisms choose a diet that preferences protein intake and that a misaligned protein:carbohydrate (N:C) ratio impacts body composition. We tested this hypothesis in juvenile mice in studies of Mus musculus and Peromyscus californicus. Reproductive females and their pups were fed isocaloric diets varying in N:C ratio. M. musculus pups were sacrificed at peak lactation (day 16) and P. californicus pups were sacrificed from peak lactation (day 20) through 85 days of age. Lean mass (primarily protein) was determined as total mass minus water, fat and ash mass. We predicted that pups on a low N:C diet would have lower lean body mass and greater fat mass. M. musculus pups at peak lactation on the low N:C diet had a lower total body mass and greater proportion of fat; contrary to predictions, lean mass was not different across treatments. P. californicus pups also exhibited slower growth as N:C ratio decreased and no difference in lean mass. However, in P. californicus pups, total fat was not different at 20 days and subsequently diverged between treatments with mice on the high N:C diet depositing greater amounts of fat. These results are generally consistent with the protein leveraging hypothesis. Growth rate is constrained by dietary protein and, for Mus, insufficient dietary protein results in increased fat deposition. Contrary to expectations, P. californicus on high N:C diets deposited fat at a higher rate suggesting that post-weaning juvenile mice may be hyperphagic beyond the need for leveraging protein.
