Higher Branched-chain Amino Acids and Lower Serine Exist in the Plasma of Nondiabetic Mice: A Comparison Between High- and Low-protein Diet Conditions

Background/aim: The effects of dietary protein and carbohydrate content on the plasma amino acid profile of patients with diabetes are not fully understood. Therefore, we examined whether there are effects of diets with differing proportions of protein and carbohydrate on the plasma amino acid concentrations of control (CT) mice and mice with type 2 diabetes (db). Materials and Methods: We used db mice as an animal model of type 2 diabetes which are genetically deficient in leptin receptor. Diets with differing proportions of protein and carbohydrates (L diet: low protein/carbohydrate ratio, H diet: high protein/carbohydrate ratio) were supplied. db Mice were fed with a restriction on the basis of the consumption by CT-L mice, such that equivalent amounts of energy and fat were consumed. In CT mice fed the L or H diets, there was no significant difference in ad libitum food intake. Results: There were significant interactions between diet and genotype with respect to water intake, urine volume, urinary glucose concentration, and plasma isoleucine, leucine, valine, branched-chain amino acids, and serine concentrations. db-H mice showed significantly higher water intake, urine volume, and urinary glucose than db-L mice. db Mice fed the L or H diets had similar plasma amino acid profiles, except for valine. In contrast, CT-H mice showed significantly higher valine and branched-chain amino acids and lower serine concentrations than CT-L mice. Thus, the CT-H mice were more similar to db mice fed either of the diets. Conclusion: There were different effects of the dietary protein or carbohydrate content on the plasma amino acid profiles between nondiabetic and diabetic mice. In particular, the profiles in nondiabetic conditions were different between the low-and high-protein diet conditions.