ADAPTATION TO PROTEIN RESTRICTION IS IMPAIRED IN INSULIN-DEPENDENT DIABETES-MELLITUS

Although mild abnormalities of amino acid metabolism frequently exist in conventionally treated insulin-dependent diabetes mellitus (IDDM), their physiologic and nutritional importance is uncertain, We tested w hether a tendency toward body N loss can be either masked or revealed in insulin-treated IDDM by changing the level of protein in the diet, After adaptation to a protein-free diet adequate in all other nutrient s, obligatory urinary N excretion of intensively treated IDDM subjects was significantly greater than normal, indicating an impaired ability to recycle endogenous amino acids during protein restriction, When th e preceding diet was high in protein, urea N production after consumpt ion of a mixed test meal matched the amount of N consumed for both nor mal and diabetic subjects, However, when the test meal was preceded by 5 d of protein restriction, conventionally treated IDDM subjects fail ed to adaptively reduce postprandial urea production as effectively as normal or intensively treated IDDM subjects, Thus, even during insuli n treatment, the ability to maximally recycle endogenous amino acids i s impaired in IDDM, as is the ability to adaptively increase dietary a mino acid retention in response to protein restriction.