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Persons with conventionally treated insulin-dependent diabetes mellitus (IDDM) appear to be impaired in their ability to reduce fed-state urea production appropriately in response to dietary protein restriction (Hoffer LJ, Taveroff A, and Schiffrin A. Am J Physiol 272: E59-E67, 1997). To determine whether these conclusions apply to whole body sulfur amino acid (SAA) catabolism, we used samples from this protocol to measure daily urinary sulfate excretion and fed-state sulfate production after a high-protein test meal before and after dietary protein restriction. Eight normal subjects and six IDDM subjects treated with twice-daily intermediate- and shortacting insulin consumed a mixed test meal containing 0.50 g protein/kg after adaptation to 4 days of high protein intake (1.28 g protein/kg body wt) and again after 5 days of dietary protein restriction (0.044 g/kg). Adaptation to protein restriction decreased daily urinary sulfate and urea-N excretion by ∼80%. Over the first 24 h of protein restriction, urinary sulfate excretion decreased more than urea-N excretion for both the normal and IDDM subjects. Under conditions of a high prior protein intake, fed-state sulfate production was normal for the IDDM subjects; protein restriction reduced fed-state sulfate production by 51% (normal subjects) and 59% (IDDM subjects; not significant). We conclude that whole body SAA metabolism is normal in conventionally treated IDDM before and after dietary protein restriction. SAA catabolism, as measured by fed-state sulfate production, may be a convenient and useful method to determine the extent of whole body protein dysregulation in IDDM. [ABSTRACT FROM AUTHOR]

Discusses a study that examined whether the addition of [sup 15]nitrogen (N) alanine to a test meal provides information about an adaptive change in fed-state amino acid catabolism. Serum amino acid concentration profiles; Postabsorptive and postmeal serum urea and amino acid concentrations; Postmeal N transfer into urea.

Discusses a study which demonstrated that sulfate production effectively depicts fed-state adaptation to protein restriction in humans. Relationship between urinary urea and sulfate excretion; Postmeal urea and sulfate metabolism; Discussion of results.

Investigates the use of sulphate production as an indicator of whole body sulphur amino acid catabolism so as to be able to examine nutritional factors regulating it. Model validation studies; Methods used in the study of sulphate production; Results of methionine administration.

Evaluates the accuracy of the tracer methods in measuring urea production rate (Ra) in humans. Utilization of intravenous infusions; Four different conditions for assessment; Calculation of urea Ra by isotopic steady-state equation; Underestimation of the total urea Ra for as long as eight hours.

Reports on a study of the kinetic and metabolic effects of infused leucine on humans. Plasma concentrations of leucine; Plasma concentrations of alpha-ketoisocaproid acid; Plasma concentrations of alpha-ketoisovalerate; Plasma enrichment of leucine.

Studies the metabolic adaptation to protein restriction in insulin-dependent diabetes mellitus. Plasma leucin and alanine responses to test meals after adaptation to high-protein diet and low-protein diet; Urea nitrogen (N) response to test meals after adaptation to high and low protein diets; Whole body N metabolism.