Urinary 3-methylhistidine excretion in juvenile-onset diabetics: evidence of increased protein catabolism in the absence of ketoacidosis.

Urinary 3-methylhistidine excretion (an indicator of protein catabolism) was measured in ten diabetic patients and in age and weight matched control subjects. The diabetic group, while receiving their usual insulin dose, excreted 42% more 3-methylhistidine than the control group (2.7 versus 1.9 mumole/kg body weight/24 hr). When the insulin dose of the diabetic subject was reduced by 15% or 25%, the concentrations of blood and urinary glucose were significantly increased by the rate of urinary 3-methylhistidine excretion was not increased further. These findings demonstrate augmented protein catabolism in diabetics even in the absence of ketoacidosis. It appears that blood and urine glucose levels are more sensitive to changes in insulin availability than protein catabolism.