Glucose promotes whole-body protein synthesis from infused aminoacids in fasting man. Isotopic demonstration.

15N-glycine constant infusion, with plateau urea enrichment as the endpoint, demonstrated a clear increase in whole-body protein synthesis when glucose was added to aminoacid infusion in fasting men. Whole-body protein-breakdown rates remained unchanged. There was an unexpected fall in whole-body nitrogen turnover when the subjects were changed from an oral intake to either of the intravenous programmes: this finding, not previously reported, may be due to the decrease in gastrointestinal enzyme synthesis and intestinal-lining cell-turnover when oral intake is replaced by total parenteral nutrition.