Effects of tuberculosis and HIV infection on whole-body protein metabolism during feeding, measured by the [15N]glycine method.

BACKGROUND Tuberculosis (TB) and HIV infection are wasting diseases that frequently occur together and have severe consequences on nutritional status. OBJECTIVE The objective was to determine the effects of TB and HIV, separately and together, on protein metabolism. DESIGN Protein metabolism was determined in the fed state in 11 healthy control subjects, in 10 patients with HIV infection without TB or other active infection (HIV group), in 10 patients with active TB without HIV infection (TB group), and in 8 patients with HIV infection and active TB (HIVTB group) with the use of oral [(15)N]glycine and measurement of enrichment in urinary urea and ammonia. RESULTS Whole-body protein flux and degradation were lower in the HIV group than in the control group (mean flux: 3.53 +/- 0.40 compared with 4.75 +/- 0.97 g. kg lean body mass(-1). 12 h(-1); P = 0.002). Protein flux, synthesis, and degradation were not significantly different between the control group and the TB and HIVTB groups. Net protein balance was strongly anabolic in the control, HIV, and TB groups but was neutral in the HIVTB group (P < 0.001 for comparison between groups). CONCLUSIONS HIV infection was associated with a significant down-regulation of whole-body protein flux. TB alone was not associated with abnormal protein metabolism, but net anabolism in the fed state was impaired in the HIVTB group.