Glutamine Extraction by the Gut Is Reduced in Patients with Depleted Gastrointestinal Cancer

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Abstract
Glutamine is an important fuel for the intestinal mucosa. However, glutamine pools may become depleted in the cancer-bearing host as a result of tumor consumption and diminished production due to nutritional depletion. As human data are lacking, the authors investigated glutamine extraction by different sites of the human intestine, including tumor and the potential relation with the degree of nutritional depletion. Thirty-two patients with gastrointestinal malignancies were studied. Blood from an artery and veins draining jejunum, ileum, colon, or tumor were sampled. Depletion was estimated by the percentage ideal body weight. Fractional glutamine extraction rate in the jejunum was 24%, three times higher than in ileum and colon. Percentage ideal body weight correlated with arterial glutamine levels (r = 0.5275, p = 0.003). In addition, arterial glutamine concentrations were correlated with extraction in the ileum (r = -0.8411, p < 0.001). Colon-containing tumor did not extract more glutamine than did nontumor-containing colon. Glutamine is a quantitatively more important substrate for the proximal intestine than for the distal gut. Nutritional depletion results in decreased arterial glutamine concentration, which in turn results in diminished extraction. Colon cancer does not function as a glutamine trap and does not contribute to glutamine depletion.