HUMAN STUDIES OF GLN IN GUT INJURY
There have been a number of relatively small human trials determining if Gln has benefit in certain diseases. None of these trials have conclusively shown benefit in a human disease, although most likely issues of statistical power and an ineffective dosage may have masked potential benefits.
In Vitro Studies of Human Biopsy Materials
The studies have supported a role of Gln in reducing proinflammatory IL-6 and IL-8 production by intestinal biopsies, while increasing anti-inflammatory IL-10 levels in the intestinal cells and circulating mononuclear cells (Coeffier et al. 2001, 2003). When extended to in vivo randomized, controlled trials, Gln appeared to reduce morbidity and gut permeability in patients with multiorgan system trauma (Houdijk et al. 1998). A number of subsequent studies confirmed beneficial findings in critically ill patients (Avenell 2006; Coeffier et al. 2008; Sevastiadou et al. 2011). Gln has been added to total parenteral nutrition (TPN) but is rarely given orally, except in experimental studies. In practice, Gln is rarely added to parenteral nutrition (PN) solutions, largely because PN with a small amount of Gln is spontaneously cyclized at room temperature to form pyroglutamic acid (a neurotoxic substance).