Playford R J, Woodman A C, Clark P, Watanapa P, Vesey D, Deprez P H, Williamson R C, Calam J
Department of Medicine, Royal Postgraduate Medical School, London, UK.
Lancet. 1993 Apr 3;341(8849):843-8. doi: 10.1016/0140-6736(93)93057-8.
Intestinal atrophy contributes to the clinical difficulties of patients who cannot eat normally. Atrophy is prevented by luminal food proteins but not by the equivalent aminoacids. This observation is not explained by current theories of intestinal physiology. Epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) are secreted into the gut lumen. We speculated that these are digested by pancreatic enzymes in fasting juice, but preserved when food proteins block the active sites of these enzymes. Studies based on molecular size and bioactivity confirmed that fasting human jejunal juice destroys EGF and TGF alpha. EGF, but not TGF alpha, was preserved when the milk protein casein or an enzyme inhibitor were present; elemental diets were ineffective. Diversion of pancreatic juice to the mid point of the small intestine in rats significantly increased luminal EGF-like bioactivity and all variables of growth in the proximal enzyme-free segment. Our findings support a novel mechanism of control of intestinal growth, which has important clinical implications. The addition of enzyme-inhibiting proteins such as casein to elemental diets may preserve intestinal integrity and function.
肠道萎缩会给无法正常进食的患者带来临床难题。腔内食物蛋白质可预防萎缩，但等量氨基酸却无法做到。目前的肠道生理学理论无法解释这一现象。表皮生长因子（EGF）和转化生长因子α（TGFα）会分泌到肠腔中。我们推测，它们在空腹胃液中会被胰酶消化，但当食物蛋白质阻断这些酶的活性位点时则得以保留。基于分子大小和生物活性的研究证实，空腹人空肠液会破坏EGF和TGFα。当存在乳蛋白酪蛋白或酶抑制剂时，EGF得以保留，而TGFα则不然；要素饮食无效。将大鼠的胰液引流至小肠中点可显著提高肠腔中EGF样生物活性以及近端无酶段的所有生长变量。我们的研究结果支持一种控制肠道生长的新机制，这具有重要的临床意义。在要素饮食中添加酪蛋白等酶抑制蛋白可能会维持肠道完整性和功能。
