Sams Laura, Paume Julie, Giallo Jacqueline, Carrière Frédéric
CNRS, Aix Marseille Université, Enzymologie Interfaciale et Physiologie de la Lipolyse UMR7282, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
GERME S.A., Technopôle Marseille Provence Château-Gombert, ZAC la Baronne, 12 Rue Marc Donadille, 13013 Marseille, France.
Food Funct. 2016 Jan;7(1):30-45. doi: 10.1039/c5fo00930h.
The development of in vitro digestion models relies on the availability of in vivo data such as digestive enzyme levels and pH values recorded in the course of meal digestion. The variations of these parameters along the GI tract are important for designing dynamic digestion models but also static models for which the choice of representative conditions of the gastric and intestinal conditions is critical. Simulating gastric digestion with a static model and a single set of parameters is particularly challenging because the variations in pH and enzyme concentration occurring in the stomach are much broader than those occurring in the small intestine. A review of the literature on this topic reveals that most models of gastric digestion use very low pH values that are not representative of the fed conditions. This is illustrated here by showing the variations in gastric pH as a function of meal gastric emptying instead of time. This representation highlights those pH values that are the most relevant for testing meal digestion in the stomach. Gastric lipolysis is still largely ignored or is performed with microbial lipases. In vivo data on gastric lipase and lipolysis have however been collected in humans and dogs during test meals. The biochemical characterization of gastric lipase has shown that this enzyme is rather unique among lipases: (i) stability and activity in the pH range 2 to 7 with an optimum at pH 4-5.4; (ii) high tensioactivity that allows resistance to bile salts and penetration into phospholipid layers covering TAG droplets; (iii) sn-3 stereospecificity for TAG hydrolysis; and (iv) resistance to pepsin. Most of these properties have been known for more than two decades and should provide a rational basis for the replacement of gastric lipase by other lipases when gastric lipase is not available.
体外消化模型的发展依赖于体内数据的可用性，例如在进餐消化过程中记录的消化酶水平和pH值。这些参数沿胃肠道的变化对于设计动态消化模型很重要，对于静态模型也很重要，在静态模型中，选择具有代表性的胃和肠道条件至关重要。用静态模型和单一参数集模拟胃消化特别具有挑战性，因为胃中发生的pH值和酶浓度变化比小肠中发生的变化要大得多。对该主题的文献综述表明，大多数胃消化模型使用的pH值非常低，不能代表进食状态。通过显示胃pH值随进餐胃排空而不是时间的变化来说明这一点。这种表示突出了那些与测试胃中进餐消化最相关的pH值。胃脂肪分解在很大程度上仍然被忽视，或者是用微生物脂肪酶进行的。然而，在人类和狗进食试验餐期间已经收集了关于胃脂肪酶和脂肪分解的体内数据。胃脂肪酶的生化特性表明，这种酶在脂肪酶中相当独特：(i)在pH值2至7范围内具有稳定性和活性，最适pH值为4 - 5.4；(ii)高表面活性，使其能够抵抗胆汁盐并渗透到覆盖TAG液滴的磷脂层中；(iii)对TAG水解具有sn - 3立体特异性；(iv)对胃蛋白酶有抗性。其中大多数特性已经为人所知超过二十年了，当没有胃脂肪酶时，这些特性应该为用其他脂肪酶替代胃脂肪酶提供合理的依据。
