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Digestion Patterns of Endogenous and Different Exogenous Proteins Affect the Composition of Intestinal Effluents in Humans^1,2,

Agnès Baglieri, Sylvain Mahé³, Robert Benamouzig^*, Laurent Savoie and Daniel Tomé

Institut National de la Recherche Agronomique, Unité de Nutrition Humaine et de Physiologie Intestinale, Faculté des Sciences Pharmaceutiques et Biologiques, 75006 Paris, France ^* Service de Gastroentérologie, Hôpital Avicenne, 93009 Bobigny, France Département de Nutrition Humaine et de Consommation, Faculté des Sciences de l'Agriculture et de l'Alimentation, Université Laval, G1K 7P4 Québec, Canada

The purpose of this work was to determine if endogenous luminal proteins are stimulated differently by various dietary proteins and if their digestibility differs from that of dietary proteins. Intestinal effluents were collected from the jejunum of four volunteers who had previously fasted or ingested either casein or soybean proteins. After separating the jejunal digested fraction (nonprotein nitrogen) by dialysis, the protein nitrogen fractions of the effluents and of the protein sources were further hydrolyzed in vitro in a digestion cell with simultaneous dialysis of the digestion by-products. The results indicated a higher (P < 0.05) gastrojejunal absorption of casein (64.5 ± 2.5%) compared with soybean protein (49.9 ± 4.1%) in humans. Compared with fasting conditions, protein ingestion increased both the total nitrogen and protein nitrogen of the endogenous nitrogen fraction slightly (P < 0.05) but had no effect on the nonprotein nitrogen fraction. The amino acid profiles of the nonprotein nitrogen in the effluents differed from those of both the protein sources and their mixtures with endogenous secretions. This was attributed to the specific release of amino acids by pancreatic enzymes as measured in vitro. The hydrolysis patterns of amino acids were determined by the structure of food proteins and their interaction with endogenous proteins. Soybean and endogenous nitrogen had equivalent digestibilities when measured in vitro.

KEY WORDS: • jejunal effluents • endogenous proteins • humans • amino acids

¹ Supported in part by a grant (01-04-91, France/Québec) from the Department of Foreign Office and a grant (FCAR, 94-ER-1576) from Ministère de l'Education (Québec).

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ To whom correspondence and reprint requests should be addressed.

Manuscript received 15 June 1994. Revision accepted 18 January 1995.