BIOAVAILABLE LEVEL AND SOURCE OF CYSTEINE DETERMINE PROTEIN-QUALITY OF A COMMERCIAL ENTERAL PRODUCT - ADEQUACY OF TRYPTOPHAN BUT DEFICIENCY OF CYSTEINE FOR RATS FED AN ENTERAL PRODUCT PREPARED FRESH OR STORED BEYOND SHELF-LIFE

被引:19
作者
BAKER, DH
HAN, YM
机构
[1] UNIV ILLINOIS,DIV NUTR SCI,URBANA,IL 61801
[2] UNIV ILLINOIS,DEPT ANIM SCI,URBANA,IL 61801
关键词
RATS; TRYPTOPHAN; CYSTINE; ENTERAL FORMULA; GLUTATHIONE;
D O I
10.1093/jn/123.3.541
中图分类号
R15 [营养卫生、食品卫生]; TS201 [基础科学];
学科分类号
100403 ;
摘要
Young rats were used in bioassays designed to assess the protein quality and tryptophan as well as cystine adequacy of the enteral product TwoCal-HN(R) that was either freshly prepared or had been stored (nonrefrigerated) in a warehouse for 10 mo (i.e., beyond shelf life). Based upon supplementation studies, cystine was observed to be the first-limiting amino acid in both fresh and expired TwoCal-HN, and tryptophan was not second limiting. Protein efficiency ratio (PER) of expired, but not fresh, TwoCal-HN was lower than that of the casein control diet, but with cystine supplementation, PER of the TwoCal-HN products was equal to or greater than the PER of the casein control. With a diet containing 10 g protein/100 g that also contained energy-furnishing ingredients simulating TwoCal-HN, maximal growth enhancement occurred with a supplement of 1 g cystine/kg diet. Both glutathione and N-acetyl-L-cysteine were observed to be equivalent to an isomolar level of L-cystine in stimulating growth. Using a chemically defined amino acid diet that was singly deficient in tryptophan, bioavailability of tryptophan was determined for casein, fresh TwoCal-HN, expired TwoCal-HN and D-tryptophan. Slope-ratio bioefficacy values relative to L-tryptophan (weight gain regressed on supplemental tryptophan intake) indicated that none of the experimental sources of tryptophan had bioavailabilities different from 100%. The results indicated that tryptophan did not deteriorate, as measured analytically or biologically, as a result of storing TwoCal-HN beyond shelf life. Adding bioavailable sources of cysteine activity to casein-based enteral products markedly improves protein quality when these products are fed to young rats.
引用
收藏
页码:541 / 546
页数:6
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