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    Ileal Digestibility of Nitrogen and Amino Acids in Human Milk and an Infant Formula as Determined in Neonatal Minipiglets
    (Elsevier Inc. on behalf of American Society for Nutrition, 2023-04) Charton E; Henry G; Cahu A; Le Gouar Y; Dahirel P; Moughan PJ; Montoya CA; Bellanger A; Dupont D; Le Huërou-Luron I; Deglaire A
    BACKGROUND: Infant formula (IF) has to provide at least the same amount of amino acids (AAs) as human milk (HM). AA digestibility in HM and IF was not studied extensively, with no data available for tryptophan digestibility. OBJECTIVES: The present study aimed to measure the true ileal digestibility (TID) of total nitrogen and AAs in HM and IF to estimate AA bioavailability using Yucatan mini-piglets as an infant model. METHODS: Twenty-four 19-day-old piglets (males and females) received either HM or IF for 6 days or a protein-free diet for 3 days, with cobalt-EDTA as an indigestible marker. Diets were fed hourly over 6 h before euthanasia and digesta collection. Total N, AA, and marker contents in diets and digesta were measured to determine the TID. Unidimensional statistical analyses were conducted. RESULTS: Dietary N content was not different between HM and IF, while true protein was lower in HM (-4 g/L) due to a 7-fold higher non-protein N content in HM. The TID of total N was lower (P < 0.001) for HM (91.3 ± 1.24%) than for IF (98.0 ± 0.810%), while the TID of amino acid nitrogen (AAN) was not different (average of 97.4 ± 0.655%, P = 0.272). HM and IF had similar (P > 0.05) TID for most of the AAs including tryptophan (96.7 ± 0.950%, P = 0.079), except for some AAs (lysine, phenylalanine, threonine, valine, alanine, proline, and serine), with small significant difference (P < 0.05). The first limiting AA was the aromatic AAs, and the digestible indispensable AA score (DIAAS) was higher for HM (DIAASHM = 101) than for IF (DIAASIF = 83). CONCLUSION: HM, compared to IF, had a lower TID for total N only, whereas the TID of AAN and most AAs, including Trp, was high and similar. A larger proportion of non-protein N is transferred to the microbiota with HM, which is of physiological relevance, although this fraction is poorly considered for IF manufacturing.
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    Tryptophan deficiency and food intake depression in pigs : a thesis presented in partial fulfilment of the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1976) Montgomery, Grant William
    Two experiments are described, in which the effects or feeding pigs on a tryptophan deficient diet or supplemented diet were investigated. The feeding patterns of 10 cross-bred pigs were measured by continuous recordings of feed-bin weights, in a double reversal design experiment. The pigs, fed ad libitum, ate an average of 9 "meals" per day (range 5 - 16) with an average meal size of 170 g. There was a distinct diurnal pattern of food intake; most meals were eaten in the light phase of the day with peaks in the early morning and at midday and a large peak mid afternoon. Pigs fed the deficient diet showed some depression in food intake on the first day and the depression had reached maximal levels by the third day. On the deficient diet pigs ate 17 - 20% less than on the supplemented diet and most of the depression in intake was accounted for by reduced meal size. In the second experiment 4 pigs were trained to eat their daily ration in a 2 h period (0900 - 1100 h) and catheters were placed in the jugular veins. A double reversal experimental design was employed, with 3 periods of 5 days, and blood samples were taken over the feeding time on the second and fifth day in each period. The levels of plasma Glucose, Urea, Amino acids, Cortisol, Insulin, and Growth Hormone were measured. There were no significant differences between diets in levels of Growth Hormone or Cortisol. On day 2, Urea levels were higher in pigs fed the supplemented diet, while on day 5 there were no significant differences between diets. The lowered food intake on the deficient diet meant that both protein quality and protein intake were altered, which may explain the differences in Urea levels. The most consistent differences in plasma Amino acids levels occurred with tryptophan, the limiting amino acid, for which the levels were lower in pigs fed the deficient diet, although the differences were not statistically significant. Glucose rose higher in pigs fed the deficient diet and the differences could not be attributed to an altered Insulin response to feeding the deficient diet. It was concluded that the early changes in glucose and tryptophan may be associated with the food intake depression on the deficient diet, but further studies would be required before the relative importance of either relationship could be established.
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    Synthesis of substrate analogues and inhibitors for phosphoribosyl anthranilate isomerase and indole-3-glycerolphosphate synthase : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Turitea, Palmerston North, New Zealand
    (Massey University, 2008) Mulchin, Benjamin Joseph
    The general biosynthetic pathway for tryptophan is known. However, little information has been gathered on how substrates and enzymes interact when phosphoribosylanthranilate isomerase (PRAI) and indole-3-glycerolphosphate synthase (IPGS) convert a substituted phenyl ring, PRA, into an indole moiety, IGP, via 1-(O-carboxyphenylamino)-1-deoxyribulose-5-phosphate (CdRP). There has been no serious synthetic approach to develop methodology to produce a plethora of substrate and product analogues of CdRP. The studies described in this thesis cover methodology focusing on secondary aryl amine formation, using reductive amination, nucleophilic substitution and epoxide ring opening, leading to CdRP analogues. Reductive aminations with D-ribose failed to produce any aryl glycosylamine precursor, possibly due to the low nucleophilicity of aryl amines such as aniline. Removing the aromaticity and using cyclohexylamine produced secondary amines in moderate yield in the presence of benzylpentanal, and NaBH3CN, at a pH of 5.5. This led to a successful reductive amination using anthranilate methyl ester. Secondary aryl amine synthesis via epoxide ring opening proved consistently reproducible. Using LiNTf2 and high equivalents of cyclohexylamine or aniline in neat conditions opened protected epoxides. This has led to the formation of advanced secondary aryl amine synthons and the development of methodology leading to target compounds with functionality at the 1,2 and 5 positions. Nucleophilic substitution using caesium base, high equivalents aniline at room temperature, gave a moderate yield of secondary aryl amines from sulfonyl and bromide good leaving groups. Raising the reaction temperature improved yields using low equivalents of aniline, with the optimal temperature being 50 °C. Ultimately using both the high equivalents of aniline or anthranilate methyl ester and warming the reaction in DMF gave the highest yields of secondary aryl amines. No overalkylated tertiary amine was isolated when a caesium base was used. Boc N-protection of 1-phenylamino-4-pentene and asymmetric dihydroxylation gave the corresponding diol, which was phosphorylated giving the protected target 1,4,5 compound. The methodology leading to the protected target 1,4,5 compound synthesis provides a means to the synthesis additional of CdRP analogues.