Supplementation, methionine

Neuschwander-Tetri et al., 1992) and pancreatitis induced by a choline-deficient methionine-supplemented diet is less severe when mice are treated with a new synthetic ascorbic-acid derivative (CV 3611) (Nonaka et al., 1991). 

As such it is an ideal protein for complementation of legumes. Villegas et al. (73) pointed out that methionine supplementation using sesame protein has several advantages over supplementation with free methionine, including an even and more adequate release into the digestive tract. 

Male Sprague Dawley rats, seven days post weanling (Bantin and Kingman, Inc., Fremont, CA) were fed pelleted rodent chow (5001, Ralston Purina Co., St. Louis, MO) or modified AIN-76 diets (BioServ, Inc., Frenchtown, NJ) with or without added sulfur amino acids. Chow, diets, and water were supplied to the rats ad libitum. The AIN-76 diet (16) was modified to contain 12% casein (normally 20% casein), and the weight difference made up with cornstarch. The normal methionine supplement was not included. The cornstarch and sucrose portions were held separately from the casein/vitamin/mineral (CVM) mixture for the purpose of mixing amino acids with the cornstarch and sucrose (CsS). Methionine (MET), methionine sulfoxide (MSO) and cysteine sulfinic acid (CSA) were obtained from Sigma Chemical Co., St. Louis, MO. Cysteine monoxide (CMO) was prepared by the method of Savige et al., (17). 

E. Hunter and R. Grimble, Cysteine and Methionine Supplementation Modulate the Effects of TNF-a on Protein Synthesis, Glutathione and Zinc Content of Liver and Lung in Rats Fed a Low Protein Die, J Nutrition 124 (1994) 2319-2328. 

Figure 2 Relative biological values—NPR and NPU—of soy protein isolate and methionine supplemented soy protein isolates, (a) Soy protein isolate (Met + Cys — 2.6g/16g N) (b) soy protein isolate supplemented with free L-methionine (Met + Cys — 3.5g/l6g N) (c) soy protein isolate supplemented with methioninc-cnriched EPM product (Met + Cys — 3.5g/16g N).

Clandinin and Yamashiro (1980) have recently pointed out that if the methionine per calorie ratio is calculated for rat diets containing 20% casein and 20% fat (4500 kcal/kg ME), the diet is apparently deficient in methionine. However, these workers were not able to demonstrate a consistent improvement in weight gains when rats were fed the diet supplemented with methionine. An experiment carried out in this laboratory indicated that methionine supplementation did improve weight gains but the choline level of the diet had no effect. Neither the choline nor the methionine status of the diet affected the incidence or severity of heart lesions (Farnworth et a ., 1982a). 

The effect of different amino acids supplements on the synthesis of PHB by recombinant E. coli was evaluated by Mahishi and Rawal. The study revealed that when the basal medium is supplemented with amino acids, except glycine and valine, all other amino acid supplements enhanced PHB accumulation in recombinant E. coli harboring PHB synthesizing genes from S. aureqfaciens. Cysteine, isoleucine, or methionine supplementation increased PHB accumulation by 60, 45, and 61%, respectively. Amino acid biosynthetic enzyme activities in several pathways are repressed by end produa supplementation. End product inhibition in the cysteine biosynthetic pathway controls the carbon flow due to sensitivity of serine transacetylase to cysteine. Hence, supplementation of cysteine favors a change in carbon flux that eliminates the requirement of acetyl-CoA for serine transacetylation which in turn provides more carbon source and acetyl-CoA for PHB synthesis. Degradation of methionine and isoleucine yields succinyl CoA, an intermediate of tricarboxylic acid cycle and allows more acetyl-CoA to enter the PHB biosynthetic pathway. 

The main form of selenium in most foods is protein-bound seleno-methionine. Supplements of selenium are provided by mineral salts containing sodium selenite, slow-release capsules and selenium-enriched yeast. 

Opaque-2 has been reported to be nutritionally superior to normal maize for the rat, pig, man and chick, but only in methionine-supplemented diets. A newer variety, Floury-2, has increased contents of both methionine and lysine and has been shown in studies with chicks to be superior to Opaque-2 maize in diets not supplemented with methionine. 

Cystine and methionine are important in the diets of poultry owing to the demands of feathering, and beans may be expected to be of limited value for poultry. Traditionally, they have been little used in poultry diets, but evidence indicates that field beans can be used to replace soya bean meal as long as adequate methionine supplementation is practised. 

The intraperitoneal injection of massive doses of uric acid has been reported to produce a transitory hyperglycemia when this compound was administered to GSH-depleted rabbits (32). The diet fed was low in cysteine and methionine but it was supplemented with 0.1 % ascorbic acid. When the fall in blood GSH level was prevented by methionine supplementation of the diet, uric-acid injection failed to induce diabetes (32). 

Young, V.R., Puig, M., Queiroz, E, Scrimshaw, N.S., and Rand, W.M. (1984). Evaluation of the protein quality of an isolated soy protein in young men relative nitrogen requirements and effect of methionine supplementation. Am J Clin Nutr 39 16-24. 

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