Amino-acid supplements action

An estimation of the amount of amino acid production and the production methods are shown ia Table 11. About 340,000 t/yr of L-glutamic acid, principally as its monosodium salt, are manufactured ia the world, about 85% ia the Asian area. The demand for DL-methionine and L-lysiae as feed supplements varies considerably depending on such factors as the soybean harvest ia the United States and the anchovy catch ia Pern. Because of the actions of D-amiao acid oxidase and i.-amino acid transamiaase ia the animal body (156), the D-form of methionine is as equally nutritive as the L-form, so that DL-methionine which is iaexpensively produced by chemical synthesis is primarily used as a feed supplement. In the United States the methionine hydroxy analogue is partially used ia place of methionine. The consumption of L-lysiae has iacreased ia recent years. The world consumption tripled from 35,000 t ia 1982 to 100,000 t ia 1987 (214). Current world consumption of L-tryptophan and i.-threonine are several tens to hundreds of tons. The demand for L-phenylalanine as the raw material for the synthesis of aspartame has been increasing markedly. 

Interestingly, the amino-terminal extensions contain putative nuclear localization sequences that appear to be involved in transport of these proteins into the nucleus (Acland et al., 1990 Amalric et al., 1991 Bugler et al., 1991 Kiefer et al., 1994). FGF-1 has also been shown to enter the nucleus, but the amino acid sequence involved in this process remains to be elucidated (Cao et al., 1993). The specific function of nuclear FGF is still unclear, but there is evidence that FGF-2 import into the nucleus is involved in the mitogenic response of endothelial cells to FGF (Bouche et al., 1987 Baldin et al., 1990). Such a nuclear mechanism of FGF action could supplement the classical signal pathway by receptor-mediated mechanisms. 

Large neutral amino acids (LNAA) are contraindicated as a sole source of protein in women with maternal PKU because LNAA do not sufficiently lower blood phenylalanine to within the desired treatment range of 120-360 pmol/L [16]. The proposed mechanism of action of LNAA is to block uptake of phenylalanine into the brain by supplementing other amino acids that share the LAT-1 transport system across the blood-brain barrier (Chap. 11). Some reduction in blood phenylalanine has been seen with LNAA use but not to the degree necessary to protect the fetus [17]. 

The term supplement has various regulatory meanings in various jurisdictions. The U.S. FDA, acting under the 1994 Dietary Supplement Health and Education Act, defines a supplement as a product for supplementing the diet, and that can consist of vitamins, minerals, herbs, botanicals, or amino acids. Other countries define the term within the drugs category. Various classes of supplements for the U.S. diet are subject to U.S. FDA control actions. These include vitamins and energy supplements. 

It must be apparent from these studies that until more is known of the fate and action of these unphyriological products, it would seem preferable to rely on enzymic or acid protein hydrolyzates which provide the amino acids in their natural form for supplemental alimentation. The single virtue claimed for crystalline amino acid mixtures, as opposed to protein digests—more rapid administration— may prove to be apparent rather than real, for it is possible that it is tiie greater loss of amino acids in the urine that allows more rapid administration. That such losses are considerable when crystalline amino acids are pven, is suggested by the work of Bassett and his associates (129) who observed a rise in the... 

Moderate vitamin B deficiency results in a number of abnormalities of amino acid metabolism, and especially of tryptophan (section 11.9.5.1) and methionine (section 11.9.5.2). In experimental animals, a moderate degree of deficiency leads to increased sensitivity of target tissues to steroid hormone action. This may be important in the development of hormone-dependent cancer of the breast, uterus and prostate, and may therefore affect the prognosis. Vitamin B supplementation may be a useful adjunct to other therapy in these common cancers certainly, there is evidence that poor vitamin Bg nutritional status is associated with a poor prognosis in women with breast cancer. 

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