Amino acids nutritional requirements

Amino Acid nutritional requirements vary with... 

Humans and Rodents Synthesize Less Than Half of the Amino Acids They Need for Protein Synthesis Many Amino Acids Are Required in the Diet for Good Nutrition... 

Many Amino Acids Are Required in the Diet for Good Nutrition... 

The synthesized or synthetic proteins previously discussed in terms of the genetic code are not necessarily the same as those that start out as nutritional or dietary proteins. However, digestive enzymes break down dietary proteins into the amino acid pool required for subsequent cell protein synthesis, as has been described. The proteins so synthesized variously become cellular structural components, enzymes and hormones, and blood plasma proteins. The latter are involved in cellular osmotic balances, that is, in ensuring a stable pressure difference across the cell walls. These blood proteins also transport substances through the vascular system, and assist in promoting inununity (Chaney, in Devlin, 1986, p. 1179ff). 

The importance of prompt nutritional support for severely injured patients cannot be overemphasized. In the catabolic state, large amounts of energy and amino acids are required to replace the losses. The nutritional workup and assessment appropriate in the trauma patient arc discussed on pages 97-99. 

For pharmaceutical purposes 2000-3000 tonnes of amino acids are required annually worldwide. More than half of this amount ends up in infusion solutions for artificial nutrition. Many amino acid derivatives are pharmacologically important acetylcysteine is mucolytic, (L)-DOPA an active agent to combat Parkinson s disease, and Oxitriptan ((S)-5-hydroxytryptophan) is an antidepressant. Specifically substituted, (D)-configured, a- and /3-amino acids find widespread application as building blocks for drug synthesis. 

On the basis of whole-animal nutritional studies, 14 amino acids are conventionally considered as essential for cultured cells arginine, cysteine, cystine, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, tyrosine, and valine. Conversely, the naturally occurring nonessential amino acids include alanine, serine, asparagine, proline, glycine, aspartic acid, and glutamic acid. Nutritional requirements for amino acids vary, both quantitatively and qualitatively, with cell type, culture condition, and genetic modification. 

RECOMMENDED DAILY ALLOWANCE OF SULFUR. Sulfur requirements are primarily those involving amino acid nutrition. 

National Research Council, 1998. Nutrient requirements of swine. 10th ed. Washington, D.C., National Academy Press. Pettigrew, J.E., 1993. Amino acid nutrition of gestating and lactating sows. Biokyowa Technical Review-5. Nuhi-Quest, Inc., St. Louis, MO. 

Pea.nuts, The proteins of peanuts are low in lysine, threonine, cystine plus methionine, and tryptophan when compared to the amino acid requirements for children but meet the requirements for adults (see Table 3). Peanut flour can be used to increase the nutritive value of cereals such as cornmeal but further improvement is noted by the addition of lysine (71). The trypsin inhibitor content of raw peanuts is about one-fifth that of raw soybeans, but this concentration is sufficient to cause hypertrophy (enlargement) of the pancreas in rats. The inhibitors of peanuts are largely inactivated by moist heat treatment (48). As for cottonseed, peanuts are prone to contamination by aflatoxin. FDA regulations limit aflatoxin levels of peanuts and meals to 100 ppb for breeding beef catde, breeding swine, or poultry 200 ppb for finishing swine 300 ppb for finishing beef catde 20 ppb for immature animals and dairy animals and 20 ppb for humans. 

Nutritional Requirements. The nutrient requirements of mammalian cells are many, varied, and complex. In addition to typical metaboHc requirements such as sugars, amino acids (qv), vitamins (qv), and minerals, cells also need growth factors and other proteins. Some of the proteins are not consumed, but play a catalytic role in the cell growth process. Historically, fetal calf semm of 1—20 vol % of the medium has been used as a rich source of all these complex protein requirements. However, the composition of semm varies from lot to lot, introducing significant variabiUty in manufacture of products from the mammalian cells. 

Amino acids promote the production of proteins, enhance tissue repair and wound healing, and reduce the rate of protein breakdown. Amino acids are used in certain disease states, such as severe kidney and liver disease, as well as in TPN solutions. (See the last section of this chapter for a more detailed discussion of TPN.) TPN may be used in patients with conditions such as impairment of gastrointestinal absorption of protein, in patients with an increased requirement for protein, as seen in those with extensive bums or infections, and in patients with no available oral route for nutritional intake ... 

When normal enteral feeding in not possible or is inadequate to meet an individual s nutritional needs, intravenous (IV) nutritional therapy or total parenteral nutrition (TPN) is required. Products used to meet the IV nutritional requirements of the patient include protein substrates (amino acids), energy substrates (dextrose and fat emulsions), fluids, electrolytes, and trace minerals (see the Summary Drug Table Electrolytes). 

Not all proteins are nutritionally equivalent. Mote of some than of others is needed to maintain nittogen balance because different proteins contain different amounts of the various amino acids. The body s requirement is for specific amino acids in the correct proportions to replace the body proteins. The amino acids can be divided into two groups essential and nonessential. There are nine essential or indispensable amino acids, which cannot be synthesized in the body histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. If one of these is lacking or inadequate, then—regardless of the total intake of protein—it will not be possible to maintain nitrogen balance since there will not be enough of that amino acid for protein synthesis. 

PN should provide a balanced nutritional intake, including macronutrients, micronutrients, and fluid. Macronutrients, including amino acids, dextrose, and intravenous lipid emulsions, are important sources of structural and energy-yielding substrates. A balanced PN formulation includes 10% to 20% of total daily calories from amino acids, 50% to 60% of total daily calories from dextrose, and 20% to 30% of total daily calories from intravenous lipid emulsion. Micronutrients, including electrolytes, vitamins, and trace elements, are required to support essential biochemical reactions. Parenteral... 

Commonly administered LVPs include such products as Lactated Ringers Injection USP, Sodium Chloride Injection USP (0.9%), which replenish fluids and electrolytes, and Dextrose Injection USP (5%), which provides fluid plus nutrition (calories), or various combinations of dextrose and saline. In addition, numerous other nutrient and ionic solutions are available for clinical use, the most popular of which are solutions of essential amino acids or lipid emulsions. These solutions are modified to be hypertonic, isotonic, or hypotonic to aid in maintaining both fluid, nutritional, and electrolyte balance in a particular patient according to need. Indwelling needles or catheters are required in LVP administration. Care must be taken to avoid local or systemic infections or thrombophlebitis owing to faulty injection or administration technique. 

Selectivity to reject Na+ and Cl-, so as to manage osmotic and electrical tension, and Ca2+ (probably also Mn2+) to prevent internal precipitation. ATP and H+ gradients may always have assisted this rejection. At the same time, K+ was taken up at a high concentration, and 10 3 M of Mg2+ was permitted internally. Na+ and H+ gradients are used to this day in the uptake of required nutritional compounds such as amino acids. 

Pig producers mainly try to approach maximal rates of lean tissue deposition and carcass index values by providing diets formulated to meet all of the known requirements. In the growing period, protein accretion increases as the supply of limiting amino acids increases (Heger et al., 2002). The dose-effect ratio can be subdivided into the nutrition-dependent phase, which is substantially linear, and the plateau phase, which is independent of nutrition supply and whose maximum depends on features of the animals, primarily characterised by the genotype (Susenbeth, 2002). 

Standard CAA products contain a balanced profile of essential, semiessential, and nonessential L-amino acids and are designed for patients with normal organ function and nutritional requirements. Standard CAA... 

Patient case A patient s daily nutritional requirements have been estimated to be 100 g protein and 2,000 total kcal. The patient has a central venous access and reports no history of hyperlipidemia or egg allergy. The patient is not fluid restricted. The PN solution will be compounded as an individualized regimen using a single-bag, 24-hour infusion of a 2-in-1 solution with intravenous fat emulsion (IVFE) piggybacked into the PN infusion line. Determine the total PN volume and administration rate by calculating the macronutrient stock solution volumes required to provide the desired daily nutrients. The stock solutions used to compound this regimen are 10% crystalline amino acids (CAA), 70% dextrose, and 20% IVFE. 

The diet must provide those amino acids which the body cannot synthesize (essential amino acids, EAA) and nitrogen in the form of nonessential amino acids (NEA). Both EAA and NEA are required for biosynthesis of proteins and other nitrogen-containing compounds necessary for homeostasis or growth. Thus, the total nitrogen content of a specific food must be considered to be nutritionally significant. 

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