Niacin requirements

That nongrowing animals require niacin implies that it is lost from the body either as intact niacin or as a modified or breakdown product of the vitamin. An amount of niacin equivalent to nearly 90% of our daily intake is excreted in the forms of N-methyl-2-p)nidone-5urinary metabolites can be used to assess niacin status. Loss of the normal quantity in the urine each day indicates that the supply in the diet is adequate. In humans, the healthy adult excretes 4 to 6 mg of N-methyl-nicoti-namide per day. An abnormally low level indicates that the dietary intake is not adequate. Measurement of urinary niacin metabolites has proven useful in determining the amoimt of niacin available in a variety of foods. The body s ability to use niacin in different foods may vary even if the foods contain identical quantities of the vitamin. One contributing factor to the low availability of niacin is the occurrence of the vitamin in the "bound form," as mentioned earlier. Excretion of normal levels of pyridone, for example, depends not only on normal absorption of the vitamin from the diet, but also on its conversion to NAD or NADP, followed by catabolism to the metabolite. 

The answer is a. (Murray, pp 627-661. Scriver, pp 3897-3964. Sack, pp 121-138. Wilson, pp 287—320.) The structure shown in the question is the vitamin tolic acid. Tetrahydrofolic acid, the active cofactor derived from lolic acid, is required in two steps of purine synthesis and thus required in the de novo synthesis of ATP and GTE CTP and TTP are pyrimidine base derivatives, and although de novo synthesis of the pyrimidine ring does not require tetrahydrofolate, the formation of thymine from uracil does. NADH and NADPH require niacin for their synthesis. 

FUNCTIONS. Following absorption, folic acid is changed, by a number of reduction reactions that require niacin, to at least five active coenzyme forms, the parent form being tetrahydrofolic acid. The principal function of these coenzymes is the transfer of single carbon units from one compound to another the one carbon unit can be formyl, forminino, methylene, or methyl groups. 

Animals generally require nicotinic acid (niadn) or nicotinamide in their diets for growtii and maintenance. Many groups of microorganisms also require niacin or its derivatives others can synthesise the vitamin. Table I lists some of the microorganisms which require nicotinic add as a growth factor. 

It had been known since 1922 that rats did not require niacin under normal dietary conditions (/). Krehl and associates (ff) in 1945 were able to show that the unessentiality of the niadn was doe to the presence of tiyptophan in the diet. This was based on the observation that the inclu-... 

In terms of amino acids bacterial protein is similar to fish protein. The yeast s protein is almost identical to soya protein fungal protein is lower than yeast protein. In addition, SCP is deficient in amino acids with a sulphur bridge, such as cystine, cysteine and methionine. SCP as a food may require supplements of cysteine and methionine whereas they have high levels of lysine vitamins and other amino acids. The vitamins of microorganisms are primarily of the B type. Vitamin B12 occurs mostly hi bacteria, whereas algae are usually rich in vitamin A. The most common vitamins in SCP are thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, choline, folic acid, inositol, biotin, B12 and P-aminobenzoic acid. Table 14.4 shows the essential amino acid analysis of SCP compared with several sources of protein. 

Most foods of animal origin contain nicotinamide in the coenzyme form (high bioavialability). Liver and meat are particularly rich in highly bioavailable niacin. Most of the niacin in plants, however, occurs as nicotinic acid in overall lower concentrations and with a lower bioavailability. The major portion of niacin in cereals is found in the outer layer and its bioavailability is as low as 30% because it is bound to protein (niacytin). If the diet contains a surplus of L-tryptophan (Ttp), e.g., more than is necessary for protein synthesis, the liver can synthesize NAD from Trp. Niacin requirements are therefore declared as niacin equivalents (1 NE = 1 mg niacin = 60 mg Trp). 

A vitamin is defined as an organic compound that is required in the diet in small amounts for the maintenance of normal metabofic integrity. Deficiency causes a specific disease, which is cured or prevented only by restoring the vitamin to the diet (Table 45-1). However, vitamin D, which can be made in the skin after exposure to sunhght, and niacin, which can be formed from the essential amino acid tryptophan, do not stricdy conform to this definition. 

Some patients, in particular those with genetic forms of hypercholesterolemia (Table 9-2), will require three or more drugs to manage their disorder. Regimens using a statin, resin, and niacin were found to reduce LDL cholesterol up to 75%.42 These early studies were conducted with lovastatin, so larger reductions would be expected with the more potent statins available today. 

With respect to vasodilation, niacin-elicited vasodilation requires the activation of GPR109A in skin Langerhans cells [34,35], which then triggers the release of arachidonic acid from membrane phospholipids and its subsequent metabolism to PGD2. The production of PGD2 then activates DPI receptors in dermal blood vessels to cause vasodilation [36]. 

FAO/WHO. 1967. Requirements of Vitamin A, Thiamine, Riboflavine and Niacin. WHO Technical Report Series No. 362. Geneva World Health Organization. 

Niacin has many common adverse drug reactions most of the symptoms and biochemical abnormalities seen do not require discontinuation of therapy. 

Type V hyperlipoproteinemia requires stringent restriction of dietary fat intake. Drug therapy with fibrates or niacin is indicated if the response to diet alone is inadequate. Medium-chain triglycerides, which are absorbed without chylomicron formation, may be used as a dietary supplement for caloric intake if needed for both types I and V. 

Niacin requires baseline tests of liver function (alanine aminotransferase), uric acid, and glucose. Repeat tests are appropriate at doses of 1,000 to 1,500 mg/day. Symptoms of myopathy or diabetes should be investigated and may require creatine kinase or glucose determinations. Patients with diabetes may require more frequent monitoring. 

Niacin requirements are dependent on the tryptophane supply and the ease with which the conversion of tryptophane to niacin can be made. Chickens and rats carry out the conversion readily. Dogs do so less readily. Monkeys and human beings carry out the process relatively ineffectively. Since this conversion involves several enzymatic steps, it is clear on the basis of gene-enzyme relationships why species differences exist. On the same basis inter-individual differences may be presumed to exist also. 

That individual monkeys have distinctive niacin needs was shown by recent work of Tappan and co-workers.59 One animal, for example, required only 11 weeks to show niacin deficiency weight loss by this animal was halted only when 30 mg. of niacin was given. Another animal required 9 months to show a niacin deficiency and then grew adequately when only 6 mg. of niacin per week was furnished. This seems to show a several-fold range in niacin needs within a small group of fine animals. The tryptophane needs of the different monkeys, as judged by growth responses, were found to vary under comparable conditions from 1 to about 3.5 gm. per week. 

NADP(H) of tryptophan (corn major dietary staple), which supplies a portion of the niacin requirement. 

The RDA for adult males is 16 mg/day and for adult females 14 mg/day. As usual, children require less and pregnant or lactating women a bit more. Niacin is not hard to come by in your diet good sources include eiuiched and whole-grain bread and bread products, fortified cereals, meat, fish, and poultry. 

Nicotinate and nicotinamide, together referred to as niacin, are required for biosynthesis of the coenzymes nicotinamide adenine dinucleotide (NAD"") and nicotinamide adenine dinucleotide phosphate (NADP" ). These both serve in energy and nutrient metabolism as carriers of hydride ions (see pp. 32, 104). The animal organism is able to convert tryptophan into nicotinate, but only with a poor yield. Vitamin deficiency therefore only occurs when nicotinate, nicotinamide, and tryptophan are all simultaneously are lacking in the diet. It manifests in the form of skin damage (pellagra), digestive disturbances, and depression. 

Primary hypercholesterolemia/mixed dyslipidemia For the treatment of primary hypercholesterolemia (heterozygous familial and nonfamilial) and mixed dyslipidemia (Frederickson Types lla and Mb) in the following Patients treated with lovastatin who require further TG-lowering or FIDL-raising who may benefit from having niacin added to their regimen patients treated with niacin who require further... 

Drug interactions InsuUn requirements may be increased by medications with hyperglycemic activity such as corticosteroids, isoniazid, certain lipid-lowering drugs (e.g., niacin), estrogens, oral contraceptives, phenothiazines, and thyroid... 

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