Deficiencies, nutritional riboflavin

In addition to the role of flavoproteins in iron metabolism, it is possible that the anemia associated with riboflavin deficiency is a consequence of the impairment of vitamin Be metabolism in riboflavin deficiency. Pyridoxine oxidase is a flavoprotein and, like glutathione reductase, is very sensitive to riboflavin depletion (McCormick, 1989). Vitamin Be deficiency can result in hypochromic anemia as a result of impaired porphyrin synthesis. Although riboflavin depletion decreases the oxidation of dietary vitamin Be to pyridoxal (Section 9.2), it is not clear to what extent there is secondary vitamin Be deficiency in riboflavin deficiency This is partly because vitamin Be nutritional status is commonly... 

Riboflavin is important in human nutrition. Riboflavin is converted to the active flavin nucleotides flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). Riboflavin deficiency has been related to foetal malformations and anaemia. 

Although the nutritional aetiology of pellagra is well established, and tryptophan or niacin will prevent or cure the disease, additional factors, including deficiency of riboflavin (and hence impaired activity of kynurenine hydroxylase) or vitamin (and hence impaired activity of kynureninase), may be important when intakes of tryptophan and niacin are only marginally adequate. 

In experimental animals a deficiency of riboflavin impairs normal growth and causes symptoms of the skin. In man the principal symptoms of ariboflavinosis are dermatitis ( pellagra sine pellagra ), cheilosis (changes around the lips), and disorders of the eyes. The nutritional supply of the vitamin is adequate in general. Excessive amounts of riboflavin in the body are excreted in urine. 

Although riboflavin is fundamentally involved in metabolism, and deficiencies are found in most countries, it is not fatal as there is very efficient conservation of tissue riboflavin. Riboflavin deficiency is characterized by cheilosis, lingual desquamation and a seborrheic dermatitis. Riboflavin nutritional status is assessed by measurement of the activation of erythrocyte glutathione reductase by FAD added in vitro. 

F. Shinmachi, I. Flasegawa, A. Noguchi, and J. Yazaki, Characterization of iron deficiency response system with riboflavin secretion in some dicotyledonous plants. Plant Nutrition for Sustainable Food Production and Environment (T, Ando, K. Fujita, T. Mae, H. Mat.sumoto, S. Mori, and J. Sekiya, eds.), Kluwer Academic Publishers, Dordrecht, 1997, p. 277. 

Nutritional Folate deficiency Iron deficiency Vitamin Bi (thiamine) deficiency Vitamin B2 (riboflavin) deficiency Vitamin Bg (pyridoxine) deficiency Vitamin B12 (cyanocobalamin) deficiency... 

In pregnant women, there is a progressive increase in the erythrocyte glutathione reductase activation coefficient (an index of functional riboflavin nutritional status Section 7.5.2), which resolves on parturition despite the daily secretion of 200 to 400 /rg (0.5 to 1 /rmol) of riboflavin into milk. This suggests that the estrogen-induced riboflavin binding protein can sequester the vitamin for fetal uptake at the expense of causing functional deficiency in the mother. 

In animals, the production of CO2 from [ Cjpalmitate or octanoate is not consistendy affected by riboflavin deficiency, possibly as a result of increased activity of carnitine palmitoyl transferase, which is more a response to food deprivation than to riboflavin deficiency. However, the production of C02 from [ C] adipic acid is significandy reduced, and responds rapidly (with some overshoot) to repletion with the vitamin. It has been suggested that the abiUty to metabolize a test dose of [ Cjadipic acid may provide a sensitive means of investigating ribodavin nutritional status in human beings (Bates, 1989, 1990). 

Table 7.5 Indices of Riboflavin Nutritional Status Adequate Marginal Deficient...

Like glutathione reductase, pyridoxine oxidase is sensitive to riboflavin depletion. In normal subjects and in experimental animals, the EGR and pyridoxine oxidase activation coefficients are correlated, and both reflect riboflavin nutritional status. In subjects with glucose 6-phosphate dehydrogenase deficiency, there is an apparent protection of EGR, so that even in riboflavin deficiency it does not lose its cofactor, and the EGR activation coefficient remains within the normal range. The mechanism of this protection is unknown. In such subjects, the erythrocyte pyridoxine oxidase activation coefficient gives a response that mirrors riboflavin nutritional status (Clements and Anderson, 1980). 

Bates CJ (1987) Human riboflavin requirements, and metabolic consequences of deficiency in man and animals. World Review of Nutrition and Dietetics 50,215-65. 

Pyridoxine phosphate oxidase is a flavoprotein, and activation of the erythrocyte apoenzyme by riboflavin 5 -phosphate in vitro can be used as an index of riboflavin nutritional status (Section 7.4.3). However, even in riboflavin deficiency, there is sufficient residual activity of pyridoxine phosphate oxidase to permit normal metabolism ofvitamin Be (Lakshmi and Bamji, 1974). Pyridoxine phosphate oxidase is inhibited by its product, pyridoxal phosphate, which binds a specific lysine residue in tbe enzyme. In tbe brain, tbe Ki of pyridoxal phosphate is of the order of 2 /xmol per L - the same as the brain concentration of free and loosely bound pyridoxal phosphate, suggesting that this inhibition may be a physiologically important mechanism in the control of tissue pyridoxal phosphate (Choi et al., 1987). 

Bates CJ (1989) Metabolism of [ C] adipic acid in riboflavin-deficient rats a test in vivo for fatty acid oxidation./owma/ of Nutrition 119, 887-91. 

Bates CJ (1990) Liberation of C02 from [ CJadipic acid and [ CJoctanoic acid by adnlt rats dnring riboflavin deficiency and its reversal. British Journal of Nutrition 63, 553-62. 

Duerden JM and Bates CJ (1985) Effect of riboflavin deficiency on lipid metabolism of liver and brown adipose tissue of sucking rat pups. British Journal of Nutrition 53, 107-15. 

Goodman SI (1981) Organic aciduria in the riboflavin-deficient rat. American Journal of Clinical Nutrition 34,2434-7. 

Lakshmi AV and Bamji MS (1974) Tissue pyridoxal phosphate concentration and pyri-doxaminephosphate oxidase activity in riboflavin deficiency in rats and man. British Journal of Nutrition 32, 249-55. 

Powers HJ, Weaver LT, Austin S, Wright AJ, and Eairweather-Tait SJ (1991) Riboflavin deficiency in the rat effects on iron utilization and loss. British Journal of Nutrition 65,487-96. 

Prentice AM and Bates CJ (1981a) A biochemical evaluation of the erythrocyte glutathione reductase (EC 1.6.4.2) test for riboflavin status. 1. Rate and specificity of response in acute deficiency. British Journal of Nutrition 45,37-52. 

White HB 3rd (1996) Sudden death of chicken embryos with hereditary riboflavin deficiency. Journal of Nutrition 126,1303S-7S. 

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