Steady-state turnover and body pool of ascorbic acid in man

Kallner, Anders; Hartmann, D; Hornig, D.

doi:10.1093/ajcn/32.3.530

Cited by 213 publications

(116 citation statements)

References 12 publications

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“…It has already been estimated that the body pool size of AA is about 1500 mg and that orally administered vitamin C appears in the urine only when this limit has been reached or exceeded [36]. The significant fall in DHA/AA ratios in all groups during the first three weeks of ascorbate supplementation implies a striking reduction in oxidative stress reflecting the role of AA as an important antioxidant.…”

Section: Discussionmentioning

confidence: 87%

Disturbed handling of ascorbic acid in diabetic patients with and without microangiopathy during high dose ascorbate supplementation

et al. 1991

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Summary. Abnormalities of ascorbic acid metabolism have been reported in experimentally-induced diabetes and in diabetic patients. Ascorbate is a powerful antioxidant, a cofactor in collagen biosynthesis, and affects platelet activation, prostaglandin synthesis and the polyol pathway. This suggests a possible close interrelationship between ascorbic acid metabolism and pathways known to be influenced by diabetes. We determined serum ascorbic acid and its metabolite, dehydroascorbic acid, as indices of antioxidant status, and the ratio, dehydroascorbate/ascorbate, as an index of oxidative stress, in 20 matched diabetic patients with and 20 without microangiopathy and in 22 age-matched control subjects. Each study subject then took ascorbic acid, 1 g daily orally, for six weeks with repeat measurements taken at three and six weeks. At baseline, patients with microangiopathy had lower ascorbic acid concentrations than those without microangiopathy and control subjects (42.1+19.3 vs 55.6 _+ 20.0, p < 0.01, vs 82.9 _+ 30.9 gmol/1, p < 0.001) and elevated dehydroascorbate/ascorbate ratios (0.87+0.46 vs 0.61 + 0.26, p < 0.01, vs 0.38 + 0.14, p < 0.001). At three weeks, ascorbate concentrations rose in all groups (p < 0.0001) and was maintained in control subjects (151.5 + 56.3 ~tmol/1), but fell in both diabetic groups by six weeks (p<0.01). Dehydroascorbate/ascorbate ratios fell in all groups at three weeks (p < 0.0001) but rose again in the diabetic groups by six weeks (p < 0.001) and was unchanged in the control subjects. Dehydroascorbate concentrations rose significantly from baseline in all groups by six weeks of ascorbic acid supplementation (p < 0.05). No significant changes were observed in fructosamine concentrations in any group during the study. Diabetes mellitus is associated with a major disturbance of ascorbic acid metabolism which is only partially corrected by ascorbate supplementation.Key words: Ascorbic acid, dehydroascorbic acid, diabetes mellitus, free radical activity, oxidative stress.Reduced levels and altered metabolic turnover of ascorbic acid (AA, vitamin C) have been reportedin severaltissues in experimen tally induced diabetes [1-3] and in diabeticpatients [4]. There are reports that high dose vitamin C regimens are associated with reversal of early signs of retinopathy [5] and normalisation of capillary strength in diabetes mellitus [6]. In the elderly non-diabetic population AA is often deficient and may be correctable by supplementation [7] -this problem might be of particular significance in elderly diabetic patients who are reported to show more rapid progress of some diabetic complications [8].Ascorbic acid functions as an important component of cellular defence against oxygen toxicity and lipid peroxidation caused by free radical mechanisms [9,10]. During scavenging of free radicals it is converted to dehydroascorbic acid, DHA, in serum and in the mitochondrial fractions of various tissues [11]. It is also a co-factor in the biosynthesis and post-translational modification of collagen...

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Section: Discussionmentioning

confidence: 87%

Disturbed handling of ascorbic acid in diabetic patients with and without microangiopathy during high dose ascorbate supplementation

et al. 1991

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“…The pooled mean concentrations for serum or plasma ascorbic acid in the above studies were 59 and 56 mmol ⋅ L −1 for athletes (n = 533) and controls (n = 193), respectively. These levels correspond to a sufficient body pool of about 1500 mg 77 .…”

Section: Vitamin Cmentioning

confidence: 93%

Micronutrients: interaction between physical activity, intakes and requirements

Fogelholm

1999

Public Health Nutr.

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The present literature review examines the following questions: (a) What is the evidence that micronutrient requirements are increased in physically active people? (b) Is there an association between physical activity and micronutrient intake? (c) Are there any significant differences between indices of micronutrient status between physically active and inactive people? The available data suggest that micronutrient requirements are increased in physically active people because of increased losses through sweat, urine and faeces, and an increased need for defence against free radicals. However the evidence is controversial, and it is not possible to make any quantitative estimations. Micronutrient requirements in moderately active people are not likely to be very much above the levels recommended for the general population. The intake of micronutrients increases with increasing energy intake. Therefore, physically highly active people (athletes) have higher micronutrient intakes than untrained subjects. However, moderate physical activity does not necessarily affect daily micronutrient intake. The available indices of micronutrient status do not support the belief that micronutrient status is compromised in highly trained athletes, even without use of dietary supplements. Hence, there are no reasons to believe that the situation would be different in people who are only moderately active. The results suggest that micronutrient status is adequate for health and functional performance in physically active people who follow a normal, mixed Western diet.

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“…It also contributes to the synthesis of carnitine, collagen and catecholamines that regulate the nervous system (Kubler and Gehler, 1970;Iqbal et al, 2004). It is needed for tissue growth and wound healing (Kallner et al, 1979), assists the formation of neurotransmitters and increases the absorption of iron. As an antioxidant, it protects the body from the harmful effects of free radicals and pollutants (Brzozowski et al, 2001;Guaiquil et al, 2001).…”

Section: Vitamin C and Vitamin C Transportersmentioning

confidence: 99%

Vitamin C and oxidative stress in the seminiferous epithelium

et al. 2011

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In this article, we focus on the fundamental role of vitamin C transporters for the normal delivery of vitamin C to germ cells in the adluminal compartment of seminiferous tubules. We argue that the redox status within spermatozoa or in semen is partly responsible for the etiology of infertility. In this context, antioxidant defence plays a critical role in male fertility. Vitamin C, a micronutrient required for a wide variety of metabolic functions, has long been associated with male reproduction. Two systems for vitamin C transport have been described in mammals. Facilitative hexose transporters (GLUTs), with 14 known isoforms to date, GLUT1-GLUT14, transport the oxidized form of vitamin C (dehydroascorbic acid) into the cells. Sodium ascorbic acid co-transporters (SVCTs), SVCT1 and SVCT2 transport the reduced form of vitamin C (ascorbic acid). Sertoli cells control germ cell proliferation and differentiation through cell-cell communication and form the blood-testis barrier. Because the blood-testis barrier limits direct access of molecules from the plasma into the adluminal compartment of the seminiferous tubule, one important question is the method by which germ cells obtain vitamin C. Some interesting results have thrown light on this matter. Expression of SVCT2 and some isoforms of GLUT transporters in the testis have previously been described. Our group has demonstrated that Sertoli cells express functionally active vitamin C transporters. Kinetic characteristics were described for both transport systems (SVCT and GLUT systems). Sertoli cells are able to transport both forms of vitamin C. These fi ndings are extremely relevant, because Sertoli cells may control the amount of vitamin C in the adluminal compartment, as well as regulating the availability of this metabolite throughout spermatogenesis.

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Steady-state turnover and body pool of ascorbic acid in man

Cited by 213 publications

References 12 publications

Disturbed handling of ascorbic acid in diabetic patients with and without microangiopathy during high dose ascorbate supplementation

Disturbed handling of ascorbic acid in diabetic patients with and without microangiopathy during high dose ascorbate supplementation

Micronutrients: interaction between physical activity, intakes and requirements

Vitamin C and oxidative stress in the seminiferous epithelium

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