Volume 89, Issue 3, March (2003), pp. 303-310 © The Author 2003
doi:10.1079/BJN2002775

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Comparison of vitamin C deficiency with food restriction on collagen cross-link ratios in bone, urine and skin of weanling guinea-pigs

C. J. Bates^CA and Harumi Tsuchiya^*
MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge CB1 9NL, UK

 (Received 15 April 2002–Revised 27 August 2002–Accepted 3 October 2002)

Mild-to-moderate vitamin C depletion in weanling guinea-pigs affects pyridinoline:deoxypyridinoline (collagen cross-link) ratios in femur shaft and urine, attributed to impairment of hydroxylation of collagen lysine. We investigated: (1) whether the picture at two time points is compatible with progressive accumulation of abnormal collagen; (2) whether any changes are seen in skin, where little deoxypyridinoline occurs; (3) whether total food restriction has similar effects. Male weanling Dunkin–Hartley guinea-pigs were fed diets containing either 0·5 (vitamin C-restricted) or 160·0–320·0 (vitamin C-adequate) mg vitamin C/d. Two groups receiving the vitamin C-adequate diet received it ad libitum. Two other groups received the vitamin C-adequate diet in a restricted amount, limited to that which permitted nearly the same growth rate as in the vitamin C-restricted groups. Animals were fed for 4 or 8 weeks; urine was collected, and vitamin C and collagen indices were measured. In the femur shaft, the hydroxyproline content per unit weight was unaffected by vitamin C restriction or by total food restriction. Deoxypyridinoline was increased and the pyridinoline:deoxypyridinoline ratio was decreased in vitamin C-restricted groups, but not in food-restricted groups. Changes in the value of the ratio were greater after 8 than after 4 weeks. Urine indices mirrored bone indices. In skin, the main effect of vitamin C restriction was to reduce hydroxyproline. Here, the cross-link ratios changed less markedly than in bone, and there was less deoxypyridinoline. We conclude that the picture at two time points is compatible with a progressive accumulation of pyridinoline-enriched collagen in vitamin C-deprived animals, that the picture in skin differs from that of bone and urine, and that cross-link changes are not produced by total food restriction.

Keywords:
Vitamin C, Collagen, Cross-links, Guinea-pig