Vitamin a status in rats submitted to graded levels of dietary restriction

Antioxidant status of pair-fed labrador retrievers is affected by diet restriction and aging

Twenty-four sibling pairs of 8-wk-old Labrador Retrievers were assigned to an experiment to determine the effects of diet restriction (75% of control-fed pair mate) on the quality and span of canine life and to identify biological markers of aging in dogs. The antioxidant status of these dogs was monitored by annual assays for serum retinol (RT), retinyl palmitate (RP), total vitamin A (VA), vitamin E (VE), selenium (Se), copper (Cu), and ceruloplasmin (Cp), plasma ascorbic acid (AA), uric acid (UA), and total peroxyl-radical trapping activity (TRAP), and whole-blood glutathione peroxidase (Gpx). Data in this report are for the 6-y period of the experiment when the dogs were between 5 and 10 y of age. Diet restriction reduced RT, VE, Cu, and Cp. Aging was associated with decreased RP, VA, VE, Se, and Cu and with increased RT, Cp, and Gpx. Female dogs had lower RP, VA, Cu, and Cp than male dogs. Litter effects were observed for VE, Cu, UA, and Gpx. Treatment effects on serum RT and Cu suggest that these variables are not as regulated homeostatically by hepatic storage as in most other species. Although the antioxidant profiles did not elucidate how diet restriction contributes to longevity, they have the potential to enhance our understanding of canine clinical nutrition and to have practical applications in formulating canine diets.

Iron deficiency in young rats alters the distribution of vitamin A between plasma and liver and between hepatic retinol and retinyl esters

We assessed whether iron deficiency alters the concentration of vitamin A (VA) in plasma or liver and the chemical distribution between hepatic unesterified and esterified retinol. Weanling male Sprague-Dawley rats (n = 10/group) were allocated to one of four diet groups: low iron (ID3, 3 mg of elemental iron/kg diet), marginal iron (ID15, 15 mg/kg), control diet food-restricted to the ID3 group (FR, 35 mg/kg), and control diet ad libitum consumption (AD, 35 mg/kg). Both ID3 and FR rats grew less than AD and ID15 rats. At the end of 5.5 wk, plasma retinol concentrations of the ID3 and FR rats were reduced >40% compared to ID15 and AD rats [Kruskal-Wallis test (K-W), P < 0.0042)]. Paradoxically, the hepatic VA concentration was greater in FR rats, with accumulation of more retinyl esters and retinol compared to the other dietary groups. Concentrations of hepatic retinyl esters and retinol did not differ among the other groups, but the molar ratio of hepatic retinyl esters to retinol was greater in ID3 rats (20.1 +/- 1.4) compared to ID15 rats (13.8 +/- 1.6, P = 0.02), AD (11.3 +/- 2.1, P < 0.0042) and FR (9.5 +/- 1.1, P < 0.0042). Iron deficiency may cause changes in liver and plasma VA that are refractory to VA intake, and thus a benefit may be derived from combining iron and VA supplements during nutrition interventions.