Abstract
Relationships between increased adiposity and fat-soluble vitamin storage and metabolism are poorly understood. To examine these associations, 6% or 21% dietary fat was fed to rats for 11 weeks and tissue vitamin A storage determined. Two levels of supplemental vitamin A were administered. At the end of the tenth week, 3,4-didehydroretinol (DR) was administered orally, and its kinetics were followed for 1 week in serum and tissues. Model-based compartmental analysis was applied to these data. Kidney total retinol (R) concentrations were elevated in rats fed 6% compared with 21% dietary fat (n = 24/group). The fractional transfer coefficient (FTC) describing the movement of tracer from plasma to extravascular stores was two times higher in the 6% compared with the 21% fat group. Consistent with the elevated renal R in 6% fat fed rats, there was a 2-fold increase in the FTC representing tracer distribution from plasma to kidney in the 6% compared with 21% fat group. Taken together with a fat main effect on renal vitamin A, our data support the evidence that faster turnover of kidney R may help set the mechanism governing vitamin A tissue distribution during deficiency. Rats fed 21% versus 6% dietary fat conserved hepatic R more efficiently.
Highlights
Relationships between increased adiposity and fat-soluble vitamin storage and metabolism are poorly understood
Considering the reported expansion of intravascular volume in obese adults [7] and the storage of vitamin A in adipose tissue [8], an important clinical question arises: do vitamin A requirements differ in obese versus lean individuals? If so, what are the driving mechanisms responsible for these differences? How nutritional status is affected in obese individuals is an emerging research area [4, 9]
fractional transfer coefficient (FTC) [L(I,J)s or the fraction of compartment J transferred to compartment I per unit time] were determined
Summary
Relationships between increased adiposity and fat-soluble vitamin storage and metabolism are poorly understood. To examine these associations, 6% or 21% dietary fat was fed to rats for 11 weeks and tissue vitamin A storage determined. Consistent with the elevated renal R in 6% fat fed rats, there was a 2-fold increase in the FTC representing tracer distribution from plasma to kidney in the 6% compared with 21% fat group. Given the reduced circulating vitamin A reported in obese adults [1, 2] and the need for clinically relevant biomarkers, it is increasingly important to understand how fat-soluble vitamin metabolism is affected by increased adiposity [3, 4]. Part of this work was presented at the Experimental Biology Meeting in 2007, Washington, DC, by A.L.E
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