AUTHOR=Backus Robert C. , Ueda Devon C. 

TITLE=Age-dependent changes in plasma concentrations of 25-hydroxyvitamin D may complicate vitamin D status assessment of immature cats

JOURNAL=Frontiers in Veterinary Science

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2024.1365204

DOI=10.3389/fvets.2024.1365204

ISSN=2297-1769

ABSTRACT=<sec id="sec1"><title>Background</title><p>Vitamin D deficiency and excess in clinically presented cats conventionally is diagnosed by comparison of patient plasma 25-hydroxyvitamin D (25 (OH)D) concentration with plasma reference intervals determined in healthy adult cats. For immature cats, validity of this vitamin D status assessment method is uncertain.</p></sec><sec id="sec2"><title>Objective</title><p>The overall objective was determination of whether plasma concentration of 25 (OH) D and other vitamin D metabolites in immature cats markedly change with developmental age as has been reported in other species.</p></sec><sec id="sec3"><title>Methods</title><p>Four male and 4 female domestic short-hair kittens from weaning were continuously presented a single nutritionally adequate growth-diet. Concentrations of 25 (OH) D and 24,25-dihydroxyvitamin D (24,25 (OH)<sub>2</sub>D), and calcitriol were quantified in plasma of jugular venous blood collected at 12, 15, 18, and 21 weeks and 1 year of age. Plasma was liquid and solid-phase extracted and fractionation by normal-phase HPLC, and 25 (OH) D and 24,25 OH)<sub>2</sub>D quantified by reverse-phase HPLC-UV and calcitriol by RIA.</p></sec><sec id="sec4"><title>Results</title><p>Plasma 3-epi-25 (OH) D and 25 (OH) D concentrations increased (<italic>p</italic> &lt; 0.001) with age so that by study end the concentrations rose by 1-and 2-fold, respectively. Concentrations of 3-epi-25 (OH) D relative to 25 (OH) D were 30% at 12 weeks and 20% at 1 year. Between ages 12 and 21 weeks, rises in 25 (OH) D concentration were positively correlated with body weight gains (<italic>ρ</italic> = 0.952, <italic>p</italic> &lt; 0.001) and 24,25 (OH)<sub>2</sub>D concentrations were consistently greater than 25 (OH) D concentrations (<italic>p</italic> &lt; 0.001). At 1 year of age, concentrations of 24,25 (OH)<sub>2</sub>D declined below those of 25 (OH) D and 3-epi-24,25 (OH)<sub>2</sub>D consistency occurred in low concentrations. Vitamin D<sub>2</sub> metabolites and sex differences in metabolite concentrations were not observed.</p></sec><sec id="sec5"><title>Conclusion</title><p>Reliance on quantification of plasma 25 (OH) D concentration for vitamin D status assessment in kittens may be confounded by developmental changes in 25 (OH) D independent of vitamin D intake. High 24,25 (OH)<sub>2</sub>D concentration and occurrence of 3-epi-25 (OH) D in plasma additionally may interfere with the quantification.</p></sec>