Evaluation of vitamin D 3 metabolites in Callithrix jacchus (common marmoset).

Vitamin D-3 (cholecalciferol) is endogenously produced in the skin of primates when exposed to the appropriate wavelengths of ultraviolet light (UV-B). Common marmosets (Callithrix jacchus) maintained indoors require dietary provision of vitamin D-3 due to lack of sunlight exposure. The minimum dietary vitamin D-3 requirement and the maximum amount of vitamin D-3 that can be metabolized by marmosets is unknown. Observations of metabolic bone disease and gastrointestinal malabsorption have led to wide variation in dietary vitamin D-3 provision amongst research institutions, with resulting variation in circulating 25-hydroxyvitamin D-3 (25(OH)D-3), the accepted marker for vitamin D sufficiency/deficiency. Multiple studies have reported serum 25(OH)D-3 in captive marmosets, but 25(OH)D-3 is not the final product of vitamin D-3 metabolism. In addition to serum 25(OH)D-3,D- we measured the most physiologically active metabolite, 1,25-dihydroxyvitamin D-3 (1,25(OH)(2)D-3), and the less well understood metabolite, 24,25-dihydroxyvitamin D-3 (24,25(OH)(2)D-3) to characterize the marmoset's ability to metabolize dietary vitamin D-3. We present vitamin D-3 metabolite and related serum chemistry value colony reference ranges in marmosets provided diets with 26,367 (Colony A, N = 113) or 8,888 (Colony B, N = 52) international units (IU) of dietary vitamin D-3 per kilogram of dry matter. Colony A marmosets had higher serum 25(OH)D-3 (426 ng/ml [SD 200] vs. 215 ng/ml [SD 113]) and 24,25(OH)(2)D-3 (53 ng/ml [SD 35] vs. 7 ng/ml [SD 5]). There was no difference in serum 1,25(OH)(2)D-3 between the colonies. Serum 1,25(OH)(2)D-3 increased and 25(OH)D-3 decreased with age, but the effect was weak. Marmosets tightly regulate metabolism of dietary vitamin D-3 into the active metabolite 1,25(OH)(2)D-3; excess 25(OH)D-3 is metabolized into 24,25(OH)(2)D-3. This ability explains the tolerance of high levels of dietary vitamin D-3 by marmosets, however, our data suggest that these high dietary levels are not required.