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, we measured the most physiologically active metabolite, 1,25-dihydroxyvitamin D
3 (1,25(OH)
2D
3), and the less well understood metabolite, 24,25-dihydroxyvitamin D
3 (24,25(OH)
2D
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)
2D
3 (53 ng/ml [
SD 35] vs. 7 ng/ml [
SD 5]). There was no difference in serum 1,25(OH)
2D
3 between the colonies. Serum 1,25(OH)
2D
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)
2D
3; excess 25(OH)D
3 is metabolized into 24,25(OH)
2D
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.
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