Abstract
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)(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.