Evaluation of 25-hydroxy-vitamin D and parathyroid hormone in Callithrix penicillata primates living in their natural habitat in Brazil

Evaluation of vitamin D3 metabolites in Callithrix jacchus (common marmoset)

Vitamin D₃ (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 D₃ due to lack of sunlight exposure. The minimum dietary vitamin D₃ requirement and the maximum amount of vitamin D₃ that can be metabolized by marmosets is unknown. Observations of metabolic bone disease and gastrointestinal malabsorption have led to wide variation in dietary vitamin D₃ provision amongst research institutions, with resulting variation in circulating 25-hydroxyvitamin D₃ (25(OH)D₃ ), the accepted marker for vitamin D sufficiency/deficiency. Multiple studies have reported serum 25(OH)D₃ in captive marmosets, but 25(OH)D₃ is not the final product of vitamin D₃ metabolism. In addition to serum 25(OH)D_3, we measured the most physiologically active metabolite, 1,25-dihydroxyvitamin D₃ (1,25(OH)₂ D₃ ), and the less well understood metabolite, 24,25-dihydroxyvitamin D₃ (24,25(OH)₂ D₃ ) to characterize the marmoset's ability to metabolize dietary vitamin D₃ . We present vitamin D₃ 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 D₃ per kilogram of dry matter. Colony A marmosets had higher serum 25(OH)D₃ (426 ng/ml [SD 200] vs. 215 ng/ml [SD 113]) and 24,25(OH)₂ D₃ (53 ng/ml [SD 35] vs. 7 ng/ml [SD 5]). There was no difference in serum 1,25(OH)₂ D₃ between the colonies. Serum 1,25(OH)₂ D₃ increased and 25(OH)D₃ decreased with age, but the effect was weak. Marmosets tightly regulate metabolism of dietary vitamin D₃ into the active metabolite 1,25(OH)₂ D₃ ; excess 25(OH)D₃ is metabolized into 24,25(OH)₂ D₃ . This ability explains the tolerance of high levels of dietary vitamin D₃ by marmosets, however, our data suggest that these high dietary levels are not required.

25-OH-vitamin D, parathyroid hormone, and calcium serum levels in captive common marmosets (Callithrix jacchus): Reference values and effect of age, sex, season, and closure of long bone epiphyses

BACKGROUND

To date, reference values for 25-OH-vitamin D, parathyroid hormone (PTH), and calcium in serum of common marmosets (Callithrix jacchus) based on a large sample size are not available.

METHODS

Serum reference values for these parameters were determined and correlated with sex, age, season of sampling, and time of long bone epiphyseal closure in captive-housed marmosets.

RESULTS AND CONCLUSIONS

The 90% reference range for serum 25-OH-vitamin D is 47.40-370.4 nmol/L, for PTH 2.10-30.51 pmol/L, and for calcium 2.08-2.63 mmol/L. Lower levels of vitamin D were measured in fall compared with the other seasons. Levels of PTH were higher in males than in females, and calcium levels were lower in younger animals compared with older marmosets. No other effects of age, sex, season, or timing of growth plate closure were found.

Vitamin D status in wild toque macaques (Macaca sinica) in Sri Lanka

The vitamin D receptor is found on most cells, including active immune cells, implying that vitamin D has important biological functions beyond calcium metabolism and bone health. Although captive primates should be given a dietary source of vitamin D, under free-living conditions vitamin D is not a required nutrient, but rather is produced in skin when exposed to UV-B light. The circulating level of 25 hydroxyvitamin D (25-OH-D) considered adequate for humans is a topic of current controversy. Levels of circulating 25-OH-D sufficient for good health for macaques and other Old World anthropoids are assumed to be the same as human values, but data from free-living animals are scant. This study reports values for 25-OH-D and the active vitamin D metabolite, 1,25-dihydroxyvitamin D (1,25[OH]₂ D) for wild, forest-ranging toque macaques (Macaca sinica) in Sri Lanka. Plasma samples were obtained from eight adult males, seven juvenile males, six young nulliparous females, nine adult females not pregnant or lactating, eleven lactating adult females, and four pregnant females. Mean values for the complete sample were 61.3 ± 4.0 ng/ml for 25-OH-D and 155.6 ± 8.7 pg/ml for 1,25[OH]₂ D. There were no significant differences for either metabolite among age and sex classes, nor between lactating and non-reproductive females. Values from the literature for circulating 25-OH-D in captive macaques are three times higher than those found in this wild population, however, 1,25[OH]₂ D values in captive animals were similar to the wild values. The data from this study indicate that anthropoid primates exposed to extensive sunlight will have circulating values of 25-OH-D generally above 30 ng/ml, providing some support for the Endocrine Society recommendations for humans. Current dietary vitamin D supplementation of captive macaques likely exceeds requirement. This may affect metabolism and immune function, with possible consequences for macaque health and biomedical research results.

Measurement of 25-hydroxyvitamin D(2&3) and 1,25-dihydroxyvitamin D(2&3) by tandem mass spectrometry: A primate multispecies comparison

Vitamin D metabolites are widely studied for their roles in bone health, immune functions, and other potential physiologic roles in humans. However, the optimal blood levels of vitamin D metabolites are still unclear. Various methods for measuring vitamin D metabolites have been used and recently liquid chromatography tandem mass spectroscopy (LC-MS/MS) has been adopted as the gold standard for vitamin D metabolite measurement. Here, we report the use of LC-MS/MS to measure 25-hydroxyvitamin D (25(OH)D(2&3)), and 1,25-dihydroxyvitamin D (1,25(OH)2D(2&3)), in three laboratory nonhuman primate species: common marmoset (Callithrix jacchus), rhesus macaque (Macaca mulatta), and cynomolgus macaque (Macaca fascicularis), and compare them to humans using the same technique. The nonhuman primates showed blood levels for 25(OH)D3 and 1,25(OH)2D3 significantly higher than human values with marmosets having the highest levels. Marmoset samples showed significantly more variability among individuals than those from macaques for both metabolites, but all three nonhuman primate species exhibited large variation within species for both 25(OH)D(2&3) and 1,25(OH)2D(2&3). Marmoset females had significantly lower values than the males for 25(OH)D3, while rhesus males showed a significant decrease in 25(OH)D3 with age. The most striking finding is the variation within species for vitamin D levels even in laboratory primates that have a controlled diet, UV exposure, and in some cases, genetic constraints. Similar variation in 25(OH)D responses to a fixed dose of oral vitamin D supplementation has been reported in humans. We suggest that these species can provide primate models for examining the factors influencing variation in the levels of vitamin D necessary for human and nonhuman primate health.