Time Course of Vitamin D Depletion and Repletion in Reproductive-age Female C57BL/6 Mice

The use of animal models in vitamin D deficiency (VDD) research, particularly in regard to maternal deficits, has increased dramatically, yet these studies may be confounded due to ill-conceived experimental timelines. We conducted 2 experiments to (1) characterize the time course of VDD induction and repletion and (2) explore the long-term consequences of VDD on calcium homeostasis and body composition in reproductive-age female mice. Eight-week-old female C57BL/6 mice were randomized to receive either a vitamin D sufficient (VDS) or VDD diet; serum was collected weekly. At week 4, VDD mice were switched to VDS diet, and serum was collected weekly until week 8. Another group of same-age female mice was maintained on VDD diet for 40 wk. Body weights and serum were collected every 2 wk until week 40, when body composition was measured by using echoMRI. Mice did not become VDD until week 3 of the VDD diet and, after decreasing slightly at 4 wk, serum 25-hydroxyvitamin D remained unchanged through 40 wk. Vitamin D repletion to 25-hydroxyvitamin D concentrations considered adequate by the Institute of Medicine took 2 to 3 wk. Prolonged VDD in mice was marked by hypocalcemia and hyperparathyroidism and led to proportional decreases in both lean and fat mass. These data provide guidance in the design of studies using mice as a maternal VDD model, especially those exploring its effects on the developmental origins of health and disease and highlight the importance of monitoring and controlling the calciotropic effects of diet-induced VDD. This study also shows that prolonged VDD in reproductive-age female C57BL/6 mice induces metabolically meaningful changes in absolute, but not relative, body composition.