Pregnancy Up-Regulates Intestinal Calcium Absorption and Skeletal Mineralization Independently of the Vitamin D Receptor
Bibliographic record
Abstract
Without the vitamin D receptor (VDR), adult mammals develop reduced intestinal calcium absorption, rickets, and osteomalacia. Intestinal calcium absorption normally increases during pregnancy so that the mother can supply sufficient calcium to her fetuses. The maternal skeleton is rapidly resorbed during lactation to provide calcium needed for milk; that lost bone mineral content (BMC) is completely restored after weaning. We studied Vdr null mice to determine whether these adaptations during pregnancy and lactation require the VDR. Vdr nulls were severely rachitic at 10 wk of age on a normal diet. Pregnancy induced a 158% increase in Vdr null BMC to equal the pregnant wild-type (WT) value. Lactation caused BMC losses that were equal in Vdr nulls and WT. Vdr nulls recovered after weaning to a BMC 50% higher than before pregnancy and equal to WT. Additional analyses showed that during pregnancy, duodenal (45)Ca absorption increased in Vdr nulls, secondary hyperparathyroidism lessened, bone turnover markers decreased, and osteoid became fully mineralized. A genome-wide microarray analysis of duodenal RNA found marked reduction of Trpv6 in Vdr nulls at baseline but a 13.5-fold increase during pregnancy. Calbindin D-9K (S100g) and Ca(2+)-ATPase (Pmca1) were not altered by pregnancy. Several other solute transporters increased during pregnancy in Vdr nulls. In summary, Vdr nulls adapt to pregnancy by up-regulating duodenal Trpv6 and intestinal (45)Ca absorption, thereby enabling rapid normalization of BMC during pregnancy. These mice lactate normally and fully restore BMC after weaning. Therefore, VDR is not required for the skeletal adaptations during pregnancy, lactation, and after weaning.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".