Thiazide Diuretics Affect Osteocalcin Production in Human Osteoblasts at the Transcription Level Without Affecting Vitamin D3 Receptors
Bibliographic record
Abstract
Besides their natriuretic and calciuretic effect, thiazide diuretics have been shown to decrease bone loss rate and improve bone mineral density. Clinical evidence suggests a specific role of thiazides on osteoblasts, because it reduces serum osteocalcin (OC), an osteoblast-specific protein, yet the mechanisms implicated are unknown. We therefore investigated the role of hydrochlorothiazide (HCTZ) on OC production by the human osteoblast-like cell line MG-63. HCTZ dose-dependently (1-100 microM) inhibited 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]-induced OC release by these cells (maximal effect, -40-50% and p < 0.005 by analysis of variance [ANOVA]) as measured by ELISA. This effect of HCTZ on OC release was caused by a direct effect on OC gene expression because Northern blot analysis revealed that OC messenger RNA (mRNA) levels were reduced in the presence of increasing doses of the diuretic (-47.2+/-4.0%; p < 0.0001 by paired ANOVA with 100 microM 13.6+/-0.49 pmol/mg protein/15 minutes; p < 0.05) in MG-63 cells. Reducing extracellular Ca2+ concentration with 0.5 mM EDTA or 0.5 mM ethylene glycol-bis(beta-amino ethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) only partly prevented the inhibitory effect of the diuretic on OC secretion (maximal effect, -22.5+/-6.9%), suggesting that thiazide-dependent Ca2+ influx is not sufficient to elicit the inhibition of OC secretion. Because OC production is strictly dependent on the presence of 1,25(OH)2D3 in human osteoblasts, we next evaluated the possible role of HCTZ on vitamin D3 receptors (VDR) at the mRNA and protein levels. Both Northern and Western blot analyses showed no effect of HCTZ (1-100 microM) on VDR levels. The presence of EGTA in the culture media reduced slightly the VDR mRNA levels under basal condition but this was not modified in the presence of increasing levels of HCTZ. The OC gene promoter also is under the control of transcription factors such as Yin Yang 1 (YY1) and cFOS. Western blot analysis revealed no changes in YY1 levels in response to HCTZ either in the presence or in the absence of 0.5 mM EGTA in the culture media. In contrast, HCTZ induced a dose-dependent increase in cFOS levels (p < 0.002 by ANOVA), a situation prevented by incubation with EGTA. These studies indicate that HCTZ inhibits OC mRNA expression independently of an effect on VDR, YY1, or extracellular Ca2+ levels but involves changes in cFOS levels. As OC retards bone formation/mineralization, the inhibition of OC production by HCTZ could explain its preventive role in bone loss rate.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".