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Contributions of Dickkopf-1 to Obesity-Induced Bone Loss and Marrow Adiposity.

ABSTRACT: Low bone strength in overweight individuals is a significant medical problem. One important determinant of mesenchymal stem cell fate into osteoblasts or adipocytes is the Wnt signaling pathway. We recently showed that Dickkopf-1 (DKK1), a potent Wnt inhibitor, is upregulated in obese mice. In this study, we investigated the role of DKK1 in the pathogenesis of obesity-induced bone loss using global and tissue-specific KO mice. Obesity was induced in 8-week-old male mice with an inducible global (Rosa26-CreERT2) or osteoprogenitor- (Osx-Cre-) specific deletion of Dkk1 with a high-fat diet (HFD) containing 60% fat. After 12?weeks, body weight, bone volume, bone fat mass, and bone turnover were assessed. Dkk1 ^fl/fl ;Rosa26-CreERT2 mice experienced a similar increase in body weight and white fat pads as control mice. A HFD significantly reduced trabecular bone mass and the bone formation rate in Cre- mice and Dkk1 ^fl/fl ;Rosa26-CreERT2 mice. Interestingly, Dkk1 ^fl/fl ;Rosa26-CreERT2 mice were protected from HFD-induced cortical bone loss. Furthermore, a HFD was associated with increased bone marrow fat in the femur, which was less pronounced in Dkk1 ^fl/fl ;Rosa26-CreERT2 mice. Mice with an osteoprogenitor-specific Dkk1 deletion showed similar results as the global knockout, showing a protection against HFD-induced cortical bone loss and an accumulation of bone marrow fat, but a similar decrease in trabecular bone volume. In summary, DKK1 appears to contribute distinctly to cortical, but not trabecular bone loss in obesity. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

SUBMITTER: Colditz J

PROVIDER: S-EPMC7285751 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Contributions of Dickkopf-1 to Obesity-Induced Bone Loss and Marrow Adiposity.

Colditz Juliane J Picke Ann-Kristin AK Hofbauer Lorenz C LC Rauner Martina M

JBMR plus 20200428 6

Low bone strength in overweight individuals is a significant medical problem. One important determinant of mesenchymal stem cell fate into osteoblasts or adipocytes is the Wnt signaling pathway. We recently showed that Dickkopf-1 (DKK1), a potent Wnt inhibitor, is upregulated in obese mice. In this study, we investigated the role of DKK1 in the pathogenesis of obesity-induced bone loss using global and tissue-specific KO mice. Obesity was induced in 8-week-old male mice with an inducible global ...[more]

PMID: 32537550

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Project description:Oxidative stress-induced reactive oxygen species, DNA damage, apoptosis, and cellular senescence have been associated with reduced osteoprogenitors in a reciprocal fashion to bone marrow adipocyte tissue (BMAT); however, a direct (causal) link between cellular senescence and BMAT is still elusive. Accumulation of senescent cells occur in naturally aged and in focally radiated bone tissue, but despite amelioration of age- and radiation-associated bone loss after senescent cell clearance, molecular events that precede BMAT accrual are largely unknown. Here we show by RNA-Sequencing data that BMAT-related genes were the most upregulated gene subset in radiated bones of C57BL/6 mice. Using focal radiation as a model to understand age-associated changes in bone, we performed a longitudinal assessment of cellular senescence and BMAT. Using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), RNA in situ hybridization of p21 transcripts and histological assessment of telomere dysfunction as a marker of senescence, we observed an increase in senescent cell burden of bone cells from day 1 postradiation, without the presence of BMAT. BMAT was significantly elevated in radiated bones at day 7, confirming the qRT-PCR data in which most BMAT-related genes were elevated by day 7, and the trend continued until day 42 postradiation. Similarly, elevation in BMAT-related genes was observed in bones of aged mice. The senolytic cocktail of Dasatinib (D) plus Quercetin (Q) (ie, D + Q), which clears senescent cells, reduced BMAT in aged and radiated bones. MicroRNAs (miRNAs or miRs) linked with senescence marker p21 were downregulated in radiated and aged bones, whereas miR-27a, a miR that is associated with increased BMAT, was elevated both in radiated and aged bones. D + Q downregulated miR-27a in radiated bones at 42 days postradiation. Overall, our study provides evidence that BMAT occurrence in oxidatively stressed bone environments, such as radiation and aging, is induced following a common pathway and is dependent on the presence of senescent cells. © 2022 American Society for Bone and Mineral Research (ASBMR).

Dataset Information

Contributions of Dickkopf-1 to Obesity-Induced Bone Loss and Marrow Adiposity.

Publications

Contributions of Dickkopf-1 to Obesity-Induced Bone Loss and Marrow Adiposity.

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