Blocking Oxidized Phospholipids Attenuates the Age-Associated, but Not the Ovariectomy- or Unloading- Induced, Bone Loss in Mice

Abstract Oxidized phospholipids (OxPL), such as oxidized phosphatidylcholine, are generated by oxidative stress (OS)-induced lipid peroxidation. E06 IgM is a natural antibody that recognizes the phosphocholine (PC) moiety of OxPLs, but not native PLs. Generation of transgenic mice expressing a single chain (scFv) form of its antigen-binding domain, “E06-scFv” mice, protects against atherosclerosis, hepatic steatosis and high fat diet-induced loss of bone mass. In addition, E06-scFv increases cancellous and cortical bone mass in both male and female adult mice fed chow diet, by increasing bone formation. Age-related bone loss is associated with increased OS and lipid peroxidation, and is characterized by a reduction in osteoblast number and bone formation. Oxidative stress is involved also in the bone loss caused by sex-steroid deficiency and elevated OS markers are found in unloading-induced bone loss, raising the possibility that an increase of OxPLs induced by OS might be contributing to the pathogenesis of these conditions as well. We aged homozygous E06-scFv transgenic female and male mice and their wild-type littermates up to 22 and 24 months respectively. Serial DXA BMD every 3 months showed that overexpression of E06-scFv attenuated the age-associated bone loss in both sexes. In addition, male and female E06-scFv transgenic mice also accumulated less fat mass than WT littermates during aging. Micro-CT analysis revealed that E06-scFv attenuated the age-associated decline in cancellous, but not cortical, bone mass. The histological analysis of the vertebrae indicated that the aged E06-scFv transgenic mice had increased osteoblasts and decreased osteoclasts compared to the WT mice. To investigate whether the beneficial effect of the E06-scFv could be seen after ovariectomy, 4.5 month old E06-scFv homozygous females and WT controls were ovariectomized (OVX). DXA and micro-CT measurements 6 weeks post- surgery indicated that, unlike aging, E06-scFv did not protect against OVX-induced bone loss in either the cancellous or the cortical compartment. Lastly, we tail-suspended 5.5 month old male mice and sacrificed them 21 days later. E06-scFv transgenic mice had similar cortical bone loss compared to WT mice. In conclusion, the E06-scFV transgene attenuates the age-associated cancellous bone loss in both female and male mice, but has no effect on the OVX- or unloading-induced bone loss. These results fully support our hypothesis that an increase in PC-OxPLs with age, caused at least in part by a decrease in natural anti-PC antibodies, contributes to the age-associated bone loss. This evidence provides proof of concept that blocking PC-OxPLs represents a therapeutic approach to countering the increase of PC-OxPLs with age and their adverse effects on age-related bone loss as well as atherosclerosis and NASH. It also confirms that the mechanisms of cancellous and cortical bone loss are distinct.

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SUN-346 A Natural Antibody Against Oxidized Phospholipids Attenuates Age-Related Bone Loss and Prevents Age-Related Glucose Intolerance in Mice

Journal of the Endocrine Society ◽

10.1210/jendso/bvaa046.640 ◽

2020 ◽

Vol 4 (Supplement_1) ◽

Author(s):

Michela Palmieri ◽

Joseph Teenamol ◽

Horacio Gomez-acevedo ◽

Joseph Lee Witztum ◽

Stavros C Manolagas ◽

...

Keyword(s):

Oxidative Stress ◽

Lipid Peroxidation ◽

Bone Loss ◽

Glucose Tolerance ◽

Bone Formation ◽

Transgenic Mice ◽

Glucose Intolerance ◽

Oxidized Phospholipids ◽

Male And Female ◽

Age Related

Abstract Lipid peroxidation produces oxidized phospholipids (OxPL) such as oxidized phosphatidylcholine. These compounds react with amino groups of proteins and lipids to form adducts called oxidation specific epitopes (OSEs), which are proinflammatory moieties present on oxidized low density lipoproteins and on apoptotic cells and, unless removed, cause extensive cell damage. Natural antibodies (NAb) produced by B-1 lymphocytes, bind OxPL and prevent their inflammatory activity. E06 is a NAb that recognizes the phosphocholine moiety of OxPL. We previously showed that transgenic expression of a single chain (scFv) form of the antigen-binding domain of E06 IgM (E06-scFv) increases cancellous and cortical bone mass in both male and female mice by increasing bone formation. Age-related bone loss is characterized by a decline in osteoblast number and bone formation, associated with increased oxidative stress and lipid peroxidation. These findings, together with the evidence that serum anti-OxPL IgM titers decrease with age, suggest that increased OxPL formation and decreased anti-OxPL antibodies may contribute to age-related bone loss. Like humans, mice exhibit an age-dependent worsening in glucose tolerance, mainly due to alteration in body composition and increased fat tissue. Chronic low grade inflammation and oxidative stress are associated with development of diabetes mellitus and B-1 lymphocytes have been shown to be protective against obesity associated inflammation, glucose intolerance, and insulin resistance. We tested the hypothesis that overexpression of E06-scFv could attenuate age-related bone loss and glucose intolerance. Serial BMD measurements by DXA of both female and male C57BL/6 E06-scFv transgenic mice (and their WT littermates) up to 22 and 24 months, respectively, showed that E06-scFv attenuated age-related bone loss at the spine and femur in both sexes. As revealed by microCT analysis, this effect was due to the attenuation of the age-associated decline in cancellous bone in both sexes. Additionally, both male and female E06-scFv transgenic mice accumulated less fat mass than WT littermates during aging. Intraperitoneal glucose tolerance test, at 15 months of age, revealed that glucose tolerance was greater in both male and female E06-ScFv mice than in respective WT littermates and did not differ from the glucose tolerance of young mice, indicating that E06-scFv improves glucose metabolism. These data suggest that OxPL impair both age-related bone loss and age-related glucose intolerance. Therefore, targeting OxPL with a neutralizing antibody such as E06, represents a prototypic therapeutic intervention that may simultaneously ameliorate important age-associated diseases.

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The bone-sparing effects of estrogen and WNT16 are independent of each other

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1520408112 ◽

2015 ◽

Vol 112 (48) ◽

pp. 14972-14977 ◽

Cited By ~ 24

Author(s):

Sofia Movérare-Skrtic ◽

Jianyao Wu ◽

Petra Henning ◽

Karin L. Gustafsson ◽

Klara Sjögren ◽

...

Keyword(s):

Bone Loss ◽

Bone Mass ◽

Trabecular Bone ◽

Cortical Bone ◽

Integration Site ◽

Mineral Density ◽

Trabecular Bone Mass ◽

Sparing Effect ◽

Total Body ◽

Cortical Bone Mass

Wingless-type MMTV integration site family (WNT)16 is a key regulator of bone mass with high expression in cortical bone, and Wnt16−/− mice have reduced cortical bone mass. As Wnt16 expression is enhanced by estradiol treatment, we hypothesized that the bone-sparing effect of estrogen in females is WNT16-dependent. This hypothesis was tested in mechanistic studies using two genetically modified mouse models with either constantly high osteoblastic Wnt16 expression or no Wnt16 expression. We developed a mouse model with osteoblast-specific Wnt16 overexpression (Obl-Wnt16). These mice had several-fold elevated Wnt16 expression in both trabecular and cortical bone compared with wild type (WT) mice. Obl-Wnt16 mice displayed increased total body bone mineral density (BMD), surprisingly caused mainly by a substantial increase in trabecular bone mass, resulting in improved bone strength of vertebrae L3. Ovariectomy (ovx) reduced the total body BMD and the trabecular bone mass to the same degree in Obl-Wnt16 mice and WT mice, suggesting that the bone-sparing effect of estrogen is WNT16-independent. However, these bone parameters were similar in ovx Obl-Wnt16 mice and sham operated WT mice. The role of WNT16 for the bone-sparing effect of estrogen was also evaluated in Wnt16−/− mice. Treatment with estradiol increased the trabecular and cortical bone mass to a similar extent in both Wnt16−/− and WT mice. In conclusion, the bone-sparing effects of estrogen and WNT16 are independent of each other. Furthermore, loss of endogenous WNT16 results specifically in cortical bone loss, whereas overexpression of WNT16 surprisingly increases mainly trabecular bone mass. WNT16-targeted therapies might be useful for treatment of postmenopausal trabecular bone loss.

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Calcitriol corrects bone loss induced by oophorectomy in rats

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1986.250.1.e35 ◽

1986 ◽

Vol 250 (1) ◽

pp. E35-E38

Author(s):

M. C. Faugere ◽

S. Okamoto ◽

H. F. DeLuca ◽

H. H. Malluche

Keyword(s):

Bone Loss ◽

Bone Mass ◽

Cortical Bone ◽

Structure Formation ◽

Bone Structure ◽

Subcutaneous Injections ◽

Calcium And Phosphorus ◽

Cortical Bone Mass ◽

Osteoid Seam ◽

Plate Width

The effects of calcitriol on histomorphometric parameters of bone structure, formation, and resorption were evaluated in 21 normal or oophorectomized rats. Twelve rats were oophorectomized; six of these received daily subcutaneous injections of 135 pmol of calcitriol for 14 wk starting 38 wk after oophorectomy. Nine rats were sham operated; five of these received the same treatment with calcitriol. There were no differences in serum calcium and phosphorus between sham-operated and oophorectomized animals and rats with or without calcitriol. Calcitriol treatment of sham-operated rats produced an increase in cancellous and cortical bone mass. Oophorectomy resulted in decreased cancellous and cortical bone mass and in a decreased ratio between mineralized and nonmineralized bone. There was no difference in bone-osteoclast interface and osteoid seam width among all groups of rats. Calcitriol corrected, at least in part, the bone loss in oophorectomized animals, normalized the ratio between mineralized and nonmineralized bone, and restored mean growth plate width to normal.

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Age-related changes in cortical bone mass: data from a German female cohort

European Radiology ◽

10.1007/s00330-005-0013-4 ◽

2005 ◽

Vol 16 (4) ◽

pp. 811-817 ◽

Cited By ~ 14

Author(s):

V. A. Molina Toledo ◽

M. Jergas

Keyword(s):

Bone Mass ◽

Cortical Bone ◽

Mass Data ◽

Age Related ◽

Cortical Bone Mass ◽

Female Cohort ◽

Age Related Changes

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Cortical bone gain following loading is site-specifically enhanced by prior and concurrent disuse in aged male mice

10.1101/705640 ◽

2019 ◽

Author(s):

Gabriel Galea ◽

Peter J Delisser ◽

Lee Meakin ◽

Lance E Lanyon ◽

Joanna S Price ◽

...

Keyword(s):

Bone Mass ◽

Cortical Bone ◽

List Type ◽

Male Mice ◽

Site Specific ◽

Female Mice ◽

Age Related ◽

Sciatic Neurectomy ◽

Bone Gain ◽

Old Mice

AbstractThe primary aim of bone anabolic therapies is to strategically increase bone mass in skeletal regions likely to experience high strains. This is naturally achieved by mechanical loading of the young healthy skeleton. However, these bone anabolic responses fail with age. Here, we applied site specificity analysis to map regional differences in bone anabolic responses to axial loading of the tibia (tri-weekly, for two weeks) between young (19-week-old) and aged (19-month-old), male and female mice. Loading increased bone mass specifically in the proximal tibia in both sexes and ages. Young female mice gained more cortical bone than young males in specific regions of the tibia. However, these site-specific sex difference were lost with age such that bone gain following loading was not significantly different between old males and females. Having previously demonstrated that prior and concurrent disuse enhances bone gain following loading in old females, we established whether this “rescue” is sex-specific. Old male mice were subjected to sciatic neurectomy or sham surgery, and tri-weekly loading was initiated four days after surgery. Disuse augmented cortical bone gain in response to loading in old male mice, but only in the regions of the tibia which were load-responsive in the young. Increased understanding of how locally-activated load-responsive processes lead to site-specific bone formation, and how the age-related diminution of these processes can be site-specifically enhanced by disuse, may lead to the next generation of strategic bone anabolic therapies.HighlightsSex differences in cortical tissue area of young and old mice are not site-specificThe loading response in young, but not old, mice is sex- and site-specificThe cortical loading response is site-specifically enhanced by disuse in old mice of both sexesThe trabecular loading response can be rescued by disuse in old male, but not female, mice

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