Variation in estradiol level affects cortical bone growth in response to mechanical loading in sheep

Devlin, Maureen J.; Lieberman, Daniel E.

doi:10.1242/jeb.02675

Cited by 25 publications

(14 citation statements)

References 45 publications

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“…As compared to the other groups, animals in the latter group grew up to 27% more periosteal bone in response to exercise (Fig. 2), 55 supporting the hypothesis that higher E 2 levels upregulate skeletal responses to exercise. Specifically, this result highlights the point that E 2 may increase the sensi- tivity of bone to mechanical loading, but this has little effect on bone growth unless loading is actually occurring.…”

Section: Do Estrogen-strain Interactions Affect Skeletal Robusticity?supporting

confidence: 70%

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Estrogen, exercise, and the skeleton

Devlin¹

2011

Evolutionary Anthropology

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Patterns of variation in bone size and shape provide crucial data for reconstructing hominin paleobiology, including ecogeographic adaptation, life history, and functional morphology. Measures of bone strength, including robusticity (diaphyseal thickness relative to length) and cross-sectional geometric properties such as moments of area, are particularly useful for inferring behavior because bone tissue adapts to its mechanical environment. Particularly during skeletal growth, exercise-induced strains can stimulate periosteal modeling so that, to some extent, bone thickness reflects individual behavior. Thus, patterns of skeletal robusticity have been used to identify gender-based activity differences, temporal shifts in mobility, and changing subsistence strategies. Although there is no doubt that mechanical loading leaves its mark on the skeleton, less is known about whether individuals differ in their skeletal responses to exercise. For example, the potential effects of hormones or growth factors on bone-strain interactions are largely unexplored. If the hormonal background can increase or decrease the effects of exercise on skeletal robusticity, then the same mechanical loads might cause different degrees of bone response in different individuals. Here I focus on the role of the hormone estrogen in modulating exercise-induced changes in human bone thickness.

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Section: Do Estrogen-strain Interactions Affect Skeletal Robusticity?supporting

confidence: 70%

“…2). 55 Further, two studies in ovariectomized (OVX) rats reported that a combination of estrogen and mechanical loading protected against OVX-induced bone loss. These studies used a raised-cage model, in which food is placed at a height that requires the animal to use a bipedal stance.…”

Section: Do Estrogen-strain Interactions Affect Skeletal Robusticity?mentioning

confidence: 99%

Estrogen, exercise, and the skeleton

Devlin¹

2011

Evolutionary Anthropology

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“…Since the sample was composed of only female individuals from a single inbred strain, variation in hormonal levels (e.g. Devlin and Lieberman, 2007) likely had at most only a minor contribution to shape differences between groups that expose femora to different mechanical loading environments. Similarities in average Ps.Ar and Ct.Ar of groups is consistent with the view that our experimental design eliminated most confounding variables.…”

Section: Effects Of Locomotor Modes On Femoral Morphologymentioning

confidence: 99%

Increased non-linear locomotion alters diaphyseal bone shape

Carlson

Judex

2007

Journal of Experimental Biology

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SUMMARY Comparative studies of vertebrate morphology that link habitual locomotor activities to bone structural properties are often limited by confounding factors such as genetic variability between groups. Experimental assessment of bone's adaptive response to altered activity patterns typically involves superimposing exercise onto a normal locomotor repertoire, making a distinction between qualitative changes to locomotor repertoires and quantitative increases in activity level difficult. Here, we directly tested the hypothesis that an increase in turning activity, without the application of exercise per se, will alter femoral cross-sectional shape. Thirty day-old female BALB/cByJ mice (n=10 per group) were single-housed for 8 weeks in custom-designed cages that either accentuated linear or turning locomotion or allowed subjects to freely roam standard cages. Consistent with a lack of difference in physical activity levels between groups, there were no significant differences in body mass, femoral length, midshaft cortical area,and individual measures of mediolateral (ML) and anteroposterior (AP) bending rigidity. However, the ratio of ML to AP diaphyseal rigidity, an indicator of cross-sectional shape, was significantly greater (P<0.05) in turning subjects than in linear or control subjects. Considering that across all groups mice were genetically identical and had equivalent levels of bone quantity and physical activity, differences in femoral shape were attributed to qualitative differences in locomotor patterns (i.e. specific locomotor modes). These data indicate that increased turning can alter distribution of bone mass in the femoral diaphysis, and that turning should be considered in efforts to understand form–function relationships in vertebrates.

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“…Bone curvature is also known to change ontogenetically and in response to applied muscular and gravitational loads (Lanyon, 1980;Richmond, 1998;Jungers et al, 2002;Main and Biewener, 2006), and bone crosssectional properties are also well known to respond to loading conditions during ontogeny (Goodship et al, 1979;Lanyon et al, 1982;Carrier, 1983;Jaworski and Uhthoff, 1986;Haapasalo et al, 1994;Pearson and Lieberman, 2004), although the effects are dependent on many factors including age, hormonal levels, and initial bone status (Forwood and Burr, 1993;Damien et al, 1998;Lee et al, 2003;Lieberman et al, 2003;Ruff, 2003a,b;Devlin and Lieberman, 2007). Although this list is not comprehensive, these studies demonstrate that many aspects of bony morphology respond to bone loading conditions during an animal's lifetime.…”

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Knee Posture Predicted from Subchondral Apparent Density in the Distal Femur: An Experimental Validation

Polk

Blumenfeld

Ahluwalia

2008

The Anatomical Record

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Spatial patterning in the apparent density of subchondral bone can be used to discriminate between species that differ in their joint loading conditions. This study provides an experimental test of two hypotheses that relate aspects of subchondral apparent density patterns to joint loading conditions. First, the region of maximum subchondral apparent density (RMD) will correspond to differences in joint posture at the time of peak locomotor loads; and second, differences in maximum density between individuals will correspond to differences in exercise level. These hypotheses were tested using three age-matched samples of juvenile sheep. Two groups of five sheep were exercised, at moderate walking speeds, twice daily for 45 days on a treadmill with either a 0% or 15% grade. The remaining sheep were not exercised. Sheep walking on the inclined treadmill used more flexed knee postures than those in the level walking group at the time of peak vertical ground reaction forces. Kinematic measurements of knee posture were compared with knee postures estimated from the spatial position of the RMD on the medial femoral condyle. Our results show that the difference in the position of the RMD between the incline and level walking groups corresponded to the difference in knee postures obtained kinematically; however, exercised and nonexercised sheep did not differ in the magnitude of apparent density. These results suggest that patterns of subchondral apparent density are good indicators of the experimental modifications in joint posture during locomotion and may, therefore, be used to investigate differences between species in habitual joint loading.

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Variation in estradiol level affects cortical bone growth in response to mechanical loading in sheep

Cited by 25 publications

References 45 publications

Estrogen, exercise, and the skeleton

Estrogen, exercise, and the skeleton

Increased non-linear locomotion alters diaphyseal bone shape

Knee Posture Predicted from Subchondral Apparent Density in the Distal Femur: An Experimental Validation

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