Different effects on bone strength and cell differentiation in pre pubertal caloric restriction versus hypothalamic
R N Joshi1, F F Safadi, M F Barbe
1Department of Kinesiology, Temple University, Philadelphia, PA 19122, USA.
Bone
|August 3, 2011
Summary
Energy restriction during puberty may help bone strength by increasing vertebral bone volume. Hypothalamic suppression, however, leads to bone loss and reduced bone strength.
Area of Science:
- Endocrinology
- Bone Biology
- Nutritional Science
Background:
- Energy restriction and hypothalamic dysfunction during puberty can impact peak bone mass accrual.
- The relationship between energy restriction and bone strength is complex, with conflicting research findings.
- Estradiol suppression is hypothesized to mediate bone loss secondary to energy restriction.
Purpose of the Study:
- To investigate the effects of energy restriction and hypothalamic suppression on bone mechanical strength.
- To examine the osteogenic capacity of bone marrow-derived cells under these conditions.
- To compare two models: gonadotropin-releasing hormone antagonist (GnRH-a) treatment and 30% energy restriction (ER) in female rats.
Main Methods:
- Female Sprague Dawley rats were divided into control, GnRH-a, and ER groups.
- GnRH-a group received daily injections, while the ER group received 70% of control intake for 27 days.
- Evaluated body weight, organ weights, bone strength, histomorphometry, serum IGF-1, osteocalcin, and osteoblast proliferation/differentiation.
Main Results:
- GnRH-a treatment suppressed uterine weight, osteoblast proliferation, bone strength, and trabecular bone volume.
- ER group showed increased osteoblast proliferation and enhanced lumbar spine trabecular bone volume compared to controls.
- ER animals maintained relative bone strength despite smaller body size, unlike GnRH-a animals which exhibited bone deficits.
Conclusions:
- Hypothalamic suppression via GnRH-a leads to bone strength deficits and bone loss.
- Energy restriction may induce an adaptive increase in vertebral bone volume for mineral storage.
- The findings differentiate the bone effects of nutritional stress from those of estradiol suppression.
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