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Bone marrow adipocytes: a neglected target tissue for growth hormone
Evelien F Gevers1, Nigel Loveridge, Iain C A F Robinson
1Division of Molecular Neuroendocrinology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom. egevers@nimr.mrc.ac.uk
Endocrinology
|September 20, 2002
Summary
Growth hormone (GH) specifically targets bone marrow adipocytes, regulating their numbers and function. This finding reveals a crucial role for GH in bone metabolism and energy homeostasis.
Area of Science:
- Endocrinology
- Bone Biology
- Adipocyte Biology
Background:
- Bone marrow contains adipocytes, osteoblasts, and chondrocytes derived from a common precursor.
- The function and regulation of bone marrow adipocytes remain largely unknown.
- Growth hormone (GH) and estrogen influence bone growth and mineralization, but their effects on bone marrow adipocytes are unclear.
Purpose of the Study:
- To investigate the role of GH and estrogen in regulating bone marrow adipocyte number, size, and function.
- To determine the impact of GH deficiency and hormonal treatments on bone marrow adipocyte and osteoblast populations.
Main Methods:
- Utilized growth hormone-deficient dwarf (dw/dw) rats, normal rats, and ovariectomized (Ovx) rats.
- Administered GH, IGF-1, PTH, or estrogen, and employed high-fat feeding.
- Quantified bone marrow adipocyte number, perimeter, area, bone area, and osteoblast activity (alkaline phosphatase).
Main Results:
- GH deficiency significantly increased bone marrow adipocyte number and size, while decreasing bone area and osteoblast number.
- GH treatment normalized bone marrow adipocyte levels and increased osteoblast-covered bone surface in GH-deficient rats.
- Estrogen influenced adipocyte number and bone parameters in ovariectomized rats, while PTH and high-fat feeding had limited effects on adipocyte number.
Conclusions:
- Growth hormone (GH) has a specific and significant action on bone marrow adipocytes, independent of general fat or bone metabolism.
- The marrow adipocyte lineage is a key target for GH action.
- GH plays a dual role in regulating both the differentiation of precursor cells into adipocytes, osteoblasts, and chondrocytes, and the metabolic activity of mature cells within bone marrow.