Irina L Tourkova, Reed A Rankin, Quitterie C Larrouture, Steve F Dobrowolski, Carlos M Isales, Harry C Blair
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引用次数: 0
Abstract
After finding that minimal amounts of adrenocorticotropic hormone (ACTH1-24) prevented osteonecrosis in rabbits, we studied bone formation at nanomolar ACTH1-24, in vivo in rabbits, and in vitro in human osteoblasts. ACTH1-24 in rabbits at 0.6 μg/kg/day had no measurable effect on cortisol. Groups of five rabbits given 0.6 μg/kg/day of ACTH1-24 enhanced trabecular bone in the rabbit femoral head relative to saline-treated controls (controls), increased bone volume/total volume (BV/TV) by micro-computed tomography, p<0.03. Xylenol orange and calcein labeling in vivo showed increased trabecular bone formation with 0.6 μg/kg/day of ACTH1-24, p = 0.0089 versus controls. In contrast, the cortex of the femoral shaft was unaffected, BV/TV p>0.95 ACTH1-24 versus controls. Bone marrow mRNA by PCR showed no change in osteoclast markers, and confirmed increased osteoblast markers, p<0.05. In vitro, ACTH1-24 elevated expression of Collagen 1, alkaline phosphatase (ALP), osteocalcin (BGLAP), and RunX2 in human osteoblasts differentiated on polyethylene terephthalate (PET) membranes. Optimal response was at 10-9 to 10-12 M. VEGF, VEGF receptors FLT-1 and FLK-1, and ACTH1-24 receptors MC2R were upregulated at 10-12 M ACTH1-24. Pathway analysis included increased BMP2, Smad1, Wnt-1, β-Catenin and TGF-β pathways. Because bone-forming osteoblasts are metabolically highly active, we studied mRNA expression of mitochondrial complex 1 (NDUFA5, NDUFS2, NDUFB1, NDUFB6) members with key roles in energy production. This increased at 10-12 M ACTH1-24. An ELISA for mitochondrial complex 1 activity showed maximum activity at 10-9 M and high activity at 10-12 M ACTH1-24. Thus, long-term very low dose ACTH1-24 increases bone formation in vivo and in vitro.
期刊介绍:
The American Journal of Physiology-Endocrinology and Metabolism publishes original, mechanistic studies on the physiology of endocrine and metabolic systems. Physiological, cellular, and molecular studies in whole animals or humans will be considered. Specific themes include, but are not limited to, mechanisms of hormone and growth factor action; hormonal and nutritional regulation of metabolism, inflammation, microbiome and energy balance; integrative organ cross talk; paracrine and autocrine control of endocrine cells; function and activation of hormone receptors; endocrine or metabolic control of channels, transporters, and membrane function; temporal analysis of hormone secretion and metabolism; and mathematical/kinetic modeling of metabolism. Novel molecular, immunological, or biophysical studies of hormone action are also welcome.