Understanding the Cellular and Molecular Mechanisms of Physical Activity-Induced Health Benefits.

The beneficial effects of physical activity (PA) are well documented, yet the mechanisms by which PA prevents disease and improves health outcomes are poorly understood. To identify major gaps in knowledge and potential strategies for catalyzing progress in the field, the NIH convened a workshop in late October 2014 entitled "Understanding the Cellular and Molecular Mechanisms of Physical Activity-Induced Health Benefits." Presentations and discussions emphasized the challenges imposed by the integrative and intermittent nature of PA, the tremendous discovery potential of applying "-omics" technologies to understand interorgan crosstalk and biological networking systems during PA, and the need to establish an infrastructure of clinical trial sites with sufficient expertise to incorporate mechanistic outcome measures into adequately sized human PA trials. Identification of the mechanisms that underlie the link between PA and improved health holds extraordinary promise for discovery of novel therapeutic targets and development of personalized exercise medicine.

Randomized trial of once-weekly parathyroid hormone (1-84) on bone mineral density and remodeling.

CONTEXT: Daily PTH administration increases bone mineral density (BMD) and reduces fracture risk. However, cost and compliance significantly limit clinical use. OBJECTIVE: Our objective was to determine whether less frequent PTH administration increases lumbar spine BMD. PARTICIPANTS, DESIGN, AND SETTING: Fifty postmenopausal women ages 45-70 yr with femoral neck BMD T-score between -1.0 and -2.0 participated in a double-blind, randomized, placebo-controlled trial at St. Joseph Hospital, Bangor, ME. INTERVENTION: Subjects received sc injections of daily PTH(1-84) (100 mug) or placebo for 1 month, followed by weekly injections (PTH or placebo) for 11 months. OUTCOMES: Change in lumbar spine dual-energy x-ray absorptiometry areal BMD (primary) was assessed. Secondary outcomes included volumetric BMD at spine and hip by quantitative computed tomography, trabecular bone microarchitecture by magnetic resonance imaging of distal radius, and biochemical bone turnover markers. RESULTS: At 12 months, lumbar spine areal BMD increased 2.1% in PTH-treated women compared with placebo (P = 0.03). Vertebral trabecular volumetric BMD increased 3.8% in PTH-treated women compared with placebo group (P = 0.08). PTH-treated women also had higher distal radial trabecular bone volume, number, and thickness compared with placebo-treated women (P < 0.04). After 1 month of daily PTH, N-terminal propeptide of type I collagen (P1NP) was markedly increased compared with placebo (P < 0 .0001), and a difference persisted, although lessened, throughout the study. Bone resorption indices were unchanged in PTH-treated women and were reduced in the placebo group. CONCLUSION: Once-weekly PTH after 1 month of daily treatment increases spine BMD, radial trabecular bone, and bone formation markers in postmenopausal women. These results suggest that less frequent alternatives to daily PTH dosing for 2 yr could be effective. Additional studies are required to define the optimal frequency of PTH administration.

One year of alendronate after one year of parathyroid hormone (1-84) for osteoporosis.

BACKGROUND: Since the use of parathyroid hormone as a treatment for osteoporosis is limited to two years or less, the question of whether antiresorptive therapy should follow parathyroid hormone therapy is important. We previously reported results after the first year of this randomized trial comparing the use of full-length parathyroid hormone (1-84) alone, alendronate alone, or both combined. In the continuation of this trial, we asked whether antiresorptive therapy is required to maintain gains in bone mineral density after one year of therapy with parathyroid hormone (1-84). METHODS: In the data reported here, women who had received parathyroid hormone (1-84) monotherapy (100 microg daily) in year 1 were randomly reassigned to one additional year with either placebo (60 subjects) or alendronate (59 subjects). Subjects who had received combination therapy in year 1 received alendronate in year 2; those who had received alendronate monotherapy in year 1 continued with alendronate in year 2. Bone mineral density at the spine and hip was assessed with the use of dual-energy x-ray absorptiometry and quantitative computed tomography (CT). RESULTS: Over two years, alendronate therapy after parathyroid hormone therapy led to significant increases in bone mineral density in comparison with the results for placebo after parathyroid hormone therapy, a difference particularly evident for bone mineral density in trabecular bone at the spine on quantitative CT (an increase of 31 percent in the parathyroid hormone-alendronate group as compared with 14 percent in the parathyroid hormone-placebo group). During year 2, subjects receiving placebo lost substantial bone mineral density. CONCLUSIONS: After one year of parathyroid hormone (1-84), densitometric gains appear to be maintained or increased with alendronate but lost if parathyroid hormone is not followed by an antiresorptive agent. These results have clinical implications for therapeutic choices after the discontinuation of parathyroid hormone.

The effects of parathyroid hormone and alendronate alone or in combination in postmenopausal osteoporosis.

BACKGROUND: Parathyroid hormone increases bone strength primarily by stimulating bone formation, whereas antiresorptive drugs reduce bone resorption. We conducted a randomized, double-blind clinical study of parathyroid hormone and alendronate to test the hypothesis that the concurrent administration of the two agents would increase bone density more than the use of either one alone. METHODS: A total of 238 postmenopausal women (who were not using bisphosphonates) with low bone mineral density at the hip or spine (a T score of less than -2.5, or a T score of less than -2.0 with an additional risk factor for osteoporosis) were randomly assigned to daily treatment with parathyroid hormone (1-84) (100 microg; 119 women), alendronate (10 mg; 60 women), or both (59 women) and were followed for 12 months. Bone mineral density at the spine and hip was assessed by dual-energy x-ray absorptiometry and quantitative computed tomography. Markers of bone turnover were measured in fasting blood samples. RESULTS: The bone mineral density at the spine increased in all the treatment groups, and there was no significant difference in the increase between the parathyroid hormone group and the combination-therapy group. The volumetric density of the trabecular bone at the spine increased substantially in all groups, but the increase in the parathyroid hormone group was about twice that found in either of the other groups. Bone formation increased markedly in the parathyroid hormone group but not in the combination-therapy group. Bone resorption decreased in the combination-therapy group and the alendronate group. CONCLUSIONS: There was no evidence of synergy between parathyroid hormone and alendronate. Changes in the volumetric density of trabecular bone, the cortical volume at the hip, and levels of markers of bone turnover suggest that the concurrent use of alendronate may reduce the anabolic effects of parathyroid hormone. Longer-term studies of fractures are needed to determine whether and how antiresorptive drugs can be optimally used in conjunction with parathyroid hormone therapy.

Perspectives on the future of bone and joint diseases.

The diseases of bones, joints, and muscles are common, chronic, and very costly to society. While the impact of these diseases falls across the age spectrum, the worldwide growth in the percentage of elderly in the population makes attention to musculoskeletal disorders and conditions particularly critical. An effective prevention strategy, driven by an understanding of the fundamental biology of bone and connective tissue, can only result from an upshift in the efforts of many sectors--public and private, academic, scientific, and patient-based--with new opportunities for partnerships and collaborative efforts flourishing. The Decade of the Bone and Joint can serve as a catalyst in this effort. The National Institutes of Health (NIH) are pleased to join with other national and international organizations to promote new activities and initiatives during the next decade. The NIH Osteoarthritis Initiative is highlighted as an example of a public-private partnership to develop resources and information on the natural history of the disease process that can drive new clinical intervention studies in osteoarthritis. Hopefully, this initiative and others will pave the way for important, scientifically driven prevention strategies during the next decade.