Effects of the peroxisome proliferator-activated receptor (PPAR)-δ agonist GW501516 on bone and muscle in ovariectomized rats.

Estrogen deficiency promotes bone loss and skeletal muscle dysfunction. Peroxisome proliferator-activated receptors (PPARs) have 3 subtypes (α, δ, and γ). PPARγ agonists induce bone loss, whereas PPARα agonists increase bone mass. Although PPARδ agonists are known to influence skeletal muscle metabolism, the skeletal effects are unsettled. This study investigated the musculoskeletal effects of the PPARδ agonist GW501516 in ovariectomized (OVX) rats. Female Sprague Dawley rats, 12 weeks of age, were allocated to a sham-operated group and 3 OVX groups; high-dose GW501516 (OVX-GW5), low-dose GW501516 (OVX-GW1), and a control group (OVX-CTR), respectively (n = 12 per group). Animals received GW501516 or vehicle (methylcellulose) daily for 4 months by gavage. Bone mineral density (BMD) was assessed by dual x-ray absorptiometry at the femur, spine, and whole body. Bone microarchitecture at the proximal tibia was assessed by microcomputed tomography, and dynamic histomorphometry was performed. Quadriceps muscle morphology and the relative expression of mitochondrial proteins were analyzed. Bone metabolism markers and metabolic markers were measured in plasma. After 4 months, the OVX-GW5 group displayed lower femoral BMD than OVX-CTR. Trabecular separation was higher in the GW-treated groups, compared with OVX-CTR. The OVX-GW5 group also exhibited lower cortical area fraction and a higher structure model index than OVX-CTR. These effects coincided with impaired bone formation in both GW groups. The OVX-GW5 group displayed elevated triglyceride levels and reduced adiponectin levels, whereas no effects on muscle morphology or mitochondrial gene expression appeared. In summary, the PPARδ agonist GW501516 negatively affected bone properties in OVX rats, whereas no effects were detected in skeletal muscle.

The need for clinical guidance in the use of calcium and vitamin D in the management of osteoporosis: a consensus report.

A European Union (EU) directive on vitamins and minerals used as ingredients of food supplements with a nutritional or physiological effect (2002/46/EC) was introduced in 2003. Its implications for the use of oral supplements of calcium and vitamin D in the prevention and treatment of osteoporosis were discussed at a meeting organized with the help of the World Health Organization (WHO) Collaborating Center for Public Health Aspects of Rheumatic Diseases (Liège, Belgium) and the support of the WHO Collaborating Center for Osteoporosis Prevention (Geneva, Switzerland). The following issues were addressed: Is osteoporosis a physiological or a medical condition? What is the evidence for the efficacy of calcium and vitamin D in the management of postmenopausal osteoporosis? What are the risks of self-management by patients in osteoporosis? From their discussions, the panel concluded that: (1) osteoporosis is a disease that requires continuing medical attention to ensure optimal therapeutic benefits; (2) when given in appropriate doses, calcium and vitamin D have been shown to be pharmacologically active (particularly in patients with dietary deficiencies), safe, and effective for the prevention and treatment of osteoporotic fractures; (3) calcium and vitamin D are an essential, but not sufficient, component of an integrated management strategy for the prevention and treatment of osteoporosis in patients with dietary insufficiencies, although maximal benefit in terms of fracture prevention requires the addition of antiresorptive therapy; (4) calcium and vitamin D are a cost-effective medication in the prevention and treatment of osteoporosis; (5) it is apparent that awareness of the efficacy of calcium and vitamin D in osteoporosis is still low and further work needs to be done to increase awareness among physicians, patients, and women at risk; and (6) in order that calcium and vitamin D continues to be manufactured to Good Manufacturing Practice standards and physicians and other health care professionals continue to provide guidance for the optimal use of these agents, they should continue to be classified as medicinal products.

The effect of teriparatide [human parathyroid hormone (1-34)] therapy on bone density in men with osteoporosis.

Teriparatide [rhPTH(1-34)] increases bone mineral density and reduces the risk of vertebral fracture in women. We randomized 437 men with spine or hip bone mineral density more than 2 SD below the young adult male mean to daily injections of placebo, teriparatide 20 microg, or teriparatide 40 microg. All subjects also received supplemental calcium and vitamin D. The study was stopped after a median duration of 11 months because of a finding of osteosarcomas in rats in routine toxicology studies. Biochemical markers of bone formation increased early in the course of therapy and were followed by increases in indices of osteoclastic activity. Spine bone mineral density was greater than in placebo subjects after 3 months of teriparatide therapy, and by the end of therapy it was increased by 5.9% (20 microg) and 9.0% (40 microg) above baseline (p < 0.001 vs. placebo for both comparisons). Femoral neck bone mineral density increased 1.5% (20 microg; p = 0.029) and 2.9% (40 microg; p < 0.001), and whole body bone mineral content increased 0.6% (20 microg; p = 0.021) and 0.9% (40 microg;p = 0.005) above baseline in the teriparatide subjects. There was no change in radial bone mineral density in the teriparatide groups. Bone mineral density responses to teriparatide were similar regardless of gonadal status, age, baseline bone mineral density, body mass index, smoking, or alcohol intake. Subjects experienced expected changes in mineral metabolism. Adverse events were similar in the placebo and 20-microg groups, but more frequent in the 40-microg group. This study shows that teriparatide treatment results in an increase in bone mineral density and is a potentially useful therapy for osteoporosis in men.