Slow-release sodium fluoride in osteoporosis

Skeletal fluorosis from instant tea

INTRODUCTION

Skeletal fluorosis (SF) can result from prolonged consumption of well water with >4 ppm fluoride ion (F(-); i.e., >4 mg/liter). Black and green teas can contain significant amounts of F(-). In 2005, SF caused by drinking 1-2 gallons of double-strength instant tea daily throughout adult life was reported in a 52-yr-old woman.

MATERIALS AND METHODS

A 49-yr-old woman developed widespread musculoskeletal pains, considered fibromyalgia, in her mid-30s. Additionally, she had unexplained, increasing, axial osteosclerosis. She reported drinking 2 gallons of instant tea each day since 12 yr of age. Fluoxetine had been taken intermittently for 5 yr. Ion-selective electrode methodology quantitated F(-) in her blood, urine, fingernail and toenail clippings, tap water, and beverage.

RESULTS

Radiographs showed marked uniform osteosclerosis involving the axial skeleton without calcification of the paraspinal, intraspinal, sacrotuberous, or iliolumbar ligaments. Minimal bone excrescences affected ligamentous attachments in her forearms and tibias. DXA Z-scores were +10.3 in the lumbar spine and +2.8 in the total hip. Her serum F(-) level was 120 microg/liter (reference range, 20-80 microg/liter), and a 24-h urine collection contained 18 mg F(-)/g creatinine (reference value, <3). Fingernail and toenail clippings showed 3.50 and 5.58 mg F(-)/kg (control means, 1.61 and 2.02, respectively; p(s) < 0.001). The instant tea beverage, prepared as usual extra strength using tap water with approximately 1.2 ppm F(-), contained 5.8 ppm F(-). Therefore, the tea powder contributed approximately 35 mg of the 44 mg daily F(-) exposure from her beverage. Fluoxetine provided at most 3.3 mg of F(-) daily.

CONCLUSIONS

SF from habitual consumption of large volumes of extra strength instant tea calls for recognition and better understanding of a skeletal safety limit for this modern preparation of the world's most popular beverage.

Advances in the diagnosis and treatment of osteoporosis

Although severely low bone density is relatively rare in the pediatric population, it can be a significant problem in many patients with chronic illness. As peak bone formation occurs during adolescence, it is crucial that pediatricians and other care providers for this patient population recognize the significance of attainment of adequate bone. Dietary intake of vitamin D and calcium should be optimized, and correction of underlying causes of poor bone density should occur whenever possible. Assessment of bone density is difficult, as each technology available has problems, and none of the technologies are well-associated with fracture risk in pediatric patients. Once diagnosis of severely low bone density is established, treatment options are limited and poorly studied. The benefits of bisphosphonate therapy appear to outweigh the risks in patients with low bone density and frequent fragility fractures, and it appears that most improvement with bisphosphonates occurs within the first 2 to 4 years. Evidence, however, is emerging that once off therapy, bone turnover remains decreased for at least several years. During that time, improvements in bone density are decreased. Many questions remain regarding duration of therapy with bisphosphonate therapy and the long-term effects on the children who receive this medication. Anabolic therapies may become important in the future, but there is currently extremely limited information regarding their use in pediatrics.

Recovery from skeletal fluorosis (an enigmatic, American case)

A 52-year-old man presented with severe neck immobility and radiographic osteosclerosis. Elevated fluoride levels in serum, urine, and iliac crest bone revealed skeletal fluorosis. Nearly a decade of detailed follow-up documented considerable correction of the disorder after removal of the putative source of fluoride (toothpaste).

INTRODUCTION

Skeletal fluorosis, a crippling bone disorder, is rare in the United States, but affects millions worldwide. There are no data regarding its reversibility.

MATERIALS AND METHODS

A white man presented in 1996 with neck immobility and worsening joint pains of 7-year duration. Radiographs revealed axial osteosclerosis. Bone markers were distinctly elevated. DXA of lumbar spine (LS), femoral neck (FN), and distal one-third radius showed Z scores of +14.3, +6.6, and -0.6, respectively. Transiliac crest biopsy revealed cancellous volume 4.5 times the reference mean, cortical width 3.2 times the reference mean, osteoid thickness 25 times the reference mean, and wide and diffuse tetracycline uptake documenting osteomalacia. Fluoride (F) was elevated in serum (0.34 and 0.29 mg/liter [reference range: <0.20]), urine (26 mg/liter [reference range: 0.2-1.1 mg/liter]), and iliac crest (1.8% [reference range: <0.1%]). Tap and bottled water were negative for F. Surreptitious ingestion of toothpaste was the most plausible F source.

RESULTS

Monitoring for a decade showed that within 3 months of removal of F toothpaste, urine F dropped from 26 to 16 mg/liter (reference range: 0.2-1.1 mg/liter), to 3.9 at 14 months, and was normal (1.2 mg/liter) after 9 years. Serum F normalized within 8 months. Markers corrected by 14 months. Serum creatinine increased gradually from 1.0 (1997) to 1.3 mg/dl (2006; reference range: 0.5-1.4 mg/dl). Radiographs, after 9 years, showed decreased sclerosis of trabeculae and some decrease of sacrospinous ligament ossification. DXA, after 9 years, revealed 23.6% and 15.1% reduction in LS and FN BMD with Z scores of +9.3 and +4.8, respectively. Iliac crest, after 8.5 years, had normal osteoid surface and thickness with distinct double labels. Bone F, after 8.5 years, was 1.15% (reference range, <0.1), which was a 36% reduction (still 10 times the reference value). All arthralgias resolved within 2 years, and he never fractured, but new-onset nephrolithiasis occurred within 9 months and became a chronic problem.

CONCLUSIONS

With removal of F exposure, skeletal fluorosis is reversible, but likely impacts for decades. Patients should be monitored for impending nephrolithiasis.

Tratamiento anabólico en la osteoporosis

Pharmacological treatment of osteoporosis is based mainly on antiresorptive agents. However, there have been recently developed a group of drugs whose mechanism of action is the direct stimulation of bone formation: these drugs are named bone anabolic therapies. Among these compounds are fluoride, growth hormone (GH), insulin-like growth factor type I (IGF-I) and statins. Two further agents with major evidences of efficacy include strontium ranelate and parathyroid hormone (PTH) and its fragments. The present work reviews the current evidences of anabolic agents used in the treatment of osteoporosis.

New anabolic therapies in osteoporosis

Anabolic agents represent an important new advance in the therapy of osteoporosis. Their potential might be substantially greater than the anti-resorptives. Because the anti-resorptives and anabolic agents work by completely distinct mechanisms of action, it is possible that the combination of agents could be significantly more potent than either agent alone. Recent evidence suggests that a plateau in BMD might occur after prolonged exposure to PTH. Anti-resorptive therapy during or after anabolic therapy might prevent this skeletal adaptation. Protocols to consider anabolic agents as intermittent recycling therapy would be of interest. Of all the anabolics, PTH is the most promising. However, there are unanswered questions about PTH. More studies are needed to document an anabolic effect on cortical bone. More large-scale studies are needed to further determine the reduction in nonvertebral fractures with PTH, especially at the hip. In the future, PTH is likely to be modified for easier and more targeted delivery. Oral or transdermal delivery systems may become available. Recently, Gowen et al have described an oral calcilytic molecule that antagonizes the parathyroid cell calcium receptor, thus stimulating the endogenous release of PTH. This approach could represent a novel endogenous delivery system for intermittent PTH administration. Rising expectations that anabolic therapies for osteoporosis will soon play a major role in treating this disease are likely to fuel further studies and the development of even more novel approaches to therapy.

New anabolic therapies in osteoporosis

While antiresorptive drugs have been the cornerstone of osteoporosis therapy, anabolic drugs are an important new advance in the treatment of osteoporosis. By directly stimulating bone formation, anabolic agents might have greater potential than the antiresorptives to increase bone mass and to decrease fractures. It is also possible that the combination of an antiresorptive agent with an anabolic agent could be more potent than either agent alone. Potential anabolic therapies for osteoporosis, including fluoride, growth hormone, insulin-like growth factor-I, strontium, and parathyroid hormone, are reviewed here. Of these, parathyroid hormone has clearly emerged as the most promising treatment at this time.

Differential effects of bacterial toxins on mitogenic actions of sodium fluoride and those of aluminum fluoride in human TE85 osteosarcoma cells

This study compared the effects of cholera toxin (CTX) and pertussis toxin (PTX) on the actions of sodium fluoride (NaF) and those of aluminum fluoride (AlF3) on cell proliferation and differentiation, as well as tyrosine phosphorylation level of mitogen activated protein kinase (MAPK) in human bone cells. NaF and AlF3 each significantly stimulated the proliferation of human TE85 osteosarcoma cells, increased cellular alkaline phosphatase (ALP) activity, and increased MAPK tyrosine phosphorylation level. CTX completely blocked the bone cell anabolic activities of both NaF and AlF3. While PTX (2 ng/ml) inhibited the bone cell actions of NaF, it had no significant effect on those of AlF3. Both CTX and PTX completely blocked the stimulatory action of AlF3 on MAPK tyrosine phosphorylation, but neither toxin had an effect on the action of NaF on MAPK tyrosine phosphorylation. In conclusion, PTX and CTX had contrasting effects on the anabolic bone cell actions of NaF and AlF3 actions. These findings argue against the hypothesis that the osteogenic activity of NaF is mediated via the formation of AlF3 in human TE85 osteosarcoma cells.

Sequential treatment with basic fibroblast growth factor and parathyroid hormone restores lost cancellous bone mass and strength in the proximal tibia of aged ovariectomized rats

This study was designed to determine whether sequential treatment with basic fibroblast growth factor (bFGF) and parathyroid hormone (PTH) can restore lost cancellous bone mass and strength at a severely osteopenic skeletal site in aged ovariectomized (OVX) rats. Female Sprague-Dawley rats were subjected to sham surgery or ovariectomy at 3 months of age and maintained untreated for the first year after surgery. At 15 months of age, groups of baseline control and OVX rats were killed and catheters were inserted in the jugular veins of all remaining rats. Two groups of OVX rats were injected intravenously (iv) daily with bFGF for 14 days at a dose of 200 microg/kg body weight. At the end of bFGF treatment, one group was killed whereas the other group was subjected to 8 weeks of treatment with synthetic human PTH 1-34 [hPTH(1-34)] consisting of subcutaneous (sc) injections 5 days/week at a dose of 80 microg/kg. Another group of OVX rats was treated iv with vehicle for 2 weeks followed by treatment with PTH alone for 8 weeks. Other groups of sham-operated control rats and OVX rats were treated iv and sc with vehicle alone. The right proximal tibia from each rat was processed undecalcified for quantitative bone histomorphometry and the left proximal tibia was subjected to biomechanical testing. Baseline and vehicle-treated OVX rats were severely osteopenic because their tibial cancellous bone volumes were less than 5% compared with mean values of 20.3% and 15.0% in baseline and vehicle-treated control rats, respectively. Treatment of OVX rats for 2 weeks with bFGF alone did not significantly increase tibial cancellous bone volume but induced marked increases in osteoid volume, osteoblast surface, and osteoid surface. Sequential treatment of aged OVX rats with bFGF and PTH increased tibial cancellous bone volume (15.1%) and load to failure to at least the level of vehicle-treated control rats. Tibial cancellous bone volume (10.8%) and load to failure also were significantly increased by treatment with PTH alone, and these variables were not significantly different from those of OVX rats treated with bFGF + PTH. However, tibial ash density was significantly greater in OVX rats treated sequentially with bFGF and PTH compared with OVX rats treated with PTH alone. Our findings suggest that sequential treatment with bFGF and PTH may be useful for restoration of lost cancellous bone in the severely osteopenic, estrogen-deplete skeleton, but it cannot be concluded with certainty that this sequential treatment has a greater bone restorative effect than treatment with PTH alone.

Hormonal preservation of bone in rheumatoid arthritis

Bone loss is a hallmark of RA. Factors influencing generalized bone loss include RA-specific factors such as the influence of disease activity and deficient sex hormone status and more general mechanisms (e.g., due to the use of glucocorticoids). Reducing disease activity has a positive effect on bone. Estrogens or androgens can restore deficiency of the sex hormones with a small positive effect on BMD. The more pronounced bone loss occurs when RA patients are being treated with glucocorticoids. This bone loss can be reduced by the concomitant use of calcium and vitamin D and, in most patients, by the use of bisphosphonates as well.

Bisphosphonates in bone diseases

Bisphosphonates are a class of drugs which are strongly attracted to the bone where they influence the calcium metabolism, mainly by inhibition of the osteoclast-mediated bone resorption. This property makes these compounds suited for the treatment of several diseases of the bone. In Paget's disease, several bisphosphonates can reduce bone pain and decrease the bone turnover 60-70%. Cyclical oral etidronate and daily oral alendronate both proved to reduce the vertebral fracture rate for postmenopausal osteoporotic woman, while most investigated bisphosphonates can increase spinal bone mass in osteoporosis. Bisphosphonates can help lowering serum calcium and reverse skeletal complications in malignancy mediated bone diseases. Oral and intravenous administration of therapeutic doses is relatively safe. In general, gastrointestinal disturbances are described most often and the oldest, least potent, bisphosphonate etidronate can induce osteomalacia. The various characteristics of bisphosphonates: physicochemical, biological, therapeutic and toxicological, vary greatly depending on the structure of the individual bisphosphonate. Even small changes in the structure can lead to enormous differences in potency. Overall, this class of drugs offers several prospects for the future.

Fluoroaluminate induces activation and association of Src and Pyk2 tyrosine kinases in osteoblastic MC3T3-E1 cells

Fluoride is known to increase bone mass in vivo, probably through stimulation of osteoblast proliferation; however, the mechanisms of fluoroaluminate action in osteoblasts have not yet been elucidated. We have previously shown that in osteoblastic MC3T3-E1 cells, fluoroaluminate stimulates G protein-mediated protein tyrosine phosphorylation (Scaronuscarona, M., Standke, G. J. R., Jeschke, M., and Rohner, D. (1997) Biochem. Biophys. Res. Commun. 235, 680-684). Although the Ser/Thr kinases Erk1, Erk2, and p70(S6K) were activated in response to fluoroaluminate, the identity of fluoroaluminate-activated tyrosine kinase(s) remained elusive. In this study, we show that in MC3T3-E1 cells, fluoroaluminate induces a 110-kDa tyrosine-phosphorylated protein that we identify as Pyk2, a cytoplasmic tyrosine kinase related to Fak (focal adhesion kinase). The tyrosine phosphorylation of Pyk2 increased in a dose- and time-dependent manner. The autophosphorylation activity of Pyk2 increased 3-fold and reached its maximum within 10 min of fluoroaluminate treatment. Fluoroaluminate also induced activation of Src and the association of Pyk2 with Src. The phosphorylation of Src-associated Pyk2 increased >20-fold in in vitro kinase assays, suggesting that Pyk2 is phosphorylated by Src. Although MC3T3-E1 cells express much more Fak than Pyk2, Src preferentially associated with Pyk2. In vitro, Pyk2 bound to the Src SH2 domain, suggesting that this interaction mediates the Src-Pyk2 association in cells. These data indicate that osteoblastic cells express Pyk2, which is tyrosine-phosphorylated and activated in response to G protein activation by fluoroaluminate, and that the mechanism of Pyk2 activation most likely involves Src. Thus, Src and Pyk2 are tyrosine kinases involved in G protein-mediated tyrosine phosphorylation in osteoblastic cells and may be important for the osteogenic action of fluoroaluminate.

Is addition of sodium fluoride to cyclical etidronate beneficial in the treatment of corticosteroid induced osteoporosis?

OBJECTIVE

To investigate whether administration of sodium fluoride (NaF) in addition to cyclical etidronate has a positive effect on bone mineral density (BMD) in patients with established osteoporosis during continued treatment with corticosteroids.

PATIENTS AND METHODS

47 patients who were receiving treatment with corticosteroids were included in a two year randomised, double blind, placebo controlled trial. Established osteoporosis was defined as a history of a peripheral fracture or a vertebral deformity, or both, on a radiograph. All patients were treated with cyclical etidronate, calcium, and either NaF (25 twice daily) or placebo. Vitamin D was supplemented in the case of a low serum 25 (OH) vitamin D concentration. BMD of the lumbar spine and hips was measured at baseline and at 6, 12, 18, and 24 months.

RESULTS

After two years of treatment, the BMD of the lumbar spine in the etidronate/NaF group had increased by +9.3% (95% confidence intervals (CI): +2.3% to +16.2%, p < 0.01), while the BMD in the etidronate/placebo group was unchanged: +0.3% (95% CI: -2.2% to +2.8%). The difference in the change in BMD between groups was +8.9% (95% CI: +1.9% to +16.0%, p < 0.01). For the hips, no significant changes in BMD were observed in the etidronate/NaF group after two years: -2.5% (95% CI: -6.8% to +1.8%); in the etidronate/placebo group BMD had significantly decreased: -4.0% (95% CI: -6.6% to -1.4%; p < 0.01). The difference between the groups was not significant: +1.5% (95% CI: -3.4% to +6.4%). No significant differences in number of vertebral deformities and peripheral fractures were observed between the two groups.

CONCLUSION

The effect of combination treatment with NaF and etidronate on the BMD of the lumbar spine in corticosteroid treated patients with established osteoporosis is superior to that of etidronate alone.