NUTRITIONAL SUPPLEMENTS FOR STIMULATING BONE GROWTH

Abstract: A food or food supplement which comprises a compound that enhances bone growth in vertebrates is described wherein the food or foodstuff is formulated so as to provide the desired bone growth enhancing effect.

Description: NUTRITIONAL SUPPLEMENTS FOR STIMULATING BONE GROWTH Technical Field The invention relates to foodstuffs and nutritional supplements which contain active ingredients that stimulate bone growth in humans and other vertebrates. More specifically, the invention concerns methods to enhance bone growth by supplementing the diet of humans and domesticated animals with edible materials that contain statins or other bone growth enhancers and by formulating such enhancers in edible form. Background Art Bone is subject to constant breakdown and resynthesis in a complex process mediated by osteoblasts, which produce new bone, and osteoclasts, which destroy bone. The activities of these cells are regulated by a large number of cytokines and growth factors, many of which have now been identified and cloned. There is a plethora of conditions which are characterized by the need to enhance bone formation. Perhaps the most obvious is the case of bone fractures, where it would be desirable to stimulate bone growth and to hasten and complete bone repair. Agents that enhance bone formation would also be useful in facial reconstruction procedures. Other bone deficit conditions include bone segmental defects, periodontal disease, metastatic bone disease, osteolytic bone disease and conditions where connective tissue repair would be beneficial, such as healing or regeneration of cartilage defects or injury. Also of great significance is the chronic condition of osteoporosis, including age-related osteoporosis and osteoporosis associated with post-menopausal hormone status. Other conditions characterized by the need for bone growth include primary and secondary hyperparathyroidism, disuse osteoporosis, diabetes-related osteoporosis, and glucocorticoid-related osteoporosis. One group of compounds suggested for enhancing bone formation comprises bone morphogenic proteins (BMPs). The BMPs are novel factors in the extended transforming growth factor β superfamily. Recombinant BMP-2 and BMP-4 can induce new bone formation when they are injected locally into the subcutaneous tissues of rats (Wozney J., Molec ReprodDev (1992) 32:160-67). These factors are expressed by normal osteoblasts as they differentiate, and have been shown to stimulate osteoblast differentiation and bone nodule formation in vitro as well as bone formation in vivo (Harris S., et al., J. Bone Miner Res (1994) 9:855-63). This latter property suggests potential usefulness as therapeutic agents in diseases which result in bone loss. The cells which are responsible for forming bone are osteoblasts. As osteoblasts differentiate from precursors to mature bone-forming cells, they express and secrete a number of enzymes and structural proteins of the bone matrix, including Type-1 collagen, osteocalcin, osteopontin and alkaline phosphatase (Stein G., et al, Curr Opin Cell Biol (1990) 2:1018-27; Harris S., et al. (1994), supra). They also synthesize a number of growth regulatory peptides which are stored in the bone matrix, and are presumably responsible for normal bone formation. These growth regulatory peptides include the BMPs (Harris S., et al. (1994), supra). In studies of primary cultures of fetal rat calvarial osteoblasts, BMPs 1, 2, 3, 4, and 6 are expressed by cultured cells prior to the formation of mineralized bone nodules (Harris S., et al. (1994), supra). Like alkaline phosphatase, osteocalcin and osteopontin, the BMPs are expressed by cultured osteoblasts as they proliferate and differentiate. Although the BMPs are potent stimulators of bone formation in vitro and in vivo, there are disadvantages to their use as therapeutic agents to enhance bone healing. Receptors for the bone morphogenetic proteins have been identified in many tissues, and the BMPs themselves are expressed in a large variety of tissues in specific temporal and spatial patterns. This suggests that BMPs may have effects on many tissues in addition to bone, potentially limiting their usefulness as therapeutic agents when administered systemically. Moreover, since they are peptides, they would have to be administered by injection. These disadvantages impose severe limitations to the development of BMPs as therapeutic agents. Small molecules that are useful in treating bone disorders in vertebrates are of the general formula Ar'-L-Ar 2 wherein Ar 1 and Ar 2 are aromatic moieties and L is a linker that separates them by a specified distance. These are disclosed in PCT application WO98/ 17267 published 30 April 1998. These compounds were assessed for usefulness in treating bone disorders by their ability to enhance the production of a reporter protein when the nucleotide sequence encoding the reporter protein is operably linked to the promoter for BMP-2. Similar compounds are disclosed for this purpose in earlier filed PCT applications WO97/15308 published 1 May 1997 and WO97/48694 published 24 December 1997. Another class of compounds comprises inhibitors of β-hydroxy-β-methyl glutaric acid CoA (HMG-CoA) reductase. These compounds also enhance bone formation; they are generically known as "statins." HMG-CoA reductase is the principal rate limiting enzyme involved in cellular cholesterol biosynthesis. The pathway is also responsible for the production of dolichol, ubiquinones, isopentenyl adenine and farnesol. HMG-CoA reductase converts 3-hydroxy-3-methyl-glutaryl CoA (HMG-CoA) to mevalonate. Addition of mevalonate at concentrations between 25-800 μM inhibits the activity of mevastatin (100, 25, or 6.25 μM) in the ABA assay described in Example 1 herein. Mevalonic acid has no effect on primary screen activities of bone growth-active compounds outside of the statin family (compounds 59-0008 (see Example 1)). These data indicate that the effect of mevastatin in the ABA assay is mediated by its effect on HMG-CoA reductase. Knowledge of inhibitors of the cholesterol biosynthetic pathway (including SAR or pharmacophore analyses) may be useful in determining appropriate modifications or analogs of the statins that maintain bone growth activity. U.S. Patent 5,280,040 discloses compounds described as useful in the treatment of osteoporosis. These compounds putatively achieve this result by preventing bone resorption. Related to these compounds are the bisphosphonates ~ the methylene bisphosphonic acids. These compounds are comprised of two phosphonic acid residues coupled through a methylene linkage. Typical representatives include the clodronates which are simple compounds wherein the phosphonic acid residues are coupled through dichloromethylene. Other representative bisphosphonates include ibandronates, the risedronates, alandronates and pamidronates. These compounds have been shown to inhibit the resorption of bone, presumably by effecting apoptosis of osteoclasts. Luckman, S.P., et al, JBone Min Res (1998) 13:581-589. Wang, G.-J., et al., JFormos Med Assoc (1995) 94:589-592 report that certain lipid clearing agents, exemplified by lovastatin and bezafibrate, were able to inhibit the bone resorption resulting from steroid administration in rabbits. However, there is no suggestion in Wang, et al, that lovastatin directly enhances bone formation. An abstract entitled "Lovastatin Prevents Steroid-Induced Adipogenesis and Osteoporosis" by Cui, Q., et al, appeared in the Reports of the ASBMR 18th Annual Meeting (September 1996) J. Bone Mineral Res. (1996) 11(S1):S510. The abstract reports that lovastatin diminished triglyceride vesicles that accumulated when osteoprogenitor cells cloned from bone marrow stroma of chickens were treated in culture with dexamethasone. Lovastatin was reported to diminish the expression of certain mRNAs and to allow the cells to maintain the osteogenic phenotype after dexamethasone treatment. Further, chickens that had undergone bone loss in the femoral head as a result of dexamethasone treatment were improved by treatment with lovastatin. Again, there is no suggestion that lovastatin directly enhances bone formation in the absence of steroid treatment. In addition, PCT publication WO99/45923 describes methods of inhibiting bone resorption by administering an HMG-CoA reductase inhibitor. Again, there is no suggestion that statins or other HMG reductase inhibitors enhance the formation of bone. The distinction between enhancing bone formation and inhibiting resorption is further elucidated by Ducy, P., et al, Nature (1996) 382:448-52 who have recently reported that osteocalcin deficient mice exhibit a phenotype marked by increased bone formation and bones of improved functional quality, without impairment of bone resorption. Ducy, et al, state that their data suggest that osteocalcin antagonists may be of therapeutic use in conjunction with estrogen replacement therapy (for prevention or treatment of osteoporosis). The present invention describes means for administering statins and other classes of compounds that enhance bone formation by including them in nutritional supplements, or by administering edible materials that naturally contain these compounds. In addition, the invention is directed to an optimum protocol for administering compounds that enhance bone formation. Disclosure of the Invention In one aspect, the invention is directed to a method to enhance bone growth in humans or other vertebrate animals by including in their diets foodstuffs or food supplements that contain effective amounts of bone growth enhancing compounds. These compounds can be the small molecule bone enhancing compounds of the formula Ar'-L-Ar 2 described hereinabove, bisphosphonates, or other bone growth enhancing agents such as BMPs. A particularly preferred group of compounds which can be administered in this was comprises the statins. Typical statins are of the formula: wherein X in each of formulas (1), (2) and (3) represents a substituted or unsubstituted alkylene, alkenylene, or alkynylene linker of 2-6C optionally containing one heteroatom which is O, N or S; Y represents one or more carbocyclic or heterocyclic rings; when two or more rings are present in Y, they may optionally be fused; and R' represents a cation, H or a substituted or unsubstituted alkyl group of 1-6C. Thus, the invention is directed to methods to treat bone disorders by directly stimulating bone formation stimulating bone formation by including in the diet of a subject in need of such stimulation, a food or food supplement which contains a bone enhancing compound, especially a statin compound. Oral administration of the compounds of the invention, in particular the statins, enhances plasma concentration by avoiding hepatic first pass effects. Thus, their effects on bone and non-hepatic tissues are enhanced. In another aspect, the invention relates to administering the compounds that stimulate bone growth on an intermittent schedule in contrast to continuous administration. Brief Description of the Drawings Figures 1A and IB show the structures and activity of statins in the screening assay of Example 1. Modes of Carrying Out the Invention The ultimate goal of the methods and compositions of the invention is to treat or ameliorate bone disorders in vertebrate subjects, particularly mammals, and more particularly humans. As used herein, "treat" or "treatment" include a postponement of development of bone deficit symptoms and/or a reduction in the severity of such symptoms that will or are expected to develop. The terms further include ameliorating existing bone or cartilage deficit symptoms, preventing additional symptoms, ameliorating or preventing the underlying metabolic causes of symptoms, preventing or reversing bone resorption and/or encouraging bone growth. Thus, the terms denote that a beneficial result has been conferred on a vertebrate subject with a cartilage, bone or skeletal deficit, or with the potential to develop such deficit. By "bone deficit" is meant an imbalance in the ratio of bone formation to bone resoφtion, such that, if unmodified, the subject will exhibit less bone than desirable, or the subject's bones will be less intact and coherent than desired. Bone deficit may also result from fracture, from surgical intervention or from dental or periodontal disease. By "cartilage defect" is meant damaged cartilage, less cartilage than desired, or cartilage that is less intact and coherent than desired. "Bone disorders" includes both bone deficits and cartilage defects. Representative uses of the compounds of the present invention include: repair of bone defects and deficiencies, such as those occurring in closed, open and non-union fractures; prophylactic use in closed and open fracture reduction; promotion of bone healing in plastic surgery; stimulation of bone ingrowth into non-cemented prosthetic joints and dental implants; elevation of peak bone mass in pre-menopausal women; treatment of growth deficiencies; treatment of periodontal disease and defects, and other tooth repair processes; increase in bone formation during distraction osteogenesis; and treatment of other skeletal disorders, such as age-related osteoporosis, post-menopausal osteoporosis, glucocorticoid-induced osteoporosis or disuse osteoporosis and arthritis, or any condition that benefits from stimulation of bone formation. The compounds of the present invention can also be useful in repair of congenital, trauma-induced or surgical resection of bone (for instance, for cancer treatment), and in cosmetic surgery. Further, the compounds of the present invention can be used for limiting or treating cartilage defects or disorders, and may be useful in wound healing or tissue repair. The compositions and the methods of the invention effect the improvement in the foregoing conditions by virtue of their ability to enhance bone formation. In the preferred embodiment of the invention, the compounds are administered to the appropriate subject as part of the subject's ordinary diet. If the subject is a human, the bone growth enhancing compounds may be artificially added to foodstuffs that are already a part of the individual's diet. A particularly useful approach is to add these compounds to fruit juices or vegetable juices, in particular fruit juices, and most favorably grapefruit juice, which is believed to exert a further beneficial effect. In general, it is preferred to add these compounds to foods that do not require cooking so as to minimize any decomposition or other chemical reactions that may be undesirable. Thus, the compounds of the invention can suitably be added to liquid components of the diet that are eaten cold, such as the fruit juices mentioned above, or even reconstituted beverages such as iced tea. Those compounds which are active ingredients but which are relatively insoluble in water may also be added to emulsions or lipid-based components such as salad dressings and salad oils. Thus, a single compound, such as a statin which enhances bone growth, or an active compound in combination with additional agents which stimulate such growth, and, if desired, in combination with other drugs, is formulated into an edible form. The edible compositions can be in the form of tablets or capsules and supplied to the diet as food supplements, as are vitamins and other herbal extracts. Such supplements can also be formulated as syrups or powders to be dissolved in fluids. The cholestin illustrated below may conveniently be formulated in this manner. The tablets or capsules may be swallowed whole or may be designed to be chewable, in which case flavoring elements are desirable. Alternatively, and preferably, the active compound or compounds are integrated into a foodstuff that becomes a part of the subject's diet. For example, concentrates of fruit juices supplemented with the active compound or compounds can be rehydrated and supplied along with meals or as midmorning or mid-afternoon refreshers. The compounds can be formulated as powders which can be sprinkled onto cold cereal or forms of cold cereal can be produced which have the compounds coated on the granules or flakes that make up the food. The compound or compounds can be integrated into spreads such as cream cheese, butter, margarine and the like and used in contexts where these spreads would be applicable. The compound or compounds are also suitable for blending with emulsions such as salad dressing and mayonnaise or water-based condiments such as catsup, mustard and cocktail sauce. Typically, the preparation of the desired foodstuff is performed at room temperature or less to preserve the chemical integrity of the compounds and of the foodstuff. Thus, such vehicles as sour cream, cottage cheese and yogurt are convenient. The compounds can also be frozen into ices, sorbets and ice creams. Milkshakes may be a particularly attractive means for administration in view of the solubility characteristics of the compounds. It will be well within the skill of the art to devise attractive recipes for the inclusion of the compounds of the invention and to blend them into foodstuffs in such a manner that patient compliance is facilitated. The bone enhancing compounds can also be provided in the form of dietary supplements where, especially, the active ingredient occurs naturally in the supplement. One particularly preferred supplement is Red Yeast Rice which is known to contain satisfactory concentrations of lovastatin. Alternatively, the lovastatin may be formulated in a cream, for example, by sonicating with whipping cream for a suitable oral dosage. Red Yeast Rice refers to a strain of yeast that grows in rice; it is most familiar as the extract used in the flavoring of Peking duck. The yeast can be grown on a rice substrate and then freeze-dried and pulverized and thus made into a suitable supplement containing lovastatin and related metabolites. The use of grapefruit juice as a vehicle is particularly advantageous, as components of grapefruit juice are known to block the clearance enzyme P450 in serum and thus prevent the clearance of the drug. Another particularly convenient formulation is in the form of a milkshake, taking advantage of the emulsified nature of the liquid to accommodate the solubility characteristics of the compounds of the invention. If the subject to be treated is a domestic animal, the active compounds can be formulated into the feed, for example, by coating solid foods with an emulsion of the active ingredient. Enhancement of bone growth may be desirable in such domestic animals as pigs, cows, sheep, domestic animals such as dogs and cats, and even chickens. Although an aspect of the invention is the administration of the active compounds orally as part of the subject's diet, the compounds can, of course, be administered by more traditional routes. Formulations for such routes may include one or more excipients, preservatives, solubilizers, buffering agents, albumin to prevent protein loss on vial surfaces, lubricants, fillers, stabilizers, etc. Methods of formulation are well known in the art and are disclosed, for example, in Remington's Pharmaceutical Sciences, latest edition, Mack Publishing Co., Easton PA, which is incorporated herein by reference. Pharmaceutical compositions for use within the present invention can be in the form of sterile, non-pyrogenic liquid solutions or suspensions, coated capsules, suppositories, lyophilized powders, transdermal patches or other forms known in the art. Local administration may be by injection at the site of injury or defect, or by insertion or attachment of a solid carrier at the site, or by direct, topical application of a viscous liquid, or the like. For local administration, the delivery vehicle preferably provides a matrix for the growing bone or cartilage, and more preferably is a vehicle that can be absorbed by the subject without adverse effects. Within the present invention, an "effective amount" of a composition is that amount which produces a statistically significant effect. For example, an "effective amount" for therapeutic uses is the amount of the composition comprising an active compound herein required to provide a clinically significant increase in healing rates in fracture repair; reversal of bone loss in osteoporosis; reversal of cartilage defects or disorders; prevention or delay of onset of osteoporosis; stimulation and/or augmentation of bone formation in fracture non-unions and distraction osteogenesis; increase and/or acceleration of bone growth into prosthetic devices; and repair of dental defects. Such effective amounts will be determined using routine optimization techniques and are dependent on the particular condition to be treated, the condition of the patient, the route of administration, the formulation, and the judgment of the practitioner and other factors evident to those skilled in the art. The dosage required for the compounds of the invention (for example, in osteoporosis where an increase in bone formation is desired) is manifested as a statistically significant difference in bone mass between treatment and control groups. This difference in bone mass may be seen, for example, as a 5-20% or more increase in bone mass in the treatment group. Other measurements of clinically significant increases in healing may include, for example, tests for breaking strength and tension, breaking strength and torsion, 4-point bending, increased connectivity in bone biopsies and other biomechamcal tests well known to those skilled in the art. General guidance for treatment regimens is obtained from experiments carried out in animal models of the disease of interest. The dosage of the compounds of the invention will vary according to the extent and severity of the need for treatment, the activity of the administered compound, the general health of the subject, and other considerations well known to the skilled artisan. Generally, they can be administered to a typical human on a daily basis as an oral dose of about 0.1 mg/kg-1000 mg/kg, and more preferably from about 1 mg/kg to about 200 mg/kg. While dietary oral administration may be preferable in most instances (for reasons of ease, patient acceptability, and the like), alternative methods of administration may be appropriate for selected compounds and selected defects or diseases. In another preferred method of the invention, the administration of the compounds, whether in the diet or by another route, is intermittent rather than continuous. Thus, preferred protocols may include administering the compounds once every three days, once every week, optionally in varying amounts at each time of administration. Such forms of administration are preferable to daily administration or consistent several times a day dosage. Thus, by "intermittent" administration is meant that the compounds or compositions containing them are provided to the subject only sporadically with substantial periods between dosages or until the results are assessed. Thus, there would be at least a one-day interval, preferably a three-day interval, and more preferably a five-day interval between any two days on which the compounds or compositions are administered, or only a single dose is administered, or there is a substantial period after dosage until results are assessed. That is, while on day 1 multiple dosages may occur (or only one) there would be no dosage the next day, at least. Or if the dosage is on a daily basis, a substantial interval is permitted to elapse before results are assessed. A single bolus dose is preferred over a multiplicity of smaller dosages. Preferred "intermittent" regimens would comprise administering the compounds or compositions every other day, every two days, every five days, or on days unevenly spaced but separated at least by a one day interval between days on which a dosage occurred. In summary, by "intermittent" dosage regime is meant either a single bolus dose or multiple dosages that comprise only a small proportion of the timeframe over which the subject is being treated. The timeframe over which treatment is administered is measured by the time between initial administration and assessment of the results. Preferred percentages of the time period occupied by dosage administration are 50% of the time, more preferably 25% of the time, and most preferably 10% of the time. Statins Preferred compounds useful in treating bone disorders by enhancing bone growth are generally classified as "statins." The structures of a number of statins, currently used as drugs to inhibit cholesterol formation, are shown in Figure 1. These include cerivastatin, marketed under the name Baycol ® by Bayer (See U.S. patents 5,006,530 and 5,177,080), lovastatin, marketed under the name Mevacor ® by Merck (See U.S. Patent 4,963,538), and simvastatin, marketed under the name of Zocar ® , pravastatin, marketed under the brand name Pravachol ® , atorvastatin, marketed under the name Lipotor ® by Warner-Lambert (See U.S. patent 5,273,995), and fluvastatin, marketed under the name Lescol ® (See U.S. patent 4,739,073). Another known statin is NK- 104 developed by NEGMA. (See Akiba, T., et al, J Toxicol Sci (1998) 23N:713-720.) All the above-cited documents are incorporated herein by reference. Additional compounds in the statin family are disclosed in U.S. patents 5,128,366; 5,260,440; and 5.354,879; and 5,093,363, all assigned to Shionogi and incorporated herein by reference. These documents emphasize statins of the formulas shown in Figure 1. In general, additional compounds of similar structure which are successful in inhibiting HMG-CoA reductase can be identified by standard assays well known in the art. The bisphosphonates, which were shown by Luckman, S.P., et al, J Bone Min Res (1998) (supra) to inhibit prenylation of proteins, and other aminobisphosphonates which have been shown to inhibit squalene synthase (Aminn, et al, J Lipid Res (1992) 33:1657) have been shown herein to stimulate bone formation directly. Inhibition of the prenylation of ras protein has also been shown to be related to bone stimulation. The compounds that are useful for administration in the methods of the invention can be verified as having bone growth enhancing activity in a number of assays as described for convenience below. The first of these is a high throughput assay that screens for compounds that stimulate the promoter of BMP -2. Other in vitro and in vivo assays more directly assess the ability of the compound to enhance bone growth. High Throughput Assay A rapid throughput screening test for compounds that stimulate bone formation by demonstration that they are capable of stimulating expression of a reporter gene linked to a BMP promoter (a surrogate for the production of bone morpho genetic factors that are endogenously produced) is described in U.S. Application Serial No. 08/458,434, filed 2 June 1995, and now allowed, the entire contents of which are incoφorated herein by reference. This assay is also described as a portion of a study of immortalized murine osteoblasts (derived from a mouse expressing a transgene composed of a BMP-2 promoter driving expression of T-antigen) in Ghosh-Choudhery, N., et al, Endocrinology (1996) 137:331-39. In this study, the immortalized cells were stably transfected with a plasmid containing a luciferase reporter gene driven by a mouse BMP-2 promoter (-2736/114 bp), and responded in a dose-dependent manner to recombinant human BMP-2. Briefly, the assay utilizes cells transformed permanently or transiently with constructs in which the promoter of a bone moφhogenetic protein, specifically BMP-2 or BMP -4, is coupled to a reporter gene, typically luciferase. These transformed cells are then evaluated for the production of the reporter gene product; compounds that activate the BMP promoter will drive production of the reporter protein, which can be readily assayed. Many thousands of compounds have been subjected to this rapid screening technique, and only a very small percentage are able to elicit a level of expression of reporter gene 5-fold greater than that produced by vehicle. BMP promoter-active compounds can be examined in a variety of other assays that test specificity and toxicity. For instance, non-BMP promoters or response elements can be linked to a reporter gene and inserted into an appropriate host cell. Cytotoxicity can be determined by visual or microscopic examination of BMP promoter- and/or non-BMP promoter-reporter gene-containing cells, for instance. Alternatively, nucleic acid and/or protein synthesis by the cells can be monitored. For in vivo assays, tissues may be removed and examined visually or microscopically, and optionally examined in conjunction with dyes or stains that facilitate histologic examination. In assessing in vivo assay results, it may also be useful to examine biodistribution of the test compound, using conventional medicinal chemistry/animal model techniques. Neonatal Mouse Calvaria Assay (In Vitro) An assay for bone resoφtion or bone formation is similar to that described by Gowen M. & Mundy G., J Immunol (1986) 136:2478-82. Briefly, four days after birth, the front and parietal bones of ICR Swiss white mouse pups are removed by microdissection and split along the sagittal suture. In an assay for resoφtion, the bones are incubated in BGJb medium (Irvine Scientific, Santa Ana, CA) plus 0.02% (or lower concentration) β-methylcyclodextrin, wherein the medium also contains test or control substances. The medium used when the assay is conducted to assess bone formation is Fitton and Jackson Modified BGJ Medium (Sigma) supplemented with 6 μg/ml insulin, 6 μg/ml transferrin, 6 ng/ml selenous acid, calcium and phosphate concentrations of 1.25 and 3.0 mM, respectively, and ascorbic acid to a concentration of 100 μg/ml is added every two days. The incubation is conducted at 37°C in a humidified atmosphere of 5% CO 2 and 95% air for 96 hours. Following this, the bones are removed from the incubation media and fixed in 10% buffered formalin for 24-48 hours, decalcified in 14% EDTA for 1 week, processed through graded alcohols; and embedded in paraffin wax. Three μm sections of the calvaria are prepared. Representative sections are selected for histomoφhometric assessment of bone formation or bone resoφtion. Bone changes are measured on sections cut 200 μm apart. Osteoblasts and osteoclasts are identified by their distinctive moφhology. Other auxiliary assays can be used as controls to determine non-BMP promoter-mediated effects of test compounds. For example, mitogenic activity can be measured using screening assays featuring a serum-response element (SRE) as a promoter and a luciferase reporter gene. More specifically, these screening assays can detect signaling through SRE-mediated pathways, such as the protein kinase C pathway. For instance, an osteoblast activator SRE-luciferase screen and an insulin mimetic SRE-luciferase screen are useful for this puφose. Similarly, test compound stimulation of cAMP response element (CRE)-mediated pathways can also be assayed. For instance, cells transfected with receptors for PTH and calcitonin (two bone-active agents) can be used in CRE- luciferase screens to detect elevated cAMP levels. Thus, the BMP promoter specificity of a test compound can be examined through use of these types of auxiliary assays. In Vivo Assay of Effects of Compounds on Murine Calvarial Bone Growth Male ICR Swiss white mice, aged 4-6 weeks and weighing 13-26 gm, are employed, using 4-5 mice per group. The calvarial bone growth assay is performed as described in PCT application WO 95/24211, incoφorated by reference. Briefly, the test compound or appropriate control vehicle is injected into the subcutaneous tissue over the right calvaria of normal mice. Typically, the control vehicle is the vehicle in which the compound was solubilized, and is PBS containing 5% DMSO or is PBS containing Tween (2 μl/10 ml). The animals are sacrificed on day 14 and bone growth measured by histomoφhometry. Bone samples for quantitation are cleaned from adjacent tissues and fixed in 10% buffered formalin for 24-48 hours, decalcified in 14% EDTA for 1-3 weeks, processed through graded alcohols; and embedded in paraffin wax. Three to five μm sections of the calvaria are prepared, and representative sections are selected for histomoφhometric assessment of the effects on bone formation and bone resoφtion. Sections are measured by using a camera lucida attachment to trace directly the microscopic image onto a digitizing plate. Bone changes are measured on sections cut 200 μm apart, over 4 adjacent lxl mm fields on both the injected and noninjected sides of the calvaria. New bone is identified by its characteristic woven structure, and osteoclasts and osteoblasts are identified by their distinctive moφhology. Histomoφhometry software (OsteoMeasure, Osteometrix, Inc., Atlanta) is used to process digitizer input to determine cell counts and measure areas or perimeters. Additional In Vivo Assays Lead compounds can be further tested in intact animals using an in vivo, dosing assay. Prototypical dosing may be accomplished by subcutaneous, intraperitoneal or oral administration, and may be performed by injection, sustained release or other delivery techniques. The time period for administration of test compound may vary (for instance, 28 days as well as 35 days may be appropriate). An exemplary, in vivo oral or subcutaneous dosing assay may be conducted as follows: In a typical study, 70 three-month-old female Sprague-Dawley rats are weight-matched and divided into seven groups, with ten animals in each group. This includes a baseline control group of animals sacrificed at the initiation of the study; a control group administered vehicle only; a PBS-treated control group; and a positive control group administered a compound (non-protein or protein) known to promote bone growth. Three dosage levels of the compound to be tested are administered to the remaining three groups. Briefly, test compound, positive control compound, PBS, or vehicle alone is administered subcutaneously once per day for 35 days. All animals are injected with calcein nine days and two days before sacrifice (two injections of calcein administered each designated day). Weekly body weights are determined. At the end of the 35-day cycle, the animals are weighed and bled by orbital or cardiac puncture. Serum calcium, phosphate, osteocalcin, and CBCs are determined. Both leg bones (femur and tibia) and lumbar vertebrae are removed, cleaned of adhering soft tissue, and stored in 70% ethanol for evaluation, as performed by peripheral quantitative computed tomography (pQCT; Ferretti, J., Bone (1995) 17:353S-64S), dual energy X-ray absoφtiometry (DEXA; Laval-Jeantet A., et al, Calcif Tissue Intl (1995) 56:14-18; J. Casez, et al, Bone and Mineral (1994) 26:61-68) and/or histomoφhometry. The effect of test compounds on bone remodeling can thus be evaluated. Lead compounds can also be tested in acute ovariectomized animals (prevention model) using an in vivo dosing assay. Such assays may also include an estrogen-treated group as a control. An exemplary subcutaneous dosing assay is performed as follows: In a typical study, 80 three-month-old female Sprague-Dawley rats are weight-matched and divided into eight groups, with ten animals in each group. This includes a baseline control group of animals sacrificed at the initiation of the study; three control groups (sham ovariectomized (sham ONX) + vehicle only; ovariectomized (ONX) + vehicle only; PBS-treated ONX); and a control ONX group that is administered a compound known to promote bone growth. Three dosage levels of the compound to be tested are administered to the remaining three groups of ONX animals. Since ovariectomy (ONX) induces hypeφhagia, all ONX animals are pair-fed with sham ONX animals throughout the 35 day study. Briefly, test compound, positive control compound, PBS, or vehicle alone is administered orally or subcutaneously once per day for 35 days. Alternatively, test compound can be formulated in implantable pellets that are implanted for 35 days, or may be administered orally, such as by gastric gavage. All animals, including sham ONX/vehicle and ONX/vehicle groups, are injected intraperitoneally with calcein nine days and two days before sacrifice (two injections of calcein administered each designated day, to ensure proper labeling of newly formed bone). Weekly body weights are determined. At the end of the 35-day cycle, the animals' blood and tissues are processed as described above. Lead compounds may also be tested in chronic ONX animals (treatment model). An exemplary protocol for treatment of established bone loss in ovariectomized animals that can be used to assess efficacy of anabolic agents may be performed as follows. Briefly, 80 to 100 six month old female, Sprague-Dawley rats are subjected to sham surgery (sham ONX) or ovariectomy (ONX) at time 0, and 10 rats are sacrificed to serve as baseline controls. Body weights are recorded weekly during the experiment. After approximately 6 weeks (42 days) or more of bone depletion, 10 sham ONX and 10 ONX rats are randomly selected for sacrifice as depletion period controls. Of the remaining animals, 10 sham ONX and 10 ONX rats are used as placebo-treated controls. The remaining ONX animals are treated with 3 to 5 doses of test drug for a period of 5 weeks (35 days). As a positive control, a group of ONX rats can be treated with an agent such as PTH, a known anabolic agent in this model (Kimmel, et al, Endocrinology (1993) 132:1577-84). To determine effects on bone formation, the following procedure can be followed. The femurs, tibiae and lumbar vertebrae 1 to 4 are excised and collected. The proximal left and right tibiae are used for pQCT measurements, cancellous bone mineral density (BMD) (gravimetric determination), and histology, while the midshaft of each tibiae is subjected to cortical BMD or histology. The femurs are prepared for pQCT scanning of the midshaft prior to biomechamcal testing. With respect to lumbar vertebrae (LN), LN2 are processed for BMD (pQCT may also be performed); LN3 are prepared for undecalcified bone histology; and LN4 are processed for mechanical testing. Statin Compounds Useful in the Invention The statin compounds useful in the methods and compositions of the invention are typically of the formula: wherein X in each of formulas (1), (2) and (3) represents a substituted or unsubstituted alkylene, alkenylene, or alkynylene linker of 2-6C optionally containing one heteroatom which is O, N or S; Y represents one or more carbocyclic or heterocyclic rings; when Y comprises two or more rings, they may optionally be fused; and R' represents a cation, H or a substituted or unsubstituted alkyl group of 1-6C. It is understood that if R' represents a cation with multiple positive charges, the appropriate number of anions is coupled with it. Formulas (1) and (2) are, respectively, the unhydrolyzed and hydro lyzed forms of the statin compounds. Preferred substituents on X (or on R' when R' is alkyl) are hydroxy, alkoxy, phenyl, amino and alkyl- or dialkylamino. The compounds useful in the invention contain at least one and generally several chiral centers. Compounds useful in the invention include mixtures of the various stereoisomers and the stereoisomeric forms of the compounds individually. Preferred stereoisomers with respect to the compound of formula (1) are of the formula: and the corresponding stereochemistry in the open chain (nonlactone or hydrolyzed) form of formula (2). In one set of preferred embodiments, X is unsubstituted; most preferably X is selected from the group consisting of -CH 2 CH 2 -; -CH=CH-; and -O≡C-, especially -CH 2 CH 2 - and -CH=CH-. Preferred embodiments of Y comprise ring systems such as naphthyl, polyhydro-naphthyl, monohydro- or dihydrophenyl, quinolyl, pyridyl, quinazolyl, pteridyl, pyrolyl, oxazoyl and the like and the reduced or partially reduced forms thereof. Preferred embodiments of the substituent Y include those of the formula: wherein the ring system may contain π-bonds; wherein R , ι i ■ s substituted or unsubstituted alkyl; each R 2 is independently a noninterfering substituent; R 3 is H, hydroxy, or alkoxy (1-6C); each m is independently an integer of 0-6, wherein each R 2 may reside in any of positions 2-7; and p is 0 or 1, depending on the position of any π-bonds. Particularly preferred embodiments include those of formulas (4a)-(4f) wherein the upper limit of n is adjusted according to the valence requirements appropriate for the particular ring system. (4a) (4b) While R 1 may be substituted alkyl, wherein the substituents may include hydroxy, aikoxy, alkylthiol, phenyl, phenylalkyl, and halo, unsubstituted alkyl is preferred. Particularly preferred embodiments of R 1 are alkyl of 1-6C, including propyl, see-butyl, t-butyl, n-butyl, isobutyl, pentyl, isopentyl, 1-methylbutyl, and 2-methylbutyl. Particularly preferred are propyl and sec-butyl. Preferred embodiments for R include H, hydroxy, =O, and substituted or unsubstituted lower alkyl (1-4C), in particular methyl, and hydroxymethyl. In the preferred embodiments, each n is independently 1 or 2 and preferred positions for substitution are positions 2 and 6 (see formula (4)). Particularly preferred embodiments of R 2 are OH, H, and lower alkyl, in particular CH 3 . Particularly preferred are embodiments wherein Y is 4(a) or 4(b), and especially embodiments having the substitution pattern indicated in formulas 4(g) and 4(h) below. As indicated above, the compounds of the invention may be supplied as individual stereoisomers or as mixtures of stereoisomers. Preferred stereoisomers are those of the formulas (4g) and (4h) as typical and appropriate for those represented by the formulas (4a)-(4f). Particularly preferred are compounds with the stereochemistry of formulas (4g) and (4h) wherein the noted substituents are the sole substituents on the polyhydronaphthyl system optionally including additional substituents at position 5. Preferred embodiments include those wherein each of R 2 is independently OH, CH 2 OH, methyl, or =O. Preferred embodiments of R 1 in these preferred forms are propyl, sec-butyl, and 2-methyl-but-2-yl. Additional preferred embodiments of Y are: wherein Z is N and both n are 1, and each K comprises a substituted or unsubstituted aromatic or nonaromatic carbocyclic or heterocyclic ring system which may optionally be spaced from the linkage position shown in formula (7) by a linker of 1-2C, including -CHOH-, -CO-, and -CHNH 2 -, for example. Aromatic ring systems are preferred. Particularly preferred are compounds of formula (7), either as shown or wherein Z is contained in a 6-membered, rather than a 5-membered aromatic ring. Thus, another group of preferred compounds of the invention is of formula (7) where Z is N and an additional substituent -=CR 6 - is inserted between Z and the bond directed to X, wherein R 6 is linear, branched or cyclic alkyl. In a preferred embodiment, R is a cyclic alkyl substituent. R 5 is H or linear, branched, cyclic substituted or unsubstituted alkyl, wherein substituents are preferably hydroxy, alkoxy, phenyl, amino and alkyl- or dialkylamino. Preferably, when R 5 is alkyl, it is unsubstituted. Substituents on the aromatic ring systems or nonaromatic ring systems included in Y can be any noninterfering substituents. Generally, the non-interfering substituents can be of wide variety. Among substituents that do not interfere with the beneficial effect of the compounds of the invention on bone formation in treated subjects include alkyl (1-6C, preferably lower alkyl 1-4C), including straight, branched or cyclic forms thereof, alkenyl (2-6C, preferably 2-4C), alkynyl (2-6C, preferably 2-4C), all of which can be straight or branched chains and may contain further substituents; halogens, including F, Cl, Br and I; silyloxy, OR, SR, NR 2 , OOCR, COOR, NCOR, NCOOR, and benzoyl, CF 3 , OCF 3 , SCF 3 , N(CF 3 ) 2 , CN, SO, SO 2 R and SO 3 R wherein R is alkyl (1-6C) or is H. Where two substituents are in adjacent positions in the aromatic or nonaromatic system, they may form a ring. Further, rings not fused to the aromatic or nonaromatic rings comprising Y may be included as substituents. These rings may be aromatic and may be substituted or unsubstituted. The compounds useful in the methods and compositions of the invention can be synthesized by art-known methods as they resemble a class of compounds known in the art to behave as antihypercholesterolemic agents. Typical among these is lovastatin, marketed by Merck as Mevacor ® . The synthesis of lovastatin and various analogs thereof is set forth in U.S. Patent No. 4,963,538, incoφorated herein by reference. In addition, methods for synthesis of lovastatin and analogous compounds such as compactin (mevastatin), simvastatin, and pravastatin are set forth in U.S. Patent Nos. 5,059,696; 4,873,345; 4,866,186; 4,894,466; 4,894,465; 4,855,456; and 5,393,893, all incoφorated herein by reference. Certain of these compounds are also produced by microorganisms as described in U.S. Patent Nos. 5,362,638; 5,409,820; 4,965,200; and 5,409,820, all also incoφorated herein by reference. Compounds described as end-products in these documents are useful in the methods of the invention. Additional analogs, including those containing aromatic embodiments of Y, are described in U.S. Patent No. 5,316,765 incoφorated herein by reference. For example, the preparation of fluvastatin is described in PCT Application WO84/02131. Other compounds are described in, for example, Roth, B.D., et al, J Med Chem (1991) 34:357-366; Krause, R., et al, JDrugDev (1990) 3(Suppl. l):255-257; Karanewsky, D.S., et al., JMed Chem (1990) 33:2952-2956. Particularly preferred are hydrolyzed or unhydrolyzed forms of lovastatin (59-0326), mevastatin (59-0327), simvastatin (59-0328) fluvastatin (59-0342), pravastatin, cerivastatin, NK-104 and atorvastatin, and compounds set forth in U.S. patents 5,354,879; 5,128,366; 5,093,363; and 5,260,440. Typical forms of these statins are shown in Figures lA and lB. The compositions of the invention may also include the bisphosphonates and their analogs. Typically, and preferably, the bisphosphonates are of the formula and the pharmaceutically acceptable salts, esters and amides thereof. Typical salts are those of the inorganic ions, such as sodium ion, potassium ion, calcium ion, magnesium ion and the like; any pharmaceutically acceptable cation may be used. Typical esters are the ethyl, methyl, isobutyl, ethylene glycol, and other typical pharmaceutically acceptable esters; typical amides are the unsubstituted -NH 2 amides as well as the alkyl and dialkyl amides. Embodiments of R 10 include halo, OR, SR, NR 2 , where R is H or alkyl (1-6C) or alkyl or arylalkyl with optional substitutions. Particularly preferred are the amino-substituted alkyl embodiments. Typically, both R 10 are not identical, although in some embodiments, such as clodronate, both R 10 are halo. Particularly preferred compounds among the bisphosphonates are risedronate, alandronate, pamidronate, clodronate and in particular ibandronate. These compounds are particularly useful in combination with the statins. The compositions may also contain, as active ingredients, compounds of the formula Ar-L-Ar wherein Ar represents an aryl substituent and L represents a linker. The active ingredients may also be supplemented by additional pharmaceuticals complementing the activity of enhancing bone growth, such as the use of estrogens to inhibit bone resoφtion. The active ingredient compounds are used alone or in mixtures of two or more active compounds in the presence of suitable accompanying excipients which permit oral administration and, preferably, incoφorate the materials into the diet of the subject. The choice of vehicle foodstuff or food supplement base will depend on the nature of the active ingredient, and in particular its solubility characteristics. As noted above, it may be necessary to utilize oils or non-aqueous, orally acceptable solvents in order to bring some of the active ingredients into solution, or emulsions or other preparations, such as liposomal preparations can be used. The liquid preparations can be directly ingested or can be coated onto or otherwise incoφorated into solid food. Suitable approaches are exemplified below. The following examples are intended to illustrate but not to limit the invention. Example 1 High Throughput Screening Thousands of compounds have been tested in the assay system set forth in U.S. Serial No. 08/458,434, filed 2 June 1995, and incoφorated herein by reference. Representative compounds of the invention gave positive responses, while the majority of (unrelated) compounds are inactive. In this screen, the standard positive control was the compound 59-0008 (also denoted "OS8"), which is of the formula: "OS8" In more detail, the 2T3-BMP-2-LUC cells, a stably transformed osteoblast cell line described in Ghosh-Choudhury, et al, Endocrinology (1996) 137:331-39, referenced above, was employed. The cells were cultured using α-MEM, 10% FCS with 1% penicillin/streptomycin and 1% glutamine ("plating medium"), and were split 1:5 once per week. For the assay, the cells were resuspended in a plating medium containing 4% FCS, plated in microtiter plates at a concentration of 5 x 10 3 cells (in 50 μl)/well, and incubated for 24 hours at 37°C in 5% CO 2 . To initiate the assay, 50 μl of the test compound or the control in DMSO was added at 2X concentration to each well, so that the final volume was 100 μl. The final serum concentration was 2% FCS, and the final DMSO concentration was 1%. Compound 59-0008 (10 μM) was used as a positive control. The treated cells were incubated for 24 hours at 37°C and 5% CO 2 . The medium was then removed, and the cells were rinsed three times with PBS. After removal of excess PBS, 25 μl of IX cell culture lysing reagent (Promega #E153A) was added to each well and incubated for at least ten minutes. Optionally, the plates/samples could be frozen at this point. To each well was added 50 μl of luciferase substrate (Promega #E152A; 10 ml Promega luciferase assay buffer per 7 mg Promega luciferase assay substrate). Luminescence was measured on an automated 96-well luminometer, and was expressed as either picograms of luciferase activity per well or as picograms of luciferase activity per microgram of protein. In this assay, compound 59-0008 (3-phenylazo-lH-4,l,2-benzothiadiazine) exhibits a pattern of reactivity which is maximal at a concentration of approximately 3-10 μM. Accordingly, other tested compounds can be evaluated at various concentrations, and the results compared to the results obtained for 59-0008 at 10 μM (which value would be normalized to 100). Alternatively, the reactivity of a compound to be tested can be compared directly to a negative control containing no compound. A variety of statin compounds (simvastatin designated OS114 or 59-0328, hydro lyzed simvastatin, mevastatin designated 59-0327, lovastatin designated 59-0326, fluvastatin designated 59-0342, and pravastatin designated 59-0329) were tested in the in vitro BMP-promoter based (designated "ABA") assay (as described at the beginning of this example above), and in some experiments were tested also in a control osteoblast/serum response element (OBSRE) cell-based assay and/or a control glucagon assay. In the negative control OBSRE assay, a murine osteoblast cell line, such as CCC-4 expressing a serum response element (SRE)-luciferase reporter gene is used (see WO96/07733). In the negative control glucagon assay, a glucagon receptor-positive BHK cell expressing a CRE-luciferase reporter gene is used (see U.S. Patent No. 5,698,672). The results of three separate determinations in the ABA assay are shown below. Most of the statins (i.e., simvastatin, hydrolyzed simvastatin, mevastatin, lovastatin, and fluvastatin) exhibited a dose-dependent stimulatory effect in the ABA assay, but not in control assays. In one experiment, simvastatin demonstrated over a 20-fold induction in the ABA assay, as compared to the non-statin, ABA stimulatory compound 59-0008. The pravastatin that was tested did not exhibit a dose-dependent stimulatory response, but since this compound was extracted from formulated pravastatin, it is possible that insufficient and/or inactive compound was tested. Example 2 In Vivo Calvarial Bone Growth Data Lovastatin and simvastatin were assayed in vivo according to the procedure described previously (see "In Vivo Assay of Effects of Compounds on Murine Calvarial Bone Growth," supra). Simvastatin provided a 1.5 fold increase in the number of osteoblasts. In one experiment, vehicle control, bFGF and varying doses of simvastatin (59-0328) and lovastatin (designated 59-0326) were tested in the in vivo calvarial bone growth assay. The results are reported as a measurement of total bone area (and % increase in area over vehicle control), as shown below. Total Bone Compound Area (μm 2 ) Control 167.7 bFGF (12.5 μg/kg/day) 242 (45%) 59-0328 10 mg/kg/day 245 (46%) 59-0328 5 mg/kg/day 202 (20%) 59-0328 lmg/kg/day 172 (2%) 59-0326 10 mg/kg/day 239 (42%) 59-0326 5 mg/kg/day 235 (40%) 59-0326 1 mg/kg/day 237 (41%) 59-0326 0.1 mg/kg/day 162 (0%) Both simvastatin and lovastatin stimulated a dose-dependent increase in total bone area. At 10 mg/kg/day, the bone stimulatory effects of these statins were comparable to the bone growth effect observed when 12.5 μg/kg/day bFGF was tested in the same assay. Example 3 In Vitro Bone Formation Selected compounds and appropriate controls were assayed in vitro (ex vivo) for bone formation activity (described above in "Neonatal Mouse Calvaria Assay (in vitro)"). Histomoφhometrical assessments of ex vivo calvaria were carried out using an OsteoMetrics bone moφhometry measurement program, according to the manufacturer's instructions. Measurements were determined using either a 10- or 20-fold objective with a standard point counting eyepiece graticule. New bone formation was determined (using a 10X objective) by measuring the new bone area formed in one field in 3 representative sections of each bone (4 bones per group). Each measurement was carried out 14 field distance from the end of the suture. Both total bone and old bone area were measured. Data were expressed as new bone area in mm 2 . Osteoblast numbers were determined by point counting. The number of osteoblast cells lining the bone surface on both sides of the bone were counted in one field using a 20X objective. Data were expressed as osteoblast numbers/mm of bone surface. Lovastatin and simvastatin and control compounds/factors bFGF and BMP-2, and a vehicle control were tested in the in vitro bone formation assay and the calvaria were analyzed histomoφhometrically, as described above. Several sets of experimental data are presented below, with % increase over vehicle control values indicated parenthetically. Osteoblast Number: Experiment 1 3 days 7 days Compound Obs/field Obs/field Control 97.25 92.7 59-0328 156 (63%) 154 (68%) BFGF 179.25 (84%) 168.7 (82%) BMP-2 127 (31%) 119 (28%) Osteoblast Number: Experiment 2 Control 90.7 59-0328 154 (70%) Experiment 3 Control 84 59-326 128 (152%) New Bone Area: Experiment 1 3 days 7 days (mm 2 xl0 ~3 ) (mm 2 xl0 "3 ) Compound Control 4.8 7.8 59-0328 8.5 (77%) 17.4 (123%) BFGF 5.7 (19%) 18.1 (132%) BMP-2 8.4 (75%) 18.7 (140%) Experiment 2 control 4.0 59-0328 15.4 (285%) Experiment 3 Control 4.5 590-326 8.2 (182%) These data show that lovastatin and simvastatin are as good as, or better than, BMP-2 and bFGF (two "gold standard" agents for bone growth; see Wozney J., Molec ReprodDev (1992) 32:160-67; WO95/24211) for inducing bone formation. As shown in Example 2, in vivo calvarial studies using lovastatin and simvastatin have provided bone growth data consistent with these in vitro observations. Example 4 Effect on Resoφtion The statins and controls were tested in an antiresoφtive assay. Briefly, 15 day timed pregnant CD-I female mice were injected with 45 Ca (25 μCi/mouse). The calvaria from the 4 day old pups were dissected out and cut in half. The excised half calvaria were placed on metal grids (at the surface) in 1 ml of BGJ medium (Sigma) containing 0.1% BSA with glutamine and Pen Strep added. The bones were incubated at 37°C in a 5% humidified incubator for a period of 24 h, and then were transferred to wells containing 1 ml medium with factors added (IL-1, PTH, and/or test compounds). The treated bones were incubated under the above conditions for a further 72 h. After this incubation period, the bones were removed and placed into 20% TCA in a scintillation vial for 1.5 h, and then counted with scintillation fluid. An aliquot of medium (0.4 ml) was also counted. The results were expressed as % 45 Ca release. This assay may be modified by including test compounds/factors or control compounds/factors in the preincubation medium (i.e., during the first 24 h). Since most of the osteoclasts are formed in the calvaria following the preincubation period, compounds or factors that affect osteoclast formation may have a greater effect during the preincubation period. In this assay, compound toxicity was indicated by obvious death of the cells in the periosteal region and within the marrow cavity of the bone organ cultures. These cells were characterized by pyknotic nuclei and vacuolated cytoplasm, characteristic of cell necrosis and distinct from apoptosis. Using this assay, simvastatin was tested for its ability to inhibit IL-1 induced bone resoφtion. Briefly, IL-1 (10 " M) was added simultaneously with simvastatin (at 0.1, 1 or 10 μM) during a 72 h incubation period. Bone resoφtion was determined by measuring Ca release. IL-1, in the absence of simvastatin, increased 45 Ca release about 2-fold over control calvaria incubated in the absence of IL-1 or simvastatin. Simvastatin at 0.1 or 1 μM concentration did not alter IL-1 induced 45 Ca release. However, simvastatin at 10 μM concentration decreased IL-1 induced 45 Ca release. Histologic evaluation indicated toxicity at the 10 μM simvastatin. Previous studies have correlated toxicity with decreased 45 Ca release. These data suggest that simvastatin does not inhibit bone resoφtion at doses effective in the primary screening assay of Example 1. These results are contrary to reports by R.G.G. Russell and colleagues that mevastatin inhibits bone resoφtion in murine calvariae in vitro. Example 5 Systemic Administration of Statins in ONX Models Lovastatin and simvastatin were analyzed in vivo using an acute ONX (prevention model) and/or chronic (treatment model) ONX model system, as described above under "Additional In Vivo Assays". Lovastatin was examined in an acute ONX study. Briefly, 59-0326 was orally administered (35, 7, or 1.4 mg/kg/day; once per day for 35 days) immediately following ovariectomy. At the end of the study, the animals' blood and tissues samples were processed, and the following data were obtained. pQCT analysis of samples removed from animals that received the 7 mg/kg/day dose showed a 20% increase in trabecular density and a 14% increase in cortical thickness. Histomoφhometric analysis by two individuals showed an increase in trabecular bone volume of 110% (pO.OOl) or 25% (p=0.0503) in the proximal tibia, and an increase of 23% (not significant) in the distal femur. The bone formation rate in the distal femur was increased 40% (p=0.052) in the 7 mg/kg/day animals. Similarly, lovastatin was orally administered (0.1 , 1 , 5, 10, 20 or 40 mg/kg/day; once per day for 35 days) immediately following ovariectomy. Two individuals histomoφhometrically analyzed samples removed from animals that received the 10 mg/kg/day dose. These analyses indicated an increase in trabecular bone volume of 38% (not significant) or 90% (p<0.02) in the proximal tibia. The bone formation rate in the proximal tibia was determined to have increased 74% (p= 0.004) in animals that received a 10 mg/kg/day dose or 37% (p<0.008) in animals that received a 1 mg/kg/day dose. In samples from animals that received the 1 mg/kg/day dose, mineral apposition rate in the proximal tibia was increased 22%. Simvastatin was also examined in a chronic ONX study. Briefly, simvastatin was orally administered (0.1, 1, 10, or 50 mg/kg/day; once per day for 10 weeks) to rats at 6 weeks post-ovariectomy. At the 10 mg/kg/day dose, a 114% (not significant) increase in the bone formation rate in the proximal tibia was measured. At the 50 mg/kg/day dose, an 86% (not significant) increase in the bone formation rate in the proximal tibia was measured. Example 6 Statin-Mediated Fracture Repair Effects of Test Compounds Simvastatin was examined for effects on surgical defects in the rabbit radius. Healing of these defects may be assessed by X-ray, histology and biomechanical strength. The test compound was weighed out in a microcentrifuge tube, and 50 μl of 1.5% sodium alginate solution was added as a carrier. This test sample was vortexed to wet all of the powder. The sample was sonicated for 20-30 min, and then vortexed again. Disks were created in the top of the microcentrifuge tube (by placing the tube lid or stopper-side down). The indent in the top of the stopper (i.e., lid) was used to form the disk (7.5 mm diameter). CaCl 2 solution (100 μl of 100 mM) was added to the sodium alginate/drug solution. The samples were allowed to sit for 5-10 min, and then the calcium-alginate disks were carefully removed. The disks were rinsed in a beaker filled with water to rinse off the excess calcium solution, and were saved in tubes using water as vehicle. All solutions and containers were sterile, and all procedures for preparations of disks were performed under a laminar flow hood under sterile conditions. Bone healing was examined as follows. Briefly, six-month old male rabbits were obtained, and were divided into 4 treatment groups (n=3 animals/group). The treatment groups received either: 1) placebo; 2) test compound (5 mg/disk); 3) test compound (10 mg/disk); or 4) an autologous bone graft. Animals were anesthetized with rabbit cocktail (1 ml 1.5 kg intramuscularly), and the right forelimb was clipped, prepped and draped for aseptic surgery. Anesthesia was maintained using isofluorane delivered with a face mask. To create a 20 mm gap defect in the right mid-radius, an incision was made over the lateral aspect of the forearm, and an osteotomy was performed with an oscillating bone saw. The simvastatin or vehicle was applied to the defect and the defect was closed in layers. No external splinting was needed, as the radius is paired with the ulna, which functions to allow normal ambulation in the rabbit. Disks were cut on strips and inserted in the fracture to cover all the defect. Radiologic evaluation was performed at zero time and at 4 weeks. Because the vehicle (placebo treatment group) prevented full healing in the control group, only X-ray results were obtained and analyzed. Accordingly, X-ray analysis 4 weeks after initiation of treatment showed callus formation at the bone treatment site in the treated (both doses), but not the placebo (vehicle or autologous bone graft) groups. Example 7 Effect of Ras Inhibition on Bone Formation The 2T3 osteoblast progenitor cell line, described by Ghosh-Choudhury, et al, Endo (1995) 137:331-339 is BMP-2 responsive and undergoes bone formation spontaneously in culture in vitro. These cells were stably transfected with the human dominant negative H-ras (Dn-ras) cDNA; this negative mutant gene contains an asparagine substitution at position 17 and production of this protein effects inhibition of endogenous ras. The Dn-ras coding sequence was under transcriptional control of the dexamethasone inducible mouse mammary tumor virus promoter. The production of the negative ras protein was confirmed by Western blot. The cells were cultured on 24-well plates at a density of 2x 10 4 /well and cultured with αMEM medium supplemented with 10% SDS for nodule formation assay indicating bone growth. Bone cell differentiation and module formation were monitored using a mineralized module formation assay described by Bharagava, et al, Bone (1986) 8:155-163 using van Kossa stain. The cultures were washed with phosphate buffered formalin, then with water and dehydrated in 70%, 95% and 100% ethanol, 2x each and then air-dried. The plates were rehydrated before staining; the water was removed, a 2% silver nitrate solution was added and the plates were exposed to sunlight for 20 minutes. The plates were rinsed with water and 5% sodium thiosulfate was added for 3 minutes and then rinsed. Modified van Gleson stain was used as a counterstain for unmineralized collagen matrix. Acid fuschin solution was added for 5 minutes and the plates were then washed and dried for image analysis. The area of van Kossa stained nodules was quantified by an automated image analysis using a video analysis program (Jandel Scientific, San Raphael, California) linked to a video screen camera equipped with metallurgical lenses. The nodule structures were also analyzed by transmission electron microscopy. When the cells containing the Dn-ras gene were activated by incubation with 10 "7 M dexamethasone, a dramatic and spontaneous formation of mineralized bone nodules resulted. This result did not occur in wild-type cells in the absence of added BMP. Thus, inhibition of ras function causes osteoblasts to differentiate and form bone. Example 8 Stimulation of In Vitro Calvarial Bone Formation by Bisphosphonates Various bisphosphonates were tested for their ability to stimulate calvarial bone formation in vitro in the assay described in Example 3 both alone and in combination with 59-0328 (simvastatin). The results were calculated as new bone area in mm 2 xl0 ~3 , as above. Dose response curves for ibandronate as a typical bisphosphonate showed a significant increase of bone formation at 10 μM ibandronate. These results are summarized below: Other bisphosphonates were tested as shown below; although alendronate, pamidronate and clodronate gave negligible effects under these conditions, risedronate showed significant increases in new bone area at 10 μM and 100 μM concentrations. The effect of ibandronate together with simvastatin was also tested. The results are shown as follows: As shown, the combination of 59-0328 with ibandronate was superior to the result with either bisphosphonate alone. Example 9 Stimulation of Bone Formation by Red Yeast Rice Red Yeast Rice is a yeast culture that uses rice as a substrate and is known to contain lovastatin and may contain other HMG-CoA reductase inhibitors. Red Yeast Rice, which is marketed as "Cholestin" was tested in the "neonatal mouse calvaria assay (in vitro)" described above and set forth in Example 3 herein. Four bones in each group were treated with either medium alone or with 100 μg/ml or 50 μg/ml of Red Yeast Rice. The bone growth was measured in terms of new bone area. The affect on growth was measured both in the absence of mevalonate and in the presence of 15 μg/ml mevalonate. The results are shown in the table below. As shown, in the absence of Red Yeast Rice, the presence of mevalonate does not matter with respect to the degree of increase in bone area. However, there is a dose dependent increase in bone area in the presence of Red Yeast Rice which is substantially reversible in the presence of mevalonate. As stated above, the effects of Red Yeast Rice are believed to be due to the presence of lovastatin and possibly related metabolites. New Bone Area Example 10 Cream Formulation of Lovastatin The formulation was prepared by sonicating lovastatin in whipping cream and diluting the original 1 μM concentration prepared with additional whipping cream. The preparation was done by preparing a high concentration of lovastatin in DMSO and then diluting in whipping cream to obtain the most concentrated solution followed by sonication. Subsequent dilutions were made with additional whipping cream. Lovastatin was tested for its affects on new bone area in the calvarial assay in vitro as used in Example 9. Four bones were used to obtain each average data point. The results are shown in the table below: Significantly greater than medium alone Significantly less than non-mevalonate treated New Bone Area (mm 2 x 10 3 ) As seen, lovastatin contained in medium alone enhances bone growth in a manner that becomes significant at 1 μM. On the other hand, the cream formulation shows bone growth stimulation at 0.04 μM and is a better bone growth stimulator at both 0.2 μM and 1 μM than lovastatin formulated in medium alone. Example 11 Effect of Intermittent Compound Administration The above described assays of the effect of compounds on murine calvarial bone growth was used to assess the effect of dosage protocol. In one experiment, the in vitro neonatal mouse calvaria assay was performed as described except that the media were changed at days 4, 7 and 11 and the calvaria were removed for assessment at day 14. Cerivastatin at a concentration of 0.25 μM was added to the medium at day 0 in one experimental group, and then removed after 1 day. In a second experimental group, one-fourth (1/4) of this concentration (0.025 μM) was added at days 0, 4, 7 and 11. The results are shown in Table 1 , where new bone formation area was measured at day 14. Significantly greater than medium alone Table 1 As shown, cerivastatin administered at a single dose of 0.25 μM represented an improvement over continuous dosage at one-quarter (1/4) this amount over a longer period. In a second experiment, the above-described in vivo assay using murine calvarial bone growth as a measure was used except that the test compound, lovastatin, was applied topically. The results were measured in terms of the percent bone volume/total volume (%BV/TV) and in terms of bone density (BMD g/cm 2 ). These results, along with the standard error, are shown in the table below. In the group which received continuous administration, 1 mg/kg/day was administered 5 days per week for 5 weeks. In the "intermittent" group, the mice received 5 mg/kg/day for 5 days on the first week but no further dosing after that. Bone volumes and densities were measured after 5 weeks in both groups. Table 2 As shown in the table, a better result was obtained for the intermittent group than was obtained where the same total amount of lovastatin was administered continuously. It was found that administration once a day for five days, followed by measurement of bone Significantly greater than control Significantly greater than 4 x 0.0625 μM group histology after another four weeks showed superior effects to daily administration of the compound until the time of observation. From the foregoing, it will be appreciated that, although specific embodiments of the invention have been described herein for puφoses of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

Claims: Claims 1. A method to enhance bone formation in a vertebrate animal which method comprises orally administering to a vertebrate subject in need of such treatment an effective amount of a composition comprising a bone growth stimulating compound wherein said bone growth stimulating compound is contained in a foodstuff or in a dietary supplement. 2. The method of claim 1 wherein the subject exhibits a bone fracture. 3. The method of claim 1 wherein said foodstuff is fruit juice. 4. The method of claim 3 wherein said fruit juice is grapefruit juice. 5. The method of claim 1 wherein the dietary supplement is Red Yeast Rice. 6. The method of claim 1 wherein said bone growth stimulating compound is a statin compound of the formula: wherein X in each of formulas (1), (2) and (3) represents a substituted or unsubstituted alkylene, alkenylene, or alkynylene linker of 2-6C optionally containing one heteroatom which is O, N or S; Y represents one or more carbocyclic or heterocyclic rings; when two or more rings are present in Y, they may optionally be fused; R' represents a cation, H or a substituted or unsubstituted alkyl group of 1-6C. 7. The method of claim 6 wherein X is selected from the group consisting of -CH 2 CH 2 -; -CH=CH-; and -C=C-. 8. The method of claim 6 wherein Y is of the formula 4(g) or a stereoisomer or mixture of stereoisomers thereof. 9. The method of claim 6 wherein Y is of formula (7) as shown. 10. The method of claim 6 wherein Y is of formula (7) where Z is spaced from the carbon bonded to X by =CR 6 -, wherein R 6 is H or linear, branched or cyclic alkyl (1- 6C). 11. The method of claim 6 wherein Y is of formula (8). 12. The method of claim 11 wherein K is substituted pyrrole. 13. The method of claim 12 wherein said substitutions comprise aromatic systems. 14. The method of claim 6 wherein K is substituted pyridyl, substituted phenyl, substituted pyrimidyl or substituted pyrrole. 15. The method of claim 6 wherein said compound is atorvastatin, or a statin described in U.S. 5,260,440, U.S. 5,093,363 or U.S. 5,128,366, or is cerivastatin, lovastatin, mevastatin, simvastatin, fluvastatin, pravastatin, or NK-104, in hydrolyzed or unhydrolyzed form. 16. The method of claim 1 wherein said subject is characterized by a condition selected from the group consisting of osteoporosis, bone fracture or deficiency, primary or secondary hypeφarathyroidism, periodontal disease or defect, metastatic bone disease, osteolytic bone disease, post-plastic surgery, post-prosthetic joint surgery, and post-dental implantation. 17. The method of claim 1 which further comprises administering to said subject one or more agents that promote bone growth or that inhibit bone resoφtion. 18. The method of claim 1 wherein said administering is on an intermittent protocol. 19. A foodstuff or food supplement to enhance bone formation in a vertebrate animal which comprises an amount, effective to promote bone formation, of a bone growth stimulating compound. 20. The food supplement of claim 19 which is Red Yeast Rice. 21. The foodstuff of claim 19 which is fruit juice supplemented with a statin. 22. A method to enhance bone formation in a vertebrate animal which method comprises administering to a vertebrate subject in need of such treatment an effective amount of a composition comprising a bone growth stimulating compound wherein said administering is intermittent. 23. The method of claim 1 wherein said administering is topical.

Inventors: GARRETT I ROSS, GUTIERREZ GLORIA E, MUNDY GREGORY R, GARRETT, I., ROSS, GUTIERREZ, GLORIA, E., MUNDY, GREGORY, R.
Applicants: GARRETT I ROSS, GUTIERREZ GLORIA E, MUNDY GREGORY R, OSTEOSCREEN INC, GARRETT, I., ROSS, GUTIERREZ, GLORIA, E., MUNDY, GREGORY, R., OSTEOSCREEN, INC.
Application year: 2001
Main classification: A23L1
IPC codes: A23L1, A61K31, A61K45, A61P1, A61P3, A61P5, A61P19, C07D207, C07D213, C07D215