Cross-sectional study of osteopenia with quantitative MR imaging and bone densitometry.

PURPOSE: To evaluation the cancellous bone-induced intravoxel spin dephasing rate (R2') and its relationship to bone mineral density and marrow fat and to examine these parameters as predictors of vertebral fracture status. MATERIALS AND METHODS: R2' and R2, the rate constants for reversible and irreversible spin dephasing, and marrow fat fraction were measured in the lumbar vertebrae and proximal femur. One hundred thirty-nine subjects (mean age, 62.4 years +/- 11.4 [SD]; 33 men, 106 women) had spinal dual-energy x-ray absorptiometric bone mineral density (BMD) T scores ranging from +3 to -5. R2', BMD, and bone marrow composition as determinants of vertebral fracture status were examined. RESULTS: Strongest single predictors of fracture status for BMD and R2' were the Ward triangle (r(2) = 0.48) and trochanter (r(2) = 0.37), respectively. Combined, the two parameters and sites increased fracture prediction (r(2) = 0. 62), whereas the combination of multiple BMD sites did not. Multivariate regression involving marrow fat fraction further improved fracture status prediction. R2' was correlated with BMD at all sites, although slopes differed by a factor of up to 2.5, which reflected differences in trabecular orientation relative to the static field. R2, the true transverse relaxation rate, was negatively correlated with marrow fat fraction. A non-age-related increase in marrow fat fraction in osteoporosis parallels earlier findings in animal models. CONCLUSION: Cancellous bone marrow R2' measured in the proximal femur provides information, which, with BMD, improves prediction of vertebral fracture status.

Effect of testosterone treatment on bone mineral density in men over 65 years of age.

As men age, their serum testosterone concentrations decrease, as do their bone densities. Because bone density is also low in hypogonadal men, we hypothesized that increasing the serum testosterone concentrations of men over 65 yr to those found in young men would increase their bone densities. We randomized 108 men over 65 yr of age to wear either a testosterone patch or a placebo patch double blindly for 36 months. We measured bone mineral density by dual energy x-ray absorptiometry before and during treatment. Ninety-six men completed the entire 36-month protocol. The mean serum testosterone concentration in the men treated with testosterone increased from 367 +/- 79 ng/dL (+/-SD; 12.7 +/- 2.7 nmol/L) before treatment to 625 +/- 249 ng/dL (21.7 +/- 8.6 nmol/L; P < 0.001) at 6 months of treatment and remained at that level for the duration of the study. The mean bone mineral density of the lumbar spine increased (P < 0.001) in both the placebo-treated (2.5 +/- 0.6%) and testosterone-treated (4.2 +/- 0.8%) groups, but the mean changes did not differ between the groups. Linear regression analysis, however, demonstrated that the lower the pretreatment serum testosterone concentration, the greater the effect of testosterone treatment on lumbar spine bone density from 0-36 months (P = 0.02). This analysis showed a minimal effect (0.9 +/- 1.0%) of testosterone treatment on bone mineral density for a pretreatment serum testosterone concentration of 400 ng/dL (13.9 nmol/L), but an increase of 5.9 +/- 2.2% for a pretreatment testosterone concentration of 200 ng/dL (6.9 nmol/L). Increasing the serum testosterone concentrations of normal men over 65 yr of age to the midnormal range for young men did not increase lumbar spine bone density overall, but did increase it in those men with low pretreatment serum testosterone concentrations.

Osteopathy and resistance to vitamin D toxicity in mice null for vitamin D binding protein.

A line of mice deficient in vitamin D binding protein (DBP) was generated by targeted mutagenesis to establish a model for analysis of DBP's biological functions in vitamin D metabolism and action. On vitamin D-replete diets, DBP-/- mice had low levels of total serum vitamin D metabolites but were otherwise normal. When maintained on vitamin D-deficient diets for a brief period, the DBP-/-, but not DBP+/+, mice developed secondary hyperparathyroidism and the accompanying bone changes associated with vitamin D deficiency. DBP markedly prolonged the serum half-life of 25(OH)D and less dramatically prolonged the half-life of vitamin D by slowing its hepatic uptake and increasing the efficiency of its conversion to 25(OH)D in the liver. After an overload of vitamin D, DBP-/- mice were unexpectedly less susceptible to hypercalcemia and its toxic effects. Peak steady-state mRNA levels of the vitamin D-dependent calbindin-D9K gene were induced by 1,25(OH)2D more rapidly in the DBP-/- mice. Thus, the role of DBP is to maintain stable serum stores of vitamin D metabolites and modulate the rates of its bioavailability, activation, and end-organ responsiveness. These properties may have evolved to stabilize and maintain serum levels of vitamin D in environments with variable vitamin D availability.

A possible new role for vitamin D-binding protein in osteoclast control: inhibition of extracellular Ca2+ sensing at low physiological concentrations.

Upon removal of its sialic acid or galactose residue, vitamin D-binding protein (DBP) becomes a potent macrophage-activating factor, DBP-MAF. Here we document a new function of DBP-MAF and its parent molecule, DBP, in osteoclast control. We show that all DBPs potently inhibit extracellular Ca2+ (cation) sensing at low nanomolar concentrations with the following rank order of potency: native DBP = sialidase-treated DBP > beta-galactosidase-treated DBP. This attenuation remains unaffected despite co-incubation either with the native DBP ligand, 1,25-dihydroxyvitamin D3, or with an asialoglycoprotein receptor modulator, asialoorosomucoid. Taken together, the results suggest that circulating DBP may play a role in the systemic control of osteoclastic bone resorption, a hitherto unrecognized action of the protein.

Cancellous bone volume and structure in the forearm: noninvasive assessment with MR microimaging and image processing.

PURPOSE: To develop and apply a method for the derivation of cancellous bone architectural parameters from in vivo magnetic resonance (MR) images of the distal radius and to evaluate these parameters as predictors of vertebral fracture status in osteopenia. MATERIALS AND METHODS: MR images (137 x 137 x 500-micron3 voxel size) were acquired with a three-dimensional partial flip-angle spin-echo pulse sequence in the distal radius of 36 women. Subjects were classified as healthy or with osteoporosis on the basis of vertebral deformity and bone mineral density (BMD). Images rated as of adequate quality in 20 subjects were processed with a method that is applicable in the limited spatial resolution regime. The method relies on histogram deconvolution to obviate binary segmentation. Cancellous bone structure was treated as a quasi-regular lattice and analyzed with spatial autocorrelation, yielding parameters that quantify intertrabecular spacing, contiguity, and a measure of longitudinal alignment called tubularity. RESULTS: Whereas neither BMD nor any of the structural parameters individually correlated significantly with vertebral deformity fraction, a simple function that involved tubularity and longitudinal spacing predicted deformity fraction well (r = .78, P < .005). CONCLUSION: Histomorphometric parameters characterizing cancellous bone in the distal radius can be derived from in vivo MR microimages and are predictive of vertebral deformity.

Hypocalcemia and skeletal disease as presenting features of celiac disease.

OBJECTIVE: To describe 15 patients examined for hypocalcemia, skeletal disease, or both in whom the diagnosis of celiac disease was subsequently made. DESIGN: Observational case series. PATIENTS: Fifteen patients (7 women and 8 men) were examined for hypocalcemia (n = 11), skeletal disease (n = 3), or both (n = 1). The diagnosis of celiac disease was subsequently made. The mean age of the patients was 62 years, and 11 patients were 60 years of age or older. RESULTS: Four patients had no gastrointestinal symptoms, 7 patients had mild or intermittent gastrointestinal symptoms, and 4 patients had persistent diarrhea. Ten patients had experienced weight loss. The serum total alkaline phosphatase level was elevated in 10 of 15 patients, the parathyroid hormone level was elevated in all patients, and the urinary calcium level was low in all 6 of the patients tested. The level of 25-hydroxyvitamin D was frankly low in 4 patients, marginal in 8 patients, and normal in 3 patients. Bone mineral density was reduced in all 8 patients in whom it was measured. CONCLUSIONS: Celiac disease should be considered in patients with unexplained metabolic bone disease or hypocalcemia, especially because gastrointestinal symptoms may be absent or mild. Advanced age does not exclude the diagnosis of celiac disease.

Osteoporosis in men.

Osteoporosis in men has not received much attention compared to that directed at the skeletal morbidity of postmenopausal osteoporosis. The available literature and an evaluation of 47 men referred to our metabolic bone disease clinic present arguments that causes for secondary osteoporosis can be identified in most instances, Major causes include hypogo-nadism, hyperglucocorticoidism, and alcohol abuse. Primary osteoporosis in men is idiopathic and has heterogeneous features. At present, no controlled, randomized therapeutic trials have been reported in men with osteoporosis. Improved screening for early detection and prevention of bone loss is needed in men with disorders, lifestyles, and/or medications that cause bone loss. Further investigations of primary osteoporosis should lead to identification of mechanisms of bone loss that can be prevented.

Seasonal diminution of vitamin D stores in the United States. Can darker winters lead to lighter bones?

Recent reports indicate that many older Americans have inadequate vitamin D sources and little to no seasonal increase in their body stores. The attendant secondary hyperparathyroidism of incipient and subtle osteomalacia could weaken cortical bone and aggravate the osteoporotic process linked to aging. Increased awareness, by physicians and our elderly, of the importance of avoiding mild, seasonal or perennial vitamin D deficiency could lead to better implementation of vitamin D supplementation schedules.

Skeletal response to immobilization in Paget's disease of bone: a case report.

The authors discuss a case of Paget's disease of the forearm in which the Pagetic radius and non-Pagetic ulna responded differently to immobilization. The high turnover state of Pagetic bone is more sensitive to physical unloading than normal bone, and thus more rapidly develops osteopenia of immobilization. The different responses to immobilization between Pagetic bone and site controlled normal bone illustrate how physical and metabolic factors interact at a skeletal site to regulate bone remodeling and bone mass.

Electrophoretic mobility shift assay identifies vitamin D binding protein (Gc-globulin) in human, rat, and mouse sera.

Serum vitamin D binding protein (DBP, also known as Gc-globulin) is a multifunctional protein capable of binding both vitamin D metabolites and actin. DBP can be visualized when analyzed by polyacrylamide gel electrophoresis followed by staining. Confirmation of its identity had previously required immunoprecipitation with specific anti-DBP antisera or occupancy of the protein with radioactive vitamin D sterols. We present studies showing that preincubation of G-actin with mammalian sera produced a discernible DBP protein band shift on native gel electrophoresis. Addition of DNaseI, a 33-kDa intracellular protein with an avid actin-binding site, to the incubations resulted in a supershift of DBP-actin complexes to an even more cathodal region of the gels. Following incubations with human, rat, and murine sera the same actin shift occurred as did the actin plus DNaseI supershift. The migrations of each complex were correlated with purified DBP migrations under identical conditions. It was confirmed that the supershifted bands contained DBP by Western blotting and detection of DBP by binding of 25-OH[3H]D3. After intravenous G-actin injections into living mice, a serum DBP-actin complex could be detected on native gels as the uncomplexed DBP band decreased in intensity. This simple, direct-staining technique appears to be suitable for identifying DBP/Gc phenotypes in human populations as well as for semiquantitatively monitoring the plasma actin-scavenger system in vivo in animal models or in human diseases.

Post-transcriptional stimulation of transforming growth factor beta 1 mRNA by TGF-beta 1 treatment of transformed human osteoblasts.

Following exogenous administration of transforming growth factor-beta 1 (TGF-beta 1) polypeptide to the human osteosarcoma cell line TE-85, we observed a 2- to 6-fold stimulation of steady-state TGF-beta 1 mRNA. The stimulation was dose- and time-dependent, as judged from Northern blot hybridization analyses. A 2- to 6-fold increase of the TGF-beta 1 polypeptide was also found in the media of these cells after TGF-beta 1 treatments. The autostimulation of TGF-beta 1 mRNA was nullified by cycloheximide treatment of the cells. The in vitro transcription rates of the TGF-beta 1 gene by isolated nuclei were not altered by TGF-beta 1 treatment. Under conditions of transcriptional inhibition, the stability of TGF-beta 1 mRNA was enhanced nearly two-fold by TGF-beta 1 treatment. Our findings indicate that TGF-beta 1 can stimulate autologous gene expression and subsequent polypeptide translation by a post-transcriptional mechanism requiring protein synthesis in human osteoblast-like cells. The recognized versatility of TGF-beta 1 autostimulation mechanisms (transcriptional and post-transcriptional) in other mesenchymal cells may apply also to skeletal cells, further underscoring the broad and potent activities of this cytokine.

Circulating vitamin D metabolites in relation to subsequent development of prostate cancer.

An emerging hypothesis suggests that vitamin D metabolites suppress the development of prostate cancer. In a recent epidemiological study, elevated levels of 1,25-dihydroxyvitamin D (1,25-D) in blood were associated with a greatly reduced risk, particularly in older men. We conducted a nested case-control study to evaluate the relationship between plasma levels of the two major vitamin D metabolites, 1,25-D and 25-hydroxyvitamin D (25-D), and subsequent diagnosis of prostate cancer. We also measured vitamin D-binding protein to investigate the influence of free metabolite levels on risk. Plasma samples from 14,916 participants in the Physicians' Health Study were collected and frozen in 1982-1983. This analysis included 232 cases diagnosed up to 1992 and 414 age-matched control participants. Vitamin D metabolite and vitamin D-binding protein assays were conducted without knowledge of case-control status. Median levels of 25-D, 1,25-D, and vitamin D-binding protein were indistinguishable between cases and controls. Analysis of risk for increasing quartiles of total or free metabolites did not reveal a pattern of decreasing risk. For 1,25-D, men in the highest quartile had an odds ratio of 0.88 (95% confidence interval = 0.53-1.45) compared to those in the lowest quartile. Significant reductions in risk were not seen in analyses restricted to older men, to cases occurring > 3 years from blood collection, or to cases presenting as aggressive prostate cancer. Nonsignificant inverse associations for 1,25-D appeared for some groups according to 25-D level, particularly when the cutoff for defining low 25-D was reduced. These results do not support the hypothesis that high circulating levels of vitamin D metabolites reduce prostate cancer risk, although small to moderate effects cannot be excluded.

Vitamin D deficiency in homebound elderly persons.

OBJECTIVE: To assess the vitamin D status in homebound, community-dwelling elderly persons; sunlight-deprived elderly nursing home residents; and healthy, ambulatory elderly persons. DESIGN: A cohort analytic study. PARTICIPANTS: Of 244 subjects at least 65 years old, 116 subjects (85 women and 31 men) had been confined indoors for at least 6 months, either in private dwellings in the community (the Hopkins Elder Housecall Program) or in a teaching nursing home (The Johns Hopkins Geriatrics Center). The 128 control subjects, a healthy ambulatory group, came from the Baltimore Longitudinal Study on Aging. All subjects were free of diseases or medications that might interfere with their vitamin D status. MAIN OUTCOME MEASURES: Serum levels of 25-hydroxyvitamin D (25-OHD) and 1,25-dihydroxyvitamin D (1,25-[OH]2D) were measured in all subjects. In a subgroup of 80 subjects, serum levels of intact parathyroid hormone (PTH), ionized calcium, and osteocalcin and intake of vitamin D (through 3-day food records) were assessed. A randomly selected cohort of sunlight-deprived subjects also had serum levels of vitamin D binding protein measured. RESULTS: In sunlight-deprived subjects overall, the mean 25-OHD level was 30 nmol/L (12 ng/mL) (range, < 10 to 77 nmol/L [< 4 to 31 ng/mL]) and the mean 1,25-(OH)2D level was 52 pmol/L (20 pg/mL) (range, 18 to 122 pmol/L [7 to 47 pg/mL]). In the sunlight-deprived subjects, 54% of community dwellers and 38% of nursing home residents had serum levels of 25-OHD below 25 nmol/L (10 ng/mL) (normal range, 25 to 137 nmol/L [10 to 55 ng/mL]). A significant inverse relationship existed between 25-OHD (ie, Log [25-OHD]) and PTH when they were analyzed together (r = -0.42; R2 = 0.18; P < .001) and for each cohort separately. All other parameters measured, except ionized calcium, differed significantly from the Baltimore Longitudinal Study Group means. The mean (SD) daily intakes of vitamin D (121 [132] IU) and calcium (583 [322] mg) were below the recommended dietary allowance only in the community-dwelling homebound population. The mean vitamin D binding protein level in the sunlight-deprived subgroup was in the normal range. CONCLUSIONS: Despite a relatively high degree of vitamin supplementation in the United States, homebound elderly persons are likely to suffer from vitamin D deficiency.

Osteoporosis: clinical assessment with quantitative MR imaging in diagnosis.

PURPOSE: To determine if the magnetic resonance (MR) imaging effective transverse relaxation rate (R2*) of trabecular bone marrow is lowered in osteoporosis. MATERIALS AND METHODS: R2* was measured in 146 women. Control subjects (n = 77; mean age, 46.6 years) had high mean spinal bone mineral densities (BMDs) and no vertebral deformities. Patients with spinal osteoporosis (n = 59; mean age, 59.7 years) had at least one thoracic vertebral deformity and/or low BMDs. RESULTS: R2* was lower in patients for L-2 through L-5 (P < .001). Average R2* of L-3 through L-5 (R2*av) was the best discriminator (64.79 sec-1 +/- 1.18 [standard error] for control subjects vs 53.39 sec-1 +/- 1.24 for patients; P < .0001). R2*av decreased with age in control subjects. The difference in R2*av in a subset of 38 age-matched pairs of patients and control subjects was 8.25 sec-1 (P < .0001). Subjects with deformities had lower 52*av than did control subjects (52.3 sec-1 +/- 1.6 vs 62.5 sec-1 +/- 1.1, P < .0001). R2*av was correlated with mean BMD (r = .54, P < .0001). CONCLUSION: Patients with osteoporosis have lower R2*s in vertebral marrow.

Severe osteoporosis in men.

OBJECTIVE: To evaluate men with severe osteoporosis for pathogenetic factors and to review the reported features of primary osteoporosis in men. DESIGN: Case series and clinical review. PATIENTS: 47 men consecutively referred to a metabolic bone center because of atraumatic (or minimally traumatic) fractures (91%) or radiographic osteopenia (9%). MEASUREMENTS: Clinical assessment, radiographs, chemical analyses of serum and urine, hormone assays, skeletal densitometry, and histomorphometry of iliac crest biopsy specimens. RESULTS: 27 of the 47 men (57%) had vertebral fractures, and 16 (34%) had appendicular fractures. Causal factors identified in 30 men (64%) included glucocorticosteroid treatment (8 men); hypogonadism (7 men); excessive alcohol consumption (7 men); and anticonvulsant use, osteomalacia, severe hyperthyroidism, or bone marrow neoplasia (8 men). Seventeen men (36%) had no medical conditions or known risk factors associated with bone disease. Spinal mineral density was well below the mean value for healthy young men in 94% of the patients with primary osteoporosis tested. Examination of biopsy specimens from 13 of 17 men with primary osteoporosis showed reduced trabecular bone volumes, normal bone formation rates, and slightly increased resorption surfaces. Fasting hypercalciuria was seen in some men (41%). In the primary osteoporosis group, eight men were followed serially (range of follow-up, 6 months to 9 years) while they were receiving a nonpharmacologic regimen (diet and activity); the mean axial bone mineral density of these men increased slightly. CONCLUSIONS: A thorough evaluation for identifiable causes of severe osteoporosis in men is warranted because definable pathogenetic factors are seen in many cases. A few men with severe osteoporosis have primary or idiopathic osteoporosis. Primary osteoporosis in men is probably caused by many factors because heterogeneous clinical, laboratory, and histologic features were seen in our series and in those of others. Further studies of primary osteoporosis are needed to define the course of the disease, to identify pathogenetic mechanisms, and to develop therapeutic interventions.

Plasma vitamin D-binding protein (Gc-globulin): multiple tasks.

The transporter of vitamin D and its metabolites in blood has received increasing attention in recent years, and is recognized to be a member of a gene family that includes albumin and alpha-fetoprotein. Identical to the group specific component (Gc-globulin) of serum, the protein is a single-chain polypeptide constitutively synthesized in liver that circulates in amounts in far excess of normal vitamin D metabolite concentrations in blood. It plays the major role in the egress of endogenously synthesized vitamin D, from skin and appears to restrain D-sterols from too rapid/excessive cell entry. Along with plasma gelsolin, it comprises the plasma actin-scavenger system that facilitates removal of actin, liberated from lysed cells, by depolymerization and prevention of polymerization. Recently, the protein has been shown to behave as a co-chemotaxin specific for the complement peptide C5a, and its sialic acid-free form has been reported to play a role in macrophage activation. The latter functions strongly implicate its participation in inflammation responses. A unifying hypothesis might also suggest the protein to provide focal D-sterol delivery to cells that are important to the resolution of tissue injuries.

Severe symptomatic osteopenia in a man with pigmented micronodular adrenal hyperplasia.

The authors describe the unusual case of a 52-year-old man with Cushing's syndrome caused by bilateral pigmented micronodular adrenal hyperplasia. The only features of hypercortisolism were hypertension and severe symptomatic osteopenia with vertebral, rib, and scapular fractures. Four years after bilateral adrenalectomy, the bone density had increased slightly, but the patient remained osteopenic and continued to have vertebral compression fractures. This case report emphasizes the importance of an indepth search for secondary causes of osteoporosis, including evaluation of adrenal function in patients who have unexplained osteoporosis. Early diagnosis and treatment is imperative to prevent severe bone loss and associated skeletal morbidity.