Current controversies in bone densitometry

Potential Functions of the BMP Family in Bone, Obesity, and Glucose Metabolism

Characteristic bone metabolism was observed in obesity and diabetes with controversial conclusions. Type 2 diabetes (T2DM) and obesity may manifest increased bone mineral density. Also, obesity is more easily to occur in T2DM. Therefore, we infer that some factors may be linked to bone and obesity as well as glucose metabolism, which regulate all of them. Bone morphogenetic proteins (BMPs), belonging to the transforming growth factor- (TGF-) beta superfamily, regulate a diverse array of cellular functions during development and in the adult. More and more studies revealed that there exists a relationship between bone metabolism and obesity as well as glucose metabolism. BMP2, BMP4, BMP6, BMP7, and BMP9 have been shown to affect the pathophysiological process of obesity and glucose metabolism beyond bone metabolism. They may exert functions in adipogenesis and differentiation as well as insulin resistance. In the review, we summarize the literature on these BMPs and their association with metabolic diseases including obesity and diabetes.

Prevalence and Risk Factors of Reduced Bone Mineral Density in Systemic Lupus Erythematosus Patients: A Meta-Analysis

Background

We aimed to conduct a meta-analysis concerning the frequency and risk factors of reduced bone mineral density (BMD) in systemic lupus erythematosus (SLE) with evidence from published studies.

Methods

A comprehensive literature search was conducted based on the EMBASE, Web of Science, PubMed, and Cochrane Library databases up to March 5th, 2017. Eligible studies reported any prevalence of reduced BMD in SLE patients. All risk factors with odds ratios or risk ratios associated with reduced BMD were extracted.

Results

71 reports with 33527 SLE patients were included. Low BMD, osteopenia, and osteoporosis at any site were presented, respectively, in 45%, 38%, and 13% of the SLE patients. The prevalence of osteoporosis increased with the advancing of age, while U-shaped associations between age and the prevalence of low BMD and osteopenia were found. Lumbar spine was indicated to have higher prevalence of osteoporosis. Age, disease duration, drugs use, and many other factors were identified as predictors of reduced BMD.

Conclusion

Low BMD, osteoporosis, and osteopenia appeared to be prevalent in patients with SLE. Risk factors of reduced BMD were various.

Alveolar bone measurement precision for phosphor-plate images

OBJECTIVES

The aim was to demonstrate methods for determining measurement precision and to determine the precision of alveolar bone measurements made with a vacuum-coupled positioning device and phosphor plate images.

STUDY DESIGN

Subjects were rigidly attached to the x-ray tube by means of a vacuum coupling device and custom cross-arch bite plates. Original and repeat radiographs (taken within minutes of each other) were obtained of the mandibular posterior teeth of 51 subjects, and cementoenamel junction-alveolar crest (CEJ-AC) distances were measured on both sets of images. In addition, x-ray transmission (radiodensity) and AC height differences were determined by subtracting one image from the other. Image subtractions and measurements were performed twice. Based on duplicate measurements, the root mean square standard deviation (precision) and least significant change (LSC) were calculated. LSC is the magnitude of change in a measurement needed to indicate that a true biologic change has occurred.

RESULTS

The LSCs were 4% for x-ray transmission, 0.49 mm for CEJ-AC distance, and 0.06 mm for crest height.

CONCLUSION

The LSCs for our CEJ-AC and x-ray transmission measurements were similar to what has been previously reported. The LSC for AC height (determined with image subtraction) was <0.1 mm. Compared with findings from earlier studies, this represents a highly precise measurement of AC height. The methods demonstrated for calculating LSC can be used by investigators to determine how large changes in radiographic measurements need to be before the changes can be considered to be (with 95% confidence) true biologic changes and not noise (i.e., equipment/observer error).

Increase in bone mass after correction of vitamin D insufficiency in bisphosphonate-treated patients

OBJECTIVE

To assess the relative contribution of vitamin D insufficiency to loss of bone mineral density (BMD) in patients taking bisphosphonates.

METHODS

Patients were eligible for inclusion if they had osteoporosis or osteopenia and demonstrated a decline in BMD during the preceding year while taking stable doses of alendronate or risedronate, plus supplemental calcium and vitamin D. Patients with previously known secondary causes of osteoporosis were excluded from the study. Eligible patients underwent prospective measurement of bilateral hip and lumbar spine BMD by dual-energy x-ray absorptiometry, serum 25-hydroxyvitamin D (25-OHD), 1,25-dihydroxyvitamin D, intact parathyroid hormone, osteocalcin, and thyroid-stimulating hormone (thyrotropin), and urinary calcium:creatinine ratio.

RESULTS

Annual BMD was assessed in 175 previously bisphosphonate-responsive patients with low BMD. Of the 175 patients, 136 (78%) had either a significant interval increase or no change in BMD, whereas 39 (22%) had a significant decrease. Of the 39 patients who lost BMD, 20 (51%) had vitamin D insufficiency (25-OHD <30 ng/mL). After a single course of orally administered vitamin D2 (500,000 IU during a 5-week period), the 25-OHD level returned to normal in 17 of the 20 vitamin D-insufficient patients and was associated with significant (P<.02) 3.0% and 2.7% increases in BMD at the lumbar spine and the femoral neck, respectively. Failure to normalize the serum 25-OHD level was associated with further loss of BMD.

CONCLUSION

Vitamin D insufficiency was the most frequently identified cause of bone loss in patients with declining BMD during bisphosphonate therapy. Correction of vitamin D insufficiency in these patients led to a significant rebound in BMD.

A comparison of the effect of alendronate and risedronate on bone mineral density in postmenopausal women with osteoporosis: 24-month results from FACTS-International

OBJECTIVES

To compare alendronate 70 mg once weekly (OW) with risedronate 35 mg OW with respect to change in bone mineral density (BMD), biochemical markers and upper gastrointestinal (UGI) tolerability over 24 months.

METHODS

This was a 12-month extension to the Fosamax Actonel Comparison Trial international study (FACTS). Postmenopausal women with osteoporosis randomly assigned to either alendronate 70 mg OW or risedronate 35 mg OW for the 12-month base study continued taking the same double-blind study medication. Efficacy measurements were BMD at the hip trochanter, lumbar spine, total hip, and femoral neck and levels of four bone turnover markers at 24 months. The primary hypothesis was that alendronate would produce a greater mean per cent increase from baseline in hip trochanter BMD at 24 months.

RESULTS

Trochanter BMD increased significantly from baseline to month 24 in both groups, with a significantly larger increase with alendronate: adjusted mean treatment difference of 1.50% (95% confidence interval: 0.74%, 2.26%; p < 0.001). Similar results were seen at all BMD sites. Significant geometric mean per cent decreases (p < 0.001) from baseline were seen for all four bone turnover markers in both groups, with significantly larger decreases (p < 0.001) with alendronate: adjusted mean treatment differences ranged from 8.9% to 25.3%. No significant differences were seen in incidence of UGI or other adverse events.

CONCLUSIONS

Alendronate 70 mg OW yielded significantly greater BMD gains and larger decreases in bone turnover marker levels than risedronate 35 mg OW over 24 months, with no difference in UGI tolerability.

The Female Athlete Triad

The female athlete triad (Triad) refers to the interrelationships among energy availability, menstrual function, and bone mineral density, which may have clinical manifestations including eating disorders, functional hypothalamic amenorrhea, and osteoporosis. With proper nutrition, these same relationships promote robust health. Athletes are distributed along a spectrum between health and disease, and those at the pathological end may not exhibit all these clinical conditions simultaneously. Energy availability is defined as dietary energy intake minus exercise energy expenditure. Low energy availability appears to be the factor that impairs reproductive and skeletal health in the Triad, and it may be inadvertent, intentional, or psychopathological. Most effects appear to occur below an energy availability of 30 kcal.kg(-1) of fat-free mass per day. Restrictive eating behaviors practiced by girls and women in sports or physical activities that emphasize leanness are of special concern. For prevention and early intervention, education of athletes, parents, coaches, trainers, judges, and administrators is a priority. Athletes should be assessed for the Triad at the preparticipation physical and/or annual health screening exam, and whenever an athlete presents with any of the Triad's clinical conditions. Sport administrators should also consider rule changes to discourage unhealthy weight loss practices. A multidisciplinary treatment team should include a physician or other health-care professional, a registered dietitian, and, for athletes with eating disorders, a mental health practitioner. Additional valuable team members may include a certified athletic trainer, an exercise physiologist, and the athlete's coach, parents and other family members. The first aim of treatment for any Triad component is to increase energy availability by increasing energy intake and/or reducing exercise energy expenditure. Nutrition counseling and monitoring are sufficient interventions for many athletes, but eating disorders warrant psychotherapy. Athletes with eating disorders should be required to meet established criteria to continue exercising, and their training and competition may need to be modified. No pharmacological agent adequately restores bone loss or corrects metabolic abnormalities that impair health and performance in athletes with functional hypothalamic amenorrhea.

Estimating the response rate in the presence of measurement error

In clinical research, it is often of interest to estimate the response rate (i.e. the proportion of subjects who achieve a clinically meaningful threshold) for a particular variable. The standard estimator of the response rate is generally biased in the presence of measurement error. The estimation accounting for the measurement error utilizing fully nonparametric (NP) methods is complicated and may not be efficient. Therefore, we propose a model-based approach assuming a parametric model for the true value and only the first few moments for the measurement error. The estimator for the true response rate and the variance for the estimator are derived. An innovative method using bootstrap simulation is proposed to check the model assumption. Simulations show that the proposed estimator outperforms a fully NP estimator if the model assumption for X holds. This method is applied to address a commonly occurring question in osteoporosis regarding response to treatment in terms of longitudinal changes in bone mineral density (BMD). Bootstrap simulations showed that the model utilized is appropriate. The proposed method can also be applied in other fields of clinical research.

Examining the Relationship Between Bone Mineral Density and Fracture Risk Reduction During Pharmacologic Treatment of Osteoporosis

Osteoporosis is a skeletal disorder characterized by compromised bone strength that predisposes the patient to an increased risk for fracture. Elements of bone strength include bone mineralization, architecture, turnover, size, and bone mineral density (BMD). Measurement of BMD is the most readily available, noninvasive method for assessing osteoporotic fracture risk and is used by the World Health Organization for diagnostic purposes. Because low BMD is predictive of increased fracture risk, it was believed that changes in BMD during pharmacologic therapy for osteoporosis would strongly predict observed fracture risk reductions. We examined the relationship between changes in BMD and reduction in fracture risk during pharmacologic therapy in postmenopausal women with osteoporosis. The correlation between BMD increases and fracture risk reduction during treatment is not consistent; larger increases in BMD do not necessarily correlate with greater reductions in fracture risk. Multiple factors, in addition to BMD, appear to contribute to the increased bone strength and decreased fracture risk achieved with approved drug therapies for osteoporosis. Until the exact relationship of these factors is fully understood, clinicians should continue to evaluate drug efficacy for osteoporosis based on the fracture risk reductions from well-designed clinical trials.

Relation between homocysteine and biochemical bone turnover markers and bone mineral density in peri- and post-menopausal women

BACKGROUND

Recently, increased plasma homocysteine (Hcy) has been suggested as an independent risk factor for osteoporotic fractures. Therefore, it is tempting to speculate that Hcy adversely affects bone metabolism. This study aimed to analyze the relation between Hcy and biochemical markers of bone metabolism and bone mineral density (BMD).

MATERIALS AND METHODS

We investigated 143 peri- and post-menopausal women [median age (25th-75th percentile), 67 (57-75) years]. All subjects underwent a detailed medical examination, measurement of bone mineral density at lumbar spine (BMD-LS) and total hip (BMD-HIP), and fasting venous blood and urine sampling. Osteocalcin (OC), serum calcium (Ca), urinary desoxypyridinoline cross-links (DPD), osteoprotegerin (OPG) and soluble receptor activator of NF-kappaB ligand (sRANKL) were studied.

RESULTS

According to BMD subjects were classified as normal (n=24), osteopenic (n=51) or osteoporotic (n=68). Median Hcy did not differ between normal, osteopenic and osteoporotic subjects (p=0.647). Partial correlation analysis, controlling for the major confounders, age, creatinine, menopause and previous fractures, revealed significant correlations between Hcy and DPD (r=0.193, p=0.022), as well as between Hcy and Ca (r=0.170, p=0.045). After adjustment for the same confounders, subsequent regression analysis confirmed significant associations of Hcy with DPD and Ca. No significant relations could be observed between Hcy and BMD-LS, BMD-HIP, OC, OPG or sRANKL.

CONCLUSION

Our results demonstrate weak, but significant, relations between Hcy and markers of organic and inorganic bone resorption, suggesting a mechanistic role of Hcy in bone metabolism. The relation between Hcy and bone resorption was not dependent on OPG or sRANKL.

Similar proportions of women lose bone mineral density with raloxifene or alendronate treatment

The ISCD recommends that bone mineral density (BMD) be monitored in patients undergoing antiresorptive therapy to identify patients with a significant BMD loss. This analysis compares the proportions of postmenopausal women treated with raloxifene 60 mg/d (n=82) or alendronate 10 mg/d (n=83) who had significant BMD loss in a randomized, double-blind, placebo-controlled trial that assessed changes in lumbar spine and femoral neck BMD from baseline to 1 yr, measured using dual-energy X-ray absorptiometry. According to ISCD criteria, significant BMD loss was defined as greater than the least significant change, calculated as precision multiplied by 2.77 (95% confidence interval). Assuming a 1% precision at the lumbar spine, the proportions of women with a loss of BMD greater than the least significant change (3%) were similar (p>0.05) between the raloxifene (3%) and alendronate (2%) groups. Assuming 2% precision at the femoral neck, the proportions of women with a loss greater than the least significant change (6%) were similar (p>0.05) between the raloxifene (1%) and alendronate (2%) groups. In conclusion, similar proportions of women did not respond to raloxifene or alendronate therapy, as measured by changes in lumbar spine or femoral neck BMD, when precision error was taken into account.

Nonresponders to osteoporosis therapy

The goal of osteoporosis therapy is reduction of fracture risk. In randomized controlled trials, relative risk of fracture is determined by comparing the absolute fracture rate of a treatment group to a control group. Fracture risk cannot be measured in individual patients being treated for osteoporosis. Since osteoporosis is a silent disease, and some patients may not respond to therapy, a surrogate test for reduction of fracture risk is often used-most commonly a bone density test. A proposed definition of nonresponse is: A decrease in bone mineral density greater than the Least Significant Change at the 95% level of confidence. The Least Significant Change is a value based on bone density measurements in patients and calculated according to well-established standards. There are other candidates for measuring responsiveness to therapy, most notably biochemical markers of bone metabolism, but none is as well validated or standardized as bone density testing. Causes of nonresponse include poor adherence, co-morbid conditions, calcium and vitamin D deficiency, malabsorption, metabolic factors, wrong dose, wrong dosing interval, and lack of efficacy. A bone density increase or stability of bone density is associated with fracture risk reduction in approved osteoporosis therapies, while a bone density decrease is cause for clinical concern. The proposed definition of nonresponse identifies a subset of patients who may require a change of therapy and/or additional medical intervention. More data are needed to develop guidelines for clinicians. Further study is suggested.