HypoparaNet: A Database of Chronic Hypoparathyroidism Based on Expert Medical-Surgical Centers in Italy.

Hypoparathyroidism is a rare disease characterized by low serum calcium levels and absent or deficient parathyroid hormone level. Regarding the epidemiology of chronic hypoparathyroidism, there are limited data in Italy and worldwide. Therefore, the purpose of this study was to build a unique database of patients with chronic hypoparathyroidism, derived from the databases of 16 referral centers for endocrinological diseases, affiliated with the Italian Society of Endocrinology, and four centers for endocrine surgery with expertise in hypoparathyroidism, to conduct an epidemiological analysis of chronic hypoparathyroidism in Italy. The study was approved by the Institutional Review Board. A total of 537 patients with chronic hypoparathyroidism were identified. The leading etiology was represented by postsurgical hypoparathyroidism (67.6%), followed by idiopathic hypoparathyroidism (14.6%), syndromic forms of genetic hypoparathyroidism (11%), forms of defective PTH action (5.2%), non-syndromic forms of genetic hypoparathyroidism (0.9%), and, finally, other forms of acquired hypoparathyroidism, due to infiltrative diseases, copper or iron overload, or ionizing radiation exposure (0.7%). This study represents one of the first large-scale epidemiological assessments of chronic hypoparathyroidism based on data collected at medical and/or surgical centers with expertise in hypoparathyroidism in Italy. Although the study presents some limitations, it introduces the possibility of a large-scale national survey, with the final aim of defining not only the prevalence of chronic hypoparathyroidism in Italy, but also standards for clinical and therapeutic approaches.

Insulin growth factor-1 correlates with higher bone mineral density and lower inflammation status in obese adult subjects.

PURPOSE: Obesity is a severe public health problem worldwide, leading to an insulin-resistant state in liver, adipose, and muscle tissue, representing a risk factor for type 2 diabetes mellitus, cardiovascular diseases, and cancer. We have shown that abdominal obesity is associated with homeostasis derangement, linked to several hormonal and paracrine factors. Data regarding potential link between GH/IGF1 axis, bone mineral density, and inflammation in obesity are lacking. Thus, aim of this study was to evaluate correlation among IGF-1, BMD, and inflammation in obese individuals. METHODS: The study included 426 obese subjects, mean age 44.8 ± 14 years; BMI 34.9 ± 6.1. Exclusion criteria were chronic medical conditions, use of medications affecting bone metabolism, hormonal and nutritional status, recent weight loss, and prior bariatric surgery. Patients underwent measurements of BMD and body composition by DEXA and were evaluated for hormonal, metabolic profile, and inflammatory markers. RESULTS: In this population, IGF-1 was inversely correlated with abdominal FM% (p < 0.001, r 2 = 0.12) and directly correlated with osteocalcin (OSCA) (p < 0.002, r 2 = 0.14). A negative correlation was demonstrated between IGF-1 levels and nonspecific inflammatory index, such as fibrinogen (p < 0.01, r 2 = 0.04) and erythrocyte sedimentation rate (p < 0.0001, r 2 = 0.03). IGF-1 was directly correlated with higher BMD, at both lumbar (p < 0.02, r 2 = 0.03) and femoral site (p < 0.04, r 2 = 0.03). CONCLUSIONS: In conclusion, our results show that higher levels of serum IGF-1 in obese patients correlate with lower inflammatory pattern and better skeletal health, as demonstrated by higher BMD and osteocalcin levels. These results lead to speculate the existence of a bone-adipose-muscle interplay modulating energy homeostasis, glucose, bone metabolism, and chronic inflammation in individuals affected by abdominal obesity.

New therapeutical horizons in the management of postmenopausal osteoporosis.

Osteoporosis is a bone metabolic disease characterized by a compromised skeletal fragility, leading to an increased risk of developing spontaneous and traumatic fractures. This disease is the consequence of an imbalance of the physiological process of bone turnover (or coupling), with the lost of the equilibrium between the activity of osteoblasts and osteoclasts. Therapy has been aimed mainly at the correction of the imbalance between bone resorption and bone formation, to protect skeletal integrity and reduce the risk of fractures. Thus, pharmacological treatments have been aimed at modulating the activity of bone cells.

Skeletal alterations in women affected by obesity.

Obesity has always been considered a protective factor for the skeleton and for osteoporosis. However, new epidemiologic and clinical data have shown that high level of fat mass might be a risk factor for osteoporosis and fragility fractures. Further, increasing evidences seem to indicate that the different components of metabolic syndrome (i.e. hypertension, increased triglycerides, and reduced high-density lipoprotein cholesterol) are also potential risk factors for the development of low bone mineral density and osteoporosis.

Evaluation of persistence and adherence to teriparatide treatment in patients affected by severe osteoporosis (PATT): a multicenter observational real life study.

INTRODUCTION: Osteoporosis is a chronic condition leading to an increased risk of developing fractures, with high morbidity and mortality in aging population. Efficacy of anti-osteoporotic treatment is based on drug potency but also on compliance and persistence to treatment regimen, which is very low, as already described for other diseases. Teriparatide (TPTD) is the first anabolic agent developed for the treatment of osteoporosis. Since it appears that persistence to Teriparatide declines over time, aim of this pilot multicenter observational study was to evaluate persistence and adherence to TPTD (20 µg daily injection regimen for 18 months) treatment (PATT) in patients affected by severe osteoporosis in an every day clinical practice. METHODS: Patients affected by severe osteoporosis were selected among those who referred to 5 different specialized centers for osteoporosis in North, Center and South of Italy. A sample of 475 women with severe postmenopausal osteoporosis treated with TPTD in accordance to the Italian osteoporosis guidelines was included. At the beginning of TPTD treatment patients were instructed on the use of the device by the referring specialist of the center, a resident fellow or a nurse. Bone biochemical markers were evaluated the same morning and after 1, 3, 6, 12 and 18 months. Patients were visited at time 0 and after 6, 12 and 18 months for clinical follow up. RESULTS: The results included observations of 441/475 patients (98% women) who completed the 18 months treatment; mean age for women was 73±8 and for men 65±9. After 6 months of TPTD treatment persistence was of 89,79%, 87,75% after 12 months and 86,85% after 18 months. Adherence was of 100% at 6,12 and 18 months. Total dropouts were 13,15% (71/441), which was usually higher within the first 6 months of TPTD treatment. Most common adverse events (arthralgies 2,7%, dizziness 1,8%, migraine 1,8%, depression 1,6%, hypertension 1,1%) were reported in 62/441 patients (14%) of patients, but were not reason for stopping treatment. CONCLUSIONS: The persistence and adherence to TPTD treatment obtained in this multicenter observational real life study was very high as compared to studies performed by others. These encouraging results suggest that different key factors such quality of information, frequency of visits, motivations given to patients, opportunity to call the doctor might play a pivotal role in the high persistence and adherence to TPTD treatment obtained in our study and need to be carefully considered before prescribing chronic anti-osteoporotic therapy.

Effects of long-acting testosterone undecanoate on bone mineral density in middle-aged men with late-onset hypogonadism and metabolic syndrome: results from a 36 months controlled study.

We evaluated the effects of long-term testosterone replacement therapy (TRT) on the bone mineral density (BMD) in obese patients with metabolic syndrome (MS) and late-onset hypogonadism (LOH). Sixty men (mean age 57 ± 10) with low serum testosterone (T < 320 ng/dL) and MS regardless the presence of osteoporosis were enrolled. Forty men received intramuscular T-undecanoate (TU) four times/year for 36 months and 20 age-matched hypogonadal men with MS in whom T treatment was contraindicated were used as controls. Hormonal, biochemical markers, vertebral and femoral BMD by dual-energy x-ray absorptiometry were measured. At baseline, overall patients had mild osteopenia (lumbar BMD= 0.891 ± 0.097 g/cm(2); femoral BMD= 0.847 ± 0.117 g/cm(2)). TU induced a significant improvement of bone mass after 36 months (lumbar BMD=1.053 ± 0.145 g/cm(2); p < 0.002; femoral BMD=0.989 ± 0.109; p < 0.003 g/cm(2)) with a 5%/year increase and a significant reduction in hs-CRP without changes in body mass index. A direct relationship between serum T and BMD increments at the lumbar (r(2) = 0.66, p < 0.0001) and femoral (r(2) =0.52, p < 0.0001) sites was demonstrated. Study adherence was 50% without serious side effects. Long-term TRT in middle-aged men with LOH and MS determines a significant increase in both vertebral and femoral BMD related to increased serum T levels, probably independently from estradiol modifications.

Effectiveness of teriparatide treatment on back pain-related functional limitations in individuals affected by severe osteoporosis: a prospective pilot study.

INTRODUCTION: Vertebral fractures have been associated with back pain, functional limitations and reduced health-related quality of life (HRQoL). Teriparatide is the first effective anabolic agent that demonstrated to significantly reduce the risk of vertebral fracture by 65%, as compared to placebo. The aims of this study were to evaluate the effectiveness of teriparatide treatment on back pain-related functional limitations and to investigate on patients HRQoL. MATERIALS AND METHODS: In this prospective observational pilot study osteoporotic patients, who were prescribed teriparatide therapy and a supplementation of calcium and vitamin D, were asked to answer to two self-administered questionnaires: the Spine Pain Index (SPI) and the SF-12 (at the recruitment, after 6, 12, and 18 months). RESULTS: Fifty-two women were evaluated (mean age of 70.58 yrs). The mean SPI score passed from 50.01 at baseline to 32.20 at 18 months. The mean SF-12 PCS score passed from 30.00 at baseline to 36.79 at 18 months, while the mean SF-12 MCS score was already within the normality range at baseline, constantly improving during the 18 months. CONCLUSION: In conclusion, 18 months of treatment with teriparatide has to be considered an effective therapeutic option for women with severe osteoporosis and vertebral fractures, in a real-life clinical setting, to improve both back pain related disability and quality of life.

Efficacy of Denosumab Therapy Following Treatment with Bisphosphonates in Women with Osteoporosis: A Cohort Study.

Denosumab is a human monoclonal antibody that neutralizes RANKL, a cytokine able to interact with the RANK receptor on preosteoclasts and osteoclasts, decreasing their recruitment and differentiation, leading to a decreased bone resorption. The aim of this observational real-life study was to analyze adherence to denosumab therapy and assess its efficacy in increasing bone mineral density (BMD) and modulating biochemical skeletal markers following previous treatments with bisphosphonates in a group of post-menopausal women with osteoporosis. Women were recruited in the specialized center from March 2012 to September 2019. Biochemical markers were recorded at baseline and every six months prior to subsequent drug injection. Dual X-ray absorptiometry was requested at baseline and after 18/24 months. Comparing BMD at baseline and after denosumab therapy in naive patients and in those previously treated with bisphosphonates, a positive therapeutic effect was observed in both groups. The results of our real-life study demonstrate, as expected, that BMD values significantly increased upon denosumab treatment. Interestingly, denosumab showed an increased efficacy in patients previously treated with bisphosphonates. Moreover, biochemical markers data indicate that osteoporotic patients, without other concomitant unstable health conditions, could be evaluated once a year, decreasing the number of specialistic center access.

Physical activity and hypocaloric diet recovers osteoblasts homeostasis in women affected by abdominal obesity.

Obesity is a multifactorial disease linked to metabolic chronic disorders such as diabetes, and hypertension. Also, it has recently been associated with skeletal alterations and low bone mineral density. We previously demonstrated that exposure of osteoblasts to sera of sedentary subjects affected by obesity alters cell homeostasis in vitro, leading to disruption of intracellular differentiation pathways and cellular activity. Thus, the purpose of the present study has been to evaluate whether sera of sedentary obese women, subjected to physical activity and hypocaloric diet, could recover osteoblast homeostasis in vitro as compared to the sera of same patients before intervention protocol. To this aim, obese women were evaluated at time 0 and after 4, 6, and 12 months of individualized prescribed physical activity and hypocaloric diet. Dual-energy-X-ray absorptiometry measurements were performed at each time point, as well as blood was collected at the same points. Cells were incubated with sera of subjects before and after physical activity as described: obese at baseline and after for 4, 6, and 12 months of physical activity and nutritional protocol intervention. Osteoblasts exposed to sera of patients, who displayed increased lean and decreased fat mass (from 55.5 ± 6.5 to 57.1 ± 5.6% p ≤ 0.05; from 44.5 ± 1.1 to 40.9 ± 2.6% p ≤ 0.01 respectively), showed a time-dependent increase of Wnt/ß-catenin signaling, versus cells exposed to sera of obese patients before intervention protocol, suggesting recovery of osteoblast homeostasis upon improvement of body composition. An increase in ß-catenin nuclear accumulation and nuclear translocation was also observed, accompanied by an increase in Adiponectin receptor 1 protein expression, suggesting positive effect on cell differentiation program. Furthermore, a decrease in sclerostin amount and an increase of type 1 procollagen amino-terminal-propeptide were depicted as compared to baseline, proportionally to the time of physical activity, suggesting a recovery of bone remodeling modulation and an increase of osteoblast activity induced by improvement of body composition. In conclusion, our results show for the first time that sera of obese sedentary women who increased lean mass and decreased fat mass, by physical activity and hypocaloric diet, rescue osteoblasts differentiation and activity likely due to a reactivation of Wnt/ß-catenin-pathway, suggesting that a correct life style can improve skeletal metabolic alteration induced by obesity.

Differences in Ventilatory Threshold for Exercise Prescription in Outpatient Diabetic and Sarcopenic Obese Subjects.

Aim of the study was to examine cardiorespiratory parameters at individual ventilatory threshold (IVT) and peak exercise capacity ([Formula: see text]) in outpatient diabetic and sarcopenic obese subjects. Seventeen obese subjects (BMI: 36.6 ± 4.1 kg·m(-1)) and sixteen SO subjects (BMI: 37.0 ± 7.3 kg·m(-1)) were compared with sixteen T2DM subjects (BMI: 37.7 ± 5.6 kg·m(-1)). All groups performed an incremental exercise test on a treadmill according to their physical ability. [Formula: see text], %HRmax, and maximal metabolic equivalent (METmax) were evaluated at maximal effort. Moreover, [Formula: see text], %[Formula: see text], %HRmax, %HRR, ΔHR, and METivt were assessed at IVT. No significant differences were found in any physiological parameters at maximal effort ([Formula: see text], %HRmax, and METmax) in all groups. On the contrary, [Formula: see text], %[Formula: see text], %HRmax, %HRR, ΔHR, and METivt were significantly lower in T2DM subjects as compared to OB and SO subjects at IVT (p < 0.05). Our results show that while at maximal effort there are no differences among groups, at IVT the physiological parameters are lower in T2DM subjects than in OB and SO subjects. Therefore, due to the differences observed in the groups, we suggest usng the IVT as a useful parameter to prescribe aerobic exercise in obese with sarcopenia or diabetes mellitus conditions.

Abdominal Fat and Sarcopenia in Women Significantly Alter Osteoblasts Homeostasis In Vitro by a WNT/ ß -Catenin Dependent Mechanism.

Obesity and sarcopenia have been associated with mineral metabolism derangement and low bone mineral density (BMD). We investigated whether imbalance of serum factors in obese or obese sarcopenic patients could affect bone cell activity in vitro. To evaluate and characterize potential cellular and molecular changes of human osteoblasts, cells were exposed to sera of four groups of patients: (1) affected by obesity with normal BMD (O), (2) affected by obesity with low BMD (OO), (3) affected by obesity and sarcopenia (OS), and (4) affected by obesity, sarcopenia, and low BMD (OOS) as compared to subjects with normal body weight and normal BMD (CTL). Patients were previously investigated and characterized for body composition, biochemical and bone turnover markers. Then, sera of different groups of patients were used to incubate human osteoblasts and evaluate potential alterations in cell homeostasis. Exposure to OO, OS, and OOS sera significantly reduced alkaline phosphatase, osteopontin, and BMP4 expression compared to cells exposed to O and CTL, indicating a detrimental effect on osteoblast differentiation. Interestingly, sera of all groups of patients induced intracellular alteration in Wnt/ ß -catenin molecular pathway, as demonstrated by the significant alteration of specific target genes expression and by altered ß -catenin cellular compartmentalization and GSK3 ß phosphorylation. In conclusion our results show for the first time that sera of obese subjects with low bone mineral density and sarcopenia significantly alter osteoblasts homeostasis in vitro, indicating potential detrimental effects of trunk fat on bone formation and skeletal homeostasis.

Trunk fat negatively influences skeletal and testicular functions in obese men: clinical implications for the aging male.

Osteocalcin (OSCA) seems to act as a negative regulator of energy metabolism and insulin sensitivity. Evidence from male rodents suggests that OSCA may also regulate testosterone (T) synthesis. Using a cross-sectional design, we evaluated OSCA, 25(OH) vitamin D, T, 17 ß -estradiol (E2), homeostasis model assessment of insulin resistance (HOMA-IR), and body composition in 86 obese (mean BMI = 34) male subjects (18-69 yr old). Independently from BMI, an inverse relationship between trunk fat percentage and plasma T (r (2) = -0.26, P < 0.01) and between HOMA-IR and OSCA levels (r (2) = -0.22, P < 0.005) was found. OSCA levels, as well as vitamin D, decreased significantly for higher BMI with significant differences above 35 (P < 0.01). A direct correlation between T and bone mineral density at lumbar (BMDL) and neck (BMDH) (P < 0.001, r (2) = -0.20; P < 0.001, r (2) = -0.24) was found, independently from age. An inverse correlation between E2 levels, BMDL, and BMDH (P < 0.001, r (2) = -0.20; P < 0.001, r (2) = -0.19) was observed. These data provide new evidences that a relationship between trunk fat mass, insulin sensitivity, OSCA and T synthesis occurs. This new relationship with skeletal health has relevant implications for the aging male, suggesting OSCA as a novel marker of metabolic and gonadal health status.

Negative association between trunk fat, insulin resistance and skeleton in obese women.

AIM: To evaluate the potential interference of trunk fat (TF) mass on metabolic and skeletal metabolism. METHODS: In this cross-sectional study, 340 obese women (mean age: 44.8 ± 14 years; body mass index: 36.0 ± 5.9 kg/m(2)) were included. Patients were evaluated for serum vitamin D, osteocalcin (OSCA), inflammatory markers, lipids, glucose and insulin (homeostasis model assessment of insulin resistance, HOMA-IR) levels, and hormones profile. Moreover, all patients underwent measurements of bone mineral density (BMD; at lumbar and hip site) and body composition (lean mass, total and trunk fat mass) by dual-energy X-ray absorptiometry. RESULTS: Data showed that: (1) high TF mass was inversely correlated with low BMD both at lumbar (P < 0.001) and hip (P < 0.01) sites and with serum vitamin D (P < 0.0005), OSCA (P < 0.0001) and insulin-like growth factor-1 (IGF-1; P < 0.0001) levels; (2) a positive correlation was found between TF and HOMA-IR (P < 0.01), fibrinogen (P < 0.0001) and erythrocyte sedimentation rate (P < 0.0001); (3) vitamin D levels were directly correlated with IGF-1 (P < 0.0005), lumbar (P < 0.006) and hip (P < 0.01) BMD; and (4) inversely with HOMA-IR (P < 0.001) and fibrinogen (P < 0.0005).Multivariate analysis demonstrated that only vitamin D was independent of TF variable. CONCLUSION: In obese women, TF negatively correlates with BMD independently from vitamin D levels. Reduced IGF-1 and increased inflammatory markers might be some important determinants that account for this relationship.

Is obesity in women protective against osteoporosis?

The belief that obesity is protective against osteoporosis has recently come into question. The latest epidemiologic and clinical studies have shown that a high level of fat mass might be a risk factor for osteoporosis and fragility fractures. Further, increasing evidence seems to indicate that different components of the metabolic syndrome, ie, hypertension, increased triglycerides, reduced high-density lipoprotein cholesterol, are also potential risk factors for the development of low bone mineral density and osteoporosis. This review considers both the older and more recent data in the literature in order to evaluate further the relationship between fat tissue and bone tissue.

Differential characteristics of bone quality and bone turnover biochemical markers in patients with hip fragility fractures and hip osteoarthritis: results of a clinical pilot study.

BACKGROUND AND AIMS: Bone density and quality alterations worsen the ability of osteoporotic bone to support prosthetic implants. The aim of our study was to evaluate potential differences in bone quality and bone turnover markers in aged individuals undergoing surgery for hip fragility fracture or hip osteoarthritis. METHODS: Eighteen subjects with hip fragility fractures (Hip Fracture Group), 35 subjects with osteoarthritis of the hip (Hip Osteoarthritis Group) and 19 subjects with normal femoral bone mineral density (Control Group) were evaluated. Serum and urinary bone markers were assayed preoperatively in all surgical patients, and within 48 hours after fracture in the Hip Fracture, Osteoarthritis and Control groups. Histomorphometric analysis was performed on surgical samples. RESULTS: A significant alteration in calcium and PTH serum levels with hyperparathyroidism was observed in the Hip Fracture Group compared with Hip Osteoarthritis and Control Groups. C-Terminal telopeptides of type I-collagen (CTx) and tartrate resistant-acid phosphatase (TRAP), markers of bone resorption, were increased in the Hip Fracture Group compared with both Osteoarthritis and Control Groups (CTx: p<0.0007 and p<0.0039 respectively; TRAP: p<0.002 and p<0.0007). All subjects were vitamin D3-deficient, but no differences were found among the different groups. In addition, histomorphometric data showed better maintained connectivity in the Osteoarthritis Group compared with the Hip Fracture Group (p<0.0001). CONCLUSIONS: Our data show significant differences in bone turnover markers in patients undergoing hip prosthesis for fragility fractures, compared with patients operated for hip osteoarthritis.

Impairment of diastolic function in adult patients affected by osteogenesis imperfecta clinically asymptomatic for cardiac disease: casuality or causality?

Osteogenesis imperfecta (OI) is a rare inherited connective disorder causing increased bone fragility and low bone mass. OI includes severe bone fragility, impaired dentinogenesis, with less common alterations in the joints, blood vessels, heart valves, skin. Interestingly, description of left ventricular rupture, aortic dissection and heart valves incompetence has been previously described. Death may occur in OI patients for cardiac disease in asyntomatic subjects. Aim of our study has been to evaluate the presence of potential subclinical cardiac disorders and to characterize cardiac functional parameters by echocardiography in adults with OI in absence of cardiac symptoms. Forty patients (21 females and 19 males) affected by type I, III, IV OI and 40 control subjects (20 females and 20 males) were evaluated in the study. Patients and controls underwent clinical examination, screening for endocrine and metabolic disorders, 12-lead electrocardiogram and echocardiogram. In particular, all subjects were evaluated by two-dimensional echocardiography with continuous- and pulse-wave Doppler. Patients and controls belonged to NYHA class I and no significant electrocardiographic alteration was documented in both groups. Thirty-eight patients (95%) showed valvular regurgitation compared to one control subject (2.5%; P<0.001). As regards the diastolic function parameters, in OI patients E wave velocity was reduced by 23% (95% CI: 9% to 29%; P<0.001), E/A ratio was reduced by 17% (95% CI: 15% to 26%; P<0.001) while isovolumetric relaxation time (IRT) was increased by 47% (95% CI: 26% to 53%; P<0.001) and E wave deceleration time (DT) was increased by 18% (95% CI: 13% to 26%; P<0.001) compared to controls. In conclusion, our data indicate that adult patients affected by OI have an altered diastolic function in absence of other metabolic alterations. These diastolic echocardiographic parameters might worsen over time, especially if other cardiovascular risk factors (e.g., smoking, hypertension, metabolic and endocrine alterations) are not carefully checked, monitored and treated. In the context of a multidisciplinary evaluation of OI patients, our data suggest that a careful cardiological evaluation of these patients is indicated beside skeletal evaluation and therapeutical skeletal options.

A new heterozygous mutation (R714C) of the osteopetrosis gene, pleckstrin homolog domain containing family M (with run domain) member 1 (PLEKHM1), impairs vesicular acidification and increases TRACP secretion in osteoclasts.

UNLABELLED: We studied phenotypic and cellular aspects in a patient with a heterozygous mutation of the PLEKHM1 gene and obtained some indications regarding the role of the protein in bone cell function. Plekhm1 is involved in osteoclast endosomal vesicle acidification and TRACP exocytosis, contributing to events involved in osteoclast-osteoblast cross-talk. INTRODUCTION: The gene PLEKHM1 encodes a nonsecretory adaptor protein that localizes to endosomal vesicles. A highly truncated Plekhm1 protein was previously found in a patient with intermediate autosomal recessive osteopetrosis. MATERIALS AND METHODS: We describe a new heterozygous mutation in the PLEKHM1 gene in a patient presenting with low vertebral and femoral T-scores and areas of focal sclerosis. Clinical evaluation, mutational analysis, assessment of in vitro osteoclast morphology and activity, transfection studies, and evaluation of osteoclast-osteoblast cross-talk were carried out. RESULTS: Direct DNA sequencing showed a heterozygous C to T substitution on cDNA position 2140 of the PLEKHM1 gene, predicted to lead to an R714C mutant protein. The mutation was not found in 104 control chromosomes. In vitro, patient's osteoclasts showed normal formation rate, morphology, number of nuclei, and actin rings but lower TRACP activity and higher endosomal pH than control osteoclasts. The patient had high serum PTH and TRACP, despite low TRACP activity in osteoclasts in vitro. HEK293 cells overexpressing either wildtype or Plekhm1-R714C showed no difference in localization of the variants, and co-transfection with a TRACP vector confirmed low TRACP activity in cells carrying the R714C mutation. RAW 264.7 osteoclast-like cells expressing the Plekhm1-R714C variant also showed low TRACP activity and reduced ability to acidify endosomal compartments compared with cells expressing the wildtype protein. Reduced intracellular TRACP was caused by increased protein secretion rather than reduced expression. TRACP-containing conditioned medium was able to increase osteoblast alkaline phosphatase, suggesting the focal osteosclerosis is a result of increased osteoclast-osteoblast coupling. CONCLUSIONS: We provide further evidence for a role of Plekhm-1 in osteoclasts by showing that a novel mutation in PLEKHM1 is associated with a complex bone phenotype of generalized osteopenia combined with "focal osteosclerosis." Our data suggest that the mutation affects endosomal acidification/maturation and TRACP exocytosis, with implications for osteoclast-osteoblast cross-talk.

Glucocorticoid-induced osteoporosis: an osteoblastic disease.

It is well-known that glucocorticoid-induced osteoporosis (GIO) is the most common form of secondary osteoporosis. It is estimated that 30% to 50% of patients receiving chronic glucocorticoid therapy suffer vertebral or hip fractures, which are often asymptomatic. Vertebral fractures occur early after exposure to glucocorticoids, at a time when bone mineral density (BMD) declines rapidly. Glucocorticoids impair osteoblast homeostasis and induce apoptosis of both osteoblasts and osteocytes, leading to suppression of bone formation. Glucocorticoids also favor osteoclastogenesis and, as a consequence, increase bone resorption. The end-point of these alterations is a net decrease in BMD and alterations in bone quality. Bisphosphonates have been approved for both prevention and treatment of GIO. At the present time, anabolic therapeutic agents are still under investigation.