Messages from the Mineral: How Bone Cells Communicate with Other Tissues.

Bone is a highly dynamic tissue, and the constant actions of bone-forming and bone-resorbing cells are responsible for attaining peak bone mass, maintaining bone mass in the adults, and the subsequent bone loss with aging and menopause, as well as skeletal complications of diseases and drug side-effects. It is now accepted that the generation and activity of bone-forming osteoblasts and bone-resorbing osteoclasts is modulated by osteocytes, osteoblast-derived cells embedded in the bone matrix. The interaction among bone cells occurs through direct contact and via secreted molecules. In addition to the regulation of bone cell function, molecules released by these cells are also able to reach the circulation and have effects in other tissues and organs in healthy individuals. Moreover, bone cell products have also been associated with the establishment or progression of diseases, including cancer and muscle weakness. In this review, we will discuss the role of bone as an endocrine organ, and the effect of selected, osteoblast-, osteocyte-, and osteoclast-secreted molecules on other tissues.

Argentine Guidelines for the Prevention and Treatment of Glucocorticoid-Induced Osteoporosis in Postmenopausal Women and Men Aged 50 Years and Older.

OBJECTIVE: The aim of this study was to provide an evidence-based framework to guide health care professionals treating patients under glucocorticoid (GC) therapy and develop guidelines for the prevention and treatment of glucocorticoid-induced osteoporosis (GIO) in postmenopausal women and men aged ≥50 years. METHODS: An expert panel on bone diseases designed a series of clinically meaningful questions following the PICO (Population, Intervention, Comparator, and Outcome) structure. Using GRADE (Grading of Recommendations Assessment, Development, and Evaluation) methodology, we made a systematic literature review, extracted and summarized the effect estimates, and graded the quality of the evidence. The expert panel voted each PICO question and made recommendations after reaching an agreement of at least 70%. RESULTS: Seventeen recommendations (9 strong and 8 conditional) and 8 general principles were developed for postmenopausal women and men aged ≥50 years under GC treatment. Bone mineral density (BMD), occurrence of fragility fractures, probability of fracture at 10 years by Fracture Risk Assessment Tool, and other screening factors for low BMD are recommended for patient evaluation and stratification according to fragility fracture risk. The treatment of patients under GC therapy should include counseling on lifestyle habits and strict control of comorbidities. The goal of GIO treatment is the nonoccurrence of new fragility fractures as well as to increase or maintain BMD in certain clinical situations. This was considered for the therapeutic approach in different clinical scenarios. CONCLUSIONS: This GIO guideline provides evidence-based guidance for health care providers treating patients.

Prevalence of Sarcopenia and Whole-Body Composition in Rheumatoid Arthritis.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic autoimmune disease that leads to joint deformity and disability, as well as muscle involvement. Sarcopenia is characterized by a progressive age-related loss of muscle mass and strength. AIM: The aim of this study was to evaluate the prevalence of sarcopenia and possible contributing factors associated with sarcopenia in RA patients. PATIENTS AND METHODS: Adult RA patients (n = 105) of both sexes and 100 subjects as control group (CG) matched by age, sex, and body mass index were included in this cross-sectional study. Whole-body composition was measured by dual-energy x-ray absorptiometry. Sarcopenia was defined according to European Working Group on Sarcopenia in Older People 2 as low muscle strength (handgrip) and low muscle mass (appendicular skeletal muscle mass [ASM] index by dual-energy x-ray absorptiometry). The association between sarcopenia and associated factors was evaluated using logistic regression analyses. RESULTS: Significantly lower percentage of lean mass and ASM were found in the whole RA group compared with controls. However, lower lean parameters (total lean mass, percentage of lean mass, and ASM) were observed only in female subjects. The ASM index was significantly lower in female subjects with RA (RA 31.0% vs CG 11.9%) without differences in male subjects. On the other hand, fat mass and most adipose indices were significantly higher in both female and male subjects with RA. Female RA patients had higher prevalence of sarcopenia and sarcopenic obesity. Through univariate logistic regression analysis, the time of corticosteroids use, cumulative corticosteroid dose, previous fragility fractures, total lean mass, and ASM were associated with sarcopenia. CONCLUSIONS: Higher prevalence of sarcopenia and sarcopenic obesity were found in female RA patients. Sarcopenia was found in younger female subjects with RA compared with healthy control subjects. Sarcopenia was associated with previous fragility fractures in female patients with RA.

Increased calcium uptake and improved trabecular bone properties in intestinal alkaline phosphatase knockout mice.

Previous studies have demonstrated a negative correlation between intestinal alkaline phosphatase (IAP) activity and calcium (Ca) absorption in the gut, as IAP acts as a protective mechanism inhibiting high Ca entry into enterocytes, preventing Ca overload. Here we evaluated Ca absorption and bone properties in knockout mice (KO) completely devoid of duodenal IAP (Akp3 -/- mice). Female C57BL/6 control mice (WT, n = 7) and KO mice (n = 10) were used to determine Ca absorption in vivo and by in situ isolated duodenal loops followed by histomorphometric analysis of duodenal villi and crypts. Bone mineral density, morphometry, histomorphometry and trabecular connectivity and biomechanical properties were measured on bones. We observed mild atrophy of the villi with lower absorption surface and a significantly higher Ca uptake in KO mice. While no changes were seen in cortical bone, we found better trabecular connectivity and biomechanical properties in the femurs of KO mice compared to WT mice. Our data indicate that IAP KO mice display higher intestinal Ca uptake, which over time appears to correlate with a positive effect on the biomechanical properties of trabecular bone.

Increase of calcium and reduction of lactose concentration in milk by treatment with kefir grains and eggshell.

Dairy products are the main source of calcium (Ca), but the loss of the consumption habit contributes to low consumption in adulthood, which leads to osteoporosis and increased fracture risk. Domestic use of kefir is straightforward and the eggshell is a natural discarded source of Ca. This paper proposes the development of an enriched Ca reduced lactose milk using eggshell and kefir. During the in vitro preparation, the pH, Ca and lactose contents were measured. Ca intestinal absorption of untreated milk and milk with kefir was compared. Finally, human volunteers consumed this dairy product and 24-h urine Ca was measured. Results showed that the beverage has lower lactose and higher Ca than untreated milk and milk with kefir. Intestinal Ca absorption was not different between both milks and an increase in urinary Ca excretion was observed in humans. This study provides a methodology to prepare at home a dairy product that could contribute to improve the Ca intake in adults.

Effects of Yerba Mate (IIex paraguariensis) on Histomorphometry, Biomechanics, and Densitometry on Bones in the Rat.

Yerba mate (Ilex paraguariensis) is a xanthine-containing beverage, which is also rich in caffeine. Because caffeine has a negative impact on bone mineral density (BMD) mainly associated with low calcium (Ca) diets, there would be expected a negative effect of yerba mate on bone. In this study, Sprague-Dawley rats were used and randomly assigned into four groups (n = 6/group): Control + Ca 0.2 g %; Control + Ca 0.9 g %; Yerba + Ca 0.2 g %; Yerba + Ca 0.9 g %. At the end of the experiment, tibias and femurs were obtained for BMD, morphometric, histomorphometric, and biomechanical analyses. While there was no difference in bone parameters between rats with and without yerba mate consumption, a negative effect of low Ca diet was observed in BMD, morphometric, histomorphometric, and biomechanical results. Interaction between Ca content in the diet and yerba mate was only found in trabecular bone volume, which would indicate that the negative effect of low Ca intake on bone volume is reversed in part by yerba mate infusion. However, yerba mate was not able to reverse the negative effect of low Ca content on biomechanical properties and trabecular connectivity. In summary, at least in our study, yerba mate would not have a negative effect on bone and would be safe for the bone health of consumers.

Vitamin D levels and bone mass in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic systemic inflammatory autoimmune disease with high prevalence of osteoporosis. Previous evidence indicates an association between vitamin D deficiency and autoimmune diseases. The aim of this study was to evaluate serum 25 hydroxyvitamin D [25(OH)D] levels, bone mineral density (BMD) and disease activity in RA patients living in Argentina. We studied 34 RA women and 41 healthy women as a control group. RA patients had lower 25(OH)D levels (20.4 ± 0.9 ng/ml) than controls (26.3 ± 1.9 ng/ml; p < 0.05). No significant differences were found in lumbar spine BMD between premenopausal (preM) or postmenopausal (postM) patients, but femoral neck BMD was significantly lower in postM RA patients (T score -2.5 ± 0.4) than in postM control subjects (T score -0.9 ± 0.3, p = 0.014). Although no linear correlation between 25(OH)D levels and disease activity (DAS-28) was found, patients with moderate-high disease activity had lower 25(OH)D levels than those with low disease activity: DAS-28 >3.2: 19.5 ± 0.88 ng/ml; DAS-28 ≤3.2: 23.7 ± 2.8 ng/ml (p = 0.047). After 1 year of vitamin D treatment 25(OH)D levels were increased while DAS-28 were decreased (n = 25; p < 0.05). We conclude that patients with RA had lower 25(OH)D levels than the control group. Low levels of 25(OH)D were associated with moderate-high disease activity suggesting the importance of optimal 25(OH)D levels in RA patients. Femoral neck BMD was lower in postM RA patients. No differences in lumbar BMD were found between preM and postM RA patients, suggesting that bone mass evaluation in RA patients should include femoral neck BMD regardless of age.

Increased Osteoblastic and Osteocytic in Vitro Cell Viability by Yerba Mate (Ilex paraguariensis).

BACKGROUND: Yerba mate (YM, Ilex paraguariensis) consumption beneficially affects the bones. However, whether YM components exert their effect on bone cells directly remains elusive. METHODS: We evaluated how main YM components affect osteoblastic (MC3T3-E1) and osteocytic (MLO-Y4) cells in vitro when administered separately or in an aqueous extract. MC3T3-E1 and MLO-Y4 cells were exposed to three different experimental conditions: (1) Caffeine, chlorogenic acid, and their combinations; (2) Caffeine, rutin, and their combinations; (3) Aqueous YM extract. RESULTS: All polyphenol and caffeine concentrations as well as that of their tested combinations significantly increased MC3T3-E1 cell viability from 16.6% to 34.8% compared to the control. In MLO-Y4 cells, the lowest rutin and the two highest caffeine concentrations significantly increased cell viability by 11.9, 14.9, and 13.7%, respectively. While rutin and caffeine combinations tended to increase MLO-Y4 cell viability, different chlorogenic acid and caffeine combinations did not affect it. Finally, the aqueous YM extract significantly increased MLO-Y4, MC3T3-E1, and differentiated MC3T3-E1 cell viability compared to the control without treatment. CONCLUSIONS: YM components (rutin, chlorogenic acid, and caffeine) positively affected bone cells, mainly pre-osteoblast cells. Moreover, the aqueous YM extract significantly increased MLO-Y4, MC3T3-E1, and differentiated MC3T3-E1 cell viabilities indicating an additional relevant nutritional property of YM infusion. Further studies would be required to elucidate the underlying effector mechanism of YM on the bones and its relationship with previously described in vivo positive effects.

Chicken eggshell as suitable calcium source at home.

AIM: Taken into consideration that the deficiency of calcium (Ca) in the diet is a common problem, the aim of this work was to study the chicken eggshell as Ca source at home. It was evaluated: (1) different mechanisms to process eggshells and find an easy way to determine the required amount of Ca at home and; (2) the flavor and the texture for eggshell fortified food. METHODS: Chemical and mechanical methods of eggshell processing were evaluated. Changes in flavor and texture were evaluated in volunteers coordinated by a professional chef. RESULTS: A single eggshell contains 2.07 ± 0.18 g of Ca; therefore half an eggshell could provide the amount of Ca needed by adult human beings per day. The best way to use chicken eggshell as Ca dietary supplement is powdered to add to bread, pizza or spaghetti as there were small changes in texture and no changes in flavor.

Whole-hand and regional bone mineral density involvement in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by symmetric polyarthritis that can lead to joint deformity, disability, and osteoporosis. We aimed to evaluate whole hand and regional BMD in RA patients compared to controls. In addition, we evaluated the BMD of dominant versus non-dominant hands in healthy subjects. We included adult female and male RA patients and control subjects matched by age, sex, and BMI. BMD (g/cm2) was measured by DXA in lumbar spine (LS), whole hand, and three regions of interest: carpus, metacarpal bones, and phalanges. Results: 44 control subjects (49.5±11.8 y) and 60 with RA (52.7±12.7 y) were included. Significant lower BMD in RA patients was found in LS (-8.7%), dominant whole hand (-9.5%), carpus, metacarpal bones, and phalanges, and non-dominant whole hand (-8.7%), metacarpal bones, and phalanges compared to controls. A significant positive correlation was found between LS and whole-hand BMD (dominant r=.63, non-dominant r=.67). Finally, the whole hand, metacarpal bones, and carpus BMD measurements were significantly higher in the dominant hand compared to the non-dominant hand without differences in the phalangeal ROI. In conclusion, hand BMD was significantly lower in RA patients compared to control subjects and there was a significant correlation with LS BMD. We demonstrated that BMD measurements of the whole-hand, and different ROI (carpus, metacarpal bones, and phalanges) by DXA would be an easily reproducible technique to evaluate bone loss. In addition, the whole hand, metacarpal bones and carpus BMD measurements were significantly higher in the dominant hand compared to the non-dominant hand without differences in the phalanges.

Threshold based on bone mineral density for therapeutic decision-making in postmenopausal women and men over 50 years old under glucocorticoid therapy.

INTRODUCTION AND AIM: T-score bone mineral density (BMD) thresholds may influence guidance for treatment in patients under glucocorticoid (GC) therapy. Different BMD thresholds have been described but there is no international consensus. The aim of this study was to find a threshold to help in treatment decision-making in the population under GC therapy. METHODS: A working group representing three scientific societies from Argentina was convened. The first team was formed by specialists with expertise in glucocorticoid-induced osteoporosis (GIO) who voted according to summary of evidence. The second team was constituted by a methodology group who coordinated and supervised each stage. We conducted two systematic reviews to synthesize the evidence. The first included trials of drugs used in GIO to analyze the BMD cut-off used as inclusion criteria. In the second, we analyzed the evidence regarding the densitometric thresholds to discriminate between fractured and non-fractured patients under GC treatment. RESULTS: In the first review, 31 articles were included for qualitative synthesis and more than 90% of the trials included patients regardless of their densitometric T-score or range of osteopenia. In the second review, 4 articles were included and more than 80% of the T-scores were in the range -1.6 to -2.0. The summary of findings was analyzed and put to a vote. CONCLUSIONS: With more than 80% agreement of the voting expert panel, a T-score≤-1.7 was considered the most appropriate for treatment in postmenopausal women and men over 50 years of age under GC therapy. This study could help in treatment decision-making in patients under GC therapy without fractures but other fracture risk factors should certainly be considered.

Effect of Teriparatide on Bone Mineral Density and Bone Markers in Real-Life: Argentine Experience.

Purpose: To evaluate the effect of teriparatide (TPTD) on bone mineral density (BMD) and bone markers under clinical practice conditions. To assess whether the results in real-life match those published in clinical trials. Methods: Cross-sectional study of postmenopausal women treated with TPTD for at least 12 months. Results: 264 patients were included in the study. Main characteristics are as follows: age: 68.7 ± 10.2 years, previous fractures: 57.6%, and previously treated with antiresorptive (AR-prior): 79%. All bone turnover markers studied significantly increased after 6 months. CTX and BGP remained high up to 24 months, but total and bone alkaline phosphatase returned to basal values at month 18. There was a significant increase in lumbar spine (LS) BMD after 6 months (+6.2%), with a maximum peak at 24 months (+13%). Femoral neck (FN) and total hip (TH) BMD showed a significant increase later than LS (just at month 12), reaching a maximum peak at month 24 (FN + 7.9% and TH + 5.5%). A significant increase in LS BMD was found from month 6 to month 24 compared to basal in both AR-naïve, and AR-prior patients (+16.7% and +10.5%, respectively), without significant differences between the two groups. Comparable results were found in FN and TH BMD. Main conclusions. As reported in real-life clinical studies, treatment of osteoporotic postmenopausal women with TPTD induced a significant increase in bone turnover markers from month 6 onward and an increase in BMD from months 6-12 with continuous gain up to month 24. The real-life results of our study matched the results of randomized clinical trials. In addition, TPTD induced an increase in BMD, regardless of the previous use of AR.

Luminal calcium concentration controls intestinal calcium absorption by modification of intestinal alkaline phosphatase activity.

Intestinal alkaline phosphatase (IAP) is a brush-border phosphomonoesterase. Its location suggests an involvement in the uptake of nutrients, but its role has not yet been defined. IAP expression parallels that of other proteins involved in Ca absorption under vitamin D stimulation. Experiments carried out in vitro with purified IAP have demonstrated an interaction between Ca and IAP. The gut is prepared to face different levels of Ca intake over time, but high Ca intake in a situation of a low-Ca diet over time would cause excessive entry of Ca into the enterocytes. The presence of a mechanism to block Ca entry and to avoid possible adverse effects is thus predictable. Thus, in the present study, Sprague-Dawley rats were fed with different amounts of Ca in the diet (0.2, 1 and 2 g%), and the percentage of Ca absorption (%Ca) in the presence and absence of L-phenylalanine (Phe) was calculated. The presence of Phe caused a significant increase in %Ca (52.3 (SEM 6.5) % in the presence of Phe v. 31.1 (sem 8.9) % in the absence of Phe, regardless of the amount of Ca intake; paired t test, P = 0.02). When data were analysed with respect to Ca intake, a significant difference was found only in the group with low Ca intake (paired t test, P = 0.03). Additionally, IAP activity increased significantly (ANOVA, P < 0.05) as Ca concentrations increased in the duodenal lumen. The present study provides in vivo evidence that luminal Ca concentration increases the activity of IAP and simultaneously decreases %Ca, acting as a minute-to-minute regulatory mechanism of Ca entry.

Extensive progressive heterotopic ossification post-Covid-19 in a man.

Heterotopic ossification (HO) is the formation of extraskeletal bone in muscle and soft tissues and could be genetic or non-genetic. The classic presentation of non-genetic HO is in young adults with a clear history of local trauma, surgery or prolonged immobilization after spinal cord and traumatic brain injuries. Genetic HO has a significant clinical severity compared to non-genetic causes and includes fibrodysplasia ossificans progressiva (FOP). FOP is an extremely rare genetic skeletal disorder characterized by congenital malformations of the great toes and progressive heterotopic ossification that forms qualitatively normal bone in characteristic extraskeletal sites affecting skeletal muscles, fascia, tendons, and ligaments. Previously, it has been reported an association between SARS-CoV-2 infection (COVID-19) and HO or FOP exacerbation with unclear etiopathogenesis. The possible mechanisms could be prolonged immobilization and systemic inflammation. Here, we describe the case of a 55-year-old apparently healthy man who suffered from a severe SARS-CoV-2 infection after that he experienced an extensive and progressive heterotopic ossification around the shoulders, the elbows, the hip, the knees, and the ankles. Because of the clinical severity, the painful soft-tissue swelling, the progressive HO, and the bilateral congenital hallux valgus deformity, a late-onset atypical FOP was suspected. Nevertheless, no variant of clinical significance has been identified in the coding regions and splicing sites in the ACVR1 gene and no deletions and/or duplications have been identified in exonic regions.

Pseudomyogenic hemangioendothelioma with bone and soft tissue involvement with favorable response to pamidronate: a case report and systematic review of the literature.

Pseudomyogenic hemangioendothelioma (PMH) can be a challenge for diagnosis and might be confused with other tumors, such as epithelioid sarcoma. Here we present a case and a systematic review of the literature to identify and discuss PMH treatment in primary bone involvement. A 25-year-old woman was referred for bone pain (10/10) in the left lower limb. Magnetic resonance imaging (MRI) showed multiple bone lesions (left femur, tibia, patella, ankle, and foot) with well-defined borders without signs of local aggressiveness. Positron Emission Tomography-Computed Tomography (PET-CT) showed multiple metabolic musculoskeletal lesions in the left lower limb. A CT scan-guided biopsy was performed. Histological and immunohistochemical findings confirmed the diagnosis of PMH. After treatment with intravenous pamidronate (90 mg/monthly), the patient had clinical improvement, mild pain 2/10 without the use of non-steroidal anti-inflammatory drugs or opiates. Follow-up was assessed by MRI and PET-CT. PET-CT showed metabolic resolution of most of the bone and muscular lesions and a significant improvement of the femoral lesion. MRI showed that the lesions in the left femur, tibia, and foot had a marked decrease in size without intravenous post-contrast enhancement and smaller lesions had disappeared. After a 3-year follow-up, PET-CT showed no metabolically active images. Literature review identified 31 records including 58 clinical cases of PMH with primary bone involvement and treatment description for qualitative analysis. Most lesions (69%) were treated by local excision or curettage. In addition, amputations were performed in a significant percentage of cases (20.7%). In the last years, mTOR inhibitors (n = 7) and anti-resorptive treatments (n = 4) were considered as alternative treatment options, especially in multifocal lesions.

Effect of fluoride on bone and growth plate cartilage.

The use of fluoride (F) for therapeutic purposes is controversial and its toxicity is a health problem. The aim of this study was to evaluate the effect of F on endochondral ossification in growing rats. Twenty-four rats of 21 days were divided into 4 groups which received 0, 20, 40 or 80 µmol F/100 g body weight/day for 30 days, through an orogastric tube. Histological evaluation of growth plate cartilage (GPC) and primary and secondary bone were analyzed on sections of the metaphysis of tibias. Total thickness of the GPC (GPC.Th), thickness of resting zone (RZ.Th), proliferative zone (PZ.Th) and hypertrophic zone (HZ.Th); bone volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp), and apoptosis by the TUNEL were measured. A hyperplasia of the proliferative zone and a significant increase in PZ.Th with 40 and 80 µmol F without changes in GPC.Th were found. In the secondary trabecular bone, presence of immature trabeculae, peritrabecular inflammatory foci and sinusoidal dilatation were observed. A significant decrease in BV/TV was also found due to a decrease in Tb.Th and a progressive increase was observed in the number of apoptotic nuclei as the dose of F increased. In conclusion, results suggest that prolonged administration (30 days) of F negatively affect the endochondral ossification with increased chondrocyte proliferation and delayed maturity of new bone, causing inflammatory damage, edema, and increased apoptotic bone cells.

Postmenopausal women with sarcopenia have higher prevalence of falls and vertebral fractures.

Recently, a new consensus of the European Working Group on Sarcopenia in Older People (EWSOP2) recommended new cut-off points for the diagnosis of sarcopenia. The aim of the present manuscript was to assess the prevalence of sarcopenia in postmenopausal women and its relationship with bone mineral density, falls and fragility fractures according to EWGSOP2. In this cross-sectional study, 250 ambulatory postmenopausal women over 60 years of age were included. Lumbar spine and hip bone mineral density (BMD) and whole-body composition were assessed by dual-energy X-ray absorptiometry (DXA). Muscle strength was evaluated by handgrip dynamometry and physical performance by a 4-m walk gait speed and five-repetition sit-to-stand test. Sarcopenia was defined according to EWGSOP2 as low muscle strength (handgrip) and low muscle mass (appendicular skeletal muscle mass index by DXA). A sarcopenia prevalence of 4% was found in the whole group increasing with age being 12.5% in = 80- year-old. A higher percentage of falls, prevalence of osteoporosis and vertebral fractures were found in the sarcopenic group. Sarcopenia increased 6.0-fold the likelihood of having a fragility fracture. Women with sarcopenia had significantly lower femoral neck BMD and higher frequency of falls and vertebral fractures. According to our results, identifying patients with sarcopenia might be a useful tool to detect adults at higher risk of falls and fractures.

Recientemente el grupo de trabajo europeo sobre sarcopenia en adultos mayores (EWGSOP2) recomendó nuevos criterios y valores de referencia para el diagnóstico de sarcopenia. El objetivo del presente trabajo fue evaluar la prevalencia de sarcopenia en mujeres postmenopáusicas en nuestro medio y su relación con densidad mineral ósea, caídas y fracturas por fragilidad. Este es un estudio de diseño transversal en el cual se incluyeron un total de 250 mujeres ambulatorias mayores de 60 años. La densidad mineral ósea (DMO) de columna lumbar y cadera y la composición corporal fueron evaluados por absorciometría dual de rayos X (DXA). La fuerza fue evaluada por dinamometría de puño; para el rendimiento físico se utilizó caminata de 4 m y la prueba de levantarse y sentarse de una silla (5 repeticiones). La sarcopenia se definió de acuerdo a EWGSOP2 como baja fuerza muscular (dinamometría) y baja masa muscular (índice de masa muscular esquelética por DXA). El 4% de las mujeres cumplía con los criterios de sarcopenia siendo aún mayor en aquellas = 80 años. Las mujeres con sarcopenia presentaron significativamente mayor frecuencia de caídas, osteoporosis y fracturas vertebrales. El riesgo de fracturas por fragilidad se vio incrementado 6 veces en las mujeres con sarcopenia. El diagnóstico de sarcopenia podría considerarse una herramienta útil para identificar a aquellos adultos con riesgo incrementado de caídas y fracturas.

High bone mass from mutation of low-density lipoprotein receptor-related protein 6 (LRP6).

Wnt/ß-catenin signaling is important for skeletal development and health. Eleven heterozygous gain-of-function missense mutations within the first ß-propeller of low-density lipoprotein receptor-related protein 5 (LRP5) are known to cause the autosomal dominant disorder called high bone mass (HBM). In 2019, different heterozygous LRP6 missense mutations were identified in two American families with the HBM phenotype but including absent lateral maxillary and mandibular incisors. We report a 19-year-old Argentinian man referred for "osteopetrosis" and nine years of generalized, medium-intensity bone pain and arthralgias of both knees. His jaw and nasal bridge were broad and several teeth were missing. Routine biochemical testing, including of mineral homeostasis, was normal. Urinary deoxypyridinoline and serum CTX were slightly increased. Radiographic skeletal survey showed diffusely increased radiodensity. DXA revealed substantially elevated BMD Z-scores. Digital orthopantomography confirmed agenesis of his maxillary and mandibular lateral incisors and his second left superior premolar. Cranial magnetic resonance imaging showed diffuse thickening of the calvarium and skull base, dilation of the sheath of the optic nerves containing increased fluid and associated with subtle stenosis of the optic canal, and narrow internal auditory canals. Mutation analyses identified a heterozygous indel mutation in exon 4 of LRP6 involving a single nucleotide change and 6-nucleotide deletion (c.678T>Adel679-684, p.His226Gln-del227-228ProPhe) leading to a missense change and 2-amino acid deletion that would compromise the first ß-propeller of LRP6. Experience to date indicates LRP6 HBM is indistinguishable from LRP5 HBM without mutation analysis, although in LRP6 HBM absence of adult lateral incisors may prove to be a unique feature.

Aggregation and inhibition of rat intestinal alkaline phosphatase by high concentrations of calcium. Reversibility of the processes.

Intestinal alkaline phosphatase (IAP) is an enzyme of the brush border of the enterocyte. The activity of IAP biphasically depends on calcium. Although calcium increases IAP activity, when calcium is higher than 20 mmole/L, IAP activity decreases and the amount of an aggregated form increases. The reversibility of the effect of calcium and the aggregation process are unknown. The isoelectric point of the enzyme was higher in the presence of calcium, but was the same for the enzyme and the aggregated form. The treatment with EGTA after calcium addition did not restore the enzymatic activity but produced desaggregation of the enzyme and increase in the monomeric subunits of IAP. It is concluded that the binding of calcium does not produce important modifications on the structure of the protein, that the inhibitory effect is not reversible and that calcium could be involved in the stability of the structure of the enzyme.