Revista de Osteoporosis y Metabolismo Mineral

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Category: 8

Vitamin D deficiency: are we identifying it properly?

Subclinical deficiency of vitamin D or vitamin D deficiency is prevalent throughout the world, and there is great variability depending on the geographic region, genetic factors and lifestyle considerations.
Moreover, researchers now believe that serum 25-hydroxyvitamin D (25OHD) levels are the best indicator of vitamin D, although there are methodological issues that limit comparability between studies and how to establish deficiency cutoffs.
There are several criteria to establish the optimal level of 25OHD, which include the degree of maximal suppression of PTH, the intestinal absorption of mediated calcium 1,25(OH)2 vitamin D or reduction of fractures. Regarding the former, several studies have analyzed 25OHD concentration required for maximum suppression of PTH and offer variable results. This has led some researchers and scientific entities to recommend 25OHD levels above 20 ng/ml (Institute of Medicine, IOM) while others advise over 30 ng/ml (Endocrine Society, International Osteoporosis Foundation). The application variable for these recommendations has generated considerable confusion in clinical practice.

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Secondary hyperparathyroidism due to vitamin D deficiency

Introduction: Vitamin D is increasingly recognized as playing a significant role in combatting many diseases. One is the development of secondary hyperthyroidism due vitamin D deficiency. To date, laboratory quantification methods of serum vitamin D were not well standardized. It could not be established with certainty from which levels of vitamin D certains abnormalities take place, like an elevation of PTH. The present study was aimed at determining below what vitamin D levels we will find abnormally high levels of PTH, carrying out the vitamin D determination in the laboratory with a standardized, reliable technique.

Methods: This descriptive, retrospective study was conducted with patients over 18 years in which determinations were made simultaneously with PTH, 25 (OH) vitamin D (25OHD) and which also have normal values ??of calcium, glomerular filtration rate and phosphorus.
For determining vitamin D, standardized electrochemiluminescence method was used with gas chromatography-mass spectrometry method. Using the Stava version 11 statistical program, the 25OHD was calculated where PTH value was above 70 pg/ml with greater sensitivity and specificity.
Results: In all, 4,083 patients were included, of whom 2,858 were women (70%) and 1,225 (30%) males. The mean age of the study population was 60.60 years (standard deviation, 15.29). 74% of the population had a serum PTH under 70 pg/ml (normal values) and 26% had a serum PTH higher tan 70 ng/ml. By constructing the ROC curve levels of 25OHD, depending on PTH values ??below or above 70 pg/ml, the area under the curve was 0.5962 (p<0.0001). The cut having jointly account the sensitivity and specificity that determined vitamin D levels to predict PTH values ??above 70 pg/ml was 24 ng/ml. Of the patients with normal PTH, 71% presented normal vitamin D values, while patients with elevated PTH (Greater than 70 pg/ml), almost half had a vitamin D below 24 ng / ml, which increased as the PTH percentage was elevated. Conclusions: The 25OHD value that presents better specificity and sensitivity to predict abnormally high PTH is 24 ng/ml, which is higher than the level reported in previous work, (about 18 ng/ml) value. The results of this study, carried out with an appropriately calibrated method, showed that 44.9% of patients with vitamin D values of less than 24 ng/ml PTH had abnormally high levels, with a normal value ??of calcium and phosphorus and normal renal function. This percentage is less in those individuals between 18 and 40 years (24%) and reaches 49% beyond 60 years. These patients could be treated with vitamin D to prevent possible secondary hyperparathyroidism due to vitamin deficiency. It is noteworthy that the method of determining vitamin D used must be properly standardized with respect to gas chromatography-tandem mass spectrometry method.

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Proper compliance of treatment for osteoporosis: we still have much to do

Osteoporosis is a common disease, its main clinical complication being bone fragility 1. This chronic, generally assymptomatic process deteriorates the bone, exposing it to fracture risk. Current treatment techniques aim to minimize the possibility of new fractures 1-4 but there is no medication to eliminate such risk. Most drugs currently available for treating osteoporosis achieve reductions of between 40 and 65% 2-4, if the medication is taken continuously over a period ranging from 3 to 5 years. This would be mere utopian, as, in fact, the patients frequently abandon their osteoporosis treatment, once they have begun.
Numerous studies have shown that adherence to osteoporosis treatment is generally low, and that in the first year the dropout rate is between 30-50% in most cases 5. One reason may be their asymptomatic condition, which does not provide the patient with a sense of improvement. Perhaps, if all goes well, the patient does not suffer fracture, but subjectively does not perceive anything. In this respect, osteoporosis differs from other chronic diseases in which symptoms return as soon as the patient discontinues treatment, such as migraines, ischemic heart disease or diabetes mellitus.

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Effect of RANK/RANKL/OPG pathway on bone demineralization and vascular calcification in chronic kidney disease

Introduction: In cases of chronic kidney disease (CKD), bone and mineral metabolism changes occur which favor soft tissue calcification. Alterations in the RANK/RANKL/OPG system could also favor vascular calcification, a major cause of morbidity and mortality in CKD.
Objective: In an in vivo experimental model of chronic renal failure progression, we assess the effect of CKD on vascular calcification and bone loss correlating these changes in the RANK/RANKL/OPG pathway. An in vitro system was used to confirm findings.
Material and Methods: Two models of vascular calcification were used: an in vivo rat model with chronic renal failure fed on a diet with different phosphorus content, and an in vitro model in vascular smooth muscle cells (VSMC) subjected to different calcifying stimuli.
Results: At 20 weeks, 50% of animals with a diet high in phosphorus presented aortic calcification accompanied by increased aortic expression of RANKL. In contrast, OPG decreased probably as a consequence of an inflammatory component.
At 20 weeks, expression of RANKL and OPG in the tibia increased, while the increase in OPG occurred at earlier stages.
In VSMC, the addition of uremic serum and calcification medium increased calcium content and expression of RANKL and OPG. The addition of OPG and silencing of RANK inhibited this increase.
Conclusions: Our results confirm RANK/RANKL/OPG system involvement in the vascular calcification process.

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Study of miRNAs expression patterns in osteoporotic bone

Objectives: To identify microRNAs (miRNAs) differentially expressed in bone samples with osteoporotic fracture compared with healthy bones.
Methods: Total RNA was extracted from fresh trabecular bone of the femoral neck of women undergoing hip replacement surgery, either because to osteoporotic fracture (n=6) or in the absence of osteoarthritis osteoporosis (based on BMD) (n=6). The samples were hybridized on an array of miRNAs and PCA diagrams and heat map were made. To compare expression levels >1.5 times and a value <0.05 Student's T test (corrected for multiple testing) was set as a threshold of significant change. Results: Both PCA analysis and the heat map showed a samples grouping whether there was fracture or not. 790 were detected miRNAs in bone samples, 82 of which were altered in the osteoporotic samples. After validation in another panel of 6 samples 6 osteoporotic and non-osteoporotic by PCR real time of the most significant miRNAs, and for which there was a test available, the miRNAs, miR-320a and miR-22-3p were confirmed. These two miRNAs were detected in cultures of primary osteoblasts, although they did not maintain the same pattern of expression in total bone samples. Conclusions: We have shown that there are differences in the expression of miRNAs in samples with osteoporotic fracture. This opens prospects for research and design of new therapies.

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The association of MMP1 1G>2G polymorphism with aortic valve

Introduction: The most common cause of aortic stenosis is active calcium accumulation in the valve cusps, which implies serious clinical consequences. Various extracellular matrix metalloproteases (MMPs) have been implicated in the development of this disease. Therefore, the possible association between a functional MMP1 polymorphism and the amount of calcium deposited on the aortic valve is studied.
Patients and methods: 45 patients undergoing valve replacement were included in the study. The calcium content in valve cusps removed during surgery was determined by computed micro-tomography. DNA was extracted from peripheral blood samples for genotyping the -1607 1G>2G polymorphism of MMP1 by PCR and subsequent digestion.
Results: Significant differences were observed in the calcium content in aortic valves in individuals with different -1607 1G>2G genotypes (p=0.042). Thus, 2G allele carriers (homozygous or heterozygous) present higher calcium levels measured as BMD (p=0.004) as well as BV/TV (p=0.002). The association with BV/TV was independent of sex, age, degree of renal function and anatomy of the valve (p=0.02). BMD tendency (p=0.07) was also observed.
Conclusion: The association between 1G>2G MMP1 polymorphism and calcium content of the aortic valve suggests that the 1G allele would have a protective effect against calcium deposits. These results support the importance of further study to confirm whether this polymorphism could be used as a possible predictor of aortic stenosis development.

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Analysis of mechanical behavior variation in the proximal femur using X-FEM (Extended Finite Element Method)

Introduction: For years, the human femur has been extensively studied experimentally with in vitro analysis. Nowadays, with computer advances, it can also be analyzed numerically. Some authors report the usefulness of finite method in predicting the mechanical behavior of this bone. There are many possibilities using the synergy between the method finite element and experimental trials. In this paper, for example, we study how they affect different osteoporotic simulations involving femur fracture loads.
The aim of this study is to predict hip fracture, both the load to which this occurs as the propagation of the crack in the bone. By applying the finite element method to the field of bio-mechanics, simulation can be carried out to show the behavior under different bone load conditions.
Material and methods: Using DICOM images, CT scan of the proximal end of the right femur of a male has been obtained bone geometry. By a computer program they have been generated dependent mechanical properties of the BMD each voxel, and then used a finite code to apply different load configurations and study values ??bone fracture elements. The numerical model has been validated in the literature.
Results: Load breaking in lateral fall configuration is approximately half the load in the case of the normal position, which agrees with different experimental studies published.
In addition, we have studied various load conditions in everyday situations, where it was observed that the load fracture is minimal in mono-podal position. Osteoporotic conditions have also been simulated which confirmed that the load fracture has been reduced by decreasing mechanical properties.
Conclusions: By using the finite element method in conjunction with DICOM medical imaging, it is possible to study the biomechanics of the hip and obtain an estimate of bone failure. In addition, different load configurations can be applied and vary the mechanical properties of bone to simulate the mechanical behavior of low osteoporotic conditions.

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Medical professionals’ perceptions regarding therapeutic adherence in patients with osteoporosis

Introduction: Adherence to oral treatment of patients with osteoporosis is low, with a high dropout rate in the first year. The most noteworthy result is the lack of therapeutic response.
Objective: To ascertain the perception of physicians working with osteoporotic patients regarding adherence of these patients.
Methods: Cross-sectional study conducted by opinion survey aimed at primary care physicians and specialists involved in osteoporosis treatment. Participants were selected by purposive sampling.
Results: The questionnaire was answered by 235 specialists encompassing rheumatology (54.5%), orthopedics (10.6%) and primary care (18.7%). In 43.8% of participants, more than 25% of patients sometimes forget to take their treatment. According to 34.9%, more than 75% of patients are aware of treatment. Side effects and management complexity are the majority reasons that lead to a change in medication, mean value of 7.94±2.06 6±2.01 points respectively on a 0-10 scale.
Conclusions: Overall, medical specialists attributed low adherence to side effects, polypharmacy and lack of communication between professionals. Dosage and space use of soluble dosage forms may be options to facilitate patient adherence to treatment with oral bisphosphonates. Improved education concerning the importance of the disease or increased patient monitoring could foster adherence.

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Functional study of promoter gene polymorphisms of sclerostin

Sclerostin, encoded by the SOST gene, inhibits the Wnt pathway and, consequently, tends to decrease bone mass. Some polymorphisms of the SOST promoter have been associated with bone mineral density (BMD), but the molecular mechanisms involved are unknown. The aim of this study was to study the functional role of one polymorphism in vitro. We cloned the proximal promoter region of SOST gene, containing different alleles at the rs851054 SNP, in luciferase reporter vectors and transfected them into the cell lines HEK-293T, SAOS-2 and HOS-TE85. We did not find significant differences in the transcriptional activity of vectors with either the A or the G allele of the SNP. The co-transfection of vectors expressing RUNX2 and OSX markedly increased the transcriptional activity of the SOST promoter constructs (A allele, 2.5±0.9 fold, p<0.05; G allele, 1.9±0.8 fold, p<0.05), without significant differences between the rs851054 alleles. Moreover, no allele differences were detected in EMSAs. In conclusion, the DNA region upstream of the TSS of the SOST gene has a strong promoter activity that is enhanced by RUNX2 and OSX. Frequent allelic variants in this region have been associated with BMD, but the mechanisms involved remain to be elucidated because no functional differences between alleles were detected in vitro.

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Comparison between two automated chemiluminescence immunoassays for quantifying 25 (OH) vitamin D

Introduction: Quantifying total blood 25 (OH) vitamin D is the most accurate marker of an individual´s vitamin D status. The gold standard technique for measurement is liquid chromatography tandem mass spectrometry (LC-MS/MS), although currently clinical laboratories tend to use chemiluminescence techniques. The objective of this study was to compare 25 (OH) vitamin D concentrations obtained by two commercially-produced automated methods and study the correlation of these methods with the LC-MS/MS reference technique.
Material and methods: The 25(OH) vitamin D levels were quantified in 1,000 serum samples from the Jimenez Diaz Biochemistry Foundation Laboratory using 2 automated methods for chemiluminescence detection: ADVIA CENTAURO® (SIEMENS) and LUMIPULSE® G1200 (Fujirebio). Among all the samples tested, the 50 most discordant to each other were sent to be evaluated by LC-MS/MS reference technique.
Results: The results indicate that there is good correlation between the two methods: CCI=0.923 (0.914-0.932), with the G1200 LUMIPULSE® ; values 10% being higher than CENTAURO®. Regarding the 50 samples selected, we can see that there is a good correlation between the two immunoassays with LC-MS/MS, although both methods significantly underestimate 25 (OH) vitamin D results with respect to the gold standard.
Discussion: Although both techniques are suitable for use, it is worth considering whether the worldwide vitamin D deficiency epidemic is due to the analysis methodology used. This variability between immunoassays could be solved by standardizing the different commercial techniques in line with NIST-produced reference materials.

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Serum dickkopf1 (DKK1), bone metabolism and atherosclerotic disease in patients with type 2 diabetes

Background and objectives: Type 2 diabetes (T2DM) is a risk factor for osteoporotic fractures and cardiovascular disease. The aims of our study were to evaluate serum Dickkopf-1(DKK1) levels in a cohort of T2DM patients and to analyze its relationships with bone metabolism and atheroesclerotic disease (AD).

Patients and methods: We studied 126 subjects: T2DM patients (n: 72, mean age 58,2±6 years) and non-diabetic subjects (n: 54, mean age 55,4±7 years). DKK-1 was measured by enzyme-linked immunosorbent assay (ELISA, Biomedica Gruppe). Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA). The presence of AD (cerebrovascular disease, peripheral arterial disease, ischemic heart disease) was recorded. Intima-media thickness (IMT) was determined by doppler ultra- sonography and aortic calcification by evaluation of lateral view conventional X-rays.
Results: We did not find significant differences in DKK1 between groups. Serum DKK1 concentrations were significantly higher in females in total sample (24,3±15,2 vs 19,6±10,2 pmol/L, p=0,046) and in T2DM group (27,5±17,2 vs 19,8±8,9 pmol/L, p=0,025). There was a positive correlation between serum DKK1 and LS BMD in total sample (r=0,183, p=0,048). However, we did not find a significant relationship with osteoporosis diagnosis or morphometric vertebral fractures. Serum DKK1 was significantly higher in T2DM patients with AD (26,4±14,5 pmol/L vs 19,1±11,6 pmol/L, p=0,026) and also in patients with abnormal IMT (26,4±;15,1 pmol/L vs 19,8±11,3 pmol/L, p=0,038). In the ROC curve analysis to evaluate the usefulness of DKK-1 as a marker for high risk of AD, the area under the curve was 0,667 (95% confidence interval: 0,538-0,795; p=0,016). A concentration of 17,3 pmol/L or higher showed a sensitivity of 71,4% and a specificity of 60% to identify an increased risk of AD.
Conclusions: Circulating DKK1 levels are higher in T2DM with AD and are associated with an abnormal IMT in this cross-sectional study. DKK1 may be involved in vascular disease of T2DM patients.

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Clinical Notes
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Original Articles
Osteology images
Poster Communications
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