Connexin43 (Cx43) is involved in bone development, but its role in adult bone homeostasis remains unknown. To overcome the postnatal lethality of Cx43 null mutation, we generated mice with selective osteoblast ablation of Cx43, obtained using a Cx43fl allele and a 2.3-kb fragment of the α1(I) collagen promoter to drive Cre in osteoblasts (ColCre). Conditionally osteoblast-deleted ColCre;Cx43–/fl mice show no malformations at birth, but develop low peak bone mass and remain osteopenic with age, exhibiting reduced bone formation and defective osteoblast function. By both radiodensitometry and histology, bone mineral content increased rapidly and progressively in adult Cx43+/fl mice after subcutaneous injection of parathyroid hormone (PTH), an effect significantly attenuated in ColCre;Cx43–/fl mice, with Cx43–/fl exhibiting an intermediate response. Attenuation of PTH anabolic action was associated with failure to increase mineral apposition rate in response to PTH in ColCre;Cx43–/fl, despite an increased osteoblast number, suggesting a functional defect in Cx43-deficient bone-forming cells. In conclusion, lack of Cx43 in osteoblasts leads to suboptimal acquisition of peak bone mass, and hinders the bone anabolic effect of PTH. Cx43 represents a potential target for modulation of bone anabolism.

artigo dE rEvisão rEviEw articlE RESUMO A prevalência de incapacidade e dependência funcional é maior em idosos e está intimamente associada à redução da massa muscular, que ocorre, até mesmo, em indivíduos saudáveis. A sarcopenia parece decorrer da interação complexa de distúrbios da inervação, diminuição de hormônios, aumento de mediadores inflamatórios e alterações da ingestão protéico-calórica que ocorrem durante o envelhecimento. A perda de massa e força muscular é responsável pela redução de mobilidade e aumento da incapacidade funcional e dependência. Quando associada à fragilidade, esta perda gera custos econômicos e sociais. Neste artigo, pretende-se avaliar aspectos relacionados à gênese da sarcopenia, bem como analisar possíveis opções terapêuticas e de prevenção.

We studied the function of osteoblast cadherins in vivo by transgenic expression of a truncated N-cadherin with dominant-negative action, driven by an osteoblast-specific promoter (OG2-NcadΔC). During the first 3 months of life, bone mineral density was reduced, whereas percent body fat was increased in transgenic animals compared with wild-type littermates, with associated decreased bone formation rate and osteoblast number, but normal osteoclast number. Osteoblast differentiation was delayed in calvaria cells isolated from transgenic mice. Likewise, the number of osteoblast precursors in bone marrow stromal cells from OG2-NcadΔC mice was decreased compared with wild-type cultures, whereas the number of adipogenic precursors was increased. In vitro, a transcriptionally active β-catenin mutant reversed the delay in osteoblast differentiation and the exuberant adipogenesis. Thus, in vivo disruption of cadherin function hinders osteoblast differentiation and favors, indirectly, bone marrow progenitor cell commitment to the alternative adipogenic lineage via interference with β-catenin signaling. This results in decreased bone formation, delayed acquisition of peak bone mass and increased body fat.

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IntroductionThe aim of the present study was to compare bone mineral density (BMD) and body composition (BC) measurements as well as identify risk factors for low BMD and osteoporotic fractures in postmenopausal women with psoriasis (Ps) and psoriatic arthritis (PsA).MethodsA cross-sectional study was carried out in 45 PsA women, 52 Ps women and 98 healthy female controls (HC). Clinical risk factors for low bone density and osteoporotic fracture were evaluated by a specific questionnaire. An X-ray absorptiometry (DXA) at the lumbar spine, total femur and total body was performed on all patients. Skin and joint outcomes were measured by specific tools (PASI, HAQ and DAS28). Morphometric vertebral fractures were evaluated by lumbar and thoracic spine X-ray, according to Genant's method.ResultsThere were no significant differences in age, body mass index (BMI), total lean mass and bone mineral density among the groups. However, the PsA group had a significantly higher body fat percentage (BF%) than the Ps and HC groups. Osteoporotic fractures were more frequently observed in PsA and Ps groups than in the HC group (P = 0.01). Recurrent falls and a longer duration of disease increased the risk of fracture (odds ratio (OR) = 18.3 and 1.08, respectively) in the PsA group (P = 0.02). Disability was the main factor related to osteoporotic fracture in the Ps group (odds ratio (OR) = 11.1) (P = 0.02).ConclusionsPs and PsA patients did not present lower BMD. However, they had a higher prevalence of osteoporotic fractures and higher risk of metabolic syndrome. Patients with a longer duration of disease, disability and recurrent falls need preventive measures.

In this cross-sectional study, we evaluated the body composition and dietary intake of 44 adolescent tennis players. After being divided into two groups (age 10-13 years and age 14-18), the players had their weight, height, and sexual maturation assessed. Dual-energy X-ray absorptiometry was used to assess body composition. Food intake was obtained from a non-consecutive 4-day food record. The data were analysed using the Virtual Nutri v.1.0 software and compared with the present recommendations for adolescent athletes or dietary reference intakes. Body mass index and body fat for tennis practice were adequate for 89% and 71% of the tennis players respectively, regardless of age group. A calorie deficit greater than 10% of energy expenditure was observed in 32% of the sample. Fifty percent of the athletes consumed carbohydrates in accordance with recommended values. Protein and lipid intakes were above recommended values, while fibre, calcium, potassium, magnesium, and folic acid intakes were below recommendation for 98%, 80%, 100%, 100%, and 98% of the tennis players respectively. The observed nutritional deficiencies represent an additional barrier for adolescents engaged in competitive sports to achieve an optimum nutrition to maintain growth, health, and performance.

OBJECTIVE: To estimate the prevalence and analyze risk factors associated to osteoporosis and low-trauma fracture in women. METHODS: Cross-sectional study including a total of 4,332 women older than 40 attending primary care services in the Greater São Paulo, Southeastern Brazil, between 2004 and 2007. Anthropometrical and gynecological data and information about lifestyle habits, previous fracture, medical history, food intake and physical activity were obtained through individual quantitative interviews. Low-trauma fracture was defined as that resulting from a fall from standing height or less in individuals 50 years or older. Multiple logistic regression models were designed having osteoporotic fracture and bone mineral density (BMD) as the dependent variables and all other parameters as the independent ones. The significance level was set at p<0.05. RESULTS: The prevalence of osteoporosis and osteoporotic fractures was 33% and 11.5%, respectively. The main risk factors associated with low bone mass were age (OR=1.07; 95% CI: 1.06;1.08), time since menopause (OR=2.16; 95% CI: 1.49;3.14), previous fracture (OR=2.62; 95% CI: 2.08;3.29) and current smoking (OR=1.45; 95% CI: 1.13;1.85). BMI (OR=0.88; 95% CI: 0.86;0.89), regular physical activity (OR=0.78; 95% CI: 0.65;0.94) and hormone replacement therapy (OR=0.43; 95% CI: 0.33;0.56) had a protective effect on bone mass. Risk factors significantly associated with osteoporotic fractures were age (OR=1.05; 95% CI: 1.04;1.06), time since menopause (OR=4.12; 95% CI: 1.79;9.48), familial history of hip fracture (OR=3.59; 95% CI: 2.88;4.47) and low BMD (OR=2.28; 95% CI: 1.85;2.82). CONCLUSIONS: Advanced age, menopause, low-trauma fracture and current smoking are major risk factors associated with low BMD and osteoporotic fracture. The clinical use of these parameters to identify women at higher risk for fractures might be a reasonable strategy to improve the management of osteoporosis.

Osteoporosis is the leading cause of fractures in the population older than 50 years. This silent disease affects primarily postmenopausal women and the elderly, and the morbidity and mortality rates are high. The main goal of treating osteoporosis is the prevention of fractures. The identification of populations at risk through early diagnosis and treatment is essential. The last Brazilian guideline for the treatment of postmenopausal osteoporosis was elaborated in 2002. Since then, new strategies for diagnosis and risk stratification have been developed, and drugs with novel action mechanisms have been added to the therapeutic arsenal. The Osteoporosis and Osteometabolic Diseases Committee of the Brazilian Society of Rheumatology, in conjunction with the Brazilian Medical Association and other Societies, has developed this update of the guidelines for the treatment of postmenopausal osteoporosis according to the best scientific evidence available. This update is intended for professionals in many medical and health specialties involved in the treatment of osteoporosis, for physicians in general and for health-related organizations.