Charlles Heldan de Moura Castro

Low peak bone mass and attenuated anabolic response to parathyroid hormone in mice with an osteoblast-specific deletion of connexin43

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.

Kinin B1 Receptor Deficiency Leads to Leptin Hypersensitivity and Resistance to Obesity

OBJECTIVE—Kinins mediate pathophysiological processes related to hypertension, pain, and inflammation through the activation of two G-protein–coupled receptors, named B1 and B2. Although these peptides have been related to glucose homeostasis, their effects on energy balance are still unknown. RESEARCH DESIGN AND METHODS—Using genetic and pharmacological strategies to abrogate the kinin B1 receptor in different animal models of obesity, here we present evidence of a novel role for kinins in the regulation of satiety and adiposity. RESULTS—Kinin B1 receptor deficiency in mice (B1−/−) resulted in less fat content, hypoleptinemia, increased leptin sensitivity, and robust protection against high-fat diet–induced weight gain. Under high-fat diet, B1−/− also exhibited reduced food intake, improved lipid oxidation, and increased energy expenditure. Surprisingly, B1 receptor deficiency was not able to decrease food intake and adiposity in obese mice lacking leptin (ob/ob-B1−/−). However, ob/ob-B1−/− mice were more responsive to the effects of exogenous leptin on body weight and food intake, suggesting that B1 receptors may be dependent on leptin to display their metabolic roles. Finally, inhibition of weight gain and food intake by B1 receptor ablation was pharmacologically confirmed by long-term administration of the kinin B1 receptor antagonist SSR240612 to mice under high-fat diet. CONCLUSIONS—Our data suggest that kinin B1 receptors participate in the regulation of the energy balance via a mechanism that could involve the modulation of leptin sensitivity.

Discriminatory ability of quantitative ultrasound measurements is similar to dual-energy X-ray absorptiometry in a Brazilian women population with osteoporotic fracture.

The discriminating ability and relevance of clinical risk factors, quantitative ultrasound (QUS) variables, X-ray-based bone mineral density (BMD) and hip axis length (HAL) measurements to evaluate the risk of osteoporotic fracture in elderly Brazilian women were examined in this study. QUS at the calcaneus (Achilles +, Lunar), HAL and BMD measurements (DPX-L, Lunar) at several anatomical sites were performed in 275 postmenopausal Caucasian women. Patients with suspected secondary osteoporosis were excluded. One hundred twenty-two (44.4%) women had had previous osteoporotic fracture. All of the subjects were over 50 years old (range 53–93) and answered a questionnaire that included details concerning aspects of lifestyle, diet, hormonal factors and drug use. Lateral thoracic and lumbar radiographs were taken and an independent radiologist reviewed the X-rays for the presence of vertebral fractures. After adjustments for age, the most relevant risk factors to discriminate patients with osteoporotic fracture from normal non-fracture controls were Stiffness index (OR 2.8 per standard deviation; 95% confidence interval 2.3, 8.7), familial history of hip fracture (OR 2.6 per standard deviation; 95% confidence interval 2.2, 5.4), femoral neck BMD (OR 2.3 per standard deviation; 95% confidence interval 1.9, 4.2), age (OR 2.1 per standard deviation; 95% confidence interval 1.6, 2.8) and weight (OR 1.9 per standard deviation; 95% confidence interval 1.5, 2.6). HAL measurements did not associate significantly with the risk of hip fracture in this population. The ability of QUS measurements discriminate between patients with fractures from those without was similar to, if not better, than X-ray-based BMD measurements. However, a combination of QUS and BMD measurements did not significantly improve fracture discrimination compared with either technique alone. Association of clinical risk factors with QUS or BMD measurements seems, on the other hand, to increase the sensibility to identify patients at risk of osteoporotic fractures.

Prevalence of low trauma fractures in long-term kidney transplant patients with preserved renal function

We evaluated the prevalence of low bone mineral density (BMD) and osteoporotic fractures in kidney transplantation (KT) patients and determined risk factors associated with osteoporotic fractures. The study was conducted on 191 patients (94 men and 97 women) with first KT for 3 years or more presenting stable and preserved renal function (serum creatinine levels lower than 2.5 mg/dl). KT patients were on immunosuppressive therapy and the cumulative doses of these drugs were also evaluated. BMD was determined by dual-energy X-ray absorptiometry at multiple sites (spine, femur and total body). Quantitative ultrasound of the calcaneus (broadband ultrasound attenuation, speed of sound, and stiffness index, SI) was also performed. Twenty-four percent (46) of all patients had either vertebral (29/46) or appendicular (17/46) fractures. We found osteoporosis and osteopenia in 8.5-13.4 and 30.9-35.1% of KT patients, respectively. Women had more fractures than men. In women, prevalent fractures were associated with diabetes mellitus [OR = 11.5, 95% CI (2.4-55.7)], time since menopause [OR = 3.7, 95% CI (1.2-11.9)], femoral neck BMD [OR = 1.99, 95% CI (1.4-2.8)], cumulative dose of steroids [OR = 1.1, 95% CI (1.02-1.12)] and low SI [OR = 1.1, 95% CI (1.0-1.2)]. In men, fractures were associated with lower lumbar spine BMD [OR = 1.75, 95% CI (1.1-2.7)], lower SI [OR = 1.1, 95% CI (1.03-1.13)], duration of dialysis [OR = 1.3, 95% CI (1.13-2.7)], and lower body mass index [OR = 1.24, 95% CI (1.1-1.4). Our results demonstrate high prevalence of low BMD and osteoporotic fractures in patients receiving a successful kidney transplant and indicate the need for specific intervention to prevent osteoporosis in this population.

Bone Mineral Density Measurements, Bone Markers and Serum Vitamin D Concentrations in Men with Chronic Non-Cirrhotic Untreated Hepatitis C

Introduction The high prevalence of chronic hepatitis C (CHC) and its consequent cirrhosis has been associated with bone fragility. Whether CHC may cause bone and mineral abnormalities in the absence of hepatocellular dysfunction is still unknown. In this study we aimed to determine the prevalence of osteoporotic vertebral fractures and low BMD measurements in men with non-cirrhotic CHC. Risk factors for low BMD and fractures were also investigated. Methods Morphometric vertebral fractures and BMD measurements were performed in 60 non-cirrhotic untreated men with CHC and 59 healthy controls, matched for age and gender, weight and current smoking. Serum CTx, calcium, phosphate, intact PTH, alkaline phosphatase and vitamin D (25OHD) concentrations were measured in all participants. Clinical risk factors for low BMD and fractures were evaluated by a structured questionnaire as well as details regarding HCV infection. Results Trochanter and total femur BMD were significantly lower in CHC patients as compared to healthy men (p = 0.04). In men 50 years and older, the prevalence of osteoporosis was significantly higher among CHC patients (p = 0.01). Lower levels of physical activities and more often report of prolonged immobilization were observed among CHC patients (p<0.05). Liver inflammation and fibrosis, viral load and genotype did not correlate with BMD measurements. Bone markers and 25OHD concentrations were similar in both groups. Only a few vertebral fractures were observed. Conclusions Our results demonstrate that non-cirrhotic untreated CHC patients have lower BMD at the femur as compared to healthy men in spite of the absence of significant bone and mineral abnormalities.

Kinin B1 Receptor in Adipocytes Regulates Glucose Tolerance and Predisposition to Obesity

Background Kinins participate in the pathophysiology of obesity and type 2 diabetes by mechanisms which are not fully understood. Kinin B1 receptor knockout mice (B1 −/−) are leaner and exhibit improved insulin sensitivity. Methodology/Principal Findings Here we show that kinin B1 receptors in adipocytes play a role in controlling whole body insulin action and glucose homeostasis. Adipocytes isolated from mouse white adipose tissue (WAT) constitutively express kinin B1 receptors. In these cells, treatment with the B1 receptor agonist des-Arg9-bradykinin improved insulin signaling, GLUT4 translocation, and glucose uptake. Adipocytes from B1 −/− mice showed reduced GLUT4 expression and impaired glucose uptake at both basal and insulin-stimulated states. To investigate the consequences of these phenomena to whole body metabolism, we generated mice where the expression of the kinin B1 receptor was limited to cells of the adipose tissue (aP2-B1/B1 −/−). Similarly to B1 −/− mice, aP2-B1/B1 −/− mice were leaner than wild type controls. However, exclusive expression of the kinin B1 receptor in adipose tissue completely rescued the improved systemic insulin sensitivity phenotype of B1 −/− mice. Adipose tissue gene expression analysis also revealed that genes involved in insulin signaling were significantly affected by the presence of the kinin B1 receptor in adipose tissue. In agreement, GLUT4 expression and glucose uptake were increased in fat tissue of aP2-B1/B1 −/− when compared to B1 −/− mice. When subjected to high fat diet, aP2-B1/B1 −/− mice gained more weight than B1 −/− littermates, becoming as obese as the wild types. Conclusions/Significance Thus, kinin B1 receptor participates in the modulation of insulin action in adipocytes, contributing to systemic insulin sensitivity and predisposition to obesity.

The relationship between lean mass, muscle strength and physical ability in independent healthy elderly women from the community

Background/ObjectivesThe association between muscle mass, strength and physical performance has been established in the elderly with co-morbidities. In this study, lean and fat mass, bone mineral density, knee extension and flexion strength and physical ability tests in healthy independent elderly women were investigated. Main determinants of lean mass, strength and physical ability were determined searching for predictors of healthy aging.MethodsA total of 100 healthy women aged ≥ 65 years considered independent and active were invited. Bone mass and body composition were assessed by DXA. The strength of the lower limb was assessed by isokinetic dynamometry, and physical ability was measured by: Timed Up and Go (TUG), Berg Balance Test (BBT) and Dynamic Gait Index (DGI).ResultsWomen were on average 70.8±4.92 years old, had BMI of 27.38±5.11 kg/m2 and fat mass of 26.96±9.62 kg or 40.65±8.06%. Total lean mass and appendicular lean mass (ALM) were 35.38±4.83 kg and 15.32±2.26 kg, respectively, while relative skeletal mass index (RSMI) was 6.51±0.77 kg/m2. Age did not correlate significantly with ALM. Age and ALM were the main determinants of the strength of the lower limb (p<0.001) while age and strength of the lower limb were significantly associated with the performance on the physical tests (p<0.001).ConclusionAge has a negative impact on the strength and the physical performance in independent healthy women without co-morbidities. Physical ability tests are positively influenced by the strength of the lower limb. These relationships suggest that muscle strength should be the parameter to be prioritized when preparing for healthy aging.

Diet, Body Composition, and Bone Mass in Well-Trained Cyclists

Cycling is believed to be associated with low bone mass. In this study, we investigate food intake, body composition, and bone mass in well-trained young adult cyclists compared with those in sedentary controls. Four-day estimated diet records were used to study dietary intake in 31 cyclists and 28 sedentary controls (all male, 24yr old on average), together with maximal oxygen uptake (VO(2max)), body composition, and bone mass measurements (dual-energy X-ray absorptiometry). The VO(2max) values were twice as high as those in the cyclists, whereas no significant difference in bone mass was observed between cyclists and controls. A total of 10 cyclists and 9 controls had low bone mass. Total-body lean mass and appendicular skeletal muscle mass were higher in cyclists (p<0.001), whereas percentage of body fat was lower (p<0.001) compared with that of the controls. Energy and macro- and micronutrient intake was higher in the cyclists than in the controls (p<0.01). Energy consumption was considered adequate in the cyclists, whereas lipid and protein intake was higher than the American College of Sports Medicine recommendation. Lipid consumption negatively correlated with bone mass in the athletes. Our results demonstrate that cycling was associated with greater aerobic conditioning and lean mass without significant association with bone mass compared with sedentary controls.

25-Hydroxivitamin D Serum Concentration, Not Free and Bioavailable Vitamin D, Is Associated with Disease Activity in Systemic Lupus Erythematosus Patients

We aim to evaluate the prevalence of vitamin D deficiency in patients with systemic lupus erythematosus (SLE) and investigate the association between total, free and bioavailable vitamin D serum concentrations and disease activity. Patients with SLE (ACR 1997) consecutively seen at UNIFESP’s outpatient’s clinics had disease activity measured after clinical and laboratory evaluation using SLEDAI (Systemic Lupus Erythematosus Disease Activity Index). 25-hydroxyvitamin D (25(OH)D) serum concentrations measured by chemiluminescence and vitamin D binding protein (DBP) measured by ELISA were used to calculate free and bioavailable vitamin D. Healthy blood donors were used as controls. A total of 142 patients (71.4%) had 25(OH)D serum concentrations below 30 ng/mL. Total 25(OH)D serum concentration was associated with disease activity categorized in 5 continuous groups of SLEDAI. 25(OH)D serum concentrations were higher among patients with SLEDAI 1–5 and lower in those with severe activity (SLEDAI≥20) (p <0.05). On the other hand, no statistically significant difference was observed for DBP, free and bioavailable vitamin D measurements in the disease activity subgroups evaluated. Vitamin D deficiency is highly prevalent among patients with SLE and was associated with higher disease activity. DBP serum level and calculation of free and bioavailable vitamin D were not associated with SLE disease activity.

Higher prevalence of morphometric vertebral fractures in patients with recent coronary events independently of BMD measurements

Cardiovascular disease and osteoporosis are important causes of morbi-mortality in the elderly and may be mutually related. Low bone mineral density (BMD) may be associated with increased risk of cardiovascular events. We investigated the prevalence of low bone mass and fractures in metabolic syndrome patients with acute coronary events. A case-control study was conducted with 150 individuals (30-80years-old) with metabolic syndrome. Seventy-one patients had had an acute coronary syndrome episode in the last 6months (cases) and the remaining 79 had no coronary event (controls). Cases and controls were matched for gender, BMI and age. DXA measurements and body composition were performed while spine radiographs surveyed for vertebral fractures and vascular calcification. Biochemical bone and metabolic parameters were measured in all patients. No statistically significant difference in BMD and the prevalence of osteopenia, osteoporosis and non-vertebral fractures was observed between cases and controls. The prevalence of vertebral fractures and all fractures was higher in the cases (14.1 versus 1.3%, p=0.003 and 22.5versus7.6%, p=0.010, respectively). Male gender (OR=0.22 95% CI 0.58 to 0.83, p=0.026) and daily intake of more than 3 portions of dairy products (OR=0.19 95% CI 0.49 to 0.75, p=0.017) were associated with lower prevalence of fractures. Cases had higher risk for fractures (OR=4.97, 95% CI 1.17 to 30.30, p=0.031). Bone mass and body composition parameters were not associated with cardiovascular risk factors or bone mineral metabolism. Patients with fragility fractures had higher OPG serum levels than those without fractures (p<0.001). Our findings demonstrated that patients with recent coronary events have a higher prevalence of vertebral fractures independently of BMD.