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The link between obesity and low bone strength has become a significant medical concern. The canonical Wnt signaling pathway is a key regulator of mesenchymal stem cell differentiation into either osteoblasts or adipocytes with active Wnt signaling promoting osteoblastogenesis. Our previous research indicated that Dickkopf-1 (Dkk1), a Wnt inhibitor, is upregulated in bone tissue in obesity and that osteoblast-derived Dkk1 drives obesity-induced bone loss. However, Dkk1 is also produced by adipocytes, but the impact of adipogenic Dkk1 on bone remodeling and its role in obesity-induced bone loss remain unclear. Thus, in this study, we investigated the influence of adipogenic Dkk1 on bone homeostasis and obesity-induced bone loss in mice. To that end, deletion of Dkk1 in adipocytes was induced by tamoxifen administration into 8-week-old male Dkk1fl/fl;AdipoQcreERT2 mice. Bone and fat mass were analyzed at 12 and 20 weeks of age. Obesity was induced in 8-week-old male Dkk1fl/fl;AdipoQcre mice with a high-fat diet (HFD) rich in saturated fats for 12 weeks. We observed that 12-week-old male mice without adipogenic Dkk1 had a significant increase in trabecular bone volume in the vertebrae and femoral bones. While histological and serological bone formation markers were not different, the number of osteoclasts and adipocytes was decreased in the vertebral bones of Dkk1fl/fl;AdipoQcre-positive mice. Despite the increased bone mass in 12-week-old male mice, at 20 weeks of age, there was no difference in the bone volume between the controls and Dkk1fl/fl;AdipoQcre-positive mice. Also, Dkk1fl/fl;AdipoQcre-positive mice were not protected from HFD-induced bone loss. Even though mRNA expression levels of Sost, another important Wnt inhibitor, in bone from Dkk1-deficient mice fed with HFD were decreased compared to Dkk1-sufficient mice on an HFD, this did not prevent the HFD-induced suppression of bone formation. In conclusion, adipogenic Dkk1 may play a transient role in bone mass regulation during adolescence, but it does not contribute to bone homeostasis or obesity-induced bone loss later in life.
Search for other papers by Shuang Ye in
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The role of G protein-coupled estrogen receptor 1 (GPER) signaling, including promotion of Ezrin phosphorylation (which could be activated by estrogen), has not yet been clearly identified in triple-negative breast cancer (TNBC). This study aimed to evaluate the prognostic value of GPER and Ezrin in TNBC patients. Clinicopathologic features including age, menopausal status, tumor size, nuclear grade, lymph node metastasis, AJCC TNM stage, and ER, PR and HER-2 expression were evaluated from 249 TNBC cases. Immunohistochemical staining of GPER and Ezrin was performed on TNBC pathological sections. Kaplan–Meier analyses, as well as logistic regressive and Cox regression model tests were applied to evaluate the prognostic significance between different subgroups. Compared to the GPER-low group, the GPER-high group exhibited higher TNM staging (P = 0.021), more death (P < 0.001), relapse (P < 0.001) and distant events (P < 0.001). Kaplan–Meier analysis showed that GPER-high patients had a decreased OS (P < 0.001), PFS (P < 0.001), LRFS (P < 0.001) and DDFS (P < 0.001) than GPER-low patients. However, these differences in prognosis were not statistically significant in post-menopausal patients (OS, P = 0.8617; PFS, P = 0.1905; LRFS, P = 0.4378; DDFS, P = 0.2538). There was a significant positive correlation between GPER and Ezrin expression level (R = 0.508, P < 0.001) and the effect of Ezrin on survival prognosis corresponded with GPER. Moreover, a multivariable analysis confirmed that GPER and Ezrin level were both significantly associated with poor DDFS (HR: 0.346, 95% CI 0.182–0.658, P = 0.001; HR: 0.320, 95% CI 0.162–0.631, P = 0.001). Thus, overexpression of GPER and Ezrin may contribute to aggressive behavior and indicate unfavorable prognosis in TNBC; this may correspond to an individual’s estrogen levels.
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Department of Endocrinology, Sahlgrenska University Hospital, Gothenburg, Sweden
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Purpose
We aimed to investigate the association between SHBG and the homeostatic model assessment of insulin resistance (HOMA-Ir) in men and women in a prospective observational study.
Methods
The Vara-Skövde cohort is a random population of 2816 participants living in southwestern Sweden, aged 30–74. It was recruited between 2002 and 2005, and followed up in 2012–2014. After excluding participants on insulin therapy or hormone replacement therapy, 1193 individuals (649 men, 544 women) were included in the present study. Fasting blood samples were collected at both visits and stored in biobank. All participants were physically examined by a trained nurse. SHBG was measured with immunoassay technique. Linear regressions were computed to investigate the association between SHBG and HOMA-Ir both in cross-sectional and longitudinal analyses, adjusting for confounding factors.
Results
The mean follow-up time was 9.7 ± 1.4 years. Concentrations of SHBG were significantly inversely associated with log transformed HOMA-Ir in all groups with estimated standardized slopes (95% CI): men: −0.20 (−0.3;−0.1), premenopausal women: −0.26 (−0.4;−0.2), postmenopausal women: −0.13 (−0.3;−0.0) at visit 1. At visit 2 the results were similar. When comparing the groups, a statistically significant difference was found between men and post-menopausal women (0.12 (0.0;0.2) P value = 0.04). In the fully adjusted model, SHBG at visit 1 was also associated with HOMA-Ir at visit 2, and the estimated slopes were −0.16 (−0.2;−0.1), −0.16 (−0.3;−0.1) and −0.07 (−0.2;0.0) for men, premenopausal and postmenopausal women, respectively.
Main conclusion
Levels of SHBG predicted the development of insulin resistance in both men and women, regardless of menopausal state.
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Center for Healthy Aging Research, Oregon State University, Corvallis, Oregon, USA
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Center for Healthy Aging Research, Oregon State University, Corvallis, Oregon, USA
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Mice are a commonly used model to investigate aging-related bone loss but, in contrast to humans, mice exhibit cancellous bone loss prior to skeletal maturity. The mechanisms mediating premature bone loss are not well established. However, our previous work in female mice suggests housing temperature is a critical factor. Premature cancellous bone loss was prevented in female C57BL/6J mice by housing the animals at thermoneutral temperature (where basal rate of energy production is at equilibrium with heat loss). In the present study, we determined if the protective effects of thermoneutral housing extend to males. Male C57BL/6J mice were housed at standard room temperature (22°C) or thermoneutral (32°C) conditions from 5 (rapidly growing) to 16 (slowly growing) weeks of age. Mice housed at room temperature exhibited reductions in cancellous bone volume fraction in distal femur metaphysis and fifth lumbar vertebra; these effects were abolished at thermoneutral conditions. Mice housed at thermoneutral temperature had higher levels of bone formation in distal femur (based on histomorphometry) and globally (serum osteocalcin), and lower global levels of bone resorption (serum C-terminal telopeptide of type I collagen) compared to mice housed at room temperature. Thermoneutral housing had no impact on bone marrow adiposity but resulted in higher abdominal white adipose tissue and serum leptin. The overall magnitude of room temperature housing-induced cancellous bone loss did not differ between male (current study) and female (published data) mice. These findings highlight housing temperature as a critical experimental variable in studies using mice of either sex to investigate aging-related changes in bone metabolism.
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The purpose of androgen deprivation therapy (ADT) in prostate cancer (PCa), using luteinizing hormone-releasing hormone agonists (LHRHa) or gonadotrophin-releasing hormone antagonists, is to suppress the levels of testosterone. Since testosterone is the precursor of estradiol (E2), one of the major undesired effects of ADT is the concomitant loss of E2, causing among others an increased bone turnover and bone loss and an increased risk of osteoporosis and fractures. Therefore, the guidelines for ADT indicate to combine ADT routinely with bone-sparing agents such as bisphosphonates, denosumab or selective estrogen receptor modulators. However, these compounds may have side effects and some require inconvenient parenteral administration. Co-treatment with estrogens is an alternative approach to prevent bone loss and at the same time, to avoid other side effects caused by the loss of estrogens, which is the topic explored in the present narrative review. Estrogens investigated in PCa patients include parenteral or transdermal E2, diethylstilbestrol (DES), and ethinylestradiol (EE) as monotherapy, or high-dose estetrol (HDE4) combined with ADT. Cardiovascular adverse events have been reported with parenteral E2, DES and EE. Encouraging effects on bone parameters have been obtained with transdermal E2 (tE2) and HDE4, in the tE2 development program (PATCH study), and in the LHRHa/HDE4 co-treatment study (PCombi), respectively. Confirmation of the beneficial effects of estrogen therapy with tE2 or HDE4 on bone health in patients with advanced PCa is needed, with special emphasis on bone mass and fracture rate.
Search for other papers by Kaisa K Ivaska in
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Department of Cell Biology and Anatomy, Department of Medicine, Turku PET Centre, Department of Radiology, Medical Imaging Centre of Southwest Finland, Department of Endocrinology, Abdominal Center: Endocrinology, Minerva Foundation Institute for Medical Research, Institute of Biomedicine, University of Turku, FI-20520 Turku, Finland
Department of Cell Biology and Anatomy, Department of Medicine, Turku PET Centre, Department of Radiology, Medical Imaging Centre of Southwest Finland, Department of Endocrinology, Abdominal Center: Endocrinology, Minerva Foundation Institute for Medical Research, Institute of Biomedicine, University of Turku, FI-20520 Turku, Finland
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Department of Cell Biology and Anatomy, Department of Medicine, Turku PET Centre, Department of Radiology, Medical Imaging Centre of Southwest Finland, Department of Endocrinology, Abdominal Center: Endocrinology, Minerva Foundation Institute for Medical Research, Institute of Biomedicine, University of Turku, FI-20520 Turku, Finland
Search for other papers by Pirjo Nuutila in
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Department of Cell Biology and Anatomy, Department of Medicine, Turku PET Centre, Department of Radiology, Medical Imaging Centre of Southwest Finland, Department of Endocrinology, Abdominal Center: Endocrinology, Minerva Foundation Institute for Medical Research, Institute of Biomedicine, University of Turku, FI-20520 Turku, Finland
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Insulin signaling in bone-forming osteoblasts stimulates bone formation and promotes the release of osteocalcin (OC) in mice. Only a few studies have assessed the direct effect of insulin on bone metabolism in humans. Here, we studied markers of bone metabolism in response to acute hyperinsulinemia in men and women. Thirty-three subjects from three separate cohorts (n=8, n=12 and n=13) participated in a euglycaemic hyperinsulinemic clamp study. Blood samples were collected before and at the end of infusions to determine the markers of bone formation (PINP, total OC, uncarboxylated form of OC (ucOC)) and resorption (CTX, TRAcP5b). During 4 h insulin infusion (40 mU/m2 per min, low insulin), CTX level decreased by 11% (P<0.05). High insulin infusion rate (72 mU/m2 per min) for 4 h resulted in more pronounced decrease (−32%, P<0.01) whereas shorter insulin exposure (40 mU/m2 per min for 2 h) had no effect (P=0.61). Markers of osteoblast activity remained unchanged during 4 h insulin, but the ratio of uncarboxylated-to-total OC decreased in response to insulin (P<0.05 and P<0.01 for low and high insulin for 4 h respectively). During 2 h low insulin infusion, both total OC and ucOC decreased significantly (P<0.01 for both). In conclusion, insulin decreases bone resorption and circulating levels of total OC and ucOC. Insulin has direct effects on bone metabolism in humans and changes in the circulating levels of bone markers can be seen within a few hours after administration of insulin.
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Division of Bone and Mineral Diseases, Washington University in St Louis, St Louis, Missouri, USA
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The prevalence of type 2 diabetes mellitus (T2DM) is increasing worldwide, especially as a result of our aging society, high caloric intake and sedentary lifestyle. Besides the well-known complications of T2DM on the cardiovascular system, the eyes, kidneys and nerves, bone strength is also impaired in diabetic patients. Patients with T2DM have a 40–70% increased risk for fractures, despite having a normal to increased bone mineral density, suggesting that other factors besides bone quantity must account for increased bone fragility. This review summarizes the current knowledge on the complex effects of T2DM on bone including effects on bone cells, bone material properties and other endocrine systems that subsequently affect bone, discusses the effects of T2DM medications on bone and concludes with a model identifying factors that may contribute to poor bone quality and increased bone fragility in T2DM.
Beijing Key Laboratory of Diabetes Research and Care, Beijing, China
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Beijing Key Laboratory of Diabetes Research and Care, Beijing, China
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Beijing Key Laboratory of Diabetes Research and Care, Beijing, China
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Beijing Key Laboratory of Diabetes Research and Care, Beijing, China
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Beijing Key Laboratory of Diabetes Research and Care, Beijing, China
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Beijing Key Laboratory of Diabetes Research and Care, Beijing, China
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Beijing Key Laboratory of Diabetes Research and Care, Beijing, China
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Background
Obesity is known as a common risk factor for osteoporosis and type 2 diabetes mellitus (T2DM). Perirenal fat, surrounding the kidneys, has been reported to be unique in anatomy and biological functions. This study aimed to explore the relationship between perirenal fat and bone metabolism in patients with T2DM.
Methods
A total of 234 patients with T2DM were recruited from September 2019 to December 2019 in the cross-sectional study. The biochemical parameters and bone turnover markers (BTMs) were determined in all participants. Perirenal fat thickness (PrFT) was performed by ultrasounds via a duplex Doppler apparatus. Associations between PrFT and bone metabolism index were determined via correlation analysis and regression models.
Results
The PrFT was significantly correlated with β-C-terminal telopeptides of type I collagen (β-CTX) (r = −0.14, P < 0.036), parathyroid hormone (iPTH) (r = −0.18, P ≤ 0.006), and 25 hydroxyvitamin D (25-OH-D) (r = −0.14, P = 0.001). Multivariate analysis confirmed that the association of PrFT and β-CTX (β = −0.136, P = 0.042) was independent of other variables.
Conclusion
This study showed a negative and independent association between PrFT and β-CTX in subjects with T2DM, suggesting a possible role of PrFT in bone metabolism. Follow-up studies and further research are necessary to validate the associations and to elucidate the underlying mechanisms.
University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
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University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
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University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
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University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
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Despite recent improvements in the composition of the diet, lower mineral bone density and overweight tendencies are incoherently described in patients with phenylketonuria (PKU). The impact of dietary factors and plasma phenylalanine levels on growth, BMI, body composition, and bone mineral density was investigated in our cohort of patients with hyperphenylalaninemia (HPA) with or without dietary treatment. The anthropometric, metabolic, BMI and other nutritional indicators and bone mineral density were compared between the group of 96 treated patients with PKU (58 classic PKU (cPKU) and 38 patients with moderate-mild PKU defined as non-classic PKU (non-cPKU)) and the untreated group of 62 patients with benign HPA. Having compared the treated and untreated groups, there were normal outcomes and no statistically significant differences in BMI, body composition, and bone mineral density. Lower body height standard deviation scores were observed in the treated as compared to the untreated group (P < 0.001), but the difference was not significant when analyzing patients older than 18 years; however, cPKU adults were shorter compared to non-cPKU treated adults (P = 0.012). Interestingly, the whole-body fat was statistically higher in non-cPKU as compared to cPKU patients. In conclusion, the dietary treatment ensured adequate nutrition without significant consequences in BMI, body composition, and bone mineral density. A low protein diet may have delayed the growth in childhood, but the treated patients gained a normal final height. Mild untreated hyperphenylalaninemia characteristic for benign HPA had no negative physiological effect on bone mineral density.
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Objective
The study aimed to assess the possible systemic effects of intratympanic dexamethasone (IT-Dex) on the hypothalamic–pituitary–adrenal (HPA) axis, inflammation, and bone metabolism.
Design
A prospective cohort study including 30 adult patients of a tertiary referral ENT clinic treated with 9.6 mg IT-Dex over a period of 10 days was carried out.
Methods
Effects on plasma and salivary cortisol concentrations (basal and after low-dose (1 μg) ACTH stimulation), peripheral white blood cell count, and biomarkers for bone turnover were measured before (day 0) and after IT-Dex (day 16). Additional measurements for bone turnover were performed 5 months after therapy. Clinical information and medication with possible dexamethasone interaction were recorded.
Results
IT-Dex was well tolerated, and no effect was detected on the HPA axis (stimulated plasma and salivary cortisol concentration on day 0: 758±184 and 44.5±22.0 nmol/l; day 16: 718±154 and 39.8±12.4 nmol/l; P=0.58 and 0.24 respectively). Concentrations of osteocalcin (OC) and bone-specific alkaline phosphatase (BSAP) did not differ after dexamethasone (OC on days 0 and 16 respectively: 24.1±10.5 and 23.6±8.8 μg/l; BSAP on day 0, 16, and after 5 months respectively: 11.5±4.2, 10.3±3.4, and 12.6±5.06 μg/l); similarly, there was no difference in the peripheral white blood cell count (5.7×1012/l and 6.1×1012/l on days 0 and 16 respectively).
Conclusions
IT-Dex therapy did not interfere with endogenous cortisol secretion or bone metabolism.
