Multifarious effects of 17-β-estradiol on apolipoprotein E receptors gene expression during osteoblast differentiation in vitro

Lipoprotein receptors in ovary of eel, Anguilla australis: molecular characterisation of putative vitellogenin receptors

Lipoprotein receptors, including low-density lipoprotein receptor (LDLr) relatives (Lrs) and LDLr-related proteins (Lrps), belong to the LDLr supergene family and participate in diverse physiological functions. In this study, novel sequences of lr and lrp genes expressed in the ovary of the short-finned eel, Anguilla australis, during early gonadal development are presented. The genes encoding the LDLr-like, Lrp1-like, Lrp1b-like, Lrp3, Lrp4-like, Lrp5-like, Lrp6, Lrp10, Lrp11, Lrp12-like, and Lr11-like proteins were found and identified by sequence and structure analysis, in addition to phylogenetic analysis. Genes encoding proteins previously implicated in follicle development and vitellogenin (Vtg) uptake in oviparous vertebrates were also identified, i.e. lr8 (including lr8 + and lr8- variants) and lrp13; their identification was reinforced by conserved synteny with orthologues in other teleost fish. Compared to other lr/lrp genes, the genes encoding Lr8 + , Lr8-, and Lrp13 were highly expressed in ovary during early development, decreasing as oocyte development advanced when induced by hypophysation. Furthermore, lr8 + , lr8-, and lrp13 were dominantly expressed in the ovary when compared with 17 other tissues. Finally, this study successfully detected the expression of both lr8 variants, which showed different expression patterns to those reported in other oviparous vertebrates and provided the first characterisation of Lrp13 in Anguilla sp. We propose that lr8 + , lr8-, and lrp13 encode putative Vtg receptors in anguillid eels.

Evaluation of Hormonal Influence in Patients with Fractures Attributed to Osteoporosis

Objective  The present study aims to evaluate the influence of hormonal levels of vitamin D, calcitonin, testosterone, estradiol, and parathyroid in patients with fractures attributed to osteoporosis when compared with young patients with fractures resulting from high-impact accidents.

Methods  Blood samples were collected from 30 elderly patients with osteoporosis-attributed fractures (T-score ≤ -2.5) (osteoporotic group), and from 30 young patients with fractures resulting from high-impact accidents (control group). Measurement of 1,25-hydroxyvitamin D (Kit Diasorin, Saluggia, Italy), calcitonin (Kit Siemens, Tarrytown, NY, USA), testosterone, estradiol, and parathyroid hormone (Kit Beckman Couter, Indianapolis, IN, United States) was performed using a chemiluminescence technique. Data were inserted into a Microsoft Excel (Microsoft Corp., Armonk, WA, USA) spreadsheet and analyzed using Statview statistical software. Results showing non-normal distribution were analyzed with nonparametric methods. The Mann-Whitney test was applied for group comparison, and a Spearman test correlated hormonal levels. Statistical significance was set at p  < 0.05. All analyzes compared gender and subjects with and without osteoporosis.

Results  Women with osteoporosis had significantly lower levels of estradiol and vitamin D ( p  = 0.047 and p  = 0.0275, respectively). Men with osteoporosis presented significantly higher levels of parathyroid hormone ( p  = 0.0065). There was no significant difference in testosterone and calcitonin levels.

Conclusion  Osteoporosis patients presented gender-related hormonal differences. Women had significantly lower levels of estradiol and vitamin D, whereas men had significantly higher parathyroid hormone levels, apparently impacting the disease.

Clinicopathologic Features of Oculopharyngodistal Myopathy With LRP12 CGG Repeat Expansions Compared With Other Oculopharyngodistal Myopathy Subtypes

Importance

Repeat expansion of CGG in LRP12 has been identified as the causative variation of oculopharyngodistal myopathy (OPDM). However, to our knowledge, the clinicopathologic features of OPDM with CGG repeat expansion in LRP12 (hereafter referred to as OPDM_LRP12) remain unknown.

Objective

To identify and characterize the clinicopathologic features of patients with OPDM_LRP12.

Design, Setting, and Participants

This case series included 208 patients with a clinical or clinicopathologic diagnosis of oculopharyngeal muscular dystrophy (OPDM) from January 1, 1978, to December 31, 2020. Patients with GCN repeat expansions in PABPN1 were excluded from the study. Repeat expansions of CGG in LRP12 were screened by repeat primed polymerase chain reaction and/or Southern blot.

Main Outcomes and Measures

Clinical information, muscle imaging data obtained by either computed tomography or magnetic resonance imaging, and muscle pathologic characteristics.

Results

Sixty-five Japanese patients with OPDM (40 men [62%]; mean [SD] age at onset, 41.0 [10.1] years) from 59 families with CGG repeat expansions in LRP12 were identified. This represents the most common OPDM subtype among all patients in Japan with genetically diagnosed OPDM. The expansions ranged from 85 to 289 repeats. A negative correlation was observed between the repeat size and the age at onset (r2 = 0.188, P = .001). The most common initial symptoms were ptosis and muscle weakness, present in 24 patients (37%). Limb muscle weakness was predominantly distal in 53 of 64 patients (83%), but 2 of 64 patients (3%) had predominantly proximal muscle weakness. Ptosis was observed in 62 of 64 patients (97%), and dysphagia or dysarthria was observed in 63 of 64 patients (98%). A total of 21 of 64 patients (33%) had asymmetric muscle weakness. Aspiration pneumonia was seen in 11 of 64 patients (17%), and 5 of 64 patients (8%) required mechanical ventilation. Seven of 64 patients (11%) developed cardiac abnormalities, and 5 of 64 patients (8%) developed neurologic abnormalities. Asymmetric muscle involvement was detected on computed tomography scans in 6 of 27 patients (22%) and on magnetic resonance imaging scans in 4 of 15 patients (27%), with the soleus and the medial head of the gastrocnemius being the worst affected. All 42 muscle biopsy samples showed rimmed vacuoles. Intranuclear tubulofilamentous inclusions were observed in only 1 of 5 patients.

Conclusions and Relevance

This study suggests that OPDM_LRP12 is the most frequent OPDM subtype in Japan and is characterized by oculopharyngeal weakness, distal myopathy that especially affects the soleus and gastrocnemius muscles, and rimmed vacuoles in muscle biopsy.

Gonadal Hormones and Bone

In both sexes, estrogen is one of the most essential hormones for maintaining bone integrity. Also, especially in men, androgen has beneficial effects on bone independent of estrogen. However, estrogen replacement therapy for postmenopausal women increases the risk of developing breast cancer and endometrial cancer, and androgen replacement therapy for partial androgen deficiency of the aging male increases the risk of developing prostate cancer. Various mechanisms have been proposed on the effects of gonadal hormones on bone, such as effects through cytokines including IL-6 and effects on the OPG/RANKL ratio. In addition, large amounts of new information deriving from high-throughput gene expression analysis raise the possibility of multiple other effects on bone cells. Both estrogen and androgen exert their effects via the estrogen receptor (ER) or the androgen receptor (AR), which belongs to the nuclear receptor superfamily. Compounds such as selective estrogen receptor modulators (SERMs) and selective androgen receptor modulators (SARMs) also bind ER and AR, respectively. However, SERMs and SARMs alter the ER or AR structure differently from estrogen or androgen, resulting in other downstream gene responses. As a result they can exert favorable effects on bone while suppressing the undesirable actions of estrogen and androgen. Elucidation of ER and AR ligand-specific and tissue-specific gene regulation mechanisms will also provide information on the signal transduction mechanisms of other nuclear receptors and will be valuable for the development of new therapeutic agents.

Heterozygous deletion of LRP5 gene in mice alters profile of immune cells and modulates differentiation of osteoblasts

Skeletal homeostasis is dynamically influenced by the immune system. Low density lipoprotein receptor-related protein-5 (LRP5) is a co-receptor of the Wnt signaling pathway, which modulates bone metabolism in humans and mice. Immune disorders can lead to abnormal bone metabolism. It is unclear whether and how LRP5 alters the balance of the immune system to modulate bone homeostasis. In this study, we used primary osteoblast to detect the differentiation of osteoblasts in vitro, the immune cells of spleen and bone marrow of 6-month old LRP5 heterozygote (HZ) and wild-type (WT) mice were analyzed by Flow cytometry. We found that LRP5^+/- could influence the differentiation of osteoblasts by decreasing the mRNA level of Osterix, and increasing the mRNA level of Runx2 and the ratio of receptor activator for nuclear factor-κB ligand/osteoprotegerin (RANKL/OPG). In the LRP5^+/- mice, percentages of NK cells, CD3e⁺ cells, and CD8a⁺ T cells were increased in both spleen and bone marrow, and percentages of CD106⁺ cells and CD11c⁺ cells were increased in spleen while decreased in bone marrow, conversely, CD62L⁺ cells were decreased in spleen while increased in bone marrow compared to the WT mice. Percentages of CD4⁺ cells, CD14⁺ cells, and CD254⁺ cells were increased in the spleen, and CTLA4⁺ cells were increased in the bone marrow of the LRP5^+/- mice. The mRNA level of Wnt signaling molecules such as β-catenin, and c-myc were decreased and APC was increased in spleen lymphocytes and bone marrow lymphocytes, and the mRNA level of Wnt3a was decreased in spleen lymphocytes while no change in bone marrow lymphocytes was seen with silencing LRP5 by specific small interfering RNA. In conclusion, heterozygous deletion of the LRP5 gene in mice could alter the profile of the immune cells, influence the balance of immune environment, and modulate bone homeostasis, which might present a potential mechanism to explore the Wnt signaling pathway in the modulation of the immune system.

Low-density lipoprotein receptor deficiency impaired mice osteoblastogenesis in vitro

Postmenopausal osteoporosis affected most elderly women with co-existence of lipid and bone metabolism disorders. However, the cellular and molecular mechanisms underlying the parallel progression and cross-talk of these systems remained unclear. In the present study, low-density lipoprotein receptor knockout (LDLR^-/-) mice were chosen to elucidate the effect of LDLR in regulating the differentiation of osteoblasts, which were responsible for bone formation and modulation of osteoclastogenesis. Primary osteoblasts were isolated from the calvarium of newborn LDLR^-/- or wild-type mice followed by osteoblastic differentiation culture in vitro. Alkaline phosphatase activity was significantly decreased in LDLR^-/- osteoblasts compared to wild-type controls, combined with calcium deposit formation delay, implying impaired osteoblastogenesis in vitro. Consistent with these findings, the expression of runt-related transcription factor 2 (Runx2) was decreased 3 days after differentiation in LDLR^-/- osteoblasts compared to wild-type controls. Moreover, the expression of Osterix was decreased 7 days after differentiation in LDLR^-/- osteoblasts compared to wild-type controls, later than Runx2.However, the osteoclastogenesis modulation role of osteoblasts was unaffected by the LDLR deficiency, evidenced by the same level of osteoprotegerin (OPG)/receptor activator of nuclear factor-κ B ligand (RANKL) axis between LDLR^-/- and wild-type control osteoblasts. Our results provide a novel insight into the role of LDLR during osteoblastic differentiation and improve understanding of cross-talk between bone and lipid metabolisms.