Accumulation of LDL/ox-LDL in the necrotic region participates in osteonecrosis of the femoral head: a pathological and in vitro study.

BACKGROUND: Osteonecrosis of the femoral head (ONFH) is a common but intractable disease that appears to involve lipid metabolic disorders. Although numerous studies have demonstrated that high blood levels of low-density lipoprotein (LDL) are closely associated with ONFH, there is limited evidence to explain the pathological role of LDL. Pathological and in vitro studies were performed to investigate the role of disordered metabolism of LDL and oxidized LDL (ox-LDL) in the femoral head in the pathology of ONFH. METHODS: Nineteen femoral head specimens from patients with ONFH were obtained for immunohistochemistry analysis. Murine long-bone osteocyte Y4 cells were used to study the effects of LDL/ox-LDL on cell viability, apoptosis, and metabolism process of LDL/ox-LDL in osteocytes in normoxic and hypoxic environments. RESULTS: In the pathological specimens, marked accumulation of LDL/ox-LDL was observed in osteocytes/lacunae of necrotic regions compared with healthy regions. In vitro studies showed that ox-LDL, rather than LDL, reduced the viability and enhanced apoptosis of osteocytes. Pathological sections indicated that the accumulation of ox-LDL was significantly associated with impaired blood supply. Exposure to a hypoxic environment appeared to be a key factor leading to LDL/ox-LDL accumulation by enhancing internalisation and oxidation of LDL in osteocytes. CONCLUSIONS: The accumulation of LDL/ox-LDL in the necrotic region may contribute to the pathology of ONFH. These findings could provide new insights into the prevention and treatment of ONFH.

Diagnostic accuracy of the Berlin questionnaire and therapeutic effect of nasal continuous positive airway pressure in OSAHS patients with glucose metabolic dysfunction.

PURPOSE: Obstructive sleep apnea-hypopnea syndrome (OSAHS) is associated with alterations in glucose metabolism. The Berlin questionnaire (BQ) is effective in identifying subjects with high risk of OSAHS. However, its validity in patients with glucose metabolic dysfunction remains unclear. Our study aims to examine the diagnostic efficacy of the BQ in detecting OSAHS in patients with glucose metabolic dysfunction and to explore the effect of nasal CPAP on glucose metabolism. METHODS: Patients with glucose metabolic dysregulation were first asked to complete the BQ and then recruited for polysomnogram (PSG). The diagnostic accuracy of the BQ and the relationships between groups with normal glucose tolerance (NGT), elevated fasting blood glucose (IFG), impaired glucose tolerance (IGT), and diabetes mellitus (DM) were analyzed. Subjects with both OSAHS and glucose dysregulation received CPAP treatment and underwent an oral glucose tolerance test. Changes in apnea-hypopnea indices (AHI) and glycemic parameters were calculated to determine the efficacy of CPAP. RESULTS: Glycosylated hemoglobin and insulin levels were statistically different between the high-risk and low-risk groups according to the BQ. For diagnosis of subjects with OSAHS who also had glucose metabolic dysfunction, the sensitivity and specificity of the BQ using AHI cut-off values at 5 events per hour were 73% and 67%. CPAP therapy effectively reduced the blood glucose, HOMA-IR, and insulin levels. CONCLUSIONS: The BQ can be considered to be an effective and economical screening tool for patieints with OSAHS who also have glucose metabolic dysfunction. Treatment with CPAP may improve glycemic parameters.

Pinocembrin ameliorates intermittent hypoxia-induced neuroinflammation through BNIP3-dependent mitophagy in a murine model of sleep apnea.

BACKGROUND: Intermittent hypoxia (IH) caused by obstructive sleep apnea (OSA) leads to neuroinflammation. Pinocembrin has been shown to have neuroprotective effects, while the therapeutic functions under IH condition are still unknown. METHODS: An OSA model was established by CIH exposure inside custom-made chambers. C57BL/6 mice were intraperitoneally injected with pinocembrin (40 mg/kg, i.p.) or vehicle (PBS containing 5% povidone; i.p.), and the changes of behavior on mice were detected by the Morris water maze test. Immunohistochemical staining, western blotting, immunofluorescence assays, and immunoprecipitation were used to investigate the association between NLRP3 inflammasome and BNIP3-dependent mitophagy. The mitochondrial morphology and mitophagosomes were detected under a transmission electron microscope. The detrimental effects of IH were tested by annexin V-FITC/PI staining, Mito SOX Red staining, and JC-1 mitochondrial membrane potential assay. RESULTS: In this study, our observations in vivo indicated that the administration of pinocembrin can restore spatial learning and memory ability and reduce neuronal apoptosis and hippocampal inflammation. Pinocembrin treatment significantly inhibited the formation of NLRP3 inflammasome and infiltration of microglia and enhanced BNIP3-mediated mitophagy in the hippocampus of IH mice. Additionally, our in vitro results show that pinocembrin protects microglial cells against IH-induced cytotoxicity by activating BNIP3-dependent mitophagy through the JNK-ERK signaling pathway. CONCLUSIONS: In summary, our findings demonstrated that pinocembrin can act as a potential therapeutic strategy for IH-induced neuroinflammation.

Association between obstructive sleep apnea and low bone mass in adults: a systematic review and meta-analysis.

Introduction: This study aimed to synthesize existing evidence on the potential association between obstructive sleep apnea (OSA) and low bone mass in adults. Methods: Electronic searches of four main databases were performed. The inclusion criteria consisted of observational studies investigating the relationship between OSA and bone mass, osteoporosis, fractures, or bone metabolism markers in adult population. Bone mineral density (BMD) and T score of lumbar and femur neck, incidence of osteoporosis and fractures, bone metabolism marker levels were extracted as primary outcomes. Results: Among the 693 relevant publications, 10 studies consisting of 158,427 participants met with the inclusion and exclusion criteria. Meta-analysis showed a significant lower BMD of lumbar (mean difference (MD) = - 0.03; 95% CI - 0.05, - 0.01; I2 = 46%), femur neck (MD = - 0.06; 95% CI - 0.12, 0.00; I2 = 71%), and a significant lower T score of lumbar (MD = - 0.42; 95% CI - 0.79, - 0.05; I2 = 63%) in the OSA group. The results suggested that both male (odds ratio (OR) = 2.03; 95% CI 1.23, 3.35; I2 = 38%) and female (OR = 2.56; 95% CI 1.96, 3.34; I2 = 0%) had higher risk of osteoporosis in the OSA group. Besides, meta-analysis also showed that bone-specific alkaline phosphatase was significantly lower in OSA patients (MD = - 1.90; 95% CI - 3.48, - 0.32; I2 = 48%). Conclusions: A potential association between OSA and lower bone mass in adults is preliminarily proved. It also seems plausible that both male and female with OSA have a higher risk of osteoporosis. Supplementary Information: The online version contains supplementary material available at 10.1007/s41105-023-00481-1.

CircESRP1 inhibits clear cell renal cell carcinoma progression through the CTCF-mediated positive feedback loop.

Circular RNA (circRNA), a closed continuous loop formed by back-splicing, has been confirmed to be implicated in a variety of human diseases including cancers. However, the underlying molecular mechanism of circRNA regulating the progression of renal cell carcinoma (RCC) remains largely unclear. In the present study, we identified a novel circular RNA, circESRP1, that derived from the ESRP1 gene locus at 8q22.1 exons. Lower expression of circESRP1 was found in clear cell RCC (ccRCC) tissues and cell lines. Besides, circESRP1 expression level showed inversely correlated with the advanced tumor size, TNM stage and distant metastasis of ccRCC. The expression level of circESRP1 exhibited a positive correlation with CTCF protein but negatively correlated with miR-3942 in 79 ccRCC tissues. In vivo experiments, we found that overexpression of circESRP1 effectively repressed xenograft tumor growth and inhibited c-Myc-mediated EMT progression. CircESRP1 acted as a sponge to competitively bind with miR-3942 as confirmed through RNA pull-down, RIP and dual-luciferase reporter assays. Moreover, CTCF, a downstream target of miR-3942, was validated to specifically promote the circESRP1 transcript expression and regulated by circESRP1/miR-3942 pathway to form a positive feedback loop. We also revealed that the circESRP1/miR-3942/CTCF feedback loop regulated the ccRCC cell functions via c-Myc mediated EMT process. This study provides a novel regulatory model of circRNA via forming a positive-feedback loop that perpetuates the circESRP1/miR-3942/CTCF axis, suggesting that this signaling may serve as a novel target for the treatment of ccRCC.

Pinocembrin alleviates glucocorticoid-induced apoptosis by activating autophagy via suppressing the PI3K/Akt/mTOR pathway in osteocytes.

Glucocorticoids are widely used in clinical practice, but are associated with potentially severe side effects like glucocorticoid-induced osteoporosis (GIOP) and glucocorticoid-associated osteonecrosis of the femoral head (GA-ONFH). Glucocorticoid-induced osteocyte apoptosis plays critical roles in the pathological processes of both GIOP and GA-ONFH. Pinocembrin is a natural flavonoid that may exert protective effects on osteocytes. The present study investigated the effects of pinocembrin on glucocorticoid-induced apoptosis of murine long bone osteocyte Y4 (MLO-Y4) cells and sought to elucidate the underlying molecular mechanism. We found that pinocembrin attenuated glucocorticoid-induced cell viability injury and apoptosis of MLO-Y4 cells. Moreover, pinocembrin increased Beclin-1 and LC3B-II level, but decreased p62 expression, suggesting that pinocembrin activates autophagy in glucocorticoid-treated MLO-Y4 cells. The protective effects of pinocembrin on glucocorticoid-induced apoptosis of MLO-Y4 cells were mimicked by a known stimulator of autophagy but prevented by a known inhibitor of autophagy. Pinocembrin also suppressed the PI3K/Akt/mTOR signaling pathway, which regulates cell autophagy, in glucocorticoid-treated MLO-Y4 cells. In conclusion, the results indicate that pinocembrin alleviates glucocorticoid-induced osteocyte apoptosis by activating autophagy via suppressing the PI3K/Akt/mTOR pathway. Pinocembrin may represent a potential natural agent for preventing and treating GIOP and GA-ONFH.