Steroids-producing nodules: a two-layered adrenocortical nodular structure as a precursor lesion of cortisol-producing adenoma

BACKGROUND

The human adrenal cortex consists of three functionally and structurally distinct layers; zona glomerulosa, zona fasciculata (zF), and zona reticularis (zR), and produces adrenal steroid hormones in a layer-specific manner; aldosterone, cortisol, and adrenal androgens, respectively. Cortisol-producing adenomas (CPAs) occur mostly as a result of somatic mutations associated with the protein kinase A pathway. However, how CPAs develop after adrenocortical cells acquire genetic mutations, remains poorly understood.

METHODS

We conducted integrated approaches combining the detailed histopathologic studies with genetic, RNA-sequencing, and spatially resolved transcriptome (SRT) analyses for the adrenal cortices adjacent to human adrenocortical tumours.

FINDINGS

Histopathological analysis revealed an adrenocortical nodular structure that exhibits the two-layered zF- and zR-like structure. The nodular structures harbour GNAS somatic mutations, known as a driver mutation of CPAs, and confer cell proliferative and autonomous steroidogenic capacities, which we termed steroids-producing nodules (SPNs). RNA-sequencing coupled with SRT analysis suggests that the expansion of the zF-like structure contributes to the formation of CPAs, whereas the zR-like structure is characterised by a macrophage-mediated immune response.

INTERPRETATION

We postulate that CPAs arise from a precursor lesion, SPNs, where two distinct cell populations might contribute differently to adrenocortical tumorigenesis. Our data also provide clues to the molecular mechanisms underlying the layered structures of human adrenocortical tissues.

FUNDING

KAKENHI, The Uehara Memorial Foundation, Daiwa Securities Health Foundation, Kaibara Morikazu Medical Science Promotion Foundation, Secom Science and Technology Foundation, ONO Medical Research Foundation, and Japan Foundation for Applied Enzymology.

Wide-scope targeted analysis of bioactive lipids in human plasma by LC/MS/MS

Quantitative information on blood metabolites can be used in developing advanced medical strategies such as early detection and prevention of disease. Monitoring bioactive lipids such as steroids, bile acids, and PUFA metabolites could be a valuable indicator of health status. However, a method for simultaneously measuring these bioactive lipids has not yet been developed. Here, we report a LC/MS/MS method that can simultaneously measure 144 bioactive lipids, including steroids, bile acids, and PUFA metabolites, from human plasma, and a sample preparation method for these targets. Protein removal by methanol precipitation and purification of bioactive lipids by solid-phase extraction improved the recovery of the targeted compounds in human plasma samples, demonstrating the importance of sample preparation methods for a wide range of bioactive lipid analyses. Using the developed method, we studied the plasma from healthy human volunteers and confirmed the presence of bioactive lipid molecules associated with sex differences and circadian rhythms. The developed method of bioactive lipid analysis can be applied to health monitoring and disease biomarker discovery in precision medicine.

Dectin-2 Deficiency Promotes Proinflammatory Cytokine Release From Macrophages and Impairs Insulin Secretion

Pancreatic islet inflammation plays a crucial role in the etiology of type 2 diabetes (T2D). Macrophages residing in pancreatic islets have emerged as key players in islet inflammation. Macrophages express a plethora of innate immune receptors that bind to environmental and metabolic cues and integrate these signals to trigger an inflammatory response that contributes to the development of islet inflammation. One such receptor, Dectin-2, has been identified within pancreatic islets; however, its role in glucose metabolism remains largely unknown. Here we have demonstrated that mice lacking Dectin-2 exhibit local inflammation within islets, along with impaired insulin secretion and β-cell dysfunction. Our findings indicate that these effects are mediated by proinflammatory cytokines, such as interleukin (IL)-1α and IL-6, which are secreted by macrophages that have acquired an inflammatory phenotype because of the loss of Dectin-2. This study provides novel insights into the mechanisms underlying the role of Dectin-2 in the development of islet inflammation.

Adrenal steroid metabolites and bone status in patients with adrenal incidentalomas and hypercortisolism

BACKGROUND

Autonomous cortisol secretion (ACS), resulting from cortisol-producing adenomas (CPA), causes endogenous steroid-induced osteoporosis (SIOP). However, the risk of endogenous SIOP cannot be explained by cortisol excess alone, and how other steroid metabolites affect bone status is unclear.

METHODS

ACS was diagnosed as serum cortisol ≥1.8 μg/dL after the 1-mg dexamethasone suppression test (DST-cortisol). Using liquid chromatography tandem mass spectrometry, 21 plasma steroid metabolites were measured in 73 patients with ACS and 85 patients with non-functioning adrenal tumors (NFAT). Expression of steroidogenic enzymes and relevant steroid metabolites were analyzed in some of CPA tissues.

FINDINGS

Discriminant and principal component analyses distinguished steroid profiles between the ACS and NFAT groups in premenopausal women. Premenopausal women with ACS exhibited higher levels of a mineralocorticoid metabolite, 11-deoxycorticosterone (11-DOC), and lower levels of androgen metabolites, dehydroepiandrosterone-sulfate, and androsterone-glucuronide. In premenopausal women with ACS, DST-cortisol negatively correlated with trabecular bone score (TBS). Additionally, 11-DOC negatively correlated with lumbar spine-bone mineral density, whereas androsterone-glucuronide positively correlated with TBS. The CPA tissues showed increased 11-DOC levels with increased expression of CYP21A2, essential for 11-DOC synthesis. Adrenal non-tumor tissues were atrophied with reduced expression of CYB5A, required for androgen synthesis.

INTERPRETATION

This study demonstrates that unbalanced production of adrenal steroid metabolites, derived from both adrenal tumor and non-tumor tissues, contributes to the pathogenesis of endogenous SIOP in premenopausal women with ACS.

FUNDING

JSPS KAKENHI, Secom Science and Technology Foundation, Takeda Science Foundation, Japan Foundation for Applied Enzymology, AMED-CREST, JSTA-STEP, JST-Moonshot, and Ono Medical Research Foundation.

Do multiple types of confirmatory tests improve performance in predicting subtypes of primary aldosteronism?

OBJECTIVE

The clinical practice guideline for primary aldosteronism (PA) places a high value on confirmatory tests to sparing patients with false-positive results in case detection from undergoing adrenal venous sampling (AVS). However, it is unclear whether multiple types of confirmatory tests are more useful than a single type. To evaluate whether the machine-learned combination of two confirmatory tests is more useful in predicting subtypes of PA than each test alone.

DESIGN

A retrospective cross-sectional study in referral centres.

PATIENTS

This study included 615 patients with PA randomly assigned to the training and test data sets. The participants underwent saline infusion test (SIT) and captopril challenge test (CCT) and were subtyped by AVS (unilateral, n = 99; bilateral, n = 516).

MEASUREMENTS

The area under the curve (AUC) and clinical usefulness using decision curve analysis for the subtype prediction in the test data set.

RESULTS

The AUCs for the combination of SIT and CCT, SIT alone and CCT alone were 0.850, 0.813 and 0.786, respectively, with no significant differences between them. The AUC for the baseline clinical characteristics alone was 0.872, whereas the AUCs for these combined with SIT, combined with CCT and combined with both SIT and CCT were 0.868, 0.854 and 0.855, respectively, with no significant improvement in AUC. The additional clinical usefulness of the second confirmatory test was unremarkable on decision curve analysis.

CONCLUSIONS

Our data suggest that patients with positive case detection undergo one confirmatory test to determine the indication for AVS.

Coexistence of bone and vascular disturbances in patients with endogenous glucocorticoid excess

Purpose

Bone and vascular diseases are considered to share pathogenic mechanisms. Excess glucocorticoids, key regulators of cardiovascular and metabolic homeostasis, may promote both diseases simultaneously. We used endogenous Cushing's syndrome (CS) to investigate whether glucocorticoid excess underlies coexisting bone and vascular diseases.

Methods

We included 194 patients with adrenal tumors (ATs): autonomous cortisol secretion (ACS, n = 97) and non-functional AT (n = 97). ACS was further classified into overt CS (n = 17) and subclinical CS (SCS, n = 80). Arterial stiffness was defined as a brachial-ankle pulse wave velocity (baPWV) ≥ 1800 cm/s.

Results

Patients with ACS had higher coexistence rates of vertebral fracture and arterial stiffness (23 % vs. 2 %; p < 0.001) and vertebral fracture and abdominal aortic calcification (22 % vs. 1 %; p < 0.001) than those with non-functional AT. In patients with ACS, baPWV was negatively correlated with trabecular bone score (TBS, r = -0.33; p = 0.002), but not with bone mineral density, and vertebral fracture was associated with arterial stiffness in the logistic regression analysis. In the multivariate analysis of variance, the degree of cortisol excess (defined as CS, SCS, and non-functional AT) determined the correlation between TBS and baPWV (partial η² = 0.07; p < 0.001). In the analysis of covariance, patients with coexisting vertebral fracture and arterial stiffness had higher levels of serum cortisol after the 1-mg dexamethasone suppression test than those without.

Conclusion

In endogenous glucocorticoid excess, bone and vascular diseases frequently coexisted, and deteriorated bone quality, not bone loss, was related to arterial stiffness. Thus, glucocorticoid excess may perturb the bone-vascular axis.

Impact of Cortisol on Reduction in Muscle Strength and Mass: A Mendelian Randomization Study

CONTEXT

Prolonged exposure to pathological cortisol, as in Cushing's syndrome causes various age-related disorders, including sarcopenia. However, it is unclear whether mild cortisol excess, for example, accelerates sarcopenia due to aging or chronic stress.

OBJECTIVE

We used Mendelian randomization (MR) analysis to assess whether cortisol was causally associated with muscle strength and mass.

METHODS

Three single-nucleotide polymorphisms associated with plasma cortisol concentrations in the CORtisol NETwork consortium (n = 12 597) were used as instrumental variables. Summary statistics with traits of interest were obtained from relevant genome-wide association studies. For the primary analysis, we used the fixed-effects inverse-variance weighted analysis accounting for genetic correlations between variants.

RESULTS

One SD increase in cortisol was associated with SD reduction in grip strength (estimate, -0.032; 95% CI -0.044 to -0.020; P = 3e-04), whole-body lean mass (estimate, -0.032; 95% CI, -0.046 to -0.017; P = 0.004), and appendicular lean mass (estimate, -0.031; 95% CI, -0.049 to -0.012; P = 0.001). The results were supported by the weighted-median analysis, with no evidence of pleiotropy in the MR-Egger analysis. The association of cortisol with grip strength and lean mass was observed in women but not in men. The association was attenuated after adjusting for fasting glucose in the multivariable MR analysis, which was the top mediator for the association in the MR Bayesian model averaging analysis.

CONCLUSION

This MR study provides evidence for the association of cortisol with reduced muscle strength and mass, suggesting the impact of cortisol on the development of sarcopenia.

Recurrent Hypoglycemia Due to a High Titer of Insulin Antibody in Response to Exogenous Insulin Administration in Two Cases of Type 1 Diabetes

In the first case, a 60-year-old man who was using continuous subcutaneous insulin infusion (CSII), developed recurrent hypoglycemia due to insulin antibodies. This is the first report of such a case using CSII. In the second case, a 70-year-old man was follow-up case who developed hypoglycemia while using human insulin. In both cases, the hypoglycemia subsided after switching to multiple daily insulin injection and/or insulin preparation. The results of Scatchard analyses of the two cases were similar to those of cases of insulin autoimmune syndrome (IAS) that improved after recovery from hypoglycemia.The clinical characteristics and Scatchard analysis data were essentially the same as those for IAS, except for the presence of insulin administration.

Whole Transcriptome Profiling of Adrenocortical Tumors Using Formalin-Fixed Paraffin-Embedded Samples

Whole transcriptome profiling is a promising technique in adrenal studies; however, whole transcriptome profiling of adrenal disease using formalin-fixed paraffin-embedded (FFPE) samples has to be further explored. The aim of this study was to evaluate the utility of transcriptome data from FFPE samples of adrenocortical tumors. We performed whole transcriptome profiling of FFPE and fresh frozen samples of adrenocortical carcinoma (ACC, n = 3), aldosterone-producing adenoma (APA, n = 3), and cortisol-producing adenoma (CPA, n = 3), and examined the similarity between the transcriptome data. We further examined whether the transcriptome data of FFPE samples could be used to distinguish tumor types and detect marker genes. The number of read counts was smaller in FFPE samples than in fresh frozen samples (P < 0.01), while the number of genes detected was similar (P = 0.39). The gene expression profiles of FFPE and fresh frozen samples were highly correlated (r = 0.93, P < 0.01). Tumor types could be distinguished by consensus clustering and principal component analysis using transcriptome data from FFPE samples. In the differential expression analysis between ACC and APA-CPA, known marker genes of ACC (e.g., CCNB2, TOP2A, and MAD2L1) were detected in FFPE samples of ACC. In the differential expression analysis between APA and CPA, known marker genes of APA (e.g., CYP11B2, VSNL1, and KCNJ5) were detected in the APA of FFPE samples. The results suggest that FFPE samples may be a reliable alternative to fresh frozen samples for whole transcriptome profiling of adrenocortical tumors.

Protective Role of DHEAS in Age-related Changes in Bone Mass and Fracture Risk

PURPOSE

Dehydroepiandrosterone sulfate (DHEAS) from the adrenal cortex substantially decreases with age, which may accelerate osteoporosis. However, the association of DHEAS with bone mineral density (BMD) and fracture is inconclusive. We conducted a Mendelian randomization (MR) analysis to investigate the role of DHEAS in age-related changes in BMD and fracture risk.

METHODS

Single nucleotide polymorphisms (SNPs) associated with serum DHEAS concentrations were used as instrumental variables (4 SNPs for main analysis; 4 SNPs for men and 5 SNPs for women in sex-related analysis). Summary statistics were obtained from relevant genome-wide association studies.

RESULTS

A log-transformed unit (µmol/L) increase in serum DHEAS concentrations was associated with an SD increase in estimated BMD at the heel (estimate, 0.120; 95% CI, 0.081-0.158; P = 9 × 10-10), and decreased fracture (odds ratio, 0.989; 95% CI, 0.981-0.996; P = 0.005), consistent with dual-energy X-ray absorptiometry-derived BMD at the femoral neck and lumbar spine. Their associations remained even after adjusting for height, body mass index, testosterone, estradiol, sex hormone-binding globulin, and insulin-like growth factor 1. The association of DHEAS with fracture remained after adjusting for falls, grip strength, and physical activity but was attenuated after adjusting for BMD. The MR-Bayesian model averaging analysis showed BMD was the top mediating factor for association of DHEAS with fracture. The association between DHEAS and BMD was observed in men but not in women.

CONCLUSION

DHEAS was associated with increased BMD and decreased fracture. DHEAS may play a protective role in decreasing fracture risk, mainly by increasing bone mass.

Machine learning based models for prediction of subtype diagnosis of primary aldosteronism using blood test

Primary aldosteronism (PA) is associated with an increased risk of cardiometabolic diseases, especially in unilateral subtype. Despite its high prevalence, the case detection rate of PA is limited, partly because of no clinical models available in general practice to identify patients highly suspicious of unilateral subtype of PA, who should be referred to specialized centers. The aim of this retrospective cross-sectional study was to develop a predictive model for subtype diagnosis of PA based on machine learning methods using clinical data available in general practice. Overall, 91 patients with unilateral and 138 patients with bilateral PA were randomly assigned to the training and test cohorts. Four supervised machine learning classifiers; logistic regression, support vector machines, random forests (RF), and gradient boosting decision trees, were used to develop predictive models from 21 clinical variables. The accuracy and the area under the receiver operating characteristic curve (AUC) for predicting of subtype diagnosis of PA in the test cohort were compared among the optimized classifiers. Of the four classifiers, the accuracy and AUC were highest in RF, with 95.7% and 0.990, respectively. Serum potassium, plasma aldosterone, and serum sodium levels were highlighted as important variables in this model. For feature-selected RF with the three variables, the accuracy and AUC were 89.1% and 0.950, respectively. With an independent external PA cohort, we confirmed a similar accuracy for feature-selected RF (accuracy: 85.1%). Machine learning models developed using blood test can help predict subtype diagnosis of PA in general practice.

Significance of Discordant Results: between Confirmatory Tests in Diagnosis of Primary Aldosteronism

Context: Current clinical guidelines recommend confirmation of positive result in at least one confirmatory test in the diagnosis of primary aldosteronism (PA). Clinical implication of multiple confirmatory tests has not been established, especially when patients show discordant results. Objective: The aim of the present study was to explore the role of two confirmatory tests in subtype diagnosis of PA. Design: Retrospective cross-sectional study. Setting: The study was conducted at two referral centers. Participants and Method: We identified 360 hypertensive patients who underwent both captopril challenge test (CCT) and saline infusion test (SIT) and exhibited at least one positive result. Among them, we studied 193 patients with PA whose data were available for subtype diagnosis based on adrenal vein sampling (AVS). Main Outcome Measure: The prevalence of bilateral subtype on AVS according to the results of the confirmatory tests. Results: Of patients studied, 127 were positive for both CCT and SIT (double-positive), while 66 were positive for either CCT or SIT (single-positive) (n = 34 and n = 32, respectively). Altogether, 135 were diagnosed with bilateral subtype on AVS. The single-positive patients had milder clinical features of PA than the double-positive patients. The prevalence of bilateral subtype on AVS was significantly higher in the single-positive patients than in the double-positive patients. (63/66 [95.5%] vs. 72/127 [56.7%], P < 0.01). Several clinical parameters were different between CCT single-positive and SIT single-positive patients. Conclusion: Patients with discordant results between CCT and SIT have a high probability of bilateral subtype of PA on AVS.

Causal Effect of Fibroblast Growth Factor 23 on Osteoporosis and Cardiometabolic Disorders: A Mendelian Randomization Study

Pathological excess of fibroblast growth factor 23 (FGF23) causes mineral and bone disorders. However, the causality of FGF23 in the development of osteoporosis remains unknown. Whether FGF23 has systemic effects on cardio-metabolic disorders beyond regulating mineral metabolism is also controversial. In this study, we evaluated the causal effect of FGF23 on osteoporosis and cardiometabolic disorders using Mendelian randomization (MR) analysis. Summary statistics for single-nucleotide polymorphisms with traits of interest were obtained from the relevant genome-wide association studies. As a result, FGF23 was found to be inversely associated with femoral neck-BMD (odds ratio [OR] 0.682, 95% confidence interval [CI] 0.546–0.853, p = 8e-04) and heel estimated BMD (eBMD) (OR 0.898, 95%CI 0.820–0.985, p = 0.022) in the inverse-variance-weighted analysis, but not lumbar spine-BMD and fractures. The results were supported by the weighted-median analysis, and there was no evidence of pleiotropy in the MR-Egger analysis. FGF23 was directly associated with FN-BMD and eBMD after adjustment for estimated glomerular filtration rate, height, and body mass index in multivariable MR analysis. On the other hand, there was no association between FGF23 and cardiometabolic traits including cardio artery disease, brachial-ankle pulse wave velocity, intima-media thickness of carotid arteries, systolic and diastolic blood pressure, fasting glucose, high and low-density lipoprotein cholesterol, and triglycerides. Therefore, FGF23 has been causally associated with bone loss. In contrast, FGF23 has not been causally associated with cardiometabolic disorders. The data of this study provides important insights into the role of FGF23 in the pathogenesis of osteoporosis and cardiometabolic disorders.

Machine Learning-Based Models for Prediction of Subtype Diagnosis of Primary Aldosteronism Using Blood Test

Context: Primary aldosteronism (PA) is a common cause of secondary hypertension and is associated with an increased risk of cardiometabolic diseases, especially in unilateral subtype. Despite its high prevalence, the case detection rate of PA is limited, partly because of no clinical models available in general practice to identify patients highly suspicious of unilateral subtype of PA, who can be cured by unilateral adrenalectomy and should be referred to specialized centers. The use of machine learning has been introduced in some fields of clinical prediction. Combining machine learning with clinical data could lead to the development of new models for predicting unilateral subtype of PA. Objective: The aim of this study was to develop a predictive model of subtype diagnosis of PA based on machine learning methods using clinical data available in general practice. Design and setting: This was a retrospective cross-sectional study in referral centers. Patients: We retrospectively analyzed 91 patients with unilateral and 138 patients with bilateral subtype of PA diagnosed according to adrenal venous sampling findings, and stratified randomly split to the training (80%) and test cohorts (20%). Four supervised machine learning classifiers; logistic regression, support vector machines, random forests (RF), and gradient boosting decision trees, were used to develop prediction models from 21 clinical variables. Classifiers were trained using stratified 10 fold cross-validation of the training cohort and hyperparameters of each classifier were adjusted using grid search to optimize the accuracy in the training cohort. Main Outcome Measures: The accuracy and the area under the receiver operating characteristic curve (AUC) for subtype prediction in the test cohort were compared among the optimized classifiers. Results: Of the four classifiers, the accuracy and AUC were highest in RF, with 95.7% and 0.990, respectively. Serum potassium levels, plasma aldosterone concentrations, and serum sodium levels were highlighted as important variables in this model. For feature-selected RF with the three variables, the accuracy and AUC were 89.1% and 0.950, respectively. With an independent external PA cohort, we confirmed a similar accuracy for feature-selected RF. Conclusions: Machine learning models developed using blood test can help predict subtype diagnosis of PA in general practice.

Investigating the causal effect of fibroblast growth factor 23 on osteoporosis and cardiometabolic disorders: A Mendelian randomization study

Pathological excess of fibroblast growth factor 23 (FGF23) causes mineral and bone disorders. However, the causality of FGF23 in the development of osteoporosis remains unknown. Whether FGF23 has systemic effects on cardiometabolic disorders beyond regulating mineral metabolism is also controversial. In this study, we investigated the causal effect of FGF23 on osteoporosis and cardiometabolic disorders using Mendelian randomization (MR) analysis. Summary statistics for single-nucleotide polymorphisms with traits of interest were obtained from the relevant genome-wide association studies. As a result, FGF23 was found to be inversely associated with femoral neck-BMD (odds ratio [OR] 0.682, 95% confidence interval [CI] 0.546-0.853, p = 8e-04) and heel estimated BMD (eBMD) (OR 0.898, 95%CI 0.820-0.985, p = 0.022) in the inverse-variance-weighted analysis, but not lumbar spine-BMD and fractures. The results were supported by the weighted-median analysis, and there was no evidence of pleiotropy in the MR-Egger analysis. FGF23 was associated with FN-BMD and eBMD after adjustment for estimated glomerular filtration rate, height, and body mass index in multivariable MR analysis. On the other hand, there was no association between FGF23 and cardiometabolic traits including cardio artery disease, brachial-ankle pulse wave velocity, intima-media thickness of carotid arteries, systolic and diastolic blood pressure, fasting glucose, high and low-density lipoprotein cholesterol, and triglycerides. Therefore, this MR study established that FGF23 was involved in bone loss and, in contrast, was not involved in cardiometabolic disorders. Our findings provide important insights into the role of FGF23 in the pathogenesis of osteoporosis and cardiometabolic disorders.

Significance of Discordant Results Between Confirmatory Tests in Diagnosis of Primary Aldosteronism

CONTEXT

Current clinical guidelines recommend confirmation of a positive result in at least one confirmatory test in the diagnosis of primary aldosteronism (PA). Clinical implication of multiple confirmatory tests has not been established, especially when patients show discordant results.

OBJECTIVE

The aim of the present study was to explore the role of 2 confirmatory tests in subtype diagnosis of PA.

DESIGN AND SETTING

A retrospective cross-sectional study was conducted at two referral centers.

PARTICIPANTS AND METHODS

We identified 360 hypertensive patients who underwent both a captopril challenge test (CCT) and a saline infusion test (SIT) and exhibited at least one positive result. Among them, we studied 193 patients with PA whose data were available for subtype diagnosis based on adrenal vein sampling (AVS).

MAIN OUTCOME MEASURE

The prevalence of bilateral subtype on AVS according to the results of the confirmatory tests was measured.

RESULTS

Of patients studied, 127 were positive for both CCT and SIT (double-positive), whereas 66 were positive for either CCT or SIT (single-positive) (n = 34 and n = 32, respectively). Altogether, 135 were diagnosed with bilateral subtype on AVS. The single-positive patients had milder clinical features of PA than the double-positive patients. The prevalence of bilateral subtype on AVS was significantly higher in the single-positive patients than in the double-positive patients. (63/66 [95.5%] vs 72/127 [56.7%], P < .01). Several clinical parameters were different between CCT single-positive and SIT single-positive patients.

CONCLUSION

Patients with discordant results between CCT and SIT have a high probability of bilateral subtype of PA on AVS.

Role of deteriorated bone quality in the development of osteoporosis in pheochromocytoma and paraganglioma

CONTEXT

Pheochromocytoma (PHEO) and paraganglioma (PGL) (PHEO and PGL: PPGLs), catecholamine-producing tumors, represent an emerging cause of secondary osteoporosis. However, despite decreased bone mineral density (BMD), vertebral fracture (VF) is not associated with BMD in PPGLs.

OBJECTIVE

To evaluate whether deteriorated bone quality is involved in the development of osteoporosis in PPGLs.

PARTICIPANTS

Trabecular bone score (TBS), used to assess trabecular bone quality, was examined in 56 patients with PPGLs and 52 with non-functional adrenal tumors (AT). Radiograph of the spine was carried out in 35 patients with PPGLs, and TBS was analyzed in 18 patients with PPGLs at follow-up.

MAIN OUTCOME MEASURE

TBS and BMD at the lumbar spine in patients with PPGLs with and without VF.

RESULTS

PPGLs had a lower TBS (n = 56, 1.338 [1.294-1.420]) than non-functional AT (n = 52, 1.394 [1.342-1.444]; p = 0.033). Among those with PPGLs, patients with VF (n = 14, 1.314 [1.289-1.346]) had a lower TBS than those without VF (n = 21, 1.383 [1.324-1.426]; p = 0.046), despite no significant difference in BMD at the lumbar spine between the two groups (p = 0.501). An optimal cut-off level of TBS for diagnosing VF in PPGLs was 1.323, and its area under the curve was 0.702. The severity of catecholamine excess and maximal size of tumor were associated with decreased TBS in PPGLs patients (p = 0.016 and p = 0.020, respectively). Surgical resection of PPGLs improved TBS at follow-up, with 2.5% increase (p = 0.007).

CONCLUSIONS

This study provides evidence for the importance of deteriorated bone quality rather than decreased bone mass in the development of VF in PPGLs.

Significance of aldosterone gradient within left adrenal vein in diagnosing unilateral subtype of primary aldosteronism

CONTEXT

The success rate of cannulation of the right adrenal vein is limited. The aldosterone gradient within the same adrenal vein branch is specific for aldosterone-producing adenoma.

OBJECTIVE

This study was performed to investigate whether the absolute aldosterone gradient within the left adrenal vein (left-AV absolute aldosterone gradient) indicates unilateral excess aldosterone.

DESIGN AND SETTING

A retrospective cross-sectional study in a single referral centre.

PATIENTS AND METHODS

In total, 123 consecutive patients with primary aldosteronism who had successful adrenal vein sampling (AVS) data were examined. The left-AV absolute aldosterone gradient was considered significant when a gradient of >4:1 in the aldosterone-to-cortisol ratio between the common trunk vein and central vein was found.

MAIN OUTCOME MEASURE

The prevalence of the unilateral subtype in patients with a significant left-AV absolute aldosterone gradient.

RESULTS

The prevalence of the unilateral subtype was higher in patients with than without a significant left-AV absolute aldosterone gradient (88.2% [15/17] vs 21.7% [23/106], P < .001). Of 60 patients with spontaneous hypokalemia, left unilateral disease on computed tomography, or both, a significant left-AV absolute aldosterone gradient was present only in patients with the unilateral subtype on AVS (42.9% [15/35]), but not in those with the bilateral subtype (0.0% [0/25]). These data were validated in an external cohort.

CONCLUSION

The presence of a significant left-AV absolute aldosterone gradient can be used to diagnose the left unilateral subtype of primary aldosteronism on AVS in patients with spontaneous hypokalemia, left unilateral disease on computed tomography or both.

Coexistence of osteoporosis and atherosclerosis in pheochromocytoma: new insights into its long-term management

Osteoporosis and atherosclerosis frequently coexist in patients with pheochromocytoma. The presence of osteoporosis may predict that of atherosclerosis and vice versa in patients with PHEO. These findings have implications for the long-term management of the pheochromocytoma and its potential chronic complications.

INTRODUCTION

Pheochromocytoma (PHEO), a catecholamine-producing tumor, is often found incidentally, and it may be present for years before it is diagnosed. However, long-term exposure to catecholamines excess may induce chronic complications, such as osteoporosis and atherosclerosis. We aimed to evaluate concomitant osteoporosis and atherosclerosis in patients with PHEO.

METHODS

Fifty-one patients with PHEO and 51 patients with a non-functional adrenal tumor were compared radiographically for the prevalence of vertebral fracture (VF), a typical osteoporotic fracture, and abdominal aortic calcification (AAC).

RESULTS

In patients with PHEO, the prevalence of AAC was higher in those with VF (58%) than in those without (6%, p < 0.001). AAC was associated with VF after adjusting for age and sex (odds ratio, 1.53; 95% confidence interval, 1.07-2.46; p = 0.003) in patients with PHEO. The degree of catecholamine excess correlated with the presence of VF and AAC (p = 0.007). The prevalence of VF was higher in patients with PHEO (37%) than those with non-functional AT (12%, p = 0.005), but the prevalence of AAC was comparable between the two groups (25% and 19%, p = 0.636). VF and AAC more frequently coexisted in patients with PHEO (22%) than in those with non-functional AT (2%, p = 0.003).

CONCLUSION

This study represents the first demonstration that osteoporosis and atherosclerosis frequently coexist in patients with PHEO. The presence of osteoporosis may predict that of atherosclerosis and vice versa in patients with PHEO. These findings have implications for the long-term management of the PHEO and its potential chronic complications.

SAT-548 Significance of Adrenal Vein Aldosterone Gradient in the Diagnosis of Unilateral Subtype of Primary Aldosteronism

Context: Adrenal vein sampling (AVS) is the standard method for subtype diagnosis in primary aldosteronism (PA), while success rate of its procedures, especially in right adrenal vein (AV), has limited. However, unilateral subtype of PA can be completely cured by surgical treatment and hence diagnostic approach for PA should be established especially when patients with apparent adrenal disease on computed tomography (CT) lack complete AVS result. In recent years, segmental AVS demonstrates that apparent aldosterone gradient in each adrenal vein branch is specific finding in aldosterone producing adenoma. Since we have reported that plasma aldosterone concentrations different in the proximal and distal regions of the left AV in some of the patients with PA, we hypothesized that solo finding of adrenal aldosterone gradient in the left AV (left AV gradient) should be the clue for unilateral subtype of PA.

Objective: The aim was to investigate whether left AV gradient indicate the left unilateral subtype of PA.

Design and Setting This study was a part of the Kyushu Adrenal Network Database for Advanced medicine (Q-AND-A) study, a cross-sectional and retrospective study in a single referral center.

Participants and AVS procedure: Of 194 PA patients who underwent AVS with cosyntropin stimulation between January 2007 and April 2019, 111 patients had available and successful AVS data. Blood samples in left adrenal veins were obtained from following two positions; the common trunk and the central adrenal vein. We calculated left AV gradient by the ratio of aldosterone-to-cortisol ratio on the higher position in left AV to that on the lower position. We determined the presence of left AV gradient if it was greater than four.

Main outcome measures: Prevalence of unilateral subtype in patients with left AV gradient who had unilateral disease on CT.

Results: Of 111 patients with complete AVS data, 43 who had left unilateral disease on CT were analyzed in present study. Twenty-nine patients were diagnosed as left unilateral subtype on AVS and 14 were bilateral subtype. Aldosterone gradient was observed only in patients with unilateral subtype (41% [12/29]), not in patients with bilateral subtype (0% [0/14]). Of 29 patients with unilateral subtype on AVS, clinical parameters, including plasma aldosterone concentrations, plasma renin activity, and serum potassium levels, were not different in those with and without left AV gradient. The receiver operative curve analysis for the diagnosis of unilateral subtype on AVS showed that the optimal cutoff value of left AV gradient was 3.3 with a sensitivity of 45% and specificity of 100%.

Conclusion: The presence of left AV gradient is the reliable finding for the diagnosis of left unilateral subtype in patients with PA who have unilateral disease on CT. However, further study in a larger number of cases is required to validate this finding.

MON-204 Pheochromocytoma and Paraganglioma: An Emerging Cause of Secondary Osteoporosis

Context: Many endocrine diseases are known to cause secondary osteoporosis, which is potentially reversible by treatment of the underlying disease itself. Pheochromocytoma (PHEO) and paraganglioma (PGL) (PHEO and PGL: PPGLs) are the rare catecholamine-producing neuroendocrine tumors, which are associated with low bone mineral density (BMD). However, PPGLs have not been recognized as a cause of secondary osteoporosis. Indeed, even the prevalence of osteoporotic fracture in patients with PPGLs is currently unknown. Furthermore, whether surgical resection contributes to the improvement of BMD has never been addressed. Objective: This study was designed to evaluate 1) whether PPGLs increase the risk of vertebral fracture (VF), which is the most common type of osteoporotic fracture and 2) whether surgical resection of PPGLs contributes to the improvement of BMD. Design and Settings: A retrospective cross-sectional study in a single referral center. Participants: Among 443 patients with adrenal tumor (AT), we included 62 patients with histologically confirmed PPGLs and 61 patients with non-functional AT. Intervention: The prevalence of VF was examined in 49 out of 62 patients with PPGLs and 61 patients with non-functional AT. In 23 out of 62 patients with PPGLs, BMD was evaluated at baseline and after surgery. Results: PPGLs had a higher prevalence of VF (43% [21/49]) than non-functional AT (16% [10/61]; p = 0.002). PPGLs were an independent risk factor for VF after adjusting for age and sex (odds ratio, 4.47; 95% confidence interval, 1.76–11.3; p = 0.001). In PPGLs, BMD expressed as Z score at the lumbar spine was significantly improved at follow-up (before -0.5±1.0, after -0.2±0.9; p = 0.005). Conclusion: This study demonstrates that PPGLs are an independent risk factor for VF and that their surgical resection contributes to the improvement of BMD in the trabecular bone. These observations support the notion that PPGLs are an emerging cause of secondary osteoporosis.

SUN-378 Unilateral Primary Aldosteronism as an Independent Risk Factor for Vertebral Fracture

Context: Primary aldosteronism (PA) is known to increase vertebral fracture (VF), although the detailed mechanism remains to be elucidated. PA consists of two subtypes: the unilateral and bilateral subtype. Patients with unilateral PA, who usually have a higher plasma aldosterone concentration than those with bilateral PA, exhibit a more severe clinical phenotype. We hypothesized that PA subtype affects the prevalence of VF.

Objective: To evaluate whether unilateral PA is associated with the prevalence of VF.

Design: Cross-sectional study in a single referral center.

Patients: We identified 210 hypertensive patients whose clinical data were available for case-detection results. One hundred and fifty-two patients were diagnosed with PA using captopril challenge tests.

Measurements: The prevalence of VF according to PA subtype.

Results: We included 113 patients with PA who were subtype classified according to adrenal vein sampling, of whom 37 patients had unilateral PA and 76 patients had bilateral PA, whereas 58 patients had non-PA. We excluded 39 patients with PA who were not subtype classified. Patients with PA had a higher prevalence of VF (28% [32/113]) than those with non-PA (12% [7/58]; p = 0.020). Moreover, unilateral PA had a higher prevalence of VF (46% [17/37]) than bilateral PA (20% [15/76]; p = 0.021). There was no significant difference between bilateral PA and non-PA. Unilateral PA was an independent risk factor for VF after adjusting for age and sex (odds ratio, 3.16; 95% confidence interval, 1.12-8.92; p = 0.017). Among patients with unilateral PA, serum cortisol concentrations after 1 mg dexamethasone suppression test were higher in those with VF (1.32 ± 0.67 g/dl) than those without (0.96 ± 0.33 g/dl; p = 0.048).

Conclusions: Unilateral PA is an independent risk factor for VF, which is associated with autonomous cortisol secretion. Thus, careful management is required to prevent the development of VF in patients with unilateral PA.

SAT-551 Sparing Confirmatory Tests in Primary Aldosteronism

Context: The current clinical guidelines suggest that confirmatory tests for primary aldosteronism (PA) may be excluded in some of patients who have elevated plasma aldosterone concentration (PAC) under plasma renin suppression. However, this has low priority evidence and is under debate in use of serum potassium. Objective: This study aimed to investigate an appropriate setting for sparing confirmatory tests in PA. Design and Setting: A retrospective cross-sectional study in a single referral center. Participants: This study included 327 patients who had hypertension under plasma renin suppression and underwent captopril challenge test (CCT) between January 2007 and April 2019. CCT results were used to diagnose PA. Main outcome measure: Diagnostic value of PAC and serum potassium in confirmation of PA. Results: Of the studied patients, 252 of 327 (77%) were diagnosed with PA. All 61 patients with PAC >30 ng/dl were diagnosed with PA. In patients with PAC between 20 and 30 ng/dl, 44 of 55 (80%) were diagnosed with PA, while all 26 with PAC between 20 to 30 ng/dl who had spontaneous hypokalemia were diagnosed with PA. Areceiver operator curve analysis showed that the sensitivity of diagnosis of PA is 100% in our patients, when PAC set at > 28.8 ng/dl and showed that the sensitivity of diagnosis of PA is 100% in our patients with spontaneous hypokalemia, who had PAC < 30 ng/dl, when PAC was set at > 19.2 ng/dl. While, the prevalence of PA was higher in patients with hypokalemia, who had PAC between 10 and 20 ng/dl than in those with PAC < 10 ng/dl. Collectively, 100 out of 102 (98%) with hypokalemia, who had PAC > 10 ng/dl were diagnosed as PA. The proportion of unilateral PA determined by adrenal vein sampling (AVS) was higher in patients who had PAC >30 ng/dl or those with spontaneous hypokalemia who had PAC between 20 and 30 ng/dl than those who did not meet the criteria (76% vs. 17%, P<0.001). Conclusion: Confirmatory tests in PA could be spared in patients who have typical features of PA and these patients had a high probability of unilateral PA on AVS.

Role of Aldosterone and Potassium Levels in Sparing Confirmatory Tests in Primary Aldosteronism

CONTEXT

The current clinical guidelines suggest that confirmatory tests for primary aldosteronism (PA) may be excluded in some of patients who have elevated plasma aldosterone concentration (PAC) under plasma renin suppression. However, this has low-priority evidence and is under debate in use of serum potassium.

OBJECTIVE

This study aimed to investigate an appropriate setting for sparing confirmatory tests in PA.

DESIGN AND SETTING

A retrospective cross-sectional study in a single referral center.

PARTICIPANTS

This study included 327 patients who had hypertension under plasma renin suppression and underwent the captopril challenge test (CCT) between January 2007 and April 2019. CCT results were used to diagnose PA.

MAIN OUTCOME MEASURE

Diagnostic value of PAC and serum potassium in confirmation of PA.

RESULTS

Of the studied patients, 252 of 327 (77%) were diagnosed with PA. All 61 patients with PAC > 30 ng/dL were diagnosed with PA. In patients with PAC between 20 and 30 ng/dL, 44 of 55 (80%) were diagnosed with PA, while all 26 with PAC between 20 to 30 ng/dL who had spontaneous hypokalemia were diagnosed with PA. The proportion of unilateral PA determined by adrenal vein sampling (AVS) was higher in patients who had PAC > 30 ng/dL or those with spontaneous hypokalemia who had PAC between 20 and 30 ng/dL than those who did not meet the criteria (76% vs. 17%, P < .001).

CONCLUSION

Confirmatory tests in PA could be spared in patients who have typical features of PA and these patients had a high probability of unilateral PA on AVS.

Pheochromocytoma and paraganglioma: An emerging cause of secondary osteoporosis

CONTEXT

Pheochromocytoma (PHEO) and paraganglioma (PGL) (PHEO and PGL: PPGLs) are catecholamine-producing neuroendocrine tumors, which are known to be associated with low bone mineral density (BMD). However, it remains unknown whether PPGLs are associated with high prevalence of osteoporotic fracture and if so, whether their surgical resection improves BMD has been addressed.

OBJECTIVE

To evaluate the risk of vertebral fracture (VF) in PPGLs and the improvement of BMD after surgery.

DESIGN AND SETTINGS

A retrospective cross-sectional study in a single referral center.

PARTICIPANTS

This study included the following patients: 1) 49 patients with PPGLs and 61 patients with non-functional AT who were examined radiograph of the spine, 2) 23 patients with PPGLs who were examined BMD at follow-up.

INTERVENTION

1) The prevalence of VF was evaluated between PPGLs and non-functional AT. 2) In PPGLs, BMD was evaluated at baseline and after surgery.

RESULTS

PPGLs had a higher prevalence of VF (43% [21/49]) than non-functional AT (16% [10/61]; p = 0.002). PPGLs were associated with VF after adjusting for age and sex (odds ratio, 4.47; 95% confidence interval, 1.76-11.3; p = 0.001). In PPGLs, BMD at the lumber spine was improved (before: 0.855 ± 0.198 g/cm², after: 0.888 ± 0.169 g/cm², mean of the difference: 0.032 g/cm², p = 0.026), with 3.8% increase.

CONCLUSION

This study demonstrates that PPGLs was associated with VF and that their surgical resection contributes to the improvement of BMD in the trabecular bone. These observations support the notion that PPGLs are an emerging cause of secondary osteoporosis.

Unilateral primary aldosteronism as an independent risk factor for vertebral fracture

CONTEXT

Primary aldosteronism (PA) is known to increase vertebral fracture (VF), although the detailed mechanism remains to be elucidated. We hypothesized that the PA subtype is associated with VF.

OBJECTIVE

To evaluate whether unilateral PA is associated with the prevalence of VF.

DESIGN

This was a retrospective cross-sectional study in a single referral centre.

PATIENTS

We identified 210 hypertensive patients whose clinical data were available for case-detection results. One hundred and fifty-two patients were diagnosed with PA using captopril challenge tests.

MEASUREMENTS

We measured the prevalence of VF, according to PA subtype.

RESULTS

One hundred thirteen patients with PA were subtype classified by adrenal vein sampling. Of these, 37 patients had unilateral PA, 76 patients had bilateral PA, 58 patients had non-PA; 39 patients with PA were not subtype-classified. Patients with PA had a higher prevalence of VF (29%, 44/152) than those with non-PA (12%, 7/58; P = .011). Moreover, unilateral PA had a higher prevalence of VF (46%, 17/37) than bilateral PA (20%, 15/76; P = .021). There was no significant difference in the prevalence of VF between bilateral PA and non-PA. Unilateral PA was an independent risk factor for VF after adjusting for age and sex (OR: 3.16, 95% confidence interval: 1.12-8.92; P = .017). Among patients with unilateral PA, serum cortisol concentrations after 1-mg dexamethasone suppression test were higher in those with VF (1.32 ± 0.67 g/dL) than those without (0.96 ± 0.33 g/dL; P = .048).

CONCLUSIONS

Unilateral PA is an independent risk factor for VF.

Seasonal Variation in Severe Glucose-lowering Drug-induced Hypoglycemia in Patients with Type 2 Diabetes

Objective Glucose-lowering drug-induced hypoglycemia is a serious complication and there have been a few reports of seasonal variations in hypoglycemia in patients with type 2 diabetes. The aim of the present study was to examine the association between severe drug-induced hypoglycemia and seasonal variations, and to elucidate the contributing factors. Methods This retrospective, single center clinical study, analyzed the cases of 125 patients who required emergency hospitalization for severe drug-induced hypoglycemia between January 1, 2001 and December 31, 2014. The period from November to April was defined as the cold season. Results Severe hypoglycemia occurred more often in the cold season than in the warm season. In the cold season, 62 of 9,981 (0.6%) emergency department visits involved patients who required hospitalization for drug-induced hypoglycemia. In contrast, in the warm season, 27 of 8,649 (0.3%) visits involved patients who required hospitalization for drug-induced hypoglycemia (p=0.002). The proportion of patients treated with sulfonylurea (SU) in the cold season was higher than that in the warm season. Even the use of low-dose SU caused hypoglycemia in the cold season. In the SU-treated group, the proportion of patients with white blood cell and/or C-reactive protein elevation was higher in the cold season than in the warm season (p=0.04). Conclusion Severe glucose-lowering drug-induced hypoglycemia occured more frequently in the cold season than in the warm season, and was associated with an inflammatory state in patients treated with SU.

Correlation Between Lateralization Index of Adrenal Venous Sampling and Standardized Outcome in Primary Aldosteronism

Objectives

The aim of this study was to investigate the impact of adrenal venous sampling (AVS) lateralization cutoffs on surgical outcomes.

Patients and Methods

Cosyntropin-stimulated AVS was used to guide surgical management of 377 patients with primary aldosteronism (PA) who were evaluated 6 months after surgery.

Main Outcome Measures

The proportion of patients that achieved clinical benefit and complete biochemical success based on the AVS aldosterone lateralization index (LI) was determined.

Results

Clinical benefit was achieved in 29 of 47 patients with an LI between 2 and 4, in 66 of 101 with an LI between 4 and 10, and in 158 of 203 with an LI > 10 (P < 0.01 for trend). Complete biochemical success was achieved in 27 of 42 with an LI between 2 and 4, in 60 of 76 with an LI between 4 and 10, and in 127 of 155 with an LI > 10 (P = 0.024 for trend). After adjustment for confounders and using those patients with an LI between 2 and 4 as a reference, a clinical benefit was associated only with those with an LI > 10 (OR, 2.30; 95% CI, 1.03 to 5.16), whereas complete biochemical success was associated with those with an LI between 4 and 10 (OR, 2.83; 95% CI, 1.14 to 7.01) or LI > 10 (OR, 3.55; 95% CI, 1.47 to 8.55).

Conclusions

Difference of clinical outcome was relatively small when strict LI diagnostic threshold was used; biochemical cure was sufficiently achieved when an LI > 4 was used. Our study by standardized outcome measures validated that an LI > 4 may be appropriate for determining unilateral disease in PA.

Paraganglioma as a risk factor for bone metastasis

Malignant pheochromocytoma (PHEO) and paraganglioma (PGL) (PHEO and PGL: PPGL) are frequently associated with bone metastasis. Bone metastasis requires long-term management and may lead to skeletal-related events (SREs) that remarkably reduce patients' quality of life (QOL). The aim of this study was to elucidate the risk factors for developing bone metastasis in patients with PPGL. The medical records of 40 consecutive adult patients with malignant PPGL at the National Hospital Organization Kyoto Medical Center between 2006 and 2016 were reviewed. SREs were defined as pathologic fracture, spinal cord compression, and the need for bone irradiation and/or surgery. PHEO (20/40) and PGL (20/40) were each present in 50% of the patients. Bone was the most frequent site of metastasis, detected in 60% (24/40). Bone metastasis was more frequent in patients with PGL (16/20, 80%) than in patients with PHEO (8/20, 40%) (p = 0.02). Half (12/24) of the patients with bone metastasis had at least one SRE. Extra-skeletal invasion of the spine, defined as local infiltration to the surrounding tissue beyond the cortical bone, was more frequently observed in patients with bone metastasis associated with SREs than without them (p = 0.001). Careful follow-up and management are warranted especially in patients with PGL as a risk factor for bone metastasis and with extra-skeletal invasion of the spine as risk factor of SREs.

Association between the risk of falls and osteoporotic fractures in patients with type 2 diabetes mellitus

Diabetes mellitus is associated with an increased risk of falls, which increases the incidence of osteoporotic fractures and accordingly decreases quality of life. However, the association between fall risk and diabetic complications is not completely understood. Therefore, the aim of this study was to examine the association between fall risk and osteoporotic fractures in patients with type 2 diabetes mellitus (T2DM). We enrolled 194 Japanese patients with T2DM and assessed their fall risk using a brief interview form that included five items covering physical and social aspects of functioning and environmental factors. We examined the associations between fall risk and the presence of diabetic complications, such as neuropathy, retinopathy, nephropathy, cardiovascular disease, cerebrovascular disease, peripheral artery disease (PAD), and osteoporotic fractures (including any fracture and vertebral fractures only). In the multivariate logistic regression analysis, a longer history of T2DM, the presence of neuropathy and PAD, and a history of any fractures were significantly and positively associated with the risk of falls. On the other hand, a lower body mass index, the presence of neuropathy, and the risk of falls were independently and positively associated with the risk of any fracture. When fractures were limited to vertebral fractures only, the association with the risk of falls remained significant. We found that the risk of falls and osteoporotic fractures were associated in patients with T2DM and that a brief screening test of the risk of falls was useful for assessing the risk of osteoporotic fractures.

Advanced Glycation End Product 3 (AGE3) Increases Apoptosis and the Expression of Sclerostin by Stimulating TGF-β Expression and Secretion in Osteocyte-Like MLO-Y4-A2 Cells

Advanced glycation end products (AGEs) cause bone fragility due to deterioration in bone quality. We previously reported that AGE3 induced apoptosis and inhibited differentiation via increased transforming growth factor (TGF)-β signaling in osteoblastic cells. Additionally, we demonstrated that AGE3 increased apoptosis and sclerostin expression and decreased receptor activator of nuclear factor-κB ligand (RANKL) expression in osteocyte-like cells. However, it remains unclear whether TGF-β signaling is involved in the effects of AGEs on apoptosis and the expression of sclerostin and RANKL in osteocytes. Effects of AGE3 on apoptosis of mouse osteocyte-like MLO-Y4-A2 cells were examined by DNA fragmentation ELISA. Expression of TGF-β, sclerostin, and RANKL was evaluated using real-time PCR, Western blotting, and ELISA kits. To block TGF-β signaling, we used SD208, a TGF-β type I receptor kinase inhibitor. AGE3 (200 µg/mL) significantly increased apoptosis and mRNA expression of Sost, the gene encoding sclerostin, and decreased Rankl mRNA expression in MLO-Y4-A2 cells. AGE3 significantly increased the expression of TGF-β. Co-incubation of SD208 with AGE3 significantly rescued AGE3-induced apoptosis in a dose-dependent manner. Moreover, SD208 restored AGE3-increased mRNA and protein expression of sclerostin. In contrast, SD208 did not affect AGE3-decreased mRNA and protein expression of RANKL. These findings suggest that AGE3 increases apoptosis and sclerostin expression through increasing TGF-β expression in osteocytes, and that AGE3 decreases RANKL expression independent of TGF-β signaling.

Simvastatin rescues homocysteine-induced apoptosis of osteocytic MLO-Y4 cells by decreasing the expressions of NADPH oxidase 1 and 2

Clinical studies have shown that hyperhomocysteinemia is associated with bone fragility. Homocysteine (Hcy) induces apoptosis of osteoblastic cell lineage by increasing oxidative stress, which may contribute to Hcy-induced bone fragility. Statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, ameliorate oxidative stress by regulating oxidant and anti-oxidant enzymes. However, the effects of statins on Hcy-induced apoptosis of osteocytes are unknown. This study was thus aimed to investigate whether or not statins prevent Hcy-induced apoptosis of osteocytic MLO-Y4 cells and regulate NADPH oxidase (Nox) expression. TUNEL staining showed that 5 mM Hcy induced apoptosis of MLO-Y4 cells, and that co-incubation of 10(-9) or 10(-8) M simvastatin significantly suppressed the apoptotic effect. Moreover, we confirmed the beneficial effect of simvastatin against Hcy's apoptotic effect by using a DNA fragment ELISA assay. However, TUNEL staining showed no significant effects of pravastatin, a hydrophilic statin, on the Hcy-induced apoptosis. Real-time PCR showed that Hcy increased the mRNA expressions of Nox1 and Nox2, whereas simvastatin inhibited the stimulation of Nox1 and Nox2 expressions by Hcy. In contrast, neither Hcy nor simvastatin had any effect on Nox4 expression. These findings indicate that simvastatin prevents the detrimental effects of Hcy on the apoptosis of osteocytes by regulating the expressions of Nox1 and Nox2, suggesting that statins may be beneficial for preventing Hcy-induced osteocyte apoptosis and the resulting bone fragility.