Growth hormone increase by luteinizing hormone-releasing hormone reflects gonadotroph-related characteristics in acromegaly.

PURPOSE: We previously showed the clinical characteristics of acromegaly with a paradoxical growth hormone (GH) response to oral glucose or thyrotropin-releasing hormone. However, the clinical characteristics of acromegaly with an increased GH response to luteinizing hormone-releasing hormone (LHRH responders) remain unclear. The aim of the present study was to evaluate the clinical characteristics, especially gonadotroph-related characteristics of LHRH responders in acromegaly. METHODS: The clinical characteristics of 33 LHRH responders and 81 LHRH nonresponders were compared. RESULTS: No differences in age, sex or basal serum levels of GH, insulin-like growth factor-1 (IGF-1), and gonadotropin were observed between the two groups. Steroidogenic factor 1 (SF-1), gonadotropin-releasing hormone receptor (GnRHR), and LH expression was more frequently observed in LHRH responders (P < 0.05). In addition, a greater increased rate of GH after LHRH loading, and the proportion of GnRHR and gonadotropin expression was observed in pituitary tumor with SF-1 expression than that without the expression (P < 0.01). LHRH responders showed a greater GH decrease in the octreotide test and a greater IGF-1 decrease after first-generation somatostatin ligand than LHRH nonresponders (P < 0.05). Furthermore, the proportion of hypointense pituitary tumors on T2-weighted magnetic resonance imaging and tumors with densely granulated type was higher in LHRH responders than in LHRH nonresponders, respectively (P < 0.05). No difference between the two groups was observed in either somatostatin receptor 2 or 5 expression. CONCLUSIONS: The increased GH response to LHRH is associated with the gonadotroph-related characteristics. This response may reflect the biological characteristics of somatotroph tumors.

The role of oxidative stress, glucocorticoid receptor and ARMC5 in lipid metabolism.

Lipid metabolism includes lipogenesis, lipolysis, and cholesterol metabolism and it exerts a wide range of biological effects. We previously found novel roles of adipocyte oxidative stress in diet-induced obesity, adipocyte glucocorticoid receptor in Cushing syndrome, and ARMC5 in adrenocortical cells. Using genetically modified mice in which oxidative stress was eliminated or augmented specifically in adipose tissues, we have been able to elucidate that obesity-induced oxidative stress inhibited healthy adipose expansion and ameliorated insulin sensitivity. Using adipocyte-specific glucocorticoid receptor knockout mice, we found that glucocorticoids also inhibited healthy adipose expansion and decreased insulin sensitivity. This was partly due to the transcriptional upregulation of ATGL. We identified ARMC5 as a novel ubiquitin E3 ligase of full-length SREBF, a master regulator of lipid metabolism. In adrenocortical cells, ARMC5 suppresses SREBF2 activity, and loss of ARMC5 may lead to cholesterol accumulation and the development of primary bilateral macronodular adrenal hyperplasia.

Primary aldosteronism patients with previous cardiovascular and cerebrovascular events have high aldosterone responsiveness to ACTH stimulation.

Aldosterone secretion in primary aldosteronism (PA) is often regulated by adrenocorticotropic hormone (ACTH) in addition to its autonomous secretion. However, the clinical characteristics and risk of cardiovascular and cerebrovascular (CCV) events in PA patients with aldosterone responsiveness to ACTH stimulation remain unclear. This study aimed to investigate the prevalence of CCV events in PA patients with high aldosterone responsiveness to ACTH stimulation. A retrospective cross-sectional study was conducted as part of the Japan Primary Aldosteronism Study/Japan Rare Intractable Adrenal Disease project. PA patients with adrenal venous sampling (AVS) between January 2006 and March 2019 were enrolled. The ACTH-stimulated plasma aldosterone concentration (PAC) of the inferior vena cava during AVS was used to evaluate aldosterone responsiveness to ACTH. We analyzed the relationship between responsiveness and previous CCV events. Logistic regression analysis demonstrated that the ΔPAC (the difference between the PAC measurements before and after ACTH stimulation) significantly increased the odds of previous CCV events in PA patients after adjusting for classical CCV event risk factors, baseline PAC and duration of hypertension (relative PAC: odds ratio [OR], 2.896; 95% confidence interval [CI], 0.989-8.482; ΔPAC: OR, 2.344; 95% CI, 1.149-4.780; ACTH-stimulated PAC: OR, 2.098; 95% CI, 0.694-6.339). This study clearly demonstrated that aldosterone responsiveness to ACTH is closely related to previous CCV events. The responsiveness of the PAC to ACTH could be useful in predicting CCV event risk.Registration Number in UMIN-CTR is UMIN000032525.

HSP47 levels determine the degree of body adiposity.

Adiposity varies among individuals with the influence of diverse physiological, pathological, environmental, hormonal, and genetic factors, but a unified molecular basis remains elusive. Here, we identify HSP47, a collagen-specific chaperone, as a key determinant of body adiposity. HSP47 expression is abundant in adipose tissue; increased with feeding, overeating, and obesity; decreased with fasting, exercise, calorie restriction, bariatric surgery, and cachexia; and correlated with fat mass, BMI, waist, and hip circumferences. Insulin and glucocorticoids, respectively, up- and down-regulate HSP47 expression. In humans, the increase of HSP47 gene expression by its intron or synonymous variants is associated with higher body adiposity traits. In mice, the adipose-specific knockout or pharmacological inhibition of HSP47 leads to lower body adiposity compared to the control. Mechanistically, HSP47 promotes collagen dynamics in the folding, secretion, and interaction with integrin, which activates FAK signaling and preserves PPARγ protein from proteasomal degradation, partly related to MDM2. The study highlights the significance of HSP47 in determining the amount of body fat individually and under various circumstances.

Favine/CCDC3 deficiency accelerated atherosclerosis and thrombus formation is associated with decreased MEF2C-KLF2 pathway.

Currently, no mouse models manifest calcification and thrombus formation, which is frequently associated with human atherosclerosis. We demonstrated that lack of Favine/CCDC3 in apoE knockout mice accelerated atherosclerosis accompanied by large cholesterol crystals and calcification, and also promoted thrombus formation in the left ventricle and arteries. Circulating Favine was detectable in WT mouse plasma. RNA-sequencing analysis of aortae in DKO mice showed similar gene expression patterns of human atherosclerosis with unstable and vulnerable plaques. Importantly, human FAVINE mRNA expressions were lower in atheroma plaque than in adjacent intact aortic tissue and decreased with the progression of atherosclerosis. Pathway analysis of aortae in DKO mice suggested the decrease of the MEF2C-KLF2-mediated transcriptional pathway. Favine insufficiency and its attenuated downstream pathways may increase atherosclerosis progression with calcification and thrombus, which have not previously been fully modeled in experimental animals. Favine and its downstream pathways may have therapeutic potential for atherosclerosis.

GRP78, a Novel Host Factor for SARS-CoV-2: The Emerging Roles in COVID-19 Related to Metabolic Risk Factors.

The outbreak of coronavirus disease 19 (COVID-19), caused by the infection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in an unprecedented amount of infection cases and deaths, leading to the global health crisis. Despite many research efforts, our understanding of COVID-19 remains elusive. Recent studies have suggested that cell surface glucose-regulated protein 78 (GRP78) acts as a host co-receptor for SARS-CoV-2 infection and is related to COVID-19 risks, such as older age, obesity, and diabetes. Given its significance in a wide range of biological processes, such as protein homeostasis and cellular signaling, GRP78 might also play an important role in various stages of the viral life cycle and pathology of SARS-CoV-2. In this perspective, we explore the emerging and potential roles of GRP78 in SARS-CoV-2 infection. Additionally, we discuss the association with COVID-19 risks and symptoms. We hope this review article will be helpful to understand COVID-19 pathology and promote attention and study of GRP78 from many clinical and basic research fields.

ARMC5-CUL3 E3 ligase targets full-length SREBF in adrenocortical tumors.

Inactivating mutations of ARMC5 are responsible for the development of bilateral macronodular adrenal hyperplasia (BMAH). Although ARMC5 inhibits adrenocortical tumor growth and is considered a tumor-suppressor gene, its molecular function is poorly understood. In this study, through biochemical purification using SREBF (SREBP) as bait, we identified the interaction between SREBF and ARMC5 through its Armadillo repeat. We also found that ARMC5 interacted with CUL3 through its BTB domain and underwent self-ubiquitination. ARMC5 colocalized with SREBF1 in the cytosol and induced proteasome-dependent degradation of full-length SREBF through ubiquitination. Introduction of missense mutations in Armadillo repeat of ARMC5 attenuated the interaction between SREBF, and introduction of mutations found in BMAH completely abolished its ability to degrade full-length SREBF. In H295R adrenocortical cells, silencing of ARMC5 increased full-length SREBFs and upregulated SREBF2 target genes. siARMC5-mediated cell growth was abrogated by simultaneous knockdown of SREBF2 in H295R cells. Our results demonstrate that ARMC5 was a substrate adaptor protein between full-length SREBF and CUL3-based E3 ligase, and they suggest the involvement of the SREBF pathway in the development of BMAH.

SARS-CoV-2 infection impairs the insulin/IGF signaling pathway in the lung, liver, adipose tissue, and pancreatic cells via IRF1.

BACKGROUND: COVID-19 can cause multiple organ damages as well as metabolic abnormalities such as hyperglycemia, insulin resistance, and new onset of diabetes. The insulin/IGF signaling pathway plays an important role in regulating energy metabolism and cell survival, but little is known about the impact of SARS-CoV-2 infection. The aim of this work was to investigate whether SARS-CoV-2 infection impairs the insulin/IGF signaling pathway in the host cell/tissue, and if so, the potential mechanism and association with COVID-19 pathology. METHODS: To determine the impact of SARS-CoV-2 on insulin/IGF signaling pathway, we utilized transcriptome datasets of SARS-CoV-2 infected cells and tissues from public repositories for a wide range of high-throughput gene expression data: autopsy lungs from COVID-19 patients compared to the control from non-COVID-19 patients; lungs from a human ACE2 transgenic mouse infected with SARS-CoV-2 compared to the control infected with mock; human pluripotent stem cell (hPSC)-derived liver organoids infected with SARS-CoV-2; adipose tissues from a mouse model of COVID-19 overexpressing human ACE2 via adeno-associated virus serotype 9 (AAV9) compared to the control GFP after SARS-CoV-2 infection; iPS-derived human pancreatic cells infected with SARS-CoV-2 compared to the mock control. Gain and loss of IRF1 function models were established in HEK293T and/or Calu3 cells to evaluate the impact on insulin signaling. To understand the mechanistic regulation and relevance with COVID-19 risk factors, such as older age, male sex, obesity, and diabetes, several transcriptomes of human respiratory, metabolic, and endocrine cells and tissue were analyzed. To estimate the association with COVID-19 severity, whole blood transcriptomes of critical patients with COVID-19 compared to those of hospitalized noncritical patients with COVID-19. RESULTS: We found that SARS-CoV-2 infection impaired insulin/IGF signaling pathway genes, such as IRS, PI3K, AKT, mTOR, and MAPK, in the host lung, liver, adipose tissue, and pancreatic cells. The impairments were attributed to interferon regulatory factor 1 (IRF1), and its gene expression was highly relevant to risk factors for severe COVID-19; increased with aging in the lung, specifically in men; augmented by obese and diabetic conditions in liver, adipose tissue, and pancreatic islets. IRF1 activation was significantly associated with the impaired insulin signaling in human cells. IRF1 intron variant rs17622656-A, which was previously reported to be associated with COVID-19 prevalence, increased the IRF1 gene expression in human tissue and was frequently found in American and European population. Critical patients with COVID-19 exhibited higher IRF1 and lower insulin/IGF signaling pathway genes in the whole blood compared to hospitalized noncritical patients. Hormonal interventions, such as dihydrotestosterone and dexamethasone, ameliorated the pathological traits in SARS-CoV-2 infectable cells and tissues. CONCLUSIONS: The present study provides the first scientific evidence that SARS-CoV-2 infection impairs the insulin/IGF signaling pathway in respiratory, metabolic, and endocrine cells and tissues. This feature likely contributes to COVID-19 severity with cell/tissue damage and metabolic abnormalities, which may be exacerbated in older, male, obese, or diabetic patients.

Ketone body 3-hydroxybutyrate enhances adipocyte function.

Ketone bodies, including 3HBA, are endogenous products of fatty acid oxidation, and Hmgcs2 is the first rate-limiting enzyme of ketogenesis. From database analysis and in vivo and in vitro experiments, we found that adipose tissue and adipocytes express Hmgcs2, and that adipocytes produce and secrete 3HBA. Treatment with 3HBA enhanced the gene expression levels of the antioxidative stress factors, PPARγ, and lipogenic factors in adipose tissue in vivo and in adipocytes in vitro, accompanied by reduced ROS levels. Knockdown of endogenous Hmgcs2 in adipocytes markedly decreased 3HBA levels in adipocytes and decreased the gene expression levels of the antioxidative stress factors, PPARγ, and lipogenic factors with increased ROS levels. Conversely, overexpression of Hmgcs2 in adipocytes increased 3HBA secretion from adipocytes and enhanced the gene expression levels of the antioxidative stress factors, PPARγ, and lipogenic factors. These results demonstrate that 3HBA plays significant roles in enhancing the physiological function of adipocytes.

Lactate dehydrogenase regulates basal glucose uptake in adipocytes.

Plasma glucose levels are homeostatically regulated within strict boundaries and are maintained through a balance between peripheral glucose uptake and hepatic glucose production. However, little is known about the regulatory mechanism of glucose uptake in adipocytes during fasting. Under fasting conditions, the expression levels of 8 glycolytic enzymes were significantly reduced in adipose tissue. Among them, we focused on lactate dehydrogenase A (LDHA), the last enzyme of the glycolytic pathway. Under fasting conditions, both LDHA and Glut1 protein levels tended to decrease in adipose tissue. To elucidate the significance of LDHA in adipocytes, we generated adipocyte-specific LDHA knockout mice (AdLDHAKO) for the first time. AdLDHAKO mice showed no apparent changes in body weight or tissue weight. Under fasting conditions, AdLDHAKO mice exhibited a significant reduction in Glut1 protein levels and glucose uptake in adipose tissues compared with control mice. Similarly, siRNA of LDHA in 3T3-L1 adipocytes reduced Glut1 protein levels and basal glucose uptake. Moreover, treatment with bafilomycin A1, an inhibitor of lysosomal protein degradation, restored Glut1 protein levels by siRNA of LDHA. These results indicate that LDHA regulates Glut1 expression and basal glucose uptake in adipocytes.

Loss of RUBCN/rubicon in adipocytes mediates the upregulation of autophagy to promote the fasting response.

Upon fasting, adipocytes release their lipids that accumulate in the liver, thus promoting hepatic steatosis and ketone body production. However, the mechanisms underlying this process are not fully understood. In this study, we found that fasting caused a substantial decrease in the adipose levels of RUBCN/rubicon, a negative regulator of macroautophagy/autophagy, along with an increase in autophagy. Adipose-specific rubcn-knockout mice exhibited systemic fat loss that was not accelerated by fasting. Genetic inhibition of autophagy in adipocytes in fasted mice led to a reduction in fat loss, hepatic steatosis, and ketonemia. In terms of mechanism, autophagy decreased the levels of its substrates NCOA1/SRC-1 and NCOA2/TIF2, which are also coactivators of PPARG/PPARγ, leading to a fasting-induced reduction in the mRNA levels of adipogenic genes in adipocytes. Furthermore, RUBCN in adipocytes was degraded through the autophagy pathway, suggesting that autophagic degradation of RUBCN serves as a feedforward system for autophagy induction during fasting. Collectively, we propose that loss of adipose RUBCN promotes a metabolic response to fasting via increasing autophagic activity.

Transforming growth factor ß1 signaling links extracellular matrix remodeling to intracellular lipogenesis upon physiological feeding events.

Adipose tissue dynamically changes its mass in response to external nutritional status, which plays an important role in maintaining the lipid homeostasis. Physiologically, feeding events are associated with the expansion of adipose tissue, but little is known about the detailed molecular mechanisms of this expansion. Here, using comprehensive transcriptome analysis, we found that levels of transforming growth factor ß1 (TGF-ß1), a key regulator of extracellular matrix (ECM) remodeling, were increased in adipose tissue under feeding conditions and associated with the lipogenic pathway. In addition, TGF-ß receptors are highly expressed in adipose tissue, and pharmacological inhibition of TGF-ß1 reduced adipose tissue mass and caused ectopic lipid accumulation in the liver. This reduced fat mass was associated with decreased gene expression in ECM remodeling and lipogenesis. Furthermore, similar results were observed in the adipose tissue of SMAD family member 3 knockout mice or upon systemic TGF-ß neutralization, with significant reductions in both ECM remodeling and lipogenesis-related genes. Mechanistically, we found that insulin-induced TGF-ß1 and cell-autonomous action remodels the ECM of adipocytes, which controls the downstream focal adhesion kinase-AKT signaling cascades and enhances the lipogenic pathway. Of note, destruction of collagens or matrix metalloproteinase/a disintegrin and metalloprotease activities, critical components of ECM remodeling, blocked TGF-ß1-mediated focal adhesion kinase-AKT signaling and the lipogenic pathway. Taken together, this study identifies a previously unknown lipogenic role of TGF-ß1 by which adipocytes can expand to adapt to physiological feeding events.

γENaC/CD9 in urinary extracellular vesicles as a potential biomarker of MR activity.

Primary aldosteronism (PA) is caused by autonomous overproduction of aldosterone, which induces organ damage directly via activation of the mineralocorticoid receptor (MR); however, no specific or sensitive biomarkers are able to reflect MR activity. Recently, it is found that urinary extracellular vesicles (uEVs) are secreted by multiple cell types in the kidney and are an enriched source of kidney-specific proteins. Here, we evaluate sodium transporters in uEVs as candidates of biomarkers of MR activity in the clinical setting. Sixteen patients were examined to determine their plasma aldosterone concentration (PAC) and renin activity, and their morning urine was collected. The protein levels of two sodium transporters in uEVs, γ-epithelial sodium channel (γENaC) and thiazide-sensitive sodium chloride cotransporter (NCC), were quantified by Western blot analysis, and their clinical correlation with PAC was determined. Consequently, we found PAC was significantly correlated with the γENaC protein level adjusted by the CD9 protein level in uEVs (correlation coefficient = 0.71). PAC was also correlated with the NCC protein level adjusted by the CD9 protein level in uEVs (correlation coefficient = 0.61). In two PA patients, treatment with an MR antagonist or adrenalectomy reduced γENaC/CD9 in uEVs. In conclusion, γENaC/CD9 in uEVs is a valuable biomarker of MR activity in PA patients and may be a useful biomarker for other MR-associated diseases.

Glutamine deficiency induces lipolysis in adipocytes.

Glutamine is the most abundant amino acid in the body, and adipose tissue is one of the glutamine-producing organs. Glutamine has important and unique metabolic functions; however, its effects in adipocytes are still unclear. 3T3-L1 adipocytes produced and secreted glutamine dependent on glutamine synthetase, but preadipocytes did not. The inhibition of glutamine synthetase by l-methionine sulfoximine (MSO) impaired the differentiation of preadipocytes to mature adipocytes, and this inhibitory effect of MSO was rescued by exogenous glutamine supplementation. Glutamine concentrations were low, and Atgl gene expression was high in epididymal white adipose tissues of fasting mice in vivo. In 3T3-L1 adipocytes, glutamine deprivation induced Atgl expression and increased glycerol concentration in culture medium. Atgl expression is regulated by FoxO1, and glutamine deprivation reduced FoxO1 phosphorylation (Ser256), indicating the activation of FoxO1. These results demonstrate that glutamine is necessary for the differentiation of preadipocytes and regulates lipolysis through FoxO1 in mature adipocytes.

Possible Involvement of Adipose Tissue in Patients With Older Age, Obesity, and Diabetes With SARS-CoV-2 Infection (COVID-19) via GRP78 (BIP/HSPA5): Significance of Hyperinsulinemia Management in COVID-19.

Aging, obesity, and diabetes are major risk factors for the severe progression and outcome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (coronavirus disease 2019 [COVID-19]), but the underlying mechanism is not yet fully understood. In this study, we found that the SARS-CoV-2 spike protein physically interacts with cell surface GRP78, which promotes the binding to and accumulation in ACE2-expressing cells. GRP78 was highly expressed in adipose tissue and increased in humans and mice with older age, obesity, and diabetes. The overexpression of GRP78 was attributed to hyperinsulinemia in adipocytes, which was in part mediated by the stress-responsive transcription factor XBP-1s. Management of hyperinsulinemia by pharmacological approaches, including metformin, sodium-glucose cotransporter 2 inhibitor, or ß3-adrenergic receptor agonist, decreased GRP78 gene expression in adipose tissue. Environmental interventions, including exercise, calorie restriction, fasting, or cold exposure, reduced the gene expression of GRP78 in adipose tissue. This study provides scientific evidence for the role of GRP78 as a binding partner of the SARS-CoV-2 spike protein and ACE2, which might be related to the severe progression and outcome of COVID-19 in patients with older age, obesity, and diabetes. The management of hyperinsulinemia and the related GRP78 expression could be a therapeutic or preventative target.

Age-dependent loss of adipose Rubicon promotes metabolic disorders via excess autophagy.

The systemic decline in autophagic activity with age impairs homeostasis in several tissues, leading to age-related diseases. A mechanistic understanding of adipocyte dysfunction with age could help to prevent age-related metabolic disorders, but the role of autophagy in aged adipocytes remains unclear. Here we show that, in contrast to other tissues, aged adipocytes upregulate autophagy due to a decline in the levels of Rubicon, a negative regulator of autophagy. Rubicon knockout in adipocytes causes fat atrophy and hepatic lipid accumulation due to reductions in the expression of adipogenic genes, which can be recovered by activation of PPARγ. SRC-1 and TIF2, coactivators of PPARγ, are degraded by autophagy in a manner that depends on their binding to GABARAP family proteins, and are significantly downregulated in Rubicon-ablated or aged adipocytes. Hence, we propose that age-dependent decline in adipose Rubicon exacerbates metabolic disorders by promoting excess autophagic degradation of SRC-1 and TIF2.

Metabolomic Analysis of Diet-Induced Obese Mice Supplemented with Eicosapentaenoic Acid.

Eicosapentaenoic acid (EPA) is an omega-3 fatty acid with anti-inflammatory effects. To determine the effects of EPA on metabolic pathways in obese adipose tissues and liver, mice were fed normal chow diet (NCD), high-fat diet (HFD), or 3% EPA-containing high fat diet (HFD+EPA) for 8 weeks. Metabolomic analysis was performed using epididymal adipose tissues (epi WAT) and liver. Metabolites that were specifically elevated in HFD+EPA, were assessed for their anti-inflammatory properties using RAW264.7 macrophage cells. Body and adipose tissue weights were significantly higher in HFD than NCD, and lower in HFD+EPA than HFD. Plasma insulin levels were significantly higher in HFD than NCD, and lower in HFD+EPA compared with HFD. Plasma monocyte chemotactic protein-1 (MCP-1) levels were higher in HFD than NCD, and tended to be lower in HFD+EPA than HFD. The levels of intermediate metabolites in the glycolytic pathways were lower in HFD compared with NCD and HFD+EPA in both epi WAT and liver, while intermediate metabolites of the TCA cycles were elevated in HFD and HFD+EPA compared with NCD in epi WAT. Among the metabolites in epi WAT, the levels of thiaproline, phenaceturic acid, and pipecolic acid were specifically elevated in HFD+EPA, but not in HFD or NCD. Treatment of RAW264.7 cells with thiaproline significantly ameliorated LPS-induced iNOS expression, while pipecolic acid inhibited LPS-induced IL-1ß expression. These results suggest that EPA normalizes glycolytic pathway intermediates in both epi WAT and liver, and induces metabolites with anti-inflammatory properties.

Adipocyte GR Inhibits Healthy Adipose Expansion Through Multiple Mechanisms in Cushing Syndrome.

In Cushing syndrome, excessive glucocorticoids lead to metabolic disturbances, such as insulin resistance, adipocyte hypertrophy, and liver steatosis. In vitro experiments have highlighted the importance of adipocyte glucocorticoid receptor (GR), but its metabolic roles in vivo have not been fully elucidated in Cushing syndrome. In this study, using clinical samples from patients with Cushing syndrome and adipocyte-specific GR knockout (AGRKO) mice, we investigated the roles of adipocyte GR and its clinical relevance in Cushing syndrome. Under chronic treatment with corticosterone, AGRKO mice underwent healthy adipose expansion with diminished ectopic lipid deposition and improved insulin sensitivity. These changes were associated with Atgl-mediated lipolysis through a novel intronic glucocorticoid-responsive element. Additionally, integrated analysis with RNA sequencing of AGRKO mice and clinical samples revealed that healthy adipose expansion was associated with dysregulation of tissue remodeling, preadipocyte proliferation, and expression of the circadian gene. Thus, our study revealed the roles of adipocyte GR on healthy adipose expansion and its multiple mechanisms in Cushing syndrome.

Obesity in Yap transgenic mice is associated with TAZ downregulation.

Obesity is characterized by an expansion of white adipose tissue (WAT) mass, which mainly consists of adipocytes. During the commitment and differentiation of adipocytes, PPARγ functions as a key transcriptional factor for adipogenesis, and is associated with its suppressive coregulator, TAZ. Previous studies have shown the importance of TAZ in adipogenesis using an in vitro model; however, the understanding of its role in adipogenesis in vivo remains limited. Here, we report a unique obese mouse model that is associated with TAZ downregulation, which arose from the overexpression of Yap, a Taz paralog. YAP activation facilitated Hippo signaling feedback, which induced a compensatory reduction in YAP, subsequently neutralizing its functional activity. This feedback also induced TAZ suppression and exclusion from the nucleus. In Yap transgenic mice, TAZ downregulation in adipose stem cells activated PPARγ, leading to their differentiation into mature adipocytes and consequently increased adipose tissue. These results highlight the in vivo necessity of TAZ for adipocyte commitment and differentiation, which could provide insight into anti-obesity therapeutics.

Impact of MR on mature adipocytes in high-fat/high-sucrose diet-induced obesity

Active glucocorticoid levels are elevated in the adipose tissue of obesity due to the enzyme 11 beta-hydroxysteroid dehydrogenase type 1. Glucocorticoids can bind and activate both glucocorticoid receptor (GR) and mineralocorticoid receptor (MR), and pharmacological blockades of MR prevent high-fat diet-induced obesity and glucose intolerance. To determine the significance of MR in adipocytes, we generated adipocyte-specific MR-knockout mice (AdipoMR-KO) and fed them high-fat/high-sucrose diet. We found that adipocyte-specific deletion of MR did not affect the body weight, fat weight, glucose tolerance or insulin sensitivity. While liver weight was slightly reduced in AdipoMR-KO, there were no significant differences in the mRNA expression levels of genes associated with lipogenesis, lipolysis, adipocytokines and oxidative stress in adipose tissues between the control and AdipoMR-KO mice. The results indicated that MR in mature adipocytes plays a minor role in the regulation of insulin resistance and inflammation in high-fat/high-sucrose diet-induced obese mice.