Targeting adipocyte ESRRA promotes osteogenesis and vascular formation in adipocyte-rich bone marrow

Excessive bone marrow adipocytes (BMAds) accumulation often occurs under diverse pathophysiological conditions associated with bone deterioration. Estrogen-related receptor α (ESRRA) is a key regulator responding to metabolic stress. Here, we show that adipocyte-specific ESRRA deficiency preserves osteogenesis and vascular formation in adipocyte-rich bone marrow upon estrogen deficiency or obesity. Mechanistically, adipocyte ESRRA interferes with E2/ESR1 signaling resulting in transcriptional repression of secreted phosphoprotein 1 (Spp1); yet positively modulates leptin expression by binding to its promoter. ESRRA abrogation results in enhanced SPP1 and decreased leptin secretion from both visceral adipocytes and BMAds, concertedly dictating bone marrow stromal stem cell fate commitment and restoring type H vessel formation, constituting a feed-forward loop for bone formation. Pharmacological inhibition of ESRRA protects obese mice against bone loss and high marrow adiposity. Thus, our findings highlight a therapeutic approach via targeting adipocyte ESRRA to preserve bone formation especially in detrimental adipocyte-rich bone milieu.

Theory-based cognitive-narrative intervention versus didactic education for promoting prompt care-seeking for acute myocardial infarction: A multisite mixed-methods randomized controlled trial

BACKGROUND

Prolonged delays by patients in making care-seeking decisions remain a significant obstacle to the effective management of acute myocardial infarction.

OBJECTIVES

This study aimed to compare the effects of a theory-based cognitive-narrative intervention with those of didactic education over a 24-month period on the participants' attitudes, beliefs, and knowledge regarding acute myocardial infarction, prehospital delay time, and the use of an ambulance. We also explored participants' engagement in the intervention.

DESIGN

This study adopted a sequential mixed-methods design comprising a multisite randomized controlled trial and a qualitative study.

METHODS

Community-dwelling adult patients with a prior history of acute myocardial infarction in the past year were recruited from four hospitals in Hong Kong. They were randomly assigned to an 8-week theory-based cognitive-narrative intervention that involved a vivid experience of complex decision-making or didactic education. The Acute Coronary Syndrome Response Index questionnaire was administered at baseline (T0) and at 3- (T1), 12- (T2), and 24-month (T3) follow-up time points. Prehospital delay time and the use of an ambulance were evaluated for those participants who had recurrent acute myocardial infarction attacks during the study period.

RESULTS

A total of 608 participants were randomly assigned to the theory-based cognitive-narrative intervention group (n = 304) or the didactic education group (n = 304). The intervention group reported greater improvements than the control group in their attitudes (β = -1.053, p = 0.002) and beliefs (β = -0.686, p = 0.041) regarding acute myocardial infarction and care-seeking at T1. These effects were sustained at T2 [attitudes (β = -0.797, p = 0.018); beliefs (β = -0.692, p = 0.047)] and T3 [attitudes (β = -0.717, p = 0.024); beliefs (β = -0.701, p = 0.032)]. Sixty-three participants experienced another acute myocardial infarction event by T2. The median delay times for the intervention and control groups were 3.13 h (interquartile range (IQR: 1.15-6.48)) and 4.82 h (IQR: 2.23-9.02), respectively. The prehospital delay time was significantly reduced in the intervention group compared with the control group (β = -0.07, p = 0.011). The qualitative findings echoed the quantitative findings, as participants indicated that the intervention helped them to understand the variable nature of the disease presentation, which enabled them to recognize the symptoms more readily.

CONCLUSION

The novel cognitive-narrative intervention used in this study effectively improved the participants' attitudes and beliefs regarding acute myocardial infarction and reduced the prehospital delay time.

TRIAL REGISTRATION

This study was registered with the International Clinical Trials Registry Platform of the World Health Organization (ChiCTR-IIC-17010576) on February 2, 2017; the first participant was recruited on January 11, 2018.

The mitotic regulator RCC2 promotes glucose metabolism through BACH1-dependent transcriptional upregulation of hexokinase II in glioma

Weighted gene co-expression network analysis (WGCNA) identified a cell-cycle module that is associated with poor prognosis and aggressiveness of glioma. One of the core members, Regulator of chromatin condensation 2 (RCC2) is a component of the chromosome passenger complex. Accumulating evidence suggests that RCC2 plays a vital role in the mitotic process and that abnormal RCC2 expression is involved in cancer development. Gene silencing experiments show that RCC2 is required for glioma cell proliferation and migration. RNA-Sequencing analysis reveals a dual role of RCC2 in both the cell cycle and metabolism. Specifically, RCC2 regulates G2/M progression via CDC2 phosphorylation at Tyrosine 15. Metabolomic analysis identifies a role for RCC2 in promoting the glycolysis and pentose phosphate pathway. RCC2 exerts effects on metabolism by stabilizing the transcription factor BACH1 at its C-terminus leading to the transcriptional upregulation of hexokinase 2 (HK2). These findings elucidate a novel PTEN/RCC2/BACH1/HK2 signaling axis that drives glioma progression through the dual regulation of mitotic cell cycle and glycolytic events.

Abstract 5647: PTEN loss is associated with elevation of cell cycle signature in human glioblastoma transcriptome

Glioblastoma is the most lethal type of brain cancer with universally poor prognosis. Despite advanced treatment, the cancer recurs frequently. Phosphatase and tensin homolog (PTEN) is a tumor suppressor gene whose mutations have been found to be one of the most frequent events in GBM. PTEN acts as a negative regulator of the phosphoinositide 3-kinase (PI3K) pathway. GBM transcriptome data from The Cancer Genome Atlas (TCGA) revealed a positive enrichment of cell cycle and PI3K pathway. Moreover, weighted gene co-expression network analysis (WGCNA) on TCGA GBMLGG cohort revealed a cell cycle-related module (‘cell-cycle’ module), which was shown to be positively correlated with PTEN mutation status. This ‘cell-cycle’ module also showed a positive correlation with glioma aggressiveness.We then utilized a nestin-cre;Pten-fl/fl mouse model to investigate the consequences of PTEN loss that may be involved in GBM. Based on our preliminary data, transcriptomic profiling of primary astrocytes derived from Pten knockout mice revealed an overlapping enrichment of cell cycle related pathways with human GBM. Four cell cycle genes, RCC1, RCC2, NEK2, and CHK2, were validated to be significantly upregulated in Pten-null astrocytes by qRT-PCR. Regulator of chromatin condensation 1 (RCC1) and Regulator of chromatin condensation 2 (RCC2) both belong to the RCC1 family. Accumulating evidence demonstrated that both RCC1 and RCC2 are involved in tumorigenesis of multiple cancers and cell cycle progression. By siRNA inhibition, we demonstrated that silencing of either RCC1 or RCC2 in glioblastoma cell lines suppresses GBM cell growth. Moreover, we found that RCC2 is essential for both G1-S and G2-M transition. Additionally, RCC2 silencing and a PI3K inhibitor LY294002 inhibit glioblastoma cell viability in a synergistic manner. In summary, PTEN deficiency leads to the alteration of cell cycle progression, which may promote tumorigenesis of glioblastoma. RCC1 and RCC2 have been demonstrated to be potential targets regulated by PTEN and affects cell viability. RCC2 was shown to be a key regulator of cell cycle progression. To further explore the RCC1 and RCC2 roles, we will find the potential downstream target of RCC1 and RCC2 and its potential therapeutic effect in vivo. Funding: This work is supported by a General Research Fund grant (#14113519) from the University Grants Committee of Hong Kong.

Citation Format: Tian Liu, Penelope Mei-Yu Or, Chi-Wai Wong, Stanley Kwok-Kuen Cheung, Yubing Wang, Yiwei Wang, Wayne Lut-Heng Ho, Andrew M. Chan. PTEN loss is associated with elevation of cell cycle signature in human glioblastoma transcriptome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5647.

Cell transcriptomic atlas of the non-human primate Macaca fascicularis

Studying tissue composition and function in non-human primates (NHPs) is crucial to understand the nature of our own species. Here we present a large-scale cell transcriptomic atlas that encompasses over 1 million cells from 45 tissues of the adult NHP Macaca fascicularis. This dataset provides a vast annotated resource to study a species phylogenetically close to humans. To demonstrate the utility of the atlas, we have reconstructed the cell-cell interaction networks that drive Wnt signalling across the body, mapped the distribution of receptors and co-receptors for viruses causing human infectious diseases, and intersected our data with human genetic disease orthologues to establish potential clinical associations. Our M. fascicularis cell atlas constitutes an essential reference for future studies in humans and NHPs.

Andrographolide prevents bone loss via targeting estrogen-related receptor-α-regulated metabolic adaption of osteoclastogenesis

BACKGROUND AND PURPOSE

Metabolic adaptation driven by oestrogen-related receptor-α (ERRα/NR3B1) is required to meet the increased energy demand during osteoclast differentiation. Here, we hypothesize that natural product, andrographolide, acts as an ERRα inverse agonist to inhibit osteoclastogenesis.

EXPERIMENTAL APPROACH

Virtual docking and site-directed mutagenesis analysis were employed to study the binding mode of andrographolide to ERRα. Co-immunoprecipitation, luciferase reporter assay, real-time polymerase chain reaction (PCR) and immunoblot analyses were performed to identify andrographolide as an ERRα inverse agonist. The pharmacological effects of andrographolide in vivo were assessed in mice models of osteopenia induced by either a high-fat diet in male or ovariectomy in female mice.

KEY RESULTS

ERRα-dependent expression of glutaminase, a rate-limiting enzyme of mitochondrial glutamine anaplerosis, is required for ex vivo bone marrow osteoclast differentiation. Andrographolide inhibited glutaminase expression induced by ERRα and co-activator peroxisome proliferator-activated receptor γ co-activator-1β (PGC-1β), leading to reduction in osteoclastogenesis. Andrographolide acted as an inverse agonist of ERRα by disrupting its interaction with co-activator PGC-1β. Phenylalanine 232, valine 395 and phenylalanine 399 of ERRα ligand-binding domain were confirmed to be essential for this effect. In contrast, glutaminase overexpression restored the impairment triggered by andrographolide. Accordingly, andrographolide suppressed osteoclastic bone resorption and attenuated bone loss in vivo.

CONCLUSIONS AND IMPLICATIONS

These findings demonstrate that andrographolide acts as an ERRα inverse agonist for perturbation of ERRα/PGC-1β/glutaminase axis-driven metabolic adaption during osteoclast differentiation, implying that andrographolide may be a promising natural compound for preventing physiological and pathological bone loss.

Shortening pre-hospital time delay in patients with acute myocardial infarction using a modelling-based narrative intervention with a virtual heart attack experience: a randomized controlled trial

Background

Prolonged delay in seeking treatment by patients with acute myocardial infarction (AMI) remains a significant therapeutic gap. Previous mass-media campaigns or brief educational interventions were largely ineffective in shortening pre-hospital patient delay. The brevity and didactic nature of these interventions are inadequate to address complex decision-making encountered by patients with AMI.

Purpose

This randomized controlled trial examined the effects of a theory-driven modelling-based narrative intervention on AMI knowledge, care-seeking intention as indicated by attitudes and beliefs regarding care-seeking for AMI, prehospital delay time and use of ambulance among AMI survivors.

Methods

A total of 285 of patients with history of at least one AMI were randomized 1:1 to modelling-based narrative intervention (n=144) and control with didactic education (n=141). The modelling-based narrative intervention comprised 4 weekly group-based interactive sessions to engage participants in mental rehearsals of the perceptual-cognitive processes in recognizing and responding to AMI symptoms through a virtual heart attack experience, then followed by a booster session one month later The control group received a 4-weekly education on factual information about AMI with traditional didactic education approach. Study endpoints included AMI knowledge, attitudes and belief about care-seeking for AMI to be measured at baseline, (T0), 3 months (T1), 12 months (T2) and 24 months (T3) after the intervention. Prehospital delay time and use of ambulance for an AMI attack were tracked since patients' enrolment until T3 endpoint of the study.

Results

Generalized estimating equation analysis indicated that the participants in the intervention group had significantly greater improvement in attitudes and beliefs about care seeking for AMI symptoms at all endpoints than those in the control group (Table 1). There were no between-group differences in the change of AMI knowledge score over the baseline and 3- or 12-month endpoints, such difference became significant at 24-month endpoint. A total of 78 participants, including 38 (26.4%) in the intervention group and 40 (28.4%) in the control groups, had experienced AMI symptoms and admitted to an emergency department during the follow-up period. The participants in the intervention group showed significant reduction in prehospital delay time than the control group (p=0.031). There was no between-group difference on use of ambulance (p=0.422) for those participants who had symptom attack during the follow-up period.

Conclusion

This study demonstrated favorable effects in shortening prehospital time delay and promoting positive attitudes and beliefs regarding care-seeking for AMI symptoms among AMI survivors. A virtual heart attack experience helped support them through a cognitive-perceptual processes in recognizing and interpreting AMI symptoms.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Early Career Scheme, Research Grants Council, Hong Kong

Abstract 1971: RCC2 promotes glioblastoma through regulation of G2-M progression

Regulator of chromatin condensation 2 (RCC2), also known as telophase disk protein of 60 kDa (TD-60), has been previously identified as a component of the chromosome passenger complex. Accumulating evidence suggested that RCC2 plays a vital role in the mitotic process and abnormal RCC2 expression is essential for cancer development including Glioblastoma Multiforme (GBM). GBM is the most lethal and frequent brain tumor. Even with the optimal therapy, the 5-year survival rate of GBM remains poor. TCGA data revealed an upregulation of RCC2 in human GBM. Our preliminary data showed that RCC2 was upregulated in PTEN knockout mice primary astrocytes, and loss of function of PTEN has been found in nearly 95% GBM patients. This indicated that RCC2 might act as a PTEN downstream regulator and promote glioblastoma progression. RCC2 has been reported to be essential for tumorigenesis which may act as a GEF for Rac1 or RalA GTPase. Coincidently, our study showed that silencing RCC2 could suppress GBM cell proliferation. Using RNA-seq, we identified 737 DEGs between control siRNA- and RCC2 siRNA-treated A1172 cells. GSEA analysis delineated G2-M progression as the most notably altered pathway by silencing RCC2. Indeed, we observed a G2-M arrest in cells with RCC2 silenced, suggesting that RCC2 is essential for G2-M progression. Additionally, the connectivity map (C-map) analysis was conducted and identified LY294002 and cephaeline as promising inhibitors for RCC2-associated gene signatures. Both LY294002 and cephaeline can synergistically inhibit glioblastoma cell viability with RCC2 silencing. In summary, our study demonstrated that RCC2 signaling is essential for GBM development. We provided evidence that RCC2 exerts a positive effect on G2-M progression. These findings may shed light on anti-RCC2 targeted therapy in GBM treatment.

Funding: This work is supported by a General Research Fund grant (#14113519) from the University Grants Committee of Hong Kong.

Citation Format: Tian Liu, Penelope Mei-Yu Or, Chi-Wai Wong, Wayne Lut-Heng Ho, Stanley Kwok-Kuen Cheung, Yubing Wang, Andrew M. Chan. RCC2 promotes glioblastoma through regulation of G2-M progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1971.

Medication-related problems in older people: how to optimise medication management

Older patients are at risk of medication-related problems because of age-related physiological changes and multiple medications taken for multiple co-morbidities. The resultant polypharmacy is frequently associated with inappropriate medication use, which in turn contributes to a range of adverse consequences, including geriatric syndromes (eg, falls, cognitive decline, urinary incontinence) and hospitalisation. In addition, medication non-adherence or discrepancies between the medications prescribed and those actually taken by patients, either intentional or unintentional, are prevalent and can lead to treatment failure. A large proportion of adverse drug events are preventable, and medication errors occur most commonly at the stages of prescribing and subsequent monitoring. There are a number of strategies to address these issues with the aim of ensuring safe prescribing. Furthermore, deprescribing with withdrawal of medications that are inappropriate or of minimal value for patients is increasingly emphasised for optimising medication management. In general, optimisation of medication management should be patient-centred, considering individual circumstances and preferences to determine the treatment goals or priorities for individual patients, and a multidisciplinary approach is recommended.

Dysfunction of estrogen-related receptor alpha-dependent hepatic VLDL secretion contributes to sex disparity in NAFLD/NASH development

Rationale: Men and postmenopausal women are more prone to developing non-alcoholic fatty liver disease/steatohepatitis (NAFLD/NASH) than premenopausal women. However, the pathological links and underlying mechanisms of this disparity are still elusive. The sex-difference in hepatic very low-density lipoprotein (VLDL) assembly and secretion may contribute to NAFLD development. Estrogen-related receptor alpha (ERRα) is a key regulator of several metabolic processes. We hypothesized that ERRα plays a role contributing to the sex-difference in hepatic VLDL assembly and secretion. Methods: VLDL secretion and essential genes governing said process were assessed in male and female mice. Liver-specific ERRα-deficient (ERRαLKO) mice were generated to assess the rate of hepatic VLDL secretion and alteration in target gene expression. Overexpression of either microsomal triglyceride transfer protein (Mttp) or phospholipase A2 G12B (Pla2g12b) by adenovirus was performed to test if the fatty liver phenotype in male ERRαLKO mice was due to defects in hepatic VLDL secretion. Female ERRαLKO mice were put on a diet high in saturated fat, fructose and cholesterol (HFHC) to promote NASH development. Wild type female mice were either ovariectomized or treated with tamoxifen to induce a state of estrogen deficiency or disruption in estrogen signaling. Adenovirus was used to overexpress ERRα in these mice to test if ERRα was sufficient to rescue the suppressed VLDL secretion due to estrogen dysfunction. Finally, wild type male mice on a high-fat diet (HFD) were treated with an ERRα inverse agonist to assess if suppressing ERRα activity pharmacologically would lead to fatty liver development. Results: ERRα is an indispensable mediator modulating hepatic triglyceride-rich very low-density lipoprotein (VLDL-TG) assembly and secretion through coordinately controlling target genes apolipoprotein B (Apob), Mttp and Pla2g12b in a sex-different manner. Hepatic VLDL-TG secretion is blunted in ERRαLKO mice, leading to hepatosteatosis which exacerbates endoplasmic reticulum stress and inflammation paving ways for NASH development. Importantly, ERRα acts downstream of estrogen/ERα signaling in contributing to the sex-difference in hepatic VLDL secretion effecting hepatic lipid homeostasis. Conclusions: Our results highlight ERRα as a key mediator which contributes to the sex disparity in NAFLD development, suggesting that selectively restoring ERRα activity in the liver may be a novel strategy for treating NAFLD/NASH.

Abstract 97: Analysis of Pten-null mouse astrocytes revealed overlapping transcribed genes with human glioblastoma transcriptome

Glioblastoma is an aggressive form of brain cancer with universally poor prognosis. Even with optimal therapy, the cancer recurs frequently. Phosphatase and tensin homolog (PTEN) is a tumor suppressor gene whose mutations are often found in multiple human cancers. PTEN encodes a lipid phosphatase and serves as a negative regulator of the phosphoinositide 3-kinase (PI3K) pathway. Cumulative evidence suggests that PTEN mutations play significant roles in tumorigenesis of glioblastoma as 60% of glioblastoma patients acquired mutations in this gene. Based on our preliminary data, transcriptomic profiling of primary astrocytes derived from Pten knockout mice revealed an overlapping enrichment of mitotic regulators and cell cycle related pathways with human GBM. 4 genes (RCC1, RCC2, NEK2, and CHK2) were validated to be significantly upregulated in PTEN KO astrocytes by qRT-PCR. Regulator of chromatin condensation 2 (RCC2) has been reported to be guanine-nucleotide exchange factor (GEF) for Rac1 and RalA GTPase and act as a regulator of cell cycle progression. Accumulating evidence revealed a pro-tumorigenic role of RCC2 in multiple cancers such as tumor growth and tumor metastasis. Via siRNA inhibition of RCC2, we demonstrated that knocking down of RCC2 in glioblastoma cell lines suppresses cell growth and RCC2 is essential for both G1-S and G2-M progression. Additionally, RCC2 knocking down and a PI3K inhibitor LY294002 inhibit glioblastoma cell viability in a synergistic manner. In summary, PTEN deficiency leads to the upregulation of RCC2, which may promote tumorigenesis of glioblastoma by dysregulating cell cycle progression.To further explore the RCC2 roles, we will find the potential downstream target of RCC2 in dysregulating cell cycle and its potential therapeutic effect in vivo. Funding: General Research Fund Grant #14113519 from The Research Grants Council of Hong Kong

Citation Format: Tian Liu, Penelope Mei-Yu Or, Chi-Wai Wong, Stanley Kwok-Kuen Cheung, Yubing Wang, Yiwei Wang, Andrew M. Chan. Analysis of Pten-null mouse astrocytes revealed overlapping transcribed genes with human glioblastoma transcriptome [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 97.

Andrographolide modulates HNF4α activity imparting on hepatic metabolism

Hepatic nuclear factor 4 alpha (HNF4α) drives the expression of apolipoprotein B (ApoB), microsomal triglyceride transfer protein (MTP) and phospholipase A2 G12B (PLA2G12B), governing hepatic very-low-density lipoprotein (VLDL) production and secretion. Andrographolide (AP) is a major constituent isolated from Andrographis paniculata. We found that AP can disrupt the interaction between HNF4α and its coactivator peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α). Virtual docking and mutational analysis indicated that arginine 235 of HNF4α is essential for binding to AP. As a consequence of antagonizing the activity of HNF4α, AP suppresses the expression of ApoB, MTP and PLA2G12B and reduces the rate of hepatic VLDL secretion in vivo. AP additionally reduced gluconeogenesis via down-regulating the expression of HNF4α target genes phosphoenolpyruvate carboxykinase (Pepck) and glucose-6-phosphatase (G6pc). Collectively, our results suggest that AP affects liver function via modulating the transcriptional activity of HNF4α.

18β-Glycyrrhetinic acid acts through hepatocyte nuclear factor 4 alpha to modulate lipid and carbohydrate metabolism

Hepatocyte nuclear factor 4 alpha (HNF4α) regulates the expression of essential genes involved in very-low-density lipoprotein (VLDL) homeostasis and gluconeogenesis.　18β-glycyrrhetinic acid (GA) is an active ingredient of Glycyrrhiza uralensis an herbal medicine used for treating liver aliments. In this study, we established that GA functions as a partial antagonist of HNF4α through HNF4α-driven reporter luciferase assay and co-immunoprecipitation experiments with co-activator PGC1α. By virtual docking and site-directed mutagenesis analysis, we confirmed that serine 190 and arginine 235 of HNF4α are both essential for GA to exert its antagonistic action on HNF4α. Importantly, GA suppressed the expression of HNF4α target genes such as apolipoprotein B (ApoB), microsomal triglyceride transfer protein (MTP) and phospholipase A₂ G12B (PLA2G12B) modulating hepatic VLDL secretion in mice fed on a high fat diet. In addition, GA also suppressed gluconeogenesis and ameliorated glucose intolerance via down-regulating the expression of HNF4α target genes glucose-6-phosphatase (G6pc) and phosphoenolpyruvate carboxykinase (Pepck). Furthermore, GA significantly lowered blood glucose and improved insulin resistance in db/db mice. In all, we established that GA acts as a partial HNF4α antagonist modulating lipid and carbohydrate metabolism.

The roles of protein disulphide isomerase family A, member 3 (ERp57) and surface thiol/disulphide exchange in human spermatozoa-zona pellucida binding

Study question

Are multimeric sperm plasma membrane protein complexes, ERp57 and sperm surface thiol content involved in human spermatozoa-zona pellucida (ZP) interaction?

Summary answer

ERp57 is a component of a multimeric spermatozoa-ZP receptor complex involved in regulation of human spermatozoa-ZP binding via up-regulation of sperm surface thiol content.

What is known already

A spermatozoon acquires its fertilization capacity within the female reproductive tract by capacitation. Spermatozoa-ZP receptor is suggested to be a composite structure that is assembled into a functional complex during capacitation. Sperm surface thiol content is elevated during capacitation. ERp57 is a protein disulphide isomerase that modulates the thiol-disulphide status of proteins.

Study design, size, duration

The binding ability and components of protein complexes in extracted membrane protein fractions of spermatozoa were studied. The roles of capacitation, thiol-disulphide reagent treatments and ERp57 on sperm functions and sperm surface thiol content were assessed.

Participants/materials, setting, methods

Spermatozoa were obtained from semen samples from normozoospermic men. Human oocytes were obtained from an assisted reproduction programme. Blue native polyacrylamide gel electrophoresis, western ligand blotting and mass spectrometry were used to identify the components of solubilized ZP/ZP3-binding complexes. The localization and expression of sperm surface thiol and ERp57 were studied by immunostaining and sperm surface protein biotinylation followed by western blotting. Sperm functions were assessed by standard assays.

Main results and the role of chance

Several ZP-binding complexes were isolated from the cell membrane of capacitated spermatozoa. ERp57 was a component of one of these complexes. Capacitation significantly increased the sperm surface thiol content, acrosomal thiol distribution and ERp57 expression on sperm surface. Sperm surface thiol and ERp57 immunoreactivity were localized to the acrosomal region of spermatozoa, a region responsible for ZP-binding. Up-regulation of the surface thiol content or ERp57 surface expression in vitro stimulated ZP-binding capacity of human spermatozoa. Blocking of ERp57 function by specific antibody or inhibitors against ERp57 reduced the surface thiol content and ZP-binding capacity of human spermatozoa.

Large scale data

N/A.

Limitations, reasons for caution

The mechanisms by which up-regulation of surface thiol content stimulates spermatozoa-ZP binding have not been depicted.

Wider implications of the findings

Thiol-disulphide exchange is a crucial event in capacitation. ERp57 modulates the event and the subsequent fertilization process. Modulation of the surface thiol content of the spermatozoa of subfertile men may help to increase fertilization rate in assisted reproduction.

Study funding/competing interest(s)

This work was supported by The Hong Kong Research Grant Council Grant HKU764611 and HKU764512M to P.C.N.C. The authors have no competing interests.

Diabetes in older people: position statement of The Hong Kong Geriatrics Society and the Hong Kong Society of Endocrinology, Metabolism and Reproduction

Following a survey on the clinical practice of geriatricians in the management of older people with diabetes and a study of hypoglycaemia in diabetic patients, a round-table discussion with geriatricians and endocrinologists was held in January 2015. Consensus was reached for six domains specifically related to older diabetic people: (1) the considerations when setting an individualised diabetic management; (2) inclusion of geriatric syndrome screening in assessment; (3) glycaemic and blood pressure targets; (4) pharmacotherapy; (5) restrictive diabetic diet; and (6) management goals for nursing home residents.

Discovery of Farnesoid X Receptor Antagonists Based on a Library of Oleanolic Acid 3-O-Esters through Diverse Substituent Design and Molecular Docking Methods

The pentacyclic triterpene oleanolic acid (OA, 1) with known farnesoid X receptor (FXR) modulatory activity was modified at its C-3 position to find new FXR-interacting agents. A diverse substitution library of OA derivatives was constructed in silico through a 2D fingerprint similarity cluster strategy. With further docking analysis, four top-scored OA 3-O-ester derivatives were selected for synthesis. The bioassay results indicated that all four compounds 3 inhibited chenodeoxycholic acid (CDCA)-induced FXR transactivation in a concentration-dependent mode. Among them 3b and 3d are more active than the parent compound OA. A molecular simulation study was performed to attempt to explain the structure-activity relationship (SAR) and the antagonistic action. To the best of our knowledge, this is the first report on semi-synthetic pentacyclic triterpenoids with FXR-modulatory activities.

Graphene Q-switched distributed feedback fiber lasers with narrow linewidth approaching the transform limit

A compact all-in-line graphene-based distributed feedback Bragg-grating fiber laser (GDFB-FL) with narrow linewidth of hundreds kHz is demonstrated and investigated in this study. Performing as an optical saturable absorber, graphene oscillates the initially kHz linewidth DFB-FL, and generates high-quality passively Q-switched pulses. Pumped with a 980 nm continuous-wave laser, the Q-switched GDFB-FL observes ~1 μs pulse durations, with pulse energies up to ~10 nJ and approaching the transform limit. The peak power is ~600 times higher than the original DFB-FL laser. By optimizing the cavity design and the graphene material, it is predicted that fast Q-switched pulses with more than MHz repetition rates and sub-100 ns pulse durations are achievable. Such transform-limited Q-switched GDFB-FLs with narrow linewidth of sub-MHz have long coherence length, good tunability, stability, compactness and robustness, with potential impact in optical coherent communications, metrology and sensing.

Activation of farnesoid X receptor promotes triglycerides lowering by suppressing phospholipase A2 G12B expression

As a novel mediator of hepatic very low-density lipoproteins (VLDL) secretion, phospholipase A2 G12B (PLA2G12B) is transcriptionally regulated by hepatocyte nuclear factor-4 alpha (HNF-4α). Farnesoid X receptor (FXR) plays a critical role in maintaining bile acids and triglycerides (TG) homeostasis. Here we report that FXR regulates serum TG level in part through PLA2G12B. Activation of FXR by chenodeoxycholic acid (CDCA) or GW4064 significantly decreased PLA2G12B expression in HepG2 cells. PLA2G12B expression was transcriptionally repressed due to an FXR-mediated up-regulation of small heterodimer partner (SHP) which functionally suppresses HNF-4α activity. We found that hepatic PLA2G12B expression was suppressed and serum TG level reduced in high fat diet mice treated with CDCA. Concurrently, CDCA treatment lowered hepatic VLDL-TG secretion. Our data demonstrate that activation of FXR promotes TG lowering, not only by decreasing de novo lipogenesis but also reducing hepatic secretion of TG-rich VLDL particles in part through suppressing PLA2G12B expression.

Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers

Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses.

Impact of skeletal-related events on survival in patients with metastatic prostate cancer prescribed androgen deprivation therapy

OBJECTIVE

To investigate the impact of skeletal-related events on survival in patients with metastatic prostate cancer prescribed long-term androgen deprivation therapy.

METHODS

This historical cohort study was conducted in two hospitals in Hong Kong. Patients who were diagnosed with metastatic prostate cancer and prescribed androgen deprivation therapy between January 2006 and December 2011 were included. Details of skeletal-related events and mortality were examined.

RESULTS

The median follow-up was 28 (range, 1-97) months. Of 119 patients, 52 (43.7%) developed skeletal-related events throughout the study, and the majority received bone irradiation for pain control. The median actuarial overall survival and cancer-specific survival for patients with skeletal-related events were significantly shorter than those without skeletal-related events (23 vs 48 months, P=0.003 and 26 vs 97 months, P<0.001, respectively). Multivariate analysis revealed that the adjusted hazard ratio of presence of skeletal-related events on overall and cancer-specific survival was 2.73 (95% confidence interval, 1.46-5.10; P=0.002) and 3.92 (95% confidence interval, 1.87-8.23; P<0.001), respectively. A prostate-specific antigen nadir of >4 ng/mL was an independent poor prognostic factor for overall and cancer-specific survival after development of skeletal-related events (hazard ratio=10.42; 95% confidence interval, 2.10-51.66 and hazard ratio=10.54; 95% confidence interval, 1.94-57.28, respectively).

CONCLUSIONS

Skeletal-related events were common in men with metastatic prostate cancer. This is the first reported study to show that a skeletal-related event is an independent prognostic factor in overall and cancer-specific survival in patients with metastatic prostate cancer prescribed androgen deprivation therapy. A prostate-specific antigen nadir of >4 ng/mL is an independent poor prognostic factor for overall and cancer-specific survival following development of skeletal-related events.

Avoiding hypoglycaemia: a new target of care for elderly diabetic patients

Optimising glycaemic control to prevent diabetes-associated complications has received much attention. The associated risk of iatrogenic hypoglycaemia, however, is inevitable and can have a significant impact on health. The prevalence of iatrogenic hypoglycaemia tends to increase with advancing age. Elderly people are intrinsically prone to hypoglycaemia. Ageing attenuates the glucose counter-regulatory and symptomatic response to hypoglycaemia, particularly in the presence of a longer duration of diabetes. Multiple co-morbidities and polypharmacy correlated with advancing age also increase the hypoglycaemic risk. In addition to the acute adverse effects of hypoglycaemia, such as fall with injury, cardiovascular events and mortality, a hypoglycaemic episode can have long-term consequences. Repeated episodes may have a significant psychological impact and are also a risk factor for dementia. Because of the heterogeneous health status of the elderly, not all will benefit from optimal glycaemic control. Setting an individual glycaemic target and formulating a management plan that takes account of the patient's circumstances combined with balancing the benefit and risk of diabetes intervention to avoid hypoglycaemia is a more practical approach to the management of elderly diabetic patients.

Vitamin B12 deficiency in the elderly: is it worth screening?

Vitamin B12 deficiency is common among the elderly. Elderly people are particularly at risk of vitamin B12 deficiency because of the high prevalence of atrophic gastritis-associated food-cobalamin (vitamin B12) malabsorption, and the increasing prevalence of pernicious anaemia with advancing age. The deficiency most often goes unrecognised because the clinical manifestations are highly variable, often subtle and non-specific, but if left undiagnosed the consequences can be serious. Diagnosis of vitamin B12 deficiency, however, is not straightforward as laboratory tests have certain limitations. Setting a cut-off level to define serum vitamin B12 deficiency is difficult; though homocysteine and methylmalonic acid are more sensitive for vitamin B12 deficiency, it may give false result in some conditions and the reference intervals are not standardised. At present, there is no consensus or guideline for diagnosis of this deficiency. It is most often based on the clinical symptoms together with laboratory assessment (low serum vitamin B12 level and elevated serum homocysteine or methylmalonic acid level) and the response to treatment to make definitive diagnosis. Treatment and replacement with oral vitamin B12 can be as effective as parenteral administration even in patients with pernicious anaemia. The suggested oral vitamin B12 dose is 1 mg daily for a month, and then maintenance dose of 125 to 250 µg for patients with dietary insufficiency and 1 mg daily for those with pernicious anaemia. Vitamin B12 replacement is safe and without side-effects, but prompt treatment is required to reverse the damage before it becomes extensive or irreversible. At present, there is no recommendation for mass screening for vitamin B12 in the elderly. Nevertheless, the higher prevalence with age, increasing risk of vitamin B12 deficiency in the elderly, symptoms being difficult to recognise, and availability of safe treatment options make screening a favourable option. However, the unavailability of reliable diagnostic tool or gold standard test makes screening difficult to carry out.

Mode-locked ultrashort pulse generation from on-chip normal dispersion microresonators

We describe generation of stable mode-locked pulse trains from on-chip normal dispersion microresonators. The excitation of hyperparametric oscillation is facilitated by the local dispersion disruptions induced by mode interactions. The system is then driven from hyperparametric oscillation to the mode-locked state with over 200 nm spectral width by controlled pump power and detuning. With the continuous-wave-driven nonlinearity, the pulses sit on a pedestal, akin to a cavity soliton. We identify the importance of pump detuning and wavelength-dependent quality factors in stabilizing and shaping the pulse structure, to achieve a single pulse inside the cavity. We examine the mode-locking dynamics by numerically solving the master equation and provide analytic solutions under appropriate approximations.

Combating against methicillin-resistant Staphylococcus aureus - two fatty acids from Purslane (Portulaca oleracea L.) exhibit synergistic effects with erythromycin

OBJECTIVES

The aims of this study were to identify the active ingredients from Portulaca oleracea L. (PO) that could provide synergism with antibiotics against methicillin-resistant Staphylococcus aureus (MRSA) and their possible mechanisms of resistance inhibition.

METHODS

High-speed counter-current chromatography (HSCCC) coupled with gas chromatography-mass spectrometry and a panel of laboratory MRSA strains were used for checkerboard and efflux inhibitory assays.

KEY FINDINGS

Linoleic and oleic acids were identified from HSCCC fraction 18 of PO with synergistic antibacterial activity when combined with erythromycin against RN4220/pUL5054. Ethidium bromide efflux inhibitory studies revealed that linoleic and oleic acids may interfere the activity of MsrA pump. By comparing among a panel of linoleic and oleic acids analogues, unsaturated fatty acids in salt form with cis configuration and an increase in number of double bonds were found to further increase the antibacterial activity when used alone or in combination with antibiotics.

CONCLUSION

This study reported for the first time that two active ingredients, namely linoleic and oleic acids, were identified from PO with synergistic antibacterial activity when combined with erythromycin against MRSA RN4220/pUL5054 and possibly act by inhibiting the efflux pumps of the bacteria cells.

Causes of Low HbA1c in Malaysian University Hospital

INTRODUCTION

Glycohemoglobin (HbA1c) most accurately reflects the previous two to three months of glycaemic control. HbA1c should be measured regularly in all patients with diabetes, and values should be maintained below 7% to prevent the risk of chronic complications. Apart from the genetic variants of haemoglobins many other conditions also known to affect HbA1c measurements. In this study we evaluated the conditions that cause low HbA1c results.

METHODS AND MATERIALS

The data was collected retrospectively HbA1c was measured in our laboratory by Biorad Variant II turbo 2.0. The method is based on chromatographic separation of HbA1c on a cation exchange cartridge. This method has been certified by National Glycohemoglobin Standardization Programme (NGSP). 58437 requests were received in a period of one year (January to December 2011). Medical records were reviewed to identify the conditions that might be associated with these low values.

RESULTS

Among 58437 samples analysed, 53 patients had HbA1c levels < 4.0%. Fourteen patients had haemoglobinopathy. In 34 patients without Hb variants had conditions such as chronic liver disease, chronic kidney disease, haemolytic anaemia, pregnancy, and anaemia of chronic disease. Five non-pregnant individuals who were screened for diabetes mellitus had HbA1c levels < 4%.

CONCLUSION

Our study underscores the importance of that both laboratories and the physicians should be aware of the factors that can influence the HbA1c results. The haematological status should be taken into consideration for proper interpretation of HbA1c results.

Synthesis and discovery of andrographolide derivatives as non-steroidal farnesoid X receptor (FXR) antagonists

Some 14β-phenoxy substituted derivatives of andrographolide were designed, synthesized and investigated as FXR novel antagonists.

Reliability and validity of the overactive bladder symptom score in Hong Kong Chinese

OBJECTIVE

To validate the Hong Kong Chinese translation of the Overactive Bladder Symptom Score questionnaire (OABSS-HKC).

DESIGN

Cross-sectional study.

SETTING

Five urology clinics of different regional hospitals in Hong Kong.

PARTICIPANTS

The Overactive Bladder Symptom Score questionnaire was translated and culturally adapted for Hong Kong Chinese, according to the Principles of Good Practice for the Translation and Cultural Adaptation Process for Patient-Reported Outcomes Measures. Chinese-speaking patients with overactive bladder symptoms were recruited from five urology clinics. The patients completed the OABSS-HKC, a 3-day micturition diary, International Prostate Symptom Scores, and the Patient Perception of Bladder Condition questionnaires (visit 1), and again after a 2-week interval (visit 2). Test-retest reliability was evaluated by the intraclass correlation coefficient and weighted Kappa coefficient. The relationship between OABSS-HKC total scores and items in the comparison measures was evaluated using Spearman's correlation coefficients.

RESULTS

The OABSS-HKC was successfully translated and culturally adapted. Fifty-one patients completed the validation study. A high level of reliability was observed between the OABSS-HKC total score answered at visit 1 and 2 for all subjects (intraclass correlation coefficient, 0.82) and among the four items answered (weighted Kappa coefficients, 0.57-0.75). The OABSS-HKC total score correlated significantly with numbers of micturitions, incontinence and urgency episodes recorded in the 3-day micturition diary, as well as the total International Prostate Symptom Scores and the Patient Perception of Bladder Condition score. However, the OABSS-HKC total score was not significantly associated with nocturia episodes, total voided volume, or number of pads used.

CONCLUSIONS

The OABSS-HKC total scores are reliable and moderately valid for the quantitative evaluation of overactive bladder symptoms in Hong Kong Chinese-speaking adults.

Intermedin in rat uterus: changes in gene expression and peptide levels across the estrous cycle and its effects on uterine contraction

BACKGROUND

The present study demonstrates the expression of intermedin (IMD) and its receptor components in the uterus of the female rat during the estrous cycle and its effect on uterine contraction.

METHODS

The gene expression level of intermedin and its receptor components and the peptide level of intermedin were studied by real-time RT-PCR and enzyme immunoassay (EIA) respectively. The separation of precursor and mature IMD was studied by gel filtration chromatography and EIA. The localization of IMD in the uterus was investigated by immunohistochemistry. The effect of IMD on in vitro uterine contraction was studied by organ bath technique.

RESULTS

Uterine mRNAs of Imd and its receptor components and IMD levels displayed cyclic changes across the estrous cycle. Imd mRNA level was the highest at proestrus while the IMD level was the highest at diestrus. IMD was found in the luminal and glandular epithelia and IMD treatment significantly reduced the amplitude and frequency of uterine contraction but not the basal tone. Both calcitonin gene-related peptide (CGRP) receptor antagonist hCGRP8-37 and adrenomedullin (ADM) receptor antagonist hADM22-52 partially abolished the inhibitory effect of IMD on uterine contraction while the specific IMD receptor antagonist hIMD17-47 completely blocked the actions. The enzyme inhibitors of NO (L-NAME) and PI3K (Wortmannin) pathways diminished the IMD effects on uterine contraction while the cAMP/PKA blocker, KT5720, had no effect, indicating an involvement of NO and PI3K/Akt but not PKA.

CONCLUSIONS

IMD and the gene expression of its receptor components are differentially regulated in the uterus during the estrous cycle and IMD inhibits uterine contraction by decreasing the amplitude and frequency.

Enrichment analysis of miRNA targets

MicroRNAs (miRNAs) are a class of ∼22-nucleotide endogenous noncoding RNAs which regulate target gene expression via repressing translation or promoting mRNAs degradation. Any individual mammalian miRNA often has more than a hundred predicted mRNA targets and that close to one thirds of all mRNA transcripts bear one or more conserved miRNA binding sites in their 3'-untranslated region. Enrichment analysis of miRNA targets has become a standard technique to elucidating hierarchical functions of miRNAs in gene regulatory networks. In this protocol, we discuss analytical methods and use of computational tools in a step-by-step manner. Important details are also provided to help researchers choose more appropriate tools for a given type of analysis. Available Web-based resources for enrichment analysis of miRNA targets are summarized.

An investigation of visual contour integration ability in relation to writing performance in primary school students

A previous study found a visual deficit in contour integration in English readers with dyslexia (Simmers & Bex, 2001). Visual contour integration may play an even more significant role in Chinese handwriting particularly due to its logographic presentation (Lam, Au, Leung, & Li-Tsang, 2011). The current study examined the relationship between children's performance in visual contour (VC) integration and Chinese handwriting. Twenty students from grade 3 to grade 6 were recruited (M=9.51, SD=1.02) from a mainstream primary school using the convenience sampling method. Ten students were identified by teachers as having handwriting problems, and the other 10 were typical students. Participants performed the VC tasks and their handwriting performance was assessed by a Chinese Handwriting Assessment Tool (CHAT) in a classroom setting. Correlation analyses revealed that VC accuracy was significantly and negatively correlated with on paper time and total writing duration. t-Test analyses revealed statistically significant differences in VC accuracy between students with typical and poor handwriting, with consistently better VC accuracy performance in all conditions in the typical handwriting group. The results may have important implications for interventions aiming at improving children's handwriting.

Influence of vaccine deposition site on post-vaccinal viraemia and vaccine efficacy in broiler chickens following in ovo vaccination against Marek's disease

In ovo vaccination against Marek's disease is a widely used technology in the broiler industry.A series of experiments was carried out to determine the site of vaccine deposition in the egg during automated in ovo vaccination, and the effect of vaccine deposition site and dose on vaccine responses following vaccination with cell-associated herpesvirus of turkeys in commercial broiler chickens. Vaccine deposition site following automated in ovo vaccination was principally influenced by the age of embryo, with egg size having a smaller effect. The frequency of vaccine deposition inside the embryo body increased as incubation progressed from day 17.5 to 19.5. In experiments using manual vaccine deposition intra-embryonically (IE) or extra-embryonically (EE) at day 18.5, EE vaccine deposition resulted in a significantly delayed development of post-vaccinal viraemia relative to both IE vaccination and subcutaneous vaccination at hatch. There were no effects of vaccine dose (2000, 4000 or 8000 plaque forming units) on the timing of post-vaccinal viraemia. The timing of post-vaccinal viraemia was found to be a good indicator of the level of protection provided by the vaccine against challenge with earlier viraemia associated with better protection. IE vaccine deposition induced significantly greater protection than EE deposition against challenge with a virulent strain of Marek's disease virus. IE deposition consistently produced a high level of protection (68 to 84%) irrespective of vaccine dose or challenge day, while EE vaccine deposition produced no or low levels of protection (0 to 27%) depending on the vaccine dose and day of challenge. The growth of challenged chickens was also affected by site of vaccine deposition, with significantly higher live weights at day 56 of age in IE compared with EE vaccinated groups. These data suggest that the site of vaccine deposition within the embryo is an important determinant of the success of in ovo vaccination.

Ultrafast supercontinuum spectroscopy of carrier multiplication and biexcitonic effects in excited states of PbS quantum dots

We examine the population dynamics of multiple excitons in PbS quantum dots using spectrally resolved ultrafast supercontinuum transient absorption (SC-TA) measurements. We simultaneously probe the first three excitonic transitions. The transient spectra show the presence of bleaching of absorption for the 1S(h)-1S(e) transition, as well as transients associated with the 1P(h)-1P(e) transition. We examine signatures of carrier multiplication (multiple excitons arising from a single absorbed photon) from analysis of the bleaching features in the limit of low absorbed photon numbers (left angle bracket N(abs) right angle bracket ∼ 10(-2)) for pump photon energies from two to four times that of the band gap. The efficiency of multiple-exciton generation is discussed both in terms of the ratio between early- to long-time transient absorption signals and of a broadband global fit to the data. Analysis of the population dynamics shows that bleaching associated with biexciton population is red shifted with respect to the single exciton feature, which is in accordance with a positive binding energy for the biexciton.

Protein kinase C epsilon affects mitochondrial function through estrogen-related receptor alpha

Members of the protein kinase C (PKC) family have been implicated in controlling cell proliferation, differentiation, and motility. Many of these processes are energy demanding. How PKCs affect mitochondrial function to regulate energy production is not well defined. Using an inhibitor Gö6983 with broad specificity, we found that inhibiting PKCs reduced mitochondrial mass and altered mitochondrial function characterized by elevations in mitochondrial membrane potential (Δψm) and reactive oxygen species (ROS) levels. These alterations indicated that Gö6983 suppressed the activities of mitochondrial regulators such as estrogen-related receptor α (ERRα). Indeed, Gö6983 dose-dependently suppressed the expression levels of ERRα-target genes peroxisome proliferator-activated receptor α (PPARα) and medium-chain acyl-CoA dehydrogenase (MCAD). Conversely, PKC activator phorbol ester (PMA) enhanced the expression level of another ERRα-target gene pyruvate dehydrogenase kinase 4 (PDK4). This PMA-mediated induction of PDK4 was blunted by an ERRα inverse agonist XCT-790, suggesting that ERRα plays a role in mediating the effects of PKCs on mitochondrial function. By over-expressing constitutively active forms of PKCs, we found that PKCε preferentially stimulated the transcription activity of ERRα. Through mutating residues on ERRα, we established that this PKCε-induced ERRα activity involves threonine 106, serine 110, and threonine 124 of ERRα. Collectively, these pieces of evidence suggest that ERRα plays an important role down-stream of PKCε to regulate mitochondrial homeostasis.

Mitogen-activated protein kinase kinases promote mitochondrial biogenesis in part through inducing peroxisome proliferator-activated receptor γ coactivator-1β expression

Growth factor activates mitogen-activated protein kinase kinases to promote cell growth. Mitochondrial biogenesis is an integral part of cell growth. How growth factor regulates mitochondrial biogenesis is not fully understood. In this study, we found that mitochondrial mass was specifically reduced upon serum starvation and induced upon re-feeding with serum. Using mitogen-activated protein kinase kinases inhibitor U0126, we found that the mRNA expression levels of ATP synthase, cytochrome-C, mitochondrial transcription factor A, and mitofusin 2 were reduced. Since the transcriptional levels of these genes are under the control of peroxisome proliferator-activated receptor γ coactivator-1α and -1β (PGC-1α and PGC-1β), we examined and found that only the mRNA and protein levels of PGC-1β were suppressed. Importantly, over-expression of PGC-1β partially reversed the reduction of mitochondrial mass upon U0126 treatment. Thus, we conclude that mitogen-activated protein kinase kinases direct mitochondrial biogenesis through selectively inducing PGC-1β expression.

Phosphatidylinositol 3-kinase affects mitochondrial function in part through inducing peroxisome proliferator-activated receptor γ coactivator-1β expression

BACKGROUND AND PURPOSE

Hyperactivation of phosphatidylinositol 3-kinase (PI3K), commonly observed in cancer, is believed to promote cancer cell growth and survival. Appropriate mitochondrial function is an integral part of cellular function. How PI3K affects mitochondrial homeostasis is not fully understood.

EXPERIMENTAL APPROACH

Mitochondrial mass, membrane potential and reactive oxygen species (ROS) were quantified by three different fluorogenic probes. Gene expression at the levels of mRNA and protein were measured by quantitative RT-PCR and Western analysis.

KEY RESULTS

Using the PI3K inhibitors LY294002 and PI103, we found that suppressing PI3K activity altered mitochondrial function. Specifically, LY294002 and PI103 suppressed the mRNA expression levels of mitochondrial regulators nuclear respiratory factors 1 and 2 (NRF1 and NRF2). As NRF1 and NRF2 are under the transcriptional control of peroxisome proliferator-activated receptor γ coactivators-1α and -1β (PGC-1α and PGC-1β), we found that suppressing PI3K activity selectively reduced both the mRNA and protein levels of PGC-1β but not PGC-1α. Reducing PGC-1β expression also led to reduced mRNA expression levels of uncoupling protein 1, 2 (UCP1 and UCP2) and superoxide dismutase 2. Correspondingly, mitochondrial membrane potential (Δψ(m)) and ROS levels were increased. Finally, we partially blunted the LY294002-mediated growth suppression by using an antioxidant or over-expressing PGC-1β.

CONCLUSIONS AND IMPLICATIONS

PI3K regulates mitochondrial homeostasis in part through PGC-1β and blocking this pathway induces ROS to arrest cell growth at the G₁ phase.

Hepatocyte nuclear factor-4 alpha regulates liver triglyceride metabolism in part through secreted phospholipase A₂ GXIIB

Hepatocyte nuclear factor-4 alpha (HNF-4α) is an important transcription factor governing the expression of genes involved in multiple metabolic pathways. Secreted phospholipase A(2) GXIIB (PLA(2) GXIIB) is an atypical member of a class of secreted phospholipases A(2) . We establish in this study that PLA(2) GXIIB is an HNF-4α target gene. We demonstrate that HNF-4α binds to a response element on the PLA(2) GXIIB promoter. Moreover, HNF-4α agonists induce PLA(2) GXIIB expression in human hepatocarcinoma cells. Importantly, PLA(2) GXIIB-null mice accumulate triglyceride, cholesterol, and fatty acids in the liver and develop severe hepatosteatosis resembling some of the phenotypes of liver-specific HNF-4α-null mice. These defects are in part due to compromised hepatic very low-density lipoprotein secretion. Finally, adenovirus-mediated overexpression of HNF-4α elevates serum triglyceride level in wild-type but not PLA(2) GXIIB-null mice.

CONCLUSION

Collectively, these evidences suggest that HNF-4α is a key physiological PLA(2) GXIIB transcriptional regulator and that PLA(2) GXIIB is a novel mediator of triglyceride metabolism in the liver.

Troglitazone induces cytotoxicity in part by promoting the degradation of peroxisome proliferator-activated receptor γ co-activator-1α protein

BACKGROUND AND PURPOSE

Troglitazone (Tro), rosiglitazone (Rosi) and pioglitazone (Pio) are anti-diabetic thiazolidinediones that function as ligands for peroxisome proliferator-activated receptor γ (PPARγ); however, Tro has been withdrawn from the market due to liver toxicity issues. Mitochondrial dysfunction induced by Tro has been suggested to be an important mechanism behind its cytotoxicity. Constitutively active nuclear hormone receptors, oestrogen-related receptor α and γ are thought to regulate mitochondrial mass and oxidative phosphorylation together with their co-activators PPARγ co-activator-1α and -1β (PGC-1α and PGC-1β). Hence, in this study, we investigated whether Tro affects the expression and activity levels of these regulators.

EXPERIMENTAL APPROACH

Cellular viability was measured by an ATP-based assay. Mitochondrial mass and reactive oxygen species (ROS) were quantified by two different fluorogenic probes. Apoptosis was measured by an Annexin-V-based kit. Gene expression at the levels of mRNA and protein was measured by quantitative RT-PCR and Western analysis. Over-expression of PGC-1α was mediated by an adenovirus.

KEY RESULTS

Tro, but not Rosi or Pio, selectively stimulated PGC-1α protein degradation. As a result, Tro reduced mitochondrial mass, and superoxide dismutases 1 and 2 expressions, but induced ROS to initiate apoptosis. Using a ubiquitin-proteasome inhibitor MG132, it was established that blocking PGC-1α degradation partially suppressed the reduction of mitochondrial mass. Importantly, over-expressing PGC-1α partially restored the Tro-suppressed mitochondrial mass and attenuated the cytotoxic effects of Tro.

CONCLUSIONS AND IMPLICATIONS

Collectively, these results suggest that PGC-1α degradation is an important mechanism behind the cytotoxic effects of Tro in the liver.

Troglitazone is an estrogen-related receptor alpha and gamma inverse agonist

As a ligand for peroxisome proliferators-activated receptor gamma (PPAR gamma), troglitazone inhibits cell growth by mechanisms besides activating PPAR gamma. In this study, we found that troglitazone interfered with the interactions between estrogen-related receptor alpha and gamma (ERR alpha and ERR gamma) and their coactivator PPAR gamma coactivator-1 alpha (PGC-1 alpha) functioning as an inverse agonist. Additionally, troglitazone suppressed the expressions of PGC-1 alpha and its related member PGC-1 beta which are key regulators of mitochondrial function. Consequently, troglitazone reduced mitochondrial mass and suppressed the expressions of superoxide dismutases to elevate reactive oxygen species (ROS) production. The increase in ROS in turn induced the expression of cell cycle inhibitor p21(WAF1). We therefore propose that ERR alpha and ERR gamma are alternative targets of troglitazone important for mediating its growth suppressive effect.