[Show abstract][Hide abstract] ABSTRACT: Steroidogenic factor 1 (SF-1) is a transcription factor expressed in the ventral medial nucleus of the hypothalamus that regulates energy homeostasis. However, the molecular mechanisms of SF-1 in the control of energy balance are largely unknown. Here, we show that nutritional conditions, such as the presence or absence of serum, affect SF-1 action. Serum starvation significantly decreased hypothalamic SF-1 levels by promoting ubiquitin-dependent degradation, and sumoylation was required for this process. SF-1 transcriptional activity was also differentially regulated by nutritional status. Under normal conditions, the transcriptional activity of hypothalamic SF-1 was activated by SUMO, but this was attenuated during starvation. Taken together, these results indicate that sumoylation and ubiquitination play crucial roles in the regulation of SF-1 function and that these effects are dependent on nutritional conditions, further supporting the importance of SF-1 in the control of energy homeostasis.
[Show abstract][Hide abstract] ABSTRACT: Mycosporine-like amino acids (MAAs) are secondary metabolites found in diverse marine, freshwater, and terrestrial organisms. Evidence suggests that MAAs have several beneficial effects on skin homeostasis such as protection against UV radiation and reactive oxygen species (ROS). In addition, MAAs are also involved in the modulation of skin fibroblasts proliferation. However, the regulatory function of MAAs on wound repair in human skin is not yet clearly elucidated. To investigate the roles of MAAs on the wound healing process in human keratinocytes, three MAAs, Shinorine (SH), Mycosporine-glycine (M-Gly), and Porphyra (P334) were purified from Chlamydomonas hedlyei and Porphyra yezoensis. We found that SH, M-Gly, and P334 have significant effects on the wound healing process in human keratinocytes and these effects were mediated by activation of focal adhesion kinases (FAK), extracellular signal-regulated kinases (ERK), and c-Jun N-terminal kinases (JNK). These results suggest that MAAs accelerate wound repair by activating the FAK-MAPK signaling pathways. This study also indicates that MAAs can act as a new wound healing agent and further suggests that MAAs might be a novel biomaterial for wound healing therapies.
[Show abstract][Hide abstract] ABSTRACT: The marine green alga Chlorella vulgaris produces secondary metabolites including functional nutrients and associated bioactive peptides for protection against harmful environmental stress, suggesting that C. vulgaris extracts may be beneficial for skin homeostasis via protection against UV radiation and reactive oxygen species (ROS). In this study, we identified a cysteine-alanine-serine (CAS) tripeptide from C. vulgaris using LC-MS/MS and NMR and investigated whether the CAS tripeptide can protect skin cells from ROS species. CAS tripeptide was added to a human skin cell line and this treatment resulted in the upregulation of antioxidant genes. In addition, we identified significant induction of procollagen C endopeptidase enhancer (PCOLCE) protein production, which is related to skin firming, due to exposure to CAS tripeptide. The combined results suggest that the microalgae-derived CAS tripeptide might be a valuable biomaterial for modulation of skin homeostasis through antioxidant activity.
No preview · Article · Nov 2015 · Science of Advanced Materials
[Show abstract][Hide abstract] ABSTRACT: Interaction of the the rust fungus Puccinia miscanthi with the biofuel plant Miscanthus sinensis during the teliospore phase was investigated by light and electron microscopy. P. miscanthi telia were oval-shaped and present on both the adaxial and abaxial leaf surfaces. Teliospores were brown, one-septate (two-celled), and had pedicels attached to one end. Transmission electron microscopy revealed numerous electron-translucent lipid globules in the cytoplasm of teliospores. Extensive cell wall dissolution around hyphae was not observed in the host tissues beneath the telia. Hyphae were found between mesophyll cells in the leaf tissues as well as in host cells. Intracellular hyphae, possibly haustoria, possessed electron-dense fungal cell walls encased by an electron-transparent fibrillar extrahaustorial sheath that had an electron-dense extrahaustorial membrane. The infected host cells appeared to maintain their membrane-bound structures such as nuclei and chloroplasts. These results suggest that the rust fungus maintains its biotrophic phase with most mesophyll cells of M. sinensis. Such a nutritional mode would permit the rust fungus to obtain food reserves for transient growth in the course of host alteration.
[Show abstract][Hide abstract] ABSTRACT: Fusarium graminearum, a member of the F. graminearum species complex, is a filamentous ascomycetous group that causes serious diseases in cereal crops. A screen of insertional mutants of F. graminearum, generated using a restriction enzyme-mediated integration method, identified a mutant designated R7048 showing pleiotropic phenotypes in several mycological traits. The vector insertion site in the R7048 genome was identified as the KpnI site within an ORF annotated as FGSG_06346 (designated FgVPS74), which showed similarity to vacuolar protein sorting-associated protein 74 in the baker yeast. Both targeted gene deletion and complementation analyses confirmed that FgVPS74 was involved in hyphal growth, conidiation, sexual development, mycotoxin production, and virulence towards host plants in F. graminearum. Electron microscopy analysis revealed no significant changes in morphology of the vacuole or other organelles, but a greater number of mitochondria were produced in the ΔFgVPS74 strain compared to the wild-type progenitor. Expression of a GFP-tagged FgVPS74 construct under its native promoter in the ΔFgVPS74 strain exhibited localization of GFP signal to putative vesicle structures, but not to the vacuolar membrane. Taken together, these findings demonstrated that a functional vacuolar protein-sorting pathway mediated by FgVPS74 is crucial for fungal growth and development in F. graminearum.
No preview · Article · Apr 2015 · The Journal of Microbiology
[Show abstract][Hide abstract] ABSTRACT: Diabetes is a risk factor for breast cancer development and is associated with poor prognosis for breast cancer patients. However, the molecular and biochemical mechanisms underlying the association between diabetes and breast cancer have not been fully elucidated. Here, we investigated estradiol response in MCF-7 breast cancer cells with or without chronic exposure to insulin. We found that insulin priming is necessary and specific for estradiol-induced cancer cell growth, and induces anaplerotic shunting of glucose into macromolecule biosynthesis in the estradiol treated cells. Treatment with ERK or Akt specific inhibitors, U0126 or LY294002, respectively, suppressed estradiol-induced growth. Interestingly, molecular analysis revealed that estradiol treatment markedly increases expression of cyclin A and B, and decreases p21 and p27 in the insulin-primed cells. In addition, estradiol treatment activated metabolic genes in pentose phosphate (PPP) and serine biosynthesis pathways in the insulin-primed cells while insulin priming decreased metabolic gene expression associated with glucose catabolism in the breast cancer cells. Finally, we found that anti-diabetic drug metformin and AMPK ligand AICAR, but not thiazolidinediones (TZDs), specifically suppress the estradiol-induced cellular growth in the insulin-primed cells. These findings suggest that estrogen receptor (ER) activation under chronic hyperinsulinemic condition increases breast cancer growth through the modulation of cell cycle and apoptotic factors and nutrient metabolism, and further provide a mechanistic evidence for the clinical benefit of metformin use for ER-positive breast cancer patients with diabetes.
Full-text · Article · Feb 2015 · Cancer biology & therapy
[Show abstract][Hide abstract] ABSTRACT: Obesity rates continue to rise throughout the world. Recent evidence has suggested that environmental factors contribute to altered energy balance regulation. However, the role of epigenetic modifications to the central control of energy homeostasis remains unknown. To investigate the role of DNA methylation in the regulation of energy balance, we investigated the role of the de novo DNA methyltransferase, Dnmt3a, in Single-minded 1 (Sim1) cells, including neurons in the paraventricular nucleus of the hypothalamus (PVH). Dnmt3a expression levels were decreased in the PVH of high-fat-fed mice. Mice lacking Dnmt3a specifically in the Sim1 neurons, which are expressed in the forebrain, including PVH, became obese with increased amounts of abdominal and subcutaneous fat. The mice were also found to have hyperphagia, decreased energy expenditure, and glucose intolerance with increased serum insulin and leptin. Furthermore, these mice developed hyper-LDL cholesterolemia when fed a high-fat diet. Gene expression profiling and DNA methylation analysis revealed that the expression of tyrosine hydroxylase and galanin were highly upregulated in the PVH of Sim1-specific Dnmt3a deletion mice. DNA methylation levels of the tyrosine hydroxylase promoter were decreased in the PVH of the deletion mice. These results suggest that Dnmt3a in the PVH is necessary for the normal control of body weight and energy homeostasis and that tyrosine hydroxylase is a putative target of Dnmt3a in the PVH. These results provide evidence for a role for Dnmt3a in the PVH to link environmental conditions to altered energy homeostasis.
Preview · Article · Nov 2014 · The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
[Show abstract][Hide abstract] ABSTRACT: Gallic acid [3,4,5-trihydroxybenzoic acid (GA)], a natural phytochemical, is known to have a variety of cellular functions including beneficial effects on metabolic syndromes. However, the molecular mechanism by which GA exerts its beneficial effects is not known. Here we report that GA plays its role through the activation of AMP-activated protein kinase (AMPK) and by regulating mitochondrial function via the activation of peroxisome proliferator-activated receptor-γ coactivator1α (PGC1α). Sirtuin 1 (Sirt1) knockdown significantly blunted GA's effect on PGC1α activation and downstream genes, suggesting a critical role of the AMPK/Sirt1/PGC1α pathway in GA's action. Moreover, diet-induced obese mice treated with GA showed significantly improved glucose and insulin homeostasis. In addition, the administration of GA protected diet-induced body weight gain without a change in food intake. Biochemical analyses revealed a marked activation of AMPK in the liver, muscle, and interscapular brown adipose tissue of the GA-treated mice. Moreover, uncoupling protein 1 together with other genes related to energy expenditure was significantly elevated in the interscapular brown adipose tissue. Taken together, these results indicate that GA plays its beneficial metabolic roles by activating the AMPK/Sirt1/PGC1α pathway and by changing the interscapular brown adipose tissue genes related to thermogenesis. Our study points out that targeting the activation of the AMPK/Sirt1/PGC1α pathway by GA or its derivatives might be a potential therapeutic intervention for insulin resistance in metabolic diseases.
[Show abstract][Hide abstract] ABSTRACT: The central actions of leptin and insulin are essential for the regulation of energy and glucose homeostasis. In addition to the crucial effects on the hypothalamus, emerging evidence suggests that the leptin and insulin signaling can act on other brain regions to mediate the reward value of nutrients. Recent studies have indicated the midbrain dopaminergic neurons as a potential site for leptin' and insulin's actions on mediating the feeding behaviors and therefore affecting the energy balance. Although molecular details about the integrative roles of leptin and insulin in this subset of neurons remain to be investigated, substantial body of evidence by far imply that the signaling pathways regulated by leptin and insulin may play an essential role in the regulation of energy balance through the control of food-associated reward. This review therefore describes the convergence of energy regulation and reward system, particularly focusing on leptin and insulin signaling in the midbrain dopaminergic neurons.
Full-text · Article · Aug 2014 · Frontiers in Psychology
[Show abstract][Hide abstract] ABSTRACT: Estrogens and prolactin share important target tissues, including the gonads, brain, liver, kidneys and some types of cancer cells. Herein, we sought anatomical and functional evidence of possible crosstalk between prolactin and estrogens in the mouse brain. First, we determined the distribution of prolactin-responsive neurons that express the estrogen receptor α (ERα). A large number of prolactin-induced pSTAT5-immunoreactive neurons expressing ERα mRNA were observed in several brain areas, including the anteroventral periventricular nucleus, medial preoptic nucleus, arcuate nucleus of the hypothalamus, ventrolateral subdivision of the ventromedial nucleus of the hypothalamus (VMH), medial nucleus of the amygdala and nucleus of the solitary tract. However, although the medial preoptic area, periventricular nucleus of the hypothalamus, paraventricular nucleus of the hypothalamus, retrochiasmatic area, dorsomedial subdivision of the VMH, lateral hypothalamic area, dorsomedial nucleus of the hypothalamus and ventral premammillary nucleus contained significant numbers of prolactin-responsive neurons, these areas showed very few pSTAT5-immunoreactive cells expressing ERα mRNA. Second, we evaluated prolactin sensitivity in ovariectomized mice and observed that sex hormones are required for a normal responsiveness to prolactin as ovariectomized mice showed a lower number of prolactin-induced pSTAT5 immunoreactive neurons in all analyzed brain nuclei compared to gonad-intact females. In addition, we performed hypothalamic gene expression analyses to determine possible post-ovariectomy changes in components of prolactin signaling. We observed no significant changes in the mRNA expression of prolactin receptor, STAT5a or STAT5b. In summary, sex hormones exert a permissive role in maintaining the brain's prolactin sensitivity, most likely through posttranscriptional mechanisms.
[Show abstract][Hide abstract] ABSTRACT: Although the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic agent, it shows limited efficacy in human pancreatic cancer cells. Protein synthesis inhibition has been reported to sensitize cancer cells to apoptosis-inducing agents, but the detailed mechanism by which protein synthesis inhibition sensitize cells to TRAIL has not been determined. To investigate the mechanism underlying pancreatic cancer cell resistance to TRAIL, we performed a small scale high-throughput compound screening in AsPC-1 pancreatic cancer cells using a bioactive small molecule library. We identified 8 compounds that reproducibly sensitize AsPC-1 cells to TRAIL-induced apoptosis. One of these compounds, emetine hydrochloride, when combined with subtoxic concentrations of TRAIL, induced massive apoptosis in AsPC-1 and BxPC-3 pancreatic cancer cells. Cell death analysis revealed that the sensitizing effects of emetine were specific to TRAIL. Emetine downregulated the expression of the TRAIL-related anti-apoptotic protein Mcl-1 in a dose- and time-dependent manner. Furthermore, specific knockdown of Mcl-1 using small interfering RNA without emetine treatment sensitized pancreatic cancer cells to TRAIL. Emetine sensitization of pancreatic cancer cells to TRAIL via Mcl-1 was confirmed under hypoxic conditions. Taken together, these findings strongly suggest that Mcl-1 is involved in pancreatic cancer cell resistance to TRAIL, and emetine facilitates the apoptosis of TRAIL-tolerant pancreatic cancer cells by specifically inhibiting Mcl-1 function.
[Show abstract][Hide abstract] ABSTRACT: Obesity, diabetes, and other metabolic complications are growing concerns for public health and could lead to detrimental life-threatening conditions. Neurons whose activities are required for energy and glucose homeostasis are found in a number of hypothalamic nuclei. In the early twentieth century, the ventral medial nucleus of the hypothalamus (VMH) was the first site reported to play a prominent role in the regulation of energy homeostasis through control of food intake and energy expenditure. Recent studies using sophisticated genetic tools have further highlighted the importance of the VMH and have extended our understanding of the physiological role of the nucleus in regulation of energy homeostasis. These genetic studies were preceded by the identification of steroidogenic factor-1 (SF-1) as a marker of the VMH. This review focuses on the emerging homeostatic roles of the SF-1 neurons in the VMH discovered through the use of genetic models, particularly highlighting the control of energy, and glucose homeostasis.
Full-text · Article · May 2013 · Frontiers in Neuroscience
[Show abstract][Hide abstract] ABSTRACT: The transcription factor FOXO1 plays a central role in metabolic homeostasis by regulating leptin and insulin activity in many cell types, including neurons. However, the neurons mediating these effects and the identity of the molecular targets through which FOXO1 regulates metabolism remain to be defined. Here, we show that the ventral medial nucleus of the hypothalamus (VMH) is a key site of FOXO1 action. We found that mice lacking FOXO1 in steroidogenic factor 1 (SF-1) neurons of the VMH are lean due to increased energy expenditure. The mice also failed to appropriately suppress energy expenditure in response to fasting. Furthermore, these mice displayed improved glucose tolerance due to increased insulin sensitivity in skeletal muscle and heart. Gene expression profiling and sequence analysis revealed several pathways regulated by FOXO1. In addition, we identified the nuclear receptor SF-1 as a direct FOXO1 transcriptional target in the VMH. Collectively, our data suggest that the transcriptional networks modulated by FOXO1 in VMH neurons are key components in the regulation of energy balance and glucose homeostasis.
Preview · Article · Jun 2012 · The Journal of clinical investigation
[Show abstract][Hide abstract] ABSTRACT: The transcription factor steroidogenic factor 1 (SF-1) is exclusively expressed in the brain in the ventral medial hypothalamic nucleus (VMH) and is required for the development of this nucleus. However, the physiological importance of transcriptional programs regulated by SF-1 in the VMH is not well defined. To delineate the functional significance of SF-1 itself in the brain, we generated pre- and postnatal VMH-specific SF-1 KO mice. Both models of VMH-specific SF-1 KO were susceptible to high fat diet-induced obesity and displayed impaired thermogenesis after acute exposure to high fat diet. Furthermore, VMH-specific SF-1 KO mice showed significantly decreased LepR expression specifically in the VMH, leading to leptin resistance. Collectively, these results indicate that SF-1 directs transcriptional programs in the hypothalamus relevant to coordinated control of energy homeostasis, especially after excess caloric intake.
Full-text · Article · Jun 2011 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: The ventral medial hypothalamic nucleus (VMH) regulates food intake and body weight homeostasis. The nuclear receptor NR5A1 (steroidogenic factor 1; SF-1) is a transcription factor whose expression is highly restricted in the VMH and is required for the development of the nucleus. Neurons expressing SF-1 in the VMH have emerged as playing important roles in the regulation of body weight and energy homeostasis. Many of these studies have used site-specific gene KO approaches, providing insights into the molecular mechanisms underlying the regulation of energy homeostasis by the SF-1 neurons of the VMH. In this brief review, we will focus on recent studies defining the molecular mechanisms regulating energy homeostasis and body weight in the VMH, particularly stressing the SF-1 expressing neurons.
Full-text · Article · Nov 2010 · Molecular and Cellular Endocrinology
[Show abstract][Hide abstract] ABSTRACT: The ventromedial hypothalamic nucleus (VMH) regulates a variety of homeostatic processes including female sexual behavior and reproduction. In the current study, we assessed the roles of steroidogenic factor 1 (SF-1) on reproductive function in the VMH using central nervous system-specific SF-1 knockout (SF-1 KO(nCre;F/-)) mice. Here we show that SF-1 KO(nCre;F/-) females exhibited marked impairment in female reproduction. Although male mice appeared to be normal in all aspects studied, including sexual behavior, SF-1 KO(nCre;F/-) females showed infertility or subfertility. Although adult SF-1 KO(nCre;F/-) females showed decreased or lacked corpora lutea, exogenous administration of gonadotropins induced the formation of multiple corpora lutea and induced normal ovulation, demonstrating that the ovaries are functionally intact. In addition, SF-1 KO(nCre;F/-) females stimulated with a synthetic GnRH agonist after priming exhibited markedly reduced LH secretion compared with wild-type littermates, arguing that disorganization in and around the VMH caused by SF-1 ablation interferes with the GnRH priming process or gonadotrope LH capacity. Furthermore, the SF-1 KO(nCre;F/-) females primed with estrogen benzoate and progesterone failed to induce steroid receptors around the VMH, consistent with impaired lordosis behavior in the SF-1 KO(nCre;F/-) females. Collectively, our results highlight that SF-1 in the VMH plays crucial roles in regulation of female reproductive function, presumably by organizing a precise neuronal connection and communication in and around the VMH.
No preview · Article · Mar 2010 · Molecular Endocrinology
[Show abstract][Hide abstract] ABSTRACT: Steroidogenic factor 1 (SF-1) is a nuclear receptor that plays important roles in the hypothalamus-pituitary-steroidogenic organ axis. Global knockout studies in mice revealed the essential in vivo roles of SF-1 in the ventromedial hypothalamic (VMH) nucleus, adrenal glands, and gonads. One limitation of global SF-1 knockout mice is their early postnatal death from adrenocortical insufficiency. To overcome limitations of the global knockout mice and to delineate the roles of SF-1 in the brain, we used Cre/loxP recombination technology to genetically ablate SF-1 specifically in the central nervous system (CNS). Mice with CNS-specific knockout of SF-1 mediated by nestin-Cre showed increased anxiety-like behavior, revealing a crucial role of SF-1 in a complex behavioral phenotype. Our studies with CNS-specific SF-1 KO mice also defined roles of SF-1 in regulating the VMH expression of target genes implicated in anxiety and energy homeostasis. Therefore, this review will focus on our recent studies defining the functional roles of SF-1 in the VMH linked to anxiety and energy homeostasis.
No preview · Article · Nov 2008 · Molecular and Cellular Endocrinology
[Show abstract][Hide abstract] ABSTRACT: Steroidogenic factor 1 (SF-1) plays key roles in adrenal and gonadal development, expression of pituitary gonadotropins, and development of the ventromedial hypothalamic nucleus (VMH). If kept alive by adrenal transplants, global knockout (KO) mice lacking SF-1 exhibit delayed-onset obesity and decreased locomotor activity. To define specific roles of SF-1 in the VMH, we used the Cre-loxP system to inactivate SF-1 in a central nervous system (CNS)-specific manner. These mice largely recapitulated the VMH structural defect seen in mice lacking SF-1 in all tissues. In multiple behavioral tests, mice with CNS-specific KO of SF-1 had significantly more anxiety-like behavior than wild-type littermates. The CNS-specific SF-1 KO mice had diminished expression or altered distribution in the mediobasal hypothalamus of several genes whose expression has been linked to stress and anxiety-like behavior, including brain-derived neurotrophic factor, the type 2 receptor for CRH (Crhr2), and Ucn 3. Moreover, transfection and EMSAs support a direct role of SF-1 in Crhr2 regulation. These findings reveal important roles of SF-1 in the hypothalamic expression of key regulators of anxiety-like behavior, providing a plausible molecular basis for the behavioral effect of CNS-specific KO of this nuclear receptor.
[Show abstract][Hide abstract] ABSTRACT: The nuclear receptor steroidogenic factor 1 (SF-1) plays essential roles in the development and function of the ventromedial hypothalamic nucleus (VMH). Considerable evidence links the VMH and SF-1 with the regulation of energy homeostasis. Here, we demonstrate that SF-1 colocalizes in VMH neurons with the cannabinoid receptor 1 (CB1R) and that a specific CB1R agonist modulates electrical activity of SF-1 neurons in hypothalamic slice preparations. We further show that SF-1 directly regulates CB1R gene expression via a SF-1-responsive element at -101 in its 5'-flanking region. Finally, we show that knockout mice with selective inactivation of SF-1 in the brain have decreased expression of CB1R in the region of the VMH and exhibit a blunted response to systemically administered CB1R agonists. These studies suggest that SF-1 directly regulates the expression of CB1R, which has been implicated in the regulation of energy homeostasis and anxiety-like behavior.
No preview · Article · Jun 2008 · Molecular Endocrinology