[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.
[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.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 11/2014; 34(46):15288-96. DOI:10.1523/JNEUROSCI.1316-14.2014 · 6.34 Impact Factor
[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.
Frontiers in Psychology 08/2014; 5:846. DOI:10.3389/fpsyg.2014.00846 · 2.80 Impact Factor
[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.
Brain research 04/2014; 1566. DOI:10.1016/j.brainres.2014.04.018 · 2.84 Impact Factor
[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.
Frontiers in Neuroscience 05/2013; 7(7):71. DOI:10.3389/fnins.2013.00071 · 3.66 Impact Factor
[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.
The Journal of clinical investigation 06/2012; 122(7):2578-89. DOI:10.1172/JCI62848 · 13.22 Impact Factor
[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.
Proceedings of the National Academy of Sciences 06/2011; 108(26):10673-8. DOI:10.1073/pnas.1102364108 · 9.67 Impact Factor
[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.
[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.
[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.
[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.
[Show abstract][Hide abstract] ABSTRACT: Chronic L-dopa treatment of Parkinson's disease (PD) often leads to debilitating involuntary movements, termed L-dopa-induced dyskinesia (LID), mediated by dopamine (DA) receptors. RGS9-2 is a GTPase accelerating protein that inhibits DA D2 receptor-activated G proteins. Herein, we assess the functional role of RGS9-2 on LID. In monkeys, Western blot analysis of striatal extracts shows that RGS9-2 levels are not altered by MPTP-induced DA denervation and/or chronic L-dopa administration. In MPTP monkeys with LID, striatal RGS9-2 overexpression--achieved by viral vector injection into the striatum--diminishes the involuntary movement intensity without lessening the anti-parkinsonian effects of the D1/D2 receptor agonist L-dopa. In contrasts, in these animals, striatal RGS9-2 overexpression diminishes both the involuntary movement intensity and the anti-parkinsonian effects of the D2/D3 receptor agonist ropinirole. In unilaterally 6-OHDA-lesioned rats with LID, we show that the time course of viral vector-mediated striatal RGS9-2 overexpression parallels the time course of improvement of L-dopa-induced involuntary movements. We also find that unilateral 6-OHDA-lesioned RGS9-/- mice are more susceptible to L-dopa-induced involuntary movements than unilateral 6-OHDA-lesioned RGS9+/+ mice, albeit the rotational behavior--taken as an index of the anti-parkinsonian response--is similar between the two groups of mice. Together, these findings suggest that RGS9-2 plays a pivotal role in LID pathophysiology. However, the findings also suggest that increasing RGS9-2 expression and/or function in PD patients may only be a suitable therapeutic strategy to control involuntary movements induced by nonselective DA agonist such as L-dopa.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 01/2008; 27(52):14338-48. DOI:10.1523/JNEUROSCI.4223-07.2007 · 6.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To establish genetic tools for conditional gene deletion in mouse neurons, we generated two independent neuron-specific enolase (Nse)-cre transgenic lines. The transgenic line termed Nse-cre(CK1) showed cre activity in most neuronal regions in the nervous system, while the Nse-cre(CK2) line exhibited a unique cre activity that has not been reported in other cre transgenic lines. Nse-cre(CK2) cre activity was detectable from embryogenesis and mostly restricted to neuronal regions. In postnatal brain, the Nse-cre(CK2) line exhibited cre activity limited to differentiated neurons in the cerebral cortex and hippocampus. Cre activity was assayed in several internal organs and sporadic activity was limited to the kidney and testis. We conclude that these cre lines will be useful for studying loss of gene function in specific neuronal populations.