scholarly journals Cellular Leptin Resistance Impairs the Leptin-Mediated Suppression of Neuropeptide Y Secretion in Hypothalamic Neurons

Endocrinology ◽  
2011 ◽  
Vol 152 (11) ◽  
pp. 4138-4147 ◽  
Author(s):  
Sandeep S. Dhillon ◽  
Sean A. McFadden ◽  
Jennifer A. Chalmers ◽  
Maria-Luisa Centeno ◽  
Ginah L. Kim ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Neuropeptide Y ◽  
Energy Homeostasis ◽  
Fluorescent Protein ◽  
Primary Cultures ◽  
Leptin Resistance ◽  
Cellular Processes ◽  
Compound C ◽  
Green Fluorescent ◽  
Induced Changes

Evidence shows that neuropeptide Y (NPY) neurons are involved in mediating the anorexigenic action of leptin via neuronal circuits in the hypothalamus. However, studies have produced limited data on the cellular processes involved and whether hypothalamic NPY neurons are susceptible to cellular leptin resistance. To investigate the direct regulation of NPY secretion by leptin, we used novel NPY-synthesizing, immortalized mHypoA-NPY/green fluorescent protein and mHypoA-59 hypothalamic cell lines derived from adult hypothalamic primary cultures. We report that leptin treatment significantly suppressed NPY secretion in the cells by approximately 20%. We found a decrease in c-fos expression upon leptin exposure, indicating deactivation or hyperpolarization of the neurons. Protein analysis indicated that leptin inhibits AMP-activated protein kinase (AMPK) activity and activates acetyl-coenzyme A carboxylase in NPY neurons, supporting the hypothesis of an AMPK-dependent mechanism. Inhibiting both AMPK with Compound C or phosphatidylinositol 3 kinase (PI3K) with 2-(4-morpholinyl)-8-phenyl-1(4H)-1-benzopyran-4-one hydrochloride prevented the leptin-mediated decrease in NPY secretion, indicating both AMPK- and PI3K-mediated mechanisms. Further, NPY secretion was stimulated by 30% by the AMPK activator, aminoimidazole carboxamide ribonucleotide. Importantly, prolonged leptin exposure in the mHypoA-NPY/green fluorescent protein cells prevented leptin-induced changes in AMPK phosphorylation and suppression of NPY secretion, indicating that NPY neurons are susceptible to leptin resistance. Our studies indicate that AMPK and PI3K pathways are involved in leptin action in NPY neurons and that leptin resistance blocks the feedback response likely required to maintain energy homeostasis.

scholarly journals Adiponectin receptors are expressed in hypothalamus and colocalized with proopiomelanocortin and neuropeptide Y in rodent arcuate neurons

2008 ◽  
Vol 200 (1) ◽  
pp. 93-105 ◽  
Author(s):  
E Guillod-Maximin ◽  
A F Roy ◽  
C M Vacher ◽  
A Aubourg ◽  
V Bailleux ◽  
...  
Keyword(s):  
Neuropeptide Y ◽  
Energy Homeostasis ◽  
Fluorescent Protein ◽  
Peripheral Tissues ◽  
Rat Hypothalamus ◽  
Ampk Phosphorylation ◽  
Hypothalamic Nuclei ◽  
Green Fluorescent ◽  
Amp Activated Protein Kinase

Adiponectin is involved in the control of energy homeostasis in peripheral tissues through Adipor1 and Adipor2 receptors. An increasing amount of evidence suggests that this adipocyte-secreted hormone may also act at the hypothalamic level to control energy homeostasis. In the present study, we observed the gene and protein expressions of Adipor1 and Adipor2 in rat hypothalamus using different approaches. By immunohistochemistry, Adipor1 expression was ubiquitous in the rat brain. By contrast, Adipor2 expression was more limited to specific brain areas such as hypothalamus, cortex, and hippocampus. In arcuate and paraventricular hypothalamic nuclei, Adipor1, and Adipor2 were expressed by neurons and astrocytes. Furthermore, using transgenic green fluorescent protein mice, we showed that Adipor1 and Adipor2 were present in pro–opiomelanocortin (POMC) and neuropeptide Y (NPY) neurons in the arcuate nucleus. Finally, adiponectin treatment by intracerebroventricular injection induced AMP-activated protein kinase (AMPK) phosphorylation in the rat hypothalamus. This was confirmed byin vitrostudies using hypothalamic membrane fractions. In conclusion, Adipor1 and Adipor2 are both expressed by neurons (including POMC and NPY neurons) and astrocytes in the rat hypothalamic nuclei. Adiponectin is able to increase AMPK phosphorylation in the rat hypothalamus. These data reinforced a potential role of adiponectin and its hypothalamic receptors in the control of energy homeostasis.

scholarly journals Isolation and Immortalization of MIP-GFP Neurons From the Hypothalamus

Endocrinology ◽  
2014 ◽  
Vol 155 (6) ◽  
pp. 2314-2319 ◽  
Author(s):  
Zi Chen Wang ◽  
Michael B. Wheeler ◽  
Denise D. Belsham
Keyword(s):  
Green Fluorescent Protein ◽  
Energy Homeostasis ◽  
Fluorescent Protein ◽  
Transgenic Animals ◽  
Unintended Effects ◽  
Hypothalamic Neurons ◽  
Related Peptide ◽  
Promoter Construct ◽  
Insulin Responsiveness ◽  
Green Fluorescent

The mouse insulin I promoter (MIP) construct was developed to eliminate the promoter activity detected with the rat insulin II promoter in specific hypothalamic neurons that may have unintended effects on glucose and energy homeostasis in transgenic models. Thus, the specificity of this novel construct must be validated prior to the widespread availability of derived Cre models. Although limited validation efforts have indicated a lack of MIP activity within neuronal tissue, the global immunohistochemical methodology used may not be specific enough to rule out the possibility of specific populations of neurons with MIP activity. To investigate possible MIP activity within the hypothalamus, primary hypothalamic isolates from MIP-green fluorescent protein reporter mice were analyzed after fluorescent-activated cell sorting. Primary hypothalamic neurons isolated from the MIP-green fluorescent protein mice were immortalized. Characterization detected the presence of hypothalamic neuropeptide Y (NPY) and agouti-related peptide, involved in the control of energy homeostasis, as well as confirmed insulin responsiveness in the cell lines. Moreover, because insulin was demonstrated to differentially regulate NPY expression within these MIP neurons, the promoter construct may be active in multiple hypothalamic NPY/agouti-related peptide subpopulations with unique physiological functions. MIP transgenic animals may therefore face similar limitations seen previously with rat insulin II promoter-based models.

scholarly journals Characterization of Leptin-Responsive Neurons in the Caudal Brainstem

Endocrinology ◽  
2006 ◽  
Vol 147 (7) ◽  
pp. 3190-3195 ◽  
Author(s):  
Kate L. J. Ellacott ◽  
Ilia G. Halatchev ◽  
Roger D. Cone
Keyword(s):  
Green Fluorescent Protein ◽  
Energy Homeostasis ◽  
Leptin Receptor ◽  
Fluorescent Protein ◽  
Physiological Role ◽  
Cell Group ◽  
Melanocortin System ◽  
Peptide Precursor ◽  
Green Fluorescent

The central melanocortin system plays a key role in the regulation of energy homeostasis. Neurons containing the peptide precursor proopiomelanocortin (POMC) are found at two sites in the brain, the arcuate nucleus of the hypothalamus (ARC) and the caudal region of the nucleus of the solitary tract (NTS). ARC POMC neurons, which also express cocaine- and amphetamine-regulated transcript (CART), are known to mediate part of the response to factors regulating energy homeostasis, such as leptin and ghrelin. In contrast, the physiological role(s) of the POMC neurons in the caudal brainstem are not well characterized. However, development of a transgenic mouse expressing green fluorescent protein under the control of the POMC promoter [POMC-enhanced green fluorescent protein (EGFP) mouse] has aided the study of these neurons. Indeed, recent studies have shown significant activation of NTS POMC-EGFP cells by the gut released satiety factor cholecystokinin (CCK). Here we show that peripheral leptin administration induces the expression of phospho-signal transducer and activator of transcription 3 immunoreactivity (pSTAT3-IR), a marker of leptin receptor signaling, in more than 50% of NTS POMC-EGFP neurons. Furthermore, these POMC-EGFP neurons comprise 30% of all pSTAT3-IR cells in the NTS. Additionally, we also show that in contrast to the ARC population, NTS POMC-EGFP neurons do not coexpress CART immunoreactivity. These data suggest that NTS POMC neurons may participate with ARC POMC cells in mediating some of the effects of leptin and thus comprise a novel cell group regulated by both long-term adipostatic signals and satiety factors such as CCK.

scholarly journals TOR1 and TOR2 Have Distinct Locations in Live Cells

2008 ◽  
Vol 7 (10) ◽  
pp. 1819-1830 ◽  
Author(s):  
Thomas W. Sturgill ◽  
Adiel Cohen ◽  
Melanie Diefenbacher ◽  
Mark Trautwein ◽  
Dietmar E. Martin ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Essential Gene ◽  
Control Cell ◽  
Variable Region ◽  
Live Cells ◽  
Cellular Processes ◽  
C Terminus ◽  
Cold Sensitive ◽  
Green Fluorescent

ABSTRACT TOR is a structurally and functionally conserved Ser/Thr kinase found in two multiprotein complexes that regulate many cellular processes to control cell growth. Although extensively studied, the localization of TOR is still ambiguous, possibly because endogenous TOR in live cells has not been examined. Here, we examined the localization of green fluorescent protein (GFP) tagged, endogenous TOR1 and TOR2 in live S. cerevisiae cells. A DNA cassette encoding three copies of green fluorescent protein (3XGFP) was inserted in the TOR1 gene (at codon D330) or the TOR2 gene (at codon N321). The TORs were tagged internally because TOR1 or TOR2 tagged at the N or C terminus was not functional. The TOR1 D330-3XGFP strain was not hypersensitive to rapamycin, was not cold sensitive, and was not resistant to manganese toxicity caused by the loss of Pmr1, all indications that TOR1-3XGFP was expressed and functional. TOR2-3XGFP was functional, as TOR2 is an essential gene and TOR2 N321-3XGFP haploid cells were viable. Thus, TOR1 and TOR2 retain function after the insertion of 748 amino acids in a variable region of their noncatalytic domain. The localization patterns of TOR1-3XGFP and TOR2-3XGFP were documented by imaging of live cells. TOR1-3XGFP was diffusely cytoplasmic and concentrated near the vacuolar membrane. The TOR2-3XGFP signal was cytoplasmic but predominately in dots at the plasma membrane. Thus, TOR1 and TOR2 have distinct localization patterns, consistent with the regulation of cellular processes as part of two different complexes.

scholarly journals Origin of Neuropeptide Y-Containing Afferents to Gonadotropin-Releasing Hormone Neurons in Male Mice

Endocrinology ◽  
2003 ◽  
Vol 144 (11) ◽  
pp. 4967-4974 ◽  
Author(s):  
Gergely F. Turi ◽  
Zsolt Liposits ◽  
Suzanne M. Moenter ◽  
Csaba Fekete ◽  
Erik Hrabovszky
Keyword(s):  
Green Fluorescent Protein ◽  
Neuropeptide Y ◽  
Enhanced Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Monosodium Glutamate ◽  
Male Mice ◽  
Combined Application ◽  
Gnrh Neurons ◽  
Arcuate Nuclei ◽  
Green Fluorescent

Abstract The origin of neuropeptide Y (NPY) afferents to GnRH neurons was investigated in male mice. Neonatal lesioning of the hypothalamic arcuate nuclei (ARC) with monosodium glutamate markedly reduced the number of NPY fibers in the preoptic area as well as the frequency of their contacts with perikarya and proximal dendrites of GnRH neurons. Dual-label immunofluorescence studies to determine the precise contribution of the ARC to the innervation of GnRH neurons by NPY axons were carried out on transgenic mice in which enhanced green fluorescent protein was expressed under the control of the GnRH promoter (GnRH-enhanced green fluorescent protein mice). The combined application of red Cy3 and blue AMCA fluorochromogenes established that 49.1 ± 7.3% of NPY axons apposed to green GnRH neurons also contained agouti-related protein (AGRP), a selective marker for NPY axons arising from the ARC. Immunoelectronmicroscopic analysis detected symmetric synapses between AGRP fibers and GnRH-immunoreactive perikarya. Additional triple-fluorescence experiments revealed the presence of dopamine-β-hydroxylase immunoreactivity within 25.4 ± 3.3% of NPY afferents to GnRH neurons. This enzyme marker enabled the selective labeling of NPY pathways ascending from noradrenergic/adrenergic cell populations of the brain stem, thus defining a second important source for NPY-containing fibers regulating GnRH cells. The absence of both topographic markers (AGRP and dopamine-β-hydroxylase) within 26% of NPY contacts suggests that additional sources of NPY fibers to GnRH neurons exist. Future studies will address distinct functions of the two identified NPY systems in the afferent neuronal regulation of the GnRH system.

Electric-Field-Induced Changes in Absorption and Fluorescence of the Green Fluorescent Protein Chromophore in a PMMA Film

2011 ◽  
Vol 115 (26) ◽  
pp. 8622-8626 ◽  
Author(s):  
Takakazu Nakabayashi ◽  
Kazuyuki Hino ◽  
Yuka Ohta ◽  
Sayuri Ito ◽  
Hirofumi Nakano ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Electric Field ◽  
Fluorescent Protein ◽  
Pmma Film ◽  
Green Fluorescent ◽  
Induced Changes
Sign in / Sign up

Export Citation Format

Share Document