FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W2143141103> ?p ?o ?g. }

• W2143141103 endingPage "354" @default.
• W2143141103 startingPage "343" @default.
• W2143141103 abstract "PI3K signaling is thought to mediate leptin and insulin action in hypothalamic pro-opiomelanocortin (POMC) and agouti-related protein (AgRP) neurons, key regulators of energy homeostasis, through largely unknown mechanisms. We inactivated either p110α or p110β PI3K catalytic subunits in these neurons and demonstrate a dominant role for the latter in energy homeostasis regulation. In POMC neurons, p110β inactivation prevented insulin- and leptin-stimulated electrophysiological responses. POMCp110β null mice exhibited central leptin resistance, increased adiposity, and diet-induced obesity. In contrast, the response to leptin was not blocked in p110α-deficient POMC neurons. Accordingly, POMCp110α null mice displayed minimal energy homeostasis abnormalities. Similarly, in AgRP neurons, p110β had a more important role than p110α. AgRPp110α null mice displayed normal energy homeostasis regulation, whereas AgRPp110β null mice were lean, with increased leptin sensitivity and resistance to diet-induced obesity. These results demonstrate distinct metabolic roles for the p110α and p110β isoforms of PI3K in hypothalamic energy regulation. PI3K signaling is thought to mediate leptin and insulin action in hypothalamic pro-opiomelanocortin (POMC) and agouti-related protein (AgRP) neurons, key regulators of energy homeostasis, through largely unknown mechanisms. We inactivated either p110α or p110β PI3K catalytic subunits in these neurons and demonstrate a dominant role for the latter in energy homeostasis regulation. In POMC neurons, p110β inactivation prevented insulin- and leptin-stimulated electrophysiological responses. POMCp110β null mice exhibited central leptin resistance, increased adiposity, and diet-induced obesity. In contrast, the response to leptin was not blocked in p110α-deficient POMC neurons. Accordingly, POMCp110α null mice displayed minimal energy homeostasis abnormalities. Similarly, in AgRP neurons, p110β had a more important role than p110α. AgRPp110α null mice displayed normal energy homeostasis regulation, whereas AgRPp110β null mice were lean, with increased leptin sensitivity and resistance to diet-induced obesity. These results demonstrate distinct metabolic roles for the p110α and p110β isoforms of PI3K in hypothalamic energy regulation. Increased understanding of the molecular and cellular mechanisms that regulate whole-body energy homeostasis is needed to gain insights into the pathophysiology of obesity and for the development of effective treatments (Barsh et al., 2000Barsh G.S. Farooqi I.S. O'Rahilly S. Genetics of body-weight regulation.Nature. 2000; 404: 644-651Crossref PubMed Scopus (644) Google Scholar, Barsh and Schwartz, 2002Barsh G.S. Schwartz M.W. Genetic approaches to studying energy balance: perception and integration.Natl. Rev. 2002; 3: 589-600Crossref Google Scholar, Morton et al., 2006Morton G.J. Cummings D.E. Baskin D.G. Barsh G.S. Schwartz M.W. Central nervous system control of food intake and body weight.Nature. 2006; 443: 289-295Crossref PubMed Scopus (1920) Google Scholar). Hypothalamic arcuate nucleus (ARC) pro-opiomelanocortin (POMC)-expressing neurons, and agouti-related protein (AgRP)- and neuropeptide Y (NPY)-expressing neurons sense peripheral and central signals that reflect nutritional status responding to nutrients, anorexigenic peripheral hormones such as leptin and insulin, and centrally derived neuropeptides and neurotransmitters (Barsh et al., 2000Barsh G.S. Farooqi I.S. O'Rahilly S. Genetics of body-weight regulation.Nature. 2000; 404: 644-651Crossref PubMed Scopus (644) Google Scholar, Barsh and Schwartz, 2002Barsh G.S. Schwartz M.W. Genetic approaches to studying energy balance: perception and integration.Natl. Rev. 2002; 3: 589-600Crossref Google Scholar, Bewick et al., 2005Bewick G.A. Gardiner J.V. Dhillo W.S. Kent A.S. White N.E. Webster Z. Ghatei M.A. Bloom S.R. Post-embryonic ablation of AgRP neurons in mice leads to a lean, hypophagic phenotype.FASEB J. 2005; 19: 1680-1682PubMed Google Scholar, Gropp et al., 2005Gropp E. Shanabrough M. Borok E. Xu A.W. Janoschek R. Buch T. Plum L. Balthasar N. Hampel B. Waisman A. et al.Agouti-related peptide-expressing neurons are mandatory for feeding.Nat. Neurosci. 2005; 8: 1289-1291Crossref PubMed Scopus (599) Google Scholar, Luquet et al., 2005Luquet S. Perez F.A. Hnasko T.S. Palmiter R.D. NPY/AgRP neurons are essential for feeding in adult mice but can be ablated in neonates.Science (New York). 2005; 310: 683-685Crossref Scopus (840) Google Scholar, Xu et al., 2005aXu A.W. Kaelin C.B. Morton G.J. Ogimoto K. Stanhope K. Graham J. Baskin D.G. Havel P. Schwartz M.W. Barsh G.S. Effects of hypothalamic neurodegeneration on energy balance.PLoS Biol. 2005; 3: e415https://doi.org/10.1371/journal.pbio.0030415Crossref PubMed Scopus (154) Google Scholar, Choudhury et al., 2005Choudhury A.I. Heffron H. Smith M.A. Al-Qassab H. Xu A.W. Selman C. Simmgen M. Clements M. Claret M. Maccoll G. et al.The role of insulin receptor substrate 2 in hypothalamic and beta cell function.J. Clin. Invest. 2005; 115: 940-950Crossref PubMed Scopus (209) Google Scholar, Claret et al., 2007Claret M. Smith M.A. Batterham R.L. Selman C. Choudhury A.I. Fryer L.G. Clements M. Al-Qassab H. Heffron H. Xu A.W. et al.AMPK is essential for energy homeostasis regulation and glucose sensing by POMC and AgRP neurons.J. Clin. Invest. 2007; 117: 2325-2336Crossref PubMed Scopus (414) Google Scholar, Morton et al., 2006Morton G.J. Cummings D.E. Baskin D.G. Barsh G.S. Schwartz M.W. Central nervous system control of food intake and body weight.Nature. 2006; 443: 289-295Crossref PubMed Scopus (1920) Google Scholar, Smith et al., 2007Smith M.A. Hisadome K. Al-Qassab H. Heffron H. Withers D.J. Ashford M.L. Melanocortins and agouti-related protein modulate the excitability of two arcuate nucleus neuron populations by alteration of resting potassium conductances.J. Physiol. 2007; 578: 425-438Crossref PubMed Scopus (49) Google Scholar). Integration of these signals by POMC and AgRP/NPY neurons regulates both their neuronal activity and the expression and release of their cognate neuropeptides and other neurotransmitters, which combine to control both short- and long-term energy balance (Barsh et al., 2000Barsh G.S. Farooqi I.S. O'Rahilly S. Genetics of body-weight regulation.Nature. 2000; 404: 644-651Crossref PubMed Scopus (644) Google Scholar, Barsh and Schwartz, 2002Barsh G.S. Schwartz M.W. Genetic approaches to studying energy balance: perception and integration.Natl. Rev. 2002; 3: 589-600Crossref Google Scholar). In these neurons, the precise intracellular signaling machinery upon which both leptin and insulin act is incompletely defined. Recent attention has focused upon class IA phosphoinositide 3-kinases (PI3Ks), which are acutely regulated by extracellular stimuli and have pleiotropic roles in cellular and organismal physiology (Vanhaesebroeck et al., 2005Vanhaesebroeck B. Ali K. Bilancio A. Geering B. Foukas L.C. Signalling by PI3K isoforms: insights from gene-targeted mice.Trends Biochem. Sci. 2005; 30: 194-204Abstract Full Text Full Text PDF PubMed Scopus (390) Google Scholar). Class IA PI3K isoforms consist of a p110 catalytic subunit (p110α, p110β, or p110δ) constitutively bound to one of five distinct p85 regulatory subunits (Vanhaesebroeck et al., 2005Vanhaesebroeck B. Ali K. Bilancio A. Geering B. Foukas L.C. Signalling by PI3K isoforms: insights from gene-targeted mice.Trends Biochem. Sci. 2005; 30: 194-204Abstract Full Text Full Text PDF PubMed Scopus (390) Google Scholar). p110α and p110β are widely expressed, while p110δ is predominantly expressed in leucocytes (Vanhaesebroeck et al., 2005Vanhaesebroeck B. Ali K. Bilancio A. Geering B. Foukas L.C. Signalling by PI3K isoforms: insights from gene-targeted mice.Trends Biochem. Sci. 2005; 30: 194-204Abstract Full Text Full Text PDF PubMed Scopus (390) Google Scholar). Class IA PI3Ks catalyze the synthesis of the lipid second messenger phosphatidylinositol (3,4,5)-triphosphate (PIP3), which engages downstream effectors such as the protein kinase B (PKB) pathway (Shepherd et al., 1998Shepherd P.R. Withers D.J. Siddle K. Phosphoinositide 3-kinase: the key switch mechanism in insulin signalling.Biochem. J. 1998; 333: 471-490Crossref PubMed Scopus (841) Google Scholar, Vanhaesebroeck et al., 2005Vanhaesebroeck B. Ali K. Bilancio A. Geering B. Foukas L.C. Signalling by PI3K isoforms: insights from gene-targeted mice.Trends Biochem. Sci. 2005; 30: 194-204Abstract Full Text Full Text PDF PubMed Scopus (390) Google Scholar). Evidence has implicated class IA PI3Ks in hypothalamic function, suggesting that they are a point of signaling integration for leptin and insulin action. Both hormones stimulate PI3K activity in mediobasal hypothalamic lysates and PIP3 production in POMC neurons (Niswender et al., 2001Niswender K.D. Morton G.J. Stearns W.H. Rhodes C.J. Myers Jr., M.G. Schwartz M.W. Intracellular signalling. Key enzyme in leptin-induced anorexia.Nature. 2001; 413: 794-795Crossref PubMed Scopus (518) Google Scholar, Niswender et al., 2003Niswender K.D. Morrison C.D. Clegg D.J. Olson R. Baskin D.G. Myers Jr., M.G. Seeley R.J. Schwartz M.W. Insulin activation of phosphatidylinositol 3-kinase in the hypothalamic arcuate nucleus: a key mediator of insulin-induced anorexia.Diabetes. 2003; 52: 227-231Crossref PubMed Scopus (415) Google Scholar). Pharmacological inhibition of PI3K activity using broad-spectrum PI3K inhibitors blocks the electrophysiological effects of leptin and insulin on POMC neurons and inhibits the acute effects of leptin upon feeding and glucose homeostasis (Hill et al., 2008Hill J.W. Williams K.W. Ye C. Luo J. Balthasar N. Coppari R. Cowley M.A. Cantley L.C. Lowell B.B. Elmquist J.K. Acute effects of leptin require PI3K signaling in hypothalamic proopiomelanocortin neurons in mice.J. Clin. Invest. 2008; 118: 1796-1805Crossref PubMed Scopus (268) Google Scholar, Morton et al., 2005Morton G.J. Gelling R.W. Niswender K.D. Morrison C.D. Rhodes C.J. Schwartz M.W. Leptin regulates insulin sensitivity via phosphatidylinositol-3-OH kinase signaling in mediobasal hypothalamic neurons.Cell Metab. 2005; 2: 411-420Abstract Full Text Full Text PDF PubMed Scopus (238) Google Scholar). However, there are significant unanswered questions regarding the precise role of class IA PI3K isoforms in the hypothalamic regulation of energy homeostasis. First, the effects of specific long-term manipulation of hypothalamic expression of the two major catalytic subunits, p110α and p110β, on body weight regulation are not known. Recent pharmacological evidence using isoform-specific PI3K inhibitors and genetic studies using conditional p110α and p110β null mice and cells have started to reveal specific roles for p110α and p110β in peripheral tissues (Chaussade et al., 2007Chaussade C. Rewcastle G.W. Kendall J.D. Denny W.A. Cho K. Gronning L.M. Chong M.L. Anagnostou S.H. Jackson S.P. Daniele N. Shepherd P.R. Evidence for functional redundancy of class IA PI3K isoforms in insulin signalling.Biochem. J. 2007; 404: 449-458Crossref PubMed Scopus (179) Google Scholar, Ciraolo et al., 2008Ciraolo E. Iezzi M. Marone R. Marengo S. Curcio C. Costa C. Azzolino O. Gonella C. Rubinetto C. Wu H. et al.Phosphoinositide 3-kinase p110beta activity: key role in metabolism and mammary gland cancer but not development.Sci. Signal. 2008; 1: ra3Crossref PubMed Scopus (210) Google Scholar, Graupera et al., 2008Graupera M. Guillermet-Guibert J. Foukas L.C. Phng L.K. Cain R.J. Salpekar A. Pearce W. Meek S. Millan J. Cutillas P.R. et al.Angiogenesis selectively requires the p110alpha isoform of PI3K to control endothelial cell migration.Nature. 2008; 453: 662-666Crossref PubMed Scopus (410) Google Scholar, Jia et al., 2008Jia S. Liu Z. Zhang S. Liu P. Zhang L. Lee S.H. Zhang J. Signoretti S. Loda M. Roberts T.M. Zhao J.J. Essential roles of PI(3)K-p110beta in cell growth, metabolism and tumorigenesis.Nature. 2008; 454: 776-779Crossref PubMed Scopus (598) Google Scholar, Knight et al., 2006Knight Z.A. Gonzalez B. Feldman M.E. Zunder E.R. Goldenberg D.D. Williams O. Loewith R. Stokoe D. Balla A. Toth B. et al.A pharmacological map of the PI3-K family defines a role for p110alpha in insulin signaling.Cell. 2006; 125: 733-747Abstract Full Text Full Text PDF PubMed Scopus (980) Google Scholar). Therefore, these molecules may have different contributions to the regulation of neuronal function. The role of PI3K signaling in AgRP neurons in the regulation of energy homeostasis has also not been determined. In the context of ongoing PI3K drug development, a key question is which of the many PI3K isoforms should be targeted to achieve specific therapeutic benefit (Marone et al., 2008Marone R. Cmiljanovic V. Giese B. Wymann M.P. Targeting phosphoinositide 3-kinase: moving towards therapy.Biochim. Biophys. Acta. 2008; 1784: 159-185Crossref PubMed Scopus (510) Google Scholar, Wymann et al., 2003Wymann M.P. Zvelebil M. Laffargue M. Phosphoinositide 3-kinase signalling—which way to target?.Trends Pharmacol. Sci. 2003; 24: 366-376Abstract Full Text Full Text PDF PubMed Scopus (362) Google Scholar). We therefore inactivated p110α and p110β in POMC or AgRP neurons to determine the role of these kinases in energy homeostasis. Mice with floxed alleles of either p110α (Pik3ca) or p110β (Pik3cb) (Graupera et al., 2008Graupera M. Guillermet-Guibert J. Foukas L.C. Phng L.K. Cain R.J. Salpekar A. Pearce W. Meek S. Millan J. Cutillas P.R. et al.Angiogenesis selectively requires the p110alpha isoform of PI3K to control endothelial cell migration.Nature. 2008; 453: 662-666Crossref PubMed Scopus (410) Google Scholar, Guillermet-Guibert et al., 2008Guillermet-Guibert J. Bjorklof K. Salpekar A. Gonella C. Ramadani F. Bilancio A. Meek S. Smith A.J. Okkenhaug K. Vanhaesebroeck B. The p110beta isoform of phosphoinositide 3-kinase signals downstream of G protein-coupled receptors and is functionally redundant with p110gamma.Proc. Natl. Acad. Sci. USA. 2008; 105: 8292-8297Crossref PubMed Scopus (299) Google Scholar) were crossed with mice that express Cre recombinase in POMC or AgRP neurons (Choudhury et al., 2005Choudhury A.I. Heffron H. Smith M.A. Al-Qassab H. Xu A.W. Selman C. Simmgen M. Clements M. Claret M. Maccoll G. et al.The role of insulin receptor substrate 2 in hypothalamic and beta cell function.J. Clin. Invest. 2005; 115: 940-950Crossref PubMed Scopus (209) Google Scholar, Claret et al., 2007Claret M. Smith M.A. Batterham R.L. Selman C. Choudhury A.I. Fryer L.G. Clements M. Al-Qassab H. Heffron H. Xu A.W. et al.AMPK is essential for energy homeostasis regulation and glucose sensing by POMC and AgRP neurons.J. Clin. Invest. 2007; 117: 2325-2336Crossref PubMed Scopus (414) Google Scholar, Xu et al., 2005aXu A.W. Kaelin C.B. Morton G.J. Ogimoto K. Stanhope K. Graham J. Baskin D.G. Havel P. Schwartz M.W. Barsh G.S. Effects of hypothalamic neurodegeneration on energy balance.PLoS Biol. 2005; 3: e415https://doi.org/10.1371/journal.pbio.0030415Crossref PubMed Scopus (154) Google Scholar, Xu et al., 2005bXu A.W. Kaelin C.B. Takeda K. Akira S. Schwartz M.W. Barsh G.S. PI3K integrates the action of insulin and leptin on hypothalamic neurons.J. Clin. Invest. 2005; 115: 951-958Crossref PubMed Scopus (327) Google Scholar) to generate POMCp110 null and AgRPp110 null mice for each isoform and relevant control strains. The floxed alleles of p110α and p110β were designed to preserve the signaling stoichiometry of the p85/p110 PI3K signaling complexes (Graupera et al., 2008Graupera M. Guillermet-Guibert J. Foukas L.C. Phng L.K. Cain R.J. Salpekar A. Pearce W. Meek S. Millan J. Cutillas P.R. et al.Angiogenesis selectively requires the p110alpha isoform of PI3K to control endothelial cell migration.Nature. 2008; 453: 662-666Crossref PubMed Scopus (410) Google Scholar, Guillermet-Guibert et al., 2008Guillermet-Guibert J. Bjorklof K. Salpekar A. Gonella C. Ramadani F. Bilancio A. Meek S. Smith A.J. Okkenhaug K. Vanhaesebroeck B. The p110beta isoform of phosphoinositide 3-kinase signals downstream of G protein-coupled receptors and is functionally redundant with p110gamma.Proc. Natl. Acad. Sci. USA. 2008; 105: 8292-8297Crossref PubMed Scopus (299) Google Scholar). In the brain, genetic inactivation of p110α or p110β was restricted to the hypothalamus, as determined by PCR analysis of the recombination event (Figures 1A and 1B). We did not detect Cre recombinase expression in the dentate gyrus or nucleus tractus solitarus (data not shown). Hypothalamic p110α lipid kinase activity in POMC- and AgRPp110α null mice (Figure 1C) and p110β activity in POMC- and AgRPp110β null mice (Figure 1D) was reduced, but expression of p85 was unaltered (Figures 1C and 1D). Expression of p110α, p110β, and p85 in muscle, liver, and fat was also equivalent in mutant and control mice (data not shown). PI3K signaling plays key roles in cellular function, but mutant mice did not show alterations in the location, population size, or somatic dimensions of POMC (see Figures S1A–S1H available online) or AgRP neurons (Figures S2A–S2H) compared to control mice. No differences were observed in basic neuronal biophysical properties in the mutant mice, although the resting membrane potential of POMCp110α null neurons was slightly hyperpolarized compared to control POMC neurons, with a concomitant reduction in firing rate (Table S1). However, this change in firing rate did not affect basal peptide release, as hypothalamic explant studies showed that release of alpha melanocyte-stimulating hormone (α-MSH) and AgRP in POMC- and AgRP-targeted mutants, respectively, was equivalent to control mice (Figures S3A–S3D). The POMC promoter also drives Cre recombinase expression in anterior pituitary corticotrophs, but corticosterone levels in all four mutant lines were equivalent to control mice (Figures S4A–S4D). POMCp110β null mice on standard chow displayed normal total body mass but an increased fat mass and fasting hyperleptinemia (Figures 2A, 2C, and 2D). Magnetic resonance imaging (MRI) at 24 weeks of age confirmed increased total body adiposity (fat mass per body weight, POMCp110β null 16.2% ± 1.2% versus control 9.5% ± 1.3%, n = 5, p < 0.01). POMCp110α null mice, in contrast, displayed normal body weight, fat mass, and leptin levels (Figures 2B–2D). POMCp110β null mice, but not POMCp110α null mice, displayed increased food intake, both daily and following an overnight fast (Figures 2E–2G), and increased linear growth (Figures S5A and S5B). Resting metabolic rate (RMR) and sensitivity to the peripherally administered MC3/4R agonist melanotan II (MT-II) were normal in both POMCp110α null and POMCp110β null mice (Figures S5C–S5F). On a high-fat diet (HFD), both POMCp110α null and POMCp110β null mice displayed increased body weight, adiposity, and hyperleptinemia, compared to controls (Figures 2H–2J). Body weight (Figure 3A), fat mass (Figure 3C), and leptin levels (Figure 3D) were significantly lower in AgRPp110β null mice. Food intake ad libitum and following an overnight fast was reduced in AgRPp110β null mice (Figures 3E and 3G). In contrast, AgRPp110α null mice displayed no significant alterations within these parameters (Figures 3B–3F). RMR and sensitivity to MT-II were normal in both AgRPp110α null and AgRPp110β null mice (Figures S6A–S6D). On HFD, AgRPp110β null, but not AgRPp110α null, mice displayed a significant reduction in body weight, fat mass, and leptin levels, compared to controls (Figures 3H–3J). In POMCp110β null mice, suppression of food intake by leptin administered into the third cerebral ventricle (i.c.v.) was equivalent to control mice at 4 hr but blunted at 24 hr postinjection (Figure 4A). Conversely, AgRPp110β null mice had increased sensitivity to i.c.v. leptin at both 4 and 24 hr postinjection, compared to controls (Figure 4B). Inactivating p110α in POMC or AgRP neurons did not affect the response to leptin (Figures S7A and S7B). A small but significant reduction in Pomc mRNA was detectable in fasted POMCp110β null mice, while Agrp and Npy mRNA were unaltered (Figure 4C). Npy mRNA was reduced in AgRPp110βnull mice, while Pomc and Agrp mRNA were unchanged (Figure 4D). No differences in the expression of Pomc, Agrp, and Npy mRNA were detected in POMCp110α null and AgRPp110α null mice (Figures S7C and S7D). Leptin also recruits the janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway to modulate the expression of arcuate neuropeptides. However, we found no alteration of leptin-stimulated STAT3 phosphorylation in POMC or AgRP neurons lacking p110β (percent leptin-stimulated POMC or AgRP neuron pSTAT3: control, 46% ± 6% versus POMC p110β null, 42% ± 5%, p = N.S.; control 54% ± 5% versus AgRP p110β null 67% ± 9% p = N.S., n = 3 animals per genotype and Figure S8). POMC and AgRP neurons have been implicated in the central regulation of glucose homeostasis (Konner et al., 2007Konner A.C. Janoschek R. Plum L. Jordan S.D. Rother E. Ma X. Xu C. Enriori P. Hampel B. Barsh G.S. et al.Insulin action in AgRP-expressing neurons is required for suppression of hepatic glucose production.Cell Metab. 2007; 5: 438-449Abstract Full Text Full Text PDF PubMed Scopus (517) Google Scholar, Parton et al., 2007Parton L.E. Ye C.P. Coppari R. Enriori P.J. Choi B. Zhang C.Y. Xu C. Vianna C.R. Balthasar N. Lee C.E. et al.Glucose sensing by POMC neurons regulates glucose homeostasis and is impaired in obesity.Nature. 2007; 449: 228-232Crossref PubMed Scopus (545) Google Scholar), but no alterations were found in fasting glucose levels, glucose tolerance, and fasting insulin levels in all four mutant lines (Figures S9A–S9H). We next used electrophysiological analysis to investigate neuronal responses to leptin and insulin in POMCp110β null and POMCp110α null mice. Consistent with previous observations (Choudhury et al., 2005Choudhury A.I. Heffron H. Smith M.A. Al-Qassab H. Xu A.W. Selman C. Simmgen M. Clements M. Claret M. Maccoll G. et al.The role of insulin receptor substrate 2 in hypothalamic and beta cell function.J. Clin. Invest. 2005; 115: 940-950Crossref PubMed Scopus (209) Google Scholar, Claret et al., 2007Claret M. Smith M.A. Batterham R.L. Selman C. Choudhury A.I. Fryer L.G. Clements M. Al-Qassab H. Heffron H. Xu A.W. et al.AMPK is essential for energy homeostasis regulation and glucose sensing by POMC and AgRP neurons.J. Clin. Invest. 2007; 117: 2325-2336Crossref PubMed Scopus (414) Google Scholar, Cowley et al., 2001Cowley M.A. Smart J.L. Rubinstein M. Cerdan M.G. Diano S. Horvath T.L. Cone R.D. Low M.J. Leptin activates anorexigenic POMC neurons through a neural network in the arcuate nucleus.Nature. 2001; 411: 480-484Crossref PubMed Scopus (1804) Google Scholar, Plum et al., 2006Plum L. Ma X. Hampel B. Balthasar N. Coppari R. Munzberg H. Shanabrough M. Burdakov D. Rother E. Janoschek R. et al.Enhanced PIP3 signaling in POMC neurons causes KATP channel activation and leads to diet-sensitive obesity.J. Clin. Invest. 2006; 116: 1886-1901Crossref PubMed Scopus (276) Google Scholar), a subpopulation of control POMC neurons (6 of 21) responded to locally applied leptin (50 nM) by long-lasting (>1 hr) membrane depolarization (Figure 5A), an action significant for the recorded population (n = 21, p < 0.05; Table 1). Although leptin depolarization of POMC neurons could be observed at resting membrane potentials (Vm) of approximately −50 mV, the magnitude of response was greater at more hyperpolarized Vm (r2 = 0.63, n = 21, p < 0.0001; Figure S10A). As previously reported, the majority of control POMC neurons were unresponsive to leptin (Table 1 and Figure S10B).Table 1Effects of Leptin and Insulin on POMC and AgRP Neuron ExcitabilityTotalResponsiveΔVm (mV)Δ Spike (Hz)ΔVm (mV)Δ Spike (Hz)+LeptinPOMC+1.3 ± 0.6∗ (21)+0.5 ± 0.3 (21)+4.5 ± 1.3 (6/21)+1.6 ± 0.4 (6/21)POMCp110α null+3.2 ± 1.4∗ (13)+1.0 ± 0.5∗ (13)+6.3 ± 1.9 (7/13)+2.2 ± 0.5 (7/13)POMCp110β null−2.1 ± 1.1 (17)+0.1 ± 0.4 (17)−6.1 ± 1.7 (7/17)−1.2 ± 0.5 (7/17)POMC + TGX-221−0.9 ± 1.6 (11)+0.3 ± 0.8 (11)−16.0 (1/11)−5.6 (1/11)AgRP−0.1 ± 1.1 (7)−0.5 ± 0.8 (7)N.R.N.R.AgRPp110α null−1.2 ± 0.9 (7)−0.9 ± 0.4 (7)N.R.N.R.AgRPp110β null0.0 ± 0.2 (7)−0.3 ± 0.4 (7)N.R.N.R.+InsulinPOMC−4.4 ± 1.1∗ (19)−2.2 ± 0.7∗ (19)−7.1 ± 1.1 (12/19)−3.4 ± 0.9 (12/19)POMCp110α null−0.6 ± 0.3 (8)−0.2 ± 0.2 (8)N.R.N.R.POMCp110β null+0.4 ± 0.9 (9)+1.0 ± 0.6 (9)N.R.N.R.POMC +TGX-221+0.9 ± 0.6 (8)−0.1 ± 0.2 (8)N.R.N.R.POMC + PI-103+1.1 ± 0.7 (7)+0.3 ± 0.6 (7)N.R.N.R.AgRP+1.4 ± 0.5∗ (13)+0.5 ± 0.3 (13)+3.8 ± 0.9 (4/13)+0.9 ± 0.3 (4/13)AgRPp110α null−4.0 ± 0.6∗ (7)−1.9 ± 0.9 (7)−4.0 ± 0.6 (7/7)−1.9 ± 0.9 (7/7)AgRPp110β null−2.7 ± 1.1∗ (11)−0.4 ± 0.3 (11)−5.2 ± 1.4 (6/11)−0.6 ± 0.4 (6/11)AgRP + wortmannin−2.0 ± 0.8∗ (10)−0.4 ± 0.3 (10)−4.2 ± 0.8 (5/10)−1.1 ± 0.3 (5/10)Changes in membrane potential (Vm) and spike firing frequency are shown for control, p110α, or p110β null POMC and AgRP neurons. PI3K activity was also blocked in POMC and AgRP neurons by PI-103 (100 nM), wortmannin (100 nM), or the p110β-selective inhibitor TGX-221 (1 μM). Statistical significance (∗p < 0.05) was determined from all neurons (Total), irrespective of their response. For qualitative purposes only, responsive neurons were distinguished by a change in Vm greater than ±2 mV. N.R., no apparent response. Numbers of cells are shown in parentheses. Data are expressed as mean ± SEM. Open table in a new tab Changes in membrane potential (Vm) and spike firing frequency are shown for control, p110α, or p110β null POMC and AgRP neurons. PI3K activity was also blocked in POMC and AgRP neurons by PI-103 (100 nM), wortmannin (100 nM), or the p110β-selective inhibitor TGX-221 (1 μM). Statistical significance (∗p < 0.05) was determined from all neurons (Total), irrespective of their response. For qualitative purposes only, responsive neurons were distinguished by a change in Vm greater than ±2 mV. N.R., no apparent response. Numbers of cells are shown in parentheses. Data are expressed as mean ± SEM. As POMCp110β null mice displayed reduced sensitivity to leptin, we examined the effect of genetic inactivation of specific PI3K catalytic subunit isoforms on leptin-mediated POMC excitability. In mice aged 8–16 weeks, leptin depolarized (n = 13, p < 0.05) the POMCp110α null neuronal population and increased their spike firing frequency (Figure 5B and Table 1), in agreement with the unchanged leptin sensitivity observed in vivo. In contrast, leptin did not depolarize POMCp110β null neurons, and indeed many POMCp110β null neurons (7 of 17) exhibited long-lasting hyperpolarization following leptin application (Figure 5C, Table 1). Subsequently, in a separate series of experiments on age- (7- and 18-week-old) and sex-matched POMCp110β null mutant mice, we first showed that food intake was elevated at both 7 and 18 weeks of age. Irrespective of age or metabolic phenotype, subsequent electrophysiological recordings from POMCp110β null neurons demonstrated that there were no alterations to POMC neuron resting membrane potential, spike firing frequency, or input resistance in comparison to littermate control POMC neurons (Table S2). Furthermore, these POMCp110β null neurons exhibited the same altered response to leptin (i.e., conversion of depolarization to hyperpolarization) that was significantly different from the leptin-mediated excitation of control POMC neurons. To exclude the possibility that compensatory changes associated with chronic ablation of p110β expression were responsible for this altered leptin response, in separate experiments on control POMC neurons, the selective p110β inhibitor TGX-221 (1 μM) (Jackson et al., 2005Jackson S.P. Schoenwaelder S.M. Goncalves I. Nesbitt W.S. Yap C.L. Wright C.E. Kenche V. Anderson K.E. Dopheide S.M. Yuan Y. et al.PI 3-kinase p110beta: a new target for antithrombotic therapy.Nat. Med. 2005; 11: 507-514Crossref PubMed Scopus (535) Google Scholar) was added to the internal pipette solution. Following a minimum of 10 min of intracellular dialysis, leptin (50 nM) application did not excite TGX-221-treated POMC neurons (n = 11, N.S.; Figure 5D and Table 1). On one occasion, a large leptin-mediated hyperpolarization was observed, which was reversibly occluded by bath-applied tolbutamide, indicating the likely involvement of ATP-sensitive K+ (KATP) channels in this hyperpolarizing response (Figure S10C). Overall, these electrophysiological outcomes reflect the decreased leptin sensitivity found in POMCp110β null mice in vivo. POMC neurons are also targets for insulin action, and consistent with previous reports (Choudhury et al., 2005Choudhury A.I. Heffron H. Smith M.A. Al-Qassab H. Xu A.W. Selman C. Simmgen M. Clements M. Claret M. Maccoll G. et al.The role of insulin receptor substrate 2 in hypothalamic and beta cell function.J. Clin. Invest. 2005; 115: 940-950Crossref PubMed Scopus (209) Google Scholar, Claret et al., 2007Claret M. Smith M.A. Batterham R.L. Selman C. Choudhury A.I. Fryer L.G. Clements M. Al-Qassab H. Heffron H. Xu A.W. et al.AMPK is essential for energy homeostasis regulation and glucose sensing by POMC and AgRP neurons.J. Clin. Invest. 2007; 117: 2325-2336Crossref PubMed Scopus (414) Google Scholar, Hill et al., 2008Hill J.W. Williams K.W. Ye C. Luo J. Balthasar N. Coppari R. Cowley M.A. Cantley L.C. Lowell B.B. Elmquist J.K. Acute effects of leptin require PI3K signaling in hypothalamic proopiomelanocortin neurons in mice.J. Clin. Invest. 2008; 118: 1796-1805Crossref PubMed Scopus (268) Google Scholar, Konner et al., 2007Konner A.C. Janoschek R. Plum L. Jordan S.D. Rother E. Ma X. Xu C. Enriori P. Hampel B. Barsh G.S. et al.Insulin action in AgRP-expressing neurons is required for suppression of hepatic glucose production.Cell Metab. 2007; 5: 438-449Abstract Full Text Full Text PDF PubMed Scopus (517) Google Scholar, Plum" @default.
• W2143141103 created "2016-06-24" @default.
• W2143141103 creator A5015164997 @default.
• W2143141103 creator A5016879889 @default.
• W2143141103 creator A5018622504 @default.
• W2143141103 creator A5021208221 @default.
• W2143141103 creator A5021420538 @default.
• W2143141103 creator A5031663089 @default.
• W2143141103 creator A5033517921 @default.
• W2143141103 creator A5036989854 @default.
• W2143141103 creator A5042671518 @default.
• W2143141103 creator A5044446961 @default.
• W2143141103 creator A5051010078 @default.
• W2143141103 creator A5057380504 @default.
• W2143141103 creator A5057615005 @default.
• W2143141103 creator A5065113225 @default.
• W2143141103 creator A5069614527 @default.
• W2143141103 creator A5080111201 @default.
• W2143141103 creator A5085481226 @default.
• W2143141103 creator A5090258133 @default.
• W2143141103 date "2009-11-01" @default.
• W2143141103 modified "2023-10-14" @default.
• W2143141103 title "Dominant Role of the p110β Isoform of PI3K over p110α in Energy Homeostasis Regulation by POMC and AgRP Neurons" @default.
• W2143141103 cites W1506453366 @default.
• W2143141103 cites W1516631422 @default.
• W2143141103 cites W1584840122 @default.
• W2143141103 cites W1653273172 @default.
• W2143141103 cites W1841050729 @default.
• W2143141103 cites W1963535279 @default.
• W2143141103 cites W1974128502 @default.
• W2143141103 cites W1974743256 @default.
• W2143141103 cites W1978981032 @default.
• W2143141103 cites W1981415589 @default.
• W2143141103 cites W1988845013 @default.
• W2143141103 cites W1991761103 @default.
• W2143141103 cites W2012496594 @default.
• W2143141103 cites W2020972524 @default.
• W2143141103 cites W2032284140 @default.
• W2143141103 cites W2034691869 @default.
• W2143141103 cites W2044823943 @default.
• W2143141103 cites W2050418518 @default.
• W2143141103 cites W2064842282 @default.
• W2143141103 cites W2071475119 @default.
• W2143141103 cites W2072556905 @default.
• W2143141103 cites W2078948501 @default.
• W2143141103 cites W2079395662 @default.
• W2143141103 cites W2087693130 @default.
• W2143141103 cites W2092284194 @default.
• W2143141103 cites W2092380207 @default.
• W2143141103 cites W2094751859 @default.
• W2143141103 cites W2096591765 @default.
• W2143141103 cites W2098623033 @default.
• W2143141103 cites W2100458159 @default.
• W2143141103 cites W2102364504 @default.
• W2143141103 cites W2102743478 @default.
• W2143141103 cites W2109627278 @default.
• W2143141103 cites W2115254413 @default.
• W2143141103 cites W2118469376 @default.
• W2143141103 cites W2124593509 @default.
• W2143141103 cites W2125793202 @default.
• W2143141103 cites W2128824908 @default.
• W2143141103 cites W2129221666 @default.
• W2143141103 cites W2132352647 @default.
• W2143141103 cites W2135244179 @default.
• W2143141103 cites W2140691623 @default.
• W2143141103 cites W2148161631 @default.
• W2143141103 cites W2152483203 @default.
• W2143141103 cites W2152620156 @default.
• W2143141103 cites W2160824260 @default.
• W2143141103 cites W2161418574 @default.
• W2143141103 doi "https://doi.org/10.1016/j.cmet.2009.09.008" @default.
• W2143141103 hasPubMedCentralId "https://www.ncbi.nlm.nih.gov/pmc/articles/2806524" @default.
• W2143141103 hasPubMedId "https://pubmed.ncbi.nlm.nih.gov/19883613" @default.
• W2143141103 hasPublicationYear "2009" @default.
• W2143141103 type Work @default.
• W2143141103 sameAs 2143141103 @default.
• W2143141103 citedByCount "143" @default.
• W2143141103 countsByYear W21431411032012 @default.
• W2143141103 countsByYear W21431411032013 @default.
• W2143141103 countsByYear W21431411032014 @default.
• W2143141103 countsByYear W21431411032015 @default.
• W2143141103 countsByYear W21431411032016 @default.
• W2143141103 countsByYear W21431411032017 @default.
• W2143141103 countsByYear W21431411032018 @default.
• W2143141103 countsByYear W21431411032019 @default.
• W2143141103 countsByYear W21431411032020 @default.
• W2143141103 countsByYear W21431411032021 @default.
• W2143141103 countsByYear W21431411032022 @default.
• W2143141103 countsByYear W21431411032023 @default.
• W2143141103 crossrefType "journal-article" @default.
• W2143141103 hasAuthorship W2143141103A5015164997 @default.
• W2143141103 hasAuthorship W2143141103A5016879889 @default.
• W2143141103 hasAuthorship W2143141103A5018622504 @default.
• W2143141103 hasAuthorship W2143141103A5021208221 @default.
• W2143141103 hasAuthorship W2143141103A5021420538 @default.
• W2143141103 hasAuthorship W2143141103A5031663089 @default.
• W2143141103 hasAuthorship W2143141103A5033517921 @default.
• W2143141103 hasAuthorship W2143141103A5036989854 @default.

• next