Estudio de los circuitos neuronales involucrados y del rol modulador de ghrelina en los aspectos hedónicos del apetito

La ingesta de alimento es una función vital para el reino animal ya que proporciona las necesidades nutricionales y energéticas. Existen, al menos, dos circuitos neuronales complementarios que la regulan: un circuito relacionado a los aspectos homeostáticos, dependiente de las reservas energéticas; y otro que regula aspectos hedónicos, relacionado con la recompensa que generan alimentos específicos.\nLa ingesta de alimento, además, está fuertemente regulada por señales periféricas, como metabolitos y hormonas, que contribuyen a la regulación precisa de los circuitos neuronales que controlan el apetito. Entre las hormonas que regulan el apetito se destaca la ghrelina, la cual se produce en el tracto digestivo y es la única hormona peptídica conocida capaz de estimular la ingesta de alimento, lo cual ocurriría mediante su acción sobre ambos tipos de mecanismos de regulación. El control de la ingesta de alimento puede sufrir alteraciones que derivan en diversas situaciones patológicas. Una de ellas es el llamado atracón alimentario (binge eating), el cual se observa con alta frecuencia y se define como un evento de hiperfagia en el que se consume una gran cantidad de alimento, en un período corto de tiempo y con la sensación de una pérdida de control de lo que se está consumiendo. Episodios de atracón alimentario se pueden observar en una gran variedad de situaciones patológicas como la bulimia, los desórdenes asociados al atracón alimentario (binge eating disorders) y algunas variantes de anorexia nerviosa, así como también pueden ocurrir en personas con sobrepeso u obesidad, e incluso en la población general. La etiología de los episodios de atracón es actualmente desconocida y, lamentablemente, no existe ningún tratamiento farmacológico para mitigarlos.Por lo tanto, el objetivo general de este trabajo de Tesis Doctoral fue estudiar en modelos murinos los circuitos neuronales activados por uno o varios eventos de ingesta de dieta rica en grasa y evaluar el potencial rol modulador de ghrelina sobre ellos.Doctor en Ciencias Exactas, área Ciencias Biológica

Estudio de los circuitos neuronales involucrados y del rol modulador de ghrelina en los aspectos hedónicos del apetito

La ingesta de alimento es una función vital para el reino animal ya que proporciona las necesidades nutricionales y energéticas. Existen, al menos, dos circuitos neuronales complementarios que la regulan: un circuito relacionado a los aspectos homeostáticos, dependiente de las reservas energéticas; y otro que regula aspectos hedónicos, relacionado con la recompensa que generan alimentos específicos. La ingesta de alimento, además, está fuertemente regulada por señales periféricas, como metabolitos y hormonas, que contribuyen a la regulación precisa de los circuitos neuronales que controlan el apetito. Entre las hormonas que regulan el apetito se destaca la ghrelina, la cual se produce en el tracto digestivo y es la única hormona peptídica conocida capaz de estimular la ingesta de alimento, lo cual ocurriría mediante su acción sobre ambos tipos de mecanismos de regulación. El control de la ingesta de alimento puede sufrir alteraciones que derivan en diversas situaciones patológicas. Una de ellas es el llamado atracón alimentario (binge eating), el cual se observa con alta frecuencia y se define como un evento de hiperfagia en el que se consume una gran cantidad de alimento, en un período corto de tiempo y con la sensación de una pérdida de control de lo que se está consumiendo. Episodios de atracón alimentario se pueden observar en una gran variedad de situaciones patológicas como la bulimia, los desórdenes asociados al atracón alimentario (binge eating disorders) y algunas variantes de anorexia nerviosa, así como también pueden ocurrir en personas con sobrepeso u obesidad, e incluso en la población general. La etiología de los episodios de atracón es actualmente desconocida y, lamentablemente, no existe ningún tratamiento farmacológico para mitigarlos.Por lo tanto, el objetivo general de este trabajo de Tesis Doctoral fue estudiar en modelos murinos los circuitos neuronales activados por uno o varios eventos de ingesta de dieta rica en grasa y evaluar el potencial rol modulador de ghrelina sobre ellos.Facultad de Ciencias Exacta

Acute High Fat Diet Consumption Activates the Mesolimbic Circuit and Requires Orexin Signaling in a Mouse Model

Overconsumption of palatable energy-dense foods has negative health implications and it is associated with obesity andseveral eating disorders. Currently, little is known about the neuronal circuitries activated by the acute ingestion of arewarding stimulus. Here, we used a combination of immunohistochemistry, pharmacology and neuronal tracing analysesto examine the role of the mesolimbic system in general, and the orexin neurons in particular, in a simple experimental testin which naı ̈ve mice are allowed to spontaneously eat a pellet of a high fat diet (HFD) for 2 h. We found that acute HFDactivates c-Fos expression in several reward-related brain areas, including the ventral tegmental area (VTA), nucleusaccumbens, central amygdala and lateral hypothalamic area. We also found that: i- HFD-mediated orosensory stimulationwas required for the mesolimbic pathway activation, ii- acute HFD differentially activates dopamine neurons of theparanigral, parabrachial pigmented and interfascicular sub-regions of the VTA, and iii- orexin neurons of the lateralhypothalamic area are responsive to acute HFD. Moreover, orexin signaling blockade, with the orexin 1 receptor antagonistSB-334867, reduces acute HFD consumption and c-Fos induction in the VTA but not in the other mesolimbic nuclei understudy. Finally, we found that most orexin neurons responsive to acute HFD innervate the VTA. Our results show that acuteHFD consumption recruits the mesolimbic system and that the full manifestation of this eating behavior requires theactivation of orexin signaling.Fil: Valdivia Torres, Lesly Spring. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Patrone, Anabela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Reynaldo, Mirta Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Perello, Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; Argentin

Considerations about rodent models of binge eating episodes

A binge eating episode is defined as an uncontrolled event of hyperphagia, in which people quickly eat a large amount of food while feeling a sense of loss of control over eating (Wolfe et al., 2009). Binge eating episodes are observed in a variety of human disorders including bulimia nervosa (BN), binge eating disorder (BED), and the binge/purge subtype of anorexia nervosa (AN) (Berger and Tanofsky-Kraff, 2012). Binge eating episodes are also present in overweight and obese people, as well as non-clinical populations under specific circumstances such as stress. The etiology of this behavior is currently unknown. The use of rodent models has been essential for understanding the pathogenesis of many human diseases; however, it is challenging to mimic all features of human binge eating in rodent models (Corwin and Buda-Levin, 2004; Perello et al., 2010a). In particular, these models should not only display the objective characteristics of a binge eating episode, namely the consumption of a large amount of food in a short period of time, but also the subjective characteristics of the feeling of loss of control. Recently, we examined the neuronal circuitries activated in naïve mice allowed to spontaneously eat a high fat diet (HFD) pellet for 2 h (Valdivia et al., 2014). We found that satiated mice with free access to regular chow rapidly consume a significant amount of HFD when exposed to it, and that HFD intake recruits centers of the mesolimbic pathway, which are known to be activated in human beings displaying binge eating behavior (see below). Experts in the field agreed that our simple model of HFD overconsumption could be relevant for studying neuronal aspects of binge eating behaviors. However, some reviewers argued that it was misleading to describe our model as a model of binge eating. Some criticisms were that our model lacked indications of feelings of loss of control, repeated feeding episodes, escalation of intake over time, a significant level of hyperphagia, and evidence that bingeing occurred in the face of aversive consequences. The notable divergence in the opinion of the journal´s reviewers made evident that a comprehensive debate about rodent binge eating models is needed. Here, we briefly present our opinion about the features that a rodent model should fulfill in order to be considered a reasonable model of binge eating episodes and its implications in terms of the neuronal circuits involved.Fil: Perello, Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Valdivia Torres, Lesly Spring. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Garcia Romero, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Raingo, Jesica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; Argentin

Considerations about rodent models of binge eating episodes

A binge eating episode is defined as an uncontrolled event of hyperphagia, in which people quickly eat a large amount of food while feeling a sense of loss of control over eating (Wolfe et al., 2009). Binge eating episodes are observed in a variety of human disorders including bulimia nervosa (BN), binge eating disorder (BED), and the binge/purge subtype of anorexia nervosa (AN) (Berger and Tanofsky-Kraff, 2012). Binge eating episodes are also present in overweight and obese people, as well as non-clinical populations under specific circumstances such as stress. The etiology of this behavior is currently unknown. The use of rodent models has been essential for understanding the pathogenesis of many human diseases; however, it is challenging to mimic all features of human binge eating in rodent models (Corwin and Buda-Levin, 2004; Perello et al., 2010a). In particular, these models should not only display the objective characteristics of a binge eating episode, namely the consumption of a large amount of food in a short period of time, but also the subjective characteristics of the feeling of loss of control. Recently, we examined the neuronal circuitries activated in naïve mice allowed to spontaneously eat a high fat diet (HFD) pellet for 2 h (Valdivia et al., 2014). We found that satiated mice with free access to regular chow rapidly consume a significant amount of HFD when exposed to it, and that HFD intake recruits centers of the mesolimbic pathway, which are known to be activated in human beings displaying binge eating behavior (see below). Experts in the field agreed that our simple model of HFD overconsumption could be relevant for studying neuronal aspects of binge eating behaviors. However, some reviewers argued that it was misleading to describe our model as a model of binge eating. Some criticisms were that our model lacked indications of feelings of loss of control, repeated feeding episodes, escalation of intake over time, a significant level of hyperphagia, and evidence that bingeing occurred in the face of aversive consequences. The notable divergence in the opinion of the journal´s reviewers made evident that a comprehensive debate about rodent binge eating models is needed. Here, we briefly present our opinion about the features that a rodent model should fulfill in order to be considered a reasonable model of binge eating episodes and its implications in terms of the neuronal circuits involved.Instituto Multidisciplinario de Biología Celula

Acute High Fat Diet Consumption Activates the Mesolimbic Circuit and Requires Orexin Signaling in a Mouse Model

Overconsumption of palatable energy-dense foods has negative health implications and it is associated with obesity andseveral eating disorders. Currently, little is known about the neuronal circuitries activated by the acute ingestion of arewarding stimulus. Here, we used a combination of immunohistochemistry, pharmacology and neuronal tracing analysesto examine the role of the mesolimbic system in general, and the orexin neurons in particular, in a simple experimental testin which naı ̈ve mice are allowed to spontaneously eat a pellet of a high fat diet (HFD) for 2 h. We found that acute HFDactivates c-Fos expression in several reward-related brain areas, including the ventral tegmental area (VTA), nucleusaccumbens, central amygdala and lateral hypothalamic area. We also found that: i- HFD-mediated orosensory stimulationwas required for the mesolimbic pathway activation, ii- acute HFD differentially activates dopamine neurons of theparanigral, parabrachial pigmented and interfascicular sub-regions of the VTA, and iii- orexin neurons of the lateralhypothalamic area are responsive to acute HFD. Moreover, orexin signaling blockade, with the orexin 1 receptor antagonistSB-334867, reduces acute HFD consumption and c-Fos induction in the VTA but not in the other mesolimbic nuclei understudy. Finally, we found that most orexin neurons responsive to acute HFD innervate the VTA. Our results show that acuteHFD consumption recruits the mesolimbic system and that the full manifestation of this eating behavior requires theactivation of orexin signaling.Facultad de Ciencias ExactasInstituto Multidisciplinario de Biología Celula

Escalation in high fat intake in a binge eating model differentially engages dopamine neurons of the ventral tegmental area and requires ghrelin signaling

Binge eating is a behavior observed in a variety of human eating disorders. Ad libitum fed rodents daily and time-limited exposed to a high-fat diet (HFD) display robust binge eating events that gradually escalate over the initial accesses. Intake escalation is proposed to be part of the transition from a controlled to a compulsive or loss of control behavior. Here, we used a combination of behavioral and neuroanatomical studies in mice daily and time-limited exposed to HFD to determine the neuronal brain targets that are activated – as indicated by the marker of cellular activation c-Fos – under these circumstances. Also, we used pharmacologically or genetically manipulated mice to study the role of orexin or ghrelin signaling, respectively, in the modulation of this behavior. We found that four daily and time-limited accesses to HFD induce: (i) a robust hyperphagia with an escalating profile, (ii) an activation of different sub-populations of the ventral tegmental area dopamine neurons and accumbens neurons that is, in general, more pronounced than the activation observed after a single HFD consumption event, and (iii) an activation of the hypothalamic orexin neurons, although orexin signaling blockage fails to affect escalation of HFD intake. In addition, we found that ghrelin receptor-deficient mice fail to both escalate the HFD consumption over the successive days of exposure and fully induce activation of the mesolimbic pathway in response to HFD consumption. Current data suggest that the escalation in high fat intake during repeated accesses differentially engages dopamine neurons of the ventral tegmental area and requires ghrelin signaling

Inter-individual Variability for High Fat Diet Consumption in Inbred C57BL/6 Mice

Since inbred C57BL/6 mice are known to show inter-individual phenotypic variability for some traits, we tested the hypothesis that inbred C57BL/6 mice display a different tendency to consume a high fat (HF) diet. For this purpose, we used a compilation of HF intake data from an experimental protocol in which satiated mice were exposed to a HF pellet every morning for 2-h over 4 consecutive days. We found that mice displayed a large degree of variability in HF intake. Since day 1 HF intake significantly correlated with HF intake in successive days, we applied a hierarchical clustering algorithm on HF intake measurements in days 2, 3, and 4 in order to classify mice into "low" or "high" HF intake groups. "Low" HF intake group showed a day 1 HF intake similar to that seen in mice exposed to regular chow, while "high" HF intake group showed a higher day 1 HF intake as compared to "low" HF intake group. Both groups of mice increased HF consumption over the successive days, but "high" HF intake group always displayed a higher HF consumption than the "low" HF intake group. As compared to "low" HF intake group, "high" HF intake group showed a higher number of dopamine neurons positive for c-Fos in the VTA after the last event of HF intake. Thus, inbred C57BL/6 mice show inter-individual variability for HF intake and such feature may be linked to a different response to the rewarding properties of the HF diet.Instituto Multidisciplinario de Biología Celula

Neuroanatomical and functional characterization of CRF neurons of the amygdala using a novel transgenic mouse model

The corticotropin-releasing factor (CRF)-producing neurons of the amygdala have been implicated in behavioral and physiological responses associated with fear, anxiety, stress, food intake and reward. To overcome the difficulties in identifying CRF neurons within the amygdala, a novel transgenic mouse line, in which the humanized recombinant Renilla reniformis green fluorescent protein (hrGFP) is under the control of the CRF promoter (CRF-hrGFP mice), was developed. First, the CRF-hrGFP mouse model was validated and the localization of CRF neurons within the amygdala was systematically mapped. Amygdalar hrGFP-expressing neurons were located primarily in the interstitial nucleus of the posterior limb of the anterior commissure, but also present in the central amygdala. Secondly, the marker of neuronal activation c-Fos was used to explore the response of amygdalar CRF neurons in CRF-hrGFP mice under different experimental paradigms. C-Fos induction was observed in CRF neurons of CRF-hrGFP mice exposed to an acute social defeat stress event, a fasting/refeeding paradigm or lipopolysaccharide (LPS) administration. In contrast, no c-Fos induction was detected in CRF neurons of CRF-hrGFP mice exposed to restraint stress, forced swimming test, 48-h fasting, acute high-fat diet (HFD) consumption, intermittent HFD consumption, ad libitum HFD consumption, HFD withdrawal, conditioned HFD aversion, ghrelin administration or melanocortin 4 receptor agonist administration. Thus, this study fully characterizes the distribution of amygdala CRF neurons in mice and suggests that they are involved in some, but not all, stress or food intake-related behaviors recruiting the amygdala

An inhibitory circuit from central amygdala to zona incerta drives pain-related behaviors in mice

Central amygdala neurons expressing protein kinase C-delta (CeA-PKCδ) are sensitized following nerve injury and promote pain-related responses in mice. The neural circuits underlying modulation of pain-related behaviors by CeA-PKCδ neurons, however, remain unknown. In this study, we identified a neural circuit that originates in CeA-PKCδ neurons and terminates in the ventral region of the zona incerta (ZI), a subthalamic structure previously linked to pain processing. Behavioral experiments show that chemogenetic inhibition of GABAergic ZI neurons induced bilateral hypersensitivity in uninjured mice and contralateral hypersensitivity after nerve injury. In contrast, chemogenetic activation of GABAergic ZI neurons reversed nerve injury-induced hyper-sensitivity. Optogenetic manipulations of CeA-PKCδ axonal terminals in the ZI further showed that inhibition of this pathway reduces nerve injury-induced hypersensitivity whereas activation of the pathway produces hypersensitivity in the uninjured paws. Altogether, our results identify a novel nociceptive inhibitory efferent pathway from CeA-PKCδ neurons to the ZI that bidirectionally modulates pain-related behaviors in mice.Fil: Singh, Sudhuman. National Center For Complementary And Integrative Health; Estados UnidosFil: Wilson, Torri D.. National Center For Complementary And Integrative Health; Estados UnidosFil: Valdivia Torres, Lesly Spring. National Center For Complementary And Integrative Health; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Benowitz, Barbara. National Center For Complementary And Integrative Health; Estados UnidosFil: Chaudhry, Sarah. National Center For Complementary And Integrative Health; Estados UnidosFil: Ma, Jun. National Center For Complementary And Integrative Health; Estados UnidosFil: Adke, Anisha P.. National Center For Complementary And Integrative Health; Estados UnidosFil: Soler Cedeño, Omar. National Center For Complementary And Integrative Health; Estados UnidosFil: Velasquez, Daniela. National Center For Complementary And Integrative Health; Estados UnidosFil: Penzo, Mario A.. National Center For Complementary And Integrative Health; Estados UnidosFil: Carrasquillo, Yarimar. National Center For Complementary And Integrative Health; Estados Unido