Endocannabinoid-controlled modulation of orexinergic neurons in obesity: switch from excitatory to inhibitory wiring

Alterazioni acute o croniche dello stato energetico provocano cambiamenti negli equilibri tra trasmissione sinaptica eccitatoria ed inibitoria e nella plasticit\ue0 sinaptica ad essi associata, favorendo l'adattamento del metabolismo energetico alle nuove esigenze omeostatiche. L'impatto di tali cambiamenti, in particolare durante l'obesit\ue0, sul segnale degli endocannabinoidi sui recettori CB1, uno dei principali modulatori della trasmissione sinaptica, e uno dei target per i farmaci anti-obesit\ue0, non \ue8 ben compreso. Gli endocannabinoidi stimolano l'assunzione di cibo e la loro sintesi e rilascio aumentano dopo deprivazione di cibo, inducendo cos\uec l'attivazione dei recettori CB1. In particolare i livelli di endocannabinoidi aumentano nell'ipotalamo e nel sangue durante brevi periodi di digiuno (1, 2) e diminuiscono in seguito a somministrazione di leptina e dopo assunzione di cibo (3, 4). Topi con riduzione dei segnali della leptina (topi db/db che esprimono un recettore difettoso della leptina), con carenza di leptina (ob/ob), e con resistenza alla leptina (resistenza acquisita a causa dell\u2019 obesit\ue0 indotta da dieta, topi HFD) presentano elevati livelli di endocannabinoidi nell'ipotalamo e nel tessuto adiposo (5). Lavori recenti mostrano che la leptina modula anche la crescita degli assoni e la plasticit\ue0 sinaptica nell'ipotalamo (6,7). In particolare, la leptina incrementa l\u2019estensione degli assoni nel Nucleo Arcuato durante lo sviluppo perinatale del topo, svolgendo cos\uec un ruolo trofico all'interno di quei circuiti che saranno oggetto delle azioni fisiologiche della leptina nella vita adulta (6). La leptina pu\uf2 anche agire sui neuroni sintetizzanti Orexina (OX) dell'ipotalamo laterale, i quali inviano proiezioni diffuse al cervello (8) svolgendo un ruolo integrativo strategico nell'alimentazione. La leptina sopprime l'attivit\ue0 dei neuroni OX, la loro biosintesi o entrambi. Inoltre, un antagonista selettivo del recettore OX1R riduce l\u2019assunzione di cibo e diminuisce l\u2019obesit\ue0 in topi ob/ob (9), suggerendo che la carenza di leptina, almeno in parte, attiva il patway dell\u2019orexina per aumentare l'assunzione di cibo. D'altra parte, il pretrattamento con dosi sub-efficaci di rimonabant, un antagonista selettivo del CB1, attenua l\u2019azione oressigenica dell\u2019OX (10), mentre dati elettrofisiologici sostengono un ruolo inibitorio dei cannabinoidi sui neuroni orexinergici in condizioni fisiologiche (11). Partendo da queste basi, abbiamo studiato se un rimodellamento del wiring neuronale orexinergico si verifica nell\u2019LH nel corso di una prolungata perturbazione nutrizionale causata da, o risultante in, carenza di segnalazione della leptina, come in topi ob/ob e topi HFD, rispettivamente, ed il suo impatto sulla funzione neuromodulatoria del sistema endocannabinoide, dato che un\u2019 alta plasticit\ue0 neuronale si verifica in questo circuito per un\u2019 adeguata regolazione del bilancio energetico (12).Acute or chronic alterations in energy status lead to changes in the balance between excitatory and inhibitory synaptic transmission and associated synaptic plasticity, facilitating adaptation of energy metabolism to new homeostatic requirements. The impact of such changes, especially during obesity, on endocannabinoid signalling at CB1 receptors, a master modulator of synaptic transmission and strength, and a target for anti-obesity drugs, is not well understood. Endocannabinoids stimulate food intake and their synthesis and release increase after food-deprivation thus inducing activation of CB1 receptors. In particular, endocannabinoid levels increase in the hypothalamus and blood during short-term fasting (1, 2) and decrease after leptin administration and feeding (3, 4). Impairment of leptin signaling (db/db mice expressing a defective leptin receptor), leptin de\ufb01ciency (ob/ob), and leptin resistance (acquired resistance due to diet-induced obesity, HFD mice) in mice showed elevated levels of Endocannabinoids in the hypothalamus and in adipose tissue (5). Recent papers show that leptin modulates also the axonal growth and synaptic plasticity within the hypothalamus (6,7). In particular, leptin increases neurite extension in the Arcuate Nucleus during mouse perinatal development, thus playing an early trophic role within those circuits that will be the target of leptin physiological actions in adult life (6). Leptin also may act on the Orexinergic-synthesizing (OX) neurons of the lateral hypothalamus, which send widespread projections to the brain (8) playing a strategic integrative role in the feeding. Leptin suppress the activity of OX neurons, the biosynthesis of OX or both. Moreover, an OX1R-selective antagonist reduced food intake and ameliorated obesity of leptin-deficient ob/ob mice (9), suggesting that leptin deficiency at least partly activates the orexin pathway to increase food intake. On the other hand, pretreatment with subeffective doses of rimonabant, a selective CB1 antagonist, attenuates the orexigenic actions of OX (10), whereas electrophysiological data support the inhibitory role of cannabinoids on orexinergic neurons in physiological conditions (11). Staring from these bases, we investigated if a remodeling of orexinergic neuronal wiring occurs in the LH during a prolonged nutritional perturbation caused by, or resulting in, leptin signalling deficiency, as in ob/ob and HFD mice, respectively, and its impact on neuromodulatory function of the endocannabinoid system, since high neural plasticity occurs in this circuitry for adequate regulation of energy balance (12)

Overlapping distribution of orexin and endocannabinoid receptors and their functional interaction in the brain of adult zebrafish

Hypocretins/Orexins neuropeptides are known to regulate numerous physiological functions, such as energy homeostasis, food intake, sleep/wake cycle, arousal and wakefulness, in vertebrates. Previous studies on mice have revealed an intriguing orexins/endocannabinoids (ECs) signaling interaction at both structural and functional levels, with OX-A behaving as a strong enhancer of 2-arachydonoyl-glycerol (2-AG) biosynthesis. In this study, we describe, for the first time in the brain of zebrafish, the anatomical distribution and co-expression of orexin (OX-2R) and endocannabinoid (CB1R) receptors, suggesting a functional interaction. The immunohistochemical colocalization of these receptors by confocal imaging in the dorsal and ventral telencephalon, suprachiasmatic nucleus (SC), thalamus, hypothalamus, preoptic area (PO) and cerebellum, is reported. Moreover, biochemical quantification of 2-AG levels by LC-MS supports the occurrence of OX-A-induced 2-AG biosynthesis in the zebrafish brain after 3 h of OX-A intraperitoneal (i.p.; 3 pmol/g) or intracerebroventricular (i.c.v.; 0.3 pmol/g) injection. This effect is likely mediated by OX-2R as it is counteracted by i.p./i.c.v administration of OX-2R antagonist (SB334867, 10 pmol/g). This study provides compelling morphological and functional evidence of an OX-2R/CB1R signaling interaction in the brain of adult zebrafish, suggesting the use of this well-established vertebrate animal model for the study of complex and phylogenetically conserved physiological functions

Influence of polyphenols from olive mill wastewater on the gastrointestinal tract, alveolar macrophages and blood leukocytes of pigs

In the last years, great importance has been given to the beneficial effects of polyphenols. Among the most relevant health promoting effects, there is the capacity to reduce the amount of free radicals and stimulate the immune response. In this study, polyphenols extracted from olive mill wastewater (OMWW), were fed to adult 'Casertana' pigs during the finishing period. No significant differences in the length of the jejunum-ileum villi and the depth of the colon crypts were detected between control and polyphenols fed pigs. Instead, intra-epithelial and lamina propria leukocytes were more abundant in pigs fed polyphenols (p < .05). Cyclooxygenase-2 immunoreactivity in the gastrointestinal tract, employed as marker of inflammation, was more intense in the control group. Superoxide anion production in primary cell cultures of both blood leukocytes and alveolar macrophages was lower in pigs fed polyphenols (p < .05). Taken together these data indicate that, according to our in vitro studies, OMWW polyphenols seem to be potent antioxidants, while the interpretation of the in vivo experiments is more problematic and further studies are necessary on the interactions between bioactive feed compounds and intestinal status. Such studies can contribute to a better understanding of both positive and negative interactions in vivo and to the identification of new functional feeds.HIGHLIGHTS The effects of polyphenols extracted from olive mill wastewater (OMWW) have been studied in pigs. Gut morphology, inflammation and immune response were investigated. OMWW polyphenols act as potent antioxidants

Chestnut shell tannins: effects on intestinal inflammation and dysbiosis in zebrafish

The aim of the present study was to test the possible ameliorative efficacy of phytochemicals such as tannins on intestinal inflammation and dysbiosis. The effect of a chestnut shell (Castanea sativa) extract (CSE) rich in polyphenols, mainly represented by tannins, on k-carrageenan-induced intestinal inflammation in adult zebrafish (Danio rerio) was tested in a feeding trial. Intestinal inflammation was induced by 0.1% k-carrageenan added to the diet for 10 days. CSE was administered for10 days after k-carrageenan induced inflammation. The intestinal morphology and histopathology, cytokine expression, and microbiota were analyzed. The k-carrageenan treatment led to gut lumen expansion, reduction of intestinal folds, and increase of the goblet cells number, accompanied by the upregulation of pro-inflammatory factors (TNFα, COX2) and alteration in the number and ratio of taxonomic groups of bacteria. CSE counteracted the inflammatory status enhancing the growth of health helpful bacteria (Enterobacteriaceae and Pseudomonas), decreasing the pro-inflammatory factors, and activating the anti-inflammatory cytokine IL-10. In conclusion, CSE acted as a prebiotic on zebrafish gut microbiota, sustaining the use of tannins as food additives to ameliorate the intestinal inflammation. Our results may be relevant for both aquaculture and medical clinic field