Systemic Administration of Orexin a Loaded Liposomes Potentiates Nucleus Accumbens Shell Dopamine Release by Sucrose Feeding

The short-chain fatty acid acetate modulates orexin/hypocretin neurons: A novel mechanism in gut-brain axis regulation of energy homeostasis and feeding

The short-chain fatty acids (SCFAs) acetate, propionate and butyrate, the major products of intestinal microbial fermentation of dietary fibres, are involved in fine-tuning brain functions via the gut-brain axis. However, the effects of SCFAs in the hypothalamic neuronal network regulating several autonomic-brain functions are still unknown. Using NMR spectroscopy, we detected a reduction in brain acetate concentrations in the hypothalamus of obese leptin knockout ob/ob mice compared to lean wild-type littermates. Therefore, we investigated the effect of acetate on orexin/hypocretin neurons (hereafter referred as OX or OX-A neurons), a subset of hypothalamic neurons regulating energy homeostasis, which we have characterized in previous studies to be over-activated by the lack of leptin and enhancement of endocannabinoid tone in the hypothalamus of ob/ob mice. We found that acetate reduces food-intake in concomitance with a reduction of orexin neuronal activity in ob/ob mice. This was demonstrated by evaluating food-intake behaviour and orexin-A/c-FOS immunoreactivity coupled with patch-clamp recordings in Hcrt-eGFP neurons, quantification of prepro-orexin mRNA, and immunolabeling of GPR-43, the main acetate receptor. Our data provide new insights into the mechanisms of the effects of chronic dietary supplementation with acetate, or complex carbohydrates, on energy intake and body weight, which may be partly mediated by inhibition of orexinergic neuron activity.

Formulation and Testing of Antioxidant and Protective Effect of Hyalurosomes Loading Extract Rich in Rosmarinic Acid Biotechnologically Produced from Lavandula angustifolia Miller

Culture of plant cells or tissues is a scalable, sustainable, and environmentally friendly approach to obtain extracts and secondary metabolites of uniform quality that can be continuously supplied in controlled conditions, independent of geographical and seasonal variations, environmental factors, and negative biological influences. In addition, tissues and cells can be extracted/obtained from the by-products of other industrial cultivations such as that of Lavandula angustifolia Miller (L. angustifolia), which is largely cultivated for the collection of flowers. Given that, an extract rich in rosmarinic acid was biotechnologically produced starting from cell suspension of L. angustifolia, which was then loaded in hyalurosomes, special phospholipid vesicles enriched with sodium hyaluronate, which in turn are capable of both immobilizing and stabilizing the system. These vesicles have demonstrated to be good candidates for skin delivery as their high viscosity favors their residence at the application site, thus promoting their interaction with the skin components. The main physico-chemical and technological characteristics of vesicles (i.e., mean diameter, polydispersity index, zeta potential and entrapment efficiency of extract in vesicles) were measured along with their biological properties in vitro: biocompatibility against fibroblasts and ability to protect the cells from oxidative stress induced by hydrogen peroxide. Overall, preliminary results disclosed the promising properties of obtained formulations to be used for the treatment of skin diseases associated with oxidative stress and inflammation.

Neurobiology of the Orexin System and Its Potential Role in the Regulation of Hedonic Tone

Orexin peptides comprise two neuropeptides, orexin A and orexin B, that bind two G-protein coupled receptors (GPCRs), orexin receptor 1 (OXR1) and orexin receptor 2 (OXR2). Although cell bodies that produce orexin peptides are localized in a small area comprising the lateral hypothalamus and adjacent regions, orexin-containing fibres project throughout the neuraxis. Although orexins were initially described as peptides that regulate feeding behaviour, research has shown that orexins are involved in diverse functions that range from the modulation of autonomic functions to higher cognitive functions, including reward-seeking, behaviour, attention, cognition, and mood. Furthermore, disruption in orexin signalling has been shown in mood disorders that are associated with low hedonic tone or anhedonia, including depression, anxiety, attention deficit hyperactivity disorder, and addiction. Notably, projections of orexin neurons overlap circuits involved in the modulation of hedonic tone. Evidence shows that orexins may potentiate hedonic behaviours by increasing the feeling of pleasure or reward to various signalling, whereas dysregulation of orexin signalling may underlie low hedonic tone or anhedonia. Further, orexin appears to play a key role in regulating behaviours in motivationally charged situations, such as food-seeking during hunger, or drug-seeking during withdrawal. Therefore, it would be expected that dysregulation of orexin expression or signalling is associated with changes in hedonic tone. Further studies investigating this association are warranted.

The role of the nucleus accumbens and ventral pallidum in feeding and obesity

Obesity is a growing global epidemic that stems from the increasing availability of highly-palatable foods and the consequent enhanced calorie consumption. Extensive research has shown that brain regions that are central to reward seeking modulate feeding and evidence linking obesity to pathology in such regions have recently started to accumulate. In this review we focus on the contribution of two major interconnected structures central to reward processing, the nucleus accumbens and the ventral pallidum, to obesity. We first review the known literature linking these structures to feeding behavior, then discuss recent advances connecting pathology in the nucleus accumbens and ventral pallidum to obesity, and finally examine the similarities and differences between drug addiction and obesity in the context of these two structures. The understanding of how pathology in brain regions involved in reward seeking and consumption may drive obesity and how mechanistically similar obesity and addiction are, is only now starting to be revealed. We hope that future research will advance knowledge in the field and open new avenues to studying and treating obesity.

Blockade of the orexin 1 receptors in the nucleus accumbens' shell reversed the reduction effect of olanzapine on motivation for positive reinforcers

Effort-based choice of high reward requires one to decide how much effort to expend for a certain amount of reward. Orexin is a crucial neuropeptide in the physiological aspect especially a variety of affective and cognitive processes. The nucleus accumbens (NAc) is a region of the neural system that serves effort-related high reward choices andthe Orexin 1 receptor (OX1R) is distributed extensively throughout the nucleus accumbens shell (AcbS). Olanzapine (OLZ), a typical antipsychotic drug, has a high affinity to D2 as an antagonist, and also partial agonistic-like action at D2 receptors has been reported. We examined the interaction of OLZ with the orexinergic receptor 1 in AcbS on effort- related high reward choice when two goal arms were different in the amount of accessible reward. The animals had to pass the barrier for receiving a high reward in one arm (HRA) or obtain a low reward in the other arm without any cost. Before surgery, all animals were selecting the HRA on almost every trial.During test days, the rats received local injections of either DMSO 20% /0.5 µl, as vehicle or SB334867 (30, 100, 300 nM/0.5 µl), as selective OX1R antagonist, within the AcbS. Other group received OLZ (32 µM/0.5 µl DMSO20%) / vehicle alone or 5 min after administration of SB334867 (300 nM/0.5 µl). The results showed that administration of OLZ in the AcbS alters rat's preference for high reward. On the other hand, blocked of the OX1R (300 nM/0.5 µl) in this region could reverse the effect of OLZ, however, administration of the OX1R antagonists alone in the AcbS led to decreasing rat's preference for high reward. This result indicates that the orexin-1 antagonist might affect some effects of antipsychotic drugs.

Chronic Red Bull Consumption during Adolescence: Effect on Mesocortical and Mesolimbic Dopamine Transmission and Cardiovascular System in Adult Rats

Energy drinks are very popular nonalcoholic beverages among adolescents and young adults for their stimulant effects. Our study aimed to investigate the effect of repeated intraoral Red Bull (RB) infusion on dopamine transmission in the nucleus accumbens shell and core and in the medial prefrontal cortex and on cardiac contractility in adult rats exposed to chronic RB consumption. Rats were subjected to 4 weeks of RB voluntary consumption from adolescence to adulthood. Monitoring of in vivo dopamine was carried out by brain microdialysis. In vitro cardiac contractility was studied on biomechanical properties of isolated left-ventricular papillary muscle. The main finding of the study was that, in treated animals, RB increased shell dopamine via a nonadaptive mechanism, a pattern similar to that of drugs of abuse. No changes in isometric and isotonic mechanical parameters were associated with chronic RB consumption. However, a prolonged time to peak tension and half-time of relaxation and a slower peak rate of tension fall were observed in RB-treated rats. It is likely that RB treatment affects left-ventricular papillary muscle contraction. The neurochemical results here obtained can explain the addictive properties of RB, while the cardiovascular investigation findings suggest a hidden papillary contractility impairment.