The Role of Ventromedial Hypothalamus Receptors in the Central Regulation of Food Intake

Oxytocin alleviates high-fat diet-induced anxiety by decreasing glutamatergic synaptic transmission in the ventral dentate gyrus in adolescent mice

A high-fat diet (HFD)-induced obesity is associated with mental disorders in adolescence. However, the mechanisms underlying these associations remain unclear. In this study, we hypothesized that synaptic remodeling occurs in the ventral hippocampus (vHP) of obese mice. To investigate this, we established a postnatal model of HFD-induced obesity in mice and observed increased body weight, elevated plasma luteinizing hormone and testosterone levels, premature puberty, and enhanced anxiety-like behavior in male subjects. We also examined the effect of HFD on the c-Fos protein expression in the ventral dentate gyrus (vDG) and explored the influence of intracerebroventricular (i.c.v) oxytocin injections on HFD-induced anxiety. Our results indicated an increase in c-Fos-positive cells in the vDG following HFD consumption. Additionally, we recorded the spontaneous synaptic activity of miniature excitatory postsynaptic currents (mEPSCs) in the vDG. Notably, HFD resulted in an elevated mEPSC frequency without affecting mEPSC amplitude. Subsequently, investigations demonstrated that i.c.v oxytocin injections reversed anxiety-like behavior induced by HFD. Moreover, the application of oxytocin in a bath solution reduced the mEPSC frequency in the vDG. These findings suggest that postnatal HFD intake induces synaptic dysfunction in the vDG, associated with the hyperactivity of vDG neurons, potentially contributing to the anxiety-like behavior in juvenile obesity.

Labeling of the serotonergic neuronal circuits emerging from the raphe nuclei via some retrograde tracers

Serotonin (5-hydroxytryptamine, 5-HT) is a very important neurotransmitter emerging from the raphe nuclei to several brain regions. Serotonergic neuronal connectivity has multiple functions in the brain. In this study, several techniques were used to trace serotonergic neurons in the dorsal raphe (DR) and median raphe (MnR) that project toward the arcuate nucleus of the hypothalamus (Arc), dorsomedial hypothalamic nucleus (DM), lateral hypothalamic area (LH), paraventricular hypothalamic nucleus (PVH), ventromedial hypothalamic nucleus (VMH), fasciola cinereum (FC), and medial habenular nucleus (MHb). Cholera toxin subunit B (CTB), retro-adeno-associated virus (rAAV-CMV-mCherry), glycoprotein-deleted rabies virus (RV-ΔG), and simultaneous microinjection of rAAV2-retro-Cre-tagBFP with AAV-dio-mCherry in C57BL/6 mice were used in this study. In addition, rAAV2-retro-Cre-tagBFP was microinjected into Ai9 mice. Serotonin immunohistochemistry was used for the detection of retrogradely traced serotonergic neurons in the raphe nuclei. The results indicated that rAAV2-retro-Cre-tagBFP microinjection in Ai9 mice was the best method for tracing serotonergic neuron circuits. All of the previously listed nuclei exhibited serotonergic neuronal projections from the DR and MnR, with the exception of the FC, which had very few projections from the DR. The serotonergic neuronal projections were directed toward the Arc by the subpeduncular tegmental (SPTg) nuclei. Moreover, the RV-ΔG tracer revealed monosynaptic non-serotonergic neuronal projections from the DR that were directed toward the Arc. Furthermore, rAAV tracers revealed monosynaptic serotonergic neuronal connections from the raphe nuclei toward Arc. These findings validate the variations in neurotropism among several retrograde tracers. The continued discovery of several novel serotonergic neural circuits is crucial for the future discovery of the functions of these circuits. RESEARCH HIGHLIGHTS: Various kinds of retrograde tracers were microinjected into C57BL/6 and Ai9 mice. The optimum method for characterizing serotonergic neuronal circuits is rAAV2-retro-Cre-tagBFP microinjection in Ai9 mice. The DR, MnR, and SPTg nuclei send monosynaptic serotonergic neuronal projections toward the arcuate nucleus of the hypothalamus. Whole-brain quantification analysis of retrograde-labeled neurons in different brain nuclei following rAAV2-retro-Cre-tagBFP microinjection in the Arc, DM, LH, and VMH is shown. Differential quantitative analysis of median and dorsal raphe serotonergic neurons emerging toward the PVH, DM, LH, Arc, VMH, MHb, and FC is shown.

The effect of intraperitoneal injection of Glycyrrhizin on central regulation of food intake in broilers injected with LPS

1. Poultry farming faces challenges regarding correct hygiene and nutrition. One of the challenges is gram-negative bacteria that stimulate pro-inflammatory reactions through lipopolysaccharide (LPS) and cause disease and anorexia. Liquorice, a medicinal plant containing glycyrrhizin (Glz; a saponin and emulsifier compound) as its main active ingredient, was injected into broilers to investigate any beneficial effects on feed intake in LPS-injected broilers.2. The study involved three experiments using 72 male broiler chickens in each, to examine the impact of Glz on feed intake, especially when challenged with lipopolysaccharide (LPS) by intra-peritoneal (IP) injection to cause inflammation (n = 24). Experiment 1 was conducted to examine the effects of intraperitoneal injection of Glz (12.5, 25 and 50 mg) on feed intake in chickens. In experiment 2, the effects of intracerebroventricular injections of LPS (6.25, 12.5 and 25 ng) were examined. The third experiment investigated the impact of IP injection of Glz on inflammation induced by LPS.3. Injection of Glz significantly increased feed intake in a dose-dependent manner. Whereas LPS significantly reduced the feed intake in feed-deprived chickens (p < 0.05).4. In conclusion, Glz can neutralise the feed intake reduction caused by inflammation in broilers, highlighting its potential role in modulating feed intake in broilers.

The effect of spexin injection and its interaction with nitric oxide, serotonin, and corticotropin receptors on the central regulation of food intake in broilers

Complex homeostatic control mechanisms are tools to adjust the food birds eat and their appetite. Birds and mammals differ in several ways considering food intake regulation. Therefore, this study aimed to investigate the special effects of the intracerebroventricular (ICV) injection of spexin and its interaction with nitric oxide, serotonin and corticotropin receptors on central food intake regulation in broilers. In the test 1, Broilers received ICV injection of saline, PCPA (p-chlorophenylalanine,1.25 µg), spexin (10 nmol) and PCPA+spexin. In test 2-7, 8-OH-DPAT, SB-242084 (5-HT2C, 1.5 µg), L-arginine (Precursor of nitric oxide, 200 nmol), L-NAME (nitric oxide synthetize inhibitor, 100 nmol), Astressin-B (30 µg) and Astressin2-B (30 µg) were injected to Broilers instead of the PCPA. Then, the amount of food received was measured up to 2 h after the injection. The food consumption was significantly decreased by Spexin (10 nmol) (P<0.05). Concomitant injection of SB-242084+spexin attenuated spexin-induced hypophagia (P<0.05). Co-injection of L-arginine+spexin enhanced spexin-induced hypophagia and this effect was reversed by L-NAME (P<0.05). Also, concomitant injection of Astressin-B + spexin or Astressin2-B + spexin enhanced spexin-induced hypophagia (P<0.05). Founded on these observations, spexin-induced hypophagia may be mediated by nitric oxide and 5-HT2C, CRF1, and CRF2 receptors in neonatal broilers.

Unravelling the Influence of Endocrine-Disrupting Chemicals on Obesity Pathophysiology Pathways

Obesity represents a global health concern, affecting individuals of all age groups across the world. The prevalence of excess weight and obesity has escalated to pandemic proportions, leading to a substantial increase in the incidence of various comorbidities, such as cardiovascular diseases, type 2 diabetes, and cancer. This chapter seeks to provide a comprehensive exploration of the pathways through which endocrine-disrupting chemicals can influence the pathophysiology of obesity. These mechanisms encompass aspects such as the regulation of food intake and appetite, intestinal fat absorption, lipid metabolism, and the modulation of inflammation. This knowledge may help to elucidate the role of exogenous molecules in both the aetiology and progression of obesity.

Molecular consequences of peripheral Influenza A infection on cell populations in the murine hypothalamus

Infection with Influenza A virus (IAV) causes the well-known symptoms of the flu, including fever, loss of appetite, and excessive sleepiness. These responses, mediated by the brain, will normally disappear once the virus is cleared from the system, but a severe respiratory virus infection may cause long-lasting neurological disturbances. These include encephalitis lethargica and narcolepsy. The mechanisms behind such long lasting changes are unknown. The hypothalamus is a central regulator of the homeostatic response during a viral challenge. To gain insight into the neuronal and non-neuronal molecular changes during an IAV infection, we intranasally infected mice with an H1N1 virus and extracted the brain at different time points. Using single-nucleus RNA sequencing (snRNA-seq) of the hypothalamus, we identify transcriptional effects in all identified cell populations. The snRNA-seq data showed the most pronounced transcriptional response at 3 days past infection, with a strong downregulation of genes across all cell types. General immune processes were mainly impacted in microglia, the brain resident immune cells, where we found increased numbers of cells expressing pro-inflammatory gene networks. In addition, we found that most neuronal cell populations downregulated genes contributing to the energy homeostasis in mitochondria and protein translation in the cytosol, indicating potential reduced cellular and neuronal activity. This might be a preventive mechanism in neuronal cells to avoid intracellular viral replication and attack by phagocytosing cells. The change of microglia gene activity suggest that this is complemented by a shift in microglia activity to provide increased surveillance of their surroundings.

A Microelectrode Array Modified by PtNPs/PB Nanocomposites Used for the Detection and Analysis of Glucose-Sensitive Neurons under Different Blood Glucose States

Hypoglycemia state damages the organism, and glucose-excited and glucose-inhibited neurons from the ventral medial hypothalamus can regulate this state. Therefore, it is crucial to understand the functional mechanism between blood glucose and electrophysiology of glucose-excited and glucose-inhibited neurons. To better detect and analyze this mechanism, a PtNPs/PB nanomaterials modified 32-channel microelectrode array with low impedance (21.91 ± 6.80 kΩ), slight phase delay (-12.7° ± 2.7°), high double layer capacitance (0.606 μF), and biocompatibility was developed to realize in vivo real-time detection of the electrophysiology activities of glucose-excited and glucose-inhibited neurons. The phase-locking level of some glucose-inhibited neurons elevated during fasting (low blood glucose state) and showed theta rhythms after glucose injection (high blood glucose state). With an independent oscillating ability, glucose-inhibited neurons can provide an essential indicator to prevent severe hypoglycemia. The results reveal a mechanism for glucose-sensitive neurons to respond to blood glucose. Some glucose-inhibited neurons can integrate glucose information input and convert it into theta oscillating or phase lock output. It helps in enhancing the interaction between neurons and glucose. Therefore, the research can provide a basis for further controlling blood glucose by modulating the characteristics of neuronal electrophysiology. This helps reduce the damage of organisms under energy-limiting conditions, such as prolonged manned spaceflight or metabolic disorders.

Circadian Rhythms Disrupted by Light at Night and Mistimed Food Intake Alter Hormonal Rhythms and Metabolism

Availability of artificial light and light-emitting devices have altered human temporal life, allowing 24-hour healthcare, commerce and production, and expanding social life around the clock. However, physiology and behavior that evolved in the context of 24 h solar days are frequently perturbed by exposure to artificial light at night. This is particularly salient in the context of circadian rhythms, the result of endogenous biological clocks with a rhythm of ~24 h. Circadian rhythms govern the temporal features of physiology and behavior, and are set to precisely 24 h primarily by exposure to light during the solar day, though other factors, such as the timing of meals, can also affect circadian rhythms. Circadian rhythms are significantly affected by night shift work because of exposure to nocturnal light, electronic devices, and shifts in the timing of meals. Night shift workers are at increased risk for metabolic disorder, as well as several types of cancer. Others who are exposed to artificial light at night or late mealtimes also show disrupted circadian rhythms and increased metabolic and cardiac disorders. It is imperative to understand how disrupted circadian rhythms alter metabolic function to develop strategies to mitigate their negative effects. In this review, we provide an introduction to circadian rhythms, physiological regulation of homeostasis by the suprachiasmatic nucleus (SCN), and SCN-mediated hormones that display circadian rhythms, including melatonin and glucocorticoids. Next, we discuss circadian-gated physiological processes including sleep and food intake, followed by types of disrupted circadian rhythms and how modern lighting disrupts molecular clock rhythms. Lastly, we identify how disruptions to hormones and metabolism can increase susceptibility to metabolic syndrome and risk for cardiovascular diseases, and discuss various strategies to mitigate the harmful consequences associated with disrupted circadian rhythms on human health.

Investigation of structural and neurobiochemical differences in brains from high-performance and native hen breeds

Selection of livestock has not only led to changes in the level of their performance but also modified their behavior. As a result, within a single species, we have to deal with different behaviors of different breeds. In our study, we assumed that the different behaviors within a species are due to differences in the morphology and physiology of behavior-related systems. Two breeds of hens were used as a model: the highly reactive, fearful and high-performance Leghorn breed and proactive, unselected Green-legged Partridge breed. The higher reactivity and fearfulness of Leghorn hens in comparison to the Green-legged Partridge breed may be related to the greater number of neurons in the paraventricular nucleus and anterior hypothalamus and the higher content of zinc and iron in the brain, as these elements are involved in neuronal conduction and myelination processes. The reactive behaviours of Green-legged Partridge hens may be associated with the lower number of neurons in the paraventricular nucleus and the anterior hypothalamus and the higher concentration of dopamine and copper ions in the brain. The analyses confirmed the hypothesis of the existence of interbreed differences in the morphology and physiology of behaviour-related systems, which most probably emerged through unintentional and correlated selection towards high production performance. Consequently, attention should be drawn that the selection of a given genotype (breed) towards a specific environment could lead to creation of highly specialised lines that may not achieve homeostasis in every maintenance system.

Mediatory role of the central NPY, melanocortine and corticotrophin systems on phoenixin-14 induced hyperphagia in neonatal chicken

Animal research indicates the neuropeptide Y (NPY), corticotrophin and melanocortin systems have a mediatory role in reward, however, how these substances interact with phenytoin-14 (PNX-14) induced food intake in birds remains to be identified. Accordingly, in this research eight tests were carried out to investigate the potential interactions of the NPY, melanocortin, as well as corticotrophin systems with PNX-14 on food consumption in neonatal chickens. In the first experiment, chickens were intracerebroventricular (ICV) injected with phosphate-buffered saline (PBS) and PNX-14 (0.8, 0.16, and 3.2 nmol). In second experiment, PBS, the antagonist of CRF₁/CRF₂ receptors (astressin-B, 30 μg) and PNX-14 + astressin-B were injected. In the rest of the experiments chicken received astressin2-B (CRF₂ receptor antagonist; 30 µg), SHU9119 (MCR₃/MCR₄ receptor antagonist, 0.5nomol), MCL0020 (MCR₄ receptor agonist, 0.5 nmol), B5063 (NPY₁ receptor antagonist, 1.25 μg), SF22 (NPY₂ receptor antagonist, 1.25 μg) and SML0891 (NPY₅ receptor antagonist, 1.25 μg) rather than astressin-B. Then, cumulative intake of food was recorded for 2 h. Based on the findings, PNX-14 (0.16 and 3.2 nmol) led to increment in food consumption compared with the control (P < 0.05). Co-administration of the PNX-14 and astressin-B promoted PNX-14-induced hyperphagia (P < 0.05). Co-injection of the PNX-14 + astressin2-B potentiated hyperphagia PNX-14 (P < 0.05). Co-injection of PNX-14 + B5063 inhibited the effects of the PNX-14 (P < 0.05). The co-administration of the PNX-14 and SML0891 potentiated hypophagic effects of the PNX-14 (P < 0.05). The results showed that PNX-14-induced hyperphagia mediates via NPY₁, NPY_5, and CRF₁/CRF₂ receptors in neonatal chickens.

FumDSB Can Reduce the Toxic Effects of Fumonisin B1 by Regulating Several Brain-Gut Peptides in Both the Hypothalamus and Jejunum of Growing Pigs

Fumonisin B₁ (FB₁) is the most common food-borne mycotoxin produced by the Fusarium species, posing a potential threat to human and animal health. Pigs are more sensitive to FB₁ ingested from feed compared to other farmed livestock. Enzymatic degradation is an ideal detoxification method that has attracted much attention. This study aimed to explore the functional characteristics of the carboxylesterase FumDSB in growing pigs from the perspective of brain–gut regulation. A total of 24 growing pigs were divided into three groups. The control group was fed a basal diet, the FB₁ group was supplemented with FB₁ at 5 mg/kg feed, and the FumDSB group received added FumDSB based on the diet of the FB₁ group. After 35 days of animal trials, samples from the hypothalamus and jejunum were analyzed through HE staining, qRT-PCR and immunohistochemistry. The results demonstrated that the ingestion of FB₁ can reduce the feed intake and weight gain of growing pigs, indicating that several appetite-related brain-gut peptides (including NPY, PYY, ghrelin and obestatin, etc.) play important roles in the anorexia response induced by FB₁. After adding FumDSB as detoxifying enzymes, however, the anorexia effects of FB₁ were alleviated, and the expression and distribution of the corresponding brain-gut peptides exhibited a certain degree of regulation. In conclusion, the addition of FumDSB can reduce the anorexia effects of FB₁ by regulating several brain-gut peptides in both the hypothalamus and the jejunum of growing pigs.