Gut-Brain Neuroendocrine Signaling Under Conditions of Stress-Focus on Food Intake-Regulatory Mediators

Glucocorticoids, stress and eating: The mediating role of appetite-regulating hormones

Disrupted hormonal appetite signaling plays a crucial role in obesity as it may lead to uncontrolled reward-related eating. Such disturbances can be induced not only by weight gain itself but also by glucocorticoid overexposure, for example, due to chronic stress, disease, or medication use. However, the exact pathways are just starting to be understood. Here, we present a conceptual framework of how glucocorticoid excess may impair hormonal appetite signaling and, consequently, eating control in the context of obesity. The evidence we present suggests that counteracting glucocorticoid excess can lead to improvements in appetite signaling and may therefore pose a crucial target for obesity prevention and treatment. In turn, targeting hormonal appetite signals may not only improve weight management and eating behavior but may also decrease detrimental effects of glucocorticoid excess on cardio-metabolic outcomes and mood. We conclude that gaining a better understanding of the relationship between glucocorticoid excess and circulating appetite signals will contribute greatly to improvements in personalized obesity prevention and treatment.

Synthetic corticotropins and the GABA-receptor system: Direct and delayed effects

The central effectors of the stress system are greatly interconnected and include, among others, a large group of peptides derived from proopiomelanocortin. In addition to natural corticotropins, a number of artificial molecules that contain some ACTH fragments in their structure are also referred to members of this family. Some of them possess a wide range of biological activity. The molecular mechanism underlying the biological activity of such peptides is partly based on allosteric modulation of various receptors. We analyzed the ability of some biologically active synthetic corticotropins (ACTH(4-7)PGP, ACTH(6-9)PGP, ACTH(7-10)PGP), and glyproline PGPL to affect the GABA-receptor system of rat brain. The effects of the peptides were studied in the isolated plasma membranes of brain cells, as well as after systemic peptide administration in the rat model of acute restraint stress. The delayed effect of stress or preadministration of each of the studied peptides on [³ H]GABA binding was different for its high- and low-affinity-specific sites. The studied peptides individually affected the binding of [³ H]GABA in their own way. Acute restraint stress caused a decrease in [³ H]GABA binding at its low-affine site and did not affected the high-affine site. Preliminary peptide administration did not influence this effect of stress.

Nutrition and Gut–Brain Pathways Impacting the Onset of Parkinson’s Disease

An emerging body of literature suggests that long-term gut inflammation may be a silent driver of Parkinson’s disease (PD) pathogenesis. Importantly, specific nutritive patterns might improve gut health for PD risk reduction. Here, we review the current literature on the nutritive patterns and inflammatory markers as a predictor for early detection of PD. This knowledge might be used to foster the detection of early nutritive patterns and preclinical biomarkers to potentially alter PD development and progression.

Treatment of Gastrointestinal Disorders-Plants and Potential Mechanisms of Action of Their Constituents

The worldwide prevalence of gastrointestinal diseases is about 40%, with standard pharmacotherapy being long-lasting and economically challenging. Of the dozens of diseases listed by the Rome IV Foundation criteria, for five of them (heartburn, dyspepsia, nausea and vomiting disorder, constipation, and diarrhoea), treatment with herbals is an official alternative, legislatively supported by the European Medicines Agency (EMA). However, for most plants, the Directive does not require a description of the mechanisms of action, which should be related to the therapeutic effect of the European plant in question. This review article, therefore, summarizes the basic pharmacological knowledge of synthetic drugs used in selected functional gastrointestinal disorders (FGIDs) and correlates them with the constituents of medicinal plants. Therefore, the information presented here is intended as a starting point to support the claim that both empirical folk medicine and current and decades-old treatments with official herbal remedies have a rational basis in modern pharmacology.

Expression Patterns of the Neuropeptide Urocortin 3 and Its Receptor CRFR2 in the Mouse Central Auditory System

Sensory systems have to be malleable to context-dependent modulations occurring over different time scales, in order to serve their evolutionary function of informing about the external world while also eliciting survival-promoting behaviors. Stress is a major context-dependent signal that can have fast and delayed effects on sensory systems, especially on the auditory system. Urocortin 3 (UCN3) is a member of the corticotropin-releasing factor family. As a neuropeptide, UCN3 regulates synaptic activity much faster than the classic steroid hormones of the hypothalamic-pituitary-adrenal axis. Moreover, due to the lack of synaptic re-uptake mechanisms, UCN3 can have more long-lasting and far-reaching effects. To date, a modest number of studies have reported the presence of UCN3 or its receptor CRFR2 in the auditory system, particularly in the cochlea and the superior olivary complex, and have highlighted the importance of this stress neuropeptide for protecting auditory function. However, a comprehensive map of all neurons synthesizing UCN3 or CRFR2 within the auditory pathway is lacking. Here, we utilize two reporter mouse lines to elucidate the expression patterns of UCN3 and CRFR2 in the auditory system. Additional immunolabelling enables further characterization of the neurons that synthesize UCN3 or CRFR2. Surprisingly, our results indicate that within the auditory system, UCN3 is expressed predominantly in principal cells, whereas CRFR2 expression is strongest in non-principal, presumably multisensory, cell types. Based on the presence or absence of overlap between UCN3 and CRFR2 labeling, our data suggest unusual modes of neuromodulation by UCN3, involving volume transmission and autocrine signaling.

The gut–brain axis in vertebrates: implications for food intake regulation

The gut and brain are constantly communicating and influencing each other through neural, endocrine and immune signals in an interaction referred to as the gut–brain axis. Within this communication system, the gastrointestinal tract, including the gut microbiota, sends information on energy status to the brain, which, after integrating these and other inputs, transmits feedback to the gastrointestinal tract. This allows the regulation of food intake and other physiological processes occurring in the gastrointestinal tract, including motility, secretion, digestion and absorption. Although extensive literature is available on the mechanisms governing the communication between the gut and the brain in mammals, studies on this axis in other vertebrates are scarce and often limited to a single species, which may not be representative for obtaining conclusions for an entire group. This Review aims to compile the available information on the gut–brain axis in birds, reptiles, amphibians and fish, with a special focus on its involvement in food intake regulation and, to a lesser extent, in digestive processes. Additionally, we will identify gaps of knowledge that need to be filled in order to better understand the functioning and physiological significance of such an axis in non-mammalian vertebrates.

Role of Somatostatin in the Regulation of Central and Peripheral Factors of Satiety and Obesity

Obesity is one of the major social and health problems globally and often associated with various other pathological conditions. In addition to unregulated eating behaviour, circulating peptide-mediated hormonal secretion and signaling pathways play a critical role in food intake induced obesity. Amongst the many peptides involved in the regulation of food-seeking behaviour, somatostatin (SST) is the one which plays a determinant role in the complex process of appetite. SST is involved in the regulation of release and secretion of other peptides, neuronal integrity, and hormonal regulation. Based on past and recent studies, SST might serve as a bridge between central and peripheral tissues with a significant impact on obesity-associated with food intake behaviour and energy expenditure. Here, we present a comprehensive review describing the role of SST in the modulation of multiple central and peripheral signaling molecules. In addition, we highlight recent progress and contribution of SST and its receptors in food-seeking behaviour, obesity (orexigenic), and satiety (anorexigenic) associated pathways and mechanism.

Characterization of unique metabolites in γ-aminobutyric acid-rich cheese by metabolome analysis using liquid chromatography-mass spectrometry

Fermented dairy products comprise many functional components. Our previous study using fermented milk showed that the γ-aminobutyric acid (GABA)-producing Lactococcus lactis 01-7 strain can produce unique metabolites such as antihypertensive peptides, whereas this study was designed to find the unique metabolites in GABA-rich cheese using the 01-7 strain. Metabolites between cheese ripening with the non-GABA-producing L. lactis 01-1 strain (control) and GABA-rich cheese ripening with a mixture of 01-1 and 01-7 strains were compared. GABA and ornithine were detected in GABA-rich cheese using an amino acid analyzer and citrate was detected in the control cheese using HPLC. Metabolome analysis using LC-MS showed that peptides with unknown function and those with antihypertensive activity were higher in the GABA-rich cheese than in the control cheese. Further analysis of the amount of the YLGY derivatives showed that the amount of YL in the GABA-rich cheese was lower than that in the control. PRACTICAL APPLICATIONS: Clarification of metabolites in cheese contributes to the improvement of cheese ripening, thereby providing consumers with unique cheese with good nutritional and functional characteristics. The use of the 01-7 strain as a cheese starter might provide a functional cheese with antihypertensive-, antioxidative-, and anxiolytic-like activities.