Effects of neuromedin U-8 on stress responsiveness and hypothalamus-pituitary-adrenal axis activity in male C57BL/6J mice

Amide-to-chloroalkene substitution for overcoming intramolecular acyl transfer challenges in hexapeptidic neuromedin U receptor 2 agonists

CPN-116 is a peptidic agonist that activates human neuromedin U receptor type 2 (NMUR2) but suffers from chemical instability due to inherent backbone isomerization on the Dap residue. To address this, a Leu-Dap-type (Z)-chloroalkene dipeptide isostere was synthesized diastereoselectively as a surrogate of the Leu-Dap peptide bond to develop a (Z)-chloroalkene analogue of CPN-116. The synthesized CPN-116 analogue is stable in 1.0 M phosphate buffer (pH 7.4) without backbone isomerization and can activate NMUR2 with similar potency to CPN-116 at nM concentrations (EC50 = 1.0 nM).

Suppressive Effects of Neuromedin U Receptor 2-Selective Peptide Agonists on Appetite and Prolactin Secretion in Mice

Neuromedin U receptor 2 (NMUR2), which is expressed in the central nervous system (CNS) including the hypothalamus, has been noted as a therapeutic target against obesity. We previously reported that intranasal administration of CPN-219, a NMUR2-selective hexapeptide agonist, suppresses body weight gain in mice; however, there is no detailed information regarding its CNS effects. Recently, in addition to appetite suppression, stress responses and regulation of prolactin (PRL) secretion have also attracted attention. NMUR2 expressed in the hypothalamic tuberoinfundibular dopaminergic neurons has emerged as an alternative target for treating hyperprolactinemia. Here, CPN-219 decreased food intake up to 24 h after administration at a dose of 200 nmol, resulting in body weight gain suppression, although grooming and anxiety-like behaviors were transiently induced. Interestingly, the restraint stress-induced increase in plasma PRL levels was significantly suppressed at a lower dose of 20 nmol, indicating the potential for drug development as an anti-PRL agent of NMUR2-selective agonists.

The neuromedin U system: Pharmacological implications for the treatment of obesity and binge eating behavior

Neuromedin U (NMU) is a bioactive peptide produced in the gut and in the brain, with a role in multiple physiological processes. NMU acts by binding and activating two G protein coupled receptors (GPCR), the NMU receptor 1 (NMU-R1), which is predominantly expressed in the periphery, and the NMU receptor 2 (NMU-R2), mainly expressed in the central nervous system (CNS). In the brain, NMU and NMU-R2 are consistently present in the hypothalamus, commonly recognized as the main "feeding center". Considering its distribution pattern, NMU revealed to be an important neuropeptide involved in the regulation of food intake, with a powerful anorexigenic ability. This has been observed through direct administration of NMU and by studies using genetically modified animals, which revealed an obesity phenotype when the NMU gene is deleted. Thus, the development of NMU analogs or NMU-R2 agonists might represent a promising pharmacological strategy to treat obese individuals. Furthermore, NMU has been demonstrated to influence the non-homeostatic aspect of food intake, playing a potential role in binge eating behavior. This review aims to discuss and summarize the current literature linking the NMU system with obesity and binge eating behavior, focusing on the influence of NMU on food intake and the neuronal mechanisms underlying its anti-obesity properties. Pharmacological strategies to improve the pharmacokinetic profile of NMU will also be reported.

Neuroanatomical characterization of the Nmu-Cre knock-in mice reveals an interconnected network of unique neuropeptidergic cells

Neuromedin U (NMU) is an evolutionary conserved neuropeptide that has been implicated in multiple processes, such as circadian regulation, energy homeostasis, reward processing and stress coping. Although the central expression of NMU has been addressed previously, the lack of specific and sensitive tools has prevented a comprehensive characterization of NMU-expressing neurons in the brain. We have generated a knock-in mouse model constitutively expressing Cre recombinase under the Nmu promoter. We have validated the model using a multi-level approach based on quantitative reverse-transcription polymerase chain reactions, in situ hybridization, a reporter mouse line and an adenoviral vector driving Cre-dependent expression of a fluorescent protein. Using the Nmu-Cre mouse, we performed a complete characterization of NMU expression in adult mouse brain, unveiling a potential midline NMU modulatory circuit with the ventromedial hypothalamic nucleus (VMH) as a key node. Moreover, immunohistochemical analysis suggested that NMU neurons in the VMH mainly constitute a unique population of hypothalamic cells. Taken together, our results suggest that Cre expression in the Nmu-Cre mouse model largely reflects NMU expression in the adult mouse brain, without altering endogenous NMU expression. Thus, the Nmu-Cre mouse model is a powerful and sensitive tool to explore the role of NMU neurons in mice.

The effects of chronic unpredicted mild stress on maternal negative emotions and gut microbiota and metabolites in pregnant rats

Background

Chronic long-term stress is associated with a range of disorders, including depression and a variety of other chronic illnesses. It is well known that maternal exposure to psychosocial stress during pregnancy significantly increases the likelihood of adverse pregnancy outcomes. The gut microbiota has been a popular topic, it is a key mediator of the gut-brain axis and plays an important role in human health; changes in the gut microbiota have been related to chronic stress-induced health impairment, however, the relationship between maternal negative emotions and abnormal gut microbiota and its metabolites during maternal exposure to chronic stress during pregnancy remains unclear.

Methods

Pregnant rats were subjected to chronic unpredicted mild stress (CUMS) to establish the rat model of chronic stress during pregnancy. The behavioral changes were recorded using sucrose preference test (SPT) and open-field test (OFT), plasma corticosterone levels were determined by radioimmunoassay, and a comprehensive method combining 16S rRNA gene sequencing and gas chromatography-mass spectrometry (GC-MS) metabolomics was used to study the effects of stress during pregnancy on the function of intestinal microbiota and its metabolites.

Results

Chronic stress during pregnancy not only increased maternal plasma corticosterone (P < 0.05), but also caused maternal depression-like behaviors (P < 0.05). Chronic stress during pregnancy changed the species composition at the family level of maternal gut microbiota, the species abundance of Ruminococcaceae in the stress group (23.45%) was lower than the control group (32.67%) and the species abundance of Prevotellaceae in the stress group (10.45%) was higher than the control group (0.03%) (P < 0.05). Vertical locomotion and 1% sucrose preference percentage in pregnant rats were negatively correlated with Prevotellaceae (r =  - 0.90, P < 0.05). Principal component analysis with partial least squares discriminant analysis showed that the integration points of metabolic components in the stress and control groups were completely separated, indicating that there were significant differences in the metabolic patterns of the two groups, and there were seven endogenous metabolites that differed (P < 0.05).

Conclusions

The negative emotional behaviors that occur in pregnant rats as a result of prenatal chronic stress may be associated with alterations in the gut microbiota and its metabolites. These findings provide a basis for future targeted metabolomics and gut flora studies on the effects of chronic stress during pregnancy on gut flora.

Lycium barbarum polysaccharide attenuates emotional injury of offspring elicited by prenatal chronic stress in rats via regulation of gut microbiota

Stress during pregnancy is not only detrimental to a woman's own physical and mental health, but can also cause changes in the intrauterine environment and even have an impact on later growth and development, this study was designed to understand the changes of gut microbiota in the maternal and offspring caused by prenatal chronic stress, and to explore the regulatory effect of LBP on gut microbiota, and then to improve the emotional damage caused by prenatal chronic stress in the offspring. A rat model of prenatal chronic stress was made and used LBP to intervene by gavage. Fresh feces of offspring were collected, the concentration of microbial metabolites were tested by ELISA. Illumina MiSeqPE300 sequencing technology was used to determine the sequence of 16S rRNA V3-V4 of microorganisms. On the PND 42, the emotional function of offspring were tested by open-field test (OFT), sucrose preference test (SPT) and tail of suspend test (TST). Results indicated that stress factors increased the plasma corticosterone level of rats during pregnancy and they appeared depressive behaviors. The body weight of offspring during prenatal chronic stress was lower than the control group, and the plasma corticosterone level was increased. Prenatal chronic stress had a significant impact on emotional performance of the offspring on OFT, SPT and TST. Alpha diversity of gut microbiota and microbiota composition in offspring of prenatal chronic stress was attenuated and some relationships existed between these parameters. LBP treatment reduced offspring's plasma corticosterone level and improved their body weight, changed the emotional function, increased the diversity of gut microbiota. Collectively, these findings disclose that prenatal chronic stress not only causes emotional injury on the offspring, but also changes the gut microbiota of the mother and offspring; LBP may regulate the intestinal flora of the mother, then reducing the influence of stress factors on the emotional injury of offspring.

Neuromedins NMU and NMS: An Updated Overview of Their Functions

More than 35 years have passed since the identification of neuromedin U (NMU). Dozens of publications have been devoted to its physiological role in the organism, which have provided insight into its occurrence in the body, its synthesis and mechanism of action at the cellular level. Two G protein-coupled receptors (GPCRs) have been identified, with NMUR1 distributed mainly peripherally and NMUR2 predominantly centrally. Recognition of the role of NMU in the control of energy homeostasis of the body has greatly increased interest in this neuromedin. In 2005 a second, structurally related peptide, neuromedin S (NMS) was identified. The expression of NMS is more restricted, it is predominantly found in the central nervous system. In recent years, further peptides related to NMU and NMS have been identified. These are neuromedin U precursor related peptide (NURP) and neuromedin S precursor related peptide (NSRP), which also exert biological effects without acting via NMUR1, or NMUR2. This observation suggests the presence of another, as yet unrecognized receptor. Another unresolved issue within the NMU/NMS system is the differences in the effects of various NMU isoforms on diverse cell lines. It seems that development of highly specific NMUR1 and NMUR2 receptor antagonists would allow for a more detailed understanding of the mechanisms of action of NMU/NMS and related peptides in the body. They could form the basis for attempts to use such compounds in the treatment of disorders, for example, metabolic disorders, circadian rhythm, stress, etc.