Interleukin-1 beta-induced anorexia and pyrexia in rat: relationship to hypothalamic neuropeptide Y

Correlation of Leptin in Patients With Type 2 Diabetes Mellitus

The exponential increase in diabetes mellitus (DM) poses serious public health concerns. In this review, we focus on the role of leptin in type 2 DM. The peripheral actions of leptin consist of upregulating proinflammatory cytokines which play an important role in the pathogenesis of type 2 DM and insulin resistance. Moreover, leptin is known to inhibit insulin secretion and plays a significant role in insulin resistance in obesity and type 2 DM. A literature search was conducted on Medline, Cochrane, Embase, and Google Scholar for relevant articles published until December 2023. The following search strings and Medical Subject Headings (MeSH terms) were used: "Diabetes Mellitus," "Leptin," "NPY," and "Biomarker." This article aims to discuss the physiology of leptin in type 2 DM, its glucoregulatory actions, its relationship with appetite, the impact that various lifestyle modifications can have on leptin levels, and, finally, explore leptin as a potential target for various treatment strategies.

Cancer Cachexia: Underlying Mechanisms and Potential Therapeutic Interventions

Cancer cachexia, a multifactorial metabolic syndrome developed during malignant tumor growth, is characterized by an accelerated loss of body weight accompanied by the depletion of skeletal muscle mass. This debilitating condition is associated with muscle degradation, impaired immune function, reduced functional capacity, compromised quality of life, and diminished survival in cancer patients. Despite the lack of the known capability of fully reversing or ameliorating this condition, ongoing research is shedding light on promising preclinical approaches that target the disrupted mechanisms in the pathophysiology of cancer cachexia. This comprehensive review delves into critical aspects of cancer cachexia, including its underlying pathophysiological mechanisms, preclinical models for studying the progression of cancer cachexia, methods for clinical assessment, relevant biomarkers, and potential therapeutic strategies. These discussions collectively aim to contribute to the evolving foundation for effective, multifaceted counteractive strategies against this challenging condition.

Cachexia, a Systemic Disease beyond Muscle Atrophy

Cachexia is a complication of dismal prognosis, which often represents the last step of several chronic diseases. For this reason, the comprehension of the molecular drivers of such a condition is crucial for the development of management approaches. Importantly, cachexia is a syndrome affecting various organs, which often results in systemic complications. To date, the majority of the research on cachexia has been focused on skeletal muscle, muscle atrophy being a pivotal cause of weight loss and the major feature associated with the steep reduction in quality of life. Nevertheless, defining the impact of cachexia on other organs is essential to properly comprehend the complexity of such a condition and potentially develop novel therapeutic approaches.

Abnormalities in Glucose Metabolism, Appetite-Related Peptide Release, and Pro-nflammatory Cytokines Play a Central Role in Appetite Disorders in Peritoneal Dialysis

Background: Appetite disorders are frequent and scantly studied in peritoneal dialysis (PD) patients and are associated with malnutrition and cardiovascular complications. Objective: We investigated the relationship between uremic insulin resistance, pro-inflammatory cytokines, and appetite-related peptides release (ARPr) with eating-behavior disorders in PD patients. Methods: We included 42 PD patients (12 suffering anorexia, 12 obese with high food-intake, and 18 asymptomatic) and 10 controls. We measured blood levels of ARPr including orexigens [neuropeptide-Y (NPY), ghrelin, and nitric-oxide], anorexigens [cholecystokinin, insulin, corticotropin-releasing factor, leptin, and adiponectin (Ad)], and cytokines (TNF-α, sTNFα-R2, and IL-6) both at baseline and after administering a standard-food stimulus (SFS). We also measured the expression of TNF-α, leptin and Ad-encoding mRNAs in abdominal adipose tissue. We compared these markers with eating motivation measured by a Visual Analog Scale (VAS). Results: Anorexics showed both little appetite, measured by a VAS, and low levels of orexigens that remained constant after SFS, coupled with high levels of anorexigens at baseline and after SFS. Obeses showed higher appetite, increased baseline levels of orexigens, lower baseline levels of anorexigens and cytokines and two peaks of NPY after SFS. The different patterns of ARPr and cytokines pointed to a close relationship with uremic insulin resistance. In fact, the euglycemic-hyperglycemic clamp reproduced these disorders. In anorexics, TNF-α fat expression was increased. In obese patients, leptin expression in fat tissue was down-regulated and showed correlation with the appetite. Conclusion: In PD, appetite is governed by substances that are altered at baseline and abnormally released. Such modulators are controlled by insulin metabolism and cytokines and, while anorexics display inflammatory predominance, obese patients predominantly display insulin resistance.

The homeostatic role of neuropeptide Y in immune function and its impact on mood and behaviour

Neuropeptide Y (NPY), one of the most abundant peptides in the nervous system, exerts its effects via five receptor types, termed Y1, Y2, Y4, Y5 and Y6. NPY's pleiotropic functions comprise the regulation of brain activity, mood, stress coping, ingestion, digestion, metabolism, vascular and immune function. Nerve-derived NPY directly affects immune cells while NPY also acts as a paracrine and autocrine immune mediator, because immune cells themselves are capable of producing and releasing NPY. NPY is able to induce immune activation or suppression, depending on a myriad of factors such as the Y receptors activated and cell types involved. There is an intricate relationship between psychological stress, mood disorders and the immune system. While stress represents a risk factor for the development of mood disorders, it exhibits diverse actions on the immune system as well. Conversely, inflammation is regarded as an internal stressor and is increasingly recognized to contribute to the pathogenesis of mood and metabolic disorders. Intriguingly, the cerebral NPY system has been found to protect against distinct disturbances in response to immune challenge, attenuating the sickness response and preventing the development of depression. Thus, NPY plays an important homeostatic role in balancing disturbances of physiological systems caused by peripheral immune challenge. This implication is particularly evident in the brain in which NPY counteracts the negative impact of immune challenge on mood, emotional processing and stress resilience. NPY thus acts as a unique signalling molecule in the interaction of the immune system with the brain in health and disease.

Neuropeptide Y, peptide YY and pancreatic polypeptide in the gut-brain axis

The gut-brain axis refers to the bidirectional communication between the gut and the brain. Four information carriers (vagal and spinal afferent neurons, immune mediators such as cytokines, gut hormones and gut microbiota-derived signalling molecules) transmit information from the gut to the brain, while autonomic neurons and neuroendocrine factors carry outputs from the brain to the gut. The members of the neuropeptide Y (NPY) family of biologically active peptides, NPY, peptide YY (PYY) and pancreatic polypeptide (PP), are expressed by cell systems at distinct levels of the gut-brain axis. PYY and PP are exclusively expressed by endocrine cells of the digestive system, whereas NPY is found at all levels of the gut-brain and brain-gut axis. The major systems expressing NPY comprise enteric neurons, primary afferent neurons, several neuronal pathways throughout the brain and sympathetic neurons. In the digestive tract, NPY and PYY inhibit gastrointestinal motility and electrolyte secretion and in this way modify the input to the brain. PYY is also influenced by the intestinal microbiota, and NPY exerts, via stimulation of Y1 receptors, a proinflammatory action. Furthermore, the NPY system protects against distinct behavioural disturbances caused by peripheral immune challenge, ameliorating the acute sickness response and preventing long-term depression. At the level of the afferent system, NPY inhibits nociceptive input from the periphery to the spinal cord and brainstem. In the brain, NPY and its receptors (Y1, Y2, Y4, Y5) play important roles in regulating food intake, energy homeostasis, anxiety, mood and stress resilience. In addition, PP and PYY signal to the brain to attenuate food intake, anxiety and depression-related behaviour. These findings underscore the important role of the NPY-Y receptor system at several levels of the gut-brain axis in which NPY, PYY and PP operate both as neural and endocrine messengers.

Evidence from knockout mice that neuropeptide-Y Y2 and Y4 receptor signalling prevents long-term depression-like behaviour caused by immune challenge

Neuropeptide Y participates in the acute behavioural responses to immune challenge, since Y2 receptor knockout (Y2⁻/⁻) mice are particularly sensitive to the short-term anxiogenic-like effect of bacterial lipopolysaccharide. The present exploratory study addressed the involvement of Y2 and Y4 receptors in the long-term behavioural responses to immune challenge. A single intraperitoneal injection of lipopolysaccharide (0.83 mg/kg) to control mice did not affect open field behaviour 3 h post-treatment but enhanced anxiety-like behaviour in Y2⁻/⁻ as well as Y4⁻/⁻ mice. Four weeks post-treatment this behavioural effect of lipopolysaccharide persisted in Y4⁻/⁻ mice but had gone in Y2⁻/⁻ mice. Depression-related behaviour in the forced swim test was enhanced 1 day post-lipopolysaccharide in control and Y2⁻/⁻ mice, but not in Y4⁻/⁻ mice. Four weeks post-treatment, the depressogenic-like effect of lipopolysaccharide had waned in control mice, persisted in Y2⁻/⁻ mice and was first observed in Y4⁻/⁻ mice. In summary, knockout of Y2 and/or Y4 receptors unmasks the ability of a single lipopolysaccharide injection to cause a delayed and prolonged increase in anxiety- and/or depression-like behaviour. These findings suggest that neuropeptide Y acting via Y2 and Y4 receptors prevents the development of long-term anxiety- and depression-like behaviour caused by acute immune challenge.

Evidence from knockout mice that peptide YY and neuropeptide Y enforce murine locomotion, exploration and ingestive behaviour in a circadian cycle- and gender-dependent manner

Peptide YY (PYY) and neuropeptide Y (NPY) have been proposed to participate in the control of energy homeostasis. Since these activities show circadian variations, we explored the circadian pattern of locomotor, exploratory and ingestive behaviour in male and/or female mice with disrupted genes for PYY (PYY-/-), NPY (NPY-/-) as well as PYY plus NPY (PYY+NPY-/-). The effect of bacterial lipopolysaccharide (LPS, 0.1 mg/kg intraperitoneally) on these behaviours was also examined. The animals were housed singly in cages fitted with sensors for water and food intake and two infrared frames for recording ambulation and rearing under a 12 h light/dark cycle for 4 days. Locomotor and exploratory behaviour was decreased in female NPY-/- as well as male and female PYY+NPY-/- mice during the photo- and scotophase, and in male PYY-/- mice during the scotophase. Significant decreases in water and food intake were seen in female NPY-/- as well as male and female PYY+NPY-/- mice during the photophase. The effect of LPS to attenuate ingestive behaviour during the light and/or dark phase was most pronounced in PYY-/- and NPY-/- mice. These findings attest to a circadian cycle- and gender-related role of NPY and PYY in the control of behaviours that balance energy intake and energy expenditure. Both peptides stimulate feeding and drinking to balance the energy demand that they generate by enforcing the circadian pattern of locomotion and exploration. In addition, they counteract the anorectic and antidipsogenic effects of immune challenge.

Regulation of agouti-related protein messenger ribonucleic acid transcription and peptide secretion by acute and chronic inflammation

Agouti-related protein (AgRP) is an orexigenic neuropeptide produced by neurons in the hypothalamic arcuate nucleus (ARC) that is a key component of central neural circuits that control food intake and energy expenditure. Disorders in energy homeostasis, characterized by hypophagia and increased metabolic rate, frequently develop in animals with either acute or chronic diseases. Recently, studies have demonstrated that proopiomelanocortin-expressing neurons in the ARC are activated by the proinflammatory cytokine IL-1beta. In the current study, we sought to determine whether inflammatory processes regulate the expression of AgRP mRNA and to characterize the response of AgRP neurons to IL-1beta. Here, we show by real-time RT-PCR and in situ hybridization analysis that AgRP mRNA expression in rodents is increased in models of acute and chronic inflammation. AgRP neurons were found to express the type I IL-1 receptor, and the percentage of expression was significantly increased after peripheral administration of lipopolysaccharide. Furthermore, we demonstrate that IL-1beta inhibits the release of AgRP from hypothalamic explants. Collectively, these data indicate that proinflammatory signals decrease the secretion of AgRP while increasing the transcription of the AgRP gene. These observations suggest that AgRP neurons may participate with ARC proopiomelanocortin neurons in mediating the anorexic and metabolic responses to acute and chronic disease processes.

Implication of neuropeptide-Y Y2 receptors in the effects of immune stress on emotional, locomotor and social behavior of mice

Neuropeptide Y (NPY) is involved in the regulation of emotional behavior, and there is indirect evidence for a role of NPY in the cerebral responses to peripheral immune challenge. Since the NPY receptors involved in these reactions are not known, we investigated the effect of Escherichia coli lipopolysaccharide (LPS) on emotional, locomotor and social behavior, body temperature and circulating corticosterone in female Y2 (Y2-/-) and Y4 (Y4-/-) receptor knockout mice. LPS (0.1mg/kg injected IP 2.5h before testing) increased rectal temperature in control and Y4-/- mice to a larger degree than in Y2-/- animals. Both Y2-/- and Y4-/- mice exhibited reduced anxiety-related and depression-like behavior in the open field, elevated plus-maze and tail suspension test, respectively. While depression-like behavior was not changed by LPS, anxiety-related behavior was enhanced by LPS in Y2-/-, but not control and Y4-/- animals. Y2-/- mice were also particularly susceptible to the effect of LPS to attenuate locomotor behavior and social interaction with another mouse. The corticosterone response to LPS was blunted in Y2-/- mice which presented elevated levels of circulating corticosterone following vehicle treatment. These data show that Y2-/- mice are particularly sensitive to the effects of LPS-evoked immune stress to attenuate locomotion and social interaction and to increase anxiety-like behavior, while the LPS-induced rise of temperature and circulating corticosterone is suppressed by Y2 receptor knockout. Our observations attest to an important role of endogenous NPY acting via Y2 receptors in the cerebral response to peripheral immune challenge.

Neuropeptide Y stabilizes body temperature and prevents hypotension in endotoxaemic rats

The on-going high mortality from sepsis motivates continuous research for novel therapeutic strategies. Neuropeptide Y (NPY), a sympathetic neurotransmitter, has been shown to increase survival in experimental septic shock in rats. This protective effect might be due to immunological, cardiovascular or thermoregulatory effects. The aim of this study was to examine the in vivo effect of peripherally administered NPY on body temperature, blood pressure and heart rate in endotoxaemic animals. In order to obtain clinically relevant data, various physiological parameters were monitored in parallel via radio-telemetry in chronically intravenously cannulated, freely behaving rats. Rats received a sublethal bolus of lipopolysaccharide (LPS, 100 microg kg(-1) I.V.) and the three parameters were continuously recorded for 72 h. Endotoxaemic rats showed a long-lasting hypotension, an initial hypothermia (-0.5 degrees C), followed by a prolonged febrile phase (+1.6 degrees C 6 h after endotoxin challenge) associated with a decrease of the circadian rhythm amplitude of temperature. Pretreatment with NPY (160 pmol kg(-1) I.V. over 75 min) prevented hypotension and significantly stabilized body temperature immediately following the application. The febrile phase was effectively reduced for at least 72 h. These telemetrically obtained findings clearly demonstrate that pretreatment with NPY positively influences two life-threatening symptoms in endotoxaemia and might be a future option for a successful clinical treatment regimen.