Decreased NPY innervation of the hypothalamic nuclei in rats with cancer anorexia

Cancer cachexia: multilevel metabolic dysfunction

Cancer cachexia is a complex metabolic disorder marked by unintentional body weight loss or 'wasting' of body mass, driven by multiple aetiological factors operating at various levels. It is associated with many malignancies and significantly contributes to cancer-related morbidity and mortality. With emerging recognition of cancer as a systemic disease, there is increasing awareness that understanding and treatment of cancer cachexia may represent a crucial cornerstone for improved management of cancer. Here, we describe the metabolic changes contributing to body wasting in cachexia and explain how the entangled action of both tumour-derived and host-amplified processes induces these metabolic changes. We discuss energy homeostasis and possible ways that the presence of a tumour interferes with or hijacks physiological energy conservation pathways. In that context, we highlight the role played by metabolic cross-talk mechanisms in cachexia pathogenesis. Lastly, we elaborate on the challenges and opportunities in the treatment of this devastating paraneoplastic phenomenon that arise from the complex and multifaceted metabolic cross-talk mechanisms and provide a status on current and emerging therapeutic approaches.

Cancer cachexia: molecular mechanism and pharmacological management

Cancer cachexia often occurs in malignant tumors and is a multifactorial and complex symptom characterized by wasting of skeletal muscle and adipose tissue, resulting in weight loss, poor life quality and shorter survival. The pathogenic mechanism of cancer cachexia is complex, involving a variety of molecular substrates and signal pathways. Advancements in understanding the molecular mechanisms of cancer cachexia have provided a platform for the development of new targeted therapies. Although recent outcomes of early-phase trials have showed that several drugs presented an ideal curative effect, monotherapy cannot be entirely satisfactory in the treatment of cachexia-associated symptoms due to its complex and multifactorial pathogenesis. Therefore, the lack of definitive therapeutic strategies for cancer cachexia emphasizes the need to develop a better understanding of the underlying mechanisms. Increasing evidences show that the progression of cachexia is associated with metabolic alternations, which mainly include excessive energy expenditure, increased proteolysis and mitochondrial dysfunction. In this review, we provided an overview of the key mechanisms of cancer cachexia, with a major focus on muscle atrophy, adipose tissue wasting, anorexia and fatigue and updated the latest progress of pharmacological management of cancer cachexia, thereby further advancing the interventions that can counteract cancer cachexia.

Appetite Regulation of TLR4-Induced Inflammatory Signaling

Appetite is the basis for obtaining food and maintaining normal metabolism. Toll-like receptor 4 (TLR4) is an important receptor expressed in the brain that induces inflammatory signaling after activation. Inflammation is considered to affect the homeostatic and non-homeostatic systems of appetite, which are dominated by hypothalamic and mesolimbic dopamine signaling. Although the pathological features of many types of inflammation are known, their physiological functions in appetite are largely unknown. This review mainly addresses several key issues, including the structures of the homeostatic and non-homeostatic systems. In addition, the mechanism by which TLR4-induced inflammatory signaling contributes to these two systems to regulate appetite is also discussed. This review will provide potential opportunities to develop new therapeutic interventions that control appetite under inflammatory conditions.

Effect of Mirtazapine on Gastric Emptying in Patients with Cancer-associated Anorexia

BACKGROUND/AIMS

The tetracyclic antidepressant mirtazapine is widely used in cancer patients suffering from anorexia. Although it is known to restore appetite, the exact mechanism remains unknown. The aim of the study was to evaluate if mirtazapine has any effect on gastric emptying in patients suffering from cancer-related anorexia.

MATERIALS AND METHODS

Solid-meal gastric-emptying study using radiolabeled meal was performed in 28 patients suffering from cancer anorexia once at baseline and repeated after 15 days of mirtazapine therapy.

RESULTS

At baseline, only 7 (25%) patients had normal gastric motility (emptying >70% at 3 h postingestion) whereas after treatment, 18 (64.2%) patients achieved this limit. Mean % gastric emptying increased from 55.2% ±21.0% to 68.9% ±21.3% (P < 0.001). Mean gastric emptying time (t_1/2) before intervention was 314.7 ± 421.0 min which decreased to 116.0 ± 106.7 min after intervention. Results were further analyzed by dividing the patients into two groups based on baseline gastric-emptying study. Group A (normal gastric emptying) consisted of seven patients, mean % gastric emptying at baseline and postintervention was 75.0% ±5.25% and 87.57% ±5.94%, respectively (P < 0.018). Group B (delayed gastric emptying) consisted of 21 patients, mean % gastric emptying at baseline and postintervention was 48.71% ±18.82% and 62.76% ±16.86%, respectively (P < 0.001).

CONCLUSION

Mirtazapine significantly improves gastric emptying in patients of prostate and breast cancer suffering from cancer-associated anorexia.

Hypothalamic inflammation and food intake regulation during chronic illness

Anorexia is a common symptom in chronic illness. It contributes to malnutrition and strongly affects survival and quality of life. A common denominator of many chronic diseases is an elevated inflammatory status, which is considered to play a pivotal role in the failure of food-intake regulating systems in the hypothalamus. In this review, we summarize findings on the role of hypothalamic inflammation on food intake regulation involving hypothalamic neuropeptide Y (NPY) and pro-opiomelanocortin (POMC). Furthermore, we outline the role of serotonin in the inability of these peptide based food-intake regulating systems to respond and adapt to changes in energy metabolism during chronic disease.

Pathophysiology of anorexia in the cancer cachexia syndrome

Anorexia is commonly present in persons with cancer and a major component of cancer cachexia. There are multiple causes of anorexia in cancer. Peripherally, these can be due to (i) substances released from or by the tumour, e.g. pro-inflammatory cytokines, lactate, and parathormone-related peptide; (ii) tumours causing dysphagia or altering gut function; (iii) tumours altering nutrients, e.g. zinc deficiency; (iv) tumours causing hypoxia; (v) increased peripheral tryptophan leading to increased central serotonin; or (vi) alterations of release of peripheral hormones that alter feeding, e.g. peptide tyrosine tyrosine and ghrelin. Central effects include depression and pain, decreasing the desire to eat. Within the central nervous system, tumours create multiple alterations in neurotransmitters, neuropeptides, and prostaglandins that modulate feeding. Many of these neurotransmitters appear to produce their anorectic effects through the adenosine monophosphate kinase/methylmalonyl coenzyme A/fatty acid system in the hypothalamus. Dynamin is a guanosine triphosphatase that is responsible for internalization of melanocortin 4 receptors and prostaglandin receptors. Dynamin is up-regulated in a mouse model of cancer anorexia. A number of drugs, e.g. megestrol acetate, cannabinoids, and ghrelin agonists, have been shown to have some ability to be orexigenic in cancer patients.

Differences in food intake of tumour-bearing cachectic mice are associated with hypothalamic serotonin signalling

BACKGROUND

Anorexia is a common symptom among cancer patients and contributes to malnutrition and strongly impinges on quality of life. Cancer-induced anorexia is thought to be caused by an inability of food intake-regulating systems in the hypothalamus to respond adequately to negative energy balance during tumour growth. Here, we show that this impaired response of food-intake control is likely to be mediated by altered serotonin signalling and by failure in post-transcriptional neuropeptide Y (NPY) regulation.

METHODS

Two tumour cachectic mouse models with different food intake behaviours were used: a C26-colon adenocarcinoma model with increased food intake and a Lewis lung carcinoma model with decreased food intake. This contrast in food intake behaviour between tumour-bearing (TB) mice in response to growth of the two different tumours was used to distinguish between processes involved in cachexia and mechanisms that might be important in food intake regulation. The hypothalamus was used for transcriptomics (affymetrix chips).

RESULTS

In both models, hypothalamic expression of orexigenic NPY was significantly higher compared with controls, suggesting that this change does not directly reflect food intake status but might be linked to negative energy balance in cachexia. Expression of genes involved in serotonin signalling showed to be different between C26-TB mice and Lewis lung carcinoma-TB mice and was inversely associated with food intake. In vitro, using hypothalamic cell lines, serotonin repressed neuronal hypothalamic NPY secretion while not affecting messenger NPY expression, suggesting that serotonin signalling can interfere with NPY synthesis, transport, or secretion.

CONCLUSIONS

Altered serotonin signalling is associated with changes in food intake behaviour in cachectic TB mice. Serotonins' inhibitory effect on food intake under cancer cachectic conditions is probably via affecting the NPY system. Therefore, serotonin regulation might be a therapeutic target to prevent the development of cancer-induced eating disorders.

Cancer cachexia pathophysiology and translational aspect of herbal medicine

About half of all cancer patients show a syndrome of cachexia, characterized by anorexia and loss of adipose tissue and skeletal muscle mass. Numerous cytokines have been postulated to play a role in the etiology of cancer cachexia. Cytokines can elicit effects that mimic leptin signaling and suppress orexigenic ghrelin and neuropeptide Y signaling, inducing sustained anorexia and cachexia not accompanied by the usual compensatory response. Furthermore, cytokines have been implicated in the induction of cancer-related muscle wasting. In particular, tumor necrosis factor-alpha, interleukin-1, interleukin-6 and interferon-gamma have been implicated in the induction of cancer-related muscle wasting. Cytokine-induced skeletal muscle wasting is probably a multifactorial process, which involves a depression in protein synthesis, an increase in protein degradation or a combination of both. Cancer patients suffer from the reduction in physical function, tolerance to anti-cancer therapy and survival, while many effective chemotherapeutic agents for cancer are burdened by toxicities that can reduce patient's quality of life or hinder their effective use. Herbal medicines have been widely used to help improve such conditions. Recent studies have shown that herbal medicines such as rikkunshito enhance ghrelin signaling and consequently improve nausea, appetite loss and cachexia associated with cancer or cancer chemotherapy, which worsens the quality of life and life expectancy of the patients. The multicomponent herbal medicines capable of targeting multiple sites could be useful for future drug discovery. Mechanistic studies and identification of active compounds could lead to new discoveries in biological and biomedical sciences.

Potentiation of ghrelin signaling attenuates cancer anorexia-cachexia and prolongs survival

Cancer anorexia-cachexia syndrome is characterized by decreased food intake, weight loss, muscle tissue wasting and psychological distress, and this syndrome is a major source of increased morbidity and mortality in cancer patients. This study aimed to clarify the gut-brain peptides involved in the pathogenesis of the syndrome and determine effective treatment for cancer anorexia-cachexia. We show that both ghrelin insufficiency and resistance were observed in tumor-bearing rats. Corticotropin-releasing factor (CRF) decreased the plasma level of acyl ghrelin, and its receptor antagonist, α-helical CRF, increased food intake of these rats. The serotonin 2c receptor (5-HT2cR) antagonist SB242084 decreased hypothalamic CRF level and improved anorexia, gastrointestinal (GI) dysmotility and body weight loss. The ghrelin receptor antagonist (D-Lys3)-GHRP-6 worsened anorexia and hastened death in tumor-bearing rats. Ghrelin attenuated anorexia-cachexia in the short term, but failed to prolong survival, as did SB242084 administration. In addition, the herbal medicine rikkunshito improved anorexia, GI dysmotility, muscle wasting, and anxiety-related behavior and prolonged survival in animals and patients with cancer. The appetite-stimulating effect of rikkunshito was blocked by (D-Lys3)-GHRP-6. Active components of rikkunshito, hesperidin and atractylodin, potentiated ghrelin secretion and receptor signaling, respectively, and atractylodin prolonged survival in tumor-bearing rats. Our study demonstrates that the integrated mechanism underlying cancer anorexia-cachexia involves lowered ghrelin signaling due to excessive hypothalamic interactions of 5-HT with CRF through the 5-HT2cR. Potentiation of ghrelin receptor signaling may be an attractive treatment for anorexia, muscle wasting and prolong survival in patients with cancer anorexia-cachexia.

Pathophysiology and treatment of inflammatory anorexia in chronic disease

Decreased appetite and involuntary weight loss are common occurrences in chronic disease and have a negative impact on both quality of life and eventual mortality. Weight loss in chronic disease comes from both fat and lean mass, and is known as cachexia. Both alterations in appetite and body weight loss occur in a wide variety of diseases, including cancer, heart failure, renal failure, chronic obstructive pulmonary disease and HIV. An increase in circulating inflammatory cytokines has been implicated as a uniting pathogenic mechanism of cachexia and associated anorexia. One of the targets of inflammatory mediators is the central nervous system, and in particular feeding centers in the hypothalamus located in the ventral diencephalon. Current research has begun to elucidate the mechanisms by which inflammation reaches the hypothalamus, and the neural substrates underlying inflammatory anorexia. Research into these neural mechanisms has suggested new therapeutic possibilities, which have produced promising results in preclinical and clinical trials. This review will discuss inflammatory signaling in the hypothalamus that mediates anorexia, and the opportunities for therapeutic intervention that these mechanisms present.

Neural control of the anorexia-cachexia syndrome

The anorexia-cachexia syndrome is a debilitating clinical condition characterizing the course of chronic diseases, which heavily impacts on patients' morbidity and quality of life, ultimately accelerating death. The pathogenesis is multifactorial and reflects the complexity and redundancy of the mechanisms controlling energy homeostasis under physiological conditions. Accumulating evidence indicates that, during disease, disturbances of the hypothalamic pathways controlling energy homeostasis occur, leading to profound metabolic changes in peripheral tissues. In particular, the hypothalamic melanocortin system does not respond appropriately to peripheral inputs, and its activity is diverted largely toward the promotion of catabolic stimuli (i.e., reduced energy intake, increased energy expenditure, possibly increased muscle proteolysis, and adipose tissue loss). Hypothalamic proinflammatory cytokines and serotonin, among other factors, are key in triggering hypothalamic resistance. These catabolic effects represent the central response to peripheral challenges (i.e., growing tumor, renal, cardiac failure, disrupted hepatic metabolism) that are likely sensed by the brain through the vagus nerve. Also, disease-induced changes in fatty acid oxidation within hypothalamic neurons may contribute to the dysfunction of the hypothalamic melanocortin system. Ultimately, sympathetic outflow mediates, at least in part, the metabolic changes in peripheral tissues. Other factors are likely involved in the pathogenesis of the anorexia-cachexia syndrome, and their role is currently being elucidated. However, available evidence shows that the constellation of symptoms characterizing this syndrome should be considered, at least in part, as different phenotypes of common neurochemical/metabolic alterations in the presence of a chronic inflammatory state.

Interleukin-6 and the hypothalamic-pituitary-adrenal activation in a tumor bearing mouse

Tumor derived cytokines have been suggested to activate the hypothalamic-pituitary-adrenal (HPA) axis; that is, increase the hypothalamic releases of corticotropin-releasing hormone (CRH) and adrenocorticotrophic hormone. The authors previously reported that tumor mice bearing a human oral squamous cell carcinoma exhibit an anorectic phenotype with increased expression of CRH mRNA in their hypothalamic paraventricular nuclei. This study examined the plasma levels of tumor-derived cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), in order to determine potential mediator(s) implicated in CRH expression in this tumor mouse model. Plasma corticosterone levels were assayed as well to confirm the HPA activation. In the results, plasma levels of IL-6, but not TNF-alpha, were increased significantly in the tumor mice compared with age-matching non-tumor controls. Plasma corticosterone levels were also increased in the tumor mice. These results together with the previous findings suggest IL-6 as a potential mediator in the control of hypothalamic CRH expression in the authors' tumor mouse model.

Expression of motilin in the hypothalamus and the effect of central erythromycin on gastric motility in diabetic rats

OBJECTIVE

To investigate the expression of motilin-immunoreactive neurons in the hypothalamus and the effect of central administration of erythromycin (EM) on the regulation of gastric motility in diabetic rats.

METHODS

The motilin immunoreactive neurons in the hypothalamus and the hippocampus were detected by immunohistochemistry with rabbit anti-motilin polyclonal antibody. To measure the gastric motility, force transducers were surgically affixed to the gastric serosa. A microinjection syringe was connected via a plastic tube to an injection cannula, which was connected with a stainless steel guide cannula. The syringe was inserted into the right lateral cerebral ventricle for microinjecting the chemicals.

RESULTS

Diabetic mellitus was successfully induced in cohorts of rats. Motilin-immunoreactive neurons significantly increased in the paraventricular (PVN) and supraoptic nuclei (SON) of the hypothalamus in the diabetic rats. Intracerebroventricular (i.c.v.) administration of EM, a motilin receptor agonist, stimulated the gastric motility of diabetic rats. EM (91.56 nmol, i.c.v.) dose-dependently increased the amplitude by (174.82 +/- 48.62)% (P<0.05), and increased the frequency by (70.43 +/- 27.11)% (P < 0.05) in 5 min. The stimulatory effect lasted more than 15 min to the end of the measurement, and can be blocked partially by the prior treatment of motilin receptor antagonist GM-109.

CONCLUSION

Motilin-immunoreactive neurons are increased in the PVN and SON of the hypothalamus in diabetic rats. Centrally administered EM may regulate gastric motility by binding to the central motilin receptors, and central motilin might be involved in regulation of gastric motility in diabetic rats.

Anorexia in cancer: role of feeding-regulatory peptides

Anorexia is one of the most common symptoms in advanced cancer and is a frequent cause of discomfort for cancer patients and their families. The pathogenesis of cancer anorexia is multi-factorial and involves most of the hypothalamic neuronal signalling pathways modulating energy homeostasis. It is considered to be the result of a failure of usual appetite and satiety signals. Loss of appetite can arise from decreased taste and smell of food, as well as from dysfunctional hypothalamic signalling pathways and cytokine production. Cytokines in particular, appear to play a key role in energy balance through persistent activation of the melanocortin system and inhibition of the neuropeptide Y pathway. The imbalance between anorexigenic and orexigenic peptides leads to suppression of appetite, and increased satiety and satiation associated with marked weight loss and decline in physical performance. High levels of serotonin also appear to contribute to these effects and recent findings implicate corticotropin-releasing factor in the pathogenesis of cancer anorexia as well. Despite significant advances in our understanding of the regulation of food intake and energy expenditure, few effective therapies are available. A better appreciation of the molecular and neuronal mechanisms that control body weight homeostasis may lead to the development of new therapies for improving the survival and quality of life of these patients.

Alteration of NPY and Y1 receptor in dorsomedial and ventromedial areas of hypothalamus in anorectic tumor-bearing rats

Although previous studies have implicated NPY in the etiology of experimental cancer anorexia, the results have been difficult to interpret. Studies have suggested that although NPY level and message were decreased in the dorsomedial hypothalamic area (DMA), they were elevated in the ventromedial hypothalamic area (VMA). To better assess specific intra-area alterations of NPY, Y(1) receptor (Y(1) R), and agouti-related peptide (AgRP) in TB rats, we used radioimmunoassay, quantitative real-time RT-PCR, and immunohistochemistry. We found that NPY and AgRP mRNA were elevated significantly in whole hypothalamus of anorectic TB rats, while Y(1) R mRNA was decreased. Based on two replicates of four pooled samples each, both NPY and AgRP mRNA appeared to be elevated in the VMA of anorectic TB rats, while only AgRP exhibited a similar increase in the DMA. Levels of NPY were elevated in the VMA of both TB and pair-fed (PF) rats, but in the DMA only PF rats exhibited a significant NPY increase. NPY and Y(1) R immunohistochemistry revealed reduced NPY staining in PVN and ARC nucleus of TB and PF rats. Y(1) R immunostaining was also reduced in the ARC and PVN of TB rats, while PF rats exhibited elevated immunostaining in the PVN. These results continue to implicate dysfunction of NPY feeding systems in experimental cancer anorexia and suggest down-regulation of Y(1) R receptors as well as possible problems in NPY translation.

Catabolic effects of gastric bypass in a diet-induced obese rat model

PURPOSE OF REVIEW

In the USA, 8-10 million people are morbidly obese, which is associated with a high frequency of comorbidities. The most effective treatment is surgery. Of around 180,000 bariatric operations performed in 2005, 80% were Roux-en-Y gastric bypass, consisting of a small gastric pouch to minimize food intake and a Roux-en-Y of distal small bowel bypassing the upper gastrointestinal tract. The precise mechanisms whereby Roux-en-Y gastric bypass achieves sustained weight loss remain unknown. To gain insight into the catabolic events of sustained weight loss we developed a diet-induced obese Roux-en-Y gastric bypass rat model. We review our rat model data from the novel viewpoint of the catabolic state, comparing it with the limited human data available and the catabolic events occurring in cancer anorexia/cachexia syndrome.

RECENT FINDINGS

Current data suggest the involvement of mechanisms other than restrictive and malabsorptive factors of the Roux-en-Y gastric bypass, classically thought of as the mechanisms responsible for weight loss. Based on available data, gastrointestinal hormones and cytokines play a key role in reducing food intake and regulating energy homeostasis. Because of the cross talk between peripheral modulators and the hypothalamus, a critical role for their interaction in the outcome of Roux-en-Y gastric bypass is emerging.

SUMMARY

In our Roux-en-Y gastric bypass rat model many of the changes in gastrointestinal hormones, adipokines and cytokines as well as in hypothalamic neuropeptides and neurotransmitters resemble the changes observed in the anorexia/cachexia rat model, suggesting that Roux-en-Y gastric bypass triggers a catabolic state responsible for loss of appetite and prolonged body weight reduction.

Omega-3 fatty acids improve appetite in cancer anorexia, but tumor resecting restores it

BACKGROUND

Tumor growth leads to cancer anorexia that is ameliorated using omega-3 fatty acids (omega-3FA). We hypothesize that omega-3FA modulates up-regulation of hypothalamic orexigenic neuropeptide Y (NPY) and down-regulation of anorexigenic alpha melanocyte-stimulating hormone (alpha-MSH) and serotonin 1B receptors (5-HT(1B)-receptors) in tumor-bearing rats.

METHODS

Twenty-eight tumor-bearing rats were fed either chow (TB-Control) or omega-3FA (TB-omega-3FA). When anorexia developed in TB-Control rats, they and a cohort of TB-omega-pi-3 rats were killed. The rest had their tumor resected (R-Control and R-omega-3FA), and when anorexic TB-Controls normalized their food intake, brains were removed for hypothalamic immunocytochemical study of NPY, alpha-MSH, and 5-HT(1B)-receptor antibodies concentrations. Comparison among slides were assessed by image analysis and analyzed by ANOVA and t test.

RESULTS

At anorexia, hypothalamic NPY in arcuate nucleus (ARC) increased by 38% in TB-omega3FA versus TB-Control, whereas alpha-MSH decreased 64% in ARC and 29% in paraventricular nucleus (PVN). Omega-3FA diet in anorexia (TB-omega-3FA vs R-omega-3FA) produced similar qualitative changes of NPY (22% increase) and alpha-MSH (31% decrease) in ARC, with concomitant decrease of 37% in 5-HT(1B)-receptors in PVN, confirming the influence of omega-3FA on the hypothalamic food intake modulators. However, after tumor resection (TB-Control vs R-Control) a 97% increase in NPY and a 62% decrease in alpha-MSH occurred that was significantly greater than in rats fed omega-3FA diet.

CONCLUSION

Tumor resection and omega-3FA modifies hypothalamic food intake activity, up-regulating NPY and down-regulating alpha-MSH and 5-HT(1B)-receptors. Tumor resection in anorexic rats on chow diet restored hypothalamic NPY, alpha-MSH, and food intake quantitatively more than in rats fed omega3FA diet.

Hypothalamic integration of immune function and metabolism

The immune and neuroendocrine systems are closely involved in the regulation of metabolism at peripheral and central hypothalamic levels. In both physiological (meals) and pathological (infections, traumas and tumors) conditions immune cells are activated responding with the release of cytokines and other immune mediators (afferent signals). In the hypothalamus (central integration), cytokines influence metabolism by acting on nucleus involved in feeding and homeostasis regulation leading to the acute phase response (efferent signals) aimed to maintain the body integrity. Peripheral administration of cytokines, inoculation of tumor and induction of infection alter, by means of cytokine action, the normal pattern of food intake affecting meal size and meal number suggesting that cytokines acted differentially on specific hypothalamic neurons. The effect of cytokines-related cancer anorexia is also exerted peripherally. Increase plasma concentrations of insulin and free tryptophan and decrease gastric emptying and d-xylose absorption. In addition, in obesity an increase in interleukin (IL)-1 and IL-6 occurs in mesenteric fat tissue, which together with an increase in corticosterone, is associated with hyperglycemia, dyslipidemias and insulin resistance of obesity-related metabolic syndrome. These changes in circulating nutrients and hormones are sensed by hypothalamic neurons that influence food intake and metabolism. In anorectic tumor-bearing rats, we detected upregulation of IL-1beta and IL-1 receptor mRNA levels in the hypothalamus, a negative correlation between IL-1 concentration in cerebro-spinal fluid and food intake and high levels of hypothalamic serotonin, and these differences disappeared after tumor removal. Moreover, there is an interaction between serotonin and IL-1 in the development of cancer anorexia as well as an increase in hypothalamic dopamine and serotonin production. Immunohistochemical studies have shown a decrease in neuropeptide Y (NPY) and dopamine (DA) and an increase in serotonin concentration in tumor-bearing rats, in first- and second-order hypothalamic nuclei, while tumor resection reverted these changes and normalized food intake, suggesting negative regulation of NPY and DA systems by cytokines during anorexia, probably mediated by serotonin that appears to play a pivotal role in the regulation of food intake in cancer. Among the different forms of therapy, nutritional manipulation of diet in tumor-bearing state has been investigated. Supplementation of tumor bearing rats with omega-3 fatty acid vs. control diet delayed the appearance of tumor, reduced tumor-growth rate and volume, negated onset of anorexia, increased body weight, decreased cytokines production and increased expression of NPY and decreased alpha-melanocyte-stimulating hormone (alpha-MSH) in hypothalamic nuclei. These data suggest that omega-3 fatty acid suppressed pro-inflammatory cytokines production and improved food intake by normalizing hypothalamic food intake-related peptides and point to the possibility of a therapeutic use of these fatty acids. The sum of these data support the concept that immune cell-derived cytokines are closely related with the regulation of metabolism and have both central and peripheral actions, inducing anorexia via hypothalamic anorectic factors, including serotonin and dopamine, and inhibiting NPY leading to a reduction in food intake and body weight, emphasizing the interconnection of the immune and neuroendocrine systems in regulating metabolism during infectious process, cachexia and obesity.

Estrogen receptor alpha and beta immunoreactive neurons in normal adult and aged female rat hippocampus: a qualitative and quantitative study

We have studied the distribution pattern and levels of expression of two estrogen receptor (ER) subtypes, ERalpha and ERbeta, in the normal adult (n = 10) and the aged (n = 10) female rat hippocampus with the objective to establish baseline data and the changes that occur during aging. Techniques including immunohistochemical localization, co-localization with double immunofluorescence and confocal microscopy, image analysis including neuronal counts/mm(2) area and measurements of optical density (OD) of immunoreactivity in immunoreactive neurons and Western blot analysis have been used. The results revealed ERalpha and ERbeta positive neurons in all subfields of the hippocampus with maximum presence in the stratum pyramidale of CA3. Some stained neurons in CA3 exhibited pyramidal neuron like morphological characteristics; such neurons were not found in CA1. All other immunoreactive neurons showed non-pyramidal neuron like morphological characteristics. Neuronal counts revealed a significant decrease in the number of immunoreactive neurons in CA3-CA1 of aged hippocampus. The percent decrease in counts of the immunoreactive neurons/mm(2) area in the aged rat (compared to the adult) was 78% for the ERalpha and 88% for the ERbeta (P < 0.001) in CA3. In CA1, it was 56% (P < 0.001) and 41% (P < 0.01) respectively. The OD of immunoreactivity was significantly decreased (P < 0.01) in CA3 but increased (P < 0.01) in the CA1 immunoreactive neurons. Western blot analysis also showed a significant decline (P < 0.01) in the levels of the ERalpha and ERbeta proteins in the aged hippocampus. Co-localization revealed that the two ER subtypes do co-exist in the same hippocampal neurons.

Cancer cachexia

Cancer cachexia is a severe debilitating disorder for which there are currently few therapeutic options. It is driven by the release of pro-inflammatory cytokines and cachectic factors by both host and tumour. Over the past few years, basic science advances have begun to reveal the breadth and complexity of the immunological mechanisms involved, and in the process have uncovered some novel potential therapeutic targets. The effectiveness of thalidomide and eicosapentaenoic acid at attenuating weight loss in clinical trials also provides a further rationale for modulating the immune response. We are now entering an exciting period in cachexia research, and it is likely that the next few years will see effective new biological therapies reach clinical practice.

Normalization of hypothalamic serotonin (5-HT1B) receptor and NPY in cancer anorexia after tumor resection: An immunocytochemical study

Tumor growth leads to anorexia and decreased food intake, the regulation of which is via the integrated hypothalamic peptidergic and monoaminergic system. Serotonin (5-HT), an anorectic monoamine acts primarily via 5-HT 1B-receptors in hypothalamic nuclei while neuropeptide Y (NPY) acts an orexigenic peptide. We previously reported that 5-HT 1B-receptors are up regulated while NPY is down regulated in tumor-bearing (TB)-related anorexia, contributing to food intake reduction. In anorectic TB rats we hypothesize that after tumor resection when food intake has reverted to normal, normalization of 5-HT 1B-receptor and NPY will occur. The aim of this study was to demonstrate normalization of these hypothalamic changes compared to Controls. In anorectic tumor-bearing rats after tumor resection (TB-R) and in sham-operated (Control) rats, distribution of 5-HT 1B-receptors and NPY in hypothalamic nuclei was analyzed using peroxidase antiperoxidase immunocytochemical methods. Image analysis of immunostaining was performed and the data were statistically analyzed. Immunostaining specificity was controlled by omission of primary or secondary antibodies and pre-absorption test. Our results show that after TB-R versus Controls a normalization of food intake, 5-H-1B-receptor and NPY expression in the hypothalamus occurs. These data, discussed in context with our previous studies, support the hypothesis that tumor resection results not only in normalization of food intake but also in reversible changes of anorectic and orexigenic hypothalamic modulators.

Omega-3 fatty acids and anorexia

PURPOSE OF REVIEW

To review the mechanisms of action of omega-3 fatty acids and their role in the brain, as well as their therapeutic implications in anorexia.

RECENT FINDINGS

Recent studies have demonstrated that omega-3 fatty acids modulate changes in the concentrations and actions of several orexigenic and anorexigenic neuropeptides in the brain, including neuropeptide Y, alpha-melanocyte stimulating hormone and the neurotransmitters serotonin and dopamine. In patients with acute and chronic inflammatory conditions, low tissue concentrations of omega-3 fatty acids and high concentrations of proinflammatory cytokines are found, in association with anorexia and decreased food intake. The data suggest that omega-3 fatty acid supplementation suppresses proinflammatory cytokine production and improves food intake by normalizing hypothalamic orexigenic peptides and neurotransmitters.

SUMMARY

Based on current data, omega-3 fatty acid supplementation has a role in the treatment of anorexia by stimulating the production and release of orexigenic neurotransmitters in food intake regulatory nuclei in the hypothalamus.

Effects of omega-3 fatty acids on orexigenic and anorexigenic modulators at the onset of anorexia

In cancer anorexia, a decrease in food intake (FI) occurs concomitant with changes in orexigenic peptides such as neuropeptide Y (NPY) and anorexigenic peptides such as alpha-melanocyte-stimulating hormone (alpha-MSH) and anorexigenic neurotransmitter serotonin. omega-3 Fatty acid (omega-3FA) inhibits cytokine synthesis, and delays tumor appearance, tumor growth, and onset of anorexia in tumor-bearing rats. We hypothesize that, in cancer anorexia, omega-3FA is associated with quantitative reversal of hypothalamic NPY, alpha-MSH, and serotonin receptor (5-HT(1B)-receptor) enhancing FI. Fischer rats were divided into: MCA tumor bearing fed chow (TB-Chow) or omega-3FA diet (TB-omega-3FA) and controls: non-tumor bearing fed chow (NTB-Chow) or omega-3FA diet (NTB-omega-3FA). Rats were euthanized at anorexia and brains were removed for hypothalamic immunohistochemical study, using NPY, alpha-MSH, and 5-HT(1B)-receptor-specific antibodies and slides assessed by image analysis. Immunostaining specificity was controlled by omission of primary or secondary antibodies and pre-absorption test. At anorexia, FI decreased (P < 0.05) in TB-Chow but did not change in TB-omega-3FA rats. In TB-omega-3FA vs. TB-Chow, NPY immunoreactivity increased 38% in arcuate nucleus (ARC; P < 0.05), and 50% in magnocellular paraventricular nucleus (mPVN; P < 0.05). alpha-MSH decreased 64% in ARC and 29% in mPVN (P < 0.05). 5-HT(1B)-receptor immunoreactivity decreased 13% only in supraoptic nucleus (P < 0.05). No immunoreactivity was found in the control sections. omega-3FA modified hypothalamic peptides and 5-HT-(1B)-receptor immunoreactivity at anorexia, concomitant with an increase in FI, were probably mediated by omega-3FA inhibition of tumor-induced cytokines.

Adrenal insufficiency in intestinal obstruction from carcinomatosis peritonei--a factor of potential importance in symptom palliation

Corticosteroids are used in the management of intestinal obstruction (IO) in carcinomatosis peritonei. There is considerable overlap in the symptoms experienced in IO and functional adrenal insufficiency (AI). The success of symptom palliation in IO may be related to the presence of AI. The aim of this preliminary study was to evaluate the incidence of functional adrenal insufficiency in patients with IO and its relation to clinical outcome and symptom control. Twenty-nine consecutive patients with IO and carcinomatosis peritonei from gastrointestinal cancers admitted to our inpatient service between January and October 2002 were analyzed. They were screened for AI using the short corticotropin stimulation test. Thirteen patients (45%) had functional AI. Differences in characteristics of patients with normal adrenal function (Group 1) and adrenal insufficiency (Group 2) were not statistically significant. Time taken to control symptoms in Group 2 was longer. Mean duration of hospitalization per month of survival was two times longer in Group 2 relative to Group 1 (7.9 versus 4.0 days, P=0.011). Functional AI may be caused by cytokines produced in advanced cancer mediating direct adrenal suppression. Prompt corticosteroid therapy in the presence of AI may facilitate IO symptom palliation.

Central, but not peripheral application of motilin increases c-Fos expression in hypothalamic nuclei in the rat brain

Previous immunocytochemical studies have shown the presence of motilin-immunoreactive neurons in specific brain areas of rats and autoradiographic studies in rabbits demonstrated motilin-binding sites in the central nervous system as well. Therefore, the aim of this study was to determine the anatomical localisation and neurochemical features of neurons activated by central administration of motilin (Mo) in rats. One week after cannulation, an intracerebroventricular injection of Mo (ICV, 3 microg/6 mul 0.9% saline) was given. For comparative purposes, a group of animals received an intravenous injection of motilin (IV, 9 microg/300 mul 0.9% saline) or an equal volume of saline. Neuronal excitation was assessed by c-Fos immunocytochemistry and combined with immunostaining for neurotransmitter markers. In contrast to the IV motilin-treated animals, the ICV motilin-treated animals displayed a significant increase in c-Fos expression in the supraoptic nuclei (SO) and paraventricular nuclei of the hypothalamus (PVH). At the level of the dorsomedial, ventromedial and lateral hypothalamic nuclei, ICV administration of motilin did not induce changes in c-Fos expression. In addition, the cerebellum did not show c-Fos expression after ICV motilin administration either. These findings might suggest distinct pathways and actions of centrally released and systemic motilin, but, particularly in rodents, do not rule out the possibility that the effects seen in the SO and PVH after ICV application are aspecific in nature. At present, we cannot exclude the fact that the results observed with motilin in rodents are due to cross-interaction with other related (e.g. ghrelin) or not yet identified receptors.

Neurobiologic changes in the hypothalamus associated with weight loss after gastric bypass

BACKGROUND

Effects of Roux-en-Y gastric bypass (RYGB) on hypothalamic food intake regulation have not been investigated. The hypothalamic arcuate nucleus (ARC) and the magnocellular (m) and parvocellular (p) parts of the paraventricular nucleus (PVN) regulate hunger and satiety, and are under control of the orexigenic neuropeptide Y (NPY), and the anorexigenic alpha-melanocyte stimulating hormone (alpha-MSH) and serotonin (5-HT). We hypothesized that after RYGB, weight loss is associated with hypothalamic down regulation of NPY and up regulation of 5-HT and alpha-MSH.

STUDY DESIGN

Obesity was induced in 12 Sprague Dawley rats using a high-energy diet for 7 weeks, and then the rats were divided into three groups (n = 4/group): RYGB, sham-operated pair-fed (PF), and sham-operated ad libitum (obese control). Ten days after operation, immunohistochemical quantification of NPY, alpha-MSH, and 5-HT(1B)-receptors in ARC and PVN was performed. Data were analyzed using ANOVA and Tukey's test.

RESULTS

Body weight decreased in RYGB (417 +/- 21 g; mean +/- SE) and in PF (436 +/- 14 g) rats 10 days after operation compared with obese control rats (484 +/- 15 g; p < 0.05 for each comparison). NPY in ARC, pPVN, and mPVN decreased by 43%, 43%, and 61%, respectively in RYGB and by 55%, 42%, and 71% in PF, respectively, compared with obese controls (p < 0.05 for each pairwise comparison). RYGB versus PF did not show differences. alpha-MSH in ARC, pPVN and mPVN increased by 35%, 175%, and 67%, respectively in RYGB and by 29%, 162%, and 116% in PF, respectively, compared with obese controls (each p < 0.05). In mPVN, alpha-MSH significantly decreased by 23% in RYGB versus PF (p < 0.05). 5-HT-(1B)-receptor in pPVN increased by 58% in RYGB and by 26% in PF, compared with obese controls (p < 0.05). Compared with obese controls, 5HT-(1B)-receptor in mPVN increased by 39% in RYGB (p < 0.05) and by 9% in PF (p > 0.05). An increase of 5-HT-(1B)-receptor in pPVN and mPVN occurred in RYGB versus PF (p < 0.05).

CONCLUSIONS

Obese rats that undergo weight loss after RYGB demonstrate changes in hypothalamic down regulation of NPY and up regulation of alpha-MSH and serotonin.

Neuropeptide Y immunoreactivity and corticotropin-releasing hormone mRNA level are increased in the hypothalamus of mouse bearing a human oral squamous cell carcinoma

We examined gene expression of corticotropin-releasing hormone and neuropeptide Y level in the hypothalamic paraventricular nucleus of mouse bearing a human oral squamous cell carcinoma. A cell line derived from a human oral squamous cell carcinoma was inoculated into the lower dorsal area of nude mice. Body weight, tumor size and daily food intake were recorded every morning. Mice were sacrificed for corticotropin-releasing hormone mRNA in situ hybridization and neuropeptide Y immunohistochemistry, when the tumor ratio reached to 11-13% of real body weight. The results were compared with the age-matching non-tumor controls injected with saline instead of carcinoma cell. Body weight gain was significantly reduced in tumor bearing mice, however, no compensatory hyperphagia was found, i.e. daily food intake of the tumor mice did not differ from the non-tumor mice. Both neuropeptide Y immunoreactivity and corticotropin-releasing hormone mRNA level were significantly increased in the hypothalamic paraventricular nucleus of tumor mice. These results suggest that a human oral squamous cell carcinoma may induce anorexia, at least partly, via increasing the hypothalamic expression of corticotropin-releasing hormone in the tumor subjects. Additionally, neuropeptide Y-induced feeding appears to be inhibited in this tumor anorexia model, and this may correlate with increased expression of corticotropin-releasing hormone.

Cancer anorexia-cachexia syndrome: cytokines and neuropeptides

PURPOSE OF REVIEW

Cancer anorexia-cachexia syndrome is observed in 80% of patients in the advanced stages of cancer and is a strong independent risk factor for mortality. Numerous cytokines produced by tumor and immune cells, interacting with the neuropeptidergic system, mediate the cachectic effect of cancer. Since there is currently no effective pharmacological treatment and the anorexia-cachexia syndrome continues to be defined biochemically, we review the role of cytokines and neuropeptides in this process.

RECENT FINDINGS

Currently data suggest that cancer anorexia-cachexia syndrome results from a multifactorial process involving many mediators, including hormones (e.g. leptin), neuropeptides (e.g. neuropeptide Y, melanocortin, melanin-concentrating hormone and orexin) and cytokines (e.g. interleukin 1, interleukin 6, tumor necrosis factor alpha and interferon gamma). It is likely that close interrelation among these mediators exists in the hypothalamus, decreasing food intake and leading to cachexia.

SUMMARY

In the pathogenesis of cancer anorexia, cytokines play a pivotal role influencing the imbalance of orexigenic and anorexigenic circuits that regulate the homeostatic loop of body-weight regulation, leading to cachexia. Interfering pharmacologically with cytokine expression or neural transduction of cytokine signals can be an effective therapeutic strategy in anorectic patients before they develop cancer anorexia-cachexia syndrome.

Interleukin-1beta system in anorectic catabolic tumor-bearing rats

PURPOSE OF REVIEW

The onset of cancer anorexia and the accompanying neurological symptoms and signs involve the general influence of cytokines on the brain. Using methylcholanthrene to induce tumors in Fischer 344 rats, we measured various specific components of the cytokine-induced anorectic reaction, including: (1) IL-1beta system components (ligand, signaling receptor, receptor accessory proteins, and receptor antagonist); (2) TNF-alpha; (3) TGF-beta1; and (4) IFN-gamma in the tumor tissue, the liver and the brain.

RECENT FINDINGS

The data show that IL-1beta, TNF-alpha and IFN-gamma messenger RNA were detected in the tumor tissue of anorectic tumor-bearing rats. In brain regions, anorexia is associated with the upregulation of IL-1beta and its receptor mRNA. All other mRNA remained unchanged in the brain regions examined.

SUMMARY

This suggests that IL-1beta and its receptor may play a significant role in this model of cancer-associated anorexia. In vivo, the characterization of cytokine components in the brain may provide data for potential pharmacological interventions to ameliorate the anorexia of disease.

Appetite and Cancer-Associated Anorexia: A Review

Appetite is governed by peripheral hormones and central neurotransmitters that act on the arcuate nucleus of the hypothalamus and nucleus tactus solitarius of the brainstem. Cancer anorexia appears to be the result of an imbalance between neuropeptide-Y and pro-opiomelanocortin signals favoring pro-opiomelanocortin. Many of the appetite stimulants redress this imbalance. Most of our understanding of appetite neurophysiology and tumor-associated anorexia is derived from animals and has not been verified in humans. There have been few clinical trials and very little translational research on anorexia despite its prevalence in cancer.

Tumor anorexia: effects on neuropeptide Y and monoamines in paraventricular nucleus

Paraventricular (PVN) concentrations of neuropeptide Y (NPY), serotonin (5-HT) and dopamine (DA) in anorectic tumor-bearing (TB) rats were measured before and after tumor resection. At onset of anorexia in TB versus non-tumor bearing (NTB) Controls 5-HT increased from 12.19+/-0.49 pg/microg to 14.89+/-0.81 pg/microg ( P<0.05 ) while DA and NPY decreased from 7.34+/-0.42 pg/microg to 4.97+/-0.56 pg/microg and 23.47+/-4.27 pg/microg to 13.64+/-1.44 pg/microg, respectively ( P<0.05 ). After tumor resection, these neuromediators normalized when compared to sham-operated NTB rats. NTB pair-fed Controls were also studied. We conclude that the increased 5-HT and the decreased DA and NPY concentrations in PVN are associated with cancer anorexia and that the NPY food stimulatory effect is linked to serotoninergic and dopaminergic systems in hypothalamus.

Cancer anorexia: clinical implications, pathogenesis, and therapeutic strategies

Anorexia and reduced food intake are important issues in the management of patients with cancer because they contribute to the development of malnutrition, increase morbidity and mortality, and impinge on quality of life. Accumulating evidence indicates that cancer anorexia is multifactorial in its pathogenesis, and most of the hypothalamic neuronal signalling pathways modulating energy intake are likely to be involved. Several factors are considered to be putative mediators of cancer anorexia, including hormones (eg, leptin), neuropeptides (eg, neuropeptide Y), cytokines (eg, interleukin 1 and 6, and tumour necrosis factor), and neurotransmitters (eg, serotonin and dopamine). These pathways are not isolated and distinct pathogenic mechanisms but are closely inter-related. However, convincing evidence suggests that cytokines have a vital role, triggering the complex neurochemical cascade which leads to the onset of cancer anorexia. Increased expression of cytokines during tumour growth prevents the hypothalamus from responding appropriately to peripheral signals, by persistently activating anorexigenic systems and inhibiting prophagic pathways. Hypothalamic monoaminergic neurotransmission may contribute to these effects. Thus, the optimum therapeutic approach to anorectic cancer patients should include changes in dietary habits, achieved via nutritional counselling, and drug therapy, aimed at interfering with cytokine expression or hypothalamic monoaminergic neurotransmission.

Cachexia and obesity: two sides of one coin?

PURPOSE OF REVIEW

Leptin, a member of the interleukin-6 superfamily of proteins, modifies the gene expression and synthetic pathway of both orexigenic (appetite-stimulating) and anorexigenic (appetite-suppressing) molecules in the hypothalamus, thereby controlling adipocyte energy stores. Lack of leptin secretion or the inability of leptin to interact with these molecules via leptin receptors, prevent leptin's effects and lead to obesity. It is not well known, however, how these feeding-regulatory molecules are affected in cachexia associated with cancer and other critical conditions in which cytokines such as interleukin-1 and interleukin-6 may have a key role.

RECENT FINDINGS

Decreased leptin and increased leptin-like signaling by cytokines in the hypothalamus are the hallmark of obesity and cachexia, respectively. Increased orexigenic and impaired anorexigenic signaling produces hyperphagia and obesity, while the reverse applies to anorexia-cachexia in which adaptive feeding response to starvation is lacking or insufficient.

SUMMARY

Imbalanced operation of orexigenic and anorexigenic circuits perturbs the homeostatic loop of body weight regulation leading to either obesity or cachexia. Modifiers of the central effects on appetite and energy metabolism could restore the balance and be effective for treating both conditions. In cachexia this may especially be true when combined with agents that target muscle and protein breakdown.